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File Extensions

File Extensions

https://www.xkcd.com/1301

https://www.explainxkcd.com/wiki/index.php/1301:_File_Extensions

[Caption above the bar chart:] Trustworthiness of Information by File Extension [A line is going down and from that gray bars charting the trustworthiness in a bar graph that goes both left and right of the line. No units or figures are given. For ease of comprehension this transcript will arbitrarily designate the highest score as [+100]; subsequent scores are estimates based on the size of their bars.] [+100]: .tex [+89]: .pdf [+85]: .csv [+67]: .txt [+65]: .svg [+49]: .xls/.xlsx [+21]: .doc [+15]: .png [+14]: .ppt [+3]: .jpg [-8]: .jpeg [-36]: .gif The various extensions are, for the most part, abbreviations of the file type.

Computer file names often end in file extensions like ".ppt" or ".exe". These extensions are a holdover from early operating systems like DOS in which filenames had a maximum eight characters followed by a period and the three-character extension. The extension was used by the operating system to determine filetype so that the system would know how to handle the file (e.g. which program could open the file). Newer operating systems and file systems now accept longer-than eight-character filenames, and extensions of greater than three characters; although most extensions remain three characters. Most extensions are created as proprietary to certain pieces of software, although software by other developers may later be designed to be able to read the format. For example, .doc is a Microsoft Word document, although because of that software's popularity, many word processors include the ability to open .doc files. Some common file extensions are not proprietary to a piece of software and may be handled by various programs; .jpg or .gif images are examples. In either case, a file's extension is generally a good indicator of what type of data the file contains. Certain file types are more prevalent for certain uses, with some being almost exclusive to one use, while other are in general use and might contain almost anything. Here, Randall presents a series of file extensions which often contain information, and he is rating the reliability of the information they generally contain from most reliable to least. Note that while the extensions .xls/.xlsx, .doc, and .ppt were originally exclusive only to Microsoft Office and users of Windows, there now exist a number of open source programs such as Open Office, Libre Office, and some Android apps that are capable of editing such files. These programs can run on systems other than just Windows, such as Linux, perhaps contributing to making them even more widespread and easy to make than before. The title text refers to how .txt files contain only plain text and nothing else, meaning that any alignment (such as for indentation, tables, or justification ) would have to be performed manually by adding in spaces or tabs. Anyone who would go through such an effort to improve their text's readability is likely to be trustworthy, and almost by definition, the opinion presented would be justified. [Caption above the bar chart:] Trustworthiness of Information by File Extension [A line is going down and from that gray bars charting the trustworthiness in a bar graph that goes both left and right of the line. No units or figures are given. For ease of comprehension this transcript will arbitrarily designate the highest score as [+100]; subsequent scores are estimates based on the size of their bars.] [+100]: .tex [+89]: .pdf [+85]: .csv [+67]: .txt [+65]: .svg [+49]: .xls/.xlsx [+21]: .doc [+15]: .png [+14]: .ppt [+3]: .jpg [-8]: .jpeg [-36]: .gif The various extensions are, for the most part, abbreviations of the file type.

Year in Review

Year in Review

https://www.xkcd.com/1302

https://www.explainxkcd.com/wiki/index.php/1302:_Year_in_Review

[Cueball is a news anchor sitting with his arms on a desk looking at Megan, a reporter shown in a feed on a screen to his right. There is a title below the feed.] Cueball: We go live to our 2013: Year in Review! Megan: Thanks! Megan: In 2013, I didn't see an aurora. Cueball: I- what? Title: Year in Review [Zoom to the top part of the screen with Megan. Her text is written above the screen without a frame around this segment of the comic.] Megan: The northern lights. I thought this would finally be the year. Megan: But it didn't happen. [Back to the original view but Cueball has turned more towards Megan, with only one arm on the desk.] Cueball: Oh. Uh... What about the rest of the year? Megan: What do you mean? Cueball: Any big news stories? Megan: Oh yeah, tons. Title: Year in Review [Same setting but Megan turns away from Cueball, who has taken both hands of the table. Megan is looking to her left at something off screen. Beat panel.] Title: Year in Review [Cueball turns back to face the viewers, both hands back on the desk, as Megan is leaving the screen, walking out to the right, her face already hidden by the frame of the feed.] Cueball: ...Well, that was 2013: Year in Review. Megan: The sky's clearing up. I'll be outside. Title: Year in Review

Many news organizations will recap the major stories of the past calendar year in late December (typically before the year has actually ended). This includes specialized news outlets such as sports stations which recap major sports stories or best plays of the year. Here, Cueball , as a news anchor , expects Megan to talk about major news stories of 2013 such as the roll-out of Obamacare , the election of Pope Francis or the death of Nelson Mandela , to give a few examples. Instead, Megan only recaps one thing which was important to her: She did not see the aurora borealis (i.e. northern lights) in 2013, the dazzling natural geomagnetic light display caused by the solar wind . In 2013 a solar maximum was expected at its solar cycle , but the activity of the sun wasn't as heavy as before. So, a northern light had been very rare in this year. Megan has never seen the northern lights, and she is frustrated that it did not happen for her in 2013, thus overshadowing all other events. She even leaves in the middle of the review when she notices the sky clearing up, as she wishes to check if there are any northern light this evening. This may very well be Randall's own frustration which is displayed here. It turns out in the title text that Megan is actually reviewing the astronomical year, only considering astronomical events. She even rates it much like a movie review, although she seems to use the A-F grade scale . She only gives the year a C- (C minus), which would usually be the lowest passable grade, so she just lets the year pass in spite of the two failing events mentioned in the title text. In the title text, Megan specifically complains about not being able to see aurorae from her house. If Megan actually represents Randall's frustration, then to expect to see it from a house in Massachusetts would be a lot to ask for. Usually, people who wish to see Northern lights will travel to an arctic area and stay away from light pollution from cities. But in years with heavy solar activity, northern light may be visible even south of Massachusetts. The title text also refers to Comet ISON . In February, a rough estimate of the comet's behavior predicted that it would become brighter than the full moon, a prediction that was widely reported by the media even though it was based on limited data and astronomers knew that it would not reach this brightness. In the end, although it was visible to the naked eye, it was never as bright as anybody hoped and apparently disintegrated on November 28, 2013, at its close approach to the sun. The title text also refers to the 2017 total eclipse , which was visible as a partial eclipse for a few hours throughout North America on August 21 Monday, including a 100-mile wide band across the United States where it was a total eclipse for a couple of minutes in the early afternoon. Eclipses are completely predictable - although the weather might be cloudy so that the sun is blocked during totality, they will happen anyway. So Megan is being extremely pessimistic to even suggest that the 2017 eclipse might get canceled. Humorously, her statement that someone might decide to cancel the eclipse makes it sound like a concert that could be canceled by the organizer. It seems that Megan thinks that the "they" who could cancel the eclipse are the same "they" that caused the comet to disintegrate and the solar activity to stay low. Anyone with the kind of power to stop a solar eclipse from happening would be god-like compared to humanity. The next time that the eclipse was mentioned was in the New Year comic for 2017: 1779: 2017 . The subject of the title text of that comic is the likelihood that the eclipse will indeed happen as planned. All in all, the comic suggests that the only events of significance to Megan (and Randall) are astronomical ones; the actions of humanity pale in comparison. The joke of Megan answering a question in an interview in an unexpected manner has been used before in 1111: Premiere . Interestingly in 1037: Umwelt there is an aurora story line where Megan stays inside at her computer even though it can be seen from her own state, letting her friend go out alone. (So not the same Megan for sure). [Cueball is a news anchor sitting with his arms on a desk looking at Megan, a reporter shown in a feed on a screen to his right. There is a title below the feed.] Cueball: We go live to our 2013: Year in Review! Megan: Thanks! Megan: In 2013, I didn't see an aurora. Cueball: I- what? Title: Year in Review [Zoom to the top part of the screen with Megan. Her text is written above the screen without a frame around this segment of the comic.] Megan: The northern lights. I thought this would finally be the year. Megan: But it didn't happen. [Back to the original view but Cueball has turned more towards Megan, with only one arm on the desk.] Cueball: Oh. Uh... What about the rest of the year? Megan: What do you mean? Cueball: Any big news stories? Megan: Oh yeah, tons. Title: Year in Review [Same setting but Megan turns away from Cueball, who has taken both hands of the table. Megan is looking to her left at something off screen. Beat panel.] Title: Year in Review [Cueball turns back to face the viewers, both hands back on the desk, as Megan is leaving the screen, walking out to the right, her face already hidden by the frame of the feed.] Cueball: ...Well, that was 2013: Year in Review. Megan: The sky's clearing up. I'll be outside. Title: Year in Review

Profile Info

Profile Info

https://www.xkcd.com/1303

https://www.explainxkcd.com/wiki/index.php/1303:_Profile_Info

[Cueball is sitting at a desk, using a desktop computer. He is filling in a form on a webpage.] First Name: John Last Name: If-you-see-this-name-in-an-ad-give-the-product-a-one-star-review-Smith [Caption below the panel:] How to deal with companies harvesting your profile for marketing

On most websites people are forced to create an account to get proper support, be it technical support or simply ordering products. This usually consists of the user's name, email address, phone number, and also the user's home address if ordering a product that must be shipped by mail. It's not uncommon for the websites/companies to then use that information for presenting new advertisements in the near future, or even sell it to others for their schemes. In 2013 (publishing of this comic), a recent trend was to allow harvesting of profile pictures and real names, mostly by automated processes with little to no human interaction. The personal information is collected in context with other information, such as the purchase or product review history, and shown to people (typically friends and contacts) who are viewing similar products. The title text references the fact that most of these companies have an "opt out" option so that your name won't be used, but then emphasizes that YouTube (a subsidiary of Google ) at the time of this comic forced YouTube user accounts to be tied to Google+ . Google+ required the use of the 'first name' and 'last name' convention typical of western cultures, where one cannot 'opt out' (though these requirements did allow for the abbreviation of names). However, this has not stopped people from using names that aren't their own, but using names like "Barack Obama" and "Chuck Norris". Some similar websites allowed the use of aliases in their initial terms of use, but then later changed their TOCs to prohibit use of "false" names. YouTube was one such system; after the merge with Google+ for authentication, both sites automatically linked your false-name account with your real name account, in some cases banning and blocking people with suspected false name accounts. To try to put a stop to his own information being used, Cueball sets his last name to "If-you-see-this-name-in-an-ad-give-the-product-a-one-star-review-Smith", a name which includes a phrase that would negatively affect any marketer's attempts to advertise an online product. [ citation needed ] This name would pass though most harvesting software as-is, and may very well end up being used in such ads, unless some very clever software is able to detect sentences as part of names or similar. In fact much spam is stopped by identifying emails through Honeypot accounts, among other methods. Hence engineering part of your profile could be a winning strategy to signal to your friends that your information is harvested without your express knowledge. [Cueball is sitting at a desk, using a desktop computer. He is filling in a form on a webpage.] First Name: John Last Name: If-you-see-this-name-in-an-ad-give-the-product-a-one-star-review-Smith [Caption below the panel:] How to deal with companies harvesting your profile for marketing

Glass Trolling

Glass Trolling

https://www.xkcd.com/1304

https://www.explainxkcd.com/wiki/index.php/1304:_Glass_Trolling

[Caption above the panel:] My Hobby: [Cueball, wearing regular glasses, is holding his smartphone up in one hand while typing, as shown with two times two small movement lines on either side of the phone. A voice from off-panel right emanates from a starburst at the frame.] Cueball: OK, Glass, check tomorrow's weather. Cueball: Ooh, snow! Off-panel voice: Oh my god, it's somehow even more annoying than if you had it. [Caption below the panel:] Saying "OK, Glass" before everything while wearing regular glasses. Google Glass was a recurring theme in xkcd in 2013.

This is another strip in the My Hobby series. Google Glass is a set of glasses frames worn like typical glasses that features an optical display and internet connectivity. It responds to voice commands starting with "OK glass " , for example to initiate video recording or to check tomorrow's weather. Strangers and other people surrounding the user would often find it annoying to hear someone talking to "himself", or to Glass . Also many people who buy the newest gadgets, like Google Glass, like to brag about it, and thus would try to say OK Glass so loud that other people will notice they have these cool new glasses. This can be very annoying in general! Randall's hobby, is saying "OK, glass " before any sentence while he is only wearing regular glasses. Like here where he (drawn as usual like Cueball , with regular glasses) is checking tomorrow's weather, not on the glasses but on his smartphone . Apparently this is even more annoying to the bystander than if he would actually wear a real Google Glass while saying so. He thus both annoys other people, mocks people who buy such glasses to brag about them, and in general mocks Google Glass. In the title text, Randall states that there is an extra benefit by doing this while only wearing regular glasses. Because when someone is finally fed up with the annoyance and rips the glasses off and stomps on them, then it would cost much less for regular glasses than if he had to replace a "Google Glass". These are very expensive - $1,500 at the time of this comic, as the title text says. (Note that regular glasses can also be very expensive, but you could choose to wear your reserve glasses for such a prank...). Also several people have claimed to been attacked while wearing Google Glass in San Francisco, with one person claiming their attacker destroyed their Glass . The "OK, Glass " keyword is not useless outside of Glass ; in the browser Chrome and the Android/iOS app Google Now , "OK, Glass " is also valid instead of "OK, Google " to initiate a voice command. While Cueball may be using this app, it is not necessarily the case, given that the caption states that Cueball enjoys prefacing everything with the phrase. It seems generally that Randall is no fan of Google Glass, which was also shown earlier in 1251: Anti-Glass . [Caption above the panel:] My Hobby: [Cueball, wearing regular glasses, is holding his smartphone up in one hand while typing, as shown with two times two small movement lines on either side of the phone. A voice from off-panel right emanates from a starburst at the frame.] Cueball: OK, Glass, check tomorrow's weather. Cueball: Ooh, snow! Off-panel voice: Oh my god, it's somehow even more annoying than if you had it. [Caption below the panel:] Saying "OK, Glass" before everything while wearing regular glasses. Google Glass was a recurring theme in xkcd in 2013.

Undocumented Feature

Undocumented Feature

https://www.xkcd.com/1305

https://www.explainxkcd.com/wiki/index.php/1305:_Undocumented_Feature

[A support window is shown.] An old Windows utility has an undocumented feature. If you open "help" and click on the background, you get dropped into a "support" chat room. Support Window: Launching support forum... [An active conversation between two people is shown.] Only a few of us ever found it. But we became friends. [Cueball and Ponytail are at computers.] We kept launching the program to check in. Eventually some of us were running VMs just to keep accessing it. [Another conversation.] As the Internet aged, so did we. [Three question marks.] We don't know who runs the server. We don't know why it's still working so many years later. Maybe we're some sysadmin's soap opera. [A group of people are shown in a bubble.] It will probably vanish someday, but for now it's our meeting place. Our hideaway. [The bubble is now smaller, and some parts of a web are shown.] A life's worth of chat, [More of the web is shown.] Buried in the deep web. [A flat landscape is shown with the sun at the horizon.] But even if it lasts forever, we won't. When we're gone, who will remember us? [Cueball and Hairy are shown standing together in a bubble.] Who will remember this strange little world and the friendships we built here? [No panel shown:] Nobody. [An empty bubble is shown.] This place is irrelevant. Ephemeral. One day it will be forgotten. [The bubble starts to fade away.] And so will we [The bubble has almost completely faded away.] [The bubble is now completely gone.] [Caption inside a new panel:] But at least it doesn't have fucking video ads. There are many examples of undocumented features in programs written for old versions of Windows, for example:

An undocumented feature is a part of a software product that is not explained in the documentation for the product. Cueball has found such a feature, a chat room intended to ask for help, accessible through the help page of some unnamed old Windows utility. The people who found the chat room started out using it for its intended purpose (helping users of the utility by contacting other users), however as time has passed they have become friends and enter the chat only to talk to each other, with no relation to computer problems. A virtual machine (or VM) is a computer program designed to emulate the hardware of a full computer. In this case, users of the old chat room create VMs only to have the old operating system installed which included the utility program. They use this setup only to access the old chat room. This is shown in the third panel where Cueball is using a modern laptop to enter the chatroom (presumably by means of a VM), whereas Ponytail is most likely using an old computer (as evidenced by the CRT monitor). A chat room like this must be hosted on some outside server, so the narrator of the comic wonders who runs this server. An obvious thought about this is if and when the server will be shut down, effectively cutting all communication among chat users. Another obvious thought is why the utility author is still maintaining the chat server, since its original purpose of allowing communication between users with problems with the utility program is no longer an issue as everybody has migrated to more modern systems. The comic suggests that the reason for doing this can be a bored sysadmin , who is just reading the messages of the chat users and following their lives but never writing anything. This would turn the chat room into a soap opera for the sysadmin. The Deep Web is a term used to refer to any information which is available online, but is hard to find (usually because there are no links to that information in web pages). The chat room described would be an example of this. From this point on, the comic takes an existentialist turn (a frequent xkcd trait), talking about how life is short, everything has to end, etc. The last panel is a reference to Facebook's recent announcement that it would start autoplaying video ads, and the title text refers to YouTube requiring its users to use their real-life identities instead of just nicknames. These last parts of the comics somehow reveal that the point of the whole comic is just to complain about aggressive money-driven policies used by modern social networks in general and Facebook in particular. It is hinted that Randall would prefer older technologies, where limited resources would forbid autoplaying videos or huge databases with every detail of every user's life. It's possible that the comic is about an actual chat room, but more likely it is a complete invention, since if it were real someone would have been able to trace its origin. However, if it is real, the participants would not want to confirm this in order to protect their privacy. The title text mentions the simplicity of this chat; even user names do not exist and other users could only be identified by their behavior because the user names are random and can change on every login. [A support window is shown.] An old Windows utility has an undocumented feature. If you open "help" and click on the background, you get dropped into a "support" chat room. Support Window: Launching support forum... [An active conversation between two people is shown.] Only a few of us ever found it. But we became friends. [Cueball and Ponytail are at computers.] We kept launching the program to check in. Eventually some of us were running VMs just to keep accessing it. [Another conversation.] As the Internet aged, so did we. [Three question marks.] We don't know who runs the server. We don't know why it's still working so many years later. Maybe we're some sysadmin's soap opera. [A group of people are shown in a bubble.] It will probably vanish someday, but for now it's our meeting place. Our hideaway. [The bubble is now smaller, and some parts of a web are shown.] A life's worth of chat, [More of the web is shown.] Buried in the deep web. [A flat landscape is shown with the sun at the horizon.] But even if it lasts forever, we won't. When we're gone, who will remember us? [Cueball and Hairy are shown standing together in a bubble.] Who will remember this strange little world and the friendships we built here? [No panel shown:] Nobody. [An empty bubble is shown.] This place is irrelevant. Ephemeral. One day it will be forgotten. [The bubble starts to fade away.] And so will we [The bubble has almost completely faded away.] [The bubble is now completely gone.] [Caption inside a new panel:] But at least it doesn't have fucking video ads. There are many examples of undocumented features in programs written for old versions of Windows, for example:

Sigil Cycle

Sigil Cycle

https://www.xkcd.com/1306

https://www.explainxkcd.com/wiki/index.php/1306:_Sigil_Cycle

A sinusoidal curve is shown. Y axis: Odds that the words I type will start with some weird symbol X axis: Time Data labels: [at first peak] $QBASIC, [at first trough] C++, [at second peak] $BASH, @$PERL, [at second trough] PYTHON, [at third peak] +GOOGLE, @TWITTER, #HASHTAGS

In computer programming , a variable is a way of storing information temporarily, for use later in the program. There are different types of variables, called data types , such as integers, strings, characters, and booleans, all of them holding different types of information. Integers hold whole numbers, strings hold text, and so on. Variables traditionally have names that identify their purpose, and a programmer should usually be able to infer from this variable name what type of variable it is. For example, if you want to store the name of the customer in a catalogue service, you might store the text in a string variable called "NameOfCustomer". Because it is fairly clear that names are made up of text, it is logical that this variable would be a string variable - if you didn't have any other information about it. A sigil in computer programming is a symbol that appears before the variable name. It is an alternative method of telling someone who is reading the program code what data type the variable is. Rather than relying on logic, then, to know that NameOfCustomer is a string, you might use a sigil "$" before the variable name, as in $NameOfCustomer, which would specify that the variable can hold text. Sigils can also specify the scope of a variable, which refers to where the variable can be used in a program, and which parts of the program can access that variable. Sigils are useful in some ways because you don't have to refer to previous program code or find where the variable is declared (created) to know what data type it is. They also provide some level typing in languages that do not explicitly declare the type of the variable. Most programming languages have a different method for storing variables, although some languages may use the same variable types under different names. The following are the programming languages referenced in the comic and how they use variables. QBASIC Variables of type string end with the $ symbol. Other symbols are used (% for integers, ! for single-precision, # for double-precision and, in some versions of BASIC, & for long integers), however the usual QBASIC program will use only the $ symbol and not any of the others, as the default type if no symbol is used is single-precision and that's OK for most numeric uses. C++ Pronounced "see plus plus." Variables are just words with regular letters. It is the name of the language itself that includes symbols. bash This is not typically thought of as a full-featured programming language, but a Unix shell. However, the shell command syntax is rich enough to be able to write simple (and sometimes really complex) programs called shell-scripts. In this language, all variable dereferences start with the symbol $. Perl In Perl, the initial character provides the context of the variable. Scalars (text, numeric and also to references to data) start with the $ character. An @ is for an array. With %, it is a hash (a loose non-sequential array, or 'dictionary' lookup). Functions can be given a preceding &, but rarely need this in straightforward use. You can use the variables $temp, @temp, %temp and &temp simultaneously and independently. There is also the * (not in a mathematical sense) which identifies a 'glob', a way to fuse or use all those types (and more!) in 'interesting' ways if you have a yen to. A block, with {} surrounding some other suitable statement(s), can potentially be typed to (re)interpret the context within. If you have a $reference which currently points to an @array, @{$reference} will let you use it as a direct array. But in simple cases, like that, this can often be shortened to @$reference, as alluded to by the "@$PERL" of the comic. (Just as $$reference would be a valid way to dereference the $reference when it points to $scalar... or even to $anotherReference that itself points to a %hash, in which case you could even use %$$reference for 'direct' access to that. Perl can be complicated, if you let it!) Python Variables are just words with regular letters. Google In the beginning, Google was only a search engine. However, it now includes many apps (such as YouTube, Gmail, Microsoft products but Google [e.g. Google docs], etc.), which included a social network called Google+ (now defunct, pronounced "google plus"). Google+ accounts were referenced with a + prefix. Twitter Twitter account IDs are identified by the leading symbol @. When an account is "mentioned" in a tweet using @, it triggers smart behavior. For example, account owners can configure Twitter to forward tweets that mention them. This feature was not present in the early days of Twitter. Hashtags In 2007 Twitter users began a convention that a # sign (whose many names include the "hash") can be prepended to words to mark them as keywords. Twitter could then be searched for those words. In 2009 Twitter recognized the existence of hashtags and began hyperlinking them. Some other microblogging services followed suit. Google+ eventually added hashtag support as did Facebook. As is noted by the comic, the use of sigils to indicate types of variables varies between programming languages, from strict enforcement in languages like Perl, to their complete absence in languages like C++ (but see Hungarian Notation ). The comic notes that the use of sigils seems to be cyclic, especially if you count things like hashtags as extensions of the pattern. The title text describes the two competing influences responsible for the cycle: The first impulse finds sigils useful to elucidate the type of the variable, especially when variable names are not very descriptive, while the latter impulse notes that descriptive variable names are much more useful for that purpose, especially in extensible languages where the built-in types form only a small part of the type system. A sinusoidal curve is shown. Y axis: Odds that the words I type will start with some weird symbol X axis: Time Data labels: [at first peak] $QBASIC, [at first trough] C++, [at second peak] $BASH, @$PERL, [at second trough] PYTHON, [at third peak] +GOOGLE, @TWITTER, #HASHTAGS

Buzzfeed Christmas

Buzzfeed Christmas

https://www.xkcd.com/1307

https://www.explainxkcd.com/wiki/index.php/1307:_Buzzfeed_Christmas

[Four carolers (Megan, Cueball, Ponytail and Hairy) are singing.] 12 Best drummers of all time 11 Pipers whose jaw-dropping good piping will make you cry You won't believe what these 10 lords leap over [Caption below the frame] Carolers outside the Buzzfeed offices perform "12 Weird things I actually got for Christmas"

Christmas caroling is a tradition in which groups of singers travel from house to house, singing carols . These carolers are in front of the BuzzFeed offices singing the The Twelve Days of Christmas , which usually contains: On the twelfth day of Christmas, my true love gave to me. 12 Drummers drumming 11 Pipers piping 10 Lords a-leaping 9 Ladies dancing 8 Maids a-milking 7 Swans a-swimming 6 Geese a-laying 5 Golden rings 4 Calling birds 3 French hens 2 Turtle doves And a partridge in a pear tree. The carolers changed the lyrics to match the style of headlines of the topics published by BuzzFeed, which usually contain a number and a superlative; for example, 13 Worst Plane Crashes of the Decade or 8 Otters Who Are So Cute We Can't Even Handle It . This method of writing headlines, referred to as clickbait , is used by several other news sites, because it is known to generate a lot of visits and therefore more ad revenue. Randall has touched on this subject before in 1283: Headlines . Carolers are usually rewarded with a gift, but the BuzzFeed writers probably didn't appreciate the song, because they threw weird stuff at them. [Four carolers (Megan, Cueball, Ponytail and Hairy) are singing.] 12 Best drummers of all time 11 Pipers whose jaw-dropping good piping will make you cry You won't believe what these 10 lords leap over [Caption below the frame] Carolers outside the Buzzfeed offices perform "12 Weird things I actually got for Christmas"

Christmas Lights

Christmas Lights

https://www.xkcd.com/1308

https://www.explainxkcd.com/wiki/index.php/1308:_Christmas_Lights

[Megan, Cueball, and Beret Guy sitting on the floor and a big spectrum with one peak is shown between them. On the right many smaller spectra are shown in a shape of a Christmas tree.]

Each light in this Christmas scene is represented by its electromagnetic spectrum , which shows in a graphical form how much energy is radiated by each wavelength of light. These graphs plot the intensity of all visible radiation. Infrared and ultraviolet are partially plotted also, represented by black. It starts with longer wavelengths on the left ( infrared ), continues with visible light in the middle from red to blue, and ends with ultraviolet at the right. There are 4 distinct spectra in this comic: In the center of the image, between Beret Guy and the couple, Cueball and Megan , appears to be a light spectrum of a fire, notable because it emits a lot of energy in the infrared band (The left zone of the spectrum), emitted typically from hot sources, and in the red and orange zone. The spike toward the left hand side of the spectrum is likely the 4.3 µm resonance wavelength of hot CO 2 characteristic of burning hydrocarbons; see Emission of radiation . Given the size of the spectrum and its positioning, this represents a fireplace at which the characters are warming themselves against the winter chill. In the right of the comic appear some spectra arranged in the form of a Christmas tree. There are 3 different spectra in this "Christmas tree": At the top appears a complicated spectrum, possibly that of a white LED, representing the tradition in some cultures of putting a star (or an angel, but still usually lit) at the top of the Christmas tree. In the branches there are two simpler spectra repeated at various places, one with a peak in the green zone, representing a green light source, and other with a peak in the red zone, representing a red light source. Both of these represent the tradition of putting colorful decoration in the tree, in this case apparently red and green colored Christmas lights. In 835: Tree a similarly strange Christmas tree has been constructed using binary trees. [Megan, Cueball, and Beret Guy sitting on the floor and a big spectrum with one peak is shown between them. On the right many smaller spectra are shown in a shape of a Christmas tree.]

Infinite Scrolling

Infinite Scrolling

https://www.xkcd.com/1309

https://www.explainxkcd.com/wiki/index.php/1309:_Infinite_Scrolling

[Megan stands at a desk, reading a book, touching it very gingerly. Cueball is standing behind her. Cueball: Why are you turning the pages like that? Megan: If I touch the wrong thing, I'll lose my place and have to start over. [Caption below the panel:] If books worked like infinite-scrolling webpages

Infinite scrolling is a technique in web design where a large data set is displayed as a seemingly infinite list, but in reality only the visible part of the list (and the surrounding data) is rendered. This is done to work around memory limitations of old browsers and mobile devices or to save on data transfer size. The problem with this technique is that if you navigate from this page to a different page and go back, the location of the scrolled data set is often lost and the top of the data set is displayed again. Also it is usually not possible to point a URL directly to a certain section of the infinite list, a practice known as deep linking . For these reasons, many prefer pagination , the method traditionally used in books, over infinite scrolling. In this comic Megan is handling the book gingerly as if it were a device with a touchscreen where the book is displayed as an infinite scrolling text. Touching a link would navigate away from the list and the current reading position would be lost. In the title text it is an ironic suggestion that the "back" button is now useless. The back-button is supposed to give you this functionality but due to the failure to implement continuous scrolling sites and deep-linking correctly they are typically useless when the user is reading infinite-scrolling data (or worse, flat-out counterproductive, giving you the wrong page). Alternatively, this might be a joke on the stereotype that web users are unable to make the most helpful or intelligent decisions, similarly to 1454: Done , 1974: Conversational Dynamics , and 2051: Bad Opinions . [Megan stands at a desk, reading a book, touching it very gingerly. Cueball is standing behind her. Cueball: Why are you turning the pages like that? Megan: If I touch the wrong thing, I'll lose my place and have to start over. [Caption below the panel:] If books worked like infinite-scrolling webpages

Goldbach Conjectures

Goldbach Conjectures

https://www.xkcd.com/1310

https://www.explainxkcd.com/wiki/index.php/1310:_Goldbach_Conjectures

[Six small panels with captions are arranged in an arch shape:] [Caption under the arch:] Goldbach Conjectures [Captions in the panels, from left to right:] Extremely weak: Numbers just keep going Very weak: Every number greater than 7 is the sum of two other numbers Weak: Every odd number greater than 5 is the sum of three primes Strong: Every even number greater than 2 is the sum of two primes Very strong: Every odd number is prime Extremely strong: There are no numbers above 7

In mathematics, a pair of related conjectures may be described as "strong" and "weak" (or often, a normal statement and a "weak" one). A strong conjecture, if true, can be used to easily prove the weaker one, but not vice versa (i.e. if the weak statement is true, that alone isn't enough to prove that the strong one is also true). Conversely, if the weak conjecture is false, that is enough to prove the stronger one false as well, but not vice versa. Weak conjectures are often easier to prove than related strong ones. Goldbach's weak and strong conjectures are a pair of real, unsolved problems relating to prime numbers (a number with exactly two positive divisors, 1 and itself). The comic states these under the labels "weak" and "strong". Randall's further conjectures extend this to a whole series of progressively "weaker" and "stronger" statements. His weak conjectures are so weak that they are obviously true; his strong conjectures are so restrictive that they are obviously false. However, for the most part, they really do maintain a weak-strong relationship. The title text gives the same treatment to the twin prime conjecture , which says that there are infinitely many pairs of primes where one is 2 more than the other (e.g. 3 and 5). The title text adds a "weak" conjecture, according to which there are simply infinitely many pairs of primes (with no mention of the distance between them). This is true; Euclid's theorem says that there are an infinite number of primes, and so you can simply pick any two (e.g. 5 and 13) and call them a pair. It also adds a "strong" conjecture where every prime is now a twin prime. This is easily proven false; 23 is prime, for example, but cannot be one of a pair as neither 21 nor 25 are. However, Randall adds a humorous hedge that some prime numbers "may not look prime at first". Lastly, the tautological prime conjecture states that it itself is true while making no statement about primes. It is not technically a tautology but more of a plain assertion. Randall has mentioned tautologies before in 703: Honor Societies . Mathematician Christian Goldbach wrote a form of his conjecture (the "strong" one of the comic) in a letter to the famous Leonhard Euler in 1742. Euler replied that he considered it certainly true, but that he could not prove it. Mathematicians have been solving related problems that are "weaker" than Goldbach's weak conjecture and working towards "stronger" ones. For example, in 1937 the weak conjecture was proven for odd numbers greater than 3 14348907 . In 1995 a version was proven based on the sum of no more than seven prime numbers, and in 2012 the ceiling was lowered to five primes. In 2013 the weak conjecture was claimed proven for numbers greater than 10 30 , while all numbers below 10 30 have been verified by supercomputers to satisfy the conjecture; these together imply that the weak conjecture is true, although there is no general proof of it for all numbers. Goldbach's strong conjecture remains unsolved. [Six small panels with captions are arranged in an arch shape:] [Caption under the arch:] Goldbach Conjectures [Captions in the panels, from left to right:] Extremely weak: Numbers just keep going Very weak: Every number greater than 7 is the sum of two other numbers Weak: Every odd number greater than 5 is the sum of three primes Strong: Every even number greater than 2 is the sum of two primes Very strong: Every odd number is prime Extremely strong: There are no numbers above 7

2014

2014

https://www.xkcd.com/1311

https://www.explainxkcd.com/wiki/index.php/1311:_2014

(This is a series of quotes from various people of various timeframes. Each quote is followed by the author, the document of publication if applicable, and the year.) Notes from the past It's desirable every thing printed should be preserved, for we cannot now tell how useful it may become two centuries hence. Christopher Baldwin 1834 I predict that a century hence the Canadian people will be the noblest specimens of humanity on the face of the earth Rev. John Bredin 1863 In the twenty-first century mankind will subsist entirely upon jellies. The Booklover 1903 The twenty-first century baby is destined to be rocked and cradled by electricity, warmed and coddled by electricity, perhaps fathered and mothered by electricity. Probably the only thing he will be left to do unaided will be to make love. Mrs. John Lane, The fortnightly 1905 To-day, in the city of New York, sixty-six different tongues are spoken. A century hence, there will probably be only one. The American Historical Magazine 1907 I often think what interesting history we are making for the student of the twenty-first century. Willian Carey Jones 1908 China may be a great shoe market a decade or a century from now. Boot and Shoe Recorder 1914 We cannot settle the problem, and I venture the prophecy that perhaps a century from now this same question may be brought before some future society and discussed very much as it is tonight. Dr. Barton C. Hirst on the subject of abortion 1914 By the twenty-first century I believe we shall all be telepaths. Gumbriel, character in Antic Hay 1923 The physician of the twenty-first century… may even criticize the language of the times, and may find that some of our words have become as offensive to him as the term "lunatic" has become offensive to us. Dr. C. Macfie Campbell 1924 Historians of the twenty-first century will look back with well-placed scorn on the shallow-minded days of the early twentieth century when football games and petting parties were considered the most important elements of a college education. Mary Eileen Ahern, Library Bureau 1926 In the year A.D. 2014 journalists will be writing on the centenary of the great war — that is, if there has not been a greater war. F.J.M, The Journalist 1934

This New Year comic is to commemorate the New Year by giving us a view of the coming year (2014) from the past. The comic includes many quotes from the 1800s and early 1900s that speak to a time close to 2014. Many of them are for the twenty-first century in general, and only three mention a year that would be 2014 exactly. All but one of them is a prediction, yet some of these are quotes from fictional literature, and therefore are not true predictions. Words are in boldface to highlight the relevant content in the quote. The grey or non-bold text is non-essential to the point Randall is interested in, and only to be used to understand the context of the quote. The title text refers to a certain British officer, Mr. Colin Shakespeare, who experimented with and promoted the use of rope suspension bridges in India. The reference to "The Bard of Avon" is a reference to Shakespeare (the playwright) , as Avon is the river on which Stratford upon Avon is set, and is where the playwright was born and spent his youth. The author of this quote under the guise of eliminating the potential confusion that might result after decades or centuries have washed away the context, ironically and possibly vindictively, makes a point to note that the bridge is not named after the playwright, but Mr. Colin Shakespeare, whom he considers considerably less intelligent. This topic was previously covered in 771: Period Speech . Two years before, another New Years comic with just the new years number as the title was released: 998: 2012 . But actually the content of this comic is more related to the comic coming out just before the 2012 comic: 997: Wait Wait , which is also a New Year comic, that took a look at what could happen in 2012, just as this one does for 2014... In 2016 another comic, with only the new year as the name theme, occurred again 1624: 2016 . For some reason this only seemed to happen in the even years, until 1779: 2017 was released, with 1935: 2018 being the next one. The style of the comic is very similar to that of 1227: The Pace of Modern Life , which was released half a year earlier. (This is a series of quotes from various people of various timeframes. Each quote is followed by the author, the document of publication if applicable, and the year.) Notes from the past It's desirable every thing printed should be preserved, for we cannot now tell how useful it may become two centuries hence. Christopher Baldwin 1834 I predict that a century hence the Canadian people will be the noblest specimens of humanity on the face of the earth Rev. John Bredin 1863 In the twenty-first century mankind will subsist entirely upon jellies. The Booklover 1903 The twenty-first century baby is destined to be rocked and cradled by electricity, warmed and coddled by electricity, perhaps fathered and mothered by electricity. Probably the only thing he will be left to do unaided will be to make love. Mrs. John Lane, The fortnightly 1905 To-day, in the city of New York, sixty-six different tongues are spoken. A century hence, there will probably be only one. The American Historical Magazine 1907 I often think what interesting history we are making for the student of the twenty-first century. Willian Carey Jones 1908 China may be a great shoe market a decade or a century from now. Boot and Shoe Recorder 1914 We cannot settle the problem, and I venture the prophecy that perhaps a century from now this same question may be brought before some future society and discussed very much as it is tonight. Dr. Barton C. Hirst on the subject of abortion 1914 By the twenty-first century I believe we shall all be telepaths. Gumbriel, character in Antic Hay 1923 The physician of the twenty-first century… may even criticize the language of the times, and may find that some of our words have become as offensive to him as the term "lunatic" has become offensive to us. Dr. C. Macfie Campbell 1924 Historians of the twenty-first century will look back with well-placed scorn on the shallow-minded days of the early twentieth century when football games and petting parties were considered the most important elements of a college education. Mary Eileen Ahern, Library Bureau 1926 In the year A.D. 2014 journalists will be writing on the centenary of the great war — that is, if there has not been a greater war. F.J.M, The Journalist 1934

Haskell

Haskell

https://www.xkcd.com/1312

https://www.explainxkcd.com/wiki/index.php/1312:_Haskell

[Megan and Cueball are discussing.] Megan: Code written in Haskell is guaranteed to have no side effects. Cueball: ...because no one will ever run it?

The comic pokes fun at Haskell , a functional programming language . Functional programming languages are based on the mathematical concept of a function, that is two calls to a function always produce the same results given the same inputs. Side effects of a function call are changes to the program state or observable interactions with the outside world, other than returning a value. As a simple example, if a sum function changes a global variable, or prints the sum before returning it, those are side effects. Functions in most other languages frequently have side effects, typically making them hard to analyze. Functional programming languages seek to avoid side effects when possible. Pure functional programming languages like Haskell push this agenda by isolating the inevitable side-effects (input/output at least) through the type system (more specifically in monads for Haskell). The first joke says that Haskell only has no side effects because no one ever uses Haskell programs. Even in a traditional procedural programming language like C , if the program does not run, it can't have side effects. In Haskell, effects are first class values. This means that you can use effects just like any value, assign them to a variable, pass them around, or manipulate them to make new and different effects. Thus, there are technically no side effects, only primary effects. The title text is a joke about Haskell's lazy evaluation . The basic concept is that a value is not computed until it is actually used. Thus, it is possible to have a name representing the entire infinite list of Fibonacci numbers . However, until a particular element of the list is accessed, no work is actually done. The joke plays on "called" (referring to calling a function) vs. "called for" (requesting). Thus, Haskell may have value, but no one has either invoked it to get that value or requested such a language. A simpler example may be: The "or" function is defined as a normal function but can conclude instantly without computing the 10000th Fibonacci number (a daunting task) since this second parameter isn't necessary : "true or whatever" is always true. In reality, Haskell is indeed actively used, though it is not one of the most popular languages. It is in particular used by some financial institutions, safety conscious start-ups and websites (there are several active web frameworks in Haskell) like Randall 's own . [Megan and Cueball are discussing.] Megan: Code written in Haskell is guaranteed to have no side effects. Cueball: ...because no one will ever run it?

Regex Golf

Regex Golf

https://www.xkcd.com/1313

https://www.explainxkcd.com/wiki/index.php/1313:_Regex_Golf

[Caption at top of panel:] Regex golf: [Megan is sitting at a laptop. Cueball is standing behind her.] Megan: You try to match one group but not the other. Megan: /m | [tn]|b/ matches Star Wars subtitles but not Star Trek . Cueball: Cool. [Caption at top of panel:] Meta-regex golf: [A close-up of Megan at her laptop.] Megan: So I wrote a program that plays regex golf with arbitrary lists... Cueball (offscreen): Uh oh... [Caption at top of panel:] Meta-meta-regex golf: [Megan typing at her laptop.] Megan: ...But I lost my code, so I'm grepping for files that look like regex golf solvers. [Cueball facepalming.] [Caption at top of panel:] ...And beyond: [Another closeup of Megan at her laptop.] Megan: Really, this is all /(meta-)*regex golf/. Cueball: Now you have infinite problems. Megan: No, I had those already.

The comic talks about regular expressions , which are a way to specify textual patterns. Given a regular expression, one can search for the pattern it specifies inside a text string. If the pattern is found, it's said that the pattern "matches" the string; if it's not found, it's said it doesn't match. The title of the comic and the first panel is based on " regex golf ", which is a discipline of " code golf ", a game in which programmers attempt to solve a given programming problem using as few characters as possible, analogous to the number of golf shots it takes to reach the goal. In regex golfing, the programmer is given two sets of text fragments, and tries to write the shortest possible regular expression which would match all elements of one set, while at the same time not matching any element from the other set. The regex golf challenge Megan faces consists of matching all subtitles of (then extant) Star Wars films, while not matching any subtitle of Star Trek movies. Subtitles are the secondary titles of the movies, after the "Star Trek: " or "Star Wars Episode N: " . For example, in Star Wars Episode I: The Phantom Menace , the subtitle is The Phantom Menace . In the first panel, she created a 12-character regex solving the challenge. Then she moved on to building a tool which would automatically build such a regex for arbitrary lists of text, which could be described as meta - regex golfing. But as she has lost this tool, she needs to search through her files and chooses a tool called " grep " to find it. This implies that she needs a regular expression that would find any code that appears to be a regex golf generator, which leads to another "meta-" layer of abstraction. At the end, Megan notes this sequence of meta-meta-... might go to infinity and Cueball quips that she now has "infinite problems" as a result of her efforts; Megan retorts that she already had "infinite problems" because she's geeky enough to run meta-versions of programs on themselves, and stubborn enough to continue on until she fails, to the exclusion of all else. This also seems to be a reference to a famous quote by Jamie Zawinski (see also 1171: Perl Problems ): The first regex Megan uses is /m | [tn]|b/ , said to match Star Wars subtitles but not Star Trek . The forward slashes / just mark the start and end of the regex. The | character means "or", so the regex matches any string that contains the patterns " m ", " [tn] " or " b " (including the spaces). The square brackets match one of the enclosed characters, meaning that " [tn] " matches either " t " or " n ". The regex is apparently case-insensitive, because it wouldn't work otherwise. The Star Wars subtitles match the parts of the regex in the following way: Note that if the animated film "Star Wars: The Clone Wars" were included, it would not be matched by " [tn] " because the T is the start of the subtitle and is not preceded by a space. None of the "Star Wars:" films titles announced since this comic ("The Force Awakens", "The Last Jedi", and "The Rise of Skywalker") match this regex. On the other hand, none of the Star Trek subtitles contains an M followed by a space, a T or an N preceded by a space, or any B, so the regex does not match any of them. Note that in the original series all subtitles start with a "T" but it's the first character so it's not preceded by a space. Here is the list that Megan probably used: "Star Trek Beyond", which was released after this comic, would incorrectly match the regex since it is the first "Star Trek" title to contain a "b". However, since "Star Trek Into Darkness" and "Star Trek Beyond" both lack a colon in their titles, it is debatable whether they can truly be considered to have subtitles. In the last panel "and beyond" Megan uses the regular expression /(meta-)*regex golf/ to describe her problem. * means "zero or more" of the preceding character/group (parentheses () group characters). So this regex matches "regex golf", "meta-regex golf", "meta-meta-regex golf", etc. In a way this is regex golf in itself, matching all levels of meta-regex golf while not matching anything else. In the title text, there is a long regex that is the solution of another regex golf challenge: matching the last names of all elected US presidents but not their opponents. Note that the list of opponents include some people who were previously or later became presidents, or whose last name matches that of another person who was president, so taken literally this is impossible. To make this work the list of opponents must exclude any names of presidents. The regular expression itself works in a very similar way to the Star Wars/Trek one, including several different patterns separated by | . Each elected president matches one pattern while each opponent matches none. The regex does not match either of the presidents elected since the comic’s release ("Trump" and "Biden"), and thus would need to be updated. The regex does match Hillary Clinton's last name, but because a person with the same last name (Bill Clinton) was president, this does not count as a mistake. There was already a losing opponent called George Clinton who ran in 1792 and 1812. Here is a list of elected president and the patterns they match: Some presidents are missing because they weren't elected but became presidents after the resignation/death of their formers. And here is a list of how many unique last names are matched by each expression: Randall's regular expression does not match presidential opponents Pinckney, King, Clay, Cass, Scott, Douglas, McClellan, Seymour, Greeley, Tilden, Hancock, Blaine, Bryan, Parker, Hughes, Cox, Davis, Smith, Landon, Willkie, Dewey, Stevenson, Goldwater, Humphrey, McGovern, Mondale, Dukakis, Dole, Gore, Kerry, McCain, or Romney. However, it must be modified slightly, because it does match John C. Fremo nt , the runner-up to James Buchanan in 1856, as discussed by Peter Norvig at xkcd 1313: Regex Golf . It also matches Aaron Bu rr , the runner-up to Thomas Jefferson in 1800. Note that Norvig provides a small amount of Python code which actually plays regex golf with arbitrary lists, and found a shorter solution than Randall's for the Star Wars vs Star Trek game ( / t|p.*e/ ). [Caption at top of panel:] Regex golf: [Megan is sitting at a laptop. Cueball is standing behind her.] Megan: You try to match one group but not the other. Megan: /m | [tn]|b/ matches Star Wars subtitles but not Star Trek . Cueball: Cool. [Caption at top of panel:] Meta-regex golf: [A close-up of Megan at her laptop.] Megan: So I wrote a program that plays regex golf with arbitrary lists... Cueball (offscreen): Uh oh... [Caption at top of panel:] Meta-meta-regex golf: [Megan typing at her laptop.] Megan: ...But I lost my code, so I'm grepping for files that look like regex golf solvers. [Cueball facepalming.] [Caption at top of panel:] ...And beyond: [Another closeup of Megan at her laptop.] Megan: Really, this is all /(meta-)*regex golf/. Cueball: Now you have infinite problems. Megan: No, I had those already.

