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ELI5: What use are coaches of top tier athletes like Federer or Tiger Woods?

What can the coach say or do to improve their game?

You don't always need to be better than someone (do you think Coach K at Duke can beat any of his players 1 on 1) at a sport to coach them, you observe them to see flaws in their game (amateurs watching TV--especially with slow motion replays can usually spot areas that require improvement). Also, a coach can focus on competition reconnaissance and strategy, allowing the athlete to focus purely on practice.

ELI5: How does car insurance work and why it is mandatory to have it?

The legal minimum is liability insurance. Since it's very easy to cause hundreds of thousands of dollars of harm to someone else, states usually require you have some way of paying any damages in such a situation. The preferred way is an insurance plan: you pay an insurer a monthly/annual amount and they agree to cover most of any claims you are responsible for paying in the event of an accident you cause.

ELI5:If humans were to ever come in contact with colours beyond our colour receptive cones, what will we see ?

An ordinary human possesses 3 colour receptive cones, while a mantis shrimp has 16. If we, humans, were to ever come into contact with the remaining 13 colours that the shrimps have access to. Would we see those colours like how a colourblind individual would see certain colours ? otherwise, what would we see ?

We come into contact with "colors" beyond our color receptive cones everyday. Your eyes are only able to pick up on certain wavelengths of electromagnetic radiation, this is what we see as light. If the wavelengths are shorter (like x-rays) or longer (like radio waves) then you simply won't be able to see them.

Continental Philosophy at an undergraduate level?

I apologize if this is not really the focus of the sub, but I'm very curious about studying Philosophy at an undergraduate level and how all that works. I'm more interested in Continental Philosophy, but what I've heard is that undergraduate philosophy courses are more about logic and the basics. How possible is it to focus on Continental Philosophy at an undergraduate level? And is there a resource somewhere that details which schools lean Continental or Analytic? Or would that only talk about graduate programs? Thanks

There are lots of programs that are strong in Continental thought. This is particularly but not solely the case when it comes to Jesuit universities (anything called “Loyola” is likely to have a decent set of Continental faculty members). Also keep in mind that you can often find people doing Continental philosophy in other departments, particularly literature programs, Romance Studies, German departments, as well as cultural anthropology and sociology, Usually a school that is predominantly Analytic will also have at least one person who works on Continental thought, too.

Why doesn't market competition drive down the cost of healthcare in the US?

It is a bit disingenuous to answer that question without first acknowledging that there is not much of a functional market in healthcare provision in the United States. We wouldn't expect competition to be very robust.

[Star Wars] How do the Sith meditate?

I know Darth Vader would meditate while in his Bacta tank, and Sidious and Plagueis both used Force meditation to offset the need for sleep, but what are they actually doing there? Meditation calms you down, and that’s pretty against the Sith philosophy.

Sith meditate a little differently than Jedi. Generally there's two types of meditation: Mindfulness and Insight. The goal of mindfulness is to focus on one thing and let it fill your mind, removing any and all distractions. This is a very simplistic summary, but it's enough to explain the differences. Jedi love this one (eg let the force move through you and whatnot). The goal of insight is to reflect on your past and yourself, using it to help define your goals and shape who you are as a person. Again, simplistic, but helps illustrate the differences. Sith love insight meditation, instead of focusing on bettering themselves they focus on their hate. Of course, both the Jedi and Sith can and do use both types, but their own variations to help connect them to their preferred connection to the Force. But they do generally have a preference. Sith use their hatred to fuel and increase their connection to the dark side and insight meditation is a very useful tool in molding and reshaping your hatred and keeping you focused on your goal When Darth Vader is in the bacta, he's not clearing his mind, he's remembering the pain of betrayal from his order, the heat against his bare flesh as he lay dying on Mustafar, and the death of his wife and how powerless he was to stop it. He endlessly reignites his hatred for weakness and Jedi.

Why don't natural anti-bacterial substances, eg. garlic, contribute to resistance like antibiotic drugs do?

There is a lot of concern these days about the prevalence and over-use of chemical antibiotics causing resistant strains of bacteria. This is pretty easy to grasp, considering the reproduction rate of bacteria. However, many anti-bacterial substances have been around in nature for a long time - foods such as [garlic](http://pubs.acs.org/subscribe/archive/mdd/v05/i04/html/04news4.html) and materials like [copper](http://en.wikipedia.org/wiki/Antimicrobial_properties_of_copper). Why haven't these natural substances not caused bacterial resistance in the same way our drugs do, especially considering they've been out there killing bacteria for a very, very long time?

The answer to this question is actually a bit complex and has more to do with the different properties of an antibiotic (e.g. penicillin) vs a material with anti-microbial activities (i.e. copper, bleach, >50% ethanol, hydrogen peroxide). An antimicrobial substance kills bacterial because it has chemical properties that make it inhospitable to life. For instance, hydrogen peroxide is a strong oxidizing agent that will react with biological compounds to render them inert. Copper is a metal with a high redox potential that will complex with organic compounds in such a way as to disrupt their chemical activity. These compounds damage ANY life-form, not just bacteria. There is literally no way for a bacteria to become "resistant" to these compounds in the same sense as it would to an antibiotic. While there are some bacteria (dubbed extremophiles) that can live in harsh environments containing these normal anti-microbial substances, they have only accomplished this by completely altering their metabolism to cope, and sometimes utilize, the chemical activity of these compounds. Antibiotics by contrast are far more specific in their microbe-killing ability. Penicillin for instance disrupts the bacterial cell wall, making it less able to separate itself from its environment and defend itself from our immune system. Penicillin has no effect on humans, or any Eukaryotes for that matter (the biologic kingdom apart from all bacteria). Other antibiotics work by disrupting other vital systems specific to bacteria, for instance their mechanism of building proteins. Because antibiotics are so specific to disrupting one essential part of a bacterium's metabolism they work at far lower concentrations than an anti-microbial and can be safely given to infected people without fear that there will be too many side effects. On the other hand, it also means that all a bacterium has to do to become resistant to an antibiotics is mutate that key part of it's metabolism that the antibiotic disrupts, maybe just enough so the antibiotic can no longer chemically bind to it. Alternatively the bacteria can begin expressing an efflux pump that just pumps foreign toxins like antibiotics out of it's cytoplasm. It does not require a dramatic change in the way the pathogenic bacteria operates to become resistant to an antibiotic, whereas becoming resistant to an anti-microbial substance takes millions of years of careful evolution. tl;dr: Anti-microbials are like napalm, they destroy all biologic compounds and are not specific to bacteria. Antibiotics are like smart bombs that target certain pathways and can thus resistance develops when that pathway is altered or the toxin is neutralized.

ELI5: Why does the offbeat in music feel so good to snap to?

There's two different ways we can answer this: historically and psychologically. In a bar of music, you usually have 4 beats: 1234. This repeats over and over to make a song. In most modern rock music, beats 1 and 3 feature a bass drum, or low heavy note, and a snare or cymbal on beats 2 and 4 to give us an idea of tempo. Historically, this pattern that makes up rock music has it's roots in the slave tradition. American rockabilly and boogie woogie beats (precursors to rock and roll) came from a mix of western instrumentation and African rhythms. That's why it feels "lame" to clap on beats 2 and 4 to a classical symphony which predates rock. Psychologically, the reason we like to snap on beats 2 and 4 is because we are participating in a "call and response" with the beat. Downbeat on 1, respond on 2, downbeat on 3, respond on 4. It's like a little minigame for your brain. There is some speculation that the reason we like this game so much is because it developed as a means for humans to work menial labor jobs together in rhythm. Whacking grain to make flour was hard work alone, so you need 2 people doing it at once. How do you alternate whacks to ensure you don't hit each other? Play a rhythm game!

In many models, dark matter WIMPs are their own anti-particles. How are they expected to generate photons on annihilation if they have no coupling to the EM field?

Via loop processes or intermediate particles. An example that we have observed is the Higgs decay to two photons. The Higgs doesn't couple to photons directly (they don't have mass and the Higgs doesn't have an electric charge) but both couple to top and W.

CMV: Prison is actually harmful to both the inmate and society.

Most argue that we should lengthen prison sentences and go harder on crime as a way to protect society from rapists, muderers, drug dealers, ect. The reality is quite the contrary. Many don't realize how traumatic prison is. All freedoms stripped from inmates: removed from family, reputation and career destroyed, no respinsibilities, forced to eat only processed and packaged food, abused by officers authority, in constant fear of being assaulted by other inmates, unsafe and unhealthy living conditions, surrounded by drug abuse, violence and bad behavior... It will absolutely ruin a person's life and cause them to leave prison even more hateful towards society and authority than they might have been before they came. Your tax dollars support this. How do you imagine 5... 10... 20 years of prison will effect a person who has served their time and been released back into society? They may leave prison with a drug addiction they didn't previously have, be rejected by society, unable to find work and filled with rage from the abuse. They may never be able to reacclimate and they have a 76.6% chance of committing another crime and returning to prison. http://www.nij.gov/topics/corrections/recidivism/pages/welcome.aspx Recitivism rates are extremely high due to this broken system. Prisons are incorrectly refered to as "rehabilitation centers" or "correction facilities," when they are actually causing unknown amounts of damage on the inmates and releasing heavily wounded people back into the world. Scandinavian prisons are essentially (actual) rehabilitation centers that heal, support, encourage and motivate inmates. This allows them finally lead healthy lives once released and this significantly benefits society by improving crime rates. Scandinavian prisons have proven extremely sucessful! Why shouldn't U.S. prisons do the same? I think it has a lot to do with how lucrative the industry is and a little to do with how punish-happy American voters and lobbyists are.

Purpose 1 of Prison: To remove a dangerous element from society to protect society from it. This is extremely beneficial to society. Purpose 2 of Prison: To act as a deterrent for future crimes in others. This is not always successful but many crimes are prevented due to fear of being caught and sent to prison. This is beneficial to society. Purpose 3 of Prison: Justice and vindication for the victim and their families. People have been wronged and action has to be taken to "balance the scales". This is extremely beneficial to society. Purpose 4 of Prison: Punishment for a crime. This is tied closely to purpose 3, but is actually separate from it. This is the only aspect that is negative and punishments are rarely a good thing. Purpose 5 of Prison: Rehabilitation. This is good for society, but not everyone is willing to rehabilitate. > Many don't realize how traumatic prison is. Actually most know exactly how traumatic it is. And it is suppose to be that way in most of our minds. You commit crimes and you forfeit your rights to comfort and freedom. Prisons are not only, or even primarily rehabilitation centers so you are correct that people erroneously call them that. As to the question of "Why shouldn't U.S. prisons do the same" as Scandinavian prison? We are not a Scandinavian country. We are a sovereign nation with our own laws, our own culture, and our own right to punish our criminals as we see fit.

Do we know anything about Neanderthal language capabilities?

There is high evidence they were able to speak because we share a specific gene (FOXP2) that is responsible for language. And because of Neanderthal anatomy we can deduce they had a higher pitched voice than us Homo Sapiens!

ELI5: Why do pigeons thrive so much better inside cities than any other bird?

Every city I ever visited had an abundance of pigeons but rarely other kinds of birds and definitely not as many/openly running/flying around. Do pigeons just thrive better in cities than other kinds of birds, if so why?

Pigeons are common in cities because buildings more closely resemble their natural nesting sites. Rock doves nest on the side of cliffs. Not in trees or shrubs. Human buildings provide lots of ledges for nesting. Combine that with the fact that they're harmless, (so we don't kill them for being pests) not tasty (so we don't kill them for food) and their natural predators cannot hunt well in cities (falcons end up nose diving into walls using their usual tactics, larger predators avoid humans) and you've got the perfect combination for a species to cohabit our cities with. Seagulls are also very common in cities in the UK for the same reason.

