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Sketchiness

Sketchiness

https://www.xkcd.com/1101

https://www.explainxkcd.com/wiki/index.php/1101:_Sketchiness

[A timeline style graph.] WORDS Arranged by how sketchy they make the sentence ´´HEY BABY, WANNA COME BACK TO MY SEX ________?`` sketchy <--------> very sketchy party --- orgy --- dungeon --- palace --- house --- shrine --- room --- basement --- truck --- platform --- van --- area --- crate --- chute --- ravine --- tarp

Sketchy is an adjective meaning not thorough or detailed, but which in modern slang is often used to connote creepiness, or a general feeling that something is not quite right. Urban Dictionary provides a good definition of "someone or something that gives off a bad feeling". In this comic, Randall rates words by how sketchy they make the sentence "Hey baby, wanna come back to my sex ____?" when inserted into the blank. As noted from the scale (which already starts at "sketchy" and goes up to "very sketchy"), the sentence itself is already inherently sketchy, in that it sounds like it would be a pickup line delivered by a person attempting to solicit sex from a stranger. The sketchiness is increased by the various words which run from the relatively common or understood to the obscure and unusual. The first few are actual terminology: A sex party or sex orgy are basically group sex parties at which multiple parties engage in sexual activity. A sex dungeon is a location where BDSM (bondage/submission — think leather and handcuffs) activity is engaged in. "Sex House" is the name of an Onion News Network parody of reality shows like Big Brother. As the scale increases, the words become simply locations where sex might take place, which increase from comfortable to unusual and creepy (i.e. sex crate, sex ravine, sex tarp). It is particularly sketchy because of the phrasing of the sentence which implies the speaker has a specific [insert word] used for sex. It might be sketchy enough to walk up to someone and suggest "let's go down in the ravine and have sex", but it is made sketchier when the phrasing suggests going to "my sex ravine". The title text continues the thought process with further possible sketchy words, beginning with more odd locations and moving on to "onslaught", an abundant wave of attack or overwhelming amount of something — in this case sex; "extractor" suggests some sort of device that might force someone to have sex; and finally "judge", suggesting the speaker has someone in mind to judge sex. Very sketchy indeed. [A timeline style graph.] WORDS Arranged by how sketchy they make the sentence ´´HEY BABY, WANNA COME BACK TO MY SEX ________?`` sketchy <--------> very sketchy party --- orgy --- dungeon --- palace --- house --- shrine --- room --- basement --- truck --- platform --- van --- area --- crate --- chute --- ravine --- tarp

Fastest-Growing

Fastest-Growing

https://www.xkcd.com/1102

https://www.explainxkcd.com/wiki/index.php/1102:_Fastest-Growing

[A man with a combover, a book, and a clipboard approaches Black Hat.] Combover: You should check us out. We're the fastest-growing religion in the country. Black Hat: "Fastest-growing" is such a dubious claim. Combover: It's true! We grew by 85% over the past year. [In a frameless panel, Black Hat shouts to someone out of frame.] Black Hat: Hey, Rob — wanna join my religion? Rob: Sure, whatever. [Black Hat turns back to Combover and produces a notepad and pen.] Black Hat: Well, looks like my religion grew by 100% this year. [Black Hat begins to walk away.] Combover: We have 38,000 members! Black Hat: Hope they're all ok with second place.

This comic talks about the misuse of percentage of growth. It can be misleading for gauging the importance or popularity of something; If you add only 4 members to an existing group of 2, you would have achieved a growth of 200 percent. In the case portrayed in this comic the claim appears to be that the other person's religion grew by 85%. Black Hat attempts humorously to show the flaw in using that statistic by growing his group by 100% (therefore, presumably, first place), which he simply does by adding his friend Rob to his religion, and thus increasing his membership from 1 to 2. The other person then says that his religion has a significant number of members (and not just one or two, but ended up with 35,000 this year, presumably having 'only' around 20,540 in the prior one), but Black Hat doesn't care and responds that he hopes they are all okay with being "in second place" since the main argument from the other guy was about being the fastest-growing. The title text ponders the ironic idea of converting only the zealous door-to-door proselytizers to a very persuasive religion of one's own. Another interpretation is that the title text could be another way that Black Hat could take the 'fastest-growing' claim out of context to make it meaningless. By composing his religion of the unwitting proselytizers of other faiths, he can claim the highest ratio of converts to current adherents. Note that the amount of people converted is often exaggerated by groups that try to spread a faith. Although the beliefs spread by his proselytizers vary widely, Black Hat is not concerned with what his so-called followers believe. Thus, he can claim the title of fastest-growing religion without having any value to his religion. Various religions and groups encourage their members to actively recruit new followers, such as the Mormon missionary . [A man with a combover, a book, and a clipboard approaches Black Hat.] Combover: You should check us out. We're the fastest-growing religion in the country. Black Hat: "Fastest-growing" is such a dubious claim. Combover: It's true! We grew by 85% over the past year. [In a frameless panel, Black Hat shouts to someone out of frame.] Black Hat: Hey, Rob — wanna join my religion? Rob: Sure, whatever. [Black Hat turns back to Combover and produces a notepad and pen.] Black Hat: Well, looks like my religion grew by 100% this year. [Black Hat begins to walk away.] Combover: We have 38,000 members! Black Hat: Hope they're all ok with second place.

Nine

Nine

https://www.xkcd.com/1103

https://www.explainxkcd.com/wiki/index.php/1103:_Nine

[Cueball stands at a microwave, which hangs on the wall above the stove.] Cueball: How long do you zap these? Character off-frame: Two minutes. Cueball: Thanks! [Buttons being pushed.] *Beep* 1 *Beep* 5 *Beep* 9 Cueball: It's ok, nine. Cueball: You are not forgotten. [Caption below the frame:] Ever since I heard the simile "As neglected as the nine button on the microwave." I've found myself adjusting cook times. The disproportionately high frequency of low digits appearing in a random number is a similar concept to Benford's Law , which states that the lower a non-zero digit is, the more likely it will appear as the first (non-zero) digit of a random number; eg, you are far more likely to encounter a number beginning with the digit 1 than a number whose first digit is 9. However, in the case of microwaves, the reason low digits are usually at the beginning of the number is more due to the relatively short times used on microwaves, whereas Benford's Law has to do with logarithmic scale. And in the case of microwaves, 3s and 0s have an increased likelihood of appearing in later digits because times are usually given in units of minutes or half-minutes, and while it is possible to extend Benford's Law to a few digits beyond the first digit, there is certainly no preference for 3 over other digits. Taken together, one could probably infer that the amount of time something is cooked in an oven, which is usually longer than things are cooked in a microwave, is more likely to include early digits such as 0, 1, 2, and 3 as opposed to digits such as 7, 8, and 9.

Most common cook times are given in either whole, half, or quarter minute increments; e.g., 2:00 min. or 1:30 min, meaning that 1, 2, 3, 4, 5, and 0 are the most used digits on the microwave (because microwave times are usually less than 6 minutes), and to use numbers like 6, 7, 8, or 9, one would have to cook something for that number of minutes. Cueball, however, feels bad for the under-used number '9,' so he microwaves his food for one minute fifty-nine seconds instead of two minutes, as a one-second difference is negligible. Also, in Randall's book Thing Explainer, every number from one to ten are in the top thousand most used words except nine, which is labeled "the number after eight", "one more than eight", or (when referring to the Ninth Amendment ) "Change After Eight". This shows how the other numbers are used much more than nine. The title text is reminiscent of comic 245: Floor Tiles . [Cueball stands at a microwave, which hangs on the wall above the stove.] Cueball: How long do you zap these? Character off-frame: Two minutes. Cueball: Thanks! [Buttons being pushed.] *Beep* 1 *Beep* 5 *Beep* 9 Cueball: It's ok, nine. Cueball: You are not forgotten. [Caption below the frame:] Ever since I heard the simile "As neglected as the nine button on the microwave." I've found myself adjusting cook times. The disproportionately high frequency of low digits appearing in a random number is a similar concept to Benford's Law , which states that the lower a non-zero digit is, the more likely it will appear as the first (non-zero) digit of a random number; eg, you are far more likely to encounter a number beginning with the digit 1 than a number whose first digit is 9. However, in the case of microwaves, the reason low digits are usually at the beginning of the number is more due to the relatively short times used on microwaves, whereas Benford's Law has to do with logarithmic scale. And in the case of microwaves, 3s and 0s have an increased likelihood of appearing in later digits because times are usually given in units of minutes or half-minutes, and while it is possible to extend Benford's Law to a few digits beyond the first digit, there is certainly no preference for 3 over other digits. Taken together, one could probably infer that the amount of time something is cooked in an oven, which is usually longer than things are cooked in a microwave, is more likely to include early digits such as 0, 1, 2, and 3 as opposed to digits such as 7, 8, and 9.

Feathers

Feathers

https://www.xkcd.com/1104

https://www.explainxkcd.com/wiki/index.php/1104:_Feathers

[Megan is walking up to Science Girl with a bow in her hair bun. Science Girl has a stack of three books in front of her, is reading another book and a fifth book lies behind her on the floor.] Megan: What are you reading about? Science Girl: Dinosaurs! Megan: Oh, yeah. [Zoom out of the same scene, with Megan standing and Science Girl looking up at her.] Megan: They've gotten all weird since when I was a kid. Megan: They used to be awesome, but now they all have dorky feathers, right? Science Girl: Yup! [Same scene in a frame-less panel. Science Girl looks down and below the two characters there is a footnote.] Science Girl: This says they now think raptors used their wings for stability, flapping to stay on top of their prey while hanging on with their hooked claws and eating it alive. *Fowler et. al., PLoS ONE 6(12), 2011 [Zoom in on the same scene, the book on the floor is outside the panel. Megan just stands staring at Science Girl who reads on. Beat panel.] [Megan is now on the floor next to Science Girl flipping through the top book she has taken from the pile.]

Dinosaurs have been a fascinating topic in popular science and have captivated children's interest since the first fossils were discovered in modern times, around the 1700s; prior discoveries in China and elsewhere were thought to be the bones of dragons or other mythical creatures. The success of the Jurassic Park movies perpetuated an erroneous understanding of the physical characteristics of dinosaurs. Since the first movie of that series, scientific evidence has emerged suggesting that Dromaeosauridae , or " raptors ", the main antagonists of that movie, looked quite different from their animatronic and CGI versions. In particular, they are now known to have been much smaller, and are believed to have had feathers and even wings, as evidenced by quill nobs observed on the arms of raptors. Denver W. Fowler is among the scientists who support this hypothesis. (incidentally, a " Fowler " is a hunter of wildfowl/birds) The comic refers to a publication by him and his colleagues (" et al. "), in the PLoS ONE , an online scientific journal ("PLoS" stands for "Public Library of Science"). Megan believes this new model of the appearance of raptors makes them much less cool, but the way in which Science Girl reformulates the facts to make them seem like even more vicious predators re-ignites her interest and makes the new raptors seem like at least as good a candidate for a good action thriller movie like the original version, if not better. Thus the phrase "the past keeps getting cooler". (Or that Megan, like Randall, has an irrational fear of raptors and is updating her knowledge of them.) Clicking on the original cartoon links to a YouTube video of a bird of prey (in this case a Secretarybird ) using its wings for stability while standing on top of a struggling prey, from which one can easily envision instead a raptor upon its prey—especially in case of some kind of "raptorphobia", as for Randall (see 87: Velociraptors and 135: Substitute ). Microraptor was a small raptor with four wings, which lets you imagine even scarier scenes. The same idea is later explored from a different perspective in 1527: Humans . [Megan is walking up to Science Girl with a bow in her hair bun. Science Girl has a stack of three books in front of her, is reading another book and a fifth book lies behind her on the floor.] Megan: What are you reading about? Science Girl: Dinosaurs! Megan: Oh, yeah. [Zoom out of the same scene, with Megan standing and Science Girl looking up at her.] Megan: They've gotten all weird since when I was a kid. Megan: They used to be awesome, but now they all have dorky feathers, right? Science Girl: Yup! [Same scene in a frame-less panel. Science Girl looks down and below the two characters there is a footnote.] Science Girl: This says they now think raptors used their wings for stability, flapping to stay on top of their prey while hanging on with their hooked claws and eating it alive. *Fowler et. al., PLoS ONE 6(12), 2011 [Zoom in on the same scene, the book on the floor is outside the panel. Megan just stands staring at Science Girl who reads on. Beat panel.] [Megan is now on the floor next to Science Girl flipping through the top book she has taken from the pile.]

License Plate

License Plate

https://www.xkcd.com/1105

https://www.explainxkcd.com/wiki/index.php/1105:_License_Plate

[Cueball is walking in from the right holding a license plate up with both hands for an off-panel Megan to see. It is possible to see the plate, but here it looks like all I's (or 1's).] Cueball: Check out my personalized license plate! Megan (off-panel): "1I1-III1"? Cueball: It's perfect! Plate: III-IIII [In this frame-less panel Megan is sitting in an office chair holding and looking at the plate while Cueball stand next to her rubbing his hands together in front of him.] Cueball: No one will be able to correctly record my plate number! Cueball: I can commit any crime I want! Megan: Sounds foolproof. [A man with hair only around his neg and glasses holds out a hand towards a bald male police officer with a black peaked cap with white emblem on the front. The police man interviews their witness holding a notepad and a pen. Another likewise caped female officer is Ponytail who walks to the left arm pointing left. There is a line of yellow police tape behind them with text partially obscured by the characters. At the top left of the panel there is a small frame with a caption:] Soon: Witness: The thief's license plate was all "1"s or something. Police officer: Oh. That guy. Ponytail: His address is on a post-it in the squad car. Yellow strip (text not visible in brackets): Poli[ce strip] do not cross [poli]ce stri[p do not] cross.

Cueball has obtained a new license plate . The license plate number one receives is often the next in sequence, available at the time and place of registration. However, in many localities, for an additional fee one can select their own "personalized" license plate number (called a vanity plate ), subject to certain criteria, and availability. In this comic, Cueball has elected to purchase the personalized license plate number "1I1-III1" or "one, letter I, one, dash, letter I, letter I, letter I and one". He believes the ambiguity between the letter I and the digit 1 on the plate will make it very difficult for anyone to correctly identify his vehicle if he commits a crime. Some localities have more distinct "1" and "I" characters in their license plate font than others, but often when a crime is committed witnesses only has a short time to look at the plate, and will then be confused. In principle his idea did work, because when the police end up interviewing a witness of a crime scene in the end of the comic, he can only say that "The thief's license plate was all "1"s or something". What Cueball does not count on is that there are no other license plates made up entirely of the letter I and the digit 1. Thus, when witnesses report a vehicle with a license plate of either/or I's and 1's, the police know exactly who the perpetrator is. Given the fact that the police still haven't caught him even though they have his address written on a Post-it note in their car, it seems like they had already thought of the same idea, and when Cueball registered such a license plate they put up the address in the police cars, as they expected him to begin committing crimes. He may already have committed more than one, but they would soon stop him before it turned into a crime spree. (An alternative interpretation is that his crime spree has so far consisted of minor offenses, so they haven't arrested him, just issued him warnings or citations -- although one would expect him to stop once it became obvious they were onto him.) Someone in New Hampshire appears to have done this in real life. The title text appears to be a conversation between Cueball and the police the next day when they show up at his address. It turns out that the police suspect Cueball of six bank robberies. Cueball responds that "all" he did was vandalize the library. But the police disregard this as a nice try to avoid being arrested because witnesses saw a license plate with all 1's and I's was used. Cueball does not understand this because he was with his car the entire time since he got the license plate. And just as he says this, he has an epiphany and states wait. OK, wow that was clever of her . It is thus clear that he suspects that Megan of having made a false license plate also with only a combination of I's and 1's. And then she has robbed six banks knowing that the police would be sure to suspect Cueball, who was so foolish to show his criminal intent by registering such a plate in the first place. Knowing that the police will assume the car is his, she has thus framed him. Hopefully for Cueball, he can prove he was not involved in the robberies, but if the police assumed that he was the one that committed the crimes, they may not have taken so much care in collecting evidence the first day of the crimes. This will have given Megan time to run away with all the money, as no one was looking for her. So she may well have left the country with no one looking for a woman. This will make it more difficult for Cueball to avoid the blame. It is clear that Megan would not be so stupid as to register another plate, because then they would know that there could be more than one criminal. Also she would not have had time to get it, if the crime spree began soon after Cueball showed the plate to her. But if the fake plate makes people tell about the 1s and Is then the police would not ask further and discover that the plate might have looked fake. Note the yellow police line seems to say Police strip do not cross , where Police line do not cross seems to be the only sentence used normally (unless it is crime scene do not cross , but that also does not fit). (Of course, this could be a pun about the fact that this occurrence is a comic strip .) [Cueball is walking in from the right holding a license plate up with both hands for an off-panel Megan to see. It is possible to see the plate, but here it looks like all I's (or 1's).] Cueball: Check out my personalized license plate! Megan (off-panel): "1I1-III1"? Cueball: It's perfect! Plate: III-IIII [In this frame-less panel Megan is sitting in an office chair holding and looking at the plate while Cueball stand next to her rubbing his hands together in front of him.] Cueball: No one will be able to correctly record my plate number! Cueball: I can commit any crime I want! Megan: Sounds foolproof. [A man with hair only around his neg and glasses holds out a hand towards a bald male police officer with a black peaked cap with white emblem on the front. The police man interviews their witness holding a notepad and a pen. Another likewise caped female officer is Ponytail who walks to the left arm pointing left. There is a line of yellow police tape behind them with text partially obscured by the characters. At the top left of the panel there is a small frame with a caption:] Soon: Witness: The thief's license plate was all "1"s or something. Police officer: Oh. That guy. Ponytail: His address is on a post-it in the squad car. Yellow strip (text not visible in brackets): Poli[ce strip] do not cross [poli]ce stri[p do not] cross.