Photos

Photos

https://www.xkcd.com/1314

https://www.explainxkcd.com/wiki/index.php/1314:_Photos

[White Hat stands next to Cueball on a roof. There's a colourful sunset; in the distance, there are three people (a blonde girl, a Cueball-like guy and Megan) taking photos of the skyline as the sun sets.] White Hat: Ugh, I hate how people take pictures instead of just enjoying the view. Cueball: Why? [White Hat turns to Cueball.] White Hat: Documenting your life distracts you from living it. You're not really— Cueball: Oh, come on. [Only both their faces.] Cueball: Trying to take a picture of a thing makes me pay more attention to it. Some of my best adventures are built around trying to photograph something. [The panel zooms in on Cueball's face.] Cueball: If "other people having experiences incorrectly" is annoying to you, think how unbearable it must be to have a condescending stranger tell you they hate the way you're experiencing your life at just the moment you've found something you want to remember. Why the fuck do you care how someone else enjoys a sunset? [Zoom back out.] White Hat: Well, they... White Hat: Because I just, uh... White Hat: ... [Cueball takes out a camera.] Click

White Hat is upset at the sight of people photographing a richly colored sunset. His argument is that by documenting it instead of simply enjoying it, they have become an observer rather than a participant in life. Cueball expresses a contrary view, saying that not only does taking a photo of something help him focus attention on it, it is also none of White Hat's business how someone else chooses to enjoy a sunset. Cueball's logic reduces White Hat to inarticulacy, then speechlessness. Cueball then takes a photograph, implying that he would most enjoy White Hat's discomfiture by recording an image of it for posterity. Randall discusses a similar situation in the title text, the common modern phenomenon of restaurant diners photographing their meal. However, in this case he says he does not like them to document as he likes to listen to them eat. This may be sarcasm since not many people love the sound of someone else chewing. [ citation needed ] However, some people are annoyed by the food images posted to sites such as Facebook and Instagram. Note that the photograph is taken quickly; the chewing is only delayed for a few seconds. This brevity in delay can also apply to the main comic, since spending a few seconds photographing a sunset is just a brief interruption in enjoying the view sans camera. This comic is referenced in Thing Explainer in the explanation Picture taker by a small drawing of people taking photos of the view from the edge of a cliff. Another Cueball standing behind those taking pictures (another than in this comic for sure) is talking to Megan : Cueball: I hate how everyone takes pictures instead of just enjoying the view. Megan: ...You say, instead of enjoying the view. See also 648: Fall Foliage about Megan taking pictures and Cueball complaining. Later in 1719: Superzoom White Hat and Cueball again discusses photography, while in 2111: Opportunity Rover White Hat shares this same opinion again. [White Hat stands next to Cueball on a roof. There's a colourful sunset; in the distance, there are three people (a blonde girl, a Cueball-like guy and Megan) taking photos of the skyline as the sun sets.] White Hat: Ugh, I hate how people take pictures instead of just enjoying the view. Cueball: Why? [White Hat turns to Cueball.] White Hat: Documenting your life distracts you from living it. You're not really— Cueball: Oh, come on. [Only both their faces.] Cueball: Trying to take a picture of a thing makes me pay more attention to it. Some of my best adventures are built around trying to photograph something. [The panel zooms in on Cueball's face.] Cueball: If "other people having experiences incorrectly" is annoying to you, think how unbearable it must be to have a condescending stranger tell you they hate the way you're experiencing your life at just the moment you've found something you want to remember. Why the fuck do you care how someone else enjoys a sunset? [Zoom back out.] White Hat: Well, they... White Hat: Because I just, uh... White Hat: ... [Cueball takes out a camera.] Click

Questions for God

Questions for God

https://www.xkcd.com/1315

https://www.explainxkcd.com/wiki/index.php/1315:_Questions_for_God

[Megan and Cueball walk together.] Megan: Horace Lamb said he would have two questions for God: why quantum mechanics, and why turbulence? Cueball: I'd have just one: What did Miss Susie's steamboat do?!

Megan is paraphrasing a famous quote from the British applied mathematician , and fellow of the Royal Society , Horace Lamb , who famously stated in 1932 : This was referring to two phenomena in physics that, at the time, were poorly understood and difficult to explain. Lamb proved to be correct in his prediction that quantum electrodynamics (QED) was easier to explain; nowadays we have a much clearer understanding of QED, while our understanding of turbulence has improved little. Richard Feynman , who was himself largely responsible for explaining QED, famously described turbulence as "the most important unsolved problem of classical physics". Cueball , in response, indicates that if he were to gain divine elucidation his question would relate to the widespread schoolyard rhyme " Miss Susie ", which typically begins with the stanza: "Miss Susie had a steamboat The steamboat had a bell Miss Susie went to heaven The steamboat went to... Hell -o operator Please give me number nine ..." The rhyming scheme between the second and fourth lines, and implied contrast with "heaven," causes the listener to fill in the word "Hell" instead of the innocuous "Hello". Therefore, Cueball is wondering what a steamboat, an object lacking will, [ citation needed ] could have done to deserve divine punishment. The title text is a reference to the 1930s pulp series " The Shadow ", whose eponymous character is a psychic vigilante. The 1937 radio plays introduction began with the line "Who knows what evil lurks in the hearts of men? The Shadow knows!" Unfortunately, since a steamboat is not a person, [ citation needed ] The Shadow would be unable to determine what heinous crimes the steamboat had committed to deserve damnation. This comic, in particular the way Megan and Cueball are walking and its reference to theology, greatly resembles the later comic 1505: Ontological Argument . [Megan and Cueball walk together.] Megan: Horace Lamb said he would have two questions for God: why quantum mechanics, and why turbulence? Cueball: I'd have just one: What did Miss Susie's steamboat do?!

Inexplicable

Inexplicable

https://www.xkcd.com/1316

https://www.explainxkcd.com/wiki/index.php/1316:_Inexplicable

[Cueball sits at a desk with a laptop, making a fist at it.] Cueball: Argh! Megan (off-screen): What? Cueball: Why do I always have these inexplicable, impossible-to-diagnose computer problems? [Megan walks up to the desk.] Cueball: After six hours of this, I've concluded nothing works or makes sense. I give up on logic. Megan: *sigh* Gimme. I'll figure it out. Cueball: You won't. [Cueball sits at his laptopless desk while Megan works on the laptop off-screen.] type type Click Megan: ? type type type Megan: ??? [Megan is back in front of the desk, clutching the laptop.] Cueball: How'd it go? Megan: Your computer is literally haunted. Cueball: Told you.

Cueball 's laptop has a problem that has resisted many hours of concentrated effort at resolution. Megan offers to help, but after trying to fix it she concludes that the laptop is “literally” possessed by an evil spirit. A similarly unresolvable problem can be seen in 1084: Server Problem . In that case, no haunting is suggested, and Megan suggests that Cueball give up and wait for the singularity . The title text continues the conversation: when Megan tries to return the laptop to Cueball, he refuses, as Megan willingly took possession of it in the first place. Both have clearly decided that they no longer want anything to do with an object housing a supernatural entity, and are trying to pass it back to one another. [Cueball sits at a desk with a laptop, making a fist at it.] Cueball: Argh! Megan (off-screen): What? Cueball: Why do I always have these inexplicable, impossible-to-diagnose computer problems? [Megan walks up to the desk.] Cueball: After six hours of this, I've concluded nothing works or makes sense. I give up on logic. Megan: *sigh* Gimme. I'll figure it out. Cueball: You won't. [Cueball sits at his laptopless desk while Megan works on the laptop off-screen.] type type Click Megan: ? type type type Megan: ??? [Megan is back in front of the desk, clutching the laptop.] Cueball: How'd it go? Megan: Your computer is literally haunted. Cueball: Told you.

Theft

Theft

https://www.xkcd.com/1317

https://www.explainxkcd.com/wiki/index.php/1317:_Theft

[An identity thief sits in front of a laptop, looking at his hands] Thief: I feel paralyzed by overwhelming existential dread. Thief: ...and yet for some reason I'm really excited about space? [Caption below the panel:] The thief who stole my identity has a lot to deal with.

The term "identity theft" refers to a thief acquiring various types of a victim's identification (for example, bank account number and/or Social Security number), thus allowing the thief to pretend to be the victim and commonly steal money from the victim's bank account, etc. This comic exaggerates the term, interpreting it as the thief literally acquiring the victim's whole personality. Like Cueball & Megan in general, the victim is implied to have some Randallian personality traits, like the love of space and existential angst. Thus, the thief is now completely overwhelmed by having an entirely new personality, not to mention one whose parts clash with each other. The title text ponders the specifics of the identity acquisition process. Presumably, even two people whose personalities are identical would still start to think different thoughts. (This is a prerequisite for the depiction in the comic; the thief is baffled by his newly acquired interests, while the victim would not be baffled by the thoughts and interests they've developed over their entire life.) It is also wondered whether the victims new doppelganger is wondering the same thing, which could imply that their thoughts have not fully diverged. A friend comments that the victim may be overthinking the situation, and that the thief only took his credit card information. (A common method of identity theft. Does not transfer personality traits [ citation needed ] .) However, the victim is overwhelmed by existential anxiety. [An identity thief sits in front of a laptop, looking at his hands] Thief: I feel paralyzed by overwhelming existential dread. Thief: ...and yet for some reason I'm really excited about space? [Caption below the panel:] The thief who stole my identity has a lot to deal with.

Actually

Actually

https://www.xkcd.com/1318

https://www.explainxkcd.com/wiki/index.php/1318:_Actually

[Six people are standing upon a white circle as if it were a miniature planet. Each person is facing the reader and says something to the person on their right. All texts are displayed as a near-continuous stream over their heads to form one circle that encloses the whole picture.] [From topmost, going clockwise.] Cueball: Actually, measurements suggest it's flat. Ponytail: Actually, it's a sphere. White Hat: Actually, it's an oblate spheroid. Megan: Actually, it's a shape defined by the EGM96 coefficients. Hairy 1: Actually, it's that plus local topography. Hairy 2: Actually, it's embedded in a universe that's curved.

The image shows a sphere, a simple model for the shape of the Earth. Six people stand on its surface, talking about ways to best describe it, starting with a flat surface, the first belief held, and ending with general relativity. As the statements form a circle, the very first statement can lead recursively off the last, as described below. The statements in detail: Actually, measurements suggest it's flat. Actually, it's a sphere. Actually, it's an oblate spheroid. Actually, it's a shape defined by the EGM96 coefficients. Actually, it's that plus local topography. Actually, it's embedded in a universe that's curved. Actually, measurements suggest it's flat. Actually... Title text The title text pulls the whole comic together, pointing out that each statement in the comic is more precise than the previous. Unlike the loop in the comic, someone who does this will likely eventually win any real-life debate. The victory will not necessarily be a result of actually proving your logical argument, however: the phrase "stand alone" refers to driving away all conversation, resulting in no one wanting to speak to the person. [Six people are standing upon a white circle as if it were a miniature planet. Each person is facing the reader and says something to the person on their right. All texts are displayed as a near-continuous stream over their heads to form one circle that encloses the whole picture.] [From topmost, going clockwise.] Cueball: Actually, measurements suggest it's flat. Ponytail: Actually, it's a sphere. White Hat: Actually, it's an oblate spheroid. Megan: Actually, it's a shape defined by the EGM96 coefficients. Hairy 1: Actually, it's that plus local topography. Hairy 2: Actually, it's embedded in a universe that's curved.

Automation

Automation

https://www.xkcd.com/1319

https://www.explainxkcd.com/wiki/index.php/1319:_Automation

"I spend a lot of time on this task. I should write a program automating it!" [Two graphs are shown, plotting workload against time.] Theory: [The line for "work on original task" is steady but then drops down to a much lower level.] [The line for the automating job increases heavily while "writing code" and then drops down when "automation takes over".] [Both lines end up with a big amount of "free time".] Reality: [The line for "work on original task" is steady with no drop to a lower level.] [The line for the automating job increases heavily while "writing code", then it increases again while "debugging", it drops down slightly while "rethinking", and grows up again with an infinite end while the task is still an "ongoing development".] [The line for "work on original task" ends up with "no time for original task anymore".]

The comic refers to the phenomenon in which computer programmers attempt to create programs to automate menial but frequent tasks, to save time and effort. These attempts often end up taking much more time than the menial tasks would have taken. The first graph reflects the assumed ideal that leads programmers into such an attempt: writing the program will take more effort initially, but once the program is complete, it will take over the routine tasks, leaving the programmer free to do something else. However, writing a program often turns out to be not that simple: programs can have defects, and certain functionalities can be hard to implement. Because of this, programmers usually spend more time than projected to finish a program. As time goes on, the desire to see it finished can consume the programmer's effort and attention, with the menial tasks left undone. The title text is a play on the word "automating." While "auto-" is indeed a prefix that means "self," the root word "mat," from the Greek "matos," in fact refers to "moving" or "acting," so "automate" effectively means "self-moving." However, the title text uses a double entendre of the word "mating", the definitions of which include "to copulate," or, in slang, "to screw" (the latter having the double meaning of giving someone a hard time). This rendition of "automating" translates to self-screwing ("screwing yourself over", giving yourself a hard time), which, according to this comic, happens when one attempts to automate a process. See also 974: The General Problem and 1205: Is It Worth the Time? or the Time management category . "I spend a lot of time on this task. I should write a program automating it!" [Two graphs are shown, plotting workload against time.] Theory: [The line for "work on original task" is steady but then drops down to a much lower level.] [The line for the automating job increases heavily while "writing code" and then drops down when "automation takes over".] [Both lines end up with a big amount of "free time".] Reality: [The line for "work on original task" is steady with no drop to a lower level.] [The line for the automating job increases heavily while "writing code", then it increases again while "debugging", it drops down slightly while "rethinking", and grows up again with an infinite end while the task is still an "ongoing development".] [The line for "work on original task" ends up with "no time for original task anymore".]

Walmart

Walmart

https://www.xkcd.com/1320

https://www.explainxkcd.com/wiki/index.php/1320:_Walmart

[Caption above the panel:] When a network tries to become everyone's one-stop hub, the Walmart of social interaction... [Cueball and Hairy standing in a supermarket, Cueball holding groceries under his arm, Hairy with a cart.] Cueball: Oh, uh, hi! Funny running into you here. Hairy: Oh, hey! Yeah! How've you been? [Caption below the panel:] ...it inevitably becomes the Walmart of social interaction.

This comic satirizes the way in which large social networks, such as Facebook (and at the time of this comics posting Google+ ), attempt to aggregate all aspects of the user's online social presence. Earlier social networks had more granular focuses; e.g. MySpace originated with a music focus, and even earlier various bulletin board systems were centered around specific topics. By contrast, many social media companies attempt to encapsulate the variety of aspects of their users' online lives, thereby aggregating their personal, professional, and private lives in a way that was previously unlikely to occur. The first comparison to Walmart , a large multi-national "big box" retailer that sells everything from gardening supplies to televisions to groceries, is apt because Walmart, too, is attempting to aggregate various aspects of your life into a single location - but rather than aggregating your social media presence, it's attempting to aggregate your shopping habits. The punch line of the joke is that social interactions at Walmart are awkward, contrived, and frequently undesired — just as they can grow to become in a social network that is insufficiently focused or too bloated. People communicate differently with different groups of people, and if they are attempting to connect with friends, they are unlikely to want their grandparents present. Similarly, if a person is attempting to buy groceries, they may not be interested in extended small talk with acquaintances with whom they may not share much in common (perhaps the fact that they both shop at Walmart is the biggest similarity they share). The title text elaborates on this idea by sarcastically implying that he wants all his older relatives to hang out where he hung out in college, likely causing extreme awkwardness. [Caption above the panel:] When a network tries to become everyone's one-stop hub, the Walmart of social interaction... [Cueball and Hairy standing in a supermarket, Cueball holding groceries under his arm, Hairy with a cart.] Cueball: Oh, uh, hi! Funny running into you here. Hairy: Oh, hey! Yeah! How've you been? [Caption below the panel:] ...it inevitably becomes the Walmart of social interaction.

Cold

Cold

https://www.xkcd.com/1321

https://www.explainxkcd.com/wiki/index.php/1321:_Cold

[It's cold, two Guys wearing knit caps (one knit cap is white the other black) are walking outside and the White Knit Cap Guy is shivering.] White Knit Cap Guy: It is brutal out. So much for global warming, huh? Black Knit Cap Guy: *sigh* This used to happen all the time. White Knit Cap Guy: What? [A dot plot showing number of days with lows below zero Fahrenheit by year since 1970.] Black Knit Cap Guy (off-screen): You're from St. Louis, right? Black Knit Cap Guy (off-screen): On average, it used to get below 0 °F there a handful of days per year. Black Knit Cap Guy (off-screen): But you haven't had a day like that since the nineties. [Above the dot plot to the left is a label in a black frame:] Days with lows < 0°F [Below the dot plot are written the years:] 1970 1980 1990 2000 2010 [Below again is written in small letters:] Source: rcc-acis.org/climatecentral [Black Knit Cap Guy has stopped walking.] Black Knit Cap Guy: Then, in 2014, when the first polar vortex hit, it dipped below zero for two days. Black Knit Cap Guy: And everyone freaked out [They continue walking.] Black Knit Cap Guy: because what used to be normal Black Knit Cap Guy: now feels too cold. White Knit Cap Guy: It is too cold! [Above the last panel is written in a black frame:] The Future: [Cueball is pointing at a patch of ice.] Cueball: Look at this— ice! In St. Louis! So much for global warming. Person off-screen: *sigh* Note that this is not the same data set as mentioned in xkcd as this is regarding freezing days and not subzero days! With the full excel dataset of the number of freezing days (i.e. below 32 °F) as obtained from the National Oceanic and Atmospheric Administration 's homepage NOAA you get the following plot: From the same dataset excel dataset we can also get the number of sub-zero days i.e. below 0 °F (which are those mentioned in the XKCD strip) - plotting those and you get the following plot: Note that this IS the same data set as mentioned in XKCD. This is subzero days! While there were a number of very cold years with outliers in the 1970s - then the clear overall trend is still that there are fewer days with cold weather over the years. So while weather is different every year (which is also illustrated by the outliers) the climate is defined by the long term trend - which is the point of this cartoon.

In this comic, Cueball (wearing a white knit cap with a pom-pom) and Cueball's friend (wearing a black knit cap) are walking outside in sub 0 °F (-17.8 °C). White Knit Cap Guy complains about the brutal cold and as a result questions whether global warming is real. Black Knit Cap Guy explains that this kind of weather used to happen all the time back before the year 2000, showing that global warming is, in fact, very real. This is illustrated in panel two by a graph showing the number of days with sub 0 °F as a function of year from 1970 to 2013 in the city of St. Louis , (where we learn that Cueball is from). It shows that these days used to be rather common between 1970 and 1999, only to be completely absent for the next 14 years until and including 2013. A source link for this graph is provided (though as of June 2014, the link is dead - see Trivia below). Cueball's friend uses this graph to explain that not a single day like this has happened since 2000, until here in 2014 where a polar vortex pushed the temperature down below zero again for two days. Since this weather is now unusual and infrequently experienced, people in St. Louis perceive it as being very cold because they have since adapted and are now unused to this sort of temperature, even though this was a common temperature to reach in past decades. This is further demonstrated when Cueball remarks that it's "too cold". Subzero Fahrenheit temperatures are very cold to be out in. See for instance the first panel of 526: Converting to Metric . In the last panel, in a future St. Louis, a Cueball discovers a thin sheet of ice, suggesting the temperature has fallen just below 32 °F (0 °C), the freezing point of water. The suggestion here is that the environment has warmed to such an extent that temperatures below 32 degrees F are very unusual, and the future Cueball repeats the same short-term fallacy that such "extreme cold" disproves global warming. Someone off-panel, presumably another Black Knit Cap Guy, sighs as the cycle continues. The comic reacts to a simplified view of global warming by amateurs, including media, who fail to understand (or choose to ignore) the difference between climate and weather . Short, random weather fluctuations like the polar vortex are taken as examples or counter-examples of climate change and global warming. To understand climate change, one must look at global (not local) and long-term (not short-term) temperature trends. Debates on the theory of global warming/climate change often center on whether the current warming trend is primarily caused by humans or is a natural change, as has happened in the past. Within the scientific community, there is an overwhelming consensus that the current trend is anthropogenic (i.e. man-made), but many in the general public (including many politicians) are hesitant to accept this. There is clearly no doubt about where Randall stands on this debate, as many of his comics and blog posts continue to plead for humanity to do something about the man-made global warming trend - especially in comic 1379: 4.5 Degrees . The title text suggests that gathering data about global warming is time-consuming and is the kind of stuff only a real nerd would do. Most people would rather hang out with friends, or at least spend their time with some more fun nerd activity. Randall has been known to use the title text to poke fun at himself over how much time he has spent researching topics and more generally how geeky his interests tend to be. Although the title text tries to deny this geeky behavior, he cannot help himself at the end by mentioning another interesting climate subject: Snowfall records . Climate change, especially global warming, is a recurring theme in xkcd. [It's cold, two Guys wearing knit caps (one knit cap is white the other black) are walking outside and the White Knit Cap Guy is shivering.] White Knit Cap Guy: It is brutal out. So much for global warming, huh? Black Knit Cap Guy: *sigh* This used to happen all the time. White Knit Cap Guy: What? [A dot plot showing number of days with lows below zero Fahrenheit by year since 1970.] Black Knit Cap Guy (off-screen): You're from St. Louis, right? Black Knit Cap Guy (off-screen): On average, it used to get below 0 °F there a handful of days per year. Black Knit Cap Guy (off-screen): But you haven't had a day like that since the nineties. [Above the dot plot to the left is a label in a black frame:] Days with lows < 0°F [Below the dot plot are written the years:] 1970 1980 1990 2000 2010 [Below again is written in small letters:] Source: rcc-acis.org/climatecentral [Black Knit Cap Guy has stopped walking.] Black Knit Cap Guy: Then, in 2014, when the first polar vortex hit, it dipped below zero for two days. Black Knit Cap Guy: And everyone freaked out [They continue walking.] Black Knit Cap Guy: because what used to be normal Black Knit Cap Guy: now feels too cold. White Knit Cap Guy: It is too cold! [Above the last panel is written in a black frame:] The Future: [Cueball is pointing at a patch of ice.] Cueball: Look at this— ice! In St. Louis! So much for global warming. Person off-screen: *sigh* Note that this is not the same data set as mentioned in xkcd as this is regarding freezing days and not subzero days! With the full excel dataset of the number of freezing days (i.e. below 32 °F) as obtained from the National Oceanic and Atmospheric Administration 's homepage NOAA you get the following plot: From the same dataset excel dataset we can also get the number of sub-zero days i.e. below 0 °F (which are those mentioned in the XKCD strip) - plotting those and you get the following plot: Note that this IS the same data set as mentioned in XKCD. This is subzero days! While there were a number of very cold years with outliers in the 1970s - then the clear overall trend is still that there are fewer days with cold weather over the years. So while weather is different every year (which is also illustrated by the outliers) the climate is defined by the long term trend - which is the point of this cartoon.

Winter

Winter

https://www.xkcd.com/1322

https://www.explainxkcd.com/wiki/index.php/1322:_Winter

[Cueball and Beret Guy, Cueball in a winter hat and Beret Guy in a beret, are walking through snow and across a patch of ice.] Beret Guy: The sky is cold and the floor water is too hard to drink. [Beret Guy looks upwards.] Beret Guy: But I have my handcoats and the spacelight is warm. [Beret Guy and Cueball continue on through woods; there are musical notes coming from the trees.] Beret Guy: Listen—the flappy planes are beeping in the stick towers. [Cueball pauses.] Cueball: Those are all the wrong words for those things. [Beret Guy replies from off panel.] Beret Guy: Maybe—but the things themselves are all right. So who cares? [Cueball continues walking, with sunlight and musical notes above.]

Beret Guy and Cueball are walking. Beret Guy is making several remarks about the situation. The air is cold, the puddles have frozen, he has mittens, the sunlight is warm, and the birds are chirping in the trees. When making these observations, however, he does not use the conventional terms. Instead he uses word compounds, similar to " Up Goer Five ". When Cueball brings up Beret Guy's odd vocabulary, he retorts by declaring that the name does not matter, as long as the things themselves are what they should be. This is the same concept that is communicated in the line from the Shakespearean play, "Romeo and Juliet": "What's in a name? That which we call a rose by any other name would smell as sweet ." The concept is similar to that discussed by Richard Feynman as the difference between knowing the name of something and knowing something. In the title text Beret Guy continues to use playful language and offers affectionate encouragement: "stay warm, little flappers", demonstrating that his intentions are kind, not obfuscatory. Additionally, it is an indirect salutation from Randall Munroe to the readers, acknowledging the remarkably cold temperatures North America was experiencing at the time. Strange synonyms are also found in 919: Tween Bromance and 2352: Synonym Date . [Cueball and Beret Guy, Cueball in a winter hat and Beret Guy in a beret, are walking through snow and across a patch of ice.] Beret Guy: The sky is cold and the floor water is too hard to drink. [Beret Guy looks upwards.] Beret Guy: But I have my handcoats and the spacelight is warm. [Beret Guy and Cueball continue on through woods; there are musical notes coming from the trees.] Beret Guy: Listen—the flappy planes are beeping in the stick towers. [Cueball pauses.] Cueball: Those are all the wrong words for those things. [Beret Guy replies from off panel.] Beret Guy: Maybe—but the things themselves are all right. So who cares? [Cueball continues walking, with sunlight and musical notes above.]

Protocol

Protocol

https://www.xkcd.com/1323

https://www.explainxkcd.com/wiki/index.php/1323:_Protocol

[Cueball is telling a story to a Computer Scientist who is seated at his desk.] Cueball: Alice sends a message to Bob saying to meet her somewhere. Computer Scientist: Uh huh. Cueball: But Eve sees it, too, and goes to the place. Computer Scientist: With you so far. Cueball: Bob is delayed, and Alice and Eve meet. Computer Scientist: Yeah? CAPTION: I've discovered a way to get computer scientists to listen to any boring story.

Alice, Bob, and Eve are role names traditionally used in describing cryptographic protocols. Rather than talking about "Person A", "Person B", "Person C", names beginning with each letter are used instead, and giving them different genders let pronouns be used to shorten discussions. For example: "Person A sends Person B a message encoded with Person B's public key" is much easier to parse when written as "Alice sends Bob a message encoded with his public key." Eve is short for "eavesdropper" - a person trying to find out what's being said in the conversations between the other people. The classic situation involves Alice wanting to send a secret message to Bob, while Eve (the eavesdropper), attempts to read the message, ideally without Alice or Bob ever finding out. Additional participants such as Carol (Person C) can be added if necessary. The list of names has become very standardised over time as described at Alice and Bob . The joke here is that any computer scientist, hearing the names used, will think that they are listening to a cryptography problem. By changing the names in a story to these role names, you can induce them to listen carefully to boring stories. The fewer the interesting details, the more it sounds like a general problem, so very boring stories are actually the easiest. The title text shows a more radical approach to the problem, for people who do not feel comfortable about lying. In this approach, you only make friends with people who have the appropriate names already. The comic title also can be interpreted in two ways. First, the computer scientist thinks the conversation is about an encryption protocol. Second, the way the conversation is carried resembles a protocol used by many data communication systems, where one side sends data while the other sends back an acknowledgement upon receiving the data. In this case, the data are the lines of the boring story. In comic 177: Alice and Bob these names are used in the same context. Instead of Alice and Bob being perfectly innocent people who just want to communicate in private, Bob is actually having an affair with Alice. Eve —his former partner— cracked the encryption to see what the message contained. Thus, this comic seems to continue the Alice/Bob romance, jealous-Eve plot, with Eve apparently confronting Alice over her text message to Bob. [Cueball is telling a story to a Computer Scientist who is seated at his desk.] Cueball: Alice sends a message to Bob saying to meet her somewhere. Computer Scientist: Uh huh. Cueball: But Eve sees it, too, and goes to the place. Computer Scientist: With you so far. Cueball: Bob is delayed, and Alice and Eve meet. Computer Scientist: Yeah? CAPTION: I've discovered a way to get computer scientists to listen to any boring story.

Weather

Weather

https://www.xkcd.com/1324

https://www.explainxkcd.com/wiki/index.php/1324:_Weather

[Cueball and Hairy are talking.] Hairy: So, how 'bout this weather? Cueball: I know, right? The whole jet stream layer is nuts! Hairy: Um, sure... Cueball: The 18z GFS forecasts 960mb by Tuesday. Think it'll verify? Hairy: What? Cueball: ...Right. Sorry. Uh, yeah! Weather sure has been crazy. [Caption below the panel:] Weather geeks have it tough.

Social norm accepts casual small-talk as an ice breaker for interaction — usually it is always safe to talk about the weather without hitting any disagreements as there are rarely any personal viewpoints about the weather — in contrast small-talk is never about political subjects or similar where chances are that there are strong personal viewpoints. In this strip Cueball is described a "weather geek", enjoying subjects such as meteorology and weather forecasting . When Hairy makes a comment about the weather, Cueball launches into a detailed technical discussion, not realizing Hairy is simply trying to engage in small-talk. Only weather geeks would have this problem, but this topic is a common opening for a conversation in casual small-talk. Cueball switches to small-talk once he realizes that Hairy is confused and didn't expect this level of technical information. As to the jargon: The title text clarifies the problem weather nuts like Cueball here have: Unlike other geeky pursuits (like, say, the Derinkuyu Underground Cities , one of the most well-known archaeological sites in Turkey ) weather is a fairly common small talk subject. As a result, weather geeks have to be constantly vigilant so as not to launch into technical monologues. [Cueball and Hairy are talking.] Hairy: So, how 'bout this weather? Cueball: I know, right? The whole jet stream layer is nuts! Hairy: Um, sure... Cueball: The 18z GFS forecasts 960mb by Tuesday. Think it'll verify? Hairy: What? Cueball: ...Right. Sorry. Uh, yeah! Weather sure has been crazy. [Caption below the panel:] Weather geeks have it tough.

Rejection

Rejection

https://www.xkcd.com/1325

https://www.explainxkcd.com/wiki/index.php/1325:_Rejection

[Cueball is walking, and a Cueball-like guy follows him.] Guy: Women say they want nice guys, but what they really want are— Cueball: —Guys who respond to rejection by belittling their judgment and self-awareness? Cueball: If so, don't worry — you'll be fine.

In popular culture women are sometimes said to not be interested in nice guys , as in common interpretations of the phrase nice guys finish last which originally belongs to baseball. The Cueball -like guy on the left in this picture is presumably frustrated and complaining because he has been rejected by a woman, and thinks it's because he's the "nice guy" type. Cueball's sarcastic interjection implies that saying that women don't want nice guys and presuming to know what women "really want" is actually showing a rejection of that woman's agency, which might be the real reason she rejected him. It fits with one of the negative connotations of "nice guy": one who does not express his true feelings and/or is passive-aggressive . The title text continues the "conversation", with Cueball implying that he believes that the first guy is bad at taking hints. He offers a "crash course" in hint taking by clarifying outright that he is trying to end the conversation while the first guy continues to follow him. Though this guy might indeed be a jerk, there are also many other reasons why a woman might reject a guy who isn't a jerk. The concept of the self-identifying "nice guy" who actually may have less than admirable motives is also explored in 513: Friends . See also the concept of "negging" as used in 1027: Pickup Artist : you belittle chicks to undermine their self-confidence so they'll be more vulnerable and seek your approval . [Cueball is walking, and a Cueball-like guy follows him.] Guy: Women say they want nice guys, but what they really want are— Cueball: —Guys who respond to rejection by belittling their judgment and self-awareness? Cueball: If so, don't worry — you'll be fine.

Sharks

Sharks

https://www.xkcd.com/1326

https://www.explainxkcd.com/wiki/index.php/1326:_Sharks

[Cueball is sitting on a throne, talking to a minion who's not shown in the panel.] Minion: The prisoner escaped and is swimming toward the mainland! Cueball: Release the sharks. Minion: Yes, sir. Minion: The sharks are swimming away. Cueball: They're escaping, too? Send sharks after them! Minion: Now those sharks are swimming away. Cueball: More sharks. Minion: ...Sir, what's going on? Cueball: Prisoners, of course! Can't let 'em escape! Minion: Sir, are you trying to turn Doom Island into a marine biology center? Cueball: Shark populations are in decline– Cueball: *ahem* Cueball: I mean, the world must fear us! Minion: Right...

This comic is a joke about the use of sharks in action movies. In these movies, sharks are often used to guard locations and dispense capital punishment. Since the idea of a guard shark is not practical, this comic suggests that villains raise sharks to help with declining shark populations in the oceans. In this comic Cueball is an evil villain who rules over a "Doom Island." In addition to commanding minions and detaining prisoners, he keeps sharks to threaten prisoners. When a prisoner escapes the island, he orders his minions to "release the sharks." However, the sharks do not hunt the prisoner, but merely swim away. The comic jokes that Cueball is using fugitives as a pretense to help with declining shark populations, and that Doom Island is just a front for a marine biology center. Cueball maintains the whole "guard sharks" idea as a cover-up, so that his minions do not catch on to the real mission. The title text plays on the idea that Cueball can't be openly concerned with his sharks' welfare without his minions catching on. He claims to be inspecting the shark cages. As a shark cage is normally used to provide protection for divers wishing to observe sharks up-close, they would not work well as cages to hold prisoners (which is their stated purpose). The comic implies that when he is "inspecting the cages" he is really performing a scientific study on the sharks, or simply observing them because he loves them. Because a real villainous lair would have no use for shark cages, it follows that Cueball owns them solely for the purpose of gratifying his interest in his sharks, thus forcing him to keep up the pretense of the cages being of some help in preventing prisoners from escaping. The shark issue is also one of the items on the chart of 1331: Frequency . "Doom Island" is most likely meant to be a generic name for the villain's lair (a trope dating back to at least the first James Bond film, Dr. No ); however, a real island of this name exists in Indonesia. In action movie trope from the '70s and '80s, evil villains use sharks to kill off enemies. Some examples are: And in the James Bond series: [Cueball is sitting on a throne, talking to a minion who's not shown in the panel.] Minion: The prisoner escaped and is swimming toward the mainland! Cueball: Release the sharks. Minion: Yes, sir. Minion: The sharks are swimming away. Cueball: They're escaping, too? Send sharks after them! Minion: Now those sharks are swimming away. Cueball: More sharks. Minion: ...Sir, what's going on? Cueball: Prisoners, of course! Can't let 'em escape! Minion: Sir, are you trying to turn Doom Island into a marine biology center? Cueball: Shark populations are in decline– Cueball: *ahem* Cueball: I mean, the world must fear us! Minion: Right...

Mobile Marketing

Mobile Marketing

https://www.xkcd.com/1327

https://www.explainxkcd.com/wiki/index.php/1327:_Mobile_Marketing

[Black Hat sits at a desk. A voice speaks from off panel, in front of Black Hat.] Off panel: CNN hired you to improve viewership. [Black Hat continues to sit at the desk.] Black Hat: ...yes, and? [Next panel, conversation continues.] Off panel: You texted "Holy crap, turn on the news" to a million random phone numbers? Black Hat: It sure did work. Off panel: Not what we meant!

Black Hat was hired by the Cable News Network ( CNN ) to increase its popularity, presumably long-term. However, all he did was text one million people implying that a huge, unbelievable event was happening. While this technically did increase viewers of CNN, this was most likely only for a few minutes before the viewers realized nothing had happened. Because of this, Black Hat did very little to help CNN. It is possible that this is the finale of a long career Black Hat has had in marketing, beginning in 125: Marketing Interview . The title text is spoken by the offscreen character who, after saying that division of CNN was firing Black Hat, told him that the online headline writing department wanted to hire him. This is because the message Black Hat texted to the million phone numbers is very similar to link bait , which are headlines or titles that, like the text message, promise highly interesting articles without being very detailed as to their nature. Thus, perhaps online, Black Hat could bring clicks up long term through this unscrupulous practice, as opposed to mass unsolicited texts. The practice of link bait has also been mentioned in 1283: Headlines . [Black Hat sits at a desk. A voice speaks from off panel, in front of Black Hat.] Off panel: CNN hired you to improve viewership. [Black Hat continues to sit at the desk.] Black Hat: ...yes, and? [Next panel, conversation continues.] Off panel: You texted "Holy crap, turn on the news" to a million random phone numbers? Black Hat: It sure did work. Off panel: Not what we meant!

Update

Update

https://www.xkcd.com/1328

https://www.explainxkcd.com/wiki/index.php/1328:_Update

[Cueball sits at a desk. A message is being displayed on Cueball's laptop screen.] Urgent : Critical update available! [The message continues.] Details : Fixes an issue that was causing random laptop electrical fires. (This update will require restarting your computer.) [Cueball clicks on Remind me later .] click

When developers responsible for fixing errors on a specific operating system release a patch, the operating system often ask users to restart the computer after installing. This is often done by popup window shown to the user where they can choose to restart immediately or choose to be reminded later. Many messages from these popups emphasize the importance of installing the updates, but Cueball is just annoyed about this. Sometimes, these issues are minor and do not affect most computers using the operating system. Often other programs, not part of the operating system, ask for a reboot because the updated routine only runs after the next reboot. Regardless, reboots can take a long time — a typical user doesn't like this. The user can choose to be reminded later multiple times. Because rebooting a computer takes a significant amount of time and closes any programs running, a user may delay the update repeatedly to avoid interrupting what they were doing at the time. The comic is making two jokes simultaneously: the core comic jokes that reboots are so tedious and disruptive it would actually be preferable for a laptop to burst into flame than to go through one, while the title text suggests that the real problem is that humans are so incapable of delayed gratification and/or risk evaluation they would rather risk bodily harm than suffer a minor inconvenience. The joke uses an "exploding laptop battery" as an exaggeration for comedic effect. Most software doesn't affect hardware issues like burning laptop batteries . [ citation needed ] However, low-level software, such as the kernel or drivers , might cause hardware to misbehave. The title text reflects the fact that the average user will have multiple applications open and a reboot would require closing them. They would then have to open all their applications again after the computer has restarted. This can also refer to a browser application having multiple tabs open. This is becoming less of an issue because browsers have an option to restart the last session again after being closed, as would happen with a reboot, but many users still don't trust it to work properly. [Cueball sits at a desk. A message is being displayed on Cueball's laptop screen.] Urgent : Critical update available! [The message continues.] Details : Fixes an issue that was causing random laptop electrical fires. (This update will require restarting your computer.) [Cueball clicks on Remind me later .] click

Standing

Standing

https://www.xkcd.com/1329

https://www.explainxkcd.com/wiki/index.php/1329:_Standing

[Cueball is running after a deer with a laptop strapped to its back, while Megan looks on.] Cueball: Humans aren't built to sit all day. This is much healthier. [Caption below the panel] My Hobby: One-upping the standing desk people

Standing desks are a current fad in modern tech companies. Supposedly more ergonomic and comfortable than sitting all day, they can be combined with treadmills or stationary bicycles to enable exercise to be taken while working. Cueball tells Megan that standing desks are inferior to his solution, strapping his laptop to a deer. The deer constantly runs away from Cueball , forcing him to chase and get exercise (and probably get kicked if he catches up). Additionally, by mentioning the common line of "humans weren't meant to sit all day", he is saying that his deer-based solution is much more similar to the task that humans evolved to do, namely hunting and gathering . Humans are in fact one of the few species built for exhaustion hunting (exactly what it sounds like), and are able to chase a prey for more than four hours in ideal conditions. This is also why one's legs feel sore when standing for extended periods but not while moving, as the valves in one's veins only work when one's legs are moving. The title text takes this a step further, saying that the deer was surprisingly ergonomic, apart from the kicks — which would, presumably, be quite debilitating. The ergonomics could be due to the soft, warm nature of the flesh compared to typical cold, hard tables. [Cueball is running after a deer with a laptop strapped to its back, while Megan looks on.] Cueball: Humans aren't built to sit all day. This is much healthier. [Caption below the panel] My Hobby: One-upping the standing desk people

Kola Borehole

Kola Borehole

https://www.xkcd.com/1330

https://www.explainxkcd.com/wiki/index.php/1330:_Kola_Borehole

[Megan and Black Hat are sitting in front of their laptops.] Megan: Ever hear of the Kola Borehole? Black Hat: No—what's that? Megan: A Soviet project to drill deep into the Earth's crust. Megan: There's a hoax report claiming that their drill broke through into a superhot cavern, and when they lowered a microphone into the hole, they heard tormented screaming. People say that's why the miners sealed the well and abandoned the project. Black Hat: Why would anyone believe that story? Megan: I guess some people think Hell is literally an underground place. Black Hat: No - I mean, why would the miners seal the opening? Why not just dig a canal connecting it to the ocean? Unless they like Hell. Megan: ...If there's ever a war between Earth and Hell, I hope I'm on your side. Black Hat: You seem nice; you probably won't be.