ELI5: why does my body tell me to scratch, when it basically worsens absolutely everything? (Scabs, rashes, bug bites, pox, poison ivy)

Typically it is due to a natural response by your immune system to foreign material. Say you had a tick or leech attached to your skin, scratching would make sense. However, your body doesn't immediately recognize the difference between a tick vs a mosquito, so in either case you get this immediate immune response that is very general referred to as **inflammation**. Inflammation involves an early stereotypical response, one of which includes the release of histamines which causes itching, particularly when released in the skin. Depending on the actual foreign material, it can take the body some time to realize exactly what is going on and for the correct immunological response to take over. In some case this the immune system never specializes enough to stop the itching and the foreign material must be completely removed first. In a worst case scenario, the immune system responds without stimuli and the itching never goes away.

[Star Wars] When Count Dooku or Darth Sidious jumped around and rolled over in mid air, was it their pure fitness strength or did they use the force?

I.e. Dooku vs Anakin and Obi-Wan in Ep3, Dooku jumps in mid air to land on the the bottom floor.

Force users both light and dark can use the force to augment and enhance their physical abilities, though it does tire the user out quite a bit. In fact, form IV of lightsaber combat, Aataru, focuses on this, making the practitioner use the force to turn them into a lightsaber tornado at the cost of strain to their body.

When economists study black markets, how do they get their data if the trade is supposedly illegal? Is there any component of black market analysis which is especially reliable and if so, why?

Data on illegal activities can come from a number of different sources. Satellite imagery has been used to estimate the extent of illegal fishing, for example. Other estimates include data on arrests or search and seizure, which can then be extrapolated to population levels. This happens for illegal wildlife trade. In short, there is a lot of administrative data that can be used to infer rates, and increasingly satellite imagery can be used to more accurately estimate illegal activities where they are recognizable from space. There are probably other ways as well, but those are the studies that I've come across.

ELI5: How do theaters determine how long movies are played? Do they decide on a percentage? Do they talk with distribution companies before hand? What if the movie doesn't meet its expectations in terms of occupancy/ticket sales?

Theaters make agreements with the distributors which lay out the percentages each will get, a guaranteed number of weeks played, and if there are theaters close together there can be some bidding on exclusivity. During that agreement phase they would have to agree on what happens if a movie tanks and how bad before they can back out on the guaranteed number of weeks.

What is more effective at cooling the body, no clothing or one layer of moisture wicking clothing?

Is a single layer moisture wicking t-shirt better than wearing no shirt at all?

Too many unknowns to answer. Scenario A - good airflow around your body -> convection is better -> no clothing Scenario B - poor airflow Evaporative cooling effect dominates -> bigger evaporative surface -> moist clothing

ELI5: Why do hot things like car engines and tabletop electric burners make ticking and clicking noises after you turn them off and they’re cooling down?

When most materials heat up, they expand. What you are hearing is the metal "shifting and popping" as it contracts once it starts cooling down again. I work in a storage facility constructed of metal and can hear the building doing the same thing once the sun comes up and it is heating up. It disturbs some of the customers because it can be quite loud sometimes.

Why do things appear darker and more colorful (e.g. stones) when they are wet?

The surface of many objects is rough on a microscopic scale, which is in large part responsible for the bright diffuse reflectance. When the microscopic roughness forming the surface is coated with water, the water fills in the tiny gaps which are otherwise filled with air. Because the difference in refractive index between the water and the stone is much less than the difference between the air and the stone, the wet rough interface will scatter less. There is also a new interface created (air/water). However, because the new boundary between the air and the water (covering the stone) is fairly smooth, it will not scatter light very much.

ELI5:Why do people assume that oxygen is needed on other planets to sustain life?

The universe is so vast, isn't there a possibility that "life" on other planets could rely on a different element for survival other than oxygen?

We don't really assume it, it's just a framework that gives us something to look for. Is it possible that there is life out there that is completely different than life as we know it (perhaps silicon based and sustained off methane)? Sure it's hypothetically possible ... but we'd have no idea what to look for, and might not even be aware of it if we saw it. So we look for life as **WE** know it, because it gives us criteria to look for rather than cluelessly fumbling around in the dark. Did that help?

[Limitless / Various] In Limitless, NZT-48 gives you maximum potential cognitive power of the human brain, and perfect instant total eidetic memory recall of anything you've experienced or seen. How would a normal person on permanent NZT state fare in worlds with more advanced sciences?

In Limitless, a normal person who gets the abilities instantly can access anything that's basically ever been encoded in their brain if it's still there, as fast as the brain can send the signals. If you read a page of a book when you were 11 years old, and you're 50, with the barest effort you can read and see that page verbatim, and even *as* you did back then. You can cross reference anything. You basically get total command of your brain's abilities. Everything you learn adds and compounds. If you were a basic person who hardly read in life, a high school dropout, working for the past 20 years as a grocery store bagger, and did nothing to expand your mind... the minute you get this, it's changed. You'll know everything you know, even if you didn't know you did. You'd instantly become the smartest person you know. If you did the reading of every piece of training material that a senior computer engineer had, when you were done at bare minimum you could do any of the work in the materials, and you'd know trivially how to find more to do more, cause you can synthesize all that together instantly. You can learn all the programming languages in a few weeks. You can learn fluency in any human language in days. Music instruments in weeks or less. Biochem. AI. Cooking of all sorts. Anything. Once you know it, you don't need to train it. It's all right there, building on and compounding on itself. All of it connected, all of it a stray thought away at your fingertips. Every single person in Limitless is set in an otherwise real world just like ours. What would happen if someone with permanent Limitless NZT abilities found themselves in the worlds of Star Wars, Star Trek, Marvel, DC, and similar, where the levels of what *can* be done *vastly* outstrip the real world? Or if someone, say, in those, a plain person, suddenly ended up like this? Here's some examples of what NZT can do to you--obviously major film and TV show spoilers: * https://www.youtube.com/watch?v=xP-ZwmCPBAs&t=4s * https://www.youtube.com/watch?v=F3Krd0qYwnQ * https://www.youtube.com/watch?v=0X7I0RNGJps * https://www.youtube.com/watch?v=Owsc2CbnqZQ * What even just a bit of the abilities can let you do: https://www.youtube.com/watch?v=pMU2Pk-SBs0

*The Fold*, by Peter Clines covers this subject extensively. The protagonist discovered at an early age that he can perfectly recall anything he's ever experienced... and how it has the potential to make him very unhappy during his lifetime. So he doesn't "feed" it, and instead works as a high school science teacher. Yadda yadda yadda. Gets pulled into events were "feeding" his ability is the only thing that can save a couple dozen universes from being consumed the Great Old Ones.

Is weathering/erosion of rock by water more due to chemical or mechanical processes?

I was reading this page: [https://opengeology.org/textbook/5-weathering-erosion-and-sedimentary-rocks/](https://opengeology.org/textbook/5-weathering-erosion-and-sedimentary-rocks/) ​ And while they indicate here that "chemical" weathering is the primary mechanism, wouldn't "mechanical" be the most significant factor? As in, moving/falling water would cause more weathering than still water over the same time period? And wouldn't faster moving water cause more weathering than slower moving water?

The answer will depend on the environment and the type of rock in question, so the things discussed in the text are simplifications (as you would sort of expect in an intro textbook). The first thing to establish is that there is a distinct difference between weathering and erosion, i.e., weathering is the break down of rocks in situ and erosion is the removal and transport of pieces/components of rock, so while we often discuss these at the same time, we need to be careful about lumping them together too much. In general, mechanical weathering will dominate in environments where chemical weathering rates are low (e.g., in cold or dry environments) and/or where rocks are more resistant to chemical weathering (e.g., they have low percentages of minerals that are susceptible to common chemical weathering processes). In contrast, chemical weathering will dominate in regions where chemical weathering is efficient (e.g., in warm, humid environments) and/or where rock types are very susceptible to chemical weathering (e.g., landscapes dominated by carbonates/limestones). Within this, there are going to be a lot of environment specific conditions that control the exact balance, e.g., how often does the region cycle through freeze thaw cycles (i.e., how important is freeze-thaw?) or how many shallow rooted trees exist (i.e., how important is tree-throw?). With reference to the speed of moving water, this is mostly relevant for erosion, not weathering, i.e., fast moving water can entrain, roll, and saltate more and larger grains than slower moving water. Things do get a little opaque in this regard as there is the potential for chemical weathering rates to be related to the speed at which solutes are fluxed away, i.e., generally chemical weathering rate will decrease as the concentration of the dissolved products of this weathering increase. Also in the opaque zone are mechanical processes like abrasion. These are typically considered erosional processes, not weathering, because while they do breakdown rocks, the breakdown isn't really in situ because (1) for abrasion to happen grains need to be moving within a fluid and (2) the products of abrasion essentially move as part of the process. This is different from mechanical weathering processes which may induce a small amount of fixed motion away from the source bedrock, but then any subsequent motion is typically thought of as erosion (and assigned to an erosive process in terms of a causative agent).

ELI5: If gas prices go up on holiday weekends due to demand, how is that not considered price gouging?

They go up in a reasonable amount to account for supply and demand and the natural flow of the invisible hand. If they were to say bump prices up by $3/gallon on a weekend, then that would be price gouging. Adjusting prices based on natural fluctuation of supply and demand is basically a core component of how to run the economics of a business, which is totally fine.

If the speed of light is the maximum speed an object can move then isn't there a maximum temperature?

From my limited experience I understand that heat comes from particles moving and bumping into each other. The faster the particles the higher the temperature. So since particles are moving arent they bound by the speed of light? And if that's true isn't there a maximum temperature since the particle speed is limited? Or maybe i'm just confused...

Temperature is technically defined as the amount of internal energy/entropy of the system. Now let's just ignore entropy for the moment, as that's a much larger discussion. In the non-relativistic picture you are correct in saying that energy and velocity appear to be linked in a simple manner. E=0.5 mv^2 . But as we get to higher velocities, E^2 -p^2 c^2 =m^2 c^4 becomes the equation of interest. Let's for the moment, throw out the m^2 c^4 since it's just a constant term that shifts the energy up uniformly for each particle. E=pc, this E being just kinetic energy alone. 'p' is the particle's momentum. p=(1-(v/c)^2 )^-1/2 mv. So as v->c the first term, called gamma, goes toward infinity. tl;dr, we can keep adding more energy even if the velocity doesn't continue to increase.

ELI5: Why sunscreen is so vital, when ancient humans did not wear it.

I searched and found nothing really similar to what I am asking. So basically my question is, with all the sunscreen pushing we have now, what did people do in ancient times? It's like a crime to go out without sunscreen nowadays but what did early greeks, englishman, chinese, etc. Other melanin-lacking people do? Did they all just contract skin cancer and die or...? And why is sunscreen even necessary? Because it seems weird to me that the human body would react so negatively to the sun- something we naturally need.

We've been gaining longer and longer lifespans the longer time goes on. We're also diagnosing things a lot more often and efficiently. Back before sunscreen people still would have gotten skin cancer and died from it, but maybe it wasn't reported or they just attributed it as 'death by unknown causes'. In Australia at least we have a MASSIVE hole in our ozone layer. Us white Australians really aren't suited to this sort of environment, we belong where it's cold and there's no sun most of the time. We'd still get sun there, but not so much as to cause sunburn on a regular basis.

Eli5 - how are western economies sustainable?

I live in the uk, but the more I think about it, the more I realise that it just seems to be series of office workers propping up each others salaries. There’s no (or small) base that actually produces goods, the farmers or the labourers as such. Why?