ADD

ADD

https://www.xkcd.com/1106

https://www.explainxkcd.com/wiki/index.php/1106:_ADD

[Cueball is holding a balloon with "Math Problem" written on it. He is running to grab a balloon labeled "Call Mom" that is floating away.] [Cueball is now holding both balloons, but looks over his shoulder and sees a balloon that reads "Check Oven".] Cueball: !! [Cueball releases the balloons he had been holding and runs for the third.] [Cueball jumps for the "Check Oven" balloon and snatches it just before it is out of reach.] LEAP Cueball: Hah! [Full width panel showing 16 balloons floating away and one Cueball is holding. The balloons are different sizes and colors, labeled as follows from left to right. Listed as * Label - color] Parking Meter - blue Taxes - green Buy Soap - red Phone Call - green Relax - yellow Inbox - blue Clean - red Beat Game - green Feed Cat - yellow Drink Water - blue Call Mom - red Math Problem - green Send Card - red Check Oven (Cueball is holding this one still) - yellow Engine Light - yellow Read - blue Breathe - blue

This comic appears to be a visual representation of the thought process of someone with Attention Deficit Disorder (ADD). Various of Cueball's thoughts or tasks that he must do are represented by balloons which are rising out of his reach. He holds the "math problem" balloon and grabs the "call mom" balloon, but notices "check oven" is rising out of his reach. He abandons the two balloons he holds to dive and grab the "check oven" balloon. Of course, this allows the other two to rise, presumably out of Cueball's reach, as the pullout reveals a plethora of other balloons already rising too high, some of which describe actions required to live, like balloons marked "breathe" or "drink water". This represents how someone with ADD quickly drops one task to take on another, only to jump to yet another task before that one is done; or alternatively, it represents how the person with ADD feels; that while they are focusing on one task, 20 others are getting away from them. The title text further reinforces this, noting that while committing to actually complete one task (represented by tying a balloon to a tree), 20 others floated away. The task he chose to complete is (as stereotypical for someone with ADD), a task that results in no necessary accomplishment — the task is to land a rocket on the moon (Mun) in Kerbal Space Program , a PC-based spaceflight simulator and video game. Additional humour comes from the fact that landing a rocket on the moon in Kerbal Space Program would require a lot of repetition through trial-and-error, making a long and involved task during which many other important tasks might be ignored normally. [Cueball is holding a balloon with "Math Problem" written on it. He is running to grab a balloon labeled "Call Mom" that is floating away.] [Cueball is now holding both balloons, but looks over his shoulder and sees a balloon that reads "Check Oven".] Cueball: !! [Cueball releases the balloons he had been holding and runs for the third.] [Cueball jumps for the "Check Oven" balloon and snatches it just before it is out of reach.] LEAP Cueball: Hah! [Full width panel showing 16 balloons floating away and one Cueball is holding. The balloons are different sizes and colors, labeled as follows from left to right. Listed as * Label - color] Parking Meter - blue Taxes - green Buy Soap - red Phone Call - green Relax - yellow Inbox - blue Clean - red Beat Game - green Feed Cat - yellow Drink Water - blue Call Mom - red Math Problem - green Send Card - red Check Oven (Cueball is holding this one still) - yellow Engine Light - yellow Read - blue Breathe - blue

Sports Cheat Sheet

Sports Cheat Sheet

https://www.xkcd.com/1107

https://www.explainxkcd.com/wiki/index.php/1107:_Sports_Cheat_Sheet

[A three-column table. Months are arrayed down the first column, the second and third columns show sports, with the divisions in partial months rather than lined up with the ends of months. American football and association football (i.e. soccer) are differentiated by small icons in brackets depicting the respective balls used.] Which sport are they arguing about? -My cheat sheet- [The second column, reproduced using approximate dates.] US: Football [ovoid ball drawn in brackets]: January 1 - February 10 Basketball: February 10 - April 20 Baseball: April 20 - May 25 Basketball: May 25 - June 15 Baseball: June 15 - August 20 Football [ovoid]: August 20 - October 5 Baseball: October 5 - October 20 Football [ovoid]: October 20 - December 31 [The third column, reproduced using approximate dates.] non-US: Football [truncated icosahedron, 20 hexagons and 12 pentagons]: January 1 - December 31 The idea of a website that supplies sports talking points to non-fans was previously used in a 2008 episode of the sitcom The IT Crowd , which might be where Randall got the idea. There, the site (Bluffball) focused on UK football, and offered the lines "Did you see that ludicrous display last night?", "What was Wenger thinking sending Walcott on that early?" and "The trouble with Arsenal is they always try and walk it in."

Randall presents a "cheat sheet" which is a handy reference guide for something that is generally expected to be memorized or known by someone familiar with the knowledge domain. Cheat sheets are commonly used in mathematical applications to list important formulas or for measurement conversions; but they may also be used in other applications. This cheat sheet allows Randall to figure out what sport other people are arguing over on the basis of the time of year and where the argument is occurring. The chart is based on the annual seasons (periods when the top professional and college leagues play) of each sport. In the United States, the chart is divided among baseball , basketball and American football . Hockey is not shown, suggesting that he may not consider hockey a sport to compare with the three listed, he does not encounter arguments about hockey (of the four major professional sports leagues in North America, the NHL is significantly behind the others in terms of attention as its appeal is traditionally limited by geography to Canada and the northern United States), or that he perhaps does not need a chart to determine when the argument is about hockey (they may be obvious for countless reasons, including the physicality of typical hockey confrontations). Also, golf is not shown as well implying Randall may not think it's an important sport. The chart suggests that football is the most popular of the three sports, or at least more popular to argue about (of the four major professional sports leagues in North America, the NFL generally has the most attention). The NFL football regular season generally runs from September to December with playoffs in January and early February. Overlapping this period of time, NCAA college football is also occurring, from September to December, with their bowl games in December and January. Almost all of this period, sports arguments are likely to be about football. The NBA basketball regular season runs from late October to mid-April with playoffs in April and into June. NCAA college basketball starts in November but peaks in March with the NCAA Basketball Tournament ( March Madness ). According to the chart, the arguments about basketball don't begin until the football season is over. They continue through the end of April, but start again at the end of May during the playoff finals. The MLB baseball regular season runs from April through September with playoffs in late September and October. When the baseball season begins, arguments shift from the ongoing basketball season to the new baseball season. As mentioned, the NBA Finals create some basketball arguments again for a few weeks. Similarly, the start of the NFL season in September makes it more likely arguments then will be about football. Baseball takes over briefly during the playoffs in October. One of the punchlines is that outside the US, all sports arguments are about association football (soccer) all year round. The two types of football are noted on the chart by an icon showing the ball used in each sport. The title text continues on the theme of this chart being for someone who doesn't know anything about sports. Randall imagines a Twitter feed where you receive a salient sports opinion each day, presumably so that you could repeat the opinion to your friends and appear knowledgeable about sports. As the feed is for those uninformed about sports, there are clarifications of important terms in brackets. The suggested Twitter message mentioned in the title text is accurate for the date of the comic. On September 11, 2012 the baseball team Boston Red Sox played the New York Yankees and won, 4 runs to 3. The Red Sox were already mathematically eliminated from the playoffs (meaning they needed to win more games than remained in the season to qualify). The Yankees were at the top of the standings, but were in a close race for the playoffs with the Baltimore Orioles (both teams had a win-loss record of 79 wins to 62 losses, with 21 games each remaining to play). To be guaranteed a spot in the playoffs, the Yankees had to win more of their remaining games than the Orioles. Losing to the Red Sox made this task harder. (For those wondering, both the Yankees and the Orioles made to the playoffs, but neither made it to the championship round, the World Series.) Traditionally, the Red Sox and the Yankees have a long-standing rivalry , especially among fans. Many Red Sox fans consider a loss by the Yankees nearly as good as a win by the Red Sox (and the Red Sox beating the Yankees the best of both worlds). If the Red Sox can't win the World Series, then at least they can help prevent the Yankees from winning it. This strip is one of several in which Randall attempts to trivialize sports (see for instance 904: Sports , 1480: Super Bowl , 1507: Metaball and 1859: Sports Knowledge ). [A three-column table. Months are arrayed down the first column, the second and third columns show sports, with the divisions in partial months rather than lined up with the ends of months. American football and association football (i.e. soccer) are differentiated by small icons in brackets depicting the respective balls used.] Which sport are they arguing about? -My cheat sheet- [The second column, reproduced using approximate dates.] US: Football [ovoid ball drawn in brackets]: January 1 - February 10 Basketball: February 10 - April 20 Baseball: April 20 - May 25 Basketball: May 25 - June 15 Baseball: June 15 - August 20 Football [ovoid]: August 20 - October 5 Baseball: October 5 - October 20 Football [ovoid]: October 20 - December 31 [The third column, reproduced using approximate dates.] non-US: Football [truncated icosahedron, 20 hexagons and 12 pentagons]: January 1 - December 31 The idea of a website that supplies sports talking points to non-fans was previously used in a 2008 episode of the sitcom The IT Crowd , which might be where Randall got the idea. There, the site (Bluffball) focused on UK football, and offered the lines "Did you see that ludicrous display last night?", "What was Wenger thinking sending Walcott on that early?" and "The trouble with Arsenal is they always try and walk it in."

Cautionary Ghost

Cautionary Ghost

https://www.xkcd.com/1108

https://www.explainxkcd.com/wiki/index.php/1108:_Cautionary_Ghost

[A man wakes up to an apparition hovering over his bed.] Apparition: ooOOOOOOOOOOooooo Man: A ghost!? Apparition: I bring a cautionary vision of things to come! Apparition: This is the future: [Two people are standing between a pair of houses. There is a tree. An airplane flies past.] Apparition: And this is the future if you give up the fight over the word "literally": [Two people are standing between a pair of houses. There is a tree. An airplane flies past. The cynical might suggest the panel is copy pasted.] [Back to the man in bed.] Man: They looked exactly the same. Apparition: ooOOOOOOOOOOOooo Man: Ok, I get it. Apparition: Seriously, this is duuuuumb.

This comic is a parody of Charles Dickens 's A Christmas Carol , where Scrooge is replaced with someone who insists on calling people out on their incorrect usage of the word "literally", and speaks to the irrelevance of correcting people's speech. In "A Christmas Carol", the ghosts of Christmas past, present, and future awaken the main character in the middle of the night to show him the negative causes and effects of his selfish and uncharitable behavior. In this comic the ghost wakes up a man who is intent on correcting people's usage of the word "literally." People often use "literally" as emphasis or exaggeration to a figurative statement, when the word's original meaning was that something had happened exactly as described. A statement such as "I literally ate 40 lbs of chocolate" might be said, when the person might have only actually eaten half a pound. A more correct statement would be "I ate a large amount of chocolate." The ghost shows the protagonist two futures, one where he keeps correcting people, and one where he stops. That the two "different" futures are exactly (i.e., literally) the same suggests that the man's struggle to get people to stop using "literally" incorrectly will have no meaningful effect on the world, and so the man (and by extension, everyone else) may as well stop wasting time and energy on it. Ironically, the title text indicates that a second apparition encouraged the man to continue the fight on a different grammatical issue, the use of the phrase "if it were," which is frequently incorrectly substituted with "if it was." "Were" is correctly used in a hypothetical condition, when referencing something that may not be true. The ghost of subjunctive past references the ghost of Christmas past and the 'Subjunctive past tense' . The following sentences illustrate the correct usages: Another xkcd comic, 725: Literally , also refers to the overly mocked usage of "literally." A similar ghost is seen in 1393: Timeghost , where it reminds Cueball about the passing of time. The comics Cyanide & Happiness and The Oatmeal offer examples of this sort of derision. [A man wakes up to an apparition hovering over his bed.] Apparition: ooOOOOOOOOOOooooo Man: A ghost!? Apparition: I bring a cautionary vision of things to come! Apparition: This is the future: [Two people are standing between a pair of houses. There is a tree. An airplane flies past.] Apparition: And this is the future if you give up the fight over the word "literally": [Two people are standing between a pair of houses. There is a tree. An airplane flies past. The cynical might suggest the panel is copy pasted.] [Back to the man in bed.] Man: They looked exactly the same. Apparition: ooOOOOOOOOOOOooo Man: Ok, I get it. Apparition: Seriously, this is duuuuumb.

Refrigerator

Refrigerator

https://www.xkcd.com/1109

https://www.explainxkcd.com/wiki/index.php/1109:_Refrigerator

[Open fridge with four conveyor belts, three in the main compartment and one on the door. There are two more containers on the door, and an ice-box underneath the second conveyor belt in the main compartment. There is a bin at the bottom of the fridge where the conveyor belts all lead to labelled "Bad."] Top conveyor belt : 3 days ^ 2 days ^ 24 hours ^ 12 hours ^ Middle conveyor belt : 1 W ^ 5 days ^ 3 days ^ 2 days ^ 1 day ^ Bottom conveyor belt : 3 M ^ 2 months ^ 1 month ^ 2 weeks ^ Door conveyor belt : 3 days ^ 1 week ^ 2 weeks ^

Randall proposes the idea of a refrigerator with conveyor belts tuned to different speeds such that food is moved along to the right (main compartment) or left (door) as time passes, with the time appropriate markings letting you know how much time is left until it spoils. When the expiry date is reached, the food will have reached the rightmost part of the refrigerator and conveniently fall into the "Bad" tray at the bottom right of the fridge. The title text is a reference to Simon Stevin's proof of a problem of equilibrium consisting on balancing a weight on an inclined plane by another weight hanging off the top end of the inclined plane. Stevin, also known as Stevinus, had the proof inscribed on his tomb, and as such the proof is commonly known as the " Epitaph of Stevinus ". Randall expresses his interest in having his own ostensibly brilliant idea likewise engraved on his own tombstone. [Open fridge with four conveyor belts, three in the main compartment and one on the door. There are two more containers on the door, and an ice-box underneath the second conveyor belt in the main compartment. There is a bin at the bottom of the fridge where the conveyor belts all lead to labelled "Bad."] Top conveyor belt : 3 days ^ 2 days ^ 24 hours ^ 12 hours ^ Middle conveyor belt : 1 W ^ 5 days ^ 3 days ^ 2 days ^ 1 day ^ Bottom conveyor belt : 3 M ^ 2 months ^ 1 month ^ 2 weeks ^ Door conveyor belt : 3 days ^ 1 week ^ 2 weeks ^

Click and Drag

Click and Drag

https://www.xkcd.com/1110

https://www.explainxkcd.com/wiki/index.php/1110:_Click_and_Drag

[This transcript only covers the first four panels as they are shown here above (i.e. before you click and drag).] [Cueball is narrating the story, all the text is written in boxes above and below him without speech lines connecting to him.] [Cueball is floating by holding onto a balloon with one hand.] From the stories I expected the world to be sad And it was [Cueball has grabbed hold of the balloon with both hands.] And I expected it to be wonderful. [The wind picks up and blows Cueball to the right.] It was. [Full width panel where the scene opens up. You see Cueball is about a tree's-height from the ground. To the right there is a tall tree with no leaves on it and a broken limb. Below him are some rocks and grass. This is the initial view of the world, that can be clicked and dragged. It is part of tile named 1 North 1 East.] I just didn't expect it to be so big . [The rest of the comic is transcribed below in the List of details and references section.] Warning: there are cheating possibilities—people have implemented ways to explore that world more easily—but the best way to enjoy this comic is to play the game, explore the comic's world the way you're supposed to, get lost in the caves or in the sky, be startled by unexpected things or happy when finding some people after lengthy click-and-dragging through a repetitive landscape. If you didn't do that already, reading any below will spoil you from truly enjoying the comic. Though you can download the full view, the easiest way to browse it is through a Zooming user interface . The 225 existing tiles are sorted by columns from West to East and from North to South in each column. (Note that this only includes the tiles that are not entirely white or black).

This comic is a take on how vast and rich the world is, and on the thrill of exploring it. The world can be described as sad, as well as it can be described as wonderful, even if this seems a bit contradictory, just because it is so big and there are so many different things happening in it all at once. Cueball comments about this while hanging from a balloon, which brings to mind the expanded perspective over the landscape attained by early experimenters in overland flight. The title text is the same as the comic title, and both of these invite the reader to Click and drag the inside of the last panel, with their mouse, and by dragging, explore what is hidden outside that panel. The image displayed at first turns out to be part of a huge landscape, filled with big or small things, humorous details, people here and there, cave mazes, things floating in the air, jokes and references, unexpected things, relaxing views, etc. The fact that we only see a small part of the landscape at once refers to the idea that we cannot in real life comprehend the whole world altogether, but only what is around us and/or in the range of our understanding at the time. The click-and-drag process, in which it is impossible to go as fast as we would want to, also draws a parallel with the fact that exploration is always done gradually, step by step, and trying something (i.e. here dragging in a certain direction) always has a cost. This click-and-drag exploration reproduces the thrill of discovering new horizons, getting lost sometimes, finding unexpected things, seeing beauty, humor, desolation or happiness here and there... which can easily captivate an xkcd reader for a long time (and as such qualifies as nerd sniping ). In comic 1416: Pixels you zoom, by scrolling, until every pixel in this image turns into new pictures, and this can be continued again and again. Once you have zoomed in, you are able to click and drag the picture just like in this comic. And in 1608: Hoverboard exactly the same idea is used again, but instead of dragging the image you fly/float around in the image with Cueball on a hoverboard . This gives a very different way to explore as he cannot go through walls or the earth etc. You also have to discover that there is a big world outside the initial play area; and where this comic tried to help people realize they should do something, both with the title and title text, Hoverboard directly tries to dissuade people from going outside with a warning message. Another major difference is that hoverboard is actually a game where you can collect coins (spread throughout the picture) and return them to the starting point to gain a score. The book Thing Explainer that was the reason for the Hoverboard game, also has a direct reference to this comic, as Cueball is seen floating with his balloon outside the cockpit in the explanation for Stuff you touch to fly a sky boat . In 1975: Right Click , the April Fools' day comic of 2018, the title is similar to this one, in that it gives away how the user should begin to interact with the comic. It is though nothing like this comic or Hoverboard. [This transcript only covers the first four panels as they are shown here above (i.e. before you click and drag).] [Cueball is narrating the story, all the text is written in boxes above and below him without speech lines connecting to him.] [Cueball is floating by holding onto a balloon with one hand.] From the stories I expected the world to be sad And it was [Cueball has grabbed hold of the balloon with both hands.] And I expected it to be wonderful. [The wind picks up and blows Cueball to the right.] It was. [Full width panel where the scene opens up. You see Cueball is about a tree's-height from the ground. To the right there is a tall tree with no leaves on it and a broken limb. Below him are some rocks and grass. This is the initial view of the world, that can be clicked and dragged. It is part of tile named 1 North 1 East.] I just didn't expect it to be so big . [The rest of the comic is transcribed below in the List of details and references section.] Warning: there are cheating possibilities—people have implemented ways to explore that world more easily—but the best way to enjoy this comic is to play the game, explore the comic's world the way you're supposed to, get lost in the caves or in the sky, be startled by unexpected things or happy when finding some people after lengthy click-and-dragging through a repetitive landscape. If you didn't do that already, reading any below will spoil you from truly enjoying the comic. Though you can download the full view, the easiest way to browse it is through a Zooming user interface . The 225 existing tiles are sorted by columns from West to East and from North to South in each column. (Note that this only includes the tiles that are not entirely white or black).

