Datasets:

nbalepur

/

doc_conflict_summary_split

like 0

[ "https://copyrightwitness.com/protect/logo_copyright", "https://wariplaw.com/what-are-the-significant-reasons-behind-copyrighting-a-logo/", "https://www.forbes.com/advisor/business/how-to-trademark-a-logo/", "https://copyrightalliance.org/is-fashion-protected-by-copyright-law/", "https://fabrikbrands.com/logo-copyright-infringement/", "https://smallbusiness.chron.com/can-put-copyrighted-logos-tshirts-57727.html", "https://talglaw.com/copyright-logo/", "https://thecopyrightdetective.com/trademark-vs-copyright/" ]

[ "support", "support", "support", "support", "support", "refute", "refute", "refute" ]

[ [ "Copyright and logos", "Logo copyright is the subject of many enquiries we receive. In particular how copyright protects logos and whether logos are suitable for registration. This page deals with the common questions surrounding this subject.", "Can I register my company logo or brand images with Copyright Witness?", "Yes. In fact, it is common for companies to register their logos with us.", "Registrations can be made for the company logo, and also for any images or artwork associated with the brand or promotional materials. This is often carried out at company start up or prior to the launch of a new product or advertising campaign.", "Copyright does not protect names in their own right, but trading names will still be automatically be subject to trademark protection against ‘passing off’.", "Passing off legislation is designed to prevent a person or organisation from poaching trade from an established company by presenting itself in a way that makes the customer believe that are dealing with the more established company. This would typically involve using the same (or similar) name or logo as the established company or falsely implying an association with the established company. For more details on this, please see our copyright and names fact sheet.", "Can a copyright registration of a logo be used in a passing off case?", "Yes, it may help. Certainly the fact that a logo was registered is evidence of the date and content of the logo. At the very least it can help to demonstrate who was using the name or logo first and who was copying.", "Copyright or trademark?", "Is a logo subject to copyright?", "Yes. A logo that includes artistic or design elements, (i.e. not just the name on its own), is legally regarded as being a work of artistic creation and therefore will be protected under copyright law.", "Copyright protects the logo as an artistic work. As copyright is an automatic international right, it therefore follows that, (other than activities specified under fair dealing rules), unauthorised copying of that logo would be an infringement.", "Could a trademark also apply?", "A trademark will apply to the logo as it is an identifying mark of the brand identity.", "Trademarks and are intended to prevent confusion in the marketplace between competing companies in the same business sector. In most jurisdictions they are automatically protected under common law against passing off (where a competitor uses the mark in a confusing/misleading way, for example to poach trade).", "It is also possible to apply for a registered trademark on a per country or region basis. Registered trademarks are administered nationally by a country's national trademark office (Copyright Witness do not register trademarks); if you are interested in obtaining a registered trademark, you should contact a trademark attorney or your national trademark office for further details.", "In practice, businesses will tend to only seek registered trademarks in countries where they have a strong trading relationship and fall back on copyright or passing off protection in the remaining countries. A registration of the logo with ourselves provides a low cost way to secure independent evidence of your prior claim in case of incidents in countries where you do not have a registered trademark." ], [ "What are the significant reasons behind copyrighting a logo?", "Importance of copyrighting a logo", "Copyright is vital for every creative individual and business. Elements such as your logo play a critical role in establishing your brand. Because of this, it is natural to feel concerned about someone copying your original works. Making your logo copyrightable by adding a copyright symbol is critical to protect your original work from being copied. We’re here to assist you in protecting your original work from copyright infringement.", "Why is copyrighting a logo so critical?", "Should I copyright or trademark my logo?", "How to copyright your logo in Washington, DC", "Gain rights to your creativity with an attorney", "A copyrighted logo is protected as an artistic work. Unauthorized usage of your logo is an infringement of copyright. No one can use any of your original works fixed in a tangible form without your permission.", ".", "Should I copyright or trademark my logo?", "“Can I copyright my logo?” is a common misconception. To answer this correctly, distinguish between what works are subject to copyright and trademark. Registrations serve various purposes, and there are numerous ways to be protected by copyright law.", "Generally, if you use your logo for commercial value, you should register ownership of the trademark. By registering your trademark, you guarantee that people identify your brand. You may protect your logo if it is your original work and is non-commercial. As with a piece of art, copyright ownership preserves your logo’s originality.", "Learn the differences between trademark and copyright protection to determine which you need.", "What is protected by copyright?", "Copyright protects your original works of authorship in a tangible medium of expression. If you use your logo for purposes other than selling products and services, you should apply for copyright registration.", "Copyrights protect items like books and articles, photographs, illustrations, web pages, music and sound recordings, and computer programs from being reproduced by others without the creator’s consent. The copyrighted material is unrelated to the commercial products or services. You may place copyright restrictions on your logo.", "Your logo can be subject to copyright if it is an original work of authorship, such as a computer-rendered design, sketch, writings, painting, or photograph.", "What cannot be copyrighted but trademarked instead?", "Trademarks help consumers recognize the origin of goods and services. Your logo serves as a trademark for the products or services you sell under your brand’s name. Using a trademark registration application allows you to prevent others from using your trademark on similar products or services.", "Typically, trademarks cover things such as business names, slogans, taglines, and logos. They are intended to serve as a source identifier for goods or services. Registering a trademark prevents others from using your mark to similar goods or services.", "If your logo is the artistic work of a professional designer, be careful to include proof of", "work made for hire from the creators to you.", "Submit payment online", "Upload or mail in a copy of your logo", "Wait for approval and your registration certificate and necessary licenses", "The Copyright Office also has an eCO FAQ page to address common concerns.", "There you have it. Nothing beats the feeling of knowing that you have exclusive rights to an original work you made from scratch.", "Determining Your Logo’s Copyright Eligibility", "Logos are not always copyright-protected material.", "If a trademark, logo, or label is only a collection of words, the United States Copyright Office will not register it. Simply using various fonts or colors, frames, and borders also does not qualify for copyright protection.", "Logos are protected under copyright law if they contain artistic or design elements.", "Examples of trademark and copyright-eligible logos include Disney characters (such as Mickey Mouse or Donald Duck), the Car Credit City logo, and the Baltimore Ravens logo.", "Copyrighting Your Logo Is Beneficial", "If you think your logo qualifies for copyright protection, the next logical question is: why bother to register the copyright? The following are a few of the many advantages.", "Labeling, packaging, or advertising content eligible for copyright can be violated without a trademark.", "Copyrights exist to safeguard your creative work. The attention is on the works’ resemblance. On the other hand, to prevent consumer confusion, trademark infringement analyses focus on a series of tests, including the relatedness of products, the validity of the mark, marketing channel overlap, and proof of real confusion.", "Trademark infringement does not require copyright infringement.", "If you want to protect your brands, trademark registration is vital.", "To recap, only artistic and design elements used in trademarks are protected by copyright laws in the US. The rest of your logo may not be protected. For example, if an infringer substitutes a different logo or label but uses the exact wording of your mark, it would likely be actionable as trademark infringement.", "Copyright registration requires only an original work of authorship that contains at least a slight amount of creativity.", "Trademark registration is more complicated. You must demonstrate that the mark identifies a provider of goods or services. Ideally, trademarks should be suggestive, arbitrary, or fanciful to obtain registration. While descriptive marks may gain commercial recognition and then registrability, typically descriptive marks must be filed for registration in the Supplemental Register. A generic trademark is not protected by trademark law. Copyright law’s requirement of minimal creativity does not analyze works of authorship with the same scrutiny.", "Even if your mark is suggestive, arbitrary, or fanciful, it is still possible that the USPTO won’t register it if it determines that it logo may confuse consumers as to the source of your goods or services. Confusion among consumers is unimportant to copyright legislation.", "In sum, even if the USPTO declines to register your trademark, copyright law may be able to help protect you.", "Gain rights to your creativity with an attorney", "Even when your trademark hasn’t been infringed in the case at hand, copyright law may be able to provide more robust protection. To obtain further legal protection for your logo, you need to include a copyright notice. A trademark registration and notice on its own may not be enough.", "Copyrights offer various legal benefits in addition to those of registered trademarks, such as punitive damages. An intellectual property lawyer can help you decide the best line of action for safeguarding your copyrights, trademarks, and other intellectual property. Whether you want to raise copyright issues or learn more about copyright violations, our team of dedicated copyright attorneys at War IP Law can provide you with the assistance you need and a plan of action.", "War IP Law PLLC", "Contact One of Our IP Attorneys", "If you have questions or need help with an intellectual property matter, use this form to ask us a question or just give us a call. We’re here to help.", "Footer Form", "First Name", "Last Name", "Email", "Phone", "I need help with:", "Copyright", "Trademark", "Patent", "Trade secrets", "Infringement claims", "Others", "I want to schedule a consultation", "The contents of this website are intended to convey general information only and not to provide legal advice. The contents of this website, the posting, and viewing of the information on this website, should not be construed as, and should not be relied upon for, legal advice in any particular circumstance or fact situation. The information presented on this website may not reflect the most current legal developments. No action should be taken in reliance on the information contained on this website. We disclaim all liability in respect to actions taken or not taken based on any content of this site to the fullest extent permitted by law. For advice on specific legal issues, an attorney should be contacted. Nothing on this website is an offer to represent you, and nothing on this website is intended to create an attorney‑client relationship. An attorney-client relationship may only be established through direct attorney‑to‑client communication that is confirmed by the execution of an engagement agreement. The content of any unsolicited email sent to War IP Law PLLC, or to any of its attorneys at an email address available on this website, will not create an attorney‑client relationship and the contents of such unsolicited email shall not be considered confidential. Therefore, do not use this website or the email addresses available on this website to provide confidential information about yourself or a legal matter to War IP Law PLLC or any of its attorneys." ], [ "Here’s How To Protect Your Business Logo With A Trademark", "Chauncey grew up on a farm in rural northern California. At 18 he ran away and saw the world with a backpack and a credit card, discovering that the true value of any point or mile is the experience it facilitates. He remains most at home on a tractor, but has learned that opportunity is where he finds it and discomfort is more interesting than complacency.", "Jane Haskins practiced law for 20 years, representing small businesses in startup, dissolution, business transactions and litigation. She has written hundreds of articles on legal, intellectual property and tax issues affecting small businesses.", "Rob is an SMB writer and editor based in New Jersey. Before joining Forbes Advisor, he was a content producer at Fit Small Business. In that role, he was responsible for writing, editing, and strategizing content geared toward small business owners. Before that, he worked at PCMag as a business analyst.", "Contributor, Contributor, Editor", "Updated: Mar 25, 2022, 2:29pm", "Editorial Note: We earn a commission from partner links on Forbes Advisor. Commissions do not affect our editors' opinions or evaluations.", "Getty", "Logos are a unique and valuable business asset that can leave lasting impressions on customers. Business owners who wish to protect a brand and its unique identifier(s) should consider trademarking a logo with the United States Patent and Trademark Office (USPTO). Trademarking a logo is a fairly straightforward process, but important considerations should go into trademarking a logo before, during and after the application filing process.", "What Is a Trademark?", "A trademark can be a word, phrase, symbol or image unique enough to register as a business’ exclusive brand. By trademarking a logo, business owners acquire legal protection against counterfeits, copycats and fraud. Other companies providing similar goods or services face harsh penalties for using a design similar to a trademarked logo, including foreign entities that import products into the U.S.", "How to Trademark a Logo", "A unique logo can be trademarked by registering it with the USPTO. Anyone can apply online on the USPTO website if the business for which they’re authorized to file is principally located inside the U.S. If based outside the U.S., a patent attorney will be required to make the filing.", "1. Determine Whether You Need a Trademark", "It’s important to first consider whether a trademark registration with the USPTO is necessary, since the process requires time, effort and money. Once a business begins to use a logo to advertise and sell goods or services, they automatically attain common law ownership and the limited protections associated with it—but only if the business can prove it was the first businesses to use the mark. Common law legal protection for a trademark only applies to the geographic area where the business operates. If nationwide protection is needed, then registering a logo with the USPTO is a wise step.", "2. Search for Existing Trademarks", "Before applying for a logo trademark, it’s important to search for existing trademarks that may bear any resemblance. An application may be rejected if the logo submitted is likely to be confused with existing logos for comparable goods or services. Logos cannot be generic and should always be unique to the business.", "Search for existing trademarked logos on the USPTO website using the Trademark Electronic Search System (TESS). Some experts, including those who wrote the USPTO website, recommend hiring an attorney or a specialized service to conduct this search on behalf of a business owner. Attorneys are trained in special techniques to perform a more thorough search before an application is submitted. This may be especially beneficial with graphic marks.", "3. Prepare the Application", "The application process can be time-consuming and complex. Because applications can be entirely rejected for small errors and fees are not refundable, it’s important to ensure each part of an application is correct before submitting. A patent and trademark attorney may be helpful with guidance for this process. Lawyers will be able to write descriptions of the logo using language that’s common and understood by the USPTO better than beginners to the process. This can save time and effort in the long run, especially in the event of any unforeseen complications.", "Prepare the following information for the application process:", "• Name, address and personal details of the entity filing for the trademark. This may be an individual or a business. (Note: Individuals and businesses who are based outside of the US will need to hire a lawyer to complete this process.)", "• Product(s) or service(s) the logo will represent, along the class of goods or services for which you’re registering the trademark.", "• A JPG image file of the final version of the logo or design. If your logo is in color, you also need a description of the colors and where they’re used", "• A JPG or PDF file of a “specimen” that shows an example of how the logo appears on the product or service itself. (This only applies to applicants with actual use in commerce, meaning the business owner has already sold goods or services using the specific logo.) Those intending to use a logo for service later will be required to show this proof later on.", "• Appropriate funds", "Also consider the final version of the logo. Will it be in color or black-and-white?.. While many logos are displayed in color on products or in marketing materials, registering for a trademark in color means that the logo is only protected if it’s displayed in those colors. A business owner must amend the initial application or re-apply for a new trademark if any changes are made to the logo’s color. If you trademark a black and white version, you can add or change colors without filing a new trademark application.", "4. File the Application", "The application can be completed on the USPTO’s website. The USPTO provides detailed instructions on how to navigate the online application, depending on the filing option. Once the application is submitted, the application status can be checked using the Trademark Status and Document Retrieval (TSDR). The USPTO recommends checking the status five to seven days after the initial application is submitted, but reports indicate that the process may take months if errors are found.", "After being received, the filing is assigned a serial number and a government trademark attorney. The examining attorney will review the materials and conduct a clearance search to make sure there aren’t any existing logos for similar goods or services that bear a resemblance to the applicant. If the application meets all of the legal requirements and there are no issues with existing logos, then the examining attorney will approve the logo for publication in a USPTO online journal. If no one files an opposition to the trademark after it is published, it will be registered.", "However, if there are any issues with the application, the examining attorney will send an office action to the applicant. The applicant must provide a response that corrects any problems listed in the office action, usually within six months. Failure to do so means the logo will not be approved.", "After the Logo Is Approved", "Once the logo is registered with the USPTO, a trademark owner will have exclusive rights to use the logo within the approved goods or services class anywhere in the U.S. The owner may sue for any unlawful use of the logo, and may file to stop foreign goods with your logo from being imported into the U.S.", "Business owners can set up a trademark watch by hiring an attorney or specialized service. The attorney or service will continuously monitor and search for illegal use of a trademarked logo. For those concerned with fraud or misuse, a service like this may be useful in catching such issues.", "Trademarks last 10 years. Be advised that renewing a trademark will be required in a decade.", "Copyright Vs. Trademark", "A copyright protects creative works like books, movies, music, artwork or computer programs. The copyrighted work has to be a “tangible medium,” meaning consumers must be able to see, hear or use it. It can’t be an undocumented idea or common string of words. A trademark, to contrast, is a unique phrase, word, symbol or design that represents a company or brand that provides goods or services. It is typically in marketing materials or to label products.", "Logos are often eligible for both trademark and copyright registration. A copyright protects the original design from unauthorized copying, while a trademark helps prevent the logo from being used by a competitor business.. Copyrights are automatically earned upon production of a work in a tangible medium, but registration adds benefit. If you hire someone to create your logo, be sure you have a written agreement giving your business the copyright to the logo. This gives you control over how it can be used and reproduced.", "Frequently Asked Questions", "How long does it take to trademark a logo?", "On average it can take anywhere from several months to over a year for a trademark application to be processed and approved. If there are complications such as re-examination or amendments to the initial application, the process may take significantly longer.", "Can I trademark a logo myself?", "Yes. Anyone can apply online to trademark a logo. However, experts often recommend that business owners hire an attorney or specialized service to handle the process from beginning to end to ensure that your application is prepared properly, and should any complications arise, they will be aptly handled.", "For businesses based outside the U.S., a U.S. patent and trademark attorney may be required to file an application.", "How much does it cost to trademark a logo?", "The USPTO offers two filing options for individuals or businesses: the TEAS Plus ($250 per class of goods/services) and the TEAS Standard ($350 per class of goods/services). There may be additional fees paid directly to an attorney or specialized service if the business owner chooses to hire them.", "Can a logo be copyrighted?", "Yes, a logo can be both copyrighted and trademarked. A logo has a copyright as soon as it has been created, but the copyright owner can also register the logo with the U.S. Copyright Office.", "Is it possible to trademark a business name?", "Yes. To trademark a business name you will need to submit an application through the U.S. Patent and Trademark Office’s website. Similar to the process of trademarking a logo, trademarking a business name can also take several months, and businesses are generally advised to hire professional assistance, such as an attorney or legal service to help ensure the process goes smoothly.", "Information provided on Forbes Advisor is for educational purposes only. Your financial situation is unique and the products and services we review may not be right for your circumstances. We do not offer financial advice, advisory or brokerage services, nor do we recommend or advise individuals or to buy or sell particular stocks or securities. Performance information may have changed since the time of publication. Past performance is not indicative of future results.", "Forbes Advisor adheres to strict editorial integrity standards. To the best of our knowledge, all content is accurate as of the date posted, though offers contained herein may no longer be available. The opinions expressed are the author’s alone and have not been provided, approved, or otherwise endorsed by our partners.", "Chauncey grew up on a farm in rural northern California. At 18 he ran away and saw the world with a backpack and a credit card, discovering that the true value of any point or mile is the experience it facilitates. He remains most at home on a tractor, but has learned that opportunity is where he finds it and discomfort is more interesting than complacency.", "Jane Haskins practiced law for 20 years, representing small businesses in startup, dissolution, business transactions and litigation. She has written hundreds of articles on legal, intellectual property and tax issues affecting small businesses.", "Rob is an SMB writer and editor based in New Jersey. Before joining Forbes Advisor, he was a content producer at Fit Small Business. In that role, he was responsible for writing, editing, and strategizing content geared toward small business owners. Before that, he worked at PCMag as a business analyst.", "The Forbes Advisor editorial team is independent and objective. To help support our reporting work, and to continue our ability to provide this content for free to our readers, we receive compensation from the companies that advertise on the Forbes Advisor site. This compensation comes from two main sources. First, we provide paid placements to advertisers to present their offers. The compensation we receive for those placements affects how and where advertisers’ offers appear on the site. This site does not include all companies or products available within the market. Second, we also include links to advertisers’ offers in some of our articles; these “affiliate links” may generate income for our site when you click on them. The compensation we receive from advertisers does not influence the recommendations or advice our editorial team provides in our articles or otherwise impact any of the editorial content on Forbes Advisor. While we work hard to provide accurate and up to date information that we think you will find relevant, Forbes Advisor does not and cannot guarantee that any information provided is complete and makes no representations or warranties in connection thereto, nor to the accuracy or applicability thereof. Here is a list of our partners who offer products that we have affiliate links for." ], [ "How Is Fashion Protected by Copyright Law?", "This week, you may have seen photographs and videos of long runways where models donned the season’s latest trends and styles. It’s Fashion Week 2022– the time of year when designers finally get to show off months of hard work through their craftmanship of various clothing and accessories.", "What you don’t see during Fashion Week is the laborious process of designers conceptualizing new creations, sketching them out, and capturing them in the fabrics and materials of the clothing they craft. But are these fashion designers rewarded for all their hard work and creativity by copyright—more to the point, are their fashion designs protected by copyright law? The short answer is that it depends.", "Copyrightability in Fashion", "According to the Merriam-Webster Dictionary, fashion is defined as “the prevailing style of a particular time.” In the fashion industry, trends and designs change from season to season in the form of various elements, which usually manifests itself in a variety of colors, silhouettes, types of fabrics, unique cuts of fabric, and prints.", "When determining whether and how fashion is protected by copyright law, it’s important to understand the scope of copyright protection for fashion items. The Copyright Act does not protect ideas, concepts, or facts. If the color of chartreuse, polka dots, or a simple balloon sleeve is the latest trend, copyright law protections do not extend to those design elements alone. In fact, the Copyright Office Compendium notes that the Copyright Office generally refuses to register “[c]ommon patterns, such as standard chevron, polka dot, checkerboard, or houndstooth designs, “geometric figures and shapes,” “alphabetic or numbering characters,” or simple arrangements of such unprotectable elements.", "For example, the Copyright Office rejected Coach’s registration application for a fabric design containing “a pattern consist[ing] of two linked ‘C’s’ facing each other alternating with two unlinked ‘C’s’ facing in the same direction.” A New York federal district court held in Coach, Inc. v. Peters, that the Copyright Office exercised its proper judgement in rejecting Coach’s application since the Copyright Office reasoned that under copyright law, mere letters of the alphabet and the arrangements of that letter ,“C,” were not sufficiently creative or original enough so that the design was protectable under copyright law.", "Fashion As a “Useful Article”", "The Copyright Act also does not extend protection to useful articles, which is defined as “an article that has an intrinsic utilitarian function that is not merely to portray the appearance of the article or to convey information.” There was a time in the not-too-distant past when the Copyright Office generally refused to register claims to copyright in clothing or costume designs on the “ground[s] that articles of clothing and costumes are useful articles that ordinarily contain no artistic authorship separable from their overall utilitarian shape.”", "But the Office changed its policy in 1991 when it released a Policy Decision about its examining practices with respect to “fanciful costumes.” Specifically, the Office noted that it would register these works “if they contain separable pictorial or sculptural authorship. The separable authorship may be physically separable, meaning that the work of art can be physically removed from the costume, or conceptually separable, meaning that the pictorial or sculptural work is independently recognizable and capable of existence apart from the overall utilitarian shape of the useful article.”", "But in 2016, the U.S. Supreme Court abandoned the physical separability test in the case, Star Athletica v. Varsity Brands. The Court set out a standard for determining copyrightability in fashion designs and for useful articles in general in a case about the copyrightability of cheerleader unforms. According to the Court, while copyright law may not protect the general notion of “style” it does protect design elements which:", "“can be perceived as two- or three-dimensional works of art separate from the” fashion item itself; and", "“qualify as a protectable pictorial, graphic, or sculptural work, either on its own or fixed in some other tangible medium.”", "This is the standard the Copyright Office and courts must use when evaluating copyrightability in useful articles like clothing and fashion accessories (including jewelry).", "So What Fashion Designs Are Protectable Under Copyright Law?", "By way of illustration, here are some design elements where fashion may be protectable under copyright law:", "Graphic Designs: Copyright law would protect the designs on the surface of fashion items just as it protects designs on the surface of a canvas or sheet of paper. For such protections to apply, copyright law only requires that the designs on the surface of fashion items (like the designs contained on the surface of any other medium) demonstrate a very minimal amount of creativity­­. The U.S. Supreme Court also addressed this issue in Star Athletica v. Varsity Brands, stating that “two-dimensional designs appearing on the surface of [clothing]” including “combinations, positionings, and arrangements” of shapes, colors, lines, etc. are protectable by copyright.”", "Textile Designs: Similarly, a producer of fabrics can rely on copyright to protect “designs imprinted in or on fabric—if the design contains a sufficient amount of creative expression.” In fact, the case Unicolors v. H&M, which is currently pending in the U.S. Supreme Court on registration issues, concerns an infringement of intricate geometric patterns that were designed by the pattern-making company Unicolors.", "Logos: Copyright law can protect logos. But the key is that logos must have sufficient creativity and originality under copyright law. The Copyright Office has refused to register copyrights in logos when the logos were deemed have simply contained common letters, typography, and geometric shapes without any elaborate or intricate arrangements that would amount to sufficient creativity under copyright law. For example, the Copyright Office has refused to register various logos of famous brands including Adidas’s “3 Bars” logo and Tommy Hilfiger’s “Flag” logo. However, designers can still generally find protections for their brands’ logos under trademark law.", "And then there are some design elements that copyright law would not protect. For those design elements, it’s important to remember that other types of intellectual property laws, including trademark and patent law, may provide protections for designers.", "Color: Copyright protection does not extend to colors. If a designer wants to protect a signature color or a unique color scheme, copyright is not the avenue. But that doesn’t mean there are no options for protection of the designer’s intellectual property. Trademark protection may be available in these instances.", "Cut: The way that design elements are cut and pieced together is not protected by copyright. The U.S. Supreme Court recently addressed this topic in the Star Athletica case, stating that copyright affords “no right to prohibit any person from manufacturing [clothing] of identical shape, cut, and dimensions.” But, again, that doesn’t mean there aren’t other kinds of protections that cover cuts. Design patents may afford protections for this type of design element. (And unlike copyright, a design patent can prevent others from creating fashions that resemble a sketch of the original design.)", "Whatever the trend, designers work hard to stay competitive and on top of the spirit of the times by laboring on their collections in time for Fashion Week 2022. It’s clear that the creativity and originality in a designer’s expression is what copyright law was meant to protect.", "If you aren’t already a member of the Copyright Alliance, you can join today by completing our Individual Creator Members membership form! Members gain access to monthly newsletters, educational webinars, and so much more — all for free!" ], [ "Logo copyright infringement: Here’s what you need to know", "Here at Fabrik, we’re always getting new ideas for concepts, just by interacting with people or seeing the many different shapes and components of the world around us.", "Unfortunately, when it comes to logo design, it’s important to know when it’s safe to act on inspiration.", "In a world that’s cluttered with millions of companies, and new startups opening their door each day, how do you know that the inspiration taken to create your logo is safe?", "Intellectual property rights can be very difficult to follow, but to help you get started on the right track, we’re going to introduce you to the basics of logo copyright infringement.", "What counts as copyright infringement?", "Intellectual property rights, such as trademarks and copyrights, can deliver both positive and negative opportunities to business owners. On one hand, getting copyright or trademark protection for your business logo means that no-one else can use it.", "However, in the same vein, logo copyright guidelines also mean that you can get into trouble if your designs are too similar in style to something else that exists in the marketplace.", "Anything original created by an artist or company can become something called “intellectual property”.", "The US laws dictate that when you design a logo, create a new product, or even paint a picture, you own intellectual property. To some extent, your intellectual property is immediately protected by IP law.", "However, legal protections come in many different forms, including:", "Patents: Used to defend inventions and innovations.", "Copyright: Used to protect literary and artistic works.", "Trademarks: Intended to distinguish the goods of a specific company.", "In the US, every designer or business automatically owns the copyright to their own work. You don’t necessarily have to register for a copyright with the US patent and trademark office.", "However, registering your copyright, or applying for a trademark can give you more peace of mind. This ensures that if someone else uses your image, you can take them to court.", "Logo copyright infringement happens when you use a critical component of a trademark (like the shape or color of a logo) in your design, without getting permission first.", "What is fair use in logo copyright infringement cases?", "Since there are millions of companies out there, and only a handful of shapes and designs to use in any standard logo, there is some flexibility in copyright law.", "The fair use doctrine refers to the exception in the Copyright Act that makes it legal to use copyrighted works without obtaining the permission of the author.", "For instance, you can reference copyrighted works in a college paper without having to pay for permission to use them. Additionally, if you’re reporting the news and you need to reference a piece of copyrighted work, that’s okay too.", "There’s also something to be said for inspiration in logo copyright infringement examples.", "If you’re inspired by the way that another brand uses colors and shapes in their logo, you wouldn’t get into trouble if you interpreted the crux of that idea differently in your own design.", "The key to success is making sure that you don’t just imitate what’s already there – you transform it into something new.", "Unfortunately, it’s very easy for something that started off as basic inspiration to transform into something problematic.", "For instance, if you think that someone would see your logo and instantly know where you got your inspiration, you’ve probably infringed on a copyright.", "One option in this case could be to request formal permission to use that copyrighted component.", "If, for example, you like the style of a certain typography in your logo and you want to create your own version of it, you can reach out to the company and ask for their permission to use their design as inspiration. They may not grant that permission, of course.", "In the same way, if you apply for a trademark or copyright on your logo, then you could prevent other people from using something that you consider to be “too similar” to your design.", "Examples of logo copyright infringement cases", "If you’re still uncertain about whether certain components of a logo protected by copyright are available to use, it might be helpful to check out some previous cases.", "For instance, in China, the 3M company brought a lawsuit against the Changzhou Huawei advanced material company. The business was using a version of the “3M” logo that included an N instead of an M.", "Although the mark was slightly different, the company had managed to acquire market share and clients simply because the logo was similar to that of 3M.", "A similar case took place for logo copyright infringement in South Korea. A chicken restaurant located in South Korea lost a legal battle with the apparel company Louis Vuitton.", "The court ruled in the favor of the design brand after dictating that the name of the restaurant, Louis Vuiton Dak, was too close in sound and style to Louis Vuitton. Additionally, the packaging and restaurant logo were very similar in style to the iconic imagery of the Louis Vuitton brand.", "Not only was the company in this case asked to stop using the logo and name that it had been building its image with, but it was hit with a fine for $14.5 million after it refused to change its appearance.", "Elsewhere, in India, the parent company of the American Eagle brand, Retail Royalty Company, filed in high court against the fashion and retail business, Pantaloons. The lawsuit claimed that the brand logo of the Pantaloons company was too similar to American Eagle’s iconic image.", "The verdict in that case took longer to establish, as the argument came from an American company. In some cases, copyrights and trademarks are only applied in the countries where companies originally set up their organizations.", "Avoiding logo copyright infringement issues", "There are clearly a lot of circumstances wherein the use of a logo that’s too similar in design or style to something else on the market can lead to significant problems for a business.", "The severity of any logo copyright infringement cases is often dependent on many things, including the nature of the copyrighted work, and the amount of copyrighted information used in the new design.", "If your new logo used a similar color to another company, for instance, but the rest of the components of that logo were different, you may not be hit with a logo copyright notice.", "The unfortunate truth, however, is that it’s difficult to know for certain whether you’re going to be held accountable for a copyright infringement issue or not.", "In most cases of copyright infringement shared by legal companies online, the issues could have been easily avoided. All you really need to do to protect yourself is make sure that you do your research.", "The answer to “How do I know if a logo is copyrighted” is to start by checking online. There are lots of tools available on the web that can help you to search for logos and determine which ones have trademark protection.", "There are also logo design experts that can do your due diligence for you.", "Can you use a logo without permission?", "Some companies assume that just because they’ve changed a few things about a popular logo, or their business is located in a different place to the original company, they don’t have to worry about copyright. Unfortunately, that’s rarely the case.", "Even if you do get away with using another company’s design for a little while, there will eventually be a moment when you’re found out.", "Knowing who owns the rights to a design and how it can be used is essential. If you’re not sure whether an element of your logo is fair use or not, then it’s best to play it safe and avoid the design completely.", "You can even consider speaking to a lawyer if you’re concerned or conducting an in-depth search if you really want to use the logo.", "In the meantime, if you want to simplify the process of getting an amazing logo, reach out to Fabrik today.", "Our co-founder, Steve Harvey, is also a regular contributor to Brand Fabrik, a flagship publication covering topics relevant to anyone in branding, marketing and graphic design. Steve shares his enthusiasm for brand naming through his articles and demonstrates his knowledge and expertise in the naming process.", "Affiliate program", "Fabrik is a participant in Amazon Service LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn advertising fees by linking to Amazon.com and other affiliated websites. Read our disclaimer here.", "Affiliate program", "Fabrik is a participant in Amazon Service LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn advertising fees by linking to Amazon.com and other affiliated websites. Read our disclaimer here." ], [ "Related", "After some success selling T-shirts, you may decide to expand your efforts by incorporating copyrighted logos. But before you can proceed, you have to know what the law says about selling shirts with copyrighted images. Trademarks or copyright can protect logos, and both forms of intellectual property protection restrict how others may use the logo. In fact, copyright and trademark violations can in some cases lead to criminal charges. Selling shirts with copyrighted images isn’t impossible, but you should never use someone else’s logos on your T-shirts or other clothing without their explicit permission. Understanding the meaning of copyright and trademark and knowing the instances in which selling shirts with copyrighted images is legal can help you develop your T-shirt logo strategy.", "Understand the Meaning of Copyright and Trademark", "One of the misunderstandings about shirts and logos is that a logo is protected by copyright. But most logos don’t have copyrights. Instead, logos are actually protected by a trademark, which is a legal protection that applies to a name, phrase or logo. Copyrights, on the other hand, are legal protections for people who create original literary, dramatic, musical and artistic works. So although many people use the words “copyright” and “trademark” interchangeably, they are quite distinct. Trademarks for logos are filed with the U.S. Patent and Trademark Office and last 10 years. However, the USPTO does require registrants to file an affidavit after the fifth year that the trademark is still active. If registrants fail to do so, the trademark is canceled and no longer under protection. If you want to use a logo, you should first check the USPTO website to determine if the trademark is still in force. If it isn’t, you may be able to use that logo.", "In some instances, you may want to appropriate a creative work of art into a logo, in which case copyright law would apply. Any works created prior to 1923 are usually considered to be in the public domain. So when it comes to shirts and logos, any logo you want to appropriate from a work of art that was made before 1923 is free and clear for your use. If a work is under copyright, however, that copyright typically lasts 70 years after the death of the creator, or 120 years after the date of first publication – whichever occurs first.", "Understand the Parody Exemption", "Both copyright law and trademark law allow the use of parody as an exemption to infringement. This is significant when it comes to shirts and logos because it means that you can use a logo that parodies an existing logo without being accused of copyright or trademark infringement. You would need to alter the original logo to such an extent that it is clear to anyone who sees the altered logo that you are engaged in parody or satire. For example, you could alter the Apple logo to include worms poking their heads out of the bitten apple. That would clearly indicate to your audience that this is a parody of the iconic Apple logo. But you have to be careful, because if the altered logo is too similar to the original logo, you could be accused of creating a copyright infringement shirt.", "Understand Licensing and Permission", "Rather than risk making a copyright infringement shirt, you can seek permission from the copyright or trademark holder. You can send an email or write a letter that specifies exactly how you intend to use the logo. The original creator may grant you permission under a licensing agreement that requires you to pay a flat fee for use of the logo, or a percentage of every shirt you sell with that logo. Failure to pay the fee or percentage agreed upon, however, will result in you selling a copyright infringement shirt.", "Sampson Quain is an experienced content writer with a wide range of expertise in small business, digital marketing, SEO marketing, SEM marketing, and social media outreach. He has written primarily for the EHow brand of Demand Studios as well as business strategy sites such as Digital Authority." ], [ "Copyright Logo Power Tips and How to Protect Your Valuable IP", "What is a copyright?", "A copyright protects works of fully formed artistic expression and authorship. The classic example of a copyright is a literary work, such as a novel or a poem.", "However, copyright protection expands to music, including the lyrics, musical composition and even live performances, artwork, dramatic pieces, and even architectural design. A copyright grants the exclusive rights to publish, sell and reproduce the work of art.", "The moment you create a fully formed piece of art or authorship, you own the copyright to it. But in a case where someone plagiarizes your work, you’ll have to be able to prove that you created the material first and that the other person copied it from you.", "By registering an actual copyright with the United States Copyright Office, you best protect your unique material from being copied by others.", "First, it creates more of a deterrent for the plagiarist. If he or she sees the copyright symbol next to your work or otherwise confirms that you own the work, he or she is less likely to copy it in the first place.", "Second, you’re protected even if the plagiarist goes forth with copying your work. If he or she is unaware you have registered the copyright, or is willing to take the risk of copying it even with a registration in place, it is easier to prove your ownership and access the legal remedies available to you.", "Can I Protect My Company’s Logo with a Copyright?", "A logo is a unique design that distinguishes a company or product. Logos are fully formed expressions that can include images and/or text, and would seem to fall under copyright law.", "Logos, however, are generally protected by trademarks. The purpose of a trademark is to protect what identifies your business or product to the consumer public. This includes the name of the company or product and any images, symbols, sounds or phrases that distinguish your company or product. Thus, a logo falls under a trademark.", "It is important to remember that a trademark must be something that distinguishes your company, product or service, so it cannot be something too generic. (This comes from the body of law that regulates trademark law, The Lanham Act.)", "Again, once your company begins doing business under a unique name and using a unique logo, it has the right to use that name and logo. Still, registering your trademark with the United States Patent and Trademark Office will better protect you from other competitors using your logo on their products and to conduct their business.", "When Should I Get a Copyright Logo?", "In addition to registering a trademark for your logo, you may also copyright the logo for additional protection. This is common in very large businesses. Companies such as Apple or Coca Cola have logos that gain instant, global recognition. So the symbol of the logo itself is highly distinguishable and profitable.", "Not only is it common for these companies to sell merchandise featuring their logos, they also make an incredible profit from selling the rights to allow others to copy or reproduce their logos. The option to let others copy and print your logo in certain circumstances is protected by your copyright.", "A logo that involves complicated design and artistic expression that a company also prints and sells on merchandise, such as mugs, hats or t-shirts, would be a candidate for copyright logo protection. This can protect that logo from being printed, copied and distributed by others. If you think your logo is exceptional and others will want to copy it, adding a copyright protection would be prudent.", "The Step-by-Step Trademark Process", "The first step, of course, is to either have your logo created or to otherwise have an idea of the logo you would like to create. Be sure your logo is distinguishable and not so generic that it may not qualify for trademark registration.", "Next, and most importantly, you will want to search the trademark registry on the USPTO database. You need to be sure that your mark, or one that is similar, has not been already registered.", "Confirming your mark is unique and distinguishable, you may now prepare and submit your trademark application with the USPTO.", "As a final step in your trademark application process, you will need to submit the appropriate registration fee. There is not a fixed fee.", "Monitor your application once you have submitted it. The USPTO usually takes several months to review an application. The USPTO has a Trademark Status and Document Retrieval website that you may visit during this time to see how it is going.", "You will receive your registered trademark after the application is approved. At this time, you may begin to use the registered trademark symbol every time you use your logo to help ensure it is protected.", "Even once you receive your trademark registration for your logo, you must maintain it. You will have to file more maintenance related documents with the USPTO office as time goes on.", "The trademark process is complicated and every part of the process would best be navigated with the assistance of a trademark lawyer. He or she can ensure you are making decisions with all the necessary legal considerations. In the long run, you’ll have the best protections for your logo this way.", "The Step-by-Step Logo Copyright Process", "The first step, of course, is to create the logo. The Copyright Office accepts many different file types for images, including .gif, .jpg, .bmp and .pdf, among many others. For hand-draws logos, scan it into an electronic format that is acceptable to the Copyright Office.", "Go to the US Copyright Office’s website and click the registration option. If you are a first-time applicant, you can create an account.", "Once you have an account, log into your account and click “register a new claim.” Then find the “start registration” option.", "This will take you through the step-by-step process of filing out the copyright application.", "Once the application is complete, select a payment option. Then you will submit payment for the application fee. The fee rates vary depending on several factors.", "Finally, you will need to send the Copyright Office a copy of the logo. You can either upload it on the registration page or otherwise you will have to send a copy via mail.", "The copyright process, like the trademark process, can be quite complicated. Your best chance of navigating any potential pitfalls is with the help of an attorney.", "Understanding the Best Way to Protect Your Logo", "Are you deciding whether to use a trademark for your logo or whether to also obtain a logo copyright? It will help to have a better understanding of what a trademark is, what a trademark protects, and how it protects it.", "The same goes for understanding a copyright. You will also want to take your particular logo into consideration, including the nature of your logo, how you intend to use it, and how you intend to protect it. Finally, you can consider the different processes of obtaining a trademark and obtaining a copyright. The time, resources and costs of each might play into your decision.", "An intellectual property attorney well versed in trademark, copyright, and company logos is an invaluable asset for your team. An attorney can properly assess the best way to protect your logo.", "The best way to protect your copyright and decide when to obtain a copyright logo can be a complex decision. Consult with an attorney who is familiar with this particular area of law and your company. Knowledge of your market and your consumer can help generate the best possible outcome.", "Author", "Ismail’s legal experience encompasses serving Fortune 500 companies, mid-sized privately held companies, and entrepreneurs. He presently serves as Corporate and Litigation Counsel to large and mid-sized businesses throughout California, Nevada, and Texas, as well as General and Personal Counsel to high-profile hospitality operators in California and Nevada. Ismail’s practice emphasizes Business and Intellectual Property matters, with a focus on healthcare, biopharmaceuticals, biotechnology, and hospitality. Ismail has counseled the firm’s healthcare provider clients in acquiring or selling assets while maximizing return and minimizing risk. He has helped clients acquire or sell over $1 billion worth of healthcare-related assets, including hospitals." ], [ "Trademark vs Copyright", "A common point of confusion for our publishing clients is trademark vs copyright. Most people seem to know that patents, another type of intellectual property (IP), cover inventions, but most do not know what protections are afforded by copyright and trademark. Both trademarks and copyrighted works are IP assets that are offered protection in the U.S. Constitution, but they differ significantly. Let’s look at the differences between trademark vs copyright, determine when protection is given under each law, and talk about obtaining the proper protection for these important intellectual property assets.", "Copyright", "What does copyright law protect?", "U.S. copyright law protects works of authorship like the following: books, songs, paintings, photographs, web content, movies, and some figures, tables, and maps where criteria of uniqueness and originality are met.", "Criteria for Copyright Protection", "United States Copyright Office Circular 34 indicates that “To be protected by copyright, a work must contain a certain minimum amount of authorship in the form of original literary, musical, pictorial, or graphic expression. Names, titles, and other short phrases do not meet these requirements.”", "What can’t copyright law protect?", "Circular 34 also indicates that “The U.S. Copyright Office cannot register claims for brief combinations of words such as:", "Names of products or services", "Names of businesses, organizations, or groups (including the names of performing groups)", "Listings of ingredients, as in recipes, labels, or formulas. When a recipe or formula is accompanied by an explanation or directions, the text directions may be copyrightable, but the recipe or formula itself remains uncopyrightable.”", "How do I get copyright protection for my works?", "It is a good idea to include a copyright statement, however. A copyright statement may alleviate any confusion as to the ownership of the work, and it may deter some would-be copiers from publishing your copyrighted works without permission.", "Copyright protection is automatic today. From the moment a work is created in a tangible form (as long as it meets the criteria of uniqueness and originality), it has copyright protection. That is from the moment content that meets the above criteria is saved on a computer, captured by writing down, or drawing on a piece of paper, it has protection. You do not have to register your copyright with the federal government to claim legal ownership of your work.", "It is wise to federally register works, however. Before you can sue for copyright infringement of your work, you must register your copyright with the federal government. Also, to collect the greatest amount in damages if you are successful in an infringement case, you must have registered the work with the U.S. Copyright Office within three months of publication. (See one of our blogs for more details.) The cost to register a copyright is minimal, but the length of time it takes to receive your notice of registration can be eighteen months or more. Make sure you register your work as soon as it is published in order to get the maximum protection under the law.", "Trademark", "What is a trademark and what does trademark law protect?", "A trademark is a word, phrase, symbol, and/or design that identifies and distinguishes the source of goods or services of one party from those of others.", "Trademark law protects brand names like Coca-Cola and Wonder Bread, images like the NBC peacock and the Nike swoosh, and taglines like Nike’s Just Do It, Wendy’s Where’s the Beef, and Allstate’s You’re in Good Hands.", "Often our clients mistakenly think that their logos are protected under copyright. It is a good idea to register a trademark for important logos instead of counting on copyright protection to save them from theft.", "The quote below from Circular 34 of the U.S. Copyright Office makes it apparent that assuming that copyright will protect an important logo is a bad practice.", "“The federal trademark statute covers trademarks and service marks—words, phrases, symbols, or designs that distinguish the goods or services of one party from those of another. The Copyright Office has no role in these matters.”", "Sometimes a logo may be found to have copyright protection in a court of law. However, logos may not always meet the criteria needed to be recognized by the courts as copyright protected or by the U.S. Copyright Office as eligible for copyright registration.", "The art in a logo must pass certain criteria to be recognized as copyrightable. To be copyright protected, works must be fixed in a tangible form, be unique, and must have a certain level of originality determined by the U.S. Copyright Office and/or in a court of law. Many logos, although certainly fixed in tangible forms, would not meet the other criteria for copyright protection. The simplicity often evidenced in really successful logos like the Nike swoosh or the Target circles within circles, may disallow any claim to the level of originality and uniqueness needed for copyright protection.", "How do I protect my trademarks?", "Federal trademark law, unlike copyright law, does not give to creations automatic protection by virtue of being created in a tangible form. State trademark laws can provide some protection if a logo is registered with a state in association with a business that is registered in that state, but the protection is limited to that state.", "Typically the “TM” symbol is carried on the logo to give notice of a claim of common-law rights in a creation. A TM symbol usually is used in connection with an unregistered mark, to inform potential infringers that a term, slogan, logo, or other ownership indicator is being claimed as a trademark. Many use the TM symbol to indicate that they are in the process of registering their mark with the federal government. It is not a given that the TM symbol will protect the work, but displaying it on your work may discourage others from stealing it.", "More about trademark vs copyright", "A federal trademark is registered under one or more of 45 international classes of use. These can be found at the U.S. Patent and Trademark Office website. Proof of interstate commerce is required to federally register a trademark. A trademark for a product for which commerce is conducted solely within one state would not qualify for federal trademark registration.", "Let’s use our company as an example of trademark vs copyright.", "Our company Integrated Writer Services, LLC is a legal liability corporation registered in the State of Colorado. We obtained the domain “TheCopyrightDetective.com” and started using it in 2011 in interstate commerce to market our services and sell goods, namely our published works. The website and all its content is protected under copyright laws.", "The first steps in the pursuit of a federal trademark came when we registered the term “Copyright Detective” in Colorado as a trade name for the company, and “The Copyright Detective” was registered with the Colorado Secretary of State as a trademark in two classes of goods and services. We displayed a “TM” after the words The Copyright Detective™ on the header of the website and elsewhere until we received federal trademark protection. Then we started to display the ® symbol.", "The circled “R” symbol means that the U.S. Patent and Trademark Office has acknowledged that the mark has been used in interstate commerce for one or more of several classes of goods and/or services. The process of filing for a federal trademark is rather complex. And the least expensive fee per class of goods/services is currently $275 each. Because of the complexity of the process and the required documentation, attorneys who specialize in trademark law are frequently engaged to file for trademark registration.", "Our company filed the phrase “The Copyright Detective” in four international classes 009 and 016 for goods and classes 041 and 045 for services. After 11 months the application was approved as a “Standard Character Mark” without claim to any particular font style, size, or color.", "Protect Your Assets", "The self education and the education of your staff on the laws and processes related to trademark vs copyright ownership is your best protection of a very important asset– your intellectual property.", "Want More About Copyright Law?", "Order your copy of Copyright Clearance for Creatives for a basic overview of copyright law and essential guidelines on when, how, and where to get permission to use copyright content in your works.", "No part of this blog or other pages on this website may be reprinted, reproduced, or utilized in any form or by any electronic means now known or hereafter invented without the express written permission from the copyright holder.", "The Copyright Detective® is a federally registered trademark of Integrated Writer Services, LLC." ] ]

[ "https://www.askamanager.org/2009/08/does-font-on-your-resume-matter-what-if.html", "https://academia.stackexchange.com/questions/88111/why-do-theoretical-computer-science-people-use-comic-sans-in-their-slides", "https://www.adobe.com/sign/hub/features/font-size-and-style-legal-documents.html", "https://scratch.mit.edu/discuss/topic/212163/?page=2", "https://workplace.stackexchange.com/questions/50702/how-do-i-tell-my-boss-to-not-use-comic-sans-as-their-main-email-typeface", "https://www.boia.org/blog/does-comic-sans-benefit-people-with-dyslexia", "https://en.wikipedia.org/wiki/Comic_Sans", "https://thetab.com/uk/edinburgh/2020/08/15/who-is-everyone-hating-on-the-comic-sans-font-and-what-is-their-problem-66563" ]

[ "support", "refute", "support", "support", "support", "support", "support", "refute" ]

