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Game Theory

Game Theory

https://www.xkcd.com/601

https://www.explainxkcd.com/wiki/index.php/601:_Game_Theory

[Cueball is sitting at a desk in an office chair typing on his computer. The text appearing above him is implied to be what is displayed on the screen.] A.I. Loaded >>> Analyze love [An hourglass appears over the computer as Cueball sits back and wait.] [The hourglass continues to display as Cueball shifts in his chair.] [A zigzag line from the computer indicates the final reply from the computer to the query.] Computer: A strange game. The only winning move is not to play.

The comic and title text is a direct reference to the movie WarGames . In the movie, the Artificial intelligence (AI) that controls the US Nuclear Weapons is asked to play Global Thermonuclear War , a real time game simulating a nuclear attack scenario. Spoilers : In the movie it then takes the simulation to the real world, planning to launch a real attack on the USSR . In the end the AI is tricked into quickly running through several scenarios of the game, and then shuts down its planned attack as a result of what it finds out. After analyzing all possible strategies, the AI reports: "A strange game. The only winning move is not to play. How about a nice game of chess?" Interpreted literally, this means that the computer has figured out that it will lose the game no matter how it plays, so it chooses to play chess instead (at the time of the movie, computers could not yet beat the best human chess players, so it would be more interesting). A more profound interpretation is that wars always end badly for all parties involved so it's better to play nicer games like chess. In this comic Cueball loads an AI and then ask it to "analyze love" (equivalent to playing the "love game"), which initially could be expected to end happily for everyone involved, as love is the opposite of war and war ends always so badly. Surprisingly, the result from the AI is similar to the war games. Thus if you "play the love game", you'll end up badly, regardless which moves you play. The title text leaves love as looking actually worse than war, since in war there's at least the "winning move" of not playing, however in love even refusing to play means that the player loses the game anyway. Randall is thus stating that you have to go after love, even though you know you will lose/get hurt sometimes, because you will for sure also lose the game, even if you pretend not to play. The AI then again suggest a game of chess, as in the movie. [Cueball is sitting at a desk in an office chair typing on his computer. The text appearing above him is implied to be what is displayed on the screen.] A.I. Loaded >>> Analyze love [An hourglass appears over the computer as Cueball sits back and wait.] [The hourglass continues to display as Cueball shifts in his chair.] [A zigzag line from the computer indicates the final reply from the computer to the query.] Computer: A strange game. The only winning move is not to play.

Overstimulated

Overstimulated

https://www.xkcd.com/602

https://www.explainxkcd.com/wiki/index.php/602:_Overstimulated

[There is a group of people. Three women and four men. They are standing around a table with a drink on it.] Man #3: Have you seen John lately? Woman #3: He and Claire blew off this party to see Jeff. Man #4: They do that a lot. Man #1: Yeah; I don't know what his problem is with hanging out lately. Man #3: He's like Katie—ever noticed how she only goes somewhere if Jeff's there? [Cueball is cringing away from all the text; none of the text is attributed to specific people.] Somebody: It's so lame how she hangs around him even when he's not single: Somebody: He likes it. Somebody: Someone seriously needs to date her. Somebody: Totally. Somebody: And honestly I feel like a jerk but I wouldn't mind if she hung around with us a little less. She needs other friends, you know! [Cueball peels a hole in the panel. The numbers '1', '2', and '3' are visible through the gap.] Somebody: Have you noticed how every dude she dates is a total druggie? Somebody: Nope Somebody: I'm glad I'm not the only one who thought that was weird. Somebody: Michelle dates potheads like Elaine but at least they both have real jobs. Somebody: Michelle does? She designs those book covers, right? Somebody: And it's not like she smokes a lot. Somebody: Elaine is one of those girls who [The previous panel's text appears again, but peeled back even further. Cueball looks up.] 1 2 3 4 5 6 7 8 9 10 11 12 Somebody: -noticed how - Somebody: Nope Somebody: -es is a tota- Somebody: -t th- -ought [Cueball starts taking down the prime numbers.] 1 4 6 8 9 10 12 14 15 2 3 5 7 11 13 [Cueball grabs and squeezes the 2, so it is half as wide and twice as tall.] [A formula: Sum with i from 1 to infinity of 1/P i = h - ie. the sum from 1 to infinity of the inverse of each prime.] [The panel shows a 2 that is 2 units tall and 1/2 wide, a 3 that is 3 units tall and 1/3 wide, and so on. Cueball is moving the 7.] [Cueball writes h = ∞. The numbers are piled on their side next to a scale.] Voice: Don't you agree? Voice: Hey, wake up. Man #1: You zoned out or something. Cueball: Sorry; I must be... tired. Man #1: I don't blame you. All day cooped up working on papers. Man #3: Must be nice to get out and relax, huh? Cueball: Yeah. [Girl #3 reaches for the glass on the table.]

After being cooped up working on papers, Cueball goes to a party, only to find himself tuning out the gossip of his friends in order to work on math problems in his head. He writes down the prime numbers on cards, and then stretches them out such that the area of the card is the same (say, 1), but one of the sides has been elongated to a length equal to the number on the card. This reduces the length on the other dimension to the reciprocal of the number on the card (i.e. 1/ n , with n being the number on the card), according to the area formula for rectangles. Stacking these reciprocals all up will eventually diverge, meaning the sum will be infinite without ever leveling off. This is referred to as the divergence of the sum of the reciprocals of the primes , and was proven by Euler in 1737. The Cambridge Aspergers Test includes questions on preferences for, and ability to cope with, social situations. It also asks the person taking the test if they have an affinity for numbers and see patterns in every day objects. Cueball could possibly score high on the Asperger's scale — or he could just be introverted, or find math more interesting than criticizing others which is generally considered in science circles a dull thing to do considering the vast variety of other topics and activities available. Introversion is an idea from psychology. Thinking about things on one's own is often relaxing for an introvert, while hanging out with other people is not. Hence the irony of the comment in the last panel. Cueball's friends fail to realize that hanging out with them is actually more stressful for him than doing math - especially when people are doing nothing but talking negatively about those not present. The title text mentions people that talk negatively about people that aren't there. A much later comic; 1176: Those Not Present , is about just that. [There is a group of people. Three women and four men. They are standing around a table with a drink on it.] Man #3: Have you seen John lately? Woman #3: He and Claire blew off this party to see Jeff. Man #4: They do that a lot. Man #1: Yeah; I don't know what his problem is with hanging out lately. Man #3: He's like Katie—ever noticed how she only goes somewhere if Jeff's there? [Cueball is cringing away from all the text; none of the text is attributed to specific people.] Somebody: It's so lame how she hangs around him even when he's not single: Somebody: He likes it. Somebody: Someone seriously needs to date her. Somebody: Totally. Somebody: And honestly I feel like a jerk but I wouldn't mind if she hung around with us a little less. She needs other friends, you know! [Cueball peels a hole in the panel. The numbers '1', '2', and '3' are visible through the gap.] Somebody: Have you noticed how every dude she dates is a total druggie? Somebody: Nope Somebody: I'm glad I'm not the only one who thought that was weird. Somebody: Michelle dates potheads like Elaine but at least they both have real jobs. Somebody: Michelle does? She designs those book covers, right? Somebody: And it's not like she smokes a lot. Somebody: Elaine is one of those girls who [The previous panel's text appears again, but peeled back even further. Cueball looks up.] 1 2 3 4 5 6 7 8 9 10 11 12 Somebody: -noticed how - Somebody: Nope Somebody: -es is a tota- Somebody: -t th- -ought [Cueball starts taking down the prime numbers.] 1 4 6 8 9 10 12 14 15 2 3 5 7 11 13 [Cueball grabs and squeezes the 2, so it is half as wide and twice as tall.] [A formula: Sum with i from 1 to infinity of 1/P i = h - ie. the sum from 1 to infinity of the inverse of each prime.] [The panel shows a 2 that is 2 units tall and 1/2 wide, a 3 that is 3 units tall and 1/3 wide, and so on. Cueball is moving the 7.] [Cueball writes h = ∞. The numbers are piled on their side next to a scale.] Voice: Don't you agree? Voice: Hey, wake up. Man #1: You zoned out or something. Cueball: Sorry; I must be... tired. Man #1: I don't blame you. All day cooped up working on papers. Man #3: Must be nice to get out and relax, huh? Cueball: Yeah. [Girl #3 reaches for the glass on the table.]

Idiocracy

Idiocracy

https://www.xkcd.com/603

https://www.explainxkcd.com/wiki/index.php/603:_Idiocracy

[Cueball is standing in front of three shelves with DVDs, holding a single DVD in his hand looking at the cover. A guy with a white rounded safari hat (Safari Hat from now on) stands behind him.] Cueball: Idiocracy is so true. Safari Hat: I know, right? It used to be that the intelligent, upper classes had more children. [Zoom on on their heads as Cueball turns towards Safari Hat.] Safari Hat: Sadly, the recent reversal of this trend has dragged IQ scores and average education steadily downward. Cueball: Depressing, huh? [Zoom out to show Cueball holding the DVD down as Safari Hat lifts on arm towards him.] Safari Hat: Yeah, except everything I just said was wrong. Cueball: Huh? Safari Hat: Wrong. False. The opposite of true. [Zoom in only on Safari Hat.] Safari Hat: You're like the religious zealots who are burdened by their superiority with the sad duty of decrying the obvious moral decay of each new generation. Safari Hat: And you're just as wrong. [Zoom out to both as before, but this time it is Cueball who holds up a finger.] Cueball: But look at how popular— Safari Hat: More harm has been done by people panicked over societal decline than societal decline ever did. [Cueball spreads out his arms (the DVD gone) as Safari Hat has walked out off the panel.] Cueball: Look — all we need is a program that limits breeding to— Safari Hat (off-panel): New theory: Stupid people reproduce more because the alternative is sleeping with you.

The title of this comic is a reference to the dystopian comedy Idiocracy . The film postulates that over about 500 years, society will suffer from a massive decrease in intellectual potential. This development is attributed to the fact that people with a lower IQ are believed to be more likely to reproduce thus more readily pass on their genes. Cueball professes his approval for the theories represented in the film, and the guy with the white safari hat agrees with him, lamenting the gradual decay in intelligence and education. (Note that Safari Hat is not the same guy as White Hat ! See below.) But in panel 3, Safari Hat suddenly reveals that all the "facts" he cited were wrong, and we learn that he doesn't support the dysgenic thesis at all. He turns to accuse Cueball of conceited self-righteousness (using religious zealots as an analogy), harshly condemning intelligence dysgenics as an excuse for feeling superior to the rest of society. Cueball's suggestion of birth control for the unintelligent only furthers his attitude. Although it is not named, one thing at work here is the Dunning-Kruger effect — that stupid people don't realize they're stupid. Safari Hat's punchline, playing on Cueball's birth control suggestion, is a direct insult: it would be better to reproduce with a stupid person than an elitist like Cueball. It's pretty clear here that Randall is voicing his opinion through Safari Hat, and using Cueball as a straw man. The title text reflects the opinion. It makes a few cheery comments on the future, but then finishes on a rather sour note about climate change . Climate change is a recurring theme in xkcd. In fact, a negative correlation between intelligence and fertility is disputed; see the Wikipedia article on the accumulation of disadvantageous genes: dysgenics . And regardless of this the actual absolute IQs in modern societies have been rising, see Flynn effect . This can be paraphrased with the statement, that if the generation of our grandparents would take a today's IQ test, they would barely score an IQ of 70 and be at the limit of intellectual disability. [Cueball is standing in front of three shelves with DVDs, holding a single DVD in his hand looking at the cover. A guy with a white rounded safari hat (Safari Hat from now on) stands behind him.] Cueball: Idiocracy is so true. Safari Hat: I know, right? It used to be that the intelligent, upper classes had more children. [Zoom on on their heads as Cueball turns towards Safari Hat.] Safari Hat: Sadly, the recent reversal of this trend has dragged IQ scores and average education steadily downward. Cueball: Depressing, huh? [Zoom out to show Cueball holding the DVD down as Safari Hat lifts on arm towards him.] Safari Hat: Yeah, except everything I just said was wrong. Cueball: Huh? Safari Hat: Wrong. False. The opposite of true. [Zoom in only on Safari Hat.] Safari Hat: You're like the religious zealots who are burdened by their superiority with the sad duty of decrying the obvious moral decay of each new generation. Safari Hat: And you're just as wrong. [Zoom out to both as before, but this time it is Cueball who holds up a finger.] Cueball: But look at how popular— Safari Hat: More harm has been done by people panicked over societal decline than societal decline ever did. [Cueball spreads out his arms (the DVD gone) as Safari Hat has walked out off the panel.] Cueball: Look — all we need is a program that limits breeding to— Safari Hat (off-panel): New theory: Stupid people reproduce more because the alternative is sleeping with you.

Qwertial Aphasia

Qwertial Aphasia

https://www.xkcd.com/604

https://www.explainxkcd.com/wiki/index.php/604:_Qwertial_Aphasia

[Caption in a frame partly above the main panels, but which breaks the top border of the two first panels frames:] I hate how when I'm talking while I type, sometimes I accidentally type a word I'm saying. [Cueball is sitting at a computer chatting with a friend. The friends message "comes" out of the computer.] Friend (from computer): Wanna go get food later? [Megan walks in to the frame, holding a small stuffed giraffe in front of her. Cueball is in the middle of typing his reply, which "comes" from the keyboard.] Megan: Check out what I found in the closet! Cueball (from keyboard): Sorry, I really shouldn't. Keyboard: Type type [Megan has stopped and Cueball turns to look at her and the giraffe, while continuing to type.] Cueball: Aww, what an adorable stuffed giraffe! Cueball (from keyboard): I can't afford to keep eating out this giraffe. Keyboard: Type type [Caption below the last panel in a frame which breaks the bottom border of the above panel:] Frequently! I meant "frequently" !

Randall has invented the term Qwertial Aphasia to describe the common experience of having a word, from a spoken conversation, accidentally spill over into something one is typing, often with humorous results. The description "Qwertial" refers to the position of the top row of letters in the most common keyboard arrangement, the QWERTY keyboard layout, as this is only something that afflicts you while typing. Aphasia is a class of medical conditions which affect the production and understanding of language. In this case Cueball is in the process of replying on the computer to his friend who just asked if they should go out to eat some food later. Cueball is about to explain why he should not, when Megan walks in and disturbs him with her stuffed toy giraffe which makes him say the word giraffe. The joke set up in the comic comes from the substitution of the word 'giraffe' for the word 'frequently' , which changes the whole meaning of Cueball's last sentence. The original sentence would have been I can't afford to keep eating out this frequently . The unintentional replacement makes 'giraffe' the object of the sentence, and implies that Cueball is eating out (slang for cunnilingus ) a giraffe. He tries to correct himself by writing that he meant frequently but the damage is done and he will be the laughing stock with his friends for a while. The title text continues the image of a giraffe as a sexual object - in particular, one which costs money . SMBC refers to the comic Saturday Morning Breakfast Cereal , a whimsical joke-a-day comic which comes with a second illustration, which can be seen by clicking on a button known as the "votey". This additional panel often serves as a second punchline in the same way as the title text does in xkcd. Zach Weiner of SMBC responded to this title text in the votey on July 2, 2009 , the day after this comic was released. [Caption in a frame partly above the main panels, but which breaks the top border of the two first panels frames:] I hate how when I'm talking while I type, sometimes I accidentally type a word I'm saying. [Cueball is sitting at a computer chatting with a friend. The friends message "comes" out of the computer.] Friend (from computer): Wanna go get food later? [Megan walks in to the frame, holding a small stuffed giraffe in front of her. Cueball is in the middle of typing his reply, which "comes" from the keyboard.] Megan: Check out what I found in the closet! Cueball (from keyboard): Sorry, I really shouldn't. Keyboard: Type type [Megan has stopped and Cueball turns to look at her and the giraffe, while continuing to type.] Cueball: Aww, what an adorable stuffed giraffe! Cueball (from keyboard): I can't afford to keep eating out this giraffe. Keyboard: Type type [Caption below the last panel in a frame which breaks the bottom border of the above panel:] Frequently! I meant "frequently" !

Extrapolating

Extrapolating

https://www.xkcd.com/605

https://www.explainxkcd.com/wiki/index.php/605:_Extrapolating

My Hobby: Extrapolating [There is a graph. Time runs along the horizontal axis; Number of Husbands on the vertical graph. Yesterday and today are labeled in time, 0 and 1 in number of husbands. Points are plotted with 0 at yesterday, 1 at today. A straight line is fitted through them.] [Cueball is holding a pointer to the graph, and looking at Megan wearing a dress and veil.] Cueball: As you can see, by late next month you'll have over four dozen husbands. Cueball: Better get a bulk rate on wedding cake.

This comic is a joke on the incorrect application of linear extrapolation . By connecting two points without any context, we can come up with incredibly funny results. Here, connecting the number of spouses yesterday (zero) and today (one) can result in a linear extrapolation to hundreds of spouses a year. Cueball presents the accumulation of husbands as though it were a phenomenon beyond the bride's ability to control. Using similar points for pregnancy (yesterday: no babies, today: one), we can get 200+ children inside a single person by the 7th month of pregnancy. This is another comic in the infrequent My Hobby series. This particular hobby has later been explored in 1007: Sustainable , 1204: Detail and 1281: Minifigs . My Hobby: Extrapolating [There is a graph. Time runs along the horizontal axis; Number of Husbands on the vertical graph. Yesterday and today are labeled in time, 0 and 1 in number of husbands. Points are plotted with 0 at yesterday, 1 at today. A straight line is fitted through them.] [Cueball is holding a pointer to the graph, and looking at Megan wearing a dress and veil.] Cueball: As you can see, by late next month you'll have over four dozen husbands. Cueball: Better get a bulk rate on wedding cake.

Cutting Edge

Cutting Edge

https://www.xkcd.com/606

https://www.explainxkcd.com/wiki/index.php/606:_Cutting_Edge

[Megan is standing. Cueball sits at a computer.] Megan: Where've you been all week? Cueball: Playing Half-Life 2! Megan: ...that came out in 2004. Cueball: I get games on a five-year lag. That way, I never have to buy a high-end system, but get the same steadily-advancing gaming experience as people who do - and at a fraction of the price. Cueball: There are no downsides! Megan: I can think of one ... [Early 2013.] Cueball: Guys! Cueball: The cake is a lie! [Musical notes surround an italic line, suggesting Cueball is singing.] Cueball: This was a triumph. Cueball: The cake is a lie! Megan and a Friend: Sigh

Half-Life 2 is a computer game, specifically a first-person shooter , released in 2004. In the above comic, Cueball plays the game in 2009. Newer games usually require more powerful computer parts, such as GPUs and RAM. The prices of these computer parts usually start expensive but drop quickly, so even a very cheap computer developed in 2009 will comfortably run a 2004 game. Additionally, the price for an older game is considerably less than those of the more recent variety. Even the price of a once-new, highly anticipated AAA game is almost definitely guaranteed to have fallen due to the presence of newer games and the relative maturity of the present game. Most of the expected sales of a game happen near the release. A game would not be deemed that lucrative after 5 years, prompting a price drop to justify its sales or even printing. Sometimes, a game will be released with several, if not all, expansion packs at a fraction of the price of purchasing them all separately during the initial release. However, the downside to Cueball's strategy is that his gaming knowledge will be five years out of date. In a subculture that moves as fast as video games, it's almost impossible for Cueball to embarrass himself harder. On the last panel, "The cake is a lie" and "This was a triumph" are references to Portal , a video game released in late 2007. The cake references originate from the promises of cake that GLaDOS , a character in the game, makes to the player. Exploring the levels reveals several hiding places that seem to have been used, in one of which the player can find the words "The cake is a lie" repeatedly scrawled on the wall. As predicted, Portal was indeed considered old-fashioned by early 2013, with the developers themselves stating they were sick and tired of the endlessly parroted jokes. Both Portal and Half-Life 2 were released by the same company, Valve , and they released Portal 2 in 2011. The song " Still Alive ", which the lyric "This was a triumph" comes from, was previously referenced in 375: Pod Bay Doors , and later referenced in 1141: Two Years . The title text also points to another flaw in this strategy: multi-player gaming requires other players, so if you play a game five years after its release, there's often nobody else to play with. It's even worse with online gaming, as the company hosting the online server may have shut it down a long time ago. However, some game communities do last longer than others. [Megan is standing. Cueball sits at a computer.] Megan: Where've you been all week? Cueball: Playing Half-Life 2! Megan: ...that came out in 2004. Cueball: I get games on a five-year lag. That way, I never have to buy a high-end system, but get the same steadily-advancing gaming experience as people who do - and at a fraction of the price. Cueball: There are no downsides! Megan: I can think of one ... [Early 2013.] Cueball: Guys! Cueball: The cake is a lie! [Musical notes surround an italic line, suggesting Cueball is singing.] Cueball: This was a triumph. Cueball: The cake is a lie! Megan and a Friend: Sigh

2038

2038

https://www.xkcd.com/607

https://www.explainxkcd.com/wiki/index.php/607:_2038

[Text above the panel:] I'm glad we're switching to 64-bit, because I wasn't looking forward to convincing people to care about the Unix 2038 problem. [Cueball's Cueball-like friends asks him a question. Cueball raises his arm above his head while answering.] Friend: What's that? Cueball: Remember Y2K? This could be even worse!

The 2038 problem is a well-known problem with 32-bit Unix-based operating systems. Unix time is stored as a 32-bit signed integer on these systems, counting the number of seconds since 1970. In 2038, we overflow the highest number we can store in signed 32-bit integers, leading to unexpected behavior. The switch to 64-bit operating systems will most likely be complete by the year 2038, which is why Randall is relieved. The reference to Y2K is a throwback to the year 2000 problem, in which people were concerned that computers storing years as two digits (e.g.: 99 to represent 1999) would cause problems when the year 2000 began because 00 could have been interpreted as 1900 by error. That Y2K issue was covered widely — with only some small mishaps — but calculating dates beyond 2038 is still not solved on many 32-bit UNIX based systems today. The "even WORSE" is possibly referring to how our increased reliance on computers means the bug could affect many more vital systems, but with Y2K passing by relatively uneventfully especially in light of the hype that preceded it caused people to take this sort of problem less seriously. The title text is a reference to the film 2012 which is about the world ending in December of 2012, at the end of the Mayan calendar . If the designers of the UNIX operating system had used 1944 as their epoch instead of 1970, then the UNIX crash due to a variable overflow would coincide with the end of the Mayan calendar. Thus, the implication is that there could have been a boring scene in the movie where the UNIX time rolls over and nothing happens and no one cares — because the world doesn't exist any more. [Text above the panel:] I'm glad we're switching to 64-bit, because I wasn't looking forward to convincing people to care about the Unix 2038 problem. [Cueball's Cueball-like friends asks him a question. Cueball raises his arm above his head while answering.] Friend: What's that? Cueball: Remember Y2K? This could be even worse!

Form

Form

https://www.xkcd.com/608

https://www.explainxkcd.com/wiki/index.php/608:_Form

[There is a sheet of paper, with a series of check boxes. A white rectangle is the focus.] Do not write in this space [Cueball is standing with a pencil, looking at the page.] [Cueball writes something on the page.] [A group of people with helmets, black goggles, and rifles look at display screens. There is a radar system on a table between them.] [The screens show sheets of paper. On one screen, it shows Cueball writing.] [One of the men arms his weapon.] Cha-click

Application forms, examination papers, etc. sometimes instruct applicants to avoid writing in blocked out areas of the page, as those areas are intended for administrative, office, or internal usage or processing. Nonetheless, a person might write in the blocked out section out of an urge to defy authority, as does Cueball in the comic. Consequences for flouting these instructions are typically trivial (e.g. perhaps the form may not be processed correctly). However, Cueball's disregard for the rules prompts the preparations for an armed response by some sort of law enforcement or private security organization, presenting a serious consequence for Cueball. The title text refers to Douglas Hofstadter , an author associated with the philosophical concept of self-reference. "This space intentionally left blank" is "Hofstadterially confusing" because if a space on a form contains the words "This space intentionally left blank", then the space is not, in fact, left blank. Douglas Hofstadter is also the subject of the comic 917: Hofstadter . A similarly harsh consequence for a trivial misdemeanor can be seen in both 292: goto and 499: Scantron . [There is a sheet of paper, with a series of check boxes. A white rectangle is the focus.] Do not write in this space [Cueball is standing with a pencil, looking at the page.] [Cueball writes something on the page.] [A group of people with helmets, black goggles, and rifles look at display screens. There is a radar system on a table between them.] [The screens show sheets of paper. On one screen, it shows Cueball writing.] [One of the men arms his weapon.] Cha-click

Tab Explosion

Tab Explosion

https://www.xkcd.com/609

https://www.explainxkcd.com/wiki/index.php/609:_Tab_Explosion

[Cueball is sitting at a computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: Huh. [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] Cueball: I never noticed that! [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: Haha, yeah. [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: So true. [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] [Cueball stares at the computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Megan (off-screen): Are you in there? Cueball: Help! [Megan walks in behind Cueball who is still sitting at the computer. The bottom of the image is covered in Megan's last line] Megan: Okay, who linked you to TVTropes? What's with that site? Cueball: Can't ... stop... Megan: It's like Rickrolling, but you're trapped all day.

TV Tropes is a popular site which allows conversation on tropes . A common joke with the site is how you will read a page, find a certain trope, which will open another tab on your web page. Then, as you read another article, you'll open even more pages. Pretty soon, this will cause an extremely long cycle of opening new pages and closing old ones. In the comic, this is exactly what happens to our unfortunate victim. He starts on a single page, then opens more and more tabs on different pages. Pretty soon, he finds himself stuck in a loop of opening pages. The last frame refers to Rickrolling , which is the practice of being linked to Rick Astley's " Never Gonna Give You Up " on YouTube. The title text refers to the comedy site Cracked.com . This site is also known for its addictive articles. Most articles are formatted in the same way the title text notes. Eventually, Cracked itself wrote a column that paid tribute to this cartoon . (See the very last line With that in mind, we present to you the 17 Worst Haircuts in The Ottoman Empire .) The original comic links to TVtropes' page of Universal tropes . TVtropes has taken notice and has a welcome letter for you at the end of the main article: "Oh, and hello to all you xkcd readers. (And thank you for the information !)" Here the "thank you" link actually links to this page, the "hello" links to the comic on xkcd and the other two links are to two articles on TVTropes, the first about xkcd and the last one being an in-joke about how "TVTropes will ruin your life". The addition of this many links is likely meant to be ironic. [ citation needed ] [Cueball is sitting at a computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: Huh. [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] Cueball: I never noticed that! [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: Haha, yeah. [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Cueball: So true. [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] [Cueball stares at the computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Click Click [Cueball is sitting at a computer.] Click [Cueball stares at the computer.] [Cueball is sitting at a computer.] Click [Cueball is sitting at a computer.] Megan (off-screen): Are you in there? Cueball: Help! [Megan walks in behind Cueball who is still sitting at the computer. The bottom of the image is covered in Megan's last line] Megan: Okay, who linked you to TVTropes? What's with that site? Cueball: Can't ... stop... Megan: It's like Rickrolling, but you're trapped all day.

Sheeple

Sheeple

https://www.xkcd.com/610

https://www.explainxkcd.com/wiki/index.php/610:_Sheeple

[A thought bubble is shared between the five occupants of a subway car (four Cueballs and one Ponytail).] All: Look at these people. Glassy-eyed automatons going about their daily lives, never stopping to look around and think! I'm the only conscious human in a world of sheep.

The people in this comic think of each other as sheep, who blindly follow direction without thinking for themselves. The word " sheeple " from the title has been used before in xkcd in the phrase " Wake up Sheeple !" In this comic, each person on the train considers themselves to be the only individual mind and everyone around them as "sheep". Ironically, the reader can see that although each of them thinks about how individual they are, they are all collectively thinking exactly the same thing, meaning that they are all sheeple. The comic can also be taken as a warning to not assume that you have more consciousness than someone else, since for all you know they could think the same about you. Ayn Rand was a Russian-born American novelist and activist whose most famous books include, Atlas Shrugged , Anthem , and The Fountainhead . She developed a philosophy known as Objectivism , which promotes individual fulfillment (or so-called "rational self-interest") at the expense of collective goals and undertakings. Sheeple coordinates with Ayn Rand's novel, Anthem , set in the distant future in which the word "I" has been abolished and the evils of the communal values have created a new dark age. A possible further irony can be found in the title text. Rand enthusiasts would seek individualism and independence from social pressures; however, a convention could be interpreted as a social collective of people who have similar interests in a subject. These ideas could arguably be construed to be opposites of each other. However, similar interests does not mean lack of individualism: this can be seen in Ayn Rand's novel "Atlas Shrugged", which features a society of like-minded people centered around the concepts of individualism and neoliberalism . [A thought bubble is shared between the five occupants of a subway car (four Cueballs and one Ponytail).] All: Look at these people. Glassy-eyed automatons going about their daily lives, never stopping to look around and think! I'm the only conscious human in a world of sheep.

Disaster Voyeurism

Disaster Voyeurism

https://www.xkcd.com/611

https://www.explainxkcd.com/wiki/index.php/611:_Disaster_Voyeurism

[Megan is watching TV. Black Hat is leaning on the back of her chair.] Megan: I've realized that I always secretly root for hurricanes. I watch the news hoping that they'll get really big and hit a city. I know my hopes don't actually affect it, but I feel bad. Black Hat: Nah, that's just natural human attraction to spectacle. It's like watching the shuttle launch because you don't want to miss it if there's a disaster. Megan: ...I guess? Black Hat: Or dressing as an intern to sneak into operating rooms, in case a patient dies and you can watch them harvest organs. Megan: Wait, you do that? Black Hat: Or stealing detour signs to direct highway drivers down backwoods roads strewn with caltrops. After the tires burst, you start shooting out their windows. Black Hat: Then, when they flee the car in terror, you hunt them on horseback, like men once did. Megan: I realized a while back that we're having entirely different conversations.

The comic is referring to a phenomenon known as gaping or rubbernecking . The terms are applied to people who stand around as spectators at the site of a disaster. Apparently, many people are attracted to terrible scenes out of a sort of morbid curiosity. While fascinated by the spectacle, most people also feel a sense of shame and guilt at the same time, unsure of whether it is morally wrong to be entertained by other's misfortunes. This feeling of conscience is expressed in the comic by Megan , who secretly cherishes hope that a hurricane might strike but feels guilt despite knowing she isn't the cause of any danger. Black Hat on the other hand regards these feelings as perfectly natural. In the comic, he gives three more examples of how he enjoys other people's misfortune, each more sinister than the last, eventually partaking in the disaster itself which is another thing entirely: It becomes clear that he actually enjoys it when other people are hit by tragedies. He reveals that he even actively promotes or causes the tragic fates of others. Him being a sadist concurs with the characterization depicted in other comics. Megan understands that the two of them are in fact leading entirely different conversations, as Black Hat is not in the least able to comprehend her scruples. The title text aims at hurricane enthusiasts in internet forums, who are distracted by their scientific curiosity from the danger a hurricane may present to humans. [Megan is watching TV. Black Hat is leaning on the back of her chair.] Megan: I've realized that I always secretly root for hurricanes. I watch the news hoping that they'll get really big and hit a city. I know my hopes don't actually affect it, but I feel bad. Black Hat: Nah, that's just natural human attraction to spectacle. It's like watching the shuttle launch because you don't want to miss it if there's a disaster. Megan: ...I guess? Black Hat: Or dressing as an intern to sneak into operating rooms, in case a patient dies and you can watch them harvest organs. Megan: Wait, you do that? Black Hat: Or stealing detour signs to direct highway drivers down backwoods roads strewn with caltrops. After the tires burst, you start shooting out their windows. Black Hat: Then, when they flee the car in terror, you hunt them on horseback, like men once did. Megan: I realized a while back that we're having entirely different conversations.

Estimation

Estimation

https://www.xkcd.com/612

https://www.explainxkcd.com/wiki/index.php/612:_Estimation

[Cueball is in a car, talking on his phone.] Cueball: I'm just outside town, so I should be there in fifteen minutes. Cueball: Actually, it's looking more like six days. Cueball: No, wait, thirty seconds. [Caption below the frame:] The author of the Windows file copy dialog visits some friends.

When moving or copying files using the Windows Explorer , a dialog box opens to inform the user of how many of the files being moved have been moved with an estimate of how long the rest of the files should take. However, this estimate is often subject to seemingly random and extreme changes from a time measured in seconds or minutes to one measured in hours or days. This is because Windows bases its estimate on the latest file transfer rate, which exaggerates short-term fluctuations. For instance, transfers of many small files are generally slower than transfers of a few large files, because of per-file overhead (time spent writing data describing the file's title, location, etc. to the disk). A brief slowdown may cause the system to display that the transfer will take a long time (based on the total amount of data yet be transferred and the current low speed), while a sudden burst of data moved quickly between memory caches will give a time that is much too small. A better implementation would keep track of the average file transfer rate over the entire operation, which would even out the bumps and give a more accurate estimate. Windows 8 avoids the problem by doing away with the time estimate. The joke in the comic is the idea that this feature was actually purposely implemented and that the person who did so actually talks like that. He tells some friends on the phone how long it will take for him to arrive at their meeting point. However, like with Windows's estimation feature, he quickly changes his estimate multiple times from the extremes of days to seconds due to small fluctuations in traffic flow (like when he has to stop on a red light and then he speeds up on green). The title text refers to the fact that if the connection is lost, and data can no longer be transmitted, the estimation just gets larger and larger as time goes on rather than realizing that no data being sent means there is no connection. This is a behavior that occurs on Microsoft network connections even when the connection is not lost. Kubuntu avoids this problem, but not that of wide fluctuations, by including only the past few seconds in its estimate. If there has been zero progress within the averaging interval, it reports "Stalled". the actual author of the windows copy dialog created a video explaining why it's so wrong. -- https://www.youtube.com/watch?v=9gTLDuxmQek [Cueball is in a car, talking on his phone.] Cueball: I'm just outside town, so I should be there in fifteen minutes. Cueball: Actually, it's looking more like six days. Cueball: No, wait, thirty seconds. [Caption below the frame:] The author of the Windows file copy dialog visits some friends.

Threesome

Threesome

https://www.xkcd.com/613

https://www.explainxkcd.com/wiki/index.php/613:_Threesome

Megan: We had a threesome last night. Cueball: How was it? Megan: Awkward - it was with a physicist. Cueball: Why's that awkward? Megan: They can't solve the three-body problem. Cueball: Ah, yes.

The N-Body Problem in physics refers to our inability to analytically solve sets of differential equations modelling gravitational attraction between more than two bodies. Simply put, there are exact equations for describing the movement of two bodies reacting to each other's gravitational pull, but no such solutions exist for systems of three or more bodies. A threesome is a sexual encounter with three people. The punchline of the comic is a play on the word "bodies": a threesome involves three (human) bodies, and it is implied that the physicist's participation in the threesome was hindered due to their inability to solve for the movement of said bodies (i.e. the physicist was apparently unable to get comfortable and sexually satisfied at the same time). According to the title text, Megan proposed that they settle for a numerical solution since a closed-form solution is unavailable. A numerical solution to predict the motion of a system would be an "open" procedural solution or simulation. On the one hand, such a solution can be more practical and less time-consuming than a closed-form solution, especially in cases (such as the three-body problem) where the latter is suspected to be impossible. On the other hand, a numerical solution is only an approximation and will tend to deviate from the exact solution over time. In the context of the comic, Megan probably was suggesting that a numerical solution would be sufficiently accurate for the duration of the threesome, but it appears that the physicist insisted that they arrive at an exact solution. A frequent observation in random n-body encounters is that one or more bodies are ejected from the system by achieving escape velocity (and loneliness), but stable solutions are possible. A closed-form solution would allow one to predict for how long such an arrangement would remain stable. Ironically, it could be that the physicist's insistence on finding an exact solution resulted in them being excluded/"ejected" from the threesome, which arguably would be very "awkward". Megan: We had a threesome last night. Cueball: How was it? Megan: Awkward - it was with a physicist. Cueball: Why's that awkward? Megan: They can't solve the three-body problem. Cueball: Ah, yes.

Woodpecker

Woodpecker

https://www.xkcd.com/614

https://www.explainxkcd.com/wiki/index.php/614:_Woodpecker

[Megan and Beret Guy are standing on a deck.] Beret Guy: A Woodpecker! pop pop pop Megan: Yup. [Woodpecker knocking against a tree.] Megan: He hatched about this time last year. pop pop pop pop [Megan leave the frame, leaving Beret Guy on the deck alone.] Beret Guy: ...Woodpecker? Beret Guy...It's your Birthday! Beret Guy: Did you know? Beret Guy: Did nobody tell you? [Beret Guy leaves the frame, changes to the tree base.] [Beret Guy brings a gift and places it at the tree trunk.] [The woodpecker comes down and opens the gift.] [The woodpecker flies away holding onto the cord of a power drill.]