Modern and wealthy economies tend towards being service based (it is one of their defining characteristics. Think about a typical "wealthy" society - just the basics but it can be extrapolated 1) Food - how many times have you encountered dysentery? Food containing things that will kill you in days/weeks? How about malnutrition? Where does the infrastructure for food safety and distribution come from? 2) Healthcare - We expect specialist care, modern and available treatment. Something like COVID-19 spreading even 150 years ago would have multiple times more death. Few people die from treatable diseases and many more diseases have become temporary inconveniences rather than a death sentence. If we fall and break an arm or leg, we don't expect that there is much chance of amputation or death through sepsis - yet that wasn't the case just a few hundred years ago. 3) Education. Where does the infrastructure to support specialist training, the basic education needed, all those things we take for granted. Basic education and literacy being universal, etc are all fairly modern. Just go to less developed countries - this kind of thing doesn't come automatically. Scientific research, technological progress can only take place within a society that has the resources to foster education from the bottom up. 4) Safety - How many people die in factories and workplaces? How many have their health and lifespan destroyed by their working environment? Contrast this to poorer nations. How are these regulations enforced? How are these improvements put in place? The legal framework and enforcement mechanisms, inspections, licensing, etc are there for a reason. Entertainment, transportation, communication, finance etc etc. The modern economy is complex and delivers a standard of living for the average person that not even kings of 200 years ago could experience. If 80% of the people are working the land or engaged in primary production, there is zero chance that there would be enough leftover labor and resources to deliver these outcomes to the average person.

how can oceanic dissolved oxygen decline if an increase in gas temperature usually means increase in dissolved oxygen?

Basically you assume oxygen has higher solubility in water as temperature increases but, unlike solids like salt or sugar, gases are much less soluble at higher temperatures. De-gassing water to prevent corrosion or make very clear ice is done by repeatedly boiling and cooling water. So yeah : higher temperatures = less oxygen in water.

ELI5: Why are some people genius at chess, but completely normal in every other thing?

Many world champions of chess immediately become grand master at the very young age, about 12-16. But they all seem totally normal in every other thing. Why aren't their intelligence show up in other things? What makes one's intelligence specific to chess? Note: English isn't my mother tongue, please keep it simple.

Chess is an extraordinarily simple game. You can learn everything there is to know about the game in a very short period of time. The issue is that it takes a great deal of intuition to become one of the greats, and intuition can't be taught. For example, you can very quickly learn how the pieces move, why it's best to keep your knights centralized or trade off bad bishops in closed positions, but seeing that abstract mate-in-four that requires you to sacrifice your queen, a rook, and a pawn is just something that you have to -see-, you can't be taught it. Chess strategy involves a lot of different aspects; it's not "seeing four moves ahead", it's understanding positions and tactics and making assumptions based on what you might do if you were your opponent. It's not even about studying the great games and trying to mimic them (it'll never happen). What grandmasters ARE good at is lateral thinking, or solving problems creatively and often indirectly using reasoning that isn't immediately obvious. This sort of approach to problem solving is very useful in a lot of different fields, but isn't the primary focus of very many.

ELI5: Why does using a tootbrush how we do not make us sick? It is never sanitised and sit in your bathroom all day.

Sorry about the terrible title I posted right before I went to sleep after I brushed my teeth.

Soap, your faucet, your tooth brush, the glass you drink water out of, all has bacteria on it. We don't live in a sterile environment and we ourselves are not sterile. You have more bacteria in your mouth, and fungal spores, than on your tooth brush. Having bacteria isn't the problem, it's having a place for bacteria to multiply and grow into a colony unopposed and for that you need food, water, shelter, and no competition. Your tooth brush has only one of those things. The job of a tooth brush is not to sterilize your mouth, it's to wash away the metabolic junk and plaque that eats away at your teeth. It denies the colonies in your mouth food and a medium to safely grow in (plaque).

[Matrix] Why the inconsistent crew requirements for hovercrafts?

In the first movie, Neo awakens to a fully crewed ship. 6-7 people minimum, all busy working with the ship. DUring the course of the movie, it drops to four (including Neo). Never again does the ship require more people than that. Also, Captain Naomi's ship only needs three (if you played the game that's tied into the movie sequel). In the sequel, Morpheus doesn't even bother replacing his crew other than Link as an Operator. So how many people does a ship require, anyway?

Pilot, operator, mechanic is the bare minimum for a ship to operate normally (flight, maintenance, and Matrix access). Could get by with a pilot only (risky/suicide mission in the Real World). Could get by with a pilot & operator if your mission requires jacking in. Other than that, smaller ships (scouts like the Logos) need smaller crews. The Hammer is a huge gunship and requires gunners and a medic to run smoothly. Nebuchadnezzar is somewhere in between. As the war went on, qualified replacements were not really available. Death/lack of training/etc. Had to get by with skeleton crews. Especially the Neb - who is going to willingly join up with that fanatic Morpheus??

Does state of matter have an effect on the absorbtion spectrum of a material?

Yes. Absorption spectra change with phase. The spectra of a material depends on all the ways the system can be excited. In a solid, for example, you can have excitations of the atomic displacements in the regular crystal lattice, what are called phonons. You can also have excitations of magnetism (magnons), spin (spinons), electrons (plasmons) etc. Many of these excitations either don't exist or have a different character in difference phases. Thus, you can't excite a transverse phonon in a gas, for example. This means the absorption resonances or bands associated with them disappear. Spectra reflects all of this and thus changes with state.

[Cyberpunk] How exactly have guns evolved?

Tabletop and video game version. What makes a cyberpunk pistol any better than a Walmart Glock?

All of the weaponry in the world by assumption needs to consider the advancements in technology. A highly cyberized and armed corporation solider can easily take small firearms like it’s nothing. Even someone with the fancy equipment against someone with high quality cybernetics like the woman in Cyberpunk 2077 announcement trailer was able to take military grade bullets just by their subdermal (armor plating grafted to the skin) protecting them. To avoid psychotic, criminal and/or violent cyborgs taking over. Weapons would need to advance to take on such threats. Of course lower grade weapons like the Walmart example exist. Even in the game you the player can buy a $1 gun. But it won’t do much against one with even below average armor and cybernetics. - Laser guns exist in the tabletop games and referenced in the video game - Some fitted with incendiary, electrical, chemical and energy rounds. - Some have built-in homing rounds. - Many guns can link to someone’s cybernetics, showing the user ammo count and charge level for the railgun variants. - As mention, railguns exist. Even for basic pistols and rifles. - This without mentioning built in weapons like wrist-mounted blades, grenades launchers and reinforced knuckles. Even at the base level, cyberpunk weapons are significantly more advanced than real world weapons.

[24] How did Jack Bauer go from a BA in English Lit. To a Master of Science in Criminology? Is this a normal study path that can lead to a career in counter-terrorism?

Yes. Because contrary to popular opinion, a degree in English lit doesn't just make students "smart in English", it also imparts analysis and reasoning skills that is applicable to all areas of employment.

Why does a spine have protrusions on it? What causes this and how are they evolutionarily useful?

The *spinous processes* that protrude from each vertebra in the spine have two main purposes. The longer ones are attachment points for ligaments and muscles, giving muscles more area to attach, and also acting like long levers to help the muscles bend, straighten, and rotate the spine. There are also smaller protrusions, called *articular processes*, that help each vertebra fit together with the vertebrae above and below it.

ELI5: How dogs are able to sense and know when something medically wrong is about to happen in a person before it actually happens?

This depends on the effect you mean. Some cancers can be smelled by dogs. There are 'cancer sniffing dogs' that have been trained to detect cancer and are better and cheaper than our imaging equipment. So they're using their superior senses to pick up on things that humans can't detect.

ELI5: Why does diplomatic immunity exist? What's the benefit?

It exists because every country wants their own diplomats to feel safe when working in other countries with very different laws, and the only way to guarantee that is to give the same courtesy to others. Imagine a world without such immunity. Canada appoints a woman as deputy ambassador to Saudi Arabia. She gets arrested and sentenced to jail time for driving a car. Massive international incident ensues. This can all be avoided with immunity. Incidentally, it's not total immunity. A country can choose to waive it for a serious offence, or can bring their diplomat home for trial under their own laws. This happened some years ago here in Canada when a Russian official killed someone while driving drunk. Canada could not prosecute. We asked Russia for permission to do so, they said no, and then recalled him and jailed him in Russia.

ELI5 - In very brief, simple terms, what is the postmodern?

I suppose I mean from a sociological perspective. This is one concept that seems to pop up everywhere, but it always seems to mean something slightly different. Relationships with media, inter-textuality, that kind of stuff I believe, but I've never been too sure. Can any of you underpin exactly what postmodern means in simple terms for me?

"Modernism" is the idea that things are getting better, or can get better. Try to improve technology, expand the methods of art, etc. Try to be the best you can be, destroy tradition, move society and the individual forwards. Write the great American novel, make the best movie ever. Art should be universal and stand alone. Post-modernism is the rejection of that idea. Maybe there /isn't/ such a thing as perfection. Maybe instead of trying to make the universal movie or novel, we should try to see things from different perspectives. In the social sciences, post-modern practice questions the idea of objective reality and the scientific method. Not necessarily discarding it, but taking an approach which allows for multiple perspectives to be reported.

Is the way of making philosophy based on "first principles" dead?

I read somewhere that Quine's "Two Dogmas of Empiricism" invalidated the pursuit of "first principles" from which truth could be determined and a system of philosophy could be constructed from. It is true? Are there philosophers still working in this way?

Systematic philosophy is alive and well, though it certainly is not as popular as in the early modern period. Just for a few names, in the analytic tradition there is Mario Bunge, and in the continental tradition you have Alain Badiou. Overall the continental traditions nowadays is much more amenable to systematic philosophy, in part because of authors like Quine and Russell in the analytic tradition arguing very forcefully against systematic philosophy. In some of the early sorts of battlecries for the analytic tradition you see their response to systematic philosophy, for instance Russell addresses it in the last chapter of *A History of Western Philosophy*. He describes a new vision for philosophy where we deal with individual problems instead of trying to solve everything all in one go.

When and why did a 5 day work week become the norm?

It stems from the 8 hour work day campaigns in the middle of the 1800s. 8 hours of rest, 8 hours of work, 8 hours of relaxation. These were fought for by the unions. The when and why also depends on the country in question. May Day or international workers day celebrates the fight for the 8 hour work day, it is also the martyrs of Haymarket in Chicago that were fighting for the 8 hour work day. The why is cause workers were working 10-16 hour work days 6 days a week, never having the time that their bosses had to enjoy time with family and have fun. Most of the 8 hour day enforcement came from the laws passed during the great depression and rise of labor unions at the same time to demand it and enforce it. Even though the US never enjoyed anything higher than 36% of the workforce being unionized, they unions had a powerful seat at the table from the 1940s to the 1960s instituting the 8 hour day nearly across the board, with exceptions of industries they did not have legal protection organize, i.e. agriculture and domestic workers. Sources for the above information Murolo, P. (2001). From the folks who brought you the weekend : a short, illustrated history of labor in the United States. New York: New Press  ;Distributed by W.W. Norton. Lichtenstein, N. (2003). State of the union : a century of American labor. Princeton, N.J.; Woodstock: Princeton University Press. Yates, M. (1998). Why Unions Matter. New York: Monthly Review Press.

ELI5: What is all the hype around 3D printers and why would it revolutionize the way we make things?

I see all these articles about how 3D printers were used to build cheaper prosthetic limbs etc, and I wonder how this cannot be achieved with conventional manufacturing, which has been around forever now.

Most traditional manufacturing processes require you to make specialized machines and molds to produce the various pieces of your product. That's fine if you are going to make a lot of something because the cost of those machines can be spread out over the thousands or millions of the product you are making, but if you only need to make a few of something, it is very cost prohibitive. With a 3D printer you can use one machine to make virtually anything you need without having to build a purpose built machine or mold that you won't be able to use to make anything else. This makes it a great alternative for making things that are one off purpose builds, like a prosthetic that is made to fit a single individual, and also for short run products and prototypes.

ELI5:Why is there one section of the audience at Obama's State of the Union that never stands up or applauds when everyone else does?

Edit: Thank you all for the quick responses! This was really puzzling me.

There are three groups in the chamber: The democrats - they will rise in support of anything the president says, that they agree with (which is pretty much all of it) The republicans - they will rise once or twice when Obama is talking about something they agree with The supreme court - they will not rise for most of the speech, so as to remain impartial towards anything that could come before the court.

What is implicit cost?

Is implicit cost the opportunity cost of a resource to be used in some other way than being allocated in the factors of production for the producer?