[ [ "It’s not a professional font. It was designed to imitate comic book lettering. It’s informal. It’s despised by graphic designers. There’s a movement to ban it.", "Am I going to disregard an otherwise great candidate over it? No. Is it going to mildly annoy me? Yes. Do you want to be mildly annoying hiring managers by using an unprofessional font on your resume and making them wonder why you don’t know it’s not professional? No. Does it potentially contribute to an overall impression of you as unprofessional? Yes.", "The test of a good resume font is one that doesn’t make the reader think about what font you used. Comic Sans fails that test.", "Post navigation", "{27 comments… read them below }", "I am totally on board with the Ban Comic Sans movement. I can't stand when I see it used in a professional setting. In most cases I would not pass on an otherwise qualified candidate, but their poor judgement would be noted. However, if they were applying for a designer position, or one where they would be in charge of sending out correspondece without oversight I would pass on them in a hearbeat.", "I think Comic Sans is completely unprofessional. If I had two candidates who were equal in other ways, I might eliminate someone just because he used this font. If the resume is on the margin, this would cause it to go in the reject pile. At the very least I would have a conversation on the first day, I would have firm conversation about never using this in the workplace. And, it would cause me to preview everything they did until I was sure that they would not use it. I think it is completely unprofessional.", "Choosing funky fonts is not where one should demonstrate their impact. Instead, he or she should show impact where it counts. For example, a graphic designer can demonstrate impact and enthusiasm by creating a custom-designed marketing piece for the prospective employer.", "Comic Sans is horrible. Totally, totally wrong in so many ways. When I was offered my current role, the service agreement was sent to me in Comic Sans. Its hard to take restrictive covenants seriously when they are in such a stupid font. First task on joining…….", "A CV is there to convey information and there are a whole world of other professional fonts available. I would seriously question a candidate using anything like this, particularly in such a quiet market.", "Here's the thing: This particular font provokes a big reaction in people. That's what it's widely known for–the fact that people hate it.", "If I received your friend's resume, I'd wonder if he's one of those people who's always wanting to do things to get a reaction out of people, or just so completely disconnected from the internet and the people it that he really doesn't have a clue that people really, really hate Comic Sans.", "Either way–not so good.", "Incidentally, a lot of people also don't like Times New Roman on a resume, because it's the default font in word. There are a whole lot of people out there who think using the default shows a lack of imagination.", "I usually tell people to use Ariel. It's easy to read, and it's reasonably non-controversial.", "In my mind, Comic Sans has a permanent association with people who write all their e-mails in boldface magenta text and emphasize words ~+*like this*+~ and still send chain forwards full of animated GIFs.", "Do you want to be or look like one of those people? No? Then don't write in Comic Sans.", "Yes, Comic Sans for a resume or any other professional document or correspondence for that matter is bad news.", "In the business world, the typeface you chose becomes part of the communication. It's akin to the outfit you wear to an interview. You MUST make sure that everything you present to a potential employer is \"on message.\"", "Do you want your resume to show up to represent you in a professional looking business suit (one of the more standard business fonts) or dressed like the green lantern?", "I'm not a big fan of Comic Sans. It implies a lack of professionalism and a little immaturity. (Didn't I just love that font for school projects when I was fifteen?) Might as well just throw on a bunch of clip-art while you're at it!", "I think it goes without saying that using Comic Sans for just about anything is a bad idea. It's arguably the most abused font around.", "There are ways to spruce up your resume without relying on Comic Sans, Papyrus, Impact, Brush Script, etc. Experiment with the layout, search for resume templates to use as a starting point and consult online resources to get a good head start on getting hired. Look for best practices. They're called that for a reason.", "Okay, I'll ask. Why is Comic Sans unprofessional? I see everyone complaining that it is, but haven't seen anyone explain why.", "And please don't say it is unprofessional because it looks unprofessional. Tell me why it looks unprofessional.", "Frankly, the whole \"anti-Comic Sans\" movement seems like a fad itself, with everyone jumping on board because no one wants to be left out. The \"I'm more anti-Comic Sans than thou\" attitude seems laughable to me.", "Finally, the fact that so many business professionals seem willing to waste their time (hopefully not their company's time) on such an insignificant bit of trivia seems unprofessional to me.", "Aesthetics are hard to rationally explain — but everyone knows what they're seeing when they see it. Comic Sans is designed to mimic comic book lettering, and it does a good job of it. Comic books don't scream professionalism.", "Personally, I'm quite fond of the Century Gothic font (I like that it mimics the way letters are written by hand without looking handwritten: http://en.wikipedia.org/wiki/Century_Gothic), and use it for almost everything I type informally. But it's sans-serif, so I've never typed a resume or cover letter in that font. Even if it might have been okay, why take the risk?", "Anonymous @ 1:59 PM: \"Unprofessional\" is probably not the best term to use. What Comic Sans is, above all, is informal. It is a typeface that screams \"don't take this to seriously\" and \".. but I may be wrong about this\". It was designed explicitly to do this, and it does it very well.", "Its original purpose was to show unsolicited on-screen hints to inexperienced computer users where it was a priority to avoid the computophobe's reflexive \"argh, it says I have to do what? My computer will explode if I don't follow this prescription to the letter\". Part of the response to this was to make the typeface as unassuming and non-authoritative as possible.", "This has given Comic Sans a reputation as a \"friendly\" typeface. But it is (depending on your point of view) either a condescending or a self-deprecating kind of friendliness, and neither \"condescending\" nor \"self-deprecating\" is a subliminal message you want to send when you apply for a job.", "How does this work? Most generally, it imitates handwriting. Hand-written notes are generally assumed to be less important and authoritative than typewritten or printed ones.", "Many people get the feeling that computer simulated handwriting is kind of cheating too — as if you want to cash in on the \"heartfelt\" connotations of handwriting without risking exposure of your actual ugly shaking hand.", "But Comic Sans does not imitate just any handwriting; it looks like a particular plain and simple 90� upright handwriting — the kind of lettershapes elementary-school students are supposed to learn. As most people grow up they develop, for better or worse, a personal rhythm and flow to their handwriting. Comic Sans seems to imitate a well-behaved 5th-grader's handwriting, or that of someone who never evolved beyond 5th grade. This helps the typeface achieve its goals of looking non-threatening, but again is a subliminal message quite different from what a job seeker wants to send.", "I consider myself reasonably computer savvy and experienced as a recruiter. I didn't realize that there were such strong feelings about font types. As I look at resumes I only consider if the information is readable, organized and tells a story. The font �issue� just seems like such a non-issue it is laughable that it has generated so many comments.", "First, let me say that using Comic Sans is not a good idea on a professional resume for an office-type job.", "Second, I always stick with Times New Roman or Arial as they are the default fonts. So, every recruiter should have them on their PC. This way when I send my resume in a Word file (as requested by the recruiter) their PC will not try to substitute with a different font (and therefore different spacing) making the line and page breaks different than I had planned.", "Third, While using Comic Sans (or anything other than the default fonts in Word (Times New Roman and Arial) is not a good idea I can certainly undestand why some job seekers do this. See Kerry's comment:", "\"There are a whole lot of people out there who think using the default shows a lack of imagination.\"", "Not that Kerry supports this stupid idea, but I have read enough on various blogs and other sites on the web to know that there are a lot of bad recruiters out there who really do think this way.", "So, yea, using Comic Sans is a not a good idea (although not in the same league as hot pink paper or wearing flip-flops to an interview – come on now!); but can you really blame some job seekers for trying something to stand out?", "This job market is the worst since the days of Jimmy Carter – people are trying anything to try to get any job. Give them some slack – will ya?", "P.S. I am only saying \"give them some slack\" so that my competition for jobs will continue to submit poor-looking resumes thereby eliminating themselves from the pool of candidates, thereby giving me an edge on the job market!", "I won't despise it too quickly. This would work if the position is for an artist, day care, or any position that would require a little off beat creativity. As long as the job seekers keeps up with the essential in how to write a resume, it's just fine. Just keep it clean and professional. No grammar errors, no I and me statement, and use specific figures when you can.", "\"I won't despise it too quickly. This would work if the position is for an artist, day care, or any position that would require a little off beat creativity.\"", "I beg to differ. I am a manager at a children's museum who has evaluated scores of resumes for positions in my marketing department, which requires a lot of creativity. Using Comic Sans absolutely does NOT imply creativity, it implies that you think it's creative, which it's not. It is overused and a terrible cliche, especially when it comes to a position working with children, which is quite the opposite of creative.", "I agree with others in that if you want to be creative, play with layout, or show examples of creativity.", "In any case, you are applying for a job. Be professional. It's that simple. I don't care how extreme this seems, but if opening a resume and encountering Comic Sans, I would first ridicule it with the rest of my staff, and then throw it on the bottom of my pile. I am unsure if I would even read it.", "sorry, it's the universal idiot font. the only way i'd call in a candidate for an interview whose resume or other documents were in comic sans is if i had literally no other qualified applicants to choose from. just the revelation that this person does not GET that it's the universal idiot font would make them unsuitable for business.", "This: “In my mind, Comic Sans has a permanent association with people who write all their e-mails in boldface magenta text and emphasize words ~+*like this*+~ and still send chain forwards full of animated GIFs.” (from Rebecca)" ], [ "I have no data to back up this observation, but it's something I have noticed consistently in research talks and teaching material: People from the theoretical CS community seem to use Comic Sans a lot, a font-face that emulates the look and feel of hand-drawn fonts in comic books. Is this merely a convention or is there a deeper reason behind it?", "EDIT1: Since a couple of users requested examples, here's what I came up with in a 5-minute search:", "@Coder I don't think I've seen a math talk with slides in comic sans even once in my life. In fact it's very rare for the slides to use any font other than \"Computer Modern\" (the default LaTeX font)...", "– user9646", "Apr 15, 2017 at 6:18", "3", "I never (I mean ever) saw any TCS presentation using Sans Serif. Are you sure you talk about TCS? and are you sure you talk about SansSerif and not Euler Math font of latex?", "6 Answers", "6", "There's no deeper reason behind it. I think people just like it, particular its informal feel.", "Theoretical computer science is a pretty informal and laid-back field. Although in many fields Comic Sans would be considered unprofessional, the standards for \"unprofessional\" in TCS are much more relaxed. For example, I've observed that it's far more common for professors and students to be on a first name basis with people in the TCS world, and the tone in which papers are written are much less formal. It is typical for times problems to be described with little narratives or jokes, and often problems retain names based on how they were originally presented. For example, there’s the Handshake Lemma, the Traveling Salesman Problem, and the Arthur-Merlin Protocols. That’s not to say that informal names and presentations of theorems don’t exist in other fields, but in TCS I would go as far as to say it is typical.", "Heck, in his recent landmark paper on Graph Isomorphism, Laszlo Babai wrote something that could very reasonably be interpreted as a sex joke. In many fields innuendoes such as the one found in his paper would be considered wildly inappropriate. I don't know if the sex joke was intentional, but the line (although it's been noticed by many people) hasn't seems to cause any blowback or embarrassment.", "\"and the way papers are written are much less formal\" I disagree with that, at least in the scientific content (unless you mean on the tone of the paper, which I agree and which you should clarify to avoid obvious misunderstandings)", "\"Theoretically computer science\" or \"Theoretical computer science\"? I don't know about any theory that predicts the formality of an academic field. (Is an academic field like a magnetic field but emitted by academies?)", "Most users do not think longer than a few seconds about their font choice and its effect. Thus it happens that they think using a comic/quirky/sloppy font is a good idea for a professional talk – even though it’s the typographical equivalent to giving your talk in a clown costume.", "Once they made this choice, this kind of users wants to realise their intention with minimum effort. Hence they browse through their list of fonts – which is most likely the same as the operating system’s default. On many popular operating systems, this will inevitably lead to Comic Sans – even though it’s rather ugly and worn-down for a clown costume.", "Now the field influences how “professional” people are. In a field where formal attire is customary, I would expect Comic Sans to be less likely – but I have already witnessed professors for medicine giving talks in tie, suit, and Comic Sans. Also the field’s predisposition to LaTeX may have an effect as it’s a little bit more difficult to use Comic Sans there.", "@astronat: There are much better fonts for that purpose. Keep in mind that Comic Sans was created in a very short time without that particular goal. There is no reason to expect that it hit the bull’s eye and is the best choice for this purpose. (Further reading).", "\"even though it’s the typographical equivalent to giving your talk in a clown costume\" - thankfully typography probably isn't even in the top 20 most important things to think about when giving a talk :-)", "I don't use it in slides, but I did consciously choose it for use for some time. My reason was that because of its design, it is very much easier to distinguish different letters visually that could be confused (i/I/l/1 etc) at first glance, and for computer based work that can be very important. The instant clarity of what I'm looking at was worth it and it was otherwise easy to read. (Spend 3 hours trying to figure out an issue only to find it's a 1 not an I, or an i not an l somewhere ..... I removed the problem by choosing a font for my text editor that excluded the problem entirely)", "It was the closest widely available font to otherwise-\"standard\" fonts like arial, to clearly shape these letters differently enough to be immediately clear.", "The reason I heard from a professor who does this is that slides in Comic Sans are more memorable. Apparently during an exam students are more likely to remember the poorly placed explanation with the spelling mistake in Comic Sans than the perfectly aligned, worded and spelled explanation in Computer Modern.", "@lighthousekeeper - I'm confused. I skimmed the article you cited, just a bit, and it looked as though the authors used Arial as the \"easy to read\" font and Comic italicized grayscale as one of the harder to read fonts. That seems contrary to what Stilez said.", "@aparente001 Indeed, this seems to be a methodological problem of this study - the authors assume that Comic Sans is hard to read (like the professor in nwp's answer did), without providing a rationale for this assumption.", "I think the reason is that a lot of academics and academic disciplines are by nature anti-establishment. What better way to show that then Comic Sans as a font.", "I think of it is the equivalent of academics wearing shorts or Hawai shirts to work etc. Basically it's saying judge us by our work not by looks, dress, fonts or other such secondary features. In a slightly different sense it's mocking the establishment with their suits and ties and cow-towing to convention and authority. Universities pride themselves on being iconoclasts.", "Now even within academia individual Departments can be less or more conservative. e.g. Economics / Business would run on the conservative side. On the other hand programmers etc. are on the liberal side.", "While the evidence on Comic Sans and dyslexia may still be anecdotal, there is indeed evidence that some fonts are easier for dyslexics to read. That's why I prefer Verdana. Plus, Verdana clearly distinguishes lower-case \"ell\", upper-case \"eye\", and number \"one\"." ], [ "What’s the best legal document font size and style?", "Make your legal documents look professional using court-approved and other common legal font styles and sizes.", "Legal documents need to be clear and legible. That’s why it’s important to use type styles that look clean and professional. Stick with approved fonts and sizes to make your documents easy to read.", "Court-approved legal document fonts.", "Fonts are important for legibility and readability. If you use an “annoying” font style, it may be difficult to read what you wrote. In a legal setting, it’s especially important to make all writing as clear and professional as possible.", "While there’s no one “official” font style for preparing legal documents, there are a few court-approved fonts that are considered most easily readable:", "Arial", "Century (and Century-related fonts like Century Schoolbook)", "Verdana", "Adobe Caslon Pro", "Adobe Sabon", "You might have noticed that Times New Roman and Calibri didn’t make the list. Although many courts and lawyers accept these “default” fonts, they’re not preferred. And — whatever you do — stay away from novelty fonts like Comic Sans. They’ll just make your document look unprofessional.", "If you’re not sure which font to use, you can always read other legal documents that have been accepted by the court or lawyer and use whichever font they chose. That way, you won’t have to wonder if your font is right.", "Font size also matters for legal documents.", "Similarly to the font style, there’s no “standard” font size for legal documents. Courts only require that the font is legible.", "Most courts and lawyers recommend using a 12-point font for legal documents. That’s large enough for anyone to be able to read and still small enough that you can fit plenty of information on a single page. Using an overly large font is obnoxious to read and takes up too many pages.", "What size paper should you use for a legal document?", "Font style and size for legal documents matter — and so does the size of the paper you use. Paper sizing can affect the legibility and flow of a legal document, which is why your choice of paper should be carefully considered.", "Generally, you'll want to use 8.5” x 14” sized paper, which gives ample space for multiple signature blocks or extra content. Margins are normally kept to the standard print size, resulting in 1” margins on every side around unless they are manually altered.", "This type of paper was also known as “foolscap” paper, and has been associated with the legal profession for hundreds of years.", "While longer legal paper is considered the best and most standard option for legal use, you may also use 8.5” by 11” (standard printer paper size) for correspondence as well. This may be more commonly seen as a type of paper used for reference materials, such as printed email citations or testimony transcriptions.", "Simplify legal font styling with Acrobat.", "Adobe solutions make creating legal documents a breeze. You can choose from pre-approved templates that include the right legal document font and size." ], [ "Make the default website font Comic Sans", "Comic Sans, as per others, look unprofessional and very childish. Keep in mind that Scratch is for all ages. Although I would not be bugged very much by font changes, some teens and adults will get annoyed", "However, I do support a feature that changes the default font; maybe an option in the account settings that deals with “site display”.", "as a teen i would definitely be annoyed by this, yes", "All joking aside, though, I would support the option to change fonts in forum posts with BBcode, or implement full settings for font change throughout. ~", "Make the default website font Comic Sans", "It probably is, since Comic Sans is usually used as a joke font and on unprofessional websites. And anyway, why would Comic Sans be used on Scratch, it is meant for comics, which is why it is called Comic Sans. If Scratch was a comic I would support.", "Make the default website font Comic Sans", "<offtopic id=“rant”> Why does Comic Sans get such a bad rep for a few people using it in not the greatest of places? Blame the person, not the font. #ComicSansForPOTUS2016 </offtopic>", "It's not that. Comic Sans is just not a professional font, yet a lot of people are using it in very professional things. At my school, our CS (well, more like learn-about-the-taskbar-and-his-friends-then-learn-about-the-childish-features-of-PowerPoint not-science. LATTAHFTLATCFOPP NS for short) textbook is printed with Comic Sans and just let me tell you that it does not look good at all.", "Comic Sans MS, commonly referred to as Comic Sans, is a sans-serif casual script typeface designed by Vincent Connare and released in 1994 by Microsoft Corporation. It is a casual, non-connecting script inspired by comic book lettering, intended for use in informal documents and children's materials.", "[…]", "Microsoft designer Vincent Connare began work on Comic Sans in October 1994. Connare had already created child-oriented fonts for various applications, so when he saw a beta version of Microsoft Bob that used Times New Roman in the word balloons of cartoon characters, he felt that the result was a formal look inappropriate for a program intended to introduce younger users to computers. His decision was to create a new face based on the lettering style of comic books he had in his office, specifically The Dark Knight Returns (lettered by John Costanza) and Watchmen (lettered by Dave Gibbons).", "EDIT: I'd just like to add that although Scratch does fit the intended use of Comic Sans, the site itself is not intended to be like that. Comic Sans is more when you are sure only kids just getting into computers are going to use it.", "Make the default website font Comic Sans", "<offtopic id=“rant”> Why does Comic Sans get such a bad rep for a few people using it in not the greatest of places? Blame the person, not the font. #ComicSansForPOTUS2016 </offtopic>", "It's not that. Comic Sans is just not a professional font, yet a lot of people are using it in very professional things. At my school, our CS (well, more like learn-about-the-taskbar-and-his-friends-then-learn-about-the-childish-features-of-PowerPoint not-science. LATTAHFTLATCFOPP NS for short) textbook is printed with Comic Sans and just let me tell you that it does not look good at all.", "Comic Sans MS, commonly referred to as Comic Sans, is a sans-serif casual script typeface designed by Vincent Connare and released in 1994 by Microsoft Corporation. It is a casual, non-connecting script inspired by comic book lettering, intended for use in informal documents and children's materials.", "[…]", "Microsoft designer Vincent Connare began work on Comic Sans in October 1994. Connare had already created child-oriented fonts for various applications, so when he saw a beta version of Microsoft Bob that used Times New Roman in the word balloons of cartoon characters, he felt that the result was a formal look inappropriate for a program intended to introduce younger users to computers. His decision was to create a new face based on the lettering style of comic books he had in his office, specifically The Dark Knight Returns (lettered by John Costanza) and Watchmen (lettered by Dave Gibbons).", "EDIT: I'd just like to add that although Scratch does fit the intended use of Comic Sans, the site itself is not intended to be like that. Comic Sans is more when you are sure only kids just getting into computers are going to use it." ], [ "Because they're my superior, I feel awkward bringing it up, but I think it's something that needs to be brought up. How do I word it to my boss so they are not offended but also change their typeface to something more professional?", "The top answer to What is wrong with Comic Sans? on the graphic design site is written with remarkable restraint. Unlike most things written on Comic Sans it is pretty non-offensive, while still getting the point across", "To answer the question title specifically, You don't. You can try all of the suggested answers below to convince him to change his ways on his own, but in a corporate setting, you cannot force your boss to do anything he doesn't want to - and if he wants to use Comic Sans and will not be convinced to change his font type, you should not risk losing your own job over it.", "Why do you think that 1) Everyone who gets the email sees what font it was composed in, rather than the font they prefer to read? and 2) Of those who do see the email in its original font, what percentage do you think actually cares? Oh, and #3: Why on earth do people use anything but ASCII text in email, anyway?", "I started to laugh, but then remembered the time when a student said she couldn't take my business class seriously because I used Comic Sans for a font. (For the record, it was Apple's Chalkboard, but still...)", "Just as an aside, it's interesting how country cultures can differ. In a country like the Netherlands it would be a total non issue to casually mention something like this to your boss and it will be seen as a sign that you actually care. A reaction like \"you should feel awkward bringing it up\" is nearly impossible to imagine over there.", "I read an interesting article the other day, which said that Comic Sans has a mixed reputation in the business. I wonder what our client thinks about it, perhaps they don't care, but just thought I should let you know.", "This gets the message across, doesn't sound condescending, ensures that your manager doesn't lose face, and also saves you from the awkwardness of \"recommending\" a font to your superior, because you are putting the decision in his hands. If your manager is a reasonable person, it is hard to imagine him taking offence to this, especially since you offered to first understand his reason rather than just pass judgement. :)", "In addition, it also lets you save face if the manager has some genuine reason. For example, if the font was the default on his computer and he hasn't figured out how to change it, or the client \"likes\" that font!", "PS: As David K pointed out in the comment, you might want to keep such an article handy. Make sure that it is from a reputed source, not a random blog, and don't send it to your manager unless he insists.", "Consider sending just one email though. One danger of splitting the message is that he can't use the information in the second message to influence his answer to the first message. You first ask him to confess he adores the font, and then tell him the entire world thinks otherwise. If you first tell him about the reputation, only then does he have a real chance to save face and, instead of admitting he loves the font, being aloof and blaming it on his secretary :-)", "@JoeStrazzere: I don't disagree, but it is a pity these non-confrontational openings are sometimes necessary for bringing up such a trivial matter. If it were me using the font with no idea of its reputation, I'd prefer a direct \"Stop using Comic Sans, it's unprofessional,\" after which we both move on to other things.", "@MarcksThomas I would prefer direct communication too, but I found out over time that the threshold for what offends them is very low for a lot of people. Over time, I have gained increased mastery over this practice of sugarcoating the most mundane things, although it makes me cringe each time I do it. :-)", "There is a website Comic Sans Criminal, which allows you to sent your boss an anonymous e-mail informing about the inappropriateness of this font. If you do choose an appropriate timing and are not known as a typography expert at work, it should not be relatable to you.", "Of course, this at most works for this particular problem and if your boss chooses to switch to Papyrus, you need a different solution. Also, you are probably burning the bridge to bring up this topic in a non-anonymous way, should this approach not work.", "Note that I have not tested this service yet and thus do not know whether the mail contains IPs or other identifiable information. Neither do I know what they do with those e-mail adresses. Use at your own risk and better test it with a mail to yourself first.", "Finally note that sharing your boss’s email may be or may be considered a breach of rules.", "I am not so sure it is a good idea to talk to your boss anonymously. This approach might get around this problem, but what about the next time he needs to have an awkward conversation with his boss? Awkward conversations are unavoidable in the workplace, you will run into them sooner or later, especially as you climb up the ladder. It is important to learn how to deal with them directly, than from behind the anonymity of internet.", "Is there a reason to avoid directly asking the question? If you have regular one-on-one's with your boss, you could ask him about this during one of them (if you aren't having them start!). He may simply be unaware of how a typeface can affect the perception of the message.", "I see no need for anonymous communication. This is an opportunity to show you are looking out for the company image and want to help.", "You could start with something like:", "Can I ask you a question about the font you use in email messages? I think you're using Comic-sans and in my experience it can carry a negative connotation, especially in a business setting. This is an area I'm interested in and I'd be happy to help select a strong font to carry our business message to our customers.", "You could also come prepared with the website mentioned @Wrzlprmft's answer. And if you do go the route of wanting to suggest alternatives that are not \"Times Roman\", come prepared with those too. Bring solutions to the table!", "Really the best way to approach your superior about something awkward is either make it a meeting or take them out for lunch. Believe it or not, bosses are people too and they do make mistakes as well. Ask him if you can treat him to a lunch, which will not only help your personal reputation but put him in a setting where he doesn't have his guard up, like most people do at work. If you want to have a meeting, send him an email to schedule something and say you wanted to talk about a few general things that are of concern to you.", "The Conversation", "There's nothing better than being blunt. Truly, there are two ways to go about telling him: professionally or comically. Going the professional route would mean explaining to him all the details of why you're concerned and really showing him that you care about this. The comedic route would result in a small joke that he may or may not brush off by the end of the work day. Either way, do whatever you feel more comfortable with. It's perfectly ok to express any concerns you have in the workplace.", "What Not To Do", "Definitely do not tell him that the font is unprofessional. He will get upset if you insult him. Rather, say that you think that this is petty, but a better font might make the emails look cleaner. Compliment him on his writing or such before you bring this up.", "Never start a conversation by saying that what you're about to say is useless or stupid. It seems to be a habit of people to degrade their topic of discussion before saying it so that they don't seem ridiculous. Make sure it is known that you really care about this topic.", "I would tend to avoid some of the the possibly over-cautious approach of these answers. Of course, subtlety and wit is very important in a corporate environment, and naturally your job is something you want to be very careful with - but brevity is the soul of wit and he/she will appreciate your honesty.", "Think of it this way, he's making a mistake - and he's unaware of it. One can either tell him, risking animosity over negative feedback, or leave him to keep making that mistake and make a fool of himself. He's (hopefully) not a tactless moron and he'll appreciate your courage to step in and try and help him out.", "It's very important that you exercise compassionate speech and comradery in a situation like this, adhering strongly to the principle of \"constructive criticism\". So long as you can stay away from patronizing him or treating him with disrespect he'll probably be very grateful that you decided to inform him.", "If it were me I'd find a time where we were both together under immediate pressure, and say something like", "Hey, I'd been meaning to talk to you actually.", "I'm a little concerned that a lot of people don't see the font you use in your emails as being appropriate for corporate communication - there's a general consensus that it's a kind of silly font. While I don't think any of us are in any way offended, this idea is pretty widespread and I'm just concious that you mightn't know of this. If you'd like I'd be interested in helping pick a font to better represent our business ...", "It might seem childish or blunt to some, but in my own experiences I've found that simple honesty rarely goes amiss - speak your mind in a respectful manner at an appropriate time and there's very little to go wrong :) Good luck!", "In the end it will come down to who the boss is, who the other party is, and their relationship. I don't deny that there are people out there who would take that badly - but if the boss in question is a stable, grounded, man or woman, then honesty is always as sensible path." ], [ "Does Comic Sans Benefit People with Dyslexia?", "Comic Sans is controversial. Since its release in 1994, the playful, Batman-inspired font has been panned as “ugly” and “unprofessional,” particularly when used in situations where comic typefaces might be inappropriate.", "Despite the criticism, Comic Sans remains one of the most popular sans-serif fonts available — and according to some disability advocates, Comic Sans has at least one potentially important application: It may be more legible for people with reading disabilities.", "Does research support using Comic Sans for accessibility?", "In accessibility discussions, it’s important to listen to the experiences of people with disabilities. If someone says that a certain font helps them read, they’re probably telling the truth.", "But it’s also reasonable to be skeptical of these claims: As we’ve discussed in other articles, dyslexia is not a vision disorder. The condition affects a person’s ability to distinguish between phonemes (the sounds that make up words).", "A number of dyslexia-specific fonts are available that claim to improve text legibility by using unique designs for every character. This is based on the idea that people with dyslexia “flip\" characters when reading.", "However, those studies did not specifically investigate Comic Sans as a dyslexia-friendly font. And the design of individual characters isn’t the only factor to consider: The spacing between letters and characters can certainly affect readability.", "Sans-serif fonts do not have extending features (called serifs) at the end of letters and numbers, so there’s usually more space between the characters. Research suggests that this improves reading speed, comprehension, and recall.", "Should I use Comic Sans for accessibility?", "Typefaces may affect web accessibility, but if you want to provide a better experience for readers, Comic Sans isn’t the only option. The best practice is to use a widely available font with no extra decorations or flourishes.", "It’s important to remember that while typeface is important, the size and color of your text will have a much greater impact on accessibility. The Web Content Accessibility Guidelines (WCAG), considered the international standard for digital accessibility, does not require the use of any specific font.", "However, it does have several important requirements for text:", "WCAG 2.1 SC 1.4.1, “Use of Color,” requires that color is not used as the only visual means of conveying information. For example, you shouldn’t use text color alone to indicate that a certain word is especially important.", "Since users can control the size of text, WCAG doesn’t have requirements for text size. The default font size for web browsers is approximately 16 pixels (px), which is roughly equivalent to 12 points (pts), so the best practice is to stay predictable.", "Creating Accessible Content for All Readers", "As a web designer or developer, your job is to provide the best possible user experience. Following WCAG helps you create content that works for as many people as possible — that includes people with dyslexia, but also people with disabilities that affect their vision, hearing, memory, cognition, and mobility." ], [ "Microsoft designer Vincent Connare began working on Comic Sans in 1994 after having already created other fonts for various applications. When he saw a beta version of Microsoft Bob that used Times New Roman in the word balloons of its cartoon characters, he believed the typeface gave the software an overly formal appearance. He believed this was inappropriate for the aesthetics of the program, which was created to introduce younger users to computers. In order to make Microsoft Bob look more suitable for its intended purposes, he decided to create a new typeface with only a mouse and cursor, based on the lettering style of comic books he had in his office, specifically The Dark Knight Returns (lettered by John Costanza) and Watchmen (lettered by Dave Gibbons).[4]", "Comic Sans Pro is an updated version of Comic Sans created by Terrance Weinzierl from Monotype Imaging. While retaining the original designs of the core characters, it expands the typeface by adding new italic variants, in addition to swashes, small capitals, extra ornaments and symbols including speech bubbles, onomatopoeia and dingbats, as well as text figures and other stylistic alternatives.[7][8][9] Originally appearing as part of Ascender 2010 Font Pack as Comic Sans 2010, it was first released on April Fools' Day, causing some to initially assume it was a joke.[10][11][12]", "Comic Sans has become most infamous for its use in serious circumstances, like warning signs and formal documents, in which it might appear too informal, unprofessional, or inappropriate.[3]", "During the summer of 2010, NBA superstar LeBron James left the Cleveland Cavaliers in free agency, in a highly publicized media affair that culminated in a TV special called The Decision. The majority owner of the team (at the time), Dan Gilbert, reacted by posting a letter to Cavalier fans. The letter was criticized for its use of Comic Sans.[14][15][16]", "In October 2012, a Dutch World War II memorial called Verzoening (\"Reconciliation\") was revealed on which the names of Jewish, Allied and German military deaths alike were written alongside each other in Comic Sans. The names were eventually scraped off after complaints from Jewish organizations, but the rewritten message was once again in Comic Sans. According to the city government, this was done because the letters fit the shape of the stone and were easily visible from a distance. It was, however, criticized for making the memorial appear \"ugly\" and \"cheap\".[17]", "In August 2015, a number of Greek Prime Minister Alexis Tsipras's Syriza party members split and formed a new party, headed by Panagiotis Lafazanis. The official document of resignation was allegedly written in Comic Sans.[19]", "In July 2018, a statue of former Chilean President Pedro Aguirre Cerda was inaugurated in Santiago. The plaques on the monument were written in Comic Sans, drawing negative attention on social media.[20]", "In October 2019, when the United States House Intelligence Committee requested that two of Rudy Giuliani's associates, Lev Parnas and Igor Fruma, present documentation regarding their involvement in the Ukraine scandal, former Trump attorney John Dowd penned a letter of explanation printed in Comic Sans.[21]", "That same month, as part of the United Kingdom's Brexit debate, the Conservative Party tweeted an image stating \"MPs must come together and get Brexit done\" using Comic Sans.[22] The post was heavily mocked, but some commentators saw it as a deliberate attempt to use the typeface's notoriety in order to bring their message to a wider audience.[23]", "A research article published by Cognition in 2010 showed disfluency could lead to improved retention and classroom performance. The article stated that disfluency can be produced merely by adopting fonts that are slightly more difficult to read.[25] In the case studies cited in the article, Comic Sans was used to introduce disfluency.[26] A 2010 Princeton University study involving presenting students with text in a font slightly harder to read found that they consistently retained more information from material displayed in fonts perceived as ugly or disfluent (Monotype Corsiva, Haettenschweiler, and Comic Sans Italic) than in a simpler, more traditional typeface such as Helvetica.[25]", "More often, however, Comic Sans is described as especially legible, and is frequently used in school settings or as an aid for people with dyslexia.[27][additional citation(s) needed] Some people have reported that typing in Comic Sans has helped to clear writer's block, claiming that its casual appearance and high legibility create less mental tension.[28] Compared to other typefaces, Comic Sans has fewer rotated and mirror-image glyphs (ex. the letters \"b\", \"d\", \"p\", and \"q\"), has particularly wide letter spacing, and is sans serif.[29][27][30]", "Several reinterpretations of Comic Sans have been created as a result of its popularity. In April 2014, font designer Craig Rozynski released a modernized version of Comic Sans called Comic Neue. In 2015, graphic designer Ben Harman created Comic Papyrus (later renamed \"Comic Parchment\" for legal reasons), which combines the features of Comic Sans with the similarly panned typeface Papyrus.[31] In 2019, Tabular Type Foundry released Comic Code, a monospaced version of the typeface.[32]", "In 2017, it was reported that Vincent Connare, the typeface's designer, had only used it once.[33]", "Because of its ubiquity and misuse, Comic Sans has been opposed by graphic designers. The Boston Phoenix reported on disgruntlement over the widespread use of the typeface, especially its incongruous use for writing on serious subjects, with the complaints urged on by a campaign started by two Indianapolis graphic designers, Dave and Holly Combs, via their website \"Ban Comic Sans\".[34] The movement was conceived in 1999 by the two designers after an employer insisted that one of them use Comic Sans in a children's museum exhibit. The website's main argument is that a typeface should match the tone of its text and that the humorous appearance of Comic Sans often contrasted with a serious message, such as a \"do not enter\" sign.[35] The movement ran until 2019, when it was renamed \"Use Comic Sans,\" which was because Dave Combs believed the hatred had \"gotten out of hand\" and \"it's gotten to be so bad that it's almost cool again.\"[36]", "Dave Gibbons, whose work was one of the inspirations for Comic Sans, said that it was \"a shame they couldn't have used just the original font, because [Comic Sans] is a real mess. I think it's a particularly ugly letter form.\"[37]", "Film producer and The New York Times essayist Errol Morris wrote in an August 2012 posting, \"The conscious awareness of Comic Sans promotes—at least among some people—contempt and summary dismissal.\" With the help of a professor, he conducted an online experiment and found that Comic Sans, in comparison with five other typefaces (Baskerville, Helvetica, Georgia, Trebuchet MS, and Computer Modern), makes readers slightly less likely to believe that a statement they are reading is true.[38]", "In the Netherlands, radio DJs Coen Swijnenberg and Sander Lantinga decided to celebrate the typeface by having a Comic Sans day on the first Friday of July. Comic Sans Day has been held since 2009. Some Dutch companies have their website in Comic Sans on this day.[39]", "According to a 2020 Twitter poll held by TES, 44% of teachers sampled used Comic Sans in their teaching resources. Comic Sans is widely used in schools due to its high legibility.[better source needed] Other reasons include:[27]", "Vincent Connare is reportedly not offended by the negative backlash over Comic Sans. At the Fourth Annual Boring Conference, he claimed to find the contempt for his work to be \"mildly amusing.\"[40] He has stated that he is proud of his creation, offering different rationales. One of these was that \"Comic Sans does what it was commissioned to do, it is loved by kids, mums, dads and many family members. So it did its job very well. It matched the brief!\" He has also referred to it as \"the best joke I've ever told.\"[41] In 2014, commenting on Comic Sans' critics and fans alike, Connare said, \"If you love it, you don't know much about typography, [but] if you hate it, you really don't know much about typography either, and you should get another hobby.\"[42][43]", "Lauren Hudgins of The Establishment argued that people who use Comic Sans should be treated with respect, not mockery, because \"people without dyslexia need empathy for those who need concessions to manage the disability.\"[44]", "On May 22, 2012, The Comic Sans Song[46] was released by YouTube content creator and musician Gunnarolla, in collaboration with musician Andrew Huang. The song makes reference to Comic Sans and features commentary around the impact the font has had on pop-culture.", "In October 2022, Comic Sans became the representative of Dyslexia Scotland and their ad campaign, There's Nothing Comic About Dyslexia.[55] The campaign's purpose is to inform people on the typeface's benefits among dyslexic people, and to encourage the creation of typefaces that are more formal, but also dyslexic-friendly.", "The song \"Tacky\" by Weird Al Yankovic, a parody of \"Happy\" by Pharrell Williams, features Yankovic listing a number of \"tacky\" behaviors ranging from stylish faux pas to obnoxious and rude behaviors as examples of what makes a person potentially \"tacky.\" Among them is writing a resume in Comic Sans.", "^Terri Stone (4 April 2011). \"Comic Sans Pro Not an April Fool's Joke |\". CreativePro.com. Archived from the original on 2015-04-18. Retrieved 2015-04-17. The Comic Sans typeface, one of Microsoft's most popular designs, has received a makeover courtesy of Monotype Imaging. Today the company has introduced the four-font Comic Sans Pro family of typefaces. Featuring elements such as speech bubbles and cartoon dingbats, Comic Sans Pro extends the versatility of the original Comic Sans, designed by Vincent Connare for Microsoft in 1994.", "^Hudgins, Lauren (2019-04-15). \"Hating Comic Sans Is Ableist\". The Establishment. Archived from the original on 2019-12-13. Retrieved 2019-12-21. Comic Sans is recommended by the British Dyslexia Association and the Dyslexia Association of Ireland...People without dyslexia need empathy for those who need concessions to manage the disability.", "^Sotomayor, Bella Vanessa (December 15, 2016). \"UNDERTALE: A Game That Is Still Amazing Today\". ComicsVerse. Archived from the original on 7 May 2020. Retrieved 20 March 2020. Some of the characters also have different fonts in their text boxes, which highlights their different personalities. For example, two brothers named Sans and Papyrus use the comic sans and papyrus fonts in their text boxes, respectively." ], [ "Who is everyone hating on the Comic Sans font and what is their problem?", "There are few things more controversial and hated than the Comic Sans font. There are memes online about it, tweets of hatred and even petitions for its removal – yes, seriously. It’s incredible that the curvature and spacing of letters can evoke such emotions.", "I have had enough of this unnecessary hatred. For one, Comic Sans is actually the most accessible font for dyslexic people.", "More importantly, how exactly is your life so boring that you have all this free time to hate on, wait for it, a font? I’m almost impressed by your passion. Almost.", "Where the font began?", "Comic Sans is a 90’s baby (like the best of us) described as “a non-connecting script inspired by comic book lettering, intended for use in informal documents and children’s materials”. Originating from comic books is pretty cool if you ask me. Vincent Connare, its inventor, cites The Dark Knight comic as one of the inspirations.", "Comic Sans is also the bad boy of all the fonts. Connare said it “was breaking the typography rules” due to the difference in heights of all the letters. So, if you’re looking to spice up your next piece of coursework, I dare you to submit it in Comic Sans.", "Where did the hatred start?", "Honestly, we’ll never know. Maybe the perception of it as childlike makes adults want to distance themselves to show they have outgrown the need for Comic Sans.", "Please know that if you ever see me using Comic Sans on my Instagram story it is because I am embroiled in a hostage situation and I’m trying to signal to you that something is very wrong", "Whether people hate the font because it’s “childish” or because they have nothing better to do, online mockery is everywhere. There’s even a website called Comic Sans Criminal to call out people for using the font. It even includes a name and shame section. I wish I were joking.", "https://www.comicsanscriminal.com/", "Whilst people are entitled to their own opinions on fonts, the argument that the font is childish and unprofessional is entirely down to systematic prejudices.", "Why Comic Sans is actually elite", "Comic Sans is listed by The British Dyslexia Association as one of the best fonts to use for people with learning disabilities such as dyslexia. Citing that it spaces the letters out more so than other fonts (*cough* Times New Roman *cough*). With it being estimated that in the UK one in ten people have dyslexia, this font’s accessibility should be celebrated.", "If you are hating on Comic Sans just because it looks unprofessional, ask yourself why? How can the way letters are arranged on a screen dictate so much meaning?", "Get off your Helvetica high horse.If a font makes reading something easier, I don’t understand the issue.", "https://www.instagram.com/p/CDp_sixh12I/", "If you have joined the band wagon of hating Comic Sans for absolutely no reason at all, please consider why you hate it so much. I am not by any means saying that the font is the best and only font that should be used. I merely want people to stop the Comic Sans witch-hunt.", "If Comic Sans were a club, it would be Hive: polarising but accessible to everyone.", "People say they don’t like it, but really, you can’t deny it is good fun." ] ]

[ "https://en.wikipedia.org/wiki/African_wolf", "https://www.seacrestwolfpreserve.org/types-of-wolves", "https://www.awf.org/wildlife-conservation/ethiopian-wolf", "https://news.mongabay.com/2018/12/pressure-mounting-for-the-home-of-wild-coffee-and-ethiopian-wolves/", "https://www.thesafaricollection.com/the-painted-wolves-of-africa/", "https://www.painteddog.org/", "https://animaldiversity.org/accounts/Canis_anthus/", "https://animaldiversity.org/accounts/Canis_simensis/", "https://www.wolfworlds.com/wolf-habitat/", "https://animalia.bio/african-golden-wolf", "https://www.nbcnews.com/id/wbna32275502", "https://www.tripadvisor.com/ShowUserReviews-g312558-d7369319-r704329337-Garden_Route_Wolf_Sanctuary-Plettenberg_Bay_Western_Cape.html", "https://www.awf.org/blog/saving-critically-endangered-ethiopian-wolf-extinction", "https://wolfsa.org.za/" ]

[ "support", "support", "support", "support", "refute", "refute", "support", "support", "support", "support", "support", "refute", "support", "refute" ]

