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Golden Hammer

Golden Hammer

https://www.xkcd.com/801

https://www.explainxkcd.com/wiki/index.php/801:_Golden_Hammer

[Black Hat is going through a door, an almost-empty bottle in his hand. A voice speaks to him from off panel.] Cueball: Seriously? This thing runs Java? It's single-purpose hardware! [Cueball is sitting at a computer, holding some device which is wired to a box, and pointing at the screen.] Cueball: I bet they actually hired someone to spend six months porting this JVM so they could write their 20 lines of code in a familiar setting. [Black Hat has a pair of bolt cutters in his hand that had been obscured in the first panel.] Black Hat: Well, you know what they say— When all you have is a pair of bolt cutters and a bottle of vodka, everything looks like the lock on the door of Wolf Blitzer's boathouse. Cueball: I'm glad you had a nice night.

Java is a programming language touted for its Portability™ (the ability for software to run on many different systems "write once, run everywhere"), which sometimes leads to it being used in systems where it really just shouldn't be used. Cueball laments that the hardware he's tinkering with, despite being used for a single purpose, has its firmware written in Java; since the microprocessor is unknown, it's quite possible the Java Virtual Machine (JVM) had to be ported over to the processor before the hardware designers could write firmware for it. Presumably, they considered this worthwhile to be able to write the control code in a language they're comfortable with, even though it probably would have been much simpler to just write the control code in whatever language they used to port the JVM in the first place. Black Hat explains that this is really an example of an age-old adage: "When all you have is a hammer, everything looks like a nail", also referred to as the " law of the instrument " or, as in the title, the "golden hammer". The hardware developers probably only knew Java, and when they thought about how to write firmware for their new device, "Java" was the only solution that occurred to them. Of course, instead of a hammer and a nail, Black Hat's analogy is about using bolt-cutters and vodka to get through the lock on Wolf Blitzer 's boathouse. Not-so-coincidentally, Black Hat is holding a pair of bolt-cutters and a bottle of vodka. The implication is that Black Hat did , in fact, break into Blitzer's boathouse the previous night, which is why he has just now entered the door at the start of the strip. The changes he makes to the adage implies that he believes vodka and boltcutters are designed specifically to be used on Blitzer's boathouse, an interpretation that fits Black Hat's warped and anarchic disposition. As he is carrying both of these items, it also implies that he has just used those instruments for exactly that purpose. Cueball however, being extremely jaded by the (mis)use of Java (or possibly unfazed as he knows Black Hat well), can only bring himself to tell that he's glad that Black Hat had a nice night. The title text implies that Black Hat had to break into a number of boathouses before he found Blitzer's, and that his boat did not survive the evening. The use of the phrase 'our night' allows us to infer that Black Hat may have been with Danish , his partner in crime. [Black Hat is going through a door, an almost-empty bottle in his hand. A voice speaks to him from off panel.] Cueball: Seriously? This thing runs Java? It's single-purpose hardware! [Cueball is sitting at a computer, holding some device which is wired to a box, and pointing at the screen.] Cueball: I bet they actually hired someone to spend six months porting this JVM so they could write their 20 lines of code in a familiar setting. [Black Hat has a pair of bolt cutters in his hand that had been obscured in the first panel.] Black Hat: Well, you know what they say— When all you have is a pair of bolt cutters and a bottle of vodka, everything looks like the lock on the door of Wolf Blitzer's boathouse. Cueball: I'm glad you had a nice night.

Online Communities 2

Online Communities 2

https://www.xkcd.com/802

https://www.explainxkcd.com/wiki/index.php/802:_Online_Communities_2

Map of Online Communities Size on map represents volume of Daily Social activity (posts, chat, etc). Based on data gathered over the Spring and Summer of 2010. [Two insets on the upper left-hand corner shows that this map is a tiny portion of the huge continent of Spoken Language, encompassing portions of the Internet, Email, and Cell Phones (SMS).] [The largest landmass on the map by far, which takes up nearly the entire northern half of the map is "Facebook" - with large states in the south-east of the country labeled 'Farmville' and 'Happy Farm'. There is a much smaller state to the west of these called 'Farm Town'. To the north of these states is a large swath of unremarkable land entitled 'Northern Wasteland of Unread Updates.' This is directly north of the large Dopamine Sea. A peninsula on the south-west, just below the Plains of Awkwardly Public Family Interactions, houses many tiny states, such as MySpace, Orkut, LinkedIn, Bebo, & Hi5. It is bordered on the south by Buzzword Bay, which contains several islands of varying sizes. Among these are YouTube and Twitter (the largest), which are separated by the Social Media Consultant Channel. To the south-east of Twitter, across the Sea of Protocol Confusion, is another, equally large island. Most of it is Skype, with the north having two largish states called AIM and Windows Live Messenger. On the south-west part of the island are two smaller states called GG and Yahoo Messenger. The Island of Skype is extremely close to, but separated by the Great Firewall (a dashed line), the large landmass of QQ. It's north shore is the Gulf of China and Grass Mud Horse Bay. Outside of these bays, over the Great Firewall are two islands called Craigslist and 2Channel. In the Dopamine Sea, off the southern shores of Farmville and Happy Farm, is MMO Isle. Its largest state is WoW, with Runescape, Lineage, Maple Story, Habbo, and the Mountains of Steam among its notable landmarks. To the southeast of the island is the Gulf of Lag, in which sits the CDC Games island, with Eve Online. To the east of Twitter is Troll Bay, with such islands as Reddit and Reddit, Digg, Stumbleupon, Delicio.us, and Wikipedia Talk Pages. To their south are the IRC isles, of which one is the tiny island of #xkcd. East of these islands, and north of Skype island, is the Sea of Memes. In this sea, to the north of Craigslist and 2Channel, is an archipelago of tiny islands. There is an inset, labeled 'Forums.' (See below.) To the southwest of Twitter island, in the Sea of Opinions, are the blog islands. These lie south of the islands in Buzzword Bay, as well. The northernmost islands in this group are centered around the Bay of Drama, on which can be found Diary Blogs, Gossip Blogs, and Livejournal. Gossip Blogs share an island with Political, Music, and Tech Blogs. To the north of this island is a smaller island called Photo Blogs. South of Diary Blogs, and off the southwest coast of Music blogs is a smaller island called Fandom Blogs. South of Tech Blogs, off of which sprouts the small peninsula of Business Blogs, is the Spamblog Straits. On the other side of the straits is a large island made up of Miscellaneous Blogs, with two states demarcated as Religious Blogs and Blog Blogs. Southwest of the Blog Islands is the Sea of Zero (0) Comments.] [An inset of a group of islands in the sea of memes located on the lower right corner of the map, labeled 'Forums'. The largest by far is 4chan and /b/. Also found here are D2JSP, JLA Frums, Fan Forum, Something Awful, and many smaller ones, too numerous to list here.] [The northeastern third of Gossip/Political/Tech Blogs island is another inset labeled 'Blogosphere (Core)'. This can be found on the lower left corner of the map. Two peninsulas in Political Blogs bookend the Bay of Flame -- these are Liberal Blogs and Conservative Blogs. Between them lie several tiny islands such as Politics Daily, CNN Politcal Ticker, and Mediaite. Off the coast of Liberal Blogs lies the island of NYTimes, off the coast of Conservative Blogs is Libertarian Isle. Between the two lies The Talk. The northern peninsula of Tech Blogs contains places such as Gizmodo, Engadget, Joystiq, and Kotaku.] [Text found between the two insets, which are directly below the main map.] ABOUT THIS MAP Communities rise and fall, and total membership numbers are no longer a good measure of a community's current size and health. This updated map uses size to represent total social activity in a community -- that is, how much talking, playing, sharing, or other socializing happens there. This meant some comparing of apples and oranges, but I did my best and tried to be consistent. Estimates are based on the numbers I could find, but involved a great deal of guesswork, statistical inference, random sampling, nonrandom sampling, a 20,000-cell spreadsheet, emailing, cajoling, tea-leaf reading, goat sacrifices, and gut instinct (i.e. making things up). Sources of data include Google and Bing, Wikipedia, Alexa, Big-Boards.com, StumbleUpon, Wordpress, Akismet, every website statistics page I could find, press releases, news articles, and individual site employees. Thanks in particular to folks at Last.fm, LiveJournal, Reddit, and the New York Times, as well as sysadmins at a number of sites who shared statistics on condition of anonymity.

This comic shows a map of internet communities where the size of each region roughly corresponds to its size, and its proximity to other regions indicates similarities. This is the successor of 256: Online Communities . It differs in that it is updated, and furthermore, instead of using the membership of whichever service to determine its size on the map, it uses its "daily social activity." The map actually has two super−maps intended to show the relative usage of types of communication: the online community map is surrounded by the much larger "countries" of E−Mail, SMS ("Instant Messaging") and "Cell Phones," which in turn are surrounded by the even huger "Spoken Language." It is unclear whether "Cell Phones" is intended to represent an independent region, or whether it is meant to be a sub-region of "Spoken Language." The ambiguity is exacerbated by the fact that cell phones are the primary medium of SMS, and are also used to access email and online communities. It's also unclear why other forms of communication, such as handwritten letters, are not included. At the title text Randall explains that, using his definition of "most activity per day," Farmville is actually the second most popular social-network farming game - the Chinese game Happy Farm was more popular at the time. This strikes many English-speaking xkcd readers as odd, because Farmville is much more famous, leading one to wonder how it could not be the most played. The phrase "browser-based social-networking-centered farming game" is an example of an overly-narrow superlative. The Facebook region deals with social networks, that is, websites oriented towards having people meet. Facebook is a social networking site that allows people to meet old real−life friends and make new friends that share similar interests. One of its most notable features is that a member can update a "status" or make normal posts about the happenings of the member's life, complete with pictures, other members "liking" these posts. The size of the Facebook region is not exaggerated; most websites seem to allow "liking" their content or allow/require logging in the website with a Facebook account. There even are cell phones with a "Facebook" button! While Facebook is the largest "country" of the Facebook Region, there are a lot of smaller "countries" that represent smaller social networks. MMOs (short form of "Massive Multiplayer Online Game") are online games where multiple people take the role of a character and play in a setting hosted by the game. Other notable regions include: The YouTube region refers to websites that are based on user-created content. YouTube is the definitive video website where people can upload videos with the purpose of public viewing, ranging from home movies through official music videos through Let's Plays of people playing video games to questionably-legal uploads of cartoons and films. Google had purchased YouTube. Many of the sites on the map are just references to viral videos at YouTube : The HTML5 swamp refers to YouTube's spotty support of HTML 5 (an update on HTML that is frequently touting its media capabilities, making HTML 5 a viable alternative to Flash). Of course, by the time the comic was written, HTML 5 was still in its infancy. The Music Video Bay refers to the amount of music videos (official or otherwise) are present in YouTube. Other counties of the YouTube region include: Snob Sound: The Isle of teenagers who just discovered macroeconomics is a joke about how teenagers tend to think that the world and the economy are a lot simpler than they actually are. Combined with the typical internet mindset, this leads to a lot of teenagers posting blogs and videos and comments on blogs and videos describing how idiotic the government and other red-tape-related adults are. The Snob Sound could refer to the large amount of people who look down on others in the surrounding websites (one example being an original artist looking down on people who draw mainly fan-art). The Iraq is a reference to Miss Teen USA 2007, in which Ms. Teen South Carolina, Lauren Katlin, said "I believe that our education like such as in South Africa and the Iraq everywhere like such as...the US should help the US and should help South Africa and should help the Iraq and the Asian countries so we are able to build up our future." The usage of "the Iraq" has became a meme. The Skype Region refers to different IM, or Instant Messaging services, that enable almost-real-time text chatting between multiple people. These often allow services like voice chat and even video calls. The Blogosphere region contains several general blog topics. Gossip Blogs: Each blog below focuses on gossip surrounding celebrities and other well-known persons. Liberal Blogs: Each blog below focuses on American political news with a "liberal" or "progressive" slant. These blogs tend to lean for the Democratic party. Bay of Flame: Conservative Blogs: Each blog below focuses on American political news with a "conservative" or Republican slant. Tech Blogs: Assorted: Forums are websites where one person post a topic to which other people can discuss. While the map has a zoomed in version, this article shall discuss the two bigger islands, first. In the zoomed-in map, there is the following: To the south and east is an archipelago of islands representing various regional and special-interest forums. Moving clockwise from 4chan island is An island contaning Map of Online Communities Size on map represents volume of Daily Social activity (posts, chat, etc). Based on data gathered over the Spring and Summer of 2010. [Two insets on the upper left-hand corner shows that this map is a tiny portion of the huge continent of Spoken Language, encompassing portions of the Internet, Email, and Cell Phones (SMS).] [The largest landmass on the map by far, which takes up nearly the entire northern half of the map is "Facebook" - with large states in the south-east of the country labeled 'Farmville' and 'Happy Farm'. There is a much smaller state to the west of these called 'Farm Town'. To the north of these states is a large swath of unremarkable land entitled 'Northern Wasteland of Unread Updates.' This is directly north of the large Dopamine Sea. A peninsula on the south-west, just below the Plains of Awkwardly Public Family Interactions, houses many tiny states, such as MySpace, Orkut, LinkedIn, Bebo, & Hi5. It is bordered on the south by Buzzword Bay, which contains several islands of varying sizes. Among these are YouTube and Twitter (the largest), which are separated by the Social Media Consultant Channel. To the south-east of Twitter, across the Sea of Protocol Confusion, is another, equally large island. Most of it is Skype, with the north having two largish states called AIM and Windows Live Messenger. On the south-west part of the island are two smaller states called GG and Yahoo Messenger. The Island of Skype is extremely close to, but separated by the Great Firewall (a dashed line), the large landmass of QQ. It's north shore is the Gulf of China and Grass Mud Horse Bay. Outside of these bays, over the Great Firewall are two islands called Craigslist and 2Channel. In the Dopamine Sea, off the southern shores of Farmville and Happy Farm, is MMO Isle. Its largest state is WoW, with Runescape, Lineage, Maple Story, Habbo, and the Mountains of Steam among its notable landmarks. To the southeast of the island is the Gulf of Lag, in which sits the CDC Games island, with Eve Online. To the east of Twitter is Troll Bay, with such islands as Reddit and Reddit, Digg, Stumbleupon, Delicio.us, and Wikipedia Talk Pages. To their south are the IRC isles, of which one is the tiny island of #xkcd. East of these islands, and north of Skype island, is the Sea of Memes. In this sea, to the north of Craigslist and 2Channel, is an archipelago of tiny islands. There is an inset, labeled 'Forums.' (See below.) To the southwest of Twitter island, in the Sea of Opinions, are the blog islands. These lie south of the islands in Buzzword Bay, as well. The northernmost islands in this group are centered around the Bay of Drama, on which can be found Diary Blogs, Gossip Blogs, and Livejournal. Gossip Blogs share an island with Political, Music, and Tech Blogs. To the north of this island is a smaller island called Photo Blogs. South of Diary Blogs, and off the southwest coast of Music blogs is a smaller island called Fandom Blogs. South of Tech Blogs, off of which sprouts the small peninsula of Business Blogs, is the Spamblog Straits. On the other side of the straits is a large island made up of Miscellaneous Blogs, with two states demarcated as Religious Blogs and Blog Blogs. Southwest of the Blog Islands is the Sea of Zero (0) Comments.] [An inset of a group of islands in the sea of memes located on the lower right corner of the map, labeled 'Forums'. The largest by far is 4chan and /b/. Also found here are D2JSP, JLA Frums, Fan Forum, Something Awful, and many smaller ones, too numerous to list here.] [The northeastern third of Gossip/Political/Tech Blogs island is another inset labeled 'Blogosphere (Core)'. This can be found on the lower left corner of the map. Two peninsulas in Political Blogs bookend the Bay of Flame -- these are Liberal Blogs and Conservative Blogs. Between them lie several tiny islands such as Politics Daily, CNN Politcal Ticker, and Mediaite. Off the coast of Liberal Blogs lies the island of NYTimes, off the coast of Conservative Blogs is Libertarian Isle. Between the two lies The Talk. The northern peninsula of Tech Blogs contains places such as Gizmodo, Engadget, Joystiq, and Kotaku.] [Text found between the two insets, which are directly below the main map.] ABOUT THIS MAP Communities rise and fall, and total membership numbers are no longer a good measure of a community's current size and health. This updated map uses size to represent total social activity in a community -- that is, how much talking, playing, sharing, or other socializing happens there. This meant some comparing of apples and oranges, but I did my best and tried to be consistent. Estimates are based on the numbers I could find, but involved a great deal of guesswork, statistical inference, random sampling, nonrandom sampling, a 20,000-cell spreadsheet, emailing, cajoling, tea-leaf reading, goat sacrifices, and gut instinct (i.e. making things up). Sources of data include Google and Bing, Wikipedia, Alexa, Big-Boards.com, StumbleUpon, Wordpress, Akismet, every website statistics page I could find, press releases, news articles, and individual site employees. Thanks in particular to folks at Last.fm, LiveJournal, Reddit, and the New York Times, as well as sysadmins at a number of sites who shared statistics on condition of anonymity.

Airfoil

Airfoil

https://www.xkcd.com/803

https://www.explainxkcd.com/wiki/index.php/803:_Airfoil

[In a frame-less picture to the left of the first panel there's a picture of a cross section of an airfoil (a plane wing), with a small black arrow pointing down on the wing from above and similar but larger arrow pointing up on the wing from below. Two lines beginning close to each other at the right respectively moves over and under the wing ending in arrow heads to the left. Just before and after the wing four small lines crossing the long arrows indicate approximately where the path of the lines stop being parallel. Above the drawing there is a caption. Below, in a speech bubble with an arrow pointing towards the next panel to the right, is the text that the teacher Miss Lenhart has just used to describe the drawing.] Handling a student who challenges your expertise with an insightful question: Miss Lenhart: So, kids, the air above the wing travels a longer distance, so it has to go faster to keep up. Faster air exerts less pressure, so the wing is lifted upward. [Miss Lenhart is shown standing while a student asks a question from off-panel.] Student (off-panel): But then why can planes fly upside down? [Miss Lenhart is pondering the question. Beat panel. Three long and curved arrows point out from the right frame of this panel, leading to each of the next three panels which are arranged vertically above each other, making the comic much deeper in this column than in the first two.] [In the top panel Miss Lenhart turns away from the students taking a hand to her chin. Overlaid on the top of the panel there is a small frame with a caption:] Right: Miss Lenhart: Wow, good question! Maybe this picture is simplified—or wrong! We should learn more. [In the middle panel Miss Lenhart stands as before. Overlaid on the top of the panel there is a small frame with a caption:] Wrong: Miss Lenhart: It's... complicated. Miss Lenhart: And we need to move on. [In the bottom panel Miss Lenhart visibly ball her hands in to fists and leans a little forward looking more down. Overlaid on the top of the panel there is a small frame with a caption:] Very wrong: Miss Lenhart: Santa Claus is your parents.

In the first panel a cross sectional drawing of a plane wing with the air moving around the wing showing a common teaching that an airfoil works because the air on top of the wing must travel faster to "keep up" with the air flowing across the bottom of the wing. The theory goes that, because the air on top of the wing is traveling faster, it must, as a result of Bernoulli's Principle , create an area of lower pressure above the wing; this causes lift (that is, the wing rises) because the higher pressure below the wing (symbolized by thick "up" arrow) pushes it up more than the low pressure above the wing. This is what the teacher Miss Lenhart is teaching as is revealed in the next panel. As it turns out, this is, to put it mildly, a vast oversimplification of how lift is truly created. Because then a student asks a particularly insightful question: Why, if the theory is true, can planes fly upside down? (If the simple airfoil theory is all that permits planes to stay up in the air, then flying upside down should reverse the pressures — pushing the plane down and causing it to crash.) Miss Lenhart thinks about it and clearly has no answer. The final set of panels posit three potential responses from Miss Lenhart, upon realizing her theory has been disproved: In the right one, Miss Lenhart realizes that perhaps the model she's been using to explain how an airfoil works is wrong (or, at a minimum, too simple). She is curious about it and suggests that this is an area for further exploration, and encourages additional study — in effect, rewarding the student for their insight. It seems that Miss Lenhart has taken the right course as it is shown later in 843: Misconceptions that she wished her students to generally avoid any common misconceptions . The title text also mentions that this is a common misconception and it is actually the first mentioned on list of common physics misconceptions on Wikipedia. In the wrong panel, Miss Lenhart, out of apparent embarrassment, avoids the question entirely, saying simply that it's complicated (and implying that such questions are outside the student's understanding). This way to continue a discussion where you wish to be right was much later used in 1731: Wrong . In the very wrong panel, not only does Miss Lenhart avoid answering the question, she attempts to distract them (or even punish them for asking such an insightful question - note that in this panel, Miss Lenhart has clenched her fists, suggesting anger) by telling the kids that Santa Claus isn't real but in fact that he is really their parents — something that would obviously distress children if they still believe in Santa Claus (in addition to distracting them from the question they've asked) and constitute harsh punishment for pointing out the teacher's ignorance. Of course most children old enough to be taught about the airflow around plane wings should be too old to believe in Santa. However, if she just wished to tell them a bit about planes she may have drawn this drawing even in very early grades making the Santa trick effective. The title text suggests additional reasons for re-thinking the common theory as to how airfoils create lift. It points out that (1) it is absurd to believe the air has to get across the airfoil's two sides in the same amount of time, and (2) the Wright brothers plane's wings were curved the same amount on both sides of the airfoil (the Wright Flyer's wings were concave, like an arch; and thus the curves were in the same direction, not reflected vertically), meaning that the distance that the air needs to travel to hug along each face of the wing is not the dispositive factor in creating lift. The strip is correct in noting that lift is a far more complicated process than the simple theory posited by Miss Lenhart. While the role of Bernoulli's Principle (that is, the difference in pressures) cannot be entirely discounted, the theory here is vastly too simple. As an initial matter, as suggested by the title text, there is no reason that the air on top of the wing should be compelled to "keep up" with the air on the bottom of the wing. Indeed, as demonstrated by the illustration below, in the time that the air below the wing travels across, the air on top of the wing has not only traveled the length of the entire top of the wing (a distance that may be farther than the distance under the wing, due to its shape), but often additional distance. Lift may be more usefully described as resulting from the deflection of air, although this explanation still does not explain how symmetrical wings will work (at least, absent effects caused by a change in the "angle of attack") nor how a plane may fly upside down. The Wikipedia article on lift provides a more detailed explanation. It in fact gives an explanation as to these two issues. It explains that with zero angle of attack, a symmetrical wing will not generate lift (though it is possible that other factors may generate other slight upward force, such as updrafts, the shape of the plane, and the angle of the engine relative to the wings. It also explains that an asymmetrical (or "cambered") wing may adjust angle of attack to compensate and still generate lift. Finally, to answer the question in the second panel in a general sense: most planes can't fly upside down for an extended period of time. While many aerobatic aircraft can sustain inverted flight with negative g forces, some others can achieve an inverted attitude only momentarily, and are experiencing positive g forces. Usually the reason for this is not the wings, which function perfectly fine upside down (albeit sometimes at lower efficiency), but the engines, which may not get fuel or oil under such conditions. It has to also be noted that if angle of attack were ignored, movable control surfaces would be useless. Almost any airplane can do a barrel roll or Aileron roll , given sufficient altitude (a Boeing 707 prototype once did this, and so did the Concorde in a demonstration). [In a frame-less picture to the left of the first panel there's a picture of a cross section of an airfoil (a plane wing), with a small black arrow pointing down on the wing from above and similar but larger arrow pointing up on the wing from below. Two lines beginning close to each other at the right respectively moves over and under the wing ending in arrow heads to the left. Just before and after the wing four small lines crossing the long arrows indicate approximately where the path of the lines stop being parallel. Above the drawing there is a caption. Below, in a speech bubble with an arrow pointing towards the next panel to the right, is the text that the teacher Miss Lenhart has just used to describe the drawing.] Handling a student who challenges your expertise with an insightful question: Miss Lenhart: So, kids, the air above the wing travels a longer distance, so it has to go faster to keep up. Faster air exerts less pressure, so the wing is lifted upward. [Miss Lenhart is shown standing while a student asks a question from off-panel.] Student (off-panel): But then why can planes fly upside down? [Miss Lenhart is pondering the question. Beat panel. Three long and curved arrows point out from the right frame of this panel, leading to each of the next three panels which are arranged vertically above each other, making the comic much deeper in this column than in the first two.] [In the top panel Miss Lenhart turns away from the students taking a hand to her chin. Overlaid on the top of the panel there is a small frame with a caption:] Right: Miss Lenhart: Wow, good question! Maybe this picture is simplified—or wrong! We should learn more. [In the middle panel Miss Lenhart stands as before. Overlaid on the top of the panel there is a small frame with a caption:] Wrong: Miss Lenhart: It's... complicated. Miss Lenhart: And we need to move on. [In the bottom panel Miss Lenhart visibly ball her hands in to fists and leans a little forward looking more down. Overlaid on the top of the panel there is a small frame with a caption:] Very wrong: Miss Lenhart: Santa Claus is your parents.

Pumpkin Carving

Pumpkin Carving

https://www.xkcd.com/804

https://www.explainxkcd.com/wiki/index.php/804:_Pumpkin_Carving

[Beret Guy, holding his arms out, stands behind a large orange pumpkin with the stem on top. It is sitting on a table. The pumpkin has been carved out as a lamp with large hole, and a lit candle is visible in the hole. The hole is in the shape of another carved out pumpkin. An interviewer speaks from off panel.] Interviewer (off-panel): So what did you— Beret Guy: I carved a pumpkin! Interviewer (off-panel): ... [Black Hat stands behind a large orange pumpkin which has not been carved out as a lamp, but the stem at the top has been removed and is placed tilting on the side of the pumpkin. It is sitting on a table. A gray box stands next to and partly in front of the pumpkin. On the end of the box there is a label at the top with unreadable text and below that some kind of drawing with a circle at the top. The interviewer speaks from off panel.] Interviewer (off-panel): Taking on teen vandals, I see. Black Hat: Heavens, no. My pumpkin simply has chest pains. In fact, I'll leave a note warning them not to smash it. Text on box: Nitro- glycerin Do Not Shake [Megan stands next to a large orange pumpkin with the stem on top. It is sitting on a table. The pumpkin has been carved out as a typical Halloween lamp. The bottom part of a white candle stick is visible in the mouth shaped hole. The hole is in the shape of a typical jack-o' lantern, with two slanted eyes, double slit nose and a smiling mouth with a tooth sticking out from both upper and lower lip, on either side of the candle stick.] Megan: My pumpkin's name is Harold. He just realized that all the time he used to spend daydreaming, he now spends worrying. He'll try to distract himself later with holiday traditions, but it won't work. [Cueball stands next to a two orange pumpkins with their stems on top, the left pumpkin is slightly larger than the right which is partly in front of the larger pumpkin. They have not been carved out even though a knife lies next to them to the right in front of Cueball on the table where they both stand. The interviewer speaks from off panel.]] Cueball: I carved and carved, and the next thing I knew I had two pumpkins. Interviewer (off-panel): I told you not to take the axiom of choice.

This comic is a reference to the American custom of making Jack-O'-Lanterns to set out on porches and front steps for the holiday of Halloween , which occurs on October 31. Typically they are made with pumpkins by emptying the inside leaving a hollow shell, carving a face or design on the side, then placing a light or candle inside. The Jack-O'-Lantern in the 3rd frame is the typical and standard design for a carved pumpkin. The comic is set up as a typical TV program where an off-screen interviewer asks four (very) different people what they have made out of their Halloween pumpkin. In the official transcript the interviewer that talks in three of the panels is called an Interlocutor: "a person who takes part in dialogue or conversation." In the first frame, Beret Guy , naturally, stays oddly on-topic by physically carving an image of a pumpkin in his pumpkin. This means his answer, "I carved a pumpkin," could apply to either the image or the medium of his artwork. In the second frame, Black Hat is shown with a container of nitroglycerin next to his pumpkin. Nitroglycerin is a highly explosive liquid that may explode violently with just a small bump. Black Hat has not carved a hole for his lamp, but it seems he has emptied the inside of the pumpkin as the stem at the top has been removed. This will make it possible to fill up the pumpkin with nitroglycerin. Teenagers are a rather impulsive and rebellious lot; as Halloween is a night with lots of meticulously erected decorations and more lax parental supervision, troublemaker teens see it as an enticing time to engage in rampant vandalism, including but not limited to pumpkin-smashing. Hence, the off-panel character presumes that Black Hat is setting up a trap to get back at these ne'er-do-wells. To top it off, Black Hat plans to put up a sign warning passers-by to not smash the pumpkin. This would only serve to tempt impulsive teenagers to disturb it, which is very likely what the sadistic and chaos-loving Classhole is hoping for. If he succeeds with his plan, with a completely hollowed out pumpkin of the shown size filled with nitroglycerin, it would seem likely that the resulting explosion would leave a largish crater, flatten wood-framed buildings nearby, shatter windows for blocks in all directions, and be more than sufficient to kill the vandal along with others in the surrounding area. This is clearly overkill for such a petty crime. [ citation needed ] Black Hat, rather unconvincingly, insists that his pumpkin is suffering from chest pains, and that the nitroglycerin is merely intended for medical treatment. While it is true that this chemical is used to treat angina (chest pain due to blocked arteries in the heart), nitroglycerin used for this purpose is dispensed in the form of small pills containing only trace amounts, and controlled by prescription. Also, pumpkins are fruits and do thus not contain nervous or circulatory systems of mammalian complexity [ citation needed ] ; even if they did, the process of pumpkin carving involves hollowing them out, making it a moot point. In the third frame, Megan is our typical emotional xkcd comic character. She is the only one out of the four who actually carved a typical jack-o'-lantern; however, she is projecting herself onto it, and has named it Harold. Her dialogue suggests it (or he) is suffering from typical holiday depression, with symptoms such as using a lot of time daydreaming, worrying, and trying to distract herself with holiday traditions, but she already knows that it won't work. Some have speculated that this is a possible reference to the classic meme Hide The Pain Harold , but this is highly unlikely; the meme only surfaced in 2011 , a year after the comic was published. In the fourth frame, Cueball is shown in front of two un-carved pumpkins exclaiming that this is the result of carving one pumpkin. He is referencing the Banach-Tarski paradox (which is made clear in the title text), a theorem which states that it is possible to split a three-dimensional ball, in this case a pumpkin, into a finite number of "pieces," and then reassemble these "pieces" into two distinct balls both identical to the original. This paradox has been proven for theoretical shapes, but requires infinitely complicated pieces which are impossible for anything made of physical atoms rather than mathematical points . The off-screen interviewer in that frame references the Axiom of Choice . This axiom is the foundation for many theorems (including the Banach–Tarski paradox) and is extremely influential to modern mathematics; however, it has been historically controversial precisely because it enables this kind of weirdness. It is called an "axiom" because it is a statement that is not meant to be proven or disproven—only accepted or rejected depending on the theoretical framework one wishes to work with. Rejecting the Axiom of Choice results in a perfectly coherent alternate form of set theory. Since the proof for the Banach–Tarski paradox relies on accepting the axiom of choice, the interviewer is suggesting Cueball's unexpected result would not have happened without using the axiom. The title text references a biblical story involving King Solomon . In the story, known as the Judgment of Solomon , two women were brought before him both claiming that a particular child was their own. Solomon tested the women by saying the only solution was to cut the baby in half and give each woman one of the halves, knowing only the real mother would fight to save her child's life even if the price was giving up the whole child to the other woman. The joke is that if Solomon had developed the Banach–Tarski theorem first, then he could have actually believed cutting the baby into pieces was a valid solution. In that scenario, he would have tried to make two whole children from the original and given one to each woman. However, since babies are not infinitely divisible, [ citation needed ] his attempt would have failed miserably and set back set theory for centuries due to the appearance that he has "proved" the theorem wrong. Note that the title text actually mentions attempts indicating that King Solomon killed several babies in this fashion. The axiom of choice and set theory was later referenced in 982: Set Theory and, much later, the axiom of choice was mentioned again in the title text of 1724: Proofs . This comic was released 20 days before Halloween in 2010, possibly to inspire people with some great ideas for their pumpkins. It has been known (particularly by Randall) that people copy his ideas, for instance this earlier post on xkcd based on 249: Chess Photo . Soon after he even made a comic, 254: Comic Fragment , that was supposed to be impossible to copy, which he mentioned himself later (see the explanation). [Beret Guy, holding his arms out, stands behind a large orange pumpkin with the stem on top. It is sitting on a table. The pumpkin has been carved out as a lamp with large hole, and a lit candle is visible in the hole. The hole is in the shape of another carved out pumpkin. An interviewer speaks from off panel.] Interviewer (off-panel): So what did you— Beret Guy: I carved a pumpkin! Interviewer (off-panel): ... [Black Hat stands behind a large orange pumpkin which has not been carved out as a lamp, but the stem at the top has been removed and is placed tilting on the side of the pumpkin. It is sitting on a table. A gray box stands next to and partly in front of the pumpkin. On the end of the box there is a label at the top with unreadable text and below that some kind of drawing with a circle at the top. The interviewer speaks from off panel.] Interviewer (off-panel): Taking on teen vandals, I see. Black Hat: Heavens, no. My pumpkin simply has chest pains. In fact, I'll leave a note warning them not to smash it. Text on box: Nitro- glycerin Do Not Shake [Megan stands next to a large orange pumpkin with the stem on top. It is sitting on a table. The pumpkin has been carved out as a typical Halloween lamp. The bottom part of a white candle stick is visible in the mouth shaped hole. The hole is in the shape of a typical jack-o' lantern, with two slanted eyes, double slit nose and a smiling mouth with a tooth sticking out from both upper and lower lip, on either side of the candle stick.] Megan: My pumpkin's name is Harold. He just realized that all the time he used to spend daydreaming, he now spends worrying. He'll try to distract himself later with holiday traditions, but it won't work. [Cueball stands next to a two orange pumpkins with their stems on top, the left pumpkin is slightly larger than the right which is partly in front of the larger pumpkin. They have not been carved out even though a knife lies next to them to the right in front of Cueball on the table where they both stand. The interviewer speaks from off panel.]] Cueball: I carved and carved, and the next thing I knew I had two pumpkins. Interviewer (off-panel): I told you not to take the axiom of choice.

Paradise City

Paradise City

https://www.xkcd.com/805

https://www.explainxkcd.com/wiki/index.php/805:_Paradise_City

[For five panels, Cueball sits on a box playing a guitar and sings.] Cueball: Take me down to the paradise city where the grass is green and the girls are pretty. Cueball: Take me down to the paradise village where the grasses burn as those cute girls pillage. Cueball: Take me down to the fire-charred counties where the law's restored by Canadian mounties. Cueball: Take me down to Orwellian regions where they retrain girls using cortical lesions. Cueball: Take me down to the paradise borough where the grass is labeled 'cause the girls are thorough. Cueball: Ohh, won't you please take me hooome...

" Paradise City " is a song by the hard rock band Guns N' Roses which appeared on their debut album Appetite for Destruction . It sings of the so-called Paradise City, an idyllic place to which the song's narrator longs to return. The location is contrasted with the depressing reality in which the persona is trapped, using for instance the image of a gas chamber. In the comic, Cueball can be seen singing different versions of the chorus. In each panel, the word "City" is substituted by another type of location and the rest of the verse is altered accordingly to keep the rhyme scheme (usually awkwardly because he has chosen difficult words to rhyme with). The sequence of stanzas describes the fate of Paradise City. It starts the original version drawing an idyllic picture. In a rather unexpected turn, however, the next stanza has the place pillaged and plundered. Chaos and anarchy reign, the once fresh and green meadows are now burned. Law and order are restored in the next verses and the other extreme starts to prevail: Paradise City has become a totalitarian dystopia . The fourth stanza refers to George Orwell's dystopian novel Nineteen Eighty-Four . The book shows a world in which mind control and omnipresent surveillance render individual thought and action impossible, and the fifth stanza shows a borough where every blade of grass has been labeled, taking the surveillance to an extreme. The concluding verses suggest that the totalitarian government has successfully brainwashed the former rebels and established an effective, yet sterile technocratic society. "Cortical lesions" in this panel could be a reference to the dystopian novel Uglies by Scott Westerfeld , which describes a society in which extreme plastic surgery is used to turn people "pretty". (SPOILER ALERT) It is later revealed in the book that this procedure is accompanied by a neurosurgical operation making the patient placid and obedient through a lobotomy . The development of the city in Cueball's song reveals that the term " Paradise " can be applied to very different and even oppositional scenarios. While the original song describes the city as a rural Eden, some might refute this conception as a bourgeois or agrarian romantic ideal. Others would fear that too much individual freedom might be dangerous and opt for security through control . Especially the picture of the last stanza is a common vision in dystopian literature (e.g. Brave New World ): Although the citizens of a future society entirely lack any personal choice or individual freedom, they deem themselves happy because education or thought control present this a necessity for a functioning society. In popular culture, the word "Paradise" is often used to describe a place of bliss and perfect harmony, as in the original religious sense of the term. It is however also frequently linked to the idea of living out one's deepest and darkest desires, therefore in some way to a place of sin . Considering the lifestyle of Guns N' Roses, it can be assumed that the "pretty girls" of the original song are not necessarily chaste. The most iconic part of Las Vegas is officially named "Paradise", although it is not entirely clear if Cueball is aware of the probable reference of the original song. The title text suggests that Paradise City is in fact a drug-induced state of ecstasy with strange and colourful hallucinations . [For five panels, Cueball sits on a box playing a guitar and sings.] Cueball: Take me down to the paradise city where the grass is green and the girls are pretty. Cueball: Take me down to the paradise village where the grasses burn as those cute girls pillage. Cueball: Take me down to the fire-charred counties where the law's restored by Canadian mounties. Cueball: Take me down to Orwellian regions where they retrain girls using cortical lesions. Cueball: Take me down to the paradise borough where the grass is labeled 'cause the girls are thorough. Cueball: Ohh, won't you please take me hooome...

Tech Support

Tech Support

https://www.xkcd.com/806

https://www.explainxkcd.com/wiki/index.php/806:_Tech_Support

[Cueball is on his cellphone, and holding up a small square piece of hardware with a foot in the other hand. Two wires go from the hardware down to the floor, where one is connected to a box on the floor with two black antennas, and then another wire goes out the other side of this, and both this and the second wire from the hardware Cueball is holding goes under his desk, on top of which is his open laptop.] Cueball: ...restart my computer? I know you have a script to follow, but the uplink light on the modem is going off every few hours. The problem is between your office and the modem. [Zoom in on Cueball's torso, still on the phone and with the hardware in hand.] Cueball: My computer has nothing to do with... OK, whatever, I "restarted my computer." Cueball: It's still down, and even if it comes back, it's going to die again in a few hours, because your— [Cueball on the phone has walked closer to his desk with the laptop, but holds down the hand with the hardware so it is below the panels frame.] Cueball: I don't have a start menu. This is a Haiku install, but that's not import— Cueball: Haiku? It's an experimental OS that I ... oh, never mind. [Cueball has paced away from his desk to the left so it is no longer in the panel. He has put the hardware down next to the box with antennas on the floor. Wires going off panel right toward the desk.] Cueball: I'm sorry, but this won't get fixed until I talk to an engineer. Can you look around for someone wearing cargo pants, maybe a subway map on their wall? [Hairy is the tech support person on the other end sitting in an office chair at a desk. A phone is hooked up on his table with two wires coming out. He is wearing a headset. He leans back in the chair and looks behind him to the right. Cueball talks to him over the phone indicated with a zigzag line.] Hairy: There's a chick two phones over with a stuffed penguin doll and a poster of some bearded dude with swords. Cueball (on the phone): Perfect. Can you put her on? Hairy: Sure. [The engineer, a woman with black hair in a ponytail, sits in an office chair at her desk typing on her lap top. She also has a headset. Behind her laptop sits a small penguin doll. Cueball talks to her over the phone indicated with zigzag lines.] Cueball (on the phone): Hey, so sorry to bother you, but my connection— Engineer: Yeah, I see it. Lingering problems from a server move. <type type> Engineer: Should be fixed now. Cueball (on the phone): Thank you so much. [Zoom in on the engineers torso. The back of the chair and the top of her laptop just inside the panel.] Engineer: No problem. Hey, in the future, if you're on any tech support call, you can say the code word "shibboleet" at any point and you'll be automatically transferred to someone who knows a minimum of two programming languages. [Zoom in on Cueball on the phone scratching his neck. The engineer talks to him over the phone indicated with zigzag lines.] Cueball: Seriously? Engineer (on the phone): Yup. It's a backdoor put in by the geeks who built these phone support systems back in the 1990's. Engineer (on the phone): Don't tell anyone. [The last panel is split in two sections. In the top part still with a zoom in on Cueball, he takes the phone down to hang up. Only this section is inside a frame. The frame is normal at the top and half way down to the left, but only a small way down on the right side. The bottom part of the frame connects these two normal parts but with a wavy line to indicate that this is the end of a dream. In the frame-less part of the panel below Cueball is sitting up in his bed, having lifted his head fro the pillow behind him to the left. He lifts him self up with one hand while the other takes the sheet down over his body. The last part it thus drawn outside the rest of the framed part of the comic.] Cueball: Oh my god, this is the greatest— Cueball: Wha— Cueball: ... Dammit.

Cueball runs into some problems with his network connection and contacts his Internet service provider's (ISP's) tech support for help. The customer service agent (represented by Hairy ) is not very helpful, giving clearly pre-scripted advice that has nothing to do with Cueball's problem. Cueball gives up and asks to speak to an engineer, i.e. someone more knowledgeable about the technology and suggest to Hairy what to look for. Noticing a woman with black ponytail who has the stuffed Tux penguin on her desk and a poster of a bearded dude with swords (a reference to Richard Stallman particularly as he stands in 345: 1337: Part 5 , and a reference to 225: Open Source ) he tells Cueball about her and Cueball recognizes the signs of a GNU / Linux geek and asks to talk to her. Hairy transfers him over to the engineer, who immediately recognizes the problem and fixes it. Then she tells him of a secret word (shibboleet - see below) which, if he speaks on the phone, will transfer him to a tech-savvy person able to help him, something installed already back in the 1990's by the geeks of that time. Cueball is elated but then at this point Cueball wakes up and unfortunately discovers the incident to be just a dream. Poor customer and technical support is a common complaint of many ISPs. Many ISPs outsource their support staff to foreign countries to reduce costs, and/or they delegate first-tier support to workers with little or no training. Typically, these workers are given general scripts that prompt the customer to try common troubleshooting steps, such as restarting the computer, without any specific knowledge of the customer's complaint. While these scripts may help resolve problems for the average customer, a representative using such a script is usually unprepared to assist someone who has a more advanced problem. Furthermore, these scripts generally assume that the problem is on the customer's end and do not acknowledge problems that occur within the ISP, such as server or line problems. Customers like Cueball in this comic often find it frustrating to deal with representatives reading from scripts. As Randall mentions in the title text, this frustration is magnified when the representative refuses to move on to the next step until the customer has performed the previous one, whether or not it necessary or helpful. In cases like this, it's often necessary to request an escalation to a higher "tier" of support, or to speak to a supervisor who presumably has more knowledge and/or influence, though even that can sometimes be a painful process. Thus, it is easy to see why Cueball would be elated to discover a way to automatically connect with the most helpful technical support representatives whenever he has a problem, and thus also why he get really disappointed when he realizes it was just a dream (dreams being a recurring theme in xkcd). Cueball is running Haiku , an open source operating system which is still in a state of active development, being in an alpha release at the publishing of the comic and in beta since 2018. While low-level tech support operators are given scripts which are predicated on the assumption that many computer problems are actually caused by the actions of clueless end users (as, in fact, they are), it's exceedingly unlikely most of these first-tier operators would have even heard of Haiku, not to mention that their scripts' assumptions would never apply to the sort of person who would be using an experimental OS as opposed to Windows , for instance. "Shibboleet" is a portmanteau of "shibboleth" and "leet". A " shibboleth " means any word, custom, or other signifier which is used by members of a group to recognize other members or those who are "in the know" about something. Its use originates in the Hebrew Bible, where the precise pronunciation of this word was used to distinguish Gileadites from Ephramites. Leet (based on the word "elite") refers to "leet-speak", a practice of character substitution and abbreviation common across the Internet (or "teh 1n73rn3t", as you would say in leet). Thus, "shibboleet" is a shibboleth used to identify someone whose computer-knowledge is "elite." Leet is again in leet written as 1337 so again a reference back to the 1337 comic series including the comic mentioned above with Stallman. Randall mentioned in the title text that this had happened to him recently, and is possibly the reason for this comic. [Cueball is on his cellphone, and holding up a small square piece of hardware with a foot in the other hand. Two wires go from the hardware down to the floor, where one is connected to a box on the floor with two black antennas, and then another wire goes out the other side of this, and both this and the second wire from the hardware Cueball is holding goes under his desk, on top of which is his open laptop.] Cueball: ...restart my computer? I know you have a script to follow, but the uplink light on the modem is going off every few hours. The problem is between your office and the modem. [Zoom in on Cueball's torso, still on the phone and with the hardware in hand.] Cueball: My computer has nothing to do with... OK, whatever, I "restarted my computer." Cueball: It's still down, and even if it comes back, it's going to die again in a few hours, because your— [Cueball on the phone has walked closer to his desk with the laptop, but holds down the hand with the hardware so it is below the panels frame.] Cueball: I don't have a start menu. This is a Haiku install, but that's not import— Cueball: Haiku? It's an experimental OS that I ... oh, never mind. [Cueball has paced away from his desk to the left so it is no longer in the panel. He has put the hardware down next to the box with antennas on the floor. Wires going off panel right toward the desk.] Cueball: I'm sorry, but this won't get fixed until I talk to an engineer. Can you look around for someone wearing cargo pants, maybe a subway map on their wall? [Hairy is the tech support person on the other end sitting in an office chair at a desk. A phone is hooked up on his table with two wires coming out. He is wearing a headset. He leans back in the chair and looks behind him to the right. Cueball talks to him over the phone indicated with a zigzag line.] Hairy: There's a chick two phones over with a stuffed penguin doll and a poster of some bearded dude with swords. Cueball (on the phone): Perfect. Can you put her on? Hairy: Sure. [The engineer, a woman with black hair in a ponytail, sits in an office chair at her desk typing on her lap top. She also has a headset. Behind her laptop sits a small penguin doll. Cueball talks to her over the phone indicated with zigzag lines.] Cueball (on the phone): Hey, so sorry to bother you, but my connection— Engineer: Yeah, I see it. Lingering problems from a server move. <type type> Engineer: Should be fixed now. Cueball (on the phone): Thank you so much. [Zoom in on the engineers torso. The back of the chair and the top of her laptop just inside the panel.] Engineer: No problem. Hey, in the future, if you're on any tech support call, you can say the code word "shibboleet" at any point and you'll be automatically transferred to someone who knows a minimum of two programming languages. [Zoom in on Cueball on the phone scratching his neck. The engineer talks to him over the phone indicated with zigzag lines.] Cueball: Seriously? Engineer (on the phone): Yup. It's a backdoor put in by the geeks who built these phone support systems back in the 1990's. Engineer (on the phone): Don't tell anyone. [The last panel is split in two sections. In the top part still with a zoom in on Cueball, he takes the phone down to hang up. Only this section is inside a frame. The frame is normal at the top and half way down to the left, but only a small way down on the right side. The bottom part of the frame connects these two normal parts but with a wavy line to indicate that this is the end of a dream. In the frame-less part of the panel below Cueball is sitting up in his bed, having lifted his head fro the pillow behind him to the left. He lifts him self up with one hand while the other takes the sheet down over his body. The last part it thus drawn outside the rest of the framed part of the comic.] Cueball: Oh my god, this is the greatest— Cueball: Wha— Cueball: ... Dammit.