The implicit cost of a resource is the opportunity cost of its expenditure that will not show up as a visible expense Let's say for example you are deciding whether to college. Let's say college costs $20,000 a month for 4 years. When you come out, you are going to take a job that makes $100,000 per year. People would be tempted to say that you're paying $80,000 for college, but that's not true. There is also the time cost of 4 years, which could have been put to the best alternative use. That's 4 years of time that you could have spent working at another job. Let's say that the best job w/o a bachelor's degree makes $80,000 (oversimplifying). Well then you're paying an explicit cost of $80k for the cost of college, AS WELL AS the implicit cost of also putting in time that could have been used to make $320k. It's implicit because you won't see a receipt during the college process that says you're $400k in the hole, but it's nevertheless true. And, that's not including interest rates on your loans and potential investments into indexes or other assets that you could have made during that time with your money So you think your $100k job is worth it when you pay off the loans, but really the degree pays itself off when your lifetime earnings with the degree outpace your potential lifetime earnings that you could have made if you put your time to the best alternative use.

CMV: Adding extra ingredients to a grilled cheese doesn't make it any less than a grilled cheese

Inspired by /u/Fuck_Blue_Shells [post about grilled cheeses versus melts](http://np.reddit.com/r/grilledcheese/comments/2or1p3/you_people_make_me_sick/), I had to come to the defense of ingredients in grilled cheeses. Cheese elitists and provolone partisanship like this is what's tearing the country apart. > This entire subreddit consist of "melts". Almost every "grilled cheese" sandwich i see on here has other items added to it. Is my burger less than a burger if I add guacamole to it? Is my hotdog less hotdog when I add relish? No, of course not. We have food combinations that compliment each other, that take it to the next level. Mixing up the cheeses and breads are a great idea, I would encourage anyone to try that, but the thinking Fuck_Blue_Shells encourages keeps the grilled cheese decades in the past. > Adding cheese to your tuna sandwich? It's called a Tuna melt. Totally different. I agree with this. However, as with a lot of things, intent matters. Think of satire. Does Fuck_Blue_Shells watch The Colbert Report and think Stephen Colbert is a true neo-conservative? Intent is everything. I made blueberry pancakes this weekend. I didn't start calling them blueberry smoosh-breads. Chocolate chips, bananas, blueberries...put what you want in there, they are still called *pancakes* at the end of the day. If you make a tuna sandwich and just happened to put cheese on top, then yes, that's a melt. The cheese is an afterthought. A good grilled cheese sandwich can be constructed with intent and purpose to deliver the most mind-shattering mouth orgasm by knowing what tastes compliment each other. Gouda, apple and bacon on sourdough. It's no accident, it's no afterthought. The cheese (as well as every other ingredient) is on purpose. If I make pancakes and just throw blueberries on the top instead of in the mixture, that's not a blueberry pancake any more than a tuna melt is a grilled cheese, because *intent* matters. By Fuck_Blue_Shells' logic, using butter on your grilled cheese is a butter melt. Using a cooking spray to grease the pan is a cooking spray melt. > But as a bland white mid-western male I am honestly the most passionate person when it comes to grilled cheese and mac & cheese. As of this post, Fuck_Blue_Shells hasn't spread his culinary segregationist message to /r/macncheese. You'd better bet that's coming next. Beware you who adds bacon to their cheese and noodles! While I admire their passion, Fuck_Blue_Shells and his followers are merely propagating a backwards and anti-progressivism when it comes to what's on your plate. What am I eating, you ask? I am eating equality. _____ > *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!*

I think you are focusing on intent when the issues are actually flavor and texture. It doesn't matter how artistic you are or what you mean to make. It only matters what's on the sandwich. And certain foods change the character of a grilled cheese. Add tuna and the sandwich tastes of tuna. The cheese takes a backstage to that powerful flavor. In contrast, when you butter your bread you never find the butter takes over the flavor. Unless you had some potent baconbutter or tuna butter or whatever. YourGouda/apple/bacon melt might be tasty. But it doesn't taste like grilled cheese. The cheese isn't up front and ccenter because bacon is a divA. Also apple changes the texture completely. You may have the best intentions in the world, but at some point a sandwich stops being a grilled cheese. That point is earlier than gGouda/apple/bacon. It is further than 'butter the bread with margarine instead of butter'. The margarine might be aka dumber idea, but it doesn't take over the sandwich.

ELI5: how do they get water and sewer up to remote homes that are high in the mountains?

If location is really remote, you can provide water and sewer on-site. For water, drill a well, install pump and filter, and (ideally) monitor quality. For sewage, dig out a septic tank that slowly cleans water and releases it into soil, or have sewage truck come pump it out every once in a while. If water well is not an option (dry climate or polluted soil), you can set up a large water tank and refill it by water truck. If you really want connection to city water and sewers, it is possible but can get expensive. Water will flow uphill with enough pressure in the pipes, so you need a powerful pump, or even a pumping station every couple mile. Sewage flows downhill due to gravity, the issue is what to do if the house is low in the valley. Then you need a sewage pump that does not get clogged by poop and other semi-solids, and a pressurized sewage pipe

I don't believe there is an overarching meaning to life. CMV

I don't think there is some thing that humans were put on earth to do. All of the theories I've heard had to do with other people, religion, or egotistical 'we have to fix everything because only we can' stuff. I think that there is no reason for life, and that people should do what they want without worrying about whether or not they're doing what they are supposed to in order to fulfill some higher purpose. It just doesn't make sense to me for there to be some reason we're all here, or even a reason why each person is here. We're here because of evolution and a natural urge to procreate, and nothing else.

You could perhaps look into the philosophy of existentialism - Jean Paul Sartre et. al. His starting point was in agreement with yours: there is no *intrinsic* meaning to life. However, it is up to you to bring your own meaning to it. Say you see a mountain. Maybe you take it as a challenge to climb it. Maybe you want to study the rocks that form it. Maybe you want to take the perfect photo. This is the meaning you bring to it.

ELI5: How can animals that eat spiders for sustenance not get bitten inside their mouth/throat sometimes? (Or do they?)

(Disclaimer: I'm not talking about poison vs venom. I understand why the digestive system negates the toxin in the spider.) Surely things that routinely eat spiders such as birds, reptiles and rodents occasionally get bitten inside their mouths and throats just by chance? Is this death for those creatures or do they have some protection against this?

It's a pretty broad question, but the answer is generally: If the animal is part of their normal diet, they likely have some sort of defense that they evolved (e.g. the grasshopper mouse's body makes venom act like pain killer instead, letting it prey on scorpions and such) So they'd have a way to deal with venom and such, up to and including just shrugging off the bites of the live prey

Do cross-eyed people see the world in double and learn to operate that way? Or does their brain learn to process the image correctly?

I assume it's the latter because I doubt anyone's eyes are 100% straight/aligned, but in that case - when a baby is born cross-eyed, do they already know how to correctly interpret images, or do their neurons have to learn?

The first several years of a childs life is when the neurons are learning how to work properly. If it is severe enough, the child will essentially block out the image from one eye. They will see single, but it will be monocular. If it isn't fixed early enough in development, the eye that is ignored will never be able to see as clearly as the other eye.

CMV: I'm a nationalist.

_____ First off: I'm from Sweden (very relevant), I'm 20 years young and male (slightly relevant). Growing up in what is today a multi-cultural society I early started to notice that in many aspects of society Sweden turned for the worse following the inflow of strangers and the multi-cultural policy of our governments. Immigrants have constituted perhaps as much as 25% of all the people that I've had contact with in my life. They've almost exclusively displayed great disrespect towards my own people and have constituted around 80% of all criminals that I've ever met. Befriending many of them I've gained insight in their mentality and way of life and have realised that they harbour a great deal of conscious hatred towards Swedes and wish to take advantage of us; they vote for the left in order to gain access to welfare but are in no way socialistic towards us. But so far it's only personal experience. So I started to do research and found out that immigrants are overrepresented in all forms of crime - and the more severe the type of crime, the greater the overrepresentation. They are by far more likely to make a living from welfare money than Swedes are. They are by far more likely to vote for the left. Their neighbourhoods are more dangerous and degenerated than the Swedish neighbourhoods. They are more likely to be religiously fundamental. They're more often involved in corruption scandals. And they are more likely to be racist, which gives the irony of multi-cultural Sweden being more racist than old homogenous Sweden - and in a sort of way kills the argument of nationalists being the racist side. My conclusions are that Swedes need a country where they constitute the vast majority and where the Swedish culture and the Swedish language predominate. I believe that patriotism is needed in order to contribute to the self-esteem of the people. I also believe that we should be open to a certain number of immigrants - regardless of background - who assimilate to our culture and wörk. In short, I want a nation state open only to natives, and to immigrants who adapt and show respect. EDIT: I have a very troublesome computer so I'm going to have to ask all of you to be patient, since it might take time for me to answer. EDIT2: Many have argued - falsely - that I claim that Swedes are superior to others. That is not true and I don't know how people get that idea. I might need to clarify myself and say that I argue that cultural homogenity is necessary for a stable society where people feel responsibilty to each other. EDIT3: Wow! 203 comments so far. I'm overwhelmed by the interest shown in this :)

Socioeconomic status, not ethnic background, is the determining factor on most of the trends you are talking about. Immigrants to any country are switching countries for a reason, and thus are usually of lower socioeconomic status. It's not because of where they are from.

ELI5: How does it hurt someone to be over-qualified for a job?

I'm planning to get my PhD, but I'm not entirely sure what I want to do for a career. I'm worried that having a PhD would make me overqualified for other jobs. I've often heard that this happens, but I do not understand why. If I have a PhD in one subject, but pursue a career in an unrelated field, will my PhD hinder my chances of getting that job?

The employer may feel that your high qualifications mean you won't be satisfied with the job, perhaps due to it being insufficiently stimulating. This might lead to you looking for other jobs and quickly quitting the old one. The employer wants to avoid hiring an employee who will leave shortly, because then they would have to go through the application/interview procedure again which wastes time (edit: oh, and money, of course). So they don't hire someone that they think will want to leave very quickly.

What do divestments in Russian assets acheive?

Norway's sov wealth fund now says it will also divest of Russian assets. But does this do anything to harm Russia at all economically? Doesn't it just mean potential Russian buyers could buy shares for a lot less than their original value, while at the same time giving them more control over their own nation's organisations? And in any case, is it even possible to offload such a large amount of assets? Who can afford to buy multiple billions of dollars worth of shares right now?

It affects their ability to raise capital in future. Imagine there’s the total supply of Russian assets and total demand for Russian assets. If one group of investors divests and no longer demands Russian assets, that has to be absorbed by the remaining pool of investors. As with any demand shift, you’d expect a price reduction and a quantity reduction. As the existing assets can’t cease to exist, the reduced quantity comes via crowding out new investment.

Trying to reverse engineer POST requests, how do I 'catch' them?

I can see the response in Developer tools, but I can't see the POST request being sent. Do I really need to MITM myself to see this?

You should be able to see the contents of POST requests in dev tools. Assuming you're talking about Chrome, under the "Headers" tab of the request detail, there should be a section "Request Payload" which contains the request body.

ELI5: why do you get the pee shivers, and what's going on to make your body do that?

Pee shivers. What's the deal?

I've asked this question here before and have yet to find a suitable answer. Edit: Did google search. The following is courtesy of Mental_Floss. The most plausible one, espoused by a number of scientists who aren't this guy, is that the shiver is a result of two parts of the autonomic nervous system (ANS) getting their streams crossed. The ANS is a control system for involuntary muscles affects things like heart and respiration rates, digestion, body temperature control and urination. The ANS has two divisions. The sympathetic nervous system (SNS) controls bladder function, among other things. It keeps the bladder relaxed and the urethral sphincter contracted so you don't have to concentrate on not peeing your pants all day. The parasympathetic nervous system (PNS) relaxes the urethral sphincter and contracts the bladder when you decide to answer nature's call. Part of the SNS response to a full bladder is the release of chemicals like catecholamines (which include epinephrine, norepinephrine and dopamine). When you finally grab a minute to urinate, the PNS takes over, and catecholamine production changes. Some sources point at the change in chemical production as the cause of the shiver, and others say it's the SNS to PNS switch itself that does it.