[ [ "It was previously classified as an African variant of the golden jackal (Canis aureus), with at that time at least one subspecies (C. a. lupaster) having been classified as a wolf. In 2015, a series of analyses on the species' mitochondrial DNA and nucleargenome demonstrated that it was, in fact, distinct from the golden jackal, and more closely related to the gray wolf and the coyote (Canis latrans).[5][6] It is nonetheless still close enough to the golden jackal to produce hybrid offspring, as indicated through genetic tests on jackals in Israel,[5] and a 19th-century captive crossbreeding experiment.[7] Further studies demonstrated that it is the descendant of a genetically admixed canid of 72% gray wolf (Canis lupus) and 28% Ethiopian wolf (Canis simensis) ancestry.[8]", "It plays a prominent role in some African cultures; it was considered sacred in ancient Egypt, particularly in Lycopolis, where it was venerated as a god. In North African folklore, it is viewed as an untrustworthy animal whose body parts can be used for medicinal or ritualistic purposes,[9][10][11] while it is held in high esteem in Senegal's Serer religion as being the first creature to be created by the god Roog.[12]", "The African wolf is intermediate in size between the African jackals (L. mesomelas and L. adusta) and the small subspecies of gray wolves,[19] with both sexes weighing 7–15 kg (15–33 lb), and standing 40 cm in height.[4] There is however a high degree of size variation geographically, with Western and Northern African specimens being larger than their East African cousins.[19] It has a relatively long snout and ears, while the tail is comparatively short, measuring 20 cm in length. Fur color varies individually, seasonally and geographically, though the typical coloration is yellowish to silvery grey, with slightly reddish limbs and black speckling on the tail and shoulders. The throat, abdomen and facial markings are usually white, and the eyes are amber-colored. Females bear two to four pairs of teats.[4] Although superficially similar to the golden jackal (particularly in East Africa), the African wolf has a more pointed muzzle and sharper, more robust teeth.[5] The ears are longer in the African wolf, and the skull has a more elevated forehead.[20]", "Various C. lupasterphenotypes, ranging from gracile jackal-like morphs to more robust wolf-like ones.", "Aristotle wrote of wolves living in Egypt, mentioning that they were smaller than the Greek kind. Georg Ebers wrote of the wolf being among the sacred animals of Egypt, describing it as a \"smaller variety\" of wolf to those of Europe, and noting how the name Lykopolis, the Ancient Egyptian city dedicated to Anubis, means \"city of the wolf\".[21][22]", "An attempt was also made in 1821 to hybridise the two species in captivity, resulting in the birth of five pups, three of which died before weaning. The two survivors were noted to never play with each other, and had completely contrasting temperaments: One pup inherited the golden jackal's shyness, while the other was affectionate toward its human captors.[7] English biologist G.J. Mivart emphasized the differences between the African wolf and the golden jackal in his writings:", "... it is a nice question whether the Common Jackal of North Africa should or should not be regarded as of the same species [as the golden jackal] ... Certainly the differences of coloration which exist between these forms are not nearly so great as those which are to be found to occur between the different local varieties of C. lupus. We are nevertheless inclined ... to keep the North-African and Indian Jackals distinct ... The reason why we prefer to keep them provisionally distinct is that though the difference between the two forms (African and Indian) is slight as regards coloration, yet it appears to be a very constant one. Out of seventeen skins of the Indian form, we have only found one which is wanting in the main characteristic as to difference of hue. The ears also are relatively shorter than in the North-African form. But there is another character to which we attach greater weight. However much the different races of Wolves differ in size, we have not succeeded in finding any constant distinctive characters in the form of the skull or the proportions of the lobes of any of the teeth. So far as we have been able to observe, such differences do exist between the Indian and North-African Jackals.", "The canids present in Egypt in particular were noted to be so much more gray wolf-like than populations elsewhere in Africa that W.F. Hemprich and C.G. Ehrenberg gave them the binomial nameCanis lupaster in 1832. Likewise, T.H. Huxley, upon noting the similarities between the skulls of lupaster and Indian wolves, classed the animal as a subspecies of the gray wolf. However, the animal was subsequently synonymised with the golden jackal by Ernst Schwarz in 1926.", "The taxonomy of the Jackals in the Near East is still a matter of dispute. On the basis of skeletal material, however, it can be stated that the Wolf Jackal is specifically distinct from the much smaller Golden Jackal.[26]", "In 1981, zoologist Walter Ferguson argued in favor of lupaster being a subspecies of the gray wolf based on cranial measurements, stating that the classing of the animal as a jackal was based solely on the animal's small size, and predated the discovery of C. l. arabs, which is intermediate in size between C. l. lupus and lupaster.[22]", "Further doubts over its being conspecific with the golden jackal of Eurasia arose in December 2002, when a canid was sighted in Eritrea's Danakil Desert whose appearance did not correspond to that of the golden jackal or the six other recognized species of the area, but strongly resembled that of the gray wolf. The area had previously been largely unexplored because of its harsh climate and embroilment in the Eritrean War of Independence and subsequent Eritrean–Ethiopian War, though local Afar tribesmen knew of the animal, and referred to it as wucharia (wolf).[13]", "The animal's wolf-like qualities were confirmed in 2011, when several golden \"jackal\" populations in Egypt and the Horn of Africa classed as Canis aureus lupaster[19] were found to have mtDNA sequences more closely resembling those found in gray wolves than those of golden jackals.[21] These wolf-like mtDNA sequences were found to occur over a 6,000 km wide area, encompassing Algeria, Mali and Senegal. Furthermore, the sampled African specimens displayed much more nucleotide and haplotype diversity than that present in Indian and Himalayan wolves, thus indicating a larger ancestral population, and an effective extant population of around 80,000 females. Both these studies proposed reclassifying Canis aureus lupaster as a subspecies of the gray wolf.[27]", "In 2015, a more thorough comparative study of mitochondrial and nucleargenomes on a larger sample of wolf-like African canids from northern, eastern and western Africa showed that they were in fact all distinct from the golden jackal, with a genetic divergence of around 6.7%,[5][28][29] which is greater than that between gray wolves and coyotes (4%) and that between gray wolves and domestic dogs (0.2%).[30] Furthermore, the study showed that these African wolf-like canids (renamed Canis lupaster, or African wolves) were more closely related to gray wolves and coyotes than to golden jackals,[5][31] and that C. l. lupaster merely represents a distinct phenotype of the African wolf rather than an actual gray wolf. The phylogenetic tree below is based on nuclear sequences:[5]", "It was estimated that the African wolf diverged from the wolf–coyote clade 1.0–1.7 million years ago, during the Pleistocene, and therefore its superficial similarity to the golden jackal (particularly in East Africa, where African wolves are similar in size to golden jackals) would be a case of parallel evolution. Considering its phylogenetic position and the canid fossil record, it is likely that the African wolf evolved from larger ancestors that became progressively more jackal-like in size upon populating Africa on account of interspecific competition with both larger and smaller indigenous carnivores. Traces of African wolf DNA were identified in golden jackals in Israel, which adjoins Egypt, thus indicating the presence of a hybrid zone.[5] The study's findings were corroborated that same year by Spanish, Mexican and Moroccan scientists analyzing the mtDNA of wolves in Morocco, who found that the specimens analyzed were distinct from both golden jackals and gray wolves but bore a closer relationship to the latter.[6] Studies on RAD sequences found instances of African wolves hybridizing with both feral dogs and Ethiopian wolves.[32]", "In 2017, it was proposed by scientists at the Oslo and Helsinki Universities that the binomial name C. anthus was a nomen dubium, on account of the fact that Cuvier's 1820 description of the holotype, a female collected from Senegal, seems to be describing the side-striped jackal rather than the actual African wolf, and does not match the appearance of a male specimen described by Cuvier in his later writings. This ambiguity, coupled with the disappearance of the holotype's remains, led to the scientists proposing giving priority to Hemprich and Ehrenberg's name C. lupaster, due to the type specimen having a more detailed and consistent description, and its remains being still examinable at the Museum für Naturkunde.[19] The following year, a major genetic study of Canis species also referred to the African wolf as Canis lupaster.[8]", "In 2019, a workshop hosted by the IUCN/SSC Canid Specialist Group recommended that because the specimen identified as Canis anthus Cuvier, 1820 was uncertain, the species should be known as Canis lupaster Hemprich and Ehrenberg, 1832 until Canis anthus can be validated.[33]", "In 2018, whole genome sequencing was used to compare members of the genus Canis. The study supports the African wolf being distinct from the golden jackal, and with the Ethiopian wolf being genetically basal to both. Two genetically distinct African wolf populations exist in northwestern and eastern Africa. This suggests that Ethiopian wolves – or a close and extinct relative – once had a much larger range within Africa to admix with other canids. There is evidence of gene flow between the eastern population and the Ethiopian wolf, which has led to the eastern population being distinct from the northwestern population. The common ancestor of both African wolf populations was a genetically admixed canid of 72% gray wolf and 28% Ethiopian wolf ancestry. There is evidence of gene flow between African wolves, golden jackals, and gray wolves. One African wolf from the Egyptian Sinai Peninsula showed high admixture with the Middle Eastern gray wolves and dogs, highlighting the role of the land bridge between the African and other continents in canid evolution. African wolves form a sister clade to Middle Eastern gray wolves based on mitochondrial DNA, but to coyotes and gray wolves based on nuclear DNA.[8]", "Between 2011 and 2015, two mtDNA studies found that the Himalayan wolf and Indian wolf were closer to the African wolf than they were to the Holarctic gray wolf.[21][5] In 2017, a study of mitochondrial DNA, X-chromosome (maternal lineage) markers and Y-chromosome (male lineage) markers found that the Himalayan wolf is genetically basal to the Holarctic gray wolf. The Himalayan wolf shares a maternal lineage with the African wolf, and possesses a unique paternal lineage that falls between the gray wolf and the African wolf.[34]", "Although in the past several attempts have been made to synonymise many of the proposed names, the taxonomic position of West African wolves, in particular, is too confused to come to any precise conclusion, as the collected study materials are few. Prior to 1840, six of the 10 supposed West African subspecies were named or classed almost entirely because of their fur color.[35]", "The species' display of high individual variation, coupled with the scarcity of samples and the lack of physical barriers on the continent preventing gene flow, brings into question the validity of some of the West African forms.[35] However, a study showed that the genetic divergence of all of the African wolves occurred between 50,000 and 10,500 years ago, with most occurring between 30,000 and 16,000 years ago during the Late Glacial Maximum (33,000–16,000 years ago). There were very dry conditions across the Sahara during this period. The study proposes that these wolves were isolated in refugia and therefore isolated for hundreds of generations, leading to genetic divergence.[36]", "A large, stoutly built subspecies with proportionately short ears and presenting a very gray wolf-like phenotype, standing 40.6 cm (16.0 in) in shoulder height and 127 cm (50 in) in body length. The upper parts are yellowish-gray tinged with black, while the muzzle, the ears and the outer surfaces of the limbs are reddish-yellow. The fur around the mouth is white.[27][37]", "A dwarf subspecies measuring only 12 inches in shoulder height, it is generally of a grayish-yellow color, mingled with only a small proportion of black. The muzzle and legs are more decidedly yellow, and the underparts are white.[37]", "The African wolf's social organisation is extremely flexible, varying according to the availability and distribution of food. The basic social unit is a breeding pair, followed by its current offspring, or offspring from previous litters staying as \"helpers\".[15] Large groups are rare, and have only been recorded to occur in areas with abundant human waste. Family relationships among African wolves are comparatively peaceful in relation to those of the black-backed jackal; although the sexual and territorial behavior of grown pups is suppressed by the breeding pair, they are not actively driven off once they attain adulthood. African wolves also lie together and groom each other much more frequently than black-backed jackals. In the Serengeti, pairs defend permanent territories encompassing 2–4 km2, and will vacate their territories only to drink or when lured by a large carcass.[4] The pair patrols and marks its territory in tandem. Both partners and helpers will react aggressively towards intruders, though the greatest aggression is reserved for intruders of the same sex; pair members do not assist each other in repelling intruders of the opposite sex.[4]", "Threat postures in C. l. lupaster (left) and C. l. anthus (right)", "The African wolf's courtship rituals are remarkably long, during which the breeding pair remains almost constantly together. Prior to mating, the pair patrols and scent marks its territory. Copulation is preceded by the female holding her tail out and angled in such a way that her genitalia are exposed. The two approach each other, whimpering, lifting their tails and bristling their fur, displaying varying intensities of offensive and defensive behavior. The female sniffs and licks the male's genitals, whilst the male nuzzles the female's fur. They may circle each other and fight briefly. The copulatory tie lasts roughly four minutes. Towards the end of estrus, the pair drifts apart, with the female often approaching the male in a comparatively more submissive manner. In anticipation of the role he will take in raising pups, the male regurgitates or surrenders any food he has to the female. In the Serengeti, pups are born in December–January, and begin eating solid food after a month. Weaning starts at the age of two months, and ends at four months. At this stage, the pups are semi-independent, venturing up to 50 meters from the den, even sleeping in the open. Their playing behavior becomes increasingly more aggressive, with the pups competing for rank, which is established after six months. The female feeds the pups more frequently than the male or helpers do, though the presence of the latter allows the breeding pair to leave the den and hunt without leaving the litter unprotected.[4]", "The African wolf's life centers around a home burrow, which usually consists of an abandoned and modified aardvark or warthog earth. The interior structure of this burrow is poorly understood, though it is thought to consist of a single central chamber with 2–3 escape routes. The home burrow can be located in both secluded areas or surprisingly near the dens of other predators.[39]", "African wolves frequently groom one another, particularly during courtship, during which it can last up to 30 minutes. Nibbling of the face and neck is observed during greeting ceremonies. When fighting, the African wolf slams its opponents with its hips, and bites and shakes the shoulder. The species' postures are typically canine, and it has more facial mobility than the black-backed and side-striped jackals, being able to expose its canine teeth like a dog.[4]", "The vocalisations of the African wolf are similar to those of the domestic dog, with seven sounds having been recorded,[17] including howls, barks, growls, whines and cackles.[4] Subspecies can be recognised by differences in their howls.[17] One of the most commonly heard sounds is a high, keening wail, of which there are three varieties; a long single toned continuous howl, a wail that rises and falls, and a series of short, staccato howls. These howls are used to repel intruders and attract family members. Howling in chorus is thought to reinforce family bonds and establish territorial status.[4] A comparative analysis of African wolf and some gray wolf subspecies' howls demonstrated that the former's howls bear similarities to those of the Indian wolf, being high-pitched and of relatively short duration.[40]", "The African wolf rarely catches hares, due to their speed. Gazelle mothers (often working in groups of two or three) are formidable when defending their young against single wolves, which are much more successful in hunting gazelle fawns when working in pairs. A pair of wolves will methodically search for concealed gazelle fawns within herds, tall grass, bushes and other likely hiding places.[4]", "Although it is known to kill animals up to three times its own weight, the African wolf targets mammalian prey much less frequently than the black-backed jackal overall.[4] On capturing large prey, the African wolf makes no attempt to kill it; instead it rips open the belly and eats the entrails. Small prey is typically killed by shaking, though snakes may be eaten alive from the tail end. The African wolf often carries away more food than it can consume, and caches the surplus, which is generally recovered within 24 hours.[39] When foraging for insects, the African wolf turns over dung piles to find dung beetles. During the dry seasons, it excavates dung balls to reach the larvae inside. Grasshoppers and flying termites are caught either in mid-air or by pouncing on them while they are on the ground. It is fiercely intolerant of other scavengers, having been known to dominate vultures on kills – one can hold dozens of vultures at bay by threatening, snapping and lunging at them.[4]", "The African wolf inhabits a number of different habitats; in Algeria it lives in Mediterranean, coastal and hilly areas (including hedged farmlands, scrublands, pinewoods and oak forests), while populations in Senegal inhabit tropical, semi-arid climate zones including Sahelian savannahs. Wolf populations in Mali have been documented in arid Sahelian massifs.[27] In Egypt, the African wolf inhabits agricultural areas, wastelands, desert margins, rocky areas, and cliffs. At Lake Nasser, it lives close to the lakeshore.[16] In 2012, African wolves were photographed in Morocco's Azilal Province at an elevation of 1,800 meters.[14][3] It apparently does well in areas where human density is high and natural prey populations low, as is the case in the Enderta district in northern Ethiopia.[42] This wolf has been reported in the very dry Danakil Depression desert on the coast of Eritrea, in eastern Africa.[13]", "The African wolf generally manages to avoid competing with black-backed and side-striped jackals by occupying a different habitat (grassland, as opposed to the closed and open woodlands favored by the latter two species) and being more active during the daytime.[43] Nevertheless, the African wolf has been known to kill the pups of black-backed jackals,[15] but has in turn been observed to be dominated by adults during disputes over carcasses.[17] It often eats alongside African wild dogs, and will stand its ground if the dogs try to harass it.[4] Encounters with Ethiopian wolves are usually antagonistic, with Ethiopian wolves dominating African wolves if the latter enter their territories, and vice versa. Although African wolves are inefficient rodent hunters and thus not in direct competition with Ethiopian wolves, it is likely that heavy human persecution prevents the former from attaining numbers large enough to completely displace the latter.[44] Nevertheless, there is at least one record of an African wolf pack adopting a male Ethiopian wolf.[45]", "African wolves will feed alongside spotted hyenas, though they will be chased if they approach too closely. Spotted hyenas will sometimes follow wolves during the gazelle fawning season, as wolves are effective at tracking and catching young animals. Hyenas do not take to eating wolf flesh readily; four hyenas were reported to take half an hour in eating one. Overall, the two animals typically ignore each other when no food or young is at stake.[46] Wolves will confront a hyena approaching too closely to their dens by taking turns in biting the hyena's hocks until it retreats.[4]", "The African golden jackal was depicted as Anubis, Vignette from the Papyrus of Ani, British MuseumWolf-shaped bronze amulet from Egypt's Ptolemaic Period (711–30 BCE)", "The wolf was the template of numerous Ancient Egyptian deities, including Anubis, Wepwawet and Duamutef.[47] The wolf was sacred in Lycopolis, whose inhabitants would mummify wolves and store them in chambers, as opposed to other areas of Egypt, where wolves were buried at their place of death. According to Diodorus Siculus in Bibliotheca historica, there were two reasons as to why the wolf was held in such high regard, the first being the animal's affinity to the dog, and the second being a legend that told of how Lycopolis received its name after a pack of wolves repelled an Ethiopian invasion. Plutarch noted in his On the Worship of Isis and Osiris that Lycopolis was the only nome in Egypt where people consumed sheep, as the practice was associated with the wolf, which was revered as a god. The importance of the wolf in Lycopolite culture continued through to the Roman period, where images of the animal were minted on the reverse sides of coins. Herodotus mockingly wrote of a festival commemorating Rhampsinit's descent to the underworld where a priest would be led by two wolves to the temple of Ceres.[48]", "Arab Egyptian folklore holds that the wolf can cause chickens to faint from fear by simply passing underneath their roosts, and associates its body parts with various forms of folk magic: placing a wolf's tongue in a house is believed to cause the inhabitants to argue, and its meat is thought to be useful in treating insanity and epilepsy. Its heart is believed to protect the bearer from wild animal attacks, while its eye can protect against the evil eye.[9] Although considered haram in Islamic dietary laws, the wolf is important in Moroccan folk medicine.[10]Edvard Westermarck wrote of several remedies derived from the wolf in Morocco, including the use of its fat as a lotion, the consumption of its meat to treat respiratory ailments, and the burning of its intestines in fumigation rituals meant to increase the fertility of married couples. The wolf's gall bladder was said to have various uses, including curing sexual impotence and serving as a charm for women wishing to divorce their husbands. Westermarck noted, however, that the wolf was also associated with more nefarious qualities: it was said that a child who eats wolf flesh before reaching puberty will be forever cursed with misfortune and that scribes and saintly persons refrain from consuming it even in areas where it is socially acceptable, as doing so would render their charms useless.[11]", "The African wolf is not common in Neolithic rock art, though it does occasionally appear; a definite portrayal is shown on the Kef Messiouer cave in Algeria's Tébessa Province, where it is shown feeding on a wild boar carcass alongside a lion pride. It plays a role in Berber mythology, particularly that of the Ait Seghrouchen of Morocco, where it plays a similar role in folktales as the red fox does in Medieval European fables, though it is often the victim of the more cunning hedgehog.[49]", "The African wolf plays a prominent role in the Serer religion's creation myth, where it is viewed as the first living creature created by Roog, the Supreme God and Creator.[12][50] In one aspect, it can be viewed as an Earth-diver sent to Earth by Roog, in another, as a fallen prophet for disobeying the laws of the divine. The wolf was the first intelligent creature on Earth, and it is believed that it will remain on Earth after human beings have returned to the divine. The Serers believe that, not only does it know in advance who will die, but it traces the tracks in advance of those who will go to funerals. The movements of the wolf are carefully observed, because the animal is viewed as a seer who came from the transcendence and maintains links with it. Although believed to be rejected in the bush by other animals and deprived of its original intelligence, it is still respected because it dared to resist the supreme being who still keeps it alive.[12]" ], [ "types of wolves", "Wolves are adapted to thrive in a variety of different environments. Gray wolves once roamed across most of the world’s northern hemisphere. Currently, there are two universally recognized species of wolves in the world, the red and the gray. However, there is a growing debate over if some subspecies are actually distinct species of wolves.", "Wolves once roamed almost all of North America. However, when the settlers arrived from Europe, the extermination of red and gray wolves began. Today, the range and population of all wolves in North America is significantly reduced and varies by region. Although the taxonomy of wolves has been an ongoing debate in the scientific community, there are two universally recognized species of wolves in the world: the gray wolf (Canis lupus) and the red wolf (Canis rufus), both of which are found in the United States. Additionally, recent genomic research suggests there are potentially more distinct species, including the eastern (Algonquin) wolf (Canis lycaon), which was previously considered a subspecies of gray wolf found in eastern North America.", "​", "United States", "Current populations of the North American gray wolf are drastically different between Alaska (~8,000-10,000 wolves) and the lower 48 states (~5,000-6,500 wolves). In Alaska, wolves inhabit about 85% of the state, including the mainland and all major islands, and have never been considered endangered in Alaska. Both the rock mountain gray and arctic subspecies call Alaska home.", "In the lower 48 states, there are 3 subspecies of gray wolves: the rocky mountain gray wolf, the great plains gray wolf and the Mexican gray wolf. The rocky mountain gray wolf is located in the northern Rocky Mountains, while the great plains gray wolves call the Western Great Lakes region their home. The Mexican gray wolf once lived throughout Arizona, New Mexico, Texas and Mexico; however, persecution drove them to near extinction. In 1998, 11 captive-reared wolves were released into a recovery area. As of 2019, there are 113 Mexican gray wolves in the wild and they are considered endangered. You can learn more about the Mexican gray wolf here!", "The United States is also home to the red wolf, a distinct species from the gray wolf. The red wolf once lived throughout the entire southeast but was driven to near extinction by government-sponsored extermination programs. Unfortunately, the red wolf is an endangered species, with less than 25 wild wolves remaining in North Carolina. However, there are dozens of captive breeding programs working together on a national recovery effort for the red wolf. You can learn more about the red wolf here!", "There is also research suggesting that there is a 3rd distinct species of wolves in the United States, the eastern wolf (Canis lycaon). The eastern wolf is found in Minnesota, Wisconsin and Michigan and is virtually indistinguishable from gray wolf subspecies in the area by physical, behavioral and ecological traits. Genetic comparison is the only way to distinguish between the eastern wolf and other gray wolf subspecies in the region.", "​", "Canada", "Canada is home to the second largest gray wolf population in the world with 60,000 wolves. Currently, Canadian wolves occupy about 90% of their historic range. Interestingly, the 10% of Canada now lacking wolves is primarily near the US-Canada border. The rocky mountain, great plains, and arctic subspecies of gray wolf are all found in Canada. Additionally, the eastern wolf is found here.", "Mexican Gray Wolf", "Eastern Wolf", "Red Wolf", "Russian Gray Wolf", "Iberian Gray WOlf", "Much like in the United States, wolves once roamed throughout much of Europe. However, human conflict and fears grew from myths and religion, and for centuries, humans have persecuted and hunted wolves in Europe. There are several countries in Europe where wolves live, and much like in North America, their range and population vary by region. Currently there are no more than 13,000 wolves in Europe (excluding Russia). There are 5 subspecies of gray wolves that are found in Europe:", "​", "Eurasian arctic wolf (aka tundra wolf)", "Russian gray wolf (aka Eurasian gray wolf)", "Italian gray wolf", "Indian gray wolf (aka desert wolf)", "Iberian gray wolf", "Eurasian arctic wolves are similar to North America's arctic wolves and reside in the northernmost latitudes of Europe. The Russian gray wolf is the largest of the gray wolf subspecies, with individuals averaging between 152-176 lbs, and is found all over Europe and the northern hemisphere of Asia. The Italian gray wolf is native to the Italian peninsula. They are a smaller subspecies, weighing between 55-77 lbs on average. It is estimated there are between 700-1,300 wild Italian wolves. The Indian gray wolf is mostly found in Southwest Asia and India, but populations have expanded into southeastern European countries such as Turkey. There are about 2,500 wild Iberian gray wolf, which roam northern Portugal and northwestern Spain. This subspecies is interesting because it has been isolated from other wolf populations, making it the most genetically distinct European subspecies. The Iberian gray wolf is also the largest wolf population in Western Europe. Iberian gray wolves are between 85-110 lbs on average.", "Italian Gray WOlf", "ASIA", "ASIA", "Gray wolves once lived throughout most of Asia. Wolves still roam many Asian countries and prey on ungulate species. The range and population of wolves in Asia varies by region. Overall, Asia has around 89,000-105,000 wolves. There are 6 subspecies of gray wolves that are found in Asia:", "​", "Eurasian arctic wolf (aka tundra wolf)", "Russian gray wolf (aka Eurasian gray wolf)", "Indian gray wolf (aka desert wolf)", "Arabian gray wolf", "Caspian Sea gray wolf", "Tibetan gray wolf (aka Himalayan gray wolf)", "Eurasian arctic wolves are similar to North America's arctic wolves and reside in the northernmost latitudes of Asia. The Russian gray wolf is the largest of the gray wolf subspecies, with individuals averaging between 152-176 lbs, and is found all over Europe and the northern hemisphere of Asia. The Indian gray wolf is mostly found in Southwest Asia and India, but populations have expanded into southeastern Europe. Due to the warmer environments that the Indian gray wolf is native to, it lacks a winter coat seen in other subspecies of gray wolves. It is also a smaller than other gray wolf subspecies. The Arabian gray wolf is the smallest of all the wolves, weighing around 45 lbs on average. This subspecies calls the Arabian Peninsula its home and is well adapted to desert life. Its pack size tends to be small (2-4 individuals) and they are omnivorous. The Caspian Sea gray wolf lives in the Caspian Steppes and is between 77-88 lbs on average.", "The Tibetan gray wolf is native to China and Nepal and is the most genetically divergent subspecies of gray wolf in the world. These wolves tend to be a lighter brown with more white around their face and on their legs. Tibetan gray wolves occupy territories at higher altitudes and have evolved to withstand low oxygen levels. These wolves weight around 75-77 lbs on average. Interestingly, Tibetan gray wolves howls at a lower frequency and for a shorter duration than other species of gray wolves.", "Indian Gray Wolf", "Tibetan Gray Wolf", "Caspian Gray Wolf", "Arabian Gray Wolf", "Africa", "Africa has the smallest gray wolf populations. There is only 1 subspecies of gray wolves that are found in Africa, the African gray wolf. The African gray wolf was formerly considered a subspecies of golden jackal and lives in several distinct, small regions in northern Africa.", "However, there is some recent research suggesting there Africa may be home another species of wolves, the Ethiopian or Abyssinian wolf (Canis simensis). The Ethiopian wolf is endangered, with about 420 left in the wild. These wolves are red in color and small, weighing between 28-36 lbs on average. More than half the population of the Ethiopian wolf are found in the Bale mountains, and rodents make up most of their diet. The social behaviors and communication between these wolves is similar to other species of wolves and their average pack size can range from 3-13 members. You can learn more about Ethiopian wolves here. ​", "​\"Closest thing to Heaven on Earth!\"", "​\"Being able to learn more about the care and conservation of these beautiful, social creatures is amazing. Better yet, you get to walk around with them and even pet and howl with them. Amazing experience!\"" ], [ "Ethiopian Wolf", "Breadcrumb", "What are Ethiopian wolves?", "Native to Ethiopia, these long-limbed, slender canids are some of the most endangered animals in Africa. They have a black, bushy tail that can reach up to 40 centimeters in length, pointed ears, and a slender snout. They are tawny red with a white underbelly and blaze on their chests, and also have white fur on their throats, which sweeps up and covers the underside of their muzzle. The female wolves tend to be paler in color than males and are smaller overall.", "Scientific Name", "Canis simensis", "Weight", "11 to 20 kilograms (24 to 42 pounds)", "Size", "Up to one meter in length (about 3 feet)", "Lifespan", "Up to 10 years", "Habitat", "Afro-alpine grasslands, rocky areas, and shrublands", "Gestation", "60 to 62 days", "Predators", "Humans", "Found in", "7", "isolated enclaves", "Fewer than", "440", "individuals remaining", "Annually, only about", "60%", "of dominant females breed successfully", "Challenges", "Agriculture is swallowing up Ethiopian wolf habitat.", "Humans currently pose the largest threat to this species. Subsistence farming in Ethiopia’s highlands is overtaking large swaths of their range, restricting them to higher and higher altitudes. The overgrazing of livestock is only exacerbating this habitat loss.", "Diseases are taking a toll.", "Population decline of the Ethiopian wolf is increasingly being tied to diseases, particularly in the Bale Mountains. Since 2008, this Ethiopian wolf population has declined by 30 percent due to consecutive epizootics of rabies and canine distemper. Rabies is a potential threat to all populations of the Ethiopian wolf, while canine distemper remains a serious concern in Bale.", "Solutions", "Our solutions to protecting and conserving the Ethiopian wolf:", "Economic Development", "Create income alternatives.", "African Wildlife Foundation is working to establish new mechanisms for ensuring local communities’ livelihoods. Our Simien Mountains Cultural Tourism project is improving infrastructure and accomodations in and around the national park. Increased revenue from community-owned and-operated tourism will reduce dependence on subsistence farming, ensuring Ethiopian wolf habitats stay protected.", "Community Empowerment", "Enlist local communities.", "In the Simien Mountains and three other locations in the Ethiopian highlands AWF engages local communities as “Wolf Ambassadors” to monitor wolves, introduce a report system to understand the causes of livestock predation by carnivores, and undertake rabies vaccinations for domesticated dogs to prevent disease outbreaks from spreading to Ethiopian wolf populations.", "Behaviors", "They are family-oriented.", "Ethiopian wolf packs are groups of extended family members, made up of all the males born into the pack during the previous years and one or two females. During breeding season, commingling between different parks is more common due to habitat saturation and the high potential for inbreeding inside the closely related pack. These interactions are highly vocal, and end when the smaller pack flees from the larger one.", "Raising Ethiopian wolf pups is a communal activity.", "Adult Ethiopian wolves in a pack will help raise each other’s pups. Wolf mothers give birth in a den they dug themselves, under a boulder or inside a rocky crevice. These dens usually consist of a highly utilized network of burrows, which can have multiple entrances and be interconnected. Pups are regularly shifted from one den to another.", "Diet", "Ethiopian wolves live together, but hunt alone.", "Unlike other wolf species, the Ethiopian wolf is a solitary hunter. Ethiopian wolf diet consists mainly of the giant mole rats and common grass rats that are abundant in their habitat. On the rare occasion, these canids will hunt cooperatively to bring down young antelopes, lambs, and hares. However, Ethiopian wolves are social animals and form packs of three to 13 individuals — this allows them to defend a territory with enough rodents to feed the entire group.", "Habitats", "Where do Ethiopian wolves live?", "As its name suggests, the Ethiopian wolf is endemic to Ethiopia. Populations are restricted to just seven isolated enclaves in the Ethiopian highlands, with the largest Ethiopian wolf population (120 to 160 individuals) found in the Bale Mountains in southern Ethiopia." ], [ "Pressure mounting for the home of wild coffee and Ethiopian wolves", "In the Harenna Forest of Bale Mountains National Park, a convergence of economic development, climate change and population growth threaten the health of the area’s ecosystem.", "by Nathan Siegel on 18 December 2018", "The region of Bale Park is vital to the survival of endemic flora and fauna, like the mountain nyala (Tragelaphus buxtoni), a large antelope, and some of the planet’s last wild coffee", "Bale is also home to other ancient forms of livelihood, such as traditional beekeeping.", "Now there’s a mounting battle to preserve the park, a crucial part of southern Ethiopia’s ecosystem and a watershed source for 12 million people.", "GOBA, Ethiopia — Abdul Mohamed has an unenviable job. He’s a park ranger tasked with protecting Harenna Forest in southern Ethiopia from illegalbe activities like logging and charcoal production. Mohamed realizes the importance of preserving it for his, and his neighbors’, livelihoods. The problem is that Mohamed and his eight colleagues are in charge of protecting an area that’s about 100 square kilometers (40 square miles). “We need more people,” he says.", "Patrolling for shenanigans can be dirty work. On the off chance that they catch someone red-handed burning charcoal or cutting trees for firewood or furniture, there are sometimes aggressive confrontations.", "“People are ready to fight,” Mohamed says. Communities that want to clear land for crops don’t understand the position of the rangers, and often start arguing or threaten violence, he says. “I get very scared!” he adds, a shocking statement from a man with his job and physical stature.", "Mohamed is on the front lines in a mounting battle to preserve Harenna Forest, part of a crucial ecosystem in southern Ethiopia’s Bale Mountains National Park. Economic development, climate change and population growth threaten the health of the park. The region is vital to the survival of endemic flora and fauna, like the mountain nyala (Tragelaphus buxtoni), a large antelope, and some of the planet’s last wild coffee, as well as ancient forms of livelihood such as beekeeping. The park serves as a watershed for 12 million people, many of whom live in the arid lowlands and rely on the park’s rivers for survival.", "Harvest season in the birthplace of Arabica", "Ashraka Kadeem, 20, in a makeshift shelter in Manyate Village on the outskirts of Harenna Forest. Photo by Nathan Siegel for Mongabay.", "On the banks of the Yadot River, which runs through the edge of Harenna Forest, Ali Nurut is in good spirits. The coffee harvest runs from mid-September to mid-November and is well underway.", "Vibrant red fruits hang from the thin coffee trees that grow at elevations of 1,300 to 1,800 meters (4,300 to 6,000 feet). The berries stand out from the wiry branches and minimal foliage of the trees. Nurut is careful to pick just the ripe ones, but moves with practiced speed and efficiency. Without stopping to answer this reporter’s questions, Nurut drops the red berries into a long cylindrical straw basket draped over his shoulder. The baskets are ubiquitous in the area this time of year.", "The land in the forest is owned by the community and then parceled out for families to pick coffee. Unlike many of his friends, Nurut’s plot of land in the rainforest is surrounded by a fence to keep out animals. He’s cleared the brush around his coffee trees, whereas his neighbors’ trees are suffocated by the intense plant life of the rainforest. Clearing allows the trees to produce more and better berries, Nurut says.", "He harvests about 120 kilograms (260 pounds) of coffee beans per year, but expects an increase this season. In previous years, he’s received the equivalent of $2.75 per kilo ($1.25 per pound). It’s a good thing, too, because “I have seven kids to support with coffee,” he says, still not breaking from the methodical work. Around 3,000 people collect coffee in the national park, says Abdul Kadeem, a member of the Sankate Coffee Association.", "As the birthplace of Arabica, southern Ethiopia is a well-known source of the world’s 100th most traded product. It is also one of the last places where endemic coffee still grows naturally in the wild. The small, unassuming fruit trees can be found in the midst of the mayhem of the rainforest.", "But these wild plants, and much of Ethiopia that is suitable for farming coffee, may soon be a thing of the past. In a 2017 study published in Nature, scientists projected increasingly unfavorable changes for coffee-farming areas in Ethiopia, including Harenna Forest. The culprit: climate change. The study predicted that up to 59 percent of such land would no longer be able to grow coffee by the end of the century because it would be too warm and dry. While other regions can move their coffee to higher altitudes, the slopes of the Bale Mountains are too steep to allow such a transition, says Justin Moat, a spatial scientist at the Royal Botanic Gardens Kew, U.K., who led the study. “No matter what kind of scenario [for climate change], by the end of the century, Bale is not looking good,” Moat told Mongabay.", "But climate change is not the only concern for those harvesting coffee in Harenna Forest. Agriculture, deforestation and livestock grazing also threaten the coffee industry. As park ranger Mohamed notes, people living on the edge of Harenna Forest clear land and use it for agriculture.", "Coffee drying outside the house of Abdul Kadeem in Manyate Village on the outskirts of Harenna Forest. Photo by Nathan Siegel for Mongabay.", "For small-scale wild-coffee producers like Nurut, who rely almost entirely on the harvest for their livelihood, that’s bad news.", "Just 100 meters (330 feet) from where Nurut works his coffee plantation, a herd of cows marches through the forest. It’s not illegal to bring livestock into the forest, but many believe grazing has an adverse impact on the forest.", "The lowland residents of Bale Mountains National Park have access to fewer resources than those living near the forest. In fact, many herders bring their livestock into the highlands of the national park to graze for weeks at a time. Farm Africa, a nonprofit based in the U.K., is trying to improve the livelihoods of people living in the lowlands so they don’t make that journey. The work is being done in the context of a nearly 7 percent loss of forest annually, according to Farm Africa.", "The wild coffee picked in Harenna Forest is often mixed with farmed coffee from nearby Delo Menna, to be roasted and exported. Locals say they can taste the difference between farmed and wild coffee. But if the global marketing machine shone a spotlight on wild coffee here and there was a boom in demand, pressure to clear away other plants to maximize the harvest of wild coffee could spike. That would hurt the forest, says Kadeem of the coffee association. A 2006 study published in Forest Ecology and Management seems to corroborate this, finding a 50 percent reduction in the number of species of lianas, small trees and shrubs in areas where plants were cleared to help the coffee grow.", "Ethiopian wolves roam the mountains", "High above Harenna Forest, where thousands are at work picking coffee, at an elevation of about 1,800 meters the rare Ethiopian wolf prowls the windswept plateaus. While there are only about 400 of the wolves left in the world, making them Africa’s rarest carnivore species, they roam freely on the Sanetti Plateau in Bale Mountains National Park. Home to the highest road in Africa, the park is one of the few Afromontane areas in Ethiopia. But the wolves are shy creatures, so it was particularly extraordinary to encounter one while hiking on the plateau. The wolf was hunting for rodents no more than 15 meters (50 feet) from us.", "Access to food isn’t the biggest concern for the survival of the Ethiopian wolf (Canis simensis), which is the size of a medium dog with a striking red coat. They wolves’ main source of food, rats, abound in the National Park; there are 3,000 kilograms of rats per square kilometer (10,500 pounds per square mile) in some meadows. The main threats come from domestic animals and pressure on the land where they hunt.", "Disease outbreaks brought by dogs that accompany livestock herders in the highlands of the park are one of the most immediate threats to the wolves. There have been successive outbreaks of rabies and canine distemper virus in recent years in the park. Three out of four wolves die in such outbreaks.", "But the wolves bounce back from each outbreak, suggesting they’ve developed some type of resilience, according to the Ethiopian Wolf Conservation Programme, which also helps vaccinate domestic dogs to avoid outbreaks. A more permanent threat to the wolves, according to the EWCP, is habitat loss.", "As human populations move farther up the mountains in search of land for farming and grazing, the wolves are squeezed into smaller areas. Barley and potatoes are grown as high as 4,000 meters (13,000 feet) in some areas, and 60 percent of the habitat potentially suitable for the wolves has been converted to agriculture, according to the EWCP.", "While the Ethiopian wolves are the most prominent endangered species in the park, the area is an endemic hotspot for both animals and plants. Bale Mountains National Park hosts a quarter of Ethiopia’s endemic mammal species, including the entire global population of the big-headed African mole-rat (Tachyoryctes macrocephalus) and largest global population of mountain nyala, as well as 6 percent of the country’s bird species. Almost half of the 1,000 known medicinal plant species in Ethiopia are found in the park.", "More mammal species would go extinct with the loss of Bale Mountains National Park than with the loss of any other area of equivalent size on the planet, according to UNESCO.", "Traditional beekeeping only for the brave", "A beehive placed about 60 ft high in an African Redwood in Harenna Forest, part of the Bale Mountains National Park, in southern Ethiopia. Photo by Nathan Siegel for Mongabay.", "Harvesting wild coffee isn’t the only traditional practice taking place in the forest. Scattered and camouflaged throughout the tallest canopies in the forest are oblong wooden contraptions: traditional beehives honed over centuries of practice.", "While every village near Harenna Forest hums with activity from the coffee harvest, these structures are a reminder of the myriad ways locals have lived in harmony with the forest for generations. The beehives are made of two large canoe-like pieces of wood, fastened together with rope. They are then placed high in native African redwood trees, usually 21 meters (70 feet) above ground, to deter daring honey badgers or potential thieves.", "When the honey is ready to harvest, the beekeeper will scale the tree with a rope and nothing else. It’s a risky business, suited only to the courageous and fit. Kadeem, who has five beehives near his house, hires someone else to harvest for him because he’s scared of heights. He says people have fallen and died.", "After reaching the hive, the beekeeper burns moss and blows smoke inside to disorientate the bees and prevent them from aggressively protecting their prized creation. Kadeem harvests about 36 kilograms (80 pounds) of honey twice a year and makes the equivalent of $1.50 per kilo (70 cents per pound). It’s less than half of what he gets for coffee, “because the coffee is for export but the honey is for local consumption.” Honey is sold as a remedy for the common cold and to make tej, a mead or honey wine.", "Honey and bees are a fixture of the traditions of Ethiopia. The northern town of Lalibela, renowned for its monolith churches cut out of the rock in the 13th century, is named after a king who, legend goes, was swarmed by bees at birth but remained unscathed. His mother saw this as a sign of his long reign and named him Lalibela, which translates to “the bees recognize his sovereignty.”", "With a pinch of salt", "Ashraka Kadeem, 20, making coffee the traditional way, by roasting and grinding the beans herself, in Manyate Village on the outskirts of Harenna Forest. Photo by Nathan Siegel for Mongabay.", "As his bees produce their honey in hives high above the ground, Kadeem remains focused on plants at eye level. At his home, the coffee beans have been separated from their berries and laid out in the sun to dry. His wife, Ashraka Kadeem, starts to prepare a traditional brew with already-dried coffee beans. Ashraka is 20 and has been making coffee like this for over half of her life; it appears she could do it with her eyes closed.", "The beans are cleaned and then roasted on a metal pan over an open fire under a makeshift canopy outside. The beans change in color from pale green to brown then black, accompanied by the familiar scent of roasted coffee. The coffee is ground in a wooden bowl until it is a fine powder. The intensive labor required is why most people buy grounds from nearby towns, but Ashraka maintains it tastes better homemade.", "The grounds are placed in a jebena, an Ethiopian coffee pot, and water is poured in. Before serving, a pinch of salt is added. Hard-core coffee drinkers the world might do a double take at this point, but it’s hard to argue with artisans in the birthplace of the drink.", "Full disclosure: the writer worked as photographer for Farm Africa on a previous trip to Ethiopia.", "Banner image: Adbul Kadeem inspecting drying coffee outside of his house in Manyate Village on the outskirts of Harenna Forest." ], [ "PAINTED WOLVES OF AFRICA", "Today we celebrate one of Africa’s most efficient hunters: the African Wild Dog. Their scientific name, Lycaon pictus, literally means ‘painted wolf’ and it’s easy to see why. Daubed with splodges of black, brown, yellow and white fur, their patchy coats give individual dogs a unique marking, a little like a fingerprint. Enormous Mickey Mouse like ears and white tipped bushy tails give them a rather endearing appearance.", "Wild dogs are Africa’s second most endangered carnivore after the Ethiopian wolf.", "Curious African wild dog", "On alert", "Many people who are lucky enough to witness these charming canines on safari are often surprised at how akin to a man’s best friend they first appear to be. Similar in size to a Labrador (although much more streamlined) they are extremely social and playful. They live in groups of anywhere between seven to 40 and greetings between pack members are an exciting occasion for all: an explosion of licking, whining, wagging of tails and rolling around. Seldom aggressive to one another, African wild dogs are, in fact, one of the most caring and strongly bonded species. The whole pack helps to care for pups as well as injured and aging members, with those in need given regurgitated meat following a hunt.", "As well as their caring and social nature, we love that the ‘top-dog’ is always a female. Packs are ruled by an alpha mating pair, although it’s the female who decides on pack membership, den location and so on. Unlike other mammals, it’s also the female that leaves the family to form their own new pack, whilst males remain in their birth group. Girl power!", "Despite the similarities many safari-goers observe with their pet pooches, wild dogs cannot be domesticated. Nor can they interbreed with domestic dogs. Tragically, African wild dogs are the most endangered carnivore on the planet. Native only to Africa, they historically roamed 39 countries across the continent. Now, they are found in only 14.", "Only 6,600 African wild dogs remain on the planet and their population is declining.", "Wild dogs on the sandy banks of the Ewaso Nyiro River at Sasaab", "Major threats include habitat loss as humans encroach on their living areas, as well as human wildlife conflict. As a nomadic species, wild dog territories can extend well over 1,000 square kilometres. Persecution from farmers, who often misguidedly blame dogs for livestock deaths, is being tackled by conservation groups such as the Mara Predator Conservation Programme (MPCP), one of the initiatives our Footprint foundation supports. Through monitoring of wild dog packs, community outreach, anti-poison campaigns and a deworming and vaccination programme, the MPCP are helping to secure a future for this endangered species. This year alone, the MPCP have vaccinated over 1,500 domestic cats and dogs in conservancies bordering the edge of the Masai Mara. This is in a bid to reduce rabies and other diseases thought to be easily transmitted to wild dogs.", "Sorry, your browser doesn't support embedded videos.", "For those yet to encounter with this rare safari animal, you might be lucky enough to spot them during a safari at Sasaab. A big family pack was recently witnessed hanging out on Leopard Rock, right next to the lodge in Westgate Conservancy. Our guests have also spotted wild dogs in Samburu National Reserve. It is always a mesmerizing moment to come across a pack, lazing in the roadside dust or trotting through the bush. Midday or afternoon seems to be when they are most frequently sighted in and around Sasaab.", "Through our unique collection of spectacular properties, online shop and Footprint foundation, we unite sustainable tourism with wildlife conservation and communities, making a difference to people and planet.", "We use cookies to give you the best online experience. By continuing to use our website, you're agreeing to our use of cookies.ContinueRead More", "Privacy & Cookies Policy", "Privacy Overview", "This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may have an effect on your browsing experience.", "Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.", "Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website." ], [ "Painted dogs are one of the most endangered species in the whole of Africa.", "Fewer than 7,000 painted dogs are left across the entire continent.", "They may not be as famous as their trunked, horned, or maned neighbours, but these painted dogs —also known as African wild or hunting dogs—are beautiful, unique, and fascinating social animals.", "Painted dogs are native to Africa, and aren’t found in the wild anywhere else on the planet. They live in small pockets across a handful of countries including Zimbabwe, the home of Painted Dog Conservation. There are roughly 700 painted dogs here, and we work with local populations of both humans and dogs—via conservation, education, and outreach programs—to help them not only survive here, but thrive.", "In Zimbabwe, painted dogs are protected under the following Statutory Instruments (SI):", "Mother knows best: Painted dogs live in matriarchal societies, with packs of up to 30 members all answering to an alpha female.", "#paintedwolfwednesday", "#repost @paintedwolf_org", "・・・", "P A I N T E D . W O L F . ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "W E D N E S D A Y ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Demystifying the ‘myth’ that is #Lycaon in the painted wolf’s Scientific name: #Lycaonpictus!⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "A painted wolf’s scientific name is Lycaon pictus translating to wolf-like creature in #Greek, and ‘pictus’ meaning painted in #Latin. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "#Paintedwolves are the only living species of the genus Lycaon, most other #canines, like grey wolves, are #canis. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "The name Lycaon comes from King Lycaon from Ancient Greek #mythology. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Lycaon, the sadistic King of #Arcadia, who lost favour with #Zeus after he tied to feed the God of Lightning human flesh at a banquet. To punish Lycaon, Zeus turned him into a half-man, half-wolf-like creature. Ever wonder were the #werewolf myth comes from?⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "While painted wolves might share a name with the cruel lupine king, they themselves are not wanting killers but empathetic, caring and tender to their pack mates. There has been no recorded attack on humans by a painted wolf in the wild. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Help create awareness for the plight of the painted wolf by participating in #PaintedWolfWednesday. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Photograph by award-winning, Nicholas Dyer Photography.", "“The continued existence of wildlife and wilderness is important to the quality of life of humans.” - Jim Fowler.", "To help save painted dogs follow LINK IN BIO.", "#mondaymotivation #savethepainteddog #pdc #painteddogs #africanwilddog #wildlife #environment", "Photo Credit: @wildxonex", "Always a beautiful sight to experience. Painted dogs are one of the most endangered species in the whole of Africa.", "Save the painted dog, LINK IN BIO.", "#Lukodetpack #endangeredspecies #painteddog", "Video Credit: Washington Moyo", "#paintedwolfwednesday", "#repost @paintedwolf_org", "・・・", "P A I N T E D . W O L F .", "W E D N E S D A Y", "#Paintedwolves don’t just communicate with hoo-calls but scent-marking too. The #wolves have scent glands located on their anus, genitals, and face.", "#Lemurs, #cheetah, hyena, lion and even #rhino using #scentmarking as a form of communication.", "Scent marking is when a #mammal produces a hormonal substance from a scent gland, or in the form of urine or feces, and deposits it in a prominent area.", "These glands allow painted wolves to communicate sexual readiness, gender, age and health with pack mates and other painted wolves.", "Unlike cheetah that uses scent posts, painted wolves tend to prefer scent marking on tall grass.", "Painted wolves scent mark more in the heart of their home range and less on the periphery of their territory.", "Wolves of higher social rank, like the #alphas, tend to scent mark more than subordinate pack members.", "Help create awareness for the plight of the painted wolf by participating in #PaintedWolfWednesday. Image by award-winning @nicholasdyerphotography", "The #dogrun, every second Saturday of the Month. Running to save an endangered species. Check the dates and join us if you are in the neighbourhood on the next run.", "#conservationmeetsfitness #zimparks #forestrycommisionzimbabwe #dete #crossdete #thedogrun #endangeredspecies #savethepainteddog #pdc #painteddog", "Question: What do you like about painted dogs?", "Me: Their big rounded lovely ears make them so attentive every time😍", "You:....................? #whatdoyoulikeaboutpainteddogs", "#savethepainteddog #pdc #painteddog #aficanwilddog #paintedwolf", "Photo Credit: David Graham.", "On the frontline of conservation.", "#repost @peterblinston", "・・・", "Two out of the ten dogs in the Wexau Pack. A great two days in the field. Culminated in successfully Collaring adult male “Peace”", "#mambanjeprimaryschool kids were so happy to be picked up this morning coming to the Iganyana Children’s Bush Camp where they will stay four days. Here, they will learn about conservation and wildlife in a way they have never before.", "We believe that engaging children (and adults) in local communities surrounding Hwange National Park is the right way to stop painted dog (and other wildlife) threats recurring in subsequent generations. “We can not expect kids to care or let alone take action to conserve something they do not have an appreciation of or love.” - @peterblinston", "To support the Iganyana Children’s Bush Camp kindly follow LINK IN BIO.", "#mambanje #mondaymotivation #iganyanachildrensbushcamp #kids #conservation #wildlife #environment #savethepainteddog #pdc #2020", "Video Credit📹: @davidkuvawoga", "Ngweshla pack feeding on a Kudu in Linkwasha yesterday. As you can see with the tall grass, Hwange has been receiving a generous portion of rains in the past few days, hopefully it keeps up the trend so that locals' crops grow and reduce the threat of poaching.", "#ngweshlapack #savethepainteddog #pdc #linkwasha", "Video Credit: Geshem Njamba", "Sights and scenes from the pre-camp meeting/assessment with kids from Mambanje Primary School who are due to come for a four-day free camp at our Iganyana Children’s Bush Camp next week.", "Before kids come to Iganyana Children’s Bush Camp, a pre-camp is conducted to prepare them in terms of what is expected of them and what to expect at the camp during their four-day stay. A pre-camp assessment is also done, kids answer a questionnaire about the environment, wildlife and conservation in general. After the camp, they will be presented with the same questionnaire to assess the impact of the camp.", "Always, the results show that kids come out of the camp better knowledgeable about, and with a positive attitude towards the environment and wildlife. An important aspect that will ensure the survival of wildlife and the habitat Hwange is endowed with.", "Follow LINK IN BIO to support the Iganyana Children's Bush Camp.", "#savethepainteddog #pdc #iganyanachildrenbushcamp #kids #education #conservation #environment #wildlfe #painteddogs #mambanjeprimaryschool #milliontrees2020 #trees #paintedwolfwednesday", "Photo Credit📸: @davidkuvawoga", "#paintedwolfwednesday", "#Repost @paintedwolf_org (@get_repost)", "・・・", "P A I N T E D . W O L F . ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "W E D N E S D A Y ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "‘To know them is to love them,’ – Africa’s most successful #predator has a softer side. Being empathetic and caring, the #paintedwolf pack is as good as their weakest member, and unlike #lions, they sympathetically care for the frail. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "In the wild, a serious injury or illness is a #deathknell for even the hardiest of African #animals but not painted wolves. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "The sick, injured and old wolves, along with puppies, take preference at the kill and will be tenderly cared for and nursed back to health. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "There are cases of #wolves surviving on three legs and recovering from serious injury due to the #empathy and dedication of their #pack mates.⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "If you can be anything in this #world, be kind, like the painted wolf. #Humanity has a lot to learn from these sociable and loving #canines. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Share the love this #PaintedWolfWednesday. Image by @nicholasdyerphotography", "“It is our deep felt belief that in order to make a difference and win in conservation, it is paramount to change lives.”", "— Wilton Nsimango -PDC Education and Community Development Programs Manager.", "@painted_dog_conservation aim to directly benefit local people by providing a way for them to earn more and access nutritionally balanced and reliable meals. To these ends, we build and establish nutritional gardens with irrigation systems next to boreholes in the local communities whose children attend our Children's Bush Camp.", "With your help, we aim to drill and manage more boreholes. To help change lives, follow LINK IN BIO.", "#mondaymotivation #kids #community #savethepainteddog #painteddogs #pdc #development", "Photo Credit📸: Molly Feltner.", "#paintedwolfwednesday", "#Repost @paintedwolf_org (@get_repost)", "・・・", "P A I N T E D . W O L F . ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "W E D N E S D A Y ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "My, what big #teeth you have! ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Relative to body size #paintedwolves have the largest #premolars of any living #carnivore, second to the #spottedhyena. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Painted wolves are considered to be hypercarnivores, which means 70% of their diet is meat. As a result of the high-protein diet, their premolars have evolved to become more carnassial, meaning blade-like. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Having teeth that are adapted to holding and slicing flesh is an advantage for the #wolves when taking down prey. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Quick cutting teeth also reduce the time at the kill. Being slightly-built - the faster the pack can eat and move on, the less likely they are to come into conflict with other big #predators, like #lion and #hyena. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Image by award-winning, @NicholasDyerPhotography. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Share your #paintedwolfwednesday stories with us.", "#paintedwolfwednesday", "#Repost @paintedwolf_org (@get_repost)", "・・・", "P A I N T E D . W O L F . W E D N E S D A Y ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "What to expect when a #paintedwolf is expecting… ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Painted wolves produce surprisingly large litters for their body size. After a gestation period of about 71–73 days the #alphafemale will give birth to between eight and eleven #puppies. Each pup clocks in at 300 – 350 grams and is born blind. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "#Paintedwolves do not have an equal gender-ratio. The sex ratio of a litter tends to be male-biased. This means more male puppies are born relative to females pups per litter. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "The #lactating #alpha will remain close to her pups for the first month. After four weeks regurgitated meat is added to the menu. #Pups are fully weaned at two months and will remain bound to the #den for a further four to eight weeks. ⠀⠀⠀⠀⠀⠀⠀⠀⠀", "⠀⠀⠀⠀⠀⠀⠀⠀⠀", "Image by award-winning, Nicholas Dyer Photography. Share your #PaintedWolfWednesday stories with us!" ], [ "Geographic Range", "African golden wolves (Canis anthus), which were considered the same species as Eurasian golden jackals (Canis aureus) until 2015, are found across northern Africa. Their range extends east to west from Somalia to Senegal and north to south from Algeria to Kenya. Thus, golden wolves occupy the Palearctic and Ethiopian faunal regions. Because golden wolves are a highly mobile species, their wide range was likely colonized naturally. Their historic range is unknown. (Karssene, et al., 2018; Koepfli, et al., 2015; Moehlman and Hayssen, 2018; Yirga, et al., 2017)", "Habitat", "African golden wolves live in elevations from 0 to nearly 5,000 m. In the eastern part of their range, golden wolves primarily live in high elevations from 2,200 to 4,620 m. However, in the Sahara Desert, they can be found anywhere between sea level and 4,459 m, in isolated mountains, which are estimated to be refugia for golden wolves in the face of climate change. (Brito, et al., 2009; Yalden, et al., 1996)", "Because of their generalist behavior and tolerance of dry habitats, golden wolves can be found in a wide range of habitats, including grasslands, coniferous temperate forests, invasive Eucalyptus forests, mangroves, dry plateaus, savannas, deserts, and semi-arid environments. However, their preferred habitat seems to be grasslands. Though golden wolves can occupy many habitats, the limiting factor seems to be access to water sources. In Tunisia, for example, differences in golden wolf distribution were best explained by the availability of water. In the Sahara Desert, golden wolves were found most frequently in areas with an annual rainfall of over 1,000 mm and were one of the few canids found in temperatures below 10°C. The only known unsuitable habitats seem to be extremely arid regions and dune fields. (Brito, et al., 2009; Karssene, et al., 2019; Moehlman and Hayssen, 2018; Yalden, et al., 1996)", "Golden wolves do not occur solely in natural habitats: depending on the area, golden wolves can rely a great deal on human settlements, such as agricultural fields and rural areas. A study in northern Ethiopia found that golden wolf density can actually increase with increasing human density, rather than decreasing to avoid human activity, as is documented for many other canids. This is thought to occur because, in these areas, humans have depleted much of the native prey sources on which golden wolves rely. Therefore, golden wolves resort to feeding on human waste products in these areas. Golden wolves are thus urban exploiters, suggesting that golden wolves may thrive in the face of a growing human population. (Yirga, et al., 2017)", "Physical Description", "African golden wolves were originally considered to be the same species as Eurasian golden jackals (Canis aureus). However, a study comparing mitochondrial DNA, microsatellites, sex chromosomes, and whole genomes showed that golden wolves have a unique gene pool from golden jackals and therefore constitute a different species. African wolves (Canis lupaster) were also concluded to be the same species as African golden wolves. This study also found that African golden wolves are more closely related to gray wolves (Canis lupus) than golden jackals. This close relation to gray wolves is interesting, considering that no gray wolves are found in Africa, but it is speculated that much of the canid diversity in Africa originated from Eurasian “wolf-like” colonizers that eventually went extinct. The first taxonomic description of an African golden wolf by Frédéric Cuvier in 1820 was also the first account that used the binomial nomenclature used for African golden wolves today: Canis anthus. Additionally, though Cuvier recognized African golden wolves as a separate species from golden jackals, the scientific community did not consider them as such until Koepfli et al.’s paper was published in 2015. (Koepfli, et al., 2015; Tedford, et al., 2009)", "Golden wolves generally have an overall coat color of golden or pale yellow, dark tawny, or gray, depending on their local habitat. For example, the first golden wolf ever described lived in mountainous terrain and had a gray coat, whereas golden wolves in desert habitat tend to be golden. Regardless of overall coat color, most golden wolves have yellow markings and individual hairs with black, white, and tan bands. Their legs, tails, the back of their ears, and the top of their muzzles are all tan in color, and a back stripe runs down the upper third of their tails, which have black tips. Their throats, chests, stomachs, the inner sides of their legs, and the undersides of their jaws are white. Their hair is longest on their necks and tails, shortest on their heads and legs, and of intermediate length on the rest of their bodies. Hair runs from front to back across the whole body except between the front legs, where it instead runs back to front. Additional morphological characteristics include bushy tails, a thick under wool during winter, pale yellow to amber eyes, 7 to 8 mammary glands on females, and a dental formula of i 3/3, c 1/1, p 4/4, m 2/3. (Koepfli, et al., 2015; Moehlman and Hayssen, 2018)", "Some sexual dimorphism occurs in golden wolves, mostly in terms of body size. Males have the same coloring and hair patterns as females, but are larger in size: males have a head and body length of 75 to 89.3 cm, a tail length of 20 to 34.7 cm, and weigh 6.3 to 15 kg. Females have a head and body length of 68 to 82.2 cm, a tail length of 20 to 29 cm, and weigh 6.5 to 10 kg. In general, females have 12% less body mass than males. There is also some sexual dimorphism in skull length in populations in East Africa, but not in North African populations. (Moehlman and Hayssen, 2018)", "Golden wolves in East Africa are smaller than golden wolves in West Africa, but otherwise look alike morphologically. There are also some small seasonal morphological differences, such as growing thick undercoats during winter and the emergence of a faint “black saddle” on their backs during some seasons. Overall, however, adult golden wolves look more or less the same, though individual identification may be possible by differences in the white markings on a their chests and throats. Even between age classes, golden wolves look very similar; adults can only be differentiated from juveniles by skeletal features. Adults have a high sagittal ridge on the front of their skulls that juveniles lack, and adults exhibit more tooth wear than young golden wolves. (Koepfli, et al., 2015; Moehlman and Hayssen, 2018)", "Compared to Eurasian golden jackals (Canis aureus) - which scientists originally believed were the same species as golden wolves - African golden wolves look very similar in craniodental anatomy, size, and color. However, golden wolves have smaller muzzles and premolars, larger molars, and narrower, more pointed canines than golden jackals. Additionally, the entire lower third of the tails of golden jackals is black, whereas the tails of golden wolves are only black on their tips. The two species also differ geographically, as golden jackals are only found in Europe and golden wolves are only found in Africa. (Koepfli, et al., 2015)", "On the eastern end of their range, golden wolves coexist with silver-backed jackals (Canis mesomelas) and side-striped jackals (Canis adustus), both of which are roughly the same size as African golden wolves. However, there are visible morphological differences between the three species: silver-backed jackals are easily identified by their red sides and legs and the silver “saddles” they have on their backs, and side-striped jackals have shorter ears, a gray stripe on their sides, and white-tipped tails. In comparison, golden wolves do not have a saddle, except for a vague black one in some seasons. They are also more gray and tan than red, do not have a side stripe, and have black-tipped tails. (Moehlman and Hayssen, 2018)", "Sexual Dimorphism", "male larger", "Range mass", "6.3 to 15 kg", "13.88 to 33.04 lb", "Range length", "68 to 89.3 cm", "26.77 to 35.16 in", "Reproduction", "African golden wolves are monogamous, like many other canid species, though this can be somewhat flexible depending on the abundance of resources and shifting population characteristics. Pair bonds last for a lifetime, and a group will thus consist of the mated pair and their previous offspring, which help to raise young. When defending their territory, mated pairs will fight off intruders intrasexually: males attack other males and females attack other females. It is speculated that this may occur because an individual male wants to make sure he is the only one mating with his female, to ensure the pups he helps raise are his. Meanwhile, an individual female wants to make sure her male does not mate with other females, so that he will fully invest in helping to raise her pups. Thus, territoriality may help enforce monogamous pairs. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Both male and female golden wolves reach reproductive maturity at 10 to 11 months of age. Their breeding season is from October to December, with parturition occurring from December to March, sometimes even stretching on into April and May. Copulatory ties last for a few minutes, followed by a gestation period of about 63 days. Litter sizes can range from 1 to 9 pups, averaging around 6 pups per litter. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "At birth, golden wolf pups are around 189 g. They are born blind and it takes 8 to 11 days for their eyes to open. Tooth eruption also occurs at 11 days. Golden wolf pups are born in underground dens, in which they stay until they are three weeks of age. Dens can have multiple openings, which are about 2 to 3 m long and about 1 m deep. Mothers stay in their dens with their pups and are supplemented by their mates. In some families, 11-to-18-year-old offspring from previous litters help raise new pups. The presence of these \"helpers\" has been shown to increase pup protection and provisioning, and thus survival. Both parents and their helpers assist in socializing the pups. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Even once pups emerge from their dens, they still rely on milk from their mother. However, they are also introduced to regurgitated food during this time. This food comes from their mothers and other adults in the group. Pups remain near their dens until they wean at 8 to 10 weeks of age. They begin assisting actively with foraging around 14 weeks of age. About 70% of pups will stay with their parents for up to two years and become helpers. During this time, they will not engage in breeding activity, even when they reach sexual maturity. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Only 30% of pups disperse before the next litter is born. It is speculated that most pups do not disperse right away because, due to high population densities at which golden wolves live, young pups would have a hard time finding a mate and establishing a territory of their own. However, once a juvenile does disperse from its family group, it is not yet known how it then finds a mate and establishes its own territory. (Moehlman, 1987)", "As typical of canids, male golden wolf parental investment is high. Mated pairs are monogamous and raise their young together. Between birth and weaning, pups rely completely on the milk of their mothers. However, their fathers and previous offspring from the mating pair, will bring food back for mothers and defend dens. Both parents also assist in socializing the pups and, after the pups are weaned, regurgitate food for them. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Lifespan/Longevity", "The maximum known lifespan of an African golden wolf in the wild was observed to be 14 years; in captivity, the maximum lifespan is 18 years. However, usual lifespan in the wild ranges from 6 to 8 years, with an average lifespan of 7 years. Many golden wolves die as pups, as they are especially susceptible to disease and den flooding at this time. Little is known about what limits the lifespan of adults. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Range lifespan Status: wild", "14 (high) years", "Range lifespan Status: captivity", "18 (high) years", "Typical lifespan Status: wild", "6 to 8 years", "Behavior", "African golden wolves are solitary, until they find a mate. Once a pair bond is formed, that pair stays together for life. The group size associated with a mating pair will grow and swell. This depends on how many pups they have and how many offspring stay to help raise the next batch of pups. In summary, golden wolves typically live in groups of two, though this number can increase with the presence of pups and helpers.", "Strong intraspecific food competition usually selects against larger group sizes, though when food is abundant, large groups have been observed sharing a scavenged carcass. (Moehlman, 1987; Moehlman and Hayssen, 2018)", "Golden wolves are primarily diurnal - they are mostly active during the day, dawn, and dusk, and are not normally seen at night. Golden wolves are also highly mobile, with males seeming to move farther than females. One male was documented to move at least 230 km - with a high of 465 km - in 98 days. Additionally, in Tunisia there is high genetic diversity among golden wolves, suggesting that connectivity and dispersal capabilities are high between populations. Not much is known about how golden wolves find one another, including mates, or how they interact with non-family conspecifics. (Karssene, et al., 2018; Karssene, et al., 2019; Moehlman and Hayssen, 2018; Yirga, et al., 2017)", "Home Range", "Golden wolves are territorial and generally keep territories of about 0.39 to 5 km^2, though they have also been documented to stray past territorial borders in order to feed on carcasses. Territories are nestled within larger home ranges, the size of which depends on the age of individuals and the type of habitat.", "Juveniles tend to have a much larger home range than adults, because of their need to spread out in search of mates and territory of their own. In woodland habitats, adult pairs have an average home range of 2.4 km^2, while dispersing juveniles have a much bigger home ranges, ranging from 5.6 to 21.7 km^2. Home range size in mountain habitats is much more variable, with adults having home ranges anywhere between 7.9 and 48.2 km^2 and dispersing juveniles having home ranges anywhere between 24.2 and 64.8 km^2. Both members of an adult pair will mark and defend their territory. They keep strict boundaries, though territories tend to overlap when individuals are part of a social group. Territories are generally held for about 8 years. (Moehlman and Hayssen, 2018)", "Communication and Perception", "Scent markings and vocalizations are the primary ways that African golden wolves communicate with each other. These forms of communication are important for marking territory, mating, predator defense, and locating family members. These actions may be coupled with other signals, such as visual displays. For example, when an individual golden wolf marks its territory, it will urinate on specific landmarks with a raised leg, rather than in a squatting position, to show any golden wolves that may be watching that it is the holder of this particular territory.", "African golden wolf vocalizations consist of howls, used for finding family members and asserting dominance, and growls and barks, which are used to warn family members of approaching predators. Barks are also used to stay in contact with group members during hunts for larger prey. Greeting ceremonies and grooming are also important ways of socializing. (Eaton, 1969; Moehlman and Hayssen, 2018)", "Food Habits", "African golden wolves primarily feed on wild boars (Sus scrofa) of all ages, though golden wolves likely only feed on adult boars as carrion, due to the dangers of actively hunting adult boars. Plant material also makes up a significant part of the diets of golden wolves. This includes various fruits, seeds, leaves and grasses for digestion and a source of water. Rabbits (Oryctolagus cuniculus) and livestock such as domestic sheep (Ovis aries) are also fairly common, as well as hares (Lepus capensis) and cats (Felis lybicalcafus) to a lesser extent. They have also been documented to eat birds (both wild and domesticated), rodents, and, more rarely, beetles. Thus, African golden wolves can be categorized as omnivores. (Amroun, et al., 2006; Eddine, et al., 2017; Karssene, et al., 2019)", "Adult pairs hunt together, but otherwise most golden wolves hunt alone. Individual golden wolves have been documented bringing down ungulates 4 to 5 times larger than themselves, though the success rate of mating pairs is higher than that of lone individuals. Adult pairs are also able to go after larger prey, such as Thomspon’s gazelle (Eudorcus thomsonii) and Abdim’s storks (Ciconia abdimii). If food is widely available, groups of up to 18 have been documented scavenging carcasses, but no documentation has been made of golden wolves hunting in large groups like their close relatives, gray wolves (Canis lupus). (Moehlman and Hayssen, 2018)", "To hunt rodents, golden wolves use their ears to pinpoint the exact location and either leap through the air to catch them or dig them out of their burrows. For ungulate prey, golden wolves generally focus on young, old, or injured individuals. They will chase these weaker individuals away from the rest of the herd, like many other canids. Golden wolves cache any leftovers for later. When a family group is on the hunt they will spread out rather than stay bunched together, with distances of a few hundred meters between each individual. They bark in order to stay in contact with one another during the hunt. (Eaton, 1969; Moehlman and Hayssen, 2018)", "Predation", "Spotted hyenas (Crocuta crocuta) are known to kill and eat African golden wolves in East Africa. Hyenas will often try to come into golden wolf dens to eat pups; when golden wolves see a hyena approaching their dens, they give a warning yowl, which alerts all of the adults nearby to chase the hyena away and bite its rump and genitals. Honey badgers (Mellivora capensis) have also been seen near golden wolf dens, but the adults have always chased them away before actual predation could be documented. Humans are also known to kill golden wolves in response to livestock predation. Besides aggressive actions by the adults guarding the den, not much is known about golden wolf anti-predator behavior. (Eddine, et al., 2017; Moehlman and Hayssen, 2018)", "Ecosystem Roles", "Due to the widespread loss of many large carnivores in northern Africa, African golden wolves have become more or less the top predator. They are also shown to be opportunists and generalists, allowing them to spread widely across the landscape into many different ecosystems. One consequence of this is that they may be putting a large exploitative competition pressure on other predators, such as the common genet (Genetta genetta). Golden wolves are also speculated to compete exploitatively with fennec foxes (Vulpes zerda) and red foxes (Vulpes Vulpes) and appear to be the superior competitor, as foxes of both species have been shown to abandon water sources and hide whenever golden wolves approach. Because of this competition, it is believed that fennec foxes began to occupy more sandy areas that were less favorable to golden wolves and both fox species shifted to nocturnal activity to avoid golden wolves. Golden wolves are also known to have dietary overlap with black-backed jackals (Canis mesomelas) and side-striped jackals (Canis adustus) in East Africa. The degree to which this competition impacts these three species has yet to be documented. (Amroun, et al., 2006; Eddine, et al., 2017; Karssene, et al., 2019; Moehlman and Hayssen, 2018)", "Predation by golden wolves may help control rodent and boar populations. They are also scavengers, and thus are important for cycling energy and nutrients throughout their ecosystem. Highly mobile species such as golden wolves are especially important in providing these services across a wide range of systems. Thus, it is likely that golden wolves provide these vital ecosystem services. (Amroun, et al., 2006; Eaton, 1969; Eddine, et al., 2017; Inger, et al., 2016)", "Golden wolves seem to have a commensalistic relationship with cheetahs (Acinonyx jubatus), as documented in Kenya by Eaton (1969). When golden wolves encounter cheetahs, they will search the vicinity for a kill and, if they find one, scavenge off of it. If there is no kill immediately nearby, golden wolves will remain around the cheetahs for a while, following their movements until either a kill is made or the cheetahs remain inactive for too long and the golden wolves move on. Considering that golden wolves only feed on carcasses abandoned by cheetahs, this does not seem to be a parasitic relationship, as cheetahs are not prohibited from getting as much as they need to eat. There are also no records of cheetahs chasing golden wolves away from kills, suggesting that cheetahs are unaffected by their scavenging.", "Additionally, cheetah and golden wolf family groups have been documented living near one another without fighting over resources or killing offspring. This suggests that there is little to no competitive relationship between the two species. In fact, it has been documented that, occasionally, golden wolves assist cheetah kills by distracting a herd while the cheetah sneaks up from behind, suggesting the relationship may be mutualistic. However, Eaton (1969) speculates that this behavior likely does not occur outside of their study area because of high competition between scavengers in other areas. Indeed, in Serengeti National Park, golden wolves are rarely observed on carcasses, and scavenged meat makes up only a small portion of their diet. This is thought to occur because of the competition with other scavengers and the danger posed to golden wolves by other scavengers and larger predators that made the kill. (Eaton, 1969; Hunter, et al., 2006)", "Several golden wolves were shown to have antibodies for canine adenovirus, a liver infection, and canine coronavirus, a highly contagious intestinal disease. Both of these diseases can be easily spread to other canids through feces. Other individuals have tested positive for canine parvovirus, another intestinal disease that can spread to other canids, and canine distemper virus, a virus that affects the respiratory, gastrointestinal, and nervous systems. Canine distemper virus is an especially noteworthy disease because it can infect all sorts of other animals, including other canids, felids, and some primates. Other parasites include Coccidia, which are intestinal parasites that can affect canids and felids, as well as hookworms, tapeworms, mange, flukes, ticks, and Toxocara canis, another intestinal parasite that affects canids. (Gherman and Mihalca, 2017; Moehlman and Hayssen, 2018)", "Economic Importance for Humans: Positive", "It has been shown that organic waste from humans is a major food source for African golden wolves, which means they can assist with waste removal. In fact, they have been documented in northern Ethiopia, along with spotted hyenas (Crocuta crocuta), to remove organic waste that may be infected, therefore sanitizing rural areas. Studies of golden wolves have also given us a better understanding of how the domestication of dogs may have taken place. (Amroun, et al., 2006; Eaton, 1969; Yirga, et al., 2017)", "Positive Impacts", "research and education", "Economic Importance for Humans: Negative", "Similar to problems with gray wolves (Canis lupus) in the United States, predation by African golden wolves on livestock is a huge issue for rural communities in Africa. Golden wolves have been predating increasingly on livestock, and thus farmers have started retaliating. Between 2014 and 2015, farmers killed over 200 wolves. This is a serious problem in some areas, like Tunisia, where livestock has been documented to make up a significant part of the diets of golden wolves. However, relative frequency of livestock in their diet seems to primarily correlate with degree of livestock protection, suggesting that tighter management of livestock may be all that is required to solve this problem. (Eddine, et al., 2017; Karssene, et al., 2019)", "Additionally, golden wolves are hosts for the protozoan parasite Babesia gibsoni, which is commonly found in domestic dogs. Golden wolves are also reservoirs to Hepatozoon canis, as well as fleas. If golden wolves continue to become more frequent in human settlements, their presence could increase the spread of these parasites, and all of the other diseases mentioned above. These diseases could be spread to pets, other golden wolves and canids that congregate in human areas, and even livestock. (Gherman and Mihalca, 2017; Maronpot and Guindy, 1970; Yirga, et al., 2017)", "Some diseases that golden wolves carry, like flatworms, have been shown to also infect humans. Golden wolves are reservoirs to parasites like filarioids, which are responsible for pink eye and various lung diseases in humans, and guinea worms, which cause severe pain where the worm migrates as well as nausea and vomiting in humans. An increase of golden wolves in human settlements may lead to an increase in infections, which could be especially devastating for rural communities that may not have the means to treat them medically. (Gherman and Mihalca, 2017)", "Conservation Status", "African golden wolves are listed as least concern but declining on the IUCN red list, and are not listed under the CITES appendices or the US Endangered Species Act. Durant et al. (2011) also documented a significant long-term decline in golden wolf populations in the Serengeti. Reasons for their decline may be due to overkill by hunters and poaching, both of which occur in the range of golden wolves, and retaliatory killing by farmers over predation of livestock. All of this is aided by the increased stock of automated weapons in places like Ethiopia. It is speculated that many golden wolves are also being affected by predator control programs for other species, primarily through the consumption of poisoned carcasses. Additionally, vehicular collisions were the source of death for at least fifty golden wolves in the Sahara Desert, which will likely have larger implications as countries develop and roads become more intricate and widespread. (Brito, et al., 2009; Durant, et al., 2011; Eddine, et al., 2017; Moehlman and Hayssen, 2018; Yalden, et al., 1996)", "Some countries in the range of golden wolves are currently or frequently in a state of war and other extreme conflict, which leads to increased habitat loss and fragmentation. Even the most remote regions, which usually experience little human presence, are affected by war, as opposing sides use these areas to gain tactical advantage. This pushes animals from places that may have once served as refugia. Because of this loss of habitat and refugia, many animals are locally extirpated. Additionally, the number of illegal killings were shown to increase drastically after a couple of years of war. The list of species killed likely includes golden wolves, because of their status as livestock predators. Outside of war-torn areas, widespread habitat loss due to human settlement, expansion, and over-grazing by livestock also occurs in the range of golden wolves. However, these are unlikely to have as large of an impact on golden wolf populations compared to the factors discussed above. Human settlements are less threatening to golden wolves likely because of how opportunistic they are, and due to their demonstrated ability to thrive in anthropogenic landscapes. (Amroun, et al., 2006; Brito, et al., 2018; Eddine, et al., 2017)", "Part of the range of golden wolves is encompassed in the Tlemcen Hunting Reserve in Algeria. There are also several national parks scattered around Ethiopia and Eritrea, though many of these are poorly staffed and thus inadequately enforced. It is likely, however, that golden wolves receive at least some protection when considering all of the parks cumulatively. (Eddine, et al., 2017; Yalden, et al., 1996)", "Contributors", "Glossary", "living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.", "Palearctic", "living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.", "acoustic", "uses sound to communicate", "agricultural", "living in landscapes dominated by human agriculture.", "altricial", "young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.", "carrion", "flesh of dead animals.", "causes or carries domestic animal disease", "either directly causes, or indirectly transmits, a disease to a domestic animal", "chemical", "uses smells or other chemicals to communicate", "crepuscular", "active at dawn and dusk", "desert or dunes", "in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.", "diurnal", "active during the day, 2. lasting for one day.", "female parental care", "parental care is carried out by females", "fertilization", "union of egg and spermatozoan", "forest", "forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.", "male parental care", "parental care is carried out by males", "monogamous", "Having one mate at a time.", "mountains", "This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.", "native range", "the area in which the animal is naturally found, the region in which it is endemic.", "nomadic", "generally wanders from place to place, usually within a well-defined range.", "omnivore", "an animal that mainly eats all kinds of things, including plants and animals", "scent marks", "communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them", "seasonal breeding", "breeding is confined to a particular season", "sedentary", "remains in the same area", "social", "associates with others of its species; forms social groups.", "solitary", "lives alone", "stores or caches food", "places a food item in a special place to be eaten later. Also called \"hoarding\"", "suburban", "living in residential areas on the outskirts of large cities or towns.", "swamp", "a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.", "tactile", "uses touch to communicate", "temperate", "that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).", "terrestrial", "Living on the ground.", "territorial", "defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement", "tropical", "the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.", "tropical savanna and grassland", "A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.", "savanna", "A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.", "temperate grassland", "A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.", "urban", "living in cities and large towns, landscapes dominated by human structures and activity.", "visual", "uses sight to communicate", "viviparous", "reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.", "Disclaimer:", "The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.", "This material is based upon work supported by the", "National Science Foundation", "Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services." ], [ "Geographic Range", "The Ethiopian wolf has a very restricted range. It is found only in six or seven mountain ranges of Ethiopia. This includes the Arssi and Bale mountains of southeast Ethiopia, the Simien mountains, northeast Shoa, Gojjam, and Mt. Guna (Ginsberg and Macdonald 1990). The largest population exists in the Bale Mountains National Park with 120-160 individuals (Sillero-Zubiri and Gottelli 1995).", "Physical Description", "Ethiopian wolves are long-limbed, slender looking canids. They have a reddish coat with white marking on the legs, underbelly, tail, face, and chin. The boundary between the red and white fur is quite distinct. White markings on the face include a characteristic white crescent below the eyes and a white spot on the cheeks. The chin and throat are also white. The tail is marked with an indistinct black stripe down its length and a brush of black hairs at the tip. The ears are wide and pointed and the nose, gums, and palate are black. Females are generally paler in color than males and are smaller overall. There are five toes on the front feet and four on the rear feet. Males measure from 928 to 1012 mm (average 963 mm) and females from 841 to 960 mm (average 919 mm). Males weigh from 14.2 to 19.3 kg (average 16.2) and females from 11.2 to 14.2 kg (average 12.8). The tail is from 270 to 396 mm in length. The dental formula is 3/3:1/1:4/4:2/3, with the lower third molar being absent occasionally. (Sillero-Zubiri and Marino, 1995)", "Reproduction", "For Ethiopian wolves, dispersal from their native packs is limited due to habitat saturation. Males generally remain in their natal pack, and a small number of females disperse in their second or third year. To combat this high potential for inbreeding inside the closely related pack, matings outside the pack occur frequently. Copulation outside the pack occurs with males of all rank, but those within the pack occur only between the dominant male and female. While copulation between males and subordinate females does occur, pups that may arise from this union rarely survive (Sillero-Zubiri et al. 1996).", "Prior to copulation, the dominant female increases her rate of scent marking, play soliciting, food begging towards the dominant male, and aggressive behavior towards subordinate females. Ethiopian wolves mate over a period of 3-5 days, involving a copulation tie that lasts up to 15 minutes.", "It is not uncommon for a subordinate female to assist in suckling the young of the dominant female. In these cases, the subordinate lactating female is likely pregnant and either loses or deserts her own young for those of the dominant female.", "Once a year between October and January, the dominant female in each pack gives birth to a litter of 2-6 pups. Gestation lasts approximately 60-62 days. The female gives birth to her litter in a den she digs in open ground under a boulder or in a rocky crevice. The pups are born with their eyes closed and no teeth. They are charcoal gray with a buff patch on their chest and under areas. At about 3 weeks, the coat begins to be replaced by the normal adult coloring and the young first emerge from the den. After this time, den sites are regularly shifted, sometimes up to 1300m.", "Development of the young occurs in three stages (Sillero-Zubiri and Gottelli 1994). The first covers weeks 1-4 when the pups are completely dependent on their mother for milk. The second occurs from week 5-10 from when the pups' milk diet is supplemented by solid food regurgitated from all pack members. It ends when the pups are completely weaned. Finally, from week 10 until about 6 months, the young survive almost solely on solid food provided from adult members of the pack. Adults have been seen providing food for young up to 1 year old. The Ethiopian wolf attains full adult appearance at 2 years of age, and both sexes are sexually mature during their second year (Sillero-Zubiri and Gottelli 1994). Data on life expectancy is inadequate, but C. simensis is likely to live 8-9 years in the wild (Macdonald 1984).", "Lifespan/Longevity", "Ethiopian wolves may live 8 to 10 years in the wild, although one wild individual was recorded living to 12 years. (Sillero-Zubiri and Marino, 1995)", "Range lifespan Status: wild", "12 (high) years", "Typical lifespan Status: wild", "10 (high) years", "Behavior", "Although it primarily does its hunting alone, C. simensis is a social animal, forming packs of 3-13 individuals (mean 6). Packs congregate for social greetings and border patrols at dawn, midday, and evening, but forage individually during the rest of the day. The Ethiopian wolf is diurnal and sleeps in the open during night, alone or in groups. Pack structure is hierarchical and well defined by dominant and submissive displays as seen with other canids. Each sex has a dominance rank with shifts occurring in males occasionally but not in females. Play-fighting among pups in the first few weeks begins to establish rank between siblings (Sillero-Zubiri and Gottelli 1994).", "Ethiopian wolf packs are territorial. C. simensis travels in packs to patrol its territory. Packs maintain the boundaries of their territories by scent marking and vocalization. Home ranges of packs are small for a canid of its size. The typical home range is 4-15 square kilometers with an average wolf density of 1/square kilometer. Skirmishes between neighboring packs are frequent.", "Canis simensis makes several types of vocalization. Alarm calls are emitted at the sight or scent of man, dogs, or unfamiliar wolves. They start with a \"huff\" and are followed by a series of \"yelps\" and \"barks.\" Greeting calls consist of \"growls\" of threat, high-frequency \"whines\" of submission, and \"group yip-howls\" given at reunion of pack members. Also, \"lone howls\" or \"group howls\" can be heard 5 km away and are used for long distance communication (Sillero-Zubiri and Gottelli 1994).", "Communication and Perception", "Food Habits", "Canis simensis is a carnivore, generally preying on rodents ranging in size from the giant mole-rat Tachyoryctes macrocephalus (900 g) to that of the common grass rats (Arvicanthis blicki, Lophuromys melanonyx; 90-120 g) (Ginsberg and Macdonald 1990). In 689 feces, murid rodents accounted for 95.8% of all prey items, and 86.6% belonged to the three species listed above (Sillero-Zubiri and Gottelli 1994). When present in the hunting range, giant mole-rats are the primary component of the diet. In its absence, the common mole-rat Tachyoryctes splendens is most commonly eaten (Malcom 1997). Canis simensis also eats goslings, eggs, and young ungulates (reedbuck and mountain nyla) and occasionally scavenges carcasses. The Ethiopian wolf often caches its prey in shallow holes (Ginsberg and Macdonald 1990).", "Prey is usually captured by digging it out of burrows. Areas of high prey density are patrolled by wolves walking slowly. Once prey is located, the wolf moves stealthily towards it and grabs it with its mouth after a short dash. Occasionally, the Ethiopian wolf hunts cooperatively to bring down young antelopes, lambs, and hares (Sillero-Zubiri and Gottelli 1994).", "Ecosystem Roles", "Ethiopian wolves are top predators in the ecosystems in which they live.", "Economic Importance for Humans: Positive", "Canis simensis helps control populations of rodents in its habitat.", "Economic Importance for Humans: Negative", "The Ethiopian wolf occasionally preys on lambs (Sillero-Zubiri 1995).", "Conservation Status", "Ethiopian wolves are considered endangered by both the IUCN and U.S. Endangered Species Act. They are protected from hunting under Ethiopian law. Effort to curb the transmission of diseases, especially rabies, to Ethiopian wolves from domestic dogs and to prevent hybridization with domestic dogs have been undertaken. In addition, monitoring of Ethiopian wolf populations continues. (Sillero-Zubiri and Marino, 1995)", "Other Comments", "A recent genetic study suggests that the C. simensis is more closely related to gray wolves and coyotes than any other African canid (jackals, foxes, wild dogs). It is hypothesized that C. simensis is an evolutionary remnant of a past invasion of North Africa by gray wolf-life ancestors (Gottelli et al. 1994).", "Contributors", "Andrew Bunker (author), University of Michigan-Ann Arbor.", "Glossary", "Ethiopian", "living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.", "altricial", "young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.", "bilateral symmetry", "having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.", "carnivore", "an animal that mainly eats meat", "carrion", "flesh of dead animals.", "chemical", "uses smells or other chemicals to communicate", "cooperative breeder", "helpers provide assistance in raising young that are not their own", "crepuscular", "active at dawn and dusk", "diurnal", "active during the day, 2. lasting for one day.", "dominance hierarchies", "ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates", "endothermic", "animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.", "monogamous", "Having one mate at a time.", "motile", "having the capacity to move from one place to another.", "mountains", "This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.", "native range", "the area in which the animal is naturally found, the region in which it is endemic.", "nocturnal", "active during the night", "sexual", "reproduction that includes combining the genetic contribution of two individuals, a male and a female", "social", "associates with others of its species; forms social groups.", "solitary", "lives alone", "stores or caches food", "places a food item in a special place to be eaten later. Also called \"hoarding\"", "tactile", "uses touch to communicate", "temperate", "that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).", "terrestrial", "Living on the ground.", "territorial", "defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement", "tropical savanna and grassland", "A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.", "savanna", "A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.", "temperate grassland", "A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.", "Disclaimer:", "The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.", "This material is based upon work supported by the", "National Science Foundation", "Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services." ], [ "Wolf Habitat", "Wolf Habitat and Distribution", "Wolves are the wild dogs of the world, and they have a vast distribution that exists in many types of habitats. They are very diverse animals. For this reason, they have a habitat that is very spread out around the world. It isn’t true that they only live in very thick forests and come out at night. Wolves have been identified in many areas that you may not even imagine them being able to survive.", "In the wild, wolves are seen to thrive in forested areas and grasslands but also exist in steppes, tundra, boreal forests, and deserts. Their extreme adaptability is surprising to many because many wild dogs usually favor one type of habitat. Their versatility is amazing and it has helped them to survive despite their status as an endangered animal.", "Most wolves are classified according to where they live and the type of vegetation that surrounds them. The coats, habitats, and classifications are all linked and habitat.", "Wolf Classification", "To classify unique species of wolves requires extensive knowledge about the wolf species and their behavior, as well as a thorough understanding of how they develop.", "There are many different species of wolf, each unique in appearance and mannerism. Many are considered hybrids of the gray wolf, the common ancestor of all wolves.", "Here are some categories of wolves that people often find to be controversial:", "African Wolf", "The African wolf is a medium-sized canid with golden to ginger-colored fur, lightly built, and relatively long legs and ears. Its coat is generally a tawny yellow to the buff color brown. It carries a characteristic black mark on its forelegs and chest, with a fainter one on its shoulders. The ears are relatively large and pointed.", "Gray Wolf", "A gray wolf is a canine with long bushy tails that are often black-tipped. Its coat color is typically a mix of gray and brown with buffy facial markings that extend down to the lower abdomen but the color can vary from solid white to brown or black.", "Red Wolf", "Nocturnal and territorial, the red wolf is a master hunter, capable of taking down prey three times its size. It has a mottled gray coat with long legs and black-tipped ears.", "Indian Plain wolf", "The Indian wolf is one of the largest subspecies of the grey wolf, comparable to the Arabian wolf and Himalayan wolf. Its fur is comparatively short and sleek, with colors ranging from almost white to dark grey or black. It occurs in a wide range of habitats across India and Nepal, although it generally avoids densely populated areas.", "Arabian Wolf", "The Arabian wolf is the smallest wolf subspecies and a desert-adapted subspecies that normally lives in small groups. It is omnivorous, eating small to medium-sized prey. With a genetic similarity to the Ethiopian wolf, it is thought that they are ancestors of each other.", "Polar Wolf (Arctic Wolf)", "The Arctic or polar wolf, also known as the white wolf or polar wolf, is a subspecies of grey wolf native to Canada’s Queen Elizabeth Islands. Its habitat is located around the Arctic Circle. It is larger than mainland gray wolves and is mostly covered with fur and few spots.", "Eurasian Wolf", "The Eurasian wolf is the largest of all grey wolf subspecies. It has a large range throughout continental Eurasia and currently exists in the wild in Eastern Europe, Middle Asia (excluding China), Central Asia, and the Himalayas. It has also been introduced to Northern America, Italy, and Japan. Wild Eurasian wolves are now rare in Western Europe. However, they can be found in the Balkans, France, Germany, and around the borders of Russia.", "Where can you find wolves?", "Like any predator, wolves tend to be found in places of an abundant supply of prey. This is why we find them in areas inhabited by deer, caribou, elk, and other herbivores.", "Some wolves species only live in the United States in forests and other areas where animals are plentiful to consume due to their dietary needs. Others live in the cold Arctic regions where there are hardly any other animals surviving there due to the bitter cold.", "There are wolves found in the mountain ranges of Colorado thanks to some reintroduction programs along the Rockies that have been very successful. Regardless of the location, these animals need to have room to roam around. Their home range can be from 33 to 6,200 km2. It will depend on the type of wolf and where they happen to reside.", "Also, research has found evidence of wolves living all along the Northern Hemisphere even though they do not have large numbers of wolves. They can be found along the plains, in the savannah deserts of Africa, and in forests that have both hardwood and softwood. As long as their basic needs are met, they can survive. Wolves are also able to adapt and propel into new territory when necessary for their survival.", "An arctic wolf in the snow", "How wolves live in the Alaskan tundra", "Most of the wolves left in the world today are found living on the frozen tundra of Alaska and Canada. Here they can live in remote areas and not be bothered like they are in other places where humans are more likely to settle. Even so, it doesn’t mean they aren’t in jeopardy due to a lack of food. Hunters go to those areas as well in the hopes of being able to successfully kill wolves.", "Wolves spend about 8 or 10 hours every day moving through their home range. They will rarely stay in one place for too long of a period. They mark their habitat with urine as well as a scent that comes from glands in their tails. These markers are to let other wolves know that such territory has already been claimed.", "It is not unprecedented for the habitat of a pack of wolves to overlap with that of other wolf packs. Generally, this is very peaceful since the different wolf packs avoid each other. However, when the size of the habitat is reduced and when food is hard to find, they can become more aggressive towards each other.", "The leading reason why wolves out there today continue to have a hard time surviving comes down to the fact that their habitat is being destroyed. People continue to want more land to place their homes on or their ranches. Businesses continue to tear down the areas that these animals inhabit. Without a vast habitat for them to live in, they struggle to find enough survival food.", "That is why they seem to be attacking more domesticated animals. They need a source of food and when that is placed in front of them, they aren’t able to differentiate between that and what nature offers them. Wolves have a bad reputation for being destructive but when you view the whole picture you will see that humans are the ones responsible for taking away their habitat.", "Where do wolves roam in Africa?", "Wolves have long been associated with Africa’s stories and pictures about wild animals. But the truth about where they actually live on the continent is surprising. In some countries, such as Ethiopia, they are often viewed as dangerous animals since livestock can be an easy target for wolves. However, they are also protected due to being a part of the country’s natural heritage.", "The Serengeti wolf is a subspecies of gray wolves. It is native to Africa and primarily found in the Serengeti region of Tanzania. While the Serengeti wolf is considered endangered, recent conservation efforts have helped maintain its population, estimated at 1,500 to 2,000 individuals.", "Other places you can find African wolves are: in the tall grass savannas of Botswana, Ethiopia, Kenya, Mozambique, Namibia, Rwanda, South Africa, and Sudan.", "Wolf footprints in Europe and Asia", "The wolf has a long history in Europe and Asia. In the early 20th century, wolves were seen as predators that needed to be eradicated from these regions. It was thought that they were going to completely wipe out the entire population of reindeer.", "However, the wolf populations were not entirely exterminated from western Europe and Asia in the mid-to-late-20th century. Many wolf populations continued to exist in wilderness areas, away from human influence. As a consequence of the increasing human population and economic growth, these areas have become surrounded by farms and cities. Human persecution of wolves is now considered one of the direct threats to wolf populations.", "Europe and Asia today represent a vast region with many different kinds of wolves. Wolves present across the region, however, can be divided into two types. Gray wolves and red wolves. Gray wolves (Canis lupus) are the most common wolf species in Europe and Asia today. These wolves are easily recognized by their large size, shaggy pelt, and bushy tail. They generally live in packs but can sometimes be found living in pairs as well.", "Deforestation and Wolves Habitat", "In several important respects, wolves are dependent upon the integrity of their habitat. The management of prey in places outside the species’ core range is also heavily influenced by habitat and ecosystem health.", "Deforestation has had a substantial effect on the way of life of the wolves. It interferes with the prey, habitat, and even the ecosystem balance. As a result, they have less food to hunt. Which increases tensions and leads to wolf attacks on humans.", "Diversity is Good, Even for Wolves", "Over the past half-century, wolves have undergone a dramatic recovery in North America. Back from the brink of extinction, their populations are now flourishing in many regions. Despite the threat to wolves’ habitat and existence, their diversified species have allowed them to survive for a long time. This characteristic has seen them withstand a lot of ecological and human stress. Although many conservation processes are going on, humans have to take a firm decision to protect the existence and habitat of these creatures to avoid extinction." ], [ "The African golden wolf (Canis lupaster) is a canine that plays a prominent role in some African cultures. It was previously classified as an African variant of the Golden jackal. In 2015, a series of analyses on the species' mitochondrial DNA and nuclear genome demonstrated that it was, in fact, distinct from the Golden jackal, and more closely related to the Gray wolf and the coyote.", "Appearance", "The African golden wolf has a relatively long snout and ears, and a comparatively short tail. Fur color varies individually, seasonally, and geographically, though the typical coloration is yellowish to silvery grey, with slightly reddish limbs and black speckling on the tail and shoulders. The throat, abdomen, and facial markings are usually white, and the eyes are amber-colored. Females bear two to four pairs of teats. Although superficially similar to the Golden jackal (particularly in East Africa), the African golden wolf has a more pointed muzzle and sharper, more robust teeth. The ears are longer in the African wolf, and the skull has a more elevated forehead.", "The African golden wolf is commonly found in Africa in the northeast and northwest, in the east from Senegal to Egypt, throughout Libya, Algeria, and Morocco in the north, and in the south to Chad, Nigeria, and Tanzania. African golden wolves are adapted to live in different habitats; in Algeria, they occur in the Mediterranean, coastal and hilly areas (including hedged farmlands, scrublands, pinewoods, and oak forests), while populations in Senegal inhabit tropical, semi-arid climate zones including Sahelian savannahs. Populations in Mali have been documented in arid Sahelian massifs. In Egypt, the African these animals inhabit agricultural areas, wastelands, desert margins, rocky areas, and cliffs. At Lake Nasser, they live close to the lakeshore.", "Biome", "Climate zones", "Habits and Lifestyle", "The African golden wolf's social organization is very flexible and differs according to the food that is available. The breeding pair is the basic unit, along with its current offspring, and perhaps members of previous litters staying on as \"helpers\". Big groups are rare, only observed in areas where there is much human waste. Relationships within African golden wolf families are comparatively peaceful. The wolves will lie with each other and groom each other. They are more active in the daytime. These animals are very territorial, with the pair patrolling and marking their territory in tandem. Both of the partners, as well as their helpers, will behave aggressively towards intruders, in particular those of the same sex. Partners do not help each other repel intruders which are the opposite sex. African golden wolves frequently groom one another, particularly during courtship, which can last up to 30 minutes. When greeting they nibble the face and neck of one another. When fighting, African golden wolves slam their opponents with their hips and bite and shake the shoulder. Their vocalizations are similar to those of the domestic dog, with seven sounds having been recorded, including howls, barks, growls, whines, and cackles. Subspecies can be recognized by differences in their howls. One of the most commonly heard sounds is a high, keening wail, of which there are three varieties; a long single-toned continuous howl, a wail that rises and falls, and a series of short, staccato howls. These howls are used to repel intruders and attract family members. African golden wolves also howl in chorus; it is thought that they do so to reinforce family bonds and establish territorial status.", "Diet and Nutrition", "African golden wolves are carnivores and scavengers. They eat small prey, including hares, rats, grass cutters, ground squirrels, snakes, lizards and ground-nesting birds, francolins, and bustards. They also eat many insects, including dung beetles, termites, larvae, and grasshoppers. They will also hunt young gazelles, warthogs, and duikers, and eat animal carcasses, fruit, and human refuse.", "Mating Habits", "African wolves are monogamous. Their courtship rituals are extremely long, during which the pair stay almost constantly together. Before mating, they patrol and mark their territory with scent. After the gestation period of about 63 days, the female gives birth to a litter of 1 to 9 pups. In the Serengeti (in Eastern Africa), pups are born in December-January. They begin to eat solid food after one month. Weaning starts at the age of 2 months and ends at 4 months. By then the young can venture up to 50 m out from the den, being semi-independent, sometimes sleeping in the open. The mother feeds her pups more often than the father or helpers do. The playing behavior of the pups becomes increasingly more aggressive, as they compete for rank, this being established after 6 months.", "Population", "Population threats", "The main threat to the African golden wolf is the loss of its habitat. As the human population grows, it results in the expansion of roads, settlements, and agriculture, which threatens this species. Losing their habitat, African golden wolves invade human settlements, where people consider them a danger to livestock and poultry, and kill them as pests.", "Population number", "The IUCN Red List and other sources don’t provide the number of the African golden wolf total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.", "Ecological niche", "As African golden wolves consume garbage and animals’ carcasses, they play a very important role in the ecosystem as scavengers. They also control increases in rodents and insect numbers, consuming them as prey items.", "Fun Facts for Kids", "African golden wolves often carry away more food than they can consume and cache the surplus, which is generally recovered within 24 hours.", "African golden wolves can catch grasshoppers and flying termites either in mid-air or by pouncing on them while they are on the ground.", "African golden wolves are fiercely intolerant of other scavengers. They dominate vultures on kills and one wolf can hold dozens of vultures at bay by threatening, snapping, and lunging at them.", "African golden wolves often feed alongside Spotted hyenas, though they will be chased if they approach too closely. Spotted hyenas in turn sometimes follow wolves during the gazelle fawning season, as wolves are effective at tracking and catching young animals.", "According to Arab Egyptian folklore the African golden wolf can cause chickens to faint from fear by simply passing underneath their roosts." ], [ "Dog domestication likely started in N. Africa", "Modern humans originated in Africa, and now it looks like man's best friend first emerged there too. An extensive genetic study points to a Eurasian — possibly North African — origin for the domestication of dogs.", "A Basenji is a dog breed indigenous to sub-Saharan Africa. Humans might have first domesticated dogs from in Africa, with Egypt being one possibility, since wolves are native to that region. iStockPhoto", "Aug. 3, 2009, 11:03 PM UTC / Source: Discovery Channel", "By By Jennifer Viegas", "Modern humans originated in Africa, and now it looks like man's best friend first emerged there too.", "An extensive genetic study on the ancestry of African village dogs points to a Eurasian — possibly North African — origin for the domestication of dogs.", "Prior research concluded that dogs likely originated in East Asia. However, this latest study, the most thorough investigation ever on the ancestry of African village dogs, indicates otherwise.", "\"Village\" dogs are local, semi-feral dogs that cluster around human settlements in much of the world.", "\"I think our results cast some doubt on the hypothesis of an East Asian origin for dog domestication that was put forward based on previous mitochondrial DNA genetic research,\" lead author Adam Boyko told Discovery News.", "Boyko, a research associate in the Department of Biological Statistics and Computational Biology at Cornell University, and his colleagues looked at three genetic markers for 318 village dogs from seven regions in Egypt, Uganda and Namibia. The scientists performed the same DNA analysis on a number of putatively African dog breeds, as well as on Puerto Rican street dogs and mixed breed dogs from the United States.", "The scientists determined genetic diversity was just as high for the African dogs as it was for the East Asian village dogs that were the focus of the earlier research.", "\"Species tend to show the highest genetic diversity near their place of origin,\" said Boyko. He explained that this is because the species have \"been there longer and therefore have had more time to accumulate diversity, and because as a species expands its range by colonizing a new region, it usually does so with a relatively small band of individuals carrying just a subset of the genetic diversity found in the ancestral population.\"", "Humans might have then first domesticated dogs from wolves in Africa, with Egypt being one possibility, since wolves are native to that region. Many existing wild species of canid, such as the Egyptian jackal, popularly featured in ancient Egyptian art, are now critically endangered.", "The new study, published in the latest issue of the Proceedings of the National Academy of Sciences, also found that some so-called \"African\" dog breeds are not really native to Africa. These include Pharaoh hounds and Rhodesian ridgebacks, which turned out to not have much indigenous African ancestry.", "On the other hand, \"Basenjis are clearly an indigenous sub-Saharan breed, and Afghan hounds and Salukis appear to be indigenous to North Africa or the Middle East,\" Boyko said.", "The pattern seems to be that if a region was colonized or otherwise settled by Europeans, dogs of that area now tend to be less indigenous. Dogs in central Namibia, for example, \"looked nearly identical genetically to dogs you would find on the streets of Puerto Rico or in animal shelters in the U.S., a pretty clear indication that these are mixes of various modern breeds.\"", "Robert Wayne, an expert on wolves and dog domestication and a professor in the Department of Ecology and Evolutionary Biology at UCLA, told Discovery News that he supports the new findings.", "\"It's clear dogs did not originate in sub-Saharan Africa, since wolves are not native to that area,\" asserts Wayne. However, he agrees that Eurasia is the more likely overall place where dogs were first domesticated, with Egypt being a possibility.", "Both Wayne and Boyko hope future genetic research on canines will continue to shed light on the origins of indigenous dog populations to better confirm and pinpoint exactly where the domestication of dogs first happened." ], [ "Wolves in South Africa???", "No, wolves are not native to South Africa, but that hasn't stopped people from bringing them in and then abandoning them. Same with wolf dogs. Obviously, these guys should never be turned loose into the South African wild since they're not native, so it's wonderful that this sanctuary exists. They do a marvelous job and the wolves, in three packs, have enough room to run and play. A worthy place to visit and to support.", "Date of experience: August 2019", "Ask jmaison about Garden Route Wolf Sanctuary", "Thank jmaison", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "Disappointed. Expected much more, especially because of the reviews. No guide provided. Roaming around aimlessly. No one to ask questions. No one available to even point us in any direction. Wolves are not endemic to Africa. So, not really an authentic experience.", "But the animal farm is fun petting expedience for the kids. Like that. But the place should just be marketed as that.", "Date of experience: August 2019", "Ask Ludmila Y about Garden Route Wolf Sanctuary", "Thank Ludmila Y", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "We were pleasantly surprised by this sanctuary. It is a must see for any animal lover. The guides are totally dedicated to the wolfs, wolf dogs and huskies. You can see the mutual love and trust in each and every one, both human and animal. The animals look happy and you can see they are well taken care off. There is lots more to see, but the wolves are the absolute high light!! Loved, loved it! Will recommend it to old and young! Pay the bit extra for the guided tour, it is very informative and you get to go into the enclosures.", "Date of experience: August 2019", "Ask Jamien S about Garden Route Wolf Sanctuary", "Thank Jamien S", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "You must visit this sanctuary if you have interest in animals and pets. We had the guided tour and we realised that there is a huge difference between dogs and wolves. There is also a touch farm with farm animals, alwways a treat to get close to animals.", "Date of experience: July 2019", "Ask willems170 about Garden Route Wolf Sanctuary", "Thank willems170", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "We last went to the Wolf sanctuary about 14 years ago but we remember not being too impressed then ! Our 10 year old has been begging us to take her as she loves wolves ! So after reading the excellent reviews we decided to go even though we prefer seeing animals in the wild ! Our 10 year old was too young for the guided tour but we hung around the guided tour and watched them go into some of the wolf areas! The wolves definitely seem to be love the guides and looked happy ! The fenced areas seem 100 percent better than before and the animals all look well and happy ! We also loved the farm yard animals especially the piglets and baby rabbits ! The Llamas were also very entertaining! My daughter is now going to adopt a wolf which she is so excited about and I can relax about knowing that the wolf is well taken care of at the Sanctuary and we can visit when we are there again!", "Date of experience: July 2019", "Ask mightymousemdsm about Garden Route Wolf Sanctuary", "Thank mightymousemdsm", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "Lovely experience seeing the wolves but there is also a farmyard with lots of lovely animals you can interact with including pigs, cows, goats, alpacas, monkeys, bunnies and many more! A lot of baby animals roaming around and you can pick up the bunnies, really wonderful experience!", "Date of experience: June 2019", "Ask Lsharp88 about Garden Route Wolf Sanctuary", "Thank Lsharp88", "This review is the subjective opinion of a Tripadvisor member and not of Tripadvisor LLC. Tripadvisor performs checks on reviews as part of our industry-leading trust & safety standards. Read our transparency report to learn more.", "This is the version of our website addressed to speakers of English in the United States. If you are a resident of another country or region, please select the appropriate version of Tripadvisor for your country or region in the drop-down menu." ], [ "Saving the critically endangered Ethiopian wolf from extinction", "Saving the critically endangered Ethiopian wolf from extinction", "About the Author", "Jacqueline Conciatore is African Wildlife Foundation's Writer & Editorial Manager. She oversees the development of articles and other content for AWF print marketing products such as the annual report. She is passionate about using storytelling and compelling content to convey the value and s ...", "More", "To make the greatest conservation impact, AWF uses a range of strategies to protect species in priority landscapes. Though our work is organized around iconic wildlife such as elephants, rhinos, and large carnivores, we design our programs to benefit local human communities as well as all indigenous wildlife and habitats. Among the key species we focus on is one of the world’s rarest canids, the Ethiopian wolf.", "Also known as the Simien fox or Simien jackal, this highland wolf numbers no more than 440, and perhaps as few as 360, making it Africa’s most endangered carnivore. Although scientists debate which canids are wolf species versus subspecies, the traditional view is that there are three wolf species in the world — the Ethiopian, red, and grey wolf. The Ethiopian wolf is the only wolf species native to Africa and is found in only seven Ethiopian mountain ranges, with the largest populations in the Bale Mountains and the second largest in the Simien Mountains.", "Endemic and endangered", "With a somewhat regal bearing, the Ethiopian wolf is the size of a coyote and looks like a red fox, sporting a tawny orange or reddish coat, white throat patch, and bushy tail. It has a narrow muzzle, long legs, and pointed ears.", "Although shy around humans, it is social with other wolves, living in packs that typically include extended family members male and female. All pack members help with raising and protecting pups.", "Wolf mothers give birth in dens dug under boulders, inside crevices or in other protected spots. These dens can have multiple entrances and a network of tunnels, and the adults regularly shift pups from one den to another.", "For food, the Ethiopian wolf depends on high-altitude rodents, especially the big-headed mole-rat, which tunnels to foraging spots but feeds above ground. The Ethiopian wolf is a loner when hunting, but even here it may rely on others for help. Scientists have noted that Ethiopian wolves forage right in the middle of gelada herds, large groups of primates of also known as “bleeding heart monkeys”. The wolves do not prey upon the geladas’ young, and the geladas do not flee from the wolves like they do from feral dogs. Researchers have found the wolves capture rodents at twice the rate when hunting in a gelada group. It is not clear why they have greater success; perhaps the geladas flush rodents out of their burrows by disturbing vegetation. Or, it could be the wolves blend in with the scattered geladas, and the rodents simply do not notice them.", "Community-led initiatives safeguard the Ethiopian wolf", "With numbers so small, Ethiopian wolves are highly vulnerable to disease outbreaks, and in the past few years, they have experienced devastating rabies and distemper outbreaks. AWF supports the Ethiopian Wolf Conservation Programme, which administers rabies and distemper vaccines to the wolves, but also to area domestic dogs, who can carry rabies and pose a significant disease threat if not vaccinated. To date, the program has vaccinated tens of thousands of dogs.", "In partnership with the Ethiopian government, the Ethiopian Wolf Conservation Programme also recruits local community members to act as Wolf Monitors and Wolf Ambassadors who track wolf populations and share conservation messages in communities. The monitors are very dedicated and work through all kinds of conditions to follow the wolf packs and keep up with their status and life events. This work is critical to ensuring a rapid response in the case of disease outbreaks.", "AWF’s work in Ethiopia incorporates our Classroom Africa program. In exchange for a conservation commitment from the Adisge community near Simien Mountains National Park, Classroom Africa rebuilt the community’s badly under-resourced school.", "The new Adisge Primary School opened its doors in 2017. For the first time, the school has enough space to enroll 7th and 8th graders. The re-design has made the Adisge school eco-friendly and comfortable, and the site includes new teacher housing as well.", "Classroom Africa fosters a conservation ethic among young people through eco-clubs and field trips to national parks and other protected areas. The goal is to develop a new generation of local conservation leaders who will be passionate about protecting wildlife.", "AWF also has invested in high-end eco-lodges in the Simiens and Bale Mountains parks that help create jobs from nature-based tourism. In addition, we support the Ethiopian Wildlife Conservation Authority, which manages both parks, to improve park infrastructure, management and strategically promote tourism." ], [ "GUARDIANS OF THE", "WOLVES", "learn all about wolves", "Families love meeting and interacting with our wolves. Bring a picnic basket and the whole family for an interactive and exciting outing.", "Join Our Wolf Pack", "Our volunteer program provides a unique opportunity to learn from our team as to how best to provide for the wolves daily and how to ensure their safety.", "Meet Our", "Wolf Pack", "Opened in 2001 in the beautiful Tsitsikamma area of South Africa, The Tsitsikamma Wolf Sanctuary (TTWS) provides a home and safe haven for unwanted and abused wolves and wolf dogs. A non-profit organisation, and the first to open in the country, our sanctuary aims to create awareness by informing and educating visitors", "through a once-in-a-lifetime encounter.", "Escape to the great outdoors, spend the day soaking up the impressive surroundings and, guided by our knowledgeable and passionate staff, get to meet these magnificent animals in surroundings", "What people had to say", "What they do here is amazing for creatures who aren't native to South Africa. The wolves are clearly well taken care of, and they don't breed any animals. I was very impressed with the tour and the stories behind each pack.", "Merilyn Prinsloo", "It was good to see all wolves and to be near them and learn about them", "George Wyatt", "Awesome work they are doing as a sanctuary for wolves!", "Eleanore Eades", "An experience like no other. I so loved learning about the wolves and getting to interact with them so closely. Thank you Robin and team for your dedication, passion, and knowledge.", "Megan Kelly Botha", "Our two little animal lovers, ages 5 and 8 loved it. Andrew was knowledgeable and a great guide.", "James Wyatt", "About Us", "The Tsitsikamma Wolf Sanctuary is a non-profit organisation in the Eastern Cape of South Africa providing a safe haven for abused and abandoned wolves." ] ]