Premiere

Premiere

https://www.xkcd.com/1111

https://www.explainxkcd.com/wiki/index.php/1111:_Premiere

[The setting is a standard entertainment newscast. Hairy as the news anchor in the studio sits behind a desk, resting his hands on the desk, starts off the segment with an inset feed to the right where Megan can be seen in front of a crowd behind her. The title of this segment is shown below the feed.] Hairy: All Hollywood is in town for tonight's star-studded premiere! We go live to our reporter on the red carpet. Hairy: How do things look? Title: Red Carpet Report [Megan switches to full-screen. Megan is standing in front of a full crowd of Cueball heads who are behind a line held up be sticks, one of which is visible behind her. She holds a large microphone up to her face.] Megan: Bleak. Megan: In 800 million years the aging, brightening Sun will boil away the oceans, and all this will be blowing sand. [Switch back to initial framing with Hairy moving his arms further away from himself and Megan now with the microphone visible.] Hairy: Oh. Um. ...Sounds pretty grim. How are the stars reacting? Megan: Hydrogen fusion. But it won't last forever. Hairy: I mean the movie stars. Megan: They won't last forever either. None of us will. Title: Red Carpet Report

This comic depicts an entertainment news television program. Hairy , as the news anchor , notes that "all Hollywood" is in town, meaning there are a lot of members of the film industry. The event is a movie premiere, a common place for reporters to interview celebrities, actors, and other people related to entertainment. Megan represents the reporter at the premiere reporting for the television program. The red carpet is a tradition whereby a long red carpet is laid out leading to the entrance of a theater as a symbol of elegance. Movie stars are said to "walk the red carpet" when they arrive and do interviews and pose for photos along this carpet, most famously seen at the Oscars . When asked the ambiguous question "How do things look?", instead of reporting on the premiere and the movie stars arriving, Megan reports on the bleak long-term outlook for the Earth as we know it. She states than in about 800 million years the Sun will become so hot that the Earth's oceans boil away . According to the Wikipedia article this will though first happen in about 1.1 billion years. But the 800 million years may have been the best estimate back in 2012 when this comic was released, see for instance this article from 2013 that states 850 million years. (The loss of oceans will still happen long before the sun turns into a red giant in about 5 billion years). When Hairy then asks how the stars are reacting (meaning how the movie stars are reacting to this news about the oceans), Megan instead replies that the stars are reacting with hydrogen fusion , the nuclear reaction of actual stars like the Sun, thus again ostensibly mistaking the intent of the question. All astronomical stars eventually die when there is not enough hydrogen (or other heavier atoms) to continue the fusion process that keeps the stars stable. Hairy then clarifies that he (of course) meant the movie stars, but Megan keeps being bleak in her reporting as she notes that they also won't last forever, and by the way no one else will. She is of course right as eventually everyone dies [ citation needed ] , just as the stars will eventually die, but of course much sooner for any living human, movie star or not. This reminding people that they will soon die is a common thing for xkcd, apart from the whole segment of comics to make one feel old , there is a specific example in 1393: Timeghost and even more so in 926: Time Vulture . In the title text Hairy ask about the buzz about the film. The buzz here refers to ongoing discussion of the movie, analogous to a continuous humming sound. Megan exclaims that she hopes this buzz distracts people from the apparently grave news she has already reported. Also, since "premiere" etymologically means "first", the title might be a pun on the comic number, which only consists of four ones (1111). The joke of Megan answering a question in an interview in an unexpected manner was used again in 1302: Year in Review . Megan had an existential crisis already in 220: Philosophy and later again in 1822: Existential Bug Reports . In the latter it was the Sun swallowing the Earth (not the oceans) that was her concern. [The setting is a standard entertainment newscast. Hairy as the news anchor in the studio sits behind a desk, resting his hands on the desk, starts off the segment with an inset feed to the right where Megan can be seen in front of a crowd behind her. The title of this segment is shown below the feed.] Hairy: All Hollywood is in town for tonight's star-studded premiere! We go live to our reporter on the red carpet. Hairy: How do things look? Title: Red Carpet Report [Megan switches to full-screen. Megan is standing in front of a full crowd of Cueball heads who are behind a line held up be sticks, one of which is visible behind her. She holds a large microphone up to her face.] Megan: Bleak. Megan: In 800 million years the aging, brightening Sun will boil away the oceans, and all this will be blowing sand. [Switch back to initial framing with Hairy moving his arms further away from himself and Megan now with the microphone visible.] Hairy: Oh. Um. ...Sounds pretty grim. How are the stars reacting? Megan: Hydrogen fusion. But it won't last forever. Hairy: I mean the movie stars. Megan: They won't last forever either. None of us will. Title: Red Carpet Report

Think Logically

Think Logically

https://www.xkcd.com/1112

https://www.explainxkcd.com/wiki/index.php/1112:_Think_Logically

[Knit Cap is sitting down at a computer touching the keyboard with one hand. Cueball is standing behind watching the screen.] Laptop: *Move* Cueball: Why'd you move your knight away? [Knit Cap turns around and rests an arm on the chair looking at Cueball who holds out both arms.] Cueball: Just think logically . The goal is checkmate, so you should always move pieces toward the other player's king. [Closeup of Cueball holding a hand to his chin.] Cueball: I guess occasionally you need to move backward, but it'd be trivial to make a list of those circumstances and- [Knit Cap is leaning back in chair facing Cueball, panel is so slim that the lap top is not included.] Knit Cap: Have you ever played chess? Cueball: Not much, but— Knit Cap: Wanna? Cueball: Uh, ok. [Knit Cap sitting and Cueball standing is playing chess with a board standing between them on a very small table or a four legged stool. The board extends quite far out on either side. Their moves are indicated above with four by Knit Cap and three towards Cueball. It is clear both from this and from the pieces visible on the board that Knit Cap is playing white] *Move* _____ *Move* *Move* _____ *Move* *Move* _____ *Move* *Move* Knit Cap: Checkmate. [In a frameless panel Cueball is standing staring at the chess board, where there clearly are more pieces on his side of the board.] [Knit Cap has turned back to the laptop with both hands on the keyboard. Cueball is standing behind the chess board holding a finger up in the air.] Cueball: This game isn't very well-designed. For starters, knights are too weak...

Chess is a centuries-old board game in which two players take turns moving one of their 16 pieces to try and checkmate the other player's king (one of the pieces). When one player is in a position to capture their opponent's king on their next move, and the opponent has no legal move available to avoid such capture, the opponent is said to be in "checkmate", and by definition immediately loses. The game, with origins around the 6th century, and with the modern rules being essentially set in the late 15th century, has a significant amount of history. The rules and traditions are well established. The knight is a piece that can only move in an L-shaped pattern (two squares in one direction, and one square perpendicular), but has the unique ability to jump over other pieces. The comic highlights two mistakes players often make in chess: complete fixation on the king at the cost of their other pieces, and failure to take advantage of the knight's movement patterns. At the same time this is a jab at how people sometimes oversimplify an argument when confronted with a topic they are not familiar with. Previously this was depicted in 675: Revolutionary and 793: Physicists . See also the Dunning–Kruger effect . The units in chess are widely agreed to be well-balanced, and Cueball's criticism of the knight shows an obvious lack of knowledge of the knight's potential. Given the long history of chess, a significant amount of writing and research has been dedicated to the game and its strategies. This is inadvertently mocked by Cueball who naively suggests it would be trivial to make a list of all situations in which a piece would move backwards (called a "retreat" in chess). Such a list — at least a partial one — certainly does exist, as do lists of numerous other chess moves and situations. Knit Cap (see the official transcript ) proceeds to demonstrate Cueball's lack of knowledge by beating him in four moves, which typically would only occur when an experienced player plays a novice. The checkmate depicted is the scholar's mate , being a classic early-game checkmate in chess. It is in fact extremely easy to defend against it, moving your knights in the two knights defense would do, thus proving Cueball's inexperience. Careful scrutiny of the board suggests a scholar's mate, something along these lines (using chess algebraic notation): 1.e4 e5 2. Bc4 Nc6 3. Qh5 Nf6 4. Qxf7#. Cueball, instead of admitting he underestimated the game, believes the failure is in the game itself. The title text indicates that Cueball attempted to suggest revisions to the rules of chess. Given that Cueball has no experience as a chess player, it is likely many of the changes are illogical or ridiculous. In the face of hundreds of years of history, it is not surprising that the chess community is ignoring them. The last major changes to the rules of chess occurred more than 400 years ago when, among other things, the pawn was given its two-space starting move and the queen was made into the most powerful piece (previously it was the weakest). The chess community's ties to the traditions of the game and their refusal to accept Cueball's suggestions are written off by Cueball as " emotional bias " suggesting his changes are logical, but that the community is letting their emotions cloud their rational decision making abilities, while in reality it is he who is being affected. If that can make Cueball feel any better, it could be pointed out to him that dozens and dozens of chess variants do exist out there. The comic may also be a jab at competitive online games whose fans call for "buffs" (power additions) and "nerfs" (power reductions) to characters they believe to be underpowered or overpowered, often with inadequate knowledge of those characters. On the other hand, some online games and multiplayer computer games in general are unbalanced since they lack centuries of history to balance themselves, unlike chess. Knit Cap is called knit hat guy in the official transcript . There are two other cases (after this comic) where a person with hair has been shown with a knit cap. The first was Randall's wife after chemotherapy in 1141: Two Years and the second time it was Knit Cap Girl in 1350: Lorenz . Two Cueballs have also been shown using knit caps in 1321: Cold . [Knit Cap is sitting down at a computer touching the keyboard with one hand. Cueball is standing behind watching the screen.] Laptop: *Move* Cueball: Why'd you move your knight away? [Knit Cap turns around and rests an arm on the chair looking at Cueball who holds out both arms.] Cueball: Just think logically . The goal is checkmate, so you should always move pieces toward the other player's king. [Closeup of Cueball holding a hand to his chin.] Cueball: I guess occasionally you need to move backward, but it'd be trivial to make a list of those circumstances and- [Knit Cap is leaning back in chair facing Cueball, panel is so slim that the lap top is not included.] Knit Cap: Have you ever played chess? Cueball: Not much, but— Knit Cap: Wanna? Cueball: Uh, ok. [Knit Cap sitting and Cueball standing is playing chess with a board standing between them on a very small table or a four legged stool. The board extends quite far out on either side. Their moves are indicated above with four by Knit Cap and three towards Cueball. It is clear both from this and from the pieces visible on the board that Knit Cap is playing white] *Move* _____ *Move* *Move* _____ *Move* *Move* _____ *Move* *Move* Knit Cap: Checkmate. [In a frameless panel Cueball is standing staring at the chess board, where there clearly are more pieces on his side of the board.] [Knit Cap has turned back to the laptop with both hands on the keyboard. Cueball is standing behind the chess board holding a finger up in the air.] Cueball: This game isn't very well-designed. For starters, knights are too weak...

Killed in Action

Killed In Action

https://www.xkcd.com/1113

https://www.explainxkcd.com/wiki/index.php/1113:_Killed_in_Action

[An old lady, a woman and Cueball are standing in the background by a coffin. A policeman and the policewoman Ponytail are standing in the foreground.] Ponytail: Good cop. It's a real shame— Ponytail: He was just one day away from getting put in the locked, heavily guarded room where all cops stay for the last day before they retire.

The comic plays with the TV and film trope of Retirony , in which a cop is killed in action only a short time before (often the day before) retirement, usually producing a sense of even greater tragedy in the timing of the death. The humor of this strip arises from the notion that, given so many policemen are killed the day before retirement, retiring cops could be sequestered in a secure facility on the day before their retirement to avoid retirony. Unfortunately this merely results in tragedy when a cop is killed the day before being sequestered. The title text is a reference to the reactionary nature of security procedures often put in place in the aftermath of an incident, and how they typically fail to address the root cause of the problem. If the logic expressed in the title text was followed repeatedly, eventually the number of days police officers spent in the secure room would encompass their entire career. A certain similarity could be drawn between this and the US Army's problematic policy of only having combat troops serve for a single year in combat during the Vietnam war (unlike during WWII, when combat units were put into the front line and left there until the war was over, with losses being made up with a constant flow of individual replacements, which was even more problematic). Having troops only serve for a single year led to a far lower rate of troops "broken" from constant combat stress, but it also led to soldiers increasingly avoiding risk once the halfway point of their year was passed and their time to go home got closer; not only that, but the stress of the last few months, knowing one was almost "home safe", yet forced into danger repeatedly could also psychologically damage men. It also created an incentive to just make it alive through the war, no matter what it took, unlike a situation where a soldier knows they are stuck there until the war is over; this can be a great incentive to fight harder, or at least to just give up any real hope that you'll live long enough to see the end anyway. They later revisited this "combat year" approach also, and tried yet another new idea. See also the paradox of the "unexpected hanging" . [An old lady, a woman and Cueball are standing in the background by a coffin. A policeman and the policewoman Ponytail are standing in the foreground.] Ponytail: Good cop. It's a real shame— Ponytail: He was just one day away from getting put in the locked, heavily guarded room where all cops stay for the last day before they retire.

Metallurgy

Metallurgy

https://www.xkcd.com/1114

https://www.explainxkcd.com/wiki/index.php/1114:_Metallurgy

[Cueball and Megan are in a weapon store talking to a bearded salesman wearing a hat.] [Salesman holds up a sword.] Salesman: This sword was forged from a fallen star. Antimony impurities make the blade surpassingly brittle and weak . [Salesman holds up a dagger.] Salesman: And this dagger is made of metal from a far-off kingdom. It glows blue. Off-panel: When orcs are near? Salesman: No, always. Radiation from the Actinium content. Megan: ...Does it have Eldritch powers? Salesman: It gives the wearer +2 to cancer risk. Cueball: I think we should find another shop.

The comic explains how weapons would really behave if they were made out of unusual materials. In fantasy stories, using unusual materials for weapons traditionally makes the weapons more powerful and cooler despite limited explanation for exactly why materials of extraterrestrial origin are so superior to their earthen counterparts. The salesman in the comic is Beret Guy which appears with a beard for only this comic. The first panel is a reference to a fairly common fantasy trope: the use of iron meteorites for making weapons and armour (for example the sword "Brisingr" of the Inheritance series, "Anglachel" in the Tolkien Legendarium or the panserbjørns' armour in Pullman's Northern Lights). The quality of such metal can be rather hit-and-miss. On one hand, iron from meteorites was often mixed with "terrestrial" iron in the early stages of human development to create relatively high quality steel for swords. Undeveloped metalworking techniques at the time meant that extraterrestrial metal was often more refined and plentiful than man-made metal ingots. With that in mind, however, research has shown that meteorites have an abundance of the chemical element Antimony (Sb) which by itself is a very brittle metal and therefore swords forged from metals harvested from meteorites may not be as strong as lore would have one think. The second panel is a reference to stories set in Middle-earth where swords such as Orcrist, Glamdring or Sting (the swords of Thorin, Gandalf and Bilbo/Frodo) glow blue when Orcs are near. The dagger in question, though, glows because of the radioactive properties of Actinium (Ac) which is also highly toxic. Definitely not a dagger you would want to carry around for your every day battles. The word "Eldritch" in the third panel means sinister, ghostly, or magical. The fourth panel mentions that the weapon gives a +2 to a player's attribute. This is a reference to role-playing games in which it is common to find items that are able to improve one's character by increasing desirable attributes. In this case, however, +2 to cancer risk, a consequence of the dagger's radioactivity, would definitely not be considered a desirable attribute to increase. This would hit harder on Randall due to his now-wife being diagnosed with breast cancer. In the title text, the salesman tries to sell Cueball another meteoric blade, this one made from a carbonaceous chondrite . Carbonaceous chondrites are rocky meteors that generally don't contain a lot of metallic iron. The salesman is either stating that the blade is simply a bunch of nonferrous meteor fragments glued together in the shape of a sword, or stating that the iron he got out of the meteor is so full of impurities that it may as well be gravel. However, because it's made of extraterrestrial material he seems confident he'll still be able to sell it on novelty value alone. [Cueball and Megan are in a weapon store talking to a bearded salesman wearing a hat.] [Salesman holds up a sword.] Salesman: This sword was forged from a fallen star. Antimony impurities make the blade surpassingly brittle and weak . [Salesman holds up a dagger.] Salesman: And this dagger is made of metal from a far-off kingdom. It glows blue. Off-panel: When orcs are near? Salesman: No, always. Radiation from the Actinium content. Megan: ...Does it have Eldritch powers? Salesman: It gives the wearer +2 to cancer risk. Cueball: I think we should find another shop.

Sky

Sky

https://www.xkcd.com/1115

https://www.explainxkcd.com/wiki/index.php/1115:_Sky

[Megan is looking down at Beret Guy, who appears to be doing a handstand on a grass lawn, with grass tuft drawn several places, including where his hands touch the grass. His hands can be seen in the grass like he is holding on to the grass. Both his legs are moving around above him, as indicated by movement lines.] Megan: What are you doing? Beret Guy: Clinging to the ceiling of a bottomless abyss. [Megan walks past Beret Guy, whose legs are still moving. She is still looking down at the grass.] Megan: You are very odd. [In a frame-less panel, Megan walks towards a mailbox looking down at it. There is grass around the base of the mailbox pole.] [As Megan passes the mailbox, she looks up towards the sky and seems to stop.] [The last panel is upside down with the grass at the top and the mailbox pointing down. Megan is clinging to the mailbox, sitting on the grass with her head under the mailbox. Ponytail approaches her, walking on the grass with her head pointing down. The text is written in the sky below them.] Ponytail: What's wrong? Megan: I looked down.

This comic is about the fact that much of the way we see the world is relative. Which way is left or right, for example, depends on the direction one is facing, so different people can give different answers and both be correct. (Contrast this to absolute directions, such as East and West, which do not change based on one's orientation.) Which way is 'down' is a little more complicated, as both the absolute and relative direction use the same word (owing to the two directions usually being the same on Earth): it can be defined as 'whichever way gravity goes / the direction things fall', but it can also be defined as 'the direction one's feet is'. In space particularly, the latter definition tends to be used as the former is rather hard to deduce. It is possible, though not too useful, to simply say that 'down' in space is 'whichever way Earth is', or perhaps even 'whichever way is opposite to the Sun'. However, even on Earth, the direction of 'down' can get muddled. Humans rely a lot on vision to determine which way is down, so in an enclosed room with no references, one can easily convince themselves (accidentally or deliberately) that down is in a different direction to gravity. Forcing yourself to think in a different perspective changes a lot of things that are usually thought of as mundanities. Beret Guy convinces himself that down is toward the sky. Megan asks him why he is clinging to the ground. He responds that he is holding on to the ground so that he does not fall into the sky. Megan at first dismisses this but later looks up, gets scared and is found by Ponytail , clinging to a mailbox afraid of falling up (down?). The title text continues this idea, where Megan "drops" a bird into the sky, and never hears it hit the "bottom". As birds can fly, and captured birds often fly away when released, its flight appeared to Megan as the bird falling upward. "Didn't hear it hit bottom" would normally mean that the pit is too deep for the sound of impact to make it back up, although in this case as the 'pit' is genuinely bottomless the bird would never hit 'bottom' even if it didn't move. [Megan is looking down at Beret Guy, who appears to be doing a handstand on a grass lawn, with grass tuft drawn several places, including where his hands touch the grass. His hands can be seen in the grass like he is holding on to the grass. Both his legs are moving around above him, as indicated by movement lines.] Megan: What are you doing? Beret Guy: Clinging to the ceiling of a bottomless abyss. [Megan walks past Beret Guy, whose legs are still moving. She is still looking down at the grass.] Megan: You are very odd. [In a frame-less panel, Megan walks towards a mailbox looking down at it. There is grass around the base of the mailbox pole.] [As Megan passes the mailbox, she looks up towards the sky and seems to stop.] [The last panel is upside down with the grass at the top and the mailbox pointing down. Megan is clinging to the mailbox, sitting on the grass with her head under the mailbox. Ponytail approaches her, walking on the grass with her head pointing down. The text is written in the sky below them.] Ponytail: What's wrong? Megan: I looked down.

Traffic Lights

Traffic Lights

https://www.xkcd.com/1116

https://www.explainxkcd.com/wiki/index.php/1116:_Traffic_Lights

This comic is an animated gif which features an array of traffic lights which are lighted signals posted at intersections to control vehicular traffic. The standard North American traffic light has three solid lights: red, yellow and green (meaning, in simplistic terms, "stop", "warning: the light will be changing to red" and "go" respectively). More complicated lights sometimes have additional signals such as arrows indicating go or stop for a specific direction such as left or right turns. However, as in the strip, sometimes an intersection has multiple lights with certain of them designated to apply solely to a specific lane or specific direction of travel. A common one is a left-turn light that allows the lights to stop or allow left-turn traffic independent of the rest of the traffic. Another common example is a light that applies only to public transit like streetcars that run on tracks on the city streets. There are also other rules and features that tend to be unique to different localities as noted in the Wikipedia article for Traffic-light signalling and operation . In this comic, Randall is commenting on the confusion that can be caused by having too many lights with multiple rules attached by creating an exaggerated example. In this strip, the right light has a sign indicating that the light and the right lane are for left turners, while the 3rd-from-left is a straight or right turn lane and the 2nd from left is right turn only. In normal course, right turns would be permitted from the right lane and left turns from the left lanes. The system in this comic would have turning traffic crossing each other, as well as the straight-ahead traffic and would cause chaos (and require very complicated traffic light phases to control). The left-most light on the post has a sign indicating that left, right and straight travel are all prohibited, which is even more confusing. The comic, as an animated gif, cycles through various phases, at first appearing somewhat normal, but then adding unusual phases. The animated gif takes about 90 seconds to cycle through the 32 discrete panels before repeating. The left post light has (unusually) left and right arrows, later becoming up and down arrows. At times the light completely shuts off, and at other times, has conflicting signals. The third-from-left light has red and yellow, and later all three lights come on at the same time, then all three lights go yellow, and then reverse with green at top and red at bottom. The bottom light then becomes an arrow. The fourth-from-left traffic light switches from a green light to a purple light at times. The right light only lights red in each position. The second-from-left light and second-from-right lights do not appear to have any quirks other than changing phases in unusual patterns. At frames 21 and 22 (see below) the colors of the latter five lights correspond to the color sequence of the letters in the Google logo. Only the first letter of the logo, which is blue, is not reproduced on the first traffic light. The title text mentions a straightforward intersection that allows going forward but not turning. Even though Randall is confused, in some places, a red light and a forward green arrow permits going forward but disallows turns. The following is a breakdown of all of the frames of the animated gif comic. The following is a closeup on the lights, and the bird. The lights from left to right are here shown top to bottom. Time advances to the right. Originally, the second light had a couple frames near the start that were different. The closeup of this was as follows:

My Sky

My Sky

https://www.xkcd.com/1117

https://www.explainxkcd.com/wiki/index.php/1117:_My_Sky

[The panel is upside-down. Beret Guy is holding onto the "ceiling", there is an upside-down cloud at the bottom of the panel.] Beret guy [to the solitary cumulus cloud.]: Oh—Hello down there! Welcome to My Sky! [The panel is now oriented in the conventional sense with the ground at the bottom. Beret Guy is standing on his feet too, and the sky now shows a second cloud.] Beret guy: It's pretty good. I like it. It's not the same color as anything . [The sky is now blanketed by alto-cirrus clouds.] Beret guy: "Wow! There are a lot of you! Good thing it's so big. [The scene now depicts a party, where Beret Guy is talking to Ponytail.] Ponytail: "And what do you do?" Beret Guy: "I'm in the cloud storage business."