ELI5: Why do fruits like pinneapples and kiwi leave a rough feeling on the tongue?

Human skin contains oils which aid in blocking out the absorption of chemicals which would harm or irritate the skin. Those oils contain proteins. Pineapple contains a chemical compound called bromelain which has the ability to break down these proteins. This enzyme is called a protease. Kiwis also contain a protease called actinidin. Because these enzymes readily breaks down proteins, bromelain is frequently used as a natural meat tenderizer. In addition, they may also induce a prickly sensation in the mouth when consumed. In pineapples the enzyme is present in all parts of the plant, it's most concentrated in the stem, the hard piece in the middle of the fruit, which is much more fibrous and chewy but still edible.

[General Superhero]What would the medical term for super powers be?

Like if I were filling out a patient form at a doctors office, how would the question asking if I had any super powers be worded, and what would the actual medical condition be named?

For arbitrarily complex medical language, it's going to depend entirely on the mechanism by which your powers were attained. Which of course depends entirely on the universe. Mutants, Metas, aliens, supers, etc. A couple of universe-agnostic possibilities: Have you ever been a participant in an event that granted you para/extra/trans-normal talents or abilities? Are you a member of a para/extra/meta/trans-human species/subgroup? Have you ever been altered on a genetic level? Are you human?

Difference between exploratory and confirmatory factor analysis

I tried doing research/ readings but I'm still pretty confused. Any explanation would be very helpful.

Hello! An EFA is for finding the factor structure of a set of items. A CFA is for confirming that factor structure. So let's say you developed a new measure of say...depression. You get like 500 people to take the measure and conduct an EFA on their responses. You learn that there are apparently 3 factors underlying the data, so you then review the text of the items to see what the common theme among each factor is - let's say sadness, lethargy, and ideation for argument sake. This process will also tell you which items are not good and should be culled from the measure. Then, you would collect ANOTHER sample of about the same size using the items that fit well from your EFA except this time you impose the factor structure you found from the EFA onto the data instead of telling the software to "find" the best factor structure. With CFA you are asking it to tell you how well the factor structure from your EFA fits the data from your new sample. If it fits it well you would say you have "Confirmed" the factor structure, thus CFA. Hope that helps!

ELI5: Why do computers start to slow down over time?

There's many different things at play here, but here's just a few. First and foremost, your software programs become more demanding over time, while your computer's physical hardware stays the same. As software is updated and made more complex, your hardware falls behind because it's still the same old hardware running new and more complex software. Another major factor is *how much* software you've installed over time. Lots of programs run automatically when you start your computer, and many users have a tendency to install many programs over the years and never uninstall them. They build up over time, and eventually your computer will have to launch a couple dozen programs every time you turn it on, and keep them all running in the background while you use your computer. There's other more subtle factors as well. Battery powered devices like cell phones are often designed to intentionally slow down as the battery ages, to prevent situations where the old battery can't supply enough power to drive the phone. If you've seen an old phone that randomly turns off even though it still has some battery remaining, that's what happens when the battery can no longer support the device at its full speed. Devices with cooling fans such as laptops, computers, and gaming consoles also fall to another culprit -- dust. Over time, dust will pile up on the cooling vents and block the flow of air through your fans. This makes it harder for your computer to stay cool. Over time, as your computer gets hotter and hotter, it will start to slow itself down to prevent heat damage to its components. This is especially common with gaming; cooling is very important because the computer is working very hard.

What advancements could quantum computing provide for future videogames?

Would CPUs and GPUs be more powerful, resulting in realistic game physics and unlimited AI? What other effects could we potentially see? I'm new to the ideas and potential of quantum computing.

Quantum computers produce probabilistic results. That is, if you ask it to add 2+2 you might get something close to 4 with error bars. Software written for a normal Turing machine (e.g. Crysis) probably won't ever transition well to a machine that is technically bad at basic math. Quantum computers are not even currently particularly fast and do not threaten encryption through raw power. They also can't really check every possible outcome at once, although Grover's algorithm can do something sort of conceptually similar where it checks O(N) possible encryption keys in O(N)^1/2 operations. Unless you are doing specialized math or cryptography and you're okay with a small chance that your computer will give you the wrong answer, then you probably don't ever want a quantum computer.

Why can't we make the 9 essential amino acids?

From what I understand, other organisms can synthesize them so where along the evolutionary period did we lose this ability?

The exact point at which our ancestors lost the ability to synthesize the amino acid is going to vary greatly between each of the nine essential amino acids, but the basic concept is the same for all of them. TL;DR: Our ancestors got sufficient quantities of them in their diet. If a species partakes in a diet that supplies it with enough of an amino acid, then there is no need for the organism to synthesize it, and in fact it becomes wasteful for the organism to be producing all the biological machinery it needs to synthesize that amino acid. So, there is no downside to not synthesizing the amino acid, and a slight downside to synthesizing it (Side note: it's always amazed me how such slight advantages propagate so readily throughout a population over the generations). As tends to happen, the organisms with the slight disadvantage have less chance of surviving and reproducing than the ones without that disadvantage, and eventually all members of the species lose the ability to synthesize the amino acid. Edit: Read /u/EvanRWT's comment about a far more likely way that such slight advantages become so widespread.

ELI5: How did Walmart become so successful?

Did it use the government to pass laws that helped it expand/corporate welfare, or does it have nothing to do with any of that?

They buy in bulk, make incredibly good deals with manufacturers, move into growing areas that are ripe for their business model, when economically feasible instead of buying from a supplier they buy the supplier, own the land their businesses sit on(mostly) and own their own shipping company. By keeping everything in house they dominate. Having unending capital can do that for you.

Eli5 why foam is always white, regardless of the color of soap or detergent?

Whenever light goes from one transparent material to another, some of the light is reflected off the surface. You can see your own reflection in a glass window. Foam has *lots* of surfaces like this, all the walls of the individual bubbles at different angles to each other, so the light goes in, bounces off the surfaces like crazy, and comes out in random directions. So what we see is white, because the scattering effect from the bubble walls is so much stronger than the absorption from the liquid's natural color. The light bounces back out of the foam before it can go through enough liquid to affect the color. You see the same thing in other situations. Crushed glass turns from clear to white. A crushed hard candy turns from a clear bright color to a pale pastel powder. And if you do something to *reduce* the amount of scattering off the surfaces, the material will become clear again. Pour water onto glass powder and it becomes clear, because there's less reflection between the water and glass than between air and glass. Pour oil onto paper and it becomes translucent.

Does isotopic abundance differ enough on the various planets enough to think about producing planet specific periodic tables?

So the relative atomic masses on our periodic table are earth specific. Would there be a significant enough difference in isotopic abundances from Earth to warrant a change in these reported masses for that planet or moon?

The periodic table is really just a guide; anyone doing real calculations should have some idea of the isotopes (or distribution of isotopes) that are involved, and they would adjust the numbers accordingly. Furthermore, the mass of the elements on the periodic table isn't really a critical part of the periodic table. It's added there as an extra piece of useful info. The periodic table is characterized by its order by atomic number and arrangement of the rows to maintain periodic patterns.

ELI5: What exactly is a watershed and how does it work? For instance, we live in the Chesapeake Bay Watershed area. I have attempted to read on the subject, and consider myself a smart gal, but this just confuses me all day.

Thanks

Pick a spot on the ground. Imagine that a raindrop falls on that spot. Imagine that it doesn't soak in, but it runs downhill. Which way will it go? Trace its path. Eventually, it will flow into a stream. That stream will flow into a bigger stream, which will flow into a river, which may flow into a bigger river, and so on, which will eventually reach the sea. The last river will have a name; let's say it's the Mississippi. That means your original spot was part of the Mississippi watershed. Sometimes large watersheds are divided into smaller watersheds named after the various rivers that flow into it; for example, the Mississippi watershed may be divided into the Ohio watershed, the Missouri watershed, and so on.

ELI5: Carbon makes steel strong. But why does too much carbon makes the steel brittle?

Carbon is added to steel to increase its strength and hardness but why does too much carbon makes it brittle? Can some explain in terms of the iron crystal lattices ?

Metals have crystals. The atoms in the metal form these grids with space in between. Regions inside metals all with the same pattern and orientation are called grains. A single metal can have many small grains or it can be few large grains Defects in metals form inside these structure at grain boundaries. Where the crystal faces one way and then suddenly a different crystal faces another, cracks form easily. Imagine a metal sword made of two grains. The boundary runs across the sword the short way, through the middle. If the sword gets hit, the crack only has to start there to make it all the way across the sword through the shortest path possible. Compared to an iron atom, a carbon atom is very small. These atoms can get in between iron atoms and force new grain boundary patterns to form around them. So if there are a lot of carbon atoms, the grain boundaries are very small. Like the lines of a jig-saw puzzle, cracks have to jog around all kinds of grain boundaries to make it all the way through the metal. No single crack can follow one grain boundary all the way through. If there are too many grains because they are super small, the metal becomes weak in a new way. It becomes soft and more malleable because of all these small slip interfaces.

ELI5: Why is Finnegan's Wake considered to be such a classic of English literature, when it's completely incomprehensible and scholars can't even agree on what the plot is?

I mean really, here's the whole book - http://www.chartrain.org/PDF/Finnegans.pdf - what the hell?

Some literature is interesting not for its themes, popularity, or plot, but because of the way it uses language and explores the English language and the written medium. Finnegan's Wake is interesting precisely *because* it's (almost) completely incomprehensible. Think of it like Marcel Duchamp's urinal, submitted to an art competition. The urinal is, of course, not beautiful, nor of any civic value, and displays no great skills of the artist. But in the absurdity of submitting a urinal to an art competition, Duchamp challenges traditional ideas about art by taking the typical discussion of what art is to an extreme conclusion. Finnegan's Wake, like Duchamp's urinal, is *interesting*. That doesn't mean it has to be *enjoyable*.

CMV: We raise children to embody "good" personality traits, but society heavily rewards "bad" behavior. In essence, by trying to raise our children to be good people, we are ultimately setting them up for failure.

NOTE: I would like to preface this by saying that we should NOT change what we preach, but I believe that society needs to stop rewarding liars, cheaters, and manipulators, and instead, needs to start rewarding the "good" behaviors that are supposed to make us better people. We frequently hear about how the rich are getting richer at the expense of the poor, how rich people are jerks or sociopaths and that's what made them successful, how some company lied through their teeth and broke a dozen laws to make a ton of money and then didn't get penalized for it, how people with power are becoming physically abusive to those without it, or how corrupt businesses and politics in general can be. These things are constantly in the news, and people wonder why the little guy can't catch a break. We try to be good people. We work hard and do our best, and yet somehow it feels like we always get the bad end of the deal. While "good" and "bad" are open to individual interpretation, people who adhere to the personality traits that we were told to embody as children are usually seen as good people, but instead of being rewarded for it, they're often punished for it. 1. Be kind = Get walked on, used, & abused - If you stand up for yourself, you're seen as being "mean". 2. Have a positive attitude and only say positive things = Don't stand up for yourself or address a problem, even if presenting a solution. Negativity is unattractive (see #1) and people don't like problems OR messengers. Instead, just ignore them and hope that they go away, even though they won't, and will only continue to get worse over time. 3. Be a hard worker and have a good work ethic = Pick up the slack and extra work for all of your coworkers and boss without any sort of thanks or compensation. You don't like that? Refer to #2. 4. Be good at what you do = There are lots of people who are good at what you do, so spend all of your time, even personal time, trying to be even better than all of them. You won't be compensated for it, but refer to #2 and #3. And never forget - there are a million people who can take your place, and your company is willing to pay your replacement, even if they won't pay you. 5. Do a lot of things = #3 + #4 x ? number of roles, and all so that no one has any idea what you actually do, so you'll be phased out. 6. Be a team player = Let your bosses walk all over you and your coworkers take credit for your work. 7. Respect your elders = Do what you're told without thinking so that they can yell at you for having a mind of your own AND for not thinking for yourself, and let them abuse you in general, because they've earned it by putting up with other people doing this to them for longer than you have. 8. Listen to those who know more than you = This is entirely based on the perception of the person giving you this advice, and therefore includes people who know nothing, and lie to you constantly about their knowledge. And of course, question nothing at all, because how much do you REALLY know? 9. Trust others and give them the benefit of the doubt = They will betray you, because they know that they can lie to you and you'll believe them. 10. Tell the truth = ... so that people can (possibly purposefully) misinterpret and get offended by every miniscule thing that you say, even if it is straight fact, so you can be seen as "unprofessional" for not towing the company line, and you can be fired for offending someone. 11. Don't lie, cheat, or steal = Give everyone else an unfair advantage, because you're "better" than them somehow by adhering to "good" behaviors that you are not in any way shape or form rewarded for. 12. Don't manipulate people = Good luck finding a customer-facing job that pays a livable wage, and definitely don't even think about standing up to your bosses or coworkers when they're trying to manipulate you, because they'll accuse you of manipulating them instead. 13. Be supportive and put others first = Make everything about everyone else and ignore your own needs. Hopefully if you only focus on them, they'll like you, and maybe one day they MIGHT care about something that you need... maybe... There's a reason that people say, "Nice guys finish last." You don't have to be a bad person to succeed in life, but being a good person makes it significantly harder, if not almost impossible, unless your personal definition of success is simply "to be a good person". That's not to say that we shouldn't teach our children to embody these traits, but we should start rewarding people for these traits instead of manipulating and abusing them and throwing all of our opportunities and money at fads and people who are already successful. If the good people don't stand up for other good people, who will? Edit: I sincerely apologize for this, but this view was created in the US based on US society. I realize that things can be very different elsewhere, and I should've mentioned this at the beginning. :)