[ "https://www.cnn.com/2020/08/18/australia/penguins-origin-australia-nz-intl-hnk-scli-scn/index.html", "https://indianapublicmedia.org/amomentofscience/where-did-penguins-come-from.php", "https://www.jpost.com/health-science/penguins-originate-from-australia-new-zealand-new-study-finds-639150", "https://www.conicet.gov.ar/sixty-million-years-of-information-on-penguins/", "https://www.nature.com/articles/s41467-022-31508-9", "https://www.pnas.org/post/podcast/origin-and-diversification-penguins", "https://www.mdpi.com/1424-2818/14/4/255", "https://pubmed.ncbi.nlm.nih.gov/16519228/" ]

[ "refute", "refute", "refute", "refute", "refute", "refute", "support", "support" ]

[ [ "Penguins originated in Australia and New Zealand – not the Antarctic, new study finds", "Penguins play before mating on King George island in Antarctica, in March 2014.", "VANDERLEI ALMEIDA/AFP/Getty Images/file", "CNN", "—", "When you think of the penguin, the image that pops to mind is usually the fuzzy bird waddling through snow or swimming in frigid Antarctic waters.", "But penguins didn’t originate in Antarctica, as scientists have believed for years – they first evolved in Australia and New Zealand, according to a new study by researchers at the University of California, Berkeley.", "The study, which was conducted in collaboration with museums and universities around the world, analyzed blood and tissue samples from 18 different species of penguins. They used this genomic information to look back in time, and trace the penguins’ movement and diversification over millennia.", "“Our results indicate that the penguin crown-group originated during the Miocene (geological period) in New Zealand and Australia, not in Antarctica as previously thought,” said the study, published on Monday in the Proceedings of the National Academy of Sciences. “Penguins first occupied temperate environments and then radiated to cold Antarctic waters.”", "Penguins originated in Australia and New Zealand 22 million years ago, researchers suggest; then, ancestors of the king and emperor penguins split off and moved to Antarctic waters, likely attracted by the abundant food supply there.", "A penguin dives from an ice block in Antarctica in March 2014.", "VANDERLEI ALMEIDA/AFP/Getty Images/file", "These findings also support the theory that king and emperor penguins are the “sister group” to all other penguin lineages – adding another piece to the long-debated puzzle on where exactly these two species sit on the family tree.", "Then about 12 million years ago, the Drake Passage – the body of water between Antarctica and the southern tip of South America – fully opened up. This allowed the penguins to swim throughout the Southern Ocean, and spread more widely to sub-Antarctic Islands as well as the warmer coastal regions of South America and Africa.", "Today, the flightless birds are still found in Australia and New Zealand – as well as Antarctica, South America, the South Atlantic, southern Africa, the sub-Antarctic, Indian Ocean islands, and subtropical regions.", "During the study, researchers also discovered a new lineage of penguin that has yet to be given a scientific description.", "Penguins are adaptable – but not enough for climate change", "The study shed light on the penguins’ adaptability to changing climates – and on the danger they now face in the modern climate crisis.", "“We are able to show how penguins have been able to diversify to occupy the incredibly different thermal environments they live in today, going from 9 degrees Celsius (48 Fahrenheit) in the waters around Australia and New Zealand, down to negative temperatures in Antarctica and up to 26 degrees (79 Fahrenheit) in the Galapagos Islands,” said Rauri Bowie, one of the lead researchers and a professor of integrative biology at UC Berkeley, in a statement from the university.", "“But we want to make the point that it has taken millions of years for penguins to be able to occupy such diverse habitats, and at the rate that oceans are warming, penguins are not going to be able to adapt fast enough to keep up with changing climate.”", "The team was able to pinpoint genetic adaptations that allowed penguins to thrive in challenging environments; for example, their genes evolved to better regulate body temperature, which allowed them to live in both subzero Antarctic temperatures and warmer tropical climes.", "But these steps of evolution took millions of years – time that the penguins don’t have now, as their populations dwindle.", "“Right now, changes in the climate and environment are going too fast for some species to respond to the climate change,” said Juliana Vianna, associate professor at the Pontifical Catholic University of Chile, in the UC Berkeley statement.", "The different elements of climate change culminate in a perfect storm. Disappearing sea ice mean fewer breeding and resting grounds for emperor penguins. The reduced ice and warming oceans also mean less krill, the main component of the penguins’ diet.", "The world’s second-largest emperor penguin colony has almost disappeared; thousands of emperor penguin chicks in Antarctica drowned when sea ice was destroyed by storms in 2016. Reoccuring storms in 2017 and 2018 led to the death of almost all the chicks at the site each season.", "Some penguin colonies in the Antarctic have declined by more than 75% over the past 50 years, largely as a result of climate change.", "In the Galapagos, penguin populations are declining as warm El Nino events – a weather phenomenon that sees warming of the eastern Pacific Ocean – happen more frequently and with greater severity. In Africa, warming waters off the southern coast have also caused penguin populations to drop drastically." ], [ "Posted February 3, 2021", "Read Transcript", "Hide Transcript", "Transcript", "D: You mean my stuffed animal, Yaël? I won it from a claw machine. But, you know, scientists have been mulling over the same question—about real penguins, though. And after sequencing the genome of the 18 species of penguins that exist today, they have a pretty good idea how these evolved. The genetic evidence reveals that today’s penguin species originated in the coastal regions of Australia and New Zealand and nearby islands in the South Pacific about 22 million years ago—not in Antarctica, as many people once thought. They’ve been on an interesting evolutionary journey ever since, diversifying and spreading to all kinds of climates.", "Y: It’s not hard to imagine how they made their way to Antarctica, but there are penguin species all the way in South America and Africa, right? How did they get all the way up there?", "D: It all started about 12 million years ago, when Drake’s Passage between Antarctica and the southern tip of South America opened up fully and the Antarctic Circumpolar Current intensified, which caused the glaciation of Antarctica and drove penguins that hadn’t adapted to live in icy regions northward. Some ended up all the way in South America and Africa, and genetic adaptations let them thrive in these new places. These adaptations allowed them to refine how they regulate their body temperature, which made it possible for different species of penguins to live in climates as varied as Antarctica and regions close to the equator.", "Y: Or even claw machines in the United States.", "D: I’m not sure if the stuffed animal species was one of the 18 in this analysis.", "(Wikimedia Commons)", "Scientists have mulling over the origin of the penguin. And after sequencing the genome of the 18 species of penguins that exist today, they have a pretty good idea how these evolved. The genetic evidence reveals that today’s penguin species originated in the coastal regions of Australia and New Zealand and nearby islands in the South Pacific about 22 million years ago—not in Antarctica, as many people once thought. They’ve been on an interesting evolutionary journey ever since, diversifying and spreading to all kinds of climates.", "It's not hard to imagine how they made their way to Antarctica, but there are penguin species all the way in South America and Africa, too. So how did they get all the way up there?", "It all started about 12 million years ago, when Drake’s Passage between Antarctica and the southern tip of South America opened up fully and the Antarctic Circumpolar Current intensified, which caused the glaciation of Antarctica and drove penguins that hadn’t adapted to live in icy regions northward. Some ended up all the way in South America and Africa, and genetic adaptations let them thrive in these new places. These adaptations allowed them to refine how they regulate their body temperature, which made it possible for different species of penguins to live in climates as varied as Antarctica and regions close to the equator." ], [ "Penguins most likely originated in Australia and New Zealand 22 million years ago, before the ancestors of the emperor and king penguins relocated to Antarctica.", "A gentoo penguin dives into the water in its enclosure at the Sea Life aquarium in central London", "(photo credit: REUTERS)", "Advertisement", "A new study from the University of California, Berkley has found that contrary to widespread beliefs, penguins evolved in Australia and New Zealand rather than Antarctica.", "As part of a collaborative effort between museums and universities from across the globe, the researchers studied and analyzed 18 different penguin species. Using the genomic information obtained from blood and tissue samples, the scientists were able to trace the movement and diversification of the penguins throughout a period of over a thousand years.", "And the findings of this study may rewrite everything scientists know about the origin of these flightless birds.", "\"Our results indicate that the penguin crown-group originated during the Miocene (geological period) in New Zealand and Australia, not in Antarctica as previously thought,\" according to the study, published on Monday in the Proceedings of the National Academy of Sciences, CNN reported. \"Penguins first occupied temperate environments and then [relocated] to cold Antarctic waters.\"", "The researchers posit that penguins likely first originated 22 million years ago, living in what is now Australia and New Zealand. However, some of them, ancestors of the emperor penguins and king penguins, eventually relocated to Antarctica, most likely due to an abundant food supply.", "Eventually, around 10 million years later, the penguins were soon able to spread throughout the region. This is due to the body of water between Antarctica and South America – now known as the Drake Passage – fully opening up. As a result, penguins soon began to inhabit Antarctica, parts of Africa, parts of South America, some islands in the Indian Ocean and other subtropical regions. Indeed, some can even still be found in Australia and New Zealand, specifically the yellow-eyed, little and other crested penguins.", "Not only does this research rewrite the understood origin of penguins, it also sheds new light on the ability of these flightless birds to adapt to new climates.", "The study was able to pinpoint specific genetic adaptations the penguins used to thrive in new environments. This includes changes in genes used to regulate body heat, allowing them to survive in both subzero and tropical temperatures, an ability to dive deeper in the sea and osmoregulation – the process enabling them to survive on salt water without fresh water.", "In addition, the study also seems to resolve a longstanding debate regarding the emperor and king penguins, which has long been hypothesized to be a sister group to all other penguins, due to being the only two species in the Aptenodytes genus.", "“It was very satisfying to be able to resolve the phylogeny, which has been debated for a long time,” Rauri Bowie, professor of integrative biology at the University of California, Berkeley, and curator in the Museum of Vertebrate Zoology (MVZ) at Berkeley, said in a statement.", "“The debate hinged on where, exactly, the emperor and king penguins were placed in the family tree, whether they are nested inside the tree closer to other lineages of penguins or whether they are sisters to all the other penguins, which is what our phylogeny showed and some other previous studies had suggested. And it fits with the rich fossil history of penguins.”", "However, the study has also shed light on the challenges penguins face today due to climate change.", "“We are able to show how penguins have been able to diversify to occupy the incredibly different thermal environments they live in today, going from 9 degrees Celsius (48 F) in the waters around Australia and New Zealand, down to negative temperatures in Antarctica and up to 26 degrees (79 F) in the Galápagos Islands,” Bowie explained. “But we want to make the point that it has taken millions of years for penguins to be able to occupy such diverse habitats, and at the rate that oceans are warming, penguins are not going to be able to adapt fast enough to keep up with changing climate.”", "“We saw, over millions of years, that the diversification of penguins decreased with increasing temperature, but that was over a longtime scale,” explained Juliana Vianna, associate professor of ecosystems and environment at the Pontifical Catholic University of Chile in Santiago.", "“Right now, changes in the climate and environment are going too fast for some species to respond to the climate change.”", "Bowie and Vianna hope to build on this research, and plan to dive into the genetic variations found throughout the disparate populations of penguins.", "“Penguins are very charismatic, certainly,” Vianna concluded. “But I hope these studies also lead to better conservation.”", "The Jerusalem Post Customer Service Center can be contacted with any questions or requests:", "Telephone: *2421 * Extension 4 Jerusalem Post or 03-7619056", "Fax: 03-5613699", "E-mail: subs@jpost.com", "The center is staffed and provides answers on Sundays through Thursdays between 07:00 AM and 14:00 PM and Fridays only handles distribution requests between 7:00 AM and 12:30 PM", "For international customers: The center is staffed and provides answers on Sundays through Thursdays between 7AM and 14PM Israel time Toll", "Free number 1-800-448-9291", "Telephone +972-3-761-9056", "Fax: 972-3-561-3699", "E-mail: subs@jpost.com" ], [ "Contrary to popular belief, penguins did not originate in the Antarctic. They originated in microcontinent called Zealand (around present-day New Zealand) and from that starting point, some 60 million years ago, they began to disperse, to evolve, to transform. Pablo Borboroglu is a CONICET researcher at the Center for the Study of Marine Systems (CESIMAR, CONICET) and co-author of a recently published international study that analyzes, over time, the adaptations that allowed these animals to live in environments with the most extreme conditions on the planet. For this study, genetic samples of current penguins and fossil species were analyzed to learn in detail their origin and evolution. The results were published in Nature Communications.", "“The geneticists identified the DNA segments that determine the evolutionary characteristics related to vision, taste of prey, in the ability to oxygenate, to remain in apnea under water, the ability to generate fat, to resist cold. This type of fossil analysis included all penguin species, not just the eighteen that currently exist. Throughout history, penguins of many shapes and sizes have inhabited the planet, including one that is one of the oldest ones of New Zealand, which they called the Monster Penguin, an animal that weighed more than 80 kilos and is estimated to have reached 1.8 meters. Seventy-five percent of the species that existed are already extinct. Three quarters of the history of penguins no longer exists. Many species collapsed because of climate change but they can still give us a lot of information,” Borboroglu explains.", "Although there are previous studies that focused on the adaptive changes of penguins, this study includes a large number of genes from extinct species that will provide information on their adaptations over time. “Sampling of fossil penguins is crucial for understanding the environmental context, improving phylogenetic resolution and dating accuracy, and reconstructing biogeographical events,” says Borboroglu.", "Currently, penguins spend more that eighty percent of their lives in the water. The bodily adaptations that explain this ability come from the past. Penguins had already lost their ability to fly 60 million years ago, before the information of the polar ice caps. Since then, their life characteristics have been shaped by rising and falling temperatures, and their bodies are highly specialized for some of the most extreme conditions on Earth.", "“Some of the genes that were analyzed are related to vision and how it was adapted to look accurately underwater and facilitate the capture of prey. They can observe a wide range of ultraviolet colors that we do not see, and they have, on the other hand, a more limited possibility of seeing other colors such as red, the first color that stops being seen in the ocean. Another of the modifications is linked to taste. They can detect salty and bitter tastes, but not sweet or sour ones. This is related to the diet they eat. All these characteristics tend to improve the efficiency of these animals under the sea. An emperor penguin, for example, can stay underwater for up to twenty-three minutes and dive up to five hundred meters deep”, describes the researcher.", "Despite all the changes that these animals have been adopted and that have made them, possibly, the most uniquely specialized birds of all the existing ones, studies indicate that their possibilities of adaptation have diminished. “60 million years ago the rate of penguin evolution was very high but it slowed down. This is related to the sea surface temperature. At times when it was warmer, the rate dropped and vice versa. Larger penguins also had a higher rate because they generally live or have lived in more extreme environments. Penguins currently have the lowest rate of evolution of all birds. At the rate of environmental change taking place, this could present a conservation problem for penguins. That is why this type of study is of vital importance to know more and more precisely the adaptive capacities that these animals were acquiring and to think about them in the context of the challenges of the present." ], [ "Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain", "the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in", "Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles", "and JavaScript.", "Subjects", "Abstract", "Penguins lost the ability to fly more than 60 million years ago, subsequently evolving a hyper-specialized marine body plan. Within the framework of a genome-scale, fossil-inclusive phylogeny, we identify key geological events that shaped penguin diversification and genomic signatures consistent with widespread refugia/recolonization during major climate oscillations. We further identify a suite of genes potentially underpinning adaptations related to thermoregulation, oxygenation, diving, vision, diet, immunity and body size, which might have facilitated their remarkable secondary transition to an aquatic ecology. Our analyses indicate that penguins and their sister group (Procellariiformes) have the lowest evolutionary rates yet detected in birds. Together, these findings help improve our understanding of how penguins have transitioned to the marine environment, successfully colonizing some of the most extreme environments on Earth.", "Introduction", "Penguins are one of the most iconic groups of birds, serving as both a textbook example of the evolution of secondarily aquatic ecology and as sentinels for the impacts of global change on ecosystem health1. Although often associated with Antarctica in the popular imagination, penguins originated more than 60 million years ago (Mya), evolving wing-propelled diving and losing the capacity for aerial flight long before the formation of polar ice sheets2. Over time, penguins evolved the suite of morphological, physiological, and behavioral features that make them arguably the most uniquely specialized of all extant birds. These adaptations have allowed penguins to colonize some of the most extreme environments on Earth.", "Previous phylogenetic studies have yielded insights into penguin evolution, yet have been limited by sampling issues (e.g., number of lineages incorporated and quality of molecular markers3,4,5,6,7). Genomic studies have shed light on the diversification of extant penguins7,8,9 but have not integrated extinct species. Because nearly three-quarters of known penguin species are represented only by fossils (e.g., 2,3), sampling extinct species is crucial for improving phylogenetic resolution and dating accuracy, reconstructing biogeographic events, and understanding the environmental context in which key adaptations arose. While several studies have included fossil penguins, these utilized only mitochondrial genomes and/or small numbers of nuclear genes (e.g., 3,4,5,6), limiting their ability to disentangle confounding processes, such as historical and ongoing introgression and incomplete lineage sorting.", "Here, we take a comprehensive approach to inferring the tempo and drivers of penguin diversification by combining genomes from all extant and recently-extinct penguin lineages (27 taxa) (Table 1), stratigraphic data from fossil penguins (47 taxa), and morphological and biogeographic data from all species (extant and extinct) (Fig. 1 and Supplementary Fig. 1; Supplementary Data 1) into a single framework for Bayesian phylogenetic analysis. This combined approach, using the fossilized birth-death process with sampled ancestors4 (see supplementary methods) offers a more complete understanding of speciation and biogeographic events over the entire history of penguin evolution. It extends our insights beyond the ~15–20 million year (Ma) history of crown penguins to include the ~50 Ma interval during which only stem penguins existed. Within this phylogenetic framework, we highlight key genes involved in marine adaptations, compare evolutionary rates in penguins to those of other birds, and reconstruct the demographic histories of individual species. Together, these extensive datasets provide new insights into the evolution of extreme ecological preferences and the genetic basis for the adaptations that enabled penguins to occupy these niches.", "Results", "Climate change drove evolution, biogeography, and demography", "Phylogenetic results (Fig. 1 and Supplementary Fig. 2) confirm previous findings, recovering Aptenodytes (king and emperor penguins) as the sister clade to all other crown penguins, with brush-tailed (Pygoscelis) penguins in turn sister to two clades uniting the banded (Spheniscus) and little (Eudyptula) penguins and the yellow-eyed (Megadyptes) and crested (Eudyptes) penguins6,7,9. Biogeographical reconstructions (Fig. 1, Supplementary Figs. 3–4 and Supplementary Data 1) support a Zealandian origin for penguins6,7. Stem penguins radiated extensively in Zealandia before dispersing to South America and Antarctica multiple times, following the eastward-flowing direction of the Antarctic Circumpolar Current (ACC) (Fig. 1). Crown penguins most likely arose from descendant lineages in South America, before dispersing back to Zealandia at least three times. Interestingly, at least two such dispersals occurred before the inferred onset of the ACC system, suggesting that early stem penguins were not dependent on currents to disperse over long distances. A second pulse of speciation coincides with the onset of the ACC, though understanding whether this pattern is real or an artifact of fossil sampling requires more collecting from early Eocene localities. We infer an age of ~14 Ma for the origin of crown penguins, which is more recent than the ~24 Ma age recovered in genomic analyses, not including fossil taxa7 (Supplementary Fig. 2b) and coincides with the onset of global cooling during the middle Miocene climate transition4,10 (Supplementary Fig. 3a). This young age suggests that expansion of Antarctic ice sheets and the onset of dispersal vectors such as the Benguela Current11 during the middle to late Miocene facilitated crown penguin dispersal and speciation, as hinted at by fossil evidence12.", "Incongruences between species trees and gene trees were identified, e.g., alternate topologies occurred at high frequencies (>10%) for several internal branches (Fig. 1c; Supplementary Fig. 5). These patterns indicate that gene tree discordance may be caused by incomplete lineage sorting (ILS) or introgression events. By quantifying ILS and introgression via branch lengths from over 10,000 gene trees, we found that the rapid speciation within crown penguins was accompanied by >5% ILS content within the ancestors of Spheniscus, Eudyptula, Eudyptes, and several subgroups within Eudyptes (Fig. 2a). Our dated tree provides a temporal framework for this rapid radiation: the four extant Spheniscus taxa are all inferred to have split from one another within the last ~3 Ma, and likewise the nine extant Eudyptes taxa likely split from one another in that same time (Fig. 1b). Many closely related penguin species/lineages are known to hybridize in the wild (see supplementary methods). Consistent with this, multiple analyses suggest that introgression also contributes to species tree—gene tree incongruence (Supplementary Figs. 6–9 and Supplementary Data 2; also see Supplementary Methods for further details). This could explain the most notable conflict in previous phylogenetic results, which showed inconsistency over whether Aptenodytes alone7 or Aptenodytes and Pygoscelis together4,5 represent the sister clade to all other extant penguins. Introgression was detected between the ancestor of Aptenodytes and the ancestor of other extant penguins, and is inferred to have occurred when the range of these ancestors overlapped in South America (Fig. 2a and Supplementary Data 2). Introgression (>9%) was also detected between Eudyptula novaehollandiae and Eudyptula minor, and several introgression events were especially pervasive in Eudyptes (Fig. 2a and Supplementary Fig. 6).", "Many extant penguin lineages began to diverge within the last 3 Ma (Fig. 1). To obtain insight into this recent phase of penguin diversification, we inferred post-speciation introgression events and estimated the time when gene flow from introgression ceased between 20 pairs of closely related lineages (see Supplementary Methods). Our results provide further evidence for recent introgression between all sampled pairings (Fig. 2b) except for Eudyptes chrysocome and E. filholi, whose ranges are geographically disparate (Fig. 1a). Almost all species exhibit a genomic signature of a period of physical isolation during the Last Glacial Period (LGP) with increased climate fluctuation and environmental uncertainty, followed by postglacial contact and introgression as Earth warmed once again (Supplementary Figs. 8–9). This strongly supports the hypothesis that penguins were impacted by ecosystem-wide, climate-driven refugia/recolonization cycles in the Southern Ocean13,14, a pattern also observed in other marine taxa during the Last Glacial Maximum (e.g.,15). As ice volumes increased during the LGP high-latitude penguin species were likely forced into isolated mid-latitude refugia. As climate warmed from the late Pleistocene to Holocene, these species moved back towards the poles, recolonizing landmasses and islands as they became habitable once again, and, notably, experiencing secondary contact with one another (e.g., on small sub-Antarctic islands).", "Today, penguins are under threat from climate change and environmental disruption (see Supplementary Methods for further citations) and half of all extant species are considered either Endangered or Vulnerable (IUCN red list categories). Understanding how past climate events have impacted penguin population size during the LGP is crucial in inferring how penguin populations may respond to future climate change. We estimated the effective population size for all recent penguin taxa except for E. warhami and M. a. waitaha (where data were too limited, Supplementary Data 2) (Fig. 2c, Supplementary Figs. 10–11 and Supplementary Data 2). These analyses provide a window into long-term population histories (very recent trends cannot be accurately recovered with these methods16). Four demographic patterns emerge for this critical time interval, illuminating disparate responses of penguins to glacial-interglacial cycles (Fig. 2c). The most prevalent pattern is shared by nine lineages (Aptenodytes patagonicus, Pygoscelis antarctica, P. papua “KER”, S. demersus, S. humboldti M. a. antipodes, M. a. richdalei, Eudyptes robustus and E. pachyrhynchus), all of which show evidence of population expansion coincident with the beginning of the LGP, followed by population decline towards the end of the LGP. In contrast to this pattern, nine lineages (A. forsteri, P. adeliae, P. papua “WAP”, P. papua “SG”, S. magellanicus, E. moseleyi, E. filholi, E. chrysolophus schlegeli, and E. sclateri) show evidence of population decline coincident with the beginning of the LGP, followed by population expansion towards the end of the LGP. Almost all of the remaining lineages show strong evidence of persistent long-term declines in populations from the early LPG to the end of LPG. All three Eudyptula taxa and Eudyptes chrysolophus chrysolophus underwent a steep population decline spanning the LGP, while three taxa (P. papua “FAL”, S. mendiculus, and E. chrysocome) show evidence of continual population decline across the last 250 thousand years (ka).", "Interestingly, taxa that increased in population size towards the end of the LGP (e.g., A. forsteri, P. adeliae, S. magellanicus, E. filholi, E. moseleyi, E. sclateri, and E. schlegeli are typically migratory, and tend to forage offshore (>50 km; see Supplementary Data 117), while taxa that decreased towards the end of the LGP (e.g., S. humboldti, S. demersus, M. a. antipodes and likely M. a. richdalei) tend to be residential, and forage inshore; see Supplementary Data 1. Taxa that disperse farther may have overcome local impacts of global climate cooling during the LGP (e.g., changes in sea-ice extent, prey abundance and terrestrial glaciation, however see18) largely by relocating to lower latitudes (e.g.,14), whereas locally-restricted taxa may have been more prone to sudden population collapses.", "Penguins have the slowest evolutionary rates among birds", "The integrated evolutionary speed hypothesis (IESH) proposes that temperature, water availability, population size, and spatial heterogeneity influence evolutionary rate19. Life history traits also impact the evolutionary rate, but such relationships remain incompletely understood in birds20. Penguins are long-lived, large-bodied, and produce few offspring, thus providing an ideal case study in how life history may impact evolutionary rate. We tested the IESH using three proxies for evolutionary rate: substitution rate, P and K2P distances between lineages and their ancestors (Supplementary Fig. 12 and Supplementary Data 3). We found that penguins and their sister group (Procellariiformes) had the lowest evolutionary rates of the 17 avian orders sampled by21 (Fig. 3a, Supplementary Fig. 13, and Supplementary Data 3). Because other aquatic orders also show slow rates (e.g., the aquatic Anseriformes show a significantly slower rate than their terrestrial sister group Galliformes), we hypothesize that the rate in penguins represents the culmination of a gradual slowdown associated with increasingly aquatic ecology. Intriguingly, we detected a trend toward decreasing rate over the first ~10 Ma of crown penguin evolution, followed by a marked uptick ~2 Ma, which suggests the onset of glacial-interglacial cycles contributed to a recent increase in evolutionary rates in penguins (Fig. 3b).", "Fig. 3: Evolutionary rates in birds.", "a Evolutionary rate in avian orders based on a ~19 Mbp alignment of highly conserved genome regions. Sphenisciformes and Procellariiformes have the lowest evolutionary rate among modern bird orders (One-sided Wilcoxon Rank sum test, P values < 0.05 for all pairs except for Sphenisciformes and Procellariiformes (P-values > 0.1)). Numbers at the tips represent the sample size in each group. Numbers at nodes represent the divergence times (Ma) between each order and its sister taxon and red dots within the boxplots indicate average values. We did not attempt to estimate the evolutionary rates for orders containing less than three sampled species (gray font; Musophagiformes, Mesitornithiformes, and Struthioniformes). Boxplots show the median with hinges at the 25th and 75th percentile and whiskers extending 1.5 times the interquartile range. Some bird images were downloaded from phylopic.org and were licensed under the Creative Commons (CC0) 1.0 Universal Public Domain Dedication. b Evolutionary rates inferred for extant penguin lineages at internal nodes from the maximum clade credibility tree, calculated using a 500 Mbp genome alignment. Gray shadows represent the 95% credible intervals. c–e Correlations between c, body mass and generation time (P value < 0.05), d generation time (gray dots, solid lines, P value < 0.001) or body mass (blue dots, dashed lines P value < 0.05) and average sea surface temperature, e substitution per site per generation time (gray dots, solid lines, P value < 0.001) or substitution per site per million years (purple dots, dashed lines P value < 0.01) and body mass among 18 penguins, estimated using phylogenetic correlation - Phylogenetic Generalized Least Squares Regression with the best-fitting model identified by Akaike Information Criterion. Correlations with linear models were shown with black lines. Source data is provided as a Source Data file.", "Extant penguin lineages show a wide range of individual rates, and phylogenetic correlation analyses (phylogenetic generalized least squares regression) shed light on potential factors influencing this disparity (Fig. 3c–e and Supplementary Data 3). Extant penguins showed a significant negative correlation between body mass and average sea surface temperature (Fig. 3d). Despite species from warmer regions having shorter generation times (Fig. 3d), a significant negative correlation was found between evolutionary rate and average sea surface temperature (Fig. 3e), suggesting that temperature may influence penguin evolutionary rates by regulating selective pressures, but not only through its effect on metabolism22. This result is in parallel with studies that show speciation rates to be higher in polar environments than in the tropics, pointing towards faster rates of evolution and more opportunities for divergence at high latitudes23,24. We propose that these patterns together reflect the signature of climate oscillations on high latitude species: polar penguins (e.g. A. forsteri/P. adeliae) were likely forced into more northerly refugia during ice ages, subsequently recolonizing Antarctica during interglacials14. These events may have led to faster evolutionary rates as these lineages underwent population contraction-expansion cycles and were periodically forced to adapt to new environments.", "Putative molecular adaptations unique to penguins", "As penguins became increasingly adapted to a flightless diving ecology, they encountered novel selection pressures that required modifications to their locomotory strategy, thermoregulation, sensory perception, and diet. We tested whether these phenotypic changes have been facilitated through the evolution of the underlying protein-coding genes (Supplementary Data 4) by identifying positively selected genes (PSGs), rapidly evolving genes (REGs), and pseudogenes that relate to specific adaptations including thermoregulation, oceanic diving, oxygenation, underwater vision, shifts in diet and taste, body size and immunity (see Figs. 4, 5 and Supplementary Methods for additional details and citations). These genes either differ in all penguins compared with other birds, differ in the genus Aptenodytes compared with other penguins, or are under distinct selective pressures within penguins (Supplementary Data 4). In the branch leading to the last common ancestor (bLCA) of penguins, 27 PSGs (false discovery rate [FDR] q < 0.05) and 13 REGs (FDR q < 0.05) were detected. In the bLCA of Aptenodytes, 25 PSGs (FDR q < 0.05) and 3 REGs (FDR q < 0.05) were detected. In the bLCA of penguins and four flightless/nearly flightless birds (Nannopterum harrisi, Rhynochetos jubatus, Zapornia atra, and Laterallus rogersi, see Supplementary Fig. 16a), five PSGs (FDR q < 0.05) and 38 REGs (FDR q < 0.05) were detected. Within penguins, 275 PSGs (FDR q < 0.01) were detected (Supplementary Data 4). We related the gene pathways and known functions of 15 PSGs and six REGs to penguin-specific adaptations (Fig. 4a). We also highlight five genes containing penguin-specific substitutions, seven pseudogenes, and two gene expansions (Fig. 4a, Supplementary Figs. 14, 15).", "Fig. 4: Adaptive genes in extant penguin lineages.", "a Genes with unique evolutionary signals in penguins and their putative adaptive function. b Gene regulatory pathways related to light transmission. c Phylogenetic tree of 45 avian species showing two mutation sites (HBA-αA, A140S, and HBB-βA, L87M) of hemoglobin genes in penguins (marked in red) and outgroups. d Positive selection at multiple sites (41, 62, 111, 113, 127, 141) on the bLCA of extant penguins for MB gene and the structural effects of amino acid substitutions in the chicken MB gene. Molecular models of the chicken MB gene and the MB gene with penguin-specific substitutions may affect the stabilization of MB. Source data is provided as a Source Data file.", "We identified three REGs that are shared by penguins and other flightless/nearly flightless birds. These genes are likely associated with the shortening, rigidity, and increased density of the forelimb bones which contribute to the flipper-like wing of penguins (Fig. 4a). TBXT and FOXP1 are related to the development of articular cartilage, tendons, and limb bones25,26. SMAD3 is involved in the transforming growth factor-beta signaling pathway, which is important for maintaining articular cartilage and stimulating osteogenesis and bone formation27. Perhaps most interestingly, TNMD, a PSG, is expressed during the differentiation and developmental phase of limb tendon, ligament, and collagen fibrils, and loss of TNMD can result in reduced tenocyte density28. We hypothesize that TNMD may be key to the nearly wholesale replacement of penguin distal wing musculature by tendons, which stiffens and reduces heat loss to the high surface area flipper (Supplementary Fig. 16a-d). We also identified two genes KCNU1 and KCNMA1 that are related to calcium sequestration to be expanded in the genomes of both penguins and grebes (Podiceps cristatus and Podilymbus podiceps) (Fig. 4a, Supplementary Fig. 15). These genes likely contribute to the high bone density characteristic of these taxa, which helps reduce buoyancy for deep diving.", "Penguins have densely-packed waterproof feathers, thick skin, and a layer of subcutaneous fat enabling them to thermoregulate in cold environments. We identified four genes under selective pressure in common ancestors of penguins that are related to thermoregulation (Supplementary Data 4). These genes (APPL1, TRPC1, EVPL) showed evidence of positive selection or rapid rates of evolution on the bLCA of extant penguins but not in other birds (Fig. 4a). The white adipose tissue of penguins is important for survival in the cold, acting as an insulative layer and an energy reserve, particularly prior to catastrophic moult29. We hypothesize several of these genes contribute to white adipose fat storage and hence survival in cold environments. APPL1 (Supplementary Fig. 16e) and TRPC1 are related to glucose levels and fatty acid breakdown through adiponectin30,31.", "Penguins function under hypoxic conditions during deep dives in part via myoglobin concentration and utilizing anaerobic metabolism32,33. We identified seven genes related to oxygenation that are under positive selection or have penguin-specific substitutions in penguins. Transferrin Receptor 1 (TFRC) shows a positive selection in penguins (Supplementary Fig. 16f). Previous experimental work in cells has reported that TFRC messenger RNA is expressed in an oxygen-dependent manner34. Importantly, TFRC is a top candidate gene for the hypoxia response of domesticated cattle35. We hypothesize that TFRC has contributed to a convergent adaptation to withstanding hypoxia in penguins. Interestingly, FIBB and ANO6, which are involved in blood coagulation, showed a signal of positive selection in Aptenodytes, but not in other genera (Supplementary Fig. 17). Among all penguins, Aptenodytes have the capacity for the deepest diving (>500 m depth)36, and thus, these gene variants may enable these species to dive to extreme depths. While none of the hemoglobin genes were PSGs (P-value: >0.05), we observed that HBA-αA (A140S) and HBB-βA (L87M) genes (Fig. 4c and Supplementary Fig. 18) show penguin-specific amino acid substitutions that are highly conserved across all penguin species, making them candidate molecular adaptations for surviving deep oceanic dives under hypoxic conditions (see also ref. 37). MB is an oxygen-binding myoglobin gene that shows positive selection at multiple sites both between penguins and other birds and among penguins (Fig. 4d and Supplementary Fig. 16g), suggesting that these penguin-specific substitutions may impact the stability of the resulting myoglobins, as seen in extreme deep-diving cetaceans38. While cormorants and petrels also undertake deep (>70 m) dives, we did not observe selection for TFRC and hemoglobin genes in these groups (Fig. 4c). Another PSG, TRPC4, is involved in the cardiovascular system39. Specifically, TRPC4 may help widen blood vessels to decrease blood pressure during deep dives40.", "Penguins frequently forage in low light, and exhibit specializations for vision in dim, blue-green marine environments41,42. Morphological research has shown that at least some penguins are cone trichromats with only three functional cone photoreceptor types, blue-shifted long-wavelength visual pigments, and no red oil droplets41. Genomic data support trichromatism in all penguins, in contrast to most other birds which are tetrachromats. The inactivation of the green cone opsin gene (RH2) in the stem penguin lineage is inferred by a 12-base pair (bp) deletion, which encompasses the codon for the critical chromophore-binding lysine (K29643) (Fig. 4a and Supplementary Fig. 19a). As all penguins share this deletion, reduced color vision must have occurred in the penguin stem lineage, similar to secondarily aquatic mammals44. Although penguins lack green cones, the functional orthologs of the remaining visual opsins in penguins strongly indicate the retention of violet (SWS1), blue (SWS2), and red (LWS) cones, plus rods (RH1) (Fig. 5a). This genetic signature is concordant with our experiments on Pygoscelis papua (see Supplementary Methods), which demonstrate a capacity for ultraviolet light perception at 365 nm, likely conferred by the SWS1 opsin. Furthermore, the peak wavelength sensitivity (λmax) of penguin LWS opsins show evidence of shifts in spectral sensitivity to better match ambient underwater light. Relative to key avian model species (e.g., Taeniopygia guttata, Columba livia, Gallus gallus) and Procellariiformes, penguins possess substitutions at five key tuning sites in LWS, four of which (A180, F277, A285, and S308) are associated with blue-shifting this pigment45 (Supplementary Fig. 19b). This suggests that this opsin has been fine-tuned for marine foraging, as observed in cetaceans44. CYP2J19, which encodes a carotenoid ketolase responsible for producing red oil droplets in avian cones46, has been inactivated in most penguins (Supplementary Data 4). Colored oil droplets are thought to fine-tune color vision46, though this comes at the cost of decreased visual sensitivity. Deactivation of CYP2J19 likely allows for higher retinal sensitivity when foraging in dim light conditions, as seen in nocturnal owls and kiwis46. Beyond these key genes, we note that two scotopic photoresponse genes, TMEM30A (PSG) and KCNV2 (REG), show evidence of selection in penguins, and two others, CNGB1 and GNB3, each have a site mutation unique to penguins (Supplementary Fig. 19c, d). These genes play an important role in the transmission of light (Fig. 4b), and may further enhance visual sensitivity at low light levels, as mutations or loss of these genes impact the result in a reduced scotopic photoresponse47,48.", "A wholesale reduction in gustation capacity appears to have accompanied the shift to underwater prey capture and consumption in penguins. We verified that penguins only retain genes associated with detecting sour and salty tastants, and lack functional copies of genes linked to umami, sweet and bitter tastants49 (Figs. 4a and 5a). The mutational loss of capacity for umami taste in penguins is puzzling, given the continued consumption of amino acid-rich prey. Intriguingly, the loss of umami has also been reported in secondarily aquatic mammals50. Potential explanations include a lower reliance on taste when swallowing food whole or weakened ability to taste prey due to cold temperatures and the sodium content of seawater (reviewed in50).", "A strong genomic indicator of diet is presented by chitinases that are expressed in the gastrointestinal tract51. The chitinase genes (CHIAs) exist as several paralogs, and the retention or loss of these paralogs in mammals has been correlated with diet51. Retention of intact CHIAs correlates with a higher degree of insectivory, and CHIA losses tend to occur in lineages that undergo dietary shifts to carnivory or herbivory. We examined CHIAs in penguins, and in contrast to most examined birds, which have one to four intact CHIAs52, penguins have a single pseudogenized CHIA. At first glance, it is perplexing that penguins would lose CHIAs, as many species consume large amounts of crustaceans. Fossil evidence, however, reveals that stem penguins focused primarily on larger prey items like fish and squid, and that adaptations for capturing smaller planktonic prey arose as recently as the Pliocene6. We propose that the two inactivating mutations shared by extant penguins (Fig. 5) evolved during a ~50 Ma interval during which stem penguins consumed little or no arthropod prey.", "Co-evolution between hosts and pathogens is pervasive in vertebrates. Given the range of different climatic niches occupied by penguins, and the differences in pathogen assemblages to which they are undoubtedly exposed, penguins may have undergone significant adaptation to local pathogen pressures53. Accordingly, we detected 51 PSGs in penguins that have a role in immunity (Supplementary Data 4). Several of these genes might be under positive selection corresponding to host-pathogen co-evolution. For instance, we confirm previous reports53,54 that the bacterial-recognizing Toll-like receptors TLR4 and TLR5 (Figs. 4a and 5b) are positively selected in penguins. Moreover, the positively selected sites located proximal (<5 Å) to the lipopolysaccharide-binding site in TLR4 (codon 276, homologous to chicken codon 30255) and at a flagellin-binding site in TLR5 (codon 3356) (Fig. 5b) are both in domains crucial for bacterial recognition. In addition, we detected several other pattern-recognition receptors, such as IFIT5, that are also under positive selection in penguins (Fig. 4a). IFIT5 is a cellular detector of viral RNA57, and we found a cluster of positively selected sites located in a connecting helix forming part of the RNA-binding cleft (codons 407, 409, 413, and 421, corresponding to human codons 412, 414, 418 and 42658,59) (Fig. 5b). This may imply that penguin IFIT5 has undergone adaptation to different viral RNA motifs in response to viral pathogen pressure. We also found evidence of positive selection at viral targets of cell entry. For example, CD81 is a co-receptor required for glycoprotein-mediated hepatitis C viral entry into cells in mammals60, and positive selection has been reported at the glycoprotein interface in bat CD8161. We also found a cluster of positively selected sites in the hepatitis C glycoprotein interface in penguin CD81 (sites 181, 182, and 186, corresponding to human sites 180, 181, and 185, and penguin site 86, corresponding to human site 185) (Fig. 5b). This may suggest that penguins have experienced co-evolution with a viral pathogen that relies on CD81 for cell entry. Finally, we detected positive selection in penguin transferrin, which is part of the “nutritional” immune system that sequesters iron from iron-scavenging pathogens62. Outbreaks of diphtheritic stomatitis in Megadyptes antipodes have caused increasing chick mortality and are hypothesized to be related to increasing susceptibility to Corynebacterium as a secondary infection63 potentially triggered by chick malnutrition due to changes in diet, and potentially iron intake. The co-evolutionary arms race to sequester and scavenge iron has also been detected in mammals and fishes (e.g.,64). Taken together, these observations illustrate that immune genes have undergone diversification in penguins. Furthermore, many positively selected sites were clustered in regions known to be involved in pathogen binding, which provides evidence for extensive host-pathogen co-evolution during the diversification of penguins into novel pathogen environments.", "Extant penguins range from ~1 kg in Eudyptula spp. to 40 kg in Aptenodytes forsteri, but giant fossil penguins exceeded 100 kg65. We found two genes associated with large body size that are under positive selection in Aptenodytes compared to all other penguin lineages (Fig. 4a). CREB3L1 is important during bone development, and vertebrates lacking CREB3L1 have underdeveloped growth66. SMARCAD1 is related to the skeleton and plays a role in transcriptional regulation, maintenance of chromosome stability, and various aspects of DNA repair. Vertebrates with mutant SMARCAD1 also have underdeveloped growth67. We hypothesize that these genes have contributed to the large body size of Aptenodytes. Although genetic data are inaccessible for stem penguins, the recovery of Aptenodytes as sisters to all other extant penguins and the large size of many stem penguins (e.g., Kumimanu and Kairuku) suggests positive selection in these genes could be ancestral for crown penguins with selection relaxed in non-Aptenodytes taxa.", "Discussion", "Our comprehensive study encompassing all extant and many fossil penguins provides a new window into the processes that have shaped >60 Ma of evolution. Our phylogenomic analyses confirm the Zealandian origin of penguins, extensive radiation before dispersal to South America and Antarctica, and the second pulse of speciation at the onset of the ACC. Our study reveals new evidence that penguin speciation events were driven by changes in global climate and oceanic dispersal, leading to allopatric speciation across the Southern Hemisphere. Recent speciation in Eudyptes, Megadyptes, Spheniscus, and Eudyptula has been rapid, with a complicated history of gene flow and ILS that make species boundaries within these taxa difficult to untangle (e.g.,5,14). Importantly, the mechanisms that have shaped penguin diversification in the past (e.g., development of major current systems, geological uplift of oceanic islands) remain important for taxa that appear to still be in the process of speciation today (e.g., within Pygoscelis papua and between Eudyptes chrysolophus chrysolophus/E. C. schlegeli, E. pachyrhynchus/E. robustus, E. chrysocome/E. filholi/E. moseleyi, and Spheniscus spp.5,14,68).", "By comparing our penguin genomes to >300 other avian genomes, we demonstrate that penguins and Procellariiformes have the lowest evolutionary rates observed among birds to date. These low evolutionary rates seem to belie the profound adaptations penguins show for a secondary aquatic existence, but a synthetic reading of the fossil record and the genomic data suggests that penguins rapidly acquired many of the key features associated with their aquatic life very early in their diversification and rates of change slowed towards the present. Genomic signals of molecular adaptations with evidence of positive selection or penguin-specific substitutions were identified in a variety of genres, including genes associated with oceanic diving, thermoregulation, oxygenation, underwater vision, taste, and immunity. Though the overall evolutionary rate in penguins is slow, we identified higher evolutionary rates in crown penguin ancestors than in extant penguins and shifts in rates in individual lineages over the past 14 Ma.", "While evolutionary rates and sea surface temperatures appear to be negatively correlated, evolutionary rates and body mass are positively correlated, suggesting that large-bodied species inhabiting colder climates are more equipped to adapt to new environments during climate events. Indeed, our demographic results reveal that penguins have had a complicated history, shaped by climatic oscillations, which has led to population crashes in those species reliant on restricted niches and ecologies. Genomic evidence highlights how some penguin populations collapsed during previous climatic shifts13,14, and the risks of future collapses are ever-present as penguin populations across the Southern Hemisphere are faced with rapid anthropogenic climate change69. While our analyses suggest that ocean temperature may regulate certain selection pressures, the current pace of warming combined with limited refugia in the Southern Ocean will likely far exceed the adaptive capability of penguins70. Over 60 Ma these iconic birds have evolved to become highly specialized marine predators, and are now well adapted to some of the most extreme environments on Earth. Yet, as their evolutionary history reveals, they now stand as sentinels highlighting the vulnerability of cold-adapted fauna in a rapidly warming world.", "Methods", "Genome sequencing, assembly, and annotation", "We analyzed 27 genomes comprising all extant and recently-extinct penguin species, subspecies, and major lineages. 21 of the high-coverage genomes have been published by members of our consortium for this project8,9. To supplement the dataset, we sequenced three high-coverage genomes from the remaining Pygoscelis papua lineages from Falkland Islands/Malvinas “FAL”, Kerguelen Island “KER” and South Georgia “SG” (see68), and partial genomes from the recently-extinct Eudyptes warhami, M. a. richdalei and M. a. waitaha (see ref. 5 and citations within). See Supplementary Methods for more detail on sample collection, extraction, sequencing, assembly and sex chromosomes. As such, we present the most comprehensive genomic dataset spanning all modern penguins, and to the best of our knowledge, present the first genomic dataset encompassing an entire multi-species vertebrate order. To compare our penguin genomes to other bird genomes, we obtained 361 bird genomes recently released by20 as part of the B10K project (https://b10k.genomics.cn), representing 36 orders and 218 families.", "Additional data on modern and fossil penguins", "We expanded the morphological dataset of6 by incorporating additional fossil penguin species and seven additional characters. The final matrix comprised 72 fossil and extant penguin taxa, two outgroup taxa, and 281 morphological characters (Supplementary Data 5). The average sea surface temperatures were obtained from spot locations from each lineage (Supplementary Data 3). Generation times of each extant lineage were obtained from the IUCN. For M. a. richdalei we used the M. a. antipodes generation time (Supplementary Data 2) (see Supplementary Methods).", "Phylogenomic inference and divergence time estimation", "We combined all penguin genomes with the morphological matrix to resolve the timing and drivers of >60 million years of penguin evolution. In doing so, we update previous phylogenies (e.g., 4,5,7,9) to include genomes and morphology from all penguin taxa, including all major P. papua lineages and recently-extinct taxa. To explore the diversification of penguins, we undertook multiple phylogenomic analyses encompassing different subsets of taxa (Fig. 1, Supplementary Figs. 2–4 and Supplementary Software).", "We aligned and merged our genomes to the 363-bird alignments from the B10K project20. The final alignments were extracted and multiple hits were filtered out for downstream analyses. We then created four alignments accounting for different subsets of taxa: (1) all putative species, subspecies and lineages (27 penguin taxa + 5 outgroups in total); (2) all extant lineages (24 penguin taxa + 5 outgroups in total), removing Eudyptes warhami, M. a. richdalei and M. a. waitaha from the former alignment; (3) all putative species and subspecies, removing P. papua “FAL”, “KER” and “SG” lineages (21 penguin taxa + 5 outgroups in total); and (4) only putative species (19 penguin taxa in total), further removing Eudyptula minor “BAN” and Eudyptes chrysolophus schlegeli. We also created one large genome alignment with all 385-bird taxa (not including Eudyptes warhami, M. a. richdalei and M. a. waitaha) (see Supplementary Methods).", "To verify the phylogenomic relationships of modern penguins, we ran coalescent-based and concatenation-based phylogenies accounting for the different subsets of taxa described above (see Supplementary Methods). The topology for all clades was strongly supported and identical using all methods (Supplementary Fig. 2 and Supplementary Data 5), except for the placement of Eudyptes warhami among Eudyptes lineages in a single phylogeny.", "We estimated the divergence time between modern taxa using the calibration points in ref. 5 (Supplementary Data 5), except we removed Pygoscelis calderensis based on recent revisions of topology7,9. We also added a “Crown Procellariiformes” (which is a sister to penguins) calibration point to calibrate the divergence between albatross and storm petrels. We also added three tip dates for extinct taxa, using the fossils Madrynornis mirandus, Spheniscus muizoni, and the fossil specimen NMNZ S.046318 (Eudyptes sp.) (see Supplementary Methods). All trees shared the same topology with our initial analyses, with the exception of the placement of the extinct Megadyptes antipodes waitaha, and had similar divergence times with each other (Supplementary Fig. 2b) We then generated a Bayesian total-evidence dating tree using the fossilized birth-death process (Fig. 1), expanding4 by including more species, genome data, and updating the morphology. We also calculated the genetic distances between our modern penguin genomes (Supplementary Fig. 12).", "Ancestral range estimation", "We estimated the ancestral distribution of penguins with the total-evidence dated phylogenomic tree and twelve models, expanding on6,7 and following6. We used ten geographical areas and six-time slices, and normalized distances against the shortest pairwise distance in the time slice in this analysis. We then undertook standard model-testing (Likelihood Ratio Test and Akaike information criterion) to identify the best-fitting model for our data. We also used a Biogeographical Stochastic Mapping method to account for the apparent dispersal/vicariance/etc events. See Supplementary Methods for more details.", "Quantifying introgression and ILS between taxa", "Controversy still remains regarding taxonomic boundaries between some closely related penguin taxa (See Supplementary Methods for more details). We undertook multiple analyses to assess the discordance of gene trees and levels of ILS and introgression (Supplementary Data 6). We first calculated the frequency of gene tree discordance for each internal branch and summarized the topologies for three different gene tree data sets. We assessed levels of ILS and introgression by quantifying them via internal branch lengths between all species (Supplementary Software). We tested the direction of introgression among lineages and assessed what genomic regions have introgressed, by analyzing 16 five-species combinations with symmetric phylogenies (Supplementary Data 2). We also examined introgression, by selecting different taxa from different genera and some closely related lineages/species. Finally, we assessed the cessation of gene flow between six closely related penguin groups. See Supplementary Methods for more details.", "Demographic history of penguins", "We undertook analyses of demographic history by profiling heterozygosity across each genome (Supplementary Fig. 10), and undertaking analyses of effective population size (Ne) over the last 1 Ma. As the number of heterozygous sites for M. a. waitaha and Eudyptes warhami remained too low, we only present analyses for M. a. richdalei. We used the species divergence time tree as an estimation of the mutation rate and detailed the divergence times in Supplementary Data 2. We focussed on the last 500 Kya, a period encompassing dramatic glacial/interglacial cycles (see Supplementary Methods).", "Comparison of evolutionary rate", "The evolutionary rate between penguins and other birds was compared using both genomic distance and rate comparisons (Supplementary Fig. 12). We calculated P and K2P distances between taxa following the formulas: P distance = p + q and K2P-distance = −1/2ln((1-2p-q)*sqrt(1-2q)). Here, p is the proportion of transitions while q is the proportion of transversions between two genomes. We also estimated the evolutionary rate of penguins using the substitution rate (substitution per site per year) = substitution per site/divergence time. The correlation relationship between the substitution rate and sea surface temperature for extant penguins was tested using a phylogenetic generalized least squares (PGLS) regression (Fig. 3 and Supplementary Data 3). We also conducted PGLS regression analysis to determine the correlation relationship between sea surface temperature and body mass or generation time (Supplementary Software). We also compared the genome size among birds to check whether the genome size has a correlation with the proportion of repeat elements (Supplementary Data 3). See Supplementary Methods for more details.", "Putative molecular adaptations", "We undertook comparative genomic analyses across all extant penguin taxa to identify genes and regulatory changes contributing to the remarkable morphological and physiological variation within penguins. We do not include Eudyptes warhami, M. a. richdalei, and M. a. waitaha or additional P. papua lineages (“FAL”, “SG”, “KER”) in these analyses. Our analyses expand on previous analyses that have only examined A. forsteri and P. adeliae (e.g., 8,49), or those that have relied on only on-site analysis for penguins (e.g., 7).", "To understand the adaptive evolution of specific phenotypes in the branch leading to the last common ancestor of penguins, we identified positively selected genes, rapidly evolving genes, and evolutionarily conserved genes for extant penguins under a branch model and a branch-site model (see Supplementary Methods). We obtained orthologous genes against the chicken genome for 44 bird species including penguins, retaining a total of 8716 high-confidence orthologous genes. These genes were used to conduct a multiple sequence alignment. We then detected positively selected genes/rapidly evolving genes in the branch leading to the last common ancestor of penguins and detected positively selected genes/rapidly evolving genes in the branches of the last common ancestor of penguins plus four flightless/nearly flightless birds (see Supplementary Methods for more details). Genes with a false discovery rate adjusted P-value less than 0.05 were treated as candidates for positive selection or rapid evolution (Supplementary Data 4). To reveal more characteristics in penguins, we predicted whether an amino acid substitution site may have an impact on the biological function of a protein, by comparing penguins to the 23 other birds, and scanning for premature stop codons in each gene alignment. We also examined specific genes individually. In addition, we annotated and undertook further qualitative comparisons of these genes identified in penguins with over 300 other avian species to explore what happens in other birds (Supplementary Data 7). See Supplementary Methods for more details. While transcriptional evidence to support adaptive inferences is highly important, such data remains unrealizable in our study due to cultural and ethical hurdles.", "Behavioral study of gentoo penguin vision", "As a representative of penguins, we undertook a behavioral study on captive P. papua at SEALIFE Kelly Tarlton’s Aquarium, Auckland, New Zealand to examine their ability to see in the ultraviolet (UV) spectrum. A Tank007 TK566 black OEM 365 nm torch (Shenzhen Grandoor Electronic Co., Ltd., China) was projected onto the snow in the enclosure, and penguins were observed to determine whether they would follow the movements of the torch’s UV projection. At least five penguins appeared to be able to follow the torch’s projection. No such interest was displayed when the torch was turned off, demonstrating that P. papua are able to see in the near UV spectrum (Supplementary Movie 1).", "Reporting summary", "Data availability", "The sequencing data and genome assemblies generated in this study have been deposited in the NCBI database under BioProject PRJNA722815 and PRJNA556735, as well as the CNSA of the CNGBdb database under the accession number CNP0000605. Appendix datasets (BioGeoBEARS results and PSMC results) have been deposited on Figshare [https://doi.org/10.6084/m9.figshare.c.5535243.v1]. Supplementary data files and source data generated in this study are provided in the Supplementary Information and Source Data file. The following datasets were also used in this study: CNSA accession number CNP0000505, and NCBI Genbank accession number NP_990272, NP_001071646, NP_001071647. Source data are provided in this paper.", "Code availability", "Analyses were performed using open-source software tools and the detailed parameters for each tool are shown in the relevant methods in Supplementary Information. The custom scripts and codes used in this study are also available in Supplementary Software files.", "Acknowledgements", "We thank the British Antarctic Survey, Institut Polaire Français (IPEV), Laura Seaman, and staff at SEALIFE Kelly Tarlton’s Aquarium, Simone Giovanardi, Misha Vorobyev, David Ainley, Jason Turuwhenua, Nic Dussex, Kieren Mitchell, Damien Fordham, Stuart Brown, James Cahill, Shanlin Liu, Yun Zhao, Fang Li, Min Wu, Yun Wang, Guangji Chen, and B10K members for sample/data collection and discussions. This project was supported by the National Key Research and Development Program of China (MOST) grant (no. 2018YFC1406901) to D.-X.Z. and the International Partnership Program of Chinese Academy of Sciences (no. 152453KYSB20170002) to G.Z. This project was also supported by the National Natural Science Foundation of China grant (no. 31901214 and No. 32170626) to S.F. and a Villum Investigator grant (no. 25900) from The Villum Foundation to G.Z. This project was also funded by the China National GeneBank.", "Source data", "Rights and permissions", "Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/." ], [ "PNAS: Welcome to Science Sessions, the podcast of the Proceedings of the National Academy of Sciences, where we connect you with Academy members, researchers, and policymakers. Join us as we explore the stories behind the science. I'm Paul Gabrielsen, and I'm speaking with Juliana Vianna of the Pontifical Catholic University of Chile and Rauri Bowie of the University of California, Berkeley. In a recent PNAS article, they and their colleagues examined genomes of 18 species of penguins to learn more about their origins. Penguins are often associated with Antarctica, but according to the authors, that's not where they started out.", "Have either of you had the opportunity to observe penguins in the field? Juliana?", "Vianna: Yes. So we have been capturing penguins for several years in different parts; Humboldt and Magellanic in the coast of Chile; in Patagonia, rockhopper penguins, macaroni penguins. And we also have been working in Antarctica for several years with gentoo, chinstrap, adélie. And I have been to South Africa as well. I could see the African penguin in the wild, and also in New Zealand the very endangered yellow-eyed penguin and the little penguin. So yeah, I am lucky to have seen 11 species of penguins already.", "Bowie: I've seen only two species of penguin, both more associated with human habitats. I've spent quite a bit of time with African penguins, rehabilitating them after an oil spill. And then I've been to New Zealand to see the smallest species, the little penguin. But I hope to see many more.", "PNAS: Tell me about the diversity of penguin species across the Southern Hemisphere.", "Vianna: Only two species of penguins are distributed around Antarctica, the entire continent. This is the emperor and adélie. You can find several other species in the Antarctic peninsula, like gentoo, adélie, chinstrap, and the macaroni penguin. And there [are] several other species that are sub-Antarctic: king, macaroni, rockhopper penguins. So they are found north and south of the Antarctic polar front and also have species that are north of subtropical front, like the northern rockhopper penguins. You can find species associated with the cold waters of Benguela Current in South Africa. And you can find species in Australia and New Zealand. And also there [are] several species in South America: Magellanic, rockhopper, Humboldt, macaroni, king. Humboldt, for example, can go up to the coast of Chile, to Peru, associated with the cold waters of Humboldt current. And the one that is the lowest latitude is the Galápagos penguin that you can find in the Galápagos islands. So this is about a general distribution.", "Bowie: I think it's just fascinating that penguins managed to occupy some of the most remote landmasses on Earth; on these really tiny little islands you can find a penguin colony. So they've been a remarkably successful seabird group from that perspective.", "PNAS: Before your study, what was known about the origin and diversification of penguins? Rauri?", "Bowie: So there's been an interesting debate in the literature with exactly where the two largest species—the very charismatic king and emperor penguins—where they fitted in the family tree for penguins. And one of the ideas was that they were closer to some of the other living penguins, some of the smallest species nested inside the family tree. And then the other idea was that they were most distantly related to all of the other ingroup—we say they were sister to the rest of the penguins. Penguins also have a rich fossil history. So although modern penguins only date back to about 20 million years, penguins go all the way back to 60 million years. So given this debate, one of the things that we wanted to try and resolve with our study was where exactly do king and emperor penguins go in the family tree. And that would then help us understand how penguins originated and where exactly their origination occurred and when. And so you know, our main conclusions resolve one of these longstanding questions. And we were able to determine that penguins originated along the coast of Australia and New Zealand and the nearby South Pacific islands, and that this occurred about 22 million years ago.", "PNAS: How do you determine where and when penguins may have originated?", "Vianna: So we use 22 genomes of 18 species, and we could reconstruct the phylogeny; and we use the recent distribution of all of these species, and we modeled the best distribution of the species. And we could find the region of New Zealand and Australia. But we also used ecological data. We obtained satellite information of sea surface temperature, chlorophyll, and also a salinity for each of the 18 species. And we model the best historical niche distribution. And we could also find that the historical maximum temperature was nine degrees Celsius, which match with the geographical region that we found. So both data, ecological and genomic, support the same timing. Rauri, maybe you want to add something?", "Bowie: No, I think that's good. So one of the things that we were able to do by reconstructing where penguins originated and using the phylogeny, as well as this large amount of ecological data that's available, is we were able to show how penguins have been able to diversify, to occupy the incredibly different thermal niches that they live in today. And so, by mapping this environmental data back across the family tree of penguins, we could show that penguins originated in temperate waters, probably around nine degrees Celsius—or about 48 degrees Fahrenheit—which is roughly the water temperatures around Australia and New Zealand today. And then from there, we see this really remarkable twin axes of radiation, one which is down into the really frigid water of Antarctica and the sub-Antarctic, which you can get down to negative degrees. And then the other is, as this Drake's passage between the tip of South America and Antarctica opened and changed how the currents flowed around the bottom of the world allowing this circular current to form, penguins were able to move up the coast of South America, eventually reaching the Galápagos islands, which of course are right on the equator.", "And so as a consequence of that, they can occur in temperatures right up to 26 degrees or even slightly warmer. So you see penguins being able to span from their ancestral conditions of around 48 degrees Fahrenheit to being able to then colonize freezing temperatures, as well as up to about 80 degrees Fahrenheit on the equator. So really occupying a broad diversity of thermal environments.", "PNAS: What did genetic adaptations allow them to do that they couldn't before?", "Bowie: So one of the advantages of using the whole genomes is that it provides a record of how genes have changed through time and allows us to estimate different levels of selection across different genes. And so we were able to take all the coding genes from the genome and look at how selection had operated. And from that, we could identify certain parts of the genome that have been what we call enriched or overemphasized in different penguin lineages. And some of the genes that came out were related to pathways, for example, that relate to how blood vessels constrict and expand. And if you think about it, that makes a lot of sense because penguins that live in really cold temperatures, if they can reduce the circulation of blood to their extremities, they can maintain a warmer core body temperature, much as many marine mammals do in the same vein. Similarly, penguins have really interesting adaptations for binding oxygen in the same way that many species that live at high altitudes do. And this fits in with some penguins being able to dive to relatively deep depths where really efficient oxygen metabolism is really important.", "And then another category that we see is related to osmoregulation. And that again, when penguins are limited with how much fresh water they may have access to, and as a consequence need to be able to drink seawater, being really efficient in your osmoregulatory pathway allows you to, for example, excrete salts and it facilitates them being able to colonize these really diverse habitats.", "PNAS: How does this finding help us better understand the penguin species we have today?", "Vianna: We have answered lots of questions about the evolution of the group. And we could understand that like big times of decrease of temperature, like the middle Miocene, was associated with the diversification of penguins as well, the intensification of the Antarctic circumpolar current and other more recent decrease of temperatures as well was associated with a great diversification in penguins. But right now, climate change is occurring too fast for some species to adapt. And so we can already see some species decreasing population sizes, like adélie and chinstrap in the Antarctic peninsula. And on the other hand, gentoo penguin, we know that came from sub-Antarctic region, it's increasing in Antarctica and expanding farther south.", "So we know that this species could adapt in the past with a large geological time scale to climate changes. But right now it's too fast for them to adapt. And we know that in South America in Chile and Galápagos, Humboldt and Galápagos penguins have been impacted by the El Niño Southern Oscillations; and with increase in temperature is associated with high mortality for both species. And El Niño is becoming more intense and more frequent with climate changes. So we expect now to use our ecological data and our genomic data to see how each one of those species were going to adapt in the future. So this is our next step in our research. And also, our data gave lots of answers about the taxonomy of the group. So, how many species there are; we could see that we didn't find many genetic differentiation, genomic differentiation between the macaroni and royal penguin, for example; but [o]n another hand, there was a debate about how many species of rockhopper penguins, and our data supports three species as well. And right now, two of them are considered by the IUCN as only one and vulnerable and decreasing. But we know that one of those—the eastern rockhopper—it has much more strong decreases in population sizes. And it's more affected by climate changes and also other impacts like fisheries and predation in the nest, also invasive species, cats, dogs, rats, and many other impacts.", "Bowie: I think I can really think of three interesting ways that our data leads to a better understanding of penguins that can influence their conservation. I think the first thing that's really important to realize is that the genetic variation that we identify and the mutations that may have facilitated penguins expanding across the Southern Hemisphere occurred over a period of millions and millions of years. And the rate at which climate's changing today is so fast that it's unforeseeable that penguins will be able to change rapidly enough to be able to adapt to these changing environments. And this is as a consequence of why we're seeing certain colonies starting to disappear, and other penguins having to redistribute their distributions or having to redistribute themselves because of changes in food resources. And then the other thing that Juliana mentioned as well is that our data gives interesting insight into actually the diversity of penguins.", "And we find one instance where perhaps what we think of as two current penguin species, macaroni and royal, should actually be considered one with a really interesting polymorphism in coloration. But in other cases, with rockhopper and gentoo penguins where the diversity has been underestimated and where we may have one species today, maybe three or four different species that are very different evolutionary histories, and have responded very differently through time to changes in environments. And there seems little doubt that, whether we want to call them species or not, they should be managed as separate entities, and so as a consequence should have much greater conservation attention placed upon them because they each represent isolated little units rather than one unit broadly distributed across the Southern hemisphere. And then the last point I think that's worth making is one of the really fantastic things that we can do with genomes is, because we have so much data, we can look back in time as far as a million years of how population sizes have changed.", "And so by doing that, we could very conclusively show that most penguins had the largest bump in population size somewhere between 40 and 70,000 years ago, so, when the world was much cooler. And the world has continuously warmed since the last glacial maximum and penguin colonies have been declining for a long time, and it's only been accelerated by these human-induced changes. So they really are in dire need of conservation attention.", "PNAS: One last question. Do you have a favorite penguin species?", "Vianna: It's difficult. The little one is very cute, but I have been working for a long time with gentoo penguin[s], and I'm really impressed how this species has adapt[ed] and have diversified in Southern Ocean and Antarctica. So gentoo penguin has taken my attention, just because of the results and the work I have done with gentoo, but I really like most of the species and it's very beautiful. And when I was in New Zealand and I could see the yellow-eyed that is very threatened and the little penguin I was fascinated, but I was very happy to see them. Rauri, do you have a favorite penguin?", "Bowie: Now you’re asking me! Um, it's always so hard. I think my favorite is the emperor penguin. They're such majestic looking animals and so charismatic, but also they have, you know, a most fascinating life history being secluded on the ice, looking after a single egg for such long periods of time and how the male and female need to cooperate to raise their young, and so I've always found them fascinating. But penguins as a whole are a really, truly remarkable group of birds as well as an adorable group of birds.", "Vianna: So yes I think emperor and Galápagos are the two extremes in terms of adaptation to the different temperature and environmental conditions, and it’s very interesting that both of them take attentions to the public. Like most of the people now talk to me and said, I didn't know there was, like, penguins in Galápagos or in the coast of Chile and Peru.", "Bowie: For me, I think one of the great results of this paper, one of the things I most enjoyed the most, is that this is a nice example of work that could never have been completed without international collaboration with people and scientists from all over the world, contributing material, contributing their expertise—Juliana in Chile, bringing her extensive knowledge of penguins and genomics, and then my lab being able to help. And so I think that's a really great example of how NSF and other funding agencies have facilitated bringing together different groups of scientists to really do science that has real implications for conservation of charismatic organisms but could never be done by one individual or one organization on their own.", "PNAS: Thanks for tuning into Science Sessions. You can subscribe to Science Sessions on iTunes, Stitcher, Spotify, or wherever you get your podcasts. If you liked this episode, please consider leaving a review and helping us spread the word." ], [ "Notice", "Notice", "All articles published by MDPI are made immediately available worldwide under an open access license. No special", "permission is required to reuse all or part of the article published by MDPI, including figures and tables. For", "articles published under an open access Creative Common CC BY license, any part of the article may be reused without", "permission provided that the original article is clearly cited. For more information, please refer to", "https://www.mdpi.com/openaccess.", "Feature papers represent the most advanced research with significant potential for high impact in the field. A Feature", "Paper should be a substantial original Article that involves several techniques or approaches, provides an outlook for", "future research directions and describes possible research applications.", "Feature papers are submitted upon individual invitation or recommendation by the scientific editors and must receive", "positive feedback from the reviewers.", "Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world.", "Editors select a small number of articles recently published in the journal that they believe will be particularly", "interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the", "most exciting work published in the various research areas of the journal.", "You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.", "Abstract", "Despite its current low diversity, the penguin clade (Sphenisciformes) is one of the groups of birds with the most complete fossil record. Likewise, from the evolutionary point of view, it is an interesting group given the adaptations developed for marine life and the extreme climatic occupation capacity that some species have shown. In the present contribution, we reviewed and integrated all of the geographical and phylogenetic information available, together with an exhaustive and updated review of the fossil record, to establish and propose a biogeographic scenario that allows the spatial-temporal reconstruction of the evolutionary history of the Sphenisciformes, discussing our results and those obtained by other authors. This allowed us to understand how some abiotic processes are responsible for the patterns of diversity evidenced both in modern and past lineages. Thus, using the BioGeoBEARS methodology for biogeographic estimation, we were able to reconstruct the biogeographical patterns for the entire group based on the most complete Bayesian phylogeny of the total evidence. As a result, a New Zealand origin for the Sphenisciformes during the late Cretaceous and early Paleocene is indicated, with subsequent dispersal and expansion across Antarctica and southern South America. During the Eocene, there was a remarkable diversification of species and ecological niches in Antarctica, probably associated with the more temperate climatic conditions in the Southern Hemisphere. A wide morphological variability might have developed at the beginning of the Paleogene diversification. During the Oligocene, with the trends towards the freezing of Antarctica and the generalized cooling of the Neogene, there was a turnover that led to the survival (in New Zealand) of the ancestors of the crown Sphenisciform lineages. Later these expanded and diversified across the Southern Hemisphere, strongly linked to the climatic and oceanographic processes of the Miocene. Finally, it should be noted that the Antarctic recolonization and its hostile climatic conditions occurred in some modern lineages during the Pleistocene, possibly due to exaptations that made possible the repeated dispersion through cold waters during the Cenozoic, also allowing the necessary adaptations to live in the tundra during the glaciations.", "1. Introduction", "Penguins (Aves, Sphenisciformes) constitute a group of birds that are exclusively marine and flightless. All the species present extreme anatomical and physiological modifications directly related with the diving habit and the adaptations to cold-temperature waters [1,2]. From an evolutionary point of view, there is consensus to include the Sphenisciformes along with other aquatic birds in Aequornithes, and within this clade they are closely related to the Procellariiformes [3,4,5,6]. More precisely, the origin of penguins would be linked to a flying ancestor that secondarily would have lost the ability to fly as they became excellent divers capable of traveling long distances ([7] and numerous later contributions) and reaching extreme depths [1,2,8].", "The Sphenisciformes would have originated at the ends of the Cretaceous [9,10,11,12,13] in Zealandia [14] or Te Riu-a-Māui (Māori) or Tasmantis, lands that emerge today as New Zealand. Their appearance and diversification would be closely related to the extinction of the large marine reptiles that played the role of top predators in the southern oceans [15]. Later, these niches became vacant and were occupied by other vertebrates such as penguins in the Southern Hemisphere ([16] and references therein). Although no Cretaceous penguins are known, the fossil record is consistent with this idea. The oldest records of penguins correspond to forms that are morphologically archaic [11,17,18,19,20] that probably acquired a great size, a non-pneumatic skeleton, a flattening of the wing bones constituting propelling blades for diving, and an incipient widening and shortening of the tarsometatarsus, during the lower Paleocene.", "These and other specializations for wing-propelled diving are already present in the Paleocene species (Kupoupou stilwelli, Waimanu manneringi, Sequiwaimanu rosieae, Kumimanu biceae, Muriwaimanu tuatahi, Crossvallia waiparensis, and Crossvallia unienwillia), although in the Eocene, forms with more extreme morphophysiological specializations are evident. In this regard, features such as the development of a blood plexus in the wing are observed early in the evolution of penguins (see details in [21]). This acquisition allowed them better thermal regulation during cold-water forays [22,23], as did the presence of highly modified feathers transformed into scales that cover the wings and substantially improve hydrodynamic skills during diving [24].", "An increase in body size and a greater adaptation for diving in cold water would have conferred an important adaptive advantage in this context, since a greater body size implies a greater diving capacity, both in terms of depth reached and the duration of the dive [25]. The maximum expression of body size was achieved in the Eocene, when Palaeeudyptes klekowskii reached more than two meters in height [26]. Although there is no consensus about how the size of Paleogene penguins should be calculated, several cases of giant species have been reported in Antarctica, South America, New Zealand, and Australia, covering almost all the areas where penguins are recorded. Thus, penguins reached their apogee with many shapes and an incredible diversity of sizes [27].", "It has been proposed that large and robust penguins would have arrived at the Peruvian coasts through two successive colonizations from different areas. The first spread, from Antarctica, would have occurred by the middle Eocene, whereas the second colonization, from New Zealand, would have occurred by the end of the Eocene. According to this proposal, based on the Eocene record of Peruvian penguins [24,28], the presence of Antarctic forms in the middle Eocene in Chile [29] and Argentina [30] is also explained. This stage does not extend beyond the Oligocene. It is not possible to determine the causes or the exact mechanisms that caused these faunal changes, but the diversity of diving birds is inversely proportional to the diversity of marine mammals, especially odontocetes cetaceans. Giant penguins were extinguished where marine mammals became successful as the top predators in the oceans [31]. A new stage in the evolution of the group begins in the Neogene, which includes the appearance of modern forms closely related to living species [32,33]. Taxonomic and morphological diversification in living species is notably less than what was known in the past, and post-Pliocene species are almost entirely attributed to modern genera [34,35].", "An example of the transition that occurred during the Neogene is the avian assemblage of Horcón, on the central coast of Chile, which reflects the existence of a mixed fauna during the Pliocene, connecting the seabird associations of the late Miocene with the modern regional avifauna [36]. However, the Cenozoic history of penguins seems to have been somewhat more complex than previously believed. The current avifauna would be the result of a series of successive colonizations and extinctions closely linked to the establishment and development of the ocean currents and the ecological dynamics of species [35,37]. A recent analysis identified New Zealand (either exclusively or with South America) as the most likely ancestral area for crown clade penguins [38].", "Despite being a group with a low current diversity (18 species), considering the species known from the fossil record, the Sphenisciformes are one of the best-known avian clades, with about 65 recognized species [6,39]. Likewise, the phylogenetic relationships have led to the proposition of various phylogenetic hypotheses, which have been possible due to the good state of preservation of many fossils and the deep and widely comparative studies of the morphological features among the described lineages. In recent years, extensive morphological knowledge and the consolidation of molecular analysis techniques have allowed phylogenetic approaches to reconstruct the evolution of penguins by integrating extant and extinct forms [17,19,32,33,35,36,40,41,42,43].", "Some approaches have generated hypotheses where the influence of events such as those that occurred during the Neogene on the biogeographic patterns and the evolution of the Sphenisciformes niche are reconstructed; however, many scenarios only consider the current species [35,43]. In this sense, the richness of the penguin fossil record [6] allows the possibility of considering and integrating all the available information to propose broader approximations in a deep time approach.", "Thanks to the vast amount of information available on the presence of species during the Cenozoic in several locations of the Southern Hemisphere and modern biogeographic analyses methodologies, it is possible to reconstruct geographical scenarios of evolution over time and to understand the influence of environmental and geological changes on the diversification of penguins. In particular, BioGeoBEARS [44,45] analysis allows the reconstruction of ancestral areas in a context of maximum likelihood and employs Bayesian modeling from a calibrated phylogeny. Some previous contributions have dealt with this topic (e.g., [28,35,38]). We focus our review on detecting ancestral areas of origin and describing the paleobiogeographical patterns of the Sphenisciformes lineage based on a broad and complete analysis of the Sphenisciformes fossil record and the most recently published phylogenetic proposal based on the total evidence for the group [32]. This approach allows us to visualize the speciation, dispersal, and extinction events that would have occurred throughout their evolutionary history, shedding more light on how the environmental changes that occurred throughout the Cenozoic could have influenced the evolution and diversification patterns of penguins. This gives us the possibility of comparing our own results with the previous proposals.", "2. Materials and Methods", "2.1. Fossil Record and Penguin Phylogenies", "According to the available scientific literature and the Paleobiology Database, we consolidated a new biogeographical and temporal matrix, considering all the records for penguin species (Table 1). In this way, we recorded the time intervals according to their chronostratigraphic distribution range and encoded the presence (1) or absence (0) of the species in each geographical area. It should be mentioned that although a single occurrence is the only data for some fossil species (e.g., Crossvallia unienwillia), the stratigraphical range provided in Table 1 corresponds to the age of the level where the fossil was collected. The same criterion applies for species with multiple records (e.g., Palaeeudyptes klekowskii), in which the stratigraphical range corresponds to the ages of the levels where it was reported. For species with an uncertain age, due to the lack of a strict stratigraphic control (i.e., Marplesornis novaezealandiae), the range includes a different-ages proposal. Table 1 includes the source of the data.", "Data from 83 species (18 living and 65 fossil ones) were obtained. Given the need for a completely resolved and calibrated phylogeny to perform the BioGeoBEARS analysis, a review of the latest phylogenies proposed for Sphenisciformes was carried out. After considering the number of species included, the consistency of the calibrated ages, the degree of resolution, and the integration of multiple information sources, we applied the Bayesian total evidence phylogeny proposed by Gavryushkina et al. [32]. Another proposal, the Bayesian Markov Chain Monte Carlo (MCMC) framework for phylogenetic analysis, takes an extensive data source from molecular sequences derived from extant species and morphological traits from extant and fossil species. It also considers the stratigraphic intervals as the fossil occurrences. The phylogenetic proposal of Gavryushkina et al. considers the evolutionary affinities of penguins according to 202 morphological characters [42] derived from reasonably complete fossil specimens (n = 36), together with molecular and morphological information from the 18 living species [32]. With this input, this approach estimates and dates species phylogenies. The Bayesian method integrates the fossil information under a new perspective, unlike other methods that only use fossils to calibrate nodes or stablished origin intervals. For our purposes, we used the maximum sampled-ancestor clade credibility tree (the MSACC tree). This tree is a summary tree derived from a posterior sample that maximizes the product of posterior clade probabilities (see details in [80], cited in [32]). Other biogeographical proposals discussed below are based on different phylogenetic approaches [38,43] and references cited therein).", "2.2. Species Considered in the Present Analysis", "The description of the first fossil penguin was followed by a great proliferation of new genera and species, which after some years were re-evaluated and, in many cases, dismissed or considered as synonyms. This work took, as a starting point, a complete review of the fossil record for the Sphenisciformes lineage (Table 1, Figure 1). Even though the list of penguin fossil species is much more extensive, rigorous analyses carried out over recent decades have established long synonymic lists of species and genera that are no longer considered valid. Table 1 follows the taxonomic arrangements proposed for Argentinian [63,64,65,66,67,68,69,70,71], Chilean [67,69,72,73,78,81], Peruvian [24,28,41,57,69,73], Antarctic [27,49,50,51,52,53,54,57,58,59], New Zealand [11,17,19,20,33,38,42,48,55,60], Australian [56,67,75], and African [76,77] taxa. This compilation is essential to obtain complementary information for the discussion and the palaeoecological analysis.", "A particular case worth commenting on is that of Eudyptula. In this work, the traditional and most widely analyzed proposal, in which Eudyptula minor would be the only modern species of the genus Eudyptula, was adopted as input for the present analysis. According to that proposal, the diversity of Eudyptula forms is reflected in the six subspecies inhabiting Australia and New Zealand [2,82]. Other more recent proposals consider that Eudyptula would be constituted by E. minor and E. novaehollandiae, species of recent divergence [83,84] that have been accepted as such by the ornithological community [85]. The inclusion of Eudyptula as the only living species does not modify or bias our results. Further, the incorporation of extinct species was constrained by several additional factors, including taxonomic status, given that some taxa are currently synonyms or have been considered non-valid taxa in subsequent revisions, and their previous inclusion in a phylogeny.", "On the other hand, Spheniscus anglicus, a species described from materials that presumably come from the Miocene Bahía Inglesa Formation of Chile [86], was excluded from this analysis due to serious irregularities. The material was bought and removed the country illegally, violating the laws for the protection of the paleontological heritage in Chile. In this context, the species’ geographical and stratigraphic origin is not reliable. In addition, the characters used for its diagnosis are not adequate, and the proposal of a new species is unjustified. For these reasons, we decided to exclude S. anglicus from our analysis, a species that has never been listed or considered in any of the subsequent specialized scientific publications.", "In short, despite not being included in the present biogeographical analysis, the information derived from all the species was not included in phylogenetic proposal of Gavryushkina et al. [32], which provided complementary information on the presence and diversity in the continental areas considered, allowing the enrichment of aspects of the discussion. The details of the fossil species considered here, and those included in our analysis, are provided in Table 1.", "2.3. Paleobiogeographical Analyses", "The biogeographic regions established for the analysis were chosen based on the extant and ancient distribution of Sphenisciformes species, as well as on geological and climatic criteria. Thus, we established six biogeographic regions or areas: north-central South America, including Galapagos (from 23° S), southern South America, southern Africa, Antarctica, Australia, and New Zealand, unlike the nine [28], ten [35], or the twelve [38] areas included in other contributions. For analysis, we proposed a flexible scenario for the dispersal events among the various study areas. This criterion was determined by the proximity and distances among the six areas and their geological histories linked to the fragmentation and drift of Gondwana since the Cretaceous and, later, during the Paleogene and the Neogene [87,88]. These drift processes triggered the oceanographical evolution of marine currents [89], which are key factors in the dispersal possibilities for penguins. Likewise, the possibilities for the colonization of areas were established based on the long-distance swimming characteristics observed in current penguins, which were presumably present in Paleogene forms according to fossil distribution since the Paleogene [33]. Given the outstanding dispersal and marine movement capacity reflected in modern species, as well as the Southern Hemisphere distribution of the fossil and modern species, a matrix of the probability of colonization was adjusted to 1 with respect to the studied areas.", "In accordance with the BioGeoBEARS analysis [44], we carried out the evaluation of three models: Dispersal—Extinction Cladogenesis (DEC); a likelihood version of the Dispersal—Vicariance model (DIVALIKE); and a likelihood version of the BayArea model (BAYAREALIKE). The DEC model considers and emphasizes changes in the range of distribution in speciation events (cladogenesis). Under that model, during events a descendant lineage will always occupy a single region of the ancestral area, considering sympatry or vicariance. The DIVALIKE model allows a daughter lineage to retain more than a single geographical region of ancestral occupation during the vicariant event. This model does not allow a daughter lineage to inherit a small rank that is sympatric to the rank of another descendant lineage. Conversely, the BAYAREALIKE model does not emphasize geographic range variation at speciation events; instead, it estimates range changes along speciation events through range expansion−contraction dynamics., We assessed these models including the Jump-dispersal (+J) parameter [44,90]. This parameter allows evolutionary founding events, where an emerging novel lineage disperses outside of the area(s) occupied by its ancestor during the speciation process.", "All the models were compared, considering the p-value for the LRT (Likelihood Ratio Test) and the value of the AIC for each evaluated scenario [91]. The estimation models using the methodologies derived from BioGeoBEARS have been applied to various bird taxa, and despite receiving criticism for the inclusion of the parameter J (the founder effect) [92], these models have been reevaluated, reinforcing, and supporting the validity of the models [93]. Thus, we incorporated founder-event speciation (+J), which results in a process that is important in island systems for birds, considering the importance of transcontinental colonization events during different bird clades diversification, and especially for penguins [35]. Specifically, models that included the +J parameter have been broadly consistent in explaining the colonization processes in biogeographic and macroevolutionary studies. Examples are the contributions on several lineages of modern birds, including the Megapodidae family within Galliformes [94], Thraupidae (Coerebinae) [90], Motacillidae [95], Coraciiformes [96], Trogoniformes [97], Rallidae [98], and those studies on fossil lineages, such as Coelurosauria clade [99], and mammals, such as horses (Equinae) [100]. With particular reference to penguins, previous works analyzed the crown group species [35] as well as fossil representatives [38]. In line with these works and the life-history traits of penguins, we considered that the +J parameter would be associated with Sphenisciformes macroevolutionary process, due to the remarkable oceanic dispersion capacity evidenced by modern and ancient forms [77,101,102]. The statistical analyses were performed using the software RASP powered by R software [103].", "3. Results and Discussion", "3.1. Paleogene History of Penguins", "According to the results obtained here, the best model was the BAYAREALIKE + J, which provided the statistical support with the lowest AICc value and the highest AICw, compared to the other models (Figures S1–S6, Table 2 and Table S1); there are significant differences between the BAYAREALIKE + J and BAYAREALIKE model scenarios (Table S2). Similar results were obtained in previous contributions [38], although in other analyses the selected model was DIVALIKE + J [35]. As we expected, our results confirmed the relevance of the +J parameter (founder events) to explain the biogeographical history of penguins, a clade with a presumably well-stablished dispersal capacity due the early development of adaptative traits to navigate across marine environments; this is supported by the analyses of Paleogene forms, including those of Waimanu [11]. In addition, the BAYAREALIKE + J, as a better model, provides support for the importance of geographical expansion−contraction dynamics to explain the evolutionary patterns of Sphenisciformes. The Cenozoic cooling trends triggered many biomic expansions−contractions in Southern Hemisphere continents, which influenced the dispersal processes and possibly the speciation and extinction patterns.", "In general terms, all the models pinpoint and concur with a center of origin for Sphenisciformes in New Zealand (Figures S1–S6). These results are consistent with previous estimates based on fossil findings, which also estimate the origin of the lineage towards the late Cretaceous [9,10,11,12,13]. This is a logical proposal given the high diversification and specialization already present in the Paleocene. The oldest records for penguins correspond to the Paleocene and are concentrated in New Zealand [17,18,19,20,104].", "The results of our analysis pinpoints New Zealand as the most likely ancestral area, and secondly points to Antarctica with slightly lower probabilities (Figure 2; see the Supplementary Materials for details). It is noteworthy that New Zealand’s importance as a center of origin is strongly supported by a high concentration of records, many of them being the oldest penguin records reported to date [6,19,20,104] (Figure 1, Table 1). It should be noted that New Zealand’s geographical proximity to the Antarctic territory during the Upper Cretaceous and the early Paleogene provides some evidence of the significance of both continents during the initial diversification of the group. Findings for the Chatham Islands, and specifically associated with the Takatika Grit, show that since the Upper Cretaceous (c.83−79 Ma) Zealandia began to present a progressive rupture with respect to West Antarctica [14,87,105], continuing until the Eocene with respect to the eastern Antarctic region [106]. At the end of this stage, Zealandia would have experienced a strong marine transgression [107,108]. This process might explain the notable radiation and rapid diversification of penguins during the Eocene for Antarctica, as compared with New Zealand. The abundant fossil record of Seymour Island (Antarctica) strongly supports this idea. In this sense, the wider Antarctic territory would have offered greater opportunities, in terms of colonization of new niches and thus the generation of diverse processes of speciation, due to geographic isolation.", "Our results, like previous findings [28,38], allow us to postulate New Zealand as a probable main ancestral territory. In addition, is important to consider the geographical proximity between New Zealand and Antarctica during the Paleogene; both territories during the Paleocene-Eocene climatic optimum would have presented very similar environmental conditions at the continental level, with cold temperate environments that would have presented periods of fluctuation towards warm temperate climates during the Early Eocene Climatic Optimum (EECO). This would have made it possible to configure humid temperate forest biomes, with tropical floristic components during several Paleogene intervals [109,110,111]. Likewise, marine estimates show significant warming of Pacific waters from the upper Paleocene to the middle Eocene [46,112,113]. This paleoenvironmental context could have favored the dispersal between New Zealand and Antarctica, given the importance that oceanic temperatures possibly played for the dispersal of the first penguins. Added to this is the Crossvallia record in Antarctica and New Zealand, which further strengthened the links between these two large areas during the first million years of the group’s evolution. Crossvallia unienwillia was a large penguin species, with a single record in the Paleocene of Seymour Island (Antarctica); due to the incompleteness of its skeleton, it has been repeatedly omitted from phylogenetic analyses. Its presence, however, indicates the presence of Sphenisciformes in Antarctica since the Paleocene [46,47]. Crossvallia waiparensis is the second species of Crossvallia that has been described for the Paleocene of New Zealand (Figure 3).", "The recent description of numerous taxa for the Paleocene of New Zealand indicates favorable conditions for the establishment and flourishing of the group. Although only two species of the genus Waimanu have been included (Figure 2), the New Zealand Paleocene sphenicofauna also includes other species such as Kupoupou stilwelli, Crossvallia waiparensis, Sequiwaimanu rosieae, and Kumimanu biceae (Figure 1 and Figure 2). Although the Antarctic record is scarce during the Paleocene, this is probably due to a taphonomic bias rather than to regional environmental conditions, since the changes in the depositional environment of the James Ross Basin during the Eocene caused a more abundant and diverse penguin record [114].", "During the middle Eocene, several lineages diversified in Antarctica, including forms of a wide spectrum of sizes, including some giant penguins such as Anthropornis grandis that reached 1.7 m high, and other tiny penguins such as Aproskoditos microtero that were only 0.35 m high. This shows great diversity, also evidenced in the number of species included in other genera, such as Delphinornis, Tonniornis, Palaeeudyptes, and others (see Table 1). This broad diversity is probably associated with niche partitioning processes powered by the development of different bill morphologies and specializations in a wide range of trophic possibilities [115,116]. Among these taxa are the forms that reached the southern and central South American coasts, allowing the establishment of the Perudyptes devriesi lineages on the Peruvian coasts. The record of taxa typically Antarctic in southern South America during the middle Eocene [29,30] supports this hypothesis (Figure 4).", "During the late Eocene and probably the early Oligocene, the Antarctic species would have completely disappeared. A highlighted diversification of the New Zealand lineages is evidenced at this time. Some colonizations in South America, such as those of Icadyptes salasi and Inkayaku paracacensis, are verified during the Eocene of Peru, and would be closely linked with the penguin fauna of New Zealand. According to our results, the three lineages (together with Perudyptes devriesi) would have independently colonized the subtropical Pacific coasts of South America during the late Eocene. These colonizations could be related with migrations produced by oceanic currents established from New Zealand to South America during the Eocene after the EEOC, with the opening of the Tasman Strait and the Drake Passage. The currents suffered notable alterations at the latitudinal level, ending in the establishment of the circum-Antarctic current, the main influencing factor in progressive Antarctic freezing during the Oligocene [117,118,119] (Figure 5).", "In this sense, we proposed that New Zealand could have played an important role as a refugee during the Oligocene for penguins that faced the climatic changes that transformed the Antarctic continent and the marine current regimes [117,118,119,120]. This idea is aligned with the presence of the Kaiika lineage, a taxa endemic to New Zealand [48], and the diversity of the genus Kairuku with three species recorded for the New Zealand Oligocene [60]. Likewise, Palaeeudyptes, of presumably Antarctic origin, would have been present in New Zealand, as evidenced, for example, by Palaeeudyptes marplesi [42]. Therefore, the fossil findings suggest that after the extinction of almost all of the Antarctic forms, Palaeeudyptes could have been one of the few lineages that would have colonized and persisted in New Zealand (Figure 5).", "3.2. Neogene History of Penguins", "According to our results, the taxa recorded in Patagonia (Argentina), would have had a New Zealand origin. Presumably, the establishment of the Antarctic circumpolar current would have allowed the dispersion of the lineages from New Zealand to southern South America, possibly given the similar environmental conditions in both places that might have been decisive for aspects related to the feeding and breeding areas. In this way, from the colonization of southern South America at the beginning of the Miocene, several lineages would have developed. First, Paraptenodyes (including P. robustus and P. antarcticus), and later, Eretiscus tonni and Palaeospheniscus (with a high diversity constituted by P. bergi, P. patagonicus, and P. biloculata), established a wide presence in southern South America, as evidenced by the fossil record of Patagonia Argentina [61,64,70,71], and reached the coasts of Chile and Peru by the middle Miocene [81,121].", "The Miocene was a crucial time for the establishment of the most modern faunas [36,71,122]. Our results suggest that from New Zealand to Southern South America, three biogeographical events that were probably related with the intensification of the Antarctic circumpolar current during the middle and late Miocene [89], deserve to be highlighted. This new scenario favors the selection of physiological and biochemical adaptations to face colder environmental regimes, an idea strongly supported by genomic studies [35,122]. Thus, our results are consistent with the biogeographical proposals from the crown group [35,38]; see also [123].", "The first event corresponds to the diversification of Spheniscus, widely recorded during the Mio-Pliocene of Chile and Peru [36]. Here, an origin in the south of South America and a dispersion towards the north, which was probably influenced by the beginning of the establishment process of the Humboldt current during the middle Miocene (15−12 Ma) is proposed. The ecological preferences of the Spheniscus lineage are consistent with colder waters and a diet based on fish [116]; it could be possible that these traits were inherited from their ancestors. This is also supported by the fossil record of these areas and even by the fossil record of Antarctic [54]. By the middle Miocene, there is a vast record of penguins attributed to Spheniscus, mainly in Chile and Perú, represented by species such as Spheniscus urbinai, S. megaramphus, S. muizoni, and S. chilensis. The diversification of the modern lineages corresponding to Spheniscus would have been relatively recent. Respectively, S. humboldti and S. demersus might have colonized the central-northern Pacific coast of South America and the coasts of southern Africa from southern South America during the Pleistocene [77,124]. In addition, and recently, S. humboldti colonized the Galapagos archipelago, allowing the origin of S. mendiculus [122]. These processes were probably related to the expansion of the polar caps during the glaciations, reaching almost 40° South latitude, altering the structure of the marine currents and the latitudinal thermal gradient [125]. Thus, our results are consistent with previous proposals [77] of multiple colonization events in Africa for Sphenisciformes. This is supported by the presence of Nucleornis insolitus, Dege hendeyi, and Inguza predemersus in the fossil record, which colonized Africa independently at the end of the Miocene (Figure 6 and Figure 7).", "A second biogeographical event corresponds to the clade Megadyptes-Eudyptes, with a probable common ancestor in New Zealand. These results are consistent with previous analyses about the biogeographical history for this clade [38]. In addition, our findings suggest a strong generalist condition for these geographical occupations. The lineage would have developed wide dispersal capacities around Antarctica, reaching multiple continental islands close to the mainland masses, which would have generated advantages in terms of the absence of possible predators and competition for resources. However, the cooling processes that intensified during the Plio-Pleistocene led to the formation and growth of ice caps in the Antarctic Ocean. Therefore, these glacial and interglacial intervals would have generated isolation and subsequent speciation in some of these lineages [35]. On the other hand, the scenarios of allopatric speciation by isolation in islands for the Eudyptes lineage are discussed by some authors, such as Frugone et al. [126], who proposed a greater effect of the thermal zonation of the Antarctic polar front and the subtropical currents on the definition of species. Consequently, the strong dispersal capacity and a more generalist condition would not have allowed the necessary genetic isolation and subsequent speciation, as seems to be evidenced in E. schlegeli and E. chrysolophus. In this way, Eudyptes would be an example of a generalist lineage that, with its different species, migrated from New Zealand throughout the Southern Hemisphere, reaching southern South America, subantarctic islands, and Africa [35,126] (Figure 6 and Figure 7).", "During the middle Miocene a third diversification process of the clade Pygoscelis-Aptenodytes is revealed in our results. The radiation center was probably from southern South America with lineages such as Madrynornis endemic to Patagonia, and a common ancestor of Pygoscelis and Aptenodytes with an outstanding skill of dispersion in the circum-Antarctic waters. These ocean currents became colder and colder since the intensification of the circum-Antarctic current 11 Ma ago, thanks to the development of biochemical and metabolic adaptations associated with thermoregulation, optimization of oxygen consumption and ATP production [35,122,126]. This would have allowed them to reach a circum-Antarctic distribution during the middle and late Miocene, as evidenced by the presence of Pygoscelis tyreei and Aptenodytes ridgeni in New Zealand, as well as the presence of P. grandis and P. calderensis in southern South America. The southern parts of Argentina and New Zealand may have been linked during the late Middle Miocene as areas of constant exchange of species with other regions, powered by the latitudinal direction of marine currents [118]. Finally, together with the cooling and the Pleistocene glaciations, processes of population isolation occurred by the formation of polar caps and the consequent changes in the currents. Some patterns triggered by glacial-interglacial intervals modified the genetic flow between populations and promoted isolation scenarios and the subsequent speciation in the Antarctic lineages. Consequently, the adaptations previously developed along the crown group lineage evolution, which allowed the occupation of more extreme thermal niches in increasingly cold waters, would have been key exaptations in the colonization and subsequent biomic specialization in extreme tundra conditions. The modern species Aptenodytes forsteri and Pygoscelis adeliae are examples of that process (Figure 6 and Figure 7).", "4. Conclusions", "Despite using a different phylogenetic proposal, a flexible scenario for dispersal possibilities, and an alternative areas delimitation, our results are broadly consistent with previous findings about the main paleobiogeographical patterns during penguins’ evolutionary history. Thus, our findings are broadly consistent with a New Zealand center of origin for Sphenisciformes during the late Cretaceous and early Paleogene, supporting the hypothesis generated by analyses proposed by diverse authors [28,38]. With respect to the Eocene, we found an outstanding diversification and dispersion of penguins geographically associated with Antarctica, due to the establishment of temperate conditions triggered by PETM and EECO. The Oligocene and early Miocene represented a turnover in the Sphenicofauna; the extinction of Antarctic lineages consolidated New Zealand and Southern South America as refuges associated with the latitudinal contraction of temperate biomes and warm marine currents. The outcomes suggest that crown group Sphenisciformes flourished during the Miocene and many adaptations from their ancestors would probably be established as exaptations to face increasingly cold environmental conditions during the Neogene. Thus, some lineages expanded their areas towards subtropical latitudes in South America and Africa, while other lineages (Pygoscelis and Aptenodytes) developed the colonization capacity for the hardest climatic environments, such as the tundra conditions in Antarctica during the Pleistocene glaciations. All these statements are, however, provisional, and subject to new findings and subsequent analyses. Although the penguin record is quite complete in comparison with those of other bird taxa, several deficiencies and important gaps are recognized during the time periods considered. We trust, however, that the efforts of numerous researchers currently working on these studies will at least partially reverse these findings.", "Funding", "This research was funded by the General Research Council (Dirección General de Investigaciones-DGI) at the Universidad Santiago de Cali (Colombia) under call No. 01-2021; La Plata University PI N955 (Argentina), and the National Scientific and Technical Research Council PIP 0096 (Argentina).", "Institutional Review Board Statement", "Not applicable.", "Informed Consent Statement", "Not applicable.", "Data Availability Statement", "The data presented in this study are available on the text in the Section 2.", "Acknowledgments", "We thank A. Givryushkina for allowing us to use her phylogenetic proposal and for being ready to collaborate with us; Leonardo Belalcazar for the computational logistical support; and Jacobo Sabogal for the opinions and technical support in graphic design and penguin illustrations. Finally, we acknowledge the anonymous reviewers who undoubtedly contributed to the improvement of the manuscript.", "Mayr, G.; De Pietri, V.L.; Love, L.; Mannering, A.; Scofield, R.P. Leg bones of a new penguin species from the Waipara Greensand add to the diversity of very large-sized Sphenisciformes in the Paleocene of New Zealand. Alcheringa2020, 44, 194–201. [Google Scholar] [CrossRef]", "Figure 1.", "Updated chronostratigraphic distribution of fossil penguins of the world (n = 65). Follow color key to geographical occurrence (see Table 1 for details): (a–k) indicates the species of penguin illustrations. On the right side (bottom-up), the living forms Aptenodytes forsteri, Pygoscelis papua, Spheniscus magellanicus, and Eudyptes chrysolophus are representatives of each genus. Penguins not at scale. Penguin illustration credits: Jacobo Sabogal.", "Figure 1.", "Updated chronostratigraphic distribution of fossil penguins of the world (n = 65). Follow color key to geographical occurrence (see Table 1 for details): (a–k) indicates the species of penguin illustrations. On the right side (bottom-up), the living forms Aptenodytes forsteri, Pygoscelis papua, Spheniscus magellanicus, and Eudyptes chrysolophus are representatives of each genus. Penguins not at scale. Penguin illustration credits: Jacobo Sabogal.", "Figure 2.", "Ancestral range estimation for Sphenisciformes based on results of high percentages for nodes considering the BAYAREALIKE + J scenario and using the six-area regime as shown in map of biogeographic areas powered in BioGeoBEARS. (a–l) indicates the species of penguin illustrations. Follow the color key for the cases of presence in more than one area. For details see the Supplementary Materials. Penguin illustration credits: Jacobo Sabogal.", "Figure 2.", "Ancestral range estimation for Sphenisciformes based on results of high percentages for nodes considering the BAYAREALIKE + J scenario and using the six-area regime as shown in map of biogeographic areas powered in BioGeoBEARS. (a–l) indicates the species of penguin illustrations. Follow the color key for the cases of presence in more than one area. For details see the Supplementary Materials. Penguin illustration credits: Jacobo Sabogal.", "Figure 3.", "Middle-Late Paleocene biogeographical events: origin of Sphenisciformes in New Zealand (Kupoupou stilwelli in the image) and early dispersion to Antarctica, evidenced by the presence of Crossvallia (in the image).", "Figure 3.", "Middle-Late Paleocene biogeographical events: origin of Sphenisciformes in New Zealand (Kupoupou stilwelli in the image) and early dispersion to Antarctica, evidenced by the presence of Crossvallia (in the image).", "Figure 4.", "Main Eocene biogeographical events: the diversification of diverse Sphenisciformes lineages in Antarctica (i.e., Palaeeudyptes and Delphinornis in the image) and early dispersal and colonization towards South America, evidenced by the presence of Perudyptes and Incayacu (in the image) and Icadyptes.", "Figure 4.", "Main Eocene biogeographical events: the diversification of diverse Sphenisciformes lineages in Antarctica (i.e., Palaeeudyptes and Delphinornis in the image) and early dispersal and colonization towards South America, evidenced by the presence of Perudyptes and Incayacu (in the image) and Icadyptes.", "Figure 5.", "Main Oligocene biogeographical events: the extinction of Sphenisciformes due to Antarctica cooling; New Zealand as a refuge and center of diversification, evidenced by the presence of many genera and species, such as the Kairuku (in the image).", "Figure 5.", "Main Oligocene biogeographical events: the extinction of Sphenisciformes due to Antarctica cooling; New Zealand as a refuge and center of diversification, evidenced by the presence of many genera and species, such as the Kairuku (in the image).", "Figure 6.", "Main Miocene biogeographical events: the colonization of lineages from New Zealand to South America due to circum-Antarctic oceanic currents (i.e., Paraptenodytes in the image); diversification and expansion of Spheniscus across South America.; origin and diversification of Megadyptes-Eudyptes clade from New Zealand; diversification of clade Pygoscelis in southern South America.", "Figure 6.", "Main Miocene biogeographical events: the colonization of lineages from New Zealand to South America due to circum-Antarctic oceanic currents (i.e., Paraptenodytes in the image); diversification and expansion of Spheniscus across South America.; origin and diversification of Megadyptes-Eudyptes clade from New Zealand; diversification of clade Pygoscelis in southern South America.", "Table 1.", "Updated checklist of the fossil penguin species of the world (n = 65), their occurrences, and stratigraphical ranges (SR) (in some cases, only an approximation is provided, corresponding to the age of the level where the fossil was collected).", "Table 1.", "Updated checklist of the fossil penguin species of the world (n = 65), their occurrences, and stratigraphical ranges (SR) (in some cases, only an approximation is provided, corresponding to the age of the level where the fossil was collected).", "* Species included in the paleobiogeographical analyses. a We agree with Jadwiszczak [52,78] regarding the prematurity of the new combination Delphinornis wimani [41] for a species that already transferred from Notodyptes to Archaeospheniscus [79]. However, we maintain the new name for this table in accordance with the phylogeny on which we have based our biogeographical analyses [32].", "Table 2.", "Summary of results for all six models evaluated under the six-area regime. Models with +J indicate those allowing for founder effect dispersals. The best-supported model is shown in bold. p is the number of parameters.", "Table 2.", "Summary of results for all six models evaluated under the six-area regime. Models with +J indicate those allowing for founder effect dispersals. The best-supported model is shown in bold. p is the number of parameters.", "Model", "LnL", "p", "AICc", "AICc wt.", "DEC", "−139.9", "2", "284", "2.6 × 10−6", "DEC + J", "−133", "3", "272.5", "8 × 10−4", "DIVALIKE", "−151.4", "2", "307.1", "2.5 × 10−11", "DIVALIKE + J", "−143.7", "3", "294", "1.8 × 10−8", "BAYAREALIKE", "−150.2", "2", "304.6", "8.9 × 10−11", "BAYAREALIKE + J", "−125.9", "3", "258.3", "1.00", "Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.", "Follow MDPI", "Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely", "those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or", "the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas,", "methods, instructions or products referred to in the content." ], [ "Abstract", "Classic problems in historical biogeography are where did penguins originate, and why are such mobile birds restricted to the Southern Hemisphere? Competing hypotheses posit they arose in tropical-warm temperate waters, species-diverse cool temperate regions, or in Gondwanaland approximately 100 mya when it was further north. To test these hypotheses we constructed a strongly supported phylogeny of extant penguins from 5851 bp of mitochondrial and nuclear DNA. Using Bayesian inference of ancestral areas we show that an Antarctic origin of extant taxa is highly likely, and that more derived taxa occur in lower latitudes. Molecular dating estimated penguins originated about 71 million years ago in Gondwanaland when it was further south and cooler. Moreover, extant taxa are inferred to have originated in the Eocene, coincident with the extinction of the larger-bodied fossil taxa as global climate cooled. We hypothesize that, as Antarctica became ice-encrusted, modern penguins expanded via the circumpolar current to oceanic islands within the Antarctic Convergence, and later to the southern continents. Thus, global cooling has had a major impact on penguin evolution, as it has on vertebrates generally. Penguins only reached cooler tropical waters in the Galapagos about 4 mya, and have not crossed the equatorial thermal barrier.", "Figures", "Figure 1", "Alternative phylogenetic hypothesis proposed for…", "Figure 1", "Alternative phylogenetic hypothesis proposed for all extant genera of penguins. Hypothesis including all…", "Figure 1", "Alternative phylogenetic hypothesis proposed for all extant genera of penguins. Hypothesis including all genera were based on (a) morphological (O'Hara 1989), (b) behavioural (Jouventin 1982), (c) myological (McKitrick 1991), (d) integumentary and breeding (Giannini & Bertelli 2004) and were compared to the topology we obtained with (e) nuclear and mitochondrial DNA sequences. Hypothesis based on (f) myology (Schreiweis 1982) and (g) DNA hybridization studies (Sibley & Ahlquist 1990) did not include all genera and, therefore, were not compared in the AU test.", "Figure 2", "Bayesian estimate of phylogenetic relationships…", "Figure 2", "Bayesian estimate of phylogenetic relationships of modern penguins. Phylogenetic reconstruction was based on…", "Figure 2", "Bayesian estimate of phylogenetic relationships of modern penguins. Phylogenetic reconstruction was based on 2802 bp of RAG-1 and 2889 bp of mitochondrial 12S and 16S rDNA, cytb and COI, excluding gaps and ambiguously aligned positions. Numbers above branches are Bayesian posterior probabilities/ML bootstrap proportions/MP bootstrap proportion, which are represented as open star when (1.0/100/100). Branches for more distant outgroups were shortened for graphic purposes. A bar represents the expected number of DNA substitutions per site. Each genus is colour-coded. Penguin drawings were modified from del Hoyo et al. (1992), with permission, from Lynx Edicions, Barcelona, Spain.", "Bayesian estimates of ancestral areas. Areas were defined as southernmost breeding regions for each species within Antarctica and the Antarctic Convergence (blue), outside Antarctic convergence and up to latitude 45 °S (green), between 45 °S and 30 °S (red), and north of 30 °S (grey). Posterior probabilities for each state are shown as a pie diagram in each internal node.", "Figure 4", "Chronogram of penguin diversification. Nodes…", "Figure 4", "Chronogram of penguin diversification. Nodes A and B were fixed at 104 and…", "Figure 4", "Chronogram of penguin diversification. Nodes A and B were fixed at 104 and 90 myr. Credibility intervals (95%) are indicated by grey bars at numbered internal nodes. Vertical dashed line indicates the K/T boundary. Periods that Antarctica was ice-covered (black continuous bars) are projected as shaded grey rectangles in the chronogram. Ocean temperature is based on high-resolution deep-sea oxygen isotope records. The MMCT is indicated by an arrow. Geological time scale is given as defined by the Geological Society of America.", "Figure 5", "Polar stereographic projection to 35…", "Figure 5", "Polar stereographic projection to 35 °S at 40, 25, 15 and 5 mya.…", "Figure 5", "Polar stereographic projection to 35 °S at 40, 25, 15 and 5 mya. Reconstructions have continents represented by present-day shorelines (ODSN 2004). Antarctica is indicated as partially (b–c) and fully covered in ice (d–f) (Shevell et al. 2004). Genera are represented by different coloured capital letters, following the coloured names indicated at the bottom. As they start to diversify, species are represented by small letters according to the first letter of common names given in figure 2, except royal penguin represented by r1. Oldest and biggest penguin fossils (Simpson 1976; Clarke et al. 2004) are numbered 1–6 and projected at (a) 40 and (b) 25 mya. The Antarctic circumpolar current, indicated by arrows in the reconstruction at 25 mya only, was formed at the end of the Oligocene." ] ]