Connected

Connected

https://www.xkcd.com/807

https://www.explainxkcd.com/wiki/index.php/807:_Connected

[Megan sits on a rock and Cueball sits on the grass.] Megan: Seriously? I like that song too! Megan: I bet no two people in the history of the world have ever been so connected ! [Caption below the frame:] I'm not sure why we romanticize "young love."

This comic criticizes our culture's tendency to romanticize young love (such as that portrayed in Romeo and Juliet and Titanic ). Although young lovers do often have intense feelings for their beloved, for many of them, like Megan here, it is an infatuation based on little substance (such as a similar taste in music) and the mercurial gales of teenagers’ minds rather than the real compatibility necessary for a long-term relationship. The title text broadens this criticism to all forms of romance. Randall appears to be stating that it is possible to love someone even if your relationship with that person doesn't conform to the impossibly high standards of "true love" that our culture so highly exalts . In fact, healthy relationships are typically not perfect and require work, change, and compromise rather than continual, effortless bliss. [Megan sits on a rock and Cueball sits on the grass.] Megan: Seriously? I like that song too! Megan: I bet no two people in the history of the world have ever been so connected ! [Caption below the frame:] I'm not sure why we romanticize "young love."

The Economic Argument

The Economic Argument

https://www.xkcd.com/808

https://www.explainxkcd.com/wiki/index.php/808:_The_Economic_Argument

[A three-column table. The headings are actually standing above the table.] Crazy phenomenon If it worked, companies would be using it to make a killing in... Are they? Remote Viewing Oil Prospecting Dowsing Auras Health Care Cost Reduction Homeopathy Remote Prayer Astrology Financial/Business Planning Tarot Crystal Energy Regular Energy Curses, Hexes The Military Relativity GPS Devices ✓ Quantum Electrodynamics Semiconductor Circuit Design ✓ Eventually, arguing that these things work means arguing that modern capitalism isn't that ruthlessly profit-focused.

The image shows fields of human life that would be greatly improved and/or allow certain people to make a lot of money if some crazy phenomena (mostly paranormal ) actually worked in reality or were testable and usable concepts. Crazy phenomena, in this case, means counter-intuitive things that go against common sense and which science often contradicts (though relativity and QM are a major part of physics, they are still counterintuitive and could be considered to sound crazy). As the comic tries to prove, if there were commercial use for it and proofs of it working, there will be high investment made in the technology to use and harness such concepts. So far only relativity and quantum electrodynamics have major evidence backing them. Specifically, the theory of relativity allows your Global Positioning System (GPS) device to synchronize with satellites a hundred miles in the air and show your current position. The design of modern circuit-boards and other electronic devices is influenced by quantum electrodynamics — smartphones or high capacity hard drives wouldn't be possible without this theory. The non-scientific/disproved concepts trying to pass as real and scientific are: The title text points out that many people still believe in non-scientific, unproven, and disproved phenomena; thus, it's possible to make a lot of money by selling those (claimed) phenomena to such people (although knowingly selling non-existent phenomena, while claiming that they work, would be fraud, and thus illegal). [A three-column table. The headings are actually standing above the table.] Crazy phenomenon If it worked, companies would be using it to make a killing in... Are they? Remote Viewing Oil Prospecting Dowsing Auras Health Care Cost Reduction Homeopathy Remote Prayer Astrology Financial/Business Planning Tarot Crystal Energy Regular Energy Curses, Hexes The Military Relativity GPS Devices ✓ Quantum Electrodynamics Semiconductor Circuit Design ✓ Eventually, arguing that these things work means arguing that modern capitalism isn't that ruthlessly profit-focused.

Los Alamos

Los Alamos

https://www.xkcd.com/809

https://www.explainxkcd.com/wiki/index.php/809:_Los_Alamos

[Cueball raising a hand points to Steve (see later) drawn as another shorter Cueball-like guy, and behind Cueball stand Hairy also looking at Steve. Partly behind Steve's head is a piece of paper on the wall with a circle around a central dot and four arrows pointing in towards the circle from each corner of the paper. Behind Hairy's head is another paper with a graph that looks like a positive third degree polynomial with three non-zero solutions. Between Cueball and Hairy at the level of their hands is a small square with two small dots at the two top corners. Seems like a part of the wall rather than a paper. During the next images the two on either side of Cueball moves their head in front or away from these papers so at least once the hole drawing can be seen. Over the panels top frame there is a frame with a caption:] Los Alamos, 1945... Cueball: We have a decision. If we've done our math right, this test will unleash heaven's fire and make us as gods. [Cueball turns towards Hairy holding his arms out.] Cueball: But it's possible we made a mistake, and the heat will ignite the atmosphere, destroying the planet in a cleansing conflagration. [In a frame-less panel Steven takes a hand to his chin, while the other two turns towards him.] Steve: Wow. Um. Question: Just to double-check— although I'm 99% sure— [Cueball, still facing Steve, face-palms himself while Hairy turns away from Steve.] Steve: Is it "SOH CAH TOA" or "COH SAH TOA"? Cueball: Oh, for the love of... can someone redo Steve's work? Hairy: I don't want to do the test anymore.

This comic refers to the Manhattan Project at Los Alamos, New Mexico , where in 1945 their development of the first nuclear weapon had progressed to the point that they were going to explode "The Gadget" at Trinity Site . There was genuine concern that some unexpected result was possible, including the scenario about the atmosphere igniting. The scientists were almost certain that it would either work as expected, or just be a dud, but were unable to rule out several other scenarios. The test proceeded, and it worked as expected. The joke part at the end is a reference to a common mnemonic device for basic trigonometric functions, namely identifying the relationships of sine , cosine , and tangent with respect to the lengths of a right triangle's edges: s ine = o pposite over h ypotenuse, c osine = a djacent over h ypotenuse, and t angent = o pposite over a djacent (in other words, SOH CAH TOA.) "Steve" becomes concerned by the seriousness of the situation, and wants to make sure that he has not made a mistake on stuff that should be very elementary to a scientist in his position. The title text mentions that there are very few jobs where one can say that with seriousness, as normal jobs do not involve technology capable of destroying worlds. [ citation needed ] A Steve is referred to in a similar situation in comic 1532: New Horizons , where his miscalculations screw up the trajectory of the New Horizons space probe, sending it to Earth instead of Pluto. He would be at least 90 years old if it was to be the same Steve though. A person named Steve also comes up with an inappropriate suggestion in 1672: Women on 20s . [Cueball raising a hand points to Steve (see later) drawn as another shorter Cueball-like guy, and behind Cueball stand Hairy also looking at Steve. Partly behind Steve's head is a piece of paper on the wall with a circle around a central dot and four arrows pointing in towards the circle from each corner of the paper. Behind Hairy's head is another paper with a graph that looks like a positive third degree polynomial with three non-zero solutions. Between Cueball and Hairy at the level of their hands is a small square with two small dots at the two top corners. Seems like a part of the wall rather than a paper. During the next images the two on either side of Cueball moves their head in front or away from these papers so at least once the hole drawing can be seen. Over the panels top frame there is a frame with a caption:] Los Alamos, 1945... Cueball: We have a decision. If we've done our math right, this test will unleash heaven's fire and make us as gods. [Cueball turns towards Hairy holding his arms out.] Cueball: But it's possible we made a mistake, and the heat will ignite the atmosphere, destroying the planet in a cleansing conflagration. [In a frame-less panel Steven takes a hand to his chin, while the other two turns towards him.] Steve: Wow. Um. Question: Just to double-check— although I'm 99% sure— [Cueball, still facing Steve, face-palms himself while Hairy turns away from Steve.] Steve: Is it "SOH CAH TOA" or "COH SAH TOA"? Cueball: Oh, for the love of... can someone redo Steve's work? Hairy: I don't want to do the test anymore.

Constructive

Constructive

https://www.xkcd.com/810

https://www.explainxkcd.com/wiki/index.php/810:_Constructive

[Cueball is talking to Megan.] Cueball: Spammers are breaking traditional Captchas with AI, so I've built a new system. It asks users to rate a slate of comments as "Constructive" or "Not constructive." [Close up of Cueball.] Cueball: Then it has them reply with comments of their own, which are later rated by other users. [Megan standing next to Cueball again.] Megan: But what will you do when spammers train their bots to make automated constructive and helpful comments? [Close up of Cueball again.] Cueball: Mission . Fucking . Accomplished .

Most online communities, including explainxkcd, face the problem of dissuading spammers from joining and participating. A common solution to this problem is the use of various systems to prevent automated bots' use of the community, while still allowing legitimate users to join. This has resulted in an arms race of sorts between spammers and communities, in which the spammers try to bypass increasingly difficult spam-prevention methods. This captcha and spamming prevention also has a downside, in that the time it takes to "prove you're human" is sometimes so long as to drive users away because their time is being wasted. This comic explores the culmination of that arms race, in which an advanced spam-prevention system, built by Cueball, is able to defeat the concept of spamming itself by forcing spammers to contribute constructively to a community. Captcha is one of the methods used to prevent lots of automated registering of fake user names used by bots and spammers. It consists of asking a person to prove that they are human before registering them as user and allowing them to post on sites or forum topics. That is done by using pictures of words and letters that humans may recognize, but bots and OCR software have trouble with. Now, artificial intelligence (AI) of bots have advanced so far, that Cueball has invented a new system. It asks the users to rate a slate of comments as constructive or not, then asks them to reply with comments of their own. Megan asks what will happen when spammers find a way around his system, such as making bots that make constructive and helpful comments? Well, it turns out that is what he is trying to accomplish in first place, a thriving community of bots and humans helping its members with constructive and helpful comments , as well as coming one step closer to the singularity . The title text investigates the consequences of such system further by thinking of people unable to give constructive and helpful comments, which are a sort of people you don't want in your online community anyway. [ citation needed ] Or it could mean that in order to join said community, they would have to learn to post helpful and constructive comments, and would then be eligible to join, thus accomplishing Cueball's goal. CAPTCHAs are a recurring theme on xkcd. [Cueball is talking to Megan.] Cueball: Spammers are breaking traditional Captchas with AI, so I've built a new system. It asks users to rate a slate of comments as "Constructive" or "Not constructive." [Close up of Cueball.] Cueball: Then it has them reply with comments of their own, which are later rated by other users. [Megan standing next to Cueball again.] Megan: But what will you do when spammers train their bots to make automated constructive and helpful comments? [Close up of Cueball again.] Cueball: Mission . Fucking . Accomplished .

Starlight

Starlight

https://www.xkcd.com/811

https://www.explainxkcd.com/wiki/index.php/811:_Starlight

[The comic consist of six black panels with white drawings. There are stars above the characters in all panels.] [Megan and Beret Guy stares at a starlit sky. The text is written above the stars and the sentence continues into the next frame. First here it becomes apparent that it is Megan who speaks the entire comment.] Megan: The starlight falls on our eyes after a journey across trillions of miles- [Zoom in on Megan and Beret Guy. The continued text is shown to come from Megan via a speech line.] Megan: dying here at last, so far from home, all so we can see some pretty dots. [Beret Guy think for a moment] [Beret Guy runs away] [Beret Guy comes back with a mirror under his arm, the starry sky can also be seen in the mirror.] [Beret Guy reached Megan, and holds it up above his head pointing it towards the stars.]

Megan talks with Beret Guy about the journey of light through the universe from its source to our eyes. In Megan's opinion, it is very sad that this journey is pointless - light's travel ends only with us seeing "pretty dots" - stars in the sky. Beret Guy then tries to return light to its birthplace by using a mirror, which reflects light back to its source. In reality, this would not work. Only a tiny fraction of the photons emanating from a star will reach the mirror and, even if the mirror is held at the perfect orientation, with dispersion (even if the mirror is perfectly smooth, the atmosphere is not) the probability that even one photon will make it back 'home' is effectively nil. However, if Beret Guy decides to exhibit another one of his strange powers , it is possible that he can find a way to actually find a way to reflect starlight back to 'home'. The title text is a reference to special relativity , which states that from the point of view of a light particle, the distance is zero because it is moving at the speed of light, so it takes no time to go anywhere. Note that the title text says that relativity saves the day again . This could be a reference to a previous comic 660: Sympathy in which a socially inept physicist touches upon using some consequences of special relativity to save a friend's deceased brother. [The comic consist of six black panels with white drawings. There are stars above the characters in all panels.] [Megan and Beret Guy stares at a starlit sky. The text is written above the stars and the sentence continues into the next frame. First here it becomes apparent that it is Megan who speaks the entire comment.] Megan: The starlight falls on our eyes after a journey across trillions of miles- [Zoom in on Megan and Beret Guy. The continued text is shown to come from Megan via a speech line.] Megan: dying here at last, so far from home, all so we can see some pretty dots. [Beret Guy think for a moment] [Beret Guy runs away] [Beret Guy comes back with a mirror under his arm, the starry sky can also be seen in the mirror.] [Beret Guy reached Megan, and holds it up above his head pointing it towards the stars.]

Glass

Glass

https://www.xkcd.com/812

https://www.explainxkcd.com/wiki/index.php/812:_Glass

[Megan is singing, Cueball is staring at a glass of water on a table.] Megan: EEEEEEEEEEEEEEEEEEEEEEEEEEE... Anything break? Cueball: No, but the water in the glass turned to wine. [Cueball picks up glass] Megan: Weird. Cueball: No, wait. This is blood. Megan: Okay, physics, quit fucking with us. Physics: You stop looking for the Higgs boson and we'll talk.

In the beginning of the comic, Megan is trying to break a wine glass like an opera singer. This is a rather famous trick where the vocalist sings at the resonant, or natural frequency of the glass and cause it to resonate more and more until it can no longer handle the stress and breaks - for more info, see the Mythbusters episode about the Earthquake Machine. If the resonant frequency of the glass is outside of the singer's range, then putting some water in the glass will lower its resonant frequency. This effect can be used to play different notes on the rim of a glass by varying the amount of water in it. For example, see this video . While Megan is trying to break the glass by hitting its resonant frequency, she is actually creating something new. This is similar to particle physics where a new particle can be identified by a resonance peak in the differencial cross-section of a scattering experiment: Known particles plus some very specific amount of energy lead to the creation of a new particle, the Higgs boson. This is represented in the comic with the water and the pitch of Megan's voice creating blood. The term "God Particle" was coined in 1993 by physicist Leon M. Lederman to describe the Higgs boson because it's "central to the state of physics today, so crucial to our final understanding of the structure of matter, yet so elusive." He originally called it the "goddamn particle", but this was considered offensive, and his editor shortened it to just "God particle", maybe to promote interest in the particle from non-academics too. Many people misinterpret the name to be some kind of link between physics and religion, so physics is getting back at them by playing pranks that resemble famous miracles from Christian tradition: Notably, the Higgs Boson was discovered in 2012, 2 years after this comic was released. So at the time, physicists were still looking for the particle. Notice that, in the last panel, the blood seems to have dripped out of Cueball 's glass onto the table and solidified instantly, further proof that physics doesn't apply in this scenario. The title text refers to the breaking of electroweak symmetry. It used to be thought that mirroring the result of any scenario would always give the same outcome as the result of the mirror of that scenario. However, it turns out that the details of the electroweak force (the electromagnetic and weak forces put together) refute this theory. As with many scientific theories, these can be used incorrectly in order to lend credibility to unrelated and nonsensical claims. This particular case is an instance of "quantum woo." Similarly, a degree can be used to lend the appearance of credibility to a person pushing such an idea, regardless of what field it was earned it or whether said person has any competence. [Megan is singing, Cueball is staring at a glass of water on a table.] Megan: EEEEEEEEEEEEEEEEEEEEEEEEEEE... Anything break? Cueball: No, but the water in the glass turned to wine. [Cueball picks up glass] Megan: Weird. Cueball: No, wait. This is blood. Megan: Okay, physics, quit fucking with us. Physics: You stop looking for the Higgs boson and we'll talk.

One-Liners

One-Liners

https://www.xkcd.com/813

https://www.explainxkcd.com/wiki/index.php/813:_One-Liners

Probability of phrases becoming action movie one liners: [Panels are arranged from More Likely on the left to Less likely on the right.] [A woman points a gun down at Cueball who is on the floor, his gun just out of reach.] Woman: You're going down the memory hole now, asshole. [Man on ground points gun up at blade-armed man standing next to a board with science on it.] Man with gun: Hey! You forgot to carry the two. [Ponytail on desk points sword at man standing on floor.] Ponytail: Looks like the Fed just lowered the interest rate. [Cueball with gun looks down at Megan slumped on floor.] Cueball: Guess you should've scrolled all the way to the bottom before clicking "Agree." [Megan holds pistol to the back of the head of Ponytail holding a rifle.] Megan with pistol: Bangarang, motherfucker.

In this comic, Randall presents a series of phrases, ordered by how likely they are to be used as a one-liner by a character in an action movie . One-liners are short, punchy phrases, typically witty or funny, and are routinely used in films by the antagonist to taunt the protagonist (or vice versa). The perfect one-liner leaves the recipient at a loss for a comeback, and should make sense immediately. If the phrase doesn't make sense or has to be explained, the effect is lost. The phrases shown adhere to the witty and punchy stereotype of a classical one-liner, but quickly become more niche and only understandable for an informed subgroup. You're going down the memory hole now, asshole. The Memory hole is a mechanism for redacting documents, photographs, etc., and a reference to George Orwell 's novel Nineteen Eighty-Four . In this instance it implies that the character on the floor is about to be 'erased' from existence. Hey! You forgot to carry the two. Cueball , lying on the ground in a fight, while his opponent has the high ground, still appears to be at an advantage since he has a gun and his opponent only has a knife, is pointing out an arithmetic error in his opponent's calculations. This may simply be Cueball adding insult to injury "I'm about to shoot you, but first I'm going to point out that you suck at math". Alternatively, it could be a ruse to distract the knife wielding opponent, or a case of well-timed nerd-sniping . It could also be that Cueball is buying time to cock or reload his gun. Alternatively Cueball is implying the missing carry caused the shown situation, and Cueball is monologuing (albeit a very short monologue), which may also serve to explain to the audience how his victory was achieved. Such an explanation would likely be necessary, as it is difficult to imagine any situation where this would be the case. A fourth way to explain the situation is that Cueball is stating with this phrase, that his opponent overlooked something small but critical, leading to a non anticipated (wrong) outcome. In this case his opponent would have overlooked that Cueball is carrying a gun, yielding to an unexpected and unfortunate outcome of his knife attack. Looks like the Fed just lowered the interest rate. Ponytail is standing on a desk with documents on it, probably in a banking or business related environment, dominating Cueball in a sword fight. The Federal Reserve System , usually referred to as The Fed, is the central banking system in the United States. The interest rates are usually lowered during a recession or a crisis, to revive the economy by providing businesses with cheap money. The dropped rates correlate with his chances to win and reflect his troubled situation. Guess you should've scrolled all the way to the bottom before clicking "Agree." A common feature encountered when registering for user accounts or installing software is a very lengthy Terms of service document, describing the things you agree to abide by. The vast majority of people simply click Agree without reading the document, essentially agreeing to anything and everything that the author decided to include, which sometimes leads to things like giving your immortal soul to a company . In the context of this panel, perhaps the user agreed to be executed at random. Bangarang, motherfucker. This phrase is very similar to the line "Yippee-Ki-Yay motherfucker" used by John McClane in the Die Hard series. Bangarang is, among other things, the Jamaican word for "uproar." It was popularized (without the addition of 'motherfucker') as the cheer of the lost boys in the film Hook . The title text is another suggested one-liner phrase, referring to an update reminder that frequently pops up when one attempts to view visual media content on a webpage. After delivering the line, the character triggers a detonator (Double colons are sometimes used in text to denote an action), presumably setting off an explosive of some kind. The phrase states that you need the latest Adobe Flash player to view this (presumably for older flash players too spectacular) explosion. Also wordplay is involved since a "flash" is one visual representation of a explosion. Of course in real life one doesn't need a "flash player" to view an explosion. [ citation needed ] Probability of phrases becoming action movie one liners: [Panels are arranged from More Likely on the left to Less likely on the right.] [A woman points a gun down at Cueball who is on the floor, his gun just out of reach.] Woman: You're going down the memory hole now, asshole. [Man on ground points gun up at blade-armed man standing next to a board with science on it.] Man with gun: Hey! You forgot to carry the two. [Ponytail on desk points sword at man standing on floor.] Ponytail: Looks like the Fed just lowered the interest rate. [Cueball with gun looks down at Megan slumped on floor.] Cueball: Guess you should've scrolled all the way to the bottom before clicking "Agree." [Megan holds pistol to the back of the head of Ponytail holding a rifle.] Megan with pistol: Bangarang, motherfucker.

Diode

Diode

https://www.xkcd.com/814

https://www.explainxkcd.com/wiki/index.php/814:_Diode

[Cueball is talking to Megan. Megan holds up a diode.] Cueball: We need to talk. Megan: Okay, but first hold the end of this diode. [They hold the diode.] Cueball: You hurt my feelings yesterday. Megan: You embarrassed me with my family last weekend. [They are still holding the diode between them.] Cueball: I'm sorry.

A diode is an electronic component that, to put it simply, blocks current traveling in one direction, but allows current going the other way. Diodes are a common component of digital circuits, such as those found in a computer. The end that rejects incoming current is marked with a line or band of paint. The comic is describing a common frustration in relationships. Sometimes one party in a relationship will feel that the other isn't listening to them, even though they themselves are being as open as possible. This is analogous to the function of a diode, which the comic indicates by literally introducing a diode into the dialogue. The diode introduced has the banded end being held by Cueball . This means his words are blocked by the diode, while Megan 's flows through to him; she never receives his protest, his pain, or his apology and thus does not feel she did anything wrong. Megan could possibly have used the diode as a way to avoid apologizing, but she must have known she risked looking like an idiot by not perceiving his apology, as illustrated by the title text: Megan didn't perceive Cueball's apology, due to it being blocked by the diode, so she berates Cueball for not apologizing. An alternative explanation is that Megan won't apologize, as she doesn't hear Cueball's complaint, and that Cueball is unhappy with her for this. [Cueball is talking to Megan. Megan holds up a diode.] Cueball: We need to talk. Megan: Okay, but first hold the end of this diode. [They hold the diode.] Cueball: You hurt my feelings yesterday. Megan: You embarrassed me with my family last weekend. [They are still holding the diode between them.] Cueball: I'm sorry.

Mu

Mu

https://www.xkcd.com/815

https://www.explainxkcd.com/wiki/index.php/815:_Mu

[Cueball spins in circles on a chair next to a desk. A graph of productivity vs Coefficient of friction of desk chair shows a curve that drops off very quickly as the coefficient of friction approaches zero, with the productivity becoming negative at low values. It plateaus in the middle of the graph, and then begins to drop less steeply as coefficient of friction increases above the optimal point.] Cueball: Wheeeeeeee

The title of the comic, "Mu", refers to the symbol μ. This letter of the Greek alphabet is commonly used in mathematics and physics in many cases and here it denotes the coefficient of friction which describes the ratio of the force of friction between two connected bodies. Desk chairs usually have the ability to turn and some chairs spin more easily than others. A desk chair which spins easily could be described as having a low coefficient of friction. The horizontal axis of the chart ranges from very easy to spin on the left, to very difficult to spin on the right. The comic shows that if the chair is too difficult to turn it is annoying and impacts productivity. However, if it is too low spinning one's chair becomes more fun than working. The title text notes that if your chair spins too easily, you can actually hurt other people's productivity by spinning competitively. [ citation needed ] In classical mechanics the angular momentum can be transferred to other objects when a rotating object does not have any friction and is rotating very fast. For example, when a reaction wheel inside a spacecraft changes its speed, it turns the entire satellite around. None of this is intuitive, as shown in this video . [Cueball spins in circles on a chair next to a desk. A graph of productivity vs Coefficient of friction of desk chair shows a curve that drops off very quickly as the coefficient of friction approaches zero, with the productivity becoming negative at low values. It plateaus in the middle of the graph, and then begins to drop less steeply as coefficient of friction increases above the optimal point.] Cueball: Wheeeeeeee

Applied Math

Applied Math

https://www.xkcd.com/816

https://www.explainxkcd.com/wiki/index.php/816:_Applied_Math

[Ponytail is standing at a whiteboard considering a logical proof. The proof assumes P and deduces P ∧ P .] Ponytail: Wow. I can't find fault with your proof. [Ponytail is still looking at the white board, the frame expands to show Megan walking away, rubbing her hands together in an evil manner.] Ponytail: You've shown the inconsistency — and thus the invalidity — of basic logic itself. Megan: Excellent. On to step two... [Megan sits down at a desk and begins to write.] Dear Dr. Knuth, [She continues to write.] I am writing to collect from you the $3,372,564.48 I am owed for discovering 1,317,408 errors in The Art of Computer Programming...

Donald Knuth is a computer scientist who has written several computer science textbooks and he offers monetary rewards for anyone finding errors in his publications. The first error found in each book is worth US$2.56. Other suggestions are worth less than $2.56, but a check is still sent out if Dr. Knuth finds them to be reasonable. Megan uses a proof to invalidate logic itself. (Of course, this means that her proof paradoxically renders itself meaningless. If logic has been disproven, her proof has no value.) According to the logic symbols at the bottom of the proof, she has proved that "the proposition (statement) is true and the proposition is false," i.e. "something is both true and false." (Specifically, ∴ means "therefore", P represents that a proposition is true, ∧ stands for "and", and an overbar negates a proposition (so P represents that a proposition is false) The negate symbol, ¬, is also used for this purpose when placed in front of a symbol). If someone were to prove this, it would indeed derail the very foundation of logic and result in the principle of explosion , which was referenced in a previous comic . Since most of the content of computer science textbooks is fundamentally based on logic, Megan's proof obviously spells doom for Dr. Knuth's, as each instance of logic can now be considered an error. After Megan's friend confirms the validity of her proof, Megan writes a letter to Dr. Knuth to collect her money for the 1,317,408 errors in The Art of Computer Programming at $2.56 each. According to the amount Megan demands as a reward, she apparently considers this textbook to have an average of more than 400 instances of logic per page (if she has the latest edition of each volume). The title text is the reply from Dr. Knuth, in which he uses Megan's logic-disproving proof against her by claiming — with no logical explanation — that the amount of money she is in fact due as a reward is only 98 cents. In logic, from a contradiction (such as "P∧ P ") can be inferred any statement, including that $3,372,564.48 = $0.98. He does this presumably to a) get out of paying her over three million dollars, b) demonstrate his contempt for or disbelief in her proof, and/or c) to show her, rather passive-aggressively, that she herself is not exempt from any ill effects resulting from her proof. If logic is proved to be false, then all mathematics are proved false and 3,372,564.48 = 0.98. Dr. Knuth could have also given her nothing, as 0 would equal 0.98 which would equal 3,372,564.48. The title of the comic, "Applied Math," is a play on Applied mathematics , "mathematical methods that are typically used in science, engineering, business, and industry," as opposed to pure math , which focuses exclusively on abstract concepts. Instead of using math to calculate something like the speed of a falling object, Megan uses it for an ostensibly more frivolous reason: to gain a huge reward via a proof of dubious validity. [Ponytail is standing at a whiteboard considering a logical proof. The proof assumes P and deduces P ∧ P .] Ponytail: Wow. I can't find fault with your proof. [Ponytail is still looking at the white board, the frame expands to show Megan walking away, rubbing her hands together in an evil manner.] Ponytail: You've shown the inconsistency — and thus the invalidity — of basic logic itself. Megan: Excellent. On to step two... [Megan sits down at a desk and begins to write.] Dear Dr. Knuth, [She continues to write.] I am writing to collect from you the $3,372,564.48 I am owed for discovering 1,317,408 errors in The Art of Computer Programming...

Mutual

Mutual

https://www.xkcd.com/817

https://www.explainxkcd.com/wiki/index.php/817:_Mutual

[Cueball and Megan are inside each others' thought bubbles.]

The comic depicts Cueball and Megan simultaneously thinking about each other. It may be a deliberate prelude to the next comic . The title text refers to the aspect of Quantum Mechanics where a system can exist in more than one state until it is observed. An observation is required in order to "collapse" the system into a particular state; the thought experiment of Schrödinger's cat is a popular way of explaining this concept. The title text proposes that, if a universe needed to be observed to exist, as with a quantum state, it would be a pretty sorry universe indeed, as who would exist to observe it if it needed to be observed in the first place? [Cueball and Megan are inside each others' thought bubbles.]

Illness

Illness

https://www.xkcd.com/818

https://www.explainxkcd.com/wiki/index.php/818:_Illness

[Randall, depicted as Cueball, is standing beneath all of this text. The last heart is much bigger than the text and comes directly from the Cueball figure.] Randall: Hey, everyone- Randall: As I mentioned on the blag, I'm going through a rough time right now. I'm dealing with a serious family illness and it's become pretty overwhelming. Randall: We're still getting a handle on everything, and I appreciate your patience while we figure it all out. Randall: Thank you to everyone who wrote in with kind wishes and words of support. They've been passed on and meant a lot. Randall: I like drawing, and might find time for it in the coming weeks, but I'm not going to push myself to stick to a schedule. Randall: However, between my stacks of notebooks, scanner, and supportive sysadmin, I should at least have something interesting to share with you in this space each M/W/F. Randall: ♡

This is the first comic about Randall 's fiancée's (now wife) cancer . It is self-explanatory, although vague on specifics. More details and related comics are on the Category:Cancer page. In the comic Randall mentions that he might not be able to (or interested in) sticking to the normal schedule. But he did manage to do that anyway. However, this comic was posted on a Friday, and the next week there were the 5 minute comics, and already the week after the next, xkcd was overtaken by guests during the Guest Week . Maybe this was his online comic colleagues who gave him a helping hand? The title text asks for readers to send him distracting games to play, then was edited to show his appreciation for the number of them sent in. [Randall, depicted as Cueball, is standing beneath all of this text. The last heart is much bigger than the text and comes directly from the Cueball figure.] Randall: Hey, everyone- Randall: As I mentioned on the blag, I'm going through a rough time right now. I'm dealing with a serious family illness and it's become pretty overwhelming. Randall: We're still getting a handle on everything, and I appreciate your patience while we figure it all out. Randall: Thank you to everyone who wrote in with kind wishes and words of support. They've been passed on and meant a lot. Randall: I like drawing, and might find time for it in the coming weeks, but I'm not going to push myself to stick to a schedule. Randall: However, between my stacks of notebooks, scanner, and supportive sysadmin, I should at least have something interesting to share with you in this space each M/W/F. Randall: ♡

Five-Minute Comics Part 1

Five-Minute Comics: Part 1

https://www.xkcd.com/819

https://www.explainxkcd.com/wiki/index.php/819:_Five-Minute_Comics:_Part_1

Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes. -- Randall [Cueball and Megan stand facing each other.] Cueball: Jupiter will make its closest approach to Earth in decades. [Cueball points behind Megan, and she turns around.] Cueball: In fact, here it comes now! [Jupiter, about the size of the characters' heads, hovers into the frame at about head-height.] Jupiter: Hey, guys. [Jupiter continues to hover through the frame as the characters watch it go.] Jupiter: Anyone need a gravitational slingshot? Megan: No, I'm good. Jupiter: Aight. [Cueball sits on a box, playing a guitar.] Cueball: ...Now I don't blame him 'cause he ran and hid, Cueball: but the meanest thing that he ever did Cueball: was before he left, he went and named me "Trig." [Cueball looks down a well.] Cueball: Oh God, a little girl is trapped down this well! [Cueball runs off screen.] [Cueball returns, leading a pony.] Cueball: It's okay, we got you that pony you always wanted! [Cueball tries to cram the pony down the well with the aid of a large stick.] Cueball: Get... in... there... Cueball: Ugh! [Cueball and Megan stand in a server room. ] Cueball: I like to get back to nature by coming out here to the server room. Cueball: The warmth, the whirr of the drives, the drone of the fans, the howl of the wolves... Megan: Wolves? Cueball: Yeah, we started a reintroduction program. Wolf: Awoooooo [Cueball stands by himself in the frame.] Cueball: Yo momma's so masculine that she... oh, wait, that's your dad. Cueball: Is your mom the lady over by the door? Aww, she looks nice! [Cueball runs toward another man who is wearing a powdered wig, holding a gun in one hand, and a flute in the other. Behind him, someone is chasing him on a motorcycle.] Cueball: Bach, activate the magic flute and teleport us home! Wagner's right behind me on his Ring Cycle! Why did I draw this? Hotness Ratings: [A close up of a girl with wavy hair.] Incredibly made-up girl on magazine cover. Girl: Airbrush! [Inset of Cueball: "Meh."] [An average girl.] Girl in your bio class. [Inset of Cueball: "Two stars."] [Girl with mussed hair in over-sized men's shirt.] Girl in your bio class wearing one of your shirts. Girl: Want some breakfast? [Cueball: "Four stars."] [Girl with another sort of shirt speaking to an older lady.] Girl in your bio class wearing one of your mom's shirts. Girl: Thanks for the great night. [Cueball: "Wat!"] [Creepy-looking girl.] Girl in your bio class wearing your mom's skin like a suit. Girl: Give Mommy a hug! [Cueball, screaming: "AAAAAAAA"]

Five-Minute Comics Part 2

Five-Minute Comics: Part 2

https://www.xkcd.com/820

https://www.explainxkcd.com/wiki/index.php/820:_Five-Minute_Comics:_Part_2

Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes. --Randall Comic #1 [A ninja is hiding under a diving board as a man runs along it.] [The man jumps on the end of the board and hits the ninja in the head, knocking him into the pool.] [The ninja floats in the water. A bullet passes through the man's head.] thwipp [The man is lying bleeding on the diving board, the ninja is still unconscious on the pool.] [A sniper is at the top of a hill. The sign in front of the hill says "Grassy Knoll".] [Someone is pointing at the diagram of the previous panel.] Off-panel voice: Wait, so what does this have to do with 9/11, again? Cueball: I said I'm getting there! Comic #2 [Cueball is studying Megan.] Cueball: You look different. Cueball: You have this... glow about you. [They stare in silence.] [A baby falls out of Megan.] plop Comic #3 Megan: Cogito ergo cogito. Off-panel voice: Playing it safe, huh? Comic #4 [Two children dressed up as ghosts are standing in front of Megan at a door, each carrying a bag.] Children: Trick or treat! [Megan doesn't move.] Child: Um hi. Why are you just standing there? Other Child: Candy? [Another silent panel as the children stare up at Megan.] [The second child looks in their bag.] Other Child: Oh God, my bag of candy. Other Child: It's filling with blood. Child: We should go. Comic #5 [A jet is flying across the panel.] Pilot: Bail out! Bail out! Bail out! [The pilot and copilot have buckets, and are bailing water out of the cockpit.] Comic #6 The following is a dramatization of real events. [Cueball is at a counter, with several jars.] Cueball: AAAAAAAAAAAAA I'm making a sandwich! AAAAAAAAAA! Comic #7 [Two people are carrying lightsabers and wearing robes.] Cueball: Oh God, my eyes won't focus right! And your robe looks... really dirty! My blacklightsaber was not a success. Comic #8 [Cueball is standing.] Cueball: Ladies and gentlemen of the jury... Off-screen voice: It seems we happen to be all ladies, actually. Cueball: ...in that case, this defense is going to appear extremely ill-advised. Comic #9 [Darth Vader is sitting between two people, at a table.] Cueball: Your sad devotion to that ancient religion hasn't helped you conjur up the stolen data tapes, or given you— Darth Vader: HEY. Wicca is a legitimate belief system! [Darth Vader is drawing a pentagram on the table.] Cueball: What are you— Darth Vader: Putting a hex on your family.

This is the second of three "five-minute comics" Randall posted during a week in November 2010. The introduction to the comic explains everything you need to know about the circumstances behind it. Randall obviously made more than three of these five minutes comics, and one of them was published later, for a short period of time by a mistake, but an android xkcd browser picked it up while it was on-line and saved it. Since then it has been added to explain xkcd. So here is a complete list of all four comics in the entire Five-minute comics series: Here is a list with explanations for each of the small comics: It turns out that, somehow, this will all lead up to a theory that perfectly explains the September 11 attacks . However, it turns out the jury consists only of women, so the "gentlemen" part is not needed. This poses a problem to Cueball's defense, which apparently relied on somewhat sexist tactics. This, sadly, is not too uncommon in real life. Instead of belief in the Force as in the movie, the "ancient religion" referred to here is actually Wicca , a modern pagan religion with two deities that is most notable for practicing magic, and is related to voodoo . So, naturally, Darth Vader puts a hex on the commander's family. (Although, to modify a quote from the Internet, Wiccans hexing you as punishment is like a hippie threatening to punch you in your aura.) The title text notes that modern Wiccans don't really practice the whole "putting hexes on people" thing, which is true. Episcopalianism probably refers to the Episcopal Church of the United States , which was founded during the American Revolution to replace the Church of England in the colonies. Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes. --Randall Comic #1 [A ninja is hiding under a diving board as a man runs along it.] [The man jumps on the end of the board and hits the ninja in the head, knocking him into the pool.] [The ninja floats in the water. A bullet passes through the man's head.] thwipp [The man is lying bleeding on the diving board, the ninja is still unconscious on the pool.] [A sniper is at the top of a hill. The sign in front of the hill says "Grassy Knoll".] [Someone is pointing at the diagram of the previous panel.] Off-panel voice: Wait, so what does this have to do with 9/11, again? Cueball: I said I'm getting there! Comic #2 [Cueball is studying Megan.] Cueball: You look different. Cueball: You have this... glow about you. [They stare in silence.] [A baby falls out of Megan.] plop Comic #3 Megan: Cogito ergo cogito. Off-panel voice: Playing it safe, huh? Comic #4 [Two children dressed up as ghosts are standing in front of Megan at a door, each carrying a bag.] Children: Trick or treat! [Megan doesn't move.] Child: Um hi. Why are you just standing there? Other Child: Candy? [Another silent panel as the children stare up at Megan.] [The second child looks in their bag.] Other Child: Oh God, my bag of candy. Other Child: It's filling with blood. Child: We should go. Comic #5 [A jet is flying across the panel.] Pilot: Bail out! Bail out! Bail out! [The pilot and copilot have buckets, and are bailing water out of the cockpit.] Comic #6 The following is a dramatization of real events. [Cueball is at a counter, with several jars.] Cueball: AAAAAAAAAAAAA I'm making a sandwich! AAAAAAAAAA! Comic #7 [Two people are carrying lightsabers and wearing robes.] Cueball: Oh God, my eyes won't focus right! And your robe looks... really dirty! My blacklightsaber was not a success. Comic #8 [Cueball is standing.] Cueball: Ladies and gentlemen of the jury... Off-screen voice: It seems we happen to be all ladies, actually. Cueball: ...in that case, this defense is going to appear extremely ill-advised. Comic #9 [Darth Vader is sitting between two people, at a table.] Cueball: Your sad devotion to that ancient religion hasn't helped you conjur up the stolen data tapes, or given you— Darth Vader: HEY. Wicca is a legitimate belief system! [Darth Vader is drawing a pentagram on the table.] Cueball: What are you— Darth Vader: Putting a hex on your family.

Five-Minute Comics Part 3

Five-Minute Comics: Part 3

https://www.xkcd.com/821

https://www.explainxkcd.com/wiki/index.php/821:_Five-Minute_Comics:_Part_3

Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes. --Randall Comic #1 Pearl Harbor. November 7th, 1941. [There is a beach, with some ships floating in a crescent shaped harbor.] [The same bay, again.] [The boats continue to move about the harbor.] [The boats do their thing. A title explains.] (We're going to be here a while, since the attack wasn't until December.) Comic #2 [Cueball is sitting on a bus, Megan in front of him. Another person is sitting in front of Megan and another person is sitting behind Cueball.] I know it's natural and all, but I really wish women on the bus wouldn't try to breastfeed me. Megan: C'mon, have some milk. Right here. Cueball: I'm reading . Comic #3 s/I think that/I saw a study once that said that/g Instant persuasiveness multiplier! Comic #4 [A newspaper front page. Billy Joel is between two policemen.] Times Billy Joel Arrested for Arson Comic #5 [One person has a cord leaving their mouth, the other is holding a handset on the end of it to their ear.] Handset: Hee hee hee... *giggle* I hear that if you drink coke and eat pop rocks, you vomit up a corded telephone handset on which you hear creepy little girls giggling. Comic #6 [Three soldiers are holding a large integral sign, while a fourth points a gun at the Little Rock High School.] 1957: Eisenhower orders the military to integrate Little Rock High School. Comic #7 [A smartphone is vibrating across a table, towards a person.] The smartphones got too smart... and developed a taste... for BLOOD! Fortunately, the only way they could move was by turning on their vibrate while on a sloped table. Comic #8 [Cueball is reading to his child.] Cueball: And the wolf went to see the 38th little pig, who had built his house out of strontium. Cueball: And the wolf was all, "Ok, what is with this shit?" The 119 Little Pigs Comic #9 [Cueball is holding up a gun.] Cueball: Fastest gun in the west! [The gun is galloping across the desert.] gallop gallop [There is a podium, with a gun in each position.] Winner! Comic #10 [A picture of a centrifuge dominates the panel.] Centrifuges: They're what separate the men from the boys. Comic #11 [A computer monitor is plugged in, and cables run into a wardrobe.] Lucy: Time passes differently in Narnia, so by putting the CPU and storage for my machine there, I was able to run through the [email protected] and [email protected] databases in about an hour. Peter: There are so many problems with that. Comic #12 [Someone is talking to Alice.] Person: One of these days, Alice... Wham, zoom, sploosh, fwoom, splash, gurlle, wheeeee, fwoosh, aren't waterslides fun?!