Beret Guy observes a woodpecker . A woodpecker is a type of bird known for using its bill to bore holes into trees to get access to and eat the insects living inside. Megan notes that the bird hatched approximately a year ago. Beret Guy seems touched by this fact, and attempts to explain to the woodpecker that it is the woodpecker's birthday. Beret Guy leaves a present by the foot of the tree where the woodpecker is nesting. The woodpecker opens the present which turns out to be a power drill, a mechanical tool that is used to bore holes into wood, much quicker than a bird normally could. Not that this would be of much use to the bird, as the bird has no electricity [ citation needed ] and so no means of powering the drill, let alone opposable thumbs [ citation needed ] with which to operate the drill. In spite of this, the woodpecker has not only unwrapped the present; it has apparently accepted it, and flies off with it. The title text appears to be Beret Guy talking to the bird still, pointing out that he can get the bird an extension cord to operate the drill because, in his mind, they are friends. In actuality, the bird may or may not care about the drill or Beret Guy. An extension cord, also, would not do much good as the bird would still have no electricity, and if it did have a source of electricity and was able to use the drill, it wouldn't be able to fly further than the length of the extension cord, which isn't far for a bird. This could be a reference to 509: Induced Current . [Megan and Beret Guy are standing on a deck.] Beret Guy: A Woodpecker! pop pop pop Megan: Yup. [Woodpecker knocking against a tree.] Megan: He hatched about this time last year. pop pop pop pop [Megan leave the frame, leaving Beret Guy on the deck alone.] Beret Guy: ...Woodpecker? Beret Guy...It's your Birthday! Beret Guy: Did you know? Beret Guy: Did nobody tell you? [Beret Guy leaves the frame, changes to the tree base.] [Beret Guy brings a gift and places it at the tree trunk.] [The woodpecker comes down and opens the gift.] [The woodpecker flies away holding onto the cord of a power drill.]

Avoidance

Avoidance

https://www.xkcd.com/615

https://www.explainxkcd.com/wiki/index.php/615:_Avoidance

[Cueball is sitting in a chair holding a phone to his ear while his Cueball-like friend talks to him.] Friend: Did you call that hot girl from the party yet? Cueball: I've been trying. [In a frame-less panel Cueball looks at his phone and talks to his friend.] Cueball: It's weird. I swear I got her the first time. But now it says the number's wrong. [Zoom in on the friend, Cueball talking to him off-panel.] Friend: What did you say she did, again? Cueball (off-panel): Voice work. At Verizon, I think. Cueball (off-panel): Why? Friend: No reason. [Megan is talking into a phone, in an italic voice. Cueball's remark is shown emanating from the phone with a zig-zag line, also the click from hanging up the phone is shown like that.] Megan: We're sorry, your call could not be completed as dialed. Cueball (over the phone): Damn. *Click* Megan: Please check the number and try again.

Megan gave her number to Cueball at a party, but now doesn't want to talk to him. Because Megan works with recording voice messages at Verizon , she can with no effort put on the characteristically semi-lifeless tone of professional automated answers, and answer the phone with the "call cannot be completed"-message . Perhaps it was even she who recorded it in the first place. In this way she avoids Cueball, hence the title. Cueball actually got through to her the first time he used her number, and since she did not know his number at the time, she took that call. After that she used her Verizon voice every time he calls. Cueball's Cueball-like friend, is suspicious, and it is him who ask if Cueball knows what Megan works with. He gets his suspicion confirmed, but seems to enjoy that Cueball hasn't understood the implications and doesn't let him in on the secret. The title text mentions a possible hobby that Randall could think of. The hobby can be interpreted as a Reverse Turing test with someone imitating an Interactive voice response system to see how long they can keep this going before the caller either gives up and hangs up, or realizes someone is making a joke on them and calls them out. This is related to Randall's Hobby series , but this time it is not specifically Randall's own hobby. [Cueball is sitting in a chair holding a phone to his ear while his Cueball-like friend talks to him.] Friend: Did you call that hot girl from the party yet? Cueball: I've been trying. [In a frame-less panel Cueball looks at his phone and talks to his friend.] Cueball: It's weird. I swear I got her the first time. But now it says the number's wrong. [Zoom in on the friend, Cueball talking to him off-panel.] Friend: What did you say she did, again? Cueball (off-panel): Voice work. At Verizon, I think. Cueball (off-panel): Why? Friend: No reason. [Megan is talking into a phone, in an italic voice. Cueball's remark is shown emanating from the phone with a zig-zag line, also the click from hanging up the phone is shown like that.] Megan: We're sorry, your call could not be completed as dialed. Cueball (over the phone): Damn. *Click* Megan: Please check the number and try again.

Lease

Lease

https://www.xkcd.com/616

https://www.explainxkcd.com/wiki/index.php/616:_Lease

[A man is holding a sheet of paper.] Man: Okay, any other concerns before you sign the lease? Cueball: I'm concerned that we're sitting here like I'm a responsible adult. I'm pretty sure I stopped growing up in my teens and have been faking ever since. Cueball: For god's sake, you're entrusting me with a building . I still make LEGO buildings sometimes. Man: Sir, does any of this impact your fulfillment of the lease terms? Cueball: I don't know what you just said because I was thinking about Batman.

Cueball is about to sign a lease to rent a building, but he's scared that he's not grown-up enough for the responsibility, presenting as evidence that he still plays with Lego building blocks. It's common for children to assume, on some level, that adults are all capable, even infallible, and have all the knowledge they need to navigate the adult world. As a result, there's often a subconscious assumption that you'll reach a point where you feel like an adult, with all the attendant knowledge and maturity. The reality is that maturation is a process, knowledge is gained over time (and often through harsh experience), and the immaturities of youth never spontaneously vanish. Most people learn to behave in ways that adult society expects of them well before such behavior comes naturally, and for some people it never does. This is probably the source of Cueball's comment that he "stopped growing up" as a teenager and has been "faking it ever since". Of course, Cueball actually isn't responsible and capable, since he drifts off to think about the fictional character Batman (who appears in comic books, often considered children's material), in the middle of a serious financial transaction. The title text references one of xkcd's most famous comics, 150: Grownups , where Megan decides to use the freedom of adulthood to fill her apartment with playpen balls. It is possible that this is a prequel to the events in that comic. After the events in this strip occur Cueball may have moved into the building where Megan lives, gets to know her and one day when he goes to see her, the events in that strip take place. From the title text we see the lender can tell that Cueball would like Megan and from the events of Grownups we see that a romantic relationship of some sort did form. [A man is holding a sheet of paper.] Man: Okay, any other concerns before you sign the lease? Cueball: I'm concerned that we're sitting here like I'm a responsible adult. I'm pretty sure I stopped growing up in my teens and have been faking ever since. Cueball: For god's sake, you're entrusting me with a building . I still make LEGO buildings sometimes. Man: Sir, does any of this impact your fulfillment of the lease terms? Cueball: I don't know what you just said because I was thinking about Batman.

Understocked

Understocked

https://www.xkcd.com/617

https://www.explainxkcd.com/wiki/index.php/617:_Understocked

[A bald bearded man with glasses standing in his open doorway outside his house and a police man wearing a black peaked cap with white emblem standing on the stoop at the top of the stairs leading down from the house are swearing at each other] Both: * [email protected] #! [The bearded man is in prison sitting on a bench behind bars.] [Cueball, as the president of the United States, is standing behind a lectern with the Presidential Seal (eagle and all) on its front.] President: To defuse this misunderstanding, I've invited both men to have a beer with me at the White House. [A policeman is standing left and looking left while the bearded man is walking towards the president both with their hands stretched out towards each other. They are in the oval room in the White House with a couch and an oval carpet and two large windows.] [The president has opened cabinet on top of another cabinet. He is looking into it with a hand on his chin.] President: Actually, it seems we're out of beer. Voice (off-panel): Is there anything else? [Zoom in on the back of the president's head viewing the shelve in the cabinet with a single labeled bottle:] Tequila [The black Presidential Limo, with grayed out windows in the rear is being driven at high speed by the president who can be seen through the regular windows in the front of the car. The bearded man has his arms up and the policeman is waving his hat and holding the bottle of tequila are standing up looking out of the sunroof.] All: WOOOOOOOOOOOO [The policeman, the bearded man, and the president are sitting on a bench behind bars in the same prison from panel two.]

On July 16, 2009, Harvard University professor Henry Louis Gates was arrested at his home in Cambridge, Massachusetts by police officer Sgt. James Crowley, after the police department received a call that Gates and another man were breaking and entering into the residence. Returning home from a visit to China, Gates had found his front door jammed, and tried to force it open with the help of his driver. Arriving at the scene and finding the front door forced open, Crowley (a Caucasian) asked the African-American Gates to show his ID or other proof that he lived there. Gates, feeling persecuted, responded with belligerence. He presented identification, but continued to talk back to the officers. Sgt. Crowley arrested Dr. Gates and charged him with disorderly conduct. The charges were dropped on July 21, but the incident sparked a national debate about racial profiling . On July 22, U.S. President Barack Obama criticized the arrest, saying that the Cambridge police "acted stupidly in arresting somebody when there was already proof he was in his own home." He also commented on the racial undertones of the incident, saying that "there is a long history in this country of African-Americans and Latinos being stopped by law enforcement disproportionately. That's just a fact." The president's remarks were furiously criticized by the law-enforcement community, and President Obama apologized two days later, saying that he could have chosen his words better, and it wasn't his intention to malign the Cambridge Police Department or Sgt. Crowley. He also invited Gates and Crowley to discuss the situation over beers to air out their differences and come to an understanding about the situation. This comic explores a hypothetical situation in which President Obama found he was all out of beer, and chooses to share tequila with Gates and Crowley instead. In pop culture, tequila is frequently represented as the "let's-get-trashed" alcohol of choice, and so in the comic, President Obama, Professor Gates and Sgt. Crowley all get trashed on tequila, take a White House limo on a joyride, and all end up behind bars. The title text goes back on the suggestion that drinking tequila rather than beer would cause this kind of behavior. It also jokingly implies that biology grad students are authorities on the effects of alcohol because they drink a lot, not because they understand how the human body works. [A bald bearded man with glasses standing in his open doorway outside his house and a police man wearing a black peaked cap with white emblem standing on the stoop at the top of the stairs leading down from the house are swearing at each other] Both: * [email protected] #! [The bearded man is in prison sitting on a bench behind bars.] [Cueball, as the president of the United States, is standing behind a lectern with the Presidential Seal (eagle and all) on its front.] President: To defuse this misunderstanding, I've invited both men to have a beer with me at the White House. [A policeman is standing left and looking left while the bearded man is walking towards the president both with their hands stretched out towards each other. They are in the oval room in the White House with a couch and an oval carpet and two large windows.] [The president has opened cabinet on top of another cabinet. He is looking into it with a hand on his chin.] President: Actually, it seems we're out of beer. Voice (off-panel): Is there anything else? [Zoom in on the back of the president's head viewing the shelve in the cabinet with a single labeled bottle:] Tequila [The black Presidential Limo, with grayed out windows in the rear is being driven at high speed by the president who can be seen through the regular windows in the front of the car. The bearded man has his arms up and the policeman is waving his hat and holding the bottle of tequila are standing up looking out of the sunroof.] All: WOOOOOOOOOOOO [The policeman, the bearded man, and the president are sitting on a bench behind bars in the same prison from panel two.]

Asteroid

Asteroid

https://www.xkcd.com/618

https://www.explainxkcd.com/wiki/index.php/618:_Asteroid

[Blondie as a news anchor is standing in front of a screen pointing to a diagram of an asteroid's trajectory path with Earth in the path. There is a caption below the screen:] Blondie: Astronomers have confirmed that the asteroid is headed for Earth. Caption: Breaking news [In a frame-less panel Blondie narrates above a picture of a rocket with fire out the end of its two lifter rockets on either side of the central main part of the rocket. It flies up and right. In an inset picture to the right and below the rocket there is an image of a rover with text on it. The rower has two legs and a drill below it, and an antenna above the main body of the rower.] Blondie (narrating): NASA has launched a heroic mission to land a rover on the asteroid, drill into it, and destroy it with nuclear bombs. Rover: NASA [Ponytail is sitting in an office chair at the control panel of a large unit using it. Cueball stands in front of it looking away from her to the right. Both are wearing headsets with microphones. A voice speaks to them from off-panel right.] Ponytail: The robot has landed successfully and planted the nukes! We're saved! Cueball: Hooray! Voice (off-panel): We're heroes! [The Little Prince is standing on his small asteroid next to his rose and a very small volcano. He is looking at the NASA rover which is partly outside the panel to the right and up. Two legs and the drill can be seen as well as part of the antenna and the part of the body with the text. The rover has drilled into the asteroid. There is a digital countdown emanating from the rover above the Prince.] 0:05... 0:04... 0:03... Rover: NASA

The comic begins with Blondie as a news anchor reporting that an asteroid is headed for Earth. The end of the world has been envisioned in many ways. One of the most common is with a really big rock hitting Earth. This has been depicted in movies several times, most famously, and released in the same year, are Armageddon and Deep Impact , but also The Day the Sky Exploded and many more. These lists of films with asteroids and meteors show how popular this theme is. There is an online calculator for asteroid impacts, but don't worry, as any rock that does hit Earth isn't likely to kill everyone . And, as seen in the what if? Diamond , speed counts too. The joke here, though, is that, after sending up a robot to blow the asteroid to smithereens, said rock is actually the home of the Little Prince from the famous tale by Antoine de Saint-Exupéry. To save our world, we must destroy his. And probably the prince along with it. If the only way to save our species is by killing off another species, is the act still ethical? In none of the world-destroying asteroid stories were said rocks actually home to intelligent life. Or any life, for that matter. A second joke that can be seen is that in said movies the "heroic" mission always involves humans in some way imperiling themselves to save humanity, rather than, say, staying safely at home and using a robotic rover to do all the dangerous stuff. The title text is a reference to the 1998 asteroid movie Deep Impact . "Crossover" is a term used to refer to a technique of taking two independent (and usually already existing) stories and creating a scene or short story in which characters from both worlds collide and interact with each other. Or, in other words, characters from one story "crossover" into the second. Fanfic is short for Fan Fiction , e.g. a fictional story written by someone who loves a particular story/series/idea so much they wanted to write their own tale about it (or one who hated said story so much they felt compelled to fix it). It suggests that most people were unwilling to read a story about people nuking miniature kingdoms to save civilization. A tough entertainment call any day. The Little Prince was referenced already back in 2: Petit Trees (sketch) and later again in 1350: Lorenz at the end of the space trip branch. [Blondie as a news anchor is standing in front of a screen pointing to a diagram of an asteroid's trajectory path with Earth in the path. There is a caption below the screen:] Blondie: Astronomers have confirmed that the asteroid is headed for Earth. Caption: Breaking news [In a frame-less panel Blondie narrates above a picture of a rocket with fire out the end of its two lifter rockets on either side of the central main part of the rocket. It flies up and right. In an inset picture to the right and below the rocket there is an image of a rover with text on it. The rower has two legs and a drill below it, and an antenna above the main body of the rower.] Blondie (narrating): NASA has launched a heroic mission to land a rover on the asteroid, drill into it, and destroy it with nuclear bombs. Rover: NASA [Ponytail is sitting in an office chair at the control panel of a large unit using it. Cueball stands in front of it looking away from her to the right. Both are wearing headsets with microphones. A voice speaks to them from off-panel right.] Ponytail: The robot has landed successfully and planted the nukes! We're saved! Cueball: Hooray! Voice (off-panel): We're heroes! [The Little Prince is standing on his small asteroid next to his rose and a very small volcano. He is looking at the NASA rover which is partly outside the panel to the right and up. Two legs and the drill can be seen as well as part of the antenna and the part of the body with the text. The rover has drilled into the asteroid. There is a digital countdown emanating from the rover above the Prince.] 0:05... 0:04... 0:03... Rover: NASA

Supported Features

Supported Features

https://www.xkcd.com/619

https://www.explainxkcd.com/wiki/index.php/619:_Supported_Features

[Cueball and a friend holding a laptop standing together.] Cueball: It took a lot of work, but this latest linux patch enables support for machines with 4,096 CPUs, up from the old limit of 1,024. Friend: Do you have support for smooth full-screen Flash video yet? Cueball: No, but who uses that?

This comic is a reference to Linux builds adding support and features that will not appeal to the majority of desktop computer and Linux users. Cueball has created a patch that allows support for processors with 4,096 cores, even though most computers have only 8 cores or fewer. He considers this to be more worthwhile an endeavor than full-featured Flash support, which was the most common way to present videos or animations on websites at the time when this comic was published, five years before the first official release of HTML5 . Flash movies are known for their bad performance and high consumption on CPU power compared with other movie formats. Cueball's friend is uninterested in the 4,096-core-processor fix, and only wants to know if it will help him with Flash video. However, as of 2013, there are commercial computer systems that can be actually configured up to 2,048 cores (4,096 threads), e.g. SGI UV 2000 . 95% of the world's supercomputers run Linux, so while Flash video on desktop Linux would directly affect more people, the high performance computing industry relies on and actually funds Linux development. It should be noted that GNU/Linux now supports flash via Gnash . The first stable release was February 15, 2012; over two and a half years after this comic was written. In a turn, Flash was officially deprecated at the end of 2020, making supporting it mostly pointless. The title text mentions the "American political satirist, writer, director, television host, actor, media critic, and stand-up comedian" Jon Stewart which further refers to his famous American late night satirical television program The Daily Show . The show is also available on the internet ( www.thedailyshow.com ), presented in Flash video. [Cueball and a friend holding a laptop standing together.] Cueball: It took a lot of work, but this latest linux patch enables support for machines with 4,096 CPUs, up from the old limit of 1,024. Friend: Do you have support for smooth full-screen Flash video yet? Cueball: No, but who uses that?

Wings

Wings

https://www.xkcd.com/620

https://www.explainxkcd.com/wiki/index.php/620:_Wings

Cueball: Titan's gravity is 14% of Earth's, and its atmosphere 50% denser. Cueball: So if you can generate 9% of your body weight in lift, you can fly on Titan. Cueball: With wings, a stage harness, a cable, and 91% of my weight in bricks, I want to test this. [There is a heap of materials on the ground. Cueball is holding a stage harness.] [Large diagram of a bridge, seemingly metal. A rope leads through pulleys tied to the bridge. One end goes to Cueball, one end to a pile of bricks.] [Cueball is standing with wings attached to his arms.] [Cueball flaps the wings, and appears to be floating.] [Cueball glides.] Cueball: It works! Megan: Except you have two problems. Cueball: What? Megan: You used hot glue on your wing joints and you have friends into Greek mythology. Cueball: Huh? [Black Hat is standing on the bridge, with a large lamp labeled "heat lamp" attached to a battery.] [The wing segments fall off Cueball and he tumbles downward.]

Cueball explains to Megan that on Saturn's moon Titan , the combination of lower gravity and a denser atmosphere make the act of flying simpler. Wings that are only capable of generating 9% of the necessary lift on Earth would allow one to fly if used on Titan. Cueball now stands in front of an apparatus to do so; he is standing in a valley with a metal arch above him, and two pulleys that have a rope going from Cueball to one pulley to the other and to the pile of bricks that weigh 91% of his weight, so if he generates enough lift to cancel out 9% of his weight, then he will be able to lift himself and fly. The experiment is a success. However, as Megan points out, his experiment has some problems. One, he used hot glue for the wing joints and two, he has friends into Greek mythology. Icarus is a character in Greek mythology who is known for his own self-powered flight, which ended when the wax holding his wings together melted and he fell to his death. This supposedly occurred because he ignored instructions not to fly too close to the Sun, a tragic example of hubris — extreme arrogance. Here, Black Hat is bringing an artificial "sun" to "Icarus" to recreate the tragedy . Black Hat is standing on top of the arch with a powerful heat source, a heat lamp . The hot glue melts, then the wings fall apart, then Cueball falls. In the title text, Randall asks that xkcd readers do not attempt to reproduce this. The reason for this is explained here . It could also simply be a media-standard "Don't try this at home" warning, as there are legitimate dangers to flying around unprotected. Sufficient height and a sudden loss of one's wings could indeed result in death (and deliberately causing someone to lose their wings and die or be injured would indeed get one arrested). One thing to note about this comic is that Cueball is still attached via pulley to the bricks. These bricks, weighing down on the other side, should (obviously) slow his fall considerably. Of course, Black Hat could also cut the rope... [ citation needed ] The calculated figure of 9% is only correct if the temperature on Titan has been raised to be the same as Earth — which, for human-powered flight, would probably be necessary anyway. At Titan's normal temperature, you would only have to generate about 3% of your Earth body weight in lift, as the atmosphere is much denser. The friction in normal ball-bearing pulleys when loaded with 182 % of a persons weight would likely be greater than 9 % of that weight. Cueball must be using futuristic super-low-friction pulleys. When the wings come off, Cueball is going to fall with an acceleration of about 0.047 g, or 21 times slower than a free fall (neglecting friction). The net downward force is 9 % of his weight, while the total inertia is 191 % of his body mass. So a fall from 21 meters (63 ft) will feel like a fall from one meter (3 ft), equivalent to the fall of someone who has hopped off a table. If he lands on his feet, he will not sustain injuries. Cueball: Titan's gravity is 14% of Earth's, and its atmosphere 50% denser. Cueball: So if you can generate 9% of your body weight in lift, you can fly on Titan. Cueball: With wings, a stage harness, a cable, and 91% of my weight in bricks, I want to test this. [There is a heap of materials on the ground. Cueball is holding a stage harness.] [Large diagram of a bridge, seemingly metal. A rope leads through pulleys tied to the bridge. One end goes to Cueball, one end to a pile of bricks.] [Cueball is standing with wings attached to his arms.] [Cueball flaps the wings, and appears to be floating.] [Cueball glides.] Cueball: It works! Megan: Except you have two problems. Cueball: What? Megan: You used hot glue on your wing joints and you have friends into Greek mythology. Cueball: Huh? [Black Hat is standing on the bridge, with a large lamp labeled "heat lamp" attached to a battery.] [The wing segments fall off Cueball and he tumbles downward.]

Superlative

Superlative

https://www.xkcd.com/621

https://www.explainxkcd.com/wiki/index.php/621:_Superlative

He has dreams. [Cueball is gesturing to Megan.] Cueball: I was in this weird cross between work and my old house... Which he'll tell you all about. He can speak French. Or could in high school, anyway. A little. Cueball: Man, I knew all these tenses and stuff once. His blog has four posts, all apologies for not posting more. [Cueball is sitting at a desk, typing.] Cueball: Sorry, I've been trying to think of stuff to put here. He is The least interesting man in the world. [Cueball is sitting at a table. Megan and Ponytail are paying no attention to him.] Cueball: I don't always drink beer, but when I do, I stick to a glass or two. Any more and I feel sick.

The comic parodies a famous advertisement campaign for the Dos Equis beer brand. In the campaign, Jonathan Goldsmith plays " The Most Interesting Man in the World ", a suave elderly gentleman with a number of astonishing life experiences and skills. The campaign's format generally includes the narrator presenting hyperbolic descriptions of the man's accomplishments, followed by the man delivering his signature catchphrase, "I don't always drink beer, but when I do, I prefer Dos Equis.", which has been widely adopted as an internet meme . Cueball plays the antithesis of the protagonist in the campaign: the least interesting man in the world. Unlike the stories in the advertisement, his affairs tend to bore the listeners. Being the generic everyman, he possesses no outstanding capabilities at all. While the original is said to "speak French... in Russian", Cueball seems to have forgotten his French altogether. He also has apparently nothing of interest to tell, either in real life or in his blog. Instead, he will talk away about his weird dreams and his success in video games. Moreover, he is unable to stand too much beer and therefore absolutely ill-qualified to advertise it. The title text is a reference to the slogan of the campaign "Stay thirsty, my friends." It also references Team Fortress 2 (TF2), a multi-platform, multi-player First-person shooter game. He has dreams. [Cueball is gesturing to Megan.] Cueball: I was in this weird cross between work and my old house... Which he'll tell you all about. He can speak French. Or could in high school, anyway. A little. Cueball: Man, I knew all these tenses and stuff once. His blog has four posts, all apologies for not posting more. [Cueball is sitting at a desk, typing.] Cueball: Sorry, I've been trying to think of stuff to put here. He is The least interesting man in the world. [Cueball is sitting at a table. Megan and Ponytail are paying no attention to him.] Cueball: I don't always drink beer, but when I do, I stick to a glass or two. Any more and I feel sick.

Haiku Proof

Haiku Proof

https://www.xkcd.com/622

https://www.explainxkcd.com/wiki/index.php/622:_Haiku_Proof

[Miss Lenhart teaching a class gestures with both hands up as Megan, sitting at the first desk on a stool, raises a hand and asks a question. Cueball sits at the desks behind her supporting his head in both hands with the elbows on the desk.] Megan: How do you know there are an infinite number of primes? Miss Lenhart: I'll answer in haiku! [In a frame-less panel, Miss Lenhart lifts a hand up while answering. Both students sit upright on their stools.] Miss Lenhart: Top prime's divisors' [Miss Lenhart floats into the air with three lines beneath her legs. Cueball looks up. Megan does not change position.] Miss Lenhart: Product (plus one)'s factors are...? [Miss Lenhart flies over the students heads with a curved line behind her. Neither student look up. The bottom frame of the panel is a curving thought/dream bobble that goes through the middle of the panel at a height just below the desk tops. Two thought circles goes from Cueball's head down to this frame, and Cueball's thoughts are shown below outside of the panel - without any frame around.] Miss Lenhart: Q.E.D., bitches! Cueball (thinking): Wow, after the 48-hour sleep-dep mark, lectures get really interesting.

In this comic Cueball attends a math class after having been awake for two full days (48 hours). After that he begins to hallucinate and dreams that the teacher Miss Lenhart (a professor in this comic) answers Megan's question, about a proof that there are an infinite number of prime numbers , in haiku . After the first line she floats up and during the third and final line she flies over the students heads. Note also that when Cueball looks up at the flying teacher when she takes off, Megan never moves her head because it's not happening in her world, and Cueball only hallucinates the teachers flies. Euclid's theorem states that there are an infinite number of primes, prime numbers being numbers that are only divisible by themselves and 1. The most notable proof of this theorem, and the one presented in this comic, was first given by Euclid himself in his Elements . A more traditional form of this proof follows: If we suppose that there are a finite number of primes, then they must have a product, i.e. p 1 p 2 ... p n = q . Now consider q + 1. If this number is prime itself, then we have discovered a new prime number, contrary to the assumption that we had listed them all. If it is not prime, it must have a prime divisor. Since all of the p k are a factor of q , they cannot be a divisor of q + 1. So q + 1 is divisible by a prime not on the list, which again is a contradiction. Therefore, there must be infinitely many primes. At the last line of the haiku, Miss Lenhart says "Q.E.D., bitches!", Q.E.D. stands for "Quod Erat Demonstrandum", which means "Thus, it has been demonstrated." This is a Latin phrase which is used to show a proof is over. Ironically, the proof is not complete. The comic essentially takes this proof and states it in the form of a haiku , which is a traditional form of Japanese poetry, which is in Japanese broken up into patterns of morae (or syllables ), a unit that measures the length of sound. A Japanese haiku consists of three lines with 5, 7 and 5 morae respectively per line. An English Haiku has 5, 7 and 5 syllables per line. The proof poem goes like this: Top prime's divisors' Product (plus one)'s factors are...? Q.E.D., bitches! Which can be divided in syllables like this: Top - prime's - di - vi - sors' Pro - duct - (plus - one)'s - fac - tors - are...? Q. - E.- D., - bit - ches! The haiku proof given is slightly off, as the first line talks about the "top prime's divisors," which makes no sense because the top prime doesn't have any divisors besides itself and one. You need to take the product of all primes, not just one. But, hey, it's a hallucination. Haiku was also referred to before in 554: Not Enough Work . The comic and title text conclude that going to class while sleep-deprived is an interesting, but entirely noneducational, experience. So, go for the sake of the hallucinations. [Miss Lenhart teaching a class gestures with both hands up as Megan, sitting at the first desk on a stool, raises a hand and asks a question. Cueball sits at the desks behind her supporting his head in both hands with the elbows on the desk.] Megan: How do you know there are an infinite number of primes? Miss Lenhart: I'll answer in haiku! [In a frame-less panel, Miss Lenhart lifts a hand up while answering. Both students sit upright on their stools.] Miss Lenhart: Top prime's divisors' [Miss Lenhart floats into the air with three lines beneath her legs. Cueball looks up. Megan does not change position.] Miss Lenhart: Product (plus one)'s factors are...? [Miss Lenhart flies over the students heads with a curved line behind her. Neither student look up. The bottom frame of the panel is a curving thought/dream bobble that goes through the middle of the panel at a height just below the desk tops. Two thought circles goes from Cueball's head down to this frame, and Cueball's thoughts are shown below outside of the panel - without any frame around.] Miss Lenhart: Q.E.D., bitches! Cueball (thinking): Wow, after the 48-hour sleep-dep mark, lectures get really interesting.

Oregon

Oregon

https://www.xkcd.com/623

https://www.explainxkcd.com/wiki/index.php/623:_Oregon

History of 19th-century Oregon [Timeline, with relevant images next to various dates.] 1805 [Two men stand at the edge of a cliff. One has a walking staff.] Arrival of Lewis & Clark 1825 Early settlers arrive 1841 Oregon Trail established 1843 Larger western migration begins 1848 [A horse is pulling a covered wagon. A gun peeks out the back.] Huge wave of 500,000+ settlers arrives from Missouri. Largely children and adolescents, most bring nothing but cartloads of bullets for hunting. 1849 [Cueball and Megan with rifles aim at something.] Overhunting begins to devastate ecosystem Dysentery epidemic. 1850 [Tombstones and bodies.] Shooting deaths skyrocket Typhoid epidemic Measles epidemic Cholera epidemic 1851 All mammals larger than squirrels wiped out by overhunting Massive famine 1852 [Sun low over a land, devoid of life. Scattered remains of corpses and skeletons.] Last survivors flee Oregon territory abandoned

This comic relates to the computer game The Oregon Trail , and humorously depicts the consequences to real-world Oregon if everyone had arrived in the same manner they did in the game. The Oregon Trail was an educational computer game released in 1971, but the version referred to is likely the more popular 1985 version. In the game, players would play as a character taking a trek west along the Oregon Trail from Missouri to Oregon. The player's journey starts in 1848 and typically takes less than one year to complete. Along the way, the player must manage resources (food, spare parts, etc.) and face risks and dangers (starvation, disease, etc.) . Most players at the time were grade-school students. The game was very popular, and thousands of players played it monthly. The game made it very easy to hunt for food. Large animals (bison, bears, etc.) were very easy and rewarding targets, where spending a single bullet could be enough to collect enough food for multiple days. There were also smaller prey available (rabbits, squirrels, etc.) which were harder to catch and provided less food. Since bullets are much lighter and cheaper than food, it was a good strategy to bring the minimum amount of food and plan to hunt for meals. Extra food can even be traded for money or other supplies, so it wasn't necessary to start the journey with anything except bullets. The comic tries to document, as though in a historical fashion, what would have been the result if all the players had been real settlers who really had prepared for their journey on the Oregon Trail in that way. The parts before 1848 are historically accurate. Starting from 1848, however, players of the game would form an unbelievably large influx of people arriving nearly simultaneously, with very little food or supplies being brought along. Massive overhunting would soon strip the land bare, all large game slaughtered for meat, with hunger, starvation and disease soon to follow. Dysentery in particular was very common in the original game and perhaps the most infamous way to die, hence its listing as the most prominent epidemic. The title text makes things rather recursive. In this alternate reality, thousands upon thousands of people fleeing from the overpopulated, devastated Oregon becomes the focus of another video game, much like The Oregon Trail in our universe. History of 19th-century Oregon [Timeline, with relevant images next to various dates.] 1805 [Two men stand at the edge of a cliff. One has a walking staff.] Arrival of Lewis & Clark 1825 Early settlers arrive 1841 Oregon Trail established 1843 Larger western migration begins 1848 [A horse is pulling a covered wagon. A gun peeks out the back.] Huge wave of 500,000+ settlers arrives from Missouri. Largely children and adolescents, most bring nothing but cartloads of bullets for hunting. 1849 [Cueball and Megan with rifles aim at something.] Overhunting begins to devastate ecosystem Dysentery epidemic. 1850 [Tombstones and bodies.] Shooting deaths skyrocket Typhoid epidemic Measles epidemic Cholera epidemic 1851 All mammals larger than squirrels wiped out by overhunting Massive famine 1852 [Sun low over a land, devoid of life. Scattered remains of corpses and skeletons.] Last survivors flee Oregon territory abandoned

Branding

Branding

https://www.xkcd.com/624

https://www.explainxkcd.com/wiki/index.php/624:_Branding

Browsing without adblock [Cueball is sitting at a computer.] [Pop-up window with red background.] The Facebook of SEX! Click now! Cueball: Sigh. *Close* [Pop-up window with green background.] Twitter for 18+ singles! Join today! Cueball: Does every porn site have to brand itself like this? *Close* [Pop-up window with blue background.] We're like Google Reader for S&M! Cueball: Really? *Close* [Pop-up window with orange background.] Try the new GitHub for lesbians! Cueball: Ok, wait, what?

This comic pokes fun at web sites (adult-themed sites in particular) which try to inflate their popularity by comparing themselves to other popular online services. The strip shows four such advertisements that appear to Cueball as he browses the Internet. Adblock is a browser extension which prevents advertisements from being displayed. Presumably Cueball normally browses the Internet with Adblock enabled, and thus would not see any of these ads. The first advertises a website that brands itself as the " Facebook of sex". Because Facebook was ubiquitous at the time of writing, this is a good branding idea. Facebook is known to most users and connotes an easy-to-use platform where it's very easy to find people, chat with them, share pictures, etc. For someone looking for sex, this would probably seem like a good site to use. There are, in fact, sites that use this branding in their advertisements and/or their user interface which is likely what inspired Randall to write this comic. Cueball sighs and moves on, probably having seen this kind of ad many times already. The second brands itself as "Twitter for 18+ singles". It is a similar but seemingly invented ad which again plays on the ubiquity and popularity of Twitter , which is a (generally) public chat forum. Despite the fact that, at the time this comic was published, it was limiting posts to 140 characters, it was still popular enough to get some attention and make someone think about going to the site. Sending messages to the world in 140 characters or less might be somewhat less of a versatile platform than Facebook for chatting with other singles, but still perhaps viable. Cueball notes that it is becoming more and more popular to brand adult sites by comparing them to popular non-adult sites. This third takes a turn for the unusual, branding itself as "Google Reader for S&M". Google Reader is a now-defunct platform that allowed users to aggregate web feeds such as RSS feeds into one place for convenience. The service is notably less well-known and popular than Facebook or Twitter, and given that it doesn't directly link you with other people, doesn't have the same connotation of allowing you to connect with others. Perhaps it would be a site that allowed you to aggregate various fan fictions, blogs, or other written works relating to S&M . However, Cueball is surprised such a site would exist. The final ad brands itself as a "GitHub for lesbians". GitHub is a website that allows developers to collaborate on software projects using the Git revision control system. The concept is absurd — GitHub has a specialized function unrelated to anyone's gender or orientation, and it's barely a social network at all; the usefulness or appeal of such a system made specific to lesbians is not apparent. Cueball is surprised and possibly even intrigued by this last ad. The title text relates to the third panel. RSS is a technology involved in Google Reader. RSS&M is a portmanteau of RSS and S&M. This is a possible way for the third web site to brand itself. Browsing without adblock [Cueball is sitting at a computer.] [Pop-up window with red background.] The Facebook of SEX! Click now! Cueball: Sigh. *Close* [Pop-up window with green background.] Twitter for 18+ singles! Join today! Cueball: Does every porn site have to brand itself like this? *Close* [Pop-up window with blue background.] We're like Google Reader for S&M! Cueball: Really? *Close* [Pop-up window with orange background.] Try the new GitHub for lesbians! Cueball: Ok, wait, what?

Collections

Collections

https://www.xkcd.com/625

https://www.explainxkcd.com/wiki/index.php/625:_Collections

Cueball: I now have every Discworld book! Megan: Eh. Building a Kindle collection seems pointless. Cueball: Yeah, I know the DRM means I'll probably lose them someday. Megan: No, pointless in general. Megan: Sure, you satisfy deep magpie-like urges by building neat collections, but you still die alone. Cueball: Sorry, sometimes I mistake your existential crises for technical insights. Megan: Sometimes I mistake this for a universe that cares.

Cueball enters, excited that he's managed to buy every one of author Terry Pratchett 's Discworld books for his Kindle e-reader . Megan says that it seems pointless to her to build a Kindle collection. Cueball interprets this to mean she thinks it's pointless to build a collection on an electronic device, perhaps due to the DRM ( digital rights management ) software common on these devices which can (for instance) make it difficult to transfer the files if the device breaks. (This was the subject of 488: Steal This Comic and DRM has been the general subject of many xkcd comics .) However, Megan is actually commenting on the futility of building up any kind of collection at all, since nothing we do can change the fact that we're inevitably going to die. And when we die, we always die alone - i.e. no one else can follow you on that last journey. And no matter how much you have collected (or earned) during this life that will not change. (A magpie is a bird traditionally thought to be drawn to collect shiny objects and bring them back to its nest.) This view is in line with those advanced by the philosophical movement known as existentialism which theorizes that life has no deep, hidden meaning and hence even things that we personally feel are meaningful (like building up collections) will not change the outcome of life in the end. Cueball obviously has seen Megan in such moods before (see 220: Philosophy ), and excuses himself for not noticing immediately (in the first panel) by the fact that he sometimes mistakes her existential crisis as technical insight. Megan deepens her crisis by pointing out that she sometimes makes the mistake to think that the universe cares. This is a disguised criticism of Cueball's behaviour, meaning that she would rather want him to care about her existential crisis, instead of simply brushing them off. The title text points out that Wondering how much shelf space to leave for a Terry Pratchett collection. (That would then be all his works not just the Discworld series...) is an excellent way to get out of an existential crisis By the time of his death Pratchett had written 41 Discworld books and more than 70 books in total. The day after Pratchett died Randall made a tribute comic to his memory in 1498: Terry Pratchett . Cueball: I now have every Discworld book! Megan: Eh. Building a Kindle collection seems pointless. Cueball: Yeah, I know the DRM means I'll probably lose them someday. Megan: No, pointless in general. Megan: Sure, you satisfy deep magpie-like urges by building neat collections, but you still die alone. Cueball: Sorry, sometimes I mistake your existential crises for technical insights. Megan: Sometimes I mistake this for a universe that cares.