Aristotle, the Greek philosopher, taught that virtues are the balancing point between two different extreme vices. For example: Courage is the balancing point between cowardice and foolhardiness. Generosity is the balancing point between profligacy and miserliness. Hope is the balancing point between delusion and despair. If you are not teaching your children that any virtue, taken too far to any one extreme, becomes a vice, then you are not teaching them very well. If you are not preparing children to face and cope with the unscrupulous and evil people in the world, you are not preparing them very well.

[Fight Club] When Tyler is present, who is in control of the body?

First, I know I'm breaking the first two rules for posting this. Kind of a simple question, when Tyler Durden is around who is actually "in control" of the Narrator's body? Does it change depending on context? When the Narrator is having a conversation with Tyler do they switch control depending on who's talking or is it more like just one is a voice in the other's head?

Whenever there is an action taken that is observable by others *and* has physical effects, it's the person doing that action that is in charge. For example: Jumping on Lou, Tyler. Destroying something beautiful, Narrator.

ELI5: Legally, if we have the right to bear arms, why can't we own bazookas, machine guns, anti aircraft guns etc?

In most states you can, it requires a Federal and State firearms license, and if you do enough selling or trading a business license. Most people who do own heavy weapons tend not to advertise much to avoid being ripped off or having a demonstration 24/7 on their lawn. But bazookas and many AA guns are considered antiques as well as fire arms, making them even easier to buy.

ELI5: Everything has Sodium Laureth Sulfate in it. What's the real difference between hand soap, shampoo and body wash?

Sodium laureth sulfate is what is called a wetting agent. Together with various chemical compounds that break surface tension and make emulsions, it becomes very effective at making the soap bubbles and lather. The thing about hair and skin is that it is hydrophobic, so water can't really rinse off dirt and grime as easily by itself. Adding sodium laureth sulfate helps correct that problem. The differences between those soaps would be whatever main ingredients, additives and moisturizers they want. Sodium laureth sulfate is not the ingredient that determines what area of the body it is for. It just boosts the cleaning power of everything.

Out of all alkali metals, why is it that Lithium used in batteries? What makes it supperior to use over other alkali metals which have properties alike.

As the title says. I am trying to understand, but I can't find anything on the internet. I'd really appreciate if someone who knows the answer would explain to me. Lithium is supposedly the least reactive out of all the alkali metals. It has one valence electron, which is willing to release to another atom. But so are all of the other alkali metals. They all have one valence electron. I don't know why or even if lithium has any advantages over other alkali metals. If yes, what are they? Please help me out reddit! Have a good one

It has the smallest atomic size, which is useful in terms of the power-to-weight ratio and for maintaining a high kinetics efficiency and low damage potential when physically moving the ion through a solid-state electrolyte.

ELI5: the difference between variance and standard deviation

Thanks to everyone for the guidance. It may not seem like much to some of you, but it has been a huge help to someone who is getting off the ground in this area.

Standard deviation is the square root of variance. Variance is used in calculations because it makes a lot of maths easier - a lot of things like error propagation are done in quadrature (i.e. on the square of the values). Standard deviation has the big advantage that it's got the same units as the original data so you can more easily interpret what it means.

ELI5: When swiping a card, you would think if you swipe slowly the machine could get a better read and accept your card. Why is this not the case? Why do you have to swipe it fast?

A magnetic stripe readers operates by listening to a magnetic field for changes created by the passing card. A card moving faster creates what could be described as a "louder" "message". Ideally, a consistent, swift swipe produces the most clear "message" for the reader to pick up on, and it is also generally easier to maintain a more consistent card speed when the card is moving over the read head faster.

Why are some skills perishable, while others are not?

Last evening I was reading a book, and it said something along the lines of 'unlike riding a bike, piloting an aircraft is a perishable skill.' This made me wonder: why are some skills perishable if we don't make use of them, while others, such as riding a bike, are things you can pick up even years later?

Some skills are motoric coordination - like riding a bike, and others are cognitive processes, like what button to push when while flying a plane. Motoric skills become hard-wired in your brain, you actually build the necessary structures that connect certain balance-governing reflexes with certain repetitive movements, like pushing the pedals while keeping the bike upright. Your entire body learns this process and it remains in your neuronal structure. Cognitive skills are basically knowledge becoming routine, so while you are doing it regularly, it becomes less and less cognitively effortfull to accomplish. If you stop doing it, however, you begin to forget what needs to be done when. Also, once you learned to fly a certain type of plane, fly it for about 5000 hours in total (over a period of some years), and then stop flying it for 10 years, if you got back into the cockpit of such a machine, you'd still remember quite a bit and would only need to "refresh your memory" for a relatively short time before being good to go again.

Why do some programs require a specific version(s) of Windows or Mac OS, but some don't?

Some programs might require Windows 7, others 7/Vista, and others 7/Vista/XP. What causes these programs to require specific versions, and why do some seem to not?

There are typically two reasons for this: **Programmers make assumptions** For example, in the Windows 95/98/ME days, any program could modify any file anywhere, so many Windows programs wrote their settings to c:\program files\app name\settings.ini or something similar. When Windows NT/2K/XP/etc. came out, programs were only allowed to write to places their users had permissions to write to - and c:\program files\ is not one of them. As a result, many programs stopped working. This can be circumvented by running the program as admin, but that has two issues; first, it's less secure. If there's a bug in the program, it can make any changes it wants to your system. Secondly, in a lot of environments (e.g. offices, schools, large enterprises, libraries) users don't have the ability to run as administrator, meaning they can't use these programs, they'll crash randomly, they won't save their settings, etc. **OSes change** Windows goes to a lot of trouble to keep things working whenever possible, but bugs still get fixed that app developers assume are ok. On Mac OS, Apple is almost militant about getting rid of old code in favour of new code. If Apple adds a better way of doing things in 10.6, then the old way will often be 'deprecated' (meaning that developers are told not to use this code because it will be removed) in 10.7, and it will be removed entirely in 10.8. This can cause problems in one of two ways; first, old apps that don't get updated will continue to run on 10.6 and 10.7, because the old ways of doing things still exist, but will not run on 10.8. New apps that are written from scratch (the proper way) in 10.7 will continue to work in 10.8 and onward, but will not run in 10.6. **Notes** Good developers are able to mitigate these issues by detecting which version of the OS is running and using the old or new ways depending on which is available, but this can be a significant amount of development work, and can introduce subtle bugs. Also, there is often a very clear signal 'which way the wind is blowing', and developers can update their apps long before there's an issue (if they have the developer time). Bad developers are especially prone to these issues. Most problems can be solved by writing code the way that Windows is designed to work, using the correct built-in functions instead of writing your own, asking Windows where to put documents instead of picking an arbitrary location, and so on. Bad developers are lazy, and instead of writing four lines of code to figure out where the documents directory is, will just use the app directory instead. They'll write their own functions because they're too lazy to look up the documentation to see if there is already a function to do what they're trying to do, and when they write it themselves they'll miss certain cases (e.g. what if the system language is in Hebrew? What if the timezone is different? What if the Windows directory isn't in c:\windows? They assume everything will always be the same as what they have and when things change in subtle ways, problems happen.

ELI5: Please explain how first, second, third and so on cousins work?

Also what does ‘once and twice removed’ cousins work in that context?

brother/sister - same parents 1st cousins - share grandparents 2nd cousins - share great grandparents and so on. Removed is by generation downwards. The children of your first cousins are your first cousins once removed. The grandchildren of your first cousins are your first cousins twice removed.

ELI5: What is oxidation exactly?

Oxidation is the process by which an atom or molecule loses electrons in a chemical reaction. Since this happens pretty much any time oxygen reacts with something and oxygen reacts with lots of things easily (see: burning things) the process got the name "oxidation."

[Star Trek] The Tamarians can only speak in metaphor, how did they develop warp drive?

A key element of working as a team (which presumably researching, developing and building a warp drive would require - along with all the preceding developments that enable it) is effective communication. Speaking only in metaphor, how did the Tamarians manage to build effective teams? Further, since their metaphoric language depends largely on historical reference, how do we get from the "first" reference to the second and so on, in order to construct a language capable of expressing enough information to build anything? Where did the words come from in the first place? A society which can only look back must surely not be able to move forward.

1) Math is seperate in their language. While they do not have direct words for numbers and operations, there is a system that is musical in nature (whistles and such) that can be used for math complex enough to develop Warp drive. 2) Children are taught language in school similar to Federation children, except teaching tends to consist of "plays" that bestow the meaning of more complicated phrases. 3) Their brains are fundamentally different from human brains and tuned to both understand and more importantly remember a vast number of such "metaphors". 4) Many people who learned English (or another language that uses Latin or similar letters) wonder how children of Asian cultures can remember such a vast array of characters to write with. The difference between Tamaranian language and other Humanoid species is similar.

How does one market a philosophy major?

My 'primary' major is biomedical engineering. I'm 2 courses short of a double major with philosophy, but I have a minor in philosophy pretty well secured. I'm trying to justify taking the two extra courses I need in order to get the major. If I didn't take these 2 philosophy courses, I could instead take two graduate level BME courses. On the surface, it feels hard to justify taking some philosophy classes over the tangible skills that I could gain from the graduate level BME classes. My BME advisor has strong opinion in favor of BME (unsurprisingly). I want to get the major, but its mostly because it feels personally important to me. I feel like the double major with philosophy and BME really accurately reflects my identity, in that I am passionate about both topics and I am able to sort of bridge the gap between humanities and engineering. But, it feels hard to justify on that basis alone. If I had a clear way of marketing degree, I would feel a lot better. I'm doing my concentration in ethics, which is good because that's probably most relevant to medicine. I also do genuinely think that the degree is valuable, in that it has improved my critical thinking skills. The problem that this advantage feels to vague to be able to really sell - if an interviewer asked me why that will be useful in my role as an engineer, I have a hard time coming up with any really clear examples of how philosophy could give me better critical thinking examples in this setting. So, how do you market your philosophy major?

IN your position, you could argue that your double degree gave you 1) analytical skills not typically learned by engineering majors, that would be very useful when interacting or leading a team, and when interacting with clients, and 2) gave you insights into ethics unmatched by most other engineers.

I’m reading Will Durant’s “The Story of Philosophy”. What should I be aware of?