This comic seems to be a follow up to 1115: Sky . Last panel refers to cloud computing and specifically cloud storage , and looks like a follow up to 1032: Networking . The obvious joke is that, instead of “cloud” (Internet-based) storage, Beret Guy 's business is literally storage of clouds. The title text is a further statement, that his first words came while looking up at the sky. Apparently, Randall just has a good grasp on what in this universe is awe-inspiring. There are some connections with both 908: The Cloud and the title text of 1444: Cloud . [The panel is upside-down. Beret Guy is holding onto the "ceiling", there is an upside-down cloud at the bottom of the panel.] Beret guy [to the solitary cumulus cloud.]: Oh—Hello down there! Welcome to My Sky! [The panel is now oriented in the conventional sense with the ground at the bottom. Beret Guy is standing on his feet too, and the sky now shows a second cloud.] Beret guy: It's pretty good. I like it. It's not the same color as anything . [The sky is now blanketed by alto-cirrus clouds.] Beret guy: "Wow! There are a lot of you! Good thing it's so big. [The scene now depicts a party, where Beret Guy is talking to Ponytail.] Ponytail: "And what do you do?" Beret Guy: "I'm in the cloud storage business."

Microsoft

Microsoft

https://www.xkcd.com/1118

https://www.explainxkcd.com/wiki/index.php/1118:_Microsoft

Megan: Remember when we prosecuted Microsoft for bundling a browser with an OS? Imagine the future we'd live in if we'd been willing to let one tech company amass that much power. Ponytail: Thank God we nipped that in the bud.

In the late 1990s Microsoft started bundling its web browser, Internet Explorer , with its Windows operating system. This effectively destroyed the Netscape company, who up until then had the most market share with its browser, Netscape Navigator . Microsoft was involved in a legal case against the U.S. government, which required Microsoft to allow IE to be uninstalled among other remedies. Removal of Internet Explorer has no clear solution as libraries and utilities associated with Internet Explorer are used across other Windows applications. The comic sarcastically states that this stopped companies from creating a monopoly on software practices. Unfortunately, platform developers such as Apple, Sony, and Microsoft have restricted third-party software distribution over the internet via their own curated online stores in recent years, and will come full circle with the introduction of Metro Applications on the Windows 8. The comic also mocks the triviality of browser debates compared to current antitrust cases concerning privacy and price fixing . Apple bundled a browser in on both its desktop and mobile platforms. Apple also requires all iOS developers to sell their apps only through the iTunes app store, paying sizeable commissions to Apple, and Apple can refuse to sell any app. In some instances, Apple has developed its own versions of popular third-party apps. [1] On Android , Google bundles in a mobile version of Chrome web browser (as of version 4.0 Ice Cream Sandwich ), but you are allowed to change the default browser. The company has a majority market share in web search engines, being the most popular search engine available. On Facebook , users face difficulties in accessing or removing their profiles and personal information, among other issues . Recently, this has been mitigated by the ability to download a zip file of all content ever posted to Facebook, but it still remains difficult to delete data from Facebook. Apple has been widely criticized for trying to force all users of Mac OS or iOS to run only content approved by Apple and distributed through the Apple App Store, each sale from which gives royalty payments to Apple. The title text refers to mocking Microsoft as Micro$oft or M$ for attempting to take too much money from consumers, and jokingly suggests that the inability to easily do this with other companies' names (Fa¢ebook? Appl€? Goog£e?) is how they succeeded at amassing power where Micro$oft failed. Megan: Remember when we prosecuted Microsoft for bundling a browser with an OS? Imagine the future we'd live in if we'd been willing to let one tech company amass that much power. Ponytail: Thank God we nipped that in the bud.

Undoing

Undoing

https://www.xkcd.com/1119

https://www.explainxkcd.com/wiki/index.php/1119:_Undoing

[Caption above the panel:] My Hobby: [A large wind turbine is spinning but the electric cord has been severed and rewired to a large fan.] [Caption in large text below the panel:] Undoing A similar understanding of the difference between a wind turbine and a fan is presented by Megan in the later comic: 1378: Turbine . This comic may be a continuation of Randall's mistrust of modern electric wind turbines (see 556: Alternative Energy Revolution ).

The comic (another in the My Hobby series) is a play on how energy from natural resources (wind, sun, water) gets turned into electricity. Wind turbines convert the windpower into rotational energy, which can then be used to produce electricity. The one seen in the image is the most commonly known wind turbine, which sees use on wind farms. Wind turbines provide a renewable resource for homes and cities and a common method for sustainable energy. Turbines have been referenced before in xkcd, in 556: Alternative Energy Revolution . In this comic, Cueball has rigged it so that the wind turbine powers a fan . He cut the power cable attaching the turbine to the power grid and spliced it with the power cord of a giant fan. The nailed-together 2x4s that form the "tower" for the fan further indicate the " jury-rigged " nature of Cueball's work. The electricity generated from the windpower is then used to power the fan, which in turn produces wind. This is in reference to the complementary nature of wind turbines and fans, which was also covered in 1378: Turbine . The undoing part refers how Cueball is using this fan to restore the wind that was used to turn the wind turbine back to the original wind flow. Wind turbines have a theoretical limit of 59% of the portion of wind captured. You can see the wind not captured detailed in the image as dotted, turbulent curly lines; turbulent flow. Cueball has placed the giant fan in the direction of the wind so that the wind it produced combines with the windpower not captured by the wind turbine. This is indicated by the lines smoothing, like they were at the start. Thus, not only is the electrical benefit undone, but also the change in natural wind currents. The title text explains that he performs the same undoing process with solar cells, where light energy is converting into electricity using photovoltaic cells , which is then used to power lightbulbs for producing light on the area below them that the sun would normally illuminate. Solar panels only convert 20-25% of the energy captured from the sun into electricity. However, Cueball points out that he sees this as a 20% gain rather than an 80% loss. Since it is Cueball's hobby to literally waste time and energy, this makes perfect sense. Incandescent light bulbs only convert at most 5% of the electricity provided into light, the rest is lost as heat energy. Thus less than 1% of the energy absorbed from the original sunlight will be released as light from the bulb. LED bulbs can do quite a bit better, approaching 90% efficiency, releasing around 17% of the original sunlight, though in different frequencies. In the case of the wind turbine and fan, the wind will unfortunately be moving at a much slower velocity than at the start as energy was lost in converting windpower to rotation energy, then to electricity, then back to rotational energy, then back to windpower. However, in the solar panel and lamp case, the light will be moving at the same speed as it entered the panel thanks to the constant nature of the speed of light, but be less bright instead. [Caption above the panel:] My Hobby: [A large wind turbine is spinning but the electric cord has been severed and rewired to a large fan.] [Caption in large text below the panel:] Undoing A similar understanding of the difference between a wind turbine and a fan is presented by Megan in the later comic: 1378: Turbine . This comic may be a continuation of Randall's mistrust of modern electric wind turbines (see 556: Alternative Energy Revolution ).

Blurring the Line

Blurring the Line

https://www.xkcd.com/1120

https://www.explainxkcd.com/wiki/index.php/1120:_Blurring_the_Line

[White Hat and Cueball are walking.] White Hat: ...No, but see, it's a movie about movies. Cueball: Sounds like masturbatory navel-gazing. [Close-up of White Hat.] White Hat: No, it's about blurring the line between metaphor and reality. White Hat: You just don't know much about art. Cueball: Seriously? [White Hat and Cueball are standing.] Cueball: I know all about blurring the line between metaphor and reality. I'm the goddamn Michael Jordan of blurring the line between metaphor and reality. [White Hat is now standing alone in the panel.] White Hat: ...Huh? [A basketball appears from nowhere and hits White Hat in the head.] BONK

A metaphor is a comparison which may be used to emphasize, explain or embellish a point, as seen in this comic when Cueball likens himself to Michael Jordan. Michael Jordan is a famous basketball player who is well known for being one of the very best basketball players (this saying was used before in 1027: Pickup Artist ). White Hat is analyzing a movie about movies when Cueball compares White Hat's description of the movie to masturbatory navel-gazing , a comment combining two expressions used to refer to a pointless activity or effort, but also specifically self-referential activity. "Mental masturbation" and "navel gazing" are relatively common terms to dismiss work that is regarded as self-indulgent, overly introspective, and self-referential. Calling navel gazing, or introspection, "masturbatory" is a metaphor speaking of it in terms of the physical act of masturbation . White Hat then defends the movie by saying that it is about blurring the line between metaphor and reality, commenting that Cueball doesn't understand art. To this Cueball retorts by likening his ability to meld metaphor and reality by using a metaphor comparing himself to Michael Jordan. He then proceeds to actually blur the line by throwing a basketball at White Hat. This can also be understood as another reality metaphor, passing the "conversational ball" to White Hat, or acting like Michael Jordan by playing basketball. The last frame is also a graphic illustration of blurring the line between metaphor and reality, where a much more "real" depiction of a basketball intrudes into the colorless stick-figure world which serves as an abstraction of our shared reality. The title text blurs the line between metaphor and reality by dragging both metaphors in the term "masturbatory navel-gazing" into reality and pointing out that literally staring at your navel is not going to be very effective at physical sexual self arousal, which is the goal of masturbation. Another comic that blurs the line of a metaphor is 1320: Walmart . [White Hat and Cueball are walking.] White Hat: ...No, but see, it's a movie about movies. Cueball: Sounds like masturbatory navel-gazing. [Close-up of White Hat.] White Hat: No, it's about blurring the line between metaphor and reality. White Hat: You just don't know much about art. Cueball: Seriously? [White Hat and Cueball are standing.] Cueball: I know all about blurring the line between metaphor and reality. I'm the goddamn Michael Jordan of blurring the line between metaphor and reality. [White Hat is now standing alone in the panel.] White Hat: ...Huh? [A basketball appears from nowhere and hits White Hat in the head.] BONK

Identity

Identity

https://www.xkcd.com/1121

https://www.explainxkcd.com/wiki/index.php/1121:_Identity

Cueball: Hey, I lost the server password. What is it, again? Megan: It's— ...Wait. How do I know it's really you? Cueball: Ooh, good question! I bet we can construct a cool proof-of-identity protocol. I'll start by picking two random— Megan: Oh good; it's you. Here's the password... Cueball: NO!

Cueball lost the server password and is asking Megan what it is. Megan correctly comments that she can't be sure through text-based messages that it's really Cueball asking for the password; it could be someone impersonating him attempting to socially engineer access to the server. Cueball answers by starting to develop a cryptographic protocol they can use for proof of identity, probably something like OTR Messaging as implemented in many XMPP chat clients or Feige–Fiat–Shamir identification scheme . In reality, it would already be too late for that — they should have prepared something beforehand. Before he even finishes, Megan answers "It's you", meaning that no one else is so geeky that they would answer like that. Cueball, dismayed at the fact that his geekery has become a defining characteristic of his and also at a lost opportunity to devise his protocol, shouts [texts?] "NO!". In the title text, Randall suggests that this is, in fact, his own personality, and that anyone reading the comic can now impersonate him. For a bonus, he notes his own fascination with the fact that birds are just modern dinosaurs , which one could use to impersonate him as well. Cueball: Hey, I lost the server password. What is it, again? Megan: It's— ...Wait. How do I know it's really you? Cueball: Ooh, good question! I bet we can construct a cool proof-of-identity protocol. I'll start by picking two random— Megan: Oh good; it's you. Here's the password... Cueball: NO!

Electoral Precedent

Electoral Precedent

https://www.xkcd.com/1122

https://www.explainxkcd.com/wiki/index.php/1122:_Electoral_Precedent

The problem with statements like "No <party> candidate has won the election without <state>" Or "No president has been reelected under <circumstances>" [Each statement below has its own panel. The year is in a caption, the precedent is stated by a standing Cueball in the main panel, and the president who broke it is below the panel.] 1788... No one has been elected president before. ...But Washington was. 1792... No incumbent has ever been reelected. ...Until Washington. 1796... No one without false teeth has become president. ...But Adams did. 1800... No challenger has beaten an incumbent. ...But Jefferson did. 1804... No incumbent has beaten a challenger. ...Until Jefferson. 1808... No congressman has ever become president. ...Until Madison. 1812... No one can win without New York. ...But Madison did. 1816... No candidate who doesn't wear a wig can get elected. ...Until Monroe was. 1820... No one who wears pants instead of breeches can be reelected. ...But Monroe was. 1824... No one has ever won without a popular majority. ...J.Q. Adams did. 1828... Only people from Massachusetts and Virginia can win. ...Until Jackson did. 1832... The only presidents who get reelected are Virginians. ...Until Jackson. 1836... New Yorkers always lose. ...Until Van Buren. 1840... No one over 65 has won the presidency. ...Until Harrison did. 1844... No one who's lost his home state has won. ...But Polk did. 1848... As goes Mississippi, so goes the nation. ...Until 1848. 1852... New England Democrats can't win. ...Until Pierce did. 1856... No one can become president without getting married. ...Until Buchanan did. 1860... No one over 6'3" can get elected. ...Until Lincoln. 1864... No one with a beard has been reelected. ...But Lincoln was. 1868... No one can be president if their parents are alive. ...Until Grant. 1872... No one with a beard has been reelected in peacetime. ...Until Grant was. 1876... No one can win a majority of the popular vote and still lose. ...Tilden did. 1880... As goes California, so goes the nation. ...Until it went Hancock. 1884... Candidates named "James" can't lose. ...Until James Blaine. 1888... No sitting president has been beaten since the Civil War. ...Cleveland was. 1892... No former president has been elected. ...Until Cleveland. 1896... Tall Midwesterners are unbeatable. ...Bryan wasn't. 1900... No Republican shorter than 5'8" has been reelected. ...Until McKinley was. 1904... No one under 45 has been elected. ...Roosevelt did. 1908... No Republican who hasn't served in the military has won. ...Until Taft. [The precedent takes up the entire panel this year. Consequently, there is no Cueball.] 1912... After Lincoln beat the Democrats while sporting a beard with no mustache, the only Democrats who can win have a mustache with no beard. ...Wilson had neither. 1916... No Democrat has won while losing West Virginia. ...Wilson did. 1920... No incumbent senator has won. ...Until Harding. 1924... No one with two Cs in their name has become president. ...Until Calvin Coolidge. 1928... No one who got ten million votes has lost. ...Until Al Smith. 1932... No Democrat has won since women secured the right to vote. ...Until FDR did. 1936... No president's been reelected with double-digit unemployment. ...Until FDR was. 1940... No one has won a third term. ...Until FDR did. 1944... No Democrat has won during wartime. ...Until FDR did. 1948... Democrats can't win without Alabama. ...Truman did. 1952... No Republican has won without winning the House or Senate. ...Eisenhower did. 1956... No one can beat the same nominee a second time in a leap year rematch. ...Until Eisenhower. 1960... Catholics can't win. ...Until Kennedy. 1964... Every Republican who's taken Louisiana has won. ...Until Goldwater. [The panel is zoomed in on Cueball's head in this frame.] 1968... No Republican vice president has risen to the Presidency through an election. ...Until Nixon. [The panel is zoomed in on Cueball's head in this frame.] 1972... Quakers can't win twice. ...Until Nixon did. 1976... No one who lost New Mexico has won. ...But Carter did. 1980... No one has been elected president after a divorce. ...Until Reagan was. 1984... No left-handed president has been reelected. ...Until Reagan was. [The panel is zoomed in on Cueball's head in this frame.] 1988... No one with two middle names has become president. ...Until "Herbert Walker". [The panel is zoomed in on Cueball's head in this frame.] 1992... No Democrat has won without a majority of the Catholic vote. ...Until Clinton did. [The precedent takes up the entire panel this year. Consequently, there is no Cueball.] 1996... No Dem. incumbent without combat experience has beaten someone whose first name is worth more in Scrabble. ...Until Bill beat Bob. 2000... No Republican has won without Vermont. ...Until Bush did. [The panel is zoomed in on Cueball's head in this frame.] 2004... No Republican without combat experience has beaten someone two inches taller ...Until Bush did. 2008... No Democrat can win without Missouri. ...Until Obama did. [This year has two panels.] 2012... [Panel one] Democratic incumbents never beat taller challengers. [Panel two] No nominee whose first name contains a "K" has lost. [Text under panels] Which streak will break?