The Kola Superdeep Borehole is the result of a scientific drilling project by the Soviet Union in what is now north-western Russia that began in 1970 and continued through 1992. It was an attempt to drill as far into the Earth as possible. The deepest hole reached 12,262 metres (40,230 ft). It remains the deepest artificial point on earth . Megan mentions the well to Hell hoax that the drilling hit a super-hot cavern which is disproved at www.snopes.com: "The Well to Hell" . Although super-hot temperature was the reason the project was abandoned, no chamber or voices were discovered. As Megan notes, the hoax plays on the popular notion that Hell is literally a physical place below us — therefore by definition, towards the centre of the Earth — whereas Heaven is above us; often depicted in the clouds. Megan suggests that the miners therefore sealed the hole to "seal in" Hell. There is no mention in the Wikipedia article about the hole being sealed; however there is a picture with the caption "The borehole itself (welded shut)". If "sealing the hole" is considered to mean filling the entire hole up with concrete or some other material, then given the potential for future scientific data, the 22 years spent drilling and the cost of sealing the hole, this would not seem to be a reasonable thing to do. Black Hat suggests that if the Hoax were true and the miners did believe they'd drilled into Hell, a better alternative to sealing the hole would have been to dig a canal to the ocean, thereby allowing water to flow into the hole and into Hell. As all of Hell is depicted as below the surface of the Earth, and characterized by fire, brimstone, and extreme heat, this would entirely fill Hell with water, drastically altering it. (Depending on the volume of Hell, this could have significant effects on the global sea level and the atmosphere.) Megan never thought of that possibility and compliments Black Hat's ingenuity by suggesting that if there were ever a real conflict with Hell, she would want to be "on his side", given his clever suggestion on how to destroy Hell. He responds by suggesting that Megan is "nice" and therefore probably won't be on his side. This suggests Black Hat considers himself evil and thinks he would be fighting for Hell or maybe on behalf of those consigned there, rather than against it. Alternatively, he thinks he is worse than the devil and that Megan would be on the "nicer" side. The title text parodies a nondescript news report of a person's death. In this case it is about Lucifer being killed by Black Hat carrying out his plan to flood Hell. However, the report is written in a non-descript way that ignores the presumed sensationalism of the story (i.e., that Hell exists and has been flooded). It is notable that "Lucifer" is often used in modern times to refer to Satan and both are used to refer to the "leader" or "keeper" of Hell, although the Bible never directly identifies them as the same entity, and he/they are never tied directly to Hell anywhere in the Bible. Much of the modern image of Hell is derived from Dante's " Inferno " along with a variety of additional details which have been added and changed throughout the years. The reference to sharks is a reference to 1326: Sharks that was released a week before. [Megan and Black Hat are sitting in front of their laptops.] Megan: Ever hear of the Kola Borehole? Black Hat: No—what's that? Megan: A Soviet project to drill deep into the Earth's crust. Megan: There's a hoax report claiming that their drill broke through into a superhot cavern, and when they lowered a microphone into the hole, they heard tormented screaming. People say that's why the miners sealed the well and abandoned the project. Black Hat: Why would anyone believe that story? Megan: I guess some people think Hell is literally an underground place. Black Hat: No - I mean, why would the miners seal the opening? Why not just dig a canal connecting it to the ocean? Unless they like Hell. Megan: ...If there's ever a war between Earth and Hell, I hope I'm on your side. Black Hat: You seem nice; you probably won't be.

Frequency

Frequency

https://www.xkcd.com/1331

https://www.explainxkcd.com/wiki/index.php/1331:_Frequency

[Repetitive events are written in grey and arranged in a grid. Each statement pulses to black and then returns to grey at an interval characteristic of the named event.]

This comic shows a number of common events, arranged in a grid. Each of the events flashes with its average frequency. For example, statistically a child is born somewhere on the world approximately every 0.24 seconds, or four times per second. Therefore, the tile "One birth" blinks about 4 times per second. The title text refers to the Pitch drop experiment which measures the flow of a piece of pitch over many years. At room temperature, tar pitch flows at a very slow rate, taking several years to form a single drop. The title text jokes that Randall tried to include a tile that flashes about once every ten years , but the tiles are all animated GIFs and while the file format supports animations of any length, the resulting file would be too big (at least 10 megabytes). A thorough analysis of the frequencies present in this comic and how they relate to the underlying technology (the GIF format) was published as Reverse Engineering xkcd's 'Frequency' . The table below lists all the events and their duration / frequency. Some events make reference to other comics. [Repetitive events are written in grey and arranged in a grid. Each statement pulses to black and then returns to grey at an interval characteristic of the named event.]

Slippery Slope

Slippery Slope

https://www.xkcd.com/1332

https://www.explainxkcd.com/wiki/index.php/1332:_Slippery_Slope

[White Hat talking to Cueball.] White Hat: Yeah, but if I'm considerate toward one person about one thing, what's next? White Hat: Being nice to other people about other things? White Hat: Where does it end?

" Slippery slope " argumentation is an informal fallacy that takes the form of "if A happens, then B will follow as a minor but expected consequence. B will lead on to C, C leads onto D, and so on. Each consequence gets progressively worse until an undesirable situation is reached." A slippery slope argument proposes that A should not be allowed, because if it is, then the resulting chain of consequences will inevitably lead to the undesirable situation. For example, someone who is trying to avoid washing the dishes might try to justify themselves as follows: "if I wash the dishes tonight, then tomorrow night, I might be asked to do the dishes and also to wipe down the kitchen counters. If I do that, then pretty soon I'll also be asked to mop the kitchen floor. If I have to mop the kitchen floor, eventually I'll be asked to mop ALL the floors of the house, and eventually this will extend to washing the windows and taking out the trash and doing laundry, and I'll be doing EVERYTHING around here and NEVER get any time to myself. Therefore, I will not wash the dishes tonight, so I can still have enough time for myself." What makes the chain of reasoning fallacious is that there is nothing about the task of "washing the dishes" that in any way implies the additional responsibilities that this person imagines (such as wiping down counters or mopping floors). The slippery slope fallacy manifests when there is no cogent basis for believing that the proposed chain of events is likely to follow, especially when the proposed course of action has a clear extent and limitation which would adequately prevent the "slope" from being "slipped down." In the above example: there is an implied extent and limitation to the defined task of "washing the dishes" - namely, the task would be complete when the household dishes have been washed. Additional household chores, like wiping down counters, would be negotiated seperately with other members of the household. It is worth noting that a fallacy has NOT been committed if there is a reasonable basis for the concern. For example, the reluctant dishwasher might live with an abuser who will foreseeably intimidate them into taking on an unreasonable share of household chores, on the faulty basis that "if you're willing to do the dishes, surely you must also be willing to wipe down the counters..." In such a scenario, "wash the dishes" may carry an encoded message of "do what you're told," in a form that appears reasonable on its surface. Thus, in assessing whether or not a slippery slope fallacy has been committed, it is important to take ALL the relevant factors into consideration, and not merely the explicitly articulated ones. In the comic, White Hat uses a slippery slope argument to Cueball to justify being inconsiderate to people. He argues that if he expends minor effort being considerate to one person, he will be expected to be considerate to everyone he meets, which - he wishes to argue - is an undesirable situation. Thus, he justifies being inconsiderate as a form of avoiding the slippery slope. This idea is extended in the title text, where he continues extrapolating the train of thought to conclude that minutes of time would be "wasted". Rather than condemning the slippery slope fallacy per se, Randall 's point here seems to be more that White Hat's priorities are callous to the point of sociopathy. All people desire to be treated with consideration and respect, and taking a few seconds to acknowledge another's feelings is (for most well-meaning people) a small price to pay for improving that person's day, or at least not making it any worse than it needs to be. As such, these seconds would not be "wasted" at all, but would be actively making the world a friendlier place. White Hat's hyperfixation on not wasting time appears ludicrous given how much good feeling he could contribute to the world for so little of his own time. (White Hat also appears to be discounting the possibility that being considerate towards others will encourage reciprocity, which could result in SAVING him time since they will be more willing to help him out should he ever find himself in need.) [White Hat talking to Cueball.] White Hat: Yeah, but if I'm considerate toward one person about one thing, what's next? White Hat: Being nice to other people about other things? White Hat: Where does it end?

First Date

First Date

https://www.xkcd.com/1333

https://www.explainxkcd.com/wiki/index.php/1333:_First_Date

[Cueball and Megan sit at an intimate dinner table. They have plates and glasses of wine in front of them.] Cueball: So, did you grow up around here? Megan: I love you. Cueball: ... huh? Megan: Waiter! One of everything on the menu. [Megan stands up. Standing on her chair, holding a plate.] Cueball: Why are you up there? Megan: I'm stuck. Megan: This plate looks delicious. Megan: Aaaoogaoag. [Megan has put the plate down and walked off-panel.] Megan: Bye. Megan: OK. Coming back now. [Megan is crouched on her chair, holding a spiral.] Cueball: You're being controlled by Twitch, aren't you? Megan: Check out this cool spiral! Cueball: It's— Megan: SAVING.

TPP, or Twitch Plays Pokémon , was the first of a creative and radical new variant of streaming gameplay videos created in early 2014 — a few days before this comic was released. Some consumers enjoyed watching video games being played by other people (usually 'popular' gamers known for entertaining gameplay), thus streaming sites dedicated to streaming gameplay were created. Twitch.tv was one such site. Whereas traditional video game streams involved the channel broadcaster or another personality playing the game, the channel "Twitch Plays Pokémon" recorded a bot playing an emulated game of Pokémon Red for Game Boy . The game inputs given by the bot were based on players' messages in the video stream itself. Thus, the watchers of the stream were playing the game themselves using chat "commands." The Pokémon character behaved incredibly erratically, frequently getting "stuck against simple obstacles" (as mentioned in the title-text) and moving about in a strange manner ("Why are you up there?"/"Bye...Okay, coming back now"). Despite this, the character advanced surprisingly far in games. They have beaten the Elite Four and Champion of generations I , II , III , IV , and V , and VI . Twitch Plays Pokémon has also completed various ROM hacks and Spin-off titles, establishing a seasonal format with multiple games each season. You can see the state of the player characters' Pokémon and inventory at game end in this Bulbapedia article . TPP surged in popularity rapidly since its inception, reaching 80,000 channel viewers within five days. Derivative channels (such as 'TwitchPlayers') soon arose, turning "Twitch Plays..." into an idea rather than a single channel; that of crowdsourcing a task, such as controlling a single person (as in the Pokémon games) for erratic and often hilarious results. The stream, which is still active as of this writing, has reached memetic status . In the above comic, Cueball and Megan are on a date. However, Megan is behaving very erratically. Cueball determines that Megan is being "controlled by Twitch," as her behavior matches well with that of the TPP protagonist (whose name, canonically, is Red ). Megan loudly declares at one point that she is "SAVING" her 'game progress', referencing the incessant saving in TPP via random button presses. The random ten-letter string she says is reminiscent of the nicknames that all of TPP's Pokémon end up with as the players move haphazardly across the game's keyboard. Her fascination with the "cool spiral" is an allusion to TPP players' fascination with the Helix Fossil , an in-game item. As user input often leads to checking of the in-game backpack followed by erratic commands to handle the items within, it was common for various valuable items to be haphazardly thrown away. However, as the Helix Fossil was a key item , it could not be tossed. It was also the first item in the Bag due to this, leading to the players' continuously selecting it whenever accessing their Bag, eventually causing them to somewhat jokingly regard it as an object of religious reverence. The title text, as explained above, simply is a light-hearted joke from Randall , empathizing with TPP as he has also spent real-life days stuck against simple obstacles, and is surprised by how far he has gotten in life despite this fact. [Cueball and Megan sit at an intimate dinner table. They have plates and glasses of wine in front of them.] Cueball: So, did you grow up around here? Megan: I love you. Cueball: ... huh? Megan: Waiter! One of everything on the menu. [Megan stands up. Standing on her chair, holding a plate.] Cueball: Why are you up there? Megan: I'm stuck. Megan: This plate looks delicious. Megan: Aaaoogaoag. [Megan has put the plate down and walked off-panel.] Megan: Bye. Megan: OK. Coming back now. [Megan is crouched on her chair, holding a spiral.] Cueball: You're being controlled by Twitch, aren't you? Megan: Check out this cool spiral! Cueball: It's— Megan: SAVING.

Second

Second

https://www.xkcd.com/1334

https://www.explainxkcd.com/wiki/index.php/1334:_Second

[Cueball in a desert standing before a rock.] Rock: Greetings, stranger. Rock: Whatever quest drives you, abandon it. Rock: You shall find no answers in these desolate wastes. Cueball: I knew I wouldn't. Cueball: I guess I... just had to see. I hate feeling desperate enough to visit the second page of Google results.

Google is a popular search engine. Google's searching algorithms are widely regarded as the most accurate and useful. If your search terms were sufficiently detailed, you will be able to find what you were looking for on the first page. Having to view the second page indicates your search terms were too vague or the answer to your query doesn't exist. When the search results typically number in the tens of millions (or more; in fact, more popular search results are in the billions), only the very first results are mapping to the real idea of the user. The second page is not helpful for the issue. Cueball , after failing to find his query in the first page of results, takes a curious peek at the second page. This is represented by a not-at-all subtle metaphor in which Cueball is about to wander into a sun-baked desert. According to the title text, he finds one vaguely relevant webpage, but it's over 14 years old. The title text refers to webrings . Webrings consist of multiple websites that are connected together, usually with a common theme. They connect from one website to the next, eventually leading back to the starting site. They were popular in the 1990s as a way of boosting your search ranking, but newer algorithms in Google and other search engines are now detecting and penalizing web sites for such tactics. Webrings were also used in pre-google days to make it easy to find websites sharing a common theme, but since one site going down broke the ring, they were very inefficient. Seeing a webring means a site has not been updated since the mid 90s. [Cueball in a desert standing before a rock.] Rock: Greetings, stranger. Rock: Whatever quest drives you, abandon it. Rock: You shall find no answers in these desolate wastes. Cueball: I knew I wouldn't. Cueball: I guess I... just had to see. I hate feeling desperate enough to visit the second page of Google results.

Now

Now

https://www.xkcd.com/1335

https://www.explainxkcd.com/wiki/index.php/1335:_Now

[The comic is a moving circle with a static outer ring.] [The outermost part of the static ring is divided in 22 segments representing the 24 hours of the day. The Noon (11 AM - 1 PM) and Midnight (11 PM - 1 AM) segments cover two hours which are not segmented. The ring is divided so it is yellow from 6 AM to 6 PM and dark grey on the other half.] Noon - 6 PM - Midnight - 6 AM [The innermost part of the static ring is light grey and divided in two sections that cower from 9 AM to 5 PM and from 10 PM to 8 AM respectively. They contain descriptions of the time intervals.] Business hours (9-5) Rude to call [The rest of the image consist of a rotating part.] [On the innermost part of the circle is the Earth as seen from the south pole. Each continent has a different color. The colors are Europe: Red Africa: Cyan Asia: Green Oceania: Purple North America: Blue-violet South America: Olive green Antarctica (The south pole): Light grey [Two segmented rings circle the map - these give the names of the continents (not the Antactica) and the color of the ring match the color of the continent on the map. Each segment cover the part of the map with the given continent. The one with Europe is merged with the one for Asia - and the color also merges from red to green along Turkey and Russia where the transition from Europe to Asia occurs.] [On the inner ring are the names of the following continents (white text on a segment with the color of the continent)] Africa Oceania South America [On the second of these rings are the names of the following continents (white text on a segment with the color of the continent)] Europe Asia North America [On the outermost ring of the moving circle are written names of regions, countries and cities of the Earth over the part of the map in which time zone they belong. All the text is color coded to match the color of the continent they belong to as given on the central map. The text is written in four lines. Below the names are sorted by color and reading from left to right first - and only sorting top to bottom if needed.] [Europe - Red text:] UK - Most of Europe - Eastern Europe [Africa - Cyan text:] West Africa - Nigeria - Egypt - East Africa [Asia - Green text:] The Levant - Iraq - Iran - Moscow - Afghanistan - Pakistan - India - Southeast Asia - Java - China - Singapore - Philippines - Japan - The Koreas - Kamchatka [Oceania - Purple text:] Perth - Brisbane - Most Australian cities - New Zealand [North America - Blue-violet text:] Alaska - US West Coast - Denver - Mexico - Chicago - Texas - Eastern Canada - US East coast - Canadian Maritimes [South America - Olive green text:] Coastal Brazil There are currently several implementations of the Now comic available for several different platforms: A script that automatically updates the wallpaper for the current time. A bash script that automatically updates the wallpaper for the current time, written for a Debian system running i3. May work well for other linux distributions as well. An Android widget version of the comic. A web-based implementation which also displays time zones. (Not working on 02017-08-16) A draggable implementation (click&drag - left and right) (Not working on 02017-08-16) An offline version of the comic made using C++ and SFML.

The picture is divided in 24 segments representing the 24 hours of the day. At noon and at midnight the break between segments is indicated by the tip of a dark grey triangle. The picture rotates by 3.75 degrees every 15 minutes, as does the Earth, so that it is constantly up to date in showing which regions are currently at which times of day. The picture change seems to happen half-way through a 15-minute time increment (that is, at 7½, 22½, 37½, and 52½ minutes after each hour), so that the picture is always correct for the nearest multiple of 15 minutes. The map projection of the earth in the middle of the picture shows an azimuthal equidistant projection with the South Pole in the center. This is unusual, as the projection typically puts the north pole in the center, but necessary in order for it to rotate clockwise. Randall was playing on projections before in 977: Map Projections . The list of cities and countries doesn't match the map exactly - notice how the continent of Australia is shifted counterclockwise of the words "most Australian cities". This is because the map is centered relative to the time zones and the local variations therein. The map shows the configuration of time zones with respect to daylight saving time (also known as summer time) at the time of the comic's initial release (February 2014); it was being observed in parts of Australia, New Zealand, Brazil, and other countries not named in this comic. If the map were to stay accurate through the year, the location of place names would have to move over the next few months as parts of the southern hemisphere went off DST and parts of the northern hemisphere went onto it; however, the map failed to change on the morning of March 9 as it should have (to recognize the start of DST in North America). In many countries " business hours " are considered to be from 9 am to 5 pm. With some exceptions, including emergencies, it is generally considered rude to place a telephone call to someone's residence during the hours when most people are asleep; Randall portrays this time period as extending from 10 pm to 8 am. This may be a reference to the 10 pm "cutoff" time discussed in an episode of "Curb Your Enthusiasm." "Rude to Call" was also the name used by a G-mail experimental opt-in feature in 2009 which added a crossed out phone symbol next to the sender if it was night in the sender's time zone when the reader loaded the email on their screen. On midnight at UTC we can see this situation: UK, Portugal West Africa Most of central Europe Nigeria, and many more countries belonging to the West Africa Time zone Eastern Europe, many countries like Bulgaria, Romania or Greece The Levant Egypt Ethiopia, Kenya, Madagascar, Somalia, and more Kaliningrad and Belarus Iraq, Kuwait, Saudi Arabia, and more. Iran is at Iran Standard Time , using an offset of UTC+03:30 Moscow Time United Arab Emirates, Mauritius, and more Afghanistan is at Time in Afghanistan , using an offset of UTC+04:30 Iran is at Iran Standard Time , using an offset of UTC+03:30 Pakistan, Western Australia, Maldives and some France former colonies. Afghanistan is at Time in Afghanistan , using an offset of UTC+04:30 India and Sri Lanka using UTC+05:30 Nepal is using a much more odd offset at UTC+05:45 Bangladesh, Bhutan... UK British Indian Ocean Territory Russia at Yekaterinburg Time , also Kazakhstan and Kyrgyzstan China only use one time zone (+08:00) but Xinjiang and Tibet unofficially use +06:00 India and Sri Lanka using UTC+05:30 Nepal is using a much more odd offset at UTC+05:45 South-east Asia like Cambodia, Indonesia, Thailand, Vietnam, and more Christmas Island belonging to Australia Russia is also using the Omsk Time Western Australia China uses only one time zone while the country spans about five. Singapore Philippines Perth Japan The Koreas Brisbane and the Australian Capital Territory, New South Wales, Queensland, Tasmania and Victoria US: Guam and Northern Mariana Islands Micronesia, New Caledonia, Solomon Islands, Vanuatu Russia Vladivostok Time Kamchatka (a Russian peninsula at the east Siberia), Kiribati, Marshall Islands, Nauru, Tuvalu and more New Zealand, Kiribati, Tonga Hawaii, Samoa French Polynesia, Cook Islands, and more Line Islands, belonging to Kiribati Alaska (some islands of Alaska is at -10:00 and a few city's are at -08:00) French Polynesia US West Coast Canada or (British Columbia and Yukon) Mexico (Baja California) US: Denver, and much more Canada: Alberta (Calgary, Edmonton), British Columbia, more Mexico, Chile, Ecuador, Nicaragua and more US: Chicago, Texas except of some most westernmost counties, and many more Eastern Canada like Ontario or Quebec US East Coast including New York and Florida. But also Cuba, Haiti, Panama and much more countries Canadian Maritimes: New Brunswick, Prince Edward Island, Nova Scotia. (Newfoundland uses UTC-03:30 ) Chile Greenland Most of the Caribbean Islands. Coastal Brazil, Argentina, Uruguay, French Guiana, the UK Falkland Islands, and more UK: South Georgia and the South Sandwich Islands Brazil: Fernando de Noronha Cape Verde Azores (part of Portugal) When first posted, the picture was exactly 12 hours off. Somewhere around 5:10 UTC, this was fixed. The original version also included a listing for Inland Brazil; this could have created a conflict with US East Coast when Daylight-Saving Time begins in the US, and it has been removed. The names used for the image files refer not to UTC (Universal Time) as one might expect but rather to the time exactly 12 hours off of that. The name of the image file linked from the page matched Universal Time during the first few hours, but the file-naming scheme did not change when the comic was corrected. [The comic is a moving circle with a static outer ring.] [The outermost part of the static ring is divided in 22 segments representing the 24 hours of the day. The Noon (11 AM - 1 PM) and Midnight (11 PM - 1 AM) segments cover two hours which are not segmented. The ring is divided so it is yellow from 6 AM to 6 PM and dark grey on the other half.] Noon - 6 PM - Midnight - 6 AM [The innermost part of the static ring is light grey and divided in two sections that cower from 9 AM to 5 PM and from 10 PM to 8 AM respectively. They contain descriptions of the time intervals.] Business hours (9-5) Rude to call [The rest of the image consist of a rotating part.] [On the innermost part of the circle is the Earth as seen from the south pole. Each continent has a different color. The colors are Europe: Red Africa: Cyan Asia: Green Oceania: Purple North America: Blue-violet South America: Olive green Antarctica (The south pole): Light grey [Two segmented rings circle the map - these give the names of the continents (not the Antactica) and the color of the ring match the color of the continent on the map. Each segment cover the part of the map with the given continent. The one with Europe is merged with the one for Asia - and the color also merges from red to green along Turkey and Russia where the transition from Europe to Asia occurs.] [On the inner ring are the names of the following continents (white text on a segment with the color of the continent)] Africa Oceania South America [On the second of these rings are the names of the following continents (white text on a segment with the color of the continent)] Europe Asia North America [On the outermost ring of the moving circle are written names of regions, countries and cities of the Earth over the part of the map in which time zone they belong. All the text is color coded to match the color of the continent they belong to as given on the central map. The text is written in four lines. Below the names are sorted by color and reading from left to right first - and only sorting top to bottom if needed.] [Europe - Red text:] UK - Most of Europe - Eastern Europe [Africa - Cyan text:] West Africa - Nigeria - Egypt - East Africa [Asia - Green text:] The Levant - Iraq - Iran - Moscow - Afghanistan - Pakistan - India - Southeast Asia - Java - China - Singapore - Philippines - Japan - The Koreas - Kamchatka [Oceania - Purple text:] Perth - Brisbane - Most Australian cities - New Zealand [North America - Blue-violet text:] Alaska - US West Coast - Denver - Mexico - Chicago - Texas - Eastern Canada - US East coast - Canadian Maritimes [South America - Olive green text:] Coastal Brazil There are currently several implementations of the Now comic available for several different platforms: A script that automatically updates the wallpaper for the current time. A bash script that automatically updates the wallpaper for the current time, written for a Debian system running i3. May work well for other linux distributions as well. An Android widget version of the comic. A web-based implementation which also displays time zones. (Not working on 02017-08-16) A draggable implementation (click&drag - left and right) (Not working on 02017-08-16) An offline version of the comic made using C++ and SFML.

Transformers

Transformers

https://www.xkcd.com/1336

https://www.explainxkcd.com/wiki/index.php/1336:_Transformers

[Two "Transformer"-esque robots are visible.] First Robot: Transform! [Both robots run to the right.] [Each robot reaches a tree and begins to climb it.] [The camera focuses on the nearer of the two robots, which is placing itself into a chrysalis hanging from the tree branch.]

The comic is a parody of Transformers , a fictional group of robots that can transform into vehicles. Transformers typically are able to transform instantaneously, often mid-stride, by manipulating and rearranging their mechanical parts. In this comic, however, Randall has the Transformers "transform" in the same manner that caterpillars "transform" via metamorphosis into butterflies or moths. The first two panels show action scenes that would be appropriate for a Transformers comic. However, the third panel shows the Transformers climbing a tree, and in the final scene they wrap silk around themselves, apparently forming a cocoon or chrysalis. The title text furthers this parallel, describing a newly transformed helicopter — presumably the post-metamorphosis state of one of the Transformers in the panels — in a manner that would be more appropriate for a freshly-emerged butterfly or moth. This xkcd comic is one of the few ones not showing just simple stick figures . [Two "Transformer"-esque robots are visible.] First Robot: Transform! [Both robots run to the right.] [Each robot reaches a tree and begins to climb it.] [The camera focuses on the nearer of the two robots, which is placing itself into a chrysalis hanging from the tree branch.]

Hack

Hack

https://www.xkcd.com/1337

https://www.explainxkcd.com/wiki/index.php/1337:_Hack

[A black image shows an image of the ISEE-3/ICE spacecraft in white. Text is written in white above it] The ISEE-3/ICE probe was launched in 1978. Its mission ended in 1997 and it was sent a shutdown signal. [The text continues, black on white, without a frame around it, between the first frame and the next.] In 2008, we learned-to our surprise-that the probe didn't shut down. It's still running and it has plenty of fuel. ...and in 2014, its orbit brings it near earth. [Megan holding up one hand and Ponytail are talking to each other.] Megan: We could send it on a new mission... Megan: Except we no longer have the equipment to send commands to it. Ponytail: Can't we— [Zoom in on Megan's head and torso as she looks towards Ponytail off-panel to the right.] Megan: NASA won't rebuild it. "Too Expensive" Ponytail (off-panel): Seriously? Megan: I know, right? Megan: So the internet found the specs Megan: And we went to work. [Megan and Ponytail are walking towards right, between Hairbun facing left and Cueball (with head phones) facing right. They are sitting at desks working on their laptops. Megan speaks, as indicated both by the story line and by her hand which is lifted up, but there is not speech line from her to the text.] Megan: We've convinced them to give us time on the Madrid DSN transmitter and hacked the maser to support the uplink. Megan: And today's the big day. [Zoom in on Cueball's head and torso, he holds a hand up to his speaker on his head phones and watches his lit screen (as indicated by lines emanating from it).] Cueball: Transmitting... Cueball: We have a signal! Cueball: We have control! [Zoom in on Megan's head and torso. She has turned away from Cueball to the right towards Hairbun.] Megan: OK, transmit the new comet rendezvous maneuver sequen— Cueball (off panel): What the hell? Megan: What? [Same setting as when Megan and Ponytail entered the control-room, but Ponytail just stands there and Megan puts a hand out towards Cueball.] Cueball: My console went dead! Hairbun: Mine too! Megan: What's happening?! [Another zoom in on Cueball's head and torso and glowing screen. He has both hands down.] Cueball: There's a new signal going out over the transmitter! Megan (off panel): A bug? Cueball: Someone else is in the system! [Zoom in on Hairbun's head and torso. She is also working on her laptop, with the glowing screen visible.] Hairbun: Kill the connection! Cueball (off panel): I can't find it! Hairbun: They're firing the probe's engines! Cueball (off panel): No!! [Back to a zoom in on Cueball. He points at his screen.] Megan (off panel): Who's doing this?? Stop them! Hairbun (off panel): I'm trying! Cueball: Look! My screen! [Same setting as when Megan and Ponytail entered the control-room, but Ponytail has a hand to her mouth and she and Megan stand close to Cueball who has taken his hands off the keyboard. The text on Cueball's laptop screen is shown above the setting, indicated with zigzag lines:] M-E-S-S-W-I-T-H- T-H-E-B-E-S-T D-I-E-L-I-K-E- T-H-E-R-E-S-T [The last four panels is outside night scenes with a black sky above. In the first of these a woman (Burn) with long hair (Megan like) and a hairy man (Crash) is seen in a swimming pool with blue water.] [A zoom out reveals that the pool is on top of a skyscraper in a vertically developed, downtown setting with lots of light in all the skyscrapers, one of which is even taller than the one with the pool. From the top of the central skyscraper speech lines come which indicate that the two from the pool is up there speaking, and we get their names from this panel.] Burn: Crash? Crash: Yeah, Burn? [Same setting but only one speech line.] Burn: Make a wish. [The last panel shows the same setting, but with the spacecraft streaking across the sky as it enters the Earths atmosphere and burns up in a way that is indistinguishable from a meteoroid.] The ISEE-3/ICE probe was launched in August 12, 1978 and tasked to study Earth's magnetic field and the solar wind. Before completing its original mission the probe was repurposed on June 10, 1982 to study the interaction between the solar wind and a cometary atmosphere. By flying through the comet Giacobini-Zinner 's tail, it became the first probe to do so. This put ISEE-3 in a heliocentric orbit . Its trajectory will bring it close to Earth on August 2014. The Deep Space Network (DSN) detected the probe again in 2008 because NASA mistakenly left its transmitters on. However, the probe was only transmitting the carrier signal at that time. A status check of the spacecraft has revealed that many of its instruments are still working and that it contains plenty of fuel. [1] It was reported that the hardware to communicate with ISEE-3/ICE had been decommissioned. The Madrid DSS complex still has the special filter required to communicate with the ICE satellite, but because of frequency conflicts S-band uplink is not supported. [2] On March 1 and 2, 2014 radio amateurs were able to detect the beacon signal from the retired NASA deep space probe ICE (International Cometary Explorer) using the 20 m radio telescope at the Bochum Observatory (Germany). [3] After this comic was published, it was established that an 18-meter satellite dish at the Johns Hopkins Applied Physics Laboratory does still have the right hardware. See Space College: ISEE-3 Reboot Project Archives for the coverage of this amazing project.

This comic is an imagined project to re-position the ISEE-3/ICE probe, and a parody of the 1995 movie Hackers . The first row (four panels) explain the history of the probe, and the true story about how the probe was coming back into signal range and seemed capable of being controlled. NASA declined to attempt to regain control of the probe, but a group of enthusiasts assembles the equipment and attempts to re-purpose the probe. The following two rows (eight panels) set up a fictional scenario: the enthusiasts have been locked out of the system, the probe is being controlled by someone else, and the message "Mess with the best, die like the rest" is communicated from the probe. This is a catch phrase of the protagonist, Crash, from Hackers . The final row is a reference to the ending of the movie, where Crash romances Burn, his romantic interest, in a rooftop pool. In the movie, while Crash and Burn swim in a rooftop pool, several buildings light up with the words "CRASH AND BURN". This was at the end of a contest and is Crash's latest hack and romantic gesture which he indicates by saying 'Beat that!'. In the comic the transmitter being used to communicate with ISEE-3 was hacked by Burn to make the probe burn up over Crash and Burn swimming in the pool providing a "shooting star" for romantic effect. The comic number is 1337, which stands for "leet", short for "elite hacker" and "leetspeek" in leetspeak . Leetspeak is a form of symbolic writing that substitutes various numbers and ASCII symbols for letters. It originates from the hacker subculture, where words were converted to leetspeek e.g. to avoid filters and triggers on chat rooms. "1337" for "leet" can most likely be explained as calculator spelling . The title text "Hack the stars" is also an allusion to Hackers , where the phrase "Hack the planet!" is used on multiple occasions. This project since became reality , as Randall noted in a blag post . See details below . [A black image shows an image of the ISEE-3/ICE spacecraft in white. Text is written in white above it] The ISEE-3/ICE probe was launched in 1978. Its mission ended in 1997 and it was sent a shutdown signal. [The text continues, black on white, without a frame around it, between the first frame and the next.] In 2008, we learned-to our surprise-that the probe didn't shut down. It's still running and it has plenty of fuel. ...and in 2014, its orbit brings it near earth. [Megan holding up one hand and Ponytail are talking to each other.] Megan: We could send it on a new mission... Megan: Except we no longer have the equipment to send commands to it. Ponytail: Can't we— [Zoom in on Megan's head and torso as she looks towards Ponytail off-panel to the right.] Megan: NASA won't rebuild it. "Too Expensive" Ponytail (off-panel): Seriously? Megan: I know, right? Megan: So the internet found the specs Megan: And we went to work. [Megan and Ponytail are walking towards right, between Hairbun facing left and Cueball (with head phones) facing right. They are sitting at desks working on their laptops. Megan speaks, as indicated both by the story line and by her hand which is lifted up, but there is not speech line from her to the text.] Megan: We've convinced them to give us time on the Madrid DSN transmitter and hacked the maser to support the uplink. Megan: And today's the big day. [Zoom in on Cueball's head and torso, he holds a hand up to his speaker on his head phones and watches his lit screen (as indicated by lines emanating from it).] Cueball: Transmitting... Cueball: We have a signal! Cueball: We have control! [Zoom in on Megan's head and torso. She has turned away from Cueball to the right towards Hairbun.] Megan: OK, transmit the new comet rendezvous maneuver sequen— Cueball (off panel): What the hell? Megan: What? [Same setting as when Megan and Ponytail entered the control-room, but Ponytail just stands there and Megan puts a hand out towards Cueball.] Cueball: My console went dead! Hairbun: Mine too! Megan: What's happening?! [Another zoom in on Cueball's head and torso and glowing screen. He has both hands down.] Cueball: There's a new signal going out over the transmitter! Megan (off panel): A bug? Cueball: Someone else is in the system! [Zoom in on Hairbun's head and torso. She is also working on her laptop, with the glowing screen visible.] Hairbun: Kill the connection! Cueball (off panel): I can't find it! Hairbun: They're firing the probe's engines! Cueball (off panel): No!! [Back to a zoom in on Cueball. He points at his screen.] Megan (off panel): Who's doing this?? Stop them! Hairbun (off panel): I'm trying! Cueball: Look! My screen! [Same setting as when Megan and Ponytail entered the control-room, but Ponytail has a hand to her mouth and she and Megan stand close to Cueball who has taken his hands off the keyboard. The text on Cueball's laptop screen is shown above the setting, indicated with zigzag lines:] M-E-S-S-W-I-T-H- T-H-E-B-E-S-T D-I-E-L-I-K-E- T-H-E-R-E-S-T [The last four panels is outside night scenes with a black sky above. In the first of these a woman (Burn) with long hair (Megan like) and a hairy man (Crash) is seen in a swimming pool with blue water.] [A zoom out reveals that the pool is on top of a skyscraper in a vertically developed, downtown setting with lots of light in all the skyscrapers, one of which is even taller than the one with the pool. From the top of the central skyscraper speech lines come which indicate that the two from the pool is up there speaking, and we get their names from this panel.] Burn: Crash? Crash: Yeah, Burn? [Same setting but only one speech line.] Burn: Make a wish. [The last panel shows the same setting, but with the spacecraft streaking across the sky as it enters the Earths atmosphere and burns up in a way that is indistinguishable from a meteoroid.] The ISEE-3/ICE probe was launched in August 12, 1978 and tasked to study Earth's magnetic field and the solar wind. Before completing its original mission the probe was repurposed on June 10, 1982 to study the interaction between the solar wind and a cometary atmosphere. By flying through the comet Giacobini-Zinner 's tail, it became the first probe to do so. This put ISEE-3 in a heliocentric orbit . Its trajectory will bring it close to Earth on August 2014. The Deep Space Network (DSN) detected the probe again in 2008 because NASA mistakenly left its transmitters on. However, the probe was only transmitting the carrier signal at that time. A status check of the spacecraft has revealed that many of its instruments are still working and that it contains plenty of fuel. [1] It was reported that the hardware to communicate with ISEE-3/ICE had been decommissioned. The Madrid DSS complex still has the special filter required to communicate with the ICE satellite, but because of frequency conflicts S-band uplink is not supported. [2] On March 1 and 2, 2014 radio amateurs were able to detect the beacon signal from the retired NASA deep space probe ICE (International Cometary Explorer) using the 20 m radio telescope at the Bochum Observatory (Germany). [3] After this comic was published, it was established that an 18-meter satellite dish at the Johns Hopkins Applied Physics Laboratory does still have the right hardware. See Space College: ISEE-3 Reboot Project Archives for the coverage of this amazing project.

Land Mammals

Land Mammals

https://www.xkcd.com/1338

https://www.explainxkcd.com/wiki/index.php/1338:_Land_Mammals

[Caption at the top of this chart:] Earth's Land Mammals by Weight [Below the caption is a light gray block with a label (in light gray as well) to indicating the value of each block:] = 1,000,000 tons [Below this there is a row with three blocks each in a different color, dark and light gray and green, each block is labeled to the right:] Humans Our pets and livestock Wild animals [The rest of the comic consist of a chart with different groups made up of these individually and differently colored blocks, each grouping representing the weight of a different mammals, except the center part, the only one with dark gray block, which represent humans. The largest group to the left is the only one larger than the humans group in the center. There are 22 groups in total, 1 human group with 358 dark gray block, 13 groups of light gray with a total of 864 blocks and 8 green groups with a total of 34 blocks for a total of 256 blocks. Both the light gray and the green groups are spread out on all sides of the human center group. Only difference is that all the green are on the very outside, whereas some of the smaller light gray groups are close to the core, far from the outside. The five largest groups of light gray blocks are labeled, as well as the smallest group consisting only of a single green block. All the labels has a line pointing to the relevant group and all of them are on the outside of the entire block. Going clockwise from the top left the labels are:] Cattle Pigs Goats Sheep Horses Elephants [At the bottom right of the comic is the following gray text with a reference:] Data from Vaclav Smil's The Earth's Biosphere: Evolution, Dynamics, and Change , plus a few other sources.

This comic shows the total weight of mankind and all other land mammals . Only a few centuries ago, humans , their pets and livestock came to make up a great proportion of the earth's land mammal biomass . Note that only land-dwelling mammals are taken into account, so for instance whales and sea cows will not be included. (Whether this only covers animals that cannot live on land or any marine mammals like for instance seals and walrus , is not clear). The design of the blocks loosely resembles a cell . This could be a reference to how these animals support humans, analogous to a cell supporting a central nucleus. If so, it seems that all the animals in this diagram, wild or domestic , in some way support human activity. The title text states that bacteria outweigh us thousands to one, without counting the several pounds of bacteria in our body that are considered part of our own weight (like Gut flora ). The aforementioned cell could also be a bacterium, making it a possible reference to the title text, since 1256 blocks have been used to sketch the "cell", and bacteria outweigh us by about this factor. This comic may be a nerd snipe from Randall , challenging his readers to figure out the missing parts. Randall also discusses animal biomass in Fairy Demographics in which he compares the biomass of "fairies" to humans, horses, and humpback whales. According to the diagram, there are 358 million tons of humans, 864 million tons of pets and livestock, of which 520 million tons comes from cattle , and 34 million tons of wild animals; for a total of 1.256 billion tons. The number of blocks represents the weight of the group in millions of tons = billions of kg. Note that some entries have the same number of blocks, and thus have the same rank. Cattle, in aggregate, are much heavier than the human population. Humans outweigh both sheep and pigs put together. This may be a surprise for people in the countries that produce the majority of meat from such animals, because here these animals outweigh the population. But there are many parts of the world where especially pigs are not eaten, and it is not every where that sheep is in great demand. And especially in the some of the most populations dense regions in the Third World meat is not something you can afford to eat on a regular basis. There are 13 distinct blocks of pets and live stock; only the top 5 are labeled - in order of weight they are: Cattle, Sheep, Pigs, Goats and Horses . Cattle, in aggregate, are much heavier than the human population, which has been inserted in the table for comparison: There are 8 distinct blocks of wild animal ( elephants and 7 others). The elephant is the only type of wild animal to be singled out in the comic. This may possibly be due to elephants being the largest land mammal. And yes, the world's heaviest land animal only takes up one square. Also interesting is that the largest group of wild animals only comes in on a tied 8 place in the ranking (which is shared between the two tables). The comic references the book The Earth's Biosphere: Evolution, Dynamics, and Change by Vaclav Smil as the source for most of the data. A few other sources have also been used, but were not referenced. On page 186 of Smil's book, there is a bar chart with the following values: Note that all labelled non-human animals are in this table. It seems that this table was the source of most of the data in the comic. Only land dwelling mammals are taken into account. Whales, wild vertebrates, and domesticated vertebrates are not included in the comic. These are guesses about the identity of the unlabeled animals [Caption at the top of this chart:] Earth's Land Mammals by Weight [Below the caption is a light gray block with a label (in light gray as well) to indicating the value of each block:] = 1,000,000 tons [Below this there is a row with three blocks each in a different color, dark and light gray and green, each block is labeled to the right:] Humans Our pets and livestock Wild animals [The rest of the comic consist of a chart with different groups made up of these individually and differently colored blocks, each grouping representing the weight of a different mammals, except the center part, the only one with dark gray block, which represent humans. The largest group to the left is the only one larger than the humans group in the center. There are 22 groups in total, 1 human group with 358 dark gray block, 13 groups of light gray with a total of 864 blocks and 8 green groups with a total of 34 blocks for a total of 256 blocks. Both the light gray and the green groups are spread out on all sides of the human center group. Only difference is that all the green are on the very outside, whereas some of the smaller light gray groups are close to the core, far from the outside. The five largest groups of light gray blocks are labeled, as well as the smallest group consisting only of a single green block. All the labels has a line pointing to the relevant group and all of them are on the outside of the entire block. Going clockwise from the top left the labels are:] Cattle Pigs Goats Sheep Horses Elephants [At the bottom right of the comic is the following gray text with a reference:] Data from Vaclav Smil's The Earth's Biosphere: Evolution, Dynamics, and Change , plus a few other sources.

When You Assume

When You Assume

https://www.xkcd.com/1339

https://www.explainxkcd.com/wiki/index.php/1339:_When_You_Assume

[Megan, standing left holding a hand up with the palm up while facing Cueball to the right.] Megan: You assumed? Megan: You know what happens when you assume- Cueball: I don't. Yet you're confidently asserting that I do. Megan: ...Oh. Hm. Cueball: Check and mate.

Prior to the events in this comic, Cueball has evidently told Megan that he made an assumption about something. Megan starts to respond with a takeoff on the modern proverb: "When you assume, you make an ass out of you and me." This proverb plays on the fact that the word "assume" may be broken down into the letters "ass", "u", and "me", and is intended to suggest that one should not make assumptions because they may turn out to be wrong and make those involved appear foolish. However, when Megan evokes the proverb in the modified form "You know what happens when you assume", Cueball astutely points out that her phrasing itself is hypocritical in that it makes the assumption that he knows what happens when you assume. Megan stops to ponder Cueball's point, to which Cueball responds " Check and Mate ": a common phrase originating from chess — suggesting triumph or having successfully countered another person's argument to which there can be no retort. However, this would not make sense unless Cueball knows that assuming is bad, and he states in the comic that he does not know what happens when someone assumes. While Megan's tone of voice implies that when someone assumes, something bad happens, she does not state this explicitly, so Cueball would have had to assume that Megan was referring to something bad. However, Megan does not point this out, likely because she is too distracted by her own shame to notice that Cueball was also making an assumption. Cueball's response demonstrates that, in life, we make assumptions almost every time we speak. This only tends to be problematic in the few instances where the assumption is wrong. The title text is a play on the original "assume" pun, breaking down the word "assert", into "ass" and "ert", with "ERT" being an acronym for " Emergency Response Team ". This comic follows a pattern similar to 1657: Insanity . [Megan, standing left holding a hand up with the palm up while facing Cueball to the right.] Megan: You assumed? Megan: You know what happens when you assume- Cueball: I don't. Yet you're confidently asserting that I do. Megan: ...Oh. Hm. Cueball: Check and mate.

Unique Date

Unique Date

https://www.xkcd.com/1340

https://www.explainxkcd.com/wiki/index.php/1340:_Unique_Date

[Cueball speaking to Megan and another Cueball-like guy.] Cueball: Whoa, it's 2014-03-10! Cueball: Under our system, that date will never happen again!! [Caption below the frame:] My Hobby: Pointing this out every day.