Newton and Leibniz

Newton and Leibniz

https://www.xkcd.com/626

https://www.explainxkcd.com/wiki/index.php/626:_Newton_and_Leibniz

[Newton with long white hair, facing right, holds up a sheet of paper, with several lines indicating the writing on it, in one hand and the other hand is also held up. He stands in front of an empty desk. A smaller frame breaking the border at the top of the frame has a caption:] Newton, 1666 Newton: I've invented calculus! [Leibniz with long black hair, facing left, holds up a sheet of paper, with several lines indicating the writing on it, in one hand. He stands in front of a desk with a book and two pieces of paper, one lying below the other paper but up above the book. A smaller frame breaking the border at the top of the frame has a caption:] Leibniz, 1674 Leibniz: I've invented calculus! [Back to a similar image of Newton, but he has now taken his arms down, still holding his paper.] Newton: Really? Sounds a little bit... [Zoom in on Newton as he puts on a pair of sunglasses in a panel without a frame. The table is not included.] [Newton now with sunglasses on, again in front of the table.] Newton: ... Derivative.

Isaac Newton and Gottfried Leibniz both developed calculus independently of each other about eight years apart, as it says in the comic. However, although Newton had begun working on calculus before Leibniz, he didn't publish it, and Leibniz was the first to publish it (see the Leibniz–Newton calculus controversy ). In calculus a derivative is the result of mathematical differentiation: the instantaneous rate of change of a function relative to its argument, and denoted df(x)/dx. As taught in schools, if a function is drawn as a graph, the derivative of that function at a given point is equal to the slope of that graph at that point. However, the literary word derivative means developed from something older or copied/adapted from others, as Newton claims is the case here. The pun is that Newton is claiming that Leibniz's mathematical derivative is a derivative, or descendant, from his earlier development of this calculus. The comic as a whole is mocking the pattern of corny one-liners that David Caruso often spurts out during the opening scenes of CSI: Miami . The one liner is followed by him dramatically pulling off or putting on his sunglasses and then the show breaks into the title sequence which starts with Roger Daltrey singing an extended "YEEEEAAAAAAAH", from the song Won't Get Fooled Again by The Who as noted in the title text. This has become a popular Internet meme and was used frequently with Michael Jackson's death . The sunglasses joke was also used in the title text of 977: Map Projections . The counts of each letter (Y E A H) in the scream are 1, 6, 6, and 6, which combined produce the year in which Newton is credited to have discovered calculus. [Newton with long white hair, facing right, holds up a sheet of paper, with several lines indicating the writing on it, in one hand and the other hand is also held up. He stands in front of an empty desk. A smaller frame breaking the border at the top of the frame has a caption:] Newton, 1666 Newton: I've invented calculus! [Leibniz with long black hair, facing left, holds up a sheet of paper, with several lines indicating the writing on it, in one hand. He stands in front of a desk with a book and two pieces of paper, one lying below the other paper but up above the book. A smaller frame breaking the border at the top of the frame has a caption:] Leibniz, 1674 Leibniz: I've invented calculus! [Back to a similar image of Newton, but he has now taken his arms down, still holding his paper.] Newton: Really? Sounds a little bit... [Zoom in on Newton as he puts on a pair of sunglasses in a panel without a frame. The table is not included.] [Newton now with sunglasses on, again in front of the table.] Newton: ... Derivative.

Tech Support Cheat Sheet

Tech Support Cheat Sheet

https://www.xkcd.com/627

https://www.explainxkcd.com/wiki/index.php/627:_Tech_Support_Cheat_Sheet

Dear various parents, grandparents, co-workers, and other "not computer people." We don't magically know how to do everything in every program. When we help you, we're usually just doing this: [There is a flowchart there. Numbers are included to improve clarity, and do not appear in the original.] Rectangle: Start. [Go to 1.] [1. Diamond] Find a menu item or button which looks related to what you want to do. [I can't find one - go to 2.] [Ok - go to 3.] [2. Diamond] Pick one at random. [I've tried them all - go to 4.] [Ok - go to 3.] [3. Rectangle] Click it. [Go to 5.] [4. Rectangle] Google the name of the program plus a few words related to what you want to do. Follow any instructions. [Go to 5.] [5. Diamond] Did it work? [Yes - go to 8.] [No - go to 6.] [6. Diamond] Have you been trying this for over half an hour? [Yes - go to 7.] [No - go to 1.] [7. Rectangle] Ask someone for help or give up. [End of flowchart.] [8. Rectangle] You're done! [End of flowchart.] Please print this flowchart out and tape it near your screen. Congratulations; you're now the local computer expert!

The main point of this comic is that many tech-savvy people may not know much about computers (and certainly don’t automatically know how to do everything someone may want help with). They just have developed an intuition which works in many situations. This intuition is shown here in the form of a diagram. In particular, the chart exposes the computer expert's secret ingredient: trial and error. A flowchart is an organizational tool for showing process flow. A box is an instruction, a diamond indicates a question, and the arrows control the flow from one symbol to another. Other flowchart comics can be found here . The title text is a sad admission that even knowing the procedure for how to fix the problem, many people will not follow it and still call their presumably more tech-savvy children. (In a minority of cases, it may be that the person did try to follow it, and still ended up at the "Ask someone for help or give up" step.) In this case the father of Megan calls her to help print the flowchart to put near his computer so he can be the computer wiz... This is one of the cases where the name Megan is used, without the character Megan being drawn in the comic. Dear various parents, grandparents, co-workers, and other "not computer people." We don't magically know how to do everything in every program. When we help you, we're usually just doing this: [There is a flowchart there. Numbers are included to improve clarity, and do not appear in the original.] Rectangle: Start. [Go to 1.] [1. Diamond] Find a menu item or button which looks related to what you want to do. [I can't find one - go to 2.] [Ok - go to 3.] [2. Diamond] Pick one at random. [I've tried them all - go to 4.] [Ok - go to 3.] [3. Rectangle] Click it. [Go to 5.] [4. Rectangle] Google the name of the program plus a few words related to what you want to do. Follow any instructions. [Go to 5.] [5. Diamond] Did it work? [Yes - go to 8.] [No - go to 6.] [6. Diamond] Have you been trying this for over half an hour? [Yes - go to 7.] [No - go to 1.] [7. Rectangle] Ask someone for help or give up. [End of flowchart.] [8. Rectangle] You're done! [End of flowchart.] Please print this flowchart out and tape it near your screen. Congratulations; you're now the local computer expert!

Psychic

Psychic

https://www.xkcd.com/628

https://www.explainxkcd.com/wiki/index.php/628:_Psychic

[Cueball is talking with Megan.] Cueball: I'm psychic, you know. Megan: There's no such thing. [In a frame-less panel they continue to talk.] Cueball: Okay, think of a number from one to one hundred. Megan: Okay. Cueball: 43. Megan: Holy shit! [Cueball lifts one hand towards Megan.] Cueball: I try not to let it affect my life too much. Megan: Wait, I can't believe this. [Cueball turns and walks away, but stretches his arm back out towards Megan, who is still just standing looking after him.] Cueball: Don't worry about it. Forget I said anything. Megan: But- Cueball: Let's get to the movie. Megan: I, uh... OK, sure. [Caption below the last two panels:] This trick may only work 1% of the time, but when it does, it's totally worth it.

A psychic is a person who is able to access information that is beyond normal sensory perception through extrasensory perception. This information may vary widely in scope and value, ranging from archaeological to the ability to read minds. Cueball describes himself as such a person, to which Megan responds with disbelief because it is a bold and unsupported claim. To prove his abilities, Cueball has Megan think of a random number from 1 to 100, which he then guesses correctly to demonstrate his ability to read minds. Megan is amazed that Cueball was correct, but he simply dismisses her disbelief and wants to go back to pretending to lead a normal life. The four panels are actually a setup to the real joke in this comic: the final sentence spoken by a narrator. It reveals that Cueball has simply played a trick on Megan and that anyone can repeat it. The joke is that, theoretically, a person can guess a random number from 1 to 100 once in one hundred tries, or 1% of the time, according to the law of large numbers . By playing this trick enough times on enough friends, the trickster is statistically likely to get a number right eventually. Assuming the person whose number he guesses is not familiar with the trick, it will appear as if the trickster is actually psychic. Should this happen, the trickster can then play the joke out as he wants, hence the "it's totally worth it" at the end. The title text appeals again to statistics. People are poor random-number generators —e.g. being less likely to pick numbers at the extremes or exactly in the middle. Knowing this, the 'psychic' could restrict his guesses accordingly, improving his odds of guessing correctly. Randall has made several smaller references to the number 42 as the answer to the ultimate question about the universe from Douglas Adams Hitchhikers Guide to the Galaxy (for instance in this message from 1608: Hoverboard , and the vision test in 1213: Combination Vision Test . This could be the reason he chose 42+1 as his guess. He both knows Megan, and knows that she knows him. So thinking that he may suspect she would choose 42, she thus adds one, to not choose that exact number... Cueball took a similar reasoning based on his knowledge of Megan and himself, and was lucky this time. Maybe thus increasing his chance to more than 1% as from the title text. [Cueball is talking with Megan.] Cueball: I'm psychic, you know. Megan: There's no such thing. [In a frame-less panel they continue to talk.] Cueball: Okay, think of a number from one to one hundred. Megan: Okay. Cueball: 43. Megan: Holy shit! [Cueball lifts one hand towards Megan.] Cueball: I try not to let it affect my life too much. Megan: Wait, I can't believe this. [Cueball turns and walks away, but stretches his arm back out towards Megan, who is still just standing looking after him.] Cueball: Don't worry about it. Forget I said anything. Megan: But- Cueball: Let's get to the movie. Megan: I, uh... OK, sure. [Caption below the last two panels:] This trick may only work 1% of the time, but when it does, it's totally worth it.

Skins

Skins

https://www.xkcd.com/629

https://www.explainxkcd.com/wiki/index.php/629:_Skins

[Cueball is packing luggage.] Voice: Where are you going? Cueball: Convention. Voice: What for? Cueball: Well, you know furries, right? Voice: Sure... [Cueball closes suitcase.] Cueball: We're furries whose animal identities have a thing for pretending to be humans. Voice: I see. [A convention. People sit behind booths in the background.] Cueball, with glasses and a mug: How's the weather? Megan: Great! I've been driving my car and having a job all day! Cueball: Did you meow? Megan: Not once!

Furries , which have been discussed in a previous comic , are people who really like anthropomorphic animals and may enjoy drawing them or dressing up as them. One of the most prominent elements of the furry community is furry conventions, where furries meet-and-greet each other, show off and engage in activities in their fursuits, sell furry-related media, and so on. Here, Cueball mentions furry identities. The grand majority of furries have a "fursona", that is, a furry animal with which they associate themselves. While there are different approaches towards creating a fursona, they tend to be an animal representation of either themselves or what they wish to be. These fursonas sometimes have quite a bit of background that explains their origins, their abilities, where they live, and their interests... even if their interests involve pretending to be humans. According to Cueball, "skins" are furries who have fursonas that like to pretend to be humans. In other words, skins are humans who pretend to be animals who pretend to be humans . The 4th panel magnifies the ridicule of the concept of skins, the skins at the convention behaving excitedly about events that actual humans usually consider mundane. This is further emphasized by the grammatically-correct but unnatural sounding phrases that they use (which could be similar to how humans imitating animal calls could sound). It is atypical to consider "having a job" to be an activity to emphasize doing in a day (it is more a description of a state of being rather than an activity as such), and even stranger to say that in response to a question about the weather. This concept would be repeated in the title text of comic 1530 . If this comic satirizes furry conventions, then the title text satirizes fursuits. In this case, there are skins who wear fursuits of their fursonas, but, since their fursonas like to pretend that they are humans, these skins wear human suits over their fursuits. Such a setup would seem unwieldy, so there are skins who avert this by simply taking off their fursuits, going to the conventions as their human selves, thus technically integrating into the whole "skin atmosphere". Possible problems from this can include the "wear a human suit" skins getting angry at the "take off the fursuit" skins for "ruining the fantasy atmosphere" (since, technically, the real-life skin is not the same that would be the fursona's human facade, especially if the skin makes no effort to change the appearance to fit the human facade), or again, because they are too "cheap" or "lazy" to make or otherwise obtain the two suits. This clash of ideals would cause a lot of drama, something that furries ( or all other subcultures ) are no stranger to. [Cueball is packing luggage.] Voice: Where are you going? Cueball: Convention. Voice: What for? Cueball: Well, you know furries, right? Voice: Sure... [Cueball closes suitcase.] Cueball: We're furries whose animal identities have a thing for pretending to be humans. Voice: I see. [A convention. People sit behind booths in the background.] Cueball, with glasses and a mug: How's the weather? Megan: Great! I've been driving my car and having a job all day! Cueball: Did you meow? Megan: Not once!

Time Travel

Time Travel

https://www.xkcd.com/630

https://www.explainxkcd.com/wiki/index.php/630:_Time_Travel

[Megan has entered the scene from the left, and has her arms raised. Cueball is eating something (possibly a bagel?) and looking over his shoulder at Megan.] Megan: I've traveled here from the year 1983 to say this: Megan: Are there any bagels left? Caption: While it's technically true, I wish she'd stop prefacing every sentence with that.

Megan prefaces her statements with "I've traveled here from the year 1983 [likely the year of her birth] to say this." The statement is (assuming 1983 to be her birth year or, at least, a year she lived during) perfectly valid, albeit not very meaningful. Its phrasing implies a form of time travel other than the normal one minute per minute that everybody is subject to, even though this is not the case. This gives more emphasis to whatever she is about to say, which is instead quite anticlimactic and mundane. Cueball notes this but still wishes that she would stop saying that as it is superfluous and captures more attention than her statement is actually worth. It would also get annoying to hear that same line repeated numerous times. The title text continues this idea of Megan inserting another superfluous - although true - forwards to her letters. It's technically true because the letter will arrive at the recipient some time in the future, but this is not the way most salutations that begin "Dear Future <name>" are meant. Many schoolchildren are assigned to write letters to their future selves as an exercise in reflection and thinking about the future, but addressing every letter this way would likely become annoying. [Megan has entered the scene from the left, and has her arms raised. Cueball is eating something (possibly a bagel?) and looking over his shoulder at Megan.] Megan: I've traveled here from the year 1983 to say this: Megan: Are there any bagels left? Caption: While it's technically true, I wish she'd stop prefacing every sentence with that.

Anatomy Text

Anatomy Text

https://www.xkcd.com/631

https://www.explainxkcd.com/wiki/index.php/631:_Anatomy_Text

Plate 15: Female breast [There is a drawing of a breast, with 'breast', 'areola', and 'nipple' labeled.] Plate 16: External female genitalia [There is a picture of external female genitalia. 'labia majora', 'labia minora', 'clitoris', 'urethral opening', and 'vagina' are labeled. Voice #1's speech bubble partly covers the middle of the genitalia.] Voice #1: HEY! Plate 17: External male genitalia [There is salt, ketchup, and mustard to one side.] Voice #2: Shit! Voice #1: What the hell? You can't do that in here. Voice #2: Megan, get off the table! Voice #2: Grab the tripod! Plate 18: Erect Penis [The picture appears to be at an angle. Megan is running.] Voice #1: We're calling the cops! Voice #2: RUN! Voice #1: TGI Friday's is a family establishment!

Megan and a person not shown person are taking photos of their own anatomy for inclusion in relevant Wikipedia articles. This is one of the few comics where Megan is named, and also one of the few comics to feature speech bubbles. It is revealed that instead of taking these photos at home or in a professional studio , they are shooting at a TGI Friday's restaurant. TGI Friday's is an American multinational restaurant chain known for its casual family-friendly atmosphere, upbeat service, and fried appetizers. Megan's and the person's behaviour is of course highly inappropriate, due to the sanitation issues relating to sitting or laying naked on the tables, as well as public decency issues; nudity is illegal in most public places, and this is compounded by the fact that there are usually children in TGI Friday's. The message implicit in the comic (and stated outright in the title text) is that careful cropping can produce useful, apparently professional reference images, even if the source photograph was not taken in a professional manner, or was pornographic in nature. Plate 15: Female breast [There is a drawing of a breast, with 'breast', 'areola', and 'nipple' labeled.] Plate 16: External female genitalia [There is a picture of external female genitalia. 'labia majora', 'labia minora', 'clitoris', 'urethral opening', and 'vagina' are labeled. Voice #1's speech bubble partly covers the middle of the genitalia.] Voice #1: HEY! Plate 17: External male genitalia [There is salt, ketchup, and mustard to one side.] Voice #2: Shit! Voice #1: What the hell? You can't do that in here. Voice #2: Megan, get off the table! Voice #2: Grab the tripod! Plate 18: Erect Penis [The picture appears to be at an angle. Megan is running.] Voice #1: We're calling the cops! Voice #2: RUN! Voice #1: TGI Friday's is a family establishment!

Suspicion

Suspicion

https://www.xkcd.com/632

https://www.explainxkcd.com/wiki/index.php/632:_Suspicion

[Rob is sitting at a computer, typing.] Rob: I've loved our online chats these past few months, Lisa. Computer: Me too. I really like you, Rob. [Rob continues to type.] Rob: It's just... now and then you mention products you like, and... I worry. Computer: What? Honey... [Rob types.] Rob: Before this goes any further, I think we should go get tested. You know, together. Computer: You don't trust me? Rob: I just want to be sure. [A web browser is open.] VK Couples Testing Test ID: 21871138 Waiting...Partner connected. (A pair of CAPTCHA images) [You] Library [Partner] Kittens Rob: Okay, mine says "library". Yours? Computer: I... uh... Rob: Oh god. Computer: I'm more than a spambot! Our love was real! Rob: Goodbye, Lisa.

Rob is having online chats with what appears at first glance to be a woman. However, he grows suspicious at the apparent consumerism dedication of the "woman" - and perhaps of the perfection of the online connection, touching on the stereotypical nerd fear that any relationship going well must contain some secret flaw - and so requests that they both "get tested". The woman on the other end of the computer does not pass a CAPTCHA test and is unable to prove she is a human. In using the phrase "get tested", the comic is making a joke that refers both to the CAPTCHA test above and the STD or VD test that couples will take to make sure they are physically free of communicable diseases. A spambot is an automated program (comparable in many ways to a robot) that sends out emails or links (such as in the title text) to simulate a human's writing but contains advertising. The test that Rob and "Lisa" take is called "VK", a reference to the Voight-Kampff empathy tests from the novel Do Androids Dream of Electric Sheep and film Blade Runner . The test in these works is intended to distinguish real humans from very realistic humanoid robots called "replicants". Both CAPTCHAs and the Voight-Kampff test are related to the Turing test , a way to measure the degree to which a computer can successfully imitate a human. The name "Lisa" may be an allusion to ELIZA , one of the first chatbots, written in 1966. According to its (her?) creator, people became "quickly and deeply emotionally involved with the computer program" during the chat. "Lisa" may also reference the computer girlfriend Lisa from the 1985 movie Weird Science The title text is the spambot's last sad goodbye — it includes lots of product advertisements and links, such as an online advertiser may insert into a search results page. 329: Turing Test is another comic dealing with Turing tests/CAPTCHAs. [Rob is sitting at a computer, typing.] Rob: I've loved our online chats these past few months, Lisa. Computer: Me too. I really like you, Rob. [Rob continues to type.] Rob: It's just... now and then you mention products you like, and... I worry. Computer: What? Honey... [Rob types.] Rob: Before this goes any further, I think we should go get tested. You know, together. Computer: You don't trust me? Rob: I just want to be sure. [A web browser is open.] VK Couples Testing Test ID: 21871138 Waiting...Partner connected. (A pair of CAPTCHA images) [You] Library [Partner] Kittens Rob: Okay, mine says "library". Yours? Computer: I... uh... Rob: Oh god. Computer: I'm more than a spambot! Our love was real! Rob: Goodbye, Lisa.

Blockbuster Mining

Blockbuster Mining

https://www.xkcd.com/633

https://www.explainxkcd.com/wiki/index.php/633:_Blockbuster_Mining

[Cueball holds a script in his hands.] Cueball: We've acquired some new rights, but I'm not sure it's in the spirit to make it a blockbuster-- Voice: Do it anyway. Take $100 million, hire Michael Bay. Cueball: But-- Voice: NEXT! [Panel is inverted, white on black background.] [Two men, played by Cueball-like actors are pointing machine guns at Harriet, played by a Megan-like actress. Harriet points two handguns back at them.] Harriet: They said if I were captured I should take my own life. Harriet: But I'd just as soon take yours. [Harriet jumps off a cliff carrying a spiral notebook and a gun, while the cliff explodes behind her. In the background is a helicopter, some mountains, and the sea.] BOOM [Panel is inverted, white and red on black background.] [A man played by a Cueball-like actor is tied to a chair. Blood is pooling on the ground below. Harriet stands in front, holding a bloody pipe.] Man: Stop! I'll talk! Harriet: No, I know everything. This is just for fun. [Crosshairs follow a Cueball-like man.] Harriet: I'll be watching. [The panel is inverted colour, white on black.] Harriet the [in red] SPY [A bloody spiral notebook, with blood streaks leading from it.] Apparently, Harriet the Spy was actually adapted into a film in 1996. Presumably [ citation needed ] it was more faithful to the novel than this xkcd.

Cueball has acquired the intellectual property rights to produce a movie, but is unsure of how to make it appealing to a wide audience. An off-screen character suggests hiring Michael Bay , a director and producer well known (and occasionally criticized) for his style of film adaptation. Cueball is unsure that the IP would be a good fit for a summer blockbuster, but is dismissed. The following panels depict violent and gritty scenes from a spy thriller, starring an unknown and brutal female spy. In the last panel, she is revealed to be Harriet the Spy , the 11 year old protagonist of a bestselling children's book written by Louise Fitzhugh, as well as other spinoff books written by various other authors. The comic references Hollywood's search for new stories to adapt to film, and how poor (not to mention violent ) some of these adaptations can be. There is additional humor in the fact that the original novel is about school-child concerns such as friends and is not violent. The film adaptation of Bridge to Terabithia had trailers that made it appear to have very little in common with the themes and tone of the novel. The actual movie is one of Hollywood's better book adaptations [1] but the trailers were extremely misleading and off-putting to fans of the novel, as in the title text. Viewers who were unfamiliar with the novel and saw the movie with expectations based on the trailer were also unprepared for the actual movie [2] . The trailer was essentially every single special-effect shot from the movie, giving the impression it was a special-effects extravaganza, which would have been very inappropriate based on the novel, and does not reflect the actual content of the movie. The film adaptation of Where the Wild Things Are was met with favorable responses from critics , the public, and the book's author . [Cueball holds a script in his hands.] Cueball: We've acquired some new rights, but I'm not sure it's in the spirit to make it a blockbuster-- Voice: Do it anyway. Take $100 million, hire Michael Bay. Cueball: But-- Voice: NEXT! [Panel is inverted, white on black background.] [Two men, played by Cueball-like actors are pointing machine guns at Harriet, played by a Megan-like actress. Harriet points two handguns back at them.] Harriet: They said if I were captured I should take my own life. Harriet: But I'd just as soon take yours. [Harriet jumps off a cliff carrying a spiral notebook and a gun, while the cliff explodes behind her. In the background is a helicopter, some mountains, and the sea.] BOOM [Panel is inverted, white and red on black background.] [A man played by a Cueball-like actor is tied to a chair. Blood is pooling on the ground below. Harriet stands in front, holding a bloody pipe.] Man: Stop! I'll talk! Harriet: No, I know everything. This is just for fun. [Crosshairs follow a Cueball-like man.] Harriet: I'll be watching. [The panel is inverted colour, white on black.] Harriet the [in red] SPY [A bloody spiral notebook, with blood streaks leading from it.] Apparently, Harriet the Spy was actually adapted into a film in 1996. Presumably [ citation needed ] it was more faithful to the novel than this xkcd.

Date

Date

https://www.xkcd.com/634

https://www.explainxkcd.com/wiki/index.php/634:_Date

[Two people are sitting at a table, with a candle-lit dinner. Cueball is holding up a sheet of paper, and Megan is scribbling.] Cueball: Both my parents were colorblind, so... Megan: Hey, if we made more than two, we'd have a better-than-even chance of adorable red hair. Cueball: Ooh, and check this: green eyes! Trivia: 30% of biologist first dates disintegrate into making Punnett squares.

Cueball and Megan (as biologists) are on a first date. As opposed to the usual romantic talk or discussion about each other's histories or character, the comic suggests that 30% of the time, two biologists on a first date will end up making Punnett squares , which non-biologists might not consider very interesting or romantic. The comic may be a play on the idea that couples on a first date might wonder about (or on a very promising date, even discuss) the traits in the other person that might be passed on to potential children. A Punnett square is a simple diagram used in biology to determine the probable resulting genotype of cross-breeding two organisms, be they plant or animal (including humans). The diagram shows all possible results of crossing a single genotype from each parent in the offspring genotype following Mendelian inheritance . For humans and most animals, there are two alleles for each gene, and each parent passes one of their alleles for each gene on to the offspring. The most simple Punnett square is a 2x2 table with a legend of the two paternal alleles on one axis (e.g.: A and A ) and the two maternal alleles on the other axis (e.g.: A and a ). Each box of the Punnett square represents a possible genetic outcome as a result of each each of the alleles being passed on to the offspring ( AA , Aa , AA and Aa ). For certain genetic traits, one genotype may determine a specific trait in the offspring; e.g. black hair in rats. Certain genotypes have dominant and recessive alleles. An offspring must have both of the recessive alleles to display the recessive trait; in the above example, if "a" was an allele for a recessive trait, the offspring could not have the recessive trait, as there is no possible aa outcome. This is the basic principles that allows statements to be made that two parents with a certain blood type or eye colour could not possibly have an offspring with a certain other blood type or eye colour. More complicated Punnett squares can factor in multiple genes and be larger in scale, but ultimately follow the same principle. The premise for the purposes of the comic is that by using Punnett squares, one can assess the likelihood of certain genetic traits (such as hair colour or colour blindness) in their offspring with another person. One would have to know their genetic makeup in general for this to be possible. While a genotype refers to the genetic makeup of an organism, a phenotype as referenced in the title text refers to the resulting traits (e.g.: Red hair is a phenotype). The traits mentioned by Cueball and Megan are all genetic traits which can be traced using Punnett squares. That said, at least two of the traits (green eyes and color blindness) are not traits determined by a simple single-gene interaction. Colour blindness can be inherited, although there are a significant number of genes that can factor into various types of color blindness. Red green color blindness, the most common variety, is sex linked to the X chromosome. Because of the way X chromosomes are passed, if Cueball's mother was colorblind then Cueball would be, though his faulty X chromosome could only be passed to a daughter who would need another faulty X from her mother to inherent colorblindness. Once thought to have fairly simple genetic factors, eye color is now known to be a factor of at least 15 different genes with almost any parent-child combination possible. Red hair is still believed to be a recessive trait associated with a small number of genes (perhaps even one gene), although other traits once thought to be determined by only one gene have since been proven otherwise. [Two people are sitting at a table, with a candle-lit dinner. Cueball is holding up a sheet of paper, and Megan is scribbling.] Cueball: Both my parents were colorblind, so... Megan: Hey, if we made more than two, we'd have a better-than-even chance of adorable red hair. Cueball: Ooh, and check this: green eyes! Trivia: 30% of biologist first dates disintegrate into making Punnett squares.

Locke and Demosthenes

Locke and Demosthenes

https://www.xkcd.com/635

https://www.explainxkcd.com/wiki/index.php/635:_Locke_and_Demosthenes

[The "real" names and the fact that the squirrel is vomiting comes from the official transcript on xkcd.] [Valentine (a.k.a. Demosthenes, with long dark hair), is laying on her back on the ground looking up at the sky with her hands behind her head. Peter (a.k.a. Locke, looking like Cueball) is attracting a squirrel with some food his hand.] Valentine: Ender's up there saving the world, but down here it's falling apart politically. What can we do? [Peter turns towards and sits down, leaning back on one hand. Valentine sits up in a similar position. Her hair looks like a mix between Megan and Hairbun's hair. The squirrel behind Peter is bending over the food Peter has thrown out for it.] Peter: I know — we get on the nets and anonymously post political opinions. People reading our articles will see our intelligence, recognize how clear and logical our arguments are, and insist that we be put in charge, so we can fix everything! Valentine: Brilliant! [Beneath the first two panel is large panel displaying a blog page. The background is light gray and then there are four white rectangular sections with rounded corners.] [There is a heading in the top central section:] Locke Powered by Wordpress [Below is the largest section, which extends below the panel. It has a scroll bar to the right which is partly scrolled down. The last sentence of a post can be seen at the top, with a time stamp below. Then follows the heading of a new post and the first line of this, which is partly cut off at the bottom of the panel:] which is why we must reach out to the Russian leadership. Posted at 3:15AM by Locke Comments (0) The Problem with China In recent months much has been made of [To the right is two sidebars. The top one shows recent posts:] Recent posts: >> A few thoughts on... Comments (0) >> Russian Aggression... Comments (1) >> Trade policy and the... Comments (0) >> And one more thing... Comments (0) >> Everyone's wrong about... Comments (1) [Below this is list of links to other websites, this section also extends below the panel. The second link is partly cut off at the bottom of the panel, so it is not possible to see that this is probably also underlined:] Blogroll: >> Demosthenes >> FiveThirtyEight

This comic re-imagines a scene from Ender's Game , by Orson Scott Card . This is shown in the first two panels depicting the siblings Locke and Demosthenes , as Cueball and the girl. Their real names are Peter and Valentine Wiggin (and these first names are used in the official transcript on xkcd). In the book these two kids write their opinions on their world's version of the internet to gain extreme political influence. Below is a synopsis: Spoiler alert! In the book Ender is an above-average-intelligence boy who is selected to become a potential leader of Earth's "Defense" Forces in the event of another Bugger invasion (later re-titled the Formic invasions). Meanwhile, Ender's two older siblings, Peter and Valentine decide to save the world from itself. They do this by asserting themselves as wise demagogues who comment on political events on what are known as the "free nets" which are nets open to comment by anyone in the world. They choose pseudonyms to write under, as no one would take the words of children seriously, choosing Locke (Peter's pseudonym), and Demosthenes (Valentine's). Eventually they gain enough respect to be invited to participate in moderated political debates in the higher class nets. By the end of the book, Peter has become the leader of the world, and Valentine runs away with Ender to a planet formerly inhabited by Buggers to live out their lives in peace. End spoiler alert! Ender's Game was published in 1985, when most people had never used (and some had never heard of) the internet. The first webpage set up with individual personal opinions (leaving out forums and bulletin board services) was online in 1994, the word "weblog" was invented in 1997 and "blog" in 1999. When Orson Scott Card wrote Ender's Game , Peter and Valentine's plan was based on a sci-fi idea expected to occur in the near future. However, this apparently science-fictional future concept is now just the mundane (and extremely un-influential) act of blogging. In 1985, Orson Scott Card's idea of how politics works in practice may have seemed a little naive, but now that blogging is an everyday phenomenon, Peter and Valentine's aspirations seem downright silly. We see their plan to win vast political influence manifest itself as a WordPress blog, and a particularly unimportant one at that, with 0 comments on most posts. The joke hinges on the underwhelming reversal of Peter and Valentine's expectations. It forms both a parody of science fiction that has been rendered outdated by technology, and also a parody of the expectations well-intentioned people have going onto the internet to express their opinions. The titles of Peter's blog posts parody the arrogance of internet commentators, with names beginning with things like "Everyone's wrong about..." This further underscores the lack of influence his WordPress blog would have and his naivete, as this is a typically unconvincing way to speak to people about politics, but someone with the arrogance to think everyone will naturally see their genius and insist they be put in charge of the world would not realise it. In the bottom right corner there are links to other blogs. One is for Demosthenes, but the other is for FiveThirtyEight , a real political blog that was founded by Nate Silver in 2008, more than a year before this comic was released. It was still owned by Nate in 2009, the year of this comic's release, but in 2010 the blog became a licensed feature of The New York Times online and in July 2013, ESPN announced that it would become the owner. The blog takes its name from the number of electors in the United States electoral college: 538. It is a website that focuses on opinion poll analysis, politics, economics, and sports blogging. Nate Silver has been referenced , several times in xkcd, though mainly in the title text, before this comic for instance in 500: Election . The title text uses Locke's full name, Peter Wiggin, and is formed as a short letter that informs him that he has become the president of the world, and that he should meet tomorrow 8:00 sharp at the United Nations (UN) headquarters. This is either a very child-like representation of how a presidential appointment might be announced or a sarcastic comment someone has left on his blog — either way, further riffing on the naivete of the plan in the first place. Also note that the note is addressed to "Peter" rather than "Locke"; Peter's attempt to remain anonymous has failed miserably. During their conversation, Peter is shown feeding a squirrel. In Ender's Game the character of Peter Wiggin is a sadistic sociopath - and there is a particular scene in the book where Valentine stumbles across a skinned squirrel still twitching in pain. xkcd has referenced Ender's Game before this, specifically in 241: Battle Room , dealing with Ender's experience during his training, and 304: Nighttime Stories , dealing with the sequels to Ender's Game. [The "real" names and the fact that the squirrel is vomiting comes from the official transcript on xkcd.] [Valentine (a.k.a. Demosthenes, with long dark hair), is laying on her back on the ground looking up at the sky with her hands behind her head. Peter (a.k.a. Locke, looking like Cueball) is attracting a squirrel with some food his hand.] Valentine: Ender's up there saving the world, but down here it's falling apart politically. What can we do? [Peter turns towards and sits down, leaning back on one hand. Valentine sits up in a similar position. Her hair looks like a mix between Megan and Hairbun's hair. The squirrel behind Peter is bending over the food Peter has thrown out for it.] Peter: I know — we get on the nets and anonymously post political opinions. People reading our articles will see our intelligence, recognize how clear and logical our arguments are, and insist that we be put in charge, so we can fix everything! Valentine: Brilliant! [Beneath the first two panel is large panel displaying a blog page. The background is light gray and then there are four white rectangular sections with rounded corners.] [There is a heading in the top central section:] Locke Powered by Wordpress [Below is the largest section, which extends below the panel. It has a scroll bar to the right which is partly scrolled down. The last sentence of a post can be seen at the top, with a time stamp below. Then follows the heading of a new post and the first line of this, which is partly cut off at the bottom of the panel:] which is why we must reach out to the Russian leadership. Posted at 3:15AM by Locke Comments (0) The Problem with China In recent months much has been made of [To the right is two sidebars. The top one shows recent posts:] Recent posts: >> A few thoughts on... Comments (0) >> Russian Aggression... Comments (1) >> Trade policy and the... Comments (0) >> And one more thing... Comments (0) >> Everyone's wrong about... Comments (1) [Below this is list of links to other websites, this section also extends below the panel. The second link is partly cut off at the bottom of the panel, so it is not possible to see that this is probably also underlined:] Blogroll: >> Demosthenes >> FiveThirtyEight

Brontosaurus

Brontosaurus

https://www.xkcd.com/636

https://www.explainxkcd.com/wiki/index.php/636:_Brontosaurus

[Cueball and Megan are sitting at a bench. Megan is holding a turtle.] Megan: Our love is like a turtle. [Megan sets down the turtle and turns to Cueball. They hold hands.] Megan: Humble and simple, enduring by virtue of perfect design. Cueball: Our love is like a brontosaurus. Cueball: Recognized as a mistaken combination long ago, lingering only out of misplaced affection for an imagined past.

Megan describes her relationship to Cueball with the simile "our love is like a turtle," a comparison often made when referring to a shy and slowly developing yet steady sort of romance. However, Cueball thinks that the Brontosaurus is a better comparison. His explanation refers to the fact that remains of a certain apatosaurine were initially named Brontosaurus excelsus by the paleontologist O.C. Marsh in 1879. This species was later determined in 1903 to be in the same genus as Apatosaurus ajax , which Marsh had named two years before B. excelsus : the older genus name is preferred according to convention (making the preferred binomial Apatosaurus excelsus ). The term Brontosaurus therefore became a scientific redundancy (a so-called junior synonym), and had this status at the time of this comic's release. Due to the correct skull for an apatosaurine not being confirmed until 1978 , the term "brontosaurus" had in the meantime become popularly associated with an apatosaurine depicted with a speculative Camarasaurus -like head, hence the "mistaken combination" mentioned in the comic. Applied to the scenario in the comic, Cueball apparently considers the relationship without any emotional foundation and only continues it out of nostalgic motives. This conclusion counteracts the initial romantic tone adopted by the turtle simile, as comparing a romance with a falsely classified fossil is one of the least charming statements imaginable. [ citation needed ] The title text aims at Randall's well-known enthusiasm for Velociraptors . Megan retorts by comparing any future sex between the two of them to be as likely as finding a Velociraptor in his house. The insult has a second barb: painting Cueball as being obsessed with movies involving Velociraptor s. Randall has previously mentioned the Brontosaurus name change in 460: Paleontology . The Apatosaurus also appears in 15: Just Alerting You and 650: Nowhere . However the status of "Brontosaurus" remains under discussion, with a 2015 study of diplodocids reporting that the more gracile fossils should be classified in a separate genus. This would re-divide the apatosaurines between the Brontosaurus and Apatosaurus genera. [Cueball and Megan are sitting at a bench. Megan is holding a turtle.] Megan: Our love is like a turtle. [Megan sets down the turtle and turns to Cueball. They hold hands.] Megan: Humble and simple, enduring by virtue of perfect design. Cueball: Our love is like a brontosaurus. Cueball: Recognized as a mistaken combination long ago, lingering only out of misplaced affection for an imagined past.