[ "https://www.nature.com/articles/s41598-019-49244-4", "https://www.nature.com/articles/s41467-021-25838-3", "https://www.discovermagazine.com/the-sciences/black-holes-ants-and-roller-coasters", "https://plato.stanford.edu/entries/descartes-physics/", "https://www.mdpi.com/2409-9287/3/2/9", "https://physics.stackexchange.com/questions/183823/mathematical-proof-of-force", "https://www.linkedin.com/pulse/cunk-physics-subhendu-mukherjee", "https://www.studysmarter.co.uk/explanations/physics/physics-of-motion/centrifugal-force/", "https://physics.stackexchange.com/questions/213456/why-is-centrifugal-force-considered-fictitious-when-its-the-one-that-feels-rea", "https://www.britannica.com/science/centrifugal-force", "https://www.wired.com/2009/04/centripetal-vs-centrifugal-word-origins/", "https://www.pumpsandsystems.com/three-fictitious-forces-one-real-force", "https://math.ucr.edu/home/baez/physics/General/Centrifugal/centri.html", "https://www.physicsclassroom.com/class/circles/Lesson-1/The-Forbidden-F-Word", "https://www.skitalk.com/threads/centripetal-force-vs-centrifugal-force.14136/", "https://www.wyzant.com/resources/answers/178331/centrifugal_force_is_fictitious_force_why_is_it_called_fictitious_force" ]

[ "support", "support", "support", "support", "support", "support", "refute", "support", "refute", "refute", "refute", "refute", "support", "refute", "refute", "refute" ]