During election season in U.S. presidential elections — and especially in election night coverage — it is common for the media to make comments like the ones set out in the first panel of this comic. Randall is demonstrating the problem with making such statements, many of which simply come down to coincidence. After the first panel the next 56 panels in this comic refer to each one of the 56 presidential elections in U.S. history before Obama's re-election in 2012. The panels depict a pre-election commentator noting a quality or condition that has never occurred to a candidate until one of the candidates in that election broke the streak. In other words, one can always find at least one unique thing about a candidate who has gone on to win (or in some cases, lose) or the circumstances under which they won (or lost) that is unique from all previous winners (or losers). It's worth noting that some of these 'firsts' were truly precedent-setting (such as the first incumbent losing, the first president to win a third term, the first Catholic president, etc.), but the fact that they hadn't happened was no assurance that there wouldn't be a first time. As the years pass on, these 'streaks' become more and more nested and complicated, and then brought by Randall to the point of absurdity by pointing out very trivial things, such as "No Democratic incumbent without combat experience has ever beaten someone whose first name is worth more in Scrabble " (1996). The flaw made by pundits while reporting such streaks is that there will always be something that has never happened before in an election, and they purport to suggest that these things are related to the candidate's win or loss. Randall considers this a logical flaw. A common one is, as noted in several panels, candidates can't win without winning certain states. The question, however, is one of cause or effect . Given that there have only been 56 elections, there are always going to be things that haven't happened before. If you go out looking for them, you're sure to find some. There is no magic about why these events haven't happened. In most cases, it is merely a coincidence. In the last two panels, two more statements like the previous are given. They were both true before the election in 2012 on November the 6th. The comic came out in the middle of the campaign on October the 17th. The statements were constructed so that the first predicts that Obama can't win over Mitt Romney , and the second that he cannot lose. As Obama won the election he thus ended the streak Democratic incumbents never beat taller challengers whereas the other streak is still valid. The title text refers to the fact that Twitter was founded in 2006. Obama won in 2008, so at the time of the comic it was true that no white male person mentioned on Twitter had ever gone on to win the presidency; although certainly some former presidents, all of whom were white males, have subsequently been mentioned on Twitter. This streak was broken in the next election year when Donald Trump won the 2016 election. During these last four weeks before the election, Randall posted no fewer than four comics related to this election. The others are: 1127: Congress , 1130: Poll Watching and 1131: Math . In 2020, Randall posted an update to this comic: 2383: Electoral Precedent 2020 . Please have someone else validate your row, as to make sure the table is accurate The problem with statements like "No <party> candidate has won the election without <state>" Or "No president has been reelected under <circumstances>" [Each statement below has its own panel. The year is in a caption, the precedent is stated by a standing Cueball in the main panel, and the president who broke it is below the panel.] 1788... No one has been elected president before. ...But Washington was. 1792... No incumbent has ever been reelected. ...Until Washington. 1796... No one without false teeth has become president. ...But Adams did. 1800... No challenger has beaten an incumbent. ...But Jefferson did. 1804... No incumbent has beaten a challenger. ...Until Jefferson. 1808... No congressman has ever become president. ...Until Madison. 1812... No one can win without New York. ...But Madison did. 1816... No candidate who doesn't wear a wig can get elected. ...Until Monroe was. 1820... No one who wears pants instead of breeches can be reelected. ...But Monroe was. 1824... No one has ever won without a popular majority. ...J.Q. Adams did. 1828... Only people from Massachusetts and Virginia can win. ...Until Jackson did. 1832... The only presidents who get reelected are Virginians. ...Until Jackson. 1836... New Yorkers always lose. ...Until Van Buren. 1840... No one over 65 has won the presidency. ...Until Harrison did. 1844... No one who's lost his home state has won. ...But Polk did. 1848... As goes Mississippi, so goes the nation. ...Until 1848. 1852... New England Democrats can't win. ...Until Pierce did. 1856... No one can become president without getting married. ...Until Buchanan did. 1860... No one over 6'3" can get elected. ...Until Lincoln. 1864... No one with a beard has been reelected. ...But Lincoln was. 1868... No one can be president if their parents are alive. ...Until Grant. 1872... No one with a beard has been reelected in peacetime. ...Until Grant was. 1876... No one can win a majority of the popular vote and still lose. ...Tilden did. 1880... As goes California, so goes the nation. ...Until it went Hancock. 1884... Candidates named "James" can't lose. ...Until James Blaine. 1888... No sitting president has been beaten since the Civil War. ...Cleveland was. 1892... No former president has been elected. ...Until Cleveland. 1896... Tall Midwesterners are unbeatable. ...Bryan wasn't. 1900... No Republican shorter than 5'8" has been reelected. ...Until McKinley was. 1904... No one under 45 has been elected. ...Roosevelt did. 1908... No Republican who hasn't served in the military has won. ...Until Taft. [The precedent takes up the entire panel this year. Consequently, there is no Cueball.] 1912... After Lincoln beat the Democrats while sporting a beard with no mustache, the only Democrats who can win have a mustache with no beard. ...Wilson had neither. 1916... No Democrat has won while losing West Virginia. ...Wilson did. 1920... No incumbent senator has won. ...Until Harding. 1924... No one with two Cs in their name has become president. ...Until Calvin Coolidge. 1928... No one who got ten million votes has lost. ...Until Al Smith. 1932... No Democrat has won since women secured the right to vote. ...Until FDR did. 1936... No president's been reelected with double-digit unemployment. ...Until FDR was. 1940... No one has won a third term. ...Until FDR did. 1944... No Democrat has won during wartime. ...Until FDR did. 1948... Democrats can't win without Alabama. ...Truman did. 1952... No Republican has won without winning the House or Senate. ...Eisenhower did. 1956... No one can beat the same nominee a second time in a leap year rematch. ...Until Eisenhower. 1960... Catholics can't win. ...Until Kennedy. 1964... Every Republican who's taken Louisiana has won. ...Until Goldwater. [The panel is zoomed in on Cueball's head in this frame.] 1968... No Republican vice president has risen to the Presidency through an election. ...Until Nixon. [The panel is zoomed in on Cueball's head in this frame.] 1972... Quakers can't win twice. ...Until Nixon did. 1976... No one who lost New Mexico has won. ...But Carter did. 1980... No one has been elected president after a divorce. ...Until Reagan was. 1984... No left-handed president has been reelected. ...Until Reagan was. [The panel is zoomed in on Cueball's head in this frame.] 1988... No one with two middle names has become president. ...Until "Herbert Walker". [The panel is zoomed in on Cueball's head in this frame.] 1992... No Democrat has won without a majority of the Catholic vote. ...Until Clinton did. [The precedent takes up the entire panel this year. Consequently, there is no Cueball.] 1996... No Dem. incumbent without combat experience has beaten someone whose first name is worth more in Scrabble. ...Until Bill beat Bob. 2000... No Republican has won without Vermont. ...Until Bush did. [The panel is zoomed in on Cueball's head in this frame.] 2004... No Republican without combat experience has beaten someone two inches taller ...Until Bush did. 2008... No Democrat can win without Missouri. ...Until Obama did. [This year has two panels.] 2012... [Panel one] Democratic incumbents never beat taller challengers. [Panel two] No nominee whose first name contains a "K" has lost. [Text under panels] Which streak will break?

The Universal Label

The Universal Label

https://www.xkcd.com/1123

https://www.explainxkcd.com/wiki/index.php/1123:_The_Universal_Label

Ingredients: Hydrogen, Time

All matter in the universe (heavier than lithium-7 ) was created through nuclear fusion of hydrogen atoms inside stars over the 13.8 billion years that have gone by since the Big Bang . A detailed explanation (for the lay person) of this process is available in this article about Making Atoms . From this article (and from the wiki article on Big Bang) it is clear that our universe began not only with hydrogen. Although the majority of atoms produced by the Big Bang were hydrogen, lots of helium and traces of lithium were also produced. Actually about 25% of the non-dark mass in the universe comes from helium created shortly after the Big Bang. In stars, however, helium is also created directly from hydrogen atoms. So it would have been enough to just start out with hydrogen in the early universe. Given enough time, all the other elements would have been created inside these originally hydrogen-only stars. To make elements heavier than helium some of the elements created by hydrogen, will have to fuse subsequentially. And in order to make elements heavier than iron, a supernova explosion is needed. But in either case it is still products of hydrogen that fuse together. In many countries, food products must have their ingredients displayed somewhere on their packaging. Because all the ingredients in any food are either hydrogen or heavier atoms created through stellar nuclear fusion from hydrogen over time, the ingredients of any items can technically be described fully as only being made from hydrogen and time. Thus this label would be the universal label. A pun on two of the meanings of the word universal . Any food is of course universal as in a part of the universe. But the label can also be a universal label as in a common label for all food or any other product in the universe, as well as the universe itself for that matter . The title text first makes it clear that this works both for any grocery as well as any non-grocery, which as described above simply means anything else. It then goes on to making a pun on the words thyme (a herb) and time , as the two words are homophones . "H" is the chemical symbol for hydrogen thus completing the pun by noticing that the word "thyme" can be made by adding the letter "h" to "tyme" which would be a homophone even closer to the word time. Randall previously made a joke on the fact that thyme and time are homophones in 282: Organic Fuel . Ingredients: Hydrogen, Time

Law of Drama

Law of Drama

https://www.xkcd.com/1124

https://www.explainxkcd.com/wiki/index.php/1124:_Law_of_Drama

[A Cartesian graph labeled 'How often someone declares that they hate "drama" and always avoid it' on the x-axis and 'Rate at which they create drama' labeled on the y-axis. The graph is a slightly exponential curve sloping upwards.]

The comic comments on how often people who label themselves as an innocent party in a debate are often far from it. Essentially, Randall seems to be graphically stating that people who claim to hate and want to avoid drama are invariably associated with it. Since correlation does not imply causation , it might be a leap — at least scientifically speaking — to actually surmise that they're the cause of it. The title text suggests that the person's attitude towards drama is wrong. Supposing that "'Drama' is just 'people being upset'", then ignoring drama is a very bad way to deal with it. By ignoring people's problems, you certainly won't be able to help them, and are at risk of causing further problems through ignorance. [A Cartesian graph labeled 'How often someone declares that they hate "drama" and always avoid it' on the x-axis and 'Rate at which they create drama' labeled on the y-axis. The graph is a slightly exponential curve sloping upwards.]

Objects In Mirror

Objects In Mirror

https://www.xkcd.com/1125

https://www.explainxkcd.com/wiki/index.php/1125:_Objects_In_Mirror

[View of a car mirror and outside view of landscape, with clouds and mountains. The mirror reads "Objects in mirror are bluer than they appear."] [Caption below the panel:] Edwin Hubble's car

"Objects in mirror are closer than they appear" is a required, although marginally ridiculous, "safety warning" required to be engraved on passenger side mirrors of motor vehicles in the USA, Canada and Korea. These mirrors in these countries are typically the only ones that are slightly convex, making objects appear smaller (and farther away) than their true size. Other countries often have convexity in driver-side and passenger-side rearview mirrors to give a larger field of view, at the cost of natural distance proportions of the mirror image, without making any statements about it on the mirror itself using engravings. This comic is a reference to the phenomena known as redshift / blueshift . Due to the Doppler effect , objects that are moving toward an observer appear bluer than they actually are (known as blueshift). Objects moving away from the observer (e.g. objects viewed in the rear-view mirror of a moving vehicle) appear redder than they actually are (known as redshift), and thus the objects are in reality bluer than they appear. This is generally relevant only in terms of high speed motion such as observation of the expansion of the universe in astrophysics. The joke is that the relative speed of any object visible in a side-view mirror would create an insignificant and unobservable redshift. Another possible explanation is that the redshift refers to the actual reflection itself. As photons are reflected in a mirror, momentum is transferred and thereby they lose a very small amount of energy. This loss of energy results in a slight redshift of the light. (This effect is similar to compton scattering .) Edwin Hubble was an astronomer credited ( amid some controversy ) with " Hubble's Law ," which states that a Doppler shift can be observed for objects in deep space moving with relative velocity to Earth and that their velocity is proportional to their distance from Earth. Probably the most famous application of the law was measurement of relative velocities of galaxies, such as those seen in the picture known as Hubble Deep Field , taken by the Hubble Space Telescope . The results proved that most galaxies keep getting farther apart as a result of expansion of the universe. This is one of many pieces of evidence supporting the Big Bang theory. The title text references that we see the universe as it was in the past (due to the distances involved and the speed of light), when it was smaller than it is today. It may also be a reference to comic 1110: Click and Drag . [View of a car mirror and outside view of landscape, with clouds and mountains. The mirror reads "Objects in mirror are bluer than they appear."] [Caption below the panel:] Edwin Hubble's car

Epsilon and Zeta

Epsilon and Zeta

https://www.xkcd.com/1126

https://www.explainxkcd.com/wiki/index.php/1126:_Epsilon_and_Zeta

THE SAGA OF EPSILON AND ZETA The 2005 Atlantic hurricane season saw devastating storms like Katrina and Rita. But less well-remembered is just how strange the season got toward the end. The forecasters at the National Hurricane Center are the best of the best. Their predictions are masterpieces of professional analysis. But in November 2005, out in the center of the Atlantic — far from any land — the atmosphere stopped making sense. And the forecasters — who'd expected the season to be long over by now — started to get a little…...unhinged. This is their story, as seen through the actual 2005 NHC Advisories: [Two men, one bald and one not, sit looking at their respective computers, at separate desks, back to back. The advisory is printed above them in caps small-caps Courier type.] Tuesday, November 29th, 2005: Tropical Storm Epsilon ... The 26th named storm of the apparently never ending 2005 Atlantic hurricane season. [The same scene, different text.] 10 PM Wed: The window of opportunity for strengthening should close in 12-24 hr. 4 PM Thu: Slow but steady weakening is expected to begin in 12-24 hours. [The man with hair now has questions marks above his head.] 4 AM Fri: Epsilon does not appear weaker. 10 AM Fri: Epsilon has been upgraded to a 65-kt hurricane. [The two still sit back-to-back.] 4 PM Sat: Epsilon has continued to strengthen against all odds ... [but] can not maintain the current intensity much longer since the environment is becoming increasingly unfavorable. [The two still sit back-to-back.] 10 PM Sat: Epsilon might or might not still be a hurricane ... but in any case it likely will not be one on Sunday. 4 AM Sun: Epsilon is downgraded to a tropical storm. [The two still sit back-to-back. The man with hair's fists are clenched.] :10 AM Sun: Morning satellite images indicate that Epsilon has restrengthened. [A closer view of just the balding man at his desk.] There are no clear reasons ... and I am not going to make one up ... to explain the recent strengthening of Epsilon and I am just describing the facts. However ... I still have to make an intensity forecast and the best bet at this time is to predict weakening ... Epsilon will likely become a remnant low. I heard that before about epsilon ... haven't you? [The two men still sit back to back, but the man with hair is now turning his head toward the other man, with his arm resting on the back of his chair. The bald man is leaning forward in his seat, toward his computer while typing.] 4 PM Mon: The cloud pattern continues to be remarkably well-organized for a hurricane at such high latitude in December. [The other man has turned back to his own screen.] 10 PM Mon: We have said this before ... but Epsilon really does not appear as strong this evening as it did this afternoon. [Just the bald guy now.] 4 AM Tue: I have run out of things to say. [The two of them again.] 10 PM Tue: The end is in sight. It really really is. But in the meantime ... Epsilon continues to maintain hurricane status. 4 AM Wed: The end is in sight ... yes ... but not quiet yet. I thought I was going to find a weakening system and instead I found that Epsilon is still a hurricane. [The two of them still.] 10 AM Thu: Convection has vanished and Epsilon is now a tight swirl of low clouds. I hope this is the end of the long lasting 2005 hurricane season. [This panel is blank and just reads: Nope.] NOPE. [The men are still at their desks. The bald man is leaning back on his chair and staring at his screen, taking his keyboard out of his desk; the other man's hair is noticeably disheveled, and he has started growing a five o'clock shadow.] Enter Tropical Storm Zeta. Friday, December 30th, 2005: An elongated area of low pressure ... which had its origins in an old frontal trough ... began developing organized convection overnight. Advisories are initiated on the 27th tropical storm of 2005. [The men are still at their desks, the man with hair is even more bedraggled-looking.] Any new storms would be in the 2006 season. 4PM Fri: Although the atmosphere seems to want to develop tropical storms ad nauseam ... the calendar will shortly put an end to the use of the Greek alphabet to name them. [The bald man is now wearing a party hat and has a party horn in his mouth, and there is confetti in the air.] But 2005's wouldn't end until Zeta did. 10 PM Sat: Zeta appeared on the verge of losing all of its deep convection a few hours ago ... but since about 21z the convection has been on somewhat of an increase again. [A close view of the man with hair at his desk.] 10 PM Sun: This is like Epsilon all over again. Most of the conventional guidance suggested that zeta should have been dissipated by now ... well ... zeta is pretty much alive at this time. I have no choice but to forecast weakening again and again. [The two of them again.] 4 AM Mon: By 24-36 hours ... a significant increase in westerly winds ... should act to shear away most of the associated convection ... and finally bring the 2005 Atlantic hurricane season to a merciful ending. 4 PM Mon: It is hard to conceive that a tropical cyclone will be able to survive for very long in such a hostile environment. therefore I have not backed off on the forecast of weakening. [The two of them again. Both men have clenched fists rested back from their keyboards, frustrated.] 10 PM Mon: Zeta is stronger than yesterday. 10 AM Wed: As you can see... I ran out of things to say. [Both men put up their keyboards...] 4 AM Thu: Satellite intensity estimates have decreased. Zeta is downgraded to a 30 kt tropical depression. [...only to start typing on them again.] 10 AM Thu: Shortly after the previous advisory had been issued ... regretfully ... the intensity ... increased to 35 kt and Zeta is a tropical storm once again. [The two of them again.] 10 PM Thu: Although it seems as if Zeta will never die ... the forecast continues to show weakening. [Both men are now leaning back in their chairs, exhausted, their keyboards put away.] 4 PM, Friday, January 6, 2006: Zeta no longer meets the criteria of a tropical cyclone... which means that both it and the 2005 Atlantic hurricane season have ended. This is the national hurricane center signing off for 2005. [The bald man still sits at his desk, the man with hair is no longer in his chair.] [Again, we see the bald man at his desk and the other guy's empty desk.] Bald guy: Actually, Zeta's cloud pattern is... Hair guy: (out of panel) NO . Bald guy: Ok.