Scribblenauts

Scribblenauts

https://www.xkcd.com/637

https://www.explainxkcd.com/wiki/index.php/637:_Scribblenauts

[Megan is sitting on bed.] [In Scribblenauts word input format.] LARGE HADRON COLLIDER Click Megan: Wow, Scribblenauts even lets you summon the LHC. [Cueball is sitting at a computer. Megan talks from off-panel.] Fwoosh Megan: And it makes a black hole! This game rules. Cueball: I guess it's okay, for a DS kids game. [In Scribblenauts word input format.] PRETENTIOUS ASSHOLE Click [Megan looks up.] Megan: Oh, hi! It worked!

Scribblenauts is a game for the Nintendo DS in which the player controls a character named Maxwell, whose goal is to get a "Starite" in each level. The player has the ability to summon over 22,000 different objects into the game by typing them on the touchscreen using the DS's stylus device. Those items are then ostensibly used to help Maxwell collect the Starite (for example, typing "ladder" to help him reach a Starite that's inside a tree), but the player can decide to forgo the objective and just type in random things for fun. The Large Hadron Collider is the world's largest and highest-energy particle accelerator, and has excited the imagination of writers and journalists in popular culture, some of whom posit the theory that a catastrophic accident at the LHC could destroy the world. One of those ideas concerned the LHC creating a black hole that would proceed to suck in all the surrounding matter. However, in the game, the LHC, when tapped, creates a comically small black hole which only kills Maxwell. Megan discovers that the LHC can be summoned in Scribblenauts, and has a fun time creating black holes with it. Cueball's snide comment is an unfortunately rather common reaction among adults towards entertainment geared for children, and the fact that Scribblenauts is a portable game just gives him another stick to beat it with. Irritated, Megan types in the phrase "pretentious asshole", and then pretends that Cueball has suddenly appeared. It is unclear whether she is reffering to Cueball spawning in-game, or his presence in the real world. Note that, in reality, Scribblenauts doesn't respond to profanity. In the title text, she types "guy who's just jealous that I beat all his Mario Kart times" (this could be a reference to 423: Finish Line and 290: Fucking Blue Shells ) and once again, Cueball "appears" right in front of her. Mario Kart is another video-game series geared towards children, and there's a version of it for the DS, which implies that Cueball's just being snooty about Scribblenauts because Megan has so thoroughly dominated him in another "DS kids game". [Megan is sitting on bed.] [In Scribblenauts word input format.] LARGE HADRON COLLIDER Click Megan: Wow, Scribblenauts even lets you summon the LHC. [Cueball is sitting at a computer. Megan talks from off-panel.] Fwoosh Megan: And it makes a black hole! This game rules. Cueball: I guess it's okay, for a DS kids game. [In Scribblenauts word input format.] PRETENTIOUS ASSHOLE Click [Megan looks up.] Megan: Oh, hi! It worked!

The Search

The Search

https://www.xkcd.com/638

https://www.explainxkcd.com/wiki/index.php/638:_The_Search

[Two ants are facing each other with their antennas almost touching. They are on a tiled floor with the two nearest rows of tiles fully shown, and those further back covered partly be the speech text of the ant to the right.] Ant: We've searched dozens of these floor tiles for several common types of pheromone trails. Ant: If there were intelligent life up there, we would have seen its messages by now. [Caption below the panel:] The world's first ant colony to achieve sentience calls off the search for us.

This comic is a commentary on the search for extraterrestrial intelligence. The ants' dialogue describes the narrow scope of their search (a few tiles, and only looking for pheromone trails), and thus they conclude that there is no other intelligent life. The irony is that humanity does of course exist, [ citation needed ] but were simply not present in the kitchen at the time of search, nor do we communicate with ant pheromones. [ citation needed ] Similarly, our ability to search outer space for other life is limited to our ability to detect specific modes of communication (i.e. radio waves) and to the very limited area of space imposed by technological limitations on transportation, range, and sensitivity of our equipment. The title text refers to the Kepler mission to discover Extrasolar planets . In August 2009, a couple of weeks before this comic, the first results of this mission were released, which showed the spacecraft to be healthy and had detected a known exoplanet. No new science results would be released until November of 2009, which Randall was anticipating. This mission has found more than 2,700 planet candidates that still have to be confirmed by other telescopes. So that's the difference to the ants. As of August 2013, two "reaction wheels" (heavy metallic discs that can be spun to impart angular momentum to the probe, mounted on the major axis; an alternative to reaction thrusters, which require a depletable supply of reaction fuel) on Kepler have failed, causing NASA to change the mission, though it will still be looking for planets with its two remaining wheels. The second part is a bait-and-switch joke; by calling the search for extrasolar planets "the second most important thing our species has ever done", it creates the expectation that the "first most important thing" will be a monumental breakthrough, such as for example the concept of language. Instead, the title text ends up just revealing that Randall likes having pizza delivered. [Two ants are facing each other with their antennas almost touching. They are on a tiled floor with the two nearest rows of tiles fully shown, and those further back covered partly be the speech text of the ant to the right.] Ant: We've searched dozens of these floor tiles for several common types of pheromone trails. Ant: If there were intelligent life up there, we would have seen its messages by now. [Caption below the panel:] The world's first ant colony to achieve sentience calls off the search for us.

Lincoln-Douglas

Lincoln-Douglas

https://www.xkcd.com/639

https://www.explainxkcd.com/wiki/index.php/639:_Lincoln-Douglas

[Abraham Lincoln stands before an audience.] Stephen Douglas: Oh yeah? Well, fourscore and seven years ago your MOM brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal! After his 1860 loss to Lincoln, Stephen Douglas's famed debating skills entered a rapid decline.

The Lincoln-Douglas debates of 1858 were a series of seven debates between Abraham Lincoln and Stephen Douglas , respectively the Republican and Democratic nominees for a U.S. Senate seat in Illinois (Douglas was the incumbent). All seven debates were devoted to the topic of slavery, a red-hot issue in the United States that played a significant role in precipitating American Civil War. Although Lincoln ultimately lost the election, he had the edited text of the debates published in a book. The book's popularity and widespread media coverage of the original debates helped put his name on the map in American politics, leading to his nomination for President of the United States by the Republican party in 1860. Lincoln went on to win the election (Douglas was one of his opponents in this race), after which point several states immediately seceded and formed a separate government, the Confederate States of America . The Confederacy attacked Fort Sumter in April 1861, sparking the American Civil War , a vicious conflict between the states that would last for four years. In 1863, the Union Army of the Potomac defeated the Confederate Army of Northern Virginia at the Battle of Gettysburg in Gettysburg, Pennsylvania. Four and a half months later, President Lincoln delivered the Gettysburg Address , to dedicate the Soldiers' National Cemetery. The Address, less than three minutes long, became one of the most famous speeches in American history; millions of schoolchildren have memorized it verbatim in the 150 years since. In this comic, Stephen Douglas heckles President Lincoln after the opening sentence of the Gettysburg Address with a juvenile "your mom" joke, which is both anachronistic and not up to Douglas's usual elegant standards of debate. The only difference from the original speech is that "our fathers" is replaced with "your mom". The title text admits that Douglas actually died soon after the election (passing away in June 1861), but suggests the webcomic Hark! A Vagrant , written by Kate Beaton , if you're looking for historical accuracy in your webcomics. Hark!'s usual topics are historical or literary figures. [Abraham Lincoln stands before an audience.] Stephen Douglas: Oh yeah? Well, fourscore and seven years ago your MOM brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal! After his 1860 loss to Lincoln, Stephen Douglas's famed debating skills entered a rapid decline.

Tornado Hunter

Tornado Hunter

https://www.xkcd.com/640

https://www.explainxkcd.com/wiki/index.php/640:_Tornado_Hunter

[Two people are in a car, which is driving past a cactus. The passenger has a pith helmet and a mustache.] Cueball: The tornado's three miles west, moving northeast at 15 mph. Passenger: Go right; get ahead of it. [A tornado is visible. The passenger pulls out a gun, and stands up in the car.] Passenger: Okay, we're in range! Stop here! [The passenger fires the gun at the tornado.] BANG Tornado: AUGH! [The tornado is split in half by the bullet.] Passenger: Big one! Must be an F-3! Cueball: I'm not sure we're doing this right. Passenger: Help me mount it on the hood. [The passenger is holding the tornado by its tail.]

This is a play on the occupations/hobbies " tornado chaser " - someone who, instead of evacuating the area like normal people, actually goes in to get a closer look at the tornado - and " big game hunter ", who often kill for trophies. Tornado chasers are typically, but not always, meteorologists . Here, the tornado chaser actually hunts the tornado with a gun like big game, the joke being that this is not possible in real life. [ citation needed ] The "F-3" is a reference to the Fujita scale used to classify tornado intensity. It goes from 1 to 5, with 5 being the highest, with an updated Enhanced Fujita scale , as mentioned in the title text, being used in the US since 2007. The title text is an aside from Randall, saying that he finds the notation for the Enhanced Fujita scale (EF-#, for example EF-5 for a level 5 tornado,) to be stupid, and suggests that we continue to use the Enhanced Fujita scale to measure the strength of tornadoes, but abbreviate it to F instead, leading to the non-stupid "F-whatever" notation, 'whatever' signifying the number of the tornado on the scale. This is the second comic about tornadoes, a recurring subject on xkcd, but it was the first to actually show a tornado. Storm chasers hunting tornadoes was also mentioned in the first comic about tornadoes 402: 1,000 Miles North and they were also shown in 752: Phobia . [Two people are in a car, which is driving past a cactus. The passenger has a pith helmet and a mustache.] Cueball: The tornado's three miles west, moving northeast at 15 mph. Passenger: Go right; get ahead of it. [A tornado is visible. The passenger pulls out a gun, and stands up in the car.] Passenger: Okay, we're in range! Stop here! [The passenger fires the gun at the tornado.] BANG Tornado: AUGH! [The tornado is split in half by the bullet.] Passenger: Big one! Must be an F-3! Cueball: I'm not sure we're doing this right. Passenger: Help me mount it on the hood. [The passenger is holding the tornado by its tail.]

Free

Free

https://www.xkcd.com/641

https://www.explainxkcd.com/wiki/index.php/641:_Free

[A shelf holds 3 boxes of cereal. Each box shows a bowl of cereal.] GenCo Ⓞat Cereal StayPuft Oat Cereal RedFarm Oat Cereal (with additional text in a star) Asbestos-free! I hate whatever marketer first realized you could do this.

Asbestos is a fibrous material most commonly known and used for its heat-resistant properties. It was commonly used in housing insulation until its astonishingly destructive effects on human lungs were discovered. The use of asbestos in housing is now banned, but asbestos is still quite common in laboratory hot pads, as well as in concrete industrial buildings where the risk of it getting into the air is minimal. The comic depicts a common advertising trick taken to an absurd extreme; quite clearly all of the cereal products depicted are asbestos-free, but most have opted not to advertise that fact (if it even occurred to them at all) because it should be obvious. A more realistic example can be found in confectionery products, wherein the term " fat free" might be applied when it's clear that sugar , gelatin , and other ingredients involved in the product are in no way related to, or contain, fat. Note that in some countries, like Germany for example, this practice is actually not allowed, since it counts as "misleading advertising". While the suggestive implication might be that competitive products do not declare as asbestos free because they cannot truthfully say this, the irony may be that the "asbestos-free" disclaimer could also cause a customer to distrust the product on the grounds of damning by faint praise —if the best thing they can say about a product is that it doesn't contain a toxic building material, do we really want to know what actually is in this stuff? The claim in the title text—that a rival product has no swine flu —is equally superfluous, as any food product containing disease-causing viruses would be subject to recalls, severe fines, and quite a few people losing their jobs; the fact that the product is actually on a supermarket shelf implies that it already has a stellar reputation for not causing serious illness. [ citation needed ] The use of it here could also be a reference to 574: Swine Flu . The competing claims, however, sets up the hopefully false risks involved in whether to choose the one with definitely no asbestos (but possibly contains swine flu) or the other that definitely has no swine flu (but may include asbestos). Misleading advertising is also the subject of the previous comic 624: Branding , and of subsequent comics 870: Advertising and 993: Brand Identity . [A shelf holds 3 boxes of cereal. Each box shows a bowl of cereal.] GenCo Ⓞat Cereal StayPuft Oat Cereal RedFarm Oat Cereal (with additional text in a star) Asbestos-free! I hate whatever marketer first realized you could do this.

Creepy

Creepy

https://www.xkcd.com/642

https://www.explainxkcd.com/wiki/index.php/642:_Creepy

[Cueball and Megan are sitting on chairs, presumably on a train.] Cueball: Hey, cute netbook. Megan: What. [Zoomed in on Cueball and Megan.] Cueball: Your laptop. I just— Megan: No, why are you talking to me. [Zoomed in on Megan.] Megan: Who do you think you are? If I were even slightly interested, I'd have shown it. [Both Cueball and Megan, with Megan pointing at Cueball.] Megan: Hey everyone, this dude's hitting on me. Voice #1: Haha Voice #2: Creepy Voice #3: Let's get his picture for Facebook to warn others. [The previous panel fades into a thought bubble of Cueball.] [Cueball and are sitting on chairs, on the train, and Megan is typing on her laptop.] Dear blog, Cute boy on train still ignoring me.

This comic displays Cueball 's fears that his attempts to strike up a conversation with Megan will only result in her rejecting him and even humiliating him in front of others for attempting to get to know her - he might even risk getting his picture on Facebook with a warning that he is a creep to be avoided. This is because he worries that others might interpret his behavior as sexual harassment , the exaggerated flip-side of his attempted courtship. It turns out in the fifth and last panel that the first four panels was just one large thought bubble on how Cueball fantasized an attempt to contact Megan would turn out. Ironically, however, Megan is actually attracted to Cueball and is dismayed that he has not spoken to her. Therefore, Cueball's fears are unfounded and are even preventing the two from meeting and possibly forming a relationship. Megan could of course also have spoken to Cueball herself, but she expects him to make a move if he is interested. Thus she also prevents herself from making contact because of her own expectations and fears of rejection. The title text is the continuation of Megan's apparent journal entry and further emphasizes the irony of the situation: in the attempt to be alluring to Cueball, Megan took out her "adorable new netbook ," the very thing Cueball stopped himself from complimenting in the first place. This comic comments on the unsettling effects of social change, particularly with respect to the advent of social media and to modern sensitivity toward a woman's (or any person's) right to be left alone in public. It points out that attempting to start a conversation with a stranger has become risky, and we have yet to evolve new customs and conventions to signal openness to such an approach. The risk is aggravated by social media, by which means an innocent misjudgment may subject one to public humiliation - or even worse someone might expect that you had intention of performing some sexual crime - if that type of info is published with a picture and/or your name on Facebook or Twitter etc. your life could be ruined without any reason. As a result, opportunities to meet other people are missed, loneliness and social isolation are increased, and one may even experience existential fears of being unattractive. Ironically, some people react to this problem by relying on the same social media to stay connected with others. [Cueball and Megan are sitting on chairs, presumably on a train.] Cueball: Hey, cute netbook. Megan: What. [Zoomed in on Cueball and Megan.] Cueball: Your laptop. I just— Megan: No, why are you talking to me. [Zoomed in on Megan.] Megan: Who do you think you are? If I were even slightly interested, I'd have shown it. [Both Cueball and Megan, with Megan pointing at Cueball.] Megan: Hey everyone, this dude's hitting on me. Voice #1: Haha Voice #2: Creepy Voice #3: Let's get his picture for Facebook to warn others. [The previous panel fades into a thought bubble of Cueball.] [Cueball and are sitting on chairs, on the train, and Megan is typing on her laptop.] Dear blog, Cute boy on train still ignoring me.

Ohm

Ohm

https://www.xkcd.com/643

https://www.explainxkcd.com/wiki/index.php/643:_Ohm

[A Cueball-like guy (Georg Ohm) is kneeling behind and holding his Cueball-like uncle by the shoulders as he is lying down.] Uncle: Remember: With great power comes great current squared times resistance. [Caption below the frame:] Ohm never forgot his dying uncle's advice.

This comic deliberately conflates the origin story of the comic-book superhero of Spider-Man with the origin of Ohm's law , as both the origin story of Spider-Man and Ohm's law deal with power, though the power is of different types. In the origin story of Spider-Man Peter Parker (who would become Spider-Man) is raised by his Aunt May and Uncle Ben. When Parker goes through various stages of teenage angst and rebellion, his Uncle Ben (in different situations depending on the comics and/or movie) advises him that "with great power comes great responsibility". Here, power is taken by the reader to refer to Parker's superhero powers, acquired from a bite from a radioactive spider and via various technologies Parker designs himself. It is to be noted, however, that Uncle Ben doesn't know about these powers in the origin stories and only means this as general advice. In contrast, in this xkcd comic, Ohm's law is supposedly delivered to Georg Ohm by a similar authority figure in the form of relating current and resistance to power (in the unit of Watts ), where power is defined as the change in energy per unit time. In real life, Ohm obviously was never "advised" about the law but instead determined experimentally that current through an Ohmic resistor was proportional to the voltage . This relationship is summarized by Ohm's law : Voltage = Current x Resistance (V=IR) Electric power is defined as: Power = Current x Voltage (P=VI - Joule's first law ) which, by replacing "Voltage" with "(Current x Resistance)" (from Ohm's law): Power = Current x (Current x Resistance) = Current² x Resistance which leads to the power equation alluded to in the comic. The joke here is that given the proportionality, by definition a great (amount of) power would involve a great (amount of) current and/or resistance (squared), as here the phrase 'great power' could be taken to mean 'a large capability to do things' or 'a numerically large quantity of (electrical) power'. There is also humor in the improbability of this scenario, the comparison with Spider-Man, as well as the suggestion that it was how Ohm derived his eponymous law. The title text takes this further, by redefining the power equation as a more generalised differential equation , which simply states that power is proportional to the change of energy per unit time (dE/dt), which is another way of stating that "power = energy per unit time". In many engineering and physics books the differential form is presented as the general form from which a specific algebraic form can be derived as the differential form is more adaptable to special cases, and therefore more general, and so the title text extends the conflation of physical power and electrical power to a more generalised form. [A Cueball-like guy (Georg Ohm) is kneeling behind and holding his Cueball-like uncle by the shoulders as he is lying down.] Uncle: Remember: With great power comes great current squared times resistance. [Caption below the frame:] Ohm never forgot his dying uncle's advice.

Surgery

Surgery

https://www.xkcd.com/644

https://www.explainxkcd.com/wiki/index.php/644:_Surgery

[A surgeon is standing over a patient on a gurney.] Patient: While you're doing the surgery, can you also implant this in my arm? Surgeon: A USB port? Patient: Just wire it up to some nerves. Surgeon: ...This won't let your brain control USB devices, you know. Patient: Sure – I just want the hardware. Patient: The rest is software; I'm sure there will be a project to patch together support eventually. Surgeon: Ah – you're a Linux user, I see. Patient: Yeah, how'd you know?

Cueball is lying down, waiting to undergo surgery, when he asks the surgeon to insert and wire up a USB port to nerves. The surgeon assumes that Cueball wants to control USB devices, but Cueball assures him that he just wants the hardware. It is revealed that he is waiting for the software update that will allow him to do as he pleases. Linux is an open source kernel for an operating system. Linux is notorious for its less-than-perfect support for hardware, although support for most hardware is eventually patched into the official kernel release. Cueball is here under the impression that support for a USB port can be patched into his arm in a similar fashion to how hardware support can be added to the Linux kernel. The " Vista -Ready" sticker in the title text is a humorous indication from the doctor that the patient is "advanced enough" to have Windows Vista installed. The irony is multilayered. There was a lawsuit against Microsoft about promoting not-so-capable computers as "Windows Vista Capable"; they could neither run Vista fully nor smoothly. On top of that, the typical Linux user would not be very enthusiastic about Windows at all; someone who runs Linux has actively chosen an alternative operating system. [A surgeon is standing over a patient on a gurney.] Patient: While you're doing the surgery, can you also implant this in my arm? Surgeon: A USB port? Patient: Just wire it up to some nerves. Surgeon: ...This won't let your brain control USB devices, you know. Patient: Sure – I just want the hardware. Patient: The rest is software; I'm sure there will be a project to patch together support eventually. Surgeon: Ah – you're a Linux user, I see. Patient: Yeah, how'd you know?

RPS

RPS

https://www.xkcd.com/645

https://www.explainxkcd.com/wiki/index.php/645:_RPS

[A sausage with mustard is sitting to the right of an empty bun.] [Caption below the panel:] Reverse Polish Sausage

Reverse Polish notation is a method of writing mathematical expressions, where operators are after their operands, not between. For example, 2 + 2 becomes 2 2 + , and (2 × 2) ÷ 3 becomes 2 2 * 3 / . This comic plays on that, by placing a Polish Sausage (a North American term for Kielbasa ) after both halves of the bun instead of between. The title text is a pun on the fact that Reverse Polish Notation is also known as Postfix notation . "Fixins" is a Southern US slang for condiments such as mustard, chopped onions, and more. The slang is derived from how you "fix" up, or prepare, your food item whenever you have items that can be customized per person after being cooked. The news section for this comic says " Comic today's you confuses here click if ", which is also written in some kind of reverse polish notation and would be " If today's comic confuses you, click here " in proper English. [A sausage with mustard is sitting to the right of an empty bun.] [Caption below the panel:] Reverse Polish Sausage

Conversations

Conversations

https://www.xkcd.com/646

https://www.explainxkcd.com/wiki/index.php/646:_Conversations

[A graph plots time vs. 3 lines.] [Dysentery cases starts high, drops to near zero with time.] [Laptop sales starts at zero, then raises.] [Frequency of conversations in which one participant is on the toilet - falls as dysentery cases falls, then rises again with laptop sales.]

This comic humorously links both dysentery and laptop computers with conversations in which one participant is on the toilet . Dysentery results from viral, bacterial, or parasitic infections in the intestine, and is characterized by severe diarrhea , which means that someone will be on the toilet frequently and/or for a long time. So when dysentery was more prevalent, people spent more time on the toilet and presumably would have to talk to other people while sitting there. Dysentery has largely subsided in the developed world, which is why the graph of dysentery cases falls to near zero over time. Laptops could cause toilet conversations because wireless internet allows people to carry their laptop anywhere around the house, even to the bathroom. They can still communicate with friends by text, voice, or even video chat, which means people can multitask by holding an online conversation while sitting on the toilet. If the chatting is just in text, then the other person won't have to know that their friend is on the toilet - Hopefully voice and video chat are less common while sitting on the toilet. There are always some conversations on the toilet, because the social conventions against it are sometimes ignored or overridden by urgent situations. This explains why the conversations graph does not reach zero in the middle. The joke in the title text is a direct reference to a previous comic regarding The Oregon Trail and dysentery. The title text refers to the popular educational computer game around the 1980s titled the Oregon Trail. The game purports to educate students about 19th-century pioneer life on the Oregon Trail in the western United States . Among the features in the game is the common occurrence for a party member to die of a disease such as cholera , typhoid , or dysentery . The title text humorously suggests that the data for the graph comes from occurrences of dysentery in the game. [A graph plots time vs. 3 lines.] [Dysentery cases starts high, drops to near zero with time.] [Laptop sales starts at zero, then raises.] [Frequency of conversations in which one participant is on the toilet - falls as dysentery cases falls, then rises again with laptop sales.]

Scary

Scary

https://www.xkcd.com/647

https://www.explainxkcd.com/wiki/index.php/647:_Scary

[Rob and his nephew (also drawn like a Cueball, but smaller) are sitting on the ground facing each other. Rob is holding a flash-light up to his face and leans back on the other arm, while crossing his legs. The nephew is sitting forward resting one arm on his lifted knees and leaning back on his other arm.] Rob: But they never found the ghost's head! Nephew: Lame story, Uncle Rob. Rob: And you could do scarier? Nephew: Sure. [Rob has removed the flash-light from his face and the nephew leans more back and has shifted a leg down so only one knee supports the arm which are now more straight.] Rob: Try me. Nephew: 9/11 happened before I was born, yet I'm old enough to have this conversation with you. [Rob has dropped the flash-light. The nephew has taken the other arm down on the ground. Beat panel.] [Rob has curled his legs up to his chin and wrapped his arms around them while the nephew relaxes even more.]

Rob is telling his eight-year-old nephew a ghost story, employing such clichéd devices as a flashlight-lit face and stock ghost story endings. The boy is unimpressed, so Rob challenges him to come up with a scarier story. Rob's nephew merely states that he was born after 9/11 , and yet he is already mentally developed enough to hold a conversation with an adult. This proves effective, as in the final panel Rob assumes the fetal position, gripped by existential dread. No hidden meaning here, but this sure is scary for many adults. What's being implied here is that time seems to be moving really quickly and we're getting older faster than we think. Events that seem like they "just happened" have happened long enough ago for a whole other person to come into existence, grow up, and learn to carry on a conversation. Every time we get reminded of this fact, it can be scary, as you then realize that you are now closer to your death... 9/11 was a terrorist attack in the United States in 2001, on September 11th. Major events such as the assassination of Kennedy , the Moon Landing of Apollo 11 or 9/11 are easily memorable. It is often said that "everyone remembers where they were when they first heard...". In consequence, these events act as milestones in our memory. They are recalled more vividly, and seem more recent. Today this is maybe also topping the Attack on Pearl Harbor which happened in 1941. The title text mentions that Randall is teaching his 8 year old relatives to say the same as in the comic — presumably to the annoyance of his older relatives who will be reminded of the fast passage of time. He does not stop here, but teaches the 14 year old's to say they are born after Toy Story — a major block buster hit from Pixar which came out in 1995. A movie many people will remember fondly and feel just came out the other day... He continues with these scary thoughts by mentioning that Pokémon (1996) came out over a decade ago and that kids born after the big Disney hit movie Aladdin from 1992 will turn 18 next year (i.e. in 2010 a year after this comic was published). Randall has both before and after this comic tried to make people feel old several times. [Rob and his nephew (also drawn like a Cueball, but smaller) are sitting on the ground facing each other. Rob is holding a flash-light up to his face and leans back on the other arm, while crossing his legs. The nephew is sitting forward resting one arm on his lifted knees and leaning back on his other arm.] Rob: But they never found the ghost's head! Nephew: Lame story, Uncle Rob. Rob: And you could do scarier? Nephew: Sure. [Rob has removed the flash-light from his face and the nephew leans more back and has shifted a leg down so only one knee supports the arm which are now more straight.] Rob: Try me. Nephew: 9/11 happened before I was born, yet I'm old enough to have this conversation with you. [Rob has dropped the flash-light. The nephew has taken the other arm down on the ground. Beat panel.] [Rob has curled his legs up to his chin and wrapped his arms around them while the nephew relaxes even more.]

Fall Foliage

Fall Foliage

https://www.xkcd.com/648

https://www.explainxkcd.com/wiki/index.php/648:_Fall_Foliage

[Cueball and Megan are standing on a cliff overlooking a forest of gorgeous orange foliage. The forest grows up a hill and behind and right of the forest there are is forest free hill and in the horizon two small mountain peaks rises up to the gray blue sky. Cueball is holding his camera down while Megan is holding her camera up taking a photo. As opposed to normal the text is written inside two speech bubbles with arrow ending pointing at the two. Also the sound of the camera is written inside a white area with small u shapes forming part of the frame for this sound.] Cueball: Instead of driving all this way, we could've just taken our summer pictures and messed with the "hue" slider in Photoshop. Megan: Hush. Camera: Click

Cueball and Megan have driven some distance from home, and Megan enjoys the pastime of leaf peeping , happily taking photographs of the beautiful fall or autumn foliage. Cueball points out that they could've stayed home and used Photoshop to alter pictures they've already taken, saving themselves the trouble of going on the trip. The hue control in such image editing programs shifts the colors around the spectrum without altering the brightness; the green leaves in a summer picture could then easily be shifted to yellow or red. Megan simply shushes him in the strip, but the title text is implied to be Megan's retort, saying that Cueball used to be a happier person, and if he will continue being like this, she would prefer to see him in old pictures rather than living with him. Or it could be that Cueball is making a response to the shush as he seems to be the more technologically inclined and more annoyed. The comic is also showing how, because of technology, many people are not as "happy" as they once were. Instead of appreciating natural beauty, Cueball simply wishes to "replicate" the experience by using Photoshop; unfortunately, this would deprive him of both the experience of beautiful fall leaves and a shared intimacy with Megan. See also 1314: Photos about people taking pictures and White Hat complaining. Later in 1719: Superzoom White Hat and Cueball again discusses photography, while in 2111: Opportunity Rover White Hat shares his anti-photography opinion again. [Cueball and Megan are standing on a cliff overlooking a forest of gorgeous orange foliage. The forest grows up a hill and behind and right of the forest there are is forest free hill and in the horizon two small mountain peaks rises up to the gray blue sky. Cueball is holding his camera down while Megan is holding her camera up taking a photo. As opposed to normal the text is written inside two speech bubbles with arrow ending pointing at the two. Also the sound of the camera is written inside a white area with small u shapes forming part of the frame for this sound.] Cueball: Instead of driving all this way, we could've just taken our summer pictures and messed with the "hue" slider in Photoshop. Megan: Hush. Camera: Click

Static

Static

https://www.xkcd.com/649

https://www.explainxkcd.com/wiki/index.php/649:_Static

[It's pitch black. Only Cueball and Megan's dialogue can be seen.] Megan: Hang on, I can't see—did you put on a condom? Cueball: It's okay. I've got a wrist thing on. Megan: A what? Let me see that. fumble Megan: This is an anti-static strap. Cueball: You mean it doesn't... Megan: No. Why would you even THINK that? Cueball: I guess I was mixed up. Cueball: Wait, so when I was replacing that RAM last week... Megan: Yeah, I THOUGHT that was weird. Cueball: Oh, but it explains why the Geek Squad fired me.

This comic describes an unlikely confusion between a condom and an antistatic wrist strap . The two characters, presumably Cueball and Megan, are in the dark and about to engage in sexual intercourse . Megan checks that Cueball has a condom on. Cueball thinks a condom isn't necessary because he has an antistatic wrist strap on. Megan finds this ridiculous. Antistatic wrist straps are important safety tools for electronics work such as handling computer parts. The wrist strap provides a conduction path directly from one's skin to an electrical ground , preventing the buildup of static electricity which, if accidentally discharged upon touching part of a circuit, can damage sensitive electronic components. Condoms , on the other hand, are an important safety tool for sex, as birth control and protection from STDs . The confusion is humorous because both items have abstract similarities, but are used in wildly different kinds of activities. In an abstract sense, both are items that you want to be sure to put on before engaging in a certain activity, wearing it throughout that activity to prevent any disastrous accidental effects. The last panel implies that in his confusion, Cueball put on a condom in order to replace the RAM in his computer the previous week. Rather than actually asking about it, Megan just thought that was weird. Geek Squad is the computer service department of the Best Buy chain of American electronics superstores. So Cueball also implies that he put on a condom while working in Best Buy, for performing computer repair, and so he was fired for indecency. The title text conveys the irrational belief that nothing can go wrong on a project while wearing an antistatic wrist band. In reality, the wrist band will only protect your electronics from electrostatic discharge , and there are plenty of other things that could go wrong on an electronics project, such as bad soldering, installing the wrong component, mechanical damage through excessive force, or even electric shock from an exposed live voltage. Or the text could be referring to even non-electronics projects, in which case the wrist band would really be pointless. [It's pitch black. Only Cueball and Megan's dialogue can be seen.] Megan: Hang on, I can't see—did you put on a condom? Cueball: It's okay. I've got a wrist thing on. Megan: A what? Let me see that. fumble Megan: This is an anti-static strap. Cueball: You mean it doesn't... Megan: No. Why would you even THINK that? Cueball: I guess I was mixed up. Cueball: Wait, so when I was replacing that RAM last week... Megan: Yeah, I THOUGHT that was weird. Cueball: Oh, but it explains why the Geek Squad fired me.

Nowhere

Nowhere

https://www.xkcd.com/650

https://www.explainxkcd.com/wiki/index.php/650:_Nowhere

[Megan is sitting on a couch with Cueball lying in her lap, his feet going out over the armrest.] Cueball: There's nowhere I'd rather be than with you here right now. [Zoom in on Megan, still showing Cueball's head in her lap.] [Further zoom in on Megan, so only most of Cueball's head can be seen. The couch is only partly sketched, and behind her thee thought bobbles lead to a day dream she is having, where we see she is imagining herself riding an apatosaurus, holding the reins going into the dinosaurs mouth.]

This is a sarcastic comic poking fun at romanticism. The phrase used by Cueball in the first panel hints at the romantic, suggesting that he is so happy to be with Megan that there is nowhere else that he would rather be right at this moment than here with her. Megan wonders if this is her viewpoint, and imagines herself riding a dinosaur, probably an Apatosaurus , suggesting that she would rather be doing just that. This, and the title text are saying that the likelihood that out of all the possibilities in the universe, the chances that the one single place you would most want to be is just sitting with your significant other is fairly low. The title text is Megan's comment to Cueball, where she asks him if he is serious, when there are like a thousand species of Dinosaurs he could be riding (or running from). Previously, in 15: Just Alerting You , a man rode on a Brontosaurus which at the time of release of this comic was thought to just be an outdated name for Apatosauruses . This was made clear a few comics earlier in 636: Brontosaurus . Apatosauruses are also mentioned in 460: Paleontology . [Megan is sitting on a couch with Cueball lying in her lap, his feet going out over the armrest.] Cueball: There's nowhere I'd rather be than with you here right now. [Zoom in on Megan, still showing Cueball's head in her lap.] [Further zoom in on Megan, so only most of Cueball's head can be seen. The couch is only partly sketched, and behind her thee thought bobbles lead to a day dream she is having, where we see she is imagining herself riding an apatosaurus, holding the reins going into the dinosaurs mouth.]

Bag Check

Bag Check

https://www.xkcd.com/651

https://www.explainxkcd.com/wiki/index.php/651:_Bag_Check

[Cueball and Megan are at a security checkpoint in an airport. A guard is holding an open backpack and a bottle of water, and Cueball is arguing with him. Megan is facepalming.] Cueball: But if you're worried about bombs, why are you letting me keep my laptop batteries? If I overvolted them and breached the cells, it would make a sizeable explosion. Megan: Oh god. Cueball: It's okay, dear. In a moment he'll realize I have a good point and return my water.

Cueball argues with a TSA agent at an airport security checkpoint over the TSA policy of prohibiting airline passengers from bringing liquids or gels in quantities greater than 3.4 ounces (100 ml) in their carry on items. To prove his point, Cueball points out that modifying the lithium ion battery in his laptop computer to be an explosive poses a more plausible risk to the aircraft than carrying an innocuous bottle of water. The joke is that now the security team is even MORE worried about him specifically and will take away his laptop and most likely detain him for questioning. The title text continues Cueball's line of argument, segueing into a protest as the situation escalates to the point of Cueball apparently being placed under arrest. This is, however, a bit of an exaggeration, as for them to place someone under arrest, they need real reason to think that they are going to do something bad, and simply knowing this information is not enough to justify this action. Interestingly, in 2017 a ban on laptops and other large, battery-equipped devices (but not smartphones) in the cabin was initiated by the United States, and followed by other countries, with the stated aim of lowering the risk of somebody bringing an explosive onto the plane inside it. Granted, this was in response to a Somali incident where a bomber snuck a laptop loaded with actual explosives (not just the batteries) onto a plane, but the similarities are still quite evident. [Cueball and Megan are at a security checkpoint in an airport. A guard is holding an open backpack and a bottle of water, and Cueball is arguing with him. Megan is facepalming.] Cueball: But if you're worried about bombs, why are you letting me keep my laptop batteries? If I overvolted them and breached the cells, it would make a sizeable explosion. Megan: Oh god. Cueball: It's okay, dear. In a moment he'll realize I have a good point and return my water.

More Accurate

More Accurate

https://www.xkcd.com/652

https://www.explainxkcd.com/wiki/index.php/652:_More_Accurate

[Cueball with a shotgun approaches a woman carrying a tray with glasses.] Cueball: Sarah! Come with me if you want to live! A robot assassin has been sent here to kill you! [Sarah holds her hands over her mouth. She has presumably dropped the tray, as it lies on the floor.] Cueball: I'm here to save you. I may not be as strong or fast as a machine, but I'll fight to keep you- [There's a huge orange and yellow explosion. The two are disintegrated and Cueball's shotgun goes flying.] BOOM [A flying robot assassin is above the bomb site.]