In this comic Cueball is excited about the current date and he states this date (the date the comic was released) as 2014-03-10, with the year first, then the month, then the day of the month. This follows the international standard as defined in the ISO 8601 standard. He then continues to point out, to Megan and another Cueball that this date will never happen again. The Gregorian calendar is the current way to count time in years, months and days. Since time moves only forward, [ citation needed ] dates will never repeat. Every date is thus equally unique, even when the digits aren't in a pattern. Many people do, however, make a big deal about dates when the digits follow an interesting pattern, such as 2000-01-01 or 2012-12-12. They might plan special events on these "unique" days. For instance, 2007-07-07 was considered a "lucky" day and had a record number of weddings. This is because humans, in general, are superstitious [ citation needed ] and like (and recognize) patterns in everyday life, also including patterns in the numbers used for stating dates. But this does not make these dates more unique than any other dates. Nevertheless, Cueball has made it into his hobby to point this daily uniqueness out, and having to listen to him, stating this fact every day, would be incredibly annoying to his friends. The title text refers to the Long Now Foundation , who uses five-digit years (e.g. this comic's date would be written "02014-03-10"). This is an effort to encourage people to think in terms of long-term benefits, rather than only the coming years or decades. The Y2K problem was due to using only two digits to store the year, which would have made dates ambiguous when it rolled from 99 back to 00. Similarly, the Maya calendar had a repeating cycle of 52 years, and even their "long count" rolled over after 7885 years. As we currently use four-digit years this may cause a Y10K problem . The Long Now Foundation designs a 10,000-year clock that should be able to run for this long — and in principle, it could display every date up to 9999-12-31. 8000 years from the date of the comic would be 10014 AD — Randall jokes that by switching to 5-digit years, we'd prove the Long Now Foundation correct, although of course by this point there would be no other way to show years except by rebooting the calendar. A previous comic on date formats was 1179: ISO 8601 . Randall addresses date formatting confusion again in the title text of 1467: Email . [Cueball speaking to Megan and another Cueball-like guy.] Cueball: Whoa, it's 2014-03-10! Cueball: Under our system, that date will never happen again!! [Caption below the frame:] My Hobby: Pointing this out every day.

Types of Editors

Types of Editors

https://www.xkcd.com/1341

https://www.explainxkcd.com/wiki/index.php/1341:_Types_of_Editors

[There are four panels, each with different headings and explanations of the headings above the panels.] [The first three panels shows two titled text boxes, one above the other, with text inside. This text is formated with both small and capital letters as opposed to all capital letters in the rest of the comic.] [Heading panel 1:] WYSIWYG What you see is what you get [Panel 1.] What you see: Hi What you get: Hi [Heading panel 2:] WYSINWYG What you see is not what you get [Panel 2.] What you see: <em>Hi</em> What you get: Hi [Heading panel 3:] WYSITUTWYG What you see is totally unrelated to what you get [Panel 3.] What you see: <em>Hi</em> What you get: The HORSE is a noble animal. [The fourth panel shows two titled text areas, the top is a black rectangle with white text in a very large font, and the bottom text area is not outlined with a border.] [Heading panel 4:] WYSIHYD What you see is how you die [Panel 4.] What you see: EATEN BY WOLVES What you get: Eaten by wolves

WYSIWYG , pronounced, "wizzy-wig" IPA /ˈwɪziˌwɪg/, is an acronym that stands for "What you see is what you get". In regards to computers, it refers to text editors in which the user can see exactly what will be published as they are typing it. The comic compares various types of editors, each one a play-on-words on WYSIWYG. The title text is a fictitious command, meta -x machineofdeath-mode, to the highly extensible Emacs text editor. Emacs operates in various "modes", which are customizations for specific purposes. Placing Emacs into "Machine of Death" mode would turn it into a WYSIHYD editor. (For another fictitious emacs command see 378: Real Programmers ). See below for why this was used. This is a reference to " Machine of Death ". This book from 2010 is a collection of short stories edited by amongst other Ryan North (of Dinosaur Comics ) mentioned here since the idea was based on one of his comics . Since Randall Munroe wrote one of the stories the reference is very likely, and would be Randall's first book promotion in xkcd, but not the last. All the stories are based around a device, the "Machine of Death", that can predict, with 100% accuracy though generally with extreme ambiguity, how people die from a drop of their blood. In many of the stories very unusual deaths are predicted, often in a very literal way, but not so you know when or where you will die. From the official home page the entire book can be downloaded for free as a PDF file . (Randall's story begins on page 421 - or page 218 of the two sided PDF file. It is simply called "?"). In 1525: Emojic 8 Ball the default question is How will I die? and can then be answered by an Emojic 8 Ball , which would make it a type of Machine of Death. [There are four panels, each with different headings and explanations of the headings above the panels.] [The first three panels shows two titled text boxes, one above the other, with text inside. This text is formated with both small and capital letters as opposed to all capital letters in the rest of the comic.] [Heading panel 1:] WYSIWYG What you see is what you get [Panel 1.] What you see: Hi What you get: Hi [Heading panel 2:] WYSINWYG What you see is not what you get [Panel 2.] What you see: <em>Hi</em> What you get: Hi [Heading panel 3:] WYSITUTWYG What you see is totally unrelated to what you get [Panel 3.] What you see: <em>Hi</em> What you get: The HORSE is a noble animal. [The fourth panel shows two titled text areas, the top is a black rectangle with white text in a very large font, and the bottom text area is not outlined with a border.] [Heading panel 4:] WYSIHYD What you see is how you die [Panel 4.] What you see: EATEN BY WOLVES What you get: Eaten by wolves

Ancient Stars

Ancient Stars

https://www.xkcd.com/1342

https://www.explainxkcd.com/wiki/index.php/1342:_Ancient_Stars

All of the panels of this comic are white-on-black. [Megan and Cueball stand facing each other, looking up at the sky.] Cueball: Just think - the light from that star was emitted thousands of years ago. It could be long gone. [Cueball looks at Megan, who is still looking up.] Megan: That's Sirius. It's eight light-years away. [Cueball looks up again.] Cueball: Oh. [Both look at one another.] Cueball: Just think - the light from that star was emitted in the previous presidential administration. Megan: Hmm, doesn't pack quite the punch.

Cueball makes the common observation that many of the visible stars in the sky are so distant that it takes thousands of years for light from that star to reach Earth. However, the brightest star Sirius is one of the nearest at a mere 8.6 light-years distance. In other words, the light that was arriving from Sirius in March 2014, when the comic was posted, was emitted some time around August 2005. The previous US president, George W. Bush , was in office from 2001 to 2009 and Megan notes that this isn't a terribly impressive observation. The title text references the fact that most normal people have a hard time imagining the large scale of astronomical numbers. For example, the distance between astronomical bodies or the size of the Sun are hard to imagine; they typically underestimate them by many orders of magnitude and think they are much smaller than they actually are. See Sci-Fi Writers Have No Sense of Scale In this case, however, people instead overestimate both the number of visible stars and their distance by quite a bit. It's frequently cited that about 5,000 to 10,000 stars are visible in the sky by the naked eye. The Bright Star Catalogue is a star catalogue that lists all stars of apparent magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth. The catalog contains 9,110 objects, of which 9,096 are stars, ten are novae or supernovae , and four objects outside of our Milky Way (two globular clusters and two open clusters ). To see most of these you need good eyes and a very dark night, and at any point you will only be able to see fewer than half of these as the rest are blocked by the Earth. This list shows the 91 brightest stars . Of these 59 are more than 100 light years away and only 6 are more than 1,000 light years away. The farthest on this list, Aludra , is "only" 3,200 light years away. Our entire Milky Way contains up to 400 billion (400x10⁹) stars and has a diameter of 100,000 light years. There are visible objects much farther away, like the Andromeda Galaxy which is 2.5 million light years away and made up of billions of stars. And a gamma ray burst GRB 080319B would have been briefly visible to the naked eye, despite being 7.5 billion light years distant. See also 1212: Interstellar Memes , 1644: Stargazing . All of the panels of this comic are white-on-black. [Megan and Cueball stand facing each other, looking up at the sky.] Cueball: Just think - the light from that star was emitted thousands of years ago. It could be long gone. [Cueball looks at Megan, who is still looking up.] Megan: That's Sirius. It's eight light-years away. [Cueball looks up again.] Cueball: Oh. [Both look at one another.] Cueball: Just think - the light from that star was emitted in the previous presidential administration. Megan: Hmm, doesn't pack quite the punch.

Manuals

Manuals

https://www.xkcd.com/1343

https://www.explainxkcd.com/wiki/index.php/1343:_Manuals

[A horizontal line has four points labeled on it, with the second point from the left marked with a dashed vertical line dividing the horizontal line into two parts.] [An arrow labeled "Solve problems" points left from the vertical line.] [An arrow labeled "Create problems" points right from the vertical line.] [The points are labeled, from left to right, "Tools that don't need a manual", "Tools that need a manual", "Tools that need a manual but don't have one", and "Tools whose manual starts with 'how to read this manual'".]

The chart shows the quality of tools regarding their manual: The title text refers to sudoers , a config file for the unix command sudo . sudo allows users to run a program with elevated permissions, as referenced in 149: Sandwich . Man pages are collections of manuals for different tools, commands, files, and functions on Unix-like systems which can be viewed with the tool man . You can type man man in a terminal to get the manpage for the manual program. See for instance also the comic 912: Manual Override . The sudoers file specifies which users have sudo access, and which commands they are allowed to run as other users (typically root). The syntax of the file is very complex, and the manpage uses the Extended Backus–Naur Form (or EBNF) to describe the syntax. The sudoers man page starts off with an explanation of EBNF's grammar, which they reference throughout the rest of the man page in describing the syntax of the sudoers file. The sudoers man page is very long, clocking in at 1504 lines. In contrast, the manpages man page only has 566 lines. The number of lines may differ between some distributions and versions. The title text also notes that the manual's assurance, "don't despair" because "the definitions below are annotated", fails to be reassuring, and instead merely emphasizes the length and complexity of the document to read. [A horizontal line has four points labeled on it, with the second point from the left marked with a dashed vertical line dividing the horizontal line into two parts.] [An arrow labeled "Solve problems" points left from the vertical line.] [An arrow labeled "Create problems" points right from the vertical line.] [The points are labeled, from left to right, "Tools that don't need a manual", "Tools that need a manual", "Tools that need a manual but don't have one", and "Tools whose manual starts with 'how to read this manual'".]

Digits

Digits

https://www.xkcd.com/1344

https://www.explainxkcd.com/wiki/index.php/1344:_Digits

[A guy is walking and Cueball is following him.] Guy: The talk is in room 8224. Cueball: Ooh, nice. Guy: What? Cueball: ...Sorry. Nothing. Great, now I'll spend the rest of my life noticing numbers that would make good 2048 combos.

2048 is a popular browser-based game in which players must move tiles in a 4 by 4 grid with numbers on them. When two tiles of the same number touch they can be merged into one tile with a value of the two tiles combined. So when two 4-tiles touch and are merged they form one 8-tile. The player can move the tiles by pressing an arrow key (or swiping in a direction on the mobile version), which will move all the tiles in that direction. Every time the player makes such a move another tile will appear on a random cell. The goal of the game is to get a tile with the number 2048. In the comic the room number can be seen as 4 tiles with the values 8, 2, 2 and 4. If these occur in the game the player can merge the two 2-tiles into one 4-tile. This will then cause two 4-tiles to lie next to each other, so these can be merged into one 8-tile. Finally, the two 8-tiles can be merged into one 16-tile. This can be done in the opposite direction as well. The title text refers to Tetris effect , which takes its name from the game Tetris . People who play Tetris for extended periods tend to imagine real-life objects (like skylines) as Tetris landscapes and pieces. Randall , as many others , apparently got hooked on Tetris so much when it came out that, for 20 years, he would look at city skylines and see Tetris-like patterns in it. Similarly, he has now been hooked onto 2048 and notices number patterns that would be desirable to obtain during the game. [A guy is walking and Cueball is following him.] Guy: The talk is in room 8224. Cueball: Ooh, nice. Guy: What? Cueball: ...Sorry. Nothing. Great, now I'll spend the rest of my life noticing numbers that would make good 2048 combos.

Answers

Answers

https://www.xkcd.com/1345

https://www.explainxkcd.com/wiki/index.php/1345:_Answers

[Cueball and Megan are talking.] Cueball: Humans are defined by our curiosity, our hunger for answers. Megan: We all spend a third of our lives lying down with our eyes closed and NOBODY KNOWS WHY. Cueball: Touché.

Cueball claims that humans are driven by their curiosity, which is never-ending. Megan responds by noting that everyone spends approximately eight hours per day in an unconscious state of sleep , but no one has yet pinned down the biological purpose of sleep. Despite this obvious mystery, most people aren't "losing sleep over it." This implies that Cueball's observed curiosity has a perceptible and proximate limit. This is not to suggest that scientists aren't researching sleep; scientists frequently conduct sleep studies — we just haven't found any satisfactory answers yet. Some popular hypotheses are to allow the brain a period to consolidate memories and to give the body a chance to repair itself. The title text quotes William Dement : people sleep "because we get sleepy." ( Secrets of sleep ). This of course is dodging the underlying issue. That this non-explanation is the best answer that a leading sleep researcher can provide, shows how little anyone knows about the subject. This may be an oblique reference to the dormitive principle of the French playwright Molière, who created a satirical character who claimed to have discovered the answer to a popular question: The reason opium makes someone sleepy, said the character, a doctor, was that it contained a "dormitive principle" (i.e., something that makes someone sleepy). In 203: Hallucinations , Randall expressed similar surprise at the lack of interest in the nature of sleep. The phrase "and nobody knows why" is commonly appended to urban legends, as in A duck's quack doesn't echo, and no one knows why . The implication is that something mysterious is going on and scientists are puzzled. 1186: Bumblebees is another "nobody knows why" example. [Cueball and Megan are talking.] Cueball: Humans are defined by our curiosity, our hunger for answers. Megan: We all spend a third of our lives lying down with our eyes closed and NOBODY KNOWS WHY. Cueball: Touché.

Career

Career

https://www.xkcd.com/1346

https://www.explainxkcd.com/wiki/index.php/1346:_Career

[Cueball stands facing a desk, behind which another person is sitting in a desk chair.] Cueball: It would start with five minutes of peeling lint from dryer traps, Cueball: followed by an hour of pressing a lightsaber handle against things and switching it on. Cueball: Then I'd retire to a life of luxury. When people ask me to describe my dream job, I'm never sure how realistic to be.

Cueball is presumably asked to answer the typical career counselor question: What is your dream job? Rather than going with the more common answers that are designed to increase the chances of landing that particular job, Cueball talks about unrealistic jobs that are whimsical, and so well compensated that a little over one hour on the clock would provide enough wealth for a luxurious retirement; of course, you can have such a job only in your dreams. He makes jobs out of tasks that people do when they are bored, whether the tasks needed to be done or not. Therefore, if he did not get the job he probably would have done them at some point anyway. Peeling lint off dryer traps can relieve boredom, but it gets tedious soon, so Cueball wants to do that only for 5 minutes, followed by an hour of holding the handle of a lightsaber against things and switching it on. The energy emitted by this fictional weapon will probably burn, melt or cut the object it is touching as demonstrated in a scene from Star Wars Episode I , where Jedi Qui-Gon Jinn uses his lightsaber to cut through a wall. Later, Star Wars: The Last Jedi turned out to demonstrate a lightsaber being placed against something before being switched on-- on the head of a Praetorian Guard. Obviously, it would be impossible to find a job like this, let alone one with a salary allowing one to retire to a life of luxury. [ citation needed ] However, Cueball thinks he will not only be paid to do it, he will be paid enough to retire to a life of luxury . The title text is poking fun at Hollywood films, particularly stories about violent professions (like mobsters, hitmen, detective or spies) where the hero is retired, but some unforeseen circumstance has forced them out of retirement to do " one last job ." Usually in these films, the jobs are overtly, improbably dangerous, often with the suggestion that they may lose their lives doing it, but the reward for doing the job (saving the world, a ton of cash, an unresolved debt) is just too great to refuse. However, in this comic the joke is that his "one last job" is also a mildly amusing task designed to relieve boredom. An alternative explanation may be that these activities are very sensationally unique and satisfying for certain types of people, such as those with autism, and that this dream job is simply getting paid absurd amounts of money for something they wanted to do anyway. [Cueball stands facing a desk, behind which another person is sitting in a desk chair.] Cueball: It would start with five minutes of peeling lint from dryer traps, Cueball: followed by an hour of pressing a lightsaber handle against things and switching it on. Cueball: Then I'd retire to a life of luxury. When people ask me to describe my dream job, I'm never sure how realistic to be.

t Distribution

t Distribution

https://www.xkcd.com/1347

https://www.explainxkcd.com/wiki/index.php/1347:_t_Distribution

[A physical bell-curve-shaped object labeled "Student's t distribution" is resting on a table. Cueball is working with it and a piece of paper.] Cueball: hmm [Cueball looks at the piece of paper.] Cueball: ...nope. [Cueball picks up the object and begins to walk off the panel with it.] [Cueball comes back onto the panel, now carrying an object shaped like a much more complex curve, with many symmetric spikes and dips, labeled "Teacher's t distribution".]

The Student's t-distribution is a class of probability distribution used in statistics to model small sample sizes. "Student" was the pseudonym of William Sealy Gosset , an employee of Guinness Brewery who discovered it. A Student's t distribution is similar to a normal symmetric bell curve distribution, but has "fatter tails"; thus, the one shown in the comic is roughly the right shape. A "Teacher's" t-distribution is a joke (pun) made up by Randall. The comic is a play on the name "Student", the pseudonym of the creator, versus the "Teacher". The idea is that a "teacher's" distribution would be more complex, and that it would be used for fitting data when the student's distribution wasn't sophisticated enough. Of course, in actuality, such a complex distribution as the one shown in the comic would have many parameters, and in practice would probably lead to overfitting and/or bias. Thus, the comic (and the title text) can be seen as making fun of the idea that more complex is always better, or perhaps of the idea that a statistician's job is to use more and more sophisticated tools to force the data to yield a "publishable" result, rather than to use the simplest appropriate tool and let the chips fall where they may. Cueball tries to "fit" a distribution to the data on the paper. This is the usual jargon for when a statistician is trying to model their data as coming from some underlying probability distribution, and the comic makes a pun with the physical meaning of "fit". In the second panel, Cueball decides that the Student's T distribution does not fit his data well (the data failed the Student t-test), and decides to pull out the more complex Teachers t-distribution instead (the teachers t-test - which the data is not allowed to continue to fail). Note that "test" is what statisticians do to data to see if it fits some distribution, but it is also another word for "examination." The Students t distribution relates the average of a small sample to the "true" population average, under the assumptions, unobjectionable in many contexts, that there is such a "true" value, and that the samples are independent and normally distributed with equal variance. As such, unless the data on Cueball's paper contain many small groups which radically violate these assumptions somehow, there is no way Cueball's data could falsify the t distribution. In particular, a single number (for the average of one group) or a small set of numbers (for the averages of several numbers) will never make a nice smooth curve, but an average statistician would see that as normal statistical noise that would even out over time, not as a reason to prefer a complex, spiky curve such as the supposed "teacher's" distribution. But of course, Cueball's access to a secret, cooler-looking distribution makes them more badass than a mere average statistician... or does it? Ironically, the Teacher's T Distribution shows equal variance, itself proving the appropriateness of the Student's T Distribution. The title text plays on the word "test". The first part of the sentence refers to a potential "Teacher t-test" which would be used in a statistical context to test for the significance of some observation, as opposed to the real "Student's t-test" which is used to determine if two sets of data differ by a statistically significant amount. On the other hand, the second part of the sentence refers to the possibility for students to take tests (or exams) until they pass - or to teachers who forces students to take the test again and again until they pass. The resulting sentence may refer to statistical fallacy, or the (conscious or unconscious) action of manipulating observations or misconducting experiments to give statistical significance to a false fact. [A physical bell-curve-shaped object labeled "Student's t distribution" is resting on a table. Cueball is working with it and a piece of paper.] Cueball: hmm [Cueball looks at the piece of paper.] Cueball: ...nope. [Cueball picks up the object and begins to walk off the panel with it.] [Cueball comes back onto the panel, now carrying an object shaped like a much more complex curve, with many symmetric spikes and dips, labeled "Teacher's t distribution".]

Before the Internet

Before the Internet

https://www.xkcd.com/1348

https://www.explainxkcd.com/wiki/index.php/1348:_Before_the_Internet

[Young girl talking to Megan, both holding smartphones.] Girl: Do you remember before the internet? Megan: Oh yeah, totally. Girl: what was it like? Megan: Not having a phone or computer to distract you? Girl: Yeah. Megan: It was SO. BORING. All the time. I just sat there. It was the worst. Girl: But wasn't it, like, more fulfilling? Engaging? Megan: Wasn't worth it. Girl: I still get bored. Megan: Not like we did.

A young Ponytail asks Megan what life was like before the Internet. The girl obviously was born after the Internet was invented. Megan responds that life was very boring without computers or mobile phones. This comic appears to be a parody of the common complaint — often done by elder people — that life was better and more fulfilling in the "good old days", in that there weren't so many distractions and people could actually get things done that were meaningful. The ages switch roles with the younger character being prepared to believe that life was more fulfilling before technology, and the elder rejecting the proposition. To Megan, even a more fulfilling and engaging life "wasn't worth" the price of what it meant to be bored in the days before smartphones and computers that could go online. Even though the ponytail girl says that she still experiences boredom in spite of having advanced technology to occupy her, Megan assures her that her version of boredom is nothing like what those in the pre-Internet days had to endure. Again, this is a reversal of the typical exchange in which a young person tries to insist that they still have social contact/get out and about/do worthwhile things in their spare time, and the elder person responds, "Not like we did." The title text continues in this vein as Megan talks about what people in her day resorted to doing when they were bored, for lack of anything better to do: they watched daytime TV . Daytime television consisted mainly of soap operas, talk shows, game shows, infomercials and children's programming and is notorious for being, in Megan's words, "soul-crushing". To round off the comparison, Megan uses a modern-day metaphor to express her extreme distaste for daytime television, saying that she would rather "eat an iPad" than go through that again. In other words, modern-day gadgets are so much better that she'd still have more fun if she were eating them than if she had to go without them. Alternatively, it could be to emphasize how unpleasant daytime TV is; eating an iPad would likely be unpleasant (e.g. it is too large to easily be swallowed whole and too hard to easily be bitten into parts), and it could poison her or give her an internal electrical or battery fire. Saying that she would rather eat an iPad would also be a powerful statement because Megan would not be able to watch movies, play games, read the news, etc… on that iPad after eating it (although she could just buy another iPad—at least if she survives the battery of the iPad that she ate leaking and/or exploding and other hazards associated with eating an iPad). Megan might just be responding with the opposite of what she's expected to say in this dialogue in order to mess with the younger girl. In reality, life was neither likely to be noticeably more fulfilling or noticeably more boring without technology: it was just life. People are equally capable of wasting their time and of doing worthwhile things regardless of what age they live in, and those who wax nostalgic about an older, better time are liable to forget that. This recalls the Hedonic treadmill theory which states that people will always be at roughly the same level of happiness regardless of positive or negative events or technological advances in civilization. [Young girl talking to Megan, both holding smartphones.] Girl: Do you remember before the internet? Megan: Oh yeah, totally. Girl: what was it like? Megan: Not having a phone or computer to distract you? Girl: Yeah. Megan: It was SO. BORING. All the time. I just sat there. It was the worst. Girl: But wasn't it, like, more fulfilling? Engaging? Megan: Wasn't worth it. Girl: I still get bored. Megan: Not like we did.

Shouldn't Be Hard

Shouldn't Be Hard

https://www.xkcd.com/1349

https://www.explainxkcd.com/wiki/index.php/1349:_Shouldn%27t_Be_Hard

[Cueball is typing on a laptop.] Cueball: What I'm trying to do is really simple. Cueball: It shouldn't be hard. Offscreen: All computers are just carefully organized sand. Everything is hard until someone makes it easy. [Cueball sits back and pauses.] [Cueball picks up and examines the laptop.] Cueball: Maybe I should turn this one back into sand. Offscreen: I'll find a blowtorch.

This comic refers to a sentiment sometimes expressed by computer users that "what I'm trying to do is really simple — it shouldn't be hard." The statement demonstrates an assumption that because the desired action is conceptually simple, it must therefore be simple to implement. There is a logic to this line of thinking, but in reality, as the off-screen character notes, a computer is a very complicated set of components which effectively can't do anything (simple or complex) until someone has programmed the functionality into it. Even more abstractly, a random silicon crystal can't do anything at all until someone has applied a complex industrial process to it that allows it to read and execute computer code in the first place. In terms of a user-interface, the "simplicity" of executing a given task may be more a function of the perceived utility and frequency-of-use of that function, and less a function of its conceptual "simplicity". For example, changing the colour of the font in a word processor is often simpler than changing the colour of the background/page, even though changing colours of two parts of the document would appear equally "simple" in concept. The different implementation is a design choice by the programmer most likely on the basis that the intended user is considered more likely to want to change the font colour than to change the page colour. This sentiment equally applies to computer programmers: most commonly when they are just beginning to learn a new computer language. Sometimes because of difficulties with the syntax rules of the language or similar problems, a programmer may spend a long time trying to get the computer to do a simple action, such as display a message on the screen, or ask the user for a number. This is also true when a programmer is working in a language which doesn't have an easy way to do something that might be simple in another language. And in computer science, it may often be very hard to differentiate the almost impossible from the easy , especially when compared to what humans can and can't do easily. The off-screen character points out that computers were "just carefully organized sand". Modern computer chips are made largely of silicon crystals, chemically a part of silicon dioxide crystals that compose the majority of sand. The character puts Cueball's goal in perspective by pointing out the large amount of complexity required to make, what is essentially sand, do even the simplest of computational tasks. The punchline of the comic is that, after considering these words of wisdom for a panel, instead of the anticipated response of Cueball coming to the realization that the off-screen character is right, and working even harder to solve his problem, Cueball instead succumbs to his annoyance and sets out to destroy his computer (which he characterizes as turning it " back into sand"). The off-screen character helpfully offers to get a blowtorch so that Cueball can melt the computer down into simple compounds and elements. The title text sees Cueball again frustrated with a task he considers "simple" (destroying the computer). Cueball appears to be oblivious to the irony in his statement that he is having trouble destroying something with household tools that required very large machines and an industrial process to create. This might be compared to trying to undo a steel weld by lighting a wooden match and trying to melt the weld with it. This points out the irony that destroying the processor is even harder to do than the task from the first picture. The melting point of silicon is 1,414 °C. Although a typical butane blowtorch that might be found in a kitchen has a maximum temperature of 1,430 °C, that temperature is at a very small point and rapidly cools. Hence it is unlikely that you could focus sufficient heat with a kitchen appliance blowtorch to actually melt silicon. The apparently simple task Cueball is trying to complete may express Randall's frustration in the creation of the crowd-sourced comic 1350: Lorenz , which was launched the next day and initially contained a large number of bugs. [Cueball is typing on a laptop.] Cueball: What I'm trying to do is really simple. Cueball: It shouldn't be hard. Offscreen: All computers are just carefully organized sand. Everything is hard until someone makes it easy. [Cueball sits back and pauses.] [Cueball picks up and examines the laptop.] Cueball: Maybe I should turn this one back into sand. Offscreen: I'll find a blowtorch.

Lorenz

https://www.xkcd.com/1350

https://www.explainxkcd.com/wiki/index.php/1350:_Lorenz

[This transcript only transcribes what can be seen in the picture shown at the top of the explanation here.] [The comic starts with two panels. In the top panel we see Knit Cap sitting at a desk in front of her laptop typing. There is a speech line up to a gray but empty speech bubble.] [The second panel below has the same gray background as the empty speech bubble above. Here is presented four options to what Knit Cap could be saying. They are marked a, b, c and d written in small white rectangles next to the text. There is a small arrow at the top pointing to the first panel:] a Hurry! We're in talks with Facebook. b These stupid tiles... I'll just play one more game. c Refresh... No new email... Refresh... No new tweets... Refresh... d Oh. Hey. There's some kind of political thing going on. [Once the reader chooses one of the options, the text will appear in the speech bubble where the gray area is replaced with the usual white background. The lower gray panel disappears. Now the comic really begins.] [A new panel is shown after the selection, again with one to four options to choose from in the new gray panel below. This will continue until it comes to an end where the reader finally only has the choice to suggest the next line.] [The order of the up to four options are random, and changes every time you begin again (or even go back to a previous frame). This means that the a–d in the transcript is not the same next time. In some few panels there are even more than four options. To see the fifth you have to reload, then you may find this fifth option next time. The first panel is one of those with five options.] [The fifth not shown above is: Let's see if BSD is any easier to install nowadays. (see image with this option in the trivia section ).] [In the first days of the comic, when it developed quickly, new options appeared only to later disappear. Gravity. Lots of it. is one of those lost options from the first panel. At one time there was also, by mistake, two versions of one of the other five mentioned above. This was later deleted. Below in the trivia section there are permalinks to all the different starting options, including the now lost gravity story.] [Although it may be impossible to finish (?), there has been an attempt to make a complete interactive transcript .] The reader is initially presented with only one panel, where Knit Cap is sitting in front of her computer. The reader is given multiple choices concerning what exactly Knit Cap is thinking. Upon choosing any option, the chosen text will appear where his gray speech bubble was (which will disappear), and then a second panel appears to the right to give continuity to the story. Each new panel may have a new set of options, or just the button "Continue", to see the next panel without making any choice in particular. Eventually, one reaches a dead end in which the story is interrupted, and the reader is presented with a text box to suggest how it should continue. Some of the suggestions given should eventually become available as new options. Normally, there are a total of 4 options to make: a/b/c/d. Their order changes constantly. Sometimes, there are 3 or fewer options, with the text box to suggest an alternative option. Sometimes, a given panel actually has 5 or more available options, although even in this case only 4 options appear at a time. Refreshing the comic changes randomly which of the available options are visible and which are hidden. As of late April 2014, the existence of 5 options seems to occur only in a few rare cases, including the first panel itself. There seem to be no longer any panels that have six options. Instead of clicking with the mouse, you can move more quickly through the panels using the keyboard: It appeared that new panels were generated by Randall in near real time, as user suggestions to dialog were submitted around the release of the comic. This text can (now) be found under the official transcript at xkcd: The dialog options could be based on click-through rates, and hence will change over time based on which choices are clicked most using A/B measurement techniques . This will mean that the most popular choices for dialog lines will prevail as the statistics build up. In some cases, dialog line options do not depend on the continuity of the storyline followed, suggesting that some parts of the story are planned. For example, several of the story lines involve one of the two main characters waking up and, for instance, telling the other character, "I had the strangest dream..." or even reliving the dream. This may be due to common submissions across story lines. Of course, there is the other option that Randall has used the first week of April to look though some input and choose himself. These possibilities are not mutually exclusive. Some of the options that were there very early were in quite poor English. Later, the same idea was still there, but in a more refined sentence. However, after the first week or two, no new panels seemed to appear, which suggests that some were drawn to match the story's progression. A " permalink " is a portmanteau of "permanent-link". Each panel has a "permalink" button which generates a unique URL for all the choices made by the reader — so a reader can save the chosen choices to compare them to other ways going through the selections. The permalinks do only save the chosen options, not the order or the visible options in the image where the permalink is recorded, so it is not possible to save a copy where the options are only in the same order as they are in the 1/120 version shown at the top. Also, if you go back in the story from a permalink, you can risk that when passing back through a panel with five options, the option you just got back from is no longer available; as it is the option randomly not shown this time. Sometimes it is possible to add your own suggestions in a panel where there are still other choices, but, if not before, the story will always reach a "final" panel (dead-end) where the reader only has the option left to "suggest a line..." By doing so, and pressing enter, this text is then shown in the speech bubble — but these suggestions can't be saved, as there are no permalink buttons after this. The reader has to do a screenshot in order to save their own remark. After a few weeks had progressed, there were probably so few new suggestions that Randall stopped changing the comic. A few images have been found months (or even more than a year) after the release, but there has been little to no reason to believe that Randall continued to make new panels after the first few weeks of April. Maybe he returned occasionally to do one once in a while; but, for certain, the options and text continue to evolve. Since this interactive comic relies on many servers in the background to provide the response to the reader's actions, there are some problems reported here: As a consequence of these bugs, many readers had trouble understanding how this interactive comic worked. There used to be a sixth option: "Gravity. Lots of it." However, it no longer appears.

This was the fifth April fools' comic released by Randall . The previous April fools' comic was 1193: Externalities from Monday April 1st 2013. The next was 1506: xkcloud released on Wednesday April 1st 2015. This comic was posted a day earlier than normal (on Tuesday instead of Wednesday) to honor April Fools' Day of 2014. This is an interactive and dynamic comic similar to the Choose Your Own Adventure series , where players flip to different pages based on the option they chose. The first picture shown on top of this page is the start of this comic, with a possible combination of text options to choose from (see above). The picture is always the same but the order of the four sentences (and the sentences themselves) is chosen randomly (and there can be more than four). The result of all the interactions by the readers led to the generation of crowd-sourced content . The title 'Lorenz' is referring to Edward Norton Lorenz who, among other subjects, was famous for Chaos theory and the Butterfly effect (mentioned later in the title text of 1519: Venus ). This comic is an example of a Choose Your Own Adventure story, as mentioned in the title text. The title text is also a reference to how the storyline of this comic will be chaotic by nature, since it includes all of the user submitted dialogue and updates over time based on statistics of user clicks. In this manner, it is a reference to the butterfly effect: a phrase coined by Edward Lorenz to describe how a small initial change can lead to wide variations in outcome in a chaotic system. Every time a story comes to a point where the user can either choose something or contribute when asked to Suggest a line , a link will appear by hovering the mouse over the bottom right corner of the last image. This is named a permalink , as it is a link that will recreate this particular story up to the point, making it permanent. It will not save the options listed below that image (i.e. the order of these will change, new options may appear, either because more than four are already present or new options will be added and some options may even disappear). An option is thus only saved by choosing it and then saving the next permalink — see more below . The best way to enjoy this comic is to try it yourself! If you didn't do that already, reading any below will spoil you from truly enjoying the comic, and maybe make some interesting discoveries yourself! So here is a spoiler alert if you read on. If you do, then see also the section below about Functionality and bugs . Any particular storyline will typically only have one or two of the many themes possible in the comic, but some very long stories may have several: see the Record section below. Several of the themes refer to previous comics or generally recurring themes in xkcd. (Most obviously is the blowtorch theme which is a reference to the previous comic 1349: Shouldn't Be Hard , where the last comment is I'll find a blowtorch as a response to Cueball's frustration over his problems.) Because it is not always ending as "well" as with a burnt PC, they might instead end up in a shark infested ocean — see the Ocean theme , which is a reference to 349: Success : a comic that came exactly 1000 comics before the other one referenced in the same computer problem theme. In that comic, the sharks had not appeared yet; but here there may be several (and sharks are also a recurring topic in xkcd). These issues with computers is generally a reference to the computer problem themes that precedes both the burning of the laptop and the ocean storylines, as Knit Cap tries to install BSD ; and when it fails, she takes her friend Hairy with her in the fall, the water, space or into a Pokémon fight (as they are the two main character of this comic). Also Cueball (as a politician vs. another politician with hair) and White Hat have small appearances, but only in a small sections of particular storyline. Only few others interact directly with the main characters in the rest of the possible stories. Other themes that are recurring in xkcd are Politics , Pokémon , Boomerangs and Dinosaurs . Dinosaurs enter the comic in the form of the green talking T-rex from Dinosaur Comics : a clip-art-based webcomic that uses the same artwork with different captions for every strip. This particular Dinosaur Comics has a title text that actually refer to Randall and xkcd, and the comic has previously appeared on xkcd in 145: Parody Week: Dinosaur Comics . A way to combine more than one storyline is to let characters wake up from a dream or a nightmare, as can be see in the Dreams theme (and dreams are also a recurring topic ). Here, it can even get recursive, so there can be dreams within dreams. One of the way to wake from a dream is, of course, by encountering a dinosaur that tries to step on your house (with you inside). Another is in reference to the possible rocket trip that may take the characters into space: see the Space theme (another recurring topic ). There are a few other topics that are covered by Randall himself, but many others will be referenced in the text in the comic. However, since most of the options the users have is in itself created by user input (including naming the characters different names), any reference made by the text is not considered part of Randall's work and thus only sporadically be mentioned below under the themes section and not be included as a category. Here is an example with a permalink where the last comment, in the ocean with a shark, references Malaysia Airlines Flight 370 that disappeared less than a month before this comic was released [and has yet to be found years later]. But this is a user input, not Randall's. Some of the idea of this comic was used again in the next year's April Fools' comic 1506: xkcloud , where user input also generated a very complex comic and the concept of permalink was used again. This comic was the first time that Knit Cap has a main part to play. Since this comic, she has been given a category as a supporting character in xkcd, but in most other comics knit cap is seen as a man. The name knit cap for his hat has also been debated . [This transcript only transcribes what can be seen in the picture shown at the top of the explanation here.] [The comic starts with two panels. In the top panel we see Knit Cap sitting at a desk in front of her laptop typing. There is a speech line up to a gray but empty speech bubble.] [The second panel below has the same gray background as the empty speech bubble above. Here is presented four options to what Knit Cap could be saying. They are marked a, b, c and d written in small white rectangles next to the text. There is a small arrow at the top pointing to the first panel:] a Hurry! We're in talks with Facebook. b These stupid tiles... I'll just play one more game. c Refresh... No new email... Refresh... No new tweets... Refresh... d Oh. Hey. There's some kind of political thing going on. [Once the reader chooses one of the options, the text will appear in the speech bubble where the gray area is replaced with the usual white background. The lower gray panel disappears. Now the comic really begins.] [A new panel is shown after the selection, again with one to four options to choose from in the new gray panel below. This will continue until it comes to an end where the reader finally only has the choice to suggest the next line.] [The order of the up to four options are random, and changes every time you begin again (or even go back to a previous frame). This means that the a–d in the transcript is not the same next time. In some few panels there are even more than four options. To see the fifth you have to reload, then you may find this fifth option next time. The first panel is one of those with five options.] [The fifth not shown above is: Let's see if BSD is any easier to install nowadays. (see image with this option in the trivia section ).] [In the first days of the comic, when it developed quickly, new options appeared only to later disappear. Gravity. Lots of it. is one of those lost options from the first panel. At one time there was also, by mistake, two versions of one of the other five mentioned above. This was later deleted. Below in the trivia section there are permalinks to all the different starting options, including the now lost gravity story.] [Although it may be impossible to finish (?), there has been an attempt to make a complete interactive transcript .] The reader is initially presented with only one panel, where Knit Cap is sitting in front of her computer. The reader is given multiple choices concerning what exactly Knit Cap is thinking. Upon choosing any option, the chosen text will appear where his gray speech bubble was (which will disappear), and then a second panel appears to the right to give continuity to the story. Each new panel may have a new set of options, or just the button "Continue", to see the next panel without making any choice in particular. Eventually, one reaches a dead end in which the story is interrupted, and the reader is presented with a text box to suggest how it should continue. Some of the suggestions given should eventually become available as new options. Normally, there are a total of 4 options to make: a/b/c/d. Their order changes constantly. Sometimes, there are 3 or fewer options, with the text box to suggest an alternative option. Sometimes, a given panel actually has 5 or more available options, although even in this case only 4 options appear at a time. Refreshing the comic changes randomly which of the available options are visible and which are hidden. As of late April 2014, the existence of 5 options seems to occur only in a few rare cases, including the first panel itself. There seem to be no longer any panels that have six options. Instead of clicking with the mouse, you can move more quickly through the panels using the keyboard: It appeared that new panels were generated by Randall in near real time, as user suggestions to dialog were submitted around the release of the comic. This text can (now) be found under the official transcript at xkcd: The dialog options could be based on click-through rates, and hence will change over time based on which choices are clicked most using A/B measurement techniques . This will mean that the most popular choices for dialog lines will prevail as the statistics build up. In some cases, dialog line options do not depend on the continuity of the storyline followed, suggesting that some parts of the story are planned. For example, several of the story lines involve one of the two main characters waking up and, for instance, telling the other character, "I had the strangest dream..." or even reliving the dream. This may be due to common submissions across story lines. Of course, there is the other option that Randall has used the first week of April to look though some input and choose himself. These possibilities are not mutually exclusive. Some of the options that were there very early were in quite poor English. Later, the same idea was still there, but in a more refined sentence. However, after the first week or two, no new panels seemed to appear, which suggests that some were drawn to match the story's progression. A " permalink " is a portmanteau of "permanent-link". Each panel has a "permalink" button which generates a unique URL for all the choices made by the reader — so a reader can save the chosen choices to compare them to other ways going through the selections. The permalinks do only save the chosen options, not the order or the visible options in the image where the permalink is recorded, so it is not possible to save a copy where the options are only in the same order as they are in the 1/120 version shown at the top. Also, if you go back in the story from a permalink, you can risk that when passing back through a panel with five options, the option you just got back from is no longer available; as it is the option randomly not shown this time. Sometimes it is possible to add your own suggestions in a panel where there are still other choices, but, if not before, the story will always reach a "final" panel (dead-end) where the reader only has the option left to "suggest a line..." By doing so, and pressing enter, this text is then shown in the speech bubble — but these suggestions can't be saved, as there are no permalink buttons after this. The reader has to do a screenshot in order to save their own remark. After a few weeks had progressed, there were probably so few new suggestions that Randall stopped changing the comic. A few images have been found months (or even more than a year) after the release, but there has been little to no reason to believe that Randall continued to make new panels after the first few weeks of April. Maybe he returned occasionally to do one once in a while; but, for certain, the options and text continue to evolve. Since this interactive comic relies on many servers in the background to provide the response to the reader's actions, there are some problems reported here: As a consequence of these bugs, many readers had trouble understanding how this interactive comic worked. There used to be a sixth option: "Gravity. Lots of it." However, it no longer appears.

Metamaterials

Metamaterials

https://www.xkcd.com/1351

https://www.explainxkcd.com/wiki/index.php/1351:_Metamaterials

[An image of a violet that is colored red.] Megan (off-screen): Violets are red [An image of a rose that is colored blue.] Megan (off-screen): And roses are blue [Megan and Cueball are standing around a table, on which a screen is in front of the rose and violet. Megan is in front of a lectern with a mic. All of this is on a stage.] Megan: When metamaterials [Same scene, but Megan moves the screen away from in front of the rose and violet. It is revealed that the flowers' actual colors are those from the original poem, i.e. the violet is blue and the rose is red.] Megan: Alter their hue.

Metamaterials , artificially-created structures typically made from several materials in a microscopic checkerboard pattern, are famous for allowing bizarre optical properties, such as invisibility cloaks . This comic imagines that metamaterials can change the color of light passing through them. In the real world a metamaterial can alter the spatial distribution of light and also its frequency, like done in fluorescent lamps — but this would not resemble the entire picture in a different color. In photography many filters are used to enhance the quality and appearance of the image. These filters do not alter colors but block some of them, so the result is shown in a different color than the original. Nevertheless, no application like this is able to switch a single color to another as it can be done by most modern computer photo programs. Megan uses a box made of her metamaterial to switch the colors of the cliché Valentine's Day poem, " Roses are red, violets are blue, sugar is sweet and so are you. " The title text references this with Randall pondering making a metamaterial that reverses the effect of instagram filters, likely by placing the material between the camera and the subject just before the picture is taken without the photographer noticing - a so-called photobombing . Instagram is a photo application that applies one of a variety of filters like hue-shift or contrast adjustments meant to simulate the look of old photographs. These filters may be able to interchange blue and red - as they are not real material filters. [An image of a violet that is colored red.] Megan (off-screen): Violets are red [An image of a rose that is colored blue.] Megan (off-screen): And roses are blue [Megan and Cueball are standing around a table, on which a screen is in front of the rose and violet. Megan is in front of a lectern with a mic. All of this is on a stage.] Megan: When metamaterials [Same scene, but Megan moves the screen away from in front of the rose and violet. It is revealed that the flowers' actual colors are those from the original poem, i.e. the violet is blue and the rose is red.] Megan: Alter their hue.

Cosmologist on a Tire Swing

Cosmologist on a Tire Swing

https://www.xkcd.com/1352

https://www.explainxkcd.com/wiki/index.php/1352:_Cosmologist_on_a_Tire_Swing

[A tall panel with Cueball and Science Girl walking together through a landscape with three trees in the background and with many small pools of water. Their reflection is showing in the pool nearest to them.] Science Girl: What was before the big bang? Cueball: I think time began with the big bang. Cueball: So it doesn't make sense to ask what came before it. Cosmologist (off panel): Look out [The next six panels are between the first tall panel and a similar panel at the end. They should be read from above and down in two columns of three images. The bottom of the first panel at the top is partly hidden by the second panel which is likewise partly hidden by the lower panel, and this repeats in the second column.] [A cosmologist looking like Megan comes swinging left past Science Girl and Cueball, who turns to look after her. She sit on an upstanding tire swing and the movement is indicated by two lines going from right to left.} Cosmologist: Wheeee Hi I'm a cosmologist on a tire swing! [The cosmologist swings back right, hanging in her arms with her body almost vertical. The other two also turns right.] Cosmologist: We don't know whether time [Going left, similar to the first of the small panels.] Cosmologist: started at the big bang. [Going right, similar to the second of the small panels, but with the cosmologist sitting more upright.] Cosmologist: It might have! [Going left, similar to the first of the small panels.] Cosmologist: Or maybe not! We don't know! Cueball: Oh. OK! [Going right, similar to previous going right panels.] Science Girl: ...Your tire swing looks fun! Cosmologist: I can't stop! [The last panel is again a full panel, with Cueball and Science Girl looking towards the right after the cosmologist who continued the last swing to the right from the last small panel, having just reach the upper part of the curve and has thus turned left to face them, before the swing will go down left again. The background is completely white with no indications of the trees and pools from the first panel.] Science Girl: Won't the swing stop on its own? Cosmologist: I thought it would, but it seems to be accelerating. Science Girl: Cosmology sounds pretty confusing. Cosmologist: Wheeeee!