[ [ "Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain", "the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in", "Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles", "and JavaScript.", "Subjects", "Abstract", "In this study, we developed a modular micronozzle system that can control the flow of fluid based on centrifugal force and synthesize functional alginate microspheres with various structures and sizes. Our method is to fabricate a programmable microreactor that can be easily manufactured without the conventional soft-lithography process using various sequences of the micronozzles with various inner diameters. To overcome the obstacles of pump-based microfluidic devices that need to be precisely controlled, we designed the programmable microreactor to be driven under centrifugal force with a combination of micronozzles, thus enabling the mass production of various functional alginate microspheres within a few minutes. The programmable microreactor designed through the arrangement of the modular micronozzles enables the formation of various types of alginate microspheres such as core-shell, Janus, and particle mixture. These materials are controlled to a size from 400 µm to 900 µm. In addition, our platform is used to generate pH-responsive smart materials, and to easily control various sizes, shapes, and compositions simultaneously. By evaluating the release process of model drugs according to the pH change, the possibility of drug delivery application is confirmed. We believe that our method can contribute to development of biomaterials engineering that has been limited by the requirement of sophisticated devices, and special skills and/or labor.", "Introduction", "The introduction of microfluidic devices in the synthesis of functional materials in the early 21st century is expected to create a new paradigm shift that can overcome the limitations of material synthesis based on traditional chemistry1,2,3. A coin-sized microfluidic reactor can precisely control laminar flow fluids through fine-patterned microchannels, and specific advantages such as perfect mixing reactions in a short time, and heating reactions with little local temperature difference are available4,5,6. Particularly, these microfluidic devices can control the size and various shapes of microdroplets according to the channel design and are sufficiently attractive to accept new synthesis techniques7,8. For example, polydimethylsiloxane (PDMS)-based flow-focusing microfluidic reactors were based on the droplet pinch-off in immiscible flows at a geometrical complex channel design9,10. Because of the surface-tension phenomenon, such methods can be performed to generate various types of functional materials that are monodisperse single spheres as well as core-shell, Janus, and multiple emulsions11,12. However, the research trends of microfluidic reactors over the past decade show that they are relatively distant from the expectations of early researchers.", "A clear gap exists between the current microfluidic technologies that can meet the recent materials trends, despite the considerable effort expended to realize the creation of new functionalities with highly controlled physicochemical parameters such as size, shape, composition, and surface property for the extension of specified applications using custom-built microfluidic reactors13,14. This could be due to the high costs associated with microfluidics, and the requirement for well-trained skillful labor15,16,17. This means that the microfluidic reactor must be made inexpensively and quickly in accordance with the design of various materials, to satisfy customers who demand prototype results in a short time18. As shown in the recent works, microfluidic reactors have been developed using glass, silicon, and PDMS polymers based on lithographic processes19,20,21. Hence, it is a passive manufacturing process to integrate the microchannels and align the center of the inner microchannel, which is an important process in manufacturing a typical flow-focusing reactor for synthesizing a functional material. Additionally, the microfluidic reactor should overcome the limitations of traditional methods of transporting fluids in microchannels using external pressure and electric fields22,23. Generally, a microfluidic reactor requires a microsyringe pump to tune the fluid flow direction and regulate the adjusted volumetric flows24. In particular, it takes a relatively long time to derive such a steady-state flow of a variety of viscous fluids by inducing conventional pumping methods, and has limitations to connect to a continuously expandable mass-production of a wide range of customized smart materials25,26,27. Hence, a limit exists in the demand for quickly changing the device design and implementing customized prototype materials according to various material designs28,29,30. Therefore, the development of end-user friendly microfluidic techniques using simple, easy, and cost-effective methods remains a challenge in the design of a variety of functional materials with monodisperse and narrow size distribution without any deformation31,32,33.", "Previously, Takeuchi et al. have reported the centrifuge-based droplet shooting device (CDSD) for the generation of 3D multi-compartmental particles using a multi-barrelled capillary34 and Kim et al. demonstrated the sensory polydiacetylene (PDA) liposome encapsulated multi-phasic alginate microparticles generation by using a custom-built needle injection system35. Although the centrifuge-based system has successfully been presented to generate the complex alginate microparticles, these techniques are still arrowed irreversible device fabrication procedure which limits their flexibility for disassembly process.", "Herein, we present a novel method to generate engineered alginate microspheres using a centrifugal-force-driven modular micronozzle system. This strategy is very attractive in that the micronozzle device preparation and operation are very easy and convenient, requiring no complicated skill but just a centrifuge and the easy combined micronozzle system. In addition, this strategy is not only useful to generate a complex alginate microsphere, fast, and reproducible manner, but can also yield scalable production. Depending on the shape and size of the engineered alginate microsphere, our programmable micro-reactor is customized by different combinations of microcentrifuge tube, microneedle, and conical tube, which are generally easily found in the laboratory. This system was operated within a few minutes by centrifugation-induced gravitational force. In addition, we show the modular micronozzles with different sequences that can be made with predetermined geometries including core-shell, Janus, and mixtures of size-controlled individual particles. Finally, we investigate the potential application in smart drug delivery systems using simultaneously generated pH-responsive model functional medicines. We envision that this universal strategy may serve as an on-demand platform for a wide range of real applications, especially for the development of advanced smart materials in biomedical engineering with new functionalities.", "Results and Discussion", "Generation of engineered alginate microspheres", "The implementation of a material-customized changeable reactor is key for determining specific individual functions to apply to various applications36,37,38,39. Figure 1 shows a schematic illustration of the modular micronozzle design for the generation of complex alginate microspheres. Our approach is based on an external gelation called the in-situ dripping direct method which is directly induced the alginate gelation without diffusion control40. Further, it is possible to fabricate programmable modular microreactors that are coded with the structure and shape of the alginate through a simple combination of micronozzles. In addition, to overcome the limitation of the conventional pump-based microreactor, which requires careful fluid control, a user friendly microreactor was implemented by inducing fluid flow using centrifugal force (Table S1). This centrifuge-based easy setup is composed of three functional parts: a modular micronozzle, a micronozzle supporter, and a collection tube (see Fig. 1B–E). The desired functional materials were produced within 3 min through the programmable modular microreactor, in which the size and shape of the alginate particle were coded according to the assembly of the micronozzles having different inner diameters. More specifically, the alginate microsphere generation mechanism was followed by a “quasi-static droplet formation”, where a breaks alginate solution off immediately the centrifugal gravity force-induced drag force (Fg) exceeds surface tension-induced counter acting force (Fs). Based on this, the alginate microspheres were generated from different modular micronozzles when a higher centrifugation was conducted than the surface tension of the alginate aqueous solution.", "Figure 1", "Centrifugal force-driven modular micronozzle system setup. (A) A schematic of the basic concept for generation of alginate microsphere. (B) A photo of centrifugal microfluidic device after assembled. The modular micronozzle consists of (C) a micronozzle and (D) a supporter. (E) A photo of assembled modular micronozzle.", "Figure 2 shows the modular micronozzle reactors that are programmed to generate the alginate particles of various shapes and sizes through a combination of two needles, i.e., independently parallel nozzles, nozzle in nozzle, and union of two nozzles. The first micronozzle was designed to simultaneously synthesize two alginate particles containing different functional particles and sizes as shown in Fig. 2A. Two micronozzles, named sequence “a, b”, were aligned in parallel to the support and mounted in a centrifuge; subsequently, two different composite microspheres were generated within a few minutes. Centrifugal force-driven gravity was induced to release each alginate solution that regularly split to form a spherical droplet. Importantly, the formation of droplets occurred in the regime of water droplets. Then, the droplets passed through the collecting tube, and the inogelation proceeded with the diffusion of the cross-linking agent (i.e., Ca2+ ions) into the droplets41. The optimal centrifuge duration was determined to be 3 min and was closely related to the conditions under which all of the alginate solution was used. The resulting alginate microspheres showed a spherical shape with an average mean diameter of 372.53 ± 5.68 μm, and a high monodisperse feature (C.V. = 1.52%).", "The second proposed micronozzle, named sequence “a ∩ b”, was fabricated to produce the core-shell microspheres by inserting one nozzle into another large diameter nozzle, as shown in Fig. 2B. A small needle can be used to deliver the core alginate fluid, while a relatively large round needle surrounding the small needle can be used for delivering the shell alginate fluid; the resulting alginate droplets are formed at the core-shell structure. To create uniformly sized and well-organized core-shell alginate microspheres, it is important that the center alignment of the small syringe needle be accurately equipped in the opening of the large round needle, and subsequently set using epoxy resin. In addition, the inserted center needle protruded 1–2 mm from the surrounding needle opening (Fig. S1A). Using this micronozzle assembly, the smaller core is efficiently encapsulated during centrifugation as a droplet generation. Subsequently, two different concentric alginate solutions, of high and relatively low concentrations, were introduced in the surrounding and center-located plastic tubes, respectively (Fig. S1B).", "Similarly, 2.0 μm of fluorescent polystyrene (PS) microsphere, as an indicator, can be loaded into the core of the alginate microspheres and identified using fluorescence microscopy image analysis, as shown in Fig. 2B. Although the same material was used, the difference between the core and shell interface can be clearly observed: the majority of fluorescence dye is encapsulated in the core, while almost no fluorescence signals can be found in the shell. This approach allows us to readily generate complex core-shell microspheres. In addition, multicompartment core-shell alginate microspheres were generated by sequential centrifugation repeating method which is followed by two-step procedures such as small core particle generation (1st step) and shell generation using core particle distributed alginate solution (2nd step) (Fig. S2).", "This simple approach is applicable to the formation of Janus-type complex microspheres to modify the modular micronozzle. The third designed micronozzle, named sequence “a ∪ b”, was designed to combine the Y-shaped modular micronozzles to synthesize the Janus alginate microsphere (Fig. 2C). The bright-field image clearly indicated that the distinct spatial separation in the alginate microsphere was successfully induced after centrifugation. Before the generation of Janus alginate microspheres, two different alginate solutions, i.e., an original alginate solution and magnetic nanoparticles (Fe3O4) dispersed in the alginate solution, were prepared and injected into the combined Y-shape micronozzles that were penetrated into the micronozzle supporter (Figs S1C and S1D). Moreover, the resulting Janus alginate microspheres showed quick response to the static magnetic field, as shown in Fig. S3. This result suggests that our novel strategy can be applied to create dual functional materials such as stimuli-responsive smart materials and microactuators42,43. Furthermore, these results suggest the significance of controlling both the shape and chemical heterogeneity of microspheres to extend their potential applications.", "Effect of control parameters for generation of alginate microspheres", "To understand the effect of various parameters for the generation of alginate microspheres in our system, we conducted control experiments by varying the conditions such as the centrifugation speed, alginate and CaCl2 concentrations, syringe diameters, and distance between the micronozzle tip and the surface of CaCl2 solution. These parameters primarily affect the size, shape, and quality of the produced alginate microspheres. First, we generated the alginate microspheres at various centrifugation speeds (rpm), while maintaining the alginate concentration at 5 wt.% to examine the relationship between rpm and microsphere size, as shown in Fig. 3A. Interestingly, monodisperse microspheres were formed by increasing the centrifugation speed. This strongly suggests the formation of droplets in the dripping regime. In addition, the centrifugation speed is closely related to the driving force of the alginate solution flow, which affects the size of the alginate microspheres as shown in Fig. S4. The bright-field images clearly show that the size of the microspheres was gradually decreased by increasing the rpm. The alginate microspheres with a narrow size distribution was formed using 400 < rpm < 2000; outside this range of centrifugation speed, the deformation of alginate microspheres was induced. By changing the speed value from 500 to 1500 rpm, we obtained alginate microspheres with a broad size from 412.01 ± 12.30 to 887.84 ± 19.86 μm. Thus, the centrifugation speed primarily affects the size of the microspheres, and the optimal condition was determined as 1000 rpm based on the C.V. values being less than 3%. As shown in Fig. 3B, the deformation of the alginate microspheres was carefully measured as a function of alginate concentration (Calginate). To define the deformation, the dimensionless deformation (D) of the microspheres is as shown in Eq. (1)34.", "$$D=\\frac{b-a}{b+a}$$", "(1)", "where a and b signify the minor and major axes of the synthesized microspheres, respectively. With different concentrations used from 3 to 8 wt.%, the deformation parameter is decreased and saturated, indicating that the microspheres are transformed from an ellipsoid to a sphere (Fig. S5). Moreover, elaborate size control can be conducted by varying the concentration of Ca2+ ions (Cca2+). When the Ca2+ ion was increased from 1 wt.% to 8 wt.%, and the other parameters were maintained as constant (i.e., Calginate = 5 wt.%, rpm = 1000, and G = 23), the size of the alginate microsphere was decreased from 654.86 ± 27.42 to 460.72 ± 5.48 μm (Figs 3C and S6). This result can be clarified by the formation of dense alginate polymer networks resulting from fast ionic crosslinking that occurred at a high concentration of Ca2+ ion, thus yielding a strong ionic binding force between COO− and Ca2+ ions. Finally, we investigated the relationship between microsphere size and syringe inner diameter (G). To examine the effect of G, needles of different gauges were used while retaining all other optimized conditions (i.e., Calginate = 5 wt.%, CCa2+ = 5 wt.%, and rpm = 1000). The achievable size of the microspheres ranges from 437.68 ± 11.85 to 569.50 ± 8.49 μm using commercially available different-gauged needles (Figs 3D and S7). Importantly, the gauge-controlled generation of the alginate microsphere could be easily estimated using Eq. (2) that describes the balance of the forces acting on the pendant drop detached from the modular micronozzle44.", "$$d={a}^{3}\\sqrt{\\frac{{d}_{0}}{g}}$$", "(2)", "where d and d0 are the diameters of the final alginate droplet and the modular micronozzle, respectively; g represents the centrifugal force driven gravity; a is the coefficient value comprising the surface tension of alginate and the micronozzle circumference. Comparing the experimental and theoretical value, the size difference confirmed the shrinkage of the alginate microsphere during ionogelation. From the comparison between the control experiment and theoretical approach, we obtained the primary control parameters for the generation of the alginate microspheres.", "Figure 3", "General trend for generation of alginate microsphere. Relationship between physical characteristic and control parameters such as (A) centrifugation speed, (B) alginate concentration, (C) CaCl2 concentration, and (D) syringe diameter. Each experiment was repeated five times.", "For the investigation of the distance between the nozzle tip and the surface of CaCl2 solution, we have conducted experiment with different distances of micronozzle reactor by changing the height of CaCl2 solution while keeping all other conditions (i.e., Calginate = 5 wt.%, CCa2+ = 5 wt.%, and rpm = 1000). As shown in Fig. S8, the distance (L) between the micronozzle tip and the surface of CaCl2 solution is an important parameter for the evolution of alginate shape. When the micronozzle tip is closed and soaked in the CaCl2 solution (i.e., L≤ 1 cm), the shape of fiber can be generated because of the inhibition of surface tension and quick gelation upon facing the CaCl2 solution. Following to a previous work by Takeuchi34, we can also find criteria for the evolution of alginate in our system. Thus, the optimal condition was determined as 3 cm (L > 1 cm) regarding to generate the alginate microspheres. Furthermore, the shape and size control can be accomplished by simply assembling the optimized control parameters although the same device was used repeatedly.", "One-step generation of different sized alginate microspheres", "The ultimate goal of this study is to develop a simple system with a universal modular micronozzle design for easy use in academic and practical applications. Among the physical parameters, the particle size, in particular, determines the functionality of that particle such as its uptake, adherence, degradation, as well as residence in circulation45,46. In addition, constant release rate (i.e., ‘zero-order‘ release) is highly ideal for the drug delivery system which can be achieved by mixing various sized microspheres47,48,49,50.", "Thus, the next challenge for confirming our accessibility is to generate different sized alginate microspheres using a modified modular micronozzle with one-pot generation. As shown in Fig. 4, we designed and created an array of modular micronozzles comprising different numbers of square holes on a micronozzle supporter, to generate the different size-controlled alginate microspheres simultaneously. For example, the modular micronozzle consists of two different gauged needles, called the “a-b” configuration herein, and can generate two types of alginate microspheres, as shown in Fig. 4A. The corresponding bright-field images demonstrated the “particle mixture” containing various sizes of the alginate microsphere. The parallelized configurations with different gauged needles were affected by the equal gravitational force through centrifugation, thus enabling various sizes of alginate microsphere to be generated. Figure 4B,C show the general hierarchical trend of the one-pot synthetic procedure for the different-size microsphere generation, and the number of alginate microspheres well-matched with the number of different micronozzles using various configurations such as “a-b-c” and “a-b-c-d,” respectively. For example, the average sizes of alginate microsphere using “a-b-c-d” configuration, which consist of 22 G, 20 G, 17 G, and 19 G, were calculated as 487.11 ± 3.60 μm, 603.78 ± 4.10 μm, 1039.72 ± 12.60 μm, and 703.72 ± 6.60 μm, respectively. Since the alginate microspheres were generated using the modular micronozzle consists of different gauged needles, the particles showed a similar trend with single micronozzle generation (Fig. S9). In addition, the results show the narrow size distributions, and that the C.V. of the alginate microspheres generated in each modular micronozzle is less than 3%. This novel strategy has demonstrated the potential for the one-pot generation of engineered microspheres with precise size control in a broad range.", "Figure 4", "Configuration of modular micronozzle using different micronozzles. One-step generation of a broad ranged microspheres with various configurations such as (A) “a-b”, (B) “a-b-c”, and (C) “a-b-c-d”. The scale bars represent 3 cm. Each experiment was repeated five times.", "Application for drug delivery system", "To evaluate the practicability of our proposed device, we synthesized the stimuli-response functional particles assuming drug delivery in the body. Stimuli-response microspheres have attracted particular attention as these materials are a potential candidate for a wide range of “smart” applications by physical stimuli including temperature change, light, and magnetic field, and chemical stimuli such as pH, ionic strength change, and chemical or biological agents51,52,53. In addition, there are various works applied to the use of alginate microspheres as a carrier for the drug delivery system54,55,56,57. Thus, we examined the potential application of the smart material synthesized through our device as a model for the oral drug delivery system. This system is known to show a drastic change in pH from the stomach (acidic pH 2) to the intestine (basic pH 5–8) in the GI tract, sequentially54. As shown in Fig. 5A, we used the modular micronozzle with “a-b” configuration and simultaneously generated two different alginate microspheres containing amino- and carboxyl-functional groups with different concentrations of alginate solution. In detail, the preparation of stimuli-responsive two different particles that is generated by one-pot procedure using “a-b” micronozzle sequence. The particle shape is a significant parameter in drug encapsulation application. Therefore, two micronozzles, such as 21 and 25 G, used for generating pH 2-responsive ellipsoid and pH 7-responsive spherical alginate microspheres simultaneously. It can be attributed for generating various types of drug encapsulated carriers and delivering diverse medications in the human body, especially gastrointestinal tract58. To visualize drug releasing, we used artificial components (i.e., polystyrene beads) as a model drug, and synthesized various sizes and shape-controlled alginate microspheres for defining the number of polystyrene beads per microsphere (Fig. 5D). The alginate microspheres were subsequently incubated with different pH aqueous solutions. As shown in Fig. 5B and the corresponding fluorescence image of Fig. 5E, the ellipsoidal-shaped microspheres swelled and released red fluorescence tagging the artificial drugs after an incubation time of 12 h at 37 °C. This occurred because the cationic polymers containing amine groups became charged quaternary ammonium salts (-NH4+), and induced swelling under low pH conditions below the pKa value threshold. On the contrary, relatively small spherical microspheres responded at pH 7 (Fig. 5C,F). The actuation of the swelling equilibrium is important information as it provides the understanding of the interaction between the polymeric networks and transportation, and the degradation of fluid in three-dimensional systems in which a microsphere will challenge at different environments. For example, the carboxyl-group-functionalized microspheres show the non-ionized form (-COOH) and decreased hydration at a low pH of 2. When the pH of the solution increases above the pKa, the carboxylic group changed to the ionized form (-COO−), leading to an increase in electrostatic repulsion, thus causing polymer expansion and higher swelling of the alginate polymer matrix, being the highest around pH 759. Apart from the various parameters discussed, the microsphere size, shape, and composition are closely related and contributed to their special function. Comparison between previous centrifuge system, our system can be used as a simple method to design biomaterials which overcome by considering all of important factors to target applications (Table S2).", "Figure 5", "Model system for possible application to drug delivery system using pH-responsive alginate microspheres encapsulating green and red fluorescence PS microsphere. Bright-field images of different alginate microspheres to apply different pH at (A) initial, (B) 2, (C) 7 and (D–F) its corresponding fluorescence images. The external temperature was maintained at 37 °C.", "Conclusion", "We presented a novel approach to a centrifugal-force driven modular micronozzle system, and its simple operation for the generation of complex engineering microspheres. The modular micronozzle device was composed of conventional available laboratory apparatus including syringe needles and centrifuge tube. The device can be turned by adjusting various sequences such as “a, b”, “a ∩ b”, and “a ∪ b”. Interestingly, our novel approach enabled the preparation of 400 µm to 900 µm microspheres with complex geometries (i.e., core-shell and Janus), and the generation of pH-responsive smart microspheres with different sizes, shapes, and compositions for applications in smart drug delivery systems.", "Despite the recent advances in centrifugal device systems, this study has some innovative points compared to previous reports; (1) We present a highly reproducible and reversible micronozzle reactor for the generation of engineered alginate microspheres. (2) Various combinations of micronozzles, such as nozzle in the nozzle and union assembling, have shown that the structure-controlled alginate particles, such as single, Janus and multi-core shells, are produced reproducibly. (3) The shape and size control can be pre-estimated and demonstrated by changing experimental parameters such as centrifugation speed, alginate and CaCl2 concentrations, syringe diameters and distance between micronozzle tip and CaCl2 solution. (4) Our modular micronozzle reactor can be mounted on any commercial conventional centrifuge to perform the generation of complex microspheres with simple preparation, low operating costs, and high reproducibility. (5) A large number of microspheres (approximately 1,000 particles per 1 mL alginate solution) can be produced in a few minutes, thus enabling mass production. Therefore, we believe that the combination of both the novel microsphere generation method and automation will create considerable progresses, not only in the real field of drug delivery and tissue engineering fields, but also in smart functional material fields applying microspheres. Using the modular micronozzle system offers several advantages that could be easily assembled, disassembled, reconfigured, and reassembled. In addition, this system would allow to be reversible, simple to use, easy to manufacture and consistent and reliable in their performance following repeated assembly and disassembly process for achieving the large-scale synthesis, cost-effectiveness, higher reproducibility and reusability.", "Fabrication of centrifugal-force driven modular micronozzle device", "The centrifugal-force driven modular micronozzle device was composed of a modular micronozzle, a micronozzle supporter, and a collection tube. These materials were obtained commercially. To fabricate the modular micronozzle, a syringe needle (KOVAX-NEEDLE®, Korea Vaccine Co., Ltd., Seoul, Korea) was inserted into the bottom of a 1.5-mL microcentrifuge tube (Eppendorf AG, Hamburg, Germany). A hole was bored by heating up the 23-gauge needle. Subsequently, connections were sealed with epoxy resin to prevent liquid leakage. Subsequently, the micronozzles were inserted into the square holes (i.e., 1 cm × 1 cm) on the tube cap as a micronozzle supporter that can bore a hole, such that the micronozzle would pass through. Finally, a 50-mL centrifuge tube (Becton Dickinson, Cowley, Oxford, UK), as a collection tube, was assembled with screws. Unlike other microfluidic methods, surface treatment was not required in this assembly.", "Generation of single alginate microsphere", "The sodium alginate (5 wt.%) solution was extruded through the micronozzle with a 23-gauge syringe needle. The resulting alginate microdroplets were directly corrected in a 5 wt.% CaCl2 aqueous solution during centrifugation. To induce the phase contrast under the bright field, the alginate aqueous solutions were prepared by dissolving with/without iron(III) ferrocyanide nanoparticles, separately. In all the experiments, a swing rotor centrifuge (Labogene, Seoul, Korea) was used, and operated at 1000 rpm for 3 min.", "Design of the modular micronozzle for generation of complex microsphere", "To produce core-shell alginate microspheres, the modular micronozzle with sequence “a ∩ b” was conducted by inserting the small micronozzles, consisting of a PCR centrifuge tube, located in the center of another big micronozzle. In this study, the different lengths of the syringe needles used for the core formation was 6 cm of the 23-gauge needle (the outer/inner diameters of which were 0.64 mm/0.32 mm), and 3 cm of the 18-gauge needle (the outer/inner diameters of which were 1.27 mm/0.84 mm), to generate the shell. In addition, a Y-shaped modular micronozzle was created by the sequence “a ∪ b” to prepare Janus alginate microspheres. First, two modular micronozzles of the same length (approximately 3 cm) of the 23-gauge syringe needles were equipped to the micronozzle supporter and were subsequently bent two times at 120° to face each other. Finally, it was set by epoxy resin to maintain the Y-shape configuration.", "Reproducibility test and characterization", "The reproducibility of the microsphere generation was verified to prepare complex alginate microspheres using different modular micronozzles (i.e., sequences of “a, b”, “a ∩ b”, and “a ∪ b”). In each case, five independent experiments were conducted. The diameters of the alginate microsphere were determined from the bright-field images captured using a digital camera connected to a microscopy system. The prepared complex alginate microspheres and pH-responsive microspheres were observed with an inverted phase microscope (Olympus IX70, Olympus Optical Co., Tokyo, Japan) in the bright-field and fluorescence modes. The alginate microsphere diameters were determined from images captured using a digital camera (ToupTek Photonics Co., Ltd., China) attached to a microscope. To measure the monodispersity of the alginate microspheres, at least 50 microspheres per batch (1 cycle centrifugation) were evaluated, and the mean average diameters and standard deviations were calculated. Based on this, the coefficient of variation (C.V.) (%) described in the following Eq. (3) was used.", "Contributions", "S.-M.K., G.-W.L., and Y.S.H. conceived the idea, designed the research and performed the experiments and analyzed the data. S.-M.K., G.-W.L., and Y.S.H. wrote the main manuscript. S.-M.K., G.-W.L., and Y.S.H. analyzed the data and figure alignment. Y.S.H. supervised the research. All authors discussed the results and reviewed the manuscript.", "Supplementary information", "Rights and permissions", "Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/." ], [ "Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain", "the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in", "Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles", "and JavaScript.", "Subjects", "Abstract", "When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating thermal convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely distributed vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being proportional ( ≈ 30%) to the cluster length. Such long-range correlation leads to the counterintuitive collective outward motion of warm vortices. Our study brings insights into the vortex dynamics that are widely present in nature.", "Introduction", "Coherent vortex structures exist ubiquitously in many flow systems ranging from small-scale turbulence to large-scale geophysical and astrophysical flows1,2,3, and their dynamics play a crucial role in determining turbulent mixing and transport in those systems. Previous studies of vortex dynamics are mainly focused on isolated vortices3,4. However, in rapidly rotating turbulent flows these vortices become densely distributed5,6, and the resulting vortex interactions may lead to markedly different dynamics compared to that of isolated vortices7,8,9. Many nonequilibrium dynamical systems in nature consisting of densely distributed, interacting entities often exhibit collective behavior, i.e., the entities self-aggregate to perform collective motions. Examples include bird flocks, bacteria swarms, and clustering of active matters10,11,12. Whether the collective behavior of vortices can arise in rotating turbulent flows is thus a question of fundamental interest.", "The fluid dynamics of rotating turbulent flows is often studied in rotating Rayleigh–Bénard convection (RBC). Despite the considerable progress achieved in studying non-rotating and weakly rotating turbulent RBC13,14,15,16,17,18, some important convection regimes that may exhibit intriguing vortex dynamics are yet to be explored (see, e.g.,19,20). Recent studies report that for rapidly rotating RBC in moderate Prandtl-number fluids, the convective flows are organized by the Coriolis force into coherent columnar vortices21,22,23,24,25,26,27,28,29,30. These columnar vortices are helical structures with either upward or downward flows. Upwelling vortices rotate in the same direction as the system (cyclones) in the lower half fluid layer, and in the opposite direction (anticyclones) in the upper half and vice versa for downwelling ones22,29. The theory of thermal wind balance, which relates the vertical variations of the fluid velocities with the horizontal temperature gradients31, provides a general description of the flow structures of the columnar vortices. From a dynamical viewpoint, however, the horizontal motions of, and the interactions between, these vortices remain to be explored in a quantitative way.", "Here, we demonstrate both experimentally and numerically the collective motion of vortices in rotating thermal convection. As a primary external force governing the motions of rotating fluids in many natural and industrial flows19,32,33, centrifugal force drives cold, denser fluid radially outward from the rotation axis and warm, lighter fluid inward. Counterintuitively, we discover that the long-range correlated vortex dynamics give rise to inverse centrifugal motion, i.e., the warm and lighter convective vortices exhibit outward motion from the rotation axis. This intriguing phenomenon occurs in a rapidly rotating regime where the strong centrifugal buoyancy breaks the symmetry in both the population and vorticity magnitude of the vortices. Our study reveals that it is through local hydrodynamic interactions that the densely distributed vortices self-aggregate into large-scale vortex clusters, in which the warm cyclonic vortices submit to the collective motion dominated by the strong anticyclones and move outwardly.", "Results", "Vortex motion and inverse centrifugation", "Our experimental apparatus was designed for high-precision flow structure measurements in rotating RBC20,30. We used cylindrical cells with an inner diameter d = 240 mm and height H = 63.0 (120.0) mm, yielding an aspect ratio Γ = d/H = 3.8 (2.0). The experiment was conducted with a constant Prandtl number Pr = ν/κ = 4.38 and in the range 2.0 × 107 ≤ Ra ≤ 2.7 × 108 of the Rayleigh number Ra = αgΔTH3/(κν) (g is the gravitational acceleration, ΔT the applied temperature difference, α, κ and ν are respectively the isobaric thermal expansion coefficient, thermal diffusivity, and kinematic viscosity of the convecting fluid). Rotation rates of up to 5.0 rad/s were used. Thus the Ekman number Ek = ν/(2ΩH2) spanned 4.9 × 10−6 ≤Ek ≤ 2.7 × 10−4, corresponding to a range of the reduced Rayleigh number 1.3 ≤ Ra/Rac ≤ 166. Here, Rac = CEk−4/3 (with the coefficient C = 8.7 − 9.63Ek1/6) is the critical value for the onset of convection34, and Ω is the rotating rate. The Froude number Fr = Ω2d/(2g) varied within 0 < Fr ≤ 0.31. The flow field at a fluid depth of z = H/4 was measured using the technique of particle image velocimetry (PIV) (see a schematic of the experimental setup in Fig. 1i). In the direct numerical simulation (DNS) we solved the Navier–Stokes equations with the Coriolis and centrifugal forces included, using the multiple-resolution version of the CUPS code35,36. The simulation was performed in a cylindrical domain with Γ = 4, Ra = 2.0 × 107, and 1.3 ≤ Ra/Rac ≤ 55 (see Supplementary Fig. 1 for a phase diagram of the present study).", "Figure 1 presents snapshots of the vortex structures at the measurement fluid height (z = H/4). At a low rotation rate when the centrifugal force is negligible (Fig. 1a), the cyclonic vortices (shown in red color) possess a greater number density and on average larger vorticity in magnitude than that of anticyclones (blue color). Both types of vortices exhibit stochastic horizontal motions as evidenced by the vortex trajectories shown in Fig. 1b. The mean-square-displacement (MSD) of the vortices becomes a linear function of time at large times, indicating a Brownian-type, normal diffusive motion20.", "However, at higher rotation rates when the centrifugal force becomes dominant, we observe strong anticyclones with a larger population than the cyclones (Fig. 1c). The anticyclones undergo outward radial motions accompanied by stochastic fluctuations along their paths (Fig. 1d) until they move close to the sidewall where their radial motion is terminated by the retrogradely traveling plumes. Compared to the anticyclones, the motion of weak cyclones is much more complex. Figure 1d indicates that in the outer region (r ≥ d/4), the cyclones move toward the cell center while in the inner region (r ≤ d/4) most of them migrate radially outward. In this rapidly rotating case, the MSD of both types of vortices indicates superdiffusive behavior (see Supplementary Movies of the vortex motions).", "To further quantify the vortex motions, we show the profiles of the mean radial velocity \\({\\langle {u}_{r}\\rangle }_{\\xi }\\) of the vortices measured in the inner region of the cell in Fig. 1e–h. These velocity profiles reveal four distinct flow regimes depending on the rotation rates: (I) A randomly diffusive regime exists in the slow rotating limit with Ra being one order in magnitude larger than Rac. In this regime the vortices move in a random manner, yielding \\({\\langle {u}_{r}\\rangle }_{\\xi }\\approx 0\\) (Fig. 1e). (II) A centrifugation-influenced regime where the magnitude of \\({\\langle {u}_{r}\\rangle }_{\\xi }\\) increases linearly with r (4Rac ≤ Ra ≤ 10Rac). We observe that warm cyclones (cold anticyclones) move radially inward (outward), which is in agreement with the centrifugal effect (Fig. 1f). (III) Inverse-centrifugal regime (1.6Rac ≤ Ra ≤ 4Rac) in which there is anomalous outward cyclonic motion (Fig. 1g), and the radial gradients of \\({\\langle {u}_{r}\\rangle }_{\\xi }\\) for both types of vortices reach a maximum. (IV) The asymptotic regime in the rapid rotation limit (Ra ≤ 1.6Rac) where the opposite radial motions of cyclones and anticyclones recover (Fig. 1h).", "We formulate a theoretical model consisting of Langevin-type equations that incorporate the centrifugal force, which governs the radial vortex motion in a background of stochastic fluctuations. As shown in Fig. 2, the model provides predictions of the first and second moments of the radial vortex displacements which replicate very well the experimental data in flow regimes (II) and (IV) (see Supplementary Note 3 for detailed discussions of the model). Nonetheless, Fig. 2 clearly shows that the inverse centrifugal motion of the cyclones in the anomalous regime (III) cannot be explained by the model. A key question is then what sets the anomalous vortex motion?", "Fig. 2: Second moments of vortex radial displacement.", "Results for anticyclones (a) and cyclones (b) with Ra = 3.0 × 107. Open symbols: experimental data. Solid lines: theoretical predictions. Insets: results of the first moments of vortex radial displacement. r0 is the initial radial position of a vortex.", "Asymmetric vorticity field in the inverse-centrifugal regime", "To gain insights into the observed phenomenon, we first examine the relative strength of vorticity between the cyclones and anticyclones. Figure 3a shows the vorticity ratio γω of the anticyclones to the cyclones. We note that in the randomly diffusive regime, γω is approximately 0.6, meaning that at the measurement height z = H/4 the cyclonic vorticity is overall larger in magnitude than the anticyclonic ones (see Fig. 1a). It is the case because when observed at the lower half of the layer, anticyclones are downwelling vortices generated from the top boundary. They travel a long distance to the measurement layer than the upwelling vortices (cyclones), and their momentum and vorticity have been largely dissipated by the background turbulence when reaching the measurement position in this flow regime27. (The vorticity magnitude of the two types of vortices are equal if measured at z = H/2. See the visualization from our DNS in the right inset of Fig. 3a.) With increasing Ω the up- and down-welling vortices evolve into columnar structures that are vertically antisymmetric in vorticity with respect to the mid-height plane25,26. One would expect that in this flow regime the measured vorticity strength of the cyclones and anticyclones become comparable, i.e., γω approaches unity. Our DNS data with the centrifugal force switched off indeed show this trend. However, when the centrifugal effect is dominant, both the experimental and DNS results reveal that γω exceed unity considerably in the inverse-centrifugal regime, indicating an asymmetric vorticity field dominated by the cold anticyclones (left inset of Fig. 3a). In the asymptotic regime where the severe rotational constraint finally weakens the convective vortices, γω eventually returns to unity, and the symmetry of the cyclonic and anticyclonic vorticity restores. Remarkably, we observe that γω(Ra/Rac) is independent of Ra and Γ over the parameter range studied.", "Fig. 3: Vorticity and temperature of cyclones and anticyclones.", "a The vorticity ratio γω = ∣〈ωa〉/〈ωc〉∣ of the anticyclones to the cyclones as a function of Ra/Rac. Here, 〈...〉 denotes a time average. Filled symbols: experimental data for Γ = 3.8 with Ra = 2.0 × 107 (circles), 3.0 × 107 (up triangles), 6.0 × 107 (squares); and for Γ = 2.0 with Ra = 1.4 × 108 (diamonds), 2.7 × 108 (left triangles). Data from DNS including (excluding) the centrifugal force are shown in open diamonds (pluses) for Γ = 4.0. The solid curve indicates the trend of the experimental data. The error bars denote representative fluctuation amplitude of γω. Inset panels: iso-surfaces of the temperature anomaly from DNS for Ra = 2.0 × 107, Ra/Rac = 2.26 (left), and Ra/Rac = 18.3 (right). The coloration represents the vorticity of the vortices. b Radial profiles of the mean temperature 〈T − Tm〉/ΔT for the vortices and the background fluid. Tm is the mean of the top and bottom fluid temperature. The length of the dashed lines indicates the temperature difference δT between the cyclones (anticyclones) and the background fluid. c Radial profiles of γω and γT = ∣〈δTa〉/〈δTc〉∣. b, c DNS data for Ra = 2.0 × 107 and Ra/Rac = 2.26.", "We now show that the asymmetry of the vorticity field in the anomalous regime results from the centrifugal effect. Figure 3b presents the radial profiles of the mean temperature of the two kinds of vortices and of the background fluid. These numerical data indicate noticeable warming of the background fluid in the inner region, owing to the centrifugal effect37,38,39. (See comparative results in Supplementary Fig. 7 when the centrifugal force is excluded.) As a result, the temperature difference δT of the cold anticyclones from the background exceeds that of the warm cyclones. Since δT is proportional to the buoyancy forcing on the vortices, it is predicted to be positively correlated to the vorticity ω in recent theoretical models24,26. Indeed Fig. 3c shows that δT and ω are both larger in magnitudes for anticyclones than for cyclones in the inner region, which explains the asymmetry of the vorticity field (γω > 1).", "Clustering and collective motion of the vortices", "In light of the broken symmetry of the vorticity field in the anomalous regime, we show below that it is the long-range correlated vortex motion that gives rise to the inverse centrifugal motion of the cyclones. Figure 4 presents the instantaneous motion of the vortices, with their spatial distribution presented in a Voronoi diagram. One sees that the adjacent vortices often self-organize into vortex clusters, i.e., the vortices move largely in the same direction. We adopt two criteria to identify vortex clusters, i.e., the distance of two neighboring vortices is smaller than 1.5 times the mean vortex diameter and the angle ϕ between their velocity vectors is within a threshold (ϕ ≤ ϕ* = 60°). Our analysis over the range 30° ≤ ϕ* ≤ 75° confirms that the results of correlated vortex motion are not sensitive to the choice of ϕ*. The direction of the motion of each cyclone i is represented by the angle θ between its velocity \\({\\overrightarrow{u}}_{i}\\) and its position vector \\({\\overrightarrow{r}}_{i}\\) from the rotation axis. We find that θ is strongly dependent on the number (N) of vortices in a cluster (inset). For isolated cyclones (N = 1), the most probable direction of motion is radially inward (θp = π). However, for clustered cyclones (N > 1) we find θp = 0 as they move outward. The standard deviation of θ decreases monotonically when N increases. Our data reveal that within large clusters the motion of weak cyclones submit to that of strong anticyclones and move outwardly in a collective manner. Their inverse centrifugal motion becomes more unidirectional with the increase of the cluster size.", "Fig. 4: Clustering of vortices.", "Results are shown in the central region for Ra = 3.0 × 107, Ra/Rac = 1.97, Fr = 0.27. Blue (yellow) circles show the centers of anticyclones (cyclones). Black arrows show the vortex velocity direction. The solid-line network represents the Voronoi diagram of the vortex centers. Examples of six vortex clusters are highlighted and marked with thick boundaries. θ denotes the angle between the position vector of a cyclone relative to the rotation axis (green cross) and its velocity. L is the largest distance between two vortices within a cluster. The background coloration represents the distribution of the quantity Q/Qstd. Inset: Probability density functions of θ of cyclones in clusters with various size N.", "By analyzing the cluster size distribution p(N), one can obtain certain insights into the physical mechanism responsible for the vortex cluster formation. Figure 5a shows that p(N) for various Ra/Rac can be well described by \\(p(N)=A{N}^{-b}{e}^{-N/{N}_{{{{{{{{\\rm{c}}}}}}}}}}\\). Here, b and Nc are the fitting parameters with their dependence of Ra/Rac plotted in the inset. For clusters in small size N, p(N) first decays as a power function N−b up to a cutoff size Nc. Studies of the collective behavior in various natural systems have revealed that local aggregation of interacting entities is the essential ingredient for the power-law decay of the group-size distributions in these systems40,41,42. In the present vortex system, each vortex is surrounded more likely by counter-rotating vortices in a densely populated state (Fig. 4). Owing to the vortex-pair interaction, adjacent vortices of opposite-sign tend to move in similar directions43 (see Supplementary Note 7 for details). Moreover, the shielded structure formed near the edge of each vortex prevents strong interactions in closer proximity26,28,30, thus avoiding vortex merging and annihilation. As a result, isolated vortices are often aggregated into neighboring clusters and move collectively. The power-law exponent, b = 1.5 ± 0.04, is found to be independent of Ra/Rac (inset of Fig. 5a), and falls within the range of previous theoretical predictions40,44. For large N we find that p(N) evolves into an exponential tail with the cutoff size Nc varying with Ra/Rac and reaching a maximum at Ra/Rac = 1.97, where the vorticity ratio γω is maximum (see Fig. 3a). The rescaled data \\(p(N){N}_{{{{{{{{\\rm{c}}}}}}}}}^{1.5}/A\\) as a function of N/Nc thus collapse onto a master curve as shown in Fig. 5b.", "Dynamical systems consisting of clustered entities often exhibit scale-invariant, collective motions12. Here, we further analyze the spatial correlation function of vortex velocity fluctuations within a vortex cluster \\(C(l)={\\sum }_{ij}[{\\overrightarrow{u^{\\prime} }}_{i}({\\overrightarrow{r}}_{i}+\\overrightarrow{l})\\cdot {\\overrightarrow{u^{\\prime} }}_{j}({\\overrightarrow{r}}_{j})\\delta (l-{l}_{ij})]/[{C}_{0}\\cdot {\\sum }_{ij}\\delta (l-{l}_{ij})]\\), where \\({\\overrightarrow{u}}_{i}^{\\prime}={\\overrightarrow{u}}_{i}-\\overrightarrow{V}\\) is the relative vortex velocity with respect to the mean cluster velocity \\(\\overrightarrow{V}={\\sum }_{i}{\\overrightarrow{u}}_{i}/N\\), lij is the distance between the vortex pair (i, j) and C0 is a normalization constant. δ(l–lij) is a Dirac function selecting pairs of vortices separated by distance l. Figure 5c shows that C(l) decreases as the distance l increases, with the decay length depending on the cluster size N. In Fig. 5d, we present the correlation function C(l/L), scaled by the cluster length L, for clusters with various sizes. This rescaling leads to the converging of the data onto a single curve representing a stretched exponential function, which crosses zero at the correlation length lc ≈ 0.3L for all cluster sizes N. Thus the correlated motions of the vortices are long-range and scale-free, i.e., there is no characteristic length scale here except the length L of the cluster. We remark that the scattering of data points at large distances (l ≈ L), owing to insufficient statistics, has negligible influence on the determination of lc.", "Discussion", "Our study has revealed the formation of large-scale coherent structures, in the form of vortex clusters, in rotating thermal convection. Within each cluster the lighter cyclones submit to collective motions dominated by the heavier anticyclones, exhibiting outward, inverse-centrifugation motion. We find that the size-distribution p(N) of the vortex clusters can be well represented by a fractional power function with an exponential cutoff. The observed robust three-half power scaling of p(N) for small N (see Supplementary Fig. 9a) suggests that the theory of aggregation40,41,42 apply to a broad range of grouping phenomena, and may provide predictions for the clustering dynamics of vortices in the present highly nonlinear, buoyancy-driven convection systems.", "For large N we find that p(N) decays exponentially and the cutoff size Nc is maximum when the centrifugal effect is dominant. Further investigations reveal that Nc is proportional to the ratio of the vortex population density over the separation rate of the vortices from the clusters (detailed in Supplementary Fig. 9c), analogous to various biological systems42,45. We thus attribute the exponential decay of p(N) to the separating and aggregating process of vortices between the clusters and the ambient flows, which maintains a statistically stable cluster-size distribution. As is shown in Supplementary Fig. 9b, the vortex separation rate reaches a minimum when the asymmetry of the vorticity fields is maximum. Thus when the interaction between adjacent vortices is dominated by the anticyclonic flows, the cluster structures possess the maximum stability against separation, leading to the largest characterized cluster size Nc.", "Last, we have discovered that the self-organized vortices exhibit scale-free correlations of velocity fluctuations, with the correlation length being approximately 30% of cluster length. This phenomenon of scale-invariant dynamics is analogous to the collective behavior observed widely in bird flocks, bacterial colonies10,11, and in active matters12. The present study sheds light from a different angle on the phenomenon of collective motion and may have broad implications in the studies of soft condensed matter, fluid physics, and biological systems.", "Methods", "Experimental setup", "In the present study, we used a cylindrical cell mounted on a rapidly rotating table. Its bottom plate was made of 35 mm thick oxygen-free copper, heated from below by a uniformly distributed electric wire heater. Its top plate was a 5 mm thick sapphire disc, cooled from above through circulating coolant. Its sidewall, made of 3 mm thick Plexiglas, was protected against the ambient temperature fluctuations by an adiabatic shield that maintained a constant temperature. Temperature inhomogeneities over the top and bottom plates and the adiabatic shield were within one percent of ΔT (temperature difference between the top and bottom plates) during the experiment. The rotating axis of the table was adjusted to be accurately parallel to the gravity. The rotation was set in the clockwise direction with the rotation vector pointing downward (see Fig. 1). The convection cell was then leveled, using a cross-test level with a precision of 0.02 mm/m placed on the top surface of the top plate, to better than 0.001 rad. For flow visualization, a PIV system was installed on the co-rotating frame. A thin light-sheet powered by a solid-state laser illuminated the seed particles in a horizontal plane at a fluid height z = H/4 (Fig. 1i). Images of the particle were captured through the top sapphire window by a high-resolution camera (2448 × 2050 pixels). Two-dimensional velocity fields were extracted by cross-correlating two consecutive particle images. Each velocity vector was calculated from interrogation windows (32 × 32 pixels), with 50% overlap of neighboring sub-windows to ensure sufficient accuracy and resolution46. For each measurement, we took image sequences at a time interval of 0.5 s with a typical acquisition time of 2.5 h. Detailed experimental schemes of vortex identification and tracking are provided in Supplementary Note 2.", "Numerical method", "In the DNS we solved the three-dimensional Navier–Stokes equations with the Boussinesq approximation", "Here, u is the fluid velocity, θ and P are the reduced temperature and pressure. The last two terms in the momentum equation (Eq. (1)) represent the Coriolis force and the centrifugal force, respectively. The equations were nondimensionalized using L, ΔT, and the free-fall velocity \\({U}_{{{{{{{{\\rm{f}}}}}}}}}=\\sqrt{\\alpha g\\Delta TL}\\). The simulations were performed in a cylindrical sample with an aspect ratio Γ = 4 and no-slip boundaries at all walls. Equations (1–3) were solved using a fully parallelized DNS code CUPS based on finite volume method with 4th order precision. To increase computational efficiency without any sacrifice in precision, we used a multiple-resolution strategy, in which the temperature equation was solved in a finer grid than the momentum one, allowing for a sufficient resolution to resolve the Batchelor and Kolmogorov length scales. The grid resolutions along radial, azimuthal and vertical directions were 140 × 384 × 160 for the momentum and pressure fields, and 280 × 768 × 160 for the temperature field. Staggered grids were used in the simulations, which allowed the grid cells corresponding to the three velocity components to be shifted by half a grid cell. Grids were refined near boundaries, so that boundary layers can be resolved. In addition, we considered the flow fields with Fr = 0, excluding the centrifugal effect.", "Data availability", "The data that support the findings of this study are available within this article, its Supplementary Information, or from the corresponding authors upon request. Source data are provided with this paper.", "Code availability", "The simulation codes that have been used to produce the numerical results of this study are available from the corresponding authors upon request when appropriate.", "Acknowledgements", "This work is supported by the National Science Foundation of China under Grant nos. 11772235, 12072144 and 11572230, an NSFC/RGC Joint Research Grant nos. 11561161004 and N_CUHK437/15, and by the Hong Kong Research Grants Council under Grant nos. 14301115 and 14302317, and by Center for Computational Science and Engineering at Southern University of Science and Technology.", "Contributions", "J.-Q.Z. and K.-Q.X. conceived and designed the research. S.-S.D., J.-Q.S., and H.-Y.L. conducted the experiments. K.L.C. and G.-Y.D. conducted the numerical simulations. J.-Q.Z. and K.-Q.X. wrote the paper.", "Supplementary information", "Source data", "Rights and permissions", "Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/." ], [ "Many physicists regarded centrifugal force less as a force than a fiction. Then a Polish astrophysicist discovered that black holes won't work without it--without it working in reverse, that is.", "Newsletter", "Sitting upside down in a roller coaster car as it hurtles across the top of a loop-the-loop is not the most suitable position for reflecting on the meaning of physics. Nevertheless, a couple of summers ago I found myself doing just that when my eight-year-old daughter, Lili, dared me to accompany her on such a ride. And at the appropriate moment, I observed that since gravity always points downward, and since our seats were above us and also pushing us downward, the only thing holding us up was the centrifugal force. What if it stopped operating, I wondered? Or worse, what if it reversed direction? Then what?", "My fellow physicists would have dismissed my concern as idle nonsense, or at least they would have until recently. But, as it happens, we have learned that there are indeed circumstances--exceptional circumstances, to be sure--under which the centrifugal force can vanish or even reverse. And this astonishing discovery has profound consequences for the way we understand all motion.", "The idea of the centrifugal force has long made physicists a bit uncomfortable. Although the force appears whenever a moving object strays from a straight path, its existence depends on the point of view of the observer. Thus when a car rounds a curve, the passengers feel pressed outward by an unseen agency they call the centrifugal force, which increases with the speed of the car and disappears when the car stops moving or the road straightens out. However, people watching the scene from the side of the road, though they too would notice the outward push, would not ascribe its cause to the centrifugal force. Instead, they would explain the effect by pointing to the inertia of the passengers--their natural tendency to keep traveling in a straight line tangent to the curve of the road. Only the riders themselves, whose frame of reference is itself tracing out a curve, would invoke the centrifugal force.", "Because the centrifugal force exists in some reference frames (such as moving automobiles and roller coaster cars) but not in others (like the road or the grounds of the amusement park), it has acquired a bad name. College texts disdainfully call it a pseudoforce. My high school physics teacher went even further, vehemently insisting that the force was fictitious and banning mention of it in his classroom. Yet, years later, on the roller coaster, it saved me from crashing to the ground. So what is it then--fictitious or real? The squabble is purely semantic: everyone agrees on the actual effect, the outward push; only the name is at issue. As a compromise, physicists have agreed to call it an inertial force, a term that implies the centrifugal force is as fundamental as the related property of inertia. Inertia is an expression of nature’s laziness--of its inherent resistance to change--and the centrifugal force is just one particular form of that tendency.", "This interpretation of the centrifugal force has remained unchallenged since the seventeenth century, so the community of physicists expressed understandable skepticism toward the recent announcement that there is still more to be learned about a matter as trivial as rounding a curve.", "Twenty years ago, while working on the theoretical swirl of gas and dust that forms a black hole, Polish astrophysicist Marek Abramowicz noticed a peculiar phenomenon. He knew that in an ordinary star like the sun, gravity tends to increase internal pressure by compressing the gas, whereas rotation decreases that pressure by causing a centrifugal force that counteracts gravity. But in Abramowicz’s computer simulation, rotation of the material had just the opposite effect: it increased the internal pressure. Instead of becoming progressively flattened at the poles with increased rotation, the way Earth did soon after it was formed and the way normal stars do, a cloud of gas collapsing in on itself to form a black hole behaves in the opposite manner: as the speed of rotation increases, the flattening tends to diminish.", "Abramowicz, who now chairs the astronomy department at Chalmers University of Technology in Göteborg, Sweden, mulled over these and a number of related puzzles for many years before he finally hit upon a simple explanation. In 1990 it occurred to him that these mysteries could be cleared up at once if near a black hole centrifugal force was pointed in the wrong direction--inward. At first his intuition, molded by decades of experience, recoiled from the thought. After all, the word centrifugal comes from the Latin for fleeing from the center, making an inward- directed centrifugal force a logical contradiction. But Abramowicz overcame his initial prejudice by arguing that centrifugal force happens to have certain properties in one place and contradictory ones in another--a bit like the planet Venus, which was sometimes called the morning star and sometimes the evening star before its true nature was understood.", "Working with a number of colleagues, Abramowicz eventually succeeded in constructing a mathematical proof of his daring conjecture. Unfortunately, the proof is couched in the language of Einstein’s general theory of relativity. This explanation of gravity makes use of a four- dimensional framework called curved space-time, which is impossible to imagine, so for a nonmathematical discussion, analogies must suffice. The following simple representation of the strange landscape in the neighborhood of a black hole combines Abramowicz’s ideas with a metaphor invented by Einstein himself.", "Imagine an ant crawling around in the desert. It is a two- dimensional creature, which means that it understands only the surface of the desert floor and has no concept of up and down or above and below. Its universe is a two-dimensional surface embedded in the three dimensions of the real world--just as our own three-dimensional space is embedded in Einstein’s unimaginable four-dimensional one. If a rock in the middle of the desert attracts the ant by means of a gravitational force, it does so because it distorts the desert floor as though it were a flexible rubber sheet. In effect, the rock creates an indentation in the sheet. The ant, believing it is crawling along a straight line, naturally follows the curved contours of the desert and is thus led willy-nilly toward the rock. General relativity can be summarized by saying that massive objects curve space-time, and curved space-time in turn shapes the orbits of all the objects that move around in it.", "Imagine that the ant crawls in a circle around the rock (see the illustrations opposite). Of course, as it moves it feels a centrifugal force, though at the walking speed of an ant that force is quite feeble. Also imagine that our ant is obsessively methodical, and to keep track of the direction of the force, the ant draws arrows in the sand. As they should, all the arrows point outward, away from the rock.", "Now suppose that the rock is replaced by a heavier one, and the hole becomes deeper and steeper. If the ant happens to crawl in a circle along the vertical wall of the hole, it will be surprised to realize that it feels no centrifugal force at all! The reason for this strange illusion is that the direction of the force at any point along this circle happens to be perpendicular to the surface--a concept that the ant cannot even imagine. Only forward, backward, left, and right have meaning for the two- dimensional insect. Downward doesn’t exist.", "Finally, imagine that the rock is really massive: it now sinks deep into the sand, creating a cave shaped like a gopher hole, with a short neck and a balloonlike cavern. Once the ant gets past the neck of the hole, where the walls are also vertical, and crawls around in a circle on the ceiling of the cavern, it begins to feel a centrifugal force again. But now, amazingly, the direction of the force is roughly opposite that of the arrows in the sand. Indeed, since the flat ant can recognize only the surface, along which it can crawl, and not the air, through which it cannot fly, it perceives the push of the centrifugal force to be directed along the shortest route toward the rock. If the ant were to crawl around the waist of the gopher hole, where the walls become vertical once more, it would find that the centrifugal force vanishes again. In the lower hemisphere, however, the ant would find that the force returns to its normal direction.", "Of course, a gopher hole is not a realistic representation of a black hole. But it furnishes an example of a simple arrangement in ordinary space where the centrifugal force seems to vanish, and even point in the wrong direction--just as it does outside a real black hole.", "But why does it do so? The secrets of the behavior of matter in strong gravitational fields are buried deep inside the inaccessible mathematical formalism of general relativity. To enhance his own understanding, Abramowicz continued searching for plausible physical explanations that could be expressed in words rather than equations yet that reached beyond mere analogies. In particular, he wondered what was special about the circle where the centrifugal force vanishes--that place in the gopher hole where the walls are vertical.", "The answer turned out to be simple and revealing. The special orbit around a black hole where the centrifugal force is inoperative is located precisely where gravity is strong enough to bend light around into a complete circle. That light is deflected by gravity was Einstein’s most revolutionary prediction in 1916, when he advanced his general theory of relativity, and has been amply verified since then. Once that basic fact is accepted, it is not difficult to imagine a gravitational field powerful enough to turn a light beam clear around so it closes in on itself. Abramowicz found that whenever an object, such as a spaceship, travels along the circular path of a light beam, it experiences no centrifugal force.", "At this point two clarifications are in order. A spaceship traveling along the circular path of a light beam outside a black hole does not move at the speed of light--no material object can reach that limit. Indeed, its speed may be as modest as an ant’s. Nor is the spaceship in a free orbit, like the moon or a communications satellite circling Earth. To keep from falling into the black hole, the spaceship must exert a powerful rocket thrust aimed straight downward, as it were, a thrust sufficient to balance and neutralize the strong gravitational pull. But as long as the orbit through space is the same one that a light beam would follow, and as long as gravity has been overcome by means of a constant counterthrust, any spaceship, regardless of weight or speed, will coast in a circle without experiencing a centrifugal force.", "Once Abramowicz got this far, he decided to go for broke. He generalized the lessons he learned from black-hole research and proceeded to demonstrate that the centrifugal force always vanishes when an object follows the path of a light beam--regardless of whether that path is straight, circular, or curved by gravity in any manner whatsoever. With that discovery he found himself back in the footsteps of Galileo. In the conventional view, the centrifugal force vanishes when an object travels in a straight line--but how do you define a straight line? Galileo might have responded to that question by appealing to the mathematical definition: a straight line is the shortest distance between two points as measured by a rigid ruler. To surveyors and experimental physicists, though, the straight line of geometry is a mere abstraction. They give a more practical, operational answer: for them a real straight line is defined by a laser beam. Abramowicz’s theorem states that even in a gravitational field the centrifugal force vanishes along straight lines, provided they are defined operationally instead of mathematically.", "Abramowicz calls this appealing idea the Principle of Seeing Is Believing, and he illustrates it graphically. Imagine that you are in outer space, near a black hole or some other strong gravitational source. You build yourself a neat rectangular laboratory, using light beams to align the edges true and square. Your ship may require a motor to keep it from crashing downward, and gravity may be pretty strong inside your lab, but otherwise everything seems normal. Now suppose you perform an experiment to find out whether an object moving in a predetermined straight line is subject to a centrifugal force. You find out that it isn’t, as predicted by Galileo, but a critic asks you how you know that your line is straight.", "Seeing is believing, answers Abramowicz. If it looks straight, you must believe that it is straight. His point is that from the perspective of a distant observer, the walls, floor, and ceiling of the lab, and even the straight line, are as bent out of shape as a room in a fun house--but as long as they follow the trajectories of light beams, they are, for the purposes of checking the laws of mechanics, straight.", "The seeing is believing principle rescues Abramowicz’s findings from remaining curiosities of exclusive interest to the tiny community of black-hole physicists. In fact, it is so general that it has implications for the way we think about motion even here on Earth, where gravity is extremely weak. In particular, the new principle boils down to a radically new way of specifying what is meant by the ancient term natural motion.", "Aristotle and other Greek philosophers found it useful to distinguish between natural and forced motion. In the heavens they singled out circular motion as natural and attempted to fit all planetary orbits into patterns composed of circles. Their ideas about common, everyday motion were more pragmatic. Understandably they considered the downward motion of a falling object natural, but in a horizontal direction, they felt, objects naturally stop moving. Carts not pulled by horses quickly come to a halt, and so do ships with furled sails. The motion of a stone flung horizontally off a cliff was explained as follows: the stone gradually loses the artificial forward impetus it received from the thrower, and its natural downward tendency takes over and eventually dominates.", "By an ingenious argument, Galileo radically redefined natural motion. He pointed out that if a marble rolls along a smooth trough tilted downward, it accelerates. If the trough is tilted upward instead, the marble decelerates. It follows that when the trough is perfectly level, the marble neither accelerates nor decelerates and thus retains its original speed. Natural motion, according to Galileo’s definition, which later served as the anchor for Newton’s mechanics, is motion in a straight line with constant velocity. In this view the downward deflection of a stone thrown forward is unnatural and must be ascribed to the effect of an external agency, namely gravity.", "Einstein revolutionized physics once more by incorporating gravity into the fabric of space and time and thus ending the practice of regarding it as an external, unnatural force. According to general relativity, the actual, parabolic path of the stone (neglecting air resistance) is also its natural trajectory. Once it has been flung into space, the stone just follows the gently curved contours of space and time until it hits the ground. Whatever is, is natural, Einstein seemed to say.", "The definition of natural motion implied by the Principle of Seeing Is Believing falls somewhere between the definitions suggested by Galileo and Einstein. A laser beam shining horizontally from the top of a cliff will bend downward almost imperceptibly. So small is the deviation from a mathematical straight line, in fact, that it is practically impossible to observe. While crossing an average room, for example, a light beam drops by less than the diameter of an atomic nucleus--a distance that is too small to measure. The bending of light is observable only in much stronger gravitational fields, such as the sun’s, which deflects starlight. Nevertheless, in principle at least, every light beam (except a vertical one) droops a little.", "The natural motion of a stone projected horizontally should now be defined as motion along the gently curved trajectory of a light beam. This definition is suggested by several considerations:", "First, by Abramowicz’s theorem, the centrifugal force--the hallmark of unnatural motion--vanishes along this trajectory.", "Second, according to the physical definition of a straight line, the natural trajectory is in fact straight.", "And finally, an even more physical way to arrive at a definition of a straight line is to hurl the stone harder and harder. According to Newtonian physics, its trajectory will approach a straight line as its speed becomes infinite. But according to the special theory of relativity, the stone’s speed can only approach the speed of light, so its path cannot become straighter than that of a light beam.", "In contrast to Einstein’s conception of natural motion, which includes the effects of gravity, the new definition requires gravity to be neutralized by some external force. The same was true for Galileo’s formulation: his marble rolling in a horizontal straight line was supported by a trough whose sole purpose was to cancel the vertical force of gravity. The new definition updates this image by taking into account the fact that the manufacturer of the trough had to check its straightness by reference to a light beam--which, according to Einstein, happens to droop a little.", "In a sense, then, the new definition of natural motion represents a step backward. It adds nothing to the predictions of general relativity, but it revives the discarded idea that gravity is an external, unnatural force. For these reasons some experts dismiss it as being fundamentally alien to general relativity. But Abramowicz rejects such criticism. He argues that the advantage of his approach lies precisely in the separation of gravitational effects from inertial ones--a separation that can lead to valuable insight into the physics hidden in a thicket of formulas. In the case of the puzzling rotational flattening of a gas cloud, for example, Abramowicz and a colleague found that their deeper understanding of the physical mechanisms allowed them to reproduce with pencil and paper the results of a complicated computer program.", "The most curious consequence of the Principle of Seeing Is Believing is the new wrinkle it adds to our understanding of the familiar concept of the centrifugal force. Consider a toy rocket that keeps a constant speed and follows a gently curved path inside the unimaginably thin wedge that exists between straight lines drawn by Galileo and Abramowicz (see the illustration on page 59), all the while providing a constant counterthrust against gravity. According to the conventional view, the rocket experiences a centrifugal force pushing it back toward the Galilean straight line, outward and upward--just what I felt on the roller coaster. But according to Abramowicz, the centrifugal force actually pushes the rocket back toward its real natural path--the line defined by a light beam. The centrifugal force, in other words, points downward! (Outside the wedge, the two predictions about the direction of the centrifugal force agree.)", "The ant we left wandering inside the gopher hole would have no trouble understanding the strange tug on that little rocket. Just imagine that the insect crawls out of its hole and wanders off toward a smaller stone--one that makes only a mild indentation in the desert sand and represents, say, the planet Earth (see the illustration opposite). The ant walks past that stone along a path that is straight as seen by a balloonist high above the desert. The balloonist, unaware of the dip in the desert floor, and accustomed to Newtonian thinking, believes that the ant feels no centrifugal force.", "But the ant itself, on the ground, and versed in the subtleties of general relativity, disagrees. As it passes the stone, its trajectory takes a little dip, which causes a centrifugal force directed downward. If this force were perpendicular to the ground, the two-dimensional ant would be unable to feel it. However, because of the slope of the land, the force is not perpendicular but inclined a bit toward the side--in the direction of the stone. The ant therefore feels a slight centrifugal force, directed inward, even though its path seems straight from the balloonist’s point of view, as well as from its own. This paradox illustrates the slender difference between Galileo’s concept of natural motion and the one implied by Abramowicz. The ant feels an inertial force despite hewing to a path that is straight and, to Galileo’s thinking, natural.", "If, on the other hand, the ant were to curve its path slightly toward the stone, it would incur an additional centrifugal force that points horizontally outward, away from the stone. The ant could pick this path in such a way that this new outward force is precisely enough to cancel the inward-directed force due to the dip. The path would look slightly bent both to the balloonist and to the ant, but it would also correspond to the path of natural motion according to Abramowicz. Like the rocket ship following the path of light around a black hole, the ant would feel no centrifugal force at all.", "This metaphor, of course, is not perfect. The balloonist, looking down in three dimensions on the ant’s two-dimensional world, has no precise analogue in our world of four-dimensional space-time. And whereas light plays a crucial role in our world as a three-dimensional yardstick, the poor ant can rely on no similarly useful tool in its world of two dimensions. Nevertheless, the essential difference between Galileo’s and Abramowicz’s ideas of natural motion holds. The curved path that the two- dimensional ant follows past the stone is roughly analogous to the path that a light beam would take when passing by Earth.", "So my panic on the roller coaster turns out not to have been altogether unfounded. Centrifugal force does not behave quite the way we thought it should. Unless the track curves downward sufficiently, the centrifugal force will vanish, or reverse, and Lili and I will plunge to our death. Fortunately it doesn’t take much of a curve to prevent that disaster. As long as the track dips below a light beam shining out horizontally from its apex, I have no cause for worry.", "But I will never again think of natural motion and the centrifugal force in the way Galileo and Newton taught us." ], [ "Descartes’ Physics", "While René Descartes (1596–1650) is well-known as one of", "the founders of modern philosophy, his influential role in the", "development of modern physics has been, until the later half of the", "twentieth century, generally under-appreciated and under-investigated", "by both historians and philosophers of science. Not only did Descartes", "provide the first distinctly modern formulation of laws of nature and", "a conservation principle of motion, but he also constructed what would", "become the most popular theory of planetary motion of the late", "seventeenth century. As the renowned historian of science Clifford", "Truesdell has observed, “[Descartes’ physics] is the", "beginning of theory in the modern sense” (Truesdell 1984, 6).", "Yet, for all of the forward-looking, seemingly modern, aspects of", "Descartes’ physics, many of Descartes’ physical hypotheses", "bear a close kinship with the Aristotelian-influenced science of", "late-Medieval and Renaissance Scholasticism. It is this unique amalgam", "of both old and new concepts of the physical world that may account", "for the current revival of scholarly interest in Descartes’", "physics.", "1. A Brief History of Descartes’ Scientific Work", "Despite his fame as a philosopher of purely metaphysical problems,", "such as the relation of the soul and body, or God’s existence,", "it would not be incorrect to conclude that Descartes was a scientist", "first and a philosopher second. Not only did Descartes’ interest", "and work in science extend throughout his entire scholarly career, but", "some of his most important metaphysical works (e.g., the", "Meditations) were prompted by a perceived need to equip his", "science with a metaphysical foundation that would be acceptable to the", "Aristotelian-influenced Scholastics. Yet, one must be careful not to", "impose modern conceptions on the “natural philosophy” of", "earlier centuries, for much seventeenth century science was", "practically indistinguishable from the more speculative metaphysics of", "the era (and thus the label “natural philosophy” is", "particularly apt for describing seventeenth century science). In fact,", "much of Descartes’ science is only part of a much larger system", "that embraces all areas of philosophical investigation, including both", "his physics and metaphysics.", "The awakening of Descartes’ interest in physics is often dated", "to late 1618, when Descartes first met Isaac Beeckman, an amateur", "scientist and mathematician who championed the new", "“mechanical” philosophy. The mechanical philosophy’s", "explanation of natural phenomena, which Descartes quickly adopted,", "rejected the use of Scholastic substantial forms (see", "Section 2).", "Rather, the mechanical approach favored a contact or impact model of", "the interaction of small, unobservable “corpuscles” of", "matter (which possess only a limited number of mainly geometric", "properties, such as size, motion, shape, etc.). Over the course of the", "next decade, Descartes worked on a large number of problems in both", "science and mathematics, with particular emphasis on the theory of", "light, mechanics (including hydrostatics), and the free-fall of", "terrestrial bodies. Much of Descartes’ output at this time is", "both highly mathematical and concerns only specific physical problems,", "not unlike the work of his contemporary Galileo. One of the", "accomplishments of these years includes his discovery of the law of", "refraction, often called Snell’s law: when light passes from one", "medium into another, the sine of the angle of incidence maintains a", "constant ratio to the sine of the angle of refraction. By the", "beginning of the 1630s, however, Descartes embarked on a more", "ambitious plan to construct a systematic theory of knowledge,", "including physics. The result was The World (1633), an", "important text in that it essentially contains the blueprints of the", "mechanical/geometric physics, as well as the vortex theory of", "planetary motion, that Descartes would continue to refine and develop", "over the course of his scientific career. Before publishing the", "treatise, however, he learned of the Church’s (1633)", "condemnation of Galileo for promoting Copernicanism, which prompted", "Descartes to withdraw his work from publication (since Descartes also", "advanced Copernicanism in The World). In the 1630s, the", "publication of the Geometry, the Optics, and the", "Meteorology, along with a philosophical introduction,", "Discourse on the Method (1637) further presented Cartesian", "hypotheses on such topics as the law of refraction, vision, and the", "rainbow. Yet, besides a brief sketch of his metaphysics and physics in", "the Discourse (Parts IV and V), a comprehensive treatment of", "his physics had to await the 1644 publication of the Principles of", "Philosophy. This work not only represents Descartes’ most", "fully developed and exhaustive investigation of physics, it also", "provides the metaphysical underpinnings of his physical system (in", "Part I). As an embodiment of his mature views, the Principles", "will thus form the basis of our examination of Cartesian physics.", "1.1 A Note on the Primary Texts", "The translations, with minor variations, are from Descartes 1979,", "1983, 1984a, 1984b, 1991, but the passages are identified with respect", "to the Adam and Tannery edition of the Oeuvres de Descartes", "(1976) according to the standard convention: “AT”,", "followed by volume and page number. Passages cited from the", "Principles, however, will be identified by “Pr”,", "followed by volume and article, and with a final “F”", "indicating the inclusion of new material from the French translation", "of 1647.", "1.2 Suggested Readings", "For recent in-depth examinations of Descartes’ physics, see", "Garber 1992a and Des Chene 1996. Schuster 2014 covers Descartes’", "early physics, from 1618 to 1633. A concise survey of Cartesian", "physics can be found in Garber 1992b. The scientific career of", "Descartes, with special emphasis on his physics, is presented in Shea", "1991; see also Gaukroger, Schuster, Sutton 2000 for the many aspects", "of his natural philosophy. Gaukroger 2002 examines the Principles", "of Philosophy, especially the physics, whereas Slowik 2002", "focuses primarily on Cartesian space and relational motion. The", "historical background to much in Descartes’ physics is also", "treated in Ariew 2011. On methodology in Descartes’ natural", "philosophy, see Smith 2009, while Hattab 2009 and Machamer and McGuire", "2009 cover the development of various ideas important to his physics.", "On the reception of Descartes’ work and early forms of", "Cartesianism, with special attention devoted to physics, see Schmaltz", "2005, 2017, and Dobre 2017.", "2. The Strategy of Cartesian Physics", "Like many of his contemporaries (e.g., Galileo and Gassendi),", "Descartes devised his mechanical theory in large part to refute the", "widely held Aristotelian-based Scholastic explanation of natural", "phenomena that employed an ontology of “substantial forms”", "and “primary matter”. Briefly, Scholastic natural", "philosophy viewed a material body as comprising both an inert", "property-less substratum (primary matter) and a quality-bearing", "essence (substantial form), with the latter providing the body’s", "causal capacities. A quantity of matter, for example, possesses", "weight, color, texture, and all of the other bodily properties, only", "in virtue of being conjoined with a determinate form (of a billiard", "ball, chair, etc.). Descartes admits that he had earlier held such a", "view of gravity, envisioning the substantial form as a kind of", "goal-directed (teleological) mental property of bodies: “what", "makes it especially clear that my idea of gravity was taken largely", "from the idea I had of the mind is the fact that I thought that", "gravity carried bodies towards the centre of the earth as if it had", "some knowledge of the centre within itself. For this surely could not", "happen without knowledge, and there can be any knowledge except in a", "mind” (AT VII 442). In a revealing passage from The", "World, Descartes declares the Scholastic hypothesis to be both an", "unintelligible and inadequate methodological approach to explaining", "natural phenomena:", "If you find it strange that I make no use of the qualities one calls", "heat, cold, moistness, and dryness…, as the philosophers [of", "the schools] do, I tell you that these qualities appear to me to be in", "need of explanation, and if I am not mistaken, not only these four", "qualities, but also all the others, and even all of the forms of", "inanimate bodies can be explained without having to assume anything", "else for this in their matter but motion, size, shape, and the", "arrangement of their parts (AT XI 25–26).", "Descartes’ plan is to reduce the class of metaphysically suspect", "properties, such as heat, weight, taste, to the empirically", "quantifiable attributes of size, shape, and motion. In other words,", "Descartes intends to replace the “mentally” influenced", "depiction of physical qualities in Scholastic natural philosophy with", "a theory that requires only the properties of extension to describe", "the manifest order of the natural world. Consequently, Descartes was", "an early exponent of what came to be known as the", "“primary/secondary” property distinction, a concept that", "was very much “in the air” among the critics of", "Scholasticism.", "Nevertheless, even if Descartes’ mechanistic natural philosophy", "shunned the metaphysics of substantial forms, his underlying", "methodology or approach to science remained very close to the", "Scholastic tradition. By the time of the composition of the", "Principles, Descartes had formulated a method that, like the", "Scholastics, strived to explain natural phenomena based on the", "allegedly simple and irrefutable “facts” and/or", "observations, drawn from rational reflection on concepts or from", "everyday experience, about the most fundamental aspects of reality.", "These supposedly basic facts thereby provide the requisite", "metaphysical foundation for his physical hypotheses: in other words,", "one proceeds from our “clear and distinct” knowledge of", "general metaphysical items, such as the nature of material substance", "and its modes, to derive particular conclusions on specific types of", "physical processes, for instance the laws of nature. This method of", "conducting science is quite contrary to the modern approach, needless", "to say, since modern scientists do not first engage in a metaphysical", "search for first principles on which to base their work. Yet, this is", "exactly the criticism that Descartes leveled at Galileo’s", "physics (in a letter to Mersenne from 1638): “without having", "considered the first causes of nature, [Galileo] has merely looked for", "the explanations of a few particular effects, and he has thereby built", "without foundations” (AT II 380; see, also, the Preface to the", "French translation of the Principles, AT IXB 5–11). The", "structure of the Principles, Descartes’ most", "comprehensive scientific work, reflects these priorities: Part I", "recapitulates the arguments (well-known from the Meditations)", "for the existence of God, mental substance, and other metaphysical", "topics; whereas the remaining Parts proceed to explain the nature of", "material substance, physics, cosmology, geology, and other branches of", "science, supposedly based on these fundamental metaphysical truths.", "This preoccupation with metaphysical foundations, and the causal", "explanations of natural phenomena derived from them, might also", "account for the absence in the Principles