This comic spoofs the Terminator series, in which a super-intelligent machine from the future time travels back in time to kill Sarah Connor . As could be expected from a movie, the antagonistic robot is a human-like android. However, we currently have military "robots" (actually vehicles controlled remotely by people) that are completely unlike anything in the movie. Originally, UAV were only used for surveillance and reconnaissance. But, now more than ever, they are used for attacks. And most importantly, they are not walking humanoids but flying machines. They are not restricted to carrying human-intended guns as in the movie but are armed with powerful explosives and long-range missiles. Thus the name of the comic: Randall points out being attacked by a flying plane-like drone -- such as the Predator drone shown in the last panel (heavily used for offensive operations by the USAF and the CIA in Afghanistan and Pakistan) -- is a much more accurate outcome should the robots rise up against humans. It is important to note that, in the actual Terminator 1 movie , this substitution would not actually be so simple. The terminator sent back in time knows Sarah Connor's name and city of residence, but not her appearance or address; it locates her by looking her up in a phone book (and ends up killing a number of other women with the same name, as well as its intended target's roommate, before finding the correct Sarah Connor.) Additionally, the terminator regularly operates inside buildings and rearms itself by picking up human small-arms. A Predator-type drone, while a superior killing system, would be unable to do any of that. A drone which could interact with and operate in the human environment with the ease the terminator displays (let alone successfully disguise itself as a human) would be a major accomplishment which no real-world project has yet come close to. One thing that keeps us short of a Terminator scenario is that most of the unmanned aerial vehicles are either pre-programmed or flown remotely by members of the military, and are not left to their own devices. The title text emphasizes this by pointing out that we have entire fleets of these drones, and notes that at some point, we entered the future. Similar buildup and Terminator reference are to be found in 1177: Time Robot . 10 years after this comic was published, almost to the day, a movie in the Terminator franchise called Terminator: Dark Fate came out which includes a scene very similar to this comic involving a Predator drone being used by the super-intelligent machine to take out its target. Also, shortly after that movie came out Randall published a comic about it with the same name. [Cueball with a shotgun approaches a woman carrying a tray with glasses.] Cueball: Sarah! Come with me if you want to live! A robot assassin has been sent here to kill you! [Sarah holds her hands over her mouth. She has presumably dropped the tray, as it lies on the floor.] Cueball: I'm here to save you. I may not be as strong or fast as a machine, but I'll fight to keep you- [There's a huge orange and yellow explosion. The two are disintegrated and Cueball's shotgun goes flying.] BOOM [A flying robot assassin is above the bomb site.]

So Bad It's Worse

So Bad It's Worse

https://www.xkcd.com/653

https://www.explainxkcd.com/wiki/index.php/653:_So_Bad_It%27s_Worse

Protip: Even at "Bad Movie Night," avoid the Star Wars holiday special. [A graph plots movie enjoyability against movie quality. It drops steadily through points marked "Good Movie" to "Okay Movie" to "Bad Movie," rises up again for "So-Bad-It's-Good (Plan 9, Rocky Horror, etc)," and then drops off the bottom of a graph with an arrow pointing to where "Star Wars Holiday Special" would be. There are three mini-panels below the graph, arranged from "Good" to "Bad" along the movie quality axis.] [Three friends are on a couch, drinking and gesticulating enthusiastically.] [The same three are sitting quietly, with a bottle on the floor.] [The three are sitting around a table, drinking and looking miserable. One seems to be passed out on the table.]

The graph in the comic shows the enjoyability of movies - going from good to okay to bad, then popping back up with " So Bad It's Good ". The term is used to describe movies that are so terrible that, ironically, watching them is actually an enjoyable experience, even if just to poke fun or marvel at the absurdity of how bad they are. The comic lists Plan 9 from Outer Space and The Rocky Horror Picture Show , two widely known films of this type. However, the graph warns of showing The Star Wars Holiday Special , as it manages to wrap back around from "So Bad It's Good" to being So Bad it's Horrible . The Star Wars Holiday Special is a prime-time comedy special based on Star Wars . It is widely known for its terrible quality, and has never been fully released (although an animated segment that introduced Boba Fett , which George Lucas has approved of, has been released as a bonus feature on a DVD). The bottom of the comic shows Cueball , Megan , and Ponytail watching a movie with alcohol - first enjoying it, then merely watching, then not watching it and unhappily drinking. The title text refers to torrents , which are a way to obtain large amounts of data over the internet. Since the Holiday Special was only aired once on television and was never released on VHS or DVD, torrents of the TV recordings are one of the few ways to actually see it. According to Munroe , he had torrented a copy of the film and intended to watch it in its entirety, in spite of its terribleness, just to cement himself as a nerd. However, he underestimated how bad it really was, and could not make it all the way through. The title text may also contain an subtle play on a line of Star Wars dialogue. In Return of the Jedi , Darth Vader says to Luke Skywalker , " Obi-Wan once thought as you do . You don't know the power of the dark side! I must obey my master." The implication here being that "kitschy nerd cred" is the "dark side" being served by those who would sit through a torrent of The Star Wars Holiday Special . Protip: Even at "Bad Movie Night," avoid the Star Wars holiday special. [A graph plots movie enjoyability against movie quality. It drops steadily through points marked "Good Movie" to "Okay Movie" to "Bad Movie," rises up again for "So-Bad-It's-Good (Plan 9, Rocky Horror, etc)," and then drops off the bottom of a graph with an arrow pointing to where "Star Wars Holiday Special" would be. There are three mini-panels below the graph, arranged from "Good" to "Bad" along the movie quality axis.] [Three friends are on a couch, drinking and gesticulating enthusiastically.] [The same three are sitting quietly, with a bottle on the floor.] [The three are sitting around a table, drinking and looking miserable. One seems to be passed out on the table.]

Nachos

Nachos

https://www.xkcd.com/654

https://www.explainxkcd.com/wiki/index.php/654:_Nachos

[Cueball is on the phone with Ponytail, who's on her computer in the other half of a split panel.] Cueball: Hello? ... Oh, hey. Looking for Megan? She's gaming. Ponytail: I know. You know what's delicious? Nachos. [Ponytail clicks on her computer while talking.] Ponytail: When you layer the cheese so it gets on every chip... then smother them in sour cream and salsa... Cueball: Mm, that IS delicious. And I've got the ingredients, too! Ponytail, on phone: You should make some! Cueball: I will! Ponytail, on phone: Hurry. [Cueball is making nachos in the microwave.] Microwave: beep beep whirrrr Megan, at her computer: My wifi signal! [Ponytail who called is at her computer.] Computer: Boom! Headshot.

Megan (in one of the few comics where she is actually named) and Ponytail are playing together on an online multiplayer shooter game. Ponytail calls Cueball , who is living with Megan, and easily persuades him to make nachos . Wi-Fi and microwave ovens both use radio frequencies around 2.4 GHz , so Cueball's cooking disrupts Megan's connection and allows Ponytail to kill Megan's character. Boom! Headshot is a catchphrase made popular through a web mockumentary series called Pure Pwnage , and is also used in the game League of Legends by the character Caitlyn. The title text points out that Megan has only herself to blame, as gaming on WiFi is susceptible to such issues, while gaming with a wired connection (e.g. Ethernet ) is not. Note: If using the microwave actually does interfere with your WiFi, then get another microwave. Not (strictly) because it would mess with the WiFi, but because your microwave has a hole somewhere and is leaking non-ionizing radiation it shouldn't. It won't kill you, but it's not operating at peak efficiency. See this video on the subject. Around the time of this comic's release, the xkcd website was temporarily redesigned using Yahoo! GeoCities . Snapshots of the site at the time can be found on the Internet Archive Wayback Machine . This was the fifth time Megan is drawn and given the name Megan in xkcd, the first time being in 159: Boombox . Once in between this and the previous of these comics ( 478: The Staple Madness ), her name was used in 596: Latitude , but she was not drawn there. [Cueball is on the phone with Ponytail, who's on her computer in the other half of a split panel.] Cueball: Hello? ... Oh, hey. Looking for Megan? She's gaming. Ponytail: I know. You know what's delicious? Nachos. [Ponytail clicks on her computer while talking.] Ponytail: When you layer the cheese so it gets on every chip... then smother them in sour cream and salsa... Cueball: Mm, that IS delicious. And I've got the ingredients, too! Ponytail, on phone: You should make some! Cueball: I will! Ponytail, on phone: Hurry. [Cueball is making nachos in the microwave.] Microwave: beep beep whirrrr Megan, at her computer: My wifi signal! [Ponytail who called is at her computer.] Computer: Boom! Headshot.

Climbing

Climbing

https://www.xkcd.com/655

https://www.explainxkcd.com/wiki/index.php/655:_Climbing

[Cueball seen from his back, as he is ascending a gray climbing wall with 16 white handles in different shapes and sizes. He is standing on one near the bottom left of the panel with his left foot, holding on to a large handle to the left of his head, and one to the right at shoulder height. His right foot is seeking hold on another handle above knee hight of his left leg.] [Cueball is seen in profile still climbing up the gray wall, which is drawn in the right part of the panel, 13 handles protruding. At the top of the panel something is protruding from the wall at more than ninety degree angle to the wall, as the line soon goes off panel at the top, but it seems to be directed at a small white half circle at the top of the panel. The line begins in front of the last of the handles at the top, a small one, and below this there is a larger handle bending up making it easy to hold on to. Cueball is holding on with his hands to two similar "easy" handles.] [Cueball climbs a bit further up till his hand reaches the up bending handle in front of the line, and his lower leg and upper knee touches the two handles his hands where on before. Here he has stopped climbing and lifts his head back to look up and sees Megan standing there above him (as she was also doing at the top of the previous panel, but cut off at leg and face). She just stands perpendicular to the wall facing down towards Cueball. The panel has panned up following Cueball so there are only 11 handles now, two more visible "above" Megan, and four from the previous panel are now below this panels frame.] [Same scene but Cueball is now looking at the wall as Megan speaks.] Megan: Your Facebook rock climbing pictures just got a lot less impressive.

This comic makes fun of a certain type of images very common on the internet. Those pictures are taken with a camera turned by 90° or rotated later by software, thus creating the illusion of people walking on walls or ceilings. While the original pictures depict the physical impossibility of a rotated gravitational force , Cueball uses the aforementioned technique to create pictures of himself on a climbing wall . Megan approaches him from above the wall, indicating that the climbing wall is in fact lying on the floor. It becomes clear that Cueball was not able to climb a real wall and therefore crawled on the floor with his camera adjusted accordingly. Her comment is a sideswipe on the practise of self-display on Facebook , which is often done with the help of image manipulation . The title text implies that Cueball has in fact stolen a real climbing wall, and that Megan wants him to return it. An alternative reading is that Cueball could be climbing a relatively easy climbing wall, and the joke is it’s so easy that Megan can walk on it, thus conveying that it could be really easy, but Cueball might perceive it as hard; thus, Megan impresses the viewers more than Cueball by showing how easy the course is. [Cueball seen from his back, as he is ascending a gray climbing wall with 16 white handles in different shapes and sizes. He is standing on one near the bottom left of the panel with his left foot, holding on to a large handle to the left of his head, and one to the right at shoulder height. His right foot is seeking hold on another handle above knee hight of his left leg.] [Cueball is seen in profile still climbing up the gray wall, which is drawn in the right part of the panel, 13 handles protruding. At the top of the panel something is protruding from the wall at more than ninety degree angle to the wall, as the line soon goes off panel at the top, but it seems to be directed at a small white half circle at the top of the panel. The line begins in front of the last of the handles at the top, a small one, and below this there is a larger handle bending up making it easy to hold on to. Cueball is holding on with his hands to two similar "easy" handles.] [Cueball climbs a bit further up till his hand reaches the up bending handle in front of the line, and his lower leg and upper knee touches the two handles his hands where on before. Here he has stopped climbing and lifts his head back to look up and sees Megan standing there above him (as she was also doing at the top of the previous panel, but cut off at leg and face). She just stands perpendicular to the wall facing down towards Cueball. The panel has panned up following Cueball so there are only 11 handles now, two more visible "above" Megan, and four from the previous panel are now below this panels frame.] [Same scene but Cueball is now looking at the wall as Megan speaks.] Megan: Your Facebook rock climbing pictures just got a lot less impressive.

October 30th

October 30th

https://www.xkcd.com/656

https://www.explainxkcd.com/wiki/index.php/656:_October_30th

[A kid dressed up in a lab coat and goggles is standing on a neighbor's doorstep.] Kid: Trick or treat! Neighbor: Nice Doc Brown costume, but today's October 30th. Kid: Great Scott, I must have overshot!

For Halloween, a child has dressed up as Dr. Emmett L. Brown (played by Christopher Lloyd ) from the Back to the Future film trilogy. In the films, Brown created a time machine out of a DeLorean DMC-12 car, which he and teenage protagonist Marty McFly use to travel through time. The joke of the comic is that Halloween is on October 31st, and by showing up dressed as Doc Brown on October 30th, the kid can make the joke that he "overshot" the time machine and went back one more day than he meant to. Doc is heard throughout the movie franchise saying "Great Scott" as an exclamation of surprise. The title text suggests an inventive use of time-travel to get ten times the candy — hitting each house at a 30-year interval up until 2300. The interval matches that of the first two BttF movies, which take place in the years 1955, 1985 (the present at the time), and 2015. Of course, one would have no idea starting off if Halloween is still being celebrated in 2300, or indeed if the human race even still exists. [A kid dressed up in a lab coat and goggles is standing on a neighbor's doorstep.] Kid: Trick or treat! Neighbor: Nice Doc Brown costume, but today's October 30th. Kid: Great Scott, I must have overshot!

Movie Narrative Charts

Movie Narrative Charts

https://www.xkcd.com/657

https://www.explainxkcd.com/wiki/index.php/657:_Movie_Narrative_Charts

[colors given approximately in HEX at first appearance] These charts show movie character interactions. The horizontal axis is time. The vertical grouping of the lines indicate which characters are together at a given time. Lord of the Rings [yellow line (fff500)] ring [thin line, here dark green (467120)] ringbearer [grey colored area (e9e9e9)] battle/event [line ending with a dot, here black] death [bar, here light brown (daccae)] army [line, here brown (9d7929), in a bar, here light brown] character leading army [grey line (b7bfb6)] wizards [brown line (9d7929)] men [blue line (4a89a8)] elves [dark brown line (6c411b)] dwarves [dark turquoise line, 143035] ents [green line (4e7629)] hobbits [signs and colors not explained by the legend] [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side, from top to bottom] [The five characters leaving off the top border of the chart] [text next to the group of five] Ship to the West [other characters leaving on the right side] [characters starting or leaving in the middle the chart] Star Wars (original triology) [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side, from top to bottom] [Characters starting or leaving not in battle/event-areas and not on the left/right side of the chart] Jurassic Park [all dinosaurs are represented by red, all men by black lines] [for dinosaurs locked up, there is a donut-sign.] [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side] 12 angry men [All lines go parallel, start and end at the borders of the chart. There are no areas of battle/event.] Juror 1 --------- Juror 1 ----------- Juror 1 ------------ Juror 1 Juror 2 --------- Juror 2 ----------- Juror 2 ------------ Juror 2 Juror 3 --------- Juror 3 ----------- Juror 3 ------------ Juror 3 Juror 4 --------- Juror 4 ----------- Juror 4 ------------ Juror 4 Juror 5 --------- Juror 5 ----------- Juror 5 ------------ Juror 5 Juror 6 --------- Juror 6 ----------- Juror 6 ------------ Juror 6 Juror 7 --------- Juror 7 ----------- Juror 7 ------------ Juror 7 Juror 8 --------- Juror 8 ----------- Juror 8 ------------ Juror 8 Juror 9 --------- Juror 9 ----------- Juror 9 ------------ Juror 9 Juror 10 --------- Juror 10 ----------- Juror 10 ------------ Juror 10 Juror 11 --------- Juror 11 ----------- Juror 11 ------------ Juror 11 Juror 12 --------- Juror 12 ----------- Juror 12 ------------ Juror 12 [Three characters enter the chart on the left side, all represented by black lines] [The lines come to a giant scribble and end up with dotted lines and question marks in the right area. One cannot see which line leads to which end.]

These charts show movie character interactions. The horizontal axis is time. The vertical grouping of the lines indicates which characters are together at a given time. A mass of colored lines weaves back and forth across the chart, representing various characters. Sauron is represented by a red bar at the bottom contained within a huge black bar with branches, that in turn represents his army of nazgul, orcs, etc. Major locations (Moria) and plot points (the breaking of the fellowship) are marked. Gandalf, especially at the beginning, jumps all over the map in a short time. Eagles appear and then disappear a couple of times. Treebeard's line is flat except for the march to Isengard. At the end, the ship to the West drifts off into a corner. The hobbits start off in the top left with Frodo, Sam, Merry, and Pippin with Bilbo with them for a short time because of the party at the beginning. They go off on their adventure and briefly encounter Gandalf. They are then split up for a short time but meet back up at Weathertop when the Nazgul attack and they meet Aragorn (Strider at that point). They meet up with the rest of what becomes the fellowship of the ring at the council of Elrond at Rivendell. The newly formed fellowship must then venture into the mines of Moria which is referenced in comic 760 and comic 1218 . After encountering the Balrog and the later death of Boromir the fellowship splits up. Frodo and Sam take the ring and go off on their own to destroy it and sneak into Mordor with the help of Gollum. Merry and Pippin are captured by the Uruk-hai but are rescued by Eomer and his army. Eomer and his army then briefly reunite with Legolas, Gimli, and Aragorn while Merry and Pippin find Treebeard and flood Isengard. While Merry, Pippin and Treebeard are flooding Isengard Aragorn, Gimli, and Legolas fight at Helm's Deep with Gandalf and Eomer and Theoden. Aragorn, Gimli, and Legolas go to wake the army of the dead while Pippin goes with Gandalf and Merry goes with the Rohirrim. All of these people rejoin for the battle of the Pelennor fields where Eowyn kills the witch king after Theoden dies along with Denethor. The orcs, men and oliphants are all destroyed and Aragorn releases the army of the dead. All the surviving members of that battle go to the Black Gate except Eowyn and Faramir. Sam and Frodo destroy the Ring, Gollum dies and everyone who is still alive is there for Aragorn's coronation. Everyone goes back to their respective homes except for Frodo, Gandalf, Elrond, Galadriel, and Bilbo who get on a ship to the west. As the title text points out, most of the plot of The Lord of The Rings occurs on a rough northwest to southeast axis, with the Fellowship of the Ring traveling from the Shire near the top of chart to Mordor at the bottom of the chart (and back again.) The most significant exception to the northwest-southeast axis is the area of the chart between "The Breaking of the Fellowship" and "Isengard Flooded." Helm's Deep and Isengard are southwest from the overall northwest-southeast axis of the movies. Luke, mostly accompanied by R2-D2, joins and parts from other sets of characters. There's a dotted alternative path on Jabba's line for the special edition. A dark line representing Vader, travels through the duel where he kills Obi-Wan and proceeds to the Death Star to meet with the main charcters for the first time. Vader travels to Hoth where all the characters escape and goes to Cloud City where Han is frozen. He then duels Luke before going for a long time alone and confronts Luke for a short time before taking him to the Death Star II where the climatic duel happens and he is killed. Leia at first with C-3PO is captured and placed on the Death Star before being rescued and proceeds to Hoth, Cloud City, the Sail Barge and finally to the Battle of Endor before reuniting with all the survivors. R2D2 and C-3PO are mostly together save for when Luke is attacking the Death Star and Luke's Jedi training. Luke's line swerves through most of the scenes, breaking away from the other characters during the Jedi Training, the duel on Cloud City and the duel on the Death Star II. Han and Chewie are always together as they go through all the scenes. Greedo, Lando and Boba all appear in their respective scenes. Yoda appears about halfway through (where Luke's Jedi training is marked). All the surviving lines group up at Endor except for Vader, the Emperor, Luke, and Lando; after the climactic duel, the latter two join the rest. The human characters are in black; dinosaurs are in red. Dilophosaurus appears briefly to eat Nedry and then fades out again. the T-Rex appears at the start and swoops down on the cars and eats Gennaro. It then weaves out until the end where it eats the raptors. The three raptors are together at the beginning, but split up about halfway through. One has a dotted portion of line between "locked up" and "escapes." In the meantime, they cut off the lines of Arnold and Muldoon. Malcolm, Grant, Sattler, Hammond and the kids all weave in and out of their respective scenes. The raptor lines all end when t-rex's swoops down to meet them at the end, and all the surviving humans leave together. This is a very famous trial film that tells the story of a jury made up of 12 men as they deliberate the guilt or acquittal of a defendant on the basis of reasonable doubt. Only one of these angry men believe the defendant may be innocent and he argues this against the other 11, eventually convincing them that there is reasonable doubt in the case. The lines are labeled Juror 1 through Juror 12. They are all perfectly horizontal and parallel. The joke in the 12 Angry Men graphic is that in the movie all 12 jurors (the angry men) are in the same room for the entire duration of the movie. They never move and they all always interact with each other, hence their lines stay straight and close to each other. This is actually not entirely true. The movie begins in the court room; a couple of times during the proceedings, a few jurors go into the washroom and have a brief discussion there; and finally, in the very last scene, two jurors have a brief exchange in front of the courthouse. In fact, this chart would actually become a useful reference to the film if each of the jury's votes sessions was shaded as battles/events, and each juror's vote shown on their line, tracking when each juror's vote switches from 'guilty' to 'not guilty'. But as far as the characters' locations, there is no need for such a narrative chart, and that is the joke. The last box is a movie called Primer from 2004, which became a cult classic. It is about a group of engineers who discover a way to travel through time, but only in one direction (backwards) and only at the speed of regular time (i.e. you have to stay in the time machine for one hour to move an hour back in time). Because of this, the story ends up having multiple versions of the same person existing at the same time; the plot and time-travel mechanics are notoriously hard to follow, so that it is almost impossible to figure out where each character is at one time, as the comic illustrates. Three lines start on the left labeled Abe, Aaron, and Granger. They enter a mass of scribbling. Somewhere vaguely towards the end, three lines emerge and fade out, all labeled with question marks. The chart for Primer is referenced in the title text of the fourth image in the what if? Plastic Dinosaurs . These charts are a reference to " Napoleon's March , " the map and statistical infographic by cartographic pioneer Charles Joseph Minard . It details the movements and losses of Napoleon's troops on his failed conquest of Russia. The size and location of Napoleon's army are represented by tapering streams similar to the design used for Sauron's and Saruman’s troops in the LotR Chart. Minard's chart is extensively discussed by Edward Tufte in his book The Visual Display of Quantitative Information , and he summarizes some of that on his website . [colors given approximately in HEX at first appearance] These charts show movie character interactions. The horizontal axis is time. The vertical grouping of the lines indicate which characters are together at a given time. Lord of the Rings [yellow line (fff500)] ring [thin line, here dark green (467120)] ringbearer [grey colored area (e9e9e9)] battle/event [line ending with a dot, here black] death [bar, here light brown (daccae)] army [line, here brown (9d7929), in a bar, here light brown] character leading army [grey line (b7bfb6)] wizards [brown line (9d7929)] men [blue line (4a89a8)] elves [dark brown line (6c411b)] dwarves [dark turquoise line, 143035] ents [green line (4e7629)] hobbits [signs and colors not explained by the legend] [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side, from top to bottom] [The five characters leaving off the top border of the chart] [text next to the group of five] Ship to the West [other characters leaving on the right side] [characters starting or leaving in the middle the chart] Star Wars (original triology) [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side, from top to bottom] [Characters starting or leaving not in battle/event-areas and not on the left/right side of the chart] Jurassic Park [all dinosaurs are represented by red, all men by black lines] [for dinosaurs locked up, there is a donut-sign.] [Characters entering the chart on the left, from top to bottom] [Characters leaving the chart on the right side] 12 angry men [All lines go parallel, start and end at the borders of the chart. There are no areas of battle/event.] Juror 1 --------- Juror 1 ----------- Juror 1 ------------ Juror 1 Juror 2 --------- Juror 2 ----------- Juror 2 ------------ Juror 2 Juror 3 --------- Juror 3 ----------- Juror 3 ------------ Juror 3 Juror 4 --------- Juror 4 ----------- Juror 4 ------------ Juror 4 Juror 5 --------- Juror 5 ----------- Juror 5 ------------ Juror 5 Juror 6 --------- Juror 6 ----------- Juror 6 ------------ Juror 6 Juror 7 --------- Juror 7 ----------- Juror 7 ------------ Juror 7 Juror 8 --------- Juror 8 ----------- Juror 8 ------------ Juror 8 Juror 9 --------- Juror 9 ----------- Juror 9 ------------ Juror 9 Juror 10 --------- Juror 10 ----------- Juror 10 ------------ Juror 10 Juror 11 --------- Juror 11 ----------- Juror 11 ------------ Juror 11 Juror 12 --------- Juror 12 ----------- Juror 12 ------------ Juror 12 [Three characters enter the chart on the left side, all represented by black lines] [The lines come to a giant scribble and end up with dotted lines and question marks in the right area. One cannot see which line leads to which end.]

Orbitals

Orbitals

https://www.xkcd.com/658

https://www.explainxkcd.com/wiki/index.php/658:_Orbitals

[Cueball is holding up a pointer in front of a diagram of a dorm apartment. On the diagram, there are two connected pairs of dots in each bedroom, and one dot on the couch.] Cueball: Thus, once all the dorm bedrooms are occupied by romantic pairs, additional roommates are forced into less restful "living room couch" orbitals. [Caption below the panel:] The Pauli Sexclusion Principle

When determining where to place electrons in atoms, three rules are generally used: the Pauli exclusion principle , the Aufbau principle , and Hund's rule . The Pauli exclusion principle, from which the pun is derived, states that no two electrons (or indeed any fermion ) can occupy the same atomic state. Therefore, any electron orbital is limited to two electrons: one with a ½ spin, and the other with a −½ spin. The Aufbau principle states that lower energy orbitals are occupied previous to high energy orbitals. Hund's rule states that electrons will try to fill orbitals individually, and only pair up when every orbital has a lone electron in it. In the comic, electrons are being equated to people, and rooms (or couches) are equated to orbitals. The reverse of Hund's rule is then followed: people will try to pair up in a room first, and only when all the couples have done so will rooms be allocated to single people. The Pauli exclusion principle here means that only two people can occupy a room at a time (should those people be romantically involved). The Aufbau principle therefore means that more restful rooms are filled previous to less restful rooms. The title text jokes about drunken party-goers, who ignore the Pauli principle perhaps out of inebriation . They then end up partying and sleeping together with many people in the living room, leaving the roommate stuck in the third desirable location, the hall lounge. [Cueball is holding up a pointer in front of a diagram of a dorm apartment. On the diagram, there are two connected pairs of dots in each bedroom, and one dot on the couch.] Cueball: Thus, once all the dorm bedrooms are occupied by romantic pairs, additional roommates are forced into less restful "living room couch" orbitals. [Caption below the panel:] The Pauli Sexclusion Principle

Lego

Lego

https://www.xkcd.com/659

https://www.explainxkcd.com/wiki/index.php/659:_Lego

[Ponytail and her father Cueball are putting away Lego bricks.] Cueball: When you take apart a Lego house and mix the pieces into the bin, where does the house go? Ponytail: It's in the bin. Cueball: No, those are just pieces. They could become spaceships or trains. The house was an arrangement. The arrangement doesn't stay with the pieces and it doesn't go anywhere else. It's just gone. [Ponytail, older, is standing at a desk. She's holding a couple of Lego bricks.] [She looks at the bricks.] [She checks off a box next to the words "Organ Donor" on a paper on the desk.]

Lego blocks are a popular building toy, which Cueball here uses to describe a philosophical conundrum: the distinction between a composition, and the collection of parts that make up that composition. For example, the Lego blocks he and his daughter, Ponytail , used to make a house are still around; they were put back into the bin, and can be used on future designs. However, the house itself, as a specific combination of those blocks, is gone. It ceased to exist when they took it apart. In essence, they "killed" the house. Those blocks could be used to build a car or an airplane, so if there is still a house in the box after it has been dismantled, then there is also a car in the box and a plane in the box, and a large number of other objects in the box: making it a very crowded box. Thus, it is more logical to consider the house to be one possible arrangement of the lego blocks that only exists when the blocks are put in that arrangement. Later in her life, Ponytail extends this thinking to humans and organ donation . The US has an opt-in system for organ donation; in the event that you die, any of your organs or tissues that remain functional after your death can be donated for transplantation or medical research, provided you've opted into the organ donor registry. Ponytail compares her organs to the Lego blocks she's carrying - even if she (the composition) dies, her organs (the pieces) can continue to serve another. As such, she is compelled to register as an organ donor. The title text is the same question asked in the first panel, from this new perspective - instead of asking where the Lego house went, the questioner (presumably a young child, possibly still Ponytail) is asking where their Grandpa went. Humans are a composition of many parts; the parts are usually buried or cremated when we die, but the composition is something else entirely. What exactly happens to a human composition after death is a question for religious debate, but we know for sure it doesn't stay here . Alternatively, if Grandpa chose to donate his organs (or, because the final decision is actually made by the deceased individual's family, if Cueball and Grandpa's other relatives choose to have Grandpa's organs donated), Grandpa would be in multiple other people, assuming that at least some of his organs were fit to be donated when he died. [Ponytail and her father Cueball are putting away Lego bricks.] Cueball: When you take apart a Lego house and mix the pieces into the bin, where does the house go? Ponytail: It's in the bin. Cueball: No, those are just pieces. They could become spaceships or trains. The house was an arrangement. The arrangement doesn't stay with the pieces and it doesn't go anywhere else. It's just gone. [Ponytail, older, is standing at a desk. She's holding a couple of Lego bricks.] [She looks at the bricks.] [She checks off a box next to the words "Organ Donor" on a paper on the desk.]

Sympathy

Sympathy

https://www.xkcd.com/660

https://www.explainxkcd.com/wiki/index.php/660:_Sympathy

Sympathy Tips for Physicists [Cueball and friend are talking.] Friend: The moment my brother died, I felt a searing pain in my heart. Right: [Cueball places his hand on the friend's shoulder.] Cueball: I'm so sorry. Wrong: Cueball: Was it instant, or was there a speed-of-light delay? Very Wrong: [Cueball thoughtfully puts his hand on his chin.] Cueball: If it was instant, with the right arrangement of moving reference frames, we could use this to send signals back in time and violate causality! How many remaining siblings do you have?

This comic plays at the lack of social skills physicists and other people in heavily scientific disciplines are stereotypically believed to have. The example displayed is a case of condolence, in which the appropriate behaviour would of course be to express compassion with the bereaved, as shown in the second panel. In the third panel, the physicist fails to display the endorsed demeanour. Instead, he takes a scientific approach towards the statement of his friend. He points out that the transmission of the pain the latter believes to have felt, is in fact limited by the speed of light and could therefore not have been 'instant'. By saying so, he betrays an absence of feeling towards his friend, as well as his inability to understand the figurative sense of the words. In the last panel, the physicist takes the previous to a bizarre extreme and reflects on the consequences that would follow if the statement of his friend were indeed literally true. According to special relativity , any object travelling faster than at the speed of light would in fact move backwards in time. The physicist therefore plans to utilize this effect in order to construct a tachyonic antitelephone , a device that allows sending information to the past. To confirm the initial condition, he makes the utterly inappropriate proposal to start a series of measurements with other family members of his friend. A correction of the misdemeanour is suggested in the title text: The antitelephone might be used to change causality and save the original brother from dying in the first place. Of course, saying the latter would not be of much help in the given scenario, although it does serve a noticeable improvement over the last two panels. Note how he says 'original brother', noting that although he would have saved his brother, another family member would have to have been killed to do so. The use of right/wrong/very wrong is also presented in 803: Airfoil . Sympathy Tips for Physicists [Cueball and friend are talking.] Friend: The moment my brother died, I felt a searing pain in my heart. Right: [Cueball places his hand on the friend's shoulder.] Cueball: I'm so sorry. Wrong: Cueball: Was it instant, or was there a speed-of-light delay? Very Wrong: [Cueball thoughtfully puts his hand on his chin.] Cueball: If it was instant, with the right arrangement of moving reference frames, we could use this to send signals back in time and violate causality! How many remaining siblings do you have?

Two-Party System

Two-Party System

https://www.xkcd.com/661

https://www.explainxkcd.com/wiki/index.php/661:_Two-Party_System

[Ponytail stands at a podium behind a lectern, giving a speech.] Ponytail: And if I'm elected, I'll try to fix some of these problems. Billy, off-panel: Yeah, right! [A boy in the audience is standing on his chair.] Billy: The real problem is the corporate-run two-party system. Until we fix that , we'll have no real change! Ponytail: Billy, I'm running for class president. We don't even have political parties. Billy: That's because the two-party, uh... estab... uh. Ponytail: Billy, did you learn about politics from the internet? Billy: I thought that one reply was all I ever needed!

Ponytail is running for class president , but gets shouted down by Billy the Political Activist (or at least, he thinks he might become one some day). Someone on the Internet must have told Billy that all he has to know about politics is that America's two-party system is broken. Because we all know the problem with believing what you read on the Internet . The United States uses Plurality voting , where each voter may make one vote per office. In most democratic countries, this system tends to reinforce the top two political parties and marginalize smaller ones (such as the Bull Moose Party , which only lasted from 1912 to 1916) though this is greatly pronounced in the United States, where the Democratic and Republican parties have passed many barriers to entry , making things much more difficult for parties other than themselves to gain any traction. Approval voting (AV) and Instant-runoff voting (IRV) are alternative voting schemes that allow support for multiple candidates. Such systems might make it easier for 3rd parties to field viable candidates. AV is a simple extension of plurality voting where each voter "approves" as many of the candidates as they wish. The winner is the candidate with the most votes. Approval voting tends to favor moderate candidates with broad appeal. IRV is a form of Ranked choice voting where a voter is allowed to select multiple choices, but must assign a rank or weight to each choice. If a candidate receives more than 50% of all 1st choice votes, they win as in a traditional election. If no candidate has a majority of 1st choice votes, the candidate with the fewest 1st choice votes is eliminated, and those 1st choice votes are replaced by their respective 2nd choice option and the resulting totals are compared for a 50%+ winner. This process is repeated until a winner is determined. [Ponytail stands at a podium behind a lectern, giving a speech.] Ponytail: And if I'm elected, I'll try to fix some of these problems. Billy, off-panel: Yeah, right! [A boy in the audience is standing on his chair.] Billy: The real problem is the corporate-run two-party system. Until we fix that , we'll have no real change! Ponytail: Billy, I'm running for class president. We don't even have political parties. Billy: That's because the two-party, uh... estab... uh. Ponytail: Billy, did you learn about politics from the internet? Billy: I thought that one reply was all I ever needed!

iPhone or Droid

iPhone or Droid

https://www.xkcd.com/662

https://www.explainxkcd.com/wiki/index.php/662:_iPhone_or_Droid

[Megan sitting at her computer is talking to Cueball standing behind her.] Megan: Well, it depends what you want. The iPhone wins on speed and polish, but the Droid has that gorgeous screen and physical keyboard. Cueball: What if I want something more than the pale facsimile of fulfillment brought by a parade of ever-fancier toys? To spend my life restlessly producing instead of sedately consuming? Cueball: Is there an app for that ? Megan: Yeah, on both. Megan: Wait, no, looks like it was rejected from the iPhone store. Cueball: Droid it is, then.

The comic starts to set up a joke about the "phone wars" between the iPhone and phones that run the Android system (in this case the Motorola Droid ), but instead just brings up a serious point criticizing the consumerism this "war" stems from. In the last line of panel 2, Cueball refers to the slogan "There's an app for that" from Apple's iPhone marketing. Then the third panel makes a joke anyway, at Apple's expense: apparently, this "enlightenment app" was rejected from Apple's app store, which is the only supported way to put software on an iPhone. Apple has become infamous for rejecting apps from their app store without adequately explaining why. Android devices, on the other hand, are not limited to an app store and can install software from any origin. Many, however, use the Google Play Store as a primary repository for apps. In the title text Cueball succumbs to the consumerism and marvels at the Motorola Droid's high (at the time) Pixel density . Apple responded 9 months later by releasing the iPhone 4 with a 326 ppi Retina Display . (Higher pixel densities are now standard for smartphones.) [Megan sitting at her computer is talking to Cueball standing behind her.] Megan: Well, it depends what you want. The iPhone wins on speed and polish, but the Droid has that gorgeous screen and physical keyboard. Cueball: What if I want something more than the pale facsimile of fulfillment brought by a parade of ever-fancier toys? To spend my life restlessly producing instead of sedately consuming? Cueball: Is there an app for that ? Megan: Yeah, on both. Megan: Wait, no, looks like it was rejected from the iPhone store. Cueball: Droid it is, then.

Sagan-Man

Sagan-Man

https://www.xkcd.com/663

https://www.explainxkcd.com/wiki/index.php/663:_Sagan-Man

[A yellow box extends across the top of the first 3 of 5 panels, introducing Sagan-Man:] Bitten by a radioactive Carl Sagan in 1995, Sagan-Man possesses the powers and abilities of Carl Sagan. [A Cueball-like character is standing on the left side of the panel, with a victim off-panel to the right.] Victim (off-panel): Help! Thief! [The Cueball-like character spins around, turning into Sagan-Man with a blue cape appearing on his back.] [Sagan-Man runs to the right towards the direction of the victim.] [Sagan-Man encounters the thief, who is holding a purse.] Sagan-Man: Hey, you! Thief: What? [Sagan-Man and the thief are now standing facing each other.] Sagan-Man: Do you realize just how crazy it is that we've BEEN TO THE MOON?

Carl Sagan was an advocate for science, space and SETI (Search for Extra-Terrestrial Intelligence). He wrote the book Contact , which was later made into the movie by the same name. While Sagan did not emit anomalous radiation in his lifetime [ citation needed ] , he did receive acclaim in the field of radiology, namely for using radiation to synthesize amino acids from simpler chemicals. This comic is parodying Spider-Man , in which Peter Parker is bitten by a radioactive spider to become Spider-Man. In this comic "a radioactive Carl Sagan" turns the person into "Sagan-Man". Apparently, Sagan-Man is able to stop thieves in their tracks by blowing their minds with inspiring scientific facts. The title text implies that Sagan-Man's vivid imagery inspires the entire "criminal class" to give up their anti-social ways and turn to space research. [A yellow box extends across the top of the first 3 of 5 panels, introducing Sagan-Man:] Bitten by a radioactive Carl Sagan in 1995, Sagan-Man possesses the powers and abilities of Carl Sagan. [A Cueball-like character is standing on the left side of the panel, with a victim off-panel to the right.] Victim (off-panel): Help! Thief! [The Cueball-like character spins around, turning into Sagan-Man with a blue cape appearing on his back.] [Sagan-Man runs to the right towards the direction of the victim.] [Sagan-Man encounters the thief, who is holding a purse.] Sagan-Man: Hey, you! Thief: What? [Sagan-Man and the thief are now standing facing each other.] Sagan-Man: Do you realize just how crazy it is that we've BEEN TO THE MOON?