This is the third of three "five-minute comics" Randall posted during a week in November 2010. The introduction to the comic explains everything you need to know about the circumstances behind it. Randall obviously made more than three of these five minutes comics, and one of them was published later, for a short period of time by a mistake, but an android xkcd browser picked it up while it was on-line and saved it. Since then it has been added to explain xkcd. So here is a complete list of all four comics in the entire Five-minute comics series: Here is a list with explanations for each of the small comics: This may also be a joke on present-day levels of awareness of the event; as it fades out of living memory, people might indeed confuse the date with November (or October) 7, despite it being "a date which will live in infamy" . Here, it's combined with elements of other common scary urban legends (phones ringing and creepy laughter) to form something bizarre. However, integration also has a meaning in mathematics. This is indicated in the comic with the soldiers lifting up a giant integral sign to place beside the school, in order to (mathematically) integrate it. Normally, an integral only makes sense on functions; however, since this is the Little Rock Nine , if we take the integral of the constant function f ( x ) = 9, we do, in fact, get 9 x + C , as stated in the title text. The posture of the three soldiers with the integral sign echoes the iconic Raising the Flag on Iwo Jima photograph. The 119 Little Pigs seems to be a variant where the pigs build their houses out of the 118 chemical elements (and bricks, presumably). The 38th little pig builds his house out of strontium , which is, of course, the 38th element on the Periodic Table. One wonders what happened to the pigs who are stuck making their houses out of elements that are gaseous or liquid at room temperature, or those whose houses would react with the air and/or undergo nuclear decay. In his book what if?, in the first comic, it shows the 92nd little pig, who built his house out of depleted Uranium, The wolf responded, "Dude". [1] Although given the water content in exhaled breath, it's easy to see how the wolf would huff, puff, and blow down the houses made of lithium , sodium , potassium , rubidium , caesium , and francium . Though making a houses out of hydrogen , helium , nitrogen , oxygen , fluorine , neon , chlorine and krypton would all be very difficult as they are gases at room temperature [ citation needed ] . Also, there would be issues such as death from the toxicity of the elements, e.g. fluorine would kill the pig and wolf. The piggies may have difficulty collecting enough metal, as they would have trouble collecting enough technetium (43), which only occurs in minute traces, and astatine , of which approximately 1 ounce exists on earth. It could be a coincidence, or possibly Randall's intent, that the wolf asks "What is this shit?" while referring to strontium while "stronzo" is an Italian (vulgar) word for "turd", pronounced almost the same (it is a common source of bad taste jokes) and stront is a Dutch word for shit. See also: 1786: Trash Here, Randall takes the pattern to a ridiculous and not-at-all threatening place. Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes. --Randall Comic #1 Pearl Harbor. November 7th, 1941. [There is a beach, with some ships floating in a crescent shaped harbor.] [The same bay, again.] [The boats continue to move about the harbor.] [The boats do their thing. A title explains.] (We're going to be here a while, since the attack wasn't until December.) Comic #2 [Cueball is sitting on a bus, Megan in front of him. Another person is sitting in front of Megan and another person is sitting behind Cueball.] I know it's natural and all, but I really wish women on the bus wouldn't try to breastfeed me. Megan: C'mon, have some milk. Right here. Cueball: I'm reading . Comic #3 s/I think that/I saw a study once that said that/g Instant persuasiveness multiplier! Comic #4 [A newspaper front page. Billy Joel is between two policemen.] Times Billy Joel Arrested for Arson Comic #5 [One person has a cord leaving their mouth, the other is holding a handset on the end of it to their ear.] Handset: Hee hee hee... *giggle* I hear that if you drink coke and eat pop rocks, you vomit up a corded telephone handset on which you hear creepy little girls giggling. Comic #6 [Three soldiers are holding a large integral sign, while a fourth points a gun at the Little Rock High School.] 1957: Eisenhower orders the military to integrate Little Rock High School. Comic #7 [A smartphone is vibrating across a table, towards a person.] The smartphones got too smart... and developed a taste... for BLOOD! Fortunately, the only way they could move was by turning on their vibrate while on a sloped table. Comic #8 [Cueball is reading to his child.] Cueball: And the wolf went to see the 38th little pig, who had built his house out of strontium. Cueball: And the wolf was all, "Ok, what is with this shit?" The 119 Little Pigs Comic #9 [Cueball is holding up a gun.] Cueball: Fastest gun in the west! [The gun is galloping across the desert.] gallop gallop [There is a podium, with a gun in each position.] Winner! Comic #10 [A picture of a centrifuge dominates the panel.] Centrifuges: They're what separate the men from the boys. Comic #11 [A computer monitor is plugged in, and cables run into a wardrobe.] Lucy: Time passes differently in Narnia, so by putting the CPU and storage for my machine there, I was able to run through the [email protected] and [email protected] databases in about an hour. Peter: There are so many problems with that. Comic #12 [Someone is talking to Alice.] Person: One of these days, Alice... Wham, zoom, sploosh, fwoom, splash, gurlle, wheeeee, fwoosh, aren't waterslides fun?!

Guest Week Jeph Jacques (Questionable Content)

Guest Week: Jeph Jacques (Questionable Content)

https://www.xkcd.com/822

https://www.explainxkcd.com/wiki/index.php/822:_Guest_Week:_Jeph_Jacques_(Questionable_Content)

[A girl is sitting on a bench, reading a book. There is a tree. Far away, Cueball has a backpack on.] Cueball's thought bubble: There she is. The most beautiful girl you've ever seen. [The focus is on the girl on the bench.] Cueball's thought bubble: Every day you take this route to class, she's sitting on that bench, reading. [It goes even closer to her face.] Cueball's thought bubble: You'd introduce yourself, but you wouldn't know what to say. Besides, she's way out of your league. [Back to the full panel.] Cueball's thought bubble: What chance could an average guy like you have with such a radiant- Girl's thought bubble: Hey. [The girl looks up at her thought bubble with a question mark over her head.] Cueball's thought bubble: E-Excuse me? Girl's thought bubble: I said hey. You come by here a lot. [The girl looks over at Cueball, who is scratching his head at his thought bubble.] Cueball's thought bubble: Oh, uh, yeah. On the way to class. Girl's thought bubble: Wanna skip class and go get a coffee? [Cueball is pondering what's happening.] Cueball's thought bubble: Sure, I'd - I'd like that a lot. Girl's thought bubble: Great, let's ditch these losers. Girl: Hey! [The thought bubbles are behind Cueball now, moving away.] Cueball's thought bubble: Man, I gotta tell you, I'm SICK of being that guy's internal monologue! So whiny! Girl's thought bubble: Seriously! I swear, he and Little Miss Daddy Issues over there were made for each other. [The two look at each other silently.]

The comic starts with Cueball 's internal dialogue telling him what he's been thinking for some time now — that the girl he's looking at is so beautiful she seems unapproachable, and "what could she ever see in a guy like you", and typical fears that a guy has that prevents him from talking to a pretty girl. Only to be interrupted by the girl's internal monologue, who introduces herself to Cueball's internal monologue and asks if he'd like to get a cup of coffee. As the internal monologues pair off and leave, they criticize the people whom they've been serving for so long, saying that they're made for one another, if only one of them would have the guts to start talking to the other. The comic was guest-written by Questionable Content webcomic artist Jeph Jacques , whose romantic comedy series has lasted, as of 2020, more than 16 years and 4000 strips. The comic follows the vertical panel style typical of Questionable Content. But the art here is more in the xkcd style, showing only stick figures. SPOILER ALERT: the following paragraph reveals some important plot details of the Questionable Content webcomic. This comic may be a reference to Marten and Faye, two characters from Questionable Content. Marten meets Faye in QC #3 but is too shy to talk to her. Faye is less shy and introduces herself to Marten. Later, Marten and Faye are living together and have a crush for each other, but they don't get together because Faye is afraid of relationships since her father killed himself. Guest Week was a series of five comics written by five other comic authors. They were released over five consecutive days (Monday-Friday); not over the usual Monday/Wednesday/Friday schedule. The five comics are: [A girl is sitting on a bench, reading a book. There is a tree. Far away, Cueball has a backpack on.] Cueball's thought bubble: There she is. The most beautiful girl you've ever seen. [The focus is on the girl on the bench.] Cueball's thought bubble: Every day you take this route to class, she's sitting on that bench, reading. [It goes even closer to her face.] Cueball's thought bubble: You'd introduce yourself, but you wouldn't know what to say. Besides, she's way out of your league. [Back to the full panel.] Cueball's thought bubble: What chance could an average guy like you have with such a radiant- Girl's thought bubble: Hey. [The girl looks up at her thought bubble with a question mark over her head.] Cueball's thought bubble: E-Excuse me? Girl's thought bubble: I said hey. You come by here a lot. [The girl looks over at Cueball, who is scratching his head at his thought bubble.] Cueball's thought bubble: Oh, uh, yeah. On the way to class. Girl's thought bubble: Wanna skip class and go get a coffee? [Cueball is pondering what's happening.] Cueball's thought bubble: Sure, I'd - I'd like that a lot. Girl's thought bubble: Great, let's ditch these losers. Girl: Hey! [The thought bubbles are behind Cueball now, moving away.] Cueball's thought bubble: Man, I gotta tell you, I'm SICK of being that guy's internal monologue! So whiny! Girl's thought bubble: Seriously! I swear, he and Little Miss Daddy Issues over there were made for each other. [The two look at each other silently.]

Guest Week David Troupes (Buttercup Festival)

Guest Week: David Troupes (Buttercup Festival)

https://www.xkcd.com/823

https://www.explainxkcd.com/wiki/index.php/823:_Guest_Week:_David_Troupes_(Buttercup_Festival)

[Megan and Cueball are leaning against each other, sitting on top of a giant moon in a black, star dotted sky. Trees are visible on the bottom of the panel.] [The scene broadens.] Megan: I've never been so happy. I— Cueball: Hold on—that guy used to dump my notebooks in high school. Give me a moment. Try to keep the moon steady. [A rock hits a Cueball on the ground on the back of the head.] [The guy falls and clutches the back of his head.] [Back to the moon again, where Cueball is leaning his head against Megan while holding a slingshot.] Cueball: I've never been so happy.

This comic is a commentary on relationships. Megan is perfectly happy sitting on the moon (which is impossible) [ citation needed ] with Cueball , the person she loves. Cueball, however, has his experience ruined when he notices a former bully of his passing by below. After hitting the bully with a rock that he shoots from the moon with his slingshot , he can share in Megan's happiness. (This is practically impossible as well. To start, the rock would most likely fall back down unless Cueball could throw it at escape velocity, but the precision required for such a throw would be extreme, and he would need to account for the movement of the Earth and Moon, as well as the Earth's rotation. Even if accounting for all of that, it would very likely disintegrate in Earth's atmosphere.) David Troupes is the author of the webcomic Buttercup Festival . Guest Week was a series of five comics written by five other comic authors. They were released over five consecutive days (Monday-Friday); not over the usual Monday/Wednesday/Friday schedule. The five comics are: [Megan and Cueball are leaning against each other, sitting on top of a giant moon in a black, star dotted sky. Trees are visible on the bottom of the panel.] [The scene broadens.] Megan: I've never been so happy. I— Cueball: Hold on—that guy used to dump my notebooks in high school. Give me a moment. Try to keep the moon steady. [A rock hits a Cueball on the ground on the back of the head.] [The guy falls and clutches the back of his head.] [Back to the moon again, where Cueball is leaning his head against Megan while holding a slingshot.] Cueball: I've never been so happy.

Guest Week Bill Amend (FoxTrot)

Guest Week: Bill Amend (FoxTrot)

https://www.xkcd.com/824

https://www.explainxkcd.com/wiki/index.php/824:_Guest_Week:_Bill_Amend_(FoxTrot)

[Jason from FoxTrot is sitting at an artist's desk with a pencil, holding a phone.] Jason: Hi, Mr. Munroe? I have a great idea! Let me draw some strips for you! Randall, through the telephone: Fat chance, kid. [Zoom in to Jason.] Jason: Sudo let me draw some strips for you. [The following are transcripts of three strips.] [Cueball and Ponytail are looking at each other.] Cueball: I find you more attractive than usual. Ponytail: You do? Is it my new haircut? [Zoom in to Cueball.] Cueball: Actually, I think it's all the weight you've been putting on. Your gravitational pull is pretty severe. [Cueball is now alone in the panel.] Cueball: Just sayin'. [Two people are in a living room. The woman is looking through a chest of drawers.] At home with the Heisenbergs Mrs. Heisenberg: I can't find my car keys. Mr. Heisenberg: You probably know too much about their momentum. [Congress is in session. The Speaker is standing on stage in front of an American Flag hanging by an ionic column, holding up a gavel. Seven Members of Congress are seen in front of the stage: a Cueball, a Hairbun, a man with glasses, a woman with long hair, and three more Cueballs. The first, fourth, and sixth members have their hands raised.] Caption: Why mathematicians should run for Congress Speaker: All those in favor of the bill say "aye." Congressman #1: Aye. Congresswoman #2: Aye. Congress–Mathematician: √-1

Bill Amend , author of the newspaper comic FoxTrot , draws for Randall in this special ' Guest Week ' edition of xkcd . In the first two panels, we see Jason Fox , a geeky 10-year-old from Amend's strip. Jason asks to draw comics for Randall. When Randall refuses, he uses the sudo command, used in Unix systems to perform an action as an administrator/super user. This forces Randall to agree. This is a reference to the very popular comic 149: Sandwich , which has now become a geek culture catch-phrase. It is a recurring theme in FoxTrot for Jason to offer to make substitute comics for artists, said comics usually involving mocking his sister Paige, and it is possible that Ponytail is representing her. This would be the first time that someone accepted his offers to make comics. In the first comic, Cueball is making a pun on the word attractive . In the first context it means a person is "good looking" or "beautiful" which the female character attributes to her hair. In Cueball's context, he means that he is feeling an increased gravitational pull from the woman, due to her increase in mass (see Gravitation ). This setup is also very typical of the Jason Fox character, who, ostensibly ten, is supposed to be too young to like girls. The female character's hair is done up in a ponytail similar to how Paige usually keeps hers, so this comic strip may also be a joke at Paige's expense. In 1927 Werner Heisenberg postulated his eponymous Heisenberg Uncertainty Principle , which roughly states that in quantum mechanics one cannot know both the position and momentum of a particle. The joke is that (presumably) Elisabeth Heisenberg does not know the position of her keys, because she knows too much about their momentum. (This is also the subject of 1473: Location Sharing .) In many parliamentary and congressional halls it is customary, when calling an issue to vote to have the people who want the issue at hand to be passed to say out loud that they agree. The customary response to this is to say "aye." The dissenters are then asked. Their response would be "nay" or "no". Then the volume (by rough decibels ) of the assenters and dissenters are weighed. If it is close, a more formal vote may be called. "Aye" is pronounced the same way as the letter "i" and " i " is the mathematical value of the square root of negative one, which can be used to represent an imaginary number . The title text of this comic draws attention to the fact that there are a number of notable people who have become famous as cartoonists, but also hold degrees in physics or have a strong interest in physics. This might seem unusual, because the average person might see physics and art as incompatible, and this is why Randall writes "an oddly large number." These people include: Guest Week was a series of five comics written by five other comic authors. They were released over five consecutive days (Monday-Friday); not over the usual Monday/Wednesday/Friday schedule. The five comics are: [Jason from FoxTrot is sitting at an artist's desk with a pencil, holding a phone.] Jason: Hi, Mr. Munroe? I have a great idea! Let me draw some strips for you! Randall, through the telephone: Fat chance, kid. [Zoom in to Jason.] Jason: Sudo let me draw some strips for you. [The following are transcripts of three strips.] [Cueball and Ponytail are looking at each other.] Cueball: I find you more attractive than usual. Ponytail: You do? Is it my new haircut? [Zoom in to Cueball.] Cueball: Actually, I think it's all the weight you've been putting on. Your gravitational pull is pretty severe. [Cueball is now alone in the panel.] Cueball: Just sayin'. [Two people are in a living room. The woman is looking through a chest of drawers.] At home with the Heisenbergs Mrs. Heisenberg: I can't find my car keys. Mr. Heisenberg: You probably know too much about their momentum. [Congress is in session. The Speaker is standing on stage in front of an American Flag hanging by an ionic column, holding up a gavel. Seven Members of Congress are seen in front of the stage: a Cueball, a Hairbun, a man with glasses, a woman with long hair, and three more Cueballs. The first, fourth, and sixth members have their hands raised.] Caption: Why mathematicians should run for Congress Speaker: All those in favor of the bill say "aye." Congressman #1: Aye. Congresswoman #2: Aye. Congress–Mathematician: √-1

Guest Week Jeffrey Rowland (Overcompensating)

Guest Week: Jeffrey Rowland (Overcompensating)

https://www.xkcd.com/825

https://www.explainxkcd.com/wiki/index.php/825:_Guest_Week:_Jeffrey_Rowland_(Overcompensating)

[Jeffrey Rowland and Randall wearing a black hat are sitting together. There is a big globe between them. Mr. Rowland has a drink with a small umbrella over it.] Jeffrey Rowland: But enough of my theories about Thanksgiving. The real reason we're here is to discuss my hypothesis that dark matter itself is what consciousness is made of... [The frame focuses on Jeffrey Rowland.] Jeffrey Rowland: Unobservable to anything that is itself conscious in much the same way the mail-man won't deliver your mail if you are watching the mail-box [Mr. Rowland raises his drink. The globe is now much smaller than in the first frame.] Jeffrey Rowland: Which brings us to my theory about ghosts- Randall Munroe: Wait did you just say Thanksgiving was invented by the Turkey Voluntary Extinction Movement?

Randall himself (looking like Black Hat ) is talking to Jeffrey Rowland (sitting with a drink), who writes the popular webcomics Overcompensating and Wigu . That it is supposed to be these two real people is clear from the official transcript on xkcd. This may be a reference to Scott Adams' God's Debris , in which a delivery guy has a long conversation about the nature of the universe with an old man. While often dealing with complex questions, the old man in the story presents arguments in a very straightforward way. Some have called some of the arguments in the book very clever and original, albeit overly simplistic. This comic could be a parody on that style of philosophy. The ridiculous theory of Jeffrey's about the correlation between Dark Matter and consciousness is perhaps a reference to Dust in author Philip Pullman's His Dark Materials series, in which Dust is the associated particle with the Rusakov "consciousness" field, interpreted in our universe as Dark Matter. He then postulates that the reason we can't see dark matter is that we are conscious ourselves, alluding to the urban legend that, much like how a watched pot never boils, the mailman will never deliver if you are watching. He then moves on to the subject of ghosts, perpetuating the idea of how far-flung and implausible his "theories" are. Traditionally, turkey is the main dish of the U.S. Thanksgiving holiday. Thus, the theory mentioned in the last panel is that turkeys started the holiday in order to drive themselves to extinction. This is a reference to the Voluntary Human Extinction Movement (which merely advocated for people not reproducing. The "Turkey Voluntary Extinction Movement" took this to a much higher level by promoting the mass slaughter of turkeys.) The title text is completely true: After a brown recluse spider bit him, Rowland started experiencing cell death in his leg. Although the wound itself is benign, it still is featured in Wikipedia articles (such as Loxoscelism ). This is the picture of the leg and this is the famous picture in the Necrosis article. Guest Week was a series of five comics written by five other comic authors. They were released over five consecutive days (Monday-Friday); not over the usual Monday/Wednesday/Friday schedule. The five comics are: [Jeffrey Rowland and Randall wearing a black hat are sitting together. There is a big globe between them. Mr. Rowland has a drink with a small umbrella over it.] Jeffrey Rowland: But enough of my theories about Thanksgiving. The real reason we're here is to discuss my hypothesis that dark matter itself is what consciousness is made of... [The frame focuses on Jeffrey Rowland.] Jeffrey Rowland: Unobservable to anything that is itself conscious in much the same way the mail-man won't deliver your mail if you are watching the mail-box [Mr. Rowland raises his drink. The globe is now much smaller than in the first frame.] Jeffrey Rowland: Which brings us to my theory about ghosts- Randall Munroe: Wait did you just say Thanksgiving was invented by the Turkey Voluntary Extinction Movement?

Guest Week Zach Weiner (SMBC)

Guest Week: Zach Weiner (SMBC)

https://www.xkcd.com/826

https://www.explainxkcd.com/wiki/index.php/826:_Guest_Week:_Zach_Weiner_(SMBC)

In the spirit of xkcd I present a proposal for a new Smithsonian museum: The Smithsonian Museum Of Dad-Trolling An entire building dedicated to deceiving children for amusement (Click to view exhibits!) The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits. Exhibit: A giant basilisk looms over children. Exhibit label: BASILISKS: Real, deadly, under your bed. Exhibit: Four magnets hang from a square arch. A child is touching two of them together. Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest. Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both. Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold. Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him. Exhibit label: Sleep: Now you're vulnerable to the boogie man! Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened. Exhibit label: Freezing water: Expands to frighten predators. Exhibit: An insect on a stick is orbited by a small sphere. Exhibit label: Anti-matter: Matter that is more than 50% ants. Exhibit: A DNA strand with the letters T, A, C, and G hanging around it. Exhibit label: DNA only has four letters because the alphabet was smaller back then. Dad, to child: Told you so. Exhibit: A bunch of molecules hang from the ceiling. Exhibit label: Molecules? In my day, we only had atoms! The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits. Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed. Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding. Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it. Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed. Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder. Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup. Exhibit: A monstrous set of jaws open upward around a bed. Sign on exhibit: Make your bed or monsters will know a kid lives there. The center right room is 'Concessions'. There are three booths. Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating. Dad: The "P" is for "phoenix". Booth: A concession stand. Sign on stand: Ground beef: Beef we found on the ground. Dad, to child: Told you. Booth: A stand shaped like a giant eye. Booth label: EYES CREAM Subtitle: How did you think it was spelled? Sign on booth: Now with more of the goo in your eyes. Same as every other creamery. The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits. Exhibit: A man is riding a dragon. Exhibit label: Genghis Khan: victory through dragons. Exhibit: A criminal in front of some windows. Exhibit label: The Crimean War: The first war against crime. Exhibit: A castle with flags hanging on it. Exhibit label: The Renaissance Subtitle: Long story short, the wizards were in control. Exhibit:A man in Jedi-style robes with a fake beard. Exhibit label: Star Wars is a documentary. No, seriously. Dad, to children: Kids, this man is a veteran. The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits. Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label. Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT. Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle. Exhibit label: Alcohol is poison. I drink to save you from it. Dad: You're welcome. Exhibit: A large bird. Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls. Exhibit: A rocket ship. Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE. In the areas outside the rooms, there are two more exhibits and restrooms, all clickable. Exhibit: A dinosaur skeleton. Exhibit label: That's right. Dinosaurs were made entirely of BONES. Dad, to kid: If you think about it, it makes sense. Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines. Dad, to kids: You gotta squint juuust right. Sign on exhibit: Magic eye trick that doesn't actually work. Restrooms: There are three doors, each with a sign. First door (male logo): Men & Boys Second door (female logo): Women & Girls Third door (unrecognizable logo): Korgmen & Spangs

This comic is drawn by a guest webcomic artist, Zach Weiner (now Weinersmith), following the theme of "Guest Week". Zach is the author of the webcomic Saturday Morning Breakfast Cereal . The original comic is interactive. It will show images of the exhibits (see below) by clicking on them. The entire comic is a hypothetical " Smithsonian Museum of Dad-Trolling, an entire building dedicated to deceiving children for amusement." It is a common occurrence that curious children will ask simple questions about science to their parents, such as, "Daddy, why is the sky blue?" and a parent could respond, "Well Susie, the sky is blue to match your dress." Guest Week was a series of five comics written by five other comic authors. They were released over five consecutive days (Monday-Friday); not over the usual Monday/Wednesday/Friday schedule. The five comics are: Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about scientific topics. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic. This section holds falsehoods that a dad might use to frighten his children. Fear is often used to discourage children from disobeying their parents. It is an interactive experience, so visitors can try something for themselves, then learn the frightening fact it indicates. This area holds concession stands, which sell food. There are misleading names on each stand. The pop-outs in this section are based on jokes parents tell their children to frighten them about food. Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about history. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic. Each exhibit is a display set up to explain uncomfortable topics that children may ask their parents about. The answers given so that the children do not ask further questions. In the spirit of xkcd I present a proposal for a new Smithsonian museum: The Smithsonian Museum Of Dad-Trolling An entire building dedicated to deceiving children for amusement (Click to view exhibits!) The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits. Exhibit: A giant basilisk looms over children. Exhibit label: BASILISKS: Real, deadly, under your bed. Exhibit: Four magnets hang from a square arch. A child is touching two of them together. Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest. Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both. Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold. Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him. Exhibit label: Sleep: Now you're vulnerable to the boogie man! Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened. Exhibit label: Freezing water: Expands to frighten predators. Exhibit: An insect on a stick is orbited by a small sphere. Exhibit label: Anti-matter: Matter that is more than 50% ants. Exhibit: A DNA strand with the letters T, A, C, and G hanging around it. Exhibit label: DNA only has four letters because the alphabet was smaller back then. Dad, to child: Told you so. Exhibit: A bunch of molecules hang from the ceiling. Exhibit label: Molecules? In my day, we only had atoms! The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits. Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed. Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding. Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it. Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed. Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder. Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup. Exhibit: A monstrous set of jaws open upward around a bed. Sign on exhibit: Make your bed or monsters will know a kid lives there. The center right room is 'Concessions'. There are three booths. Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating. Dad: The "P" is for "phoenix". Booth: A concession stand. Sign on stand: Ground beef: Beef we found on the ground. Dad, to child: Told you. Booth: A stand shaped like a giant eye. Booth label: EYES CREAM Subtitle: How did you think it was spelled? Sign on booth: Now with more of the goo in your eyes. Same as every other creamery. The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits. Exhibit: A man is riding a dragon. Exhibit label: Genghis Khan: victory through dragons. Exhibit: A criminal in front of some windows. Exhibit label: The Crimean War: The first war against crime. Exhibit: A castle with flags hanging on it. Exhibit label: The Renaissance Subtitle: Long story short, the wizards were in control. Exhibit:A man in Jedi-style robes with a fake beard. Exhibit label: Star Wars is a documentary. No, seriously. Dad, to children: Kids, this man is a veteran. The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits. Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label. Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT. Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle. Exhibit label: Alcohol is poison. I drink to save you from it. Dad: You're welcome. Exhibit: A large bird. Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls. Exhibit: A rocket ship. Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE. In the areas outside the rooms, there are two more exhibits and restrooms, all clickable. Exhibit: A dinosaur skeleton. Exhibit label: That's right. Dinosaurs were made entirely of BONES. Dad, to kid: If you think about it, it makes sense. Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines. Dad, to kids: You gotta squint juuust right. Sign on exhibit: Magic eye trick that doesn't actually work. Restrooms: There are three doors, each with a sign. First door (male logo): Men & Boys Second door (female logo): Women & Girls Third door (unrecognizable logo): Korgmen & Spangs

My Business Idea

My Business Idea

https://www.xkcd.com/827

https://www.explainxkcd.com/wiki/index.php/827:_My_Business_Idea

[Cueball is sitting at his desk, pointing at his laptop.] Cueball: Dude! I had this idea like five years ago, and some company just got rich doing it! - I want my cut. [Cueball starts typing.] Person off-screen: That's not how it works. Cueball: Sure it is. I'm applying for my share now. Person: Wait, what? [A browser window with the title 'Department of Ideas'. It has a series of text boxes.] Date you had the idea: Like five years ago. Proof you had it: I told my friend Mike - you can ask him! I was all "you know what would make a great business idea?" and he was all... Their profit so far: $20,000,000 Share you deserve (be fair!): [Drop-down.] 25% 30% 35% Mailing address: 137 Ash Tree Ln [Cueball still at the laptop, above him is a SUBMIT button, and it shows a pointing hand cursor.] CLICK [Last panel set slightly lower than the rest.] [Cueball is in front of an open box full of cash, with cash in his hand. A FedEx delivery guy is on the other side of the box with his PDA and pen.]

Many people have shared Cueball 's experience of seeing someone else make a profit from an idea that they themselves had. This comic plays with the thought of what would happen if intellectual property thinking was taken to an extreme, and if companies or people were keener on "setting things right" than money. The title text is an extension of the comic with increasingly extreme thinking. In reality, having a great idea alone, of course, does not create a profitable business; there must generally be an enormous amount of effort put in to create a business from scratch, popularize it, and keep it standing. Having done none of this, Cueball would probably not deserve close to the "30% cut" he claims even if intellectual property did work the way it is presented here. This comic originally was shared with the name 1721: Business Idea , but then this comic was renamed. There were no other relations between the ideas for the two comics, see the trivia section below. [Cueball is sitting at his desk, pointing at his laptop.] Cueball: Dude! I had this idea like five years ago, and some company just got rich doing it! - I want my cut. [Cueball starts typing.] Person off-screen: That's not how it works. Cueball: Sure it is. I'm applying for my share now. Person: Wait, what? [A browser window with the title 'Department of Ideas'. It has a series of text boxes.] Date you had the idea: Like five years ago. Proof you had it: I told my friend Mike - you can ask him! I was all "you know what would make a great business idea?" and he was all... Their profit so far: $20,000,000 Share you deserve (be fair!): [Drop-down.] 25% 30% 35% Mailing address: 137 Ash Tree Ln [Cueball still at the laptop, above him is a SUBMIT button, and it shows a pointing hand cursor.] CLICK [Last panel set slightly lower than the rest.] [Cueball is in front of an open box full of cash, with cash in his hand. A FedEx delivery guy is on the other side of the box with his PDA and pen.]

Positive Attitude

Positive Attitude

https://www.xkcd.com/828

https://www.explainxkcd.com/wiki/index.php/828:_Positive_Attitude

[Cueball sits hunched with his knees drawn up to him on a hospital bed, hooked up to an IV. A friend stands by.] Cueball: I'm sick and I'm scared. Friend: Well, remember - having a good attitude is the most important thing. Think positively and you'll get better. [Darkness surrounds Cueball on the bed. The friend is off-screen.] Cueball: So if I'm sad or afraid or feel like crap sometimes, then... Friend: ...then if you don't recover, it will be your fault. [Cueball clutches his hands to his face and leans back.] Cueball: Well that makes me feel even worse. Friend: See? You're doing this to yourself. Cueball: No! Friend: Stop it! Cueball: Argh! [Close up on Cueball, holding up his hand, pointing to himself.] Cueball: Okay, you know what? Screw this. My attitude isn't my problem. - My disease is my problem, and I'm treating it. - I'm going to be glum and depressed and pessimistic some days, and I'm going to get better anyway. [Cueball sits on the edge of the bed, his friend still standing in front of him.] Cueball: Wait, that ended up sounding optimistic. Friend: I guess you suck at pessimism. Cueball: Maybe I'll be better at it tomorrow.

Cueball feels bad because he's sick, and his friend tells him to think positively because that will make him feel better. After thinking a bit Cueball notices that, following that reasoning, if he feels bad it is his fault for being so pessimistic. That makes him feel even worse as now he's not only sick, but also feels guilty of his own sickness. In the fourth panel, he throws away all the previous reasoning and decides his mood is not the problem: the problem is that he's sick. Also, he decides that whatever he feels now he'll finally get better because he's treating his disease. In the last panel Cueball notices his last comment was actually optimistic, so that makes him feel better. At this point, it should be expected that Cueball's friend would say "see? looking at things in an optimistic way actually helps". However, he puts optimism as something bad by using the phrase "you suck at pessimism". Cueball then tries to be optimistic at his "sucking" by thinking he'll "be better at pessimism tomorrow". Of course, being good at pessimism is something he should avoid, as it was his very problem in the first few panels. The title text takes a serious turn, and acts as an advice for people feeling bad for being sick. The point is that sickness makes one feel bad enough by itself without having to feel guilty for feeling bad when one's sick. In the first panel, Cueball is connected to a monitor and an IV ( Intravenous therapy ). In a real hospital this might be recording data, such as heart rate (HR) and peripheral oxygen saturation (SpO 2 ) however in the comic, INT, CON and CHR are also recorded. These may be a reference to character stats in some role playing games. In the "Adventurer Conqueror King" system, INT=Intelligence. CON=Constitution and CHR=Charisma. [Cueball sits hunched with his knees drawn up to him on a hospital bed, hooked up to an IV. A friend stands by.] Cueball: I'm sick and I'm scared. Friend: Well, remember - having a good attitude is the most important thing. Think positively and you'll get better. [Darkness surrounds Cueball on the bed. The friend is off-screen.] Cueball: So if I'm sad or afraid or feel like crap sometimes, then... Friend: ...then if you don't recover, it will be your fault. [Cueball clutches his hands to his face and leans back.] Cueball: Well that makes me feel even worse. Friend: See? You're doing this to yourself. Cueball: No! Friend: Stop it! Cueball: Argh! [Close up on Cueball, holding up his hand, pointing to himself.] Cueball: Okay, you know what? Screw this. My attitude isn't my problem. - My disease is my problem, and I'm treating it. - I'm going to be glum and depressed and pessimistic some days, and I'm going to get better anyway. [Cueball sits on the edge of the bed, his friend still standing in front of him.] Cueball: Wait, that ended up sounding optimistic. Friend: I guess you suck at pessimism. Cueball: Maybe I'll be better at it tomorrow.

Arsenic-Based Life

Arsenic-Based Life

https://www.xkcd.com/829

https://www.explainxkcd.com/wiki/index.php/829:_Arsenic-Based_Life

[Three people, a curly, dark-haired girl with a ponytail (identifiable from context and hairstyle as Felisa Wolfe-Simon), Megan, and Cueball, stand looking at a laptop screen, which is sitting on a desk. Dr. Wolfe-Simon is pointing at the screen. There is no speech line down to her, but from her posture it must be assumed she does the talking written above the three.] Wolfe-Simon: Our arsenic-based DNA discovery is cool, but these reporters are expecting life on Titan! Our press conference will be such a letdown! [Wolfe-Simon turns around to face Megan, zooming in so Cueball is not in the frame.] Wolfe-Simon: Okay, we need to make it more exciting for them. How do you make an event entertaining? Megan: Dunno, I suck at parties. Music, I guess? [Wolfe-Simon turns back around and leans over to start typing on the computer, while the other two look on. Megan puts her hand to her chin.] Wolfe-Simon: WikiHow says you can "serve cocktails and hors d'œrves that fit the theme of your event." Megan: Easy enough! [Wolfe-Simon stands on a podium behind a lectern ready to deliver the news, while Cueball stands amongst the audience, holding a tray with three drinks glasses. A fourth glass lies at foot of the lectern on the podium. Two Cueball-like guys in the audience are lying on the floor, one of them having fallen backwards in his chair, while a third Cueball-like guy is still standing but has his hands up to his throat as he is suffocating. Finally, Ponytail is slumped over in her seat with her head on her chest. One empty chair is still standing.] The words "hors d'oerves" at the comic are just a misspelling by Randall for "hors d'oeuvres" (in French "hors d'œuvre" both singular and plural). The English pronunciation of these words is awr-DURVZ /ɔrˈdɜrvz/, with the R before the V, not after, which explains the mistake. [2] As opposed to the original French pronunciation, where the v and r keep the same order. [3]

This comic is about the December 2010 announcement of the (since refuted) discovery of a strain of extremophile bacteria that incorporate arsenic instead of phosphorous into some of their biochemistry. The first three panels depict a group of scientists—including one shown with long, curly hair bound in a ponytail, identifiable from this hairstyle as Felisa Wolfe-Simon, the post-doctoral research associate who spearheaded the arsenic research (see 2421: Tower of Babel for another female scientist who is identifiable by her hairstyle)—preparing for their press conferences announcing the details of the discovery. The trio are worried that the press conference about their discovery will be less exciting to the reporters, because the press are expecting news of life on Saturn 's largest moon, Titan . The researchers decide to try and make the event more exciting, but they don't know how to throw a good party. As a result, they look up advice on the internet and decide to serve cocktails and hors d'œuvres to fit the theme of the event. The final panel shows the result, where the reporters are either dead or dying. It is implied that in order to fit the theme the researchers have laced the food and drinks with arsenic. Arsenic is a chemical element which is known to be poisonous to humans and most other life forms. In 2010 NASA announced the discovery of bacteria GFAJ-1 (an abbreviation for "get Felisa a job") and claimed it to be able to sustain itself when starved of phosphorus, by substituting arsenic for a small percentage of its phosphorus. Most scientists did not believe in this and it was disproven in 2012. [1] The comic draws its humor by picking on both scientists and reporters. It is a common theme in xkcd to show scientists who may be extremely clever within their field, but sometimes lack common sense and are inept at social situations. Reporters are often criticized for over sensationalizing discoveries and hunting for exciting stories. [Three people, a curly, dark-haired girl with a ponytail (identifiable from context and hairstyle as Felisa Wolfe-Simon), Megan, and Cueball, stand looking at a laptop screen, which is sitting on a desk. Dr. Wolfe-Simon is pointing at the screen. There is no speech line down to her, but from her posture it must be assumed she does the talking written above the three.] Wolfe-Simon: Our arsenic-based DNA discovery is cool, but these reporters are expecting life on Titan! Our press conference will be such a letdown! [Wolfe-Simon turns around to face Megan, zooming in so Cueball is not in the frame.] Wolfe-Simon: Okay, we need to make it more exciting for them. How do you make an event entertaining? Megan: Dunno, I suck at parties. Music, I guess? [Wolfe-Simon turns back around and leans over to start typing on the computer, while the other two look on. Megan puts her hand to her chin.] Wolfe-Simon: WikiHow says you can "serve cocktails and hors d'œrves that fit the theme of your event." Megan: Easy enough! [Wolfe-Simon stands on a podium behind a lectern ready to deliver the news, while Cueball stands amongst the audience, holding a tray with three drinks glasses. A fourth glass lies at foot of the lectern on the podium. Two Cueball-like guys in the audience are lying on the floor, one of them having fallen backwards in his chair, while a third Cueball-like guy is still standing but has his hands up to his throat as he is suffocating. Finally, Ponytail is slumped over in her seat with her head on her chest. One empty chair is still standing.] The words "hors d'oerves" at the comic are just a misspelling by Randall for "hors d'oeuvres" (in French "hors d'œuvre" both singular and plural). The English pronunciation of these words is awr-DURVZ /ɔrˈdɜrvz/, with the R before the V, not after, which explains the mistake. [2] As opposed to the original French pronunciation, where the v and r keep the same order. [3]

Genetic Analysis

Genetic Analysis

https://www.xkcd.com/830

https://www.explainxkcd.com/wiki/index.php/830:_Genetic_Analysis

Cueball: Did my genetic tests come back? Megan: Yeah. Sit down. Cueball: Is it bad news? What are my risk factors? [Cueball is now sitting in the chair awaiting her answer. Megan looks down at the clipboard.] Megan: We can't be sure about this, but we've analyzed genes on several of your chromosomes and it's hard to avoid the conclusion: [Megan puts down the clipboard and looks at Cueball as she delivers her news. Cueball puts his hands to his face in dismay.] Megan: At some point, your parents had sex. Cueball: Oh God! Megan: Stay calm! It's possible it was just once! Cueball: I... I need to be alone.

Genetic testing is a medical procedure where researchers analyze your DNA and family history to determine if you have elevated risk factors for diseases such as heart conditions and cancer. Here, the doctor appears to be delivering the results of Cueball 's genetic test but instead tells him that his parents had sex at some point. People generally don't like thinking about their parents having sex, but it obviously happened, since having sex is usually the precondition for having children, [ citation needed ] so this test result is completely unsurprising. If the doctor only came to this conclusion after analyzing genes on several of Cueball's chromosomes, this could have been done in order to verify that Cueball's DNA indeed resembles the DNA of his supposed parents i.e., that the people whom he has always viewed as his parents are indeed his genetic parents. However, the alternative might be even more disturbing. The title text notes that he could be an in-vitro fertilization baby, which does not require the parents to directly have sex. However, it seems to suggest that Cueball's mother was very attractive in her college years (or that she was pregnant). Thus, Cueball's mother probably did have sex (regardless of whether or not it was with Cueball's father). This is a reference to the stereotype that college students engage in large amounts of sex. Cueball: Did my genetic tests come back? Megan: Yeah. Sit down. Cueball: Is it bad news? What are my risk factors? [Cueball is now sitting in the chair awaiting her answer. Megan looks down at the clipboard.] Megan: We can't be sure about this, but we've analyzed genes on several of your chromosomes and it's hard to avoid the conclusion: [Megan puts down the clipboard and looks at Cueball as she delivers her news. Cueball puts his hands to his face in dismay.] Megan: At some point, your parents had sex. Cueball: Oh God! Megan: Stay calm! It's possible it was just once! Cueball: I... I need to be alone.

Weather Radar

Weather Radar

https://www.xkcd.com/831

https://www.explainxkcd.com/wiki/index.php/831:_Weather_Radar

[A black dot on a pixelated weather radar screen.] Sigh. Just a few clouds. [The clouds develop into orange, to the left of the dot.] Whoa! Huge storm out of nowhere! [The orange becomes red, and the storm moves towards the dot.] It's growing! And headed right for me! Awesome! [The storm splits in half.] Hey! What's it... [The two halves of the storm pass by the dot.] Dammit! Again?! When the folks at the weather offices see you refreshing the radar too often, they start teasing you.

A weather radar is a device which uses the reflection of radio waves from rain or snow to detect where there is rainfall. The information from the radar is then shown on a map. In this case green means light rain while red or white represent very heavy rain - possibly a thunderstorm . These maps can be quite beautiful and mesmerizing to look at. In this case the speaker (who is located where the black dot is) enjoys watching interesting, unexpected events on the radar and is surprised to see a massive, unexpected storm heading straight for him. A storm indeed appears but splits in half and passes either side of him. The reaction of the speaker shows that this has happened before. The caption suggests that this happens when the people who run the radar notice you looking at the page enough they tease you by adding a fake storm coming towards you which then disappears just as it approaches the speaker. The title text explores how our perceptions are often inaccurate - someone may think that there are fewer storms than when they were young or that certain songs come up more often on their MP3 player, even when they don't. There are lots of these types of biases in judgement . [A black dot on a pixelated weather radar screen.] Sigh. Just a few clouds. [The clouds develop into orange, to the left of the dot.] Whoa! Huge storm out of nowhere! [The orange becomes red, and the storm moves towards the dot.] It's growing! And headed right for me! Awesome! [The storm splits in half.] Hey! What's it... [The two halves of the storm pass by the dot.] Dammit! Again?! When the folks at the weather offices see you refreshing the radar too often, they start teasing you.

Tic-Tac-Toe

Tic-Tac-Toe

https://www.xkcd.com/832

https://www.explainxkcd.com/wiki/index.php/832:_Tic-Tac-Toe

[The comic comprises two large square maps, each divided into nine sections, some of which are further subdivided in the same way. The subdivisions continue down for up to five levels, and the lower map has more tiny diagrams than the upper. The smallest divisions at every scale are completed tic-tac-toe games. At the smallest divisions some of the moves are too small to see.] Complete map of optimal Tic-Tac-Toe moves Your move is given by the position of the largest red symbol on the grid. When your opponent picks a move, zoom in on the region of the grid where they went. Repeat. Map for X: [The first square map.] Map for O: [The second square map.]

In what follows we will use numpad notation for tic-tac-toe, i.e.: Each map shows every possible combination of moves which will result in that side winning or tying. It assumes that X moves first, and its optimal move is X7. Any corner would do, so X1, X3 and X9 are also optimal moves. The map for X has a big red X7 (650×650 pixels), and the 8 remaining grids have a smaller (210×210) black X7. The map for O has more combinations, because in this case X is not assumed to be optimal. All 9 subgrids have one big (210×210) black X and one big red O. Note that only optimal moves are shown. For example, you can't find a grid beginning with X2 in Map of X, because X2 is not an optimal move. In map for O you can find a 660×660 grid beginning with X2. Since the optimal answer is O5, you won't find X2, O8, for example. Example 1 The largest red X in Map for X is X7. This means that O must go to cell 7 in Map for O. The largest red O in this subgrid is the center cell O5. Therefore X must magnify cell 5 in the map for X and look for a big red X, which is X3, i.e. in the cell (6, 4) in a 9×9 grid. This can be repeated until one of the players wins or there is a tie. Example 2 Download http://xkcd.com/832_large/ and edit it. Delete the upper part. Now you have a picture sized 2040×2150 pixels, with title MAP FOR O. Assume X used the center cell, X5. You as O must magnify the center cell in the 3×3 map for O. Better still, select that cell and delete everything else. Now you have a picture sized 670×670 pixels, with a big red O7 and a big black X5. You must move O7 this time. Assume X moves X9. In your drawing program you select cell 9, which is 220×220 pixels. Look for the biggest red O, which is O1. You can see you blocked a winning move. Now X, naively, plays X3 You select cell 3 in your drawing program, which is 73×73 pixels and looks like this The O in cell 4 is red, which is your winning move. Title text The title text is a reference to the 1983 movie WarGames . In that movie, by playing Tic-Tac-Toe the AI realizes that some games cannot be won when all the players play flawlessly, and subsequently concludes that the only way to win at the nuclear warfare "game" is not to play. 1) In Map for X, the grid for X7, O9, X1, O4, X3 (i.e. go to Map for X, select cell 9, and then select cell 4) shows the same picture for O5 and O6. Those pictures belong to O6. The correct pictures should be: 2) In Map for X, the grid for X7, O1, X9, O8, X3 (i.e. go to Map for X, select cell 1, and then select cell 8) shows the same picture for O2 and O5. Those pictures belong to O2. The correct pictures should be: 3) In Map for O, the grid for X8, O5, X2, O6 (i.e. go to Map for O, select cell 8, and then select cell 2) shows the same picture for X1 and X3. Those pictures belong to X3. The correct pictures should be: 4) In Map for O, the grid for X2, O5, X8, O4 (i.e. go to Map for O, select cell 2, and then select cell 8) shows the same picture for X7 and X9. Those pictures belong to X7. The correct pictures should be: 5) In Map for O, the grid for X6, O5, X4, O2 (i.e. go to Map for O, select cell 6, and then select cell 4) shows the same picture for X1 and X7. Those pictures belong to X1. The correct pictures should be: 6) Typography coloring issue: in Map for O, X5, O7, X3, O1, X4, O6, the O6 should be red to show that it's the latest move, instead of black. 7) Another typography coloring issue: in Map for O, X1, O5, X4, O7, X3, O2, X6, O9, X8, the X8 is red, but in Map for O all X should be black. 8) In Map for O, there are eight "strategy" mistakes, when the O player could have won the game but doesn't. These can be found on: The same on six other symmetrical games to the above. 9) In Map for O, there are four further "strategy" mistakes, when the O player could have won the game but doesn't. These can be found on: The squares for X2 and X3 should be: and respectively. The same on three other symmetrical games to the above. 10)  In the map for O, center panel (first move X5), in the third level nested panel for X5, O7, X2, O8, X9, O1, move X2 from the second level "parent" panel is missing. The panel is depicted as: where [] are the fourth-level nested panels, but should be: Same for the symmetrical game X5, O7, X6, O4, X1, O9, where X6 is missing. http://xkcd.com/832_large/ [The comic comprises two large square maps, each divided into nine sections, some of which are further subdivided in the same way. The subdivisions continue down for up to five levels, and the lower map has more tiny diagrams than the upper. The smallest divisions at every scale are completed tic-tac-toe games. At the smallest divisions some of the moves are too small to see.] Complete map of optimal Tic-Tac-Toe moves Your move is given by the position of the largest red symbol on the grid. When your opponent picks a move, zoom in on the region of the grid where they went. Repeat. Map for X: [The first square map.] Map for O: [The second square map.]