Cueball and the curious Science Girl walk through a landscape with trees in the background and with many small pools of water. The setting of trees interspersed with these many small pools resembles the Wood between the Worlds , a meta-verse described in C.S. Lewis's The Magician's Nephew ; each pool leads into a different universe — one of these is ours, another is Narnia , and Charn (the world of Jadis the White Witch ) is also visited through these pools. Science Girl asks about the time before the Big Bang . Cueball says he thinks there was no time before — which is implied by most forms of the Big Bang theory. But then they happen upon a cosmologist , Megan , on a swing who has several other theories about the universe. Simply put, the tire swing is a symbolic representation of our universe. Scientific observations tell us that both space and time began with the Big Bang ~13.8 billion years ago. We don't know if there was such a thing as "before" the universe, or what that might be. The first 6 panels reference ongoing speculation about where the universe came from and why it even exists in the first place. The last two panels relate to recent observations of the accelerating universe in which galaxies are now receding from each other at higher and higher speeds, due to dark energy . The swing itself is likely a reference to the Cyclic Model , where the universe expands from a Big Bang, then contracts back in on itself under its own gravity for a Big Crunch , before bouncing outward again in another Big Bang, and repeating the whole process. On the other hand, the swing is accelerating as the universe — so it may also be a reference to the entire universe. We are all "trapped" on this swing — and it's accelerating! For the layman (and most scientists as well) cosmology is pretty confusing as Science Girl states at the end, to which the cosmologist just replies Wheeeee! and enjoys her ride with this accelerating swing/universe. Another interpretation of the acceleration may referring to the physics of orbital motion in which a centrifugal force is always causing constant acceleration toward the center of the motion. The title text references questions about the shape of the universe and what could lie "outside" of it. By the current understanding on physics laws, we can't see outside of the observable universe , but it's likely that the universe is bigger than this observable universe and uniform on large scale. Even though nobody can leave our own universe, Megan bets that such unknown worlds do exist - because this universe is here, and it must have come from somewhere — like her tire. The shape of our universe was visited soon after in 1365: Inflation where we can see what the outer boundaries of our universe looks like. Science Girl is seen later in conjunction with a tire swing in 1659: Tire Swing ; maybe she is preparing to become a cosmologist herself. Also this may explain from where the tire came from... [A tall panel with Cueball and Science Girl walking together through a landscape with three trees in the background and with many small pools of water. Their reflection is showing in the pool nearest to them.] Science Girl: What was before the big bang? Cueball: I think time began with the big bang. Cueball: So it doesn't make sense to ask what came before it. Cosmologist (off panel): Look out [The next six panels are between the first tall panel and a similar panel at the end. They should be read from above and down in two columns of three images. The bottom of the first panel at the top is partly hidden by the second panel which is likewise partly hidden by the lower panel, and this repeats in the second column.] [A cosmologist looking like Megan comes swinging left past Science Girl and Cueball, who turns to look after her. She sit on an upstanding tire swing and the movement is indicated by two lines going from right to left.} Cosmologist: Wheeee Hi I'm a cosmologist on a tire swing! [The cosmologist swings back right, hanging in her arms with her body almost vertical. The other two also turns right.] Cosmologist: We don't know whether time [Going left, similar to the first of the small panels.] Cosmologist: started at the big bang. [Going right, similar to the second of the small panels, but with the cosmologist sitting more upright.] Cosmologist: It might have! [Going left, similar to the first of the small panels.] Cosmologist: Or maybe not! We don't know! Cueball: Oh. OK! [Going right, similar to previous going right panels.] Science Girl: ...Your tire swing looks fun! Cosmologist: I can't stop! [The last panel is again a full panel, with Cueball and Science Girl looking towards the right after the cosmologist who continued the last swing to the right from the last small panel, having just reach the upper part of the curve and has thus turned left to face them, before the swing will go down left again. The background is completely white with no indications of the trees and pools from the first panel.] Science Girl: Won't the swing stop on its own? Cosmologist: I thought it would, but it seems to be accelerating. Science Girl: Cosmology sounds pretty confusing. Cosmologist: Wheeeee!

Heartbleed

Heartbleed

https://www.xkcd.com/1353

https://www.explainxkcd.com/wiki/index.php/1353:_Heartbleed

Megan: Heartbleed must be the worst web security lapse ever. Cueball: Worst so far. Give us time. Megan: I mean, this bug isn't just broken encryption. Megan: It lets website visitors make a server dispense random memory contents. Megan: It's not just keys. It's traffic data. Emails. Passwords. Erotic fanfiction. Cueball: Is everything compromised? Megan: Well, the attack is limited to data stored in computer memory. Cueball: So paper is safe. And clay tablets. Megan: Our imaginations, too. Cueball: See, we'll be fine.

The Heartbleed bug refers to a critical bug in the OpenSSL cryptographic library. This bug was publicly revealed on Monday, 7 April 2014. Due to a programming error in OpenSSL versions 1.0.1 through 1.0.1f — meaning the bug had existed for two years — attackers could read random server memory by sending specially prepared HeartbeatRequest messages to an affected server. OpenSSL is a very commonly used library to implement SSL/TLS , a cryptographic protocol not only used to secure web traffic but also for mail clients and much more. Only the user and the server can read the communication. On the web the protocol is https:// (HTTP Secure), instead of the open http:// standard. SSL is often used to protect sensitive web traffic, such as login requests, which contains the user names and passwords in the requests. The server sends a certificate to the browser before the secure connection is established. If the certificate is registered the browser accepts it automatically, otherwise the user gets a popup to accept or reject this insecure certificate. A vulnerability that lets an attacker read random clumps of memory on the server would possibly let an attacker find recent username/password requests, allowing them to gain unauthorized access to user accounts. Even worse, this vulnerability could read the server's private key, enabling anyone to impersonate the server and/or decrypt any future traffic that relies on that key, and any previously-obtained prior traffic also, unless a "perfect forward secrecy" cipher is used. Furthermore, the Heartbleed exploit occurs during the handshake phase of setting up a connection, so no traces of it are logged, i.e. you can be attacked and never be the wiser. More information is available at heartbleed.com or under the reference CVE-2014-0160 at nvd.nist.gov . In the last panel, Megan interprets Cueball's question ("is everything compromised?") expansively. She responds that, being a computer bug, Heartbleed can only affect information which is stored on computers. Cueball concludes that information recorded in analog media, such as that written on paper or etched in clay tablets, is safe. Megan adds that imaginations are also unaffected by Heartbleed, and Cueball is reassured. The reader may wonder how our society would fare in the face of the leakage of all electronically stored private information, but having our imaginations intact is certainly reassuring. The title text cites the Tears in rain soliloquy , the dying words of the replicant and main antagonist Roy Batty (played by Rutger Hauer ) in the 1982 film Blade Runner , implying that the 64KiB HeartBleed buffer is so complete it includes memories from replicant brains. This is ironic as in the soliloquy, Roy Batty stated "All those moments will be lost in time". The title text also suggests to patch OpenSSL oneself, which might refer to the patched version of OpenSSL by Debian, which turned out to be vulnerable in 2008, and was the topic of 424: Security Holes . In addition to the below, see xkcd's explanation in the next comic. Transport Layer Security (TLS), the successor to SSL , is a protocol that provides end-to-end encryption for data transmitted over the internet, and is described in RFC 5246 . The Heartbeat extension to TLS introduced in 2012 (described in RFC 6520 ) provides a protocol for keeping an encrypted TLS session alive (preventing inactivity timeouts), so you do not have to do a costly TLS handshake with the server for subsequent transfer of information. The Heartbeat protocol involves the client sending a packet with an arbitrary payload (often a random 16 to 32 byte number) that the server periodically sends back to the client to tell the client that the TLS session is still alive. When the client sends the packet to a vulnerable version of OpenSSL, the OpenSSL server reads a payload_size from the header sent by the client. This is a 2-byte number (0 to 0xffff=65535) that is supposed to describe the size of the payload. The OpenSSL library writes the payload to memory, but it does not check that the size of the payload written to memory matches the payload_size taken from the client's header. When the vulnerable server sends back the Heartbeat KeepAlive response to the client, it will readout payload_size number of bytes and send them back to the client. If you send a payload that is actually 16 bytes, but claims it is 0xffff bytes you will read the next 64KiB of memory of the vulnerable process starting from wherever the payload was written. An attacker can repeat this attack many times and can do this attack early in the TLS handshake, so the attack will not in any way be logged unless they are logging every incoming packet which is not typical and would result in many passwords being logged. As private keys often have an identifiable format, it is often possible for an attacker to find the private TLS key, so if they eavesdrop on network traffic they can decrypt and/or alter it. For more detailed information see: 1 , 2 , 3 . It is worth noting that modern operating systems use a virtual memory abstraction above physical memory. This means every process can only access memory assigned to it, so it would be impossible for a vulnerable web server to read memory assigned to another process (like a text editor that has erotic fan fiction stored to memory) on the same computer. For more info, see: 4 . It also should be noted that this heartbleed bug only affects certain versions of OpenSSL, and does not affect other TLS/SSL implementations, or OpenSSH which does not even use the TLS protocol, but uses the SSH-2 protocol (described in RFC 4251 ). SSH is typically used for remote logins on unix and linux computers. Vulnerable sysadmins need to update to a patched version of OpenSSL or one with the Heartbeats disabled. Unless their TLS keys were protected by hardware, they probably also need to revoke their old TLS keys, and generate new TLS keys. To learn how to do this visit Leo Green . There you will find all the information you need. Users of vulnerable systems should change their passwords after the sysadmins have revoked their old key and issued new ones (as their passwords may have been compromised). Users can check whether a given website is vulnerable via a Heartbleed test also available as open source . The Lastpass heartbleed diagnostic also indicates whether the signature on the TLS key predates the publication of the heartbleed vulnerability. The vulnerable commit was introduced Dec 31st, 2011 by Robin Seggelmann, the first co-author of the heartbeats RFC, and went live when OpenSSL version 1.0.1 was released on 2012-03-14 and the vulnerability was widely announced 2014-04-07. Megan: Heartbleed must be the worst web security lapse ever. Cueball: Worst so far. Give us time. Megan: I mean, this bug isn't just broken encryption. Megan: It lets website visitors make a server dispense random memory contents. Megan: It's not just keys. It's traffic data. Emails. Passwords. Erotic fanfiction. Cueball: Is everything compromised? Megan: Well, the attack is limited to data stored in computer memory. Cueball: So paper is safe. And clay tablets. Megan: Our imaginations, too. Cueball: See, we'll be fine.

Heartbleed Explanation

Heartbleed Explanation

https://www.xkcd.com/1354

https://www.explainxkcd.com/wiki/index.php/1354:_Heartbleed_Explanation

[Caption above the panels:] How the Heartbleed Bug works: [Meg, a girl with more curly hair than Megan, stands to the left in a panel. At the center of the panel is a black and gray server with red and green diode lights showing. During all six panels the server stays the same. Meg is standing with her arms down in four panels. It will be noted when she does not. Meg talks to the server. The server "thinks" all the time, i.e. we see its memory in all panels. The top and bottom line is breaking the edge of the thought bubble making it difficult to discern. In every second panel it replies to Meg. In these panels the number of letters requested by Meg is highlighted with yellow color.] [Meg speaks, server thinks:] Meg: Server, are you still there? If so, reply "POTATO" (6 letters). Server thinking: wants pages about "boats". User Erica requests secure connection using key "4538538374224" User Meg wants these 6 letters: POTATO. User Ada wants pages about "irl games". Unlocking secure records with master key 5130985733435. Maggie (chrome user) sends this message: "Hi [Server thinks, the same as above, although cut a little different at the edges, with POTATO highlighted in yellow and it replies the highlighted part in a rectangular speak bubble.] Server thinking: wants pages about "boats". User Erica requests secure connection using key "4538538374224" User Meg wants these 6 letters: POTATO. User Ada wants pages about "irl games". Unlocking secure records with master key 5130985733435. Maggie (chrome user) sends this message: "Hi Server: POTATO [Meg speaks, server thinks:] Meg: Server, are you still there? If so, reply "BIRD" (4 letters). Server thinking: User Olivia from London wants pages about "man bees in car why". Note: Files for IP 375.381.283.17 are in /tmp/files-3843. User Meg wants these 4 letters: BIRD. There are currently 348 connections open. User Brendan uploaded the file selfie.jpg (contents: 834ba962e2ceb9ff89bd3bff8c ... [Server thinks, the same as above, although cut a little different at the edges, with BIRD highlighted in yellow and it replies the highlighted part in a rectangular speak bubble. Meg has taken her hand to her chin thinking:] Server thinking: User Olivia from London wants pages about "man bees in car why". Note: Files for IP 375.381.283.17 are in /tmp/files-3843. User Meg wants these 4 letters: BIRD. There are currently 348 connections open. User Brendan uploaded the file selfie.jpg (contents: 834ba962e2ceb9ff89bd3bff8c ... Server: BIRD Meg: Hmm... [Meg has taken her hand down again and speaks, server thinks, now with her line at the top:] Meg: Server, are you still there? If so, reply "HAT" (500 letters). Server memory: a connection. Jake requested pictures of deer. User Meg wants these 500 letters: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's master key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User [Server thinks, the same as above, although cut a little different at the edges, with everything from (and including) "HAT" highlighted in yellow and it replies the highlighted part and even more in a rectangular speak bubble. Meg has taken a note book and a pen and it writing something.:] Server memory: a connection. Jake requested pictures of deer. User Meg wants these 500 letters: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's master key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User Server: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User Amber requests pages

The Heartbleed bug has received a lot of news coverage recently and was also the topic of the previous comic 1353: Heartbleed . This comic explains how the bug may have been discovered and can be exploited to reveal a server's memory contents. A Megan -like character named Margaret (or "Meg") sends heartbeat requests to the server, the server responds to the heartbeat request by returning the contents of the body of the request up to the number of letters requested. The first two requests are well formed, requesting exactly the number of characters in the request body. The server's memory is showing Meg's request with many other requests going on at the same time. Meg then ponders this and tries to another request asking for "HAT" but requests that it be 500 letters long instead of only 3; the server —not checking it or simply unaware that 500 letters is larger than the request body— returns "HAT" plus 497 letters that happened to be next to the word "HAT" in its memory (more will follow than are shown in the server's speak bubble as there are only 251 letters/symbols in the shown reply). Included are many sensitive bits of information, including a master key and user passwords. One of the passwords shown is "CoHoBaSt", a reference to 936: Password Strength , which suggests using " co rrect ho rse ba ttery st aple" as a password. Often popular explanations of security bugs require the issue to be simplified a lot and to leave out a lot of details. In this case Randall didn't have to do much simplifying; the bug is actually that simple. Also, it should be noted that any client which can connect to the server typically can exploit this bug in the underlying OpenSSL software — the use of the term "User Meg" does not imply that Meg had to authenticate first. Although Randall shows Meg recording the data by hand, on paper, it is more likely that a person exploiting the bug would have a computer record the data, perhaps on its hard drive or on a flash drive. The title text is a reference to Are You There God? It's Me, Margaret. , a novel by Judy Blume , and plays off of the "server, are you still there?" line in every panel where she did start a request. The novel is the theme of another comic 1544: Margaret too. Meg can be a nickname for Margaret as well as Megan who Margaret resembles. [Caption above the panels:] How the Heartbleed Bug works: [Meg, a girl with more curly hair than Megan, stands to the left in a panel. At the center of the panel is a black and gray server with red and green diode lights showing. During all six panels the server stays the same. Meg is standing with her arms down in four panels. It will be noted when she does not. Meg talks to the server. The server "thinks" all the time, i.e. we see its memory in all panels. The top and bottom line is breaking the edge of the thought bubble making it difficult to discern. In every second panel it replies to Meg. In these panels the number of letters requested by Meg is highlighted with yellow color.] [Meg speaks, server thinks:] Meg: Server, are you still there? If so, reply "POTATO" (6 letters). Server thinking: wants pages about "boats". User Erica requests secure connection using key "4538538374224" User Meg wants these 6 letters: POTATO. User Ada wants pages about "irl games". Unlocking secure records with master key 5130985733435. Maggie (chrome user) sends this message: "Hi [Server thinks, the same as above, although cut a little different at the edges, with POTATO highlighted in yellow and it replies the highlighted part in a rectangular speak bubble.] Server thinking: wants pages about "boats". User Erica requests secure connection using key "4538538374224" User Meg wants these 6 letters: POTATO. User Ada wants pages about "irl games". Unlocking secure records with master key 5130985733435. Maggie (chrome user) sends this message: "Hi Server: POTATO [Meg speaks, server thinks:] Meg: Server, are you still there? If so, reply "BIRD" (4 letters). Server thinking: User Olivia from London wants pages about "man bees in car why". Note: Files for IP 375.381.283.17 are in /tmp/files-3843. User Meg wants these 4 letters: BIRD. There are currently 348 connections open. User Brendan uploaded the file selfie.jpg (contents: 834ba962e2ceb9ff89bd3bff8c ... [Server thinks, the same as above, although cut a little different at the edges, with BIRD highlighted in yellow and it replies the highlighted part in a rectangular speak bubble. Meg has taken her hand to her chin thinking:] Server thinking: User Olivia from London wants pages about "man bees in car why". Note: Files for IP 375.381.283.17 are in /tmp/files-3843. User Meg wants these 4 letters: BIRD. There are currently 348 connections open. User Brendan uploaded the file selfie.jpg (contents: 834ba962e2ceb9ff89bd3bff8c ... Server: BIRD Meg: Hmm... [Meg has taken her hand down again and speaks, server thinks, now with her line at the top:] Meg: Server, are you still there? If so, reply "HAT" (500 letters). Server memory: a connection. Jake requested pictures of deer. User Meg wants these 500 letters: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's master key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User [Server thinks, the same as above, although cut a little different at the edges, with everything from (and including) "HAT" highlighted in yellow and it replies the highlighted part and even more in a rectangular speak bubble. Meg has taken a note book and a pen and it writing something.:] Server memory: a connection. Jake requested pictures of deer. User Meg wants these 500 letters: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's master key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User Server: HAT. Lucas requests the "missed connections" page. Eve (administrator) wants to set server's key to "14835038534". Isabel wants pages about "snakes but not too long". User Karen wants to change account password to "CoHoBaSt". User Amber requests pages

Airplane Message

Airplane Message

https://www.xkcd.com/1355

https://www.explainxkcd.com/wiki/index.php/1355:_Airplane_Message

[There is a plane with a banner behind.] Banner: Adriamycin, one of our most potent chemotherapy drugs, comes from the dirt from an Italian castle. My hobby: Breaking into airplane hangars and replacing the ads on their giant banners with cool facts.

Large banners are sometimes flown behind airplanes to advertise a product or event to a large number of people. Here, Randall suggests replacing the ad with some interesting facts. This would tell people who see the banner something new and interesting about the world, rather than try to sell them something. He presents two possible facts: Adriamycin , a cancer therapy, and Iry-Hor , the earliest human we know by name. The chemotherapy drug doxorubicin , trade name Adriamycin, is based on a strain of the bacterium Streptomyces peucetius , first isolated from a soil sample taken at Castel del Monte in Andria , Italy. As mentioned at the title text Iry-Hor was an ancient, predynastic pharaoh of ancient Egypt — no earlier documents exist today. This fact is also placed at exactly 3100 BC (or BCE ) in 1732: Earth Temperature Timeline . The week after that comic came out improving cancer research was the subject of 1736: Manhattan Project . That became the first cancer related comic since this one, even though more than two years had passed and with cancer being a recurring subject on xkcd... It could be a coincidence, but seems strange that both facts were directly/indirectly referenced within two weeks more than two years later, and there is even a banner in the cancer comic... [There is a plane with a banner behind.] Banner: Adriamycin, one of our most potent chemotherapy drugs, comes from the dirt from an Italian castle. My hobby: Breaking into airplane hangars and replacing the ads on their giant banners with cool facts.

Orbital Mechanics

Orbital Mechanics

https://www.xkcd.com/1356

https://www.explainxkcd.com/wiki/index.php/1356:_Orbital_Mechanics

How Well I Understand Orbital Mechanics: [There is a graph with the x-axis labeled as 'time' increasing to the right. The y-axis is unlabeled but it can be assumed that it could be labeled 'understanding'.] The line stays flat until the first bump, which is annotated "Took High School Physics". The line decreases, then grows to a higher maximum with the annotation "Got Physics Degree". There is a small amount of decrease until a gradual bump in the graph labeled "Actual Job At NASA". It gradually decreases to pre-NASA levels, but then begins to increase exponentially. The annotation reads "Started Playing Kerbal Space Program".

Randall roughly plots how high school physics, undergraduate-level physics and a job at NASA somewhat increased his knowledge of orbital mechanics . But this learning was apparently nothing compared to the "direct" experience of playing Kerbal Space Program , a rocket building and piloting sandbox game . Orbital mechanics can be somewhat counterintuitive. The art of changing orbits involves relative velocities, positions, and times in complex interactions. As soon as you try deviating from a perfectly regular orbit, or start having to deal with N-body problems and orbital resonances , you have to coordinate your movements in possibly counterintuitive ways. One example is that if you want to reach an object ahead of you, on the same orbit, you actually have to 'brake' to reach a lower orbit. Once at that lower orbit, your angular velocity is faster, and you can start to overtake your target. After that manoeuver, you then have to accelerate to increase your orbital altitude again, which will end up reducing your angular speed so that you intercept your target. At the title text Randall admits that at the time when he did work at NASA he was not involved in orbital mechanics—which is also true for most other NASA employees—but everybody was talking about this which in the end did increase his knowledge a little, as can be seen in the curve after the Job at NASA arrow. How Well I Understand Orbital Mechanics: [There is a graph with the x-axis labeled as 'time' increasing to the right. The y-axis is unlabeled but it can be assumed that it could be labeled 'understanding'.] The line stays flat until the first bump, which is annotated "Took High School Physics". The line decreases, then grows to a higher maximum with the annotation "Got Physics Degree". There is a small amount of decrease until a gradual bump in the graph labeled "Actual Job At NASA". It gradually decreases to pre-NASA levels, but then begins to increase exponentially. The annotation reads "Started Playing Kerbal Space Program".

Free Speech

Free Speech

https://www.xkcd.com/1357

https://www.explainxkcd.com/wiki/index.php/1357:_Free_Speech

Cueball: Public Service Announcement: The Right to Free Speech means the government can't arrest you for what you say. Cueball: It doesn't mean that anyone else has to listen to your bullshit, or host you while you share it. Cueball: The 1st Amendment doesn't shield you from criticism or consequences. Cueball: If you're yelled at, boycotted, have your show canceled, or get banned from an Internet community, your free speech rights aren't being violated. Cueball: It's just that the people listening think you're an asshole, [A picture of a partially open door is displayed.] Cueball: And they're showing you the door.

Both on the Internet and in the physical world, people with unpopular or poorly thought out opinions may complain that their freedom of speech is being restricted because others express their distaste for those opinions. As a defense, these individuals may invoke the First Amendment to the United States Constitution , which provides, among other things, freedom of speech for any entity or person under legal jurisdiction of the U.S. More specifically, it states that "Congress shall make no law [...] abridging the freedom of speech, or of the press". Originally intended as a restriction on the powers of U.S. federal government, which the Constitution defines, structures, and delimits, over time the First Amendment, as well as several others, were "incorporated" via the Fourteenth Amendment to apply to state and local governments as well. This protection of free speech, however, does not extend to illegal activities (for example, the concept of a "clear and present danger"), and it does not compel others to listen to or acknowledge the speech. The intended targets of the speech may simply choose to stop listening, or to speak louder in protest. An example of this is the incident involving the TV program Duck Dynasty in December 2013, in which television network A+E Networks suspended the host after he made homophobic remarks , causing some to comment that his rights had been infringed upon. Similarly in April 2014 controversy erupted when Brendan Eich was forced to resign as CEO of Mozilla because it was revealed he had donated money to anti-gay marriage efforts in California. In actuality, the First Amendment was never meant to provide immunity from any and all consequences. Cueball , representing Randall , is addressing those who use the freedom of speech argument as a defense against societal censorship. He states that one’s legal right to take a stance on an issue does not require others to listen to said stance. In addition, he also states that this right does not require a commercial or social entity—such as a TV network, a website, or its community—to support a person in spreading their message, even if it had supported you in the past. If someone says something which others find unjustified or offensive, they should be ready to accept the consequences of others' responses. The title text points out that regardless of how free speech works, anyone appealing to it as a defense for their argument or opinion is not being persuasive in any case. If the only thing that someone can say in support of an argument is effectively that it is not illegal , then they are severely undermining it by essentially admitting that they don't have any better defense for it. It should be noted that the first panel of this comic conflates, under certain schools of thought about justice and rights, a right such as free speech and the legal protections of such. Many viewpoints consider rights to be granted by the government; others consider rights to be innate regardless of what the government does. The former is frequently reflected throughout governments in Europe while the latter is more common throughout the Americas. According to the former, the first panel is technically correct by definition, because the right of free speech is granted by the government's laws and, as such, can only affect the government's influence: thus, the 1st Amendment grants the right to free speech, which by definition cannot be restricted by congress. According to the latter, the first panel is strictly nonfactual because the 1st Amendment only recognizes that the right of free speech exists and, rather than delimiting the right, it instead proscribes the government's actions. However, between these two school of thought, the remaining panels aren't affected by whether or not the first panel is factual by definition. Cueball: Public Service Announcement: The Right to Free Speech means the government can't arrest you for what you say. Cueball: It doesn't mean that anyone else has to listen to your bullshit, or host you while you share it. Cueball: The 1st Amendment doesn't shield you from criticism or consequences. Cueball: If you're yelled at, boycotted, have your show canceled, or get banned from an Internet community, your free speech rights aren't being violated. Cueball: It's just that the people listening think you're an asshole, [A picture of a partially open door is displayed.] Cueball: And they're showing you the door.

NRO

NRO

https://www.xkcd.com/1358

https://www.explainxkcd.com/wiki/index.php/1358:_NRO

Cueball and a friend are in a remote area. The friend is holding a Where's Waldo? book towards the sky. Laptop: [ Target located ] Cueball: Got him. Left edge, two inches down. The National Reconnaissance Office has an unusual approach to Where's Waldo .

Where's Waldo? (the North American renaming of the British Where's Wally? ) is a children's puzzle book in which you have to locate 'Waldo', a character with a distinctive striped shirt and hat, in a picture crowded with hundreds of characters. This is harder than it sounds, since the characters are both very small and quite densely packed on the page, and the pages (especially in later books) are often littered with "decoy" characters wearing similar articles of clothing to Waldo's. In some cases, almost all characters as well as several objects have the red-and-white stripes. Cueball and his friend are using satellite imaging to find Waldo, by holding the book up to the sky and viewing it on the computer, presumably using some advanced image processing software to identify Waldo among the crowd. This would require a very advanced camera, as resolutions are usually much lower than would be necessary to resolve the characters in a Where's Waldo book. But since Cueball works at the National Reconnaissance Office (NRO), the US government agency responsible for operating spy satellites, he probably has access to some powerful satellite-mounted cameras. The humor in this being, while he could be using that power for much more important things, he's instead trying to solve a simple game. Further, the Cueballs could probably hook up the image parsing software to a smaller camera on the ground, rather than a satellite-mounted camera. They would get even better results without using a camera by scanning the image and running it through the same image processing software. The title text is implying that the Cueball operating the computer has accidentally launched a drone at the co-ordinates, which would be where he and his friend are standing. The drone is presumably a military drone armed with explosive weaponry — not a good thing for those on the receiving end. Cueball and a friend are in a remote area. The friend is holding a Where's Waldo? book towards the sky. Laptop: [ Target located ] Cueball: Got him. Left edge, two inches down. The National Reconnaissance Office has an unusual approach to Where's Waldo .

Phone Alarm

Phone Alarm

https://www.xkcd.com/1359

https://www.explainxkcd.com/wiki/index.php/1359:_Phone_Alarm

[A flowchart:] [Alarm goes off] → [Beep beep beep beep!] ↺ One line with an arrow goes back to: [Beep beep beep beep!] → Another line goes to: ["???"] → Then: [Answer phone in dream] → [Talk] → [Hang up] → Finally a line goes back to: [Beep beep beep beep!] My problem with phone alarms

The flowchart shows a problem Randall has with using alarms built into phones. Notably, that the sound is similar to a normal ring tone (probably related to 479: Tones ), making it sound like someone is calling him, and not waking him up. This results in him having a false awakening , where he dreams about answering the phone, talking, and eventually hanging up. Of course this doesn't stop the actual phone from ringing, and he ends up answering the phone again. The looping arrow around the "beep beep" box implies that the phone keeps ringing only until he attempts to answer it, which would be quite a coincidence. This is an example of an endless loop , where there is no given way for the flowchart to end, just as in 1195: Flowchart . Now, smartphones typically support customization of tones for different apps so that your alarm doesn't have to sound like your ringtone and many apps load their own distinctive tone now by default. The title text, consisting of Randall shouting at the phone in his dream, enforces the fact that he can't tell between his ringtone and his alarm. In doing so he believes that a prank caller is harassing him which infuriates him. Alternatively, "the worst person in the world" could just refer to the confused logic in dreams, where a caller could, inexplicably yet unquestionably, be the worst person in the world. A list of all the flowchart comics can be found here . [A flowchart:] [Alarm goes off] → [Beep beep beep beep!] ↺ One line with an arrow goes back to: [Beep beep beep beep!] → Another line goes to: ["???"] → Then: [Answer phone in dream] → [Talk] → [Hang up] → Finally a line goes back to: [Beep beep beep beep!] My problem with phone alarms

Old Files

Old Files

https://www.xkcd.com/1360

https://www.explainxkcd.com/wiki/index.php/1360:_Old_Files

[Cross-sectional view of what look vaguely like stratigraphic layers underground. A crevice leads down through these concentric layers to a cave-like cavity in the middle, where Cueball is going through the deepest, most central, and incidentally smallest of the files. Above, Megan stands at "ground level", looking down into the crevice.] Megan: You OK down there? Documents (47 GB) misc.txt Video projects Old desktop (12 GB) Facebook pics Pics from other camera Temp Misc PDFs MP3 Recovered from drive crash (4 GB) Temp Work misc Audio books My Documents (570 MB) Downloads Kazaa shared AYB EV Override Angband GIFs FIGHT CLUB.wmv Elasto Mania AIM Direct Connect files 4chan ICQ logs High school Zip disk (94 MB) Korn MIDI Photos3 (Prom) lovenote.txt Gorilla.bas Dream.txt James.txt AOL (Citadel) QBasic NYET Jokes.txt AAAFILES (9.4 MB) TXT (850 K) Cueball (deep inside the AAAFILES section looking at his txt files): Oh my god. I wrote poetry .

This comic came out the day after Sky News published the story of original Andy Warhol artwork, created in 1985 on an Amiga 1000 , which was recovered from recently found floppy disks. Cueball is shown literally digging through a pile of old files; which is a metaphor for looking through old files on his computer. The layers of the pile are arranged much like geological rock formations where older strata are deeper down than younger layers. The files are in concentric layers because each directory is embedded in the previous directory. Therefore, the "Documents" folder contains an "Old Desktop" folder, which contains a folder with files recovered from an older system, which itself contains a "My Documents" folder, which contains a folder with files copied from a Zip Disk from high school. The result is that files from high school have survived in his present-day machine. These older folders serve as a time capsule of sorts, storing old files from AOL , NYET, and Kazaa . These files are meant to be analogous to the fossils and artifacts found in lower, older rock layers. The sizes of the files decrease as Cueball goes deeper, since data storage has gotten cheaper over time. When the Zip Drive first came out, it cost $200 USD (plus $20 per 100 MB floppy). As of 2019, $200 could buy you at least an 8 TB portable external hard drive. In the 1990s, during AOL's heyday, 10+ GB hard drives were prohibitively expensive and a terabyte of data was unimaginable to most users. Deep down, Cueball discovers several files he is surprised about, including a poetry file which embarrasses him as he does not remember writing poetry. In the title text, he mentions also finding an " Animorphs Novel", which may be a text copy of one of the original books or a fan fiction of the Animorphs series (his reaction of quickly eradicating it may either be to prevent him being caught with a presumably-illegal copy of an Animorphs book or as a result of embarrassment at his fan fiction - the former is less likely than the latter considering some of the other files mentioned, so it is most likely a fan fiction). The series was released between 1996 and 2001, consistent with the fact that these files were created during Cueball/ Randall's high school years. The series was extremely popular at the time. Animorphs has already been mentioned in the title text of 1187: Aspect Ratio , and later it was the main joke in 1380: Manual for Civilization and 1817: Incognito Mode . The folders and files in detail: Documents (47 GB): A large folder containing many of Cueball 's personal files. Old desktop (12 GB): A backup from a former computer. Recovered from drive crash (4 GB): When a hard drive crashes, some or all data may be recovered. My Documents (570 MB): Windows XP user accounts came with a "My Documents" folder that was widely used for storing personal files. The items in this archive came from the era when Windows XP was popular. High school Zip disk (94 MB): The most popular form of superfloppy , introduced in 1994 with a capacity of 100 MB. AAAFILES (9.4 MB): Some of Cueball 's oldest documents, likely prefixed with "AAA" to put the folder at the top of an alphabetically-sorted list. TXT (850 K): Old text files, which include poetry he didn't remember writing. [Cross-sectional view of what look vaguely like stratigraphic layers underground. A crevice leads down through these concentric layers to a cave-like cavity in the middle, where Cueball is going through the deepest, most central, and incidentally smallest of the files. Above, Megan stands at "ground level", looking down into the crevice.] Megan: You OK down there? Documents (47 GB) misc.txt Video projects Old desktop (12 GB) Facebook pics Pics from other camera Temp Misc PDFs MP3 Recovered from drive crash (4 GB) Temp Work misc Audio books My Documents (570 MB) Downloads Kazaa shared AYB EV Override Angband GIFs FIGHT CLUB.wmv Elasto Mania AIM Direct Connect files 4chan ICQ logs High school Zip disk (94 MB) Korn MIDI Photos3 (Prom) lovenote.txt Gorilla.bas Dream.txt James.txt AOL (Citadel) QBasic NYET Jokes.txt AAAFILES (9.4 MB) TXT (850 K) Cueball (deep inside the AAAFILES section looking at his txt files): Oh my god. I wrote poetry .

Google Announcement

Google Announcement

https://www.xkcd.com/1361

https://www.explainxkcd.com/wiki/index.php/1361:_Google_Announcement

[Cueball is standing at a lectern marked Google.] Cueball: The rumors are true. Google will be shutting down Plus— Cueball: Along with Hangouts, Photos, Voice, Docs, Drive, Maps, Gmail, Chrome, Android, and Search— Cueball: To focus on our core project: Cueball: The 8.8.8.8 DNS Server.

At the time of this comic's release, Vic Gundotra had recently left Google . Because he was the head of Google+ , this had caused many people, including TechCrunch , to theorize that Google+ was going to be shut down, despite the continuing comments from Google that it would remain active and updated. It lasted five more years, finally being closed on April 2nd, 2019. Google has a history of closing popular services . The comic extrapolates this to an announcement that Google would be closing all its popular services, up to and including its e-mail service, Gmail, and even the core business of the company, its Internet search engine, to wholly concentrate on a relatively obscure part of its product lineup. According to Google, its Public DNS servers (Domain Name System servers), better known by their IPv4 addresses 8.8.8.8 and 8.8.4.4 , are supposed to be a faster alternative to using one's ISP's DNS servers (because of caching effects due to a large user base), as well as less susceptible to censorship. When Turkey started blocking access to Twitter and YouTube in March 2014, Turkish ISPs first did this on the DNS level by manipulating the results from their own name servers. The most popular workaround was using Google's DNS server instead, so much so that its address was written as graffiti on the side of a building . The joke may also be related to the fact that 8.8.8.8 is an IP address heavily used by network administrators to perform connectivity tests ( ping ) because it is easy to remember and fast to type. Google would want to concentrate on this feature to build a business model using that fact. The reason behind this decision may be that Google considers a DNS server, a fairly low-level component of the Internet's service stack, to be the optimal place to collect information on its users, an accusation leveled at Google ever since it introduced the service. The title text refers to the impression held by some that Google will shut down services that prove less popular than desired at short notice, even though they may in fact have a significant user base. A recent example of that is the closure of the RSS aggregation service, Google Reader, in July 2013. While the same DNS service is provided under both addresses, the more memorable 8.8.8.8 is likely to receive far more requests than 8.8.4.4. [Cueball is standing at a lectern marked Google.] Cueball: The rumors are true. Google will be shutting down Plus— Cueball: Along with Hangouts, Photos, Voice, Docs, Drive, Maps, Gmail, Chrome, Android, and Search— Cueball: To focus on our core project: Cueball: The 8.8.8.8 DNS Server.

Morse Code

Morse Code

https://www.xkcd.com/1362

https://www.explainxkcd.com/wiki/index.php/1362:_Morse_Code

[Cueball and Megan are lying in a grassy, lonely plain.] Cueball: When the French navy retired morse code in 1997, they broadcast a final message: "Calling all. This is our last cry before our eternal silence." Cueball: I wonder if I can find my Livejournal login. Megan: Hey, I like Livejournal. Cueball: It's a nice place to go for some peace and quiet, I suppose. Randall is no stranger to LiveJournal. xkcd started on LiveJournal [1] before xkcd.com was created and is no longer live today. The blog was updated parallel to the website up to 2006 whereupon the introduction of a new RSS feed and automated update tools for the website allowed Randall to shut it down. The Morse code for the final message "this is our final cry on 500 khz before eternal silence" is: A period is a very short tone while the hyphen represents a slightly longer one. Between each character there is a small pause. This message was typically sent within less than half a minute.

Cueball recounts the last message sent in morse code by the French maritime radio station Le Conquet radio upon retiring its 500 kHz channel. The poetic, and potentially angsty-sounding nature of the message reminds him of the on-line journal website LiveJournal , which was popular until the late 2000s (it was launched in 1999), and stereotypically used by angst-ridden teenagers to post song lyrics, poems, or cryptic messages to express their emotions and possibly fish for attention. Since Cueball never uses his LiveJournal account any more, he wonders if he can find the password again. He might be considering posting the final Morse Code message as his own last and final message on his LiveJournal. The popularity of the site died down considerably with the arrival of social networking sites like MySpace , Facebook , Google Plus and the advent of microblogging platforms like Twitter and Tumblr . LiveJournal has also lost a lot of users since a Russian company bought them out; Russian dissidents used LiveJournal to present their opinions, and the Russian government used to retaliate by creating "denial of service" attacks which make LiveJournal unusable for all its users, sometimes for days. Nowadays (May 2014) LiveJournal is still quite popular among Russian-speaking people, including dissenters, but its administration was forced to show HTTP 451 error in some cases (e. g., when a user with a Russian IP is trying to read Alexei Navalny blog) with new laws. Thus when Megan is upset with his desire to let LiveJournal die out like the Morse Code, Cueball describes it as "a nice place to go for some peace and quiet". The title text is Megan's (or Randall's ) sarcastic remark indicating that Facebook is no less filled with angst-ridden thoughts than LiveJournal was, nor is it free from problems or controversies around other issues such as security or privacy. [Cueball and Megan are lying in a grassy, lonely plain.] Cueball: When the French navy retired morse code in 1997, they broadcast a final message: "Calling all. This is our last cry before our eternal silence." Cueball: I wonder if I can find my Livejournal login. Megan: Hey, I like Livejournal. Cueball: It's a nice place to go for some peace and quiet, I suppose. Randall is no stranger to LiveJournal. xkcd started on LiveJournal [1] before xkcd.com was created and is no longer live today. The blog was updated parallel to the website up to 2006 whereupon the introduction of a new RSS feed and automated update tools for the website allowed Randall to shut it down. The Morse code for the final message "this is our final cry on 500 khz before eternal silence" is: A period is a very short tone while the hyphen represents a slightly longer one. Between each character there is a small pause. This message was typically sent within less than half a minute.

xkcd Phone

xkcd Phone

https://www.xkcd.com/1363

https://www.explainxkcd.com/wiki/index.php/1363:_xkcd_Phone

[An image of a smartphone standing up with a small dot on the side and a single button at the bottom. Many labels are pointing to different parts of it. Clockwise from the top left they read:] Runs custom blend of Android and iOS Simulates alternative speed of light (default: 100 miles per hour) and adjusts clock as phone accelerates Wireless Accelerometer detects when phone is in free fall and makes it scream When exposed to light, phone says "Hi!" FlightAware partnership: Makes airplane noise when flights pass overhead Realistic case Clear screen Side-facing camera Introducing The xkcd Phone Your mobile world just went digital®

This comic is a parody of a multitude of mobile-technology related issues that, when brought together, create a general satire of smartphone advertising. It was the first entry in the ongoing xkcd Phone series with the next 1465: xkcd Phone 2 released about nine months later. The advertised features here either make previously useful capabilities useless or add features nobody wants. Except for "your mobile world (going) digital", which is old news. The first generation of cell phones (introduced in the early 1980s) used analog radio signals to send voice traffic - and this was the standard used by the first ever smartphone, the IBM Simon. But the second generation (2G) standards, introduced from 1991 onwards, were digital, and analog services had been phased out by 2010 in most countries, long before this comic was published in 2014. To market something as "going digital" implies that the corporation has found a way to integrate computers and/or the internet into a market that previously existed without them; the market for mobile phones has always involved computers, [ citation needed ] making the xkcd phone's marketing feel dated and clueless. From the top, going clockwise: The ominous warnings and disclaimers in the title text are probably a reference to the Saturday Night Live parody ad for Happy Fun Ball ( watch on YouTube ). [An image of a smartphone standing up with a small dot on the side and a single button at the bottom. Many labels are pointing to different parts of it. Clockwise from the top left they read:] Runs custom blend of Android and iOS Simulates alternative speed of light (default: 100 miles per hour) and adjusts clock as phone accelerates Wireless Accelerometer detects when phone is in free fall and makes it scream When exposed to light, phone says "Hi!" FlightAware partnership: Makes airplane noise when flights pass overhead Realistic case Clear screen Side-facing camera Introducing The xkcd Phone Your mobile world just went digital®

Like I'm Five

Like I'm Five

https://www.xkcd.com/1364

https://www.explainxkcd.com/wiki/index.php/1364:_Like_I%27m_Five

Cueball: What've you been up to? Megan: Doing tons of math for my thesis. Cueball: Can you explain it like I'm five? Megan: "Oh my god, where are your parents?"

Megan tells Cueball that she is working on her math thesis . A thesis consists of original research and generally deals with material that is difficult for the uninitiated to understand. Cueball anticipates that it will be difficult to understand, and asks her to "explain it like I'm five". "Explain it like I'm five" is a way of asking for a simpler explanation of some difficult topic, in a way that a five-year-old child would be able to understand. Megan sarcastically (or perhaps not) treats Cueball as if he is an actual 5-year-old without his parents, expressing her concern that a 5-year-old is without any supervision. This is an example of idiomatic language being taken literally, something that Randall has explored in other comics as well, such as 1454: Done . In the title text, Megan feigns concern that she will have to abandon her work to take care of this supposed lost child and takes this role-playing further by refusing to respond to Cueball until he phrases his comments as a 5-year-old would. The common expression "Explain it like I'm five" is inspired by a line by Groucho Marx in his movie Duck Soup . " Why a four-year-old child could understand this report! Run out and find me a four-year-old child, I can't make head or tail of it. " [1] Cueball: What've you been up to? Megan: Doing tons of math for my thesis. Cueball: Can you explain it like I'm five? Megan: "Oh my god, where are your parents?"