Academia vs. Business

Academia vs. Business

https://www.xkcd.com/664

https://www.explainxkcd.com/wiki/index.php/664:_Academia_vs._Business

[Cueball sits at a desk in front of a computer, leaning back in his chair with both hands down to his side. There are cans on the desk and more crushed ones on the floor.] Cueball: I just wrote the most beautiful code of my life. [Zoom in on Cueball and top half of desk.] Cueball: They casually handed me an impossible problem. In 48 hours and 200 lines, I solved it. [Curved lines with arrows divide the comic into two possible end panels, labeled "Academia" and "Business."] Academia: Professor: My god... this will mean a half-dozen papers, a thesis or two, and a paragraph in every textbook on queuing theory! Business: Boss: You got the program to stop jamming up? Great. While you're fixing stuff, can you get Outlook to sync with our new phones?

Cueball has solved some tricky and very important problem in computer science, related to queueing theory . The comic splits into two timelines. Showing the brilliant computer code he'd written to somebody who actually knows computer code allows the academic to see the programmer's true brilliance and get him much-earned plaudits from the academic community. In the alternate timeline – implied to be what actually happens – the boss, not possessing that knowledge, simply sees the results and not the means Cueball used to attain them. He then gives Cueball another assignment. This, sadly, is the usual course of events in bureaucracy, which only seems to care about your results, not how you came about them. To drive in the point, the boss asks Cueball to do something as simple as setting up email on the office phones, a stark contrast to the skill and creativity Cueball would have needed to write his code in the first panel. The references in the title text are to the P versus NP problem , a famous unsolved problem in computer science, and the "magical constant" (0x5f375a86) used in finding the fast inverse square root , i.e. solving y=1/√x as fast as possible through a program – no-one knows quite who came up with this very useful bit of code (Now believed to be devised by Greg Walsh at Ardent Computer in consultation with Cleve Moler, the creator of MATLAB. see wikipedia), but it was discovered hiding in the graphics code of the video game Quake III Arena . Note that the actual constant used in the Quake III source code is 0x5f375 9df , but the constant in the title text works also, and is actually slightly more accurate as shown in this paper: Fast inverse square root by CHRIS LOMONT (Purdue university, 2003) . The title text may be a reference to Stephen Jay Gould 's quotation: “I am, somehow, less interested in the weight and convolutions of Einstein’s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops.” originally about how great minds are suppressed due to racism and their genius go unknown, but could be interpreted as general exploitation by the commercial world. [Cueball sits at a desk in front of a computer, leaning back in his chair with both hands down to his side. There are cans on the desk and more crushed ones on the floor.] Cueball: I just wrote the most beautiful code of my life. [Zoom in on Cueball and top half of desk.] Cueball: They casually handed me an impossible problem. In 48 hours and 200 lines, I solved it. [Curved lines with arrows divide the comic into two possible end panels, labeled "Academia" and "Business."] Academia: Professor: My god... this will mean a half-dozen papers, a thesis or two, and a paragraph in every textbook on queuing theory! Business: Boss: You got the program to stop jamming up? Great. While you're fixing stuff, can you get Outlook to sync with our new phones?

Prudence

Prudence

https://www.xkcd.com/665

https://www.explainxkcd.com/wiki/index.php/665:_Prudence

[A small girl, with hair like Megan, is running towards a closed wardrobe.] Voice (off-panel): Everyone hide! 99... 98... 97... [The girl opens one of the two doors on the wardrobe.] Wardrobe: click [The girl is looking inside the wardrobe through the fully opened door.] Girl: !!! [The girl puts a hand to her chin.] [The girl walks away.] [The girl returns with an armful of electronics including lots of wires and a rover with wheels.] [The girl is kneeling, typing on a laptop, which has a cord extending into the wardrobe.] [In a forest with many tall leafless trees the Mars rover is approaching a lamppost with a lit candle. Behind it stands a faun with horns, goatee beard and hooves holding an umbrella.]

This comic references the fantasy novel series The Chronicles of Narnia by C. S. Lewis . In the first published book (second chronologically), The Lion, the Witch and the Wardrobe , Lucy discovers the fictional world of Narnia which can be accessed through a wardrobe, and she walks into it without ever considering the risks. Her three older siblings do not believe her, so she travels back alone again. But this second time her brother Edmund follows her, and he is seduced by the White Witch in order for her to be able to kill him and his three siblings (see title text explanation below). Thus proving that it was a rather dangerous move to just walk into the wardrobe. The comic mocks the imprudent behavior shown by the protagonist Lucy of the novel, who enters the world of Narnia without knowing anything about its dangers. In the comic, Lucy (drawn as a child version of Megan , clearly not adult as she only just reaches the wardrobes handles with her head), discovers the magical wardrobe while playing hide-and-seek , like in the book. Unlike in the original book, Lucy does not precipitately set foot into Narnia. Instead, she fetches her technical equipment and sends a remote-controlled probe through the wardrobe door in order to sound the situation first. The probe encounters Mr. Tumnus the faun with his umbrella at a lamppost in a snowy wood on the last panel. This picture is the first impression of Narnia in the novels and was apparently Lewis' original idea for the series. The probe is clearly modeled after Mars rovers like Spirit and Opportunity, which Randall depicted for the first time only a few comics later in 681: Gravity Wells and then in 695: Spirit . The probe looks even more like the one in 1504: Opportunity . This also explains the title of the comic, as it is the name of Lucy's probe. The naming scheme is similar to the two probes mentioned above that were already on Mars at the time of this comics release. And even more so like the upcoming Curiosity rover which was first launched two years after this comic, but had been named earlier in the year this comic was released. Lucy was curious in the first Narnia book, but in this comic she is prudent . The White Witch mentioned in the title text is the main antagonist in the novel. She originally lures Edmund with a hot drink and magical Turkish delight after her sleigh passes right by him. In the scenario mentioned in the title text, she is confused when she rolls up to the rover and then tries to tempt the probe with a firmware update accordingly. The procedure of sending a probe first through a portal has also been used in the early Stargate episodes. This draws a parallel between the wardrobe in Narnia and the Stargate, both connecting two distant worlds. The stargate probe can be seen here . Megan (or Lucy) also takes a scientific approach to Narnia in one of the comics of 821: Five-Minute Comics: Part 3 . In that comic she uses the different passage of time in Narnia to her advantage (it usually runs much faster than on Earth). That effect would have been a problem with controlling the rover in this comic. [A small girl, with hair like Megan, is running towards a closed wardrobe.] Voice (off-panel): Everyone hide! 99... 98... 97... [The girl opens one of the two doors on the wardrobe.] Wardrobe: click [The girl is looking inside the wardrobe through the fully opened door.] Girl: !!! [The girl puts a hand to her chin.] [The girl walks away.] [The girl returns with an armful of electronics including lots of wires and a rover with wheels.] [The girl is kneeling, typing on a laptop, which has a cord extending into the wardrobe.] [In a forest with many tall leafless trees the Mars rover is approaching a lamppost with a lit candle. Behind it stands a faun with horns, goatee beard and hooves holding an umbrella.]

Silent Hammer

Silent Hammer

https://www.xkcd.com/666

https://www.explainxkcd.com/wiki/index.php/666:_Silent_Hammer

[Black Hat is hammering something on a table.] Cueball: What— Black Hat: Silent hammer. I've made a set of silent tools. Cueball: Why? Hammer: woosh woosh woosh Black Hat: Stealth carpentry. Breaking into a house at night and moving windows, adjusting walls, etc. [He takes his silent hammer over to a tool bench with other things on it. Two boxes underneath are labeled "Drills" and "Non-Drills."] Black Hat, narrating: After a week or so of questioning his own sanity, the owner will stay up to watch the house at night. I'll make scratching noises in the walls, pipe in knockout gas, move him up to his bed, and never bother him again. [The events he's describing are shown in two mini-panels below.] [Zoom in on Black Hat, with Cueball off-panel to the left.] Cueball, off-panel: Nice prank, I guess, but what's the point? Black Hat: Check out the owner's card, on the table. Cueball, off-panel: Chair of the American Skeptics Society? Oh, god. Black Hat: Yeah, this doesn't end well for him.

Black Hat has created a set of tools that work in complete silence so that he can go to the house of the chairman of the American Skeptics Society late at night, do some rearranging of walls and moving of windows, just to screw with him in typical Black Hat fashion. Imagine how surprised the person must be when they wake up and discover their whole house has been rearranged! A skeptic is someone who questions knowledge, facts and beliefs, especially of supernatural phenomena like the existence of poltergeists which Black Hat is trying to imitate with his rearranging and scratching noises. The American Skeptics Society is a non-profit organization dedicated to promoting skeptical and critical thinking in education and public discourse. The executive director and chief editor of the Skeptic Magazine , Michael Shermer , is a leading proponent of skepticism, and has written many books and articles debunking pseudoscience, fringe science, quack medicine, alien abductions, conspiracy theories and supernatural phenomena . The Skeptic Society website and Skeptic magazine feature a lot of material debunking anecdotal accounts of these phenomena, explaining how events like "hauntings" could have occurred without supernatural intervention. One of the premises of modern skepticism is that the supernatural is not rejected out of hand; if someone came up with a proper scientific hypothesis that predicted something supernatural and that hypothesis was proven beyond reasonable doubt, a skeptic would accept that the supernatural thing in question was probably correct. In the title text Cueball realizes that Black Hat has (probably intentionally) ruined his antique table by demonstrating his silent hammer. Black Hat's tools are seen in two boxes labeled "Drills" and "Non-Drills", likely a reference to the phrase "this is not a drill", used to differentiate an emergency situation from a practice of procedure for such. Note that this comic is numbered 666 (number) , which is often associated with supernatural things due to it being consider the "number of the beast" by some people. [Black Hat is hammering something on a table.] Cueball: What— Black Hat: Silent hammer. I've made a set of silent tools. Cueball: Why? Hammer: woosh woosh woosh Black Hat: Stealth carpentry. Breaking into a house at night and moving windows, adjusting walls, etc. [He takes his silent hammer over to a tool bench with other things on it. Two boxes underneath are labeled "Drills" and "Non-Drills."] Black Hat, narrating: After a week or so of questioning his own sanity, the owner will stay up to watch the house at night. I'll make scratching noises in the walls, pipe in knockout gas, move him up to his bed, and never bother him again. [The events he's describing are shown in two mini-panels below.] [Zoom in on Black Hat, with Cueball off-panel to the left.] Cueball, off-panel: Nice prank, I guess, but what's the point? Black Hat: Check out the owner's card, on the table. Cueball, off-panel: Chair of the American Skeptics Society? Oh, god. Black Hat: Yeah, this doesn't end well for him.

SkiFree

SkiFree

https://www.xkcd.com/667

https://www.explainxkcd.com/wiki/index.php/667:_SkiFree

[A screenshot of SkiFree, with the abominable snowman running towards the player.] [Megan is sitting at her computer with her hands on the keyboard and thinking to herself:] Megan (thought bubble): I've always thought of the SkiFree monster as a metaphor for the inevitability of death. [Cueball comes up behind her in a frameless panel.] Cueball: SkiFree, huh? You know, you can press "F" to go faster than the monster and escape. [The screenshot again. The player is zooming away from the monster.] [Megan sits at her computer in silence, with her hands now down to to her side.]

SkiFree is a video game released in 1991 which enjoyed popularity on the desktop computers of the time. In the game, you're a downhill skier who attempts to ski down a hill while avoiding obstacles which cause you to crash (which slows you down). At the start of the game, you can choose to go down three different timed/scored courses, or ignore them all and ski freely. Beyond the end of the courses you can continue skiing downhill. You can also move (slowly) uphill and sideways. If you ski too far down the hill a monster similar to one in the comic will begin to chase you; contact with the monster ends the game. Since it's much faster than you normally, you'll get caught. The monster also appears if you travel too far in the sideways or upwards directions. One of the lesser known commands in SkiFree is the 'F' key, which speeds you up, even faster than the monster. A second monster appears slightly further down the hill but by skiing downhill diagonally with the F key it is possible to evade both. The joke here is that Megan has thought long and hard about the concept of the monster, relating it to the inevitability of death, and is nonplussed by the revelation that there is a simple mechanism that may allow her to escape it, thus ruining the poetic metaphor. The title text refers to pendants or talismans that are worn to protect oneself from harm or to remind oneself of an important truth. Megan, seeing that the F key allowed her to evade inevitable death in the game, comes to believe that the F key confers some sort of immortality. Alternatively, it may be symbolic as the monster in SkiFree seemed insurmountable (just like death) but might have a discovery in the future (the 'F' key) that can overcome it. [A screenshot of SkiFree, with the abominable snowman running towards the player.] [Megan is sitting at her computer with her hands on the keyboard and thinking to herself:] Megan (thought bubble): I've always thought of the SkiFree monster as a metaphor for the inevitability of death. [Cueball comes up behind her in a frameless panel.] Cueball: SkiFree, huh? You know, you can press "F" to go faster than the monster and escape. [The screenshot again. The player is zooming away from the monster.] [Megan sits at her computer in silence, with her hands now down to to her side.]

Pandora

Pandora

https://www.xkcd.com/668

https://www.explainxkcd.com/wiki/index.php/668:_Pandora

[There is a venn diagram of two circles. The left circle is labeled "Music You Like." The right circle is labeled "Deeply Embarrassing Music." The segment on the left is labeled "What Pandora Plays," and the intersection is labeled "What Pandora Plays If Anyone Is Around."]

Pandora is a website which automatically plays songs of a certain genre based upon the user's previous musical selections. Unlike normal radio, it adapts itself to each individual user's preferences, producing playlists that the user should find enjoyable based on the user's taste in music. In other words, Pandora plays music you will probably like. One may not want friends to find out that one enjoys certain songs and/or certain kinds of songs ("embarrassing music"), for fear of looking childish, sentimental, etc. A recent example is the soundtrack to the 2013 film Frozen : although enjoying popularity and critical acclaim, it is considered by many to be embarrassing music, because they do not want others to know that they like a soundtrack to a Disney animated film. One certainly does not want one's embarrassing music to be played on Pandora when others are around. The frequency of this depends on individual circumstances, but generally one's embarrassing music is a small fraction of all music one likes. However, due to biased memory , people remember cases where embarrassing music is played in others' presence far better than those where "acceptable music" is played. So it appears that when others are around Pandora only plays embarrassing music. The title text presents an example of this, the music in question being the soundtrack to Enchanted , a fantasy romantic comedy film produced by Walt Disney Pictures. Despite the user proclaiming that the Pandora algorithm is terrible to explain why it's playing the Enchanted soundtrack, after a short period of silence the user quietly begins singing along to the song " That's How You Know " from the soundtrack, which is apparently the song currently playing. [There is a venn diagram of two circles. The left circle is labeled "Music You Like." The right circle is labeled "Deeply Embarrassing Music." The segment on the left is labeled "What Pandora Plays," and the intersection is labeled "What Pandora Plays If Anyone Is Around."]

Experiment

Experiment

https://www.xkcd.com/669

https://www.explainxkcd.com/wiki/index.php/669:_Experiment

[Darkness.] [Cueball is standing next to a laptop, looking groggy.] Cueball: Ugh... Cueball: What happened? [Cueball begins to regain some awareness, with his speech eventually fading out.] Cueball: Where am I? FWOOOOOOSH Cueball: Help! Someone help me (unintelligible speech due to loss of air in dome) [Cueball holds his hands to his mouth.] [Cueball looks shocked.] [Cueball tries to run, but has no traction against the ground.] [Cueball falls down.] [Cueball lies prone and motionless.] [Black Hat and Danish watching from outside the dome, with Black Hat holding a clipboard as if to take notes.] [Black Hat and Danish outside the dome. Black Hat is now holding the clipboard down to his side.] Black Hat: Huh. Looks like physics professors don't like working in frictionless vacuums after all. Danish: They're such liars.

Problems in the study of kinematics often idealize the environment of the problem for the sake of simplicity. Specifically, it is assumed that objects are moving in a vacuum and that there is no friction . Then the complicated effects of air resistance and surface frictions can be ignored, and the more basic principles of momentum and energy can be explored. In more advanced physics, it is often easier or necessary to ignore friction if the process being studied is very complicated. So it could be said that "physics professors like working in a frictionless vacuum". In the comic, Black Hat and Danish have interpreted that statement to mean that physics professors like doing their work while they are in a frictionless vacuum, instead of liking to work with problems which are set in a frictionless vacuum. Apparently, they have drugged a physics professor and put him in a glass dome (with his laptop so he can work) which they can evacuate and make frictionless. The professor wakes up confused from the drugs, and as the air is pumped out to make a vacuum (presumably slowly enough to prevent explosive decompression from coming into play), his words fade to silence because sound waves requires a substance such as air to travel through. As he starts to panic, he tries to run, presumably for the door we see in the last panels. However, without friction on the floor, he cannot exert any force to move forward, and his feet skate uselessly on the ground until he loses balance and falls. At this point he is probably suffering from asphyxiation . Black Hat and Danish are observing from outside the dome, and decide that physics professors have lied about liking to work in frictionless vacuums. The title text refers to another common idealization, of an infinite plane of uniform density . An infinite plane extends forever in two dimensions, which makes calculations easier because surface-related properties are identical everywhere. "Uniform density" could refer to the mass density of the plane, or more likely an electric charge density, which makes a common problem in basic electromagnetism involving calculating the electric field . The "other two physicists" that Black Hat and Danish are experimenting on are lost on the infinite plane, since there are no edges or landmarks anywhere to give them direction. It should be noted that, although a vacuum can be approximated using a vacuum pump , frictionless surfaces and infinite planes are only imaginary constructs and do not exist in our universe. [ citation needed ] [Darkness.] [Cueball is standing next to a laptop, looking groggy.] Cueball: Ugh... Cueball: What happened? [Cueball begins to regain some awareness, with his speech eventually fading out.] Cueball: Where am I? FWOOOOOOSH Cueball: Help! Someone help me (unintelligible speech due to loss of air in dome) [Cueball holds his hands to his mouth.] [Cueball looks shocked.] [Cueball tries to run, but has no traction against the ground.] [Cueball falls down.] [Cueball lies prone and motionless.] [Black Hat and Danish watching from outside the dome, with Black Hat holding a clipboard as if to take notes.] [Black Hat and Danish outside the dome. Black Hat is now holding the clipboard down to his side.] Black Hat: Huh. Looks like physics professors don't like working in frictionless vacuums after all. Danish: They're such liars.

Spinal Tap Amps

Spinal Tap Amps

https://www.xkcd.com/670

https://www.explainxkcd.com/wiki/index.php/670:_Spinal_Tap_Amps

[Nigel Tufnel of Spinal Tap is showing off his amplifier to Cueball.] Nigel: These amps go to 11. Cueball: Is that louder? Nigel: It's one louder. Normal Person: Cueball: Why not make 10 louder and make 10 the highest? Engineer: Cueball: But 11 doesn't have any units. It's an arbitrary scale mapping outputs— Nigel: Zzzz Smart Engineer: Cueball: For $2,000 I'll build you one that goes to 12.

This comic is in reference to the 1984 mock documentary This Is Spinal Tap about the tour of the fictional rock band Spinal Tap. Here we see lead guitarist Nigel Tufnel (a character portrayed in the movie by Christopher Guest ) explaining to Cueball how the volume dial on his amp goes all the way up to eleven . This is impressive to Nigel since guitar amplifiers generally only have ten as the maximum setting. This leads him to believe his amp is "one" louder than other amplifiers . In reality, the loudness of an amplifier is largely dependent on how much power is supplied to its electronics. Markings on the volume dial are merely an aspect of appearance and has no influence on the maximum achievable loudness. The highest mark could just as easily be labelled 'Maximum', which would then accurately describe the meaning of that setting. Thus, the phrase "goes to eleven" is often used sarcastically to mock people or statements that rely on arbitrary numbers without comparable units or context. The comic then extends the joke by presenting three types of reactions from different people: The title text further plays on the fact that the amp's levels are on an arbitrary scale. Many products are sold at a certain price per unit weight, volume, etc. (e.g., $2.99/lb for grapes). Nigel calculates that the $2000 cost for going up to 12 would equal to $2000 / 12, or less than $200 per unit of something, but he is unable to articulate what that "something" is, confirming the third panel observation of the normal engineer. Also, he already has an amplifier that goes up to eleven, so the one additional unit would cost him $2,000 unless he sells the old amplifier. However, he decides that it's a good deal anyway, and it looks like the smart engineer has made a sale. [Nigel Tufnel of Spinal Tap is showing off his amplifier to Cueball.] Nigel: These amps go to 11. Cueball: Is that louder? Nigel: It's one louder. Normal Person: Cueball: Why not make 10 louder and make 10 the highest? Engineer: Cueball: But 11 doesn't have any units. It's an arbitrary scale mapping outputs— Nigel: Zzzz Smart Engineer: Cueball: For $2,000 I'll build you one that goes to 12.

Stephen and Me

Stephen and Me

https://www.xkcd.com/671

https://www.explainxkcd.com/wiki/index.php/671:_Stephen_and_Me

[Beret Guy is speaking into a microphone standing in front Ponytail who is filming him with a camera, a coiled wire from the camera going down her bag and in front of her feet there is a sign. Megan is walking towards them with a briefcase looking down.] Beret Guy: I'm documenting my quest to meet with the CEO of Volvo. Megan: Get lost. Sign: Volvo Cars [In a frame-less panel two security guards/police officers with peaked caps with white emblems are attempting to restrain Beret Guy and taking the camera away from Ponytail, or at least lifting it up in the air. Beret Guy is leaning to the right standing like a bow trying to get to the CEO. There is no sign of the sign.] Beret Guy: Wait! I've come so far! Just let me see him! [They've reached the CEO, Cueball, sitting in an office chair behind his desk, which has the Volvo logo on it with the arrow up and out to the right of the circle around the word. He is sitting leaning his elbows on the table top where there is a round item on a foot as at the front of the desk as well as a box for the intercom. Ponytail is filming with the camera, and Beret Guy stand with the microphone down.] CEO: All right, you've reached me. What is it you want to talk about? Logo: Volvo [Same setting with Beret Guy talking into the microphone and the CEO leaning forward, pushing the bottom of the intercom. The other small item has disappeared.] Beret Guy: Do you realize how much your company's name sounds like "vulva"? CEO: Security? Logo: Volvo

This is a reference to the 1989 documentary Roger & Me , in which director Michael Moore attempted to confront General Motors CEO Roger E. Smith over the company's closure of factories in his home town of Flint, Michigan. Moore uses the documentary to demonstrate his belief that the factory closures had a crippling effect on the local economy, and his objective is to ask the CEO pointedly about GM's disregard for the lives affected by their business decisions. In this strip, Beret Guy mirrors Moore's determination to speak with the CEO of the auto company Volvo Cars , only to reveal that his burning question is actually trivial and juvenile in nature, comparing the company name with the outer parts of the female genitals. "Stephen" is probably Steve Odell , the CEO of Volvo Cars in 2009, a subsidiary of Ford by that time, and later taken over by the Chinese company Zhejiang Geely Holding Group . As for Beret Guy's question itself, the two words are related: Volvo is Latin for 'I roll', and is at the root of volva, vulva 'wrapper, covering' . However, the similarity that Beret Guy (or Randall) hears is likely due to American English, which strongly approximates the pronunciation of u and a in vulva to that of the o' s in Volvo . Volvo was founded and is headquartered in Sweden, where the similarity would not be as striking. [Beret Guy is speaking into a microphone standing in front Ponytail who is filming him with a camera, a coiled wire from the camera going down her bag and in front of her feet there is a sign. Megan is walking towards them with a briefcase looking down.] Beret Guy: I'm documenting my quest to meet with the CEO of Volvo. Megan: Get lost. Sign: Volvo Cars [In a frame-less panel two security guards/police officers with peaked caps with white emblems are attempting to restrain Beret Guy and taking the camera away from Ponytail, or at least lifting it up in the air. Beret Guy is leaning to the right standing like a bow trying to get to the CEO. There is no sign of the sign.] Beret Guy: Wait! I've come so far! Just let me see him! [They've reached the CEO, Cueball, sitting in an office chair behind his desk, which has the Volvo logo on it with the arrow up and out to the right of the circle around the word. He is sitting leaning his elbows on the table top where there is a round item on a foot as at the front of the desk as well as a box for the intercom. Ponytail is filming with the camera, and Beret Guy stand with the microphone down.] CEO: All right, you've reached me. What is it you want to talk about? Logo: Volvo [Same setting with Beret Guy talking into the microphone and the CEO leaning forward, pushing the bottom of the intercom. The other small item has disappeared.] Beret Guy: Do you realize how much your company's name sounds like "vulva"? CEO: Security? Logo: Volvo

Suggestions

Suggestions

https://www.xkcd.com/672

https://www.explainxkcd.com/wiki/index.php/672:_Suggestions

[Cueball is sitting at his computer. Facebook sidebar messages appear on the top of each panel, with a user photo of Susie (looking like Megan leaning forward so her hair hangs down the sides of her face) and a few lines of text.] Facebook: Susie Reconnect with her [Phone icon] Send her a text Cueball: Come on, Facebook. I know I shouldn't. Facebook: Susie She'd come over [Bed icon] You don't have to fall asleep alone. Cueball: It's been so hard to stop. But she's falling for me, and I can't keep getting her hopes up like this. Facebook: Susie Life is complicated [Icon of stick figures embracing] She's so warm against you. You both want it. Cueball: (pulling out phone) Maybe if I just make it clear it's not going to be a thing... Cueball: Yeah, we'll just have a talk. Facebook: Susie Oh yeah. Mmm... [Webcam icon] Leave your webcam on so I can watch. Cueball: Okay, this feature is getting creepier and creepier.

Social networking site Facebook routinely suggests reconnecting with Facebook friends whom you haven't interacted with on the website for a while. This is taken to its logical extreme in this comic when that Facebook feature repeatedly, in an increasingly voyeuristic fashion, tries to get Cueball to hook up with his occasional friend-with-benefits Susie, despite the fact that Cueball knows she's falling for him and doesn't want to lead her on. According to the title text, Cueball and Susie (who is drawn as a sexy version of Megan ) do end up hooking up, even against Cueball's better judgement, as so often happens between people who're physically attracted to one another. And he apparently left the webcam on as well, because the Facebook feature is now giving suggestions on what Cueball should do to her, mid-coitus. Obviously, this is not something that Facebook, a social networking site, can do, yet. [ citation needed ] [Cueball is sitting at his computer. Facebook sidebar messages appear on the top of each panel, with a user photo of Susie (looking like Megan leaning forward so her hair hangs down the sides of her face) and a few lines of text.] Facebook: Susie Reconnect with her [Phone icon] Send her a text Cueball: Come on, Facebook. I know I shouldn't. Facebook: Susie She'd come over [Bed icon] You don't have to fall asleep alone. Cueball: It's been so hard to stop. But she's falling for me, and I can't keep getting her hopes up like this. Facebook: Susie Life is complicated [Icon of stick figures embracing] She's so warm against you. You both want it. Cueball: (pulling out phone) Maybe if I just make it clear it's not going to be a thing... Cueball: Yeah, we'll just have a talk. Facebook: Susie Oh yeah. Mmm... [Webcam icon] Leave your webcam on so I can watch. Cueball: Okay, this feature is getting creepier and creepier.

The Sun

The Sun

https://www.xkcd.com/673

https://www.explainxkcd.com/wiki/index.php/673:_The_Sun

[Caption above the first panel, which is lower than the rest:] Coming this March from the makers of The Core ... [Ponytail is standing on a raised platform looking through a huge telescope (exiting the panel to the left) in an observatory. To her right is a large station with three screens and two Cueball-like guys are standing on the floor to the of that right. Behind them is another station with a large panel showing two circles with an arrow pointing from the top left to the bottom right.] Ponytail: The sun's fusion is failing! Man 1: Does that make sense? Man 2: Whatever. [Zoom in on the scene where Ponytail throws up her arms as she turns towards the two Cueball, still standing on the platform, but the rest of the background is white. The first Cueball turns around and points to the other Cueball who has also turned around and has taken a phone of the hook, the curled cord disappearing at the panels right edge.] Ponytail: If we don't send a ship to restart it, it could go out completely! Man 1: Call NASA! Man 2 (into the phone): Assemble our hottest astronauts. [Another Cueball-like guy has taken the call, and still stands with the phone in hand, the cord attached to the phone hook on the panels left edge. He stands with the helmet of a space suit under his other arm, obviously being an astronaut. Behind him is a fourth Cueball-like guy, Megan and another Ponytail.] Astronaut: The earth bathed in eternal darkness? A night without a dawn? Not on my watch! Astronaut: Saddle up. [The same four characters are shown in silhouette on gray background (still only one with helmet under arm), casting huge shadows towards the bottom of the panel from the dim sun in the top center of the panel. Above the sun is written a tagline (for the movie) and at the bottom of the panels with shadows falling over it is a second smaller tagline:] It's Daylight saving time. Never fall back.

This comic makes fun of science fiction disaster movies , especially the 2003 film The Core in which a group of scientists travel through the Earth's mantle to place a series of nuclear devices in order to speed up the slowing rotation of the Earth's core and prevent a complete collapse of Earth's magnetic field. The comic is also a pun on "Daylight Saving Time", using it to mean saving the sun's light rather than its usual meaning of the semi-annual shift in clocks to "save" daylight for a more useful part of the day. This comic presents the next film from the makers of The Core . In this case an astronomer, Ponytail , discovers that the Sun's fusion is failing. The two Cueball -like guys behind her are not impressed; one is disbelieving and the other is not interested ("whatever"). But then Ponytail rallies them by pointing out the impeding doom for Earth and they call NASA . A group of astronauts at NASA takes the call and the leader (another Cueball-like guy) describes what could happen in trailer-like fashion: Then he tells his team of astronauts - a fourth Cueball-like guy, Megan and another Ponytail - to "saddle up", and the comic finishes with the poster (a copy of the one for The Core with the Sun in place of the Earth's mantle) of this new movie called The Sun (hence the title of the comic) with two taglines: The movie describes a scenario in which "the sun's fusion is failing". This is in fact the exact plot of the British science fiction film Sunshine from 2007, released two years before this comic, which was about a group of astronauts sent on a mission to reignite a dying Sun with a battery of nuclear bombs. The sun 's energy comes from nuclear fusion reactions among the extremely hot, dense hydrogen nuclei in its core. The idea of the sun's fusion failing is rather ridiculous from a scientific perspective, because the fusion reactions are well understood and the sun has enough hydrogen to fuel it for about 5 billion more years. Even if the sun's hydrogen was getting low, it would start fusing helium and begin expanding into a red giant . This would then make the Earth uninhabitable. In other words, if the sun stopped fusing, we wouldn't have to worry about less sunlight, we would have to worry about more. In any case, it appears to be failing and the solution is to send a team of astronauts to the sun to restart the fusion. The team leader is motivated by concern that if the sun's fusion stops, there will be no more light, and so the earth will be in perpetual darkness. The poster in the final panel gives the movies two taglines, both puns. Daylight saving time (DST) refers both to the policy of changing clocks and to the scenario in this movie in which it is time for the team to literally save the sun's daylight from being extinguished. "Never fall back" is an additional word play on the mnemonic used (in the States at least) to remember the direction to change clocks. The mnemonic, "spring forward, fall back" indicates that in the springtime, clocks get set ahead by an hour, while in fall the clocks are set backwards an hour. The phrase "fall back", however, can also mean to retreat from a battle. Randall seems to believe that DST makes little sense today and he has made it clear in several comics that he is not a fan — or at least not a fan of the twice-yearly transitions between the two semi-arbitrary time standards. As DST is the main joke of the comic (and the title of the next movie), the comment from the astronaut about this not happening "on my watch" may be a pun relating to his wristwatch. He would not wish to have DST on his watch! This meaning is made clear in the title text (see below). The comic makes fun of these disaster movies in a couple of ways. The characters in the first panel acknowledge that the scenario doesn't make sense scientifically, but are prepared to sacrifice scientific value for the plot. Also, in the second panel, the team is to be composed of NASA 's "hottest astronauts", which makes fun of the fact that the characters in movies are much more attractive than average, and the fact that they will be much hotter when they reach the sun. The team leader expresses his concern with a few buzz phrases often used in such films. An alternative explanation, which would make sense scientifically, is that the sun had never stopped working, and Ponytail merely assumed that something was wrong with the sun when the sunrise did not occur at its normal time, but that was only because the clocks had been sent an hour ahead for DST, and not because of anything wrong with the sun, which continued working properly, oblivious to earth clocks. The title text continues the lunacy (solacy?) of the situation with the cliché of the "obligatory bad guy" — a person in the plot who acts antagonistic, often for the flimsiest of reasons. There is also the common complaint, especially among the technologically inept, that he can't figure out how to change the time, relating back to DST, and using the phrase "on my watch" as a pun here (if you interpret "watch" in the sense of a wristwatch). The phrase "on my watch" was used in the comic itself, but it isn't clear whether it was intended as a pun. It's possible that Randall realized he missed his chance to make a great pun with that phrase, inspiring the title text. Note that while four different Cueballs in a comic is not uncommon , it is rare that two different Ponytails are shown in one comic. [Caption above the first panel, which is lower than the rest:] Coming this March from the makers of The Core ... [Ponytail is standing on a raised platform looking through a huge telescope (exiting the panel to the left) in an observatory. To her right is a large station with three screens and two Cueball-like guys are standing on the floor to the of that right. Behind them is another station with a large panel showing two circles with an arrow pointing from the top left to the bottom right.] Ponytail: The sun's fusion is failing! Man 1: Does that make sense? Man 2: Whatever. [Zoom in on the scene where Ponytail throws up her arms as she turns towards the two Cueball, still standing on the platform, but the rest of the background is white. The first Cueball turns around and points to the other Cueball who has also turned around and has taken a phone of the hook, the curled cord disappearing at the panels right edge.] Ponytail: If we don't send a ship to restart it, it could go out completely! Man 1: Call NASA! Man 2 (into the phone): Assemble our hottest astronauts. [Another Cueball-like guy has taken the call, and still stands with the phone in hand, the cord attached to the phone hook on the panels left edge. He stands with the helmet of a space suit under his other arm, obviously being an astronaut. Behind him is a fourth Cueball-like guy, Megan and another Ponytail.] Astronaut: The earth bathed in eternal darkness? A night without a dawn? Not on my watch! Astronaut: Saddle up. [The same four characters are shown in silhouette on gray background (still only one with helmet under arm), casting huge shadows towards the bottom of the panel from the dim sun in the top center of the panel. Above the sun is written a tagline (for the movie) and at the bottom of the panels with shadows falling over it is a second smaller tagline:] It's Daylight saving time. Never fall back.

Natural Parenting

Natural Parenting

https://www.xkcd.com/674

https://www.explainxkcd.com/wiki/index.php/674:_Natural_Parenting

[Cueball and Megan are looking down at a baby, throwing its arms in the air, standing between them.] Cueball: Oh man, we made a baby. Megan: Don't panic. Don't panic. Baby: Baby! [Cueball looks at Megan, who still look down at the baby, which now looks down at her feet.] Cueball: Parenting can't be that hard. Let's just do what comes naturally. [In a frame-less panel they all three just stand there, they look down and the baby has spread it's arms out. Beat frame.] [A caption is in a frame at the top of the panel. Cueball and Megan are looking down between them. There are now two babies, one larger looking at Cueball's feet the smaller looking at Megan's feet.] Soon: Megan: Aw, crap.

This comic relates to the anxiety of having a first child, particularly an unplanned child, and is a play on the double meaning of the expression "do what comes naturally". Doing what comes naturally is a euphemism for couples pairing off and forming intimate relationships, including sex. It is also advice given to new parents, advising them not to second guess themselves so much, to alleviate the stress that comes with parenting. The couple Cueball and Megan find themselves as unexpected parents. Both parents experience anxiety over how to manage their life with the child. The new father defuses the situation and states that parenting can not be that hard and they should just do what comes naturally. Naturally the couple find themselves with a second child. This adds insult to injury as now they have two children and still no idea about how to parent. As the first child was an "accident" the birth of the child was because of instinctual urges. Therefore, assuming nothing has changed in their relationship it would be natural if they produced another child. The title text claims that parenting can't be too hard because, up to the present, all of your ancestors have produced an unbroken line of children who figured out how to raise at least one child that is able to continue this unbroken chain. Randall jokes that this is the "mother" of all sampling biases : Had anyone of one's ancestors completely failed at being parents, that person would never exist. Therefore, this sampling is heavily skewed by sampling only those that were all successful in at least one instance. It does not take into account the number of people in the past who do not have any lineage today to speak of, or the number times our ancestors failed at being parents to children we are not directly descended from. The baby says, "Baby!", either copying Cueball, or saying its name, Pokémon-style. This is also the topic of 441: Babies and 1384: Krypton . [Cueball and Megan are looking down at a baby, throwing its arms in the air, standing between them.] Cueball: Oh man, we made a baby. Megan: Don't panic. Don't panic. Baby: Baby! [Cueball looks at Megan, who still look down at the baby, which now looks down at her feet.] Cueball: Parenting can't be that hard. Let's just do what comes naturally. [In a frame-less panel they all three just stand there, they look down and the baby has spread it's arms out. Beat frame.] [A caption is in a frame at the top of the panel. Cueball and Megan are looking down between them. There are now two babies, one larger looking at Cueball's feet the smaller looking at Megan's feet.] Soon: Megan: Aw, crap.