Convincing

Convincing

https://www.xkcd.com/833

https://www.explainxkcd.com/wiki/index.php/833:_Convincing

[Cueball and Megan are talking. Megan has a board.] Cueball: I think we should give it another shot. Megan: We should break up, and I can prove it. [The second panel is the graph. A series of points moves steadily downward.] Our Relationship. [Cueball looks at the graph.] Cueball: Huh. Cueball: Maybe you're right. Megan: I knew data would convince you. Cueball: No, I just think I can do better than someone who doesn't label her axes.

This comic is a typical xkcd compilation. Relationships , math , graphs and of course, the twist. At 523: Decline Cueball's fascination with graphs seems to have retaliated against him. Cueball wants to get back together with Megan , but she declines and shows him a graph showing why. She thinks that the downward trend of the graph will convince him that their relationship is also in decline. But, Cueball takes that as this is a woman who does not follow proper protocol, since she does not label the axes (plural for axis) on her graph. We do not even know the unit of measure on the graph, let alone what each axis corresponds to. For all we know, the horizontal axis could be labeled "Time" and the vertical axis could be labeled "Crappiness of Relationship" or "Unawesomeness of Relationship". In that case, a downward trend would be a positive thing. In the twist, Cueball sees that he can do better than this woman and switches his position and decides he is going to break up with her. Cueball has already broken up with people over graphs before (see 539: Boyfriend ). Ironically, he or a different Cueball gave a similar graph with vaguely-labelled axes in 523: Decline . The title text points out the irony that if the axes had been labelled, then Cueball would be able to use it to determine exactly how much better a relationship he could get, since he could read how crappy the present one is. Yet he would lose the twist at the end, so that the graph data would have to convince him and not the lack of labels. "Someone who doesn't label her axes" sounds like an inversion of "someone who labels her exes", which is an accusation sometimes levelled in break-up situations. [Cueball and Megan are talking. Megan has a board.] Cueball: I think we should give it another shot. Megan: We should break up, and I can prove it. [The second panel is the graph. A series of points moves steadily downward.] Our Relationship. [Cueball looks at the graph.] Cueball: Huh. Cueball: Maybe you're right. Megan: I knew data would convince you. Cueball: No, I just think I can do better than someone who doesn't label her axes.

Wikileaks

Wikileaks

https://www.xkcd.com/834

https://www.explainxkcd.com/wiki/index.php/834:_Wikileaks

[The logo of Anonymous (but without the question mark), a black formal suit with no head, is talking.] Anonymous: We are Anonymous. We are legion. We are no one and everyone. Anonymous: And we are here to fight for WikiLeaks. [The panel is presented as the front page of WikiLeaks, in a browser.] New Leak: Names, addresses, IPs, and phone numbers of everyone in Anonymous. Download Now Anonymous: ...Dammit, Julian.

This comic references WikiLeaks , a site to which classified data can be sent for publication, while nobody would know who leaked the data. Many people dislike WikiLeaks, but proponents claim that, since government is supposed to work for the people, all government information should be available to anyone who wants to see it. WikiLeaks' actions are illegal in most countries, and the people maintaining WikiLeaks stay anonymous, with the notable exception of Julian Assange , the spokesperson. Among the supporters of Wikileaks are the 4chan-based activism/hacker group Anonymous , who, for the week or so prior to this comic's release, used DDoS attacks to take down servers for companies that aided the governments of the world in taking down Wikileaks and its CEO, Julian Assange. Amazon, PayPal and MasterCard were all targets of Anonymous. The claim 'We are legion' is a reference to Mark chapter 5 in the Bible, in which Jesus throws out a group of demons that call themselves Legion, "for we are many." The comic imagines an ironic scenario in which WikiLeaks, the organization Anonymous fought to protect, stays true to their mission of releasing secrets to the public, and publishes the personal information of Anonymous members. The joke in the comic notes a contradiction in Anonymous's position, relying on strict secrecy of its members' private information while supporting an anti-secrecy organization like WikiLeaks. This may be a reference to an incident in 2009 when WikiLeaks published a leaked list of some of their anonymous donors, following their then-policy of complete impartiality regarding leaks. In theory, Anonymous consists of everyone who takes steps to remain anonymous, not merely the hackers and criminals. In practice, Julian would merely have to post a list of Wikileaks contributors. The title text appears to be a news wire from during the Vietnam War when Lyndon B. Johnson was President in the United States. The students were calling to protest the War, in what xkcd implicates as the first DDoS attack. A DDoS attack is a Distributed Denial of Service attack, one of Anonymous' favorite tactics, in which the attackers send vast quantities of traffic from many different points to take down a web server, or, in the case of the title text, a phone network. Taken as a whole, the title text satirizes news reports in which a DDoS attack is confused with an actual hack, as only in the latter does the attacker gain (partial) access to the system itself. [The logo of Anonymous (but without the question mark), a black formal suit with no head, is talking.] Anonymous: We are Anonymous. We are legion. We are no one and everyone. Anonymous: And we are here to fight for WikiLeaks. [The panel is presented as the front page of WikiLeaks, in a browser.] New Leak: Names, addresses, IPs, and phone numbers of everyone in Anonymous. Download Now Anonymous: ...Dammit, Julian.

Tree

Tree

https://www.xkcd.com/835

https://www.explainxkcd.com/wiki/index.php/835:_Tree

[There is a binary Christmas tree, with each node a ball, and lights strung between parent and child nodes. Beneath it is a heap of presents - sorted with the largest on top, smaller presents connected to it with string. Next to the tree is Cueball and his parents, Hairbun and another Cueball.] Cueball: It's a Christmas tree with a heap of presents underneath! Mother: ...We're not inviting you home next year.

Cueball turns his family's living room Christmas tree into a cringingly-awful programming pun. His parents, Hairbun and a father-Cueball, are so unamused, he's not welcome back next year. Trees are data structures in computer science, based on two simple rules: A binary tree is a tree where each node has spaces for exactly 2 children. The "Christmas tree" is a basic representation of a binary tree - the star at the top is the root node, and the lights running down indicate the connections between parent and child. Contrary to what the terms "root" and "leaf" might imply, trees in computer science are typically represented upside-down, with the root on top and the leaves fanning out below. The Christmas tree is constructed based on no apparent rules, but the main power of binary trees comes in organizing them according to specific rules. Because code that runs later can assume the data is organized in this specific way, it can use different algorithms that make things run faster. One way of doing this is with a heap. A heap is a special kind of tree (usually a binary tree, but in this case a quaternary tree), subject to one additional rule: "Less than" in this case can refer to any comparison that can be made between two nodes - in this case, it's based on the size of the presents. Of course, there's a cost to all this; the heap must first be placed in that order. Not only that, but if a node gets removed from the heap, the heap has to be "rebuilt" to put it back in the right order. This is referenced in the title text - if Billy opens the root present, several comparisons must be done to shift other presents in its place to preserve the heap rule. In 1308: Christmas Lights a similar strange Christmas tree has been constructed using the electromagnetic spectrum. [There is a binary Christmas tree, with each node a ball, and lights strung between parent and child nodes. Beneath it is a heap of presents - sorted with the largest on top, smaller presents connected to it with string. Next to the tree is Cueball and his parents, Hairbun and another Cueball.] Cueball: It's a Christmas tree with a heap of presents underneath! Mother: ...We're not inviting you home next year.

Sickness

Sickness

https://www.xkcd.com/836

https://www.explainxkcd.com/wiki/index.php/836:_Sickness

[The three panels are arranged diagonally, upper left to bottom right.] [Two people, Cueball and White Hat, are walking past a tree.] White Hat: So, has this sickness opened you up to looking for answers beyond science? Cueball: ...no, not really. [Cueball turns to face White Hat.] Cueball: We've groped for comfort before the slings and arrows of fortune for millennia, and I begrudge nobody their sources of solace. Cueball: But Science provides tools . Cueball: $100 billion a year in scientific studies and medical R&D has bought us some pretty damn powerful slings and arrows of our own. Cueball: This world is amazing, and I'm going to live to experience more of it thanks to people who refused to gracefully accept the ineffability of reality. Cueball: I find my courage where I can, but I take my weapons from science. Cueball: Because they work , bitches.

This comic was published 2 months after Randall 's then fiancée, now wife, was diagnosed with breast cancer (see Category:Cancer ), which is likely what inspired this comic - even though Cueball sounds like he is the one afflicted by the sickness. The comic is thus about the existential questions that might arise from such a crisis. The moral could be interpreted as that you shouldn't begrudge your fellow human being, regardless of where they find comfort. Also, any sentence is instantly funny if, at the end of it, you address your audience as "bitches". It may also be a reference to 54: Science . "Slings and arrows of fortune" is an allusion to the " To be, or not to be " soliloquy in William Shakespeare's Hamlet, Prince of Denmark . Hamlet asks himself whether it is "Nobler in the mind to suffer / The Slings and Arrows of outrageous Fortune" (to resign oneself to one's fate and endure what may come), or to "take Arms against a Sea of troubles, / and by opposing end them" (to commit suicide and end suffering); he ultimately concludes that we would rather face the dangers and pains we know on Earth than whatever unknown new ones may come in the afterlife. Cueball appears to agree with Hamlet, thanking "the people who refused to gracefully accept the ineffability of reality": Religion and spirituality can give him the moral courage to face his death, but he'd much prefer to not die in the first place, and won't have to, thanks to medical and scientific innovation. (Actually he will have to eventually. Medical and scientific innovation simply delay the inevitable events of death and entropy.) The title text is a pun based on Cueball's newfound confidence, asserting that his statement "because they work, bitches" has a 95% confidence interval. [The three panels are arranged diagonally, upper left to bottom right.] [Two people, Cueball and White Hat, are walking past a tree.] White Hat: So, has this sickness opened you up to looking for answers beyond science? Cueball: ...no, not really. [Cueball turns to face White Hat.] Cueball: We've groped for comfort before the slings and arrows of fortune for millennia, and I begrudge nobody their sources of solace. Cueball: But Science provides tools . Cueball: $100 billion a year in scientific studies and medical R&D has bought us some pretty damn powerful slings and arrows of our own. Cueball: This world is amazing, and I'm going to live to experience more of it thanks to people who refused to gracefully accept the ineffability of reality. Cueball: I find my courage where I can, but I take my weapons from science. Cueball: Because they work , bitches.

Coupon Code

Coupon Code

https://www.xkcd.com/837

https://www.explainxkcd.com/wiki/index.php/837:_Coupon_Code

[The panel shows an online shopping form.] Shipping: $14.08 Total: $80.02 If you have a coupon code, enter it here: [An empty form.] Check out [In a frameless panel, Cueball is looking at his computer.] [The empty form is now filled in. The rest of the panel shows the same page.] Form: In 1987, you quietly took something from the house of a dying woman. You thought nobody knew. You were wrong. [Cueball is sitting at his computer.] Click [The form is updated.] Shipping: $14.08 Total: $80.02 ---------------- Discount Applied: -$80.02 Final price: $0.00 Thank you -Your order has been placed-

Some online stores allow you to enter a coupon code for a discount on one of their products. Coupon codes may be a single, simple word related to the product or seller or a complex sequence of characters. In this comic, Cueball is buying something online, and he comes across the option to use a coupon code for a discount before checking out. Instead of entering a coupon code, which is often a random sequence of numbers and letters, he chooses to enters a long and detailed blackmail message in the normally short coupon code form, hoping that blackmail could scare the seller and serve the way a coupon code would. This works so well that, instead of just receiving a small discount on the items he bought, Cueball is discounted the full price of the product he's buying. The humor comes from the fact that Cueball's intimidation works as if the online seller checking the coupon codes was an actual person, and not a computer, which is how coupon codes are checked. In addition, his blackmail message was far too detailed and specific that it could only be used on a certain person and would have virtually no chance of succeeding, unless he knows the seller so well that he even knows about crimes he did secretly. The title text references 325: A-Minus-Minus ; it has become a running gag that bobcats are occasionally sent by mail by Black Hat in various comics. By blackmailing the seller, it is unlikely that the seller will want to antagonize Cueball by sending him something that may lead to his injury. [The panel shows an online shopping form.] Shipping: $14.08 Total: $80.02 If you have a coupon code, enter it here: [An empty form.] Check out [In a frameless panel, Cueball is looking at his computer.] [The empty form is now filled in. The rest of the panel shows the same page.] Form: In 1987, you quietly took something from the house of a dying woman. You thought nobody knew. You were wrong. [Cueball is sitting at his computer.] Click [The form is updated.] Shipping: $14.08 Total: $80.02 ---------------- Discount Applied: -$80.02 Final price: $0.00 Thank you -Your order has been placed-

Incident

Incident

https://www.xkcd.com/838

https://www.explainxkcd.com/wiki/index.php/838:_Incident

[Rob is sitting at a computer. The computer's prompt is shown.] [Megan approaches.] Rob: Hey — who does sudo report these "incidents" to ? Megan: You know, I've never checked. [Santa Claus is sitting at a desk supported by candy canes, with a red monitor. On the wall are two lists labeled 'naughty' and 'nice'. He is in the process of adding a line to the 'naughty' list.]

This comic was posted on Christmas Eve . While Christmas is principally a Christian holiday, celebrating the birth of Jesus on December 25, there are many traditions around it, among them a tradition that on Christmas Eve Santa Claus will make his round delivering gifts to good children. Rob sits behind a UNIX computer and tried to change his user account from his normal access to the access of a super user by using the command " sudo su ". Sudo is a famous phrase in xkcd lore, made famous by comic 149: Sandwich . Before allowing administrator access (as root user), it asks for a password. The field is blank because, in most UNIX systems, the characters of the password are not shown. When Rob is unable to use the command his account is not authorized and the system says that the incident "will be reported" (usually to the system administrator, so they can see if someone is making repeated attempts at accessing administrator privileges). In the comic, however, sudo and the system report the incidents to Santa Claus , who, in Christmas lore, makes a list of who is naughty and who is nice. If you are nice then you get presents, while if you are naughty, you get a lump of coal. When sudo reports to Santa that Rob's account is not authorized, he puts Rob on the naughty list. In the title text, which is a parody of the famous Christmas song, "Santa Claus Is Coming To Town", /var/spool/mail/root is the root (superuser) mailbox on a Linux system, where the incident described in the comic would commonly be reported to. [Rob is sitting at a computer. The computer's prompt is shown.] [Megan approaches.] Rob: Hey — who does sudo report these "incidents" to ? Megan: You know, I've never checked. [Santa Claus is sitting at a desk supported by candy canes, with a red monitor. On the wall are two lists labeled 'naughty' and 'nice'. He is in the process of adding a line to the 'naughty' list.]

Explorers

Explorers

https://www.xkcd.com/839

https://www.explainxkcd.com/wiki/index.php/839:_Explorers

[A black bishop, Ba3, and a white knight, Nc3, are on a three by three chessboard. Both are on white squares. There is a heap of supplies at b2, also a white square. The chessboard is mounted on rockets and appears to be flying through the air.] Ba3: Mission Control, come in. This is Ba3 on the capsule calling Ke5 on the home board. We're on track and approaching the Coast of Catan. Our ETA is— Nc3: Control, this is Nc3. Bishop put all our food in the center so I can't get it. I demand— Ba3: Control, knight will get his food back when he stops hopping around bragging about how comfy the black squares are. I swear to God, I'm this close to capturing him and completing the misson alone.

This comic blends board games such as chess , The Settlers of Catan , and Battleship , with exploration , making possible references to space exploration and the Age of Discovery . The typical representation of explorers has them travel from their homeland aboard a ship to unknown distant places. The travel can get very long, implying the need for food supplies on the ship; and the fact that the crew members have to live together with little room (the ship) for such a long time, with possibilities of failure, getting lost or dying for various reasons, can often lead to tensions between some of them. In the Age of Exploration the explorers were mainly sailors from Europe traveling on the sea to other continents, whereas in space exploration they are astronauts or robots from Earth traveling in space to other planets (or whatever celestial bodies), but the general concepts of exploration remain the same. Here the explorers are two chess pieces, a knight and a bishop; they have left their "home board", presumably a full 8x8 chess board, aboard a smaller "capsule" made of a small 3x3 chess board in motion. It could be drifting in the sea; rolling along a hard surface on wheels or casters, as indicated by the small circles by each corner; or flying through space with the circles as rockets. The drawing is somewhat ambiguous. They are apparently headed for a Settlers of Catan board, and already passed near a Battleship board, so these game boards are like islands or regions which the chess pieces explore, coming from a chess board. Ba3, Nc3 and Ke5 are the identification of chess pieces and their respective position: Ba3 is a bishop on the A3 square, Nc3 a knight on the C3 square, and Ke5 a king on the E5 square. Chess is pretty much a representation of the structure of medieval European society (with the king and queen being the most crucial pieces, the bishops representing the somewhat powerful clergy, the knights corresponding to the armies, the rook alluding the castles, and the pawns being, as the medieval working classes, the most numerous and disposable assets); so chess pieces exploring other places, approaching the "coast of Catan", and reporting to the king ("calling Ke5"), is reminiscent of explorers from Europe who under their king's jurisdiction set sail to other continents during the Age of Exploration. The explorers are communicating with a " mission control ", which is common in space exploration. Also, an "ETA" is an estimated time of arrival . In chess, the knight and the bishop have different move constraints. The knight can only move two squares horizontally and one square vertically, or two vertically and one horizontally, so on the capsule the knight explorer can only go from one corner square to a black square, or vice-versa. The bishop can only move diagonally, so this bishop is bound to move only on the white squares. The knight is also the only piece that can "jump" over other pieces, which seems to annoy the bishop, hence the "hopping around"; apparently the bishop put all the food onto the middle square, which the knight can't reach, because the knight was taunting him about his not being able to get onto a black square. The two pieces are from the opposite chess camps (one black and the other white). This can be a reference to multinational space mission crews, where formerly opponent nations joined their efforts on space missions. But in chess it also means they can capture each other, by getting on the square where the other stands. Here, with the chess turn-by-turn gameplay, the knight won't be able to capture the bishop (except of course in case of error or dumb move), since the bishop will always be able to escape, whereas the bishop is actually one or two moves away from capturing the knight. So saying that he's "this close" to capturing him is a play on words, he is "this close" as in a few moves away, as well as "this close" as in severely annoyed and about to act on it. Assuming it’s the bishop’s turn this capture could be accomplished by the Bishop moving to C1, there after the knight would be forced to move to either A2 or B1. The Bishop then moves to B2. The knight then must move to C1 or C3 if it moved to A2, or A3 or C3 if it moved to B1 – all valid positions from which the Bishop could capture. If it’s the knights turn, the situation is the same except the Bishop would simply move to B2 regardless of the knight move. Finally, the title text adds two jokes. The Settlers of Catan board has an hexagonal grid, which means the chess pieces will have difficulty to move on it, since they are used to moving on a square grid. This can draw a parallel with explorers facing, in distant lands, weather conditions, wild animals, atmosphere or whatever condition, to which they are not used at all in their homeland. Battleship is a game where players send shots on the opponent's board, which is why the chess capsule received shots when it passed within firing range of a Battleship board; in pure chess style, it's the pawns of the crew, the least valuable and most disposable chess pieces, who took the shots. It could also be a reference to the en passant chess move, where, under certain conditions, a pawn can be captured after having "passed within firing range" (so to speak) of an enemy pawn; this could explain why only the pawns were lost in passing Battleship. [A black bishop, Ba3, and a white knight, Nc3, are on a three by three chessboard. Both are on white squares. There is a heap of supplies at b2, also a white square. The chessboard is mounted on rockets and appears to be flying through the air.] Ba3: Mission Control, come in. This is Ba3 on the capsule calling Ke5 on the home board. We're on track and approaching the Coast of Catan. Our ETA is— Nc3: Control, this is Nc3. Bishop put all our food in the center so I can't get it. I demand— Ba3: Control, knight will get his food back when he stops hopping around bragging about how comfy the black squares are. I swear to God, I'm this close to capturing him and completing the misson alone.

Serious

Serious

https://www.xkcd.com/840

https://www.explainxkcd.com/wiki/index.php/840:_Serious

[Cueball is standing next to a table. There is a can on the table.] [The label on the can reads, "Serious Putty".] [Cueball is looking at the table again.] [He reaches out to touch the can. The can speaks.] Can: Don't touch me.

This comic is a play on words with the child's putty known as " Silly Putty ", which is "silly" because it likes to be played with. Whereas Serious Putty does not even liked to be touched. As it says in the title text PuTTY is a Windows Terminal client. Impact is a font that is distributed with Windows that is used in the vast majority of " meme " image macros, such as lolcat pictures. [Cueball is standing next to a table. There is a can on the table.] [The label on the can reads, "Serious Putty".] [Cueball is looking at the table again.] [He reaches out to touch the can. The can speaks.] Can: Don't touch me.

Audiophiles

Audiophiles

https://www.xkcd.com/841

https://www.explainxkcd.com/wiki/index.php/841:_Audiophiles

[Cueball and Megan are talking over the telephone. The first two panels are split diagonally. Cueball is at a store, holding a box, and Megan is consulting with him.] Cueball: Do we have an RCA-to-3.5mm female-female plug? I'm getting some speakers for the new Xbox, since the monitor doesn't have any. Megan: Are they crappy laptop speakers? Ugh. [Cueball is standing next to a sale rack.] Cueball: Does it matter? I just want to hear if I'm getting shot at, not savor every detail of a beautiful musical soundscape. Megan: You've never heard a beautiful musical soundscape. You listen to 96kbps flv rips from YouTube. [Megan is walking.] Cueball: Whatever. I'm just going to get these $20 speakers. Five watts will be plenty. Megan: Five watts for a living room sound system? Is that a joke? [Zoomed in panel on Cueball]: Cueball: No, this is a joke: How many audiophiles does it take to change a lightbulb? Megan: How many? Cueball: I'll tell you later—you wouldn't appreciate the punchline over this 12kbps cell phone codec. click

Cueball is buying some new speakers for his television, and asks Megan if they have the right cord to hook them up. Megan begins chiding him for using "crappy laptop speakers", i.e. low-powered, low-quality speakers that don't faithfully reproduce the sound. Cueball and Megan reproduce the two extremes of the arguments: Cueball simply wants to play a first-person shooter video game (whose soundtrack will either be obscured by gunfire or completely absent during gameplay), regardless of the sound quality, whereas Megan, the audiophile, values music everywhere. Cueball seems to think that's unnecessary, and Megan snipes back that he's never heard beauty, so he wouldn't know; after all, he thinks low-bit-rate re-encodings from YouTube (at the time, notorious for dodgy sound quality) are perfectly fine music. Cueball, frustrated with Megan's perfectionism, states that he's just going to buy cheap 5-watt speakers. While 5 watts may be a lot if you're trying to fill the immediate area with sound from your MP3 player, it'd sound tiny and hollow coming out of a television across the room. An incredulous Megan protests, calling his ideas "a joke." An exasperated Cueball tells a lightbulb joke , the content of which implies that the content doesn't matter to her, only the quality in which it's delivered to her ear. Megan promptly hangs up because of the bad joke (or possibly because of the bad audio quality?). The title text is referring to a forum post from audioholics.com (post #29, "We gathered up a 5 [sic] of our audio buddies...."), where a user did a blind audio test using Monster cable and coat hangers with soldered on alligator clips, and the audiophiles were unable to discern any difference. Randall instead just uses coat-hangers to connect his speakers, not getting that the point of the test was not to extol the high transmission quality of coat hanger wire but to lampoon the belief that supposedly high-quality speaker cables make an audible difference in the audio output. [Cueball and Megan are talking over the telephone. The first two panels are split diagonally. Cueball is at a store, holding a box, and Megan is consulting with him.] Cueball: Do we have an RCA-to-3.5mm female-female plug? I'm getting some speakers for the new Xbox, since the monitor doesn't have any. Megan: Are they crappy laptop speakers? Ugh. [Cueball is standing next to a sale rack.] Cueball: Does it matter? I just want to hear if I'm getting shot at, not savor every detail of a beautiful musical soundscape. Megan: You've never heard a beautiful musical soundscape. You listen to 96kbps flv rips from YouTube. [Megan is walking.] Cueball: Whatever. I'm just going to get these $20 speakers. Five watts will be plenty. Megan: Five watts for a living room sound system? Is that a joke? [Zoomed in panel on Cueball]: Cueball: No, this is a joke: How many audiophiles does it take to change a lightbulb? Megan: How many? Cueball: I'll tell you later—you wouldn't appreciate the punchline over this 12kbps cell phone codec. click

Mark

Mark

https://www.xkcd.com/842

https://www.explainxkcd.com/wiki/index.php/842:_Mark

[Cueball and Science Girl are talking.] Science Girl: What's that on your arm? Cueball: The mark of a secret society. Science Girl: If it's secret, why tell me- Cueball: Because I know nothing. I can't betray them because I don't know who they are. I was chosen by an agent 20 years ago. That was my first and last direct contact. Cueball: It's safer that way. Six years later I found a piece of paper in the street with an address on it. The next day I found a can of kerosene in my garage that I'm sure I never bought. [The panel represents these actions by highlighting the mentioned objects in a world of gray.] I didn't know whose house it was. I just knew that I'd been given my orders. And I carried them out. [A dark figure holding the kerosene is silhouetted against a flame.] Cueball: I don't know who or what we're fighting. Cueball: Maybe we're the bad guys. Cueball: It doesn't matter to me. Cueball: It's enough to know that there are forces working beneath the chaos of life, and I'm a part of them. Cueball: That whatever this "Pen Fifteen" club is, Cueball: I'm in it.

In this comic, Science Girl asks Cueball about a mark on his arm. He apparently believes he is part of a secret society, so secret that he doesn't know anything about the society. His belief in the existence of the society, and that he is a part of it, stem from one contact with an 'agent'. Most people would immediately dismiss the idea of such a secret society, especially with no evidence of its existence, and no knowledge of the goals or even whether it is inherently good or evil. Six years after being 'chosen', Cueball finds the scrap of paper with an address on it, and the can of kerosene . Both of these events are not unlikely, and easily explained as simple coincidences, but Cueball somehow sees this as a command that he must burn down the house. Cueball shows that he is willing to put other people's lives at risk, destroy property and possessions, and face the possibility of prison, all because of one event six years prior. Cueball's belief in the society, his delusional linking of the address and kerosene, and his actions in burning down the house, show how badly he wants to be part of something bigger, and to find meaning in the "Chaos of Life". The punchline refers to an old grade school/middle school prank (Urban Dictionary: pen 15 club , Pen 15 .) You'd typically walk up to an unsuspecting schoolmate and ask them if he wants to join the Pen Fifteen Club. You'd tell them that to join, you merely have to write the club name on them. You'd then write "PEN15" on their hand or arm, and everyone would laugh at them because it looks like "PENIS". (In a common variant, it is simply called the Pen Club, 15 is the victim's "member number", and the pranksters write "PEN13" and "PEN14" on themselves.) In this case, Cueball fell victim to this prank as a child without ever figuring out the joke, and the ink somehow never got washed off by showers or baths or removed by shedding skin. In reality, it would be unlikely for such a mark to last for so long. While methods of making someone's skin more permanently do exist, it is hard to imagine someone tattooing or branding "PEN15" on their friend's arm as a prank. As for the title text, solipsism is the philosophical idea that only your own mind is sure to exist while other minds can't be really known and so those other minds are not proved to be real. In this context it might mean that the only one who can conspire would be you, hiding the truth from yourself. [Cueball and Science Girl are talking.] Science Girl: What's that on your arm? Cueball: The mark of a secret society. Science Girl: If it's secret, why tell me- Cueball: Because I know nothing. I can't betray them because I don't know who they are. I was chosen by an agent 20 years ago. That was my first and last direct contact. Cueball: It's safer that way. Six years later I found a piece of paper in the street with an address on it. The next day I found a can of kerosene in my garage that I'm sure I never bought. [The panel represents these actions by highlighting the mentioned objects in a world of gray.] I didn't know whose house it was. I just knew that I'd been given my orders. And I carried them out. [A dark figure holding the kerosene is silhouetted against a flame.] Cueball: I don't know who or what we're fighting. Cueball: Maybe we're the bad guys. Cueball: It doesn't matter to me. Cueball: It's enough to know that there are forces working beneath the chaos of life, and I'm a part of them. Cueball: That whatever this "Pen Fifteen" club is, Cueball: I'm in it.

Misconceptions

Misconceptions

https://www.xkcd.com/843

https://www.explainxkcd.com/wiki/index.php/843:_Misconceptions

[Miss Lenhart the teacher is standing in front of a board, looking at a laptop computer she is holding in one hand while elocuting.] Miss Lenhart: Okay, middle school students, it's the first Tuesday in February. Miss Lenhart: This means that by law and custom, we must spend the morning reading through the Wikipedia article List of Common Misconceptions , so you can spend the rest of your lives being a little less wrong. Miss Lenhart: The guests at every party you'll ever attend thank us in advance. [Caption below the panel:] I wish I lived in this universe.

The Wikipedia article List of common misconceptions gives a list of commonly-repeated anecdotes that are widely believed to be true, but actually are not. The teacher, Miss Lenhart , is announcing that since it is the first Tuesday in February , by law and custom the reading of this article is requirement to stem the repetition of these incorrect anecdotes. (Funnily enough the comic was released the first Wednesday in January, which could just as well have been written in the comic). She continues to make it clear that this is to make the students in general a little less wrong, and the main outcome will be that the guest of any future parties the students ever attend, will not have to listen to them retell these misconceptions and for that these guest will thank those who have decided on this new law in advance. In the caption below the comic Randall expresses his wishes that he lived in a parallel universe where this rule had been used for many years. So he would not have to listen to all these stories at every party he goes to. Since Randall likes to correct people if they are wrong (see 386: Duty Calls ), not having to discuss with those that believe these misconceptions, would make his parties much better. The title text refers to a specific one of these false stories about glass : That glass , while seeming solid, is actually an extremely viscous liquid and will flow over time, as is seen on older buildings where the window panes are thicker at the bottom. In reality, older manufacturing processes did not produce glass panes with as uniform thickness as modern processes, and people tended to install the uneven panes with the thicker side at the bottom for stability. Glass simply does not flow at room temperature; it's more viscous than solid lead by a factor of over a billion . The fact that glass is solid at room temperature was again referenced in a foot note, under the pipe with glass, in 1649: Pipelines . [Miss Lenhart the teacher is standing in front of a board, looking at a laptop computer she is holding in one hand while elocuting.] Miss Lenhart: Okay, middle school students, it's the first Tuesday in February. Miss Lenhart: This means that by law and custom, we must spend the morning reading through the Wikipedia article List of Common Misconceptions , so you can spend the rest of your lives being a little less wrong. Miss Lenhart: The guests at every party you'll ever attend thank us in advance. [Caption below the panel:] I wish I lived in this universe.

Good Code

Good Code

https://www.xkcd.com/844

https://www.explainxkcd.com/wiki/index.php/844:_Good_Code

[The comic is a flowchart In order to explain this in text, follow the line numbers. Options follow on new lines without numbers.] How to write good code. [10.] Start Project. [Go to 20.] [20.] Do things right or do them fast? Fast [Go to 30.] Right [Go to 40.] [30.] Code fast. [Go to 35.] [35.] Does it work yet? No [Go to 30.] Almost, but it's become a mass of kludges and spaghetti code. [Go to 50.] [40.] Code well. [Go to 45.] [45.] Are you done yet? No. [Go to 40.] No, and the requirements have changed. [Go to 50.] [50.] Throw it all out and start over. [Go to 10.] [60.] ? [Go to 70.] [70.] Good code.

The comic references the common meme of programmers that one can't actually write good code. Either the code is done quickly with shoddy "code style", weak logical structure, or any number of other kludges and hacks which turn maintenance of the code into a nightmare; or else it is written well and beautifully structured, but can never be completed before changes in the situation cause the original code design to be insufficient for one or multiple reasons. Either situation eventually leads to the need to completely start from scratch, designing and writing the program's code all over again. Of course, the writing of this new program is also locked in the perpetual cycle of choosing between ugly/bad code that works marginally well, or good/pretty code that never gets completed before being obsolete. Additionally, the humorous point is being further emphasized for the primary target audience, programmers, by using an infinite loop - or more precisely, 2 possible loops and 1 forced loop in the flowchart itself. Also, of particular note, is the fact that Randall (the author) drives home the point of the inescapability of the infinite loop(s) by the use of the additional, disconnected, and logically unreachable portion of the flowchart. This disconnect points out that the only way to actually get to "Good Code" using the flow chart would be to follow a path of actions — which does not start at the prescribed place — for which there is only an unknown and possibly unknowable starting action which no one has ever discovered previously. Other flowchart comics, several of which are also infinite loops, can be found here . The title text, "You can either hang out in the Android Loop or the HURD loop," makes a dig at both communities: claiming that Android developers always opt for fast, ugly code, necessitating frequent fixes and updates, while Hurd developers perennially choose to "do the job right" but can therefore never seem to finish their project. The GNU Hurd Project aims to create the kernel for the GNU Operating System (the kernel being the central and most indispensable component). The GNU Project is most famous these days as a result of GNU/Linux (commonly called just "Linux"), which is an operating system that uses the Linux kernel with the GNU system environment. From the beginning the GNU Project has planned to design their own kernel, the Hurd , virtually from scratch, and given a relatively clean slate with which to work, elected to employ a number of promising and theoretically elegant design concepts . Despite or, as Randall suggests, because of this, the Hurd has been mired in development hell for many years (for decades, in fact) with little progress towards actual usability outside of a small community of kernel hackers. While runnable GNU/Hurd operating systems do exist, they're still basically experimental, and the Hurd remains a collection of research software the design goalposts for which keep receding as other, more pragmatically-engineered technologies continue to be developed (the Linux kernel itself being the canonical first instance of this). Finally, the official transcript of this comic is itself somewhat humorous (an additional inside joke , if you will) in that it converts the flowchart into a simple list of instructions (aka pseudo-code) using numbered lines as reference points for identifying which instruction to read and follow next. This process is basically identical to the oft-maligned programming technique of using so-called " goto loops ." — Furthermore, there is also a slight cross-reference between infinite loops and goto loops which is probably being referenced, in that goto loops are often criticized (whether accurately or not) as being more likely to create unintended infinite loops in code... primarily because of the difficulty inherent in keeping track of possible entry and exit paths, especially when making edits to the code at a later time. [The comic is a flowchart In order to explain this in text, follow the line numbers. Options follow on new lines without numbers.] How to write good code. [10.] Start Project. [Go to 20.] [20.] Do things right or do them fast? Fast [Go to 30.] Right [Go to 40.] [30.] Code fast. [Go to 35.] [35.] Does it work yet? No [Go to 30.] Almost, but it's become a mass of kludges and spaghetti code. [Go to 50.] [40.] Code well. [Go to 45.] [45.] Are you done yet? No. [Go to 40.] No, and the requirements have changed. [Go to 50.] [50.] Throw it all out and start over. [Go to 10.] [60.] ? [Go to 70.] [70.] Good code.

Modern History

Modern History

https://www.xkcd.com/845

https://www.explainxkcd.com/wiki/index.php/845:_Modern_History

[Warzone. A soldier in modern American combat gear holding a rifle turns to face Cueball, who is wearing an ersatz copy of the same uniform and clutching a wooden rifle.] Sound effect: BLAM BLAM Sound effect: KABOOM Soldier: Will you please stop imitating everything I do? Cueball: Will you please stop... My Hobby: real time war reenactment.

War reenactment is a hobby in which people act out a battle from some previous time period. Theoretical "real-time" war reenactment takes this one step further by having someone act out a war that is actually happening at the time. This would be annoying for the actual soldiers, as it would be hard to do your job if someone was right behind you imitating (and distracting) you. It would also be hard for the reenactor to get to the war zone without getting killed or detained. The title text refers to how someone would research the character that someone would play in a normal war reenactment for a more enjoyable and accurate reenactment. Once again, the title text makes a real-time version of this, having someone actually live the life of the real-time fighter. This is not a good idea for several reasons. [ citation needed ] [Warzone. A soldier in modern American combat gear holding a rifle turns to face Cueball, who is wearing an ersatz copy of the same uniform and clutching a wooden rifle.] Sound effect: BLAM BLAM Sound effect: KABOOM Soldier: Will you please stop imitating everything I do? Cueball: Will you please stop... My Hobby: real time war reenactment.

Dental Nerve

Dental Nerve

https://www.xkcd.com/846

https://www.explainxkcd.com/wiki/index.php/846:_Dental_Nerve

Megan: Dear Ke$ha, Megan: It's hard to describe the pain of a deeply infected dental nerve. [Megan putting her hands in a bowl.] Megan: To get an idea, put your hands in a bowl full of ice cubes. Hold them there for 90 seconds. Megan: Now imagine that pain in your jaw, every minute of every hour, bright and searing, washing out everything. You can't party all night. You can barely stand up. There's only the pain. Megan: So, some friendly advice: When you wake up in the morning, before you brush your teeth with a bottle of Jack, Megan: Brush them with actual toothpaste.

Ke$ha is a pop/rap singer, and this strip refers to her 2009-10 hit single " Tik Tok ." The song begins with the following lyrics, of which the title text is a parody: Wake up in the morning feeling like P. Diddy Grab my glasses, I'm out the door, I'm gonna hit this city Before I leave, brush my teeth with a bottle of Jack 'Cause when I leave for the night, I ain't coming back. A "bottle of Jack" refers to the Jack Daniel's brand of whiskey. The strip depicts Megan warning Ke$ha not to neglect dental hygiene by using whiskey instead of toothpaste to freshen her breath, due to the severe pain that could result if she let the nerves in her teeth become infected. The title text displays dental-hygiene-friendly lyrics, with emphasis on certain syllables (as all-caps) to imitate the rhythm of the original song. Megan: Dear Ke$ha, Megan: It's hard to describe the pain of a deeply infected dental nerve. [Megan putting her hands in a bowl.] Megan: To get an idea, put your hands in a bowl full of ice cubes. Hold them there for 90 seconds. Megan: Now imagine that pain in your jaw, every minute of every hour, bright and searing, washing out everything. You can't party all night. You can barely stand up. There's only the pain. Megan: So, some friendly advice: When you wake up in the morning, before you brush your teeth with a bottle of Jack, Megan: Brush them with actual toothpaste.

Stingray Nebula

Stingray Nebula

https://www.xkcd.com/847

https://www.explainxkcd.com/wiki/index.php/847:_Stingray_Nebula

[Cueball and his Cueball-like friend to the left is shown as white silhouettes against a dark sky. They're sitting on top of a grassy hill also shown inverted as white.] Cueball: I know things are tough right now. When I was going through some difficult times as a kid, I would go up on the roof and look through my telescope. [Zoom in on the twos white heads and upper torso only.] Cueball: One day I found a tiny star in Ara that seemed friendly. Cueball: There were millions like it, but I decided that this one was mine. [Zoom in only on Cueball's head and torso.] Cueball: When things got bad, I'd go find that star, and think of my favorite Tolkien quote. It's from Sam's time in Mordor. [The next panel is diagonally downward to the right of the previous. The upper left corner overlaps. A single star is shown above the highest peak in a jagged chain of mountains with at least five other large peaks and several smaller ones. Above the star in the black sky is a long quote.] "There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the shadow was only a small and passing thing: There was light and high beauty forever beyond its reach." — The Return of the K in g [Back to normal panels below the quote panel. Larger zoom than in panel two both showing the same of the two.] Friend: That's comforting! Cueball: It was rather undercut in 1987, when the light from my star's explosion reached Earth. The debris forms the Stingray Nebula. [Zooming further out even than the first panel, showing more of the grassy mound below the two.] Friend: There's probably a lesson there. Cueball: "Never trust an unstable asymptotic giant branch star. Stick with main sequences and dwarfs." Friend: I'll, uh, keep that in mind.

The Stingray Nebula , in the constellation Ara , is the youngest known planetary nebula in the galaxy. It was formed by an asymptotic giant branch (AGB) B1 supergiant , which blasted out the gas while becoming a white dwarf in 1987. Well, it happened about 18,000 years ago, but the light of the incident reached the Earth in 1987. This comic went from a reassuring comic about stars at night giving hope in the darkness, but then as with most xkcd's, it took a turn. In this case, the twist is that because Cueball 's star he got attached to exploded into a nebula, we should only become attached to stars that aren't quite as volatile as the one that formed the Stingray Nebula. While talking about his star, Cueball shares with his friend a quote from the Lord of the Rings: The Return of the King , the third installment in J.R.R. Tolkien's epic fantasy series. Sam and his friend Frodo were forced to travel through Mordor , a land of fire and death, to destroy the malevolent One Ring . The journey's hardship took a psychological toll on each of them. Cueball compares his struggles as a kid, and his friend's struggles in the present, to Sam and Frodo's arduous journey through Mordor. Both he and Sam were able to find beauty and solace in the glimmering of some distant light. By attaching their hopes, woes and feelings to this small point of hope, they both get a sense of perspective and comfort in the fact that there is beauty in a greater sense before them. The title text ties into the Tolkien quote. Eärendil , with a Silmaril strapped to his ship, Vingilot, is the Tolkienian myth explanation for the planet Venus , which has historically been mistaken for a star due to its brightness, being known as the "morning star" or "evening star". Venus will eventually (in billions of years time) be engulfed by the sun's expansion into a red giant. The source of Sam's comfort is also temporary in the long term. [Cueball and his Cueball-like friend to the left is shown as white silhouettes against a dark sky. They're sitting on top of a grassy hill also shown inverted as white.] Cueball: I know things are tough right now. When I was going through some difficult times as a kid, I would go up on the roof and look through my telescope. [Zoom in on the twos white heads and upper torso only.] Cueball: One day I found a tiny star in Ara that seemed friendly. Cueball: There were millions like it, but I decided that this one was mine. [Zoom in only on Cueball's head and torso.] Cueball: When things got bad, I'd go find that star, and think of my favorite Tolkien quote. It's from Sam's time in Mordor. [The next panel is diagonally downward to the right of the previous. The upper left corner overlaps. A single star is shown above the highest peak in a jagged chain of mountains with at least five other large peaks and several smaller ones. Above the star in the black sky is a long quote.] "There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the shadow was only a small and passing thing: There was light and high beauty forever beyond its reach." — The Return of the K in g [Back to normal panels below the quote panel. Larger zoom than in panel two both showing the same of the two.] Friend: That's comforting! Cueball: It was rather undercut in 1987, when the light from my star's explosion reached Earth. The debris forms the Stingray Nebula. [Zooming further out even than the first panel, showing more of the grassy mound below the two.] Friend: There's probably a lesson there. Cueball: "Never trust an unstable asymptotic giant branch star. Stick with main sequences and dwarfs." Friend: I'll, uh, keep that in mind.

3D

3D

https://www.xkcd.com/848

https://www.explainxkcd.com/wiki/index.php/848:_3D

[People are lined up to see a movie.] Premiering Tonight: String Theory: An Exposé Presented In 3D! [The people are in a dark theater, fiddling with their glasses.] ??? [The people angrily approach black hat, who's sitting at a desk.] Megan: Your movie was a ripoff. Cueball: It wasn't 3D at all! Black Hat: Was too. Black Hat: It's just that the third dimension is tightly rolled up and too small to observe at normal energies.

String theory hypothesizes that there are many more than 3 dimensions , it's just that we can't see the rest because they're "rolled up." A common metaphor is an ant on a tightrope — it has two degrees of freedom, one along the rope and one around it, but from far away we can only see one. So Black Hat released his 2D movie about string theory in "3D", and claimed that the third dimension was there — just too small to see. The title text refers to a linear particle accelerator , or "LINAC", which is used to create high-energy particles. Incidentally, the glasses give their particles one mega-electronvolt (symbol MeV ) of energy, which is not particularly high for a particle accelerator. The title text suggests that such moviegoers should try the accelerators at the European Organization for Nuclear Research, CERN , since they are widely known for producing the highest energies in the millions of MeV, and thus have the best chance of unraveling the small dimensions of string theory. On the xk3d prank site created along with 880: Headache , the 3D on this comic is not visible. [People are lined up to see a movie.] Premiering Tonight: String Theory: An Exposé Presented In 3D! [The people are in a dark theater, fiddling with their glasses.] ??? [The people angrily approach black hat, who's sitting at a desk.] Megan: Your movie was a ripoff. Cueball: It wasn't 3D at all! Black Hat: Was too. Black Hat: It's just that the third dimension is tightly rolled up and too small to observe at normal energies.