I’m new to philosophy and was recommended lots of starting points. I went with Will Durant’s book. I’ve been told there are flaws and biases in every “history of philosophy” book, be it Russell or Kenny, so I’m wondering if there are any glaring problems with it that I should know of. Or anything it doesn’t cover that I should look into myself?

The Story of Philosophy is quite an accessible introduction to the discipline. Just know that Durant wrote in the early 20th century, so obviously, a lot of philosophers who came after the book was written are not mentioned. In addition, one can question the philosophers that he picks. There's no mention of the earliest Greek philosophers prior to Socratics, and while the inclusion of Francis Bacon is commendable, he leaves out Descartes, the father of modern philosophy! He also leaves out Hobbes, Locke, Hume, and Rousseau, while Hegel is reduced to a critical footnote at the end of the chapter on Kant. There's an entire chapter on Herbert Spencer (who is neither a good nor an important philosopher), which could have been replaced by one on either John Stuart Mill or on Kierkegaard. That said, it's unreasonable to expect an introductory book to have everything on everyone; such a book would be a massive and unreadable tome. Durant's book is as good a starting point as any other. It's good that you are aware of the biases of different authors. The more books you read, the more you will get a better picture of the different philosophers and schools of philosophy, and how they are characterized.

CMV: The solution to Adblock is more entertaining ads and/or better targeting

A lot of people run adblock. It sucks for content creators. That much is pretty obvious and I think we can all agree on. That being said, I'm generally a fan of targeted advertising. For example, I tend to hang out a fair amount on /r/buildapc and related subreddits, so when I'm watching a twitch stream and an ad for a new motherboard comes along, I'm OK with that. I'm not OK with getting an ad for laundry detergent. In Spanish, which I don't speak. I already tend to whitelist channels or sites I care about, but I think having better targeted advertising would make more people likely to whitelist more things. On the entertainment end of things, I know the advertising agencies are capable of some really entertaining stuff. If every ad was of comparable quality to, for example, the Old Spice ads with Isaiah Mustafa, there would be a lot of times where I'd be stoked for an ad break, because I'd probably have myself a bit of a chuckle. So in broader terms: don't want people running adblock? make ads that people want to watch, and serve them to the people who want to watch them. Edit: I'd like to add that a lot of people are pointing out potential privacy implications. I totally understand why other people worry about that, but I don't, so that will not be an effective path to Cing my V. _____ > *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!*

One of the key complaints against targeted advertising is that it often leads to tracking your online habits in order to deliver topical content. Many people are uncomfortable with that tracking as a perceived invasion of privacy. Are you ok with the trade off in privacy in order to see more topical adds.?

ELI5: why are smart people more prone to depression?

Smart people, by nature, have more of a realization (or understanding if you will) of the world and how it works. As well, smart people have a bigger ability to conceptualize things that might happen ("What if?"), and will see more inherent dangers of the world. Then, as mentioned, there's a certain disconnect people have, mentally, when they can't interact with others socially on their own level. Truly, the more knowledge and wisdom one has, the more sorrow and grief that comes with it. Pair that with the realization of how truly vain the world is in so many ways (which comes with being "smart" after a while), and the depression and loneliness comes. Simply for not "fitting in" as it were.

ELI5, why if you jump inside a moving train you will land on the same spot, but if you jump on the roof of a moving train, you land on a different spot?

seen it on twitter and I can’t get my head around it EDIT: thanks guys I get it now 😅

In most cases you'll see in high school physics, both should give the same result. But there is a big factor that high school physics (and depending on your field, uni physics) igbores: air. When you jump inside a train, the air inside it is moving along with the train as well. But the air outside of the train is still with respect to the ground, or moving with the speed of the train, in the opposite direction, with respsect to the train. The air then pushes against you, and when you jump, it blows you back. Of course this depends on how fast the train is going, and how strong the wind blows (and in what direction), but in general, that's what happens.

Aren't some experiments very hard or expensive, and thus not reproducible? Why isn't this a problem?

One of the tenets of science is the idea that experiments should be replicated to be verified. But some experiments are too complicated to be so. Giant expensive experiments like the LHC, or complicated ones like the Phoenix landers, experiments that depend on a given political will like the collecting of moon rocks, some things that are sheer luck like finding the Antikythera mechanism and maybe even some truly opporunistic experiment like the Voyagers that depended on a very precise planetary alignment to get their slignshots – those are things that are probably not being replicated, or at least not in the exact way. We sent other probes to mars and the outer solar system, but never to the exact same spot the previous ones were ("yes we don't see those Voyager bubbles but maybe they're there and not here"). So what happens when one of these experiments come up with some incredible piece of data? How can scientists assure themselves this wasn't a fluke, a experimental error or the aliens playing a prank on us?

So the trick with particle colliders, is that you generally build two or more experiments simultaneously. RHIC has STAR and PHENIX still operational, LHC has ATLAS, CMS, ALICE, LHCb all running simultaneously. That's how we "verify/reproduce" the data. Recall a few weeks ago, the hubbub over the mass bump in the CDF experiment at Tevatron. They claimed it was a bump in the data approaching 4-5 sigma over background. But the sister experiment at the Tevatron, D-Zero, did not find the bump, so it's likely to be improper background subtraction/error etc. And finally, each time we build new experiments we reproduce the old data. LHC has been "recovering the standard model" in its initial turn-on. Reproducing results that other detectors have seen before it.

Instead of breathing would it be possible to just oxygenate our blood?

Like instead of breathing through the lungs, just directly oxygenate the blood and have it enter the blood stream.

This is what is done during some heart surgeries, using a heart-lung machine to mechanically oxygenate the blood. It takes venous blood out of the patient and passes it along membranes to oxygenate it, then reconnects to the patient's arteries. However, there are complications associated with using a machine to do imperfectly what our lungs are very good at. Studies have shown that many patients who have been on a heart-lung machine suffer minor brain damage afterwards.

ELI5:why is it harder for weed smoke to set off my fire alarm compared to a little smoke from my burnt grilled cheese sandwich.

There are two types of smoke detectors: optical and ionizing ones. I don't know if ionizing smoke detectors have a harder time detecting weed smoke than sandwich smoke, so I'll focus on optical smoke detectors, which are more common in households anyway. Optical smoke detectors have a light barrier inside of them. If smoke particles enter the detector, they reduce the amount of light that reaches the end of the light barrier. The smoke from your burnt sandwich contains alot of soot, which has lots of big molecules. It's pretty easy for a smoke detector to detect these. Your weed burns relatively cleanly and doesn't contain as much big particles as the sandwich smoke.

ELI5: Whem pouring liquid from one container to another (bowl, cup), why is it that sometimes it pours gloriously without any spills but sometimes the liquid decides to fucking run down the side of the container im pouring from and make a mess all around the surface?

Might not have articulated it best, but I'm sure everyone has experienced this enough to know what I'm trying to describe.

Surface tension. Water wants to stick to hard surfaces. This is what causes a meniscus in a test tube, for example. That "u" shape at the top of the water. The attraction between the surface and the water molecules is stronger than the attraction of the water molecules to each other. So, when pouring, the force of the gravity on the water needs to overcome this surface tension to pull the water away from the container. When the angle between glass wall and vertical direction is small, the component of gravity perpendicular to container wall is small and surface tension is stronger, causing the water to stick to the container and run down the outside.

ELI5: Why do so many people believe that if your urine isn't clear you aren't drinking enough water and is there any truth to it?

To understand this, you have to know why we have urine at all. Your blood has to have a very precise chemical balance for your body to be able to work. If it's off even a little bit, you will get sick and eventually die, unless it's corrected. Your kidneys have the job of doing the corrections. They work by filtering out any excesses, returning blood that is chemically "balanced", and they are very good at it. The stuff they filter out is basically urine. The most important things filtered out are extra water, extra salt, and urea, a chemical produced continually by the body. Another chemical filtered out by the kidneys is urobilin, which makes urine yellow. Removing certain amount of water is necessary to the process, whether your blood has excess water or not. If you are dehydrated, meaning you have not been drinking as much water as your body needs, your kidneys will do their job by removing the bare minimum amount of water to get the other stuff out. That means the urine will be concentrated. Think of it as being like strong tea. Because everything including urobilin is concentrated, its color will be dark yellow. This is actually normal first thing in the morning because you don't drink water while you're sleeping. During the day, it's a reliable sign that your body could really use more water. But it doesn't have to be clear for you to be healthy; a well-hydrated person's urine will still be light yellow unless they are drinking much *more* water than they need.

Can someone explain the concept of gravitational potential between 2 masses?

I am struggling with the concept of gravitational potential. I know that by definition it is the work done in moving a unit mass from infinity to a point in the gravitational field (GPE per unit mass), but I don't truly grasp what this means and its significance. I also don't really get how gravitational potential is defined between 2 bodies, such as the earth and the moon. If we talk about bringing an object from infinity into the gravitational field of Earth I can visualise that, but how do you define the potential at a point where 2 fields act (such as that of the moon and the earth)? Where is 'infinity' in this case? Is there a point of 0 potential between the 2 bodies, where essentialy the strengths of the gravitational fields are equal and there is no resultant force on a body at that point, so no gravitational potential? I am only doing A2 physics (pre university) so a simple explanation will suffice.

The "brought in from infinity" thing is useful mathematically but can be confusing physically. The gravitational potential between two objects is basically how much *more* energy they have if they're far apart than if they're touching (not exactly a technical definition). So you can have an object on the Earth and raise it to some height, and that object gains gravitational potential equivalent to the work required to raise it to that height. You can do the same with the moon, consider how much work would be required to raise it from the surface to the height of its current orbit. That is the gravitational potential of the moon in this scenario. Because only the *difference* in potential between two points matters, you can set the "zero" to be anywhere you want. For things falling near Earth's surface, it's useful to treat the surface as being at zero potential, while for mathematical reasons it's useful to treat "infinitely far away" as the zero point for celestial dynamics.

ELI5: What is Dialectical Materialism?

A dialectic is an interaction between two things, sometimes opposites. Materialism is a method of reasoning that primarily believes objective reality exists without any observation, that the person observing doesn't create the object they view. One consequence is that a materialist has to seek the truth as a thing outside themselves rather than trusting that their subjective view of reality creates the truth. Dialectical materialism is a way to parse reality through looking at new information in relation to what you already knew, two sides of the dialectic both related to observing objective reality. The usual formula is hypothesis plus antithesis equals synthesis, but its less formal than that in practice. A common example of dialectical materialism in action is when a scientific hypothesis is tested, the new data proves part of the old wrong and when they are synthesized the new hypothesis becomes the accepted scientific truth.

If possible, could someone give a layman's description of what 'information' is (in reference to the Black hole information paradox the and holographic principle)?

E.g. What information is contained within a hydrogen atom, or a water molecule or a cup of tea? Can this information be expressed by numbers or equations? Why is it said that information can't be destroyed? (I have tried reading the wikipedia articles on these subjects and they went right over my head. If there is no easy way of explaining this and it really is something that needs several years of post-graduate study to understand, I'll accept that and occupy my mind with something else.)

In the context of the black hole information paradox, "information" basically refers to everything that's exactly conserved. For example, electric charge conservation is never violated, so the charge of a particle, or the net charge of a system, is information in this context.

ELI5: Why are shoe sizes separated into men and women's categories instead of one neutral scale?

I was at the mall today and went to a Footlocker just browsing shoes and then left without getting anything. However, in another section of the mall there was a Women's Footlocker selling the exact same shoes as the other Footlocker. I've bought women's shoes of the same design for myself in colors not available in men's shoes before (I'm a guy) and they fit the same exact way that the mens shoes do (gotta buy 2 sizes up in women's shoes though because I'm in the US and not sure if it's the same in other countries). So why hasn't the US shifted to one scale if both men's and women's sizes overlap with eachother?

Men's shoes are not only longer than women's (higher size number) but also wider than the length would strictly indicate. In the sizes you'd ordinarily buy women's shoes, you probably wouldn't notice - but a man with size 12 feet would probably feel very pinched if he tried to wear a size 14 woman's shoe.