Revolutionary

Revolutionary

https://www.xkcd.com/675

https://www.explainxkcd.com/wiki/index.php/675:_Revolutionary

Cueball: Yes, science is an open process in which a good idea can come from anybody. Cueball: Yes, widely-believed theories are on occasion overturned by simple thought experiments. Cueball: And yes, your philosophy degree equips you to ask interesting questions sometimes. [Cueball is talking to a philosopher with a goatee, who is sitting at a computer.] Cueball: But you did not just overturn special relativity, a subject you learned about an hour ago, with your "racecar on a train" idea. Philosopher: You just don't like that I'm turning a rational eye to your dogma. Hey, what's the email for the president of physics?

The comic contrasts brilliant revolutionary scientific thought with the simplistic arrogance of assuming one understands the current scientific theory enough to correct it (see the Dunning Kruger effect ). The character with the goatee has a degree in philosophy , and perhaps has certain ideas of his own about how the world should fundamentally be described by physics. He has studied Einstein's theory of special relativity for less than an hour and thinks he has found a flaw. When confronted about this, he considers the objection as based in dogma , and remains so confident that he wants to email the "president of physics". His ignorance of the field is emphasized by thinking that the entire field of physics has a president - although certain important organizations such as the American Physical Society do have presidents. Cueball concedes that it is possible for such a revolutionary idea to come from a relative outsider. One example is Albert Einstein 's own formulation of special relativity , which came while he was working at a patent office in Switzerland, although he did already have a Ph.D in physics. A thought experiment considers some hypothesis, theory, or principle for the purpose of thinking through its consequences. The "racecar on a train" idea alludes to thought experiments involving frames of reference , which are important in relativity. Special relativity was famously established using some thought experiments about moving objects. However, some searchers elaborated more complicated thought experiments and claimed they had proven relativity was self-contradictory. Examples include twin paradox (both of the twins are younger than the other, until you stop assuming acceleration phases can be neglected) or ladder paradox (ladder is both smaller and larger than the garage, until you consider seriously the problems with defining simultaneity for remote locations in relativity). Apparently the philosopher complicated Einstein's train thought experiment by adding a racecar, and found contradictions which prove special relativity is inconsistent. However, most likely scenario is that the "racecar on a train" is too complicated for goatee man to find correct conclusions. A too complex case may be impossible to prove consistent with relativity using intuition alone: complete solving involves calculation using Lorentz transformations. The title text is posing a question about the likelihood of two scenarios (possibly to the person with the philosophy degree): This might be a self-referential title text as this question could be considered a simple thought experiment. The philosopher should be able to overturn his theory using this simple thought experiment which reflects the second panel. While his theory is not widely believed the joke is that the philosopher could overturn his first thought experiment (racecar on train) with this thought experiment. Randall hints that believing you have found fundamental flaws in a theory is much easier than doing more research on it. This is possibly a statement about using Occam's Razor in arguments, which says the simpler answer is the more likely one, which is commonly brought up in philosophy . Usually, when someone with little understanding of the subject thinks that they have found a flaw, it takes only a little bit more reading to discover that the flaw is in fact completely explained already. Cueball: Yes, science is an open process in which a good idea can come from anybody. Cueball: Yes, widely-believed theories are on occasion overturned by simple thought experiments. Cueball: And yes, your philosophy degree equips you to ask interesting questions sometimes. [Cueball is talking to a philosopher with a goatee, who is sitting at a computer.] Cueball: But you did not just overturn special relativity, a subject you learned about an hour ago, with your "racecar on a train" idea. Philosopher: You just don't like that I'm turning a rational eye to your dogma. Hey, what's the email for the president of physics?

Abstraction

Abstraction

https://www.xkcd.com/676

https://www.explainxkcd.com/wiki/index.php/676:_Abstraction

[Cueball is sitting at a computer.] An x64 processor is screaming along at billions of cycles per second to run the XNU kernel, which is frantically working through all the POSIX-specified abstraction to create the Darwin system underlying OS X, which in turn is straining itself to run Firefox and its Gecko renderer, which creates a Flash object which renders dozens of video frames every second because I wanted to see a cat jump into a box and fall over. I am a god.

The comics points out the large number of levels of abstraction working together at any given time in today's computers. Programs on current computers do not run "directly on hardware". Instead, the hardware (in this case, a processor of the x86-64 architecture) is controlled by the operating system kernel (in this specific case, XNU is the kernel used in Apple-branded devices). Many operating systems offer a standardized interface called POSIX , which wraps the services offered by the different operating systems so that applications do not need to cope with the differences between the operating systems. Darwin is the name of the core set of components on which the Apple's OS X operating system runs. And using this operating system, the user runs the Firefox web browser. However, the browser itself contains further abstraction layers: Gecko is the engine handling the display of web pages on the screen, but in this case, it only allows a separate software, Adobe Flash Player , to render a video requested by the user. And all of this work is, in this case, done only because the user wanted to watch a funny cat Flash video on the Internet; which makes the user feel like he is a god. The title text refers to Maru the cat , a cat who became very popular on YouTube for, among other things, jumping into a box. Cueball questions his god-like capabilities by wondering why can't he own Maru. Flash was discontinued at the very beginning of 2021 . Flash was a video player that was used to make videos play without having a dedicated website for it. It was used in games and videos, as demonstrated by Cueball watching a Flash video of a cat jumping into a box. [Cueball is sitting at a computer.] An x64 processor is screaming along at billions of cycles per second to run the XNU kernel, which is frantically working through all the POSIX-specified abstraction to create the Darwin system underlying OS X, which in turn is straining itself to run Firefox and its Gecko renderer, which creates a Flash object which renders dozens of video frames every second because I wanted to see a cat jump into a box and fall over. I am a god.

Asshole

Asshole

https://www.xkcd.com/677

https://www.explainxkcd.com/wiki/index.php/677:_Asshole

[Cueball and Megan watch Beret Guy drive by in an SUV.] Cueball: Look at that asshole in his SUV, thinking he's so badass while he guzzles gas driving around suburbia. Beret Guy: Oh no! Am I an asshole? I hope not! [Beret Guy trades in his keys at the dealership.] [Now he is driving by in a hybrid sedan. Cueball and Megan are still there.] Megan: Look at that smug asshole thinking he's better than us because he drives a hybrid. Beret Guy: ... [He trades in his keys again.] [Cueball and Megan is standing.] Off-panel: RUMBLE [Beret Guy drives a backhoe in and smacks Cueball and Megan out of the panel with the digger.] [He drives off, whistling.]

SUVs are large personal vehicles with big engines and a huge amount of cargo space, and are notorious gas-guzzlers and therefore emblematic of pollution caused by cars. Stereotypically, SUV owners drive them because they're compensating for failures in other parts of their lives, and as an example of conspicuous consumption. Upon hearing Cueball call him an asshole for driving an SUV, Beret Guy , not wanting to appear to be such, trades his SUV in at the dealership for a hybrid subcompact. Hybrid cars are vehicles that are powered by both gasoline and electrical motors, allowing them to consume less fuel and therefore pollute less. But stereotypically, people drive them so that they can feel superior to others about having reduced their emissions, and that's exactly what Megan says, this time, when Beret Guy happens to drive past them again. Quite annoyed now, Beret Guy trades in his car again, this time to get an excavator (a large construction vehicle) and smack them with it. After doing this, he actually does appear quite smug and pleased with himself. In the title text we hear some crashing sounds and then we hear a report by an eyewitness to a police officer. Beret Guy apparently used the excavator to smash into a bakery and steal scones, one of Beret Guy's beloved bakery products - see 452: Mission and the title text of 1030: Keyed . See also 434: xkcd Goes to the Airport where Beret Guys obsession with bakeries was first mentioned. [Cueball and Megan watch Beret Guy drive by in an SUV.] Cueball: Look at that asshole in his SUV, thinking he's so badass while he guzzles gas driving around suburbia. Beret Guy: Oh no! Am I an asshole? I hope not! [Beret Guy trades in his keys at the dealership.] [Now he is driving by in a hybrid sedan. Cueball and Megan are still there.] Megan: Look at that smug asshole thinking he's better than us because he drives a hybrid. Beret Guy: ... [He trades in his keys again.] [Cueball and Megan is standing.] Off-panel: RUMBLE [Beret Guy drives a backhoe in and smacks Cueball and Megan out of the panel with the digger.] [He drives off, whistling.]

Researcher Translation

Researcher Translation

https://www.xkcd.com/678

https://www.explainxkcd.com/wiki/index.php/678:_Researcher_Translation

If a researcher says a cool new technology should be available to consumers in... What they mean is... The fourth quarter of next year The project will be canceled in six months. Five years I've solved the interesting research problems. The rest is just business, which is easy, right? Ten years We haven't finished inventing it yet, but when we do, it'll be awesome. 25+ years It has not been conclusively proven impossible. We're not really looking at market applications right now. I like being the only one with a hovercar.

This comic suggests a translation from the statements of the researcher of a potential new technology . For example, these statements might be found in an article in a popular science magazine which highlights some cutting-edge research. It reflects the idea that researchers tend to be too optimistic about the future of their research project. "The fourth quarter of next year": Even if a technological development seems very close to completion, it could still be canceled by some authority other than the lead researcher. This might be due to poor management, or a poor business plan, or even a poor scientific basis which the researcher is hiding or ignoring. "Five years": The researcher has solved the interesting scientific problems, and assumes that the concept could be picked up by a business, developed to be usable outside of a research lab, designed into a prototype, have a manufacturing process, marketed, and made available to consumers, in only five years. In reality, a lot of exciting-sounding technology may not reach consumers for many years because of difficulties in the business side of things. "Ten years": Not only does the researcher assume that the business end of things will go smoothly, they also assume that the rest of their research will go smoothly. In reality, a lot of unforeseen problems could arise during research. "25+ years": "It has not been conclusively proven impossible" indicates that it has been proven impossible in some context. The researcher simply refuses to accept the impossibility until the proof is conclusive. "We're not really looking at market applications right now.": In contrast to the above chain of assumptions, in this case the researcher has a working technology but wants to keep it to themselves. Title text: "20 years away indefinitely": Sometimes the technological or engineering challenges for a certain application seem like they could be overcome in 20 years, but in reality the challenges are very difficult. The more the challenges are studied, the harder they are found to be, although there is always hope that a few more advances will do it. An example is fusion power , which has been conceptualized since at least 1946 as a potentially unlimited source of clean energy, but remained an elusive achievement despite projects such as the National Ignition Facility and ITER . The first commercial plant is still indefinitely 20 years away. A similar table was shown in 1497: New Products . If a researcher says a cool new technology should be available to consumers in... What they mean is... The fourth quarter of next year The project will be canceled in six months. Five years I've solved the interesting research problems. The rest is just business, which is easy, right? Ten years We haven't finished inventing it yet, but when we do, it'll be awesome. 25+ years It has not been conclusively proven impossible. We're not really looking at market applications right now. I like being the only one with a hovercar.

Christmas Plans

Christmas Plans

https://www.xkcd.com/679

https://www.explainxkcd.com/wiki/index.php/679:_Christmas_Plans

[Cueball is standing behind a friend, who is sitting at a computer.] Cueball: Hey, will you be in town the day after Christmas? Friend: Couldn't say— Friend: I'm Jewish. Cueball: But... how does being Jewish keep you from knowing your plans? Friend: I know my plans— Friend: I just don't know when Christmas is. Cueball: Really? Why not look it up? Friend: Well, I'm also a physicist. Cueball: So? Friend: I believe that since I don't observe Christmas, it can't have a definite date.

This comic centers around a joke about Quantum superposition in physics - if you don't observe something, it has all possible states, not a specific one. It is a double-entendre with the word observe meaning both "look at" (physics sense) and "celebrate" (a holiday). One of the most famous examples on this is the Schrödinger's cat paradox. In this comic, a Jewish physicist does not know when Christmas is. Being a physicist, he believes that since he doesn't observe Christmas, it therefore has no definite date. Adding to the joke, the physicist's observation is actually valid for certain other holidays (such as Easter) that don't have a definite (i.e. annual) date. Because Easter's date seemingly bounces around at random, it could be said to exist in a superposition of all possible Easter dates, and as he doesn't observe (celebrate) Easter, the physicist would be unlikely to check which date it falls this year. Thus, he would be unsure of when the holiday is celebrated. The title text refers to another principle in physics where the act of measuring something must also change it in some way. If one drops a thermometer into a mug of water, energy spent (or released) when heating (or cooling) the mercury in the thermometer changes the temperature of the water in the mug by a small amount. The only way not to interfere with the temperature of the water in the mug is not to measure it. [Cueball is standing behind a friend, who is sitting at a computer.] Cueball: Hey, will you be in town the day after Christmas? Friend: Couldn't say— Friend: I'm Jewish. Cueball: But... how does being Jewish keep you from knowing your plans? Friend: I know my plans— Friend: I just don't know when Christmas is. Cueball: Really? Why not look it up? Friend: Well, I'm also a physicist. Cueball: So? Friend: I believe that since I don't observe Christmas, it can't have a definite date.

December 25th

December 25th

https://www.xkcd.com/680

https://www.explainxkcd.com/wiki/index.php/680:_December_25th

[On one side, a family of four gathered around a Christmas tree, the daughter and son looking excitedly at the presents under the tree; on the other, a character wearing a party hat, sitting dejectedly before a birthday cake. The panel edges are decorated with holly and a wreath.] Happy Birthday to those of you born on the 25 th ! Sorry you get kinda shafted by the overlap with Christmas.

On Christmas Day, most kids whose families celebrate the holiday get Christmas presents. And kids who were actually born on the 25th may feel a little put off because they don't get a special day all to themselves like their siblings and friends do. A lot of families alleviate this by celebrating the child's birthday on a day other than the 25th, so the kid will still get their own party. Unfortunately, the child may not get double presents, but may instead end up getting one gift per gift-giver as both a Christmas gift and a birthday gift. In the title text, Randall provided a "lovely" image for the people turning 27 on this date (Christmas Day, 2009) that would surely have them reaching for the brain bleach. [On one side, a family of four gathered around a Christmas tree, the daughter and son looking excitedly at the presents under the tree; on the other, a character wearing a party hat, sitting dejectedly before a birthday cake. The panel edges are decorated with holly and a wreath.] Happy Birthday to those of you born on the 25 th ! Sorry you get kinda shafted by the overlap with Christmas.

Gravity Wells

Gravity Wells

https://www.xkcd.com/681

https://www.explainxkcd.com/wiki/index.php/681:_Gravity_Wells

Main Text Gravity Wells scaled to Earth surface gravity This chart shows the "depth" of various solar system gravity wells. Each well is scaled such that rising out of a physical well of that depth — in constant Earth surface gravity — would take the same energy as escaping from that planet's gravity in reality. Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface. The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale. Depth = (G × PlanetMass) / (g × PlanetRadius) G = Newton's constant g = 9.81 m/s 2 Planetary Descriptions To Sun, very very far down Mercury Venus Earth - 6379 km [originally 5,478 km] Moon - 288 km Mars - 1,286 km Ganymede Io Jupiter [A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.] Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity. If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star. Europa Titan Two alarms: Weeoooeeoooeeooo Saturn Rings Uranus Neptune Megan: An even more glorious dawn awaits! Mars Inset [Mars gravity well, with one of the Mars rovers on its surface, with its moons Deimos and Phobos as smaller gravity wells.] [Figure of a man (to scale) in Deimos's gravity well.] You could escape Deimos with a bike and a ramp. [Figure of a man (to scale) in Phobos's gravity well.] A thrown baseball could escape Phobos. Earth Inset [Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.] Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back. It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s 2 Earth gravity. Hence, Earth's well is 6,000 km deep.

The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system — including some moons and Saturn's rings. An object traveling along an upward slope loses energy, while an object traveling along a downward slope gains energy. Escaping a planet or moon's orbit requires enough energy (e.g. by walking, jumping, or rocket) to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy required to exit orbit. The peak to the right indicates the maximum energy required to exit orbit. In order to exit orbit with the minimum amount of energy, you would have to travel towards the center of the solar system; to exit orbit with the maximum amount of energy, you would have to travel away from the center of the solar system (the Sun). In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects. The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to Earth's surface gravity. The Sun's gravity well is not shown in its entirety, but is just indicated on the far left as "Very very far down" . Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun, the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planet's gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distances between the planets are condensed, the gravitational potential - from the gravity pulling toward the sun - accumulates quicker. This is the reason for the large peaks between the planets. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface. The following items are listed from top to bottom and left to right. The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with Newton's constant and 9.81 m/s² as constants, where 9.81 m/s² is the acceleration of a free falling body at Earth's gravity. The calculation for a gravity well is: depth = (G * Planet-mass ) / (9.81 m/s 2 * Planet-radius) where G is Newton 's gravitational constant , and 9.81 m/s 2 is the acceleration rate of a free falling body on earth at sea level (g). The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is known as a performing a slingshot or a gravity assist , and is done to gain speed or to brake when needed. The use of rocket engines are more effective when used at a high speed slingshot maneuver, which is known as the Oberth effect , where most energy is going into moving the rocket as opposed to moving the exhaust — conserving the maximum useful energy. On earth the same principle is used when launching rockets. Rockets are always launched in an eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. The size of the gravity-well as described in this comic is not accounting for these factors. Therefore, leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed. The following table was adapted from the table in Escape velocity , using h = V_e ^2 / 2 g : Main Text Gravity Wells scaled to Earth surface gravity This chart shows the "depth" of various solar system gravity wells. Each well is scaled such that rising out of a physical well of that depth — in constant Earth surface gravity — would take the same energy as escaping from that planet's gravity in reality. Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface. The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale. Depth = (G × PlanetMass) / (g × PlanetRadius) G = Newton's constant g = 9.81 m/s 2 Planetary Descriptions To Sun, very very far down Mercury Venus Earth - 6379 km [originally 5,478 km] Moon - 288 km Mars - 1,286 km Ganymede Io Jupiter [A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.] Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity. If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star. Europa Titan Two alarms: Weeoooeeoooeeooo Saturn Rings Uranus Neptune Megan: An even more glorious dawn awaits! Mars Inset [Mars gravity well, with one of the Mars rovers on its surface, with its moons Deimos and Phobos as smaller gravity wells.] [Figure of a man (to scale) in Deimos's gravity well.] You could escape Deimos with a bike and a ramp. [Figure of a man (to scale) in Phobos's gravity well.] A thrown baseball could escape Phobos. Earth Inset [Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.] Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back. It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s 2 Earth gravity. Hence, Earth's well is 6,000 km deep.

Force

Force

https://www.xkcd.com/682

https://www.explainxkcd.com/wiki/index.php/682:_Force

[Two EMTs are rushing Darth Vader away from a front door on a stretcher.] [There is a room with a desk in the foreground and a full-length mirror in the corner. On the desk is a laptop displaying the Wikipedia page for autoerotic asphyxiation.] The sexual potential of the force choke was already explored in the title text of 307: Excessive Quotation .

This comic features Darth Vader , the main antagonist from the original Star Wars trilogy. Autoerotic asphyxiation is a sexual practice in which lack of oxygen is induced to enhance sexual stimulus. The technique is considered extremely dangerous, especially without supervision, as loss of consciousness can result in continued strangling which can quickly be fatal. In the films, Vader possesses the ability to restrict the airway of anyone without having to touch them, using only the so-called " force ". This practise has therefore been called force-choking. The comic assumes that Vader used this technique against himself, with the help of a mirror, in order to become sexually aroused. Lord Vader has apparently force-choked himself to the point of unconsciousness (or possibly even death) and is being transported from his house on a stretcher by two Emergency Medical Technicians (EMTs). The title text is a pun on the term "choking the chicken", a colloquial expression referring to male masturbation . "Force-choking the chicken" might mean a technique of self-gratification by use of the "force" without having to apply one's hands. [Two EMTs are rushing Darth Vader away from a front door on a stretcher.] [There is a room with a desk in the foreground and a full-length mirror in the corner. On the desk is a laptop displaying the Wikipedia page for autoerotic asphyxiation.] The sexual potential of the force choke was already explored in the title text of 307: Excessive Quotation .

Science Montage

Science Montage

https://www.xkcd.com/683

https://www.explainxkcd.com/wiki/index.php/683:_Science_Montage

[Two columns of four panels are shown below two captions.] Left: Movie Science Montage Right: Actual Science Montage [Below the four rows of panels in the two montages will be described, Movie first then Actual as the two are synchronized in time.] [ Movie : Cueball passes a test tube to Ponytail sitting at a large control console to the left looking at it's glowing screens at the bottom. At the top there is a flashing lamp. Both are wearing lab coats and goggles. A a hamster ball and a Newton's cradle stand on a shelf above them.] [ Actual : Cueball stand behind Ponytail, also here both are in lab coats with goggles. Ponytail place a sample from a test tube into a small device standing on a table. An analog clock on the wall above them is at five minutes past ten.] [ Movie : A small glowing sample has been placed next to a rat inside a cage standing on a table. Ponytail, is holding a glowing implement up towards the cage; she has another rat in her hand and also a rat sitting on top of her head. Cueball is speaking into a device with a curled wire going to the wall.] Caged Rat: Squeak! [ Actual : Cueball is behind Ponytail standing in front of the machine which is working on the sample. The clock on the wall above them is at ten minutes past ten.] Machine: ...whirrrrrr... [ Movie : Zoom in on Ponytail who pulls on two levers on a machine, which is shooting a beam of some sort downwards onto a sample, possibly the same as in the cage with the rat.] [ Actual : Cueball and Ponytail still waits for their sample to be analyzed in the small device. The clock on the wall above them is at twenty five minutes past eleven. Cueball has removed his goggles and is holding them in his hand.] Machine: ...whirrrr... Machine: Bing! [ Movie : Zoom in on Cueball who is operating a complicated-looking chemical apparatus with a scope, flasks, coils, and bubbles.] Cueball: Paint flecks from the killer's clothing match an antimatter factory in Belgrade! Ponytail (off panel): Let's go! [ Actual : Cueball look over Ponytail's shoulder while she examine the sample she has just taken out of the small device. He has put his goggles back on. The clock is hidden behind their spoken text. Presumably this occurs right after the bing .] Cueball: Okay, we've determined there's neither barium nor radium in this sample. Ponytail: Probably.

This comic makes fun of the artificially dramatized and simplified depiction of science in movies. The unstated premise seems to be that the scientists are trying to get information about a murderer based on a sample obtained from his clothing. The movie version of events involves the two scientists Cueball and Ponytail doing exciting things with a control console, lab rats , a device with some kind of beam (perhaps a laser), and a complicated chemical apparatus. The scientists quickly arrive at the firm conclusion that paint on the clothes is from an " antimatter factory" in Belgrade , Serbia . While not directly used in the study, a Newton's cradle in motion can be seen in the first panel, a device notoriously useless in any serious scientific study, but very often used in movies, for instance as a prop in the office of a professor. There is also a hamster wheel . According to the official transcript it is a hamster ball but it is clearly not a ball as it has spokes, and thus resembles a hamster running wheel, probably for the rats shown in the next panel. The actual science version shows the same scientists putting a sample into a device (likely a mass spectrometer or a centrifuge ). The device apparently takes about 1 hour and 20 minutes to analyze the sample (according to the clock on the wall moving from about 10:05 to 11:25). At the end of this process, the only thing learned is that there is probably no barium or radium in the sample. This conclusion is not very helpful on its own, and is not even very certain. There are several major concepts about science and technology that movies tend to distort for the purposes of a more exciting plot, both illustrated here. One is that the work involves a lot of different exciting-looking gadgets. Another is that the analysis can be done very quickly, and results in very certain and significant conclusions. Besides this, the scientists often seem to have access to a database full of trivial information from around the world. In reality, a scientific analysis of some sample or data often only requires a single boring-looking machine, takes quite some time, and provides a limited result that must be interpreted very carefully to have any meaning at all. The title text further illustrates a movie science scene, depicting someone deducing the presence of nanobots simply by observing the behavior of a perturbed lab rat. The Helvetica Scenario is a fictional experiment, presented in Switzerland (Helvetia is the Latin name for the country), which assumes that removing only the nucleus (the center of an atom) of a "calcium molecule" in one's skin, but still leaving the electron shell at its position, would cause a massive reaction ending up in heavy mutations. The Helvetica scenario was made up by the BBC comedy show Look Around You in the pilot episode, which can be seen here . "Code grey" may refer to Grey goo , a hypothetical doomsday scenario involving nanobots. In 1242: Scary Names Grey goo is on the chart and the Helvetica scenario is mentioned in the title text. Antimatter is also referenced in 826: Guest Week: Zach Weiner (SMBC) , 1621: Fixion and 1731: Wrong as well as being the subject of the what if? Antimatter . It was also mentioned in another what if? : Lake Tea . [Two columns of four panels are shown below two captions.] Left: Movie Science Montage Right: Actual Science Montage [Below the four rows of panels in the two montages will be described, Movie first then Actual as the two are synchronized in time.] [ Movie : Cueball passes a test tube to Ponytail sitting at a large control console to the left looking at it's glowing screens at the bottom. At the top there is a flashing lamp. Both are wearing lab coats and goggles. A a hamster ball and a Newton's cradle stand on a shelf above them.] [ Actual : Cueball stand behind Ponytail, also here both are in lab coats with goggles. Ponytail place a sample from a test tube into a small device standing on a table. An analog clock on the wall above them is at five minutes past ten.] [ Movie : A small glowing sample has been placed next to a rat inside a cage standing on a table. Ponytail, is holding a glowing implement up towards the cage; she has another rat in her hand and also a rat sitting on top of her head. Cueball is speaking into a device with a curled wire going to the wall.] Caged Rat: Squeak! [ Actual : Cueball is behind Ponytail standing in front of the machine which is working on the sample. The clock on the wall above them is at ten minutes past ten.] Machine: ...whirrrrrr... [ Movie : Zoom in on Ponytail who pulls on two levers on a machine, which is shooting a beam of some sort downwards onto a sample, possibly the same as in the cage with the rat.] [ Actual : Cueball and Ponytail still waits for their sample to be analyzed in the small device. The clock on the wall above them is at twenty five minutes past eleven. Cueball has removed his goggles and is holding them in his hand.] Machine: ...whirrrr... Machine: Bing! [ Movie : Zoom in on Cueball who is operating a complicated-looking chemical apparatus with a scope, flasks, coils, and bubbles.] Cueball: Paint flecks from the killer's clothing match an antimatter factory in Belgrade! Ponytail (off panel): Let's go! [ Actual : Cueball look over Ponytail's shoulder while she examine the sample she has just taken out of the small device. He has put his goggles back on. The clock is hidden behind their spoken text. Presumably this occurs right after the bing .] Cueball: Okay, we've determined there's neither barium nor radium in this sample. Ponytail: Probably.

We Get It

We Get It

https://www.xkcd.com/684

https://www.explainxkcd.com/wiki/index.php/684:_We_Get_It

[Cueball and a friend are talking.] Cueball: Avatar? Yeah, I saw it last week with... [Cueball walks out of the panel.] [Cueball returns with a ladder and megaphone.] [Cueball stands on top of the ladder, shouting through a megaphone.] Cueball: ...MY GIRLFRIEND. Friend: You know, if this phase of your relationship lasts more than a week, I'm legally allowed to stab you both. Cueball: What phase? Cueball: So, did I mention I'm seeing someone?

Avatar is a 2009 movie that was very popular in theaters, becoming the highest-grossing at that time before being overtaken by Avengers: Endgame in 2019. The comic illustrates how someone in a new relationship tends to be overly eager and giddy to let everyone know about it, while others tend to not be all that interested. The character on the left is so excited to let everyone know, that he goes off panel to get a ladder and a loudspeaker. The second character thinks it should be legal to murder (or at least wound) him for this annoyance if he acts like this for more than a week. The first character is so giddy that he doesn't notice what he has done and even tries to mention his girlfriend again. The title text describes a very harsh way to respond to this annoyance. Since someone in the position of the first character is so excited about the new romantic commitment in their life, their friend brings up the much greater and more serious commitment of marriage. If they have only been dating for a week or less, it is probably much too early for them to seriously think about marriage. The friend then implies that if they aren't already excited to marry her, then he doesn't really love her. The end result is that the first character doesn't want to talk about his relationship anymore. [Cueball and a friend are talking.] Cueball: Avatar? Yeah, I saw it last week with... [Cueball walks out of the panel.] [Cueball returns with a ladder and megaphone.] [Cueball stands on top of the ladder, shouting through a megaphone.] Cueball: ...MY GIRLFRIEND. Friend: You know, if this phase of your relationship lasts more than a week, I'm legally allowed to stab you both. Cueball: What phase? Cueball: So, did I mention I'm seeing someone?

G-Spot

G-Spot

https://www.xkcd.com/685

https://www.explainxkcd.com/wiki/index.php/685:_G-Spot

[To the left of the main comic there is an explanation text without a frame around it:] A study published in the journal of sexual medicine suggests that the g-spot may not actually exist. We go live to the researchers' press conference: [Two reporters with microphones, Ponytail and a Cueball-like guy, stand below a podium where Cueball stands behind a lectern. Ponytail reach out with her microphone towards Cueball:] Ponytail: Is it true you've been unable to find evidence that the G-spot exists? [Zoom in on Cueball and the top of the lectern:] Cueball: My research is in solar cells. I think you have the wrong press conference. [Beat panel with the same view as before.] [Same view but now Cueball hangs his head.] Cueball: But... yes.

The G-Spot is, as the BBC has quoted saying in the title text, an elusive erogenous zone some women claim to have that can be stimulated to enhance their sexual experience. In this comic, a live press conference has been held due to a peer-reviewed study suggesting the G-Spot may not exist. But the press have entered the wrong meeting where Cueball (the researcher) has performed a study on solar cells. So initially he tries to claim that he has not been researching the G-Spot. But he also ends up shamefully admitting that he has tried but failed finding it anyway. That is, he has had difficulty making his lover orgasm through the use of G-spot stimulation. In the title text Randall notes that he could not read the lead from the BBC story: The elusive erogenous zone said to exist in some women may be a myth, say researchers who have hunted for it. with a straight face. This is probably because Randall assumes that "hunted for it" means the researchers had frequent sexual intercourse. [To the left of the main comic there is an explanation text without a frame around it:] A study published in the journal of sexual medicine suggests that the g-spot may not actually exist. We go live to the researchers' press conference: [Two reporters with microphones, Ponytail and a Cueball-like guy, stand below a podium where Cueball stands behind a lectern. Ponytail reach out with her microphone towards Cueball:] Ponytail: Is it true you've been unable to find evidence that the G-spot exists? [Zoom in on Cueball and the top of the lectern:] Cueball: My research is in solar cells. I think you have the wrong press conference. [Beat panel with the same view as before.] [Same view but now Cueball hangs his head.] Cueball: But... yes.

Admin Mourning

Admin Mourning

https://www.xkcd.com/686

https://www.explainxkcd.com/wiki/index.php/686:_Admin_Mourning

[The text is over a white-on-black terminal showing a bit of output from ps -el | grep sam, with processes running from root and sam.] When a user dies, their connections time out, but their screen sessions linger. [The end of the command line is a |grep sam.] The server's uptime grows because you can't bring yourself to reboot and wipe out their last earthly presence [The processes listed are screen, zsh, irssi, and grep sam.] the ghost in zshell.

The background images show the output from the ps command of Unix-like computer systems, which lists all running processes including all interactive users logged in to the server. If a user did not log out, their processes would continue to run until stopped by a reboot. If some specific user dies while logged in, the running sessions still appear in the ps output and be a reminder to other users. This comic depicts an administrator unwilling to reboot a machine that has still running processes from a deceased user named "sam". When a session is closed its descendent processes sent the HUP (Hang-up) signal, which normally causes them to terminate. However, the popular utility screen enables a user to detach and reattach that output, thus surviving over sessions. The final joke refers to the command line interface being called a shell , and to a particular type of shell called zshell ( /bin/zsh in the final panel), making a pun with the expression " Ghost in the Shell ", which is the title of a popular manga series, originally derived from the expression " ghost in the machine ", used by philosopher Gilbert Ryle to describe Descartes' theory of mind-body dualism. The phrase "su to the user" refers to the ability of a system administrator — i.e. the superuser, aka root — to switch to another user account (using the su command , which stands for s ubstitute u ser) without needing the target user's password, as would normally be necessary, which in this case would give the impression that sam's ghost were using the account. [The text is over a white-on-black terminal showing a bit of output from ps -el | grep sam, with processes running from root and sam.] When a user dies, their connections time out, but their screen sessions linger. [The end of the command line is a |grep sam.] The server's uptime grows because you can't bring yourself to reboot and wipe out their last earthly presence [The processes listed are screen, zsh, irssi, and grep sam.] the ghost in zshell.

Dimensional Analysis

Dimensional Analysis

https://www.xkcd.com/687

https://www.explainxkcd.com/wiki/index.php/687:_Dimensional_Analysis

My Hobby: Abusing dimensional analysis [On a blackboard.] (Planck energy/Pressure at the Earth's core) x (Prius combined EPA gas mileage/Minimum width of the English Channel) = π [Cueball indicates this equation with a pointer in front of a class.] Cueball: It's correct to within experimental error, and the units check out. It must be a fundamental law. Student: But what if they build a better Prius? Cueball: Then England will drift out to sea.

Cueball has a hobby — showing correct calculations according to the dimensional analysis — but with ridiculous correlations of uncorrelated events and measurements. Here Cueball is giving a talk and uses this trick to convince his listeners that the Toyota Prius combined EPA gas mileage is somehow connected to the constant π via the Planck energy , the pressure at the Earth's core and the width of the English Channel . Scientists — often physicists — use dimensional analysis to quickly check if a given formula can possibly relate to a physical system, because if you end up with an equation claiming that Joules are meters, something is clearly wrong. Dimensional analysis here refers to the check if both sides of the equation arrive at the same physical unit when the units of all variables get plugged into the equation. This requires knowledge of the system of units and the relation between different physical units. Cueball uses the following equation to make a mockery of the practice: The right hand side is dimensionless, it's the constant π = 3.14... which is defined by the relation of two lengths, the circumference and the diameter of a circle. The left hand side requires to plug in the dimensions of the named physical quantities: When plugged into the left hand side this amounts to: Using the following unit relations (this does not reduce units to the seven SI base units, but does use some derived units for cancelation): Note that for dimensional analysis constant factors are not taken into account. Here square brackets are used to denote dimensional analysis. In the above equation the unit of energy (joule) as well as all the unit of volume (cubic meter) cancel out each other. Another aspect of the comic is, that sometimes dimension analysis of equations that were not derived but rather "made up" can provide insight. However, in reality such an equations would have to be somehow "motivated", which is more of an art than science and requires great experience in the field the equation should relate to. The presented equation combines values that have no immediate causal relation with each other, so it does not make sense. Furthermore, since the values have absolutely no causal relation to each other, the ratios presented are simple coincidence; despite Cueball's claim, building a better Prius would not cause any changes to the English Channel. [ citation needed ] The title text also refers to this, as a higher pressure at Earth's core could also balance the equation, keeping the result constant equal to π . The Planck energy is an absolute, however, so it is not mentioned as a way to balance the next version of Prius. The Planck energy is the only nearly exact value we do have. Compared to other Planck values it is very large (macroscopic). Pressure at the core of the Earth ranges from 330 to 360 gigapascals. Using a simple value like this: Prius combined EPA gas mileage : For the third generation (from 2010) the City mileage is 51 mpg and the Highway mileage is 48 mpg. But it is the combined EPA gas mileage which is used in the equation and that is 50 miles per gallon. Minimum width of the English Channel is about Calculating from these values you will get π = 3.54... that is pretty close to π = 3.14... while using a Planck value. According to Cueball this will be within the experimental error (the combined error for all four numbers - none are exact numbers). For instance if you tried the ePrius you would probably get closer to that target — as the mileage in real life usually is somewhat lower than the value given — and that would reduce the result. Wolfram|Alpha can find most of the statistics and do the calculations. My Hobby: Abusing dimensional analysis [On a blackboard.] (Planck energy/Pressure at the Earth's core) x (Prius combined EPA gas mileage/Minimum width of the English Channel) = π [Cueball indicates this equation with a pointer in front of a class.] Cueball: It's correct to within experimental error, and the units check out. It must be a fundamental law. Student: But what if they build a better Prius? Cueball: Then England will drift out to sea.