of Descartes’", "more mathematical work in physics, such as his discovery of the law of", "light refraction. As he argued in the Rules for the Direction of", "the Mind (1628), pure mathematicians are only concerned with", "finding ratios and proportions, whereas natural philosophers are", "intent on understanding nature (AT X 393–395). The development", "of modern physics, which is inextricably intertwined with modern", "mathematics, thus stands in sharp contrast to the latent Scholasticism", "evident in Descartes’ metaphysical approach to physics.", "3. Space, Body, and Motion", "Descartes’ many hypotheses concerning space and body are best", "appreciated when viewed as a continuation of a long debate within", "Medieval/Renaissance philosophy centered upon the Aristotelian dictum", "that whatever possessed dimensionality was body (see, Grant 1981).", "While some philosophers, such as Telesio, Campanella, and Bruno, held", "space to be always filled with matter (i.e., a plenum) yet somehow", "independent of matter, others, like Patrizi and Gassendi, endorsed a", "more absolutist notion that allowed spaces totally devoid of matter", "(i.e., vacuum). Rejecting these anti-Aristotelian ideas of empty", "space, Descartes equated the defining property, or", "“essence”, of material substance with three-dimensional", "spatial extension: “the extension in length, breadth, and depth", "which constitutes the space occupied by a body, is exactly the same as", "that which constitutes the body” (Pr II 10). Consequently, there", "cannot exist a space separate from body (Pr II 16), since all spatial", "extension simply is body (and he rejects the possibility of a vacuum", "that is not extended). If, for example, God removed the matter within", "a vessel (such that nothing remained), then the sides of the vessel", "would immediately become contiguous (but not through motion; Pr II", "18). It is important to note that Descartes’ claim, that the", "vessel’s sides must become contiguos, was a fairly common view", "among the Scholastics, since they also accepted the idea that spatial", "extension required a substance to ground extension (see, Grant 1981,", "122). Descartes argues that, with respect to the empty vessel, that", "“nothingness cannot possess any extension”, since", "“all distance is a mode of extension, and therefore cannot exist", "without an extended substance” (Pr II 18). While Descartes", "accepts a substance-property metaphysics, the rejection of the empty", "vessel scenario seems more motivated by his nominalism, which is the", "view that only particulars exist, whereas universals are only names", "and abstractions from particluar things. As he states in an earlier", "section of the Principles as regards numbers, “when", "number is not being considered in any created things, but only in the", "abstract or in general, it is merely a mode of thought” (Pr I", "58).", "Descartes’ actual concept of “space” can be regarded", "as a sort of conceptual abstraction from this bodily spatial", "extension, which he also dubs “internal place”:", "We attribute a generic unity to the extension of the space [of a", "body], so that when the body which fills the space has been changed,", "the extension of the space itself is not considered to have been", "changed or transported but to remain one and the same; as long as it", "remains of the same size and shape and maintains the same situation", "among certain external bodies by means of which we specify that space.", "(Pr II 10F)", "Relative to an arbitrarily chosen set of bodies, it is thus possible", "to refer to the abstract (generic) spatial extension of a portion of", "the plenum that different extended bodies successively", "“occupy”; and, presumably, by this process of abstraction", "the internal place of the entire plenum can be likewise constructed.", "Descartes takes a similar view of time, which is judged to be a", "generalized abstraction from the “durations” of particular", "bodies (where duration is an attribute of substance; Pr II", "56–57; see Gorham 2007 for more on time in Descartes). Also like", "the Scholastics, Descartes rejects any form of atomism, which is the", "view that there exists a smallest indivisible particle of matter.", "Rather, he holds that since any given spatially extended length is", "divisible in thought, thus God has the power to actually divide it (Pr", "II 20). The material entities that interact in Descartes’", "physics come in distinct units or corpuscles (see", "Section 7),", "which explains the “corpuscularian” title often", "attributed to his mechanical system, but these corpuscles are not", "indivisible.", "Descartes’ Principles of Philosophy also presents his", "most extensive discussion of the phenomena of motion, which is defined", "as “the transfer of one piece of matter or of one body, from the", "neighborhood of those bodies immediately contiguous to it and", "considered at rest, into the neighborhood of others” (Pr II 25).", "Descartes attempts to distinguish his “proper” conception", "of motion, as a change of the “neighborhood” of contiguous", "bodies, from the common or “vulgar” conception of motion,", "which is change of internal place (Pr II 10–15, 24–28).", "The surface of these containing bodies (that border the contained", "body) is also called the “external place” of the contained", "body. Descartes notes that the vulgar concept of motion allows a body", "to simultaneously take part in many (possibly contradictory) motions,", "as when a sitting passenger on a ship views himself as at rest", "relative to the parts of the ship, but not at rest relative to the", "shore (Pr II 24). Yet, when motion is viewed as a translation of the", "contiguous neighborhood, a body can only partake in one motion, which", "dispels the apparent contradiction (since the body must either be at", "rest, or in translation away from, its contiguous neighborhood).", "Nevertheless, Descartes’ hypothesis of motion may sanction a", "species of relative motion, since his phrase, “considered at", "rest”, implies that the choice of which bodies are at rest or in", "motion is purely arbitrary. According to the “relational”", "theory (or at least the more strict versions of relationism), space,", "time, and motion are just relations among bodies, and not separately", "existing entities or properties that are in any way independent of", "material bodies. Motion only exists as a “relative", "difference” among bodies: that is, the bodies do not possess", "individual, determinate properties of speed, velocity, acceleration", "(e.g., body C has the speed property of “5 miles per", "hour”); rather, all that really exists is a difference in their", "relative speed, velocity, and acceleration (e.g., there is a speed", "difference among bodies C and B of “5 miles", "per hour”). Several passages in Descartes’ analysis of", "motion seem to support this strong variety of relationism: “we", "cannot conceive of the body AB being transported from the", "vicinity of the body CD without also understanding that the", "body CD is transported from the vicinity of the body", "AB” (Pr II 29). Hence, “all the real and positive", "properties which are in moving bodies, and by virtue of which we say", "they move, are also found in those [bodies] contiguous to them, even", "though we consider the second group to be at rest” (Pr II 30).", "This form of relational motion has been dubbed the “reciprocity", "of transfer” in the recent literature. Yet, as will be discussed", "in a later section, Descartes also holds that rest and motion are", "different bodily states, a view that is incompatible with a strict", "relationism as regards motion. Therefore, Cartesian reciprocity of", "transfer only satisfies relationism (along with its ban on individual", "bodily states of motion) for moving bodies (i.e., when there is a", "translation manifest between a body and its contiguous neighborhood).", "Many of the difficulties associated with Cartesian physics can be", "traced to the enormous ontological burden that Descartes places on his", "hypothesis of motion. In a later section we will examine the problem", "of integrating his account of motion with the Cartesian laws of", "nature, but a brief discussion of the apparent circularity of", "Descartes’ definitions of motion and body is required at this", "point. After describing motion as the transference of a body from the", "surrounding neighborhood of bodies, Descartes states that by", "“one body, or one part of matter, I here understand everything", "which is simultaneously transported” (Pr II 25). The problem, of", "course, is that Descartes has defined motion as a change of contiguous", "bodies, and then proceeds to define body as that which moves", "(translates, transports). Although this circularity threatens the", "entire edifice of Cartesian physics, it is possible that Descartes", "intended both motion and body to possess an equal ontological", "importance in his theory, such that neither is the more fundamental", "notion (which serves as the basis for constructing or defining the", "other notion). Yet, their intrinsic interrelationship entails that any", "attempted definition of one must inevitably incorporate the other. The", "problem with this reconstruction of Descartes’ reasoning,", "however, is that Descartes explicitly deems motion to be a", "“mode” of extension; where a mode is a lesser ontological", "category that, roughly, can be understood as a way that extension", "manifests itself, or as a “property” of extension (Pr I", "53; shape is also mentioned as a mode of extension). Finally, another", "difficulty implicit in Descartes’ theory is the fact that a", "resting body, according to the definition of body and place, would", "seem to “blend” into the surrounding plenum: that is, if a", "body is “everything which is simultaneously transported”,", "then it is not possible to discern a resting body from the surrounding", "plenum matter that forms the external place of that resting body. In", "addition, Descartes rejects any explanation of the solidity of a body", "that employs a bond among its particles (since the bond itself would", "be either a substance or property, and thus the solidity of the bond", "would presumably need to be explained; Pr II 55). A macroscopic", "material body is, essentially, held together just by the relative rest", "of its constituent material parts. This raises the obvious difficulty", "that the impact of such bodies should result in their dispersion or", "destruction (for there is nothing to hold them together). These sorts", "of complications prompted many later natural philosophers, who were", "generally sympathetic to Descartes’ mechanical philosophy, to", "search for an internal property of matter that could serve as a type", "of individuating and constitutive principle for bodies; e.g.,", "Leibniz’ utilization of “force”.", "Related to the alleged circularity of the definitions of motion and", "body, as well as the problem of resting bodies, is the difficulty in", "reconciling Descartes’ definition of “substance”", "with his claim that individual bodies are substances. If, as Descartes", "believes, substances are not dependent on other things in order to", "exist (Pr I 51), then any part of extension (which is a body, via Pr", "II 10, as explained above) would not qualify as a substance since it", "depend on its contiguous neighbors to delimit and define its boundary.", "Yet, Descartes often declares that individual bodies are substances;", "e.g., “the two halves of a portion of matter, no matter how", "small they may be, are two complete substances” (AT III 447).", "One of the most popular replies to this difficulty, from Spinoza", "(Ethics, Part I, Prop. 15) to many contemporary commentators", "(e.g., Keeling 1968, Lennon 1993, Sowaal 2004, Schmaltz 2020, and", "numerous others), is to declare that only the whole plenum is a", "substance, and not any of its constituent parts. The problem with this", "attempted solution, however, is that it lacks textual support, as is", "evident in the Pr I 51 quotation above. Likewise, some of these", "reconstructions, such as Lennon’s, would seem to violate central", "aspects of Cartesian physics and metaphysics, for he interprets motion", "as a phenomenal contribution of the mind, such that the plenum and its", "parts do not move or change at all. Along these same lines, some", "scholars (e.g., Schaffer 2009) have concluded that Descartes was a", "supersubstantivalist, i.e., the view that space (spacetime, in the", "modern setting) is the only predicable or fundamental substance. While", "Descartes’ identification of corporeal substance and space (see", "above, Pr II 10) might seem to support this reading,", "supersubstantivalism takes space as primary, and matter as secondary", "or derived from space (see Sklar 1974, 222). Descartes, on the", "contrary, takes matter or body as primary and space as a derived,", "abstract concept: “the same extension which constitutes the", "nature of body also constitutes the nature of space, and . . . these", "two things differ only in the way that the nature of the genus or", "species differs from that of the individual” (Pr II 11). Whereas", "space is a genus or species concept for Descartes (which is a", "universal; Pr I 59), space is the individual for the", "supersubstantivalist, and thus ascribing supersubstantivalism to", "Descartes violates his nominalism (Pr II 8). Indeed, the reason that", "Descartes seeks to equate bodily and spatial extension in this part of", "the Principles is that he strives to reject any view that", "treats space as a separate, usually incorporeal, entity that is", "independent of matter (e.g., the popular imaginary space tradition,", "which was a forerunner to the absolutist or substantivalist", "conception): “That corporeal substance, when distinguished from", "its quantity or extension, is confusedly conceived as if it were", "incorporeal” (Pr II 9).", "4. The Laws of Motion and the Cartesian Conservation Principle", "Foremost among the achievements of Descartes’ physics are the", "three laws of nature (which, essentially, are laws of bodily motion).", "Newton’s own laws of motion would be modeled on this Cartesian", "breakthrough, as is readily apparent in Descartes’ first two", "laws of nature: the first states “that each thing, as far as is", "in its power, always remains in the same state; and that consequently,", "when it is once moved, it always continues to move” (Pr II 37),", "while the second holds that “all movement is, of itself, along", "straight lines” (Pr II 39; these two would later be incorporated", "into Newton’s first law of motion). By declaring that motion and", "rest are primitive states of material bodies without need of", "further explanation, and that bodies only change their state when", "acted upon by an external cause, it is not an exaggeration to claim", "that Descartes helped to lay the foundation for the modern theory of", "dynamics (which studies the motion of bodies under the action of", "forces). For the Aristotelian-influenced Scholastics who had", "endeavored to ascertain the causal principles responsible for the", "“violent” motions of terrestrial bodies (as opposed to", "their “natural” motions to specific regions of the", "plenum), the explanation for these forced, unnatural motions seemed to", "lie in some type of internal bodily property, or external agent, that", "was temporarily possessed by, or applied to, a body—an", "explanation that accounts for the fact that the body’s motion", "both originates and concludes in a state of rest (since, while on the", "earth’s surface, the terrestrial element has no natural", "motions). According to the medieval “impetus” theory, for", "example, these violent motions occur when a quality is directly", "transferred to a body from a moving or constrained source, say, from a", "stretched bow to the waiting arrow. This property causes the observed", "bodily motion until such time that it is completely exhausted, thus", "bringing about a cessation of the violent movement (and the", "arrow’s fall back to earth). Implicit in the Scholastic view is", "the basic belief that a terrestrial body continuously resists change", "from a state of rest while situated upon the earth, since the", "depletion of the impetus property eventually effects a corresponding", "return of the body’s original motionless, earthbound condition.", "Descartes, on the other hand, interpreted the phenomena of motion in", "an entirely new light, for he accepts the existence of inertial motion", "(uniform or non-accelerating motion) as a natural bodily state", "alongside, and on equal footing with, the notion of bodily rest. He", "argues, “because experience seems to have proved it to us on", "many occasions, we are still inclined to believe that all movements", "cease by virtue of their own nature, or that bodies have a tendency", "towards rest. Yet this is assuredly in complete contradiction to the", "laws of nature; for rest is the opposite of movement, and nothing", "moves by virtue of its own nature towards its opposite or own", "destruction” (Pr II 37). While one can find several natural", "philosophers whose earlier or contemporary work strongly foreshadowed", "Descartes’ achievement in the first and second", "laws—namely, Galileo and Isaac Beeckman (see Arthur", "2007)—the precise formulation put forward in the Principles", "of Philosophy is quite unique (especially as regards the second", "law, since both Galileo and Beeckman appear to sanction a form of", "circular inertial motion, which possibly betrays the influence of the", "Scholastic’s circular motion of the celestial element). A", "fascinating blending of Scholasticism and the new physics is also", "evident in the above quotation, since Descartes invokes the logic of", "contrary properties in his statement that “nothing moves by", "virtue of its own nature towards its opposite or own", "destruction”. That is, rest and motion are opposite or contrary", "states, and since opposite states cannot (via the Scholastic", "principle) transform into one another, it follows that a body at rest", "will remains at rest and a body in motion will remains in motion.", "Consequently, Descartes has employed a Scholastic/Medieval argument to", "ground what is possibly the most important concept in the formation of", "modern physics, namely inertia. Yet, it is important to note that", "Descartes’ first and second laws do not correspond to the modern", "concept of inertia, since he incorrectly regards (uniform,", "non-accelerating) motion and rest as different bodily states, whereas", "modern theory dictates that they are the same state.", "While Descartes’ first and second laws deal with the rest and", "motion of individual bodies, the third law of motion is expressly", "designed to reveal the properties exhibited among several bodies", "during their collisions and interactions. In short, the third law", "addresses the behavior of bodies under the normal conditions in his", "matter-filled world; when they collide: “The third law: that a", "body, upon coming in contact with a stronger one, loses none of its", "motion; but that, upon coming in contact with a weaker one, it loses", "as much as it transfers to that weaker body” (Pr II 40). In the", "following sections of the Principles, Descartes makes", "explicit the conserved quantity mentioned in this third law:", "We must however notice carefully at this time in what the force of", "each body to act against another or resist the action of that other", "consists: namely, in the single fact that each thing strives, as far", "as in its power, to remain in the same state, in accordance with the", "first law stated above….This force must be measured not only by", "the size of the body in which it is, and by the [area of the] surface", "which separates this body from those around it; but also by the speed", "and nature of its movement, and by the different ways in which bodies", "come in contact with one another. (Pr II 43)", "As a consequence of his first law of motion, Descartes insists that", "the quantity conserved in collisions equals the combined sum of the", "products of size and speed of each impacting body. Although a", "difficult concept, the “size” of a body roughly", "corresponds to its volume, with surface area playing an indirect role", "as well. This conserved quantity, which Descartes refers to", "indiscriminately as “motion” or “quantity of", "motion”, is historically significant in that it marks one of the", "first attempts to locate an invariant or unchanging feature of bodily", "interactions. To give an example, if a body B of size 3 and", "speed 5 collides with a body C of size 2 and speed 4, then", "the total quantity of motion of the system is 23, a quantity which", "remains preserved after the collision even though the bodies may", "possess different speeds.", "Moreover, Descartes envisions the conservation of quantity of motion", "as one of the fundamental governing principles of the entire cosmos.", "When God created the universe, he reasons, a certain finite amount of", "motion (quantity of motion) was transmitted to its material occupants;", "a quantity, moreover, that God continuously preserves at each", "succeeding moment. (For more on the difficult issue of God’s", "continuous recreation or preservation of the material world, see,", "e.g., Gorham 2004, Hattab 2007, and Schmaltz 2008).", "It is obvious that when God first created the world, He not only moved", "its parts in various ways, but also simultaneously caused some of the", "parts to push others and to transfer their motion to these others. So", "in now maintaining the world by the same action and with the same laws", "with which He created it, He conserves motion; not always contained in", "the same parts of matter, but transferred from some parts to others", "depending on the ways in which they come in contact. (Pr II 62)", "In the Principles, Descartes conservation law only recognizes", "a body’s degree of motion, which correlates to the scalar", "quantity “speed”, rather than the vectorial notion", "“velocity” (which is speed in a given direction). This", "distinction, between speed and velocity, surfaces in Descartes’", "seven rules of impact, which spell out in precise detail the outcomes", "of bodily collisions (although these rules only describe the", "collisions between two bodies traveling along the same straight line).", "Descartes’ utilization of the concept of speed is manifest", "throughout the rules. For example:", "Fourth, if the body C were entirely at rest,…and if", "C were slightly larger than B; the latter could", "never have the force to move C, no matter how great the speed", "at which B might approach C. Rather, B", "would be driven back by C in the opposite direction:", "because…a body which is at rest puts up more resistance to high", "speed than to low speed; and this increases in proportion to the", "differences in the speeds. Consequently, there would always be more", "force in C to resist than in B to drive, ….", "(Pr II 49F)", "Astonishingly, Descartes claims that a smaller body, regardless of its", "speed, can never move a larger stationary body. While obviously", "contradicting common experience, the fourth collision rule does nicely", "demonstrate the scalar nature of speed, as well as the primary", "importance of quantity of motion, in Cartesian dynamics. In this rule,", "Descartes faces the problem of preserving the total quantity of motion", "in situations distinguished by the larger body’s complete rest,", "and thus zero value of quantity of motion. Descartes conserves the", "joint quantity of motion by equipping the stationary object C", "with a resisting force sufficient to deflect the moving body", "B, a solution that does uphold the quantity of motion in", "cases where C is at rest. That is, since B merely", "changes its direction of inertial motion, and not its size or degree", "of speed (and C equals zero throughout the interaction), the", "total quantity of motion of the system is preserved. For Descartes,", "reversing the direction of B’s motion does not alter", "the total quantity of motion, a conclusion that is in sharp contrast", "to the later hypothesis, usually associated with Newton and Leibniz,", "that regards a change in direction as a negation of the initial speed", "(i.e., velocity). Thus, by failing to foresee the importance of", "conjoining direction and speed, Descartes’ law falls just short", "of the modern law for the conservation of momentum.", "In this context, the complex notion of “determination”", "should be discussed, since it approximately corresponds to the", "composite direction of a body’s quantity of motion. In some", "passages, Descartes apparently refers to the direction of a", "body’s motion as its determination: “there is a difference", "between motion considered in itself, and its determination in some", "direction; this difference makes it possible for the determination to", "be changed while the quantity of motion remains intact” (Pr II", "41). Yet, a single motion does not have just one determination, as is", "clear in his critique of Hobbes’ interpretation of", "determinations: “What he [Hobbes] goes on to say, namely that a", "‘motion has only one determination,’ is just like my", "saying that an extended thing has only a single shape. Yet this does", "not prevent the shape being divided into several components, just as", "can be done with the determination of motion” (April 21, 1641;", "AT III 356). In the same way that a particular shape can be", "partitioned into diverse component figures, so a particular", "determination can be decomposed into various constituent directions.", "In his Optics, published in 1637, Descartes’ derivation", "of his law of refraction seemingly endorses this interpretation of", "determinations. If a ball is propelled downwards from left to right at", "a 45 degree angle, and then pierces a thin linen sheet, it will", "continue to move to the right after piercing the sheet but now at an", "angle nearly parallel with the horizon. Descartes reasons that this", "modification of direction (from the 45 degree angle to a smaller", "angle) is the net result of a reduction in the ball’s downward", "determination through collision with the sheet, “while the one", "[determination] which was making the ball tend to the right must", "always remain the same as it was, because the sheet offers no", "opposition at all to the determination in this direction” (see", "Figure 1).", "Figure 1. Diagram from the", "Optics.", "Descartes’ determination hypothesis also incorporates a certain", "quantitative element, as revealed in a further controversial", "hypothesis that is often described as the “principle of least", "modal action”. In a letter to Clerselier (February 17th, 1645),", "Descartes explains:", "When two bodies collide, and they contain incompatible modes,", "[either different states of speed, or different determinations of", "motion] then there must occur some change in these modes in order", "to make them compatible; but this change is always the least that may", "occur. In other words, if these modes can become compatible", "when a certain quantity of them is changed, then no larger quantity", "will change (AT IV 185).", "This principle can be illustrated with respect to our previous example", "involving the fourth collision rule. If both B and C", "were to depart at the same speed and in the same direction after", "impact, it would be necessary for the smaller body B to", "transfer at least half of its quantity of motion to the larger", "stationary body C. Yet, Descartes reasons that it is easier", "for B in this situation to merely reverse it direction than", "to transfer its motion:", "When C is the larger [body], B cannot push it in", "front of itself unless it transfers to C more than half of", "its speed, together with more than half of its determination to travel", "from left to right in so far as this determination is linked with its", "speed. Instead it rebounds without moving body C, and changes", "only its whole determination, which is a smaller change than the one", "that would come about from more than half of this determination", "together with more than half of its speed (AT IV 186).", "Consequently, reversing B’s direction of motion, a", "change of one mode (determination), constitutes a lesser modal change", "than a transference of motion between two bodies, which alters two", "modes (speed and determination). In this passage, it is important to", "note that if B were to transfer motion to C, it", "would change both half of B’s speed and half of its", "determination, even though the direction of B’s", "quantity of motion is preserved. As a result, a body’s", "determination is apparently linked to its magnitude of speed.", "5. The Problem of Relational Motion", "As discussed in previous sections, there are various ways in which", "Descartes’ laws of motion violate a strict relationism. One of", "the most problematic instances involves the relational compatibility", "of the fourth and fifth collision rules. Whereas the fourth rule", "concludes that a large object remains at rest during impact with a", "smaller moving body, such that the smaller body is deflected back", "along its initial path, the fifth rule concludes that a large body", "will move a smaller stationary object, “transferring to [the", "smaller body] as much of its motion as would permit the two to travel", "subsequently at the same speed” (Pr II 50). From a relational", "standpoint, however, rules four and five constitute the same type of", "collision, since they both involve the interaction of a small and", "large body with the same relative motion (or speed difference) between", "them. One might be tempted to appeal to the basic Cartesian tenet that", "motion and rest are different intrinsic states of bodies, or the", "reciprocity of transfer thesis, to circumvent this difficulty (see", "section 3): i.e., there is an ontological difference between a body", "that is, or is not, undergoing a translation with respect to its", "contiguous neighborhood, and this is sufficient to distinguish the", "case of rule four from rule five (since the large body is really at", "rest in four, and really in motion in five).", "The problem with this line of reasoning, however, is that it only", "works if one presupposes that the two bodies are approaching one", "another, and this is not a feature of the system that can be captured", "by sole reference to the contiguous neighborhood of each individual", "body. Even if there is reciprocity of transfer between a body and its", "neighborhood, it is still not possible to determine which collision", "rule the impact will fall under, or if the bodies will even collide at", "all, unless some reference frame is referred to that can compute the", "motion of both bodies relative to one another. Suppose, for instance,", "that a certain spatial distance separates two bodies, and that one of", "the bodies is, and the other is not, undergoing a translation relative", "to its neighboring bodies. Given this scenario, it is not possible to", "determine if; (i) the translating body is approaching the", "non-translating body, or (ii) the spatial interval between them", "remains fixed and the translating body simply undergoes a change of", "neighborhood (i.e., the neighborhood moves relative to a stationary", "body). In short, Descartes’ reciprocity of transfer thesis", "underdetermines the outcome of his bodily collisions, as well as the", "capacity to apply, and make predictions from, the Cartesian collision", "rules. The context of the collision rules also supports the view that", "the motions of the impacting bodies are determined from an external", "reference frame, rather than from the local translation of their", "contiguous neighborhoods. In elucidating the fourth rule, for", "instance, Descartes states that B could never move C", "“no matter how great the speed at which B might", "approach C” (Pr II 49)—and only an external perspective,", "not linked to the bodily reciprocity of transfer, could determine that", "B “approaches” C. Such admissions make", "it very difficult to reconcile Descartes’ physics with a strict", "relational theory of space and motion, although it may be compatible", "with weaker forms of relationism that can countenance various external", "reference frames, structures, or other methods for determining the", "individual states of bodily motion. These weaker relationist", "strategies (or even non-relational, absolutist interpretations) of", "Descartes’ physics come at a high price, however, since the", "reciprocity of transfer thesis must be abandoned. For these reasons,", "it is more likely that Descartes’ reciprocity of transfer thesis", "is intended to counter any interpretation that regards motion as", "caused by a bodily property, as some Scholastics had held (such as", "Buridan), rather then defend relational motion (see Maier 1982 on", "these earlier views of motion). That is, if there is nothing in the", "moving body that differs from its neighborhood of contiguous bodies", "(see Pr II 30), then a body’s motion is not due to it possessing", "a special property that its neighborhood lacks.", "6. “Force” in Cartesian Physics", "Despite the mechanistic, non-teleological character of", "Descartes’ analysis of motion and bodily interactions, there are", "many seemingly metaphysical and qualitative traits in Cartesian", "physics that do not sit comfortably with his brand of reductionism", "(i.e., that material bodies are simply extension and its modes). In", "fact, returning to the Cartesian laws of nature (section 4), it is", "evident that Descartes has allotted a fundamental role to the action", "of bodily “forces” or “tendencies”: for", "example, the tendency of bodies to follow straight lines, the", "resistance to motion of a large resting body (to a smaller moving", "body), etc. In The World, he states: “the virtue or", "power in a body to move itself can well pass wholly or partially to", "another body and thus no longer be in the first; but it cannot no", "longer exist in the world” (AT XI 15). As an early remark", "concerning his conservation principle, this explanation seems to", "envision force much like a property or “power” possessed", "by individual material objects, similar to the qualitative,", "metaphysical properties of the Scholastics (as in the", "“impetus” theory). For these reasons, the nature of bodily", "forces or tendencies is a philosophical question of much interest in", "the study of Descartes’ physics.", "In order to better grasp the specific role of Cartesian force, it", "would be useful to closely examine his theory of centrifugal effects,", "which is closely associated with the second law of nature. Besides", "straight-line motion, Descartes’ second law also mentions the", "“center-fleeing” (centrifugal) tendencies of circularly", "moving material bodies: “all movement is, of itself, along", "straight lines; and consequently, bodies which are moving in a circle", "always tends to move away from the center of the circle which they are", "describing” (Pr II 39). At first glance, the second law might", "seem to correspond to the modern scientific dissection of centrifugal", "force: specifically, the centrifugal effects experienced by a body", "moving in a circular path, such as a stone in a sling, are a normal", "consequence of the body’s tendency to depart the circle along a", "straight tangential path. Yet, as stated in his second law, Descartes", "contends (wrongly) that the body tends to follow a straight line away", "from the center of its circular trajectory. That is, the force exerted", "by the rotating stone, as manifest in the outward “pull”", "on the impeding sling, is a result of a striving towards straight line", "inertial motion directed radially outward from the center of the", "circle, rather than a striving towards straight line motion aimed", "along the circle’s tangent. Descartes does acknowledge, however,", "the significance of tangential motion in explicating such", "“center-fleeing” tendencies, but he relegates this", "phenomenon to the subordinate status of a composite effect. By his", "reckoning, the tendency to follow a tangential path exhibited by a", "circling body, such as the flight of the stone upon release from the", "sling, can be constructed from two more basic or primary inclinations:", "first, the tendency of the object to continue along its circular path;", "and second, the tendency of the object to travel along the radial line", "away from the center. Thus, Descartes is willing to admit that", "“there can be strivings toward diverse movements in the same", "body at the same time” (Pr III 57), a judgment that seems to", "presuppose the acceptance of some type of “compositional”", "theory of tendencies analogous to his dissection of determinations.", "Yet, since he believes that “the sling, …, does not", "impede the striving [of the body along the circular path]” (Pr", "III 57), he eventually places sole responsibility for the production", "of the centrifugal force effects on the radially directed component of", "“striving”. He states, “If instead of considering", "all the forces of [a body’s] motion, we pay attention, to only", "one part of it, the effect of which is hindered by the", "sling;…;we shall say that the stone, when at point A,", "strives only [to move] toward D, or that it only attempts to", "recede from the center E along the straight line", "EAD” (Pr III 57; see Figure 2).", "Figure 2. Diagram that accompanies Pr", "III 57.", "Descartes’ use of the terms “tendency” and", "“striving” in his rotating sling example should not be", "equated with his previous concept of a determination of motion. A", "determination is confined to a body’s actual motion, whereas a", "body’s tendency towards motion only occurs at a single instant.", "He states: “Of course, no movement is accomplished in an", "instant; yet it is obvious that every moving body, at any given moment", "in the course of its movement, is inclined to continue that movement", "in some direction in a straight line,…” (Pr II 39). In", "another passage in the Principles, Descartes identifies these", "strivings as a “first preparation for motion” (Pr III 63).", "Hence, while determinations necessitate a span of several instants,", "tendencies towards motion are manifest only at single instants. This", "is a crucial distinction, for it partitions Cartesian dynamics into", "two ontological camps: forces that exist at moments of time, and", "motions that can only subsist over the course of several temporal", "moments. In many parts of the Principles, moreover, Descartes", "suggests that quantity of motion is the measure of these bodily", "tendencies, and thus quantity of motion has a dual role as the measure", "of non-instantaneous bodily motion as well as the instantaneous bodily", "tendencies (see Pr III 121).", "Given his rejection of the Scholastic qualitative tradition in", "physics, Descartes’ depiction of centrifugal effects as due to a", "“tendency” or “striving” of moving bodies thus", "raises a host of intriguing ontological questions (and may even reveal", "a vestigial influence of his earlier Scholastic training). That is,", "even as his penchant for a geometrical world view increased, as", "manifest in the identification of extension as matter’s primary", "quality, Descartes continued to treat inertial motion and its", "accompanying force effects as if they were essential characteristics", "of bodies. Descartes’ own remarks on the ontological status of", "inertial force, furthermore, disclose a certain degree of ambiguity", "and indecision. In a 1638 letter, (six years before the", "Principles), he concludes:", "I do not recognize any inertia or natural sluggishness in", "bodies…; and I think that by simply walking, a man makes the", "entire mass of the earth move ever so slightly, since he is putting", "his weight now on one spot, now on another. All the same, I agree", "…that when the largest bodies (such as the largest ships) are", "pushed by a given force (such as a wind), they always move more slowly", "than others. (AT II 467)", "In this passage, Descartes seems to deny the existence of inertial", "force if conceived as a form of Scholastic quality that material", "bodies can possess; rather, bodies are “indifferent to", "motion”, so even the slightest weight should move the entire", "earth. On the other hand, he is willing to acknowledge the commonly", "observed fact that larger objects are much harder to set in motion", "than smaller objects. Consequently, although Descartes finds the", "existence of “forces of resistance” (or “natural", "sluggishness”) problematic, as is the case with such similar", "properties as weight, he does not entirely relegate inertia to the", "phenomenological status of the so-called secondary properties of", "matter (such as color, taste, etc., which only exist in the mind). The", "main reason for this inclusion of inertial force effects into", "scientific discourse can probably be traced to Descartes’", "classification of motion as an intrinsic characteristic or", "“mode” of extension (see", "Section 3).", "As the concluding sections of the Principles state: “I", "have now demonstrated [there] are nothing in the [material] objects", "other than…certain dispositions of size, figure and", "motion…” (Pr IV 200). Since inertial forces are a", "consequence or a by-product of motion, as the product of the size", "times speed of bodies, Descartes apparently did not object to", "incorporating these phenomena within the discussion of the modes of", "material substance.", "Yet, even if Descartes described force as an intrinsic fact of", "material interactions, the exact nature of the relationship between", "force and matter remains rather unclear. In particular, is force a", "property actually contained or present within bodies? Or, is it some", "sort of derivative phenomenal effect of the action of speed and size,", "and thus not present within extension? On the former interpretation", "(as favored by Alan Gabbey 1980, and Martial Gueroult 1980), forces", "exist in bodies in at least one important sense as “real”", "properties or modes whose presence occasions the Cartesian laws of", "nature. While many of Descartes’ explanations might seem to", "favor this interpretation (e.g., “[a body] at rest has force to", "remain at rest”, Pr II 43), Daniel Garber charges that such", "views run counter to Descartes’ demand that extension alone", "comprise the essence of matter. Garber suggests that we view Cartesian", "force as a sort of shorthand description of the dynamical regularities", "maintained in the world by God, and not as some form of quality", "internal to bodies: “The forces that enter into the discussion", "[of the Cartesian collision laws] can be regarded simply as ways of", "talking about how God acts, resulting in the law-like behavior of", "bodies; force for proceeding and force of resisting are ways of", "talking about how, …, God balances the persistence of the state", "of one body with that of another” (Garber 1992a, 298; see also", "Hatfield 1979, Des Chene 1996, and Manchak 2009, for more approaches).", "In various passages associated with the conservation principle,", "Garber’s interpretation apparently gains credibility. For", "instance: “So in now maintaining the world by the same action", "and with the same laws with which He [God] created it, He conserves", "motion; not always contained in the same parts of matter, but", "transferred from some parts to others depending on the ways in which", "they come in contact” (Pr II 42). In retrospect, however, it", "must be acknowledged that Descartes’ classification of material", "substance with extension, as exemplified in his demand that there", "exists nothing in bodies except “certain dispositions of size,", "figure and motion”, is so open-ended and equivocal as to easily", "accommodate both of the interpretations surveyed above. All that can", "be safely concluded is that Descartes envisioned the forces linked", "with bodily inertial states as basic, possibly primitive, facts of the", "existence of material bodies—a broad judgment that, by refusing", "to take sides, opts out of this difficult ontological dispute.", "7. Cartesian Cosmology and Astrophysics", "Descartes’ vortex theory of planetary motion proved initially to", "be one of the most influential aspects of Cartesian physics, at least", "until roughly the mid-eighteenth century. A vortex, for Descartes, is", "a large circling band of material particles. In essence,", "Descartes’ vortex theory attempts to explain celestial", "phenomena, especially the orbits of the planets or the motions of", "comets, by situating them (usually at rest) in these large circling", "bands. The entire Cartesian plenum, consequently, is comprised of a", "network or series of separate, interlocking vortices. In our solar", "system, for example, the matter within the vortex has formed itself", "into a set of stratified bands, each lodging a planet, that circle the", "sun at varying speeds. The minute material particles that form the", "vortex bands consist of either the atom-sized, globules (secondary", "matter) or the “indefinitely” small debris (primary", "matter) left over from the impact and fracture of the larger elements;", "tertiary matter, in contrast, comprises the large, macroscopic", "material element (Pr III 48–54). This three-part division of", "matter, along with the three laws of nature, are responsible for all", "cosmological phenomena in Descartes’ system, including gravity.", "As described in Pr III 140, a planet or comet comes to rest in a", "vortex band when its radially-directed, outward tendency to flee the", "center of rotation (i.e., centrifugal force; see", "Section 6)", "is balanced by an equal tendency in the minute elements that comprise", "the vortex ring. If the planet has either a greater or lesser", "centrifugal tendency than the small elements in a particular vortex,", "then it will, respectively, either ascend to the next highest vortex", "(and possibly reach equilibrium with the particles in that band) or be", "pushed down to the next lowest vortex—and this latter scenario", "ultimately supplies Descartes’ explanation of the phenomenon of", "gravity, or “heaviness”. More specifically, Descartes", "holds that the minute particles that surround the earth account for", "terrestrial gravity in this same manner (Pr IV 21–27). As for", "the creation of the vortex system, Descartes reasons that the", "conserved quantity of motion imparted to the plenum eventually", "resulted in the present vortex configuration (Pr III 46). God first", "partitioned the plenum into equal-sized portions, and then placed", "these bodies into various circular motions that, ultimately, formed", "the three elements of matter and the vortex systems (see Figure", "3).", "Figure 3. Plenum vortices in the", "Principles, Pr III 53.", "Besides the ontological economy of only requiring inertial motion and", "its attendant force effects, Descartes’ choice of circularly", "moving bands of particles may have also been motivated by worries", "over, for lack of a better term, “plenum crowding”. In the", "Principles, he argues: “It has been shown…that", "all places are full of bodies…. From this it follows that no", "body can move except in a complete circle of matter or ring of bodies", "which all move at the same time” (Pr II 33). Circular motion is", "therefore necessary for Descartes because there are no empty spaces", "for a moving object to occupy. Although the world is described as", "“indefinitely” large (Pr I 26–27, with only God", "receiving the more positive description, infinite), the non-circular", "motion of a single body could violate the Cartesian conservation", "principle by resulting in an indeterminate material displacement. As", "an aside, it is enormously difficult to reconcile Descartes’", "collision rules with his claim that all bodily motion occurs in", "circular paths; moreover, since the bodies that comprise the circular", "path all move simultaneously, it seems to follow from the definition", "of “body” (see", "Section 3)", "that there is only one moving body (and not many).", "Returning to the vortex theory, Descartes allots a considerable", "portion of the Principles to explicating various celestial", "phenomena, all the while adopting and adapting numerous sub-hypotheses", "that apply his overall mechanical system to specific celestial events.", "One of the more famous of these explanations is the Cartesian theory", "of vortex collapse, which also provides an hypothesis on the origins", "of comets (Pr III 115–120). Briefly, Descartes reckons that a", "significant amount of first element matter constantly flows between", "adjacent vortices: as the matter travels out of the equator of one", "vortex, it passes into the poles of its neighbor. Under normal", "conditions, primary matter flows from the poles of a vortex into its", "center, i.e., the sun, which is itself comprised of primary matter.", "Due to centrifugal force, these particles press out against the", "surrounding secondary globules as they begin their advance towards the", "equator (Pr III 120–121); the pressure exerted by the primary", "and secondary elements (on a person’s optic nerve) also serving", "as the cause of light (Pr III 55–64, IV 195). Since the adjacent", "vortices also possess the same tendency to swell in size, a balance of", "expansion forces prevents the encroachment of neighboring vortices. On", "occasion, however, a buildup of larger elements on the sun’s", "surface, identified as sunspots, may conspire to prevent the incoming", "flow of first element matter from the poles. If the sunspots", "ultimately cover the entire surface of the sun, the vortex’s", "remaining primary matter will be expelled at the equator, and thus it", "no longer has a source of outward pressure to prevent the encroachment", "of neighboring vortices. Once the vortex is engulfed by its expanding", "neighbors, the encrusted sun may become either a planet in a new", "vortex, or end up as a comet passing through many vortices.", "On the whole, the vortex theory offered the natural philosopher a", "highly intuitive model of celestial phenomena that was compatible with", "the mechanical philosophy. The theory was regarded as superior to", "Newton’s theory of universal gravitation since it did not posit", "a mysterious, occult quality (gravity) as the cause of the planetary", "orbits or the free-fall of terrestrial objects. The vortex theory", "likewise provided a built-in explanation for the common direction of", "all planetary orbits. Additionally, the vortex theory allowed", "Descartes to endorse a form of Copernicanism (i.e., sun-centered", "world) without running afoul of Church censorship. Since the alleged", "motion of the earth was one of the Church’s principal objections", "to Galileo’s science, Descartes hoped to avoid this objection by", "placing the earth at rest within a vortex band that circled the sun,", "such that the earth does not undergo a change of place relative to the", "containing surface of the neighboring material particles in its vortex", "band (Pr III 24–31; and section 3). Through this ingenious", "maneuver, Descartes could then claim that the earth does not", "move—via his definition of place and motion—and yet", "maintain the Copernican hypothesis that the earth orbits the sun.", "“The Earth, properly speaking, is not moved, nor are any of the", "Planets; although they are carried along by the heaven” (Pr III", "28). In the long run, however, Descartes’ vortex theory failed", "for two fundamental reasons: first, neither Descartes nor his", "followers ever developed a systematic mathematical treatment of the", "vortex theory that could match the accuracy and predictive scope of", "the (continuously improving) Newtonian theory; and second, many", "attempts by Cartesian natural philosophers to test Descartes’", "various ideas on the dynamics of circularly moving particles (e.g., by", "using large spinning barrels filled with small particles) did not meet", "the predictions advanced in the Principles (see Aiton", "1972)." ], [ "Notice", "Notice", "All articles published by MDPI are made immediately available worldwide under an open access license. No special", "permission is required to reuse all or part of the article published by MDPI, including figures and tables. For", "articles published under an open access Creative Common CC BY license, any part of the article may be reused without", "permission provided that the original article is clearly cited. For more information, please refer to", "https://www.mdpi.com/openaccess.", "Feature papers represent the most advanced research with significant potential for high impact in the field. A Feature", "Paper should be a substantial original Article that involves several techniques or approaches, provides an outlook for", "future research directions and describes possible research applications.", "Feature papers are submitted upon individual invitation or recommendation by the scientific editors and must receive", "positive feedback from the reviewers.", "Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world.", "Editors select a small number of articles recently published in the journal that they believe will be particularly", "interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the", "most exciting work published in the various research areas of the journal.", "You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.", "Abstract", "The epistemological rupture of Copernicus, the laws of planetary motions of Kepler, the comprehensive physical observations of Galileo and Huygens, the conception of relativity, and the physical theory of Newton were components of an extremely fertile and influential cognitive environment that prompted the restless Leibniz to shape an innovative theory of space and time. This theory expressed some of the concerns and intuitions of the scientific community of the seventeenth century, in particular the scientific group of the Academy of Sciences of Paris, but remained relatively unknown until the twentieth century. After Einstein, however, the relational theory of Leibniz gained wider respect and fame. The aim of this article is to explain how Leibniz foresaw relativity, through his critique of contemporary mechanistic philosophy.", "1. Introduction", "Leibniz was of the belief that space and time are not real entities but virtual relationships and mathematical concepts. He was led to this conclusion through the problem of the relationship of the mind with space, the study of the nature of the continuous in various mathematical fields, and the observation of linear and centrifugal movement, as well as the confrontation with atomism based on the assumption of the inexistence of vacuum. Space is an order of coexisting phenomena, as time is an order of successive phenomena. Today we call this view Relationalism: spatial and temporal relationships between objects and events are immediate and not reducible to space-time point relations, and all movement is the relational movement of bodies. The controversy about the ontological status of space and time began with the distinction between primary and secondary qualities developed by Democritus, Galileo, Descartes, and Locke.", "According to Descartes, primary qualities (e.g., height, width, depth), unlike secondary qualities (e.g., roughness, color), are perceptible with an accuracy that depends on the position of the observer to the physical objects. Primary properties reveal the true nature of the body. Through this distinction, Descartes output meanings, which Leibniz also analyzed. These were: (1) observability; (2) the primary, true nature of the body, the object; and (3) spatial dimensions, as physical characteristics of the physical object. From the above premises, Newton concluded that there is a similar distinction between sensible space and time, where the sensible secondary properties appear, and the completely differently theorized, mathematically defined space and time, where unseen masses and atoms of physics exist. On account of this distinction, Newton introduced the terms “absolute and relative, true, and apparent, mathematical and common” (Principia: The Mathematical Principles of Natural Philosophy, Definition VIII, Scholium). Since we can imagine that extramundane space without bodies, as an extension, is independent of the bodies, then the space, according to Newton, is certainly not material, but has its own way of existence. Furthermore, absolute and relative motion can be identified by their properties, their causes, and their effects. The absolute acceleration developed during rotation that is observable by the diverting forces from its axis is the high spot of the Newtonian argument [1].", "In summary, Newtonian science distinguished absolute from relative space and time. Absolute, genuine, and mathematical time, in itself, flows regularly due to its nature, without dependence on anything from the exterior. Its other name is continuity. Relative, apparent, and common time is a certain perceptible, external, detailed, and unstable measure of the duration of movement. Absolute space, due to its own nature, without dependence on any factor from the outside, always remains the same and motionless. Relative space is a certain mobile dimension or measure of absolute space [2]. The famous controversy between Leibniz and Newton was not direct, but was mediated by Clarke, an English theologian. The fields of dispute were meant to be observability, measurement, and experiment. The relational theory of Leibniz was articulated in juxtaposition to the theory of Newton. Leibniz believed that space is something completely relative. That is to say, space is the order of coexistence, as the time is an order of sequences. Space implies, in terms of possibility, an order of things that exist at the same time, considered as if they existed together, without examining their form of existence. The frame of reference of space and time involves natural objects and their relations, events, and processes. Space is nothing other than the order of existence of objects which are observed as they exist together. For relational theory, the possibility of a material universe as an ensemble that moves either in space or in time is without meaning, as space and time do not exist independently from the order of bodies and incidents in the Universe. All relational theories for space-time attribute territorial, time, and space-time relations to material objects. Yet relations are not an absolute reality within the things, but a determination that thought, intellect, adds to things. All relations are ostensible, that is to say they are well consolidated phenomena. Space-time relations are not ontologically prior to the relations between natural bodies.", "1.1. Innate Mathematical Concepts", "According to Leibnizian relationalism, extension or space, surfaces, lines, and points are nothing beyond rational entities, innate ideas, and relations of orders, namely orders of coexistence. Relational truths are based on incidents of a representational nature that take the form subject—predicate. The utmost indivisible units include all their predicates in such a way that the relations are ostensible and reducible to categorical constitutive parts, that is to say attributes. The space, defined as a series of coexistence is not an empirical but a rational truth: it is a virtual entity. It belongs to a set of entities that are characterized by uniformity and contain no variety. The concepts of space and time, as well as other entities of pure mathematics, are not generalizations extracted from raw empirical material. They are already in our minds, and emerge with experience [3]. Space is a concept which does not correspond to an actual entity, it is innate idea and geometrical concept [4]. It belongs to the set of innate ideas that are objects of mathematical science.", "The spatial extension is infinitely divisible and divided. Nevertheless, the true infinite, strictly speaking, is found only in the Absolute [5] (V, p. 144), while space is indefinitely extensive [6] (p. 278). According to Leibniz, the moments and the points are not parts of time and space, but only terms [5] (VI, p. 152). Simple terms referring to things come prior to the sums. The parts are real, defined, and prior in comparison to the whole; but in reference to the ideal entities, such as time and space, unity precedes, and the simple terms follow. The parts are only possible, indistinct, arbitrary divisions, following the whole.", "Leibniz [7] compared the number with extension and with mathematical bodies. Whereas number has no existence without the things measured, the extension and the mathematical bodies are meaningless without entities that act or bear, or without movement. Space, time, and infinity are not real sets; and therefore, we have no positive idea about them [5] (VI, p. 159). Extension is a reduction from the extended, while the extended is a continuum whose parts exist at the same time [5] (V, p. 136). The mathematical entities are ideal, as for instance the “shape”, which is never exact and strictly specific in nature. It is not even a universally true and clear quality outside thought ([6] (p. 343); [5] (II, p. 199)). The mathematical entities are modalities ([6] (p. 523); [5] (II, p. 195)), undefined quantities, with which we can access the discrete quantities of the real world [5] (VII, pp. 562–563).", "1.2. The Continuous", "In contrast to Newton, who believed that each point-material object coincides with a point of substantial space, Leibniz treated points as extremities or modalities or modes. The location, without doubt, is nothing more than a way of something, like the former or the latter [4] (pp. 101–102). A mathematical point itself is nothing but a way, namely an extremity [5] (II, pp. 347–348). The extension derives from the position but adheres also continuity to the position. Points are positioned in place, but they neither sustain continuity, nor can they stand by themselves [6] (p. 598).", "The ideal, virtual continua are inherent mathematical ideas and they are not composed of parts or points, nor of moments, because the perception of the moment does not contain a sequence [5] (VI, p. 152). The continuum is everywhere dense, i.e., solid, homogeneous and ceaseless, a plenum, i.e., without breakage of continuity (uninterrupted) [8].", "For Leibniz, space is infinitely divisible—in the Aristotelian sense of possibility. Space and time are an order of potentialities ([6] (p. 583); [5] (p. 568)). The spatial relationships, although they build up space, are antecedent and parasitic upon space. The Leibnizian space is not the simple sum of the ideal spatial relations but is prior to its parts and divisions. Entities of none, one, or two dimensions: flat, curved surfaces, straight lines, curves and points are the signs of mental division operations in the Euclidean framework [9,10].", "“I observe, that the traces of moveable bodies, which they leave sometimes upon the immoveable ones on which they are moved; have given men occasion to form in their imagination such an idea, as if some trace did still remain, even when there is nothing unmoved. But this is a mere ideal thing, and imports only, that if there was any unmoved thing there, the trace might be marked out upon it. And ’tis this analogy, which makes men fancy places, traces and spaces; though those things consist only in the truth of relations, and not at all in any absolute reality”.", "(The Leibniz-Clarke Correspondence, V, p. 47)", "Thus appears the unrelenting, the completeness of space, which is quondam, as it is not composed of extensional pieces of finite or infinite dimensional areas, separated from each other by two-dimensional boundaries, but is simply divisible, potentially divided. The apparent change and spatial extension are not authentically continuous, because their sequence is terminated. However, there are differences here: the spatial extension is a static representation, it lacks a privileged set of directions and forms a three-dimensional continuum. The apparent change is irreversible and therefore directional; it forms a linear or one-dimensional real continuum, as explained in [4] (pp. 103; 137).", "1.3. The Time and the Monad", "The Leibnizian theory of time is not articulated with completeness, though it is closely connected with the Monadology. In an early letter to Jacob Thomasius [5] Leibniz (1962, IV) wrote that time is nothing else beyond measure of motion. Since each magnitude is a number that consists of parts, why should the definition of time [11] by Aristotle (IV, p. 219) as a number of change surprise us?", "Newton believed that a number of specific events concurrent with one another, they are simultaneous with a certain point in time. According to Leibniz, however, moments constitute only apparent change. A certain phenomenal duration is really dense or actually infinitely divisible, as the physical objects are. Nevertheless, time is uniform or homogeneous; we can divide it an infinite number of times, but it remains prior to its parts, due to the fact that it does not consist of them. It is an idealized entity that refers to the order of succession-relations in the changing phenomena, when we remove the peculiarities of their relata. The truths concerning the time structure are eternal and determine the changing of the phenomena [4] (pp. 134–136).", "The fundamental law of being is temporality or succession [6] (p. 26). An empty space is something that we can imagine, but a gap in time incomprehensible [5] (VI, p. 155). Leibniz wrote to De Volder [6] that time, in contrast to space, is included both in spiritual and in material things, and therefore in perception, the activity of the Monad.", "2. The Monads", "The philosophical stimulation for the writing of Monadology was the problem of the Cartesian mind–body dualism. Leibniz was impressed by the belief that the pineal gland was associated with the communication between cognition and extension, the search for continuity between soul and body. He also sought to quash the naturalistic theory of Locke, who considered space as the common basis of the interaction between mind and matter. Leibniz did not think “that substance is constituted by extension alone, since the concept of extension is incomplete. Nor do I think that extension can be conceived in itself, but I consider it an analyzable and relative concept, for it can be resolved into plurality, continuity, and coexistence or the existence of parts at one and the same time” [6] (p. 516).", "Leibniz formulated the Monadology gradually, by taking the appropriate distances from Cartesianism. Regarding the substance in two of his early works he noted: “1. Substance is being which subsists in itself; 2. Being which subsists in itself is that which has a principle of action within itself (...) no body is to be taken as substance, apart from a concurrent mind (...) Whatever is not substance is accident or appearance...” (Theological Writings Related to the Catholic Demonstrations, III, I). In addition he wrote, “I call substance whatever moves or is moved” (Dissertatio de Arte Combinatoria, I, Def. 2).", "The monad is simple, unified, indivisible, unborn, and imperishable. It is simple because it has no parts. The monads form compounds, composites, accumulations (aggregata) of simple things. They do not have an extension or form, and they are not visible. However, they are the real elements of natural things. Each unique substance expresses the whole universe in its own way and includes in its concept all events with all their circumstances and all the continuity of external things. The monads are endowed with perception and they are self-reactive. One monad can be distinguished from another by its perceptions, the representation of plurality in the simple, and appetitions, its tendencies, the striving from one perception to another. The nature of the monad is the representation. A monad represents the entire universe, but more distinctly it represents the body that constitutes its entelechy [12] (Monadology, p. 62).", "The primary feature of the monads, their primary power is perception. Perception is a certain conjunction of the simple with the multiple; it is also the distinction, the identification and the selection, it is the creation and the harmony, as insisted in [13]. The monad as ultimum subsistens is the ultimate basis of all properties and determinations, as ultimum perdurabile is the foundation of any change and as vis activa is itself the source of activity [14]. Pure perceptions concern active states of the active primitive force, in other words the first entelechy which is the soul of living beings. All simple substances or created monads are entelechies of bodies [12] (Monadology, p. 18). The composition of the monadic entelechies gives the substantial form to the inorganic world, the principle of impetus. The unclear perceptions relate to potential situations of the passive primitive force (materia prima), derived from the spontaneity of the monad. Apart from the primary forces, there also exist derived ones: by the aggregation of materia prima, secondary matter is being produced, which is governed by active forces as the vis viva, namely the kinetic energy, and the conatus, expressing the potential speed. The secondary material however is governed by passive forces as well: inertia and antitypia, namely impenetrability, which will be analyzed by the physical theory of Leibniz.", "2.1. The Immutable World of Monads Is Not in Space-Time", "The spatial extension belongs to the domain of phenomena, while the monads are not placed in space; they only represent each other with spatiotemporal characteristics. A representation of a monad of the real world of representational monads is a real condition of the monad, which along with coexisting monads—which are found in suitable corresponding situations—formulate the real world of the monads. A monad beholds the world of phenomena as if it were, in itself, in the center of this vision.", "All substances are active. Space and time are produced by the monads and their primary characteristics, their properties. In concert with the principle of perfection and with its equivalent principle of the predetermined harmony, Leibniz concluded that space is a relation inherent in the cross-sectional situations, i.e., the perceptions of monads, whereas the mutual agreement of the monads is such that every perception of a given unit corresponds precisely to a perception of any other unit. The power or activity, and not the extension or passive receptivity, is the deterministic property of the reality [15,16].", "A possible interpretation of the Leibnizian theory may be closer to the Kantian philosophy: space and time do not exist as completely independent instances or continua, but they make sense only in the subjectively generated contents of the observer’s consciousness. The monad is this energetic observer, who after all lacks any windows; the monad is not located in space. However, it knows the space because it possesses the ability to perceive both the innate, necessary, tautological truths of reason, and the contingent truths of empirical facts [17,18].", "2.2. The Monadic Change and the Mathematical Concept of Series", "The Leibnizian philosophy of science is divided into three levels, the metaphysical, the conceptual (of the mathematical entities), and the apparent (of bodies). The metaphysical is the level of the mind. The monad or the mind does not accept influences but only affects the body and its representations. The idealizations of space and time are, as we have seen, orders of coexistence or succession. The concept of order originates from the ideal level, while the concepts of succession and coexistence reflect the phenomena. The monads are prerequisites and foundations of the phenomena ([6] (p. 536); [5] (II, p. 268)), they dispose neither a gradual onset, nor a gradual ending, but an abrupt onset and abrupt end [12] (Monadology, 6). Leibniz describes the monad as a focus of perception, of an anterograde situation that surrounds and represents the multiplicity within unity [12] (Monadology, 14). The monadic reality is changing entirely, moving from one state to another. This real change is a prerequisite for the good consolidation of apparent change. The monadic alteration is not just a virtual thing or an apparent time-like order, but a real time-like order [4].", "“There is, moreover, a definite order in the transition of our perceptions when we pass from one to the other through intervening ones. This order, too, we can call a path. But since it can vary in infinite ways, we must necessarily conceive of one that is most simple, in which the order of proceeding though determinate intermediate states follows from the nature of the thing itself, that is, the intermediate stages are related in the simplest way to both extremes”.", "This change in the order of perceptions appears to have a distinct and discontinuous nature: each present state of a substance is a consequence of its previous situation. Clearly, the changes are not truly continuous, that is, there appear interruptions, ruptures of continuity. However, they are characterized by density, because the dense causal connections at the level of phenomena must be correct representations of dense causal connections, with dynamic form. Other times the change is characterized as continuous and flows in conformity with an internal principle. The action of the internal principle that brings about the passage from one perception to another is called appetition [12] (Monadology, pp. 10; 11; 15).", "Two substances are never completely identical to each other: each monad is different from others. Leibniz would liken their difference with the difference between geometrical figures such as the circle, the ellipse, and the parabola. One may consider them as conic sections, obtained in accordance with the law of continuity throughout infinitely small subtle shifts (Discourse on Metaphysics, p. 53). The essence of the monad is beyond finite analysis and one can access it only through the law of individual series. The procured force is the situation at present, in its trend towards a next state, or the prior implication of the next state. Meanwhile, the primary active force exists implying everything that will happen, that is, the nature of the primary active force consists in a law of duration of a progressive series that persists with no obstacle. The procured force is a term of the series, while the active force is the law of the series.", "The problems of perception are translatable into terms of geometry, differential analysis, perspective, minimum perceptions etc. The complicated and infinitesimal movements of substances are represented by extreme curves of curves, namely by geometric models which mount the vibration of the monad with its maximum and minimum curve. The curve of the maxima is always increasing, and the curve of the minima always decreases. Progression emerges when the increase is greater than the decrease. The order is more fundamental than the disorder, as the real against the phenomenon. It is impossible to find in space the ultimate privileged spot from where one can approach the universal harmony. The sun is privileged and non-privileged from the viewpoint of the fixed stars. In an equivalent way, there is no privileged point of time [13].", "Leibniz proposed a new mathematical model inspired by the theory of infinite series. However, although aware of the distinction between divergent and convergent series, he did not propose a criterion for their distinction. Anyway, he tended to choose the most perfect series. In terms of combinatorics the “richest” series is one that involves differences and reversals. There is a class of negative or reciprocating type, for the one, the unity: without parts, without form, without division. It does not involve death, initiation, change. There is a progressive class with clearly aggregative characteristics for the multiple: parts, shape, division, dissolution, destruction, beginning, creation, increase, decrease, every form of influence. These reverse features of the one and the multiple are not expressed in accordance with an arbitrary order, but follow the development of two laws, of composition and analysis: they are synthesized by external parts, which directly unfold into the elemental world of geometry and mechanics, attributing the onset of motion in a naturalistic way. The latter two classes are sequences of positive or negative geometrical and mechanical propositions, which order the sum of the terms. They are also sequences of negative or positive propositions of a new set of terms, established by the primary relationship of the analysis of the parts, i.e., of the access to dividing up the indivisible, the atom or the element; of dissolution of heaps of cohesion, resistance, impermeability; of destruction and passing to complexity; and of change, reduction and attenuation, i.e., intersection of some part of a compound [13].", "3. Space, Time, and Motion in the Physical Theory of Leibniz", "Descartes believed that the essence of things is the extension which they occupy in space. He reduced all the characteristics of the bodies in modes of extension, supposing that physical changes are movements in space. Leibniz, after 1676, when he turned more clearly against Cartesianism, was confident that the data we observe are limited to material things, their properties, and relations [19]. The Leibnizian Relationalism is based on two key aspects: (1) space-time is not a substance, namely there is no substratum of spatial, temporal, and spatiotemporal points, endowed with spatiotemporal relations ontologically prior to the spatiotemporal relationship between physical objects and events; and (2) the motion is relative, and all spatiotemporal relations are arranged between physical objects and events.", "On the contrary, Newton, while accepting that many relationships have no observational consequences, showed that the absolute acceleration of a physical object that rotates is itself observable. To depict the forces generated by the circular motion, he used two mental experiments, the centrifugal forces on the surface of the water in a rotating bucket, and the tension of a string joining two spheres rotating about their center of mass. According to these representations, linear accelerations create observable forces. Newton attributed these absolute accelerations and generated forces to absolute space, which is an unchanging reference system. Therefore, the Newtonian science considered as absolute the differences between state of rest, uniform motion, and accelerated motion. Samuel Clarke, in his renowned correspondence with Leibniz, pinpointed the importance of absolute acceleration. If the movement of the water in the thought experiment was only relative, yaw forces from the rotation axis would be zero. Leibniz however refused to accept absolute acceleration, although he claimed that we must distinguish between “mere relative change” and “absolute true motion of a body”. Leibniz made this distinction only with respect to the cause of movement: In each movement of two material objects, the body that really moves is the cause of the change in itself:", "“I find nothing in the Eighth Definition of the Mathematical Principles of Nature, nor in the Scholium belonging to it, that proves, or can prove, the reality of Space in itself. However, I grant there is a difference between an absolute true motion of a body, and a mere relative change of its situation with respect to another body. For when the immediate cause of the change is in the body, that body is truly in motion; and then the situation of other bodies, with respect to it, will be changed consequently, though the cause of that change be not in them”.", "(The Leibniz-Clarke Correspondence, V, p. 53)", "This is not the absolute motion of Newton, but true motion relative to another body. Leibniz characterized the true motion as a subcase of relative motion: the actual motion is relative movement whose cause is the body that really moves. He believed that the centrifugal and centripetal movements are examples of dead forces [potentia mortuus] that are infinitely weaker than the living force. What was, according to Leibniz, real and absolute in motion was the driving force, a tendency to move that consists in vis viva, a real and substantial entity, a fundamental absolute quantity which is inherent in substances [20,21,22].", "3.1. The Matter, the Body, and the Coincident Movement", "Newtonian physics was unthinkable without corpuscles. On the contrary, Leibniz rejected the existence of ultimate, indivisible, firm material particles [23]. Matter is real multiplicity, a cumulative entity consisting of an infinite number of units [5] (p. 379). It is discontinuous and actually infinitely divided. However, there is no part of space without matter [5] (pp. 278–279). The matter itself is homogeneous, equally divisible anywhere, and varies with the motion [6] (p. 407).", "To the above premises corresponds the logical consequence that there are no atoms with infinite rigidity. Matter is itself in flux [6] (p. 415). The body is extended, mobile, and resistant [6] (p. 277). Each body is simultaneously fluid and solid [6] (p. 407). Leibniz believed that the solidness or the unity of the bodies originates from the mind, and there are as many minds as vortices, and as many vortices as solid bodies [24] (pp. 114–132).", "The sense is the natural resistance of the body against what is trying to divide it; it is a kind of reaction. The human body is a hydraulic–pneumatic machine containing liquids, which act not only through their weight and other mechanisms that are overt to our senses, but also in certain hidden ways as solution, precipitation, congealment, filtration, evaporation, etc. [6] (pp. 162; 282–283). In a letter to Remond [25] (pp. 74–75), Leibniz distinguished between matter and the body. Matter is nothing but impenetrability and extension. It is an inert material without spirit, without a principle of activity, and for this reason, without motion. The body on the other hand is a combination of matter and an activity principle that may cause motion. Leibniz insisted, in contrast to Descartes, that space and extension are different from the body, because otherwise the motion of the body would not be a real thing. The essence of the body is not to be extended but to move [26] (p. 10).", "Writing to Arnauld, [5] Leibniz (1962, I, p. 75) insisted that the essence of the body is motion, or a principle of motion, and that extension is unrelated to a principle like this. Therefore, the existence of a body is not subject to spatial or extensional conditions, as there exists “in omni corpore principium intimum incorporeum substantiale a mole distinctum, et hoc illud esse, quod veteres, quod Scholastici substantiam dixerint, etsi nequiverint se distincte explicar, multo minus sententiam suam demonstrare” [5] (I, p. 62). Unlike Descartes, Leibniz did not consider immobility as opposed to the motion. Immobility is a special limiting case of motion, as well as equality is a limiting case of inequality. In a digression of his criticism to the epistemology of Locke, Leibniz noted that no substance in the nature is devoid of activity and that “there is never a body without movement, because—more generally—there is never a substance that lacks activity. (...) But I believe that reason also supports this, and that is one of my proofs that there are no atoms—because if there were atoms, there could be atoms that underwent no change and were perfectly at rest” [27] (New Essays on Human Understanding, Preface).", "In his Critical Thoughts on the General Part of the principles of Descartes, Leibniz presents interesting thought experiments with two cubes, which are perfectly adjacent and then separated, when other bodies collide vertically with one or with both of them (in opposite directions), to show that atomists do not give a sufficient reason neither of the consistency of atomic compounds nor of their dissolution, namely why atoms do not coalesce huge and more than adamantine, completely indestructible compounds. The primary cause of the indestructible continuum is the movement, specifically coincident movement and the impenetrability. The bodies are solid when their movements coincide. The internal movements are subtle, rapidly unfolding even in solids, as occurs in the winter when “the permanent internal motion of the parts of matter acting in harmony alone predominates in most liquids; hence they harden and sometimes freeze solid” [6] (p. 408).", "3.2. The Vacuum", "Leibniz claimed that there are no bodies at rest, because otherwise they would not differ from vacuum. If a body were at rest, it could do not have any cohesion or consistency, because it could be impelled and divided by motion, no matter how small it may be (Letter to Antoine Arnauld, G, I, 71).", "“From this there follows a demonstration of the Copernican hypothesis and many other novelties in natural science. The other proposition is that all motion in a plenum is homocentric circular motion and that no rectilinear, spiral, elliptical, oval, or even circular motion around different centers can be understood to exist in the world, unless we admit a vacuum. It is unnecessary to speak of the rest here. I mention these because something follows from them which is useful for my present purpose. From the latter principle it follows that the essence of body does not consist in extension, that is, in magnitude and figure, because empty space, even though extended, must necessarily be different from body”.", "The vacuum remains only a possibility, as in the above inscrutable passage. “Empty space can in no way be distinguished from the perfectly fluid. There is no perfectly fluid body. There is no vacuum” [6] (p. 278), because the actual division of the bodies sprawls out until their ultimate minimum points. Leibniz believed that the same reason that shows that extramundane space is illusory, proves that every empty space is an imaginary thing. To deny the existence of the vacuum, Leibniz juxtaposed with the Newtonian argument (that the fall of bodies in a fluid depends on the specific density of the fluid), the inadequacy of empirical induction. Clarke insisted that the different resistances of mercury and water are produced by their different densities and therefore there is a need for more of a vacuum where there is less resistance. Leibniz would find the chance to correct that different densities depend not so much to the quantity of matter, but on the difficulty of finding space [viscosity], which creates resistance. Furthermore, with regard to the experimental data of Guericke and Torricelli, Leibniz proposed the following counterargument: “glass has small pores which the beams of light, the effluvia of the loadstone, and other very thin fluids may go through” (The Leibniz-Clarke Correspondence, V, p. 34).", "Leibniz once wrote that he agreed with Huygens that the concept of empty place and extension alone is the same. He added that “mobility or antitypy themselves cannot be understood from extension alone but from the subject of extension, by which place is not merely constituted but filled” [6] (p. 390).", "3.3. Movement, Vortices, and Energy", "From the natural system of the Cartesian philosophy Leibniz rejected, as we have seen, the matter-extension concept, but maintained the principle of plenitude, according to which every extended space should be complete with matter. Descartes had conceived as a fundamental physical principle the law of conservation of the quantity of motion, the absolute constancy of momentum (m.v; mass times the velocity equals momentum). However, experiments of Galileo and Huygens had shown that the m.v is not constant: the dynamic proportional measure of the size of an object is not its geometrical dimensions but its mass, while the speed of a body is proportional to the root of the distance it travels [28]. The quantity of the fundamental physical concept of vis viva m.v2 vaguely describes the conservation of energy. Leibniz generalized the principle of conservation of energy as a fundamental metaphysical principle.", "The laws of motion depend on the metaphysical principle of equality of cause and effect: if the effect were greater we should have mechanical perpetual motion, while if it were less, we should not have continuous motion. Leibniz also denied the possibility of generating a state of entropy, considered by Newton in his Optics. There can be no reduction or increase of the amount of energy. He could not accept that in a system, action is generated only with the increase of energy from a lower to a higher level. Moreover, Leibniz accepted Descartes’ view that the motion in an infinite universe, where there is no vacuum, firstly implies an infinite number of vortices, an idea firstly conceived by Leucippus. The space was filled with an ether of ultrafine particles and the rotation of the Sun caused circular motions, vortices, in the ether, which pushed the planets around the Sun like boats in a whirlpool [28].", "The question of the gravity was associated with the theory of vortices, supported by Descartes, Huygens, and Leibniz, and the refusal of the latter to accept the action at a distance, because it is not observable. Leibniz considered as the cause of both gravity and planetary attraction the cycloidal motion of ether (De Causa Gravitatis, et Defensio Sententiae Autoris de veris Naturae Legibus contra Cartesianos), a very thin fluid, from traction spokes, which disturbs the material in infinite ways, on all sides, with the result however that the movement of planetary bodies converges to a certain direction in a particular region, whereas the more massive bodies tend towards the center of the vortex. Correspondence between Huygens and Leibniz [6], which discusses the theory of Newton, throws light on their differences with Newton. The planets do not just move in ellipses, but they also move all at the same level in the same direction around the sun.", "Therefore, Leibniz rejected Newtonian attraction, because it could produce movements only in a wider rather than a limited area of three-dimensional space. In another letter, Leibniz wrote prescriptively to Abbe Conti that the most different causes engage with one another in our explanation of gravity and we simultaneously have spherical radiation, magnetic attraction, the dislodgement of spinning material, the inner motion of the fluid, and the circulation of the atmosphere, which all together cooperate to the production of centrifugal and centripetal force. Furthermore, in Tentamen de Motuum Celestium Causis, Leibniz, based on Kepler’s laws, described the fluid orbs that move the planets.", "4. Arguments", "The key features of the Newtonian conception of absolute space and time were, according to [29], as follows. Absolute motion, absolute space, and time are inherent in a substratum of spatial or space-time points. These structures are endogenous (intrinsic) in space and time, unchanged and stable. The mathematical realism of Newton, in terms of space and time, was proven fertile in the field of observation [30].", "By contrast, the arguments of Leibniz are relational. They are based on an armory of principles. At the level of logical necessity there are two self-evident principles: the principle of perfection and the principle of identity. The principles of plenitude and harmony are involved in the principle of perfection; the principle of contradiction is included in the principle of identity. As for the law of sufficient reason, it is based on the perfection of the universe and the possibility of analysis that is presupposed by the principle of identity. At the level of existence, the principles of continuity and individual differentiation (principle of indiscernibles) are derived by the law of perfection. The law of the best possible includes in particular: the principle of maximum and minimum in mathematics, least action or extremum in physics, and the law of the parsimony in the methodology. Furthermore, under certain temporal and spatial conditions, the sufficient reason implies mechanical causality, while identity becomes equivalent in its various forms—equality in algebra, congruence and similarity in geometry, equivalence in symbolic logic, and conservation of power, with all its derivative forms, in dynamics [6] (p. 45), [31].", "4.1. The Argument about Observability", "To make sense with an assertion of the existence of an entity or an attribute of the world, should the presence or absence of that entity or attribute, or a change in such a characteristic, have observational consequences. Let us suppose that space itself exists as