Inflation

Inflation

https://www.xkcd.com/1365

https://www.explainxkcd.com/wiki/index.php/1365:_Inflation

[Megan sits at a computer, conversing with Ponytail.] Megan: Imprinted on the sky are the gravity waves that were sloshing across the universe when it was this big. Megan: So really, we're using the entire universe as a giant microscope pointed at itself when it was small. [Megan turns to face the computer.] Ponytail: That's neat. Megan: Yeah. But... Ponytail: But what? Megan: Well, look. Ponytail: Oh. Hmm. Megan: Yeah. Ponytail: What... Megan: I don't know. [Below is an image of the universe showing the cosmic microwave background, featuring a series of circles and the Spalding basketball logo, as though the universe had been imprinted with the image of a basketball.]

The comic is inspired by the now disproven BICEP2 discovery of gravitational waves from the early universe, hence providing evidence for the cosmic inflation hypothesis. Megan is excited about this and tells Ponytail all about it. She is impressed by the fact that these waves were created when the universe was extremely small and the expanding universe has "imprinted" the gravity waves. (See also 1642: Gravitational Waves ). She compares this to the nature of a microscope - which optically expands a small image, just like the universe has done to itself. Ponytail is impressed by it until Megan looks at the image captured by the Wilkinson Microwave Anisotropy Probe (WMAP) . The concept of an expanding universe is sometimes explained by the "balloon model", where the two-dimensional skin represents our three-dimensional universe and the inflation of the balloon represents expansion over time. But instead of showing a balloon, Randall uses a basketball, which cannot inflate as easily as a balloon. The elliptical Mollweide projection of this cosmic microwave background (CMB) image of the sky makes the map look a bit like a basketball. Randall further exaggerates this by superimposing the traditional curves that are visible on a basketball and the Spalding company logo over the original image available at the bottom here. The mentions of scale and basketballs in this comic might be a reference to the "If the Earth were the size of a basketball" comparison, similarly to 1074: Moon Landing and 1515: Basketball Earth . Megan and Ponytail are both disconcerted by this, and the title text references the 1996 basketball movie Space Jam by promising images of main characters Michael Jordan and Bugs Bunny if the polarization of the view is changed to E-mode , a type of polarization of the cosmic background radiation arising from the radiation scattering off non-uniform plasma. The image was updated between 7 AM and 8:30 AM EST on May 7. Originally the Spalding logo was shown from left-to-right; however, in the updated image, the Spalding logo is shown in reverse. The WMAP image has the correct orientation in both versions. This was likely due to a mistake on Randall's part, as the comic suggests the universe is contained inside a Spalding basketball. Seen from the inside, the Spalding logo would be shown in reverse, as seen in the updated image. The first image can be found here . Both the original and updated version don't exactly match the pattern on a typical basketball. Most basketballs are divided into eight identical (ignoring reflection) pieces in a pattern that allowed traditional leather basketballs to be made from a single template, while the image shows a pattern that would split a basketball into two types of pieces. [Megan sits at a computer, conversing with Ponytail.] Megan: Imprinted on the sky are the gravity waves that were sloshing across the universe when it was this big. Megan: So really, we're using the entire universe as a giant microscope pointed at itself when it was small. [Megan turns to face the computer.] Ponytail: That's neat. Megan: Yeah. But... Ponytail: But what? Megan: Well, look. Ponytail: Oh. Hmm. Megan: Yeah. Ponytail: What... Megan: I don't know. [Below is an image of the universe showing the cosmic microwave background, featuring a series of circles and the Spalding basketball logo, as though the universe had been imprinted with the image of a basketball.]

Train

Train

https://www.xkcd.com/1366

https://www.explainxkcd.com/wiki/index.php/1366:_Train

Train: [On the upper edge of a circle representing the Earth, Cueball is in a train car looking to his left.] Cueball:...almost... [The train tracks run between another person standing at the 2:00 position, and Hairy standing at the 9:30 position. There's yet another person standing at the 6:00 position, between some snow-capped mountains and some low hills.] [There's a counterclockwise arrow in the middle of the circle, and motion lines indicate that everyone and everything on the planet is moving counterclockwise, except for the train, which is motionless.] A machine that grabs the Earth by metal rails and rotates it until the part you want is near you

This comic, which appeared the day before National Train Day , plays on the fact that a choice of a reference frame is arbitrary, leading to the "Principle of relativity" in Albert Einstein 's theories of special relativity and general relativity . But at speeds much lower than the speed of light it also applies to the newtonian mechanics . Rather than viewing this situation as a train causing itself to move relative to an immobile Earth, Randall provides the unconventional perspective of a train remaining fixed in space while causing the Earth itself and all the stars in the sky to rotate instead. In principle either perspective is equally valid — though in practice different trains often move in mutually-exclusive directions, thus each train would have to define its own frame of reference. It is said that Einstein once asked a ticket collector, "What time does Oxford stop at this train?" Changing the reference frame into the inside of the train only means that you see the outside world in a different reference, since the train doesn't really move the Earth (the train's engine and the friction of the wheels aren't even remotely powerful enough) it simply appears that way from the inside. From the Newtonian perspective this choice of frame is valid, but results in unnecessarily complicated math; the equation of motion would include terms for centrifugal, Coriolis and other so-called "fictional forces" (see 123: Centrifugal Force ). Newton supposes the existence of "inertial frames", in which these forces are zero, and the surface of the Earth approximates an inertial frame well. In General Relativity, the presence of mass in a system curves the spacetime around of it. The train-earth system could be modelled in general relativity, taking the train as fixed. However the resulting equations would be complex, and not amenable to an exact solution. The title text expands on this to include elevators, which change a person's position relative to the center of the Earth. From a passenger's perspective, it would appear as though the Earth's position was instead being changed in space. These examples use the train and the elevator as fixed points to define relative travel. The more common method to define movement is to use the Earth's surface as fixed point, but other reference points could be the Earth's center , the Sun , predefined "fixed" stars or the center of our galaxy . Each of these would result in a completely different movement speed: The train, as seen from an inertial frame, doesn't seem to rotate the earth, but it does in fact have a minute, immeasurable effect on the Earth's rotation (see what-if? 41: Go West and 162: Angular Momentum ). Train: [On the upper edge of a circle representing the Earth, Cueball is in a train car looking to his left.] Cueball:...almost... [The train tracks run between another person standing at the 2:00 position, and Hairy standing at the 9:30 position. There's yet another person standing at the 6:00 position, between some snow-capped mountains and some low hills.] [There's a counterclockwise arrow in the middle of the circle, and motion lines indicate that everyone and everything on the planet is moving counterclockwise, except for the train, which is motionless.] A machine that grabs the Earth by metal rails and rotates it until the part you want is near you

Installing

Installing

https://www.xkcd.com/1367

https://www.explainxkcd.com/wiki/index.php/1367:_Installing

[Cueball and Megan are standing next to each other.] Cueball: Installing things has gotten so fast and painless. Cueball: Why not skip it entirely, and make a phone that has every app "installed" already and just downloads and runs them on the fly? [Caption below the panel:] I felt pretty clever until I realized I'd invented webpages.

This comic refers to the kind of "inventions" which seem new from the point of view of a smartphone (handheld computer ) user, but have already been around for a long time on desktop or laptop /notebook computers. Cueball has a clever idea to skip the installing of applications on mobile phones: he would host the applications online instead, and provide links to the servers. The apps wouldn't stay on the phone all the time; instead the phone would download each app again every time the user wanted to run it. However, web pages and web applications already work like this. Clicking a link will make the browser download a web page and render HTML code and JavaScript that it links to. The page usually isn't saved long-term on the user's computer; instead the browser downloads it again when needed. HTML5 does however offer the option of caching web application files locally so it can remain operational when there is no network connection. In the title text, Cueball's idea for local application storage already exists in the HTTP protocol as cookies . The more flexible web storage was originally part of the HTML5 specification, but it's now in a separate specification. Native phone applications and web applications are not completely interchangeable. Web applications may not allow access to more advanced or platform-specific resources. Projects like Apache Cordova make these resources available to web applications by creating a native application wrapper for the web application. [Cueball and Megan are standing next to each other.] Cueball: Installing things has gotten so fast and painless. Cueball: Why not skip it entirely, and make a phone that has every app "installed" already and just downloads and runs them on the fly? [Caption below the panel:] I felt pretty clever until I realized I'd invented webpages.

One Of The

One Of The

https://www.xkcd.com/1368

https://www.explainxkcd.com/wiki/index.php/1368:_One_Of_The

[Cueball is a news anchor sitting in front of a screen showing the Gateway Arch with some landscape features around it.] Cueball: ...And he went on to design the Gateway Arch, one of the most recognizable arches in St. Louis. [Caption below the panel:] Pet peeve: Reporters unnecessarily hedging with "one of the"

Another of Randall's many Pet Peeves , this times on reporters. Cueball is a news anchor describing the Gateway Arch as one of the most recognizable arches in St. Louis . In this case the designer the reporter is likely referring to is Eero Saarinen . When describing things, reporters try to make only factual statements. If reporters use absolutes (that something is the largest or the smallest thing of its class, or that it is unprecedented, to give several examples) they risk making errors: it is possible that some other example of the thing exists that is even larger or even smaller or that there was some similar incident in the past, and they were not aware of it. If a reader or viewer points out the existence of that thing, even if obscure or trivial, the reporter must issue a correction. As a result, reporters learn to hedge by using formulations such as "one of the biggest" or "a rare example of." Randall states that it is his pet peeve when reporters avoid absolutes unnecessarily — that is, in cases where there's vanishingly little risk of error. As an absurd example, Randall depicts one such reporter using this language about the Gateway Arch. As the most well-known monument in Missouri and the largest free-standing arch in the world, it's indisputable that this would be the most recognizable arch in St. Louis. In the title text, Randall jokes about what could happen if you misunderstand the practice of avoiding absolutes; he thus appears to think it is an ostentatious display of faux objectivity, as opposed to a correction-avoiding strategy. The title text refers to novelty mugs (and T-shirts, and other printed items) that use superlative descriptions such as "World's Greatest Mom" or "World's Greatest Dad." Obviously, such a statement is an expression of personal affection on the part of the family member who gave such a gift and is not meant to be understood as a literally true fact about the world. Using a parody of reporter-speak (like giving a mug to your mother that says "one of the world's greatest moms") would ruin the compliment by suggesting to her that you thought some other people's moms were as good or better. The title text also refers to Mother's Day , which in the US was three days before this comic was published. [Cueball is a news anchor sitting in front of a screen showing the Gateway Arch with some landscape features around it.] Cueball: ...And he went on to design the Gateway Arch, one of the most recognizable arches in St. Louis. [Caption below the panel:] Pet peeve: Reporters unnecessarily hedging with "one of the"

TMI

TMI

https://www.xkcd.com/1369

https://www.explainxkcd.com/wiki/index.php/1369:_TMI

[Cueball is sitting at a desk, looking at a laptop.] Cueball: Ugh, TMI. Offscreen: Oh? What? Cueball: Just... Everything. Offscreen: True.

"TMI" is an acronym that means "too much information". It is typically used as a response to someone "oversharing" — telling personal details ("Sorry I just missed your call - I was urinating when the phone rang") that the listener would rather not have heard. Here, however, Cueball may be using it in a more literal and absolute sense: he feels overwhelmed by the colossal amount of information that is now generally available to anyone with an Internet connection. The title text amplifies this interpretation by evoking the image of an individual person who is overcome as he stands at the edge of the ocean, contemplating its vastness. [Cueball is sitting at a desk, looking at a laptop.] Cueball: Ugh, TMI. Offscreen: Oh? What? Cueball: Just... Everything. Offscreen: True.

President

President

https://www.xkcd.com/1370

https://www.explainxkcd.com/wiki/index.php/1370:_President

[Ponytail and Science Girl are walking together.] Ponytail: I can't imagine anyone who grew up on the Internet being able to run for President. [Closeup of Science Girl.] Science Girl: Why? Because it'd mark the handover of a world that no longer needs you to a generation you don't understand? [Ponytail and Science Girl have stopped walking and are facing each other.] Science Girl: ...Or because there would be embarrassing pictures of us as teenagers? [Closeup of Ponytail.] Ponytail: Um. The pictures one? Science Girl (off-screen): Pictures of teens! How will we even survive??

This strip shows a discussion between an adult and a teenager about an aspect of the future. Randall likes this setup, allowing to put in perspective the various "decay" predictions and shows his optimism. Here, the subject is scandal. How will a generation that is documenting and leaving behind a permanent public record of its juvenile misadventures - immature and impolitic writings, photographs of inebriation at parties posted on Facebook, Twitter posts about breakups, etc. - produce successful future politicians? Won't future opposition researchers and reporters have enough embarrassing material to destroy any Millennial's public reputation? In previous generations, juveniles were freer to go through this phase of development without leaving behind a digital record, making it easier to sidestep or paper over rumors of youthful misbehavior. See, e.g., George W. Bush, who dismissed questions about his rumored use of drugs in his youth by saying only, "When I was young and irresponsible, I was young and irresponsible." The child's answer, in addition to teasing the adult about her generation's coming obsolescence, is that the next generation will be fine because in the future no one will care. The title text amplifies this optimistic message, suggesting that old blog posts by former teenagers will just seem boring, not salacious. Randall offers no explanation for this upbeat spin, but it is a recurring topic and some have argued elsewhere that the potential power of Internet-chronicled youthful indiscretions will be defused because everyone will be in the same boat, making future voters (and, in another context, employers) more tolerant of such things. The strip also contains an existential twist, as shown in the child's answer. It alludes to every generation's dismissal of the next, as actually being due to psychological insecurities. We may disguise our dismissals by attacking their faults & different lifestyles. But in truth, these dismissals are actually rooted in our innate fear of becoming obsolete, useless, surpassed, and lost in a bewildering world that has passed us by. [Ponytail and Science Girl are walking together.] Ponytail: I can't imagine anyone who grew up on the Internet being able to run for President. [Closeup of Science Girl.] Science Girl: Why? Because it'd mark the handover of a world that no longer needs you to a generation you don't understand? [Ponytail and Science Girl have stopped walking and are facing each other.] Science Girl: ...Or because there would be embarrassing pictures of us as teenagers? [Closeup of Ponytail.] Ponytail: Um. The pictures one? Science Girl (off-screen): Pictures of teens! How will we even survive??

Brightness

Brightness

https://www.xkcd.com/1371

https://www.explainxkcd.com/wiki/index.php/1371:_Brightness

[A black panel with white text and a white Megan who is standing staring at the ground.] Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet. [Caption below the panel:] Exoplanet astronomers at night

Exoplanets are planets outside of our solar system, and exoplanet astronomers are astronomers who attempt to discover and study such planets. Megan is using a common exoplanet discovery technique to discover a planet around a nearby star. When a planet passes between an observing astronomer and a star, the planet will block some tiny part of the light coming from that star, causing it to appear dimmer for some amount of time. The Kepler telescope used this technique to find evidence for exoplanets. But here Megan is standing on the surface of the Earth at night, looking at the ground, and therefore presumably looking in the direction of the sun. By observing that it is completely occluded at night, she correctly concludes that the Sun is orbited by at least one planet: the Earth. This is obviously an absurd usage of that method. Reasons include the fact that exoplanets are not big enough to block out all of their stars' light when seen from Earth [ citation needed ] , making what Megan says a massive understatement, and that the period of the brightness oscillations would correspond to the length of a day, not a year as it would for exoplanets. The title text alludes to using more complicated techniques to observe light reflected by small planets like the Earth, for example by detecting polarized light reflected from the planet's atmosphere. In some sense, observing the light that reflects off of the Earth during the day is in fact how we see everything around us. It also implies that astronomers, who because of their career choice are more likely to work at night, might be completely unaware of Earth's existence in the daytime and thus surprised to "discover" it from their nighttime work. [A black panel with white text and a white Megan who is standing staring at the ground.] Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet. [Caption below the panel:] Exoplanet astronomers at night

Smartwatches

Smartwatches

https://www.xkcd.com/1372

https://www.explainxkcd.com/wiki/index.php/1372:_Smartwatches

A USE FOR SMARTWATCHES: [Depicted are two smartwatches, both labelled as "Working" and showing generic colour displays, and one smartphone labelled as "Dead" with a blank screen.] [A hacksaw cutting through the smartphone, throughout the middle of the long edge of the case.] [The two smartwatches are shown with the wristband and case broken around the edge of the display because the displays with the associated electronics are removed. Arrows are shown coming from the smartwatch cases to the smartwatch displays, then from the displays to the smartphone case halves.] [The smartphone halves are installed with the smartwatch components and a hinge with screws beside is shown. Another view shows the hinge screwed into the back of the smartphone case.] [The smartphone with the working smartwatch components installed is shown, with the hinge three-quarters open and fully closed - resembling an early flip-phone.] World's first flip iPhone

Smartwatches are fairly recent innovations which function something like smartphones which are attached to one's wrist, although the screens are often shorter than those of typical smartphones, and they typically need to be attached via bluetooth to a smartphone. This comic shows someone " Case modding " some smartwatches and a broken smartphone; that is, taking the electronic innards of two smartwatches and putting them into the sawn-in-half case of a smartphone before attaching the two halves with a hinge, allowing it to open and close like flip phones, a type that was popular before the rise of smartphones. The Western Electric Model 2500 is the last standard desk-style domestic telephone set issued by the Bell System in North America. It contains the # key and the * key, so it can be said it has same application features as the first cellphones, but it's obviously much bigger, and of course not wireless. Smartphones usually have much more functionality. Case modding is the art of building machines (usually computers) into nicely shaped non-standard cases. The opinion about "niceness" of the result vary, as usual in art. The point is that changing the case doesn't change the functionality, so the niceness (or, usually, "coolness") is generally the only relevant feature (although, badly done modding can affect cooling). It appears that Randall has a rather low opinion of smartwatches, as he suggests that it would be better to take out their screens and mount them onto a dead iPhone than to use them the way smartwatches are normally used. However, Randall's suggestion to cut open the dead phone with a hacksaw is unsound for several reasons: 1. Any attempt to saw through glass will cause it to shatter. To cut glass, one needs to grind it, not saw it. 2. Even if the phone is dead, the battery may be charged (if dead means that the battery is dead, not that the phone does not work, in which case the procedure destroys a perfectly functional iPhone). Saw blades conduct electricity, so the person might get electrocuted. 3. Some batteries contain chemicals that are toxic or explosive. Even if the battery is discharged, sawing through it is very dangerous. To add which, the hinge depicted in the cartoon is an ordinary household hinge. It is overly large for using in electronics compared to hinges on old clamshell-style cell phones, and drilling holes in the watch cases to attach one would potentially damage the internal electronic circuits. It could also puncture the battery, causing it to catch fire. Either render the watch useless. 4. Also, it's possible the watches wouldn't fit that nicely into the iPhone. While no phones such as the one depicted existed at the time of the comic (2014), in November 2019, Motorola officially announced a new Android phone, to be released under the Razr name, which is extremely similar in form-factor to the fictitious phone shown in this comic, albeit with a single flexible OLED screen, rather than two separate screens. A USE FOR SMARTWATCHES: [Depicted are two smartwatches, both labelled as "Working" and showing generic colour displays, and one smartphone labelled as "Dead" with a blank screen.] [A hacksaw cutting through the smartphone, throughout the middle of the long edge of the case.] [The two smartwatches are shown with the wristband and case broken around the edge of the display because the displays with the associated electronics are removed. Arrows are shown coming from the smartwatch cases to the smartwatch displays, then from the displays to the smartphone case halves.] [The smartphone halves are installed with the smartwatch components and a hinge with screws beside is shown. Another view shows the hinge screwed into the back of the smartphone case.] [The smartphone with the working smartwatch components installed is shown, with the hinge three-quarters open and fully closed - resembling an early flip-phone.] World's first flip iPhone

Screenshot

Screenshot

https://www.xkcd.com/1373

https://www.explainxkcd.com/wiki/index.php/1373:_Screenshot

[Caption above the panel:] When someone posts a screenshot of their phone, [The panel shows the screen of an Android phone. At the top there is a black Android status bar with icons like WiFi, battery charge and the time, all in white:] 85% 10:02 PM [Below the status bar is the open program, which is an internet browser, which shows the address field with an unreadable address and the tap icon to the right and the three dots for options. Below that is the page viewed in the browser. It seems to be a post from a person. Below the address bar is a picture of a user with dark hair in a square frame. To the right are two lines of unreadable user information. The post contains a picture posted by the user, and it is a screenshot of a chat/SMS conversation from another phone. The screen is light blue and the conversations has three blue speech bubbles to the left and two replies in between those in green to the right. All posts are unreadable, as are all other words in the picture. At the bottom of the picture the top of another users post, i.e. half the users image, can be seen. At the top of the picture, the status bar from this iPhone screen shot can be seen with icons both left, center and right. To the right the charge icon battery shows a very low charge, indicated with a small red line at the bottom of the battery. Around this low charged battery icon there is drawn a large red circle like spiral, circling the battery symbol two or three times, and four exclamation marks are written above this. The only thing that can be read in the picture is the charge percentage:] !!!! 6% [Caption below the panel:] I can't pay attention to the content if their battery is low.

Randall is viewing a screenshot of a text-message exchange via his own phone's web browser. Such screenshots are frequently posted online, to show content ranging from humorous typos to creepy behavior . In this screenshot, in addition to the text messages' content, we see a battery bar reflecting a charge of 6%; this effectively " photobombs " (or distracts Randall from) the actual content of the original screenshot. On the other hand, the phone on which the shot is viewed is charged at a healthy 85%. The phone the screenshot is taken from is an iPhone, while the phone being viewed is an Android. Another iPhone screenshot was the joke in 1815: Flag . The title text suggests that Randall has plugged in his phone to quell the anxiety induced by the 6% charge in the screenshot, mistaking it for the actual battery indicator of his own phone. This measure is obviously unsuccessful, as charging his own phone does nothing to change the charge of the phone in the picture. A similar phenomenon is when a screenshot is viewed and the viewer attempts to use the controls (e.g. buttons) in the image. Randall's fear of losing power to his phone was later explored in 1802: Phone and 1872: Backup Batteries , where he brings extra batteries and it is also part of the joke in comic 1965: Background Apps . An alternative interpretation for the title text is that the screenshot was posted as part of a thread asking why their phone isn't charging. This would be ironic, as Randall's focusing on the battery level means his eyes are being drawn to the very problem being spoken about, yet he is too distracted by it to read that this is the problem! This may also be a reference to mirror neurons . Mirror neurons are according to many neurobiologists a biological basis of empathy. If you see someone stick a needle in their hand, it feels as if you hurt yourself and some people experience a tightness of the chest when hearing a wheezing asthma patient on the radio. Here, Randall's mirror neurons start to fire as he feels the anxiety associated with a phone losing battery power. Screenshot quality was discussed later in 1863: Screenshots . This comic is one of a small set of comics with the same or almost the same title as another comic (only plural form of word screenshot being difference). [Caption above the panel:] When someone posts a screenshot of their phone, [The panel shows the screen of an Android phone. At the top there is a black Android status bar with icons like WiFi, battery charge and the time, all in white:] 85% 10:02 PM [Below the status bar is the open program, which is an internet browser, which shows the address field with an unreadable address and the tap icon to the right and the three dots for options. Below that is the page viewed in the browser. It seems to be a post from a person. Below the address bar is a picture of a user with dark hair in a square frame. To the right are two lines of unreadable user information. The post contains a picture posted by the user, and it is a screenshot of a chat/SMS conversation from another phone. The screen is light blue and the conversations has three blue speech bubbles to the left and two replies in between those in green to the right. All posts are unreadable, as are all other words in the picture. At the bottom of the picture the top of another users post, i.e. half the users image, can be seen. At the top of the picture, the status bar from this iPhone screen shot can be seen with icons both left, center and right. To the right the charge icon battery shows a very low charge, indicated with a small red line at the bottom of the battery. Around this low charged battery icon there is drawn a large red circle like spiral, circling the battery symbol two or three times, and four exclamation marks are written above this. The only thing that can be read in the picture is the charge percentage:] !!!! 6% [Caption below the panel:] I can't pay attention to the content if their battery is low.

Urn

Urn

https://www.xkcd.com/1374

https://www.explainxkcd.com/wiki/index.php/1374:_Urn

[Cueball is standing in a classroom with Megan at a desk.] Cueball: Imagine that you're drawing at random from an urn containing fifteen balls - six red and nine black. Megan: OK. I reach in and... ...My grandfather's ashes?!? Oh God! Cueball: I... what? Megan: Why would you do this to me?!?

A common tool for explaining concepts in elementary probability theory are games involving the drawing of coloured balls from a container, such as a bag, or hat. In older statistics related texts, a convention developed of describing the container as an urn. This is so common that such problems are often called urn problems . While an urn can have many uses, in modern times the most common context in which it is used is to contain the burned remains of deceased individuals after a cremation . This is likely because as interior decor has grown more minimalist, other types of urn became less common and the association of the word urn with cremation has become ubiquitous in the vernacular. Megan , when asked to imagine drawing balls from an urn, imagines a cremation urn containing not only balls, but also human remains. She may be referring to a real grandfather who has been cremated, or is simply improvising a joke at Cueball's expense. The title text refers to two distinct scenarios in the coloured ball experiment: The balls may be replaced between each drawing, or not. In the former case, each draw is independent of the previous, in the latter the chances of picking a particular (remaining) ball the next time have increased. Megan (or rather Randall if it is he who speaks in the title text) would prefer to put the ashes back into the urn. She might also want to have her grandfather back, and be playing with the word "replacement". The distinction between repeated drawing with and without replacement is used in most presentations of elementary probability because it illustrates a subtle but important theoretical distinction: if the balls are replaced, one at a time, before drawing the next, the number of balls of a certain colour has the binomial distribution , but if the balls are not replaced, so that the same ball cannot be drawn twice, you instead get the hypergeometric distribution . There are myriad reasons why Megan would want to draw with replacement, the most simple of which being that she has nowhere to put ashes other than in their designated urn. Ashes by their nature need a container, or they will make a mess; cremated remains in particular come with the additional requirement that the container be respectful to the deceased. [Cueball is standing in a classroom with Megan at a desk.] Cueball: Imagine that you're drawing at random from an urn containing fifteen balls - six red and nine black. Megan: OK. I reach in and... ...My grandfather's ashes?!? Oh God! Cueball: I... what? Megan: Why would you do this to me?!?

Astronaut Vandalism

Astronaut Vandalism

https://www.xkcd.com/1375

https://www.explainxkcd.com/wiki/index.php/1375:_Astronaut_Vandalism

[A signpost with three arrows.] [Arrow pointing up:] Space 62 [Arrow pointing right:] Jackson 115 [Arrow pointing left:] Memphis 98

Signs like this normally show the distance to places on earth's surface. This sign also has an arrow pointing away from earth and towards "space", with a distance of 62 miles (100 km), due to "astronaut vandalism". The 62 mile distance is the Kármán line , one of the conventional demarcations of the beginning of " outer space ". We think of space as being very far away. This comic puts into perspective that it's really a lot closer to space than to many destinations we're used to getting to by car or airplane. We think of 62 miles as being an easy trip on the ground, but that same 62 miles is incredibly hard when going vertically, against the force of gravity. The title text references the fact that while the Fédération Aéronautique Internationale (FAI) defines the Kármán line , the boundary between Earth's atmosphere and outer space (i.e., the start of space), to be 100 kilometers (62 miles) above mean sea level, the U.S. Air Force and other military branches will award astronaut wings to rated astronauts who fly higher than 50 miles (80 km). In 2005 NASA changed from using the FAI definition to using the USAF definition for consistency across organizations, and thus some NASA test pilots who had flown the X-15 retroactively received astronaut wings for their greater-than-50 mi (80.5 kilometers) flights. (Air Force pilots of the X-15 in the 1960s had long since received astronaut wings for such flights.) Thus in the title text, Air Force pilots surreptitiously change the sign to conform to their definition of "space". Although most authorities use the FAI definition of space - the Kármán line - since the FAI is the international organization of record for aeronautics, there are good scientific reasons for the U.S. Air Force definition. The line is named for Theodore von Kármán , who originally calculated the height at which an vehicle would have to travel faster than orbital velocity to generate lift from wings, therefore making the vehicle an object in orbit rather one using air to generate lift. Von Kármán originally calculated this height as 51.9 miles (83.6 km) - closer to the USAF definition than to what is now called the Kármán line. Additionally, the boundary between the mesosphere and the thermosphere is traditionally taken to be 53 miles (85 km), also close to the Air Force definition. On the other hand, some newer research suggests the mesopause (the line between the mesosphere and thermosphere) may have peaks between 53 and 62 miles (85-100 km). Also the turbopause - the line where gas molecules cease mixing atmospherically and begin stratifying by molecular weight as if they are in orbit - is generally taken to be about 100 kilometers (62 miles). All of the atmospheric boundaries are variable, however, changing from day to day and season to season with no clear boundary. Additionally, objects cannot reliably orbit below 130-150 km (80-93 miles) due to drag from even the sparse atmosphere in the lower thermosphere. Despite this comic associating "space" with having a definite start the way you might definitely know when you cross the city limits of a town, the reality is that the transition from atmosphere to space takes place gradually over tens of kilometers. Interestingly, since it is too high for aircraft and high altitude balloons, but too low for spacecraft in orbit, this "near space" transition region is one of the least-visited and least-used regions of the larger atmosphere. This comic thus both points out that the limit where space starts is arbitrarily chosen and also that space is often much closer than, for instance, two nearby cities in some randomly chosen location in the US. The two distances shown on the signpost can occur only at certain points on Earth. One possible location is Grenada, MS, which is about 100 miles from Memphis, TN and about 114 miles from Jackson, MS. Alternatively "Jackson" could mean Jackson, TN, in which case Tupelo, MS or Kenneth, MO are both viable options for the location of the signpost. However, in Tupelo the roads to Jackson and Memphis meet at a right angle, instead of pointing in opposite directions as in the comic. [A signpost with three arrows.] [Arrow pointing up:] Space 62 [Arrow pointing right:] Jackson 115 [Arrow pointing left:] Memphis 98

Jump

Jump

https://www.xkcd.com/1376

https://www.explainxkcd.com/wiki/index.php/1376:_Jump

[In the first panel Cueball is seen as a stop motion cartoon (12 drawings of the same Cueball) as he is jumping down a small hill — jumping longer and longer between sentences. Jump is written over the head of Cueball that perform the jump until he floats.] Cueball: I love these dreams Jump Cueball: Each jump is a little longer Jump Cueball: Each push off the ground a little softer Jump Cueball: Until I G l i d e [In the second panel Cueball (five drawings) glides over a fence and the dunes before the beach — then he glides out over the sea. The fourth Cueball just passing over the sea looks back towards the shore. Four birds are flying behind him around the coast line.] [In the third panel Cueball (four drawings) glides across the open sea — three birds circling around the first Cueball, a fish is jumping out of the water splashing down again beneath the second Cueball.] sploosh Cueball: ...I hope this is a dream. ...I hope this is a dream. Or that I'm at least following the curve of the Earth around to land...

Cueball is presumably experiencing a common dream subject, flying or floating. As in many varieties of such a dream , the ability to fly, float or glide only gradually manifests, going from longer and longer jumps to a sort of flight or hovering. In Cueball's case, his jumps become longer and 'lighter' until at last he is gliding just above the surface of the Earth. He has apparently had such a dream before, with just such a flight mechanic manifesting itself, as he indicates that he 'loves' these dreams. In his presumed dream, Cueball finally achieves his gliding flight just as he reaches the shoreline, and his gliding carries him over the water's edge and out to sea. After a moment's reflection, he realizes that if he were really gliding out to sea without any real apparent means of control, his situation would presumably be rather perilous — death by starvation or thirst, gradually slowing down and becoming 'stuck' over the water with no way to land, the loss of his gliding ability as suddenly as it came, etc., all suggest themselves as possible perils he would now be subject to if, in fact, his 'dream' were actual reality. Thus he eventually indicates that he hopes it is a dream, in contrast to his feeling at the comic's opening. The title text adds a further worry not immediately apparent unless one considers the possibility that Cueball's 'gliding' will continue in a straight line in relation to the Earth's surface. In that case he would continue moving straight while the Earth's surface would curve away beneath him, sending him out into space instead of the relatively preferable scenario of merely floating across the ocean to the opposite shore. After all, if the laws of physics had changed to permit hovering/flying, consequences would be unpredictable — i.e. there'd be no assurance one would maintain a constant hovering height rather than take leave of the planet as one flies forth. One thing about miracles is that all bets are off! Also note that this situation is similar to the case of Newton's cannonball . However, that is actually in very-low-earth-orbit — and you would need to be going 7,300 m/s, or about 16,000 mph (26,000 km/h) to stay in orbit. At that speed, of course, air friction would quickly destroy the cannonball or person. This is clearly not the case in the dream. Getting weightless and drifting around was a fantasy in 226: Swingset . The comic 417: The Man Who Fell Sideways has some resemblance to this one. In 942: Juggling , Cueball throws some balls and later a book. They miss the ground . In the book Thing Explainer Cueball jumps to score with a basketball in the explanation for Playing Fields only to find that he keeps rising steadily along a straight curve up above the hoop. Very similar to this jump that just lets Cueball float straight afterwards. [In the first panel Cueball is seen as a stop motion cartoon (12 drawings of the same Cueball) as he is jumping down a small hill — jumping longer and longer between sentences. Jump is written over the head of Cueball that perform the jump until he floats.] Cueball: I love these dreams Jump Cueball: Each jump is a little longer Jump Cueball: Each push off the ground a little softer Jump Cueball: Until I G l i d e [In the second panel Cueball (five drawings) glides over a fence and the dunes before the beach — then he glides out over the sea. The fourth Cueball just passing over the sea looks back towards the shore. Four birds are flying behind him around the coast line.] [In the third panel Cueball (four drawings) glides across the open sea — three birds circling around the first Cueball, a fish is jumping out of the water splashing down again beneath the second Cueball.] sploosh Cueball: ...I hope this is a dream. ...I hope this is a dream. Or that I'm at least following the curve of the Earth around to land...

Fish

Fish

https://www.xkcd.com/1377

https://www.explainxkcd.com/wiki/index.php/1377:_Fish

[Cueball and Megan are walking down a hill.] Cueball: The Fermi paradox keeps getting worse. If planets are common, where is everybody? Megan: Imagine you're a scuba diver looking at the ocean floor. You know there's a fish there, but you can't see it. Why? Cueball: Maybe the fish looks like sand. Megan: Yeah... [Zoom out to the Earth from space.] Megan: ...and what would that tell you about the ecosystem? [Earth moves slightly out of the panel.] [Earth moves halfway out of the panel.] [Blank panel.] [A shark swims through space.]

The Fermi paradox is the contradiction that arises between high estimates of the likelihood of extraterrestial life and the fact that no evidence for it has thus far been found. Cueball and Megan are having a conversation regarding this — since new planets are found all the time around distant stars, Cueball comments that this makes it an even greater paradox. Megan suggests that perhaps our search for extraterrestrial life is like looking at a patch of ocean floor looking for a fish. The diver knows that there must be a fish somewhere, but is unable to actually find it. She then goes on to ask why the fish would be hidden — i.e. camouflaged, and what it means about the remaining fish. The suggestion is that the fish would be hidden to avoid being eaten by predators, and perhaps the reason no extraterrestrial life is sending any sign of existence back is that they fear they might be destroyed soon after they revealed their location. Maybe they have even actively tried to hide the presence of their entire planet if they obtain the technological means. This potentially refers to the Deadly Probes scenario where a space faring species has developed deadly probes that self replicate and spread through the void between the stars - homing in on radio signals and destroying young civilizations in the cradle... The camouflaged fish could be identified by using more sophisticated technologies like infrared cameras. Looking at the Earth from space beyond Low Earth orbit only with the naked eye wouldn't show any hint to our ecosystem . This is like the actual possibility in astronomy when observing exoplanets — the nature of those more than 1,500 known planets is unknown due to the lack of better technologies to the scientists. And there are a couple of hundred billion planets at our galaxy still camouflaged to human scientists. The final panels take the metaphor further, suggesting that there is literally a planet sized shark swimming through space eating planets, and since the view is panning away from earth and over to the shark, the shark seems to be heading our way. It looks like Earth is the next fish, presumably because we did not reach a high enough technology level in time to recognize the danger and hide. This also explains the title text that has the theme from the movie Jaws playing while astronomers look into their telescopes. This may also be a reference to the film Alien , which was pitched with the three word proposal " Jaws in Space." Stephen Hawking famously warns, "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans." Chinese sci-fi author Liu Cixin wrote an award-winning sci-fi trilogy called the Remembrance of Earth’s Past trilogy, which draws on a similar idea; the title of the second book, The Dark Forest , is a reference to the same Fermi paradox solution described in the comic. Even Carl Sagan called the practice of Broadcasting and Signaling presence of Life on Earth "deeply unwise and immature," and recommended that "the newest children in a strange and uncertain cosmos should listen quietly for a long time, patiently learning about the universe and comparing notes, before shouting into an unknown jungle that we do not understand." [Cueball and Megan are walking down a hill.] Cueball: The Fermi paradox keeps getting worse. If planets are common, where is everybody? Megan: Imagine you're a scuba diver looking at the ocean floor. You know there's a fish there, but you can't see it. Why? Cueball: Maybe the fish looks like sand. Megan: Yeah... [Zoom out to the Earth from space.] Megan: ...and what would that tell you about the ecosystem? [Earth moves slightly out of the panel.] [Earth moves halfway out of the panel.] [Blank panel.] [A shark swims through space.]

Turbine

Turbine

https://www.xkcd.com/1378

https://www.explainxkcd.com/wiki/index.php/1378:_Turbine

[Megan is talking to a wind turbine.] Megan: I'll hold up a big kite, and you blow air at me until I lift off! Megan: What do you think of that idea? Wind turbine: I'm not a huge fan.

A wind turbine uses wind to rotate its blades in order to generate electricity. It is visually very similar to an (electric) fan which however does the exact opposite: it uses electricity to rotate its blades in order to generate wind. The complementary nature of these two machines was previously highlighted in 1119: Undoing . The punchline of this comic is a pun on the other meaning of the word " fan " which qualifies someone as liking or supporting something (here, an idea). Megan suggests to have the turbine blow air at her so she could lift off with a kite, something which would be conceivable with a huge fan, but is impossible here precisely because the turbine is not a fan and therefore can't generate wind. So the ( anthropomorphically -speaking) turbine's response is twofold: 1) it's a turbine and not a huge fan, which makes the idea impossible, and 2) for this very reason it doesn't like the idea - i.e. it is not a fan of the idea. The title text alternatively suggests building a makeshift trebuchet . The idea is that when the kite's string gets tangled in the turbine's blades, the kite will be spun around and it will fling the attached rock (this setup is more similar to a traction trebuchet than to the more common counterweight trebuchet). [Megan is talking to a wind turbine.] Megan: I'll hold up a big kite, and you blow air at me until I lift off! Megan: What do you think of that idea? Wind turbine: I'm not a huge fan.

4.5 Degrees

4.5 Degrees

https://www.xkcd.com/1379

https://www.explainxkcd.com/wiki/index.php/1379:_4.5_Degrees

Without prompt, aggressive limits on CO 2 emissions, the Earth will likely warm by an average of 4°-5°C by the century's end. HOW BIG A CHANGE IS THAT? [A ruler chart is drawn inside a frame.] In the coldest part of the last ice age, Earth's average temperature was 4.5°C below the 20th century norm. Let's call a 4.5°C difference one "Ice Age Unit." [A ruler with five main divisions — each again with 3 smaller quarter division markers. Above it the five main divisions are marked as follows with 0 in the middle:] -2 IAU -1 IAU 0 +1 IAU +2 IAU [Next to the 0 marking a black arrow points toward 0.25 on the scale and above it is written:] Where we are today [The rest of the text is below the ruler.] [To the far left below -2 IAU a curved arrow points to the left. Below it is written:] Snowball earth (-4 IAU) [Below -1 IAU a black arrow point toward this division. Below the arrow is written:] 20,000 years ago [Below this an image of a glacier. At the top of the image is written:] My neighborhood: [At the bottom of the image is an arrow pointing to the glacier:] Half a mile of ice [Below 0 IAU a black arrow point toward this division. Below the arrow is written:] Average during modern times [Below this an image of Cueball standing on a green field with a city skyline in the background. At the top of the image is written:] My neighborhood: Cueball: Hi! [Below +1 IAU a black arrow point toward this division. Below the arrow is written:] Where we'll be in 86 years [Below this a white image. At the top of the image is written:] My neighborhood: [Below this is a very large:] ? [Below +2 IAU a black arrow point toward this division. Below the arrow is written:] Cretaceous hothouse +200m sea level rise No glaciers Palm trees at the poles The oldest known animal fossils ( sponges ) are from the Snowball Earth, while flowering plants became the dominant plant species during the Cretaceous period. It is believed that the entire Earth was frozen for the first time about 2,400 to 2,100 million years ago, which could have been a result of the Great Oxygenation Event . The 200m sea level rise given in the last panel for a "Cretaceous Hothouse" (i.e. if all ice on earth melted, including the Antarctic ice cap) could not be explained by this melt-off alone. If all the ice melted the water level would only increase by about 60-80m, according to Antarctica , IPCC Third Assessment Report (section 11.2.3 on Greenland and Antarctic Ice Sheets) and Sea Level and Climate: USGS Water-Science School . Additional sea level rise can be expected from thermal expansion of seawater, and indeed the main reason for rising sea level at the moment is actually caused by this expansion of the sea due to increasing temperature. But the high-end 500-year projection for a 4x increase in CO 2 , at expansion of the sea , is for an additional 2m due to thermal expansion, with a decreasing rate of growth over time. (Some of the sea level change in the Cretaceous are due to changes in bathymetry.) The 5th and most recent Intergovernmental Panel on Climate Change (IPCC AR5) presents four alternative trajectories for future concentrations of greenhouse gasses, termed Representative Concentration Pathways (RCPs): RCP2.6, RCP4.5, RCP6, and RCP8.5. They are named after possible ranges of radiative forcing values in the year 2100 relative to pre-industrial values (+2.6, +4.5, +6.0, and +8.5 W/m2, respectively). The hottest of these, RCP8.5, is predicted to result in a warming of 2.6 °C to 4.8 °C for the 2081−2100 period, and between 3 and 5.5 by the year 2100 ( Working Group I Summary for Policymakers ). The lack of internationally binding agreements makes breaching an increase of 2 °C more and more likely.