Complex Conjugate

Complex Conjugate

https://www.xkcd.com/849

https://www.explainxkcd.com/wiki/index.php/849:_Complex_Conjugate

[Cueball, holding a marker pen down in one hand, is standing at a whiteboard with two equations, one of which is the time-dependent Schrodinger equation and the other shows what the wavefunction equals, but from there it becomes unreadable. Below is a graph with a bell-shaped curve. There are also other unreadable markings on the board below the second equation and next to the graph.] Cueball: Okay, anyone who's feeling like they can't handle the physics here should probably just leave now. [In a frame-less panel Cueball is seen writing on the whiteboard. This is seen from the side of the board, so it is just a thin line with a shelf at the bottom for putting the pen on.] Cueball: Because I'm multiplying the wavefunction by its complex conjugate. Cueball: That's right. [Dramatic zoom in on Cueball appears to be writing the final part of his next equation.] Cueball: Shit just got real .

This was the second comic with one of Randall's fun facts . This comic is a joke on the phrase "Shit just got real", which means "something has suddenly increased in difficulty and become genuinely challenging or dangerous". Cueball is standing in front of a board delivering a lesson, and is about to multiply a wavefunction by its complex conjugate. A wave function is a mathematical description of a quantum system which uses complex values - numbers that have both a real part and an imaginary part. Multiplying a wavefunction by its complex conjugate is a common thing to do, as it yields the probability density of where a particle is likely to be found, which is a real-valued function. Complex numbers can be written in the form a + bi, where a is the real part and bi is the imaginary part. i is the imaginary unit, defined so that i² = -1. The complex conjugate of a complex number simply reverses the sign on the imaginary part - so for the number above, the complex conjugate is a - bi. Multiplying the complex number by its own complex conjugate therefore yields (a + bi)(a - bi). If you multiply out the brackets, you get a² + abi - abi - b²i². The abi cancel each other out, and i² can be replaced by -1. Thus, the result is a² + b², a real number, so "shit just got real" as Cueball promised. The title text notes that you can make this joke in class every time a calculation is performed that drops the imaginary part from a complex number, but warns that it would be so annoying that the professor will eventually find a way to have the class without you in it. Because nonreal numbers are often considered to have no physical significance, turning them into real numbers to produce a final answer is so common that this joke would quickly become tedious. The wave function shown on Cueball's board is the time-dependent Schrödinger equation , a differential equation that the wavefunction Ψ, which determines the possible positions of a quantum particle over time, always satisfies. The derivative should be written with ∂Ψ on the top; the omission of the Ψ may be a mistake. [Cueball, holding a marker pen down in one hand, is standing at a whiteboard with two equations, one of which is the time-dependent Schrodinger equation and the other shows what the wavefunction equals, but from there it becomes unreadable. Below is a graph with a bell-shaped curve. There are also other unreadable markings on the board below the second equation and next to the graph.] Cueball: Okay, anyone who's feeling like they can't handle the physics here should probably just leave now. [In a frame-less panel Cueball is seen writing on the whiteboard. This is seen from the side of the board, so it is just a thin line with a shelf at the bottom for putting the pen on.] Cueball: Because I'm multiplying the wavefunction by its complex conjugate. Cueball: That's right. [Dramatic zoom in on Cueball appears to be writing the final part of his next equation.] Cueball: Shit just got real .

World According to Americans

World According to Americans

https://www.xkcd.com/850

https://www.explainxkcd.com/wiki/index.php/850:_World_According_to_Americans

THE WORLD According to a Group of AMERICANS who turned out to be unexpectedly good at geography, derailing our attempt to illustrate their country's attitude toward the rest of the world. [Left to right, up to down.] [North of Canada.] Hey so what projection should we use? I'll aim for "Robinson." [North America.] Alaska; Canada; Hudson Bay; Québec; United States Did you know Maine is actually the US state closest to Africa?; Bermuda (British!) [Central America.] Baja California (Mexico); Mexico; Central America; Panama Canal; Gulf of Mexico; Cuba; Hispañola; POR.; Jamaica Do we have to label all the Virgin Islands? [South America.] Rest of South America (spanish-speaking); Brazil (portugese-speaking); French, and I think Dutch and English; Tierra del Fuego [Greenland.] Greenland (still too big!); Yeah but the Peters map is awful; Iceland [Europe.] British Isles; Ireland ; Gibralter; Scandanavia; Western Europe; Eastern Europe; Black sea; Middle East [Africa.] Morocco; Algera; Sahara Desert; West Africa; Sudan; Rainforest DRC; Lake Victoria; Somalia; Angola; Mozambique; South Africa; Cape Horn; Madagascar [West of DRC.] So this is one of those things where you point out our ignorance and stereotypes? Yeah – I mean, I freely admit I don't know the African map very well, which speaks volumes in itself. [West Asia.] Russia; Aral sea (Gone); Various former Soviet states; Afghanistan & Pakistan; India; Mostly Muslim; Mostly Hindu [Indian Ocea.] Sri Lanka; Boxing Day Quake Wait, "Boxing day"? There's no way you're American. I read BBC News, OK? [East Asia.] Mongolia; Tibet (contested); China; Southeast Asia [Pacific Ocean.] Kamchatka Pennisula, but I admit I only know this one from Risk. Koreas; Japan, duh.; Taiwan (actually called "The Republic of China." – it's complicated.); Phillipines; Malaysia; Indonesia; Sulawesi; Paupa New Guinea; Australia; Tasmania; New Zealand [South of Africa.] Should we include Antarctica? Let's not – these guys are looking impatient.

There's a somewhat well-circulated image on the internet entitled " The World According to Americans " which plays on the stereotype of the ignorant American. In it, the entirety of Eastern Europe and most of Asia are entitled "commies" and the Middle-East as "evil-doers," and so on. Later, other people created similar maps to re-do the concept. It later spread to other cultures. This comic is an anti-joke playing on that idea. You expect to see something which plays on the stereotypes that exist in American culture of various parts of the world. However, instead, the map is remarkably well-informed, and shows how sampling bias can be used to conflate results. See below the table of items in the map . The title text jokes that in fact the only reason that the map is fairly well annotated is that the group of people labeling it were actually on the way back from a geography bee . This could add weight to the 'Ignorant American' stereotype as these individuals should know more than the common person, implying that if even apparent geography buffs use vague labels such as "rest of South America" and "various former Soviet states" instead of using more detailed labels, the average American must be even less geographically knowledgeable (Although, as the illustrators wrote below Cape Horn, the reason they did not draw Antarctica or many South American, Middle Eastern and British countries and the lack of detail may be because the people who asked them to draw this map were beginning to 'look impatient' since they did not get the expected ignorant result.) A landlocked country is a country that does not border any major bodies of water. Furthering the concept, a doubly-landlocked country is a country that not only has no connection to water, but is only bordered by other landlocked countries. As the title text states, there are only two such countries in the world as of 2012: Uzbekistan and Liechtenstein . This is the type of fact that may be stereotypically expected of a geography bee competitor. THE WORLD According to a Group of AMERICANS who turned out to be unexpectedly good at geography, derailing our attempt to illustrate their country's attitude toward the rest of the world. [Left to right, up to down.] [North of Canada.] Hey so what projection should we use? I'll aim for "Robinson." [North America.] Alaska; Canada; Hudson Bay; Québec; United States Did you know Maine is actually the US state closest to Africa?; Bermuda (British!) [Central America.] Baja California (Mexico); Mexico; Central America; Panama Canal; Gulf of Mexico; Cuba; Hispañola; POR.; Jamaica Do we have to label all the Virgin Islands? [South America.] Rest of South America (spanish-speaking); Brazil (portugese-speaking); French, and I think Dutch and English; Tierra del Fuego [Greenland.] Greenland (still too big!); Yeah but the Peters map is awful; Iceland [Europe.] British Isles; Ireland ; Gibralter; Scandanavia; Western Europe; Eastern Europe; Black sea; Middle East [Africa.] Morocco; Algera; Sahara Desert; West Africa; Sudan; Rainforest DRC; Lake Victoria; Somalia; Angola; Mozambique; South Africa; Cape Horn; Madagascar [West of DRC.] So this is one of those things where you point out our ignorance and stereotypes? Yeah – I mean, I freely admit I don't know the African map very well, which speaks volumes in itself. [West Asia.] Russia; Aral sea (Gone); Various former Soviet states; Afghanistan & Pakistan; India; Mostly Muslim; Mostly Hindu [Indian Ocea.] Sri Lanka; Boxing Day Quake Wait, "Boxing day"? There's no way you're American. I read BBC News, OK? [East Asia.] Mongolia; Tibet (contested); China; Southeast Asia [Pacific Ocean.] Kamchatka Pennisula, but I admit I only know this one from Risk. Koreas; Japan, duh.; Taiwan (actually called "The Republic of China." – it's complicated.); Phillipines; Malaysia; Indonesia; Sulawesi; Paupa New Guinea; Australia; Tasmania; New Zealand [South of Africa.] Should we include Antarctica? Let's not – these guys are looking impatient.

Na

Na

https://www.xkcd.com/851

https://www.explainxkcd.com/wiki/index.php/851:_Na

[A flowchart with 11 similar boxes on a line connected with arrows. After 8 there is two branches, one up (with three boxes above the rest of the 11 boxes) and one down to one box. After 10 there is one branch down to a larger box with two lines, and after that the last arrow is longer before reaching the last and 11th box. From this box there is an arrow that loops around to the last box again. This arrow is labeled.] Na → Na → Na → Na → Na → Na → Na → Na → Na → Na → Na Up 8 branch:→ Hey → Hey → Goodbye Down 8 branch:→ Batman! Down 10 branch:→ Katamari Damacy! Loop: Land of 1,000 Dances I can't believe I forgot Hey Jude. I don't get do-overs, but I couldn't resist making a fixed version . Protip: m.xkcd.com is a clean, mobile-friendly version of xkcd.com. Protip: Scripts can fetch comics and metadata automatically.

The repetition of the syllable "na" is often used to sing a tune without using any of the actual words. While this is normally done to practice or demonstrate a tune, repeated "na"s are also a part of some songs' lyrics, as shown in this comic. Following the various paths of the diagram forms the words of several well-known tunes, with each song branching off after the appropriate number of "na"s. The top entry refers to the song " Na Na Hey Hey Kiss Him Goodbye ," originally recorded by Steam . The tune is often sung by the home fans of American sporting events at the end of a victory as a means of taunting the away team. The left bottom entry refers to the theme song of the '60s TV show Batman . The middle bottom entry refers to the theme song of the video game Katamari Damacy , which was also the cause of the Accident in comic 161. The right bottom entry refers to the song " Land of a Thousand Dances ," originally recorded by Chris Kenner . The title text jokes that the tune's incessant repetition of "na" has annoyed Randall to the point that he does not have the patience to listen to the whole song. There are likely countless other songs that uses "Na Na Na" as part of the lyrics. Some will be more popular than others. A very popular song that goes: Naaa Naaa Naaa Na Na Na Naaa, Na Na Na Naaaa, Hey Jude was left out. Hey Jude must have been brought to Randall's attention after this comic was released, as he made a comment about it in the comic header the day after this comic was released, see Trivia below. This is one of many flowchart comics. A full list can be found here . [A flowchart with 11 similar boxes on a line connected with arrows. After 8 there is two branches, one up (with three boxes above the rest of the 11 boxes) and one down to one box. After 10 there is one branch down to a larger box with two lines, and after that the last arrow is longer before reaching the last and 11th box. From this box there is an arrow that loops around to the last box again. This arrow is labeled.] Na → Na → Na → Na → Na → Na → Na → Na → Na → Na → Na Up 8 branch:→ Hey → Hey → Goodbye Down 8 branch:→ Batman! Down 10 branch:→ Katamari Damacy! Loop: Land of 1,000 Dances I can't believe I forgot Hey Jude. I don't get do-overs, but I couldn't resist making a fixed version . Protip: m.xkcd.com is a clean, mobile-friendly version of xkcd.com. Protip: Scripts can fetch comics and metadata automatically.

Local g

Local g

https://www.xkcd.com/852

https://www.explainxkcd.com/wiki/index.php/852:_Local_g

[Cueball is sitting at a desk, working, with a a laptop in front of him. Megan is behind him. Cueball has turned his head to talk to Megan] Cueball: Did you know that because of centrifugal * force and the shape of the Earth, "gravity" can vary by nearly half a percent between major cities? * Yes, centrifugal. xkcd.com/123 [Closeup on Cueball, who is looking down at some notes.] Cueball: That's not a lot, but it could affect, say, pole vaulting. In a 5m jump, it could make a difference of 2cm. [Zoomed out on Cueball, who is typing on his laptop. Megan is behind him, with her hand on her chin.] Megan: Huh, interesting. Cueball: I'm going to write an article reevaluating vaulting records to take this into account. Three days later: [Cueball is sitting in an armchair. Megan is behind him, and is pointing behind her.] Megan: Good job. There's an angry mob of athletes outside. [Cueball looks off the balcony. A mob of athletes is out of frame.] Athlete: That record was mine! Athlete: How dare you cast doubt on our honor? Athlete: Have you no respect ?! Athlete: Make him pay! Cueball: Hey, the math doesn't lie. Suck it, jocks. [Megan stands next to Cueball, who is walking away to the right] Megan: Dude, don't provoke them. Cueball: Whatever. The building's locked. Let 'em vent for a- crash Off-panel Athlete: GET HIM! [Megan stands next to Cueball. They are both in shock. Megan has her hand on her mouth.] Cueball: Crap! Cueball: How did the pole vaulters get up to our balcony? [Beat frame with only Megan. Cueball is out of frame.] Megan: ... [Beat frame with just Cueball.] [Zoom in on Megan and Cueball, who is facepalming.] Megan: That might be the stupidest question I've ever heard. Cueball: Right.

Cueball explains in the first panel, that the centrifugal force (not be confused with the centripetal force , which is made clear in 123: Centrifugal Force , cited in the first frame of this comic) along with variations in the earth's shape causes the gravitational force to vary by half a percent between some cities. These variations could have a significant effect on certain sporting events; for example, Cueball explains that a pole vaulter might jump 2 cm higher in a city with a smaller gravitational force. So Cueball writes an article reevaluating pole vaulting world records based on the city in which the record was accomplished. His article suggests that some athletes should not have received an award for breaking a record because they did so in a city with a below-average gravitational force. These pole vaulters whose records were questioned by Cueball's article angrily stage a protest outside of Cueball's apartment. Then Cueball proceeds to taunt them reasoning that they can't harm him because his building is locked. Cueball and Megan then hear a crash indicating that the protesters have managed to reach the apartment's balcony. When Cueball asks out loud how the pole vaulters reached the balcony, Megan stares at him for a moment and then he realizes the stupidity of that question: the pole vaulters pole-vaulted onto the balcony. In the title text Randall explains that in fact the gravity force at the Olympic Games at Rio de Janeiro in 2016 compared to London in 2012 will make a difference of more than one centimeter, mainly because Rio de Janeiro is much closer to the equator than London resulting in an increased centrifugal, or, perhaps centripetal if you prefer to be more contrasting, force. [Cueball is sitting at a desk, working, with a a laptop in front of him. Megan is behind him. Cueball has turned his head to talk to Megan] Cueball: Did you know that because of centrifugal * force and the shape of the Earth, "gravity" can vary by nearly half a percent between major cities? * Yes, centrifugal. xkcd.com/123 [Closeup on Cueball, who is looking down at some notes.] Cueball: That's not a lot, but it could affect, say, pole vaulting. In a 5m jump, it could make a difference of 2cm. [Zoomed out on Cueball, who is typing on his laptop. Megan is behind him, with her hand on her chin.] Megan: Huh, interesting. Cueball: I'm going to write an article reevaluating vaulting records to take this into account. Three days later: [Cueball is sitting in an armchair. Megan is behind him, and is pointing behind her.] Megan: Good job. There's an angry mob of athletes outside. [Cueball looks off the balcony. A mob of athletes is out of frame.] Athlete: That record was mine! Athlete: How dare you cast doubt on our honor? Athlete: Have you no respect ?! Athlete: Make him pay! Cueball: Hey, the math doesn't lie. Suck it, jocks. [Megan stands next to Cueball, who is walking away to the right] Megan: Dude, don't provoke them. Cueball: Whatever. The building's locked. Let 'em vent for a- crash Off-panel Athlete: GET HIM! [Megan stands next to Cueball. They are both in shock. Megan has her hand on her mouth.] Cueball: Crap! Cueball: How did the pole vaulters get up to our balcony? [Beat frame with only Megan. Cueball is out of frame.] Megan: ... [Beat frame with just Cueball.] [Zoom in on Megan and Cueball, who is facepalming.] Megan: That might be the stupidest question I've ever heard. Cueball: Right.

Consecutive Vowels

Consecutive Vowels

https://www.xkcd.com/853

https://www.explainxkcd.com/wiki/index.php/853:_Consecutive_Vowels

[Megan stands at the left while Cueball comes from right holding up a chart.] Cueball: I was running a factor analysis on this huge database, and check out what it found: [An xy-graph plotting "sexual arousal" against "consecutive vowels." The trendline through the dots is a smooth exponential increasing curve.] [Frameless panel:] Megan: Huh? This chart makes no sense. What- Cueball: "Queueing" [Zoom in, Megan grabs Cueball.] Megan: FUCK ME NOW.

After running some analysis on a database, Cueball shows Megan a chart depicting the relationship between sexual arousal and consecutive vowels, showing that a high amount of consecutive vowels is linked to higher sexual arousal. At first, it could be theorised to be due to drawn out moans or screams during lovemaking and orgasm (Ooooh! Yeeeees!). Megan says she doesn't get it, but Cueball interrupts her with "queueing", a word with 5 consecutive vowels. This immediately arouses Megan, who grabs Cueball and shouts "FUCK ME NOW." It turns out that the consecutive vowels themselves appear to cause arousal, rather than arousal causing the use of consecutive vowels. The title text shows that Cueball is fearful that there may be a voyeur peeking at them, but as "voyeur" has 4 consecutive vowels because "y" is a vowel in this case, Cueball gets turned on as well. [Megan stands at the left while Cueball comes from right holding up a chart.] Cueball: I was running a factor analysis on this huge database, and check out what it found: [An xy-graph plotting "sexual arousal" against "consecutive vowels." The trendline through the dots is a smooth exponential increasing curve.] [Frameless panel:] Megan: Huh? This chart makes no sense. What- Cueball: "Queueing" [Zoom in, Megan grabs Cueball.] Megan: FUCK ME NOW.

Learning to Cook

Learning to Cook

https://www.xkcd.com/854

https://www.explainxkcd.com/wiki/index.php/854:_Learning_to_Cook

[A flowchart.] I should cook more! --> Buy ingredients --> Put some in a pan --> Cook --> Does it taste good? --> (arrows marked "Kinda" and "No" both lead to) Put leftovers in fridge --> (hours pass) --> Order pizza --> (days pass) --> Throw away leftovers --> (weeks pass) --> Throw away remaining ingredients as they go bad --> (months pass) --> (arrow leads back to beginning)

This comic shows the plight of Randall who occasionally motivates himself to cook. After buying ingredients and cooking them, the food always ended up either tasted "kinda good" or not good, therefore - although he puts the leftovers in the fridge - hours later he orders pizza instead of eating the leftovers. A few days later he first throws away the leftovers, and some weeks later also the unused ingredients. After some months he is motivated again to cook more and the loop repeats. This discontinued effort may be part of the reason his cooking does not improve much over time. The title text describes that buying ingredients for a single meal might be more expensive than eating at a restaurant, but it would be compensated if there are enough leftovers to eat again from it or cook several meals. Of course, this idea is vitiated if he gives up cooking after a single try and throws away all remaining food. [A flowchart.] I should cook more! --> Buy ingredients --> Put some in a pan --> Cook --> Does it taste good? --> (arrows marked "Kinda" and "No" both lead to) Put leftovers in fridge --> (hours pass) --> Order pizza --> (days pass) --> Throw away leftovers --> (weeks pass) --> Throw away remaining ingredients as they go bad --> (months pass) --> (arrow leads back to beginning)

1999

1999

https://www.xkcd.com/855

https://www.explainxkcd.com/wiki/index.php/855:_1999

It's easy to forget, as we heap awards on The Social Network , That before there was Facebook, MySpace, or even Friendster... One website dreamed bigger than them all. [Cueball and another are talking.] Cueball: People like doing stuff. So why not build a website that offers that? Another: Offers what? What would I do there? Cueball: Anything! The only limit is yourself! [Another scene. Hacker, wearing headphones and oblivious, working at computer. Cueball runs in to interrupt; Another holds him back.] Cueball: Hey, we need more— Another: Don't–he's wired in. Hacker: The infinite is possible. Another: Or baked. It's hard to tell. [Cueball and another at table in bar.] Cueball: It's time to monetize. We could make millions! Another: No way. A million dollars isn't cool. You know what's cool? Cueball: A billio– Another: Circles. [Long shot in bar. Drinks on table in foreground; dim figures in doorway in background; Cueball, alone, shouting into the distance.] Cueball: Hey–a tip: drop the dot. Cueball: Just "Zombocom". Cueball: It's cleaner.

This comic is a parody of the movie The Social Network , a movie about the founding of the popular social network site Facebook. Here, scenes from the movie are reimagined to feature Zombo.com instead. Zombo.com, also known as Zombocom, is a website that was created in 1999 and using only Flash animations . The animation consists of a circle of quickly pulsating dots and a friendly deep male voice repeatedly welcoming the visitor to "Zombocom" and explaining that there was no limit to what could be done at the site, or rather, no limit except yourself. The message repeats while, ironically, there is absolutely nothing that can be done at the site until the message completes, at which point a link saying "Sign up for our newZletter" appears, linking to a page saying that the selected option is not available yet. If the link is not clicked, the Flash player will reset. Thus, you can still do nothing on the site. The humor of the parody comes in substituting Facebook, a site that, at the time this comic was made, was a useful and popular website; for Zombo.com, a novelty site which gained attention for its complete uselessness. You can visit the site at zombo.com . The last four panels are all direct parodies of specific scenes from The Social Network . The second panel is a takeoff of the scene where Facebook founder Mark Zuckerberg comes up with the idea for the site, saying that people like checking up on their friends and acquaintances, so why not build a site that lets them do that? Because Zombo.com has no actual function, in this version the founder can't specify what he wants the site to do. The third panel is taken from a scene where Zuckerberg is seen intensely focused on programming the site, his headphones insulating him from the outside world. His assistant describes his state as "wired in" and demands that he not be disturbed. In the comic, as Zombo.com is a very simple site which does not need much coding, the assistant offers the possibility that the founder is stoned. Indeed, it's one of the few conceivable reasons that one would be this focused on such a useless website. As "the infinite is possible" is a phrase in Zombo.com's audio clip, it is also plausible that the founder is currently recording the clip, and the assistant is telling the others not to bother him for fear of adding background noise to the clip. The fourth panel is taken from a scene where co-founder Eduardo Saverin tries to push for monetization of Facebook, while investor and consultant Sean Parker argues against. The actual dialogue is "You don't even know what the thing is yet. How big it can get, how far it can go. This is no time to take your chips down. A million dollars isn't cool, you know what's cool? A billion dollars." Here, instead of a billion dollars, the Parker character argues "Circles," playing off Zombo.com's un-lucrative nature and the silliness of the design. The final panel is taken from a scene where Parker advises Zuckerberg to change the name of the site from TheFacebook to just Facebook, calling it "cleaner." Here, he advises to change the name of Zombo.com to just Zombocom. Why the website is pronounced "Zombocom" rather than the more expected Zombo Dot Com is a mystery known only to its creators; perhaps, like in the movie, they also considered it cleaner. The title text is a reference to a quote from the movie, specifically a conversation between Zuckerberg and Delpy (Zuckerberg is the first quote). In the actual film, Zuckerberg answers "twenty-two thousand" rather than just "twenty-two". This is a joke to the effect that, back in 1999, there weren't really that many people on the internet, and very few of them would have gone to Zombo.com. It's easy to forget, as we heap awards on The Social Network , That before there was Facebook, MySpace, or even Friendster... One website dreamed bigger than them all. [Cueball and another are talking.] Cueball: People like doing stuff. So why not build a website that offers that? Another: Offers what? What would I do there? Cueball: Anything! The only limit is yourself! [Another scene. Hacker, wearing headphones and oblivious, working at computer. Cueball runs in to interrupt; Another holds him back.] Cueball: Hey, we need more— Another: Don't–he's wired in. Hacker: The infinite is possible. Another: Or baked. It's hard to tell. [Cueball and another at table in bar.] Cueball: It's time to monetize. We could make millions! Another: No way. A million dollars isn't cool. You know what's cool? Cueball: A billio– Another: Circles. [Long shot in bar. Drinks on table in foreground; dim figures in doorway in background; Cueball, alone, shouting into the distance.] Cueball: Hey–a tip: drop the dot. Cueball: Just "Zombocom". Cueball: It's cleaner.

Trochee Fixation

Trochee Fixation

https://www.xkcd.com/856

https://www.explainxkcd.com/wiki/index.php/856:_Trochee_Fixation

Girl: Robot ninja! Pirate doctor laser monkey! Narwhal zombie badger hobo bacon kitty captain penguin raptor Jesus! Megan: We'd been seeing this brain damage for years, but only recently did our linguists identify the pattern behind it. Megan: The patients fixate on animals and types of people whose names are trochees (two syllables, with the accent on the first). The malfunction causes a rush of dopamine whenever these trochees are heard or spoken. [Chart shows "internet" and "brain," with arrows marked "trochees" traveling both ways between them. An arrow marked "dopamine" loops from the brain back to the brain.] The warning signs appear in childhood: [Child sits in front of TV.] Child: Yeah! Mighty teenage morphin' ninja power mutant turtle rangers! Social reinforcement focuses the fixation on a few dozen words. Cueball (off-panel): Is there a cure? [Girl is reclining under a big machine pointed at her face.] Megan: We're about to try a radical trocheeotomy. Cueball: Rip out her vocal chords? I'm in favor. Megan: No, we're modifying her vocabulary* to erase the words she's fixated on. *Digitoneurolinguistic hacking! It's totally real! Ask Neal Stephenson. Megan: Either the gap will be filled by normal words, or she'll just generate a new set of trochees. Megan: Here goes. [She pulls the lever on a large panel.] kachunk bzzzZZZZZZ [Girl is waking up.] Girl: ...GzZhRmPh ... Girl ...banjo turtle! Girl: Jetpack ferret pizza lawyer! Dentist hamster wombat plumber turkey jester hindu cowboy hooker bobcat scrapple! Megan (off-panel): Sigh. Megan: Time for plan B. Cueball: Someone get a brick.

A trochee is a type of poetic foot . A foot is a measure in poetry; it consists of stressed beats and unstressed beats. A trochee is a foot that consists of one stressed beat followed by an unstressed beat. "Trochee" itself is an example of this as you stress the first syllable and don't stress the second syllable ("TROH-kee".) Trochee fixation is supposedly caused by people experiencing rushes of dopamine when they hear or speak trochees during their youth. Due to the rush of dopamine, they become more fixated on trochees. In the endless quest for dopamine, they continue to search for trochees (typically on the internet) while also producing more places to encounter trochees meaning more fixation for others with the disorder. Megan proposes a "radical trocheeotomy" which appears to be a type of psychosurgery due to the erasing of memory. Cueball misinterprets Megan's intent as a " tracheotomy ", which he mistakenly believes to be a removal of the girl's vocal cords, of which he is in favor. Megan proceeds with the trocheeotomy, but luckily it does not have the intended effect. Though the previous trochees have been forcefully and unkindly removed, the girl immediately generates new ones: "BAN-jo," "TUR-tle," "JET-pack," "FER-ret," and so on. The correct way of removing the fixation would be to alter mesolimbic pathway . Megan, not realizing this, succumbs to attempting to removing the girl's trochee fixation via cranially-applied brick. Depending on how hard the girl is hit with the brick she may have memory loss and potentially forget all the trochees she knows, but if this method is carried out she will have significant brain damage and will likely start fixating on trochees that she hears. There are references to Teenage Mutant Ninja Turtles and Mighty Morphin' Power Rangers , both of which are examples of actual, trochaic TV show titles. Additionally, there is a reference to sci/fi author Neal Stephenson who has written Snow Crash , Anathem and many other books. "Jetpack ferret" could be a reference to 20: Ferret , although the ferret in question only had wings. Huffman coding is a lossless data compression algorithm that works by organizing characters into a tree structure (called a Huffman tree) with the most used characters in a string closer to the top. The characters in the string are then replaced by the sequence of bits representing their place in the tree, allowing for characters that are used very often to be represented with only a handful of bits compared to the 16 or 32 bits usually needed (depending on the character set used). In highly repetitive data this can cut down the file size immensely, which is what Randall is implying by saying you would only end up with 30–40 bytes. Most of the " random " stuff said on the Internet has been said before, and isn’t particularly random either, following predictable patterns. Trochee and other types of poetry "feet" is the subject of 1383: Magic Words , and the trochaic form is explored further in 1412: Teenage Mutant Ninja Turtles . On the blag , Randall published statistics about the occurrence number of certain combinations (now obviously inaccurate). Girl: Robot ninja! Pirate doctor laser monkey! Narwhal zombie badger hobo bacon kitty captain penguin raptor Jesus! Megan: We'd been seeing this brain damage for years, but only recently did our linguists identify the pattern behind it. Megan: The patients fixate on animals and types of people whose names are trochees (two syllables, with the accent on the first). The malfunction causes a rush of dopamine whenever these trochees are heard or spoken. [Chart shows "internet" and "brain," with arrows marked "trochees" traveling both ways between them. An arrow marked "dopamine" loops from the brain back to the brain.] The warning signs appear in childhood: [Child sits in front of TV.] Child: Yeah! Mighty teenage morphin' ninja power mutant turtle rangers! Social reinforcement focuses the fixation on a few dozen words. Cueball (off-panel): Is there a cure? [Girl is reclining under a big machine pointed at her face.] Megan: We're about to try a radical trocheeotomy. Cueball: Rip out her vocal chords? I'm in favor. Megan: No, we're modifying her vocabulary* to erase the words she's fixated on. *Digitoneurolinguistic hacking! It's totally real! Ask Neal Stephenson. Megan: Either the gap will be filled by normal words, or she'll just generate a new set of trochees. Megan: Here goes. [She pulls the lever on a large panel.] kachunk bzzzZZZZZZ [Girl is waking up.] Girl: ...GzZhRmPh ... Girl ...banjo turtle! Girl: Jetpack ferret pizza lawyer! Dentist hamster wombat plumber turkey jester hindu cowboy hooker bobcat scrapple! Megan (off-panel): Sigh. Megan: Time for plan B. Cueball: Someone get a brick.

Archimedes

Archimedes

https://www.xkcd.com/857

https://www.explainxkcd.com/wiki/index.php/857:_Archimedes

[Cueball is standing normally.] Cueball: In the words of Archimedes, [Cueball extends his left arm slightly.] Cueball: Give me a long enough lever and a place to rest it [Cueball is now holding a gun in his right hand.] Cueball: Or I will kill one hostage every hour.

This comic references a famous quote made by Archimedes : δῶς μοι πᾶ στῶ καὶ τὰν γᾶν κινάσω , which could translate as "Give me a long enough lever and a place to rest it, and I will move the Earth". Archimedes was illustrating the power of force multiplication by stating that, in theory, even a mass as immense as the entire planet Earth could be moved by a single human being using a simple lever . While Archimedes is theoretically correct, in practice the lever would need to be millions of light years long, and the person operating it would need to push it by several light years to move the Earth even a microscopic amount. In fact, a much simpler way to move the Earth, which achieves similar distances, is to jump in the air - by Newton's third law, the same amount of force that is applied to you will also be applied to the Earth. Here, Cueball begins as if he is quoting Archimedes, but then produces a gun and threatens to execute hostages if he does not receive the lever, indicating that he is, for some reason, actually trying to enact Archimedes' thought experiment for real. The title text references another famous proverb, "Give a man a fish, and you feed him for a day. Teach a man to fish, and you feed him for a lifetime." The quote starts out the same, but again ends with a sentence that is more fitting for an action movie. [Cueball is standing normally.] Cueball: In the words of Archimedes, [Cueball extends his left arm slightly.] Cueball: Give me a long enough lever and a place to rest it [Cueball is now holding a gun in his right hand.] Cueball: Or I will kill one hostage every hour.

Milk

Milk

https://www.xkcd.com/858

https://www.explainxkcd.com/wiki/index.php/858:_Milk

[Couple sitting opposed, Megan on couch reading book and Cueball a chair with a laptop.] Megan: The fact that I have breasts doesn't mean you could milk me now. I'd have to be lactating. [A beat passes.] [In the third panel, Megan's legs are not seen, probably tucked under the armchair to feel more secure.] Cueball (thinking): Oh my god she's psychic.

Megan and Cueball are sitting quietly, engaged in their own solo pursuits. Without any preamble, Megan answers a question that has not been asked, pointing out to Cueball that he would not be able to obtain milk from her breasts right now, as she is not lactating . Cueball is flabbergasted that she seems to have read his mind, as this was exactly what he was wondering. Megan, like any healthy adult female mammal , is capable of producing milk from her mammary glands . However, this facility is not always available; Megan would have to become pregnant and give birth to trigger the bodily changes that result in normal lactation. The title text indicates that this is not proof of Megan's psychic powers, as Cueball seems quite obsessed with this particular topic, although, if you interpret it as a response to Cueball's thoughts in the last panel it could remain ambiguous. [Couple sitting opposed, Megan on couch reading book and Cueball a chair with a laptop.] Megan: The fact that I have breasts doesn't mean you could milk me now. I'd have to be lactating. [A beat passes.] [In the third panel, Megan's legs are not seen, probably tucked under the armchair to feel more secure.] Cueball (thinking): Oh my god she's psychic.

(

(

https://www.xkcd.com/859

https://www.explainxkcd.com/wiki/index.php/859:_(

[Caption inside an oblong panel:] (An unmatched left parenthesis creates an unresolved tension that will stay with you all day.

In programming, punctuation is often used to mark sections of code. Paired punctuation marks must always be matched up with a corresponding closing mark, otherwise a so-called syntax error occurs. The programming language Lisp (also featured in 224: Lisp is known for large numbers of nested/paired parentheses. Even in literary works intended only for human consumption, the absence of a matching closing parenthesis as appears in this sentence or other "balanced" punctuation sets creates a mental expectation of eventual closure and completion that remains unfulfilled even long after the unmatched mark is encountered. There is also reference to 312: With Apologies to Robert Frost which could contain the missing parentheses. It can also be interpreted as a metaphor , which compares the reader with a Lisp interpreter . The interpreter looks for the parenthesis until the end of the file, where it eventually halts, and prints out the error. The comic claims that if you read an unmatched parenthesis, you will look for it for the rest of the day too. It also refers to an awkward feeling when you see something out of place in a piece of literary text (like unmatched parentheses, spellying error or a randomly-plac,ed comma.. Finally, in some countries (Russia in particular) they use just parentheses instead of text smileys so that :) turns into ) and :( becomes (. Hence Russians can magically resist the unresolved tension of the comic but may feel a bit sad instead as a side effect. The title text refers to the same issue as already highlighted in 327: Exploits of a Mom : if your scripts trust external input, you sometimes will be surprised. At the time of this comic, there were quite a few websites that would grab the xkcd comic three times a week and publish them on their own site. This comic likely broke at least some of the websites because of either the unmatched brace or the extra unmatched markup that is in the title text. [Caption inside an oblong panel:] (An unmatched left parenthesis creates an unresolved tension that will stay with you all day.

Never Do This

Never Do This

https://www.xkcd.com/860

https://www.explainxkcd.com/wiki/index.php/860:_Never_Do_This

[Cueball walks toward Megan holding a pocket microscope.] Cueball: Check it out—a pocket microscope! Megan: Ooh! Let's look at stuff! [Cueball holds a pencil; Megan peers at a quarter through the microscope.] Cueball: The tip of this pencil is neat . Megan: This quarter is really scratched. Cueball: Let's look at the skin under our fingernails! Minutes later... [Cueball and Megan curl up in a black pit of despair.] Cueball and Megan: oh god oh god

Cueball shows his new pocket microscope to Megan . With the curiosity of scientists, they quickly decide to use the microscope to look at a number of different things. But after they use the microscope to inspect what is under their fingernails, they both sink into a catatonic state . Our fingers are how we interact with the world, and all manner of things get trapped under our fingernails; different kinds of dirt, fungus, spores, fragments of insects, insect droppings and so on. Such things that obviously look pretty horrific when magnified a few hundred times. Cueball and Megan never suspected what they would find, and seem unable to process or deal with the horror they have uncovered. The title text refers to Rule 34 (see 305: Rule 34 ), an internet meme which states "If it exists, there is porn of it. No exceptions.". The book referenced is "The Secret House: 24 hours in the strange & wonderful world in which we spend our nights and days" by David Bodanis and is a study in microphotography . It features extreme close-ups of everyday phenomena in the common house, but as seen from a microscopic perspective. "Rule 34" states that there must be porn of this nature, but it is not clear what form this would take. You would, however, probably be able to see the individual sperm cells . Randall may have done this check himself - and now chooses to warn others not to make the same mistake. Thus, the title: Never Do This . He later gives the same type of advice against using a UV lamp in the bathroom through this comic: 1469: UV . Given his likely negative feelings towards Valentine's Day , as seen in the most of his Valentines comics , it may not be a coincidence he send this gross comic out on February 14. He did not draw any Valentines related comic this year as he for instance did the two years before and the year after. [Cueball walks toward Megan holding a pocket microscope.] Cueball: Check it out—a pocket microscope! Megan: Ooh! Let's look at stuff! [Cueball holds a pencil; Megan peers at a quarter through the microscope.] Cueball: The tip of this pencil is neat . Megan: This quarter is really scratched. Cueball: Let's look at the skin under our fingernails! Minutes later... [Cueball and Megan curl up in a black pit of despair.] Cueball and Megan: oh god oh god

Wisdom Teeth

Wisdom Teeth

https://www.xkcd.com/861

https://www.explainxkcd.com/wiki/index.php/861:_Wisdom_Teeth

Cueball, on phone: Hey! Know how you've been bugging me to play Minecraft for the past year? I'm game. Megan, on phone: But you said you didn't want to "get hooked and spend days on end moving virtual cubes around while sitting motionless." What changed? Cueball, on phone: I'm having my wisdom teeth out, and I'll be useless and doped up on painkillers for the next few days, so that actually sounds like the perfect distraction. Megan, on phone: Oh. I'll set you up on our server! 72 hours later... [Megan sitting at computer.] Megan, on phone: Hey — starting to feel better? Enjoying the game? Let's see what you've... What the hell? Where IS everything? [View of a Minecraft screen showing a vast empty expanse of land. In Cueball's hotbar is, from left to right, an stone pickaxe, sword, and shovel, seven feathers, 42 torches, a non-enchanted bow, a blank space, 64 blocks of stone and a clock. He has full health and 15 armor points.] Megan, offscreen: ...You made the entire continent perfectly flat? Cueball, offscreen: And sorted it into layers. Megan, offscreen: ... Cueball, offscreen: I feel good about things. This is a good game. [Cueball sitting on the floor at his laptop, bleeding from the mouth, surrounded by bloody wadded-up tissues and holding a bottle of medication.] Megan, on phone: ...What exactly is in the painkillers they gave you? Cueball, woozy: I can't read the label because I'm a hologram.

Wisdom teeth , as many people are no doubt painfully aware , are the third set of molars found in humans. Because human jaws are smaller than other ape jaws, most of us don't have room for a third set of molars, and the teeth become impacted so they grow straight into the other teeth, requiring a painful, debilitating procedure to remove them. Because recovering from dental surgery often entails a period of rest following the operation and the use of prescription painkillers (which have a tendency to make a person go a little loopy), Cueball prepares to play Minecraft the entire time. Minecraft is a PC game known for its addictive qualities; the game itself primarily revolves around a three-dimensional world in which the goal of the player is centered on the aspects of structural creation using blocks found in the environment and the creation of different materials for use in building these structures. Despite its addictive nature, the game doesn't provide the player with a goal, so most people take to building lots of nifty stuff, such as large cities, computers made from the game's built-in redstone (electricity) mechanics, massive scale replicas of Earth, etc. Cueball's conversation with Megan indicates that he has previously decided against playing Minecraft precisely due to its addictive gameplay and lack of internal goal, deeming it unproductive. However, 'productivity' is not something that Cueball believes he can achieve post-extraction, and so Cueball decides that addictive gameplay and lack of internal goal "sounds like the perfect distraction". Unfortunately for Megan (and any other users of her server), Cueball, while intoxicated with painkillers, has instead opted to flatten an entire continent and sort it into layers (by type of block, presumably). While there's no real indication of how big the continent is, as Minecraft worlds are randomly generated, sea level in Minecraft is at Y level 64, which means he sorted at least 65 layers of a continent large enough to be sufficiently developed, so it is clear that this task would take a lot of time. Collecting a block in Minecraft takes a certain minimum amount of time, depending on the block type, so even if he did everything as fast as he possibly could, there's still a substantial lower bound. Ironically, in the second panel Megan says she'll set Cueball up on her server, which indicates she probably uses a whitelist to secure the server from griefers who might destroy structures created by others, not expecting that Cueball would do exactly that. The last panel simply illustrates that painkillers tend to make one loopy. The title text refers to people waking up during surgery. Because anesthesia requires a lot of careful calibration and dosage - there's a reason anesthesiologists are paid hundreds of dollars an hour to be there, after all - it's possible to sometimes get it wrong, resulting in the patient waking up in the middle of the surgery. The three most important parts of anesthetics used for surgery are an analgesic (blocks pain), a sedative (puts you to sleep), and a paralytic (keeps you from moving). The worst-case scenario that most people hear about is when the analgesic and sedative are under-dosed, but the paralytic is correct, leaving the person awake, able to feel pain, but unable to alert the surgeons that anything is wrong. As a result, some countries and medical institutions have passed laws requiring surgeons to monitor brain activity so that these problems can be quickly remedied. The situation the title text is describing, with both the sedative and paralytic wearing out (leaving the person able to write notes), would be quite unlikely. As for confiscating all the pens, it was probably just to keep the patient from disturbing the procedure while the anesthesiologist corrected the dosage. Sorting a Minecraft world into layers like this would be a near impossible task, especially in the version of Minecraft , Beta 1.2, that was current when this comic was released, which did not even include the enchantment system that allowed for tools that could mine exceptionally fast, meaning that even the sheer time to mine out such a large area would be astronomical, not even considering the time to replace the blocks in proper layers, or to gather resources for the many tools you would need. In later versions of Minecraft , it is possible to naturally generate worlds that resemble the world in this comic using the "superflat" world generation mode, but this was not a feature in Minecraft when this comic was released. Cueball, on phone: Hey! Know how you've been bugging me to play Minecraft for the past year? I'm game. Megan, on phone: But you said you didn't want to "get hooked and spend days on end moving virtual cubes around while sitting motionless." What changed? Cueball, on phone: I'm having my wisdom teeth out, and I'll be useless and doped up on painkillers for the next few days, so that actually sounds like the perfect distraction. Megan, on phone: Oh. I'll set you up on our server! 72 hours later... [Megan sitting at computer.] Megan, on phone: Hey — starting to feel better? Enjoying the game? Let's see what you've... What the hell? Where IS everything? [View of a Minecraft screen showing a vast empty expanse of land. In Cueball's hotbar is, from left to right, an stone pickaxe, sword, and shovel, seven feathers, 42 torches, a non-enchanted bow, a blank space, 64 blocks of stone and a clock. He has full health and 15 armor points.] Megan, offscreen: ...You made the entire continent perfectly flat? Cueball, offscreen: And sorted it into layers. Megan, offscreen: ... Cueball, offscreen: I feel good about things. This is a good game. [Cueball sitting on the floor at his laptop, bleeding from the mouth, surrounded by bloody wadded-up tissues and holding a bottle of medication.] Megan, on phone: ...What exactly is in the painkillers they gave you? Cueball, woozy: I can't read the label because I'm a hologram.

Let Go

Let Go

https://www.xkcd.com/862

https://www.explainxkcd.com/wiki/index.php/862:_Let_Go

[Reddit page.] Luke (thinking): I shouldn't be looking at Reddit. Why can't I stop? [CNN page.] Luke (thinking): Refreshing CNN again. Do news stories so affect my life that I benefit from checking them more than once a day? [Shutdown screen.] Luke (thinking): I should at least check Faceb... no. Screw it. I can't do my job when I'm distracting myself every five minutes like this. [Cueball and Princess Leia looking at a battlefield screen.] Cueball: His computer's off. Luke - You've switched off your targeting computer. What's wrong? Luke: Nothing. I'm all right.