What broad distinction can be made in the fields of study between mathematical logic as practiced by mathematicians and philosophical logic as practiced by philosophers?

I understand that they both rely on the same, or at least very similar, foundation, but when I look at mathematicians vs philosophers who work with logic at my university, they almost exclusively publish with other mathematicians or philosophers respectively? Are the differences stylistic or goal oriented? or more abstract?

>Are the differences stylistic or goal oriented? or more abstract? Rather goal-oriented. Usually philosophers and mathematicians are interested in different things. Mathematicians are not interested in, say, paraconsistent/relevant/deontic logics, or the problem of absolute generality, or formal theories of truth, because usually there is not much of interest there for mathematicians. Philosophers, on the other hand, are not that interested in proving some obscure fact (like that there exists an upper bound of something) about first-order logic with two variables. And even when mathematicians and philosophers coincide in the object of study, they are interested in different aspects of that object: mathematicians will not use type theory to discuss higher-order metaphysics. This does not mean, of course, that philosophers and mathematicians cannot significantly influence each other, and it can be difficult to determine whether a work is strictly mathematical or philosophical logic (just think about Tarski or Kripke). >they almost exclusively publish with other mathematicians or philosophers In addition to the above, this is also largely due to institutional, administrative, and publishing reasons.

CMV: Modern Feminism is doing the opposite of what they hope to achieve

Edit: the issue is primarily with the extremist activists who would preach their ideology of feminism under the same banner as a more sensible group. Extremists being individuals who would put down the other gender in the fight for equality. My view is primarily that the second-third wave of feminism causes more harm than good by causing animosity towards the people preaching it. It may seem like an overstatement, but any time I hear the word patriarchy spoken seriously, or see that what should be a fight for equal rights is really just a focus on one half of the population, they are causing more of a divide than if they were to say nothing at all. Saying this, there are very real issues in the middle-east that I can say do warrant feminism as there is a true patriarchy there, and I feel that the western-world's feminist problems are a joke compared to say, institutionalized racism or the middle-east. CMV. (p.s. The majority, but not all, of my experience with this issue comes from online, I've only met a couple of radical modern-feminists in real life).

First wave feminism primarily focused on ways in which women were legally oppressed, and made great strides in that. The problem is that we still have a great deal of *cultural* oppression. The concept of "patriarchy" is perhaps not the best way to phrase things, but it's really not about male-hating. It's about an entire culture designed around women being primarily valuable for their appearance and reproductive potential, rather than as fully actualized human beings. Sure, plenty of cultures *still* have that legal oppression that is much more obvious (and therefore, actually, much easier to fight). That doesn't mean that there's nothing left for feminism to fight in western cultures. Women still experience glass ceilings, are expected to take primary child care duties, and are rated as more *competent* when they wear makeup. That's what 2nd wave feminism was focused on, and if you don't think they were successful, then you have a very strange view that culturally the 1950s and 2010 present the same opportunities to women, and there's nothing that has improved with regards to women's actual opportunities. We're still only *now* seeing the possibility of a female president in the U.S., and as long as the people in power are largely men we'll still have a long way to go even on the things 2nd wave feminism is concerned with. 3rd wave feminism is primarily about how 1st and 2nd wave feminism have largely only improved the lot of (comparatively) rich white women in the modern era. Indeed, one of their bigger focuses is on *exactly* those legal barriers that women still face in much of the 3rd world, and in subcultures imported from those areas. Don't confuse the rhetoric of the extremist members of a movement for the goals of the movement itself.

ELI5: Why does our body start to shake after holding a strenuous position for like an extended period of time?

e.g. planking or wall-sits and starting to shake before failure.

In short, holding a position or working out requires muscular stimulation which involves neural signals from the brain. These signals come in the form of neurotransmitters, which can get depleted after strenuous exercise. Low levels of these neurotransmitters mean muscle contractions are not as fluid and prolonged, so we feel our muscles "shake" as some muscle fibers fire and others do not. It's similar to a lawnmower engine: as the available gasoline supply declines, the engine sputters and dies.

[Final Fantasy] Why are martial artists doing so much damage?

I'm a white mage, and I'm in a party with a knight, a ninja, and a martial arts master. We're pretty badass. We just defeated Tiamat, which was no easy feat with no offensive spell power except that one lightning gauntlet we found in the castle of ordeals...which I really don't have time to use because I'm always healing somebody! Right now we're on a random dungeon crawl with outrageously hard bosses but tons of easy nuisance monsters and everyone in my party is doing crazy damage to everything! We just fought a band of 4 goblins like the ones we killed as newbs in the forest outside Cornelia and each of the damagers in my party are inflicting at --minimum-- 15x the amount of damage it took to kill the same monster back when they were a threat to us. I mean, the ninja will decapitate one blue goblin in a single strike, and then cut off each appendage from the corpse and leave the whole graven package neatly skewered on a nearby tree branch. Now, it's really cool that he can do this all in about 15 seconds flat, but once you've seen it about 80 times, it seems like overkill. The master will hit a madpony with a paralyzing blow and then shatter every other major bone in its body with a serious of acrobatic and strength achievements that inspire awe...but again, far beyond the point at which the threat was terminated. Our knight is far less elegant, but equally over-effective. He just carries the biggest, sharpest sword he can find and bashes it into everything while grunting desperately until the creature is nothing but a fine red paste (or green, or purple, depending on what they bleed). As a guy who'se always conserving spell points and preparing to need more as dangers grow, I wish my comrades would realize it's a marathon, not an exhibition. Why are they so overzealous in attaching weaker monsters?!

As a mage, you get better with study, but martial types need practice. What you see as overkill, they see as a chance to practice techniques in real world but low stress situations. Drilling the techniques when they can pay attention to each muscle twitch means that they are perfected when fighting for their lives and needing to focus on tactics.

ELI5: How come the Female Immune system not reject (treat as foreign material) human semen during reproduction?

Isn't semen/sperm considered "non-self" by the female immune system?

We have many types of immunity, classified as “innate” or “adaptive”. The adaptive immune system is the one that recognises foreign things like colds and flus. However, this response has to be custom-manufactured by the body for each foreign thing and takes three or four days to start fighting the infection. In contrast, fertilisation from a sperm can happen as soon as half an hour after sex. Our innate immune system does not specifically recognise sperm and does not seem to be effective against them (semen, the fluid that sperm are ejaculated in, may help protect them too). Having said that, a baby is actually considered a foreign invader by the woman’s immune system and it self-suppresses in order to avoid killing the baby, and the same seems to apply to the sperm.

ELI5: Why is there serotonin in snake venom if that chemical is the chemical that makes us happy?

Your body repurposes the same chemicals for multiple uses. Serotonin is used in the brain to modulate your mood, but it’s also used in the circulatory system to control blood vessel constriction and blood clotting. The snake doesn’t much care about your mood, but it does want to blow up your circulatory system with a huge dose of chemicals that interfere with normal behavior.

ELI5: DNA Transcription and the roles of mRNA, rRNA, and tRNA

ty in advance

So in the nucleus of all our cells, we have strands of DNA, which provides a code for the creation of proteins out of little building blocks called amino acids. There has to be a method for the code in the DNA to be interpreted to turn into proteins. This is where we have mRNA (messenger), tRNA (transfer), and rRNA (ribosomal). mRNA literally performs the job of the "messenger". A little "computer" if you will, called RNA polymerase, basically "reads" the DNA code and interprets it (analogous to turning a book into a summary), making a strand of mRNA (this process involves copying the DNA code, and removing the introns, which are useless segments). This mRNA moves out of the nucleus and goes toward a ribosome, which is the construction plant for making proteins. The ribosome is made out of rRNA. Now the ribosome is the construction plant, but it cannot fetch the materials by itself. So when mRNA comes over and gives the ribosome instructions on how to make a protein, tRNA "fetch" the building blocks needed to build it (the building blocks are called amino acids). The tRNA has a structure such that it ends up attracting the amino acids (similar to a magnet), and it carries the amino acids to the ribosome. The ribosome then takes these building blocks, and joins them together to make proteins.

[Lord of the Rings] How do the Nazgul/Ringwraiths work?

I know they're undead, but past that, I don't know what's going on there. Their bodies are gone, but they're corporeal somehow or something? Can someone explain that one to me.

There is the world, and the unseen world. The Maiar seem to be native to the Unseen World, but can fashion bodies to appear in the regular world. Sauron is cursed to always seem evil to men in corporeal form. Presence in Unseen World can be equated to magical power. Looking upon the Two Trees gave the Eldar a presence in the Unseen World, and this is the source of their "glow." Men don't have have any native presence in the Unseen World. The Rings of Power have the effect of bringing the wearer into the Unseen World. This makes them invisible to persons in the regular world and allows them powers they don't normally have. They see and can be seen by other beings in the Unseen World. Glorfindel could not join the Fellowship of the Ring because he had an exceptionally strong presence in the Unseen World and would be trivially easy for the Ringwraiths to detect. The Ringwraiths were kings of Men who wore rings subject to the One Ring. They gained a presence in the Unseen World, and thereby power. They also became subject to Sauron's will, as Sauron provided the rings.

[General Sci-fi] What advantages (if any) do walking vehicles have over wheeled ones?

Examples such as [this](http://img1.wikia.nocookie.net/__cb20071022025719/starwars/images/e/e9/At-st_large_pic.jpg), [this](http://img2.wikia.nocookie.net/__cb20090425021909/starwars/images/5/5e/AT-TE_TCW.jpg) and [this](http://imageserver.moviepilot.com/call-of-duty-advanced-warfare-walking-tank-call-of-duty-advanced-warfare-future-tech-will-change-gameplay-forever.jpeg?width=1280&height=720). What are the benefits of these types of war vehicles over ones that use wheels or tank tread? Are there any?

Ambulation has several advantages over wheels: 1) Climbing terrain- A fully articulated set of walking limbs can adjust to all most any grade, providing they can apply enough force to the surface the limb is on to maintain traction. Also, in the process, because of the jointed nature of the limbs, the body can be kept pointed in an appropriate direction for any other task while the limbs are busy scaling an obstacle. Lastly, articulated walking limbs give the ability to simply 'step over' barriers shorter than their 'hips'. 2) Maneuverability- Articulated limbs give instant translation to lateral motion. The ability to transfer from full speed forward motivation to strafing in a very small space and without having to turn the body of the vehicle is extremely effective. The vehicle also has enhanced evasive ability because the vehicle can move in three axes quickly allowing it to provide a more difficult target or lower it's profile for concealment, or raise itself to a considerable height for attack. Sufficiently powered limbs can jump, which gives them an entire other dimension with which to maneuver and do battle in. 3) Last ditch offense/defense- If all else fails...kick.

CMV: Freedom of religion should be removed from law.

Since we where I live we have freedom of speech I would like to propose to remove the freedom of religion from the law. 1. There is no hard line between any belief (pink unicorns) and say Islam. (saying one believes in pink unicorns does not grant some sort of super status, calling it Christ is different for some reason) 2. Good argument for cutting all state funding related to religion (since no special treatment is required, no special reason to give away tax money is directly justified, we dont randomly give taxes to anyone saying anything.) 3. The state should never acknowledge the justifications or existence of religions or its implications, its something they should be either completely neutral towards or only accept things that belong to the realm of truth and therefor not religion or 7 legged sheep. 4. Freedom of religion can be put under freedom of speech, since you can say whatever you see fit , just dont run to the state to support your claims or once again give you a special hat. 5. Its an old fashioned basis for law , if you want to truly divorce state from law then simply don't mention it or treat them differently. *EDIT* Thanks everyone for the high quality responses and thought provoking arguments. Ill try to respond to all the arguments made. _____

An important part of the freedom of religion, half of the US First Amendment's portion regarding religion, is the freedom from imposition of religion. The government at all levels (in the US due to the combination of the 1st and 14th amendments and judicial incorporation doctrine) from federal to a local school district is prohibited from imposing religion on people. The freedom from imposition of religion and the freedom to believe and practice as you wish are inseparable.