This comic represents the impacts due to climate change by demonstrating the changes in climate that should be expected with a given change in global temperature. This is done by detailing the world's climate in geologic periods where the global average temperature has changed by one or more "Ice Age Units," or IAU. The comic defines an IAU as the difference in global temperature between today and the last ice age, about 4.5 °C. An IAU of 0 represents modern global temperature. It was later followed with a similar but much more elaborate chart in 1732: Earth Temperature Timeline . One IAU unit happens to be the expected increase in global temperature the world will see by the end of year 2100. The prediction of 4-5 degrees Celsius of warming may not appear significant, but is easy to see as a substantial difference when comparing today to the last ice age. An IAU of -4 is associated with Snowball Earth . Snowball earth is a near-total freezing of the entire surface around 650 million years ago, in the Cryogenian . This may have been the greatest ice age known to have occurred on Earth. An IAU of -1 is associated with the last ice age. During this time Randall's neighborhood was buried under an ice sheet. An IAU of +1 is the predicted global temperature by the end of year 2100. While it makes sense to assume it's just as drastic a difference as -1 IAU, we still don't know the actual nature of what it would be, which is why it is represented by a question mark in the comic. An IAU of +2 is associated with the "Hothouse Earth" of the early Cretaceous period . At this time there were " palm trees at the poles" as there were polar forests during Cretaceous summers. (Average temperature of North Pole during the summer is 0 °C or 32 °F. 0+2*4.5 = 9 °C = 48.2 °F, hot enough for trees to grow at the North Pole under hypothetical 2 IAU scenarios) An increase of 4.5 °C (+1 IAU) seems like a small change in temperature, but the changes it would cause are likely very large as it can also be described as halfway to palm trees at the poles. The topic of ice coverage over various cities has previously been covered in 1225: Ice Sheets . The image of Boston from that comic is reused at the top of the huge chart in 1732: Earth Temperature Timeline . This comic shows the extreme extent to which global warming can (and will) change our environment. Randall presented this view earlier in 164: Playing Devil's Advocate to Win . Climate change, especially global warming, is a recurring theme in xkcd. This is because many still believe the conspiracy theory that global warming is a hoax. The title text expands, demonstrating that the potential impacts of an increase by the IPCC report's best case scenario of 2 °C, about half an ice age unit, makes controlling climate change seem more urgent. The figure of 2 °C is the most commonly agreed temperature target that assumes the creation of aggressive emissions limits at the time of the publishing of the comic. The 4.5 degree increase is predicted by the bern2.5cc simulation (a moderate simulation) of the A1FI scenario. In the A1FI scenario the world has a high dependence on fossil fuels, experiences "very rapid economic growth", a declining world population by 2050, as well as a high rate of increase in energy efficiency after 2050. Without prompt, aggressive limits on CO 2 emissions, the Earth will likely warm by an average of 4°-5°C by the century's end. HOW BIG A CHANGE IS THAT? [A ruler chart is drawn inside a frame.] In the coldest part of the last ice age, Earth's average temperature was 4.5°C below the 20th century norm. Let's call a 4.5°C difference one "Ice Age Unit." [A ruler with five main divisions — each again with 3 smaller quarter division markers. Above it the five main divisions are marked as follows with 0 in the middle:] -2 IAU -1 IAU 0 +1 IAU +2 IAU [Next to the 0 marking a black arrow points toward 0.25 on the scale and above it is written:] Where we are today [The rest of the text is below the ruler.] [To the far left below -2 IAU a curved arrow points to the left. Below it is written:] Snowball earth (-4 IAU) [Below -1 IAU a black arrow point toward this division. Below the arrow is written:] 20,000 years ago [Below this an image of a glacier. At the top of the image is written:] My neighborhood: [At the bottom of the image is an arrow pointing to the glacier:] Half a mile of ice [Below 0 IAU a black arrow point toward this division. Below the arrow is written:] Average during modern times [Below this an image of Cueball standing on a green field with a city skyline in the background. At the top of the image is written:] My neighborhood: Cueball: Hi! [Below +1 IAU a black arrow point toward this division. Below the arrow is written:] Where we'll be in 86 years [Below this a white image. At the top of the image is written:] My neighborhood: [Below this is a very large:] ? [Below +2 IAU a black arrow point toward this division. Below the arrow is written:] Cretaceous hothouse +200m sea level rise No glaciers Palm trees at the poles The oldest known animal fossils ( sponges ) are from the Snowball Earth, while flowering plants became the dominant plant species during the Cretaceous period. It is believed that the entire Earth was frozen for the first time about 2,400 to 2,100 million years ago, which could have been a result of the Great Oxygenation Event . The 200m sea level rise given in the last panel for a "Cretaceous Hothouse" (i.e. if all ice on earth melted, including the Antarctic ice cap) could not be explained by this melt-off alone. If all the ice melted the water level would only increase by about 60-80m, according to Antarctica , IPCC Third Assessment Report (section 11.2.3 on Greenland and Antarctic Ice Sheets) and Sea Level and Climate: USGS Water-Science School . Additional sea level rise can be expected from thermal expansion of seawater, and indeed the main reason for rising sea level at the moment is actually caused by this expansion of the sea due to increasing temperature. But the high-end 500-year projection for a 4x increase in CO 2 , at expansion of the sea , is for an additional 2m due to thermal expansion, with a decreasing rate of growth over time. (Some of the sea level change in the Cretaceous are due to changes in bathymetry.) The 5th and most recent Intergovernmental Panel on Climate Change (IPCC AR5) presents four alternative trajectories for future concentrations of greenhouse gasses, termed Representative Concentration Pathways (RCPs): RCP2.6, RCP4.5, RCP6, and RCP8.5. They are named after possible ranges of radiative forcing values in the year 2100 relative to pre-industrial values (+2.6, +4.5, +6.0, and +8.5 W/m2, respectively). The hottest of these, RCP8.5, is predicted to result in a warming of 2.6 °C to 4.8 °C for the 2081−2100 period, and between 3 and 5.5 by the year 2100 ( Working Group I Summary for Policymakers ). The lack of internationally binding agreements makes breaching an increase of 2 °C more and more likely.

Manual for Civilization

Manual for Civilization

https://www.xkcd.com/1380

https://www.explainxkcd.com/wiki/index.php/1380:_Manual_for_Civilization

[Brian Eno is talking to an unseen audience.] Brian Eno: Hi. I'm music's Brian Eno, co-founder of the Long Now Foundation. [Panel 2 shows he is standing on a stage.] Brian Eno: As part of our mission to promote long-term thinking, we've asked experts to help us assemble a collection of books from which civilization can be rebuilt if it ever collapses. [Panel 3 shows he is holding a manuscript with a long list of book titles.] Brian Eno: Today we're sharing the results — the first ever Manual for Civilization . [Panel 4 shows him reading from the manuscript.] Brian Eno: *Ahem* Animorphs #1: The Invasion Animorphs #2: The Visitor Animorphs #3: The Encounter Unseen Audience member: ...are they all Animorphs Books? Brian Eno: No! There's also Megamorphs and The Andalite Chronicles .

Brian Eno is a musician and a co-founder of the Long Now Foundation . He is explaining to an audience that one of the missions of the Long Now is a Manual for Civilization - a collection of reference materials that can help rebuild society in case it collapses. But in Randall's version, the experts have made a list composed of many books from the Animorphs series. Animorphs is a series of books written by K.A. Applegate . It follows a group of five children (later, an alien joins as the sixth member), that try to stop the parasitic aliens, the Yeerks, by transforming into animals. A Yeerk that enters a human has complete control over their host, and can read their memories. Because the Yeerks can imitate their host almost perfectly, humanity is slowly being taken over without knowing it, and for this reason the children cannot contact the authorities and are on their own in the battle against the Yeerks. When asked if all the books on the experts' list are from the Animorph series, Eno misses the point of the question by saying No! , only to mention the Megamorphs books and The Andalite Chronicles , both of which are side stories to the Animorph universe. There are other books like these which aren't mentioned here — but it is clear from the last two panels that it is a quite long list — and it seems to be written in two columns, so maybe all 54 Animorphs books and all ten side stories could be included on the list. In suggesting that a series of children's novels make up the blueprint for rebuilding civilization, Randall is spoofing the idea of such libraries (since such books would be largely useless in terms of providing the detailed instructions that would be necessary). However, due to the surprisingly deep and introspective nature of Animorphs books, which several generations have grown up on, it may also entirely be possible that Randall is expressing his fondness for the series by suggesting that reading the books would be sufficient for creating the moral foundations of a functional civilization. The title text makes it completely ludicrous by saying an entire wing of the library will be devoted to the book (#26) where two main characters who have been attracted to each other since the beginning of the series finally kiss. While this is a momentous event for fans of the book series, the information is of no consequence for the rebuilding of civilization [ citation needed ] . This comic may also be inspired by Isaac Asimov 's Foundation series , where Hari Seldon claimed that the Galactic Empire is going to collapse in three hundred years, there is no way to stop it but his group of scientists are writing Encyclopedia Galactica to help people rebuild civilization. [Brian Eno is talking to an unseen audience.] Brian Eno: Hi. I'm music's Brian Eno, co-founder of the Long Now Foundation. [Panel 2 shows he is standing on a stage.] Brian Eno: As part of our mission to promote long-term thinking, we've asked experts to help us assemble a collection of books from which civilization can be rebuilt if it ever collapses. [Panel 3 shows he is holding a manuscript with a long list of book titles.] Brian Eno: Today we're sharing the results — the first ever Manual for Civilization . [Panel 4 shows him reading from the manuscript.] Brian Eno: *Ahem* Animorphs #1: The Invasion Animorphs #2: The Visitor Animorphs #3: The Encounter Unseen Audience member: ...are they all Animorphs Books? Brian Eno: No! There's also Megamorphs and The Andalite Chronicles .

Margin

Margin

https://www.xkcd.com/1381

https://www.explainxkcd.com/wiki/index.php/1381:_Margin

[Written on the right margin of a page:] I have discovered a truly marvelous proof that information is infinitely compressible, but this margin is too small to... ...oh never mind :(

This is a reference to Fermat's Last Theorem , of which Pierre de Fermat claimed he had a proof that was too large to fit in the margin of a copy of Arithmetica . Despite its simple formulation, the problem remained unsolved for three centuries; it was cracked only with advanced techniques developed in the 20th century, leading many to believe that Fermat didn't actually possess a (correct) proof (see trivia ). In the comic, the person writing in the margin attempts to pull a similar trick, without actually having any proof, by claiming that he has found a proof that information is infinitely compressible, but pretending not to be able to show it due to lack of space in the margin. In this particular case, however, this approach backfires, precisely because if information was actually infinitely compressible, the writer would be able to fit the proof in the margin (due to his own proof). The writer realizes that if he had a proof he should be able to fit it into the margin, and thus he realizes that he cannot pull this trick. Or perhaps the writer really thought he had a proof, but then realized that his statement was a counterexample, and was disappointed that his idea for a proof was wrong. What it seems he did not realize, is that it would be impossible to read the proof if the writer actually was able to compress his proof to fit in the margin. This is because you would need to know the algorithm described in the proof before you could decompress the proof text so you can read it. So he could actually have used this trick instead, writing that he had compressed it into - say a dot " . " - and then people would have to find his proof to read it. And since they cannot find such a proof - they could not check his dot. Unfortunately this would also have backfired - because there is already a proof that this is not possible ! Another thing that he probably didn't realize, is that finding a proof for something being possible does not necessarily mean inventing an actual algorithm to do that particular thing. If the person claimed having found a non-constructive proof for such an algorithm, his statement at least wouldn't contradict itself. The title text, yet another protip , makes a reference to the Shannon–Hartley theorem , which limits the maximum rate at which information can be transmitted. Setting the font size of text only changes its representation on the screen, and not the actual characters themselves. Trying to decrease the amount of space needed to store or transmit it like advised would be nonsensical. Another possible interpretation is that if you set the font size to 0, the text cannot be seen, and therefore, nothing is being transmitted period. In the case of actual printed paper, decreasing the font size is valid technique for information compression (more information on the same page), as used in ie. microform . However, this comes at the cost of an increased spatial bandwidth (number of black/white transitions per distance). In the end, the resolution of the printer/paper/microscope chain limits the minimal font size that remains useable (above the Nyquist rate ). [Written on the right margin of a page:] I have discovered a truly marvelous proof that information is infinitely compressible, but this margin is too small to... ...oh never mind :(

Rocket Packs

Rocket Packs

https://www.xkcd.com/1382

https://www.explainxkcd.com/wiki/index.php/1382:_Rocket_Packs

[Text above the frame.] Rocket packs are easy. [In the frame: Cueball is lying face down on the ground with his Rocket Packs on his back and his calves severely burned.] Cueball: Ow. [Text below the frame.] The hard part is inventing the calf shields.

In the early 20th century, visions of the future usually stipulated that everyone would travel around with rockets strapped to their backs. However, this has not yet come to pass, at least for the majority of consumers. In this comic, Randall is pointing out that the problem with personal rocket packs - more commonly called jet packs - is not how to attach a rocket to someone's back, but other practical considerations. One might be how to keep the hot exhaust from burning the user's calves . Many jet pack designs actually do have ways to deal with this, such as moving the rockets farther from the user, but there are many other practical issues which have made this an impractical form of travel given current technology. The title text starts with the trope " I want my jet pack ", a theme also explored in 864: Flying Cars . It continues with pointing out that if people did start using rocket packs, there would also be more injuries, raising health care costs. That's something that people usually don't consider when imagining a future where these devices are commonplace. So the year when the comic was published the demand was: 'It's 2014--I want my jetpack [and also my free medical care covering all my jetpack-related injuries]!' [Text above the frame.] Rocket packs are easy. [In the frame: Cueball is lying face down on the ground with his Rocket Packs on his back and his calves severely burned.] Cueball: Ow. [Text below the frame.] The hard part is inventing the calf shields.

Magic Words

Magic Words

https://www.xkcd.com/1383

https://www.explainxkcd.com/wiki/index.php/1383:_Magic_Words

[Cueball and Megan are in a bed.] Megan: Can you repeat "Story Water Paper Doorway" at the start, then switch to "Disarm Adele's Giraffe Grenade" as we get going, and finally "Strawberry Scorpion Poetry" as I finish? [Below the frame.] Linguist with a foot fetish

Typically the term " foot fetish " refers to a sexual attraction to people's feet. Here, though, Megan is a linguist, so for her the term "foot" refers not to the body part but to the term's meaning in prosody . In this context, "foot" means, per Wikipedia, "the basic metrical unit that generates a line of verse in most Western traditions of poetry," and thus "foot fetish" means an attraction to words that follow such a format. Common types of feet (which are all referenced in this comic) include Megan thus wishes that Cueball first use a trochee during foreplay, then switch to an iamb during her main stimulation phase (intercourse or some other type that still enables Cueball to speak freely), and finally switch to a dactyl as she orgasms. According to the title text, after sex she wishes for him to hold her while he whispers the word "anapest" in her ear. But for a linguist like Megan, this is just four different types of "foot" stimulation - thus she can be called a woman with a foot fetish. [Cueball and Megan are in a bed.] Megan: Can you repeat "Story Water Paper Doorway" at the start, then switch to "Disarm Adele's Giraffe Grenade" as we get going, and finally "Strawberry Scorpion Poetry" as I finish? [Below the frame.] Linguist with a foot fetish

Krypton

Krypton

https://www.xkcd.com/1384

https://www.explainxkcd.com/wiki/index.php/1384:_Krypton

[Cueball and Megan are standing near a telescope.] Cueball: The distant planet Krypton is becoming unstable! Baby crying (from outside the panel): Waaaaaa Megan: That crying baby is really annoying. [Cueball and Megan looking at each other.] [Spaceship taking off.] [Spaceship passing another spaceship on route to distant planet.] [Planet exploding.]

This comic is an inverse version of the origin story of the superhero character Superman . In the Superman story, Jor-El and his wife Lara notice that their home planet Krypton is about to be destroyed in a giant explosion, so they decide to send their baby Kal-El to Earth to save him - and there he becomes Superman. In this comic, Cueball and Megan also notice that the planet Krypton is about to explode, but instead of attempting to save a baby from Krypton, they decide to send a baby to Krypton from Earth so that it'll stop annoying them with its crying. In the fourth panel both spaceships can be seen. The rocket containing the Earth baby arrives at planet Krypton, while the crystal star shaped spaceship containing Kal-El leaves Krypton towards Earth - this is a reference to the version of the spaceship depicted in the 1978 Superman movie , (see trivia section ). In the fifth and last panel we see Krypton explode into multiple pieces, also emitting a disc-like wave from the assumed equator. In the Superman movie, Kal-El carries with him a lot of information pre-recorded by his parents. During the very long trip he listens to the recordings, one of which explains that the Sun and gravity of Earth will give him (Kal-El) great powers (this is the way he becomes Superman). The title text is a satirical version of this information, given to the Earth baby during his trip: That Megan & Cueball do not have the faintest idea (or care about) what the sun and gravity of Krypton will do to it - but their best guess at what these mostly will do to it is to "make you out of earshot from Earth", which was their original reason for shipping the baby off in the first place. [Cueball and Megan are standing near a telescope.] Cueball: The distant planet Krypton is becoming unstable! Baby crying (from outside the panel): Waaaaaa Megan: That crying baby is really annoying. [Cueball and Megan looking at each other.] [Spaceship taking off.] [Spaceship passing another spaceship on route to distant planet.] [Planet exploding.]

Throwing Rocks

Throwing Rocks

https://www.xkcd.com/1385

https://www.explainxkcd.com/wiki/index.php/1385:_Throwing_Rocks

[Beret Guy is throwing a rock in the water while talking to Megan who walks down to him.] Beret Guy: Every day I make a little leaf boat, then throw rocks until it sinks or floats away. [Rock lands in water, near a leaf boat.] Rock: Plunk Beret Guy: It's pointless, but at least it's relaxing. [Megan and Beret Guy are both holding rocks. Megan looks down at her rock.] Megan: Every day, I read the comments on a news article. [The two throw their rocks.]

Beret Guy is showing Megan one of his daily activities: Building a leaf boat and throwing rocks at it. He acknowledges that the hobby is useless, but relaxing. In contrast, Megan contemplates one of her own daily activities: reading online comments on news articles. Realizing that it is an equally pointless, but presumably much less relaxing activity, she joins Beret Guy in throwing rocks at his leaf boat. It is an unfortunate property of news articles that their comments become dominated by those which are deliberately offensive or devolve into flame wars . An additional metaphor may compare the article to the leaf boat while comparing the thrown stones to the flaming comments, essentially taking this most likely carefully constructed, fragile and perhaps beautiful creation (article or leaf boat) and lobbing offenses (comments or thrown stones) at it until it is dragged into the abyss (Internet "graveyard" or pond). The title text makes it clear that they hit the leaf with a stone. The rest is a pun on the name of the 11th century Viking explorer Leif Erikson , who is believed to have been the first European to discover and settle North America which he named " Vinland ". [Beret Guy is throwing a rock in the water while talking to Megan who walks down to him.] Beret Guy: Every day I make a little leaf boat, then throw rocks until it sinks or floats away. [Rock lands in water, near a leaf boat.] Rock: Plunk Beret Guy: It's pointless, but at least it's relaxing. [Megan and Beret Guy are both holding rocks. Megan looks down at her rock.] Megan: Every day, I read the comments on a news article. [The two throw their rocks.]

People are Stupid

People are Stupid

https://www.xkcd.com/1386

https://www.explainxkcd.com/wiki/index.php/1386:_People_are_Stupid

[White Hat and Cueball are standing next to each other.] White Hat: Well, you know, people are stupid. Cueball: *Sigh* [They have moved a little further apart.] Cueball: No, people aren't stupid. On average, people are of average intelligence. When you say "people are stupid," you mean stupid compared to your expectations. [Close up of Cueball.] Cueball: What you're really saying is "other people aren't as smart as me. " Cueball: And maybe you're right! In which case [White Hat is presented with a trophy by Cueball.] Cueball: I'd like to bestow upon you the [In the panel there is a close up of the trophy plaque (the text is in a frame):] First Annual Award for Excellence in Being Very Smart Cueball: May you continue to grace our internet with your wisdom

G. K. Chesterton wrote in an essay : "It is stupid to say that “most people” are stupid. It is like saying “most people are tall,” when it is obvious that “tall” can only mean taller than most people. It is absurd to denounce the majority of mankind as below the average of mankind." It is a common thing for people on the Internet (on forums and comments sections of various websites) to make vague generalizations about the "stupidity of all people" or "losing faith in humanity," for instance when the topic is actually the stupidity or irrational/extreme behavior of one individual or group of individuals. The comment can come in any type of Internet forum, regardless of the subject. However, the overall world population ("people") is not more stupid than the average - by definition. There is also no other human population to compare to to draw the conclusion this population is stupid. So it is a stupid comment that White Hat makes. The award being given to him by Cueball is thus a very sarcastic one. It is possible that for a non-normal distribution of intelligence a median individual could be less intelligent than the mean. However, the statement as it is usually formulated (including here), "People are stupid," refers to humanity as a whole. White Hat's anecdotal and subjective experience has led him to make a statistically impossible statement. White Hat's self-perceived superiority may be an example of the Lake Wobegon effect , so named because Lake Wobegon (a fictional city) is "where all the women are strong, all the men are good looking, and all the children are above average". The last panel may be a reference to the First Annual Montgomery Burns Award for Outstanding Achievement in the Field of Excellence which is a fictional award in the story of The Simpsons episode Brother, Can You Spare Two Dimes? where it is presented to Homer Simpson . In the title text the other phrase about having lost their faith in humanity also gets a comment on the way from Cueball. There are people who use this phrase every time someone disagrees with them or say something they think is stupid. He jokes that he will let humanity (everyone other than the guy who makes the comment) know that he has lost faith in them - and very sarcastically remarks that humanity will probably be crushed (i.e. the rest of the world does not care if that guy has lost faith in them). [White Hat and Cueball are standing next to each other.] White Hat: Well, you know, people are stupid. Cueball: *Sigh* [They have moved a little further apart.] Cueball: No, people aren't stupid. On average, people are of average intelligence. When you say "people are stupid," you mean stupid compared to your expectations. [Close up of Cueball.] Cueball: What you're really saying is "other people aren't as smart as me. " Cueball: And maybe you're right! In which case [White Hat is presented with a trophy by Cueball.] Cueball: I'd like to bestow upon you the [In the panel there is a close up of the trophy plaque (the text is in a frame):] First Annual Award for Excellence in Being Very Smart Cueball: May you continue to grace our internet with your wisdom

Clumsy Foreshadowing

Clumsy Foreshadowing

https://www.xkcd.com/1387

https://www.explainxkcd.com/wiki/index.php/1387:_Clumsy_Foreshadowing

[Heading and text above the panel:] Today's News North Korea threatens U.S. over upcoming movie Shark populations booming off east coast SpaceX to attempt new rocket launch today [Arrow pointing down towards the comics only panel.] [Cueball, holding a towel, walks past a TV with a news report shown on-screen.] Cueball: Bye! See you tonight! Offscreen person: Have a good day! TV: Researchers are reporting record numbers of sharks... [Caption below the panel:] To make news stories seem way more ominous, imagine you're hearing them from a background TV in a movie as the main character leaves.

Many action/thriller movies, during the first few minutes, have a background news report that foreshadows the onset of some kind of danger, such as shark attacks, nuclear warfare etc. Randall suggests taking the same approach to random news stories from real life, in order to make them more ominous. In this case we see three random headings from news stories, which could all be made even more interesting if the setting is correct. The first of the three stories mentioned above the frame North Korea threatens U.S. over upcoming movie comes from North Korea's official Korean Central News Agency who a few days before this comic was released threatened the US with war over the Seth Rogen movie The Interview , promising "stern" and "merciless" retaliation if the film is released. The threat generated some hype for the at-the-time unreleased movie. No one, however, really took North Korea's threat seriously, but if you put this into such a news report at the beginning of a film, this could be a film about a film leading to a new war with North Korea. (Note: In late 2014 North Korea was accused of carrying out a devastating cyber attack on Sony Pictures, the studio responsible for the film. These accusations were widely believed initially, though independent analysists have since cast doubt. This news report would likely have been seen in a film about the real life attack or film that features a similar fictional attack for its plot. This is an example of an xkcd comic coming true.) The second one is about Shark populations booming off east coast . The news in the link is from a week before this comic was released, and is about the preservation of the Great white sharks . Not that terrifying, especially since sharks are way less dangerous than people tend to fear, in part due to movies like Jaws . However, if you put this headline into a news report running in the background, as when Cueball leaves the house with a bathing towel in the main frame of the comic, as if he was going to the beach, then it suddenly becomes a very ominous story , that will not bode well for Cueball and his friends. The last of the three stories is about SpaceX to attempt new rocket launch today . SpaceX is a space transport services company and on March 13, 2014 they reported a launch date for their first OG2 mission containing 6 satellites on a dedicated Falcon 9 rocket. This date was April 30, 2014 as can be read at the bottom of the news link, which is the news list for this OG2 mission. The launch continued to be postponed several times, and the last date given before this comic was released was June the 24th, three days before this comic was released. This launch was canceled on the 23rd and the day before this comic was released it was yet again postponed, this time until July 14 (almost three weeks, after the previous four proposed launch dates had been 20, 21, 22 and 24 June). So at this point in time, any news regarding SpaceX attempting to launch a rocket, will not generate much fuss, as they are most likely postponing again, but if you put the news bite into the start of a movie, then the launch would probably stay on schedule - but would then go horribly wrong, setting the action packed story in progress. Just over a year later on June 28, 2015 SpaceX mission CRS-7 exploded just after launch. The preliminary findings of the investigation however point to a failure of a steel strut, which would be hard to turn into a good story. The title text news hosts were unexpectedly fired from ABC's 'The View' today references ABC's The View where two of the co-hosts, Sherri Shepherd and Jenny McCarthy , were simultaneously reporting leaving the program (fired or resigned? - sources vary), the day before this comic appeared. Sherri after seven years, Jenny after less than one year as co-host. According to the news link above there were "no word on who will be replacing the hosts, but the network says they will have a team together when the show launches its new season this fall." Again a not very interesting news story. The title text though continues the news by saying: ABC will likely announce new... The humorous suggestion is that the news about The View will go on to foreshadow some looming disaster, a comically unlikely premise for an action/thriller movie. Alternatively, it could be used as a plot device if the character will be hired as a replacement—or the character is listed as a potential replacement and tries to dig up dirt on the competition or otherwise compete for the position. [Heading and text above the panel:] Today's News North Korea threatens U.S. over upcoming movie Shark populations booming off east coast SpaceX to attempt new rocket launch today [Arrow pointing down towards the comics only panel.] [Cueball, holding a towel, walks past a TV with a news report shown on-screen.] Cueball: Bye! See you tonight! Offscreen person: Have a good day! TV: Researchers are reporting record numbers of sharks... [Caption below the panel:] To make news stories seem way more ominous, imagine you're hearing them from a background TV in a movie as the main character leaves.

Subduction License

Subduction License

https://www.xkcd.com/1388

https://www.explainxkcd.com/wiki/index.php/1388:_Subduction_License

[Beret Guy is looking at some mail he has received while Cueball is at his computer desk at the other side of the room.] Beret Guy: Sweet! I finally got my subduction license! Cueball: Your what? [Beret Guy starts sinking into the ground, causing it to ripple.] Cueball: ...What are you doing? [Beret Guy sinks further, forming a miniature mountain range in front of him. Cueball is frantically trying to keep his computer steady as his desk tilts.] Cueball: Stop it! Stop it! [Beret Guy is waist-deep, and snow caps have formed on the mountains. Cueball is falling backwards from his desk and out of his chair, and the monitor unplugs itself from his computer.] Cueball: Augh!

In structural geology , subduction is the mechanism by which one tectonic plate disappears under another. This process usually creates a mountain range on the second tectonic plate as water entrained in the subducting plate rises into the second plate and provokes volcanism , often resulting in a volcanic arc . In this comic, Beret Guy is very happy because he has just received his subduction license , which may be a play with business term production license . His roommate Cueball very reasonably asks him: Your what? But instead of answering him, Beret Guy begins to move towards him in their small room. It turns out that the license has literally enabled him to initiate subduction. As he moves towards Cueball, he slowly sinks under the floorboards of the room, and in this process he creates a small mountain range on the floor. In the end, much to Cueball's consternation, these mountains turn his desk and chair over. Cueball actually falls out of the frame in the final panel, where Beret Guy is already halfway down beneath the floor. This would not be possible in real life. [ citation needed ] The title text plays on the double meaning of the word "normal", which Cueball means in the sense of "like most people, not strange," but which Beret Guy interprets in the geological sense. While subduction occurs when two plates crash into each other, a normal fault occurs when two plates are moving away from each other. Here, "normal" is used in the sense of "perpendicular," as the result of a normal fault is often that part of the crust moves vertically downward, forming a graben . A similarly atypical license was mentioned previously in 410: Math Paper . Puns on geological terms (including types of faults) were previously made in 1082: Geology . This comic was featured in a page of Thing Explainer as part of the explanation of the Big flat rocks we live on . Only the last three panels were used, probably because the words in the first panel were way too uncommon for the book - see more details here . Subduction was again mentioned in 1829: Geochronology . [Beret Guy is looking at some mail he has received while Cueball is at his computer desk at the other side of the room.] Beret Guy: Sweet! I finally got my subduction license! Cueball: Your what? [Beret Guy starts sinking into the ground, causing it to ripple.] Cueball: ...What are you doing? [Beret Guy sinks further, forming a miniature mountain range in front of him. Cueball is frantically trying to keep his computer steady as his desk tilts.] Cueball: Stop it! Stop it! [Beret Guy is waist-deep, and snow caps have formed on the mountains. Cueball is falling backwards from his desk and out of his chair, and the monitor unplugs itself from his computer.] Cueball: Augh!

Surface Area

Surface Area

https://www.xkcd.com/1389

https://www.explainxkcd.com/wiki/index.php/1389:_Surface_Area

[At the top of a map is a heading, with two sub headings and a note in brackets:] Space Without the space The Solar System's solid surfaces stitched together (Excluding dust and small rocks) [Below the headings there is a map with several distinct areas. Each area is labelled with a name or a description. This label is noted inside the area, except for areas that are too small; here the label is written outside and a line indicates which area the label belongs to. Only exception is the largest area, on which the contours of the Earth's continents are drawn. Surrounding the map is wavy lines to indicate that this is either an island or one big super-continent placed in an even larger ocean.] [Here below are the labels given as they appear in "normal" reading order in as read from left to right in the three main rows as will be indicated:] [Row one, above the line defined by the general top of the Earth area:] Io Callisto Europa Ganymede Ceres Vesta Asteroids (1 km+) [Here – above the Asteroids area before the Triton area - is a small unlabelled area (the only other except Earth)] Triton Asteroids (100 m+) Oberon Miranda Ariel Umbriel Titania [Row two, the unlabelled Earth area's row, but here only given those that are directly written to the right of this area:] Tethys Enceladus Dione Iapetus All human skin Rhea Titan [Row three, all the remaining items that are mainly below the Earth area:] Mercury The Moon Various small moons, comets, etc Mars Makemake Haumea Eris Pluto Charon Venus

This map shows the total surface areas of all terrestrial planets , dwarf planets , moons , asteroids and minor planets that are larger than 100 m in the Solar System . They have all been represented as regions of a single massive landmass - a supercontinent like Pangaea - which is clearly surrounded by some kind of ocean. On the area that signifies Earth the continents are drawn using a map projection that keeps the scale of the continents correct. (This is something that Randall cares about as can be seen in 977: Map Projections ). The parts of the surface of the Earth that are covered by oceans are also included in the surface area of the Earth (i.e. the map shows the Earth's crust ). An extra layer of 3–4 km of water seems rather insignificant when comparing to the Earth's radius of 6,370 km. The Moon has been inlaid in this map next to Antarctica which thus makes a great comparison of how small the Moon is compared to the Earth (there is room for more than 13 lunar surfaces on the Earth). Similarly, it is clear that the planet Venus is almost as big as the Earth. This is also the general idea of the map - to give an idea about how big the Earth is and how small many of the other known planets etc. are; both compared to Earth and to each other. The map drawn on the Earth is probably there mainly as a guide to size, because none of the features that are known on some of the other objects, especially The Moon (i.e. craters and " seas ") and on Mars (i.e. Olympus Mons ), are included. The objects mentioned by name on the map are all but one amongst those that have reached hydrostatic equilibrium and these are all included on this List of gravitationally rounded objects of the Solar System . The one named object that is not on the above list is the asteroid Vesta , which is included because it is the second largest object in the Asteroid belt . It is placed right next to the largest object in this belt, the dwarf planet Ceres , which is no longer considered an asteroid. And next to these two are the rest of the asteroids in two areas (see below), which thus groups all asteroids together. The only object from the above list, (that qualifies for having a solid surface in hydrostatic equilibrium), which is not included is the Saturn moon Mimas , which is also clearly the smallest object on the list. This moon should have been located amongst the other five smaller moons of Saturn between the Earth and Titan (the largest of Saturn's moons). Mimas has a surface area of 490,000 km 2 which is somewhat smaller than the smallest included Saturn moon Enceladus with a surface area of 799,000 km 2 . Generally the moons that belong to a given planet (for those with more than one moon large enough to be included), have been clustered together. Apart from the six (not seven...) moons of Saturn to the right of Earth, the four Galilean moons moons of Jupiter are located above the Earth, the five included moons from Uranus is located at the top to the far right. The last planet to have many moons is Neptune , but only Triton is included. This is a fairly large moon, and the only of the 14 known moons of Neptune to be on the above list. However, there is one other moon, Proteus which is notable for being as large as a body of its density can be without being pulled into a spherical shape by its own gravity. It has a length of 424 km in the longest direction, and a mean radius of 210 km. A rough calculation of its surface area from this mean radius gives an area of 550,000 km 2 , making the surface area slightly larger than Mimas. As there is an unlabeled area located right next to the other Neptune moon Triton, it is most likely that this small area should represent Proteus , and that it is an error that it was not labeled. As this is the smallest area, the cut-off of objects could have been at 500,000 km 2 , as Vesta is also larger than this, which would make room for Proteus, but explain the missing Mimas. Two of the included objects also have moons that are large enough to be included: Earth, of course, and the dwarf planet Pluto with its moon Charon . In both cases these moons have been inlaid in the area of their mother planet. Whereas the moons of the gas giants and the asteroids have been located above and to the right of the Earth, the planets and dwarf planets have been included below earth (along with the two moons mentioned above). Mercury , Mars and Venus all touching Earth, and then below them the four Trans-Neptunian dwarf planets - the Plutoids . On the list from above there are, however, also these 10 objects which have not been included with name on the map. These object are, however, only likely candidates for being dwarf planets (depending on whether they have reached hydrostatic equilibrium or not), and on the map they have thus been relegated to the sections without individual names. These object are thus probably grouped together (along with other relatively small objects like comets and smaller moons) in the area labeled Various small moons, comets, etc , which is located at the bottom of the map between Mercury and Mars. The surface area for all of these object, when the surface area have been estimated, are larger than 1 million square kilometer, and thus larger than several of the named objects. So it is not the size that is the reason why such objects as Sedna and Quaoar are not included with name, but probably the fact they are not investigated enough yet. The remaining objects in the Solar System with a solid surface are the minor planets, which on the map has been labeled as asteroids even though these objects are grouped together in several other "belts" than the Asteroid belt. Here they have been assigned to two regions at the top of the map. Above the right part of the Earth area is the area Asteroids (1 km+) which include any object not already included larger than 1 km. (As these objects are no longer round it is the largest dimension, the length, that should be at least 1 km long). And finally the area Asteroids (100 m+) thus include any object not already included larger than 100 m. Most of the rest of the objects that have been included in these three sections can likely be found on this List of Solar System objects by size . Tiny objects smaller than 100 m down to space dust are excluded altogether as explained in the note below the headings. This is probably because their total surface area is impossible to estimate accurately, and also because any estimate would likely be too large to fit easily into the map. Between Earth and Titan is a tiny speck noted all human skin , which is an interesting sort of solid surface. A rough estimate of the average body surface area and thus of the average area of all humans skin can be made from these average values and from population pyramids as this pyramid for 2015 . Average adults have a skin area of around 1.7-1.8 m 2 , but as a large part of the human population are children (with skin area down to about 0.25 m 2 for infants) the total average will be smaller. By extrapolating the given values an average area of about 1.6 m 2 can be found. This would make the area 7.2 billion × 1.6 m 2 ≈ 11,500 km 2 . This is 60 times smaller than the smallest of the labeled moons Miranda (of Uranus) with a surface area of 700,000 km 2 . The title text jokingly claims that this comic is not actually for information, but rather is something Randall thinks we should really do – that is, to stitch all the solar system's solid surfaces together, as the sub-sub heading says. To do this, we would need a giant spool of thread and then something he has to go get in Seattle… which presumably must be the Space Needle , a needle-like tower in Seattle, which should then be used in this grand project. This could also have been a reference to the Seattle seamstresses if it weren't for the fact that it's not. Since the land areas are on the surfaces of spheres, this would seem impossible as it would involve lots of deformation and be particularly challenging. It will also be very gruesome when he comes to the part of collecting (and stitching) all human skin together. The inclusion of this speck on the map is, however, also there to make it clear what the real intention is with the planets. Their surface is to be "skinned" of them, as you would have to do with the humans! Then it is all these "planet skins" that should be stitched together using the space needle. This also explains the ragged edges, and why the continents keep their correct size. It would make Randall into a planetary version of The Silence of the Lambs movies character Buffalo Bill , a serial killer who tried to make a suit out of the skin from the women he killed. Randall would also need quite a lot of space for the very large ocean. However, the whole supercontinent is just somewhere between 3-4 times larger than the area of the Earth. And the area of the entire image is less than 9 times the area of the earth. As the formula for calculation surface areas for spheres (4*π*r 2 ) goes with the radius (r) squared, the diameter of the planet needed for the experiment do not need to be larger than 3 times that of the earth. Although there are no objects in the Solar System with this particular size, it is still smaller than the gas giants , the smallest of these have a radius of almost 4 times that of the earth. Exoplanets with this range of diameters have certainly been found, however, already at 1.7 times the earth radius most planets size to be of the Super-Earth type and turns in to the gas dwarf type of planets. So an ocean of the size needed are not easy to come by. As has been explained above the earth's surface is included disregarding surface water (oceans) and the same is valid for other objects with surface water, as the Saturn moon Titan which has great lakes (or even oceans) of liquid methane on the surface or the Jupiter moon Europa which is covered in a deep ocean with a thick cap of ice. (Interestingly this moon is placed on the map very near to the continent of Europe - maybe for easy comparison of these two areas). The gas giants Jupiter, Saturn, Uranus, and Neptune have, however, not been included because they do not have any "solid surfaces"; even if they had a solid core (which is itself not clear), this would not comprise any "surface". The gas giants are believed to lack any well-defined surface at all, with the gases that make them up simply becoming thinner and thinner with increasing distance from the planets' centers, eventually becoming indistinguishable from the interplanetary medium. But if they were included via some sort of surface definition, the map of this comic would become a tiny speck amongst the map of the gas giants. Similarly, the surface of the Sun is also not considered a solid surface but hot plasma ; if it were included it would reduce even a map of the gas giants to a tiny speck. The map is drawn in a similar style to the two maps of the Internet that Randall has created in the past: Below is a table listing the object roughly in the order they would be read of the map (the same order as in the transcript.) But they can be sorted by each of the columns. The data is taken when possible from the following table: List of gravitationally rounded objects of the Solar System , and surface area is given with three significant digits. For Vesta and Proteus (the most likely candidate for the unlabeled area next to Triton) the area is calculated from their mean radius (i.e. they are not spherical). See also above in the explanation, also for calculating the area of all human skin. The surface for a given object is also given as a Fraction of Earth's surface , and from this the number of times the object could be placed on the Earth's surface is given as one divided by this fraction. For instance it can be seen that The Moon's surface can be placed more than 13 times on top of that of the Earth. [At the top of a map is a heading, with two sub headings and a note in brackets:] Space Without the space The Solar System's solid surfaces stitched together (Excluding dust and small rocks) [Below the headings there is a map with several distinct areas. Each area is labelled with a name or a description. This label is noted inside the area, except for areas that are too small; here the label is written outside and a line indicates which area the label belongs to. Only exception is the largest area, on which the contours of the Earth's continents are drawn. Surrounding the map is wavy lines to indicate that this is either an island or one big super-continent placed in an even larger ocean.] [Here below are the labels given as they appear in "normal" reading order in as read from left to right in the three main rows as will be indicated:] [Row one, above the line defined by the general top of the Earth area:] Io Callisto Europa Ganymede Ceres Vesta Asteroids (1 km+) [Here – above the Asteroids area before the Triton area - is a small unlabelled area (the only other except Earth)] Triton Asteroids (100 m+) Oberon Miranda Ariel Umbriel Titania [Row two, the unlabelled Earth area's row, but here only given those that are directly written to the right of this area:] Tethys Enceladus Dione Iapetus All human skin Rhea Titan [Row three, all the remaining items that are mainly below the Earth area:] Mercury The Moon Various small moons, comets, etc Mars Makemake Haumea Eris Pluto Charon Venus

Research Ethics

Research Ethics

https://www.xkcd.com/1390

https://www.explainxkcd.com/wiki/index.php/1390:_Research_Ethics

[Megan is facing Cueball and Ponytail.] Megan: Facebook shouldn't choose what stuff they show us to conduct unethical psychological research. Megan: They should only make those decisions based on, uh... Megan: However they were doing it before. Megan: Which was probably ethical, right?

This comic references the recent revelation that Facebook engaged in a " psychological experiment " by selectively showing users more "positive" or "negative" posts on their news feed and recording the users' comments to see if the change affected the positivity or negativity of their posts. Further experiments have since been revealed such as one that tested security measures by locking users out of their accounts . Here, Megan is commenting on the fact that, while the media is calling this control over what content the user sees " unethical ," Facebook, and other companies like Google , must, one way or another, control what content the user sees, whether to present users with a limited selection of all postings, or to tailor ads to particular users; even if the regular algorithms are not set up for psychological experiments, they are still "manipulating" what posts users see or don't see. As Megan points out, no one really knows what the "normal" constraints are of the algorithm which chooses which posts are shown on news feeds. This comic is parodying the strong reaction to what is basically already a common practice. Accumulation, control and analysis of user-generated information can be a part of the terms of service / end-user license agreement of a Website or software. In such a scenario, the user has effectively signed his/her consent to being part of such research. Unfortunately, most users don't read the terms before clicking the "I agree" option, so it can come as a shock when the service uses the data in a way the user hadn't anticipated. The title text ironically/sarcastically accepts that Facebook has access to all of its users thoughts through posts and photos, and they can read them for research or other purposes, but contrasts this with a suggestion which likely mirrors how Facebook would respond to such a request that Facebook's code is private and can not be revealed to us. The title text basically appears to be musing that this is backwards, and our personal data should be considered MORE private than Facebook's programming code, which may be proprietary, but is not personal private data. It is as if your neighbor was spying on you while you left all your shades open, but you felt it to be inappropriate to find out what he knew about you because that's his business. Asking for the source code might similarly be equivalent to asking for the specifications of the binoculars your neighbor used for spying. [Megan is facing Cueball and Ponytail.] Megan: Facebook shouldn't choose what stuff they show us to conduct unethical psychological research. Megan: They should only make those decisions based on, uh... Megan: However they were doing it before. Megan: Which was probably ethical, right?

Darkness

Darkness

https://www.xkcd.com/1391

https://www.explainxkcd.com/wiki/index.php/1391:_Darkness

[Ponytail is a news anchor at a media desk and she reports:] Ponytail: ...getting reports that the darkness has spread as far west as Texas. Let's go live to our reporter in Houston. [From a breaking news window in the bottom right corner of the panel, Cueball as a newscaster stands in darkness with two people walking behind him:] Cueball: It's been thirty minutes since the sun vanished... [Caption below the panel]: Caption: "Genie, for my last wish, make everyone in the media forget about the day-night cycle."

Ponytail as a news anchor describes the sunset as though it were an unprecedented, newsworthy event, rather than something mundane that happens every day. They even have a reporter ( Cueball ) on the spot reporting from where the darkness has spread so far. The sunset is a common event. Isaac Asimov based his short story Nightfall on a fictional civilization that doesn't know darkness because the planet is always illuminated by the six stars surrounding it. The story describes how people would react (mass insanity, fall of civilization) when the orbital motion of the planet eventually leads to five of the suns setting, plus one in eclipse. Describing mundane occurrences in unusual detail, to show off how odd they really are, is something Randall has done before (for instance about dreaming in 203: Hallucinations ). But the caption below the main panel adds another twist to the joke by showing that the news report wasn't a mere imagine spot, but something actually happening due to the interference of Randall's final wish to his genie , which caused all news reporters to forget the day-night cycle. Another possible meaning is that this comic is a reference to the way the media often talk about global warming as if each weather occurrence had meaning outside of its context like in 1321: Cold . That take on the weather and the day-night cycle being denied because of a skewed point of view was also used on the Daily Show . The segment " Unusually Large Snowstorm " from February 10, 2010, used the same trope. Several Daily Show correspondents have different views on the weather based on where they are, ending with a correspondent who equates nighttime with everlasting darkness. The caption references the fact that there is a limit to the number of wishes. It is a common rule, often used in fiction, that you get three wishes from a genie in a bottle . There usually is an added stipulation that no wish may be used to acquire more wishes. In the title text, however, it is stated that Randall has managed to bypass the three wish limit rule. This was accomplished by using his second wish to simply make the genie unable to remember granting the speaker any wishes. He has thus used the same trick on the genie as he used here on the media. The media wish turns out not to have been his last (i.e. third), but rather wish number 406. This shows just how far, "make someone forget something", can go by applying it to the genie. There is possibly an inconsistency in the comic, when seen from the title text's perspective. Since his second wish, all his wishes would have been seen as the first by the genien and thus, if the title text is true, he could have said: "Genie, for my first wish, make everyone in the media forget about the day-night cycle." However, in the light of the title text (to be seen as an add on, and thus not always related directly to the comics image) he appears to voluntarily end the whole scenario by explicitly declaring it over. Whether this would finally trigger the genie to end the wishing-cycle is unknown, and depends upon the exact priority of the genie's induced amnesia over its end-of-wishes habits. It is interesting that it was his second wish that gave him unlimited wishes. What did he wish for on wish #1? Maybe he wasted the first wish because he did not believe the genie was able to grant wishes – a common error. On the other hand, he may have used the first wish to learn how to make his second wish circumvent the three rule limit. His first wish could have been to read the genie's mind to determine what he could wish for to give him unlimited wishes. [Ponytail is a news anchor at a media desk and she reports:] Ponytail: ...getting reports that the darkness has spread as far west as Texas. Let's go live to our reporter in Houston. [From a breaking news window in the bottom right corner of the panel, Cueball as a newscaster stands in darkness with two people walking behind him:] Cueball: It's been thirty minutes since the sun vanished... [Caption below the panel]: Caption: "Genie, for my last wish, make everyone in the media forget about the day-night cycle."