This comic seems to be a parody of songs such as The Ballad of John and Yoko that tell the story of two people falling in love, with the noticeable variation that the 'protagonists' are hurricanes instead of people. The Atlantic hurricane season normally runs from June to November. Randall is imagining the situation in the National Hurricane Center when the 2005 season was extended more than a month by the appearance of Hurricane Epsilon and Tropical Storm Zeta . He imagines the situation as NOAA meteorologists watch with amazement (and increasing annoyance as they were presumably unable to move off to other things such as post-season analysis) as Hurricane Epsilon and Zeta continued to exist far beyond the normal end-of-season date (November 30). The monospaced text in most of the panels is material taken from actual NHC reports from that season. The commentary has been edited to fit the comic's format, but it's otherwise faithful to the actual reports. While the only change to Forecaster 1 is when he's celebrating New Year's Eve, Forecaster 2 is visibly losing it after the appearance of Zeta in late December, with unkempt hair and an unshaven beard. The last report of the 2005 season was issued on January 6, 2006. A full analysis of the 2005 hurricane season can be found here . NHC reports on Epsilion and Zeta: Randall has discussed the seemingly erratic nature of hurricanes before. This may, however, have been a response to the recent Hurricane Sandy . The text also seems to be a parody of horror stories/movies, and their theme of writing. THE SAGA OF EPSILON AND ZETA The 2005 Atlantic hurricane season saw devastating storms like Katrina and Rita. But less well-remembered is just how strange the season got toward the end. The forecasters at the National Hurricane Center are the best of the best. Their predictions are masterpieces of professional analysis. But in November 2005, out in the center of the Atlantic — far from any land — the atmosphere stopped making sense. And the forecasters — who'd expected the season to be long over by now — started to get a little…...unhinged. This is their story, as seen through the actual 2005 NHC Advisories: [Two men, one bald and one not, sit looking at their respective computers, at separate desks, back to back. The advisory is printed above them in caps small-caps Courier type.] Tuesday, November 29th, 2005: Tropical Storm Epsilon ... The 26th named storm of the apparently never ending 2005 Atlantic hurricane season. [The same scene, different text.] 10 PM Wed: The window of opportunity for strengthening should close in 12-24 hr. 4 PM Thu: Slow but steady weakening is expected to begin in 12-24 hours. [The man with hair now has questions marks above his head.] 4 AM Fri: Epsilon does not appear weaker. 10 AM Fri: Epsilon has been upgraded to a 65-kt hurricane. [The two still sit back-to-back.] 4 PM Sat: Epsilon has continued to strengthen against all odds ... [but] can not maintain the current intensity much longer since the environment is becoming increasingly unfavorable. [The two still sit back-to-back.] 10 PM Sat: Epsilon might or might not still be a hurricane ... but in any case it likely will not be one on Sunday. 4 AM Sun: Epsilon is downgraded to a tropical storm. [The two still sit back-to-back. The man with hair's fists are clenched.] :10 AM Sun: Morning satellite images indicate that Epsilon has restrengthened. [A closer view of just the balding man at his desk.] There are no clear reasons ... and I am not going to make one up ... to explain the recent strengthening of Epsilon and I am just describing the facts. However ... I still have to make an intensity forecast and the best bet at this time is to predict weakening ... Epsilon will likely become a remnant low. I heard that before about epsilon ... haven't you? [The two men still sit back to back, but the man with hair is now turning his head toward the other man, with his arm resting on the back of his chair. The bald man is leaning forward in his seat, toward his computer while typing.] 4 PM Mon: The cloud pattern continues to be remarkably well-organized for a hurricane at such high latitude in December. [The other man has turned back to his own screen.] 10 PM Mon: We have said this before ... but Epsilon really does not appear as strong this evening as it did this afternoon. [Just the bald guy now.] 4 AM Tue: I have run out of things to say. [The two of them again.] 10 PM Tue: The end is in sight. It really really is. But in the meantime ... Epsilon continues to maintain hurricane status. 4 AM Wed: The end is in sight ... yes ... but not quiet yet. I thought I was going to find a weakening system and instead I found that Epsilon is still a hurricane. [The two of them still.] 10 AM Thu: Convection has vanished and Epsilon is now a tight swirl of low clouds. I hope this is the end of the long lasting 2005 hurricane season. [This panel is blank and just reads: Nope.] NOPE. [The men are still at their desks. The bald man is leaning back on his chair and staring at his screen, taking his keyboard out of his desk; the other man's hair is noticeably disheveled, and he has started growing a five o'clock shadow.] Enter Tropical Storm Zeta. Friday, December 30th, 2005: An elongated area of low pressure ... which had its origins in an old frontal trough ... began developing organized convection overnight. Advisories are initiated on the 27th tropical storm of 2005. [The men are still at their desks, the man with hair is even more bedraggled-looking.] Any new storms would be in the 2006 season. 4PM Fri: Although the atmosphere seems to want to develop tropical storms ad nauseam ... the calendar will shortly put an end to the use of the Greek alphabet to name them. [The bald man is now wearing a party hat and has a party horn in his mouth, and there is confetti in the air.] But 2005's wouldn't end until Zeta did. 10 PM Sat: Zeta appeared on the verge of losing all of its deep convection a few hours ago ... but since about 21z the convection has been on somewhat of an increase again. [A close view of the man with hair at his desk.] 10 PM Sun: This is like Epsilon all over again. Most of the conventional guidance suggested that zeta should have been dissipated by now ... well ... zeta is pretty much alive at this time. I have no choice but to forecast weakening again and again. [The two of them again.] 4 AM Mon: By 24-36 hours ... a significant increase in westerly winds ... should act to shear away most of the associated convection ... and finally bring the 2005 Atlantic hurricane season to a merciful ending. 4 PM Mon: It is hard to conceive that a tropical cyclone will be able to survive for very long in such a hostile environment. therefore I have not backed off on the forecast of weakening. [The two of them again. Both men have clenched fists rested back from their keyboards, frustrated.] 10 PM Mon: Zeta is stronger than yesterday. 10 AM Wed: As you can see... I ran out of things to say. [Both men put up their keyboards...] 4 AM Thu: Satellite intensity estimates have decreased. Zeta is downgraded to a 30 kt tropical depression. [...only to start typing on them again.] 10 AM Thu: Shortly after the previous advisory had been issued ... regretfully ... the intensity ... increased to 35 kt and Zeta is a tropical storm once again. [The two of them again.] 10 PM Thu: Although it seems as if Zeta will never die ... the forecast continues to show weakening. [Both men are now leaning back in their chairs, exhausted, their keyboards put away.] 4 PM, Friday, January 6, 2006: Zeta no longer meets the criteria of a tropical cyclone... which means that both it and the 2005 Atlantic hurricane season have ended. This is the national hurricane center signing off for 2005. [The bald man still sits at his desk, the man with hair is no longer in his chair.] [Again, we see the bald man at his desk and the other guy's empty desk.] Bald guy: Actually, Zeta's cloud pattern is... Hair guy: (out of panel) NO . Bald guy: Ok.

Congress

Congress

https://www.xkcd.com/1127

https://www.explainxkcd.com/wiki/index.php/1127:_Congress

A history of The United States Congress Partisan and ideological makeup [The comic is divided into three massive sections, SENATE, PRESIDENCIES, and HOUSE. Timelines run backwards down the page between each section. In the HOUSE and SENATE sections, shifting, curving red and blue areas of different brightness illustrate the shifting balance of power between "Members of Left-Leaning Parties" and "Members of Right-Leaning Parties". Under PRESIDENCIES, different administrations are labeled and wars are shaded in gray. There are notes throughout all sections.] [There are additional notes on the right.] LEGEND [Square containing ribbons of color merging upwards with larger areas] : Branches join in when new members enter Congress and cause an ideological bloc to grow. (Note: If the new member is elected as another retires from the same ideological bloc, no change is shown.) [Square containing ribbons of color splitting off from larger areas] : Branches split off when members leave Congress, causing their ideological bloc to shrink. (Note: If the new member is elected as another retires from the same ideological bloc, no change is shown.) [Square showing yellow dotted line crossing from red to blue area] : The yellow line marks the midpoint, which indicates which side has control of the chamber. [Square in which curve briefly separates from blue area] : If a bloc loses members in one election and gains them in the next, the exiting stream may rejoin. This does not necessarily mean the same people returned. [Square showing white dashed line labeled Lyndon Johnson on top of ribbon merging with main area] : Future (and past) US Presidents who served in Congress are shown with white dashed lines. Other noteworthy members are shown with thin solid lines. [Square in which tinted area marked "Whig" sits over mix of red and blue areas] : Tinted white outlines mark the approximate membership of some of the smaller political parties. HOW IDEOLOGY IS CALCULATED Each member of Congress is assigned to an ideological category using DW-NOMINATE, a statistical system created by political scientists Keith Poole and Howard Rosenthal. This system rates each member of Congress's ideological position position [sic] based on their votes. DW-NOMINATE is purely mathematical and involves no judgement on the content of bills. Instead, members of Congress are placed on a spectrum based on how consistently they vote together. While people argue that ideology is many-dimensional, Poole and Rosenthal found that nearly all Congressional voting behavior - especially in the modern era - can be accurately predicted by using just one ideological variable. This variable turns out to roughly correspond to position on the classic economic liberal/conservative spectrum. Because members of Congress have served in overlapping terms with past members in a chain back to the first Congress, the system allows comparison of ideology across time - even accounting for individual members' ideological drift. (Note: Scores are comparable across time but not between chambers.) For more detail, see Poole and Rosenthal's website, voteview.com.

It appears that the (at the time) upcoming 2012 election has put Randall into a political state of mind, as this is the second comic in a few weeks that has dealt with political history ( 1122: Electoral Precedent ). As with that comic, this comic goes through the entire history of the U.S. Federal Government . Also notably, Randall makes a number of observations that are akin to the type of observations Randall denounces in 1122 (e.g. for 1928, Randall notes that no Republican has since won the presidency without a Nixon or a Bush on the ticket). Just around the election he posted two more comics related to this: 1130: Poll Watching and 1131: Math . In the U.S. Federal Government , one of the checks and balances is a bicameral United States Congress , which consists of two "houses": the Senate , its "upper" house; and the House of Representatives ("the House"), its "lower house". The Senate consists of 2 senators elected from each state (thus 100 total), while the House consists of 435 voting representatives (a number decided upon in 1911 by law) whose apportionment is split between the states proportional to their population; although each state gets at least one (the House also has non-voting representatives from non-state territories like Puerto Rico and the District of Columbia ). Every ten years, the House is reapportioned based on the latest census. The most populous state as of 2012 is California which has 53 seats in the House. Senators serve 6-year terms with elections held every 2 years for one-third of the seats. Members of the House (called Representatives or Congressmen/women) serve 2-year terms with all of the seats contested every 2 years. In order for a bill to become a law, it must be passed by both the House and the Senate. In a way, this theoretically ensures that the bill is supported both by the majority of states (the Senate), and the majority of the population (the House). The President may then sign the bill into law, he may "veto" the bill, or he may do nothing, in which case it becomes a law if and only if Congress is in session after a waiting period of 10 days (not including Sundays). In politics, there is a scale that represents the political beliefs of a politician. The scale goes from " left " to " right " of "center" — which generally describes a balancing point of beliefs (sometimes called "left-wing" or "right-wing"). The "left" is a general belief in social justice, and is sometimes associated with socialism . Modern left-wingers generally prioritize equality, and support policies like welfare and government-subsidized healthcare. This trends toward having a larger federal government. In the U.S., "liberal" is a term often used to denote left-leaning tendencies. The "right" generally believe in personal responsibility and individual liberty, which is often termed conservative . This trends towards having less regulation and thereby a smaller federal government. The goal is to keep the nation stable, and reducing the interference by the government with a person's wealth. This ostensibly means lower taxes, because the government does not provide as much. Politicians typically align themselves into groups of similar beliefs and positions called "parties". In the U.S., there have generally been two dominant parties, although there have been times where three or more parties have shared roughly equal influence and support. In today's politics (which is apparently known as (the second part of) the fifth era of political parties, or Fifth Party System , as noted on the outside edges of the comic) of the two current primary U.S. political parties, the Democrats are the left-leaning party, and the Republicans are the right-leaning party. The dominant parties are generally considered "moderate" in their left- or right-wing leanings, as either party appears to requires the support of a majority (or a few percent under) of voters to win. However, this is complicated by a process called gerrymandering where election boundaries are redrawn to allow a political advantage to the party currently in power. Thus a popular majority state wide or any ratio of votes to representatives will not necessarily be reflected in delegates awarded, an example being the Republicans' REDMAP 2012 report ( [1] ). Smaller parties often run candidates with more extreme views, but such candidates rarely win, due to a more limited number of possible supporters ensuring that even a relatively large minority would have zero chance of representation. (see Duverger's law ). The comic effectively consists of three separate charts: The left- and right-hand charts are the main charts; they represent the Senate and House respectively, and purport to show the left- and right-wing leanings of each legislature through U.S. history. There is a legend on the right that sets out fairly clearly how the charts work, but basically Randall has split each wing into three levels including the very moderate or "Center" right or left, and the more extreme or "Far" right or left, as well as the average left and right without prefix. A dotted yellow line represents the balance of power in each legislature, and white lines represent the leanings of certain notable people including presidents. Some presidents are not indicated, because they were never senators or congressmen (most of these were state Governors, such as Clinton , Bush and 2012 candidate Mitt Romney ). As may be noted from the chart, Barack Obama is considered "left" while Paul Ryan is considered "far right". It's also notable that the "center right" ideology appears to be completely eradicated from the House and is waning in the Senate (although a similar trend is shown around 1900 with the centrists making a comeback thereafter). On either side of these charts, there are descriptions or explanations for expansions and contractions of each ideological group. The center chart appears to primarily act as a timeline. Each president is listed with their leanings indicated by a left or right arrow. Wars are shaded in grey. Other notable events are also indicated. On either side of the center chart (although somewhat mixed in with the aforementioned Senate/House explanations), there are also references to the primary parties of each era showing how they evolved (left-leaning parties on the left, and right-leaning parties on the right). Finally, there's a little extra commentary on the right side, below the legend. The title text refers to two political parties in American history: the Federalists and the Jacksonians. Note that this means the two parties are not strictly contemporaries. There are features of both the modern Republican and Democratic parties in each, so depending on the topic presented, it may take a long time to figure out that they are not these modern parties until the topic of discussion changes. They do, however, make a nice dichotomy. The Federalists are one of the oldest political parties in American History. Federalists were seen as conservative in their time, and similarly to modern Republicans much of their support came from bankers and businessmen and they were committed to a fiscally sound and government, but on the flip side they favored a strong central government, regulation of industry, a national banking system, and were protectionistic. The Jacksonian party is one of the four branches of the Democratic Party that developed during the political chaos after the Federalist party died out in the War of 1812. The Jacksonians were considered liberal for their time, they believed in one man, one vote, regardless of standing, and their mascot was a donkey and they're the ancestors of the modern Democratic Party, but on the flip side they did not want a strong national government and believed that the government should have limited impact in the regulation of industry, going so far as to end the bank of the United States, and were fiercely expansionistic. Network news channels regularly feature talking heads , supposed 'experts' who offer their opinion on the topical political stories. Where these talking heads are strongly aligned with a particular party, and are unconcerned with anything other than winning, they could be described as a partisan hacks . A history of The United States Congress Partisan and ideological makeup [The comic is divided into three massive sections, SENATE, PRESIDENCIES, and HOUSE. Timelines run backwards down the page between each section. In the HOUSE and SENATE sections, shifting, curving red and blue areas of different brightness illustrate the shifting balance of power between "Members of Left-Leaning Parties" and "Members of Right-Leaning Parties". Under PRESIDENCIES, different administrations are labeled and wars are shaded in gray. There are notes throughout all sections.] [There are additional notes on the right.] LEGEND [Square containing ribbons of color merging upwards with larger areas] : Branches join in when new members enter Congress and cause an ideological bloc to grow. (Note: If the new member is elected as another retires from the same ideological bloc, no change is shown.) [Square containing ribbons of color splitting off from larger areas] : Branches split off when members leave Congress, causing their ideological bloc to shrink. (Note: If the new member is elected as another retires from the same ideological bloc, no change is shown.) [Square showing yellow dotted line crossing from red to blue area] : The yellow line marks the midpoint, which indicates which side has control of the chamber. [Square in which curve briefly separates from blue area] : If a bloc loses members in one election and gains them in the next, the exiting stream may rejoin. This does not necessarily mean the same people returned. [Square showing white dashed line labeled Lyndon Johnson on top of ribbon merging with main area] : Future (and past) US Presidents who served in Congress are shown with white dashed lines. Other noteworthy members are shown with thin solid lines. [Square in which tinted area marked "Whig" sits over mix of red and blue areas] : Tinted white outlines mark the approximate membership of some of the smaller political parties. HOW IDEOLOGY IS CALCULATED Each member of Congress is assigned to an ideological category using DW-NOMINATE, a statistical system created by political scientists Keith Poole and Howard Rosenthal. This system rates each member of Congress's ideological position position [sic] based on their votes. DW-NOMINATE is purely mathematical and involves no judgement on the content of bills. Instead, members of Congress are placed on a spectrum based on how consistently they vote together. While people argue that ideology is many-dimensional, Poole and Rosenthal found that nearly all Congressional voting behavior - especially in the modern era - can be accurately predicted by using just one ideological variable. This variable turns out to roughly correspond to position on the classic economic liberal/conservative spectrum. Because members of Congress have served in overlapping terms with past members in a chain back to the first Congress, the system allows comparison of ideology across time - even accounting for individual members' ideological drift. (Note: Scores are comparable across time but not between chambers.) For more detail, see Poole and Rosenthal's website, voteview.com.

Fifty Shades

Fifty Shades

https://www.xkcd.com/1128

https://www.explainxkcd.com/wiki/index.php/1128:_Fifty_Shades

[Cueball is sitting on the floor watching his TV standing on a small table. He is leaning back on one arm resting the other arms hand on his knee. Light is coming out from the TV screen, as shown with nine small lines. A a high sound is shown above the TV in a starburst and the sound of a dog barking is coming out from the screen with a line indicating this. Above the drawings ther are two paragraphs of text:] As with most famous books, I've never actually read Fifty Shades of Grey. I only know the plot from watching the Wishbone version. Dog in movie: Bark! Dog in movie: Bark! Sound: Smack! Dog in movie: Bark!:

Fifty Shades of Grey is a best-selling novel featuring large quantities of BDSM sex. Wishbone was a children's TV show about a dog who draws parallels between literature and real life in his dreams, reenacting many literary classics. The show was especially praised in its time for refusing to censor the more unpleasant aspects of its source work. Many people within Randall 's age group have experienced more literary classics through Wishbone than by actually reading them; this phenomenon lead to the formation of a Facebook group (now replaced by a page ) with over 70,000 members dedicated to that idea. In the comic, Cueball claims to have learned all that he knows about Fifty Shades of Grey from the Wishbone adaptation of the book. Knowing the faithful nature of Wishbone' s adaptations, an episode on the book would likely involve age-inappropriate material for children, as the sounds emanating from the TV would suggest. In the title text: Part of the title text joke is that the latter two works would not likely be the subject of Great Illustrated Classics or Wishbone . However, the title text may be actually technically 100% correct, if Randall hasn't ever had an in-depth conversation about either of the latter two works. The book was later made into a film which was referenced in 1585: Similarities almost three years later. [Cueball is sitting on the floor watching his TV standing on a small table. He is leaning back on one arm resting the other arms hand on his knee. Light is coming out from the TV screen, as shown with nine small lines. A a high sound is shown above the TV in a starburst and the sound of a dog barking is coming out from the screen with a line indicating this. Above the drawings ther are two paragraphs of text:] As with most famous books, I've never actually read Fifty Shades of Grey. I only know the plot from watching the Wishbone version. Dog in movie: Bark! Dog in movie: Bark! Sound: Smack! Dog in movie: Bark!:

Cell Number

Cell Number

https://www.xkcd.com/1129

https://www.explainxkcd.com/wiki/index.php/1129:_Cell_Number

[10 boxes for 10 digits of a U.S. phone number. The first three are grouped by parentheses. A hyphen separates the second set of three and the last four.] [Label titled "Your seven random digits" pointing at seven empty boxes.] [Label titled "Where you lived in 2005" pointing at three empty boxes preceding the seven.] Structure of a US cell phone number.

This comic references the pattern for US telephone numbers, which are ten digits in length. Unlike in other countries, there is no quick way to determine whether that number is for a land-line or mobile customer. In either case, the first three digits are referred to as the " area code ", a term dating back to before the proliferation of mobile phones, when specific codes were assigned to geographic regions. The next three digits had some rules based on the telephone exchange but as Randall says, those and the final four numbers are essentially meaningless. In the early days of the mobile era, the geography-based numbering still applied to new mobile lines, so mobile phones would have the same area code as owners' home numbers. Late in 2003, US telephone service providers were required to support "number portability", meaning that customers could theoretically take their mobile phone number with them to a new provider, even when moving to a distant new location. In the early days this wasn't always very easy to do, but became commonplace within a couple years. Since most users opt to keep their numbers constant whenever possible, numbers generally stopped changing after about 2005, instead of shifting when people moved like they were forced to in previous years. Therefore, examination of a given phone number will likely tell you where its owner was living at that time, since their number would not have changed after 2005 due to the portability law. "+1" is the international call prefix for the North American Numbering Plan. Google Voice is an alternate voice over IP service. Upon signing up, users can choose any available new 10-digit number without regard to geographic area. Among other things, this allows the earlier users to choose "cool numbers" if desired, such as ones that correspond to phonewords or have a pleasing pattern. In the past, this "vanity numbering" was typically only available to businesses via toll-free numbers . Some mobile service providers began allowing similar customization after the portability law, but often still restricted new numbers by area code, keeping the availability of "cool numbers" low until Google Voice launched. [10 boxes for 10 digits of a U.S. phone number. The first three are grouped by parentheses. A hyphen separates the second set of three and the last four.] [Label titled "Your seven random digits" pointing at seven empty boxes.] [Label titled "Where you lived in 2005" pointing at three empty boxes preceding the seven.] Structure of a US cell phone number.

Poll Watching

Poll Watching

https://www.xkcd.com/1130

https://www.explainxkcd.com/wiki/index.php/1130:_Poll_Watching

[Cueball kneels on his desk chair, hunched over a laptop] Cueball: This Tuesday will be huge! Cueball: If Obama wins the election, it could generate news coverage devastating to Romney's position in the tracking polls! Offscreen character: ... Maybe you should take a break.