It is human nature to lose interest in difficult or boring tasks, and instead do something easier, more interesting or more rewarding in the short term. While procrastination and distraction from more important tasks has always been present, this comic casts a light on the internet and the huge potential for distraction which it provides. The first two frames in this comic are the set-up, and contain the websites CNN and Reddit and thoughts over the top of them. These types of websites are regularly updated with new content are prime candidates for distraction. The thought bubbles indicate that the reader is fully aware that they shouldn't be looking at these websites, but is unable to stop himself. Even the very rational thought that checking news stories more than once a day is bordering on pointless doesn't seem to stop him. In the third frame, it starts to look a little different as the screen is not a computer but is in fact the targeting computer from Luke Skywalker's X-wing . At this point it becomes clear that there are far more important tasks at hand, namely flying the craft. Even then, Luke has an internal conflict and considers checking Facebook , but mentally checks himself, and to prevent himself from further compulsive browsing shuts down the system. The thought bubble at the bottom is one that is probably familiar to many people (especially students), where he realizes that he has to turn off the computer to actually concentrate on the important task. In the fourth frame, we finally get the movie reference from Star Wars as Princess Leia and one of the Rebel Alliance's officers are gathered around the holographic table that allows them to follow the battle. In the movie, Luke turns off his targeting computer because he uses the force to fire the torpedoes at the right time. But in this comic, Luke turns off the computer because he keeps getting distracted by Reddit and CNN. When they ask whether he is alright, he responds in the way most people would who have nearly been caught wasting time on the internet. This is however a quote of what he actually replies in the movie. See the Destruction of Death Star scene on YouTube. The Let Go remark from Obi-Wan Kenobi that had given the title to this comic occurs about two minutes into the clip . Though here it is a reference to let go of refreshing websites... The headlines on CNN read 'Bees?', 'Where is Oman ?', and 'iReport (we mean you, that is.)'. The headline Bees? could be a reference to Cards Against Humanity . One of the white cards says exactly that. It could also just be a question to the picture above - if it was bees following the guy. The headline Where is Oman? is below a map where land is white. It shows Cyprus, Northern Egypt and the Middle East with the Mediterranean Sea, the Red Sea and the Persian Gulf (seas are grey). Oman is not on this map as it is not situated on the Persian Gulf; it's on the Gulf of Oman and on the Arabian Sea, both of which can be considered parts of the Indian Ocean. The title text is a serious solution to a procrastination problem that we see in the comic, later explained to take the form of simply rebooting the computer. Randall just used the honor system, rather than enforcing this behavior with a program, but he solicited suggestions from his commenters for browser addons, for people who could not simply reboot their computers for whatever reason. At the time, a commenter suggested DelaySites, but that addon is no longer available; nowadays, Mozilla recommends LeechBlock NG (also available for Chrome ), which can be configured to implement the loading delay or block websites entirely, with additional parameters for adjusting time limits for browsing and the time of day and days of the week that each behavior is active. [Reddit page.] Luke (thinking): I shouldn't be looking at Reddit. Why can't I stop? [CNN page.] Luke (thinking): Refreshing CNN again. Do news stories so affect my life that I benefit from checking them more than once a day? [Shutdown screen.] Luke (thinking): I should at least check Faceb... no. Screw it. I can't do my job when I'm distracting myself every five minutes like this. [Cueball and Princess Leia looking at a battlefield screen.] Cueball: His computer's off. Luke - You've switched off your targeting computer. What's wrong? Luke: Nothing. I'm all right.

Major in the Universe

Major in the Universe

https://www.xkcd.com/863

https://www.explainxkcd.com/wiki/index.php/863:_Major_in_the_Universe

[Cueball before a professor.] Cueball: How can I pick a major? I'm interested in everything! Can't I major in "the universe"? Professor: Okay. First, I'll need papers on every European trade summit that did not result in an agreement. Then, spend a year memorizing every microprocessor instruction set ever used in a production chip. [Cueball scratches head.] Cueball: What I meant was I just want to read Malcolm Gladwell books and drink. Professor: We all do, sweetie.

Several authors are referenced here. Malcolm Gladwell is a Canadian author who wrote such books as "The Tipping Point", "Outliers" and "Blink." Steven Levitt is one of the co-authors of the book Freakonomics and the Freakonomics blog on NYTimes.com. Robert Krulwich is a science correspondent for NPR (National Public Radio, for those outside of the US) and a co-host of the show Radiolab . A. J. Jacobs is a journalist who immerses himself in different ideas and lives them out for periods of time. For example, he lived for a year according to all the rules in the bible literally . In this comic, Cueball as a college student, meeting with his adviser or professor ( Hairbun ) trying to decide what to major in. He decides to major in "The Universe", but when his adviser details the real work required of that major, Cueball scratches his head and tells what he really means. If you have not read Malcolm Gladwell's books, their disparate parts are usually tied together by a common thread. For example, in Blink , a motif of intuitive judgments ties together the examples of the Getty kouros , John Gottman's marriage studies , the Millennium Challenge war game , speed dating , and Paul Ekman's FACS , to name a few. These books have been criticized for supposedly presenting an incomplete picture of such phenomena, but they are hugely entertaining and eloquent. Randall is making fun of people who claim to have a broad range of interests, but apparently just to deflect attention from the fact that they are too lazy to master even one field. [Cueball before a professor.] Cueball: How can I pick a major? I'm interested in everything! Can't I major in "the universe"? Professor: Okay. First, I'll need papers on every European trade summit that did not result in an agreement. Then, spend a year memorizing every microprocessor instruction set ever used in a production chip. [Cueball scratches head.] Cueball: What I meant was I just want to read Malcolm Gladwell books and drink. Professor: We all do, sweetie.

Flying Cars

Flying Cars

https://www.xkcd.com/864

https://www.explainxkcd.com/wiki/index.php/864:_Flying_Cars

[Cueball, looking right, is talking on his phone held up to his left cheek. The reply from Megan is shown to come from the phone with a zigzag line.] Cueball: It's 2011. I want my flying car. Megan (over the phone): Dude. [In a frame-less panel Megan, looking left, is talking with Cueball over her phone, which she holds up to her left cheek.] Megan: You're complaining to me using a phone on which you buy and read books, [Zoom in on topless Megan as she takes the phone down in front of her looking at it and talking to it.] Megan: And which you were using to play a 3D shooter until I interrupted you with what would be a video call if I were wearing a shirt. [Cueball is now also looking down at his phone held in front of him, talking to it. Again the reply from Megan is shown to come from the phone with a zigzag line.] Cueball: Can't I have a flying car, too? Megan (over the phone): You'd crash it while texting and playing Angry Birds.

Cueball is complaining to Megan , on a phone call on his smartphone , about the lack of flying cars even though it is the year 2011. This is a reference to the joke "where's my flying car?" This was explored further in 1623: 2016 Conversation Guide where Randall proposes that flying cars would in fact just be helicopters. Megan counters that phone technology has taken off. For example in many science fiction movies it was predicted that by now we would have flying cars, but in the same movies the computer technology was pretty much similar to what they had achieved at the time of the movies release (see for instance Blade Runner set in 2019; even back in 2011 very few believed that flying cars would roam the streets by then.) The flying car is still not perfected (although there are some prototypes flying today). But almost any computer technology shown in old movies pales in comparison to the current state of smartphones and other computers. Cueball chooses to be resentful about the lack of flying cars while calling her from a phone on which he can buy and read books. He should instead be amazed at the current state of computers and communication technology. She continues to say that she even interrupted him in playing a 3D shooter game on his phone, when she called him. And the call could have been a video call , had it not been because Megan chose not to do so, since she is currently shirtless. Typically, Cueball keeps fixating on the flying car. Megan assumes that if he ever had a flying car he would crash it while using his smartphone to text or play Angry Birds (a game released in 2009, two years before this comic). Given that many car accidents happens because people use their phones while driving , this seems a realistic assumption. The title text references RealDoll , known as "the world's finest lovedoll", but specifically an android version, which the world has yet to see. This is a direct callback to the android series . It also refers to jet packs , another invention that many people were expecting to have by this point in time. Cueball complain on in the title text that there is not enough space on the backseat of his flying car to have sex with his android girlfriend when they are both wearing their jet packs. (Maybe they would wear those for safety purposes when flying in a car while having sex... Even if it is a self-driving flying car...) This strip is quoted at the top of the TV Tropes article I Want My Jet Pack , having a similar theme to the strip. [Cueball, looking right, is talking on his phone held up to his left cheek. The reply from Megan is shown to come from the phone with a zigzag line.] Cueball: It's 2011. I want my flying car. Megan (over the phone): Dude. [In a frame-less panel Megan, looking left, is talking with Cueball over her phone, which she holds up to her left cheek.] Megan: You're complaining to me using a phone on which you buy and read books, [Zoom in on topless Megan as she takes the phone down in front of her looking at it and talking to it.] Megan: And which you were using to play a 3D shooter until I interrupted you with what would be a video call if I were wearing a shirt. [Cueball is now also looking down at his phone held in front of him, talking to it. Again the reply from Megan is shown to come from the phone with a zigzag line.] Cueball: Can't I have a flying car, too? Megan (over the phone): You'd crash it while texting and playing Angry Birds.

Nanobots

Nanobots

https://www.xkcd.com/865

https://www.explainxkcd.com/wiki/index.php/865:_Nanobots

[Megan and commander are on a space station.] Megan: Commander! Come quick! It's the nanobots—they've STOPPED! Megan: They devoured 40% of the Earth, and then just... quit! They're just sitting there! Why?! Ponytail: It's a mystery. ...unless... What's the volume of each nanobot? Megan: A few cubic microns. Why? Ponytail: I think the year 1998 just bought us some time. [Earth's surface, covered in mountains of nanobots.] In the swarm: Nanobot: What do you mean, "Run out of addresses?" Other Nanobot: Look, we should've migrated away from IPv6 AGES ago...

Megan and Ponytail are in orbit while nanobots are devouring the earth in a swarm. The nanobots stop after devouring 40% of the planet. This is a take on the " Grey goo " scenario in which self-replicating nanobots destroy the earth while creating more and more of themselves non-stop. However, the nanobots are only able to destroy 40% of the planet because (40% of the earth's mass) = (# of IPv6 addresses) x (A few cubic microns) x (density of nanobots). Without more IP addresses, the nanobots cannot continue to replicate (assuming that each nanobot must be individually addressable). IPv6 supports approximately 3.4×10 38 addresses, while the Earth's mass is around 5.972×10 24 kg. Assuming "a few cubic microns" is the minimum of 2 µm 3 (according to 1070: Words for Small Sets ), the nanobots would have a density of 4 g/cm 3 , a bit less dense than the earth. This is a joke on the shortage of IPv4 addresses. The only difference is that we are on IPv4 and the nanobots are on IPv6 . 1998 is when the IPv6 Specification (RFC 2460) was published and IETF is the Internet Engineering Task Force. Note that an April fool joke for IPV9 exists and would have guaranteed Earth's doom in this comic's scenario. [Megan and commander are on a space station.] Megan: Commander! Come quick! It's the nanobots—they've STOPPED! Megan: They devoured 40% of the Earth, and then just... quit! They're just sitting there! Why?! Ponytail: It's a mystery. ...unless... What's the volume of each nanobot? Megan: A few cubic microns. Why? Ponytail: I think the year 1998 just bought us some time. [Earth's surface, covered in mountains of nanobots.] In the swarm: Nanobot: What do you mean, "Run out of addresses?" Other Nanobot: Look, we should've migrated away from IPv6 AGES ago...

Compass and Straightedge

Compass and Straightedge

https://www.xkcd.com/866

https://www.explainxkcd.com/wiki/index.php/866:_Compass_and_Straightedge

I learned in high school what geometers discovered long ago: [Cueball, holding a compass and straightedge, looks sad.] Using only a compass and straightedge, it's impossible to construct friends.

Compass and straightedge constructions are a class of problems in classical geometry. They take the form "Using only a compass and a straightedge, construct X", where X is a geometric figure such as a regular pentagon. The subject is typically covered in high school mathematics. Three such constructions ( squaring the circle , trisecting the angle and doubling the cube ) remained unsolved for thousands of years before being shown impossible with the use of modern algebraic techniques. The comic begins as if it were stating a problem in classical geometry but veers into an observation that no amount of technical knowledge can substitute for human companionship. An additional layer of humor is that Cueball is a stick figure so technically it is possible to create friends with a straightedge and a compass, a figure constructed like Cueball is. Yet two other layers are the reference to the "straight edge" subculture that believes that one can find fun, friends and partners without alcohol and drugs and the fact that it claims one can construct a awesome birthday party using only two means that together often fail to construct even simple geometrical objects. Ferdinand von Lindemann was a German mathematician who showed in 1882 that pi is not a zero of any polynomial with rational coefficients, i.e. it is a transcendental number. Transcendental numbers cannot be constructed with straightedge and compass. This proves that squaring the circle (a problem where it is required to construct a square with the same area as a given circle) is impossible, being as the sides of the square would need to be √π times the radius of the circle, and pi is not constructible. I learned in high school what geometers discovered long ago: [Cueball, holding a compass and straightedge, looks sad.] Using only a compass and straightedge, it's impossible to construct friends.

Herpetology

Herpetology

https://www.xkcd.com/867

https://www.explainxkcd.com/wiki/index.php/867:_Herpetology

[Ponytail is standing on a podium looking right while pointing behind her with a pointer stick on a sketch showing a Cladogram, i.e. a large tree split that split up several time. Starting with one line at the bottom, this splits left and right and then both continues up. The left does not split again. The right splits again in a similar way, with the right not splitting anymore. The left, now in the middle splits a final time. All four ends are at the same hight and have labels above them written at 45 degree angle. A small frame sits over the top of the panels frame. Inside there is a caption:] Ornithology conference: Ponytail: As you can see, herpetology is a silly field; reptiles are actually more closely related to birds and mammals than to amphibians. Ponytail: It should really be broken up, with lizards folded into ornithology. Labels: Amphibians Reptiles Birds Mammals [Megan is standing on a podium looking left while pointing behind her with a pointer stick on a sketch similar to the previous panel. Starting with one line at the bottom, this splits left and right and then both continues up. The left does not split again. The right splits again in a similar way. All three ends are at the same hight and have labels above them written at 45 degree angle. The top of the right part that split in two, including the labels has been encompassed by a dotted line which also has a label written over this line at the top left. A small frame sits over the top of the panels frame. Inside there is a caption:] Herpetology conference: Megan: As you can see, ornithologists are actually assholes. Labels: Nice people Ornithologists Douchebags Dotted-line: Assholes

Herpetology is the branch of zoology that studies reptiles and amphibians . Ornithology is the branch of zoology that studies birds . At an ornithology conference, Ponytail is using the Cladistics method by showing a Cladogram to argue that the combining of amphibians and reptiles into a single field of study is misguided. In terms of their evolutionary history , reptiles are more closely related to birds (and even to mammals) than to amphibians. She states, in a patronizing way, that the study of reptiles should more properly be combined into her own field. Herpetologists would rightly see this view as a threat to their territory, their budgets and even their existence. The claim made by the ornithologist is fundamentally correct; the evolutionary history of those groups did actually diverge in that way. So, instead of arguing the science, Megan , the presenter at the herpetology conference resorts to a personal attack on the profession of ornithology. At their own conference, they retaliate with a chart that purports to demonstrate that douchebags and ornithologists are more closely related to each other than either are to nice people , and they can therefore be grouped into an encompassing asshole classification. Since the intent of the earlier presentation was presumably to rile herpetologists rather than achieve any particular scientific goal, this response seems appropriate. In the title text, birds are class Aves which is a subset of the suborder Theropoda which is a subset of the order Saurischia and the superorder Dinosauria . Under the normal rules of classification, this means that all birds are technically dinosaurs. This was also shown in more detail later in 1211: Birds and Dinosaurs . [Ponytail is standing on a podium looking right while pointing behind her with a pointer stick on a sketch showing a Cladogram, i.e. a large tree split that split up several time. Starting with one line at the bottom, this splits left and right and then both continues up. The left does not split again. The right splits again in a similar way, with the right not splitting anymore. The left, now in the middle splits a final time. All four ends are at the same hight and have labels above them written at 45 degree angle. A small frame sits over the top of the panels frame. Inside there is a caption:] Ornithology conference: Ponytail: As you can see, herpetology is a silly field; reptiles are actually more closely related to birds and mammals than to amphibians. Ponytail: It should really be broken up, with lizards folded into ornithology. Labels: Amphibians Reptiles Birds Mammals [Megan is standing on a podium looking left while pointing behind her with a pointer stick on a sketch similar to the previous panel. Starting with one line at the bottom, this splits left and right and then both continues up. The left does not split again. The right splits again in a similar way. All three ends are at the same hight and have labels above them written at 45 degree angle. The top of the right part that split in two, including the labels has been encompassed by a dotted line which also has a label written over this line at the top left. A small frame sits over the top of the panels frame. Inside there is a caption:] Herpetology conference: Megan: As you can see, ornithologists are actually assholes. Labels: Nice people Ornithologists Douchebags Dotted-line: Assholes

Nolan Chart

Nolan Chart

https://www.xkcd.com/868

https://www.explainxkcd.com/wiki/index.php/868:_Nolan_Chart

[Diamond-shaped four-panel diagram with each panel labeled. Two arrows indicate axis up along the left and right lower side of the diamond:] [Left]: Political opinions [Right]: Love of diamond-shaped diagrams [Top panel]: Internet libertarians [Left panel]: Democrats, Republicans [Right panel]: Baseball fans [Bottom panel]: Other

The Nolan Chart is a visual representation of the political spectrum that measures not only liberal vs conservative tendencies but also libertarian and statist tendencies. Libertarians tend to like Nolan Charts because they feel that the Democratic/Republican spectrum, the most common visualization of political beliefs, isn't nuanced enough to explain libertarian beliefs. In this comic, it is taken to a different end. On one side are both Democrats and Republicans and on the other side are baseball fans. In the typical Nolan Chart, Libertarians are in the top quadrant, but in this one "Internet Libertarians" take the spot because they love the Nolan Charts (which are found online) and have a lot of political opinions. Nolan may also refer to baseball Hall of Famer Nolan Ryan . In the title text, the NFPA-compliant chemical manufacturers are mentioned because of this diagram . Sir Charles Wheatstone was the inventor of the Wheatstone bridge , which is also diamond-shaped . The title text also refers to Nate Silver, who previously worked for Baseball Prospectus and now writes a data-driven political and sports blog called FiveThirtyEight for ESPN. He is both a lover of diamond-shaped diagrams (baseball) and has political opinions. Politically-active kite designers both would have strong political opinions (it comes with the territory of being politically active) and would love diamond-shaped diagrams, presumably because they would be interested in blueprints of kites. [Diamond-shaped four-panel diagram with each panel labeled. Two arrows indicate axis up along the left and right lower side of the diamond:] [Left]: Political opinions [Right]: Love of diamond-shaped diagrams [Top panel]: Internet libertarians [Left panel]: Democrats, Republicans [Right panel]: Baseball fans [Bottom panel]: Other

Server Attention Span

Server Attention Span

https://www.xkcd.com/869

https://www.explainxkcd.com/wiki/index.php/869:_Server_Attention_Span

[Single server in a server rack.] Server: Hi! I'm a server! Who are you? [Mobile device with a web browser.] Browser: I'm a browser. I'd like to see this article. Server: Oh boy! I can help! Let me get it for— ...Whoa! You're a smartphone browser? Browser: Yeah. Server: Cooool! Hey, I've got this new mobile version of my site! Check it out! Isn't it pretty? Browser: Sure, but this is just your mobile site's main page. Where's the article I wanted? Server: What article? Browser: The one I— Server: Who are you? Browser: I— Server: Hi! I'm a server!

The comic shows - in human language - part of the conversations that a browser and web server do in order to get the right page. The protocol they use is called HTTP . This comic makes fun of the issue that many web-servers that see a mobile browser will automatically suggest to load the mobile version of the website, but then serve the front page of the mobile site, not the page the user had requested. In quite a few sites, there is no 1-to-1 correspondence of pages between the regular and the mobile site, so this problem is difficult to solve and very annoying. A second issue with HTTP is identified in the last panel. HTTP is a stateless protocol . After serving the web page, the connection is severed. Any new request for a page will have to start afresh - which is where the server starts with again: "Hi! I'm a server!" Of course, browsers do not have egos nor do they hold grudges but it can be annoying for users. This design issue can also slow down the browsing experience. The title text is a joke that all the other servers in the rack think the web server is being childish. /var/log/syslog is where Linux (used by the vast majority of servers) and other POSIX systems store their system log messages. The 'trying to start conversation' comment is probably a joke on ARP discovery packets that are sent out to the network to see who is who. All servers send out ARP packets to see what other machines are on the network, but some machines send them out every 5 minutes, which can be extremely annoying for someone monitoring network traffic logs. The coffee comment is another jab at web servers. Some websites use Java , or other JVM based languages ( Apache Groovy , Scala , etc.) as the back end of the website, as opposed to using PHP or ASP . Of course, java is another word for coffee, so a web server running on coffee is likely to be well-caffeinated, and well-caffeinated people tend to bounce off the walls with enthusiasm. [Single server in a server rack.] Server: Hi! I'm a server! Who are you? [Mobile device with a web browser.] Browser: I'm a browser. I'd like to see this article. Server: Oh boy! I can help! Let me get it for— ...Whoa! You're a smartphone browser? Browser: Yeah. Server: Cooool! Hey, I've got this new mobile version of my site! Check it out! Isn't it pretty? Browser: Sure, but this is just your mobile site's main page. Where's the article I wanted? Server: What article? Browser: The one I— Server: Who are you? Browser: I— Server: Hi! I'm a server!

Advertising

Advertising

https://www.xkcd.com/870

https://www.explainxkcd.com/wiki/index.php/870:_Advertising

Mathematically Annoying Advertising: A ∪ B = {x:x ≤ 15 or x > 15} = ℝ [line graph representing the above equation.] When discussing real numbers, it is impossible to get more vague than "up to 15% or more". [" FREE! *" in large text, with substantial illegible fine print.] If someone has paid $x to have the word "free" typeset for you and N other people to read, their expected value for the money that will move from you to them is at least $(x / (N+1)) [Graph representing inverse relationship between "amount you spend" on the y axis and "amount you save" on the x axis.] It would be difficult for the phrase "the more you spend the more you save" to be more wrong. Randall changed the image name from advertising.png to mathematically_annoying.png, since adblocking extensions interpreted it as an ad and made the comic blank. He had the same problem again just three months later with 906: Advertising Discovery .

This comic pokes fun at millions of advertising tricks, analyzing them mathematically. The equation at the top of the panel expresses the same thing using set theory notation. It reads out as: The union of sets A and B equals the set of all x, such that x is less than or equal to 15, or greater than 15, which equals the set of all real numbers . The same is expressed again with a number line ; the numbers being interpreted as percentages . The first range, ending with a black dot, indicates that everything below, as well as the number 15, is included ("up to 15%"). The second range beginning with a white dot indicates that it only includes numbers strictly bigger than 15 ("more than 15%"). The two ranges combined clearly cover the entire number line. The phrase "up to 15% or more" may be a reference to the Geico slogan at the time: a phone call lasting "15 minutes could save you 15% or more on car insurance." However the reference is unclear, as the words " up to 15%" are not actually used by Geico. Though Geico's advertising is also referenced in 42: Geico . We are even given a little formula to calculate the average amount of money they expect to make from the readers. The assumption is that they expect to generate at least as much income from the ad as what they paid to print and publish it in the first place. The title text compares Randall's realization of the "FREE"-fraud to the revelation that Santa Claus is not real. Mathematically Annoying Advertising: A ∪ B = {x:x ≤ 15 or x > 15} = ℝ [line graph representing the above equation.] When discussing real numbers, it is impossible to get more vague than "up to 15% or more". [" FREE! *" in large text, with substantial illegible fine print.] If someone has paid $x to have the word "free" typeset for you and N other people to read, their expected value for the money that will move from you to them is at least $(x / (N+1)) [Graph representing inverse relationship between "amount you spend" on the y axis and "amount you save" on the x axis.] It would be difficult for the phrase "the more you spend the more you save" to be more wrong. Randall changed the image name from advertising.png to mathematically_annoying.png, since adblocking extensions interpreted it as an ad and made the comic blank. He had the same problem again just three months later with 906: Advertising Discovery .

Charity

Charity

https://www.xkcd.com/871

https://www.explainxkcd.com/wiki/index.php/871:_Charity

Cueball: I'm going to buy this $10 game I want, and I'm donating $10 for malaria eradication. Megan: If you actually cared, you'd skip the game and donate all $20. Megan: What's more important? Games, or mosquito nets and medicine for kids? (Caption above the comic) Later: Cueball: I think I'm going to buy these two $10 games I want. Friend: Cool; which ones? Following the publication of this comic, comments responding to anti-malaria charities, celebrities who raise money for charity, and charity directors in general, by figuring out reasons that they're not really as good as they seem, were posted on the discussion page for this comic . However, this did not lead to internet arguments.

Organizations such as Steam often offer sales where certain games are available for low prices--in order to compel or persuade buyers to make donations to worthwhile charities. Cueball is participating in one of these purchases (to fight malaria ), but Megan 's snide denigration of Cueball's act of charity as inadequate and self-serving has dissuaded him from any act of charity at all. Many people donating to charity are in fact buying a feeling that they are good people doing good things. If you take this feeling away, many people stop donating, which is shown on the third panel. This also shows the stupidity of the situation: donating some of your money to charity can result in insults and arguments, while donating nothing at all does not. However, whatever somebody's internal motivation was, charity is a good thing. Therefore the proper response is to neither care what people say about you nor attack other people's charitable giving. The action that Randall recommends here is the right one, which is to donate anyway without caring about what others say or do. Clicking on the original image leads to the website of Nothing But Nets , an organization that distributes mosquito bed nets in Africa for the eradication of malaria. A subtext here is that the friendship between Cueball and Megan has been strained or even broken. Cueball has picked a new friend to talk to, who reacts positively to his decision. In the title text, Randall expresses an opinion critical of "respond[ing] to someone else doing something good by figuring out a reason that they're not really as good as they seem", in part because supporting charity shouldn't cause "internet arguments." Cueball: I'm going to buy this $10 game I want, and I'm donating $10 for malaria eradication. Megan: If you actually cared, you'd skip the game and donate all $20. Megan: What's more important? Games, or mosquito nets and medicine for kids? (Caption above the comic) Later: Cueball: I think I'm going to buy these two $10 games I want. Friend: Cool; which ones? Following the publication of this comic, comments responding to anti-malaria charities, celebrities who raise money for charity, and charity directors in general, by figuring out reasons that they're not really as good as they seem, were posted on the discussion page for this comic . However, this did not lead to internet arguments.

Fairy Tales

Fairy Tales

https://www.xkcd.com/872

https://www.explainxkcd.com/wiki/index.php/872:_Fairy_Tales

[Megan sits in an armchair, reading a book looking over her shoulder at Cueball as he walks in.] Megan: Are there eigenvectors in Cinderella? Cueball: ...No? Megan: The prince didn't use them to match the shoe to its owner? Cueball: What are you talking about? Megan: Dammit. [In this frame-less panel Megan is shown in a flashback as a little girl lying in bed, head on pillow and hands held on the edge of the blanket at her throat. Hairbun with glasses, as her mom, is sitting on the edge of the bed reading, while her head is hanging down. Above and below there are two frames with Megan's narration. Hairbun's reading text is smaller than the other text in this comic.] Megan (narrating): My mom is one of those people who falls asleep while reading, but keeps talking. She's a math professor, so she'd start rambling about her work. Mom: But while the ant gathered food ... Mom: ...zzzz... Mom: ...the grasshopper contracted to a point on a manifold that was not a 3-sphere... Megan (narrating): I'm still not sure which versions are real. [Cueball now stands in front of the arm chair. Megan has put the book away, and is leaning her head on her left arm which rests on the armrest of the chair.] Cueball: You didn't notice the drastic subject changes? Megan: Well, sometimes her versions were better. We loved Inductive White and the (n−1) Dwarfs . Megan: I guess The lim x→∞ (x) Little Pigs did get a bit weird toward the end...

Eigenvectors are a mathematical concepts that can be applied to a matrix . A matrix is mostly displayed as an rectangular array of elements used to describe the state of objects in physics. In pure mathematics they can be much more complex. The most important issue to the understanding of the comic is that a matrix can be transformed through various processes. These transformations can include rotation, movement and scaling of the object described by the matrix. An eigenvector refers to elements of the vector space of the matrix which remain unchanged (except possibly being scaled to be longer or shorter) after the transformation is applied. The prefix 'eigen-' applied to the term is adopted from the German word eigen for "self-" or "unique to", "peculiar to", or "belonging to." As the eigenvector remains unchanged through the transformation of the matrix it can be used to describe something unique about that matrix. The concept of an eigenvector has nothing to do with the fairy tale Cinderella ; therefore Megan confuses Cueball when she asks whether it occurred in the story of Cinderella. The story of Cinderella includes Cinderella going to a ball in disguise, dancing with a prince and then leaving early and quickly, so that she accidentally leaves a glass slipper behind. The prince then uses the shoe to find Cinderella. Megan says that the way she learned it, the prince used an eigenvector and corresponding eigenvalue to match the shoe to its owner. This is a somewhat logical mathematical connection to make as eigenvectors, unchanged properties of mathematical matrices that may allow for mathematical identification of the changed matrix, correspond to the unchangeable property of the shoe (size) that allowed the prince to correctly identify the owner of the shoe even after the shoe was misplaced. Eigenvectors are sometimes used in facial-recognition software to match 2 faces. Megan explains that her mother, a math professor (drawn as Hairbun with glasses) would continue to talk when she fell asleep in the midst of reading bed time stories, and then would ramble on mixing the adventures with the math from her work. The middle panel refers to the story of The Ant and the Grasshopper with the addition of what is likely a reference to the Poincaré conjecture , a (now-misnamed) theorem in mathematics. Megan explains that even today she is not sure which versions are the real ones. Cueball cannot understand how she would not have noticed the drastic subject changes (which seems obvious to adults, but maybe not to small children). Megan then mentions two other story changes, the first Inductive White and the ( n −1) Dwarfs was better than the original. The story is a combination of Snow White and the Seven Dwarfs with the principle of induction . But The lim x→∞ (x) Little Pigs was a little weird toward the end. That story combines the Three Little Pigs with mathematical limits . The reason it got weird toward the end was because the number of pigs tends to infinity as the story progresses. Each of the stories has a varied degree of similarity to the mathematical concepts that were mixed in as though her mom began to talk about a mathematical principle that may have been brought to mind while reading the story or already on her mind. In the title text Megan mentions another adventure: Goldilocks' discovery of Newton's method for approximation . Newton's method for approximation is a method for finding successively better approximations to the zeroes (or roots) of a real-valued function. In Goldilocks , the protagonist finds successively better porridge and comfier chairs in a house where three bears lived. In the same way, in the Mom's version of the fairy tale, she would find successively better approximations to zeroes instead of successively better bowls of porridge, and Megan notes that it was surprising how few changes that story needed compared to the original adventure. [Megan sits in an armchair, reading a book looking over her shoulder at Cueball as he walks in.] Megan: Are there eigenvectors in Cinderella? Cueball: ...No? Megan: The prince didn't use them to match the shoe to its owner? Cueball: What are you talking about? Megan: Dammit. [In this frame-less panel Megan is shown in a flashback as a little girl lying in bed, head on pillow and hands held on the edge of the blanket at her throat. Hairbun with glasses, as her mom, is sitting on the edge of the bed reading, while her head is hanging down. Above and below there are two frames with Megan's narration. Hairbun's reading text is smaller than the other text in this comic.] Megan (narrating): My mom is one of those people who falls asleep while reading, but keeps talking. She's a math professor, so she'd start rambling about her work. Mom: But while the ant gathered food ... Mom: ...zzzz... Mom: ...the grasshopper contracted to a point on a manifold that was not a 3-sphere... Megan (narrating): I'm still not sure which versions are real. [Cueball now stands in front of the arm chair. Megan has put the book away, and is leaning her head on her left arm which rests on the armrest of the chair.] Cueball: You didn't notice the drastic subject changes? Megan: Well, sometimes her versions were better. We loved Inductive White and the (n−1) Dwarfs . Megan: I guess The lim x→∞ (x) Little Pigs did get a bit weird toward the end...

FPS Mod

FPS Mod

https://www.xkcd.com/873

https://www.explainxkcd.com/wiki/index.php/873:_FPS_Mod

[Cueball is sitting in a chair in front of his TV holding a gamepad while playing a video game. Every time he shoots the sound is written inside a ring of small curved lines to indicate the noise. Text on the screen is noted after each round of blasts with a zigzag line from the screen and between each entry.] Blam Game: He once built a treehouse. Blam Game: She has 110 unread emails that she was hoping to get to tonight. Blam blam Game: He was the only one who took care of the plants back at base. [Caption below the panel:] No one liked my FPS mod that gives you three-second snippets from the bios of people you shoot.

FPS stands for First Person Shooter , which is a type of video game (like Halo or Duke Nukem ) in which you are looking at the world from the first person perspective of the character you are controlling. Randall notes in the caption that no one liked his FPS mod (short for "modification" of the FPS game), and in the title text it is clear that Cueball who played this modified version no longer enjoys the game. FPS games are controversial for their (supposed) quality of encouraging violence such as killing (especially other human beings). One point of the controversy is that, while virtual enemies are just pixels on a screen, real enemies have actual lives, emotions, and the like. In the games, there is a disconnect between the act of killing and its emotional cost, thus leading to the controversy that FPS games encourage wanton killing (or violence in general) to solve problems instead of considering the other party. Randall makes reference to this by adding a mod that gives biographical snippets of the enemy you shoot in the game, thus giving Cueball the perspective of the enemy he just shot, and causing emotional consequence and remorse by removing the disconnection between pixel and life. The comic can also be a reference towards making games more realistic. Giving the enemies a life above being mere targets definitely makes the game more realistic, but such a game may not be that enjoyable. This has been explored previously in 772: Frogger . Having lots of unread e-mails was mentioned in 2389: Unread . The third comment ("take care of the plants back at base") may be referring that many FPS videogames have some sort of base that you must defend or start the game in. These games do not usually feature any way to take care of plants. [ citation needed ] The title text talks about how gender is portrayed in games. For some people it is more emotionally affecting to kill a woman, as women are considered biologically "weaker" than men by many societies, and societal norms state that men must protect them. Gender equality is a highly debated topic with many different viewpoints, where one's conscious reasoned views may sometimes stand at odds to subconscious feelings. When a player becomes aware that killing women bothers one more than killing men, it exposes an inconsistency in the player's own logic, one that's very uncomfortable to confront. In the 1993 post-apocalyptic novel The Fifth Sacred Thing , the eco-pacifist residents of San Francisco defeat an invading army using a similar tactic. Rather than engage in armed defense, the family and friends of each dead San Franciscan speak directly to the soldiers who killed them, saying, "My wife was the mother of five children, and I loved her dearly," or "My cousin liked baseball." Eventually the soldiers suffer psychological breakdowns and defect en masse , rather as Cueball seems to do in the title text. Amusingly, the 2014 game Watch Dogs does something quite similar to this; the in-game "Profiler" provides a brief summary of a targeted enemy, and if the enemy does not have a gameplay-relevant feature (i.e. "Can call for backup"), it will mention their hobbies or interests. Like most other games in the Sniper Elite series, the 2017 Third Person Shooter Sniper Elite 4 allows the player to track and see brief overviews of any visible enemy by "Tagging" them with binoculars. However, Sniper Elite 4 has the distinction of also being very similar to Randall's mod in that it displays short character bios in the "Allied Intelligence" section of the overviews when Tagging in the campaign mode. They range from the mundane (year of conscription, former occupation) to the dark (Sapper Oswald Sander's brutal murder of a cowering fifteen year old makes even his fellow soldiers suspect him) to the comedic (Ewald Amsel regularly steals chocolate from his best friend Wolfram Wasser; Wolfram Wasser wonders who's stealing his supply of chocolates and has sworn to kill them). The 2012 Third Person Shooter Spec Ops: The Line also has a section where one of the antagonists will chide you with radio message when you kill one of the enemy soldiers, often with short sympathetic descriptions of the enemy you just killed (although he'll sometimes admit he didn't actually know or like that particular person). As this game is a deconstruction of the military-style shooting games of its time and their portrayal of violence, evoking a negative emotional response in the player when killing these enemies is very much intentional. The game Borderlands 2 directly references this comic with the Morningstar, a unique aftermarket talking Hyperion sniper rifle which berates the user in a nagging, whiny voice any time they reload, kill an enemy, swap weapons, or score a critical hit. The weapon is obtained from the mission Hyperion Contract 873 (a reference to this comic being comic number 873) and is referred to as "the Hyperion ex-K seedy experimental weapon" upon completion of the mission. [Cueball is sitting in a chair in front of his TV holding a gamepad while playing a video game. Every time he shoots the sound is written inside a ring of small curved lines to indicate the noise. Text on the screen is noted after each round of blasts with a zigzag line from the screen and between each entry.] Blam Game: He once built a treehouse. Blam Game: She has 110 unread emails that she was hoping to get to tonight. Blam blam Game: He was the only one who took care of the plants back at base. [Caption below the panel:] No one liked my FPS mod that gives you three-second snippets from the bios of people you shoot.

Time Management

Time Management

https://www.xkcd.com/874

https://www.explainxkcd.com/wiki/index.php/874:_Time_Management

[Cueball sits at a desk with a computer. There's a schedule on the wall next to it. Cueball is typing.] The key to leading a productive life is time management. type type Choose goals, build a schedule, and have the WILLPOWER to follow it- or be LEFT BEHIND by those of us who DO. type type type [We see the schedule in closeup.] SCHEDULE 7:00am Wake up 7:15am-8:00am Post on productivity blogs about my schedule 8:00am-whenever Fuck around

In the first two panels we see snippets from Cueball 's posting on blogs explaining the importance of time management and its benefits. The schedule on the wall is a direct contradiction to the initial ideas and follows a very simple plan for the day, making willpower only seem necessary for getting up on time and posting on these blogs, leaving the rest of the day to do whatever he wants. The title text explains what the schedule is about, possibly alluding that Cueball's goal in life is to be successful at messing around, not actually being successful at what would in common be considered someone would do to become successful. It could also suggest someone who has a (shallow ego driven?) goal of "success" itself, but who may not much care about what they are achieving for itself. Thus, achieving it is would not be an intrinsic reward to them — to borrow an concept from Eliezer Yudkowsky , they are clearly ambitious, but they don't truly have an ambition. These people are probably not be the type of people Randall enjoys spending time with, since the reward for him is primarily the interesting world around him, as he has occasionally pointed out. At the same time, it could also be expressing a general skepticism of people in fields like internet marketing or inspirational coaching (who are usually also selling a product) and therefore are potentially just out to make a buck on you, especially the ones who have a free blog with a paid product, since it is often significantly more expensive than, say, buying a book on time management at the bookstore. Since this comic came out (and before) there have been many comics about wasted time and general time management , see the Time management category . [Cueball sits at a desk with a computer. There's a schedule on the wall next to it. Cueball is typing.] The key to leading a productive life is time management. type type Choose goals, build a schedule, and have the WILLPOWER to follow it- or be LEFT BEHIND by those of us who DO. type type type [We see the schedule in closeup.] SCHEDULE 7:00am Wake up 7:15am-8:00am Post on productivity blogs about my schedule 8:00am-whenever Fuck around

2009 Called

2009 Called

https://www.xkcd.com/875

https://www.explainxkcd.com/wiki/index.php/875:_2009_Called

[Cueball is at computer. Megan is standing behind him, looking at clothes on the floor.] Megan: Is this a three wolf moon shirt? Megan: Dude, 2009 called, and they- Cueball: OH MY GOD! Cueball: DID YOU WARN THEM? Cueball: ABOUT HAITI AND JAPAN? Megan: What? No, I- Cueball: You ASSHOLE! See also:

The comic deconstructs a snowclone or common idiom - "X called, they want their Y back." Usually, X is a year (like 2009 here), and Y is something very popular in that year that is seen as ridiculous in the present day. Here, Megan notices a Three-Wolf Moon T-shirt that Cueball apparently owns. The Three-Wolf Moon is a shirt of three wolves howling at the moon that reached meme status when several people posted ironic reviews giving it supernatural powers on Amazon around late 2008. Megan says the snowclone, but before she can finish, Cueball pretends to take it literally (that is, that the year 2009 actually called her) and admonishes her for not telling them about the February 2010 earthquake in Haiti and the March 2011 earthquake and tsunami in Japan . The comic was posted shortly after the latter, so it is reasonable to assume that it was created as a response to the disaster. Knowing Cueball, he's either preempting Megan's attempt to humiliate him and giving her a pretty good burn, or Cueball, being Cueball, actually thinks the past called. The title text continues the snowclone by implying a terrible future awaits in 2017. Likewise, non-apocalyptic events, such as political protests, can generate "yelling and screaming". Given the public's general inclination to focus on the negative the prediction of a "bad future" may have worked with any date. 2017 has occurred, and the world hasn't exploded. [ citation needed ] In hindsight, 2020 would work better for the joke. [insert hindsight is 2020 joke here] [Cueball is at computer. Megan is standing behind him, looking at clothes on the floor.] Megan: Is this a three wolf moon shirt? Megan: Dude, 2009 called, and they- Cueball: OH MY GOD! Cueball: DID YOU WARN THEM? Cueball: ABOUT HAITI AND JAPAN? Megan: What? No, I- Cueball: You ASSHOLE! See also:

Trapped

Trapped

https://www.xkcd.com/876

https://www.explainxkcd.com/wiki/index.php/876:_Trapped

[Cueball is on a corded wall phone.] Cueball: Hello? 911? I'm trapped! Cueball: It's dark and I can't see anything except these two distorted splotches of light! Cueball: Help! [Ponytail, a 911 operator is in an office, wearing a headset.] Ponytail: Splotches of light? Your... eyeballs? Cueball (over phone): I think that's what they are! There's meat everywhere! [Focus on Ponytail's head.] Ponytail: ...so you're a brain. Cueball (over phone): Yes! Ponytail: Yeah, we all are. You're not trapped. Use your body to walk around and experience reality. Cueball: But everything's just signals in my sensory cortices! How can I be sure they correspond to an external world?! Ponytail (over phone): I'm sorry, but we can't send a search-and-rescue team into Plato's cave.

Cueball 's brain seems to be unaware it is in his body, and is freaked out by the fact that all the information it receives is through Cueball's sensory organs. The brain has no means of verifying that the information received from the senses indeed corresponds to the actual outside world, and is thus in Plato's cave. The 911 operator references Plato's cave . This is a reference to an allegory by Plato in which he creates a world in which prisoners are chained against a wall and know only the shadows that cross the wall and how they create their own reality from those shadows. They would create words for the things they were seeing, but that would only correspond to the shadows and not the physical things themselves. The title text is also about Plato's cave and treats it like an actual cave with prisoners; Randall is saying that Socrates , Plato's teacher, should have just gone into the cave and brought the prisoners out instead of dealing with the extended allegory. The tranquilizer gun is for the prisoners, so they don't completely freak out while being taken out of the cave. [Cueball is on a corded wall phone.] Cueball: Hello? 911? I'm trapped! Cueball: It's dark and I can't see anything except these two distorted splotches of light! Cueball: Help! [Ponytail, a 911 operator is in an office, wearing a headset.] Ponytail: Splotches of light? Your... eyeballs? Cueball (over phone): I think that's what they are! There's meat everywhere! [Focus on Ponytail's head.] Ponytail: ...so you're a brain. Cueball (over phone): Yes! Ponytail: Yeah, we all are. You're not trapped. Use your body to walk around and experience reality. Cueball: But everything's just signals in my sensory cortices! How can I be sure they correspond to an external world?! Ponytail (over phone): I'm sorry, but we can't send a search-and-rescue team into Plato's cave.

Beauty

Beauty

https://www.xkcd.com/877

https://www.explainxkcd.com/wiki/index.php/877:_Beauty

[Ponytail and Cueball are discussing science. They are interrupted by an off-panel shout.] Ponytail: The problem with scientists is that you take the wonder and beauty out of everything by trying to analyze it. Megan (off panel): Dude! [Megan runs across this frame less panel, carrying a microscope and a yellow slime mold.] Megan: My plasmoidal slime molds have heightened pigment production! Check out that yellow color! That actually makes them zinc-resistant. Amazing, huh? [A close up of Megan's hands holding the yellow slime mold up to Ponytail who takes her hands up to her mouth.] Ponytail: It looks like dog barf. Megan (off panel): Hah, yeah! F. Septica is nicknamed "dog vomit slime mold." Cool, huh? Check out my slides! [Megan has set down the microscope on the floor of the panel, and the slime mold is jiggling in her hands, while Cueball watches but Ponytail looks away.] Ponytail: Okay, never mind: What's wrong with scientists is that you do see wonder and beauty in everything. Ponytail: Oh God, it's moving! Megan: It wants to hug you! So cute!