Dominant Players

Dominant Players

https://www.xkcd.com/1392

https://www.explainxkcd.com/wiki/index.php/1392:_Dominant_Players

Dominant players over time [Below this heading there are three panels with charts showing different players career paths - that is their rating a function of the year. Most of the paths are grey, but some are red (there will be a note for these). Some parts of several paths are dashed. Somewhere on each path the players name will be written curving along so it follows the path. Several places an event or some information is noted and points to a given time on the path. If it is not clear where it belongs an arrow will point to the correct place. Each chart has a heading and for the two last charts there is an explanation. There is no scale on the y-axis (rating) but the x-axis (time) has the years given in ten years interval. A thin line indicates these decades. The years are all written at the top, except the first for the first chart, which is written below, and this year is missing in the bottom chart.] [Below the transcript for each chart will follow this order: Heading/sub heading, explanation, time scale, player names with any information for this player, in the order their name appear on the time scale.] [Basketball chart:] Basketball (NBA/ABA) Player Efficiency Rating 1950 1960 1970 1980 1990 2000 2010 [Red] George Mikan [Red] Bob Pettit Neal Johnston [Neil misspelled.] Elgin Baylor [Red] Wilt Chamberlain Becomes the first and so far only player to score 100 points in a game Jerry West The Guy in the NBA logo [Red] Kareem Abdul Jabbar [Missing hyphen between the two last names.] Airplane Bob Mcadoo Julius Irving [Erving misspelled.] Moses Malone Magic Johnson HIV announcement [A part of the path is dashed after this.] [Red] Michael Jordan Baseball career [A part of the path is dashed after this.] Space Jam Second retirement [A part of the path is dashed after this.] Larry Bird Karl Malone David Robinson [Red] Shaquille O'Neal Kevin Gariett [Red] LeBron James The Decision Dwyane Wade Kevin Durant [Chess chart.] Chess Elo Rating The modern Elo rating system dates back to about 1970. Computer analysis (like Kenneth Regan's) lets us rate historical players, but this has only been done rigorously for a few tournaments. Dashed lines are rough estimates only. [All paths are dashed up until the late nineteen sixties:] 1950 1960 1970 1980 1990 2000 2010 [The first player has no path, as his time was before 1940. An arrow points toward the left to these earlier times:] José Capablanca Terrifying chess God [Red] Alexander Alekhine [His path ends in a starburst.] [Red] Mikhail Botvinnik Tigran Petrosian David Bronstein Mikhail Tal Mikhail Tal [his name is written twice on the path, the second time above Boris Spassky when their paths intertwine.] [Red] Bobby Fischer Vanished… [Text under a starburst.] Reappeared then vanished again. He had problems. [Text under two starbursts connected with a path. This appears much later than the first starburst.] Boris Spassky Boris Spassky [his name is written twice on the path, the second time below Mikhail Tal when their paths intertwine.] Victor Korchnoi [Red] Anatoly Karpov [Red] Garry Kasparov Loses to Deep Blue Judit Polgar (See below) [The text is written beneath her name.] Vladimir Kramnik Levon Aronian [Red] Magnus Carlsen [Chess (women) chart:] Chess (women) Elo Rating For a long time, sexism, a lack of role models, and institutional hostility largely kept women from pursuing serious chess careers. With the expansion of women's tournaments and prizes starting in the 1970s, this has begun to change. [All paths are dashed up until the late nineteen sixties.] 1960 1970 1980 1990 2000 2010 [Red] Vera Menchik Died in a missile attack on London [next to a starburst.] Sonja Graf Rating particularly uncertain Olga Rubtsova Elisaveta Bykova Kira Zvorykina Kira Zvorykina (born 1919) continued playing in tournaments into the 21st century [Text above Elisvetas path, no arrows.] Zvorykina [Written on top of the path when her path reappears much later.] Alexandra Nicolau [Red] Nona Gaprindashvili Alla Kushnir [Red] Maia Chiburdanidze Pia Cramling Pia Cramling [her name is written twice on the path, the second time below the path of Xie Jun after their paths have intertwined.] Xie Jun Xie Jun [her name is written twice on the path, the second time above the path of Pia Cramling after their paths have intertwined.] Susan Polgar Sofia Polgar [Red] Judit Polgar Sisters [The three Polgars are linked by a thin dashed line, snaking between their names.] Wins a game against Kasparov, making her the first woman to beat the world #1 Becomes first woman to rank in the overall top 10 Antoaneta Stefanova Anna Muzychuk Koneru Humpy [In western style the name should be Humpy Koneru, but the comics version is the native form.] Hou Yifan

The comic shows the rise and fall of players' strengths in two games, basketball and chess . For chess, there is an overall chart, and a women's chart. For basketball, it uses the player efficiency rating (PER), the most commonly used player statistic . Note that that player efficiency ratings and similar "aggregate scores" are the subject of much discussion in basketball due to known deficiencies . For chess, it uses the Elo rating . Elo was adopted by the World Chess Federation, FIDE , in 1970, so the rating is extrapolated backwards in time (among other methods, such as using Kenneth Regan's computer analysis - as written in the Chess panel) and are thus shown as dashed lines prior to 1970. The charts show the players career paths as a function of time with the rating on the y-axis. There is no scale on the y-axis . Included are mainly players that could be said to have been among the dominating players at some time in their career. If a player has been the best player over a longer time period (a seriously dominating player) then their career path will be drawn in red, the rest are in gray. There can be more than one red path at a time, but only because the dominating player has played before or after they became dominating. It seems like it has to be at least five years, as there are at least two players that have been no. 1 for four years, without being upgraded to a red curve. The only ones that have managed this with three years or less (on the chart) are those that begin the chart, and thus could have been no. 1 a few years before. This can all be seen in the data tables below. The title text mentions Vera Menchik who is also the first female chess player listed at the left of the bottom panel. In January 1926 she won the first Girls' Open Championship at the Imperial Club in London, but as can be seen in the last panel she was killed near the end of World War II, 38-year-old, while still holding the title of women's world champion. She, her sister, and mother were killed in a V-1 flying bomb attack which destroyed their home in 1944. The title text mentions her specifically because of the club named after her: The "Vera Menchik Club" . When in 1929, Menchik entered the Carlsbad , Viennese master, usually a tournament only for male chess players, one of the other chess players, Albert Becker , ridiculed her entry by proposing that any player whom Menchik defeated in tournament play should be granted membership into the Vera Menchik Club. In the same tournament, Becker himself became the first member of the "club", much to his ridicule. It should be noted that she did end in last place vs. his fifth place, but that must just have made the defeat even tougher to take for Albert. Albert was the first, but far from the last male chess player to enter the Vera Menchik Club. No less than 19 other male chess players are listed on Wikipedia belonging to this club, amongst them Max Euwe who went on to become World Chess Champion (1935–37). So it can for sure be said that the club accumulated a "large and illustrious roster". One and a half year later a comic, named after Magnus Carlsen , was released ( 1628: Magnus ). This comics also compares chess players (Magnus) to other (sporting) events. Magnus was ranked no. 1 on the chess world rank when both comics were released. Why is chess divided in an overall (with only one woman included) and basketball not? First of all, there is very little focus on women's basketball (as for most women's sport). This may be the same for chess, but at least here the physical strength advantage for men is no direct advantage. Thus a great woman chess player may play just as interesting chess as a man. Whereas women would typically have no chance if playing on a basketball team with men. But why are women then not represented better on the overall chess ranking? This is explained and may be another reason it is included. In the Chess (women) panel it says: "For a long time, sexism, a lack of role models, and institutional hostility largely kept women from pursuing serious chess careers. With the expansion of women's tournaments and prizes starting in the 1970s, this has begun to change". So now at least one woman has shown that her skills is enough to compete with the best men. With the long careers chess players usually have, then maternity leave can destroy a woman's chance at reaching the ultimate top. This could be the case for the number one woman who now has two children. The x-axis is divided in decades from 1950 until 2010. In the Basketball section the curves begins to appear right after 1950. For both chess panels there are curves further back than 1950 (with even a reference to a player from before 1940). For all three panels the paths continue up till present day (2014). In all cases there is no scale on the y-axis with the rating, thus it is difficult to find the absolute scale. It is also difficult to compare between the two chess panels. The scale on the two chess panels are, however, the same, as can be seen by comparing the curve of Judit Polgar on each chart. This curve is exactly the same, with the same elevation between the point where her curve enters the Chess panel up to the top point. This also means that any women player whose curve rises above this entry point (around 1989) should also be visible in the Chess chart. See below for inclusion criteria. In general not all possible players are included in these charts. For instance it is mentioned that Judit Polgar was the first woman ranked in the over all top 10. But only six players are shown on the over all chart around 2005, where she was ranked 8th. So some male players, better than her at that time, have not been included. This is a general trend for all three charts. From the Woman's panel below it is also clear that some of the other women would be ranked high enough to be visible on the upper chart as mentioned in the Scales section above. But still only Judit is shown there. 9 out of 12 of the women that are on the chart after 1989 would be visible if included in the overall chart. However, none of them could be called dominant when comparing to the best men in the same time period. And thus they are not included. Maybe the same could be said about Judth, but then she is included for scale, and because she is so good that she can compete with, and sometimes beat, the best. Some NBA players (like Tim Duncan , Charles Barkley , Oscar Robertson , Kobe Bryant , and Chris Paul ) have been left out of the chart in favor of players with lower career and yearly efficiency ratings. Similarly can be mentioned for instance the no. 1 ranked chess player Veselin Topalov from Bulgaria, who was ranked first both in 20062007 and in 2008-2010 for a total of less than two years. And there are likely several others ( see below ). An example of the above for Basketball would be the 2008–2009 season which was unique in that it was the only season in which more than one player posted an efficiency ratings of over 30.0 on the Player efficiency rating (see at the bottom of this section on Wikipedia). In that season three players broke this barrier: LeBron James (31.76), Dwyane Wade (30.46), and Chris Paul (30.04). LeBron is shown to top that season, But Dwayne is far below (thus the scale does not fit?) and Chris is not on the list at all (i.e. he was not deemed to be a dominant player). So is this Randall's subjective list of players that he has deemed to be "Dominant Players" and not a full list of the best ranked players during the time period? Of course it is his choice which players he put into the list, but missing players (when worse has been included earlier) can be explained if the missing players never were among the most dominant player over a length of time. It is not a list of the best players of all time, or of a single season, but a chart of the dominant players over a longer time period. If a player only has had a very short time where their careers peaked - they should not be included. Also if there most of the time where at least two others that were more dominant than they ever where - they should not be included. To tell if this explains all the excluded players mentioned/referenced above, that would take some investigation. An investigation we can assume Randall has taken upon himself before posting this comic. This of course will still make it his subjective list. For basketball any given player will at least have been the 2nd best (of those included) at some (longer) period of their career. And to become selected for a red curve, they need to be the best for at least five years - the first players curve is no. 1 less than five year, but he could have been no. 1 also before 1951. The same is valid for the Chess players (again the first players curve is red, but stops just as it enters the panel). Only exception is Judit Polgar. She is never better than 3rd of those selected. And she was never better than 8th in the world. So her inclusion is a mentioned probably only to compare her with the men. For the woman chess players there are the same criteria for red, except that Sonja Graf is not red although she is the only chess player on the list for more than a decade. Maybe you need to be better than someone else to become red? There are also included several women who never reaches 2nd place on the chart. Three of these reaches 3rd place and two only 4th. One of these, Anna Muzychuk, is still on the rise, so she might be on the chart, because she could possibly become first or second if she can continue to improve. The other, Sofia Polgar, is included to show that all three Polgar sisters are chess masters. None of the above can explain why former World Champion Chess Grandmaster Viswanathan Anand has not been included in the Chess Chart. Anand is one of only thirteen players in history to break the 2800 mark on the FIDE rating list and and still(as of 2020) has the eighth highest FIDE ranking at peak ever. He occupied the number one position in several rating lists between 2007 and 2011. The reason could possible be because Randall may be a huge fan of Magnus Carlsen, and thus biased against Anand - there is some evidence for this in 1287: Puzzle . In the title text of that comic it seems that Randall makes fun of Anand in a match against Magnus. The interpretation of the comic and its comment, however, appear to be a double-edged matter of debate. However, since the release of 1628: Magnus , named after Magnus, there can be no doubt that Randall is a fan of Magnus. Anand can for instance be found in the Chessmetrics devised by statistician Jeff Sonas . In the graph from 1995-2005 of Sonas famous research from 2005, Anand becomes the best during 2004. It can, however, also be seen that Randall does not agree with Sonas - this is very clear in this graph from 1940-1960 . Here Mikhail Botvinnik clearly plays way better than Alexander Alekhine in 1946, where Alexander dies. This is not shown like this in the comic. Maybe the death of Alexander becomes the more interesting in the comic, if you believed he was the best at the time. Note that all nine (male) names listed in the comics chart between the lines at 1950 and 2000 are included in this graph from 1950-2000 . In this chart it is clear that Bobby Fischer was by far the best in the years before he disappeared. However, he was caught by Anatoly Karpov just before which is not shown in the comic. On the other hand, he seems to have reached a significant higher rating than Kasparov ever did, which is also not the case in the comic. Chess players Vladimir Kramnik and Levon Aronian , who have faced each other on multiple occasions in the 2010s, are shown as having their career paths entwined. It is a general trend observed every time two players paths cross each other more than once. The one on top the first time, will be below the second time and so forth. It is just more clear with these two than anywhere else. In two cases these crossing path occurs with so long time between the first appearance, that the names is written twice on the path. In the Chess panel it is Mikhail Tal and Boris Spassky and for the Chess (women) panel it is Pia Cramling and Xie Jun . This can make it difficult to get an overview of how few chess players there are compared to basketball players. Dominant players over time [Below this heading there are three panels with charts showing different players career paths - that is their rating a function of the year. Most of the paths are grey, but some are red (there will be a note for these). Some parts of several paths are dashed. Somewhere on each path the players name will be written curving along so it follows the path. Several places an event or some information is noted and points to a given time on the path. If it is not clear where it belongs an arrow will point to the correct place. Each chart has a heading and for the two last charts there is an explanation. There is no scale on the y-axis (rating) but the x-axis (time) has the years given in ten years interval. A thin line indicates these decades. The years are all written at the top, except the first for the first chart, which is written below, and this year is missing in the bottom chart.] [Below the transcript for each chart will follow this order: Heading/sub heading, explanation, time scale, player names with any information for this player, in the order their name appear on the time scale.] [Basketball chart:] Basketball (NBA/ABA) Player Efficiency Rating 1950 1960 1970 1980 1990 2000 2010 [Red] George Mikan [Red] Bob Pettit Neal Johnston [Neil misspelled.] Elgin Baylor [Red] Wilt Chamberlain Becomes the first and so far only player to score 100 points in a game Jerry West The Guy in the NBA logo [Red] Kareem Abdul Jabbar [Missing hyphen between the two last names.] Airplane Bob Mcadoo Julius Irving [Erving misspelled.] Moses Malone Magic Johnson HIV announcement [A part of the path is dashed after this.] [Red] Michael Jordan Baseball career [A part of the path is dashed after this.] Space Jam Second retirement [A part of the path is dashed after this.] Larry Bird Karl Malone David Robinson [Red] Shaquille O'Neal Kevin Gariett [Red] LeBron James The Decision Dwyane Wade Kevin Durant [Chess chart.] Chess Elo Rating The modern Elo rating system dates back to about 1970. Computer analysis (like Kenneth Regan's) lets us rate historical players, but this has only been done rigorously for a few tournaments. Dashed lines are rough estimates only. [All paths are dashed up until the late nineteen sixties:] 1950 1960 1970 1980 1990 2000 2010 [The first player has no path, as his time was before 1940. An arrow points toward the left to these earlier times:] José Capablanca Terrifying chess God [Red] Alexander Alekhine [His path ends in a starburst.] [Red] Mikhail Botvinnik Tigran Petrosian David Bronstein Mikhail Tal Mikhail Tal [his name is written twice on the path, the second time above Boris Spassky when their paths intertwine.] [Red] Bobby Fischer Vanished… [Text under a starburst.] Reappeared then vanished again. He had problems. [Text under two starbursts connected with a path. This appears much later than the first starburst.] Boris Spassky Boris Spassky [his name is written twice on the path, the second time below Mikhail Tal when their paths intertwine.] Victor Korchnoi [Red] Anatoly Karpov [Red] Garry Kasparov Loses to Deep Blue Judit Polgar (See below) [The text is written beneath her name.] Vladimir Kramnik Levon Aronian [Red] Magnus Carlsen [Chess (women) chart:] Chess (women) Elo Rating For a long time, sexism, a lack of role models, and institutional hostility largely kept women from pursuing serious chess careers. With the expansion of women's tournaments and prizes starting in the 1970s, this has begun to change. [All paths are dashed up until the late nineteen sixties.] 1960 1970 1980 1990 2000 2010 [Red] Vera Menchik Died in a missile attack on London [next to a starburst.] Sonja Graf Rating particularly uncertain Olga Rubtsova Elisaveta Bykova Kira Zvorykina Kira Zvorykina (born 1919) continued playing in tournaments into the 21st century [Text above Elisvetas path, no arrows.] Zvorykina [Written on top of the path when her path reappears much later.] Alexandra Nicolau [Red] Nona Gaprindashvili Alla Kushnir [Red] Maia Chiburdanidze Pia Cramling Pia Cramling [her name is written twice on the path, the second time below the path of Xie Jun after their paths have intertwined.] Xie Jun Xie Jun [her name is written twice on the path, the second time above the path of Pia Cramling after their paths have intertwined.] Susan Polgar Sofia Polgar [Red] Judit Polgar Sisters [The three Polgars are linked by a thin dashed line, snaking between their names.] Wins a game against Kasparov, making her the first woman to beat the world #1 Becomes first woman to rank in the overall top 10 Antoaneta Stefanova Anna Muzychuk Koneru Humpy [In western style the name should be Humpy Koneru, but the comics version is the native form.] Hou Yifan

Timeghost

Timeghost

https://www.xkcd.com/1393

https://www.explainxkcd.com/wiki/index.php/1393:_Timeghost

[Cueball and Megan are approached by a floating ghost] Timeghost: ...ooOOOOOOOOooo... Tiiiime is passiiiing! Megan: Ugh. Timeghost. Cueball: Huh? Megan: Here come the factoids. [Timeghost floats around.] Timeghost: Forrest Gump came out closer to the Vietnam War than to the present daaay. Megan: Go away! Timeghost: The average new grand-parents are younger than Keanu Reeeeves! Cueball: That can't be right... [Megan clutches her head, possibly attempting to cover her ears.] Timeghost: Today's new parents were ten when Eminem got big. Daaaaaad muuuuusic. They remember Simpsons season 5 or 6 at the earliest . Megan: Argh! Cueball: How long has it been doing this? [Megan and Cueball looks up at the Timeghost as it delivers its most scary message.] Timeghost: The staaaaart of my haunting is now further away than your deaaaths! Megan: Will you sto- - WHAT!? Timeghost: ooOOOOOOOoo

Megan has been haunted by a Timeghost for some time. It is obviously not the first time the ghost arrives to let Megan know that "...ooOOOOOOOOooo... Tiiiime is passiiiing!" The ghost is dedicated to making people feel old by having them think about the passage of time. It is shown to reference time periods related to well-known people and events, such as famous actors and the release of movies and TV shows. Megan is just annoyed that it is back and wishes it to go away. But then when Cueball ask "How long has it been doing this?" the ghost suddenly predicts that Megan and Cueball will die in a shorter amount of time than the time that has passed since the ghost began its hauntings. This disturbs Megan who stops her complaining and asks " What!? " This is not the first time she has been haunted by the ghost but it has probably not been that long, so this is a very scary thought to her (and Cueball). We do, however, not know how long the ghost has been haunting Megan. Also the "staaaaart of my haunting" may refer to the first time the ghost haunted anyone, not just Megan. This could be a long time ago and thus be true for anyone it meets today. Or it could mean since the start of this particular manifestation, meaning their deaths are imminent! It is also possible Timeghost is being deliberately ambiguous in an effort to frighten them even more. This is of course only scary if you believe the ghost can predict the future, which is not what it has been doing so far. There is no example in the comic where it makes a prediction that we know is accurate - only comparing time spans we can look up - see below. But one thing about the prediction is true - they will eventually die . And this is the scary part about realizing how old you are and that you are quickly getting older: You will die, and "soon" (for some value thereof). The comic seems to be using "factoid" to mean a small fact. " Factoid " can also mean a "questionable or spurious statement presented as a fact", but this does not seem to be intended usage here. In this instance, some of the factoids are easily verifiable, while others are reasonable assumptions based on the number of years passed since the individual events. Several sources advocate the use of the word "factlet" to express a brief interesting fact, while using the word "factoid" for unverifiable or untrue statements passed as fact. While factoids tend only to have mostly only entertainment value, the last fact from the ghost is a prediction of the future (Megan and Cueball's death) which is actually of some practical value if it can be trusted. "Timeghost" might be a literal interpretation of Zeitgeist , which is a German term for "spirit of time" and refers to the school of thought that influences or dominates the art and culture of a time period. All the events and people mentioned in this comic may be considered influences on present day art and culture. In the title text Megan calls Ghostbusters (from the 1984 movie) to help get rid of the Timeghost. This of course makes the ghost state that "people born years after that movie came out are having a second chiiiild right now" making her feel old once more. Randall has covered making people feel old several times in 647: Scary , 891: Movie Ages , 973: MTV Generation (in which White Hat utters Cueball's "That can't be right" line), and 1477: Star Wars . Also see the blag post Odd Temporal Milestones . This is, however, so far the only one that makes a prediction of anyone's death. A similar ghost with a much different agenda was seen in 1108: Cautionary Ghost . Similarly annoying fact(oids) were given in 1272: Shadowfacts . Timeline [Cueball and Megan are approached by a floating ghost] Timeghost: ...ooOOOOOOOOooo... Tiiiime is passiiiing! Megan: Ugh. Timeghost. Cueball: Huh? Megan: Here come the factoids. [Timeghost floats around.] Timeghost: Forrest Gump came out closer to the Vietnam War than to the present daaay. Megan: Go away! Timeghost: The average new grand-parents are younger than Keanu Reeeeves! Cueball: That can't be right... [Megan clutches her head, possibly attempting to cover her ears.] Timeghost: Today's new parents were ten when Eminem got big. Daaaaaad muuuuusic. They remember Simpsons season 5 or 6 at the earliest . Megan: Argh! Cueball: How long has it been doing this? [Megan and Cueball looks up at the Timeghost as it delivers its most scary message.] Timeghost: The staaaaart of my haunting is now further away than your deaaaths! Megan: Will you sto- - WHAT!? Timeghost: ooOOOOOOOoo

Superm*n

Superm*n

https://www.xkcd.com/1394

https://www.explainxkcd.com/wiki/index.php/1394:_Superm*n

[Cueball is reaching for an item on a high shelf. Superman is rushing towards him.] Superman: I'll get it! I'm 5 inches taller and 7% stronger than the average man! [Caption below the panel:] The new supermoon-inspired Superman reboot

By depicting how unimpressive the superhero Superman would be if his increase in powers, when compared to humans, were the same as the moon's increase in apparent size during a supermoon , Randall points that the use of the term supermoon is an exaggeration. This comic was released two days after such a supermoon and there was a hype in 2014 because there were three supermoons in a row as NASA said. A supermoon is an informal astronomical event where a full moon occurs when it is closest to earth, causing the moon to appear 10% brighter and about 7% larger than the average full moon appears. This is due to the apsidal precession of moon's elliptic orbit which has an orbital eccentricity of about 0.0549. The conditions for a supermoon happen once every 411 days, and the loose definition of the term means that the supermoon lasts for about two or three full moons. Returning to the not-so-Superman, the average American adult man is 69 inches tall, with a standard deviation of 2.9 inches. Not-so-Superman, at an assumed 74 inches (188 cm) tall, is within the 94th percentile - certainly a tall man, but by no means phenomenal. Basketball players, by way of example, are often more than 80 inches tall. "7% stronger" (most likely a reference to how the supermoon is 7% larger) is a bit harder to quantify, but it communicates "not actually impressive" to the reader all the same. For example, if an average man can lift 50 kg, the not-so-Superman would lift 53.5 kg. The comic's title makes use of an asterisk that is being used as a wildcard. When using search queries an asterisk represents one or more characters. Therefore, Superm*n can represent the strings "Superman" and "Supermoon". The title text refers makes this same comparison with Spider-Man . Spider-Man is capable of firing large amounts of webbing, can cling to surfaces with superhuman gripping abilities, and has a sixth sense, "spider sense", that warns him about impending danger. The title text describes trivially minimal versions of these powers, analogous to the trivial size and brightness difference between a "supermoon" and a normal full moon. This also shows a much more accurate depiction of an actual spider's abilities, where they can produce several inches of a thin web, not the unrealistic amounts depicted in use by Spider-Man. Supermoon is also referenced in panel 25 of 1052: Every Major's Terrible and shortly thereafter in 1080: Visual Field . In both cases displaying the same distaste for the formulation. Although not as clearly as here. Since then other comics have referred to the term, see this list . [Cueball is reaching for an item on a high shelf. Superman is rushing towards him.] Superman: I'll get it! I'm 5 inches taller and 7% stronger than the average man! [Caption below the panel:] The new supermoon-inspired Superman reboot

Power Cord

Power Cord

https://www.xkcd.com/1395

https://www.explainxkcd.com/wiki/index.php/1395:_Power_Cord

[Beret Guy enters to find Cueball on a chair typing on a laptop. Cueball's power cord is unplugged from the wall.] Cueball typing: Type type [Beret Guy picks up the power cord. Cueball continues typing.] Cueball typing: Type type [Beret Guy blows into the plug end of the cord. The laptop abruptly inflates and Cueball jerks back.] Beret Guy: PBBBBT Laptop: FOOMP [Beret Guy walks away, leaving Cueball climbing up his chair to retrieve his inflated laptop which is now floating away.]

In this comic, we see Beret Guy walking in from the left, as Cueball is sitting on a couch, typing on a laptop on his lap , with its power cord unplugged. Instead of connecting it to the wall socket , Beret Guy picks it up and blows air into the loose end of the cord, as if inflating a balloon — and the laptop inflates. It then floats away, making Cueball grab for it as Beret Guy casually walks away. (See an instance where Cueball inflates something in a similar unexpected way in 1798: Box Plot ). It is not possible to inflate a laptop like this [ citation needed ] , and (with rare exceptions ) it is not possible to inflate anything by blowing down a power cord. Beret Guy has previously demonstrated several supernatural abilities , for instance with power cords, such as in 1293: Job Interview . In general, human breath should not be buoyant enough to lift much in an atmosphere of ordinary air. The only chemical difference between dry air and dry exhaled breath is the conversion of oxygen (molecular weight = 32) to carbon dioxide (MW=44), not counting substances in such low concentrations that their effect on the average molecular weight of the air (MW=29) is negligible. A change of concentration of the CO 2 from 0.04% to about 4% is typical. This increases the average molecular weight. However, exhaled breath is also usually much more humid than air, increasing the concentration of water (MW=18) from a typical value of 1% to approximately 5%, which decreases the average molecular weight. The two changes approximately cancel each other. Because humans are warm-blooded, human breath is slightly warmer than the surrounding air, and therefore has slightly fewer molecules per unit volume. This is also true of hot air balloons, but they operate at much higher temperatures than human breath and are therefore able to obtain a greater amount of net buoyancy. There is a standard cartoon convention that inflating something with breath nonetheless makes it lighter than air. Also, given Beret Guy's many manifestations of inexplicable phenomena, it is not too far fetched to believe his body is, in fact, expelling some form of lighter-than-air gas, similar to the character Rigel on Farscape who could "fart helium". The title text involves some jokes on Unix systems. On Unix, everything is a file ; even most of the hardware can be referenced by a (virtual) file. These virtual files usually are in /dev or another virtual filesystem like /sys or /proc. While /dev/input really exists and points to the input system (mice, keyboards, gamepads, etc.), /dev/inside doesn't. gzip is a common tool to compress files. The first joke is to compress the air inside the laptop (with the command gzip /dev/inside ) in order to deflate the laptop back to normal size. It is a pun with the literal meaning of "deflate", which is also the DEFLATE algorithm used by gzip (compressing files is also called "deflating"). Another joke is " piping ", the act of using the output of one operation as the input to another. As the output of the gzip command would be compressed air, a physical pipe could be used to direct the air somewhere useful. The output of a command can also be redirected to a file. Since the hardware is a file, the suggestion is to direct the air to /dev/input (which, in this case, means the keyboard, but would actually be a directory on real system, which can't normally be piped into) to clean it, similar to "compressed air" dusting cans. The complete command would be gzip /dev/inside | /dev/input . As this might cause a spray of unpleasant detritus (compare 237: Keyboards are Disgusting ), the reader is advised to avert their eyes. [Beret Guy enters to find Cueball on a chair typing on a laptop. Cueball's power cord is unplugged from the wall.] Cueball typing: Type type [Beret Guy picks up the power cord. Cueball continues typing.] Cueball typing: Type type [Beret Guy blows into the plug end of the cord. The laptop abruptly inflates and Cueball jerks back.] Beret Guy: PBBBBT Laptop: FOOMP [Beret Guy walks away, leaving Cueball climbing up his chair to retrieve his inflated laptop which is now floating away.]

Actors

Actors

https://www.xkcd.com/1396

https://www.explainxkcd.com/wiki/index.php/1396:_Actors

[Caption above the Panel:] Who are today's 10 hottest actors? [Cueball is holding a clipboard, taking notes, while Megan aims an infrared thermometer off screen.] Megan: 81.5, but I think it got part of his shirt. HEY JUSTIN — HOLD STILL! [Caption below the Panel:] We grab an infrared thermometer and find out!

This comic plays on different meanings of the word "hottest". In the opening question, "Who are today's 10 hottest actors?" the word "hottest" would typically refer to an actor's popularity, success, demand, or attractiveness. Cueball and Megan interpret the word "hottest" as asking them to list the 10 actors who have the highest surface temperature, and we see them measuring "Justin's" (possibly referring to Long , Theroux , Bieber or Timberlake or any of the several other Justin s in show business [1] ) surface temperature using an infrared thermometer (the thermometer typically has a laser pointer to know the approximate location where the radiometric temperature comes from). The measured temperature of 81.5 is presumably reported in degrees Fahrenheit , corresponding to 27.5 °C . This temperature is below the average human internal body temperature of 98.6 °F /37 °C as skin is cooler; Megan also believes that another object (Justin's shirt) was also measured within the infrared thermometer field of view, lowering the reported measurement. With such a measurement of hotness , the hottest actor on any given day would probably be whoever is exercising, sick with a fever, or whoever has been outside in the sun the longest and/or has been sunburned, since this typically causes skin to be hot. Or, an animal actor, of a species with a higher body temperature than humans. ( Category:Films about birds ) Randall here excludes the fact that accurately deriving surface temperature from bright (radiance) temperature requires knowing the emissivity of the object. Since not all objects radiate with the same efficiency, two objects with the same surface temperature will emit different thermal radiance, but if emissivity is not taken into account they will report different surface temperatures. The title-text references the temperatures of Hollywood's rising stars, this time interpreting stars as actual stars, not famous people. In this case, the star ξ Persei in the Perseus constellation (which is located in, and responsible for the fluorescence of, an object called the California Nebula ), one of the hottest stars (35,000 kelvins , Sun : 5,800 K) visible to the naked eye. The star also has similar declination (+35° 47′) as the latitude of Hollywood (34° N) so it is literally rising there every night. Comic 1111: Premiere is another comic based on "star" puns. [Caption above the Panel:] Who are today's 10 hottest actors? [Cueball is holding a clipboard, taking notes, while Megan aims an infrared thermometer off screen.] Megan: 81.5, but I think it got part of his shirt. HEY JUSTIN — HOLD STILL! [Caption below the Panel:] We grab an infrared thermometer and find out!

Luke

Luke

https://www.xkcd.com/1397

https://www.explainxkcd.com/wiki/index.php/1397:_Luke

[Darth Vader is holding up what appears to be the handle of a powered-down lightsaber looking down at it while talking to Luke Skywalker, drawn with thin hair hanging down his forehead.] Darth Vader: I see you have constructed a new lightsaber. Luke Skywalker: ...Yes. Luke Skywalker: That is definitely what I did. [Caption below the panel:] Vader finds Luke's Fleshlight.

This comic takes place in a scene from the third theatrically-released Star Wars movie, Return of the Jedi , wherein Darth Vader confronts his son, Luke Skywalker , who had recently surrendered to Imperial soldiers. In the movie Vader notes that Luke Skywalker has constructed a new lightsaber following the loss of his original during their duel on Cloud City , Luke Skywalker's original lightsaber actually having been Anakin Skywalker's second lightsaber, Anakin who later turned into Darth Vader. In this comic, however, Darth Vader has accidentally discovered his son's fleshlight (a male sex toy designed to imitate one of various orifices, most commonly a vagina), which he apparently brought with him on the attack on the Forest Moon of Endor . From a certain point of view , a fleshlight could be mistaken for the handle of a lightsaber, without the blade extended. Like many teenagers, Luke Skywalker is attempting to hide evidence of his sexual activity from a parent. References to fleshlights are a recurring theme in xkcd. The title text refers to the fact that if Darth Vader turned the fleshlight on, instead of creating a blade of pure plasma or energy suspended in a force containment field the device would simply vibrate, revealing it for what it really is. Randall is also punning on "being turned on" as slang for being sexually aroused. In a later comic another version of this scene is displayed in 1433: Lightsaber . This time not so embarrassing for Luke, but much more dangerous. In that comic Luke should really have said "Don't turn it on". In 1637: Salt Mine , Ponytail makes a very similar remark to the one that Luke makes here. [Darth Vader is holding up what appears to be the handle of a powered-down lightsaber looking down at it while talking to Luke Skywalker, drawn with thin hair hanging down his forehead.] Darth Vader: I see you have constructed a new lightsaber. Luke Skywalker: ...Yes. Luke Skywalker: That is definitely what I did. [Caption below the panel:] Vader finds Luke's Fleshlight.

Snake Facts

Snake Facts

https://www.xkcd.com/1398

https://www.explainxkcd.com/wiki/index.php/1398:_Snake_Facts

Snake Facts: Snake venom evolved from saliva, which means that it all started with a snake whose mouth was sliiiightly more gross than usual. [Picture of a snake below the text above.] Snake: Hi guys! Off-panel voice: Eww, it's Frank. [Map of South America with gray shade in the form of a snake. Text to the left of it.] The world's longest snake is found in Brazil, Peru, and Chile. It is believed to be over 60 years old. [Picture of a snake skeleton between the first and the second of the lines below.] If you laid all the bones in a snake end-to-end, you would have a snake Given the habitat listed for the second factoid, it is likely the comic is referring to the Green Anaconda ( Eunectes murinus ) .

This is the first comic using Facts in the title, but only the second to use a fact that is not a Fun fact . The comic lists a few factoids about snakes, ranging from the mildly informative to the strictly tongue-in-cheek . The first factoid references the hypothesis that snake venom was an evolutionary development of saliva that, over time, gradually became more toxic as snakes with saliva that was able to assist in subduing their prey possessed an evolutionary advantage. It then posits that the evolutionary branch that developed into venomous snakes began with a snake whose mutation gave him a mouth that was 'slightly more gross than usual', probably in reference to bad breath . Additionally, the comic illustration accompanying the second factoid colors in a ' habitat range' on a map of South America that is snake-shaped, implying that when it states 'The longest snake is found in Brazil , Peru , and Chile ' that this snake is so long that it literally stretches from Brazil, across part of Peru, into Chile, and that the 'habitat' shaded on the map is, in fact, this mammoth snake's silhouette . The age, length and location of the snake are so exaggerated that they are obviously untrue, but may be a reference to the green anaconda , one of the world's largest snakes, which inhabits this region. The final factoid is entirely tongue-in-cheek. Many factoids come in the form "If you laid all the X end to end, Y would occur" (e.g. "If you laid all the veins and arteries in the human body end-to-end, they would stretch 60,000 miles"). The Y portion of the factoid is supposed to be surprising; therefore, it is ironic that the factoid in the comic, "If you laid all the bones in a snake end to end, you would have a snake.", is obvious and not at all exciting. Clearly, you would not have an entire snake, literally, but you would have a skeleton that was recognizably that of a snake and could reasonably be referred to as 'a snake'. A common example that pokes fun at this format is, "If you laid every elephant from end to end between the Earth and the Moon, then you'd have a lot of dead elephants." The title text presents the amusing idea that 'snakes' as we know them are not, in fact, a suborder of reptiles but are instead human digestive tracts that, rather than being a system of organs, are creatures capable of escaping from their 'host' human and living independently. The idea seems to follow from the superficial resemblance between snakes and the human digestive tract as long, roughly tubular collections of animal matter, which can process the food entering the top end, and get rid of the waste through the other end. Randall had previously posted an incorrect map , that included the snake's habitat in Bolivia instead of Peru. Snake Facts: Snake venom evolved from saliva, which means that it all started with a snake whose mouth was sliiiightly more gross than usual. [Picture of a snake below the text above.] Snake: Hi guys! Off-panel voice: Eww, it's Frank. [Map of South America with gray shade in the form of a snake. Text to the left of it.] The world's longest snake is found in Brazil, Peru, and Chile. It is believed to be over 60 years old. [Picture of a snake skeleton between the first and the second of the lines below.] If you laid all the bones in a snake end-to-end, you would have a snake Given the habitat listed for the second factoid, it is likely the comic is referring to the Green Anaconda ( Eunectes murinus ) .

Chaos

Chaos

https://www.xkcd.com/1399

https://www.explainxkcd.com/wiki/index.php/1399:_Chaos

[Cueball is staring at a whiteboard covered with equations and graphs.] Cueball: For two decades, I've studied phase space, nonlinear equations, and strange attractors. [Cueball keeps staring at a whiteboard covered with equations and graphs for two more panels before in the third panel he exclaims:] Cueball: And there is nothing in here about dinosaurs escaping.

This comic pokes fun at the 1993 film Jurassic Park , which features a theme park filled with cloned dinosaurs. In the film, chaos ensues when all the dinosaurs escape and begin terrorizing their creators. The list of chaos topics, phase space , nonlinear equations , and strange attractors , comes directly from the movie, in which Dr. Ian Malcolm (portrayed by Jeff Goldblum), a mathematician and chaos theorist brought in to inspect the park prior to its grand opening, suggests that the dinosaurs' escaping could have been predicted based on mathematical chaos models. Cueball explains that although he has also studied chaos theory, he has never seen where chaos models predict that dinosaurs would escape. Cueball's confusion highlights the contrast between the mathematical definition of chaos – shown in the graphs on the whiteboard – and its common meaning – a state of utter confusion or disorder (as illustrated in the film). The whiteboard shows a bifurcation diagram of the logistic map (one of the simplest examples of the mathematical concept of chaos, also featured in what-if 105 ) and a dragon curve , which appeared on the section title pages of the novel Jurassic Park , upon which the film was based. The title text references the scene in Jurassic Park in which Goldblum, as Malcolm, while making small talk with Drs. Alan Grant (portrayed by Sam Neill) and Ellie Sattler (portrayed by Laura Dern) during the helicopter ride to the park, responds to a remark with an odd-sounding laugh . The laugh has gained minor Internet notoriety after being used as the central sample in at least one remix . The comic may be timely, as a remastered 3-D version of the film was released in April 2013, and the fourth installment (and the first of a new planned trilogy) of the Jurassic Park film series, Jurassic World , was released in June 2015. [Cueball is staring at a whiteboard covered with equations and graphs.] Cueball: For two decades, I've studied phase space, nonlinear equations, and strange attractors. [Cueball keeps staring at a whiteboard covered with equations and graphs for two more panels before in the third panel he exclaims:] Cueball: And there is nothing in here about dinosaurs escaping.

D.B. Cooper

D.B. Cooper

https://www.xkcd.com/1400

https://www.explainxkcd.com/wiki/index.php/1400:_D.B._Cooper

[Cueball is using a baton to point towards a projector.] D.B. Cooper ("Dan Cooper") Hijacked a plane in the 1970s. On landing, demanded money and parachutes. Jumped from plane mid-flight and was ne ver found. Vanished mysteriously with large amount of money Real age/name unknown Ambiguous, possibly affected speaking style ("negotiable American currency") Fate unknown [Cueball has his palm out.] Tommy Wiseau ("Johnny") Wrote, directed, and starred in The Room , a film widely hailed as "The Citizen Kane of b ad movies." Appeared mysteriously with large amount of money Colleague says he's much older than he claims. Ambiguous, possibly affected speaking style ("You are tearing me apart, Lisa!") Background unknown [Two images captioned "Cooper (FBI sketch)" and "Wiseau (Flickr photo by Al Pavangkanan)".] Offscreen voice: This is the dumbest theory I've ever heard. Cueball: But it explains everything!!

In 1971, a man referred to by the media as D. B. Cooper hijacked a Boeing 727 and escaped with $200,000 in ransom money (equivalent to $900,000 in 2003 or $1,250,000 in 2020). While the FBI maintains that Cooper was most likely killed when he parachuted from the plane, they have never determined his identity, and the investigation was called off in 2016, making it the United States' only unsolved plane hijacking. (This mystery was later referenced in 1501: Mysteries , and then again in 2452: Aviation Firsts .) In 2003, Tommy Wiseau released The Room , which is considered by many to be the worst film ever made, but has also earned a sizable number of fans who uphold it as a prime example of a film that is " so bad, it's good ". In the decade since, Wiseau has become something of an icon alongside his infamous movie, of which he was the producer, writer, director, and main star. Surprisingly little, however, is known about him. The comic refers to "The Room" as "...the ' Citizen Kane ' of bad movies." This is a comparison between what is widely considered the best film of all time, which was, coincidentally the first film produced by, written by, directed by, and starring Orson Welles and what is widely considered the worst film of all time, the first film produced by, written by, directed by, and starring Tommy Wiseau. This comic points to similarities between several details of Cooper and Wiseau's stories: The comic then compares an FBI sketch of Cooper with a photograph of Wiseau, apparently to claim that they have similar appearances. The only real similarity is that they're both wearing sunglasses. However, these are only a few cherry-picked aspects of their lives, and do not seriously suggest that they are the same person. For example, even if we assume that Wiseau was born in 1950, and that Cooper was only 35 (probably the youngest age which can be mistaken for mid-40s) in 1971, that leaves a 14-year gap between their ages. Likewise, Cooper was said to have either an American or Canadian accent, while Wiseau's bizarre accent is certainly not North American. While Cueball 's theory in this comic is clearly a joke on Randall 's part, given Randall's known distaste for conspiracy theories, this may also be making fun of people who base theories off of minor details while ignoring contradictory ones and bigger-picture questions. The question in the title text, for instance, notes that Cooper would have gone through a huge amount of effort just to produce a movie; a similar rhetorical device is often used against convoluted conspiracy theories, where one points out a vastly simpler way for the supposed conspirators to have accomplished their goals. The title text goes on to attribute such a weird motive for hijacking to the impression that "people are very strange these days," which is another quote from The Room . [Cueball is using a baton to point towards a projector.] D.B. Cooper ("Dan Cooper") Hijacked a plane in the 1970s. On landing, demanded money and parachutes. Jumped from plane mid-flight and was ne ver found. Vanished mysteriously with large amount of money Real age/name unknown Ambiguous, possibly affected speaking style ("negotiable American currency") Fate unknown [Cueball has his palm out.] Tommy Wiseau ("Johnny") Wrote, directed, and starred in The Room , a film widely hailed as "The Citizen Kane of b ad movies." Appeared mysteriously with large amount of money Colleague says he's much older than he claims. Ambiguous, possibly affected speaking style ("You are tearing me apart, Lisa!") Background unknown [Two images captioned "Cooper (FBI sketch)" and "Wiseau (Flickr photo by Al Pavangkanan)".] Offscreen voice: This is the dumbest theory I've ever heard. Cueball: But it explains everything!!