This is a comic about the 2012 U.S. presidential election , as it was posted the day before the election on November 6, 2012 ("this Tuesday"). It is the third comic on the subject, the previous two being 1122: Electoral Precedent and 1127: Congress . And the next comic 1131: Math continues the issue raised in this one. In the comic, Cueball is glued to his laptop reading media coverage of the election. The offscreen character remarks that Cueball should take a break, suggesting that Cueball has been reading media coverage for quite a while. Cueball is so caught up in media coverage that he is speculating on the effect that incumbent President Obama winning the election (and the resulting news coverage) could have on challenger Mitt Romney 's campaign. The joke is that the end-goal of Romney's campaign is to win the election. If Obama wins, the campaigning is already over, regardless of media coverage. Cueball is simply so invested that he overanalyzes potential scenarios and fails to see the big picture. Specifically, he has become so concerned with following the polls that he's lost sight of their purpose as a predictive tool. After the election is over, polling becomes trivial since the result they are intended to forecast is already known (and so in reality will not be conducted at all). This is possibly intended as a rebuke to those pundits ( talking heads ) who seemingly care more about (or whose jobs are contingent on caring more about) the "game" of analyzing and predicting the politics of the race rather than caring about the actual policies the candidates are likely to pursue after coming into office. The title text repeats this theme with Nate Silver , an American statistician, psephologist , and writer (among other things). He has a political blog called FiveThirtyEight which was originally written under a pseudonym. The Blog and its associated website primarily discuss tracking polls in respect to elections. Thus, the choices made on Tuesday (election day) will have massive and permanent effects on FiveThirtyEight's charts, which will obviously change to reflect the actual votes cast — but all the charts will have become trivial since the purpose of the blog is to predict the results. This is a parody of the bold statements often made during campaigns, such as that the choices made on election day could have massive and permanent effects on such things as your health care, the economy, your job, etc. Polls and pundits are also referenced in the next comic, 1131: Math , published the day after the election. [Cueball kneels on his desk chair, hunched over a laptop] Cueball: This Tuesday will be huge! Cueball: If Obama wins the election, it could generate news coverage devastating to Romney's position in the tracking polls! Offscreen character: ... Maybe you should take a break.

Math

Math

https://www.xkcd.com/1131

https://www.explainxkcd.com/wiki/index.php/1131:_Math

[A frame with a bar chart showing 58% blue and 42% red. A header shows a range between 53-63%] Forecast [An arrow below the chart is pointing at the line between the blue and the red sections of the chart with a heading] Result [Below the frame is a caption] Breaking: To surprise of pundits, numbers continue to be best system for determining which of two things is larger.

In another election-themed comic (this one posted the day after the 2012 U.S. presidential election November 7, 2012)—(see also 1122: Electoral Precedent , 500: Election , 1127: Congress , and 1130: Poll Watching )—this comic shows a bar graph representing expected (see note below) electoral college votes in the election, including a dotted line indicating the 270 electoral votes needed to win, a span of projections ("Forecast"), and the actual result. The forecast range is to the right of the 270 line, showing that the blue candidate Obama (the Democratic candidate is the blue candidate and the Republican candidate is the red candidate according to a convention used since the 2000 election) was always projected to win by statisticians like Nate Silver and others. The only question among these people was by how much he was going to win. (The Electoral College votes are expectations until each state's voting results are announced early in November, and the electors actually vote in December and may change the situation somewhat.) Randall is attempting to use this particular election to imply that polling data accurately indicates the likely outcome of a presidential election. However, the close match between prediction and result in this one election could be a coincidence; the outcome of U.S. presidential elections frequently differs from projections. Notably, in 1948, the Chicago Tribune printed a headline which turned out to be false and in 2016, polling data indicated that Clinton would defeat Trump. By contrast, most of the media was calling the election too close to call, with some news outlets actually projecting a Mitt Romney win. Essentially the large number of Republican pundits who helped increase the pressures of right wing self-referencing media denial, the tendency of media to give any issue at least two dramatically or fictionally equal voices (for supposed "fairness") regardless of the relative merits of the two sides, and the desire to present the election as a suspenseful "horse race" resulted in a lot of talking heads (i.e. pundits) disbelieving the polls. These factors shaped the "too close to call" narrative, leading to the punch line of this story: You don't need to believe in science or statistics for it to effectively describe or predict reality. The progressively more radicalized elements of this era are known for disregarding scientific or statistical consensus which reflects reality but does not conform to their world view. However, many of them were correct in their belief (in defiance of statistical data to the contrary) that Donald Trump would be elected in 2016. For those unfamiliar with the US Presidential electoral process : Unlike other political offices, the election for president is not a direct election. Instead, each state is apportioned a certain number of "Electoral College" votes based on the number of House of Representatives seats (which is based on population) and Senate seats. For the most part (and there is perennial discussion on whether this should be changed) the candidate that receives the most popular votes in a given state receives all the Electoral College votes for that state. With 538 electoral votes total, receiving 270 Electoral College votes ((half of 538) + 1) is sufficient to be declared president-elect. For this reason, sometimes one candidate actually receive more popular votes (more people voted for the candidate) but have fewer Electoral College votes. This happened three times in the nineteenth century with elections of John Quincy Adams in 1824 , Rutherford B. Hayes in 1876 and Benjamin Harrison in 1888 . Then it did not happen again until the election of George W. Bush in 2000 and Donald Trump in 2016 . The title text is a subversion of what everyone else was saying at that time: that the election was unpredictable. Pundits often declare events to be "too close to call" when poll results are very close; Randall is saying that the only thing that is "too close to call" is the difference between the results and the predicted results, as the outcome is all but certain. [A frame with a bar chart showing 58% blue and 42% red. A header shows a range between 53-63%] Forecast [An arrow below the chart is pointing at the line between the blue and the red sections of the chart with a heading] Result [Below the frame is a caption] Breaking: To surprise of pundits, numbers continue to be best system for determining which of two things is larger.

Frequentists vs. Bayesians

Frequentists vs. Bayesians

https://www.xkcd.com/1132

https://www.explainxkcd.com/wiki/index.php/1132:_Frequentists_vs._Bayesians

[Caption above the first panel:] Did the sun just explode? (It's night, so we're not sure) [Two Cueball-like guys stand on either side of a small table with a small black device on it. The device has white lines (ventilation) and two small antennas and a button on top. When the device speaks it uses in Westminster typeface. The Guy on the left, called Frequentist Statistician in the 2nd panel, points to the device. The guy on the right, called Bayesian Statistician in the 3rd panel, is just looking at the device. Above the spoken word from the device is a sound.] Frequentist Statistician: This neutrino detector measures whether the sun has gone nova. Bayesian Statistician: Then, it rolls two dice. If they both come up as six, it lies to us. Otherwise, it tells the truth. Frequentist Statistician: Let's try. Detector! Has the sun gone nova? Sound: Roll Device: YES. [Two panels side by side are beneath the first panel. together they are broader than the top panel. Above each panel is a caption. In the left panel only the left statistician is shown with the device on the table. And in the right panel only the right statistician is shown with the device on the table. both are just looking at the device.] Frequentist Statistician: Frequentist Statistician: The probability of this result happening by chance is 1/36=0.027. Since p<0.05, I conclude that the sun has exploded. Bayesian Statistician: Bayesian Statistician: Bet you $50 it hasn't.

This comic is a joke about jumping to conclusions based on a simplistic understanding of probability. The " base rate fallacy " is a mistake where an unlikely explanation is dismissed, even though the alternative is even less likely. In the comic, a device tests for the (highly unlikely) event that the sun has exploded. A degree of random error is introduced, by rolling two dice and lying if the result is double sixes. Double sixes are unlikely (1 in 36, or about 3% likely), so the statistician on the left dismisses it. The statistician on the right has (we assume) correctly reasoned that the sun exploding is far more unlikely, and so is willing to stake money on his interpretation. The labels given to the two statisticians, in their panels and in the comic's title, are not particularly fair or accurate, a fact which Randall has acknowledged: [1] The " frequentist " statistician is (mis)applying the common standard of " p <0.05". In a scientific study, a result is presumed to provide strong evidence if, given that the null hypothesis , a default position that the observations are unrelated (in this case, that the sun has not gone nova), there is less than a 5% chance that the result was merely random. (The null hypothesis was also referenced in 892: Null Hypothesis .) Since the likelihood of rolling double sixes is below this 5% threshold, the "frequentist" decides (by this rule of thumb) to accept the detector's output as correct. The " Bayesian " statistician has, instead, applied at least a small measure of probabilistic reasoning ( Bayesian inference ) to determine that the unlikeliness of the detector lying is greatly outweighed by the unlikeliness of the sun exploding. Therefore, he concludes that the sun has not exploded and the detector is lying. A real statistician (frequentist or Bayesian) would probably demand a lower p -value before concluding that a test shows the Sun has exploded; physicists tend to use 5 sigma, or about 1 in 3.5 million, as the standard before declaring major results, like discovering new particles. This would be equivalent to rolling between eight and nine dice and getting all sixes, although this is still not "very good" compared to the actual expected likelihood of the Sun spontaneously going nova, as discussed below. The line, "Bet you $50 it hasn't", is a reference to the approach of a leading Bayesian scholar, Bruno de Finetti , who made extensive use of bets in his examples and thought experiments. See Coherence (philosophical gambling strategy) for more information on his work. In this case, however, the bet is also a joke because we would all be dead if the sun exploded. If the Bayesian wins the bet, he gets money, and if he loses, they'll both be dead before money can be paid. This underlines the absurdity of the premise and emphasizes the need to consider context when examining probability. It is also possible that the use of the sun is a reference to Laplace's Sunrise problem . The title text refers to a classic series of logic puzzles known as Knights and Knaves , where there are two guards in front of two exit doors, one of which is real and the other leads to death. One guard is a liar and the other tells the truth. The visitor doesn't know which is which, and is allowed to ask one question to one guard. The solution is to ask either guard what the other one would say is the real exit, then choose the opposite. Two such guards were featured in the 1986 Jim Henson movie Labyrinth , hence the mention of "A LABYRINTH GUARD" here. A labyrinth was also mentioned in 246: Labyrinth Puzzle . As mentioned, this is an instance of the base rate fallacy . If we treat the "truth or lie" setup as simply modelling an inaccurate test, then it is also specifically an illustration of the false positive paradox : A test that is rarely wrong, but which tests for an event that is even rarer, will be more often wrong than right when it says that the event has occurred. The test, in this case, is a neutrino detector. It relies on the fact that neutrinos can pass through the earth, so a neutrino detector would detect neutrinos from the sun at all times, day and night. The detector is stated to give false results ("lie") 1/36th of the time. There is no record of any star ever spontaneously exploding—they always show signs of deterioration long before their explosion—so the probability is near zero. For the sake of a number, though, consider that the sun's estimated lifespan is 10 billion years. Let's say the test is run every hour, twelve hours a day (at night time). This gives us a probability of the Sun exploding at one in 4.38×10 -13 . Assuming this detector is otherwise reliable, when the detector reports a solar explosion, there are two possibilities: Clearly the sun exploding is not the most likely option. Indeed, Bayes' theorem can be used to find the probability that the Sun has exploded, given a result of "yes" and the prior probability given above: [Caption above the first panel:] Did the sun just explode? (It's night, so we're not sure) [Two Cueball-like guys stand on either side of a small table with a small black device on it. The device has white lines (ventilation) and two small antennas and a button on top. When the device speaks it uses in Westminster typeface. The Guy on the left, called Frequentist Statistician in the 2nd panel, points to the device. The guy on the right, called Bayesian Statistician in the 3rd panel, is just looking at the device. Above the spoken word from the device is a sound.] Frequentist Statistician: This neutrino detector measures whether the sun has gone nova. Bayesian Statistician: Then, it rolls two dice. If they both come up as six, it lies to us. Otherwise, it tells the truth. Frequentist Statistician: Let's try. Detector! Has the sun gone nova? Sound: Roll Device: YES. [Two panels side by side are beneath the first panel. together they are broader than the top panel. Above each panel is a caption. In the left panel only the left statistician is shown with the device on the table. And in the right panel only the right statistician is shown with the device on the table. both are just looking at the device.] Frequentist Statistician: Frequentist Statistician: The probability of this result happening by chance is 1/36=0.027. Since p<0.05, I conclude that the sun has exploded. Bayesian Statistician: Bayesian Statistician: Bet you $50 it hasn't.

Up Goer Five

Up Goer Five

https://www.xkcd.com/1133

https://www.explainxkcd.com/wiki/index.php/1133:_Up_Goer_Five

US Space Team's Up Goer Five The only flying space car that's taken anyone to another world (explained using only the ten hundred words people use the most often) [A list of Saturn-V parts, top to bottom, with their "Up Goer" description follows.] [Launch Escape System (LES)]: Thing to help people escape really fast if there's a problem and everything is on fire so they decide not to go to space [LES side nozzle]: Thing to control which direction the escaping people go [LES fuel]: Stuff to burn to make the box with the people in it escape really fast [LES bottom nozzles]: Place where fire comes out to help them escape [Apollo spacecraft.] [Command Module (CM)]: Part that flies around the other world and comes back home with the people in it and fall in the water. [CM capsule parts]: People box, door, chairs [Service Module (SM)]: Part that goes along to give people air, water, computers and stuff. It comes back home with them but burns up without landing. [SM oxygen tanks]: Cold air for burning (and breathing). This part had a VERY big problem once. [Lunar Module (LM)]: Part that flies down to the other world with two people inside [LM descent stage]: Part that stays on the other world (it's still there) [LM feet]: Feet that go on the ground of the other world [Instrument Unit]: Ring holding most of the computers [S-IVB third stage]: Part that falls off third (this part flew away from our world into space and hit the world we were going toward) [Fuel tanks]: Wet and very cold [Liquid hydrogen (LH2) tank]: The kind of air that once burned a big sky bag and people died and someone said "Oh, the [humans]!" (used for burning) [Liquid oxygen (LOX) tank]: The part of air you need to breathe, but not the other stuff (used for burning) [Helium pressurizing tanks]: Things holding that kind of air that makes your voice funny (it's for filling up the space left when they take the cold air out to burn it.) [J-2 engine nozzle]: Fire comes out here [S-II second stage]: Part that falls off second [LH2 tank]: More sky bag air (for burning) ( cold + wet) [LOX tank]: More breathing-type air (for burning) ( cold + wet) [Tank-to-engine fuel lines]: Thing that brings in cold wet air to burn [J-2 engine nozzles (qty. 5)]: Fire comes out here [S-IC first stage]: Part that falls off first [LOX tank]: More breathing-type air (for burning) ( cold + wet) [Helium pressurizing tank]: More funny voice air (for filling up space) [LOX fill line]: Opening for putting in cold wet air [RP-1 fuel tank]: This is full of that stuff they burned in lights before houses had power.It goes together with the cold air when it's time to start going up. [F-1 engine nozzles (qty. 5)]: Lots of fire comes out here. [Bottom of spacecraft]: This end should point toward the ground if you want to go to space. If it starts pointing toward space you are having a bad problem and you will not go to space today.

This comic is an illustration that will later be used in Randall 's book ' Thing Explainer ', where he took it upon himself to explain a number of things, including the Saturn V rocket shown here, using only the one thousand most commonly-used words in the English language. This comic is a diagram of the Saturn V rocket. "Saturn" isn't a very common word apparently, and neither is rocket, so Randall decided to use "Up Goer" which is a fair approximation of a craft designed to lift a payload from the earth to space, although perhaps 'thing that goes up fast' may or may not be simpler. The Saturn V vehicle, which was in use by NASA from 1967 to 1972, is the vehicle as a whole. The engines of the Saturn V (the part that makes it go up) were divided into three stages. The first stage ( S-IC ) had five F-1 engines which burned refined kerosene mixed with oxygen as its fuel. That stage burned for 2 minutes 48 seconds and pushed the whole thing up about 61 kilometers (~38 miles) into the sky. After it fell away the S-II stage was activated. It used 5 J-2 engines in the same configuration as the F-1s, and burned liquid hydrogen mixed with liquid oxygen for 6 minutes 35 seconds pushing the astronauts up to 184 kilometers (114.5 miles). The third stage ( S-IVB ) was a single J-2 engine burning liquid hydrogen and liquid oxygen. This stage was used in two parts, the first was to put the spacecraft into a stable orbit around Earth to perform a systems check and make sure the craft will be safe for going to the moon. This would usually take three orbits around Earth. As they came around the Earth they would burn the second part of the fuel, which is called a trans-lunar injection which put them on course for the moon. The first burn took 2 minutes 45 seconds, which put them in orbit 185 kilometers (115 miles) high. It was first used as the launch vehicle for the Apollo 4 mission, and it was used as the launch vehicle for most of the subsequent Apollo missions (the exceptions being Apollo 7, Skylab 2-4, and the Apollo-Soyuz Test Project missions, which were launched using the smaller Saturn IB launch vehicle). One of the last missions of this design was the unmanned launch of Skylab , the U.S.'s first space station; for this payloader configuration, the Saturn V launch vehicle was officially designated the Saturn INT-21 . The Service Module (SM) Oxygen tanks have a note that states "This part had a VERY big problem once". This is a reference to the Apollo 13 mission. 55 hours after launch, mission control requested the oxygen tanks contents be stirred to get an accurate reading of its contents. There was a large bang , and power fluctuated throughout the craft. NASA had to scramble to ensure the safe return of the astronauts. Needless to say, the moon landing for that mission was canceled. The Hindenburg disaster is referenced in the text "The kind of air that once burned a big sky bag and people died and someone said "oh, the [humans]!". The term "big sky bag" is used as the closest approximation of zeppelin which is a big bag filled with a lighter-than-air gas which makes the whole contraption float. The phrase "oh, the [humans]" is a workaround of the simple-words rule, technically containing only the word humans, while being read "concentration of humans" or "humanity". The Hindenburg on the day of the disaster was filled with hydrogen , despite being initially designed for use with helium . Helium cannot catch fire as it is a noble gas and thus completely inert, but helium was unavailable due to a US export ban on the element. The risks seemed acceptable at the time because the Germans had a history of flying hydrogen-based passenger airships. The original quote is "Oh, the humanity!" (See this video about the Hindenburg disaster - the quote appears at 0:47). In the book Thing Explainer in the explanation for The pieces everything is made of (i.e. the Periodic table ) hydrogen is again "named" by using a picture of the burning Hindenburg and also this quote is said by Cueball standing next to the square with the element with his hands over his mouth. See more below regarding the book. The bottom tank, which Randall describes as "...full of that stuff they burned in lights before houses had power" is highly refined kerosene, called RP-1 , it is similar to jet fuel, burns well and is not likely to explode; unlike liquid hydrogen , which is much more likely to explode. Earlier flirts with simple words can be found in 547: Simple and 722: Computer Problems . The use of simple words was revisited again in 1436: Orb Hammer and 1322: Winter . The comic is based on NASA-MSFC 10M04574 produced at Marshal Space Flight Center. Randall omitted the "S". The image was for sale as a poster from up-ship.com which Randal mentioned. A different scan is downloadable from Heroic Relics . The phrase "You will not go to space today" has become something of a catchphrase for xkcd — variants of it recur in the title text of images in four What If? articles: Randall has in 2015 written an entire book with this type of simplified language blueprints. Thing Explainer was published by Houghton Mifflin Harcourt on November 24, 2015 and actually had a copy of this comic in it. On the day of the book's release Randall also released a comic with a game, to celebrate the book: 1608: Hoverboard . In this game the space capsule used for landing back on earth is shown, thus both referencing the book and this comic. This part of the space ship can also be seen in the book above the Sky toucher and the moon landing is also depicted in Worlds around the sun . When the book was released Randall had Minute Physics do a "commercial" version of this comic . The news about the upcoming release of the book was sent out on the Blag in May as New book: Thing Explainer . After that, the book was advertised at the top of the xkcd page with link to the Blag article and links to Preorder at Amazon, Barnes & Noble, Indie Bound, and Hudson. Also, there were two other news with links: "In other news, Space Weird Thing is delightful , and I feel surprisingly invested in @xkcdbracket's results." (The link was removed sometimes before Monday the 10th of August 2015. within two weeks of the brackets final result was revealed.) The song Space Weird Thing is a tribute to David Bowie 's Space Oddity rewritten in the simple language used in this comic, which is also attributed in the text about the YouTube video. The other news item is related to 1529: Bracket , see that comic for more details. US Space Team's Up Goer Five The only flying space car that's taken anyone to another world (explained using only the ten hundred words people use the most often) [A list of Saturn-V parts, top to bottom, with their "Up Goer" description follows.] [Launch Escape System (LES)]: Thing to help people escape really fast if there's a problem and everything is on fire so they decide not to go to space [LES side nozzle]: Thing to control which direction the escaping people go [LES fuel]: Stuff to burn to make the box with the people in it escape really fast [LES bottom nozzles]: Place where fire comes out to help them escape [Apollo spacecraft.] [Command Module (CM)]: Part that flies around the other world and comes back home with the people in it and fall in the water. [CM capsule parts]: People box, door, chairs [Service Module (SM)]: Part that goes along to give people air, water, computers and stuff. It comes back home with them but burns up without landing. [SM oxygen tanks]: Cold air for burning (and breathing). This part had a VERY big problem once. [Lunar Module (LM)]: Part that flies down to the other world with two people inside [LM descent stage]: Part that stays on the other world (it's still there) [LM feet]: Feet that go on the ground of the other world [Instrument Unit]: Ring holding most of the computers [S-IVB third stage]: Part that falls off third (this part flew away from our world into space and hit the world we were going toward) [Fuel tanks]: Wet and very cold [Liquid hydrogen (LH2) tank]: The kind of air that once burned a big sky bag and people died and someone said "Oh, the [humans]!" (used for burning) [Liquid oxygen (LOX) tank]: The part of air you need to breathe, but not the other stuff (used for burning) [Helium pressurizing tanks]: Things holding that kind of air that makes your voice funny (it's for filling up the space left when they take the cold air out to burn it.) [J-2 engine nozzle]: Fire comes out here [S-II second stage]: Part that falls off second [LH2 tank]: More sky bag air (for burning) ( cold + wet) [LOX tank]: More breathing-type air (for burning) ( cold + wet) [Tank-to-engine fuel lines]: Thing that brings in cold wet air to burn [J-2 engine nozzles (qty. 5)]: Fire comes out here [S-IC first stage]: Part that falls off first [LOX tank]: More breathing-type air (for burning) ( cold + wet) [Helium pressurizing tank]: More funny voice air (for filling up space) [LOX fill line]: Opening for putting in cold wet air [RP-1 fuel tank]: This is full of that stuff they burned in lights before houses had power.It goes together with the cold air when it's time to start going up. [F-1 engine nozzles (qty. 5)]: Lots of fire comes out here. [Bottom of spacecraft]: This end should point toward the ground if you want to go to space. If it starts pointing toward space you are having a bad problem and you will not go to space today.