Many people believe that over-analysis is boring and only serves to detract from the beauty, wonder, or emotional moments of the subject. This is especially compounded in literature classes, but it's a gripe common throughout many studies. Keats in particular is said to have joked that Newton had "destroyed all the poetry of the rainbow , by reducing it to the prismatic colors". Many experts and professionals, however, disagree greatly, claiming that they see more wonder and excitement in those subjects than they did before. Ponytail 's statement to Cueball in the first panel is proved wrong by Megan 's actions throughout the comic and the statement in the title text, to the point where she retracts and changes her statement. Megan comes in, excited about slime molds , in particular F. septica . Slime molds are not particularly attractive [ citation needed ] — in fact, the average person would probably say they were gross and slimy. Ponytail is rather grossed out and horrified by the mold, and changes her statement in response to Megan's enthusiasm for the mold, in keeping with Ponytail's own disgust. She thinks that Megan is crazy to see the wonder in such a disgusting-looking creature. F. septica is a remarkable species. As the comic says, it can tolerate extremely high zinc levels. The yellow pigment bonds to the zinc and renders it biologically inactive. As with other slime molds, it forms a multi-nucleate mass which can move like an amoeboid. It changes to a sponge-like form before releasing spores. Although the taxonomy is still fluid, the slime molds are distinct enough to be classified as neither animals, plants or fungi, but form a kingdom of their own, with some types of amoeba. In the title text the hagfish is described as the best hugger as it can create a huge blanket of slime around it self in a few seconds, which is uses as a defense against predators, and maybe also to move out of its own "prey", which is often dead fish and whales that it burrow into to feed. "Their unusual feeding habits and slime-producing capabilities have led members of the scientific and popular media to dub the hagfish as the most 'disgusting' of all sea creatures." Nevertheless, they too fascinate researchers, and the slime may have various medical applications. See for instance the slime in this video and active slime defense (and knotting) in this video . [Ponytail and Cueball are discussing science. They are interrupted by an off-panel shout.] Ponytail: The problem with scientists is that you take the wonder and beauty out of everything by trying to analyze it. Megan (off panel): Dude! [Megan runs across this frame less panel, carrying a microscope and a yellow slime mold.] Megan: My plasmoidal slime molds have heightened pigment production! Check out that yellow color! That actually makes them zinc-resistant. Amazing, huh? [A close up of Megan's hands holding the yellow slime mold up to Ponytail who takes her hands up to her mouth.] Ponytail: It looks like dog barf. Megan (off panel): Hah, yeah! F. Septica is nicknamed "dog vomit slime mold." Cool, huh? Check out my slides! [Megan has set down the microscope on the floor of the panel, and the slime mold is jiggling in her hands, while Cueball watches but Ponytail looks away.] Ponytail: Okay, never mind: What's wrong with scientists is that you do see wonder and beauty in everything. Ponytail: Oh God, it's moving! Megan: It wants to hug you! So cute!

Model Rail

Model Rail

https://www.xkcd.com/878

https://www.explainxkcd.com/wiki/index.php/878:_Model_Rail

[Cueball to the left and his friend, who also looks like Cueball, are standing in the friend's rather large basement, where the celling is held up by six thin columns, and the walls are shown angling in towards a point of perspective, to display how big the room is.] Friend: I want to build a perfect HO-scale (~1/87) model train layout of my town. Cueball: In your basement? Bad idea. Never make a layout of the area you're in. [Zoom in on the two friends without the basement visualized.] Friend: Why not? Cueball: Because it'd include a little 10" replica of your house. [Zoom in Cueball's friend who takes his hand to his chin.] Friend: So? That's be cool! I'd make tiny replicas of my rooms, my furniture— Cueball (off-screen)l: —And your train layout? [Beneath this first row of the comic is the zoom-out of how the full model would look in the basement. The town lies beneath some small mountains. There is some water with a bridge over it continuing to the roads going through the city. There is no frame around this section, but instead there follows five zoom-outs, each one going from the friend's house, that proceeds to a circular frame. Within each of these is shown a nested model. Starting to the right of the main model, and then moving down, then left, and then down and right. Each layer has a broken arrow above the model between two vertical lines to indicate the scale, the length being written between the two parts of the arrow. Some foreign objects are also labeled to help understand the scale.] [Layer 1, the model with the two friends standing to the left of it.] 18 m [Layer 2, looks exactly as the model, but without the friends.] 21 cm [Layer 3, with a mosquito shown for comparison. It stands over half the model covering the mountains.] 2.4 mm [Layer 4, with a strand of spider silk (labeled) shown for comparison. The silk is much thicker than the roads, almost as thick as the mountains and much longer than the model. But the model still looks fairly much like the original one.] 28 μm Spider web [Layer 5, with a cold virus (labeled) shown for comparison. It covers roughly a quarter of the model, taking up the water part of the model. At this level the whole model becomes notably "fuzzy" as individual atoms are discernible, and most of the features apart from the mountain is indiscernible. There may be two viruses. The other would then be to the right of the one in the water but above the model. The label stands between them.] 320 nm Cold virus [Layer 6, is simply spheres (atoms) at this point. The mountain near the back is the only noticeable feature, consisting of five atoms jutting out from the surface of atoms, which is by no mean flat.] 37 Å [Beneath these six versions of the model is a caption:] The Matryoshka limit: It is impossible to nest more than six HO layouts [Back to the two friends in the basement, still not showing the basement.] Friend: My God. Cueball: Yeah. It's the second rule of model train layouts: No nesting. [Zoom in on the heads of the two friends.] Friend: ...What's the first rule? Cueball: "Do not talk about model train layouts." That rule was actually voted in by our friends and families. Friend: Philistines.

In model rail construction, the HO scale refers to the most popular scale for modeling railroads, in which 3.5 millimeters in the model corresponds to 1 real-world Imperial foot. As the comic suggests, it works out to a ratio of about 1:87.1 (or 3048:35 exactly, which equals 1:87.08̄5̄7̄1̄4̄2̄8). In Europe, the scale is defined as exactly 1:87 instead, to avoid references to non-metric measurements. This comic features two Cueballs conversing; we'll refer to them as Lefty and Righty to avoid confusion. The conversation takes place in Lefty's basement. Lefty is apparently a less-experienced train modeler, and he tells Righty that he wants to make an HO model layout of his town. However, the more-experienced Righty points out that this is a bad idea, due to nesting. To make it a perfectly accurate model, Lefty would have to include a model of his house, which includes his basement, which includes the model. So, he would have to make a model of the model, which will include a smaller model of the model, and so forth. This is illustrated in the comic. At the end of these six nested models The Matryoshka limit is stated: "It is impossible to nest more than six HO layouts". Matryoshka dolls are toys of Russian origin that can be stacked inside one another. Here, the "Matryoshka limit" is the hard barrier that follows as a result of the nesting. Matter is not infinitely divisible; once one gets to the level of atoms, it is impossibly difficult to go any smaller. The unit shown in the last diagram is the ångström , a very small unit of measurement (1/10000th of a micrometre , 1/10 of a nanometre , 100 picometres or 10 −10 m) which was created when humans started discovering objects on an atomic scale, such as crystal structures or wavelengths. The last nested model looks like the atoms on a surface as seen using a scanning tunneling microscope (STM). The rules of model train layouts reference the 1999 cult classic Fight Club , where the first rule of Fight Club is "do not talk about Fight Club." However, while the club instituted the rule because their activities were morally and legally questionable, the rule in the comic was instituted by friends and family members who were apparently sick of hearing the train enthusiasts talk about model train layouts all the time. The second rule of Fight Club is "you do not talk about Fight Club", repeated for emphasis, but evidently Cueball and his friend are good enough at following the first rule of model train layouts that they only had to be told once. The "Philistines" comment is not referring to citizens of ancient Philistia (at least not directly), but rather the philosophy of Philistinism . Friedrich Nietzsche defined a Philistine as someone who is purely negative in how they define style, i.e. they know exactly what they hate and don't really have anything they like. A common stereotype for artists is to refer to anyone who dislikes their work as "Philistines," thus dismissing their criticism as being part of a larger personality defect on the critic's part rather than any particular failing of the artwork in question. The title text references HO scale and, more specifically, whether it should be spelled with the letter "O" or the number zero (0). Such debates often seem petty to the "layman", yet the people involved in the debates can form very strong feelings for their side. Randall recognizes "nerdy tendencies" almost immediately when he gets the urge to take a side. [Cueball to the left and his friend, who also looks like Cueball, are standing in the friend's rather large basement, where the celling is held up by six thin columns, and the walls are shown angling in towards a point of perspective, to display how big the room is.] Friend: I want to build a perfect HO-scale (~1/87) model train layout of my town. Cueball: In your basement? Bad idea. Never make a layout of the area you're in. [Zoom in on the two friends without the basement visualized.] Friend: Why not? Cueball: Because it'd include a little 10" replica of your house. [Zoom in Cueball's friend who takes his hand to his chin.] Friend: So? That's be cool! I'd make tiny replicas of my rooms, my furniture— Cueball (off-screen)l: —And your train layout? [Beneath this first row of the comic is the zoom-out of how the full model would look in the basement. The town lies beneath some small mountains. There is some water with a bridge over it continuing to the roads going through the city. There is no frame around this section, but instead there follows five zoom-outs, each one going from the friend's house, that proceeds to a circular frame. Within each of these is shown a nested model. Starting to the right of the main model, and then moving down, then left, and then down and right. Each layer has a broken arrow above the model between two vertical lines to indicate the scale, the length being written between the two parts of the arrow. Some foreign objects are also labeled to help understand the scale.] [Layer 1, the model with the two friends standing to the left of it.] 18 m [Layer 2, looks exactly as the model, but without the friends.] 21 cm [Layer 3, with a mosquito shown for comparison. It stands over half the model covering the mountains.] 2.4 mm [Layer 4, with a strand of spider silk (labeled) shown for comparison. The silk is much thicker than the roads, almost as thick as the mountains and much longer than the model. But the model still looks fairly much like the original one.] 28 μm Spider web [Layer 5, with a cold virus (labeled) shown for comparison. It covers roughly a quarter of the model, taking up the water part of the model. At this level the whole model becomes notably "fuzzy" as individual atoms are discernible, and most of the features apart from the mountain is indiscernible. There may be two viruses. The other would then be to the right of the one in the water but above the model. The label stands between them.] 320 nm Cold virus [Layer 6, is simply spheres (atoms) at this point. The mountain near the back is the only noticeable feature, consisting of five atoms jutting out from the surface of atoms, which is by no mean flat.] 37 Å [Beneath these six versions of the model is a caption:] The Matryoshka limit: It is impossible to nest more than six HO layouts [Back to the two friends in the basement, still not showing the basement.] Friend: My God. Cueball: Yeah. It's the second rule of model train layouts: No nesting. [Zoom in on the heads of the two friends.] Friend: ...What's the first rule? Cueball: "Do not talk about model train layouts." That rule was actually voted in by our friends and families. Friend: Philistines.

Lamp

Lamp

https://www.xkcd.com/879

https://www.explainxkcd.com/wiki/index.php/879:_Lamp

[Cueball stumbles on a lamp, lying on the ground.] [Cueball picks it up.] Rub rub [The lamp sprays fluids.] Splort [Cueball holds the lamp at arm's length, a puddle of fluid on the ground.]

Cueball finds a lamp. It has a shape which suggests it is a magic lamp, which might contain a genie . Traditionally, genies grant three wishes to whoever rubs their lamp, thus freeing them. Cueball rubs the lamp, but instead of releasing a genie, the lamp appears to ejaculate. Cueball is grossed out by this and holds the lamp away from him. The imagery and style of the comic are intentionally similar to male stimulation and ejaculation. The act of rubbing one's genitals to stimulate orgasm is well known and well documented in both literature and science. However, almost anyone would be disturbed by unintentionally giving sexual pleasure to a stranger. In the title text, a discussion is shown between Cueball and the lamp. Cueball states that what happened was NOT one of the three wishes he would have asked for if a genie had been released, and the lamp retorts, "Who said anything about YOUR wishes?", implying that the lamp's wish was to receive "handy" stimulation (or possibly that the last user of the lamp wished for that to happen to the next owner). Genies are also mentioned in at least four other comics: In the song Genie in a Bottle , from 1999 by Christina Aguilera , the sexual comparison of rubbing a genie in bottle is very clear in the song, although here it is a woman genie that needs to be rubbed in the right way to be let out. [Cueball stumbles on a lamp, lying on the ground.] [Cueball picks it up.] Rub rub [The lamp sprays fluids.] Splort [Cueball holds the lamp at arm's length, a puddle of fluid on the ground.]

Headache

Headache

https://www.xkcd.com/880

https://www.explainxkcd.com/wiki/index.php/880:_Headache

[Megan has a bike, and is wearing a helmet. Cueball is at a computer.] Megan: Wanna go for a bike ride? Cueball: Nah, I hate 3D stuff. It gives me a headache. When you think about it, this excuse can get you out of almost anything.

This was the second April fools' comic released by Randall , but in principle the first real one to be released on April 1st, which in 2011 fell on a Friday, a normal release day for xkcd. The previous fools comic was literally Not Found . After this comic Randall began releasing April Fools comic every year on April 1st disregarding the weekday of that date. The next was 1037: Umwelt released on Sunday April 1st 2012, the first to use another day of the week than Monday, Wednesday or Friday. Some people suffer from headaches, eyestrain, motion sickness and other problems when watching 3D movies , playing 3D games, watching 3D television , playing hand-held Nintendo 3DS , etc. In this comic, Cueball is using the excuse that 3D gives him a headache to get out of going outside into the real world, where everything is in 3D . Instead he stays inside and looks at his 2D computer monitor. In the title text, he says he will only go to flat places (i.e. places where everything he could see would be 2D-like). This comic was released on April Fools' Day . The April fools joke for 2011 made every comic on the site 3D, thus forcing people like Cueball to endure 3D even at their computer screens. An exception to this is 848: 3D , for which the third dimension is not visible. The 3D view is still available at xk3d.xkcd.com for all comics prior to this one. In his Øredev 2013 talk Randall mentions that a few of his friends created this 3D view and told him just 1.5 hours before the scheduled comic for that day would go live. Randall quickly drew a 3D themed comic to match. The title text suggests that Cueball is only comfortable seeing objects with visible flat surfaces like flat movie and TV screens (which the entertainment industry would not call "3D"). [Megan has a bike, and is wearing a helmet. Cueball is at a computer.] Megan: Wanna go for a bike ride? Cueball: Nah, I hate 3D stuff. It gives me a headache. When you think about it, this excuse can get you out of almost anything.

Probability

Probability

https://www.xkcd.com/881

https://www.explainxkcd.com/wiki/index.php/881:_Probability

[A plot of percent vs. years, with a solid and a dashed line. The solid line starts at 100%, and drops constantly. The dashed line starts around 85%, rises to 95% after 5 years, then drops.] [A simple table.] 5 years 81% 10 years 77% [Cueball and Megan are sitting on a bench, next to an Intravenous drip hanging from a rack. Cueball is holding a paper.] Cueball: You know, probability used to be my favorite branch of math Cueball: Because it had so many real-life applications. [They embrace, faces together.]

Cueball and Megan are sitting on a hospital bed, reading a piece of paper with the statistics for breast cancer survival. It looks like Megan has just been diagnosed with breast cancer. The thick line represents the survival rate distribution (probability to be alive after X years, unconditioned): 81% are alive at 5 years, while 77% survive to 10 years. The dashed line represents the hazard function (the negative derivative of the thick line divided by the value of the thick line at each point, i.e. how fast the thick line falls with respect to the current value, or the risk of failing/dying at time t+Δt after having survived until time t as Δt approaches zero), which is the rate between the density of the failure distribution and the survival function. Cueball expresses how he used to find probability enjoyable because of its applicability to the real world, but now sees things differently facing a painful situation involving it. Randall wrote this comic after his fiancee was diagnosed with breast cancer. Two months after posting this strip, he posted this blog post explaining the cancer comics . The title text is a reference to 55: Useless , where his normal approach also fails him regarding love. Cueball's (and Randall's) normal approach — math — isn't much help in dealing with these types of emotional situations. [A plot of percent vs. years, with a solid and a dashed line. The solid line starts at 100%, and drops constantly. The dashed line starts around 85%, rises to 95% after 5 years, then drops.] [A simple table.] 5 years 81% 10 years 77% [Cueball and Megan are sitting on a bench, next to an Intravenous drip hanging from a rack. Cueball is holding a paper.] Cueball: You know, probability used to be my favorite branch of math Cueball: Because it had so many real-life applications. [They embrace, faces together.]

Significant

Significant

https://www.xkcd.com/882

https://www.explainxkcd.com/wiki/index.php/882:_Significant

[A girl with a black ponytail runs up to Cueball, who subsequently points off-panel where there are presumably scientists.] Girl with black ponytail: Jelly beans cause acne! Cueball: Scientists! Investigate! Scientist (off screen): But we're playing Minecraft! Scientist (off screen): ...Fine. [Two scientists. The man has safety goggles on, Megan has a sheet of notes.] Scientist with goggles: We found no link between jelly beans and acne (p > 0.05). [Back to the original two.] Cueball: That settles that. Girl with black ponytail: I hear it's only a certain color that causes it. Cueball: Scientists! Scientist (off screen): But Miiiinecraft! [20 identical small panels follow, 4 rows 5 columns. The exact same picture as in panel 2 above. The scientist with goggles are stating the results and Megan holds some notes in her hand. The only difference from panel to panel is the color and then in the 14th panel where the result is positive and there is an exclamation from off screen.] Scientist with goggles: We found no link between purple jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between brown jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between pink jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between blue jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between teal jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between salmon jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between red jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between turquoise jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between magenta jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between yellow jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between grey jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between tan jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between cyan jelly beans and acne (p > 0.05). Scientist with goggles: We found a link between green jelly beans and acne (p < 0.05). Voice (off screen): Whoa! Scientist with goggles: We found no link between mauve jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between beige jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between lilac jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between black jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between peach jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between orange jelly beans and acne (p > 0.05). [Newspaper front page with a picture with three green jelly beans. There are several sections with unreadable text below each of the last three readable sentences.] News Green Jelly Beans Linked To Acne! 95% Confidence Only 5% chance of coincidence! Scientists...

This comic is about data dredging (aka p -hacking), and the misrepresentation of science and statistics in the media. A girl with a black ponytail comes to Cueball with her claim that jelly beans cause acne and Cueball then commission two scientists (a man with goggles and Megan ) to do some research on the link between jelly beans and acne. They find no link, but in the end the real result of this research is bad news reporting! First some basic statistical theory. Let's imagine you are trying to find out if jelly beans cause acne. To do this you could find a group of people and randomly split them into two groups - one group who you get to eat lots of jelly beans and a second group who are banned from eating jelly beans. After some time you compare whether the group that eat jelly beans have more acne than those who do not. If more people in the group that eat jelly beans have acne then you might think that jelly beans cause acne. However, there is a problem. Some people will suffer from acne whether they eat jelly beans or not and some will never have acne even if they do eat jelly beans. There is an element of chance in how many people prone to acne are in each group. What if, purely by chance, all the group we selected to eat jelly beans would have had acne anyway while those who didn't eat jelly beans were the lucky sort of people who never get spots? Then, even if jelly beans did not cause acne, we would conclude that jelly beans did cause acne. Of course it is very unlikely that all the acne prone people end up in one group by chance, especially if we have enough people in each group. However, to give more confidence in the result of this type of experiment, scientists use statistics to see how likely it is that the result they find is purely by chance. This is known as statistical hypothesis testing . Before we start the experiment, we choose a threshold known as the significance level. In the comic the scientists choose a threshold of 5%. If they find that more of the people who ate jelly beans had acne and the chance it was a purely random result is less than 1 in 20, they will say that jelly beans do cause acne. If however, the chance that their result was purely by random chance is greater than 5% they will say they have found no evidence of a link. The important point is this – there could still be a 1 in 20 chance that this result was purely a statistical fluke . At first the scientists do not want to stop playing the addictive game Minecraft , but they do eventually start. Minecraft was previously referenced in 861: Wisdom Teeth . The scientists find no link between jelly beans and acne (the probability that the result is by chance is more than 5% i.e. p > 0.05) but then Megan and Cueball ask them to see if only one colour of jelly beans is responsible. They test 20 different colors each at a significance level of 5%. If the probability that each trial gives a false positive result is 1 in 20, then by testing 20 different colors it is now likely that at least one jelly bean test will give a false positive. To be precise, the probability of having no false positive in 20 tests is 0.95 20 = 35.85%. Probability of having no false positive in 21 tests (counting the test without color discrimination) is 0.95 21 = 34.06%. This leads to a big newspaper headline saying Green Jelly Beans Linked To Acne where it is said that they have 95 percent confidence with only a 5% chance of a coincidence. Unfortunately, although this number has been reported by the scientists' stats package and would be true if green jelly beans were the only ones tested, it is also seriously misleading. If you roll just one die, one time, you aren't very likely to roll a six... but if you roll it 20 times you are very likely to have at least one six among them. This means that you cannot just ignore the other 19 experiments that failed. There are good methods for handling this problem, notably Bayesian inference , but they can be difficult to use and explain, and complexity does not sell newspapers. In the title text we find out that the scientists repeated the experiment (another key part of the scientific method), but now they no longer find any evidence for the link between acne and green jelly beans. They try to tell the reporter something, maybe that it was probably a coincidence, but the reporters are not interested since that is not news. So they do not listen to what the scientist has to say and instead uses the information they have to make another major headline saying Research conflicted and recommend more study on the link. But that was just what the scientist already did. This is (sadly) often an issue with more serious matters than jelly beans and acne – at any one time there are many studies about possible links between substances (e.g. red wine) and illness (e.g. cancer). Because only the positive results get reported, this limits the value any single study has - especially if the mechanism linking the two things is not known. In 2015 some journalists demonstrated the same problem: just how gullible other news outlets are with the same sort of flawed "experimental design": How, and why, a journalist tricked news outlets into thinking chocolate makes you thin - The Washington Post [A girl with a black ponytail runs up to Cueball, who subsequently points off-panel where there are presumably scientists.] Girl with black ponytail: Jelly beans cause acne! Cueball: Scientists! Investigate! Scientist (off screen): But we're playing Minecraft! Scientist (off screen): ...Fine. [Two scientists. The man has safety goggles on, Megan has a sheet of notes.] Scientist with goggles: We found no link between jelly beans and acne (p > 0.05). [Back to the original two.] Cueball: That settles that. Girl with black ponytail: I hear it's only a certain color that causes it. Cueball: Scientists! Scientist (off screen): But Miiiinecraft! [20 identical small panels follow, 4 rows 5 columns. The exact same picture as in panel 2 above. The scientist with goggles are stating the results and Megan holds some notes in her hand. The only difference from panel to panel is the color and then in the 14th panel where the result is positive and there is an exclamation from off screen.] Scientist with goggles: We found no link between purple jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between brown jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between pink jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between blue jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between teal jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between salmon jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between red jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between turquoise jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between magenta jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between yellow jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between grey jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between tan jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between cyan jelly beans and acne (p > 0.05). Scientist with goggles: We found a link between green jelly beans and acne (p < 0.05). Voice (off screen): Whoa! Scientist with goggles: We found no link between mauve jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between beige jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between lilac jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between black jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between peach jelly beans and acne (p > 0.05). Scientist with goggles: We found no link between orange jelly beans and acne (p > 0.05). [Newspaper front page with a picture with three green jelly beans. There are several sections with unreadable text below each of the last three readable sentences.] News Green Jelly Beans Linked To Acne! 95% Confidence Only 5% chance of coincidence! Scientists...

Pain Rating

Pain Rating

https://www.xkcd.com/883

https://www.explainxkcd.com/wiki/index.php/883:_Pain_Rating

[Ponytail in a doctor's coat is carrying a clipboard and consulting with Cueball, who's sitting on a high medical table one arm down the other holding on to this arm at the inside of the elbow.] Ponytail: Any pain? Cueball: My arm really hurts. [Zoom out of same scene to include Megan is standing behind Ponytail.] Ponytail: How would you rate the pain, from one to ten, where ten is the worst pain you can imagine? [This frame-less panel zooms in on Cueball sitting on the table.] Cueball: The worst pain I can imagine? [Zoom in on the top of Cueball who ponders this, raising a thoughtful hand to his jaw.] [Same image but Cueball appears to be shocked having taken both hands in front of his mouth, four small lines coming out from the top of his head.] [Zoom out again as Cueball huddles up on the table, legs all the way up to his chin, arms tightly folded around the knees. Ponytail leans back towards Megan, both whispering as indicated with smaller font.] Cueball: One. Ponytail: ...What the hell is wrong with his imagination? Megan: It's not a normal place.

In medical examinations, a doctor will sometimes ask the patient to assess their pain , to give the doctor a rough idea of the patient's condition. Cueball is asked by doctor Ponytail to compare the pain in his arm with the worst pain that he can imagine; however, a one-to-ten scale is not useful for Cueball because in his imagination the worst possible pain reduces him to a huddled ball, makes him forget his injured arm (which he somehow is able to bend without screaming), and rescales his current pain to a 1. Apparently, he has the capacity to imagine pain so intense that it dwarfs any possible real-world pain, thus skewing the scale, and this is what his friend Megan refers to when Ponytail asks what is wrong with his imagination. (According to the official transcript Megan is the patient's friend, and Ponytail is a doctor). The title text further emphasizes that idea: If the pain was higher than one on his pain scale, it would already be so high that he would be reduced to uncontrollable screaming. A similar doctor Ponytail is shown in 996: Making Things Difficult with Megan and again in 1713: 50 ccs along with both Cueball and Megan. In 647: Scary Cueball (as Rob ) also ends up in such a huddled up position. [Ponytail in a doctor's coat is carrying a clipboard and consulting with Cueball, who's sitting on a high medical table one arm down the other holding on to this arm at the inside of the elbow.] Ponytail: Any pain? Cueball: My arm really hurts. [Zoom out of same scene to include Megan is standing behind Ponytail.] Ponytail: How would you rate the pain, from one to ten, where ten is the worst pain you can imagine? [This frame-less panel zooms in on Cueball sitting on the table.] Cueball: The worst pain I can imagine? [Zoom in on the top of Cueball who ponders this, raising a thoughtful hand to his jaw.] [Same image but Cueball appears to be shocked having taken both hands in front of his mouth, four small lines coming out from the top of his head.] [Zoom out again as Cueball huddles up on the table, legs all the way up to his chin, arms tightly folded around the knees. Ponytail leans back towards Megan, both whispering as indicated with smaller font.] Cueball: One. Ponytail: ...What the hell is wrong with his imagination? Megan: It's not a normal place.

Rogers St.

Rogers St.

https://www.xkcd.com/884

https://www.explainxkcd.com/wiki/index.php/884:_Rogers_St.

[A person with long curly hair is standing to the right of a hanging crocked on the wall behind him. A person speaks from off-panel (a judge of some sort, according to the official transcript). Given the title text there is reason to believe the long haired "woman" is indeed a man named Bobby Tables.] Sign: Auditions Judge: Seriously? Judge: Sorry, no, that's a huge mood killer. Judge: Next! [Caption below the panel] Before I have a kid, I'm moving to Rogers Street in Cambridge, MA, and then getting a cat named "Mister" Just to guarantee the kid will never go into porn.

This comic is a reference to the game of creating your "porn star name" by putting your pet's name as your first name and the street you grew up on as your last name. For example: Max (Dog's name) Pine (Street name). In this comic, Randall would have named his cat "Mister" and had moved to "Rogers" Street and so his kid's porn name would be " Mister Rogers " (from the children's show Mister Rogers' Neighborhood , and previously the topic of 767: Temper ), which is pretty high on the unsexy name scale (if there was one) especially for a porn actor, although it may attract people with weird sexual fetishes. In this way, Randall has prevented his kid from getting into porn. In the title text, he references the other way of creating a porn star name by using your middle name as your first name and the street still as your last name. Additionally, the title text references comic 327: Exploits of a Mom in which Mrs. Roberts puts SQL instructions into her son's name so that it will mess with the database at school. In the comic, the kid's name is Robert'); DROP TABLE students;-- and we are led to believe the person in the comic above may be the same Little Bobby Tables . His middle name supposedly would be '); DROP TABLE students;-- , which is something incomprehensible about dropping tables (In SQL , commands are separated by semicolons ; , and strings of text are often delimited using single quotes ' . Parts of commands may also be enclosed in parentheses ( and ) . Data entries are stored as "rows" within named "tables" of similar items (e.g., Students ). The command to delete an entire table (and thus every row of data in that table) is DROP TABLE , as in DROP TABLE Students; ). If this is indeed Bobby Tables shown trying to get into porn using his pet and street name, then he has grown considerably since his last appearance from the above mentioned comic where he talks to his mother Mrs. Roberts , the famous hacker, who gave him the name with the code. Given his developing curly hair and looks that have taken him to the porn industry, it was clever of her to move to Roger St... But that seems her way, being clever with names. Here's a link to the location of Rogers Street, which is near Kendall Square in Cambridge, Massachusetts. [A person with long curly hair is standing to the right of a hanging crocked on the wall behind him. A person speaks from off-panel (a judge of some sort, according to the official transcript). Given the title text there is reason to believe the long haired "woman" is indeed a man named Bobby Tables.] Sign: Auditions Judge: Seriously? Judge: Sorry, no, that's a huge mood killer. Judge: Next! [Caption below the panel] Before I have a kid, I'm moving to Rogers Street in Cambridge, MA, and then getting a cat named "Mister" Just to guarantee the kid will never go into porn.

Recycling

Recycling

https://www.xkcd.com/885

https://www.explainxkcd.com/wiki/index.php/885:_Recycling

[Cueball is picking through various items of trash or recycling on a conveyor belt. A juice bottle, empty cardboard box, opened tin can, bottlecap, crumpled and flat sheets of paper, a soda or pop can, and miscellaneous junk are visible.] Cueball: This guy tears the labels off his cans, so he clearly understands they're going to be sorted somewhere— Cueball: Yet in the same batch he includes a bottle with like an ounce of congealed juice in it. Cueball: What an asshole. I worry a lot about what the people at the recycling center think of me.

Recycling plants often can only process one type of material at a time, which necessitates some form of sorting facility. Randall shows some degree of thoughtfulness in separating his paper from metals for the convenience of the people working at the facility, but then he leaves congealed juice in a bottle, rendering it unrecyclable without cleaning and extra effort on the part of the recycling facility. Obviously, this would be very annoying, causing the Cueball in the comic (who works in one such facility) to call him an asshole. The title text implies that the workers know his address, most likely from various envelopes and junk mail that he has recycled. As always, Randall is both a self-conscious man and a paranoid man. [Cueball is picking through various items of trash or recycling on a conveyor belt. A juice bottle, empty cardboard box, opened tin can, bottlecap, crumpled and flat sheets of paper, a soda or pop can, and miscellaneous junk are visible.] Cueball: This guy tears the labels off his cans, so he clearly understands they're going to be sorted somewhere— Cueball: Yet in the same batch he includes a bottle with like an ounce of congealed juice in it. Cueball: What an asshole. I worry a lot about what the people at the recycling center think of me.

Craigslist Apartments

Craigslist Apartments

https://www.xkcd.com/886

https://www.explainxkcd.com/wiki/index.php/886:_Craigslist_Apartments

[The comic is a single panel, presented as an apartment search.] [Title bar.] All apartments Search for: [_______] in: All apartments ( ) Title only (*) Entire post Search Rent: [Min] [Max] 0+ BR [ ] Cats [ ] Dogs [ ] Has image [Date bar.] Fri Apr 15 [Begin the apartment listings.] $1600 / 2BR ~~~ Hardwood floors, utilities included. Cats ok, limit one per square foot. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $2300 / 3BR !!!!!!!! Elegant apartment permanently lit by strobe light!!!! No floor. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $980 / 1BR New "hammock"-style dwelling. Water and heat free from same dispenser. Viking landlord. $1550 / 2BR (one inside the other). Has running water, in a sense. Free heat in short, intense bursts. Klein stairs. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $3200 / 1BR W/trimmed carpet and pert fixtures. Previous tenants clean. Call now, want you inside. $120/night (no animals) $2100 / 3BR on scenic Ash Tree Lane. Builder unknown; house has always existed. Walls shift; center of house may contain minotaur. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $600 / 5BR Three floors w/pool, rooftop garden, beautiful glass facade, no catch, 5-min drive to historic Pripyat. $7100 / 60BR Sleek modern w/extreme running water. Previous tenants may resist entry. Contains all new wiring and is a submarine. $1616 / 3BR + 2Bath, tub full of blood. Closet full of board games which play themselves. Pets ok but won't survive long.

This is a comic about the potential pitfalls in finding an apartment on Craigslist . Just as in Craigslist, some of the posts are re-posted several times. Additionally, lots of posts use lots of tildes, exclamation points or asterisks as above to set their posts apart from others. BR means bedroom, e.g. 3BR means that apartment has 3 bedrooms (common measurement of apartment size). This ad is aimed at "crazy cat ladies/bachelors" who compulsively keep a number of animals much greater than is appropriate to the living space. This is the first repetition of an entry that appears multiple times. It is also extremely generic, telling the reader little useful about the house. The square house might be a garage, or just a regular square house. Beside that, most houses have a door in front, there's nothing special about a door. [ citation needed ] It's possible this refers to an elevator. The different places it appears on the page could be the different floors it stops on. A strobe light is a very bright light that, instead of remaining on, flashes very quickly. It's frequently used in parties. A constant strobe light and the stated lack of a floor would probably make living in the apartment somewhat difficult. It is not clear whether "no floor" means a dirt floor with no foundation or tiling, or whether there is literally some form of pit where a floor would be. This is a post to live as an oarsman on a Viking ship . The water and heat presumably both come from the sky, in the form of rain and sunlight. This is a vague ad for a very unusual apartment. First off, the ad indicates that the two bedrooms are nested. This is an impractical layout, and it is very rare to see this. [ citation needed ] Possibly this refers to a tesseract , a four-dimensional cube. This conjecture is supported by mention of a Klein Bottle. Running water "in a sense" is both vague and concerning. The note about heat is similar. Short intense blasts of heat are not a comfortable way to heat a room. Depending on how intense the blasts are, they also may be dangerous or deadly. (Alternatively, the house could have a geyser inside, which would explain both the 'free heat in short, intense bursts', along with the 'water that runs in a sense'.) A Klein bottle is a surface which has no difference between "inside" and "outside", similar to a mobius strip but with an extra dimension. It is physically impossible to build a Klein bottle in a three-dimensional space. It isn't certain what Klein stairs are, but they probably aren't very useful. This may be a pun on "clean" stairs. This is a disguised "adult services" (sex) posting, with references to trimmed pubic hair, an attractive body, and a lack of STDs . Craigslist no longer allows posts for this, because prostitution is illegal in most places in the US. This post tries to evade the adult services ban by pretending to be something else. "No animals" would normally be assumed to mean "no pets", but in this context probably refers to STDs (possibly crabs or scabies ) or bestiality . This Minotaur house is an ad for the house in the novel House of Leaves . It may also refer to the Labyrinth in Ancient Greek mythology. This is an ad for a residence in the Chernobyl Nuclear Power Plant , located near to the town of Pripyat , in northern Ukraine. The NPP is a 3-level structure, and contains a pool for temporary spent nuclear fuel storage. The rooftop now has plants growing on it after years of neglect, and the glass facade references radioactive glassy minerals created by the explosion. Pripyat was founded in 1970 to serve the power plant, so is only 'historic' in the sense that it is associated with the Chernobyl disaster. This house is a submarine, as indicated by the advertisement, presumably operated by a navy. The "previous tenants", being members of the armed forces, would undoubtedly resist entry of someone attempting to board their submarine. The sixty bedrooms refers to the crew members' bunks on board the ship, which are in extremely tight quarters and can be very uncomfortable. This may also be a reference to 496: Secretary: Part 3 , which makes reference to Black Hat stealing a submarine, presumably for 405: Journal 3 - apparently this is him trying to get rid of it. This is an ad for a house in a generic horror movie. Appearing in the title text, this is a reference to the Death Star in Star Wars . Alderaan is the home planet of Princess Leia , which was obliterated by the Death Star. Mandatory parking references the tractor beams used to drag nearby ships (such as the Millennium Falcon) into the base. The garbage disposal refers to an iconic scene from Star Wars aboard the Death Star, in which the heroes are in danger of being crushed to death inside a trash compactor chamber. It seems somewhat inconvenient that this "apartment" has over a million bedrooms but only three bathrooms. The guest rooms are probably the detention blocks such as Detention Block AA-23 . [The comic is a single panel, presented as an apartment search.] [Title bar.] All apartments Search for: [_______] in: All apartments ( ) Title only (*) Entire post Search Rent: [Min] [Max] 0+ BR [ ] Cats [ ] Dogs [ ] Has image [Date bar.] Fri Apr 15 [Begin the apartment listings.] $1600 / 2BR ~~~ Hardwood floors, utilities included. Cats ok, limit one per square foot. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $2300 / 3BR !!!!!!!! Elegant apartment permanently lit by strobe light!!!! No floor. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $980 / 1BR New "hammock"-style dwelling. Water and heat free from same dispenser. Viking landlord. $1550 / 2BR (one inside the other). Has running water, in a sense. Free heat in short, intense bursts. Klein stairs. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $3200 / 1BR W/trimmed carpet and pert fixtures. Previous tenants clean. Call now, want you inside. $120/night (no animals) $2100 / 3BR on scenic Ash Tree Lane. Builder unknown; house has always existed. Walls shift; center of house may contain minotaur. $1100 / **** GREAT DEAL SQUARE HOUSE DOOR IN FRONT!!! **** $600 / 5BR Three floors w/pool, rooftop garden, beautiful glass facade, no catch, 5-min drive to historic Pripyat. $7100 / 60BR Sleek modern w/extreme running water. Previous tenants may resist entry. Contains all new wiring and is a submarine. $1616 / 3BR + 2Bath, tub full of blood. Closet full of board games which play themselves. Pets ok but won't survive long.

Future Timeline

Future Timeline

https://www.xkcd.com/887

https://www.explainxkcd.com/wiki/index.php/887:_Future_Timeline

THE FUTURE According to Google search results Events for each year determined by the first page of Google search results for the phrases: "By <year>" "In year" "By the year <year>" "In the year <year>" "Will * by the year <year>" "Will * in the year <year>" "In <year>, * will" "By <year>, * will" 2012 World population reaches 7 billion Flying cars reach market Canada cuts greenhouse emissions to 6% below 1990 levels as per Kyoto Apocalypse occurs 2013 National debt paid off through President Clinton's plans Microchipping of all Americans begins Homelessness ended in Massachusetts Health care reform law repealed 2014 US leaves Afghanistan GNU/Linux becomes dominant OS 2015 New Horizons reaches Pluto Health care law causes hyperinflation 192 UN member nations achieve millennium development goals: Extreme poverty and hunger eradicated Universal primary education implemented Women empowered, gender equality reached Environmental stability ensured 2016 Baby boomers begin turning 65 Android takes 38% of the smartphone market Android takes 45% of the smartphone market Windows Phone overtakes iOS in smartphones 2017 China completes unmanned Lunar sample-return mission Social Security stops running surplus US budget balanced Newspapers become obsolete and die out Cosmetic surgery doubles 2018 Social Security stops running surplus Jesus returns to Earth 2019 Social Security stops running surplus Every baby has genes mapped at birth 2020 Solar power becomes cheaper than fossil fuels Keyboards and mice become obsolete New Tappan Zee bridge constructed 2021 US debt reaches 97% of GDP US unemployment falls to 2.8% Restored caliphate unifies Middle East Lake Mead evaporates 2022 Kilimanjaro snow-free HTML 5 finished Newspapers become obsolete and die out 2023 Jesus returns to Earth (again) US debt passes 100% of GDP All unprotected ancient forests gone from Pacific Northwest 2024 Atlantis begins to reappear Orangutans extinct in wild China lands men and women on the moon NASA sets up permanent moon base Female professionals pass males in pay 2025 World population reaches 8 billion Two billion people face water shortages 62 MPG cars introduced US power fades 2026 Atlantis emerges completely Rock Bands die out US debt paid off Car accidents cease West coast falls into ocean 2027 Japan introduces new fastest maglev train Lyndon Larouche-planned Mars colony established Social Security stops running surplus 2028 Tobacco outlawed 40% of coral reefs gone US debt paid off Social Security stops running surplus 2029 Social Security trust fund exhausted Computers pass the Turing Test Aging reversed Wikipedia reaches 30 million articles 2030 Half of Amazon rain forest lost to logging Cancer deaths double from 2008 levels Arctic ice-free in summer 2031 Computers controlled by thought Realtors replaced by technology Social Security trust fund exhausted 2032 "Big One" hits San Francisco US elects first married lesbian president Entire world converted to Christianity 2033 Kilimanjaro ice disappears India becomes superpower Europe reaches Mars 2034 US diabetes cases double, treatment costs triple US builds autonomous robot army 2035 80% of America's energy comes from renewable sources Himalayan glaciers down 80% in size Arctic sea lane opens 2036 80% of US has access to high-speed rail Asteroid Apophis hits/misses Earth 2037 Arctic ice-free in September Social Security trust fund exhausted 2038 32-bit timestamps role over, causing Y2K-level chaos "Big One" hits California 2039 US population hits 400 million Severe heat waves become commonplace Scientology becomes majority religion in US 2040 Arctic summers ice-free Nanotechnology makes humans immortal 2041 Social Security trust fund exhausted 2042 2043 World population passes 9 billion 2044 Mankind genetically engineered to be happy Childhood obesity reaches 100% 2045 Humans and machines merge 2046 World's natural resources depleted 2047 World ruled by banks and corporations Tobacco industry fails US begins using autonomous attack drones 2048 Salt-water fish extinct from overfishing Unisex bathing suits cover body from shoulder to ankle Entire US population overweight 2049 $1.000 computer exceeds computational ability of humanity Singularity occurs Fishing industry collapses 2050 80% of Earth's population lives in urban centers China controls space Sex with robots possible Cars banned from European cities One million species extinct from climate change 2051 Atmosphere escapes into space 2052 Medicare, Medicaid, and Social Security spending exceed total US revenue 2053 US budget balanced Majority of Americans in prison Cars driven by dogs 2054 Hunger becomes unimaginable global problem 2055 Atmospheric CO2 doubled Oil runs out Copper, tin, lead, gold, and nickel all exhausted 2056 RFID-tagged driverless cars Robots given same rights as humans 2057 150 Japanese settlers on Mars Colorado River runs dry 2058 Smoking ends in New Zealand 2059 Humans have domesticated robots 2060 Human race lives in peace Extreme droughts across much of Earth Global temperature rise reaches 4°C Oil runs out again 2061 Halley's comet returns 2062 Uganda hosts World Cup The Jetsons 2063 First human clones reach adulthood Population of Moon reaches 100,000 Population of Mars reaches 10,000 Spacecraft exceed speed of light 2064 Clean Air Act finishes reducing haze in national parks to natural levels 2065 Last coral reefs die out Chernobyl cleanup complete 2066 Cyprus achieves its goal 2067 Americans live in domed cities and watch 3D TV Redheads go extinct 2068 Ozone hole over Antarctic finishes recovering Lord Jesus rules the Earth from Throne in Jerusalem. Entire world population gay due to chemicals in the water 2069 Public masturbation legalized 2070 World population peaks City-scale flooding disasters 60% of world's energy comes from renewable sources 2071 Europe's temperatures rise by 3°C World summer temperatures rise by 5°C 2072 US retirement age is set to 75 2073 Oceans do not rise one foot 2074 Number of 100-year-olds reaches one million Supertyphoons hit Japan 2075 US retirement age set to 69 2076 Average scientific paper has more than 24 authors Social Security trust fund exhausted 2077 2078 Newspapers become obsolete and die out 2079 US debt reaches 716% of GDP Lodgepole pines disappear from Northwest Floods commonplace Religion marginalized 2080 Federal spending reaches 70% of GDP UK population doubles 2081 2082 World population declines to one billion 2083 2084 Robot policemen introduced 2085 US deficit reaches 62% of GDP 2086 2087 2088 Japan becomes all-robot country 2089 World halts fossil fuel use 2090 Global warming hits 7°C Global warming hits 4°C 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 Global warming around 5-7°C Sea levels have risen by a meter or more Joshua trees nearly extinct Earth's climate resembles that of the Cretaceous Germany tropical Emperor penguins extinct Arctic permafrost thaws Rising seas flood coastal cities Rain forests mostly gone due to climatic shifts All coral reefs gone Gillette introduces 14-bladed razor 2101 WAR WAS BEGINNING