Self-Description

Self-Description

https://www.xkcd.com/688

https://www.explainxkcd.com/wiki/index.php/688:_Self-Description

[A pie chart which is mainly white with a black slice of about 30 degree towards the bottom left. The two sections are labeled with a line going from the label to the sections. The line going into the black section turns white in in this last part.] Fraction of this image which is white Fraction of this image which is black [A bar graph labeled with a label over the Y-axis. There are three black bars with a label below each bar. Bar 1 is of medium height, bar 2 highest and bar 3 the lowest.] Amount of black ink by panel: 1 2 3 [A scatter-plot with a label over the Y-axis. In the bottom left corner of the graph, the two axis has a tick just away from the origo, and these are labeled with zeros. The graph shows the whole comic scaled proportionally to fit the axes. The scale is too small to actually read any of the text in this representation, which would of course be the same as that noted here for the two previous panel and for this panel here below:] Location of black ink in this image: 0 0

This comic is self-referential , because every graph is dependent on the whole comic. If you were to change anything in the comic, you would change the ink distribution, and would therefore have to update all three graphs. This would result in further changes that would have to be considered. In the first panel's pie chart , "this image" refers to the entire comic image, the one that can be downloaded from xkcd (and the entire comic as displayed here above). This is a little confusing as it would be easy to misunderstand this meaning, and believe that the first panel only refers to itself. The title text though makes it clear that it is the entire comic that is called image here. The image size is 740x180 or 133200 pixels. Out of those, 14228 pixels are black (gray pixels are accounted based on their brightness). The ratio of black pixels to the size of the image is 0.1068, so the pie chart segment describing black part should be about 38.5 degrees wide, which is indeed true for the pie chart in the image. In the second panel the amount of black used in each panel is displayed in a bar chart . This actually makes this panel the one that uses most black. The first panel (including the border) has 4944 black pixels, the second 6180 and the third 3103. The first bar is about 70 pixels high, the second about 87 and the third about 43, which roughly checks out. It is hard to measure the exact height of the bars as the axis and bars themselves are not straight. The third panel features a scatter plot labeled "Location of black ink in this image." It is the first quadrant of a cartesian plane with the zeroes marked. The graph is the whole comic scaled proportionally to fit the axes, so the last panel also has to contain an image of itself having an image of itself ad infinitum thus displaying the Droste effect , a type of visual recursion . The title text refers to the comic's own self-reference, but it is also self-referencing because of the character count in it. It would be difficult to write this sentence, as just one more character would not be solved by writing 243, as "three" has two more characters than "two", and "four" has only one more character... "The graph of panel dependencies is complete and bidirectional, and every node has a loop." This means that if we draw a dot corresponding to each panel, and then we draw arrows connecting the dots to indicate dependencies, the resulting graph is complete (meaning that all the points are connected to one another) and bidirectional (meaning that if point A has an arrow to point B, then point B also has an arrow to point A). "Every node has a loop" means that each point also has an arrow connecting to itself. This is an observation of the interdependent relationship between description and creation that pertains to all things perceived by humans, including the concept of "Self". Self-reference was used very early for instance in 33: Self-reference , but never so famously as here. See other self-references here . [A pie chart which is mainly white with a black slice of about 30 degree towards the bottom left. The two sections are labeled with a line going from the label to the sections. The line going into the black section turns white in in this last part.] Fraction of this image which is white Fraction of this image which is black [A bar graph labeled with a label over the Y-axis. There are three black bars with a label below each bar. Bar 1 is of medium height, bar 2 highest and bar 3 the lowest.] Amount of black ink by panel: 1 2 3 [A scatter-plot with a label over the Y-axis. In the bottom left corner of the graph, the two axis has a tick just away from the origo, and these are labeled with zeros. The graph shows the whole comic scaled proportionally to fit the axes. The scale is too small to actually read any of the text in this representation, which would of course be the same as that noted here for the two previous panel and for this panel here below:] Location of black ink in this image: 0 0

FIRST Design

FIRST Design

https://www.xkcd.com/689

https://www.explainxkcd.com/wiki/index.php/689:_FIRST_Design

Team Member 1 (out of panel): Wow, this is a much better design. Team Member 2 (out of panel): Let's build it. [A blueprint depicting a robot design for the FIRST competition. It consists of a standard mobile platform, with a pusher blade at the front. Additional parts include an umbrella on top and a trailer unit consisting a telescoping pole with a matchbox and match on top.] Referee (out of panel): Go! CLICK [A FIRST competition field, with teams at opposite ends. Various robots appear on the field, and the team whose design appears above activates their robot.] [The robot's trailer unit detaches as the telescoping pole begins to extend, and the mobile platform with umbrella rolls forward.] VRRR CLICK [Telescoping pole extends further.] VRRRR [Telescoping pole extends further.] VRRRR [Telescoping pole extends further, approaching a sprinkler head fixture.] VRRR [Telescoping pole stops extending, placing the matchbox and match very near the sprinkler head fixture.] [The mobile platform stops moving.] [The umbrella deploys, extending beyond the dimensions of the mobile platform.] FWOOMP [The match box and match are lit beneath the sprinkler head.] FWOOSH [The heat from the match triggers the sprinkler's valve, and water sprays out of the sprinkler into the room below.] PSSSSHH [Water pours from the sprinkler onto the competition field, causing the electrical components of the opposing team's robotics platform to short and malfunction. The opposing team appears distressed and confused.] FZZZT BWooooooo!!! [The initial robot, still protected by its umbrella, pushes along the balls toward the goal zone without any difficulty.]

Two members of a team are designing a robot for the 2010 FIRST Robotics Competition , in which teams design robots to push soccer balls into their team's goals. The final design for this team's robot is a trailer with a matchbox on a telescoping pole and the actual robot, a mobile platform with an umbrella on top and pusher in front. This is an underhanded design, exploiting the presence of a heat-activated sprinkler system at the venue and lack of water resistance in the opposing team's equipment. When the event starts, the robot moves off and deploys its umbrella. The trailer extends its arm, causing a lit match to set off the sprinkler, which causes the opposing robots to short out and malfunction. This allows the umbrella-protected robot to score goals without opposition. This may also be referencing how FIRST is famous for its bending of the rules, as loopholes are not only not against the rules, they are encouraged. This would be shown best by how Team 67 designed a robot that utilized a loophole, which allowed them to control a robot using an Xbox Kinect during the time where the robot is supposed to be autonomous. (This loophole has been removed in the rules for more recent competitions.) Note, however, that this would be simply illegal based of the 2010 FRC Breakaway rules , as rule S01 under section 7.3.1 Safety prevents dangerous robots from competing and R02 points E and F under section 8.3.1 Safety & Damage Prevention prevent "Flammable gases" and "Any devices intended to produce flames or pyrotechnics.". This rule could be bypassed if the sprinkler could also be triggered by smoke, which is the case in at least some venues, in which case a few capacitors in a circuit designed to destroy them could trigger the sprinkler system. In addition, this comic may be a reference to the water game meme in FRC, where most students really want a game to involve water, even though this is unlikely to ever happen due to the safety concerns about using electronics near water. The title text is an excuse presented by the umbrella robot team, presumably because they won but are facing disqualification. This excuse seems weak because none of the venues have a rooftop pool. [ citation needed ] The comment "the pool on the roof must've sprung a leak" is a quote from the 1995 movie "Hackers". Team Member 1 (out of panel): Wow, this is a much better design. Team Member 2 (out of panel): Let's build it. [A blueprint depicting a robot design for the FIRST competition. It consists of a standard mobile platform, with a pusher blade at the front. Additional parts include an umbrella on top and a trailer unit consisting a telescoping pole with a matchbox and match on top.] Referee (out of panel): Go! CLICK [A FIRST competition field, with teams at opposite ends. Various robots appear on the field, and the team whose design appears above activates their robot.] [The robot's trailer unit detaches as the telescoping pole begins to extend, and the mobile platform with umbrella rolls forward.] VRRR CLICK [Telescoping pole extends further.] VRRRR [Telescoping pole extends further.] VRRRR [Telescoping pole extends further, approaching a sprinkler head fixture.] VRRR [Telescoping pole stops extending, placing the matchbox and match very near the sprinkler head fixture.] [The mobile platform stops moving.] [The umbrella deploys, extending beyond the dimensions of the mobile platform.] FWOOMP [The match box and match are lit beneath the sprinkler head.] FWOOSH [The heat from the match triggers the sprinkler's valve, and water sprays out of the sprinkler into the room below.] PSSSSHH [Water pours from the sprinkler onto the competition field, causing the electrical components of the opposing team's robotics platform to short and malfunction. The opposing team appears distressed and confused.] FZZZT BWooooooo!!! [The initial robot, still protected by its umbrella, pushes along the balls toward the goal zone without any difficulty.]

Semicontrolled Demolition

Semicontrolled Demolition

https://www.xkcd.com/690

https://www.explainxkcd.com/wiki/index.php/690:_Semicontrolled_Demolition

[Cueball is holding up a pointer to a screen with an image of the World Trade Center towers mid-disaster.] Cueball: Based on my analysis, I believe the government faked the plane crash and demolished the WTC north tower with explosives. Cueball: The south tower, in a simultaneous but unrelated plot, was brought down by actual terrorists. [Caption below the panel:] The 9/11 truthers responded poorly to my compromise theory.

The World Trade Center towers were destroyed in the September 11, 2001 attacks ( 9/11 in American date notation). The planned attack was for two planes to collide with the north and south towers simultaneously, but what ended up happening was that plane 1 hit the north tower at 8:46 am , and the second plane hit the south tower a little less than 20 minutes later . In the ensuing investigation many people raised questions that didn't seem to get a satisfactory answer for several months, if not years. Many people, who called themselves 9/11 Truthers , began to claim that the whole thing was a government conspiracy, in what has come to be known as the "controlled demolition plot" (referenced by the title of this comic), which alleges that the towers were brought down not by the fires caused by the planes but by demolition charges intentionally placed there by the government. Cueball proposes a compromise to make both those who believe in the conspiracy and those who don't happy. Since there is only a government related video of a plane flying into the north tower — done by a man who was with FDNY fire fighters — that was a government conspiracy. But it just so happened that the government decided to demolish the north tower on the same day that terrorists decided to demolish the south tower. The title text is a restatement of the Golden Mean fallacy : that the truth can be found in a compromise between two opposite positions. In this comic, one of the positions is a fanciful conspiracy theory and the other is a sober fact-based conclusion. The error of this fallacy is apparent here, as it can lead to even more ridiculous conclusions. In this case, the compromise theory would make no one happy because both sides would have to concede claims which they have already dismissed as bogus, as well as accept an incredibly unlikely coincidence. On January 6, 2016, The Onion , a satirical news site, reported that the government has confirmed Cueball's theory by releasing an article titled, Government Admits It Was Only Behind Destruction Of North Tower. This is one of the compromises Cueball (or Randall) has proposed, most of which will also be unlikely to be accepted... [Cueball is holding up a pointer to a screen with an image of the World Trade Center towers mid-disaster.] Cueball: Based on my analysis, I believe the government faked the plane crash and demolished the WTC north tower with explosives. Cueball: The south tower, in a simultaneous but unrelated plot, was brought down by actual terrorists. [Caption below the panel:] The 9/11 truthers responded poorly to my compromise theory.

MicroSD

MicroSD

https://www.xkcd.com/691

https://www.explainxkcd.com/wiki/index.php/691:_MicroSD

[Cueball and a friend approach a table.] Cueball: Hey, what's up? Friend: Shhhhh. Cueball: Hrm? Friend: There's a microSD card on your table. [A 16GB microSD card sits next to an assortment of coins for size reference.] Cueball (out of panel): So? Friend (out of panel): I dunno, high storage densities freak me out. A whole aisle of library shelves on something smaller than a dime. [The two people stand near the table, the friend peering at the coins and card on the table.] Friend: Libraries are unnerving enough-millions of ideas surrounding you, towering over you. These cards fill me with that same reverence, that same intimidation. [Cueball stands alone.] Friend (out of panel): ...that same faint arousal. Maybe I'll just touch it. Cueball: If you lose that card I'm NOT helping you find it.

microSD is one format of the Secure Digital memory card format, used in digital cameras, cell phones, and other devices. It is very small, only 15×11×1 mm, but can hold large amounts of data. The US dime in contrast has a diameter of 17.91 mm. When this comic was published in January 2010 the maximum capacity for microSD cards was 16GB. The current maximum capacity is 1TB (as of January 2021). The main character in the comic (on the right) thinks about all the ideas that could be expressed by the data in the microSD card, or in a library. He feels not just reverent and intimidated, but sexually aroused by the thought. As he begins to touch it, his friend is disgusted by what might happen if he uses the card as some kind of sex toy, and does not want to help him locate the card if it gets "lost" inside a body cavity. The title text seems to be the main character thinking about how much data the card holds, in terms of floppy disks and the iTunes music library, and feeling aroused by these thoughts. Randalls claims in the title text do check out. A high-density floppy disk with a FAT format holds about 1.4 MB of data, and has dimensions of 90×94×3 mm, for a volume of about 2.5 cm³. A refrigerator carton is the large cardboard box that fridges are delivered in. A typical refrigerator carton may be 1800×700×700 mm, a volume of about 0.9 m³. So a fridge carton could hold about thirty-five thousand 90 mm floppies, or roughly 50GB. This is comparable to the storage on a single microSD card. A soda can (500 ml = 500 cm³) could hold three thousand microSD cards or store 50TB of data (3000TB today). However, the iTunes store claims to hold thirty-five million songs (as of Summer 2016), and allowing for about 2MB per song gives 70 TB of music. The claim that a soda can could hold the iTunes library seems to be unreasonable, but it was reasonable at the time. Related to this topic is this xkcd What If blog entry . [Cueball and a friend approach a table.] Cueball: Hey, what's up? Friend: Shhhhh. Cueball: Hrm? Friend: There's a microSD card on your table. [A 16GB microSD card sits next to an assortment of coins for size reference.] Cueball (out of panel): So? Friend (out of panel): I dunno, high storage densities freak me out. A whole aisle of library shelves on something smaller than a dime. [The two people stand near the table, the friend peering at the coins and card on the table.] Friend: Libraries are unnerving enough-millions of ideas surrounding you, towering over you. These cards fill me with that same reverence, that same intimidation. [Cueball stands alone.] Friend (out of panel): ...that same faint arousal. Maybe I'll just touch it. Cueball: If you lose that card I'm NOT helping you find it.

Dirty Harry

Dirty Harry

https://www.xkcd.com/692

https://www.explainxkcd.com/wiki/index.php/692:_Dirty_Harry

[Detective "Dirty" Harry Callahan stands near a wall, pointing a revolver at another figure, presumably a suspect, reclined on the ground. A shotgun is on the ground next to the reclined figure.] Harry Callahan: I know what you're thinking--"Did he fire six shots or only five?" In all this excitement, I- Suspect: Six. Definitely six. Harry Callahan: Shit. Dirty Harry Meets Rain Man

The comic references Dirty Harry and Rain Man , two classic American films, from very different genres. Dirty Harry is an action thriller about a police officer named "Dirty" Harry Callahan, who's notorious for being aggressive with criminals and quick to resort to lethal force. His weapon of choice is a .44 magnum revolver (which holds six rounds of ammunition). The comic references one of the most famous scenes in the film, in which Harry has a criminal at gunpoint, following a fire-fight. As the criminal considers reaching for his own gun, Harry claims to have lost track of how many bullets he's fired, meaning that there may or may not be one round left in his gun, and coldly tells his opponent "you must ask yourself one question: do I feel lucky?". The implication being Harry will definitely fire if the man reaches for his gun, and his life will depend on whether there are any bullets left. Rain Man is a comedy-drama about the relationship between two brothers. One of the brothers, Raymond (AKA "Rain Man"), is autistic and has an eidetic memory . Several times in the film he encounters a number of objects that would be difficult for most people to count (such as toothpicks spilled from a box) and immediately knows how many there are. The comic portrays a mash-up between the two films, in which Dirty Harry faces Rain Man, instead of a less numerically gifted adversary. Rain Man accurately tracks every bullet fired, and knows that Harry's gun is now empty (with the implication that he can safely grab the gun and kill Harry). The title text implies that Randall tends to obsess about tracking quantities, even while watching action films, and thus gets 'distracted' keeping track of how many rounds each person fires. He jokes that energy guns shown in science fiction are intended to counter this tendency, because they're not limited to a specific number of shots. [Detective "Dirty" Harry Callahan stands near a wall, pointing a revolver at another figure, presumably a suspect, reclined on the ground. A shotgun is on the ground next to the reclined figure.] Harry Callahan: I know what you're thinking--"Did he fire six shots or only five?" In all this excitement, I- Suspect: Six. Definitely six. Harry Callahan: Shit. Dirty Harry Meets Rain Man

Children's Fantasy

Children's Fantasy

https://www.xkcd.com/693

https://www.explainxkcd.com/wiki/index.php/693:_Children%27s_Fantasy

[Kid is sitting on the ground with his chin in his hand.] Kid: I'm such a loser- POP [Princess sticks her head through a portal.] Princess: Come quickly, young one! Kid: Holy crap, a portal! Princess: My kingdom needs you! [He falls through.] Kid: AAAAAA [We see him on horseback, helmeted wielding a sword. There's a castle on the horizon and two moons in the sky. There are a few other riders as well.] [Kid, with helmet and sword, stands before King, Princess, and another warrior. Princess is holding out a ring.] King: You've saved our kingdom and found your self-confidence. Now it's time to return home. Goodbye, young hero! Princess: Take this ring to remember us! [Kid stands alone, holding the ring.] Kid: Well, I guess I spend the rest of my life pretending that didn't happen or knowing that everyone I love suspects I'm crazy. Kid: This'll be a fun 70 years.

Children's fantasy stories such as The Chronicles of Narnia and The Phantom Tollbooth involve a kid who is magically transported out of their time to some fantastic realm, goes through trials and becomes a hero, and then is returned to their own mundane world at about the same time they left with no one else realizing or believing what happened to them. The growth of the protagonist often involves learning self-confidence. The comic illustrates this type of story and considers what the rest of the child's life would really be like as they reach adulthood. If they tell their friends, spouse, and family what happened to them, no one will believe them and these loved ones will think them a bit crazy. If they don't tell anyone, they are pretending that the episode never happened. Either way, it seems this would not be an enjoyable experience to live with for their entire adult life. The title text continues the thought by pointing out the impossibility of contributing anything to the scientific world after visiting a magical world, as the child would know many scientific baselines, and, indeed, most regularly practiced scientific theory to be false, but would be unable to say anything or convince anyone of what they knew. [Kid is sitting on the ground with his chin in his hand.] Kid: I'm such a loser- POP [Princess sticks her head through a portal.] Princess: Come quickly, young one! Kid: Holy crap, a portal! Princess: My kingdom needs you! [He falls through.] Kid: AAAAAA [We see him on horseback, helmeted wielding a sword. There's a castle on the horizon and two moons in the sky. There are a few other riders as well.] [Kid, with helmet and sword, stands before King, Princess, and another warrior. Princess is holding out a ring.] King: You've saved our kingdom and found your self-confidence. Now it's time to return home. Goodbye, young hero! Princess: Take this ring to remember us! [Kid stands alone, holding the ring.] Kid: Well, I guess I spend the rest of my life pretending that didn't happen or knowing that everyone I love suspects I'm crazy. Kid: This'll be a fun 70 years.

Retro Virus

Retro Virus

https://www.xkcd.com/694

https://www.explainxkcd.com/wiki/index.php/694:_Retro_Virus

[Cueball is using a computer.] Cueball: Argh, this is frustrating. Friend (off-panel): What? Cueball: This Windows box has a virus and I can't get RegEdit to- Friend (off-panel): Haha, cleaning viruses? Man, what a blast from the past! Friend: Check it out! Dude's cleaning Win32 viruses! Remember that? Ponytail (off-panel): It's like we're back in 2003! Cueball (small): Hey, XP's still the most- Friend: Did you get the virus from Kazaa? Ponytail (with laptop): Guess what I just read on Howard Dean's Friendster!? Cueball (head in hands): Guys...

This comic uses the word "retro" as a reference to retro style and "virus" as a reference to computer viruses . This portmanteau is also a double entendre for a retrovirus , which is a type of biological virus. Cueball finds himself needing to clean a virus off his Windows machine. Unfortunately, the registry editor (regedit), a key tool in manipulating Windows, is affected. A coworker comes over and mentions that it has been a while since he has worried about cleaning viruses in the Win32 API . Cueball responds that Windows XP operating system is still the most popular (which it was in 2010, and remained until mid-2012), but is drowned out by another coworker ( Ponytail ) who exclaims that it is as if they are back in 2003. Back then, Windows XP machines were the standard in many places, and were far more often targeted by viruses than other systems, e.g. Linux , Mac OS X , etc. In the final panel, Cueball's coworkers continue to make fun of him by referencing things that were important back in 2003 like Howard Dean , Friendster or Kazaa . Such things have since fallen largely out of prominence. The title text is a reference to the year of Linux on the desktop , which is an expectation that in an upcoming year, Linux will make a large breakthrough and be widely adopted by businesses and personal users. The expectation has been around since about 2000, however, and has not exactly happened (although non-desktop devices running Android , a Linux-based OS, are now very common). If it were to happen, the large market share enjoyed by Windows OSes would fade away. [Cueball is using a computer.] Cueball: Argh, this is frustrating. Friend (off-panel): What? Cueball: This Windows box has a virus and I can't get RegEdit to- Friend (off-panel): Haha, cleaning viruses? Man, what a blast from the past! Friend: Check it out! Dude's cleaning Win32 viruses! Remember that? Ponytail (off-panel): It's like we're back in 2003! Cueball (small): Hey, XP's still the most- Friend: Did you get the virus from Kazaa? Ponytail (with laptop): Guess what I just read on Howard Dean's Friendster!? Cueball (head in hands): Guys...

Spirit

Spirit

https://www.xkcd.com/695

https://www.explainxkcd.com/wiki/index.php/695:_Spirit

[The Spirit rover is on the surface of Mars.] Day 1 of 90 Spirit (thinking): 89 days to go! Day 88 of 90 Spirit (thinking): Two days until I go home! Day 91 of 90 Spirit (thinking): ? Day 103 of 90 Spirit (thinking): Maybe I didn't do a good enough job. Day 127 of 90 Spirit (thinking): Maybe if I do a good enough job, they'll let me come home. Day 857 of 90 Spirit (thinking): I thought I analyzed that rock really well. Spirit (thinking): It's okay, I'll do the next one better. Day 1293 of 90 Spirit (thinking): Sandstorm. Power dying. Spirit (thinking): But a good rover would keep going. A good rover like they wanted. Day 1944 of 90 Spirit (thinking): Oh no. whirrrr Spirit (thinking): I'm stuck. whirrrr Spirit (thinking): Did I do a good job? Spirit (thinking): Do I get to come home? Spirit (thinking): Guys? [ Spirit rests in the middle of a vast Martian landscape.]

Anthropomorphism (or personification) is attribution of distinctly human characteristics to animals or non-living things. We make parallels between ourselves and objects, to the point where some people even jocularly worry about hurting the feelings of, say, an automobile. We call ships "she." We see human faces in objects like the arrangement of lights on the front of a car. The Spirit Mars rover , like many high-functioning robots in real life and fiction, shares many physical similarities with a human being or animal. It has a head, eyes, neck, body, legs, feet, arms, and a hand. And it strikingly resembles robots from fiction, such as Johnny 5 from Short Circuit , or WALL-E from the film with the same name. Thus, this comic explores what the Spirit rover's life would be like if it had a human personality. The rover lasted 5¼ active years on the Martian surface, far exceeding its expected mission duration of 90 Martian days. A sentient robot might assume that after its initially planned 90 Martian day mission was over, it would get to return home. This assumes, of course, that the rover never understood that the mission was a one-way trip, and that the expectation was that it would simply fail after ninety days. When no one comes to return it home, Spirit , possibly in a pun on its name, keeps its hopes alive while continuously analyzing rock after rock for years. It would be cruelty of the absolute worst kind to abandon a human on an uninhabited planet with no intention of ever bringing them home, [ citation needed ] so it feels horrifying when we anthropomorphize the rover. One is rather heartened that the Spirit rover is, in fact, just a programmed machine. Furthermore, even if it were sentient, Spirit has little reason to think of earth as its home, as it had always been designed for Mars, and would have little purpose on earth. Additionally, a sentient machine might be expected to understand the limitations on its own lifespan, and so would expect to survive only three months. From that perspective, surviving for years would seem like a victory, rather than cruelty. One alternative version of the strip (see below) makes a similar point. It is worth pointing out that Opportunity , the rover's twin, has been even more wildly successful and was only shut down in February 2019 ( 2111: Opportunity Rover ). More than five years after this comic, when Opportunity had passed a Marathon distance, Randall celebrated this rover with the comic 1504: Opportunity . The title text has an apparent miscount: January 26, 2010, is more like sol (Martian day) 2156 by JPL's mission status site, not 2274. The final contact with Spirit was on sol 2210 (March 22, 2010). Alternative versions The strip had a strong emotional impact on the fans of the rover, who created a number of alternative versions and endings for it. In a blog post Randall mentioned this upbeat rewrite of the comic. Several others were made , including a silent one. Many alternative endings were also proposed: [The Spirit rover is on the surface of Mars.] Day 1 of 90 Spirit (thinking): 89 days to go! Day 88 of 90 Spirit (thinking): Two days until I go home! Day 91 of 90 Spirit (thinking): ? Day 103 of 90 Spirit (thinking): Maybe I didn't do a good enough job. Day 127 of 90 Spirit (thinking): Maybe if I do a good enough job, they'll let me come home. Day 857 of 90 Spirit (thinking): I thought I analyzed that rock really well. Spirit (thinking): It's okay, I'll do the next one better. Day 1293 of 90 Spirit (thinking): Sandstorm. Power dying. Spirit (thinking): But a good rover would keep going. A good rover like they wanted. Day 1944 of 90 Spirit (thinking): Oh no. whirrrr Spirit (thinking): I'm stuck. whirrrr Spirit (thinking): Did I do a good job? Spirit (thinking): Do I get to come home? Spirit (thinking): Guys? [ Spirit rests in the middle of a vast Martian landscape.]

Strip Games

Strip Games

https://www.xkcd.com/696

https://www.explainxkcd.com/wiki/index.php/696:_Strip_Games

Frequency of Strip Versions of Various Games n = google hits for "strip <game name>" / google hits for "<game name>" (at the time of this writing) Frequent (n > 1%) -Poker -Spin the Bottle -Beer Pong -Never Have I Ever -Truth or Dare Rare (1% >= n > 0.01%) -Chess -Blackjack -Tennis -Settlers of Catan -Pictionary Extremely Rare (0.01% >= n > 0) -Cricket -Magic: the Gathering -Stickball -Agricola -Jumanji Nonexistent (n = 0) -Poohsticks -Podracing -Iterated Prisoner's Dilemma -Chess by Mail -Conway's Game of Life

The frequency of strip versions of various games is measured by means of Google search results. Strip versions of popular games are a common activity at parties, especially when alcohol is involved. The obligation to remove pieces of clothing is supposed to add an extra zest to the game. A very widespread variant is Strip Poker , followed by strip versions of regular party games like Truth or Dare or Spin the Bottle . However, the comic also suggests playing other games in a way that involves stripping. In reality, playing such games as "Strip Tennis " or "Strip Agricola " is rather unusual. The Chris Van Allsburg picture book Jumanji and the Robin Williams movie adaptation Jumanji are about a magical board game that manifests dangerous creatures and traps from the jungle and lost civilization therein; a theoretical Strip Jumanji would probably not remain very titillating during the chaos (evidently, therefore, "strip Jumanji" refers to the real-life board game based on the movie ). The last column features games of which strip versions are (according to Google) nonexistent. While the other columns named sports or board games where a strip variant would be at least conceivable, the last one includes the zero-player Game of Life and the Iterated Prisoner's Dilemma , which is a theoretical example in game theory . It is therefore left to the reader to imagine how a strip version of these pseudo-games would appear. "Global Thermonuclear War" in the title text is a reference to the film " WarGames ", where a young hacker accesses a US military supercomputer and starts a nuclear war simulation, believing it to be only a computer game. The film ends by showing the computer that nuclear war is "a strange game" in which "the only winning move is not to play", and proposes "a nice game of chess". Strip global thermonuclear war is a patently absurd idea; while it is a common trope for people to engage in one last moment of intimate pleasure before certain doom, foreplay (including strip games of any type) is a time-consuming practice, and time is something you don't have much of considering that the bomb could drop on your place of residence at any moment. Besides all that, the act of betting on which city is going to go up next in a nuclear inferno tends not to be an effective aphrodisiac for most people. [ citation needed ] But at least you wouldn't be wearing your radioactive clothes! Frequency of Strip Versions of Various Games n = google hits for "strip <game name>" / google hits for "<game name>" (at the time of this writing) Frequent (n > 1%) -Poker -Spin the Bottle -Beer Pong -Never Have I Ever -Truth or Dare Rare (1% >= n > 0.01%) -Chess -Blackjack -Tennis -Settlers of Catan -Pictionary Extremely Rare (0.01% >= n > 0) -Cricket -Magic: the Gathering -Stickball -Agricola -Jumanji Nonexistent (n = 0) -Poohsticks -Podracing -Iterated Prisoner's Dilemma -Chess by Mail -Conway's Game of Life

Tensile vs. Shear Strength

Tensile vs. Shear Strength

https://www.xkcd.com/697

https://www.explainxkcd.com/wiki/index.php/697:_Tensile_vs._Shear_Strength

[A space elevator occupies the height of the frame, consisting of a base, a cable extending out into space, and an elevator unit with standard elevator features such as sliding doors and up/down buttons. A banner flutters in the breeze attached to the cable going up above the elevator. There is text on the banner. Text appear in four lines split across the elevator cable itself, the rhyming portions of the text is on the right side of the cable. Five individuals stand at the base of the elevator. To the left are Megan, a Cueball-like guy with his arms raised, and Ponytail, who is holding a bottle of champagne/sparkling wine which is bubbling out down the neck of the bottle. To the right is Black Hat, who cuts the cable with a pruning shear like it was part of the ceremony as a ribbon cutting. Finally further right is Cueball who sees what Black Hat is doing. He is very alarmed holding a hand to his mouth while holding the other out towards Black Hat.] Banner: Space Elevator Banner: Grand opening After countless engineers spend trillions over fifty years, a modern babel disappears because some fuck brought pruning shears. Pruning shears: Snip Cueball: !!

Tensile strength represents how hard you can pull on something without it breaking. Shear strength represents how hard you can try to cut it without it breaking. Many materials have great tensile strength but low shear strength (such as dental floss — try to break it by just pulling on two ends), including whatever this space elevator is made of. The material clearly has extremely high tensile strength because it can hold the elevator in place, with one end on the ground and one in space, but it can be cut with a simple pair of pruning shears. This also highlights the fact that "shear strength" and "shears" are etymologically related . A space elevator is a proposed construction that would make space travel easier. It consists of a long string attached to the Earth (near equator) on one end and a counterweight (beyond the geostationary orbit ) on the other end, kept taut and in one place by the gravity and centrifugal forces. This would make it possible to carry spacecraft into the orbit by simple mechanical means, as opposed to requiring the use of rockets as is the case nowadays, saving a lot of energy and resources. The phrase "a modern Babel" refers to the biblical story of the Tower of Babel (later referenced in 2421: Tower of Babel ), in which humans endeavor to build a tower reaching heaven. Their arrogance angers God and prompts him to sabotage the project. A space elevator can be seen as a modern equivalent of a tower to heaven. [ citation needed ] Additionally, the expression "a modern Babel" may be used figuratively to describe huge projects (especially buildings or human-made structures) that fail because they are too ambitious. The title text makes the point that even before Black Hat cut the space elevator's cable in two, it was ruined by the holes in it for the banner. The holes would reduce the surface area of the cross section of the pole, reducing its ability to keep the elevator attached to the ground. The flag and holes would also potentially make it impossible for the elevator to travel up the pole, making the entire elevator useless. [A space elevator occupies the height of the frame, consisting of a base, a cable extending out into space, and an elevator unit with standard elevator features such as sliding doors and up/down buttons. A banner flutters in the breeze attached to the cable going up above the elevator. There is text on the banner. Text appear in four lines split across the elevator cable itself, the rhyming portions of the text is on the right side of the cable. Five individuals stand at the base of the elevator. To the left are Megan, a Cueball-like guy with his arms raised, and Ponytail, who is holding a bottle of champagne/sparkling wine which is bubbling out down the neck of the bottle. To the right is Black Hat, who cuts the cable with a pruning shear like it was part of the ceremony as a ribbon cutting. Finally further right is Cueball who sees what Black Hat is doing. He is very alarmed holding a hand to his mouth while holding the other out towards Black Hat.] Banner: Space Elevator Banner: Grand opening After countless engineers spend trillions over fifty years, a modern babel disappears because some fuck brought pruning shears. Pruning shears: Snip Cueball: !!

You Hang Up First

You Hang Up First

https://www.xkcd.com/698

https://www.explainxkcd.com/wiki/index.php/698:_You_Hang_Up_First

[Cueball is sitting on a bed, on the phone.] Cueball: You hang up first. [Megan is lying on a bed, on the phone.] Megan: No, you hang up first. Cueball: No, you hang up first. Megan: No, you fucking hang up first! Cueball: You hang up first, or we're OVER! Megan: Then I guess we're fucking OVER! Cueball: FINE! Megan: ... Cueball: ... Megan: You move on and find somebody else first.

Telephone conversations end when someone hangs up. There's a traditional cliche of young romantic partners, both of whom are so besotted that they can't bear to hang up on the other. As a result, the end of the call devolves into a cycle where each one teasingly insists that the other one hang up first. It's a sweet, if somewhat mawkish display of how infatuated they are with each other. As xkcd often does, this comic takes the cliche to its logical extreme with Cueball and Megan , by turning it into an argument resulting in their breakup. What's normally a cutesy game between lovers becomes a battle of wills, leading them to break up because neither is willing to back down. And then, even after they break up, both are still unwilling to back down, with Megan insisting that Cueball "move on and find somebody else first." [Cueball is sitting on a bed, on the phone.] Cueball: You hang up first. [Megan is lying on a bed, on the phone.] Megan: No, you hang up first. Cueball: No, you hang up first. Megan: No, you fucking hang up first! Cueball: You hang up first, or we're OVER! Megan: Then I guess we're fucking OVER! Cueball: FINE! Megan: ... Cueball: ... Megan: You move on and find somebody else first.

Trimester

Trimester

https://www.xkcd.com/699

https://www.explainxkcd.com/wiki/index.php/699:_Trimester

[Cueball is wearing a lab coat, and talking to Megan, who is sitting on a desk. He also has a clipboard.] Cueball: Well, until the second trimester, the baby hasn't decided which opening it will exit through. Megan: What? Cueball: We'll hope for one of the lower ones, so it won't be fighting gravity. [Caption below the panel:] Did you know you can just BUY lab coats?

Some pregnancies are different than others, but a universal truth except in cases of Cesarean section is that a baby will always exit a woman's body through the vagina. Cueball is wearing a white lab coat and holding a clipboard, looking like a doctor, telling Megan that until the second trimester, the baby may decide instead to exit through any opening, including the mouth, anus, nose, navel, etc. This does not normally happen in real life. [ citation needed ] The caption reveals the truth, that Cueball simply bought the lab coat, he is not a doctor, and is either pranking Megan, or is impersonating a physician for some other reason. The expectation that a person in a white coat is a medical expert, or at least a scientist, can be seen in the studies of the placebo effect: people who receive a "sugar pill" from a person who has the authority implied by wearing a lab coat will experience a greater placebo effect than those who receive identical pills from a person in mufti . This leads to more doctors wearing a white coat while working, and due to that a reinforcement of the expectation of white coats belonging to doctors. In some medical schools students receive a white coat as part of their graduation and qualification ceremony. The title text implies also that in addition to faking being a doctor, he has also faked being a Nobel laureate, on the logic that people will not choose to verify this claim. [Cueball is wearing a lab coat, and talking to Megan, who is sitting on a desk. He also has a clipboard.] Cueball: Well, until the second trimester, the baby hasn't decided which opening it will exit through. Megan: What? Cueball: We'll hope for one of the lower ones, so it won't be fighting gravity. [Caption below the panel:] Did you know you can just BUY lab coats?

Complexion

Complexion

https://www.xkcd.com/700

https://www.explainxkcd.com/wiki/index.php/700:_Complexion

I get frustrated trying to judge whether acne creams are having any effect. In the spirit of a controlled trial, I used one on just half my face for a few weeks. [A graph shows pimples vs. time, with two lines: one remains one steady, and one is declining.] It was cool seeing the effects so clearly, so I got some friends to try different treatments in an impromptu study. [Cueball looks in a mirror, sees a half-pimpled face, and applies a treatment.] [Cueball is talking to Ponytail and Megan, each with some pimples also.] Cueball: Okay, you try the salicylic acid first. Ponytail: Wait, we should randomize the trials. Got a coin? Cueball: Okay, call it. Heads, she gets the- (Off-panel): YOU! [Batman runs into frame and punches Cueball. The coin goes flying.]

Cueball suffers from acne . Like many others afflicted with the same condition, he uses skin care products designed to treat acne. Unlike most other people, he does his own controlled trial by using them on only one half of his face and measuring the effects; the blemishes on the treated half of his face are noticeably diminished, while the untreated half remains the same, allowing him to isolate the effects of the cream versus the effects of time. He convinces his friends to try the same experiment with different treatments so they can find out which works the best. In order to properly randomize the trials, he flips a coin. However, because half of his face is "scarred" (with acne blemishes), he's flipping a coin, and appears to be threatening someone with acid, he's mistaken for the Batman villain Two-Face . (Two-Face flips a coin to decide whether his victims will live or die, and was badly burned by acid on exactly one half of his face.) Cueball is subsequently punched by Batman; the title-text implies this has happened before. Salicylic acid and benzoyl peroxide are both chemicals known for their skin care effects (salicylic acid in particular is also used to treat psoriasis ). I get frustrated trying to judge whether acne creams are having any effect. In the spirit of a controlled trial, I used one on just half my face for a few weeks. [A graph shows pimples vs. time, with two lines: one remains one steady, and one is declining.] It was cool seeing the effects so clearly, so I got some friends to try different treatments in an impromptu study. [Cueball looks in a mirror, sees a half-pimpled face, and applies a treatment.] [Cueball is talking to Ponytail and Megan, each with some pimples also.] Cueball: Okay, you try the salicylic acid first. Ponytail: Wait, we should randomize the trials. Got a coin? Cueball: Okay, call it. Heads, she gets the- (Off-panel): YOU! [Batman runs into frame and punches Cueball. The coin goes flying.]