a substance. In that case, it makes sense to ask: What is the position of the whole material world in space? How fast does the world, as a whole, move with respect to substantial space? However, only with observation can we determine the spatial relationships between the physical objects, the movements of material objects, positioning with respect to one another, etc. There are no available observations for an understandable identification of the position of the world as a whole in the substantial space, nor of its speed in reference to the substantial space, etc. Therefore, it becomes clear that such claims do not make sense according to the principle of verification, and there can be no substantial space [3] (pp. 173–174). Here is a Leibnizian version of the argument:", "“Motion does not indeed depend upon being observed; but it does depend upon being possible to be observed. There is no motion, when there is no change that can be observed. And when there is no change that can be observed, there is no change at all”.", "(The Leibniz-Clarke Correspondence, V, p. 52)", "4.2. The Principle of Indiscernibles", "“To suppose two things indiscernible, is to suppose the same thing under two names”.", "(The Leibniz-Clarke Correspondence, IV, p. 6)", "“Space is something absolutely uniform; and without the things that are placed in it, a point in space does not differ in any respect whatsoever from another point in space”.", "(Ibid, III, 5)", "The arguments based on the principle of indiscernibles usually take the following form: Suppose we have the possible worlds A and B, such that they are identical to each qualitative attribute. Then A is the same possible world as B.", "In his correspondence with Clarke, Leibniz used two similar arguments. Firstly, imagine a second universe like ours, except that all matter is shifted and placed in another location in the absolute space, without any change in the relationship between objects. If the space is Euclidean both places are exactly the same, so there would be no observable differences. Secondly, imagine a universe just like ours, except that the absolute speed of each piece of material varies and differs in an unchanging, fixed amount, without any change in the relationship of one object to another. Since the two speeds differ only by an amount that remains constant, no observable differences will be reported. The two universes are not distinguishable. If there were absolute space, the particles would have completely different motions, therefore the supposition of an absolute space is contradictory to the principle of indiscernibles. The absolute space and absolute space-time are not observable, and they give birth to indistinguishable situations. The principle of indiscernibles is based on the principle of sufficient reason.", "4.3. The Principle of Sufficient Reason", "Suppose that a theory allows us to distinguish between two different states of the world, A and B. Nevertheless, it is impossible in principle to discover the causal reason: why A should be real, instead of B, or vice versa. Then the theory must be rejected.", "“... if space was an absolute being, there would something happen for which it would be impossible there should be a sufficient reason”.", "(The Leibniz-Clarke Correspondence, ΙΙΙ, p. 5)", "The principle of sufficient reason declares that everything that exists in a state of affairs s, exists for an integrated reason, which (1) constitutes the necessary and sufficient condition for s; (2) shows clearly and precisely why it takes place s instead of another; (3) provides, when possible, a full description, a complete explanation of s; and (4) does not require another reason of the same type.", "4.4. The Principle of Plenitude", "The universe is plenteous, everything is a plenum, and all matter is interlinked [12] (Monadology, 61), so that each movement can have effects even on the most remote bodies and each body is influenced by the bodies with which it comes into contact, and also by those who come into contact with the latter, and so on. Clarke had the impression that, with the principle of plenitude, Leibniz identifies space with matter. The latter, convinced that absolute space and absolute space are only a representation of relations, replied in compliance with the principle of plenitude:", "“I don’t say that matter and space are the same thing. I only say, there is no space, where there is no matter; and that space in itself is not an absolute reality. Space and matter differ, as time and motion. However, these things, though different, are inseparable.”", "“But yet it does not at all follow that matter is eternal and necessary; unless we suppose space to be eternal and necessary; a supposition ill grounded in all respects”.", "4.5. The Principle of Continuity", "How a continuum can be constructed of discrete points? The source of the difficulties with the composition of the continuous lies in the fact that we grasp matter and time as substances. The Leibnizian gateway from the labyrinth of the composition of the continuous is to view the world of the continuously extended matter as secondary and derivative [28] (p. 83).", "In 1687, Leibniz produced the principle of continuity by considering the concept of infinity in geometry. Later, he solved the problem by considering real but strictly individual dynamic centers, whose qualitative, causal, gradual interaction generates mechanical interactions at the level of phenomena and consequently apparent changes articulated in the virtual continua of space and time [33] (p. 142).", "The mechanistic philosophers of the seventeenth century denounced active principles. With the principle of inertia alone, they explained every motion of matter. Leibniz criticized Descartes focusing on his failure to see that motion must be established with energy. At the same time, the Enlightenment movement supported a European and global international cooperation and Gottfried Wilhelm Leibniz had correspondents ranging from London to Beijing [34].", "5. Conclusions", "The spatial and temporal structures of the Newtonian theory are intrinsic, inherent in a substratum of spatiotemporal points, while in the ideal space-time of Leibniz the relations are external (extrinsic) to space and time. Relations are interface determinations completely independent of the possible phenomenal relata, while the structures of absolute space and time are unchanged and stable.", "The Leibnizian arguments do not always appear convincing. In fact, with his argument of a world where the West would take the place of the East, Leibniz tries to combine the principle of sufficient reason with the principle of indiscernibles, in an obscuring manner, when asking for the sufficient reason of the displacement, while probably begging the question. The argument would seem invalid according to logic, because Leibniz asks “why every thing was not placed the quite contrary way, for instance, by changing East into West,” eliminating a required premise that should describe the coordinates of East and West. In another argument again, when assuming that we change the position of the world within space, Leibniz maintains as immutable the internal spatial relationships of physical objects, one in relation to the other, which seems contradictory to the very own Leibnizian belief that there is no body that does not move. However, one should consider the strongest argument of Leibniz, based on the infiniteness of the world. In comparison with the infinite, any displacement may be insignificant.", "A powerful argument against the Leibnizian relationalism is developed in [35] (pp. 189–206): Important complications emerge if we introduce coordinate systems in space and time. Places and dates acquire now internal relations which should stay untouched by any permutation. The introduction of inertial temporal and spatial coordinates is embedded within an empirical rationalism that encounters space, time, and space-time dimensions in a non-relational manner. Furthermore, the various possible worlds are not different names for the same subject: they are distinguishable. Another Leibnizian argument referred to time: if the world were created a few million years earlier, it would be indistinguishable from this one here, since “the beginning, whenever it was, is always the same thing” (The Leibniz-Clarke Correspondence, IV, p. 15). There is a confusion around the dubious principle of indiscernibles: if two objects x and y are exactly alike, they are also numerically identical, regardless of the permanent or contiguous character of their similarity. Genuinely logical, however, is only the principle of the indiscernibility of the identicals: if k and l are numerically identical, that is, they are simply different names for the same object, then k and l are exactly alike [36].", "Clarke emphasized the issue of inertial phenomena, referring to the example of Galileo with the ship. The movement of the ship is really a different situation with truly different effects even though they may be beyond our perception. A sudden stop of the ship would bring about other more tangible effects. Clarke noted that the argument about Newton’s absolute motion is mathematical and that it demonstrates according to real effects the absolute motion, therefore cannot be answered by simply asserting the opposite. The space and the time are not only an order of things; they are real quantities. Mathematization established the actual inertial motion, as described by Newton, as an indispensable concept for a consistent physics.", "Of special significance was Leibniz’s counterargument against the mathematical argument of Newton regarding absolute acceleration: Leibniz supported that the Absolute is the inherent in the body force or motive power, the vis viva. This interpretation was an overt subterfuge, in conflict with the first law of Newtonian mechanics, the law of inertia, which explains that a point mass either moves linearly and smoothly or remains at rest, unless acted upon the influence of external forces or when the forces affecting are cancelled out. Leibniz’s objection was based on the following distinction: that the vis viva refers only to impacts, while the observed pendulum movement, the rotation, and the orbits are manifestations of the dead force (m.dv), infinitely smaller than the vital force [37].", "Nevertheless, Newton clarified the absolute motion with his first law. Absolute motion is created or modified only by the impact of force to the (moving) body, and it changes with any impact of force upon it, while the relative movement can be changed or created, without the influence of force on the relatively moving body, and it is not necessary to change with every impact of force upon it. The principle of inertia is an empirical principle, manifested as: (1) inertia of a body that remains in rest, insofar it is not influenced, but also by the impact of forces, as an escape from rest either with distractions or with resistance or gradually; and (2) as the inertia of a body that moves linearly and smoothly, insofar it is not influenced, but also as a change of direction, or an acceleration or deceleration under the impact of forces.", "We conclude that the two thought experiments and the arguments of Newton intended to establish the absolute circular motion and the absolute acceleration during rotation, and they are connected to the second law of conservation of momentum, and, indeed, of the angular momentum. According to this law, the angular momentum of a particle or the main torque of an inertial system is modified only by the influence of external forces, whereas internal forces can only change the torque of parts of the system and the angular velocity. Newton concentrated his attention on the issue of absolute acceleration during rotation, because a simple variation of the angular speed, can be, according to the second law, the effect of internal forces. The absolute acceleration, however, may increase the moment of inertia, the angular momentum of the system overall. In modern parlance, the dimensionality of angular velocity is T-1, and the one of angular acceleration T−2.", "Leibniz tended to pinpoint an explanation originated with Huygens, who referred to the cycloidal motion of ether that disturbs the matter in countless ways, from all sides, in order to address, in a somewhat limited way, the inertia as resistance, absolute due to the viscosity of the fluid and relative due to its density. With such claims, he derived the conclusion that every motion is either rectilinear or is reduced to a synthesis of rectilinear movements. The accelerated motion, either curved or rectilinear, was represented by Leibniz with polygonal infinitesimals as a series of smooth rectilinear motions interrupted by impulses of dead force. Newton, however, represented the accelerated motion with a continuous curve and the forces and accelerations involved are finite and not infinitesimal [37].", "From Relationalism to Relativity", "The concept of Leibnizian space came prior to that of spatial relations, but it was not an absolute framework of measurement. A position in space was determined only in relation to another position, as far as the latter could be regarded as fixed. That is exactly what led Anapolitanos [4] (p. 103–104) to evaluate the theory of Leibniz not only as relationalist, but also as relativistic theory, since one of the basic postulates of the special theory of relativity is that there is no preferential spatial system of reference. Leibniz however remained attached to metaphysical notions such as that of the mind, as the cause of motion. The dominant scientific theory, until the appearance of the theory of relativity, was that space and time were absolute reference systems of things, objects, and events. The argumentation of Leibniz questioned the verifiability of absolute space, because in any systems of coordinates with relatively uniform motion we have not a means to distinguish the absolute uniform motion. “How would the world be, if there was a reportable unobservable change?” “The same”, would Leibniz reply [38,39]. The Newtonian, however, might support the following: it is not true that in any possible world, observability, i.e., observational conditions, disprove the existence of real space", "Nevertheless, in the special theory of relativity, we still have an absolute motion, in terms of a class of highly abstract and unobservable entities. The speed of light is always the same in all systems of coordinates, whether or not the light source is moving, and with any way it may move. How does the speed of light remain constant in two coordinate systems that are in relative uniform motion? This has to do with the relativity of time introduced by the Lorentz transformations.", "The contribution of Leibniz in theoretical physics of space and time was operative, though not prescriptive. The emphasis on the concept of relation has contributed indirectly to the discovery of the main results of the theory of relativity, according to the Lorentz transformations: the relativity of simultaneity, the time dilation, and the length contraction of the bodies. The special theory of relativity accepts the fixedness of relations only for systems of coordinates that move with relative uniform motion: the time is determined by clocks, the spatial coordinates by sets of rods, and the movement may affect clocks and rods, as shown by the effects of the electromagnetic field; events that in a reference system coincide or occur at the same point in space, in other inertial systems can occur at different times or in different places in space, while the deletion of points of the space-time manifold is used by relativists to construct cosmological models.", "The motivation of Einstein, when he formulated the general theory of relativity, was, besides the problem of gravity, a thought experiment to eliminate the absolute motion. However, he only revised the concept of absolute space, which was replaced by the concept of the displacement field, which is a component of the total field. There is no space without field, the space is now a quality of the field. The structures yet are endogenous, the metric of space is a function of the distribution of matter and energy, and the laws of physics are accepted in every system of reference [30].", "The relativity of motion presupposes variable structures, frames of reference of the Riemannian geometry. The acceleration here is a result of the curvature of space-time, which produces dramatic changes in the observable gravitational effects. The equivalence of all spatial points, i.e., the homogeneity of space, the isotropy, i.e., the equivalence of all space directions, and the homogeneity of the time, in the light of Leibniz’s saying that a point in space does not differ in any respect whatsoever than any other, seem to conform to relationalism, but in fact, the principles of the general theory are realistic propositions. They apply exactly to the absolute space-time and approximately to real systems, while the validity of the general theory is not limited to inertial systems.", "Wilson, N.L. Individual Identity, Space, and Time, in the Leibniz Clarke Correspondence. In The Philosophy of Leibniz and the Modern World; Leclerc, I., Ed.; Vanderbilt University Press: Nashville, TN, USA, 1973. [Google Scholar]", "Follow MDPI", "Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely", "those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or", "the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas,", "methods, instructions or products referred to in the content." ], [ "I remembered reading an paper a while ago which tried to prove whether force actually exists, or if it a man made construct to aid our understanding of the world. However, I can't seem to find the article any more (Google typically comes up with people asking about centrifugal force).", "I think they went into momentum space and tried to derive force from there, with their result being that force turned out to be a man-made construct. My memory might be hazy though (otherwise I would have been able to find the paper again).", "In short, is force a man-made construct, and is it possible to derive via working in momentum space?", "$\\begingroup$Everything that is not a direct space or time measurment is a manmade construct. Since this is actually the only thing we can interact with this world and call reality: by displacements in space and time.$\\endgroup$", "$\\begingroup$I think it depends on your definition of \"exists\". Physicists have a very simple approach to that. We accept that one can manipulate the physical world and that this manipulation can produce repeatable results. Whenever we find something that is repeatable to a high degree, we try to cast its \"easiest\" human made description into a law or a theory. That's all \"force\" is: a human description for a repeatable phenomenon. Technically, of course, there is an even more naive answer: if it can hurt you, then you better believe that it exits... and boy, can \"force\" hurt you!$\\endgroup$", "2 Answers", "2", "Force is a concept which describes, and can be used to manipulate, real phenomena that exist regardless of the existence of the human race.", "Newton's second law (Acceleration = Force / Mass) is a definition of force. Mass certainly exists, as do velocity and its time derivative, acceleration. There is no reason to suppose that force does not exist. Force describes the interaction between mass and motion.", "But, one could argue that without the human race, there would be no need for the concept of force. Mass and motion would continue to occupy a place in the universe, and any species that wished to investigate them probably would have to use a concept similar to force.", "All concepts are man-made constructs. All concepts are made of language, and all language is man-made, be it linguistic, mathematical, or otherwise symbolic. But I don't think that this makes force any less real than mass and motion, which also could be called concepts.", "Momentum = Mass * Velocity", "Acceleration = time derivative of Velocity", "Force = Mass * Acceleration", "One could say that Momentum is a concept describing the real phenomena of Mass and Velocity, and that Force is a conception of the concept of Momentum. But this is a lot more real than speculating how many angels can stand on the tip of a pin.", "Without defining what a thing is, it makes little sense to discuss the ontology of a thing. Does an apple exist? First, one must say what an apple is; once we agree on that, it's straightforward to show (by example) that apples exist.", "Given a definition of force, force certainly does exist; we can point to time derivatives of momentum that we observe, and say \"there is something that corresponds to what I call force; then, force exists.\"", "All of this depends on your ontology, but I think the one I've presented is pretty reasonable and straightforward. It nevertheless is, ultimately, a question of philosophy, so you have to decide on what you believe about the nature of knowledge and reality before you can give yourself a personally satisfactory answer to whether forces \"exist\"." ], [ "Cunk on Physics", "Subhendu Mukherjee", "Content, data analytics consultant and trainer", "It is quite something to get ChatGPT to take a stab a British humour. Here I asked it to create a Philomena Cunk script (https://www.netflix.com/tudum/articles/what-is-cunk-on-earth-explained) on Centrifugal Force. And this is what I got", "Hello, I’m Philomena Cunk, and this is Moments of Wonder. Today, I’m going to talk about centrifugal force, which is one of the most important forces in the world, along with gravity, electricity, and the force that makes you want to eat crisps. Centrifugal force is the force that makes you feel like you’re being pushed outwards when you’re spinning around. For example, when you’re on a roundabout, or a rollercoaster, or a washing machine. But what is centrifugal force? Where does it come from? And why does it hate us so much? To find out more, I spoke to an expert on forces, Professor Brian Cox.", "Cunk: So, Professor Cox, what is centrifugal force?", "Cox: Well, centrifugal force is not actually a real force. It’s what we call a fictitious force, or a pseudo-force.", "Cunk: A fictitious force? Like Santa Claus?", "Cox: No, not like Santa Claus. A fictitious force is a force that only appears to exist because of the motion of the observer.", "Cunk: The motion of the observer? Like when you’re watching a film and you feel like you’re moving with the camera?", "Cox: No, not like that either. A fictitious force is a force that arises from the inertia of an object that is moving in a non-inertial frame of reference.", "Cunk: A non-inertial frame of reference? Like when you’re drunk and you can’t tell which way is up?", "Cox: No, not like that at all. A non-inertial frame of reference is a frame of reference that is accelerating or rotating relative to an inertial frame of reference.", "Cunk: An inertial frame of reference? Like when you’re sitting still and nothing is happening?", "Cox: Yes, exactly. An inertial frame of reference is a frame of reference that is not accelerating or rotating relative to any other frame of reference.", "Cunk: So, let me get this straight. Centrifugal force is a force that only exists because we’re moving in circles and we don’t like it?", "Cox: Well, yes, that’s one way of putting it.", "Cunk: And why do we move in circles anyway? What’s the point of that?", "Cox: Well, there are many reasons why we move in circles. For example, the Earth rotates around its axis and orbits around the Sun. The Moon orbits around the Earth. The planets orbit around the Sun. The stars orbit around the center of the galaxy. And so on.", "Cunk: And why do they do that?", "Cox: Well, they do that because of another force called gravity.", "Cunk: Gravity? What’s that?", "Cox: Gravity is the force that attracts every object with mass to every other object with mass.", "Cunk: So gravity is like love?", "Cox: No, not like love. Gravity is a fundamental physical phenomenon that governs the structure and evolution of the universe.", "Cunk: So gravity is like God?", "Cox: No, not like God. Gravity is a natural phenomenon that can be described by mathematical equations and tested by experiments.", "Cunk: So gravity is like magic?", "Cox: No, not like magic. Gravity is a scientific concept that can be understood by reason and evidence.", "Cunk: So gravity is like…I don’t know what gravity is like.", "Cox: Well, maybe you should watch my series on The Wonders of the Solar System and The Wonders of the Universe.", "Cunk: Maybe I should. Thank you for your time, Professor Cox.", "Cox: You’re welcome.", "So there you have it. Centrifugal force is a fake force that makes us feel sick when we spin around. And gravity is a real force that makes us spin around in the first place. Join me next time on Moments of Wonder when I’ll be asking: What are numbers? And why do they hate me so much?" ], [ "Centrifugal Force", "If you've ever been on a merry-go-round, you must have noticed an invisible force trying to pull you away from the center of the spinning wheel. Well coincidentally, this invisible force is also our topic for the article. The reason why you feel like you were being pushed away from the center is due to a pseudo force called the…", "Content verified by subject matter experts", "Free StudySmarter App with over 20 million students", "Explore our app and discover over 50 million learning materials for free.", "If you've ever been on a merry-go-round, you must have noticed an invisible force trying to pull you away from the center of the spinning wheel. Well coincidentally, this invisible force is also our topic for the article. The reason why you feel like you were being pushed away from the center is due to a pseudo force called the Centrifugal force. The physics behind this phenomenon could one day lead to the invention of artificial gravity! But what is a pseudo force, and how is this force being applied? Keep reading to find out!", "Centrifugal force definition", "Centrifugal force is a pseudo force experienced by an object that moves along a curved path. The direction of the force acts outwards from the centre of the rotation.", "When a moving vehicle makes a sharp turn, the passengers experience a force that pushes them in the opposite direction. Another example is if you tie a bucket filled with water to a string and spin it. The Centrifugal force pushes the water to the base of the bucket as it spins and stops it from spilling, even as the bucket tilts.", "Why is it a Pseudo Force?", "But then if we are able to see the effects of this phenomenon every day, then why is it called a pseudo force? To understand this we will need to introduce another force - but this one acts towards the center of the circle and is real.", "Centripetal force is a force that allows an object to move along a curved path by acting towards the center of rotation.", "Any physical object that has a mass and is rotating about a point will require a pulling force towards the center of the rotation. Without this force, the object will move in a straight line. In order for an object to move in a circle, it must have a force. This is called the centripetal force requirement. An inward-directed acceleration necessitates the application of an internal push. Without this inward force, an object would continue to move on a straight line parallel to the circle's circumference.", "The circular motion would be impossible without this inward or centripetal force. The centrifugal force acts simply as a reaction to this centripetal force. This is why centrifugal force is defined as a sensation that throws objects away from the center of rotation. This can also be attributed to the inertia of an object. In an earlier example, we spoke about how passengers are thrown in the opposite direction when a moving vehicle makes a turn. This is basically the passenger's body resisting a change in their direction of motion. Let us look at this mathematically.", "Centrifugal Force Equation", "Because centrifugal force is a pseudo force or sensation. we will first need to derive the equation for centripetal force. Remember both these forces are equal in magnitude but opposite in direction.", "Imagine a stone tied to a string that is being rotated uniform speed. Let the length of the string be \\(r\\), which makes it also the radius of the circular path. Now take a picture of this stone that is being rotated. What's interesting to note is that the magnitude of the tangential velocity of the stone will be constant at all points on the circular path. However, the direction of tangential velocity will keep changing. So what is this tangential velocity?", "Tangential velocity is defined as the velocity of an object at a given point in time, that acts in a direction that is tangential to the path it is moving along.", "The tangential velocity vector will point towards the tangent of the circular path followed by the stone. As the stone is being rotated this tangential velocity vector is constantly changing its direction.", "And what does it mean when the velocity keeps on changing; the stone is accelerating! Now according to Newton's first law of motion, an object will continue to move in a straight line unless an external force acts on it. But what is this force that is making the stone move around in a circular path? You might recall when you spin the stone you're basically pulling the string, creating tension that produces a pulling force on the stone. This is the force that is responsible for accelerating the stone around the circular path. And this force is known as Centripetal force.", "The magnitude of a centripetal force or radial force is given by newtons second law of motion: $$\\overset\\rightharpoonup{F_c}=m\\overset\\rightharpoonup{a_r},$$", "where \\(F_c\\) is the centripetal force, \\(m\\) is the mass of the object and \\(a_r\\) is the radial acceleration.", "Every object moving in a circle has radial acceleration. This radial acceleration can be represented as: $$\\overset\\rightharpoonup{a_r}=\\frac{V^2}r,$$", "where \\(a_r\\) is the radial acceleration, \\(V\\) is the tangential velocity and \\(r\\) is the radius of the circular path.", "combining this with the equation for centripetal force and we get; $$\\overset\\rightharpoonup{F_c}=\\frac{mV^2}r$$", "This gives another equation for centripetal force as: $$\\overset\\rightharpoonup{F_c}=mr\\omega^2$$", "But wait, there's more! According to Newton's third law of motion, every action will have an equal and opposite reaction. So then what could possibly act in the opposite direction of centripetal force. This is nothing but centrifugal force. Centrifugal force is called a pseudo force because it only exists due to the action of centripetal force. The centrifugal force will have a magnitude equal to that of the centripetal force in the opposite direction, which means the equation for calculating the centrifugal force is also:", "$$\\overset\\rightharpoonup{F_c}=mr\\omega^2$$", "where mass is measured in \\(\\mathrm{kg}\\), radius in \\(\\mathrm{m}\\) and \\(\\omega\\) in \\(\\text{radians}/\\text{sec}\\). Let's now use these equations in a few examples.", "We will need to convert the unit for angular velocity from degrees/ sec into radians/ sec before using it in the above equation. This can be done using the following equation \\(\\mathrm{Deg}\\;\\times\\;\\pi/180\\;=\\;\\mathrm{Rad}\\)", "Centrifugal force examples", "Here we will go through an example in which we will apply the principles of centrifugal force.", "A \\(100\\;\\mathrm g\\) ball, attached to the end of a string, is spun around in a circle with an angular speed of \\(286\\;\\text{degrees}/\\text{sec}\\). If the string's length is \\(60\\;\\mathrm{cm}\\), what is the centrifugal force experienced by the ball?", "The ball experiences a centrifugal force of \\(125\\;\\mathrm N\\) It can also be looked at from another perspective. The centripetal force required to keep a ball of the above specifications in circular motion is equal to\\(125\\;\\mathrm N\\).", "Relative Centrifugal Force Units and Definition", "We spoke about how centrifugal force can be used to create artificial gravity. Well, we can also represent the centrifugal force generated by a spinning object relative to the amount of gravity we experience on earth", "Relative centrifugal force (RCF) is the radial force generated by a spinning object measured relative to the earth's gravitational field.", "RCF is expressed asunits of gravity, \\(\\mathrm{G}\\). This unit is used in the process of centrifugation instead of just using RPM as it also accounts for the distance from the center of rotation. It is given by the following equation. $$\\text{RCF}=11.18\\times r\\times\\left(\\frac{\\text{RPM}}{1000}\\right)$$ $$\\text{Relative}\\;\\text{Centrifugal}\\;\\text{Force}=11.18\\times\\mathrm r\\times\\left(\\frac{\\text{Revolutions}\\;\\text{Per}\\;\\text{Minute}}{1000}\\right)^2$$", "A centrifuge is a machine that uses centrifugal force to separate substances of different densities from each other.", "you might wonder why force is expressed in units of gravity, well as you know the unit of gravity actually measures acceleration. When RCF experienced by an object is \\(3\\;\\mathrm g\\) , it means that the force is equivalent to three times the force experienced by an object free falling at a rate of \\(g\\;=\\;9.81\\;\\mathrm{m/s^2}\\).", "This brings us to the end of this article. Let's look at what we've learned so far.", "Centrifugal Force - Key takeaways", "Centrifugal force is a pseudo force experienced by an object that moves in a curved path. The direction of the force acts outwards from the center of the rotation.", "Centripetal force is the force that allows an object to rotate around an axis.", "The centrifugal force is equal to the magnitude of the centripetal force but acts in the opposite direction.", "Tangential velocity is defined as the velocity of an object at a given point in time, that acts in a direction that is tangential to the circle.", "This equation for centrifugal force is given by \\(\\overset\\rightharpoonup{F_c}=mr\\omega^2\\)", "Always remember the unit for angular r velocity while using the above equation must be in \\(\\text{radians}/\\text{sec}\\).", "This can be done using the following conversion factor \\(\\text{Deg}\\;\\times\\;\\pi/180\\;=\\;\\text{Rad}\\)", "Frequently Asked Questions about Centrifugal Force", "Centrifugal force is a pseudo force experienced by an object that moves in a curved path. The direction of the force acts outwards from the center of the rotation.", "Examples of centrifugal force are, when a moving vehicle makes a sharp turn, the passengers experience a force that pushes them in the opposite direction. Another example is if you tie a bucket filled with water to a string and rotate it. The Centrifugal force pushes the water to the base of the bucket as it spins and stops it from spilling outside.", "The centripetal force acts towards the center of rotation whereas the centrifugal force acts away from the center of rotation.", "The formula for calculating centrifugal force is Fc=mrω2, where m is that mass of the object, r is the radius of the circular path and ω is the angular velocity.", "Centrifugal force is used in the working of centrifuges, centrifugal pumps, and even centrifugal automobile clutches", "Final Centrifugal Force Quiz", "Centrifugal Force Quiz - Teste dein Wissen", "Question", "What is Centrifugal force?", "Show answer", "Answer", "Centrifugal force is a pseudo force experienced by an object that moves in a curved path. The direction of the force acts outwards from the center of the rotation.", "Show question", "Question", "What direction does the centrifugal force act in?", "Show answer", "Answer", "Away from the center of rotation.", "Show question", "Question", "What is the unit in which centrifugal force is expressed?", "Show answer", "Answer", "Newtons.", "Show question", "Question", "Centrifugal force is a pseudo force.", "Show answer", "Answer", "True.", "Show question", "Question", "The magnitude of the centrifugal force is equal to which other force?", "Show answer", "Answer", "Centripetal force.", "Show question", "Question", "The formula for centrifugal force is...", "Show answer", "Answer", "\\(\\vec{F}_c=mr\\omega ^2\\).", "Show question", "Question", "Which of the following changes during uniform circular motion?", "Show answer", "Answer", "Magnitude of velocity.", "Show question", "Question", "The direction of radial acceleration is ...", "Show answer", "Answer", "Towards the center of rotation.", "Show question", "Question", "Centrifugal force and the tangential velocity vector are always ...", "Show answer", "Answer", "Perpendicular to each other.", "Show question", "Question", "Which of the following is NOT an example of centrifugal force at work?", "Show answer", "Answer", "Earth revolving around the sun.", "Show question", "Question", "How does the mass of an object moving with a constant angular velocity affect the centrifugal force it experiences?", "Show answer", "Answer", "Increases as mass increases.", "Show question", "Question", "If the string tied to a stone which is moving in uniform circular motion breaks, the stone will travel...", "Show answer", "Answer", "Tangentially, in the direction of the velocity vector.", "Show question", "Question", "What is the unit for angular velocity?", "Show answer", "Answer", "\\(\\mathrm{radians/sec}\\).", "Show question", "Question", "How do we convert radians into degrees?", "Show answer", "Answer", "\\(\\text{Radians}=\\text{degree}\\times\\dfrac{\\pi}{180}\\).", "Show question", "Question", "A \\(100\\,\\mathrm{g}\\) ball, attached to the end of a string, is spun around in a circle with an angular speed of \\(5\\,\\mathrm{radians/sec}\\). If the string's length is \\(0.6\\,\\mathrm{m}\\), what is the centrifugal force experienced by the ball?", "Join millions of people in learning anywhere, anytime - every day", "This is still free to read, it's not a paywall.", "You need to register to keep reading", "StudySmarter is commited to creating, free, high quality explainations, opening education to all. By registering you get free access to our website and app (available on desktop AND mobile) which will help you to super-charge your learning process.", "This is still free to read, it's not a paywall.", "You need to register to keep reading", "StudySmarter is commited to creating, free, high quality explainations, opening education to all. By registering you get free access to our website and app (available on desktop AND mobile) which will help you to super-charge your learning process.", "Company", "Product", "Help", "This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept", "Privacy & Cookies Policy", "Privacy Overview", "This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.", "Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.", "Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website." ], [ "Why is centrifugal force considered fictitious, when it's the one that feels real to us when we are moving in a circle? I understand the explanation regarding the reference frames: if our body is the reference frame, and it is rotating, a fictitious centrifugal force needs to be made up to cancel the centripetal force and explain why we appear to be stationary in relation to ourselves. However, if we are in a round up ride, we feel pushed againsts the wall, rather than towards the center of the ride, which would be the centripetal force. So if centrifugal force is the fictitious one, wouldn't that be like saying that the force we feel pushing us againsts the wall is only in our minds?", "$\\begingroup$You may not have given enough thought to what \"we feel pushed\" means. If you think through some more day-to-day instances you'll find that there are two different ways to interpret that phrase. One that is consistent with the way we talk about gravity and one consistent with the way we talk about everything else. There is a reason for this. How does it feel if a friend pushes you unexpectedly from behind; how does your body move and how do your loose limbs move. What happens if a sliding sidewalk stops unexpectedly (noting that it is only in contact with your feet).$\\endgroup$", "3 Answers", "3", "Suppose you're in a fast car and you stomp on the accelerator. You feel pressed into the back of the seat. In which direction are you accelerating? Forward, obviously, but you feel a force pushing against your back. Now you turn a corner. Your seatbelt, and maybe the door next to you, press against your side. In which direction are you accelerating? In this case, it's not so obvious, but it's inward, not outward. There is no centrifugal force here.", "In both cases, the side on which you feel the force is opposite the direction in which you are accelerating.", "$\\begingroup$So which force makes us feel pushed againsts the wall in a round up ride? From your answer I understand it is not the centrifugal force. Is that a third law partner to the centripetal force? I'm a little confused about how to name the force acting on our body outward from the the center of rotation, which feels like a real force.$\\endgroup$", "$\\begingroup$@Auggie -- There is no outward force acting on you. The forces acting on you are gravitation, which pulls you downward, friction against the wall, which opposes gravity, and the normal force by the wall, which pushes you toward the center of the ride.$\\endgroup$", "$\\begingroup$So, just to clarify, when you say there is no outward force acting on us, you mean in an inertial reference frame, right? what about in a rotating reference frame? And then, going back to my original question, is the force that we feel in the outward direction only an illusion? I'm a beginner and an amature, so I appreciate your patience :)$\\endgroup$", "$\\begingroup$@Auggie - What you feel in that ride is very similar to what you feel in an accelerating car when the back seat of the car pushes on you. I hope you agree that there's no force pushing you into the seat. It's the same for the ride. That push by the wall of the ride (or by the back of the car seat) against you propagates through your body. Your body is a mix of bones, cartilage, and soft tissues that respond differently to that push. You feel that push internally as well as externally.$\\endgroup$", "The reason we feel that we are pushed outwards is due to inertia. Inertia is the resistance to movement. It is measured by mass. When we have more movement, it makes it harder to get us moving.", "In a car that is on a curve, for example, our inertia makes us want to keep on going forward. Going forward in this case would make us feel that we are being pushed outwards. Therefore, there is no centrifugal force in this case.", "Sometimes, the centrifugal force is referred to the reaction force of the centripetal force. But usually, it refers to a ficitious force used to simplify thr mathematics.", "$\\begingroup$The idea of centrifugal force is not used to simplify the mathematics. Just the opposite. Centrifugal force exists only in the rotating frame of reference, and it complicates things. Much simpler to analyze the situation from a non-rotating frame of reference, where it becomes obvious that a body can not revolve around the center unless a real force continually pushes it toward the center.$\\endgroup$", "We say fictitious because the actual source of the centrifugal acceleration is somewhat indirect and the experience one has results from the unbalanced forces acting on the reference frame, not a force. Note, it is an acceleration not a force.", "For instance, imagine yourself on a swing. The swing seat is constrained to move in a circular arc by two opposing forces, gravity and tension. Those are the only two forces acting on the seat, yet while swinging, the seat is not in an inertial reference frame. So if you sit in the seat and constrain yourself to the seat (i.e., you don't fall off), you will be accelerated just like the seat because the tension and gravitational forces do not balance. The only place in the arc where you do not accelerate is same place where the seat would rest in equilibrium (i.e., just hanging there if left alone). Note that there is no centripetal or centrifugal force here, just tension and gravity. These two terms only apply to discussions of the acceleration of the reference frame or object. They are not forces and should not be called forces.", "The point is that centrifugal acceleration only exists in non-inertial reference frames, namely frames of reference that are accelerating. It is not a force, only a term in the acceleration vector resulting from the frame of reference in which you calculate the acceleration. There is a useful animation found on the Coriolis effect Wikipedia page." ], [ "centrifugal force, a fictitious force, peculiar to a particle moving on a circular path, that has the same magnitude and dimensions as the force that keeps the particle on its circular path (the centripetal force) but points in the opposite direction.", "A stone whirling in a horizontal plane on the end of a string tied to a post on the ground is continuously changing the direction of its velocity and, therefore, has an acceleration toward the post. This acceleration is equal to the square of its velocity divided by the length of the string. According to Newton’s second law, an acceleration is caused by a force, which in this case is the tension in the string. If the stone is moving at a constant speed and gravity is neglected, the inward-pointing string tension is the only force acting on the stone. If the string breaks, the stone, because of inertia, will keep on going in a straight line tangent to its previous circular path; it does not move in the outward direction as it would if the centrifugal force were real.", "Although it is not a real force according to Newton’s laws, the centrifugal-force concept is a useful one. For example, when analyzing the behaviour of the fluid in a cream separator or a centrifuge, it is convenient to study the fluid’s behaviour relative to the rotating container rather than relative to the Earth; and, in order that Newton’s laws be applicable in such a rotating frame of reference, an inertial force, or a fictitious force (the centrifugal force), equal and opposite to the centripetal force, must be included in the equations of motion. In a frame of reference attached to the whirling stone, the stone is at rest; to obtain a balanced force system, the outward-acting centrifugal force must be included.", "Centrifugal force can be increased by increasing either the speed of rotation or the mass of the body or by decreasing the radius, which is the distance of the body from the centre of the curve. Increasing the mass or decreasing the radius increases the centrifugal force in direct or inverse proportion, respectively, but increasing the speed of rotation increases it in proportion to the square of the speed; that is, an increase in speed of 10 times, say from 10 to 100 revolutions per minute, increases the centrifugal force by a factor of 100. Centrifugal force is expressed as a multiple of g, the symbol for normal gravitational force (strictly speaking, the acceleration due to gravity). Centrifugal fields of more than 1,000,000,000g have been produced in the laboratory by devices called centrifuges." ], [ "Centripetal: This is the force needed to make something move in a circle. The force could actually be a number of things such as: friction, gravity, tension in a rope or any combination. Centripetal force is a name for a real force that has the role of making something move in a circle. This force is always directed towards the center of the circle of motion.", "So, the two key differences: centripetal is real and pushing towards the center of the circle. Centrifugal is fake and pushes away from the center. To look up their word-origins, I used the Online Etymology Dictionary. First I looked up \"centripetal\".", "The problem is that these two origins seem to say the same thing. Center and fall or flee, which I interpret as \"away from\". Not good. If you look at the other interpretations of petition, it says \"a request, solicitation\". Also, \"to require, seek, go forward\". This is better. Centripetal force is the force REQUIRED for circular motion. Centrifugal force is the force that makes something flee from the center.", "Wildfires were once rare across the Aloha State. But drought, invasive species, and human development have pushed Hawaii into a fiery new age.", "Matt Simon", "WIRED is where tomorrow is realized. It is the essential source of information and ideas that make sense of a world in constant transformation. The WIRED conversation illuminates how technology is changing every aspect of our lives—from culture to business, science to design. The breakthroughs and innovations that we uncover lead to new ways of thinking, new connections, and new industries." ], [ "Breadcrumbs", "You are here:", "Three Fictitious Forces & One Real Force", "Two schools of thought exist with regard to centrifugal force. The one I support views it as a false force. The other side believes that it is real. That is the side that also believes Elvis is alive and well, but do not let that influence your opinion.", "In fact, its perceived existence depends on our frame of reference. It is one of three important forces in physics called fictitious forces. The other two fictitious forces are the Coriolis force and Newton’s (or Euler’s) simple force due to acceleration. The major difference between a fictitious force and a real force is that real forces are based on the interactions of matter.", "Force Due to Acceleration When you step on the gas pedal and your car accelerates, you feel what you think is a force pushing you backward in your seat. Once acceleration ends and speed is constant, that force seems to disappear. Of course, no force pushes you backward. It is the result of the forward force necessary to allow you to accelerate with the car.", "Newton’s simple force due to acceleration is best described by Einstein’s equivalence principle. It states that one cannot distinguish between a real and a fictitious force when in the same frame of reference. Therefore, a spaceship accelerating at 32 feet/second/second in outer space would create a force indistinguishable from that of gravity to an observer inside the ship.", "Einstein suggested that even gravity could be a false force, but he concluded that gravity (or any component of gravity) could be considered a false force only at a single point. This led him to suggest that the geometry of the earth and that of the universe cannot be explained in Euclidean terms. Gravity in four-dimensional space—where the sum of the angles of a triangle does not necessarily equal 180 degrees—can be considerably different.", "Coriolis Force The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system. The object does not actually deviate from its path. It appears to because of the motion of the coordinate system. In the case of Earth, it is a result of the Earth’s eastward rotation and its differing tangential velocities at various latitudes.", "If a long range gun is fired toward the North Pole from a point on the equator, its projectile will land to the east of its due north path. This occurs because the projectile is moving faster eastward at the equator than is its target further north.", "The opposite occurs when the direction is toward the equator. If an airplane leaves Anchorage, Alaska and flies directly toward Miami, Fla., it will be over Mexico when it crosses Miami’s latitude. The Coriolis force also causes hurricanes to spin counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. It does not, however, have any proven effect upon the vortex rotation of toilets in either hemisphere.", "Centrifugal Force The Dutch physicist and inventor of the pendulum clock, Christian Huygens, coined the term centrifugal force in 1659. Huygens believed that centrifugal force was a real force. His theory was supported by the German mathematician Gottfried Leibniz. Isaac Newton seemed to support the theory initially, but he eventually disagreed. He coined the term centripetal force in 1684 to describe what he thought was the only force that acted upon a body in circular motion.", "Figure 1. The direction of travel of a can swinging counterclockwise on a string", "It was not until the mid-1700s that our current understanding of centrifugal force as a fictitious force became entrenched. In 1746, Daniel Bernoulli said, “The idea that centrifugal force is fictitious emerges unmistakably.”", "Figure 1 shows a can attached to a string swinging in a counterclockwise direction. It is a common misconception that centrifugal force pulls outward on the can. If the string were to break, that force would cause the can to travel outward (eastward). In fact, if the string breaks, the can will move in a straight line, tangent to its circular path. It does so simply because no centrifugal force acts on it.", "The only real force acting on the can, prior to the string breaking (neglecting gravity), is the centripetal force (from the Latin meaning “center-seeking”) supplied by the string. It is this centripetal force that holds the can in a circular path. Similarly, the Earth’s gravity provides the centripetal force that holds the moon in a nearly circular orbit. It is the friction between a car’s tires and the road that provides the centripetal force necessary for it to round a curve.", "Suppose that a person is inside the whirling can. The can presses against his feet and provides the centripetal force that holds him in a circular path. From our frame of reference outside the can, it is clear that this effect is due to inertia or the tendency of an object to follow a straight line path (as dictated by Newton’s first law). If, however, we change our frame of reference from inertial (stationary) to that of the rotating can, we lose our original perspective and experience something different. We will feel a force that pulls our bodies toward the bottom of the can. Although it feels real, it is not a force at all. It is the effect of inertia on our bodies. To observers in a rotating system, centrifugal force seems to be a real force.", "What about that machine we refer to as a centrifugal pump? Is its operation based on centrifugal force? If so, it must operate under false pretenses. Although mathematically complex, centrifugal pump operation is intuitively straightforward. The pump’s impeller uses its vanes to channel or guide a fluid through an ever-increasing radius while containing it within a rotating system. This process causes the liquid to accelerate continuously as it navigates the radius and reaches some maximum velocity just as it reaches the impeller periphery. It then flows into the pump’s volute where velocity is transformed into pressure.", "What then should we call such a pump? Maybe we could call it a radial accelerator pump or a rotational inertia pump or simply an impeller pump. Although many descriptions may be more accurate, I’m afraid that we are stuck with centrifugal.", "Joe Evans is responsible for customer and employee education at PumpTech, Inc., a pump & packaged system manufacturer & distributor with branches throughout the Pacific Northwest. He can be reached via his website www.PumpEd101.com. If there are topics that you would like to see discussed in future columns, drop him an email.", "Sponsored by", "PTFE or Teflon-coated packing is one of the industry’s most common valve packing styles. PTFE fibers have a high resistance to chemicals, making them an excellent choice for sealing valves and rotating equipment." ], [ "Does centrifugal force hold the Moon up?", "In the 1960s, Wernher von Braun put together a series of articles about space flight, some of which were published", "in Popular Science Monthly. Eventually they were collected and made into the book Space", "Frontier, (1st ed., Holt, Rinehart and Winston). It's a very readable book, and talks about how", "rockets work, and flight and safety in space. In one of the articles, von Braun explains why a satellite is able", "to stay up while in Earth orbit.", "He begins the article by asking what would happen if we could throw an object horizontally, but at faster and", "faster speeds, such as in the picture shown here. \"Eventually\", he writes, \"the curvature of the downward-bent", "trajectory would become equal to the curvature of the earth\". This is almost well and good. (It's not", "quite right to say that the curvatures of the orbit and Earth's surface are the same, even for circular motion, but", "this is a minor error compared with what comes next.) The important point is that as the bullet moves faster and", "faster, a magical speed is reached where the curved Earth drops away from the bullet precisely as fast as the bullet", "falls to the ground; added to which, the direction of \"down\" keeps changing. As a result, the bullet never gets any closer to the", "ground—it's in orbit. This is actually a marvellous special feature of an inverse square force like", "gravity; it would not be guaranteed to happen if gravity were not inverse square. In general, orbits are", "ellipses, and one such is drawn on the left. A picture just like this was originally included by Sir Isaac", "Newton in his Principia of 1687.", "After this fine start, von Braun then proceeds to muddy the water. He says that as the bullet is shot at ever", "faster speeds, \"its trajectory will be less deflected because the centrifugal force is increased by its higher speed,", "and more effectively counteracts the Earth's gravitational pull\". At this point, physicists baulk.", "Centrifugal force? What has that got to do with satellite motion?", "Next, von Braun draws a picture of a satellite in Earth orbit. Acting on the satellite are two forces:", "gravity, pulling the satellite toward Earth, and this centrifugal force, pushing the satellite away. He writes", "\"A circular orbit occurs whenever a small mass, travelling through the gravitational field of a big one, happens to", "have a speed at which the centrifugal force is precisely strong enough to balance the large body's gravitational", "pull.\" And later, \"If the balance between gravitational and centrifugal force is not perfect, [...] the small", "body will describe an elliptical path around the large one.\"", "What would Newton say? He too would draw the forces acting on the satellite, and would then proceed to apply", "his \"force = mass × acceleration\"; but first, he'd want to choose an \"inertial frame\" within which to", "do this, since his laws only work in inertial frames. An inertial frame is one in which, if we throw a ball, it", "moves away from us with constant velocity (i.e. constant speed in a straight line). Since this doesn't quite", "happen on Earth, the frame Newton would choose would be something more all-encompassing, outside of Earth. One", "good approximation would be the frame of the Solar System, within which the Sun is at rest, and Earth revolves fairly", "accurately in a circle around it, once a year. An inertial frame like this is presumably what von Braun is", "using, because anything noninertial won't tie in too well with his picture of Earth plus satellite.", "In an inertial frame, if there really were two equal-but-opposite forces on the satellite as von Braun drew them,", "then the total force on it would be zero. So it would not accelerate; it would move in a straight line with", "constant speed. Since the orbiting satellite doesn't move in a straight line, neither von Braun's picture nor", "his explanation are correct.", "Nothing holds the Moon up!", "In reality, nothing holds the Moon up. As Newton's inertial frame analysis predicts, the Moon is completely", "under gravity's thrall; in other words, it falls, because in such a frame there's only one force on the Moon:", "gravity. Gravity accelerates it. That doesn't mean its speed must necessarily change, or that it must get", "closer to Earth (although actually both of these things do ebb and flow slightly during the month, but that's not an", "important point). If Newton's F = ma is solved for the general case of falling under gravity, the motions", "that result are lines, circles, ellipses, parabolae, and hyperbolae. In one of those great correspondences", "between Nature and pure mathematics, these are precisely the curves that result if we take a cone and slice it in any", "direction.", "Even if the Moon's orbit were circular, its direction of travel would still be changing, which is one kind of", "acceleration. (Remember that acceleration is a change in velocity, meaning that acceleration can change an", "object's speed, or it can change merely the direction of motion, or both.) The Moon, and every other satellite,", "fall just as surely as an apple does when pulled down by gravity. Whereas the apple changes its speed but not", "its direction of motion, the Moon changes its direction of motion, but not its speed. The real difference", "between a satellite and an apple falling from a tree, is that for the fast sideways-moving satellite, the direction of", "\"down\" is always changing. But the satellite really is falling, and in fact a near-Earth satellite has almost", "the same acceleration that a falling apple has. If it's above us now, then in about 45 minutes, for a low", "satellite, it will have fallen so far down that it'll be on the other side of Earth. By then, the direction of", "down has reversed completely, and the satellite will again fall down for those who live on the opposite side of Earth,", "returning to us about 90 minutes after we first saw it. Of course, it never hits Earth because of its", "ever-present sideways motion. The Moon is much farther away where gravity is weaker, so it takes fully two weeks", "to fall to the other side of Earth.", "So what is centrifugal force?", "So why was the concept of centrifugal force invented?", "Centrifugal force was invented to allow us to do proper bookkeeping in a noninertial frame, if we insist on using", "such a frame to work with Newton's laws (and there might be a good reason for wanting to do so). For a simple", "example of a noninertial frame, consider what happens when you stand in a bus while the driver brakes. For a few", "moments, every passenger moves forward. The heavier ones feel a strong force that acts on their large mass,", "while the lighter ones feel a small force acting on their small mass. All feel the same acceleration. This", "is called a fictitious force, because it's a force that we invoke to explain why we are suddenly accelerated", "forward. In the (almost) inertial frame of the outside street, this force doesn't exist. The real force", "there is a single simple one provided by the friction of the ground on the bus tyres, and transmitted through its", "brakes to its body. This force accelerates the bus backwards—or, to use the more intuitive expression,", "decelerates the bus. Unless the passengers hang on, they will continue to move forwards until something inside", "the bus stops them.", "Depending on our choice of frame then, there are two forces to choose from when analysing why the passengers are", "impelled forward:", "In the inertial street frame, there is a braking force that pushes backwards on the bus. This is a", "bona-fide force, in the sense that it's produced in an inertial frame. It acts on the bus only, so unless", "we hold on, we'll continue to move forward at constant velocity.", "In the noninertial frame of the decelerating bus, the force is a mysterious force that acts on us, but not", "on the bus. It pushes us forwards, and has a strength that is proportional to how massive we are.", "Our fellow passenger, twice as massive as ourself, will feel twice as much force, but by F = ma, both we", "and they will feel the same acceleration. This is certainly a more complicated force to explain than the", "simple one that pushes on the bus in the street frame. Such a mass-dependent force is an indicator that", "something is awry—we have chosen to use a noninertial frame, and if we demand Newton's laws to hold in", "such a frame, then we'll have to invoke this fictitious force.", "It's worth pointing out that although the force impelling us forward in the bus's frame when the brakes are applied", "is conventionally called fictitious, it is real enough for the bus passengers! It might be a less natural force", "to use from a fundamental point of view of explaining why Nature works in the way that she does, but that does not", "mean that a fictitious force is not \"real\", that it is some kind of make-believe thing that will go away if we", "concentrate hard enough. The word \"fictitious\" merely means that the force vanishes when we shift our frame of", "reference to one that is inertial, because inertial frames hold a very special position in physics. But as a", "means of quantifying how the passengers in a bus lurch forward when the brakes are applied, a fictitious force is", "entirely appropriate and as real as any other—in the frame of the bus. There it must be included in", "Newton's laws, as all forces must.", "Centrifugal force is such a fictitious force, invented purely to balance the books, when we analyse a situation in", "a rotating frame. Because circular motion involves acceleration (perhaps just a changing direction—not", "necessarily a changing speed), a rotating frame is also accelerated, just as the bus was. We feel a centrifugal", "force when the bus goes around a corner. If we made a better choice of frame (say, the almost-inertial street", "frame), then we'd see the situation for what it is: the bus feels a simple force due to the friction of the road on", "its tyres, while the passengers feel no force at all—until their natural constant velocity motion gets checked", "by the body of the bus, which pushes on them to get them around the corner along with the bus. But in the", "noninertial bus frame, there is a strange force that pushes sideways on the passengers until they press against the", "inside wall of the bus.", "So centrifugal force is a fictitious force invoked to make Newton's laws work in a rotating frame. (For that", "matter, Coriolis force is another fictitious force that we introduce in Earth's gently rotating frame, to explain why", "large air masses, moving due to pressure differences, feel forces that work to create winds.) Centrifugal force", "has absolutely nothing at all to do with the motion of a satellite, as long as we do our calculations within an", "inertial frame. If we choose a noninertial frame, then we'll certainly need to invoke a centrifugal force.", "But a noninertial frame isn't fundamental—it has no use for explaining why the satellite orbits", "Earth.", "A good intuitive case in point is that of geosynchronous satellites. These are placed in orbit about 36,000", "km above Earth's equator, at just the right height that they orbit Earth in one day. Since Earth rotates once in", "the same period, these satellites always hover above the same point on its surface. From an inertial frame (say,", "the Solar System), there is nothing special about geosynchronous satellites. They feel only gravity, and respond", "to it by falling, while retaining the sideways motion given to them when they were initially released from the rocket", "that sent them up. But from the point of view of someone standing on Earth's surface and defining himself to be", "at rest, a geosynchronous satellite just hovers in one place, as if it were somehow overcoming the gravity force that", "acts upon it. Remember though, that the rotating Earth is a noninertial frame, and we will need to invoke a", "centrifugal force to make Newton's F = ma work. So we can certainly say that in this unnatural frame", "there is a centrifugal force holding the satellite up. But it's precisely because noninertial frames are so", "unnatural, that we are forced into inventing this fictitious force to keep the books balanced. If we want to", "calculate things in this frame, then that's fine. Keep the centrifugal force, and everything will work out", "right. And for whatever reason, it might well be useful to do our calculations in this noninertial frame.", "But to explain why the satellite stays up, we need to choose an inertial frame. In that frame, the", "centrifugal force vanishes, the satellite no longer stays up, and the question evaporates.", "Is gravity itself a fictitious force?", "A few lines up, I wrote that the force we feel when the bus is braking is weird, in that its strength is", "proportional to our own mass. But what about gravity? That also has a strength that is proportional to our", "mass! Could gravity be a fictitious force too?", "Yes, that's exactly how gravity is viewed these days. This is the content of Einstein's General theory of", "Relativity. Einstein conjectured that perhaps we've been looking at things in the wrong way. Newton viewed", "the orbit of a satellite, or the parabolic flight of a projectile, or the fall of an apple, to be complicated motions", "caused by the action of this mysterious force called gravity. But Einstein turned the problem on its head, and", "decided that satellites, projectiles, and apples are all following a motion that is as simple as any motion can be,", "provided they are viewed on the stage of a curved spacetime. The ones whose motion through spacetime is very", "complicated are ourselves, standing on Earth's surface.", "This change of view wasn't just made for the sake of a different viewpoint. Einstein's change in viewpoint", "enabled him to make predictions that differ to corresponding ones made by Newton's theory. And it is Einstein's", "predictions that have been verified experimentally to a very high accuracy.", "So gravity can be treated as a fictitious force. But it's a sort of \"higher order\" fictitious force when", "compared to the everyday one we experience in a bus: unlike the very uniform force that pushes us forward in a braking", "bus, gravity can't be made to completely vanish by a simple change of frame. Added to that, the mathematics of", "curved spacetimes is more complicated than using F = ma. So for everyday use, it's completely sufficient", "to treat gravity as a good old bona-fide force, just like the mechanics books tell us to do.", "And what of the Nazi senior SS officer Wernher von Braun? He is often regarded as the father of modern rocketry and of", "putting a man on the Moon, even though he took his key ideas from Robert Goddard. The main reason von Braun got rockets", "to work was his access to huge Nazi funding and slave labour, things that Goddard did not possess, and which von Braun never", "acknowledged or apologised for. But it's clear from his book above that von Braun didn't understand what a physicist will", "regard as the first thing about orbital dynamics. His role in the history of the American space programme needs", "re-evaluating. The scientists who really did understand orbital dynamics would have succeeded in putting men on the", "Moon even if von Braun had never been enlisted as head of the programme." ], [ "The Forbidden F-Word", "When the subject of circular motion is discussed, it is not uncommon to hear mention of the word centrifugal. Centrifugal, not to be confused with centripetal, means away from the center or outward. The use of or at least the familiarity with this word centrifugal, combined with the common sensation of an outward lean when experiencing circular motion, often creates or reinforces a common student misconception. The common misconception, believed by many physics students, is the notion that objects in circular motion are experiencing an outward force. \"After all,\" a well-meaning student may think, \"I can recall vividly the sensation of being thrown outward away from the center of the circle on that roller coaster ride. Therefore, circular motion must be characterized by an outward force.\" This misconception is often fervently adhered to despite the clear presentation by a textbook or teacher of an inward force requirement. As discussed previously in Lesson 1, the motion of an object in a circle requires that there be an inward net force - the centripetal force requirement. There is an inward-directed acceleration that demands an inward force. Without this inward force, an object would maintain a straight-line motion tangent to the perimeter of the circle. Without this inward or centripetal force, circular motion would be impossible.", "Evaluate Your Own Experiences", "So why then is this student misconception of an outward or centrifugal force so prevalent and so stubbornly adhered to? Perhaps like all misconceptions, the notion of a centrifugal force as lodged in a person's head has a particularly lengthy history. Part of that history is certainly attributable to the experience of a circular motion - either as a passenger or driver in an automobile or perhaps on an amusement park ride. Even learned physics types would admit that circular motion leaves the moving person with the sensation of being thrown outward from the center of the circle. But before drawing hasty conclusions, ask yourself three probing questions:", "Does the sensation of being thrown outward from the center of a circle mean that there was definitely an outward force?", "If there is such an outward force on my body as I make a left-hand turn in an automobile, then what physical object is supplying the outward push or pull?", "And finally, could that sensation be explained in other ways that are more consistent with our growing understanding of Newton's laws?", "If you can answer the first of these questions with \"No\" then you have a chance. But if you quickly conclude that the outward feeling means there is an outward force, then you at least must admit that your conclusion is contrary to all that has been discussed in Lesson 1 and that you don't believe that Newton's laws accurately describe circular motion. The sensation of being thrown outward is attributable to the idea of inertia, rather than the idea of force. When making that left-hand turn in the car, your tendency to be thrown rightward across the seat (that would be outward or away from the center of the circle) was not due to a force. It was due to your tendency to travel in a straight line while the car seat was making its turn. In fact, you were not thrown rightward at all; you moved in a perfectly straight line. If an airborne camera had collected the motion on film from above and we could watch the instant replay, then it would be a no-brainer - the car turned left and your body kept going straight. Finally, your body hits the door on the right side of the car and the door provides an inward push on your body to cause your body to begin moving in circular motion. But until hitting the door, your body's tendency was to follow its inertial path.", "The Law of Inertia Explains the Feeling of an Outward Force", "A common physics demonstration involves using a flat whiteboard with a tennis ball on top of it. The whiteboard is carried along in a straight-line path; the ball rest on top of the whiteboard and follows the same straight-line path. Then suddenly, the board is turned leftward to begin a circular motion; yet the ball keeps moving straight. Ultimately, the ball rolls off the right-edge of the board and continues in its straight-line inertial path. Without an unbalanced force on the ball, the ball continues in its original motion. The whiteboard merely moved out from under the ball as it makes its turn. If you could watch carefully, then you could view the ball's path from the perspective of an airborne camera. It's a no brainer - the ball moves straight while the whiteboard turns. And finally, the ball travels off the \"outside edge\" of the whiteboard. Relative to the circular motion of the whiteboard, the ball moves away from the center of the circle. But explaining the motion of the ball does not require that we imagine or dream up the existence of an outward or centrifugal force. The motion of the ball is explained by the tendency of an object in motion to continue in motion in the same direction. INERTIA!", "Now suppose that a block is attached to the top of the whiteboard on the \"outside\" of the ball with such an orientation that it would apply an inward force upon the ball. When the whiteboard is turned, the block would turn as well and supply the centripetal force required to move the ball in a circle. Without the block, the ball would have moved along the straight-line path, moving to position 1 after say 0.1 seconds, then to position 2 after 0.2 seconds, then to position 3 after 0.3 seconds, and so on. But with the block supplying an inward force, the ball moves inward towards the center of the circle relative to its straight-line path. Instead of being at position 1, the ball is closer to the center at position 1'. And instead of being at position 2 after 0.2 seconds, the ball is forced inwards towards position 2'. And instead of being at position 3 after 0.3 seconds, the ball is forced inwards towards position 3'. The inward net force accelerates the ball inward, causing it to deviate from its straight-line path that is directed tangent to the circle.", "If you were the tennis ball in the first example above, then you might feel like you were being pushed outwards. After all, you would travel through the outside door of the whiteboard. Yet it is clear from the diagram and the discussion that you are not deviating from any straight-line path. It is merely that the whiteboard is moving inward relative to your path and you are moving outward relative to the whiteboard's path. But this sensation of relative motion does not give reason for supposing that an outward force exists. This notion of an outward force is merely fictitious. Newton's law of inertia - \"an object in motion continues in motion with the same speed and in the same direction unless acted upon an unbalanced force\" - provides a more reasonable explanation for the sensations experienced by those who are in circular motion. A centrifugal or outward net force simply does not exist. No physical object could ever be identified that was pushing you outwards. And if there was a physical object pushing or pulling you outwards (e.g., in the rightwards direction when taking a left-hand turn), then you certainly would not turn in the circle that you are turning in.", "An object moving n circular motion is at all times moving tangent to the circle; the velocity vector for the object is directed tangentially. To make the circular motion, there must be a net or unbalanced force directed towards the center of the circle in order to deviate the object from its otherwise tangential path. This path is an inward force - a centripetal force. That is spelled c-e-n-t-r-i-p-e-t-a-l, with a \"p.\" The other word - centrifugal, with an \"f\" - will be considered our forbidden F-word. Simply don't use it and please don't believe in it.", "Flickr Physics Photo", "Pilots at an air show perform a loop-the-loop. The pilots are oriented upside down at the top of the loop. They do not fall out due to inertia and centripetal force. Their natural tendency is to continue tangent to the curved path, but the gravitational force (and perhaps some normal force) pushes them center-ward. This centripetal force allows for circular motion.", "We Would Like to Suggest ...", "Sometimes it isn't enough to just read about it. You have to interact with it! And that's exactly what you do when you use one of The Physics Classroom's Interactives. We would like to suggest that you combine the reading of this page with the use of our Race Track Interactive. You can find this in the Physics Interactives section of our website. The Race Track Interactive immerses a learner in a game-like environment in which s/he must select the proper force direction in order to guide a car around a track in the least number of moves. (Don't forget about the centripetal force requirement.)" ], [ "Out on the slopes", "A lead weight swinging on a string around in a circle has it's centripetal force (centrally directed force) applied by the string, and cutting the string will result in the lead weight flying off at a right angle to the inward force vector, not actually outward.", "The force the snow exerts on skis acts in the same way the string does. It directs inward forces on the skier which result in a turn.", "I have a difficult time understanding what centrifugal force is supposed to be, because it's really not a force in the same way. People seem to use it to describe the sensation one feels when being acted on by centripetal force.", "For instance, in a turn the force is most definitely centrally directed but we feel as if we are being pushed outward. That feeling is not a force, but it is a real feeling.", "So in common usage I would say centripetal forces are the actual forces that act on us in a turn, whereas centrifugal (forces) are the sensations we perceive while being acted on by centripetal forces but are not real forces? Does that make sense?", "The term you are looking for is 'fictitious force'. https://en.wikipedia.org/wiki/Fictitious_force The word 'fictitious' here is a technical physics term and is NOT synonymous with 'not real'. People who attempt to simplify this concept are the ones creating the problem.", "So in common usage I would say centripetal forces are the actual forces that act on us in a turn, whereas centrifugal (forces) are the sensations we perceive while being acted on by centripetal forces but are not real forces? Does that make sense?", "You're trying to dip your toe into the inertial reference frame while being inside a rotating one. Your definition is usable IF and only if you are very very pedantic about who what and where is turning - but it doesn't simplify anything.", "Skiing the powder", "Centripital is an adjective meaning towards the centre, e.g. towards the centre of the circle matching the arc your skis are making. It can be used to describe the force acting on your skis at the ski/snow interface in any reference frame.", "Centrifugal is an adjective meaning fleeing or away from the centre, e.g. away from the centre of the circle matching the arc your skis are making. It can be used to describe the force acting on the snow at the ski/snow interface in any reference frame.", "Usually, we choose the biggest thing around as our frame of reference, and consider it stationary, e.g the ground. All of Newton's laws work fine (so long as we are not moving near the speed of light). They work for forces applied at interfaces like the ski/snow interface and for body forces like gravity deemed to exist from studying falling objects over centuries.", "Sometimes we can simplify the math by choosing a different frame of reference, e.g. a train traveling at constant speed down a track. All of Newton's laws work fine (so long as we are not moving near the speed of light).", "Now if we choose the train as our frame of reference and the conductor is slamming on the brakes, and we examine the situation armed with Newton's laws, we observe that objects in the train are being pulled to the front of the train by a body force, just as they are being pulled down by gravity. Using this accelerated (speed changing or direction changing or both changing wrt to our usual earth-based frame of reference) frame of reference a force related to the acceleration of the frame of reference exists and Newton's laws work out.", "Now if we choose the train as our frame of reference and it is traveling at constant speed around a curve, and we examine the situation armed with Newton's laws, we observe that objects in the train are being pulled to the outside of the curve by a body force, just as they are being pulled down by gravity. Using this accelerated (speed changing or direction changing or both changing wrt to our usual earth-based frame of reference) frame of reference a force related to the acceleration of the frame of reference exists and Newton's laws work out.", "In skiing physics we usually stick to two frames of reference: fixed to the ground is one of them; accelerating in a curve with the skier is the other one, sometimes used because it matches our experience. Do not try to use both frames of reference at the same time!", "Out on the slopes", "I have a difficult time understanding what centrifugal force is supposed to be, because it's really not a force in the same way. People seem to use it to describe the sensation one feels when being acted on by centripetal force.", "So in common usage I would say centripetal forces are the actual forces that act on us in a turn, whereas centrifugal (forces) are the sensations we perceive", "have a difficult time understanding what centrifugal force is supposed to be, because it's really not a force in the same way. People seem to use it to describe the sensation one feels when being acted on by centripetal force.", "Skiing the powder", "If you are going to mention speed of light why not also include the realm of the very small where Newtonian physics also breaks down.", "And we don't have to be going anywhere near the speed of light. The GPS satellites meander along at a mere 14,000 kph yet their clocks must be adjusted for both special (for the speed differential) and general relativity (for the gravitational field differential) otherwise positional errors would accumulate at the rate of about 10 km per day.", "Since my post pinged by the moderator (valid point), I'll rephrase it more politely: Since skier speeds and sizes are well within the domain of newtonian physics could we kindly refrain from invoking relativity, quantum mechanics and the Higgs-Boson in these discussions.", "Out on the slopes", "Centrifugal is perfectly appropriate for use when discussing forces and acceleration within a rotating frame of reference relative to an inertial frame of reference.", "You're trying to dip your toe into the inertial reference frame while being inside a rotating one. Your definition is usable IF and only if you are very very pedantic about who what and where is turning - but it doesn't simplify anything .", "In skiing physics we usually stick to two frames of reference: fixed to the ground is one of them; accelerating in a curve with the skier is the other one, sometimes used because it matches our experience. Do not try to use both frames of reference at the same time!", "Getting on the lift", "I reckon most of the confusion comes down to one person in the discussion speaking (or writing) colloquially, while the other is using the more strictly defined & 'more correct' language of physics.", "If you ask me my weight I'll happily reply that I weigh 83 kg.", "This is, 'of course' , wrong.", "I do NOT weigh 83 kg... my mass is 83 kg, whereas my weight is about 813 N (when not moving around on the planet Earth ;-) ... in other words when my mass is accelerated upon by Earth's gravitational field ). If I jump up and down on some bathroom scales I can see my weight changing due to acceleration effects I am exerting on my body.", "Of course... if you ask a Nobel prize winning Physicist in a bar how much he weighs... they're not going to answer in the proper scientific units because they'll sound like a weirdo", "So... the stone whirling around in a circle on the end of a piece of string is continuously accelerating - and centripetal force along the string towards your finger (the centre of rotation) keeps it going round in that circle. Cut the string, and the object will move off at a tangent to the arc it was travelling on when you cut it as it no longer has the string to exert that centripetal force and provide the necessary acceleration...", "which bings up confusion between speed and velocity and acceleration... again due to colloquial English vs Sciencey speak.", "We 'normally' (colloquially) think of say a car accelerating when its speed is increasing... and kind of forget that what we are really dealing with is velocity and acceleration, and that velocity takes account of both direction and speed.", "What this means is that any time your direction is changing your velocity changes... so anything ( a rock on the end of a piece of string being spun in a circle, a car going round a corner, a skier making as turn ) is accelerating (even though our speed may be constant.. our velocity isn't).", "So a skier making a turn (or a driver taking a sharp left hand corner at speed, sitting in supportive Recaro seats) will feel that centripetal force being exerted on themselves - there is no centrifugal force to 'throw' you into the trees... there's just the risk of loss of centripetal accleration due to dodgy tyres or badly tuned ski edges and/or bad technique", "Disclosure - I am not a Physicist.", "ps having brought up mass and weight thanks to gravity... here's an 'amusing' misconception to wrap your head around...", "\"Einstein showed through the use of complex mathematics that gravity is not a force per se, but a consequence of the curvature of spacetime. Einstein discovered that massive objects bend the spacetime around it, and we perceive of this bending of spacetime as a force.\"", "Say what now?", "Scroll down to #8 of this link for the rest https://futurism.com/moon-will-turned-giant-particle-detector", "entering the Big Couloir", "Cut the string, and the object will move off at a tangent to the arc it was travelling on when you cut it as it no longer has the string to exert that centripetal force and provide the necessary acceleration", "So in the rotating frame of reference- This is the same as \"inertial\"?", "You would feel a cessastion of the force pushing from the right, then a force of friction from the front slowing you down? Assuming counterclockwise/left turning and flat hill.", "To be relevant for a moment, when you are pulling a high-force turn and your edges let go, it feels to you like you suddenly start going sideways. But to a stationary observer standing nearby, it is apparent that you are \"really\" still going mostly forward.", "If you are puzzzled, or just want to see all the fun ground out of a joke, you can go to the volunteer site \"xkcd explained.\" I do like their tag line, though : \"Explain xkcd: It's 'cause you're dumb.\"", "About SkiTalk", "SkiTalk, Powered by Pugski.com, is managed under the stewardship of Phil and Tricia Pugliese, two of the snow sport industry's most respected and read reviewers and product testers. SkiTalk evolved from Pugski.com's original tag line, \"SkiTalk at a Higher Level.\" Pugski.com was founded in 2015." ], [ "1 Expert Answer", "Let's assume that you are driving a truck with constant velocity (same speed and same direction). Next to you on the truck seat/bench is a basketball. While you are buckled in, the basketball is not. As you and the truck approach an intersection, you decide to make a left turn. As you make the left turn, the basketball on the truck bench begins to roll to the right, away from you, towards the passenger door. The basketball makes contact with the door and the door stops the basketball as you continue the left turn. So what happened to the truck and the basketball in terms of forces? Newtons 2nd law states that only a net force can change the constant velocity of an object. For the truck, the net force that changed its velocity is the force of friction between the tires and the road. Since you were attached/glued/part of the truck by holding on to the steering wheel and buckled in by your seat belt, you had no choice but to move left with the truck. However, the basketball moved to the right, as if some \"net force\" changed its motion. This so called \"net force\" is known as the centrifugal force. In reality, the basketball was following Newton's 1st law of motion. The 1st law states that objects at rest or moving with constant velocity want to keep doing that, to be at rest or to move with constant velocity until a net force changes their condition. The basketball was not part of the truck like the driver. So the basketball continues to move in the original straight line of the truck until it makes contact with the door and then the door applies a force to it making it move to the left. The ball rolled to the right due to its inertia or mass. The ball \"wanted\" to continue in a straight line with constant speed. There was not a force that made it move to the right. Inertia made the basketball continue in a straight line and thus appear to move right as if some force moved it. That is why the centrifugal force is fictitious. It does not exist. From a frame of reference point of view, the truck moved left compared to the road while the basketball did not deviate from its straight line path compared to the road. When you compare the basketball to the driver, the ball moved right as if some \"force\" moved it. However, it was not a force, it was inertia. It resisted going left until the door forced it to go left." ] ]