This comic uses the same strategy as comic 715: Numbers , in which Randall uses Google to search for phrases and then charts the results. This one is charted as a timeline, whereas 715 was charted as line graphs. It is a list of things predicted or announced by anyone at any time (the ones you see on Google search using "by the year..." or similar statements). "2101 - War Was Beginning" is a reference to the opening narration of video game Zero Wing ; the same narration is famous for the internet meme " All your base are belong to us ". As there are not any other out and out references in the comic, and the rest are actually results that you can find using Randall's methods, "War Was Beginning" was probably the only thing he got when he googled 2101 as well. Certain events in this comic, e.g. "Social Security stops running surplus", are repeated multiple times. Also, certain bizarre events, like "Apocalypse occurs", or "Flying cars reach market", happen before rather plausible things, like "'Big one' hits California". Certain events, like "Japan is a robot-only country" or "Gillette introduces 14-blade razor" may be related to the recurring theme 605: Extrapolating . The title text is a reference to a reoccurring scaremonger theory that European people will become a minority or extinct as other ethnicities outbreed them. For maximum scaremongering they will claim this could happen in the near future, complete with extrapolated graphs. In the years since this comic was published these conspiracy theories have come to be known as "the great replacement" or "white genocide". Scaremongers are banking on the idea their target audience will rarely bother to fact check, as analysis of their extrapolations usually reveals incorrect methodology if not outright lies. This comic has similar features to 1413: Suddenly Popular , 1093: Forget , and 891: Movie Ages . THE FUTURE According to Google search results Events for each year determined by the first page of Google search results for the phrases: "By <year>" "In year" "By the year <year>" "In the year <year>" "Will * by the year <year>" "Will * in the year <year>" "In <year>, * will" "By <year>, * will" 2012 World population reaches 7 billion Flying cars reach market Canada cuts greenhouse emissions to 6% below 1990 levels as per Kyoto Apocalypse occurs 2013 National debt paid off through President Clinton's plans Microchipping of all Americans begins Homelessness ended in Massachusetts Health care reform law repealed 2014 US leaves Afghanistan GNU/Linux becomes dominant OS 2015 New Horizons reaches Pluto Health care law causes hyperinflation 192 UN member nations achieve millennium development goals: Extreme poverty and hunger eradicated Universal primary education implemented Women empowered, gender equality reached Environmental stability ensured 2016 Baby boomers begin turning 65 Android takes 38% of the smartphone market Android takes 45% of the smartphone market Windows Phone overtakes iOS in smartphones 2017 China completes unmanned Lunar sample-return mission Social Security stops running surplus US budget balanced Newspapers become obsolete and die out Cosmetic surgery doubles 2018 Social Security stops running surplus Jesus returns to Earth 2019 Social Security stops running surplus Every baby has genes mapped at birth 2020 Solar power becomes cheaper than fossil fuels Keyboards and mice become obsolete New Tappan Zee bridge constructed 2021 US debt reaches 97% of GDP US unemployment falls to 2.8% Restored caliphate unifies Middle East Lake Mead evaporates 2022 Kilimanjaro snow-free HTML 5 finished Newspapers become obsolete and die out 2023 Jesus returns to Earth (again) US debt passes 100% of GDP All unprotected ancient forests gone from Pacific Northwest 2024 Atlantis begins to reappear Orangutans extinct in wild China lands men and women on the moon NASA sets up permanent moon base Female professionals pass males in pay 2025 World population reaches 8 billion Two billion people face water shortages 62 MPG cars introduced US power fades 2026 Atlantis emerges completely Rock Bands die out US debt paid off Car accidents cease West coast falls into ocean 2027 Japan introduces new fastest maglev train Lyndon Larouche-planned Mars colony established Social Security stops running surplus 2028 Tobacco outlawed 40% of coral reefs gone US debt paid off Social Security stops running surplus 2029 Social Security trust fund exhausted Computers pass the Turing Test Aging reversed Wikipedia reaches 30 million articles 2030 Half of Amazon rain forest lost to logging Cancer deaths double from 2008 levels Arctic ice-free in summer 2031 Computers controlled by thought Realtors replaced by technology Social Security trust fund exhausted 2032 "Big One" hits San Francisco US elects first married lesbian president Entire world converted to Christianity 2033 Kilimanjaro ice disappears India becomes superpower Europe reaches Mars 2034 US diabetes cases double, treatment costs triple US builds autonomous robot army 2035 80% of America's energy comes from renewable sources Himalayan glaciers down 80% in size Arctic sea lane opens 2036 80% of US has access to high-speed rail Asteroid Apophis hits/misses Earth 2037 Arctic ice-free in September Social Security trust fund exhausted 2038 32-bit timestamps role over, causing Y2K-level chaos "Big One" hits California 2039 US population hits 400 million Severe heat waves become commonplace Scientology becomes majority religion in US 2040 Arctic summers ice-free Nanotechnology makes humans immortal 2041 Social Security trust fund exhausted 2042 2043 World population passes 9 billion 2044 Mankind genetically engineered to be happy Childhood obesity reaches 100% 2045 Humans and machines merge 2046 World's natural resources depleted 2047 World ruled by banks and corporations Tobacco industry fails US begins using autonomous attack drones 2048 Salt-water fish extinct from overfishing Unisex bathing suits cover body from shoulder to ankle Entire US population overweight 2049 $1.000 computer exceeds computational ability of humanity Singularity occurs Fishing industry collapses 2050 80% of Earth's population lives in urban centers China controls space Sex with robots possible Cars banned from European cities One million species extinct from climate change 2051 Atmosphere escapes into space 2052 Medicare, Medicaid, and Social Security spending exceed total US revenue 2053 US budget balanced Majority of Americans in prison Cars driven by dogs 2054 Hunger becomes unimaginable global problem 2055 Atmospheric CO2 doubled Oil runs out Copper, tin, lead, gold, and nickel all exhausted 2056 RFID-tagged driverless cars Robots given same rights as humans 2057 150 Japanese settlers on Mars Colorado River runs dry 2058 Smoking ends in New Zealand 2059 Humans have domesticated robots 2060 Human race lives in peace Extreme droughts across much of Earth Global temperature rise reaches 4°C Oil runs out again 2061 Halley's comet returns 2062 Uganda hosts World Cup The Jetsons 2063 First human clones reach adulthood Population of Moon reaches 100,000 Population of Mars reaches 10,000 Spacecraft exceed speed of light 2064 Clean Air Act finishes reducing haze in national parks to natural levels 2065 Last coral reefs die out Chernobyl cleanup complete 2066 Cyprus achieves its goal 2067 Americans live in domed cities and watch 3D TV Redheads go extinct 2068 Ozone hole over Antarctic finishes recovering Lord Jesus rules the Earth from Throne in Jerusalem. Entire world population gay due to chemicals in the water 2069 Public masturbation legalized 2070 World population peaks City-scale flooding disasters 60% of world's energy comes from renewable sources 2071 Europe's temperatures rise by 3°C World summer temperatures rise by 5°C 2072 US retirement age is set to 75 2073 Oceans do not rise one foot 2074 Number of 100-year-olds reaches one million Supertyphoons hit Japan 2075 US retirement age set to 69 2076 Average scientific paper has more than 24 authors Social Security trust fund exhausted 2077 2078 Newspapers become obsolete and die out 2079 US debt reaches 716% of GDP Lodgepole pines disappear from Northwest Floods commonplace Religion marginalized 2080 Federal spending reaches 70% of GDP UK population doubles 2081 2082 World population declines to one billion 2083 2084 Robot policemen introduced 2085 US deficit reaches 62% of GDP 2086 2087 2088 Japan becomes all-robot country 2089 World halts fossil fuel use 2090 Global warming hits 7°C Global warming hits 4°C 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 Global warming around 5-7°C Sea levels have risen by a meter or more Joshua trees nearly extinct Earth's climate resembles that of the Cretaceous Germany tropical Emperor penguins extinct Arctic permafrost thaws Rising seas flood coastal cities Rain forests mostly gone due to climatic shifts All coral reefs gone Gillette introduces 14-bladed razor 2101 WAR WAS BEGINNING

Heaven

Heaven

https://www.xkcd.com/888

https://www.explainxkcd.com/wiki/index.php/888:_Heaven

[The panel shows the display of a Tetris game. A large oddly shaped piece is falling towards the board. The piece fits into the gaps exactly to complete six rows at once. The next piece is simply a very long brick. All the pieces at the bottom are made from possible tetris pieces.] Next Top 0002187 Score 0002186 Level 5 [Below the panel:] Heaven

This comic shows the popular video game Tetris , in which you use different shaped pieces to fill in lines to score points. Filling multiple lines by adding a single piece results in bonus points. Normally all pieces are made up of four small squares. This has also been the case for all the pieces at the bottom of the game; however, some parts of some blocks have been erased when a line has been deleted because it was full. Heaven, in Tetris , is when you get the perfect piece that fills out all the other pieces on the board. The falling piece here is really odd, but it fits the 18 bare spaces exactly to make it possible to remove 6 lines in a row—compared to the four that is normally possible using the tall brown piece. On top of the heavenly feeling of getting a piece that fits—the top score is also about to be smashed, as the player was at the moment only one point til reaching it! The next piece, shown to the right, which shall come after the special one, is much taller than the normally possible straight brown piece—a normal one can be seen at the bottom right of the game. This next piece seems to be ten tall, which when rotated fits the cleared bottom of the well perfectly. The title text compares this experience with sex, complete with an orgasm and the feelings you get right after sex. After "the brief feeling of satisfaction" from the orgasm you are bored, ennui means a feeling of utter weariness and discontent resulting from satiety or lack of interest, but at the end you want more. A fan has made a modified version of the classic Tetris game, where at a certain frequency, a heavenly perfectly-fitting block comes along. The game can be found here (Flash game, no longer works). Also see comic 724: Hell , which presents an opposing situation in which the game is designed to be impossible to play. Choosing to post a comic called Heaven as number 888 is not a coincidence—as in Christian numerology, the number 888 represents Jesus and in Chinese numerology it represents triple fortune. [The panel shows the display of a Tetris game. A large oddly shaped piece is falling towards the board. The piece fits into the gaps exactly to complete six rows at once. The next piece is simply a very long brick. All the pieces at the bottom are made from possible tetris pieces.] Next Top 0002187 Score 0002186 Level 5 [Below the panel:] Heaven

Turtles

Turtles

https://www.xkcd.com/889

https://www.explainxkcd.com/wiki/index.php/889:_Turtles

[There is a turtle.] Off-panel: Oh, crap, I deleted the file! [There is a turtle.] Turtle (thinking): I am a turtle. [There is a turtle.] Off-panel: No, wait, there it is. [There is a turtle.] Turtle (thinking): I am a turtle. [There is a turtle.] 50 Years Later: Turtle (thinking): I am a turtle. [Caption below the panel:] Turtles have it figured out, man.

This comic is about the frivolousness of many modern problems. While an offscreen character is panicking over deleting a file, the turtle is content with just being a turtle. The text saying "turtles have it figured out, man" indicates that Randall appreciates this simpler mode of thought. Based on its appearance, it is possible that the turtle is a tortoise (biologists call all testudines turtles, and tortoises are the family of land-based turtles), which is also supported by the fact that tortoises tend to have much longer livespans (100 to 150 years) than sea turtles and terrapins (approximately 80 years). An alternative explanation could be that the satisfaction of knowledge that the creature has poses an obstruction to his venturing out and finding its true identity. It was told that it's a turtle, thus, it continues to believe, even though it's wrong. The minor panicking of humans actually is a driving force of our sentience. The title text is possibly a reference to 231: Cat Proximity . It also resembles Towelie's Catchphrase from South Park . The text at the bottom 'Turtles have it figured out, man' could be a reference to the turtle in Finding Nemo , who speaks in a similar manner. [There is a turtle.] Off-panel: Oh, crap, I deleted the file! [There is a turtle.] Turtle (thinking): I am a turtle. [There is a turtle.] Off-panel: No, wait, there it is. [There is a turtle.] Turtle (thinking): I am a turtle. [There is a turtle.] 50 Years Later: Turtle (thinking): I am a turtle. [Caption below the panel:] Turtles have it figured out, man.

Etymology

Etymology

https://www.xkcd.com/890

https://www.explainxkcd.com/wiki/index.php/890:_Etymology

[Four people are sitting around a small round table in a room with large windows, presumably the cantina from Star Wars: A New Hope . The four are Obi-Wan Kenobi in a cloak and with beard, Luke Skywalker with black hair down his forehead and down his neck, Han Solo with shorter black hair and the hairy creature is Chewbacca. On the table is two cylinders, a white and a smaller black. Outside the window is two alien creatures walking by. Closest is a creature looking like a Rodian (like Greedo) and further back is a creature with two black horns on top of a regular Cueball like appearance, in the vein of Devaronians. They walk in a street outside with buildings behind.] Han Solo: Han Solo. I'm captain of the Millennium Falcon . [Zoom in on Luke:] Luke Skywalker: What's that? [Zoom in on Han:] Han: It's the ship that made the Kessel Run in less than 12 parsecs! [Zoom in on Luke:] Luke: No, what's a falcon? [Zoom in on a silent Han. Beat panel.]

This comic references one of the scenes from the sci-fi classic Star Wars set in Mos Eisley Cantina at the spaceport on Tatooine , a wretched hive of scum and villainy. In this scene Obi-Wan Kenobi (with the beard) and Luke Skywalker on the left are trying to get off the planet secretly and they enlist help from Han Solo and Chewbacca . Han Solo tells Luke he is captain of the famous ship the Millennium Falcon . When Luke asks what that is, Han brags "It's the ship that made the Kessel Run in less than 12 parsecs !" But it turns out that what Luke asks about is what a falcon is. Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time. Randall wonders what Luke would say to Han if he had no idea what a falcon was. Normally in sci-fi aliens would have some familiarity with Earth and the things you can find on it, such as falcons. However, Star Wars takes place "a long time ago in a galaxy far, far away" where nobody knows Earth even exists, possibly before falcons exist, thus how could the Millennium Falcon be named after an animal they have no knowledge about? This could be an example of a translation convention made for the sake of the audience; presumably, fast birds of prey exist in the Star Wars universe, one of which is the namesake of Han Solo's ship, which is then artistically translated from Basic to English as "Falcon". Likewise with the parsec, which is a unit defined by the distance of a star from the Earth which experiences a par allax of one arc sec ond when viewed six months apart (i.e. it is the length of a triangle with a base of 1 AU and the opposite angle of 1 arcsec). A galaxy which is home to space-faring civilizations will have units of similar magnitudes, which are converted into parsecs for our convenience. In the Star Wars novelization, this joke is made in reference to a duck: [1] Having grown up on a desert world, Luke would have no idea of what a duck or any other kind of waterfowl is, while Obi-Wan Kenobi could have seen such creatures during his time as a Jedi (Captain Panaka uses the "sitting ducks" metaphor in The Phantom Menace , so they are known to exist in Star Wars canon). Perhaps Luke would have understood if Obi-Wan had used a desert bird as an analogy. In the title text, Randall muses over the fact that he as a child did not have any problems dispensing his disbelief in a distant galaxy full of humans, but was still derailed by the language. It would seem unlikely that another galaxy has creatures so similar to humans, while at the same time being filled with so many other types of creatures. The bit about Indo-European roots is another reference to etymology. English is a language descended from a language called Proto-Indo-European, or PIE (along with most languages in Europe, West and South Asia), thus many words in these languages can ultimately be traced back to PIE. Randall wonders how the vocabulary in Star Wars can also be traced back to PIE despite the lack of Europe or Asia in that universe. [Four people are sitting around a small round table in a room with large windows, presumably the cantina from Star Wars: A New Hope . The four are Obi-Wan Kenobi in a cloak and with beard, Luke Skywalker with black hair down his forehead and down his neck, Han Solo with shorter black hair and the hairy creature is Chewbacca. On the table is two cylinders, a white and a smaller black. Outside the window is two alien creatures walking by. Closest is a creature looking like a Rodian (like Greedo) and further back is a creature with two black horns on top of a regular Cueball like appearance, in the vein of Devaronians. They walk in a street outside with buildings behind.] Han Solo: Han Solo. I'm captain of the Millennium Falcon . [Zoom in on Luke:] Luke Skywalker: What's that? [Zoom in on Han:] Han: It's the ship that made the Kessel Run in less than 12 parsecs! [Zoom in on Luke:] Luke: No, what's a falcon? [Zoom in on a silent Han. Beat panel.]

Movie Ages

Movie Ages

https://www.xkcd.com/891

https://www.explainxkcd.com/wiki/index.php/891:_Movie_Ages

The 2011 Guide to Making People Feel Old -Using Movie Release Dates- [A chart with 2 columns. First column is labeled 'Their Age,' and is numbered 16 through 35 & 'over 35.' The second column is labeled 'You Say' and is divided into four sub-columns. The first sub-column reads '"Did you realize that...' from 16-35, and the third sub-column says 'Came Out' from 16-35.] Age 16: Snakes on a Plane... Half a decade ago?" 17-19: Revenge of the Sith... More than half a decade ago?" 20: Finding Nemo... Eight years ago?" 21-22: Shrek... Ten years ago?" 23-25: The Matrix... Not the last decade, but the one before that ?" 26: Toy Story... Over fifteen years ago?" 27: The Lion King... Seventeen years ago?" 28: Jurassic Park... Eighteen years ago?" 29: Terminator 2... Twenty years ago?" 30-32: Home Alone... More than twenty years ago?" 33-35: The Little Mermaid ... Closer to the moon landing than the present day? Over 35: "Hey, did you see this chart? You match your age to movie - oh, right, sorry, it only goes up to 35. I guess it's not really aimed at older people."

Based on the person you are talking to, take their age on the far left, add "Did you realize that..." add the corresponding movie that is across from their age then "...came out..." add the phrase at the end of row. E.g. - If a person is 30, then it would go a little something like this "Did you realize that Home Alone came out more than 20 years ago?" This would make people feel old because certain movies that they felt were close to them are actually aging quickly. In a way, this chart likens the age of the movie to the age of the person, as the person is about 10 years older than the movie, but as movies have shorter "life cycles" and seem to lose glory quickly, it seems that the movie is very old. However, the age at which a movie is accepted to be old is not nearly as large as the age at which a person is accepted to be old, so the person is not actually that old. This makes it seem that the person is far older than they actually are. And since this chart is designed to make someone feel old, anyone over 35 gets lumped in with "older people," which no one likes. The title text states that if you are 15 or younger it is probably already too late to be a child prodigy . This may be a reference to 447: Too Old For This Shit , in which Randall believes that anyone over the age of 11 has already missed out on their chance to become famous. Randall has covered making people feel old several times in 647: Scary , 973: MTV Generation , 1393: Timeghost and 1477: Star Wars . The 2011 Guide to Making People Feel Old -Using Movie Release Dates- [A chart with 2 columns. First column is labeled 'Their Age,' and is numbered 16 through 35 & 'over 35.' The second column is labeled 'You Say' and is divided into four sub-columns. The first sub-column reads '"Did you realize that...' from 16-35, and the third sub-column says 'Came Out' from 16-35.] Age 16: Snakes on a Plane... Half a decade ago?" 17-19: Revenge of the Sith... More than half a decade ago?" 20: Finding Nemo... Eight years ago?" 21-22: Shrek... Ten years ago?" 23-25: The Matrix... Not the last decade, but the one before that ?" 26: Toy Story... Over fifteen years ago?" 27: The Lion King... Seventeen years ago?" 28: Jurassic Park... Eighteen years ago?" 29: Terminator 2... Twenty years ago?" 30-32: Home Alone... More than twenty years ago?" 33-35: The Little Mermaid ... Closer to the moon landing than the present day? Over 35: "Hey, did you see this chart? You match your age to movie - oh, right, sorry, it only goes up to 35. I guess it's not really aimed at older people."

Null Hypothesis

Null Hypothesis

https://www.xkcd.com/892

https://www.explainxkcd.com/wiki/index.php/892:_Null_Hypothesis

[A student works at a desk, and Cueball is talking to Megan.] Cueball: I can't believe schools are still teaching kids about the null hypothesis. Cueball: I remember reading a big study that conclusively disproved it years ago.

This comic (and the title text) are based on a misunderstanding. The null hypothesis is the hypothesis in a statistical analysis that indicates that the effect investigated by the analysis does not occur, i.e. 'null' as in zero effect. For example, the null hypothesis for a study about cell phones and cancer risk might be "Cell phones have no effect on cancer risk." The alternative hypothesis, by contrast, is the one under investigation - in this case, probably "Cell phones affect the risk of cancer." After conducting a study, we can then make a judgment based on our data. There are statistical models for measuring the probability that a certain result occurred by random chance, even though in reality there is no correlation. If this probability is low enough (usually meaning it's below a certain threshold we set when we design the experiment, such as 5% or 1%), we reject the null hypothesis, in this case saying that cell phones do increase cancer risk. Otherwise, we fail to reject the null hypothesis, as we have insufficient evidence to conclusively state that cell phones increase cancer risk. This is how almost all scientific experiments, from high school biology classes to CERN, draw their conclusions. It is very important to note that a null hypothesis is a specific statement relative to the current study. In mathematics, we often see terms such as "the Riemann hypothesis" or "the continuum hypothesis" that refer to universal statements, but a null hypothesis depends on context. There is no one " the null hypothesis." It refers to a method of statistical analysis (and falsifiability , not a specific hypothesis). Given that, Megan 's response would probably be to facepalm. [A student works at a desk, and Cueball is talking to Megan.] Cueball: I can't believe schools are still teaching kids about the null hypothesis. Cueball: I remember reading a big study that conclusively disproved it years ago.

65 Years

65 Years

https://www.xkcd.com/893

https://www.explainxkcd.com/wiki/index.php/893:_65_Years

[A graph titled 'Number of Living Humans Who Have Walked on Another World' - its y-axis is numbered 5, 10, 15, its x-axis increments every ten years from 1960-2040. The line of the graph has a bracket above it that says '65 Years', starting at 1969, ending in 2034. The line starts at 1969 and increases steeply to 12 by 1972. It then plateaus until the early nineties, declines gradually to 9 between 1991-1999, and then plateaus again. From 2011-2035, which is labeled 'Projected Actuarial Tables', the line branches into three and begins to decline more steeply to zero. The area between the first and second branch is shaded and labeled '5th percentile' and the area between the second and third branch is shaded and labeled '95th percentile.']

Randall is showing the number of still living humans who have walked on another world for the 65-year period that begins in 1969 (when a human first walked on the moon). Up to 2011 (when the comic was drawn), he has drawn a single line for the actual figures. For the subsequent years, he has drawn three lines using actuarial tables or life tables (such tables show, for each age, the probability that a certain person will die within the next year). The line marked "5TH PERCENTILE" indicates that there is a 95% probability that the number alive in a given year will be above that line and a 5% probability that the number alive will be below that line. For example, this line indicates a 5% chance that all Apollo moon walkers will be dead by 2023, and a 95% chance that at least one will still be alive by that year. The line marked "95TH PERCENTILE" indicates that there is a 5% probability that the number alive in a given year will be above that line and a 95% probability that the number alive will be below that line. For example, this line indicates a 95% chance that all Apollo moon walkers will be dead by 2035, and a 5% chance that at least one will still be alive by that year. The middle line is not identified, but is probably the "50TH PERCENTILE" (see these tables ). If so, it indicates that there is a 50% probability that the number alive in a given year will be above that line and a 50% probability that the number alive will be below that line. For example, this line indicates a 50% chance that all Apollo moon walkers will be dead by 2028 (see previous link), and a 50% chance that at least one will still be alive by that year. Although the term other world would include all other worlds on which humans have walked, there is currently only one other world on which humans have walked, which is the moon. The humans that have walked there are the 12 Apollo astronauts who landed on the Moon between 1969 and 1972. In particular, Neil Armstrong and Buzz Aldrin landed in July 1969. Pete Conrad and Alan Bean landed in November. Alan Shepard and Edgar Mitchell : February 1971. David Scott and James Irwin : July 1971. John Young and Charles Duke : April 1972. Eugene Cernan and Harrison Schmitt : December 1972. Irwin died in 1991. Shepard and Conrad died in 1998 and 1999 respectively, making the total 9 as of the date this comic was published. Since then Armstrong died in 2012, Mitchell in 2016, Cernan in 2017, Young on January 6, 2018, and Bean on May 26, 2018. The current (April 2021) number is 4, which lies close to the middle line (the supposed 50TH PERCENTILE). The oldest living person to have landed on the moon is Aldrin at 91. Also living are Scott at 88, Schmitt at 85, and Duke at 85. The chart assumes that no other humans will go to walk on another world within the time-frame plotted and the title text implies that this is primarily an economically determined decision. While noting that not exploring space is a justifiable and sensible decision which may also be made by many hypothetical cultures on other worlds, the text implies a grandness to a civilization that would be given the opportunity to discover, study and memorialize the 'one-world graves' of other civilizations by choosing to explore space despite the economic difficulty. This also implies that the likely consequence of not exploring space is that a civilisation which chooses to do this is doomed to go extinct fairly rapidly while those which do explore and colonise may last long enough to be safely established on multiple worlds and discover the remains of civilisations which acted on a purely economic basis and hence ensured their own collapse. High five for exoplanet archaeology. [A graph titled 'Number of Living Humans Who Have Walked on Another World' - its y-axis is numbered 5, 10, 15, its x-axis increments every ten years from 1960-2040. The line of the graph has a bracket above it that says '65 Years', starting at 1969, ending in 2034. The line starts at 1969 and increases steeply to 12 by 1972. It then plateaus until the early nineties, declines gradually to 9 between 1991-1999, and then plateaus again. From 2011-2035, which is labeled 'Projected Actuarial Tables', the line branches into three and begins to decline more steeply to zero. The area between the first and second branch is shaded and labeled '5th percentile' and the area between the second and third branch is shaded and labeled '95th percentile.']

Progeny

Progeny

https://www.xkcd.com/894

https://www.explainxkcd.com/wiki/index.php/894:_Progeny

[Cueball sits at a computer; Megan stands behind him.] Cueball: Wow — researchers taught a computer to beat the world's best humans at yet another task. Does our species have anything left to be proud of? Megan: Well, it sounds like we're pretty awesome at teaching. Cueball: Huh? What good is that ?

This comic is a reference to IBM's computer Watson that beat humans at Jeopardy (see 1002: Game AIs ). The IBM team created a computer that could formulate a response to a Jeopardy-style question. Jeopardy is a game played where the contestants are given the answer to a question, and must devise the question. A question might be "Its largest airport was named for a World War II hero; its second largest, for a World War II battle", to which the contestant must answer "What is Chicago?". When going up against two Jeopardy champions, Watson was able to beat them both (by some margin, although he did answer the above-mentioned question incorrectly with "Toronto"). Megan chimes in that we are "pretty awesome at teaching" which is very true. Humans are the best (on this planet) at teaching other things to do a set of tasks. We train dogs, cats, lizards, birds, other people, and now we are getting quite good at teaching a computer, a simple machine completely of our own design, to mimic our own thought patterns and make decisions similar to what we would make. (See also 1263: Reassuring ). The title text makes fun of teaching our children values about not trying to win by any means (i.e. but while playing fair) by suggesting we are just trying to hold on to our ability to beat them in something. [Cueball sits at a computer; Megan stands behind him.] Cueball: Wow — researchers taught a computer to beat the world's best humans at yet another task. Does our species have anything left to be proud of? Megan: Well, it sounds like we're pretty awesome at teaching. Cueball: Huh? What good is that ?

Teaching Physics

Teaching Physics

https://www.xkcd.com/895

https://www.explainxkcd.com/wiki/index.php/895:_Teaching_Physics

Cueball: Understanding gravity: Space-time is like a rubber sheet. Massive objects distort the sheet, and- Student: Wait. Student: They distort it because they're pulled down by... what? Cueball: sigh Cueball: Space-time is like this set of equations, for which any analogy must be an approximation. Student: Boooooring.

The comic makes fun at the idea that physics is only interesting because teachers use interesting analogies, despite the fact that they are over-simplified and don't help when more complex theory is taught. The comic refers to the classic "Ball on a rubber sheet" metaphor as a way to explain general relativity , even though the metaphor breaks when trying to explain what causes gravity. The fourth panel highlights this with the statement that space-time is a set of equations , for which no analogy can fully explain. The title text continues the teacher's frustration with coming up with an analogy by stating that there is some analogy that is both understandable and precise, and if he were the famous physicist/teacher Richard Feynman he could come up with it. Professor Feynman was famous for his physics lectures and their ability to both entertain and educate his students, from the beginning student to the more advanced graduate students. Recordings of his lectures are still available and applicable to today's audience. Another comic shows how to play with this 1158: Rubber Sheet . Cueball: Understanding gravity: Space-time is like a rubber sheet. Massive objects distort the sheet, and- Student: Wait. Student: They distort it because they're pulled down by... what? Cueball: sigh Cueball: Space-time is like this set of equations, for which any analogy must be an approximation. Student: Boooooring.

Marie Curie

Marie Curie

https://www.xkcd.com/896

https://www.explainxkcd.com/wiki/index.php/896:_Marie_Curie

[Ponytail is looking up at a picture on the wall showing Marie Curie with a white hair bun. She seems to be standing in front of a laboratory table with samples strewn over the surface. Her arms are in front of her like she is working with these samples. A voice comes from off-panel (and is revealed in the next panels to be Zombie Marie Curie.] Ponytail: My teacher always told me that if I applied myself, I could become the next Marie Curie. Zombie Marie Curie (off-panel): You know, I wish they'd get over me. [Inserted panel mainly inside the first panel, but extending a bit it, with a close up of Ponytail who turns her face around swiftly towards the zombie, as indicated by two speed lines curving around her head, even breaking the panels frame.] Ponytail: Zombie Marie Curie! [Ponytail has turned towards Zombie Marie Curie, drawn as Hairbun, who is walking towards Ponytail in typical zombie fashion both arms stretched out, with a battered and weathered look Stuff is falling off behind her, presumably mainly earth from when she dug herself out of her grave, and she is leaving a trail of this behind her, and it keeps falling from both of her hands and her body.] Zombie Marie Curie: Not that I don't deserve it. These two Nobels ain't decorative. But I make a sorry role model if girls just see me over and over as the one token lady scientist. [Close up of Zombie Marie Curie holding a hand up. She clearly has two large pieces of earth stuck to her face, and her hair is in disarray even with the hair bun keeping it in place.] Zombie Marie Curie: Lise Meitner figured out that nuclear fission was happening, while her colleague Otto was staring blankly at their data in confusion, and proved Enrico Fermi wrong in the process. Enrico and Otto both got Nobel Prizes. Lise got a National Women's Press Club award. Zombie Marie Curie: They finally named an element after her, but not until 60 years later. [Zoom out to both Ponytail and Zombie Marie Curie both with their arms down.] Zombie Marie Curie: Emmy Noether fought past her Victorian-era finishing-school upbringing, pursued mathematics by auditing classes, and, after finally getting a Ph.D, was permitted to teach only as an unpaid lecturer (often under male colleagues' names). Ponytail: Was she as good as them? Zombie Marie Curie: She revolutionized abstract algebra, filled gaps in relativity, and found what some call the most beautiful, deepest result in theoretical physics. Ponytail: Oh. [Close up of Zombie Marie Curie.] Zombie Marie Curie: But you don't become great by trying to be great. You become great by wanting to do something, and then doing it so hard that you become great in the process. [Zoom out to both Ponytail and Zombie Marie Curie.] Zombie Marie Curie: So don't try to be the next me, Noether, or Meitner. Just remember that if you want to do this stuff, you're not alone. Ponytail: Thanks. Zombie Marie Curie: Also, avoid radium. Turns out it kills you. Ponytail: I'll try.

The comic begins with Ponytail stating that her teacher told her that if she worked hard (applied herself) she could be the next Marie Curie . But then a distorted zombie Marie Curie (drawn as zombie Hairbun ) walks in and informs Ponytail that she is not the only influential woman scientist, and would wish people would get over her "as the only important female scientist". She then mentions two other important women in science. Marie Curie was a pioneering research scientist, most famous for her work with radiation, and in isolating Radium , and Polonium . She died from aplastic anemia contracted from exposure to radiation from the extremely radioactive isotopes of Radium and Polonium that she would carry around in her pockets. She ends up warning Ponytail against exposure to radium, stating that it kills you , although as the title text points out, obviously not permanently as she came back as a zombie. The conversation between Ponytail and Zombie Marie Curie refers to the fact that Marie is often singled out as the only significant female scientist. Marie points out that this is a poor version of the truth, for two reasons. Firstly, there have been many other significant female scientists, and secondly, Marie asserts that the most significant events in theoretical physics and mathematics do not arise because of an individuals desire for fame, but from passion for the subject and a great deal of dedication and hard work. As examples of important women scientists the comic mentions Lise Meitner and Emmy Noether . Lise Meitner was one of the major contributors in the discovery of nuclear fission for which her male colleague Otto Hahn was awarded a Nobel Prize in 1944. In the process she proved that Enrico Fermi had made some wrong assumptions, but he also got a Nobel prize whereas she only got a National Women's Press Club award as "Woman of the Year" in 1946. As a somewhat late consolation, the element Meitnerium was named after her in 1997 almost 30 years after her death. (She is later mentioned again in 1584: Moments of Inspiration ). Noether's Theorem is widely considered one of the most beautiful and significant theorems used in physics, and its repercussions are still being widely explored to this day. She had to learn mathematics by taking auditing classes at University of Erlangen since she was refused the opportunity to take classes because she was a woman . And later she had to teach without getting paid and under male colleagues' names, meaning that students would only take the course if they thought some "real" male teacher was guiding Emmy. Much later Emmy was referenced in the title text of 2595: Advanced Techniques . Marie asserts at the end that Ponytail is not alone, meaning that there are many important female scientists out there, and also many young woman wanting to become scientists. But could also be a reference to the fact that, as mentioned, female scientists might be less likely to receive medals or other tokens of support and encouragement. Zombies are a recurring theme in xkcd, particularly zombie scientists, which has also occurred twice before with Richard Feynman in 397: Unscientific and Paul Erdős in 599: Apocalypse . [Ponytail is looking up at a picture on the wall showing Marie Curie with a white hair bun. She seems to be standing in front of a laboratory table with samples strewn over the surface. Her arms are in front of her like she is working with these samples. A voice comes from off-panel (and is revealed in the next panels to be Zombie Marie Curie.] Ponytail: My teacher always told me that if I applied myself, I could become the next Marie Curie. Zombie Marie Curie (off-panel): You know, I wish they'd get over me. [Inserted panel mainly inside the first panel, but extending a bit it, with a close up of Ponytail who turns her face around swiftly towards the zombie, as indicated by two speed lines curving around her head, even breaking the panels frame.] Ponytail: Zombie Marie Curie! [Ponytail has turned towards Zombie Marie Curie, drawn as Hairbun, who is walking towards Ponytail in typical zombie fashion both arms stretched out, with a battered and weathered look Stuff is falling off behind her, presumably mainly earth from when she dug herself out of her grave, and she is leaving a trail of this behind her, and it keeps falling from both of her hands and her body.] Zombie Marie Curie: Not that I don't deserve it. These two Nobels ain't decorative. But I make a sorry role model if girls just see me over and over as the one token lady scientist. [Close up of Zombie Marie Curie holding a hand up. She clearly has two large pieces of earth stuck to her face, and her hair is in disarray even with the hair bun keeping it in place.] Zombie Marie Curie: Lise Meitner figured out that nuclear fission was happening, while her colleague Otto was staring blankly at their data in confusion, and proved Enrico Fermi wrong in the process. Enrico and Otto both got Nobel Prizes. Lise got a National Women's Press Club award. Zombie Marie Curie: They finally named an element after her, but not until 60 years later. [Zoom out to both Ponytail and Zombie Marie Curie both with their arms down.] Zombie Marie Curie: Emmy Noether fought past her Victorian-era finishing-school upbringing, pursued mathematics by auditing classes, and, after finally getting a Ph.D, was permitted to teach only as an unpaid lecturer (often under male colleagues' names). Ponytail: Was she as good as them? Zombie Marie Curie: She revolutionized abstract algebra, filled gaps in relativity, and found what some call the most beautiful, deepest result in theoretical physics. Ponytail: Oh. [Close up of Zombie Marie Curie.] Zombie Marie Curie: But you don't become great by trying to be great. You become great by wanting to do something, and then doing it so hard that you become great in the process. [Zoom out to both Ponytail and Zombie Marie Curie.] Zombie Marie Curie: So don't try to be the next me, Noether, or Meitner. Just remember that if you want to do this stuff, you're not alone. Ponytail: Thanks. Zombie Marie Curie: Also, avoid radium. Turns out it kills you. Ponytail: I'll try.

Elevator Inspection

Elevator Inspection

https://www.xkcd.com/897

https://www.explainxkcd.com/wiki/index.php/897:_Elevator_Inspection

[Two Cueball-like guys and Ponytail, lifting her arms above her head, are in an elevator. Cueball standing next to the door reads the sign above the control panel.] Cueball: It says here that the elevator inspection certificate is on file in the building office. Friend: Whoa, cool! Let's go look at it! Ponytail: That sounds fun! [Caption below the panel:] Industry tip: Building owners know this never happens. Those signs mark elevators which have never been inspected.

This was the first of Randall's Tips , that was not a pro tip but more specific an Industry tip. In the United States, all elevators are subject to building codes and must be inspected on a somewhat-regular basis by city officials. After the inspector runs his rounds, the elevator's passing grade is noted in a certificate which is visibly placed in the elevator. Alternatively, it can be dumped in a filing cabinet in the building office where the owner can forget about it, and a placard is given to the elevator letting the passengers know where the certificate is (usually the aforementioned building office). This comic is portraying a scenario which supposedly never happens. No-one is ever actually interested in seeing the elevator's certificate, and nobody gets this excited about going to a building office. So, as the caption humorously suggests: many elevators start using the placards for elevators that have not been inspected. No one cares enough to go to the building office and search the files for the certification. And as the title text says, even inspectors themselves get bored before they can get to the building office. The moral of this comic is if you see an elevator with a notice that says that the "elevator inspection certificate is on file", you do not really know whether the notice is true, and so building owners use the certificates as substitutes for the bother and expense of actually getting their elevators inspected. The flaw in this logic is that, if an elevator were to fail catastrophically, the inspection certificate would almost certainly be retrieved and examined as part of the investigation. If the elevator had not been inspected as required, there would be very serious legal consequences. Hence, failing to carry out regular inspections would carry substantial risks. [Two Cueball-like guys and Ponytail, lifting her arms above her head, are in an elevator. Cueball standing next to the door reads the sign above the control panel.] Cueball: It says here that the elevator inspection certificate is on file in the building office. Friend: Whoa, cool! Let's go look at it! Ponytail: That sounds fun! [Caption below the panel:] Industry tip: Building owners know this never happens. Those signs mark elevators which have never been inspected.

Chain of Command

Chain of Command

https://www.xkcd.com/898

https://www.explainxkcd.com/wiki/index.php/898:_Chain_of_Command

[A flowchart shows the President at the top, with an arrow to the Secretary of Defense, and then fourteen arrows leading to a series of boxes labeled Unified Combat Commanders. On the side, a box with a dotted outline has a dotted arrow leading to the president. It's labeled "Engineer Who Installed the Red Button."] US NUCLEAR CHAIN OF COMMAND

The President of the United States is at the top of the US Nuclear Chain of Command , but the engineer is de facto above him because the engineer is in charge of configuring how the button works, and thus could have installed an override so that they could block the President's use of the button and/or use it themself. The "Red Button" is a simplification denoting procedures for the worst-case scenario, i.e. launching all strategic nuclear capabilities. This button shouldn't be pressed for what is happening currently. [ citation needed ] This paradoxical situation applies in many other fields. In a major corporation commercially sensitive information is generally hidden from employees at lower levels but available to management, but the systems administrator (who usually sits low on the hierarchy and doesn't manage any other employees) can access not only the sensitive information but the raw data that it's calculated from. Not only that, but the systems administrator is usually responsible for controlling who has access to the information - making them the most powerful person in the company (as far as the IT infrastructure is concerned). Many managers think of themselves as being "above" engineers and have trouble coming to grips with this concept. Themistocles , mentioned at the title text, was an Ancient Greek politician. In the title text is a similar joke placed at the top of the chain of command, this time in Ancient Greece. It refers to Plutarch's Life of Themistocles : Of his son, who lorded it over his mother, and through her over himself, he said, jestingly, that the boy was the most powerful of all the Hellenes; for the Hellenes were commanded by the Athenians, the Athenians by himself, himself by the boy's mother, and the mother by her boy. The part about television advertisements is a proposal that, by controlling the "infant sons" of important political figures (as well as the aforementioned Red Button engineer), one could control said political figures, and thus the entire world. Dora the Explorer is a bilingual (Spanish/English) educational show for young children, something a busy person like the President (or the engineer) might turn on for their child, and advertisements are known to influence young kids' decisions. [A flowchart shows the President at the top, with an arrow to the Secretary of Defense, and then fourteen arrows leading to a series of boxes labeled Unified Combat Commanders. On the side, a box with a dotted outline has a dotted arrow leading to the president. It's labeled "Engineer Who Installed the Red Button."] US NUCLEAR CHAIN OF COMMAND

Number Line

Number Line

https://www.xkcd.com/899

https://www.explainxkcd.com/wiki/index.php/899:_Number_Line

[Number line ranging from −1 to 10.] [Arrow pointing left, towards negative numbers] Negative "imitator" numbers (do not use) [Line right before the number one] 0.99... (actually 0.0000000372 less than 1) [Line at the golden ratio.] Φ Parthenon; sunflowers; golden ratio; wait, come back, I have facts! [Line at a region between two and 2.2] forbidden region [Line at Euler's number.] e [Line a bit before 3] 2.9299372 (e and pi, observed) [Line at π.] π [Line at 3.5 with ᛟ as the numeral] Gird – accepted as canon by orthodox mathematicians [Line a bit after 4.] site of battle of 4.108 [Blob between 4.5 and 6.5 labeled unexplored.] [Line at seven.] Number indicating a factoid is made up ("every 7 years...", "science says there are 7...", etc) [Line at eight.] Largest even prime [Line at 8.75.] If you encounter a number higher than this, you're not doing real math

Once again, Randall seems to be just messing around, this time with a number line. The title text is a literalism joke; at the time the comic was published, all Wikipedia articles with incomplete lists began with the message template "This list is incomplete; you can help by expanding it." In the case of the List of numbers page, one could infer the absurd notion that Wikipedia wanted to have the list include every number from negative infinity to infinity. But because all Wikipedia articles are necessarily finite, such a list would always be incomplete, no matter how much it was expanded. It may also be referencing his previous statements about Wikipedia being the home of compulsive list-makers, who make the most astonishingly complete lists imaginable. As of 2021, Wikipedia's List of numbers page, as well as all pages including lists that cannot ever reach a state of completion, are headed by the message template "This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources." [Number line ranging from −1 to 10.] [Arrow pointing left, towards negative numbers] Negative "imitator" numbers (do not use) [Line right before the number one] 0.99... (actually 0.0000000372 less than 1) [Line at the golden ratio.] Φ Parthenon; sunflowers; golden ratio; wait, come back, I have facts! [Line at a region between two and 2.2] forbidden region [Line at Euler's number.] e [Line a bit before 3] 2.9299372 (e and pi, observed) [Line at π.] π [Line at 3.5 with ᛟ as the numeral] Gird – accepted as canon by orthodox mathematicians [Line a bit after 4.] site of battle of 4.108 [Blob between 4.5 and 6.5 labeled unexplored.] [Line at seven.] Number indicating a factoid is made up ("every 7 years...", "science says there are 7...", etc) [Line at eight.] Largest even prime [Line at 8.75.] If you encounter a number higher than this, you're not doing real math

Religions

Religions

https://www.xkcd.com/900

https://www.explainxkcd.com/wiki/index.php/900:_Religions

[Cueball and Megan talking.] Megan: So are you worried about the rapture? Cueball: No, unless it figures out how to open doors. Megan: I said rapture. Cueball: Oh, I'm not really into that. I'm the kind of Christian who only goes to church on Christmas and Easter, and then spends the other 363 days at the mosque. Megan: ...I don't think that's a thing. Cueball: Our rabbi swears it's legit. Cueball: What religion are you? Megan: Experimentalist Monotheism. Cueball: Which is? Megan: We believe there's one god, but we're trying to find the error bars on that number.

The late Harold Camping , a Christian pastor, wrongly predicted that the world would end in May 21, 2011. Since it didn't, he moved the date to October 21 of that year, and when that passed uneventfully, he recanted his belief that the end time could be calculated. In the Christian belief , the end of the world is called "the second coming" (referencing the return of Jesus); some sects believe this will be preceded by an event called "the Rapture." The first frame is a reference to raptors in Jurassic Park , and certainly not Randall's first raptor joke . In this film, the raptor dinosaurs get much more dangerous once they learn how to open doors. Cueball mishears Megan , which is why he thinks she said "raptor" instead of "Rapture". In the second frame, Cueball describes his personal approach to religion, starting by saying that he is Christian but only attends church services on Christmas and Easter. This is a well-known phenomenon among lapsed Christians , and if Cueball is not a regularly practicing Christian, it would certainly explain why he isn't particularly interested in this fundamentalist aspect of Christian belief. However, from here, his description takes a turn towards the ridiculous, when he says that every other day of the year is spent "at the mosque". Not only are mosques the place of worship for a completely different religion (specifically, Islam ), they also generally hold communal services only on Fridays, so for Cueball to present this practice so matter-of-factly is quite absurd. When Megan questions the ubiquity of his practices, he replies by saying that this practice is vetted by his rabbi - a spiritual leader in Judaism , a third separate religion. While all three of these are Abrahamic religions , and as such have some overlap in their beliefs and texts, combining them all into one religion would be far from a simple process; either Cueball is simply being contrarian for comedic purposes, or he is involved in a very strange religious sect indeed. The third frame is a math joke in which Megan references error bars which are used on graphs to indicate the uncertainty. So, Megan believes in one God (monotheism), as she says in the comic. But if she is still trying to find the error bars, and from the title text it is "one, plus or minus one", that could be in the range of zero ( atheism ) to two ( bitheism ). With larger error bars, this could also reference the doctrine of the Trinity , which holds that there is "one God in three Divine persons": the Father, the Son (Jesus), and the Holy Spirit. Some consider this position to be polytheistic, as others would consider atheism to merely leave the number and nature of gods undefined (and, as a seperate concept, agnosticism rendering it as untestable whatever the hypothetical value might be). The title text is a supposed excerpt from the holy text of experimental monotheism. 1 Corinthians is a book of the Christian Bible . Megan refers to chapter 8 verse 6 (±2), which would be verses 4–8 . Verse 4 says "...There is no God but one". Confusingly, verse 6 says "yet for us, there is but one God, the Father, from whom all things came and for whom we live; and there is but one Lord, Jesus Christ, through whom all things came and through whom we live." (That could be self-consistent if the passage assumed that Jesus Christ is a lord but not a god, but little, if any, mainstream denominations of Christianity seem to follow such a doctrine). [Cueball and Megan talking.] Megan: So are you worried about the rapture? Cueball: No, unless it figures out how to open doors. Megan: I said rapture. Cueball: Oh, I'm not really into that. I'm the kind of Christian who only goes to church on Christmas and Easter, and then spends the other 363 days at the mosque. Megan: ...I don't think that's a thing. Cueball: Our rabbi swears it's legit. Cueball: What religion are you? Megan: Experimentalist Monotheism. Cueball: Which is? Megan: We believe there's one god, but we're trying to find the error bars on that number.