Logic Boat

Logic Boat

https://www.xkcd.com/1134

https://www.explainxkcd.com/wiki/index.php/1134:_Logic_Boat

[A person shows up at a boat docked at the edge of a river. The person has brought along a head of cabbage, a goat, and a wolf.] Problem: The boat only holds two, but you can't leave the goat with the cabbage or the wolf with the goat. [The wolf looks curiously at the cabbage that's been left behind while the person goes off with the goat.] Solution: 1. Take the goat across. [The goat remains tied up on the far side. The wolf watches the person come back.] 2. Return alone. [The wolf sits and waits as the person goes off.] 3. Take the cabbage across. 4. Leave the wolf. Why did you have a wolf? [The wolf goes off.]

The comic is a play on the classic wolf, goat and cabbage puzzle belonging to the river crossing puzzles , and first known from Propositiones ad Acuendos Juvenes , with the same setting as here. The three possessions change between various retellings but it typically involves a carnivorous animal (wolf, lion etc.), a herbivore (goat, sheep, chicken, goose etc.), and some plant based food (cabbage, grain, beans etc.). The objective is to ferry all three possessions to the other side of a river safely in a small boat , with the limitation of only being able to transport one possession per crossing. The crossing order must take into account that the carnivore would eat the herbivore if left alone together, and the herbivore would eat the food. The traditional solution would be: (Note that, since the conditions for this problem are symmetric, an alternate solution would be to transport the wolf on Trip 3 and the cabbage on Trip 5.) By leaving the wolf behind, four steps are saved — the comic's "step 4" is just a comment — and the troublesome wolf, a wild and dangerous animal not usually kept by humans, is eliminated from the picture. This could be seen a jab on the common assumption that logic puzzles only have one correct solution. Thus one often keeps the other person thinking and guessing until they arrive at the pre-defined solution, no matter how many other creative good solutions they come up with. Also note that the "problem" given doesn't even state an objective, just three prerequisites. Alternatively, this could be a jab at the fact that the conditions of some puzzles are very strange. Both the fourth step and title text are evidence of this - questioning why you would have a wolf or a cabbage respectively. Yet, even though it is unlikely that you would ever find yourself in the situation and odd rules as stated by the puzzle in real life, [ citation needed ] the puzzle demands that you solve it and reach the criteria it asks. The title text says that cabbages are also unnecessary, but goats are fine. The reasons for these opinions are less obvious than the one about the wolf, but still understandable. Many people, presumably including the narrator, do not like the taste of cabbage. Many are also fond of goats, finding them cute. The same opinion about goats is in 1282: Monty Hall . The river crossing puzzle was the main focus of 2348: Boat Puzzle . It was referenced in 589: Designated Drivers . [A person shows up at a boat docked at the edge of a river. The person has brought along a head of cabbage, a goat, and a wolf.] Problem: The boat only holds two, but you can't leave the goat with the cabbage or the wolf with the goat. [The wolf looks curiously at the cabbage that's been left behind while the person goes off with the goat.] Solution: 1. Take the goat across. [The goat remains tied up on the far side. The wolf watches the person come back.] 2. Return alone. [The wolf sits and waits as the person goes off.] 3. Take the cabbage across. 4. Leave the wolf. Why did you have a wolf? [The wolf goes off.]

Arachnoneurology

Arachnoneurology

https://www.xkcd.com/1135

https://www.explainxkcd.com/wiki/index.php/1135:_Arachnoneurology

[Beret Guy holding a protractor and handling a fork-like stand with black knobbly protrusions. On the table is some sticks, a set square and a ruler. There is also a large book titled: Spider Psychology [Beret Guy places his creation in a cobwebbed corner.] [Spiders weave webs around Beret Guy's creation. One of them hangs down above it from the ceiling.] [Beret Guy pulls a shirt made of spider silk away from his creation. At the top of the panel is a frame that breaks the main panels frame. Inside this it says:] Six weeks later:

Beret Guy uses spider psychology (that he has obviously learned from the heavy volume of a book lying on the table with that title) to engineer a forked object in such a way that spiders will weave a silk shirt around it. After six weeks he can take the finished shirt off the "rack", and after optionally removing some stray spiders it should be ready for use. Usually extracting spider silk is a complicated process and getting enough to weave a shirt would take very long and be very expensive. But making such an impossible project work is a typical behavioral pattern for Beret Guy, who continues to do amazing things with animals and other things from nature. The prefix arachno- means "(related to) spiders". Arachnology , for example, is the scientific study of spiders. Neurology is a branch of medicine dealing with disorders of the nervous system , which includes the brain . So the title of the comic can be translated into the scientific study of spider brains . The title text mentions the book lying on the table, giving not only the title and the edition (21st) but also summing up some more (non-existent and increasingly far-fetched) fields of science related to spiders, which may as well exist if spider psychology has such a big standard work. Apart from adding the word forensic in one case, all five fields come from combining only the same two words "arachno" and "neuro" (sometimes one of them more than once) and ending any combination with "-ology". Especially funny is the neuro-arachnoneurology, which is explained to be the field where it is the brains of the scientist who study spiders brains, that are examined. The last one seems to be related to arachnophobia , the fear of spiders, as arachnoarachnology is spiders with spiders on top - i.e. too many spiders . Arachnophobia seems to be a problem for Randall himself, according to the What if? Spiders vs. the Sun . In this he links to an article about a factory that was covered in plenty enough spider web silk to make shirts to a whole regiment of soldiers. This is the first comic with special mentioning of a science related directly to spiders. The next was 1747: Spider Paleontology . [Beret Guy holding a protractor and handling a fork-like stand with black knobbly protrusions. On the table is some sticks, a set square and a ruler. There is also a large book titled: Spider Psychology [Beret Guy places his creation in a cobwebbed corner.] [Spiders weave webs around Beret Guy's creation. One of them hangs down above it from the ceiling.] [Beret Guy pulls a shirt made of spider silk away from his creation. At the top of the panel is a frame that breaks the main panels frame. Inside this it says:] Six weeks later:

Broken Mirror

Broken Mirror

https://www.xkcd.com/1136

https://www.explainxkcd.com/wiki/index.php/1136:_Broken_Mirror

[Black Hat and Cueball stand in a bedroom. There is a broken mirror on the floor at Black Hat's feet.] Black Hat: Oops. Guess this means seven more years of the illusion that my actions somehow influence the indifferent hand of probability which governs our lives. [Black Hat looks down at the broken shards of glass on the floor.] Cueball: Plus like half an hour of sweeping. Black Hat: No, I think I'll leave it. Cueball: You'll get glass in your feet. Black Hat: Eccles. 9:2—All things come alike to all: to the clean, and to the unclean. Black Hat: My fate is as these shards. Cueball: Dude, chill. It's just a vanity mirror. Black Hat: All is vanity mirrors. Judging from the damage done to the wall and the way the mirror landed face up, it is likely that Black Hat intentionally broke the mirror. The way Cueball and Black Hat appears and the subject has some similarities to the next comic 1137: RTL . See the trivia section for that comic.

It is a common superstition that breaking a mirror will result in 7 years of bad luck. Black Hat mocks the superstition, claiming that all is random, but ultimately cause the superstition to become true as his nihilistic apathy prevents him believing that cleaning the glass on the floor will have a significant impact. The joke is that Black Hat will likely get glass in his feet as long as he refuses to clean it, and thus the broken mirror will have a lasting impact. Black Hat breaks a mirror and sarcastically claims that it will bring bad luck for 7 years, implying that the broken mirror will have no impact on his life. After Cueball reminds Black Hat that the broken mirror will at least cause him to clean up the glass. Black Hat responds with a quote from Ecclesiastes that explains "being clean" (doing good) or "being unclean" (doing bad) things does not affect whether good or bad things happen to us. Due to Black Hat's interpretation of Ecclesiastes , he is not going to clean the shards, and thus be "unclean", and feels nihilistically that this will not significantly alter his life. Of course, it will have an impact as he will get glass in his feet if he does not clean it. Black Hat continues saying that "My fate is as these shards" this mirrors another quote from Ecclesiastes "For what happens to the sons of men also happens to animals". Cueball tries to cheer up Black Hat by reminding him that life is not that bad, "it's just a vanity mirror". Black Hat responds saying, " All is vanity mirrors". "All is vanity" another quote from Ecclesiastes, this line is repeated throughout the book and refers to impermanence of man and his creations. As the mirror just broke, its impermanence is apparent. It is possible that this is a reference to the now-defunct webcomic Men in Hats and its character Aram, specifically in this page . Aram has been described as the inspiration for Black Hat in 29: Hitler . In the title text Cueball says "I see you're in this mood again" to which Black Hat responds, "I am always in this mood". This is a reference to Black Hat being a nihilist in his other appearances. Breaking mirrors is also mentioned in 2447: Hammer Incident . The rejection of the idea that good things happen to good people, and therefore the rejections of concepts like karma, is one of the primary tenets of the Abrahamic faiths. The argument goes that if people deserve what happens to them, then they don't deserve help. This, and the pursuit of justice (fairness, and truth) are the core beliefs that prescribe that each person has an individual responsibility to help others, so that justice can be achieved. Since Black Hat is by no means charitable, this belief clearly never took root. [Black Hat and Cueball stand in a bedroom. There is a broken mirror on the floor at Black Hat's feet.] Black Hat: Oops. Guess this means seven more years of the illusion that my actions somehow influence the indifferent hand of probability which governs our lives. [Black Hat looks down at the broken shards of glass on the floor.] Cueball: Plus like half an hour of sweeping. Black Hat: No, I think I'll leave it. Cueball: You'll get glass in your feet. Black Hat: Eccles. 9:2—All things come alike to all: to the clean, and to the unclean. Black Hat: My fate is as these shards. Cueball: Dude, chill. It's just a vanity mirror. Black Hat: All is vanity mirrors. Judging from the damage done to the wall and the way the mirror landed face up, it is likely that Black Hat intentionally broke the mirror. The way Cueball and Black Hat appears and the subject has some similarities to the next comic 1137: RTL . See the trivia section for that comic.

RTL

‮LTR

https://www.xkcd.com/1137

https://www.explainxkcd.com/wiki/index.php/1137:_RTL

[Cueball is standing behind Black Hat who is sitting down with a laptop on his lap.] Cueball: And that's not even the worst part! The worst part is that— Black Hat types a command on the PC: U+202e Cueball: ‮—They didn't even... Cueball: ‮...What the hell? Cueball: ‮How did you... Cueball: ‮...Asshole.

U+202e is a unicode control character that changes all subsequent text to right-to-left (RTL, as the title references). In the comic, Black Hat tires of Cueball 's complaining and inserts a U+202e character in the middle of Cueball's speech, turning his complaints into gibberish - sentences that must be read from right-to-left. The title of the comic builds on this theme, with the title of the webpage it is hosted on being LTR in some browsers (see trivia ), the reverse of the comic name. What Cueball actually tries to say after Black Hat's change is: — They didn't even... ...What the hell? How did you... ...Asshole. When multiple writers work on the same text, arguments can often arise with some writers resorting to vandalizing the works of other writers. The title text takes this up a level, suggesting the use of U+202e and other direction control characters in editor wars to disrupt other people's work. If you ever get involved in such a war, note that U+202c returns text back to its normal direction. [Cueball is standing behind Black Hat who is sitting down with a laptop on his lap.] Cueball: And that's not even the worst part! The worst part is that— Black Hat types a command on the PC: U+202e Cueball: ‮—They didn't even... Cueball: ‮...What the hell? Cueball: ‮How did you... Cueball: ‮...Asshole.

Heatmap

Heatmap

https://www.xkcd.com/1138

https://www.explainxkcd.com/wiki/index.php/1138:_Heatmap

[Three near-identical charts of the 48 contiguous United States are shown with heatmaps depicting population density. The first chart is labelled "Our site's users," the second chart is labelled "Subscribers to Martha Stewart Living ," and the third chart is labelled "Consumers of furry pornography." Cueball is standing with a stick pointing at the charts.] Cueball: The business implications are clear. Pet peeve #208: Geographic profile maps which are basically just population maps

Another of Randall's many Pet Peeves , this time on maps . This one has also been numbered #208, like the first comic on the subject 238: Pet Peeve #114 . In the comic, Cueball compares three heatmaps, showing the location of "our site's users," "subscribers to Martha Stewart Living " and "consumers of furry pornography." The three maps are nearly identical, leading Cueball to come to the conclusion that his site's userbase largely consists of fans of Martha Stewart and furry porn, and that the audience (presumably the owners/operators of the website) should adjust their content or advertising to cater to these demographics. However, Cueball's analysis is faulty; the actual reason the maps are the same is they all match the population concentration in the U.S., not because there is any statistically-significant relation between geographic location and any of the mentioned sub-populations. A heatmap is a graph showing three-dimensional data on a two-dimensional image, with each pixel's colour representing the value of the data at that position. It does not necessarily have anything to do with heat, but a heatmap may resemble a thermal image. In this comic, red represents the highest numerical values, then yellow and green, with white the lowest values, in all three maps. The title text reflects a similar situation in world maps where the website written in English is read by English-speaking users no matter the location, because their ISP and search providers direct them primarily to English websites, so the visitors' geographic graph matches the graph of the global English-speaking population. [Three near-identical charts of the 48 contiguous United States are shown with heatmaps depicting population density. The first chart is labelled "Our site's users," the second chart is labelled "Subscribers to Martha Stewart Living ," and the third chart is labelled "Consumers of furry pornography." Cueball is standing with a stick pointing at the charts.] Cueball: The business implications are clear. Pet peeve #208: Geographic profile maps which are basically just population maps

Rubber and Glue

Rubber and Glue

https://www.xkcd.com/1139

https://www.explainxkcd.com/wiki/index.php/1139:_Rubber_and_Glue

[Playground. Young Megan is balancing on a swing, two Cueball-like kids are swinging and two more kids, a young Cueball and a young Hairy are approaching a reading young Black Hat, whose hat is almost too big for his small head.] Hairy: Whatchya reading, Hatboy? Black Hat: The CRC Handbook of Chemistry and Physics. Cueball: You are such a loser, it's painful . Black Hat: I'm rubber, you're glue. [In a frame-less panel Hairy and Cueball looks down on Black Hat sitting with his book in his lap on the ground between them. He looks back up over his shoulder at Hairy.] Hairy: Yeah, well— Black Hat: Glue can't speak. Black Hat: You try to scream, but your mouth fills with glue. Black Hat: Your face is glue. Your body is glue. [Black Hat has left the book on the ground behind him and has risen. Hairy and Cueball is now together to the right and Black Hat advances towards them arms stretched out. Hairy steps backwards away from him.] Black Hat: I wrap my rubber arms around your sticky bulk. Black Hat: Your neoprene base bonds instantly with my surface. Black Hat: Never to let go. [Zoom in on Black Hat's head. He is holding his arms up in front of him clapping them together. Hairy shouts from off panel.] Black Hat: You are glue. I am rubber. Black Hat: Staring at you with my dead, rubber eyes- Black Hat: Forever. Hairy (off-panel): Moooom!

"I'm rubber, you're glue; whatever you say bounces off me and sticks to you" is a school-ground retort used by children to suggest that one's insults are being ignored by the intended recipient of the insult and counter that the insult rather refers to the insulter . On a deeper level, it may imply that a person insulting others is an indication of their own insecurity and weakness. In this comic, a young Black Hat is reading a chemistry and physics handbook, which leads to a literal and graphic visualization of the phrase. He uses the retort to frighten the children bullying him (young versions of Hairy and Cueball ). Black Hat takes the traditional saying and twists it into a creepy thought by saying that they are both literally glue and rubber and that they are permanently stuck together, which scares Hairy and Cueball and prompts them to call for their mothers. The book is the CRC Handbook of Chemistry and Physics . It is also nicknamed the 'Rubber Bible' or the 'Rubber Book', as CRC originally stood for "Chemical Rubber Company". The title text says that I (meaning him) and you (Hairy and Cueball, although it could possibly be the reader) are both rubber. Rubber is not a living object, so it is stuck in "vulcanized horror" in the position it was sculpted in. This could be a reference to how powerless we are in the changing of the world. Young Black Hat also taunts young Hairy later in 1753: Thumb War . [Playground. Young Megan is balancing on a swing, two Cueball-like kids are swinging and two more kids, a young Cueball and a young Hairy are approaching a reading young Black Hat, whose hat is almost too big for his small head.] Hairy: Whatchya reading, Hatboy? Black Hat: The CRC Handbook of Chemistry and Physics. Cueball: You are such a loser, it's painful . Black Hat: I'm rubber, you're glue. [In a frame-less panel Hairy and Cueball looks down on Black Hat sitting with his book in his lap on the ground between them. He looks back up over his shoulder at Hairy.] Hairy: Yeah, well— Black Hat: Glue can't speak. Black Hat: You try to scream, but your mouth fills with glue. Black Hat: Your face is glue. Your body is glue. [Black Hat has left the book on the ground behind him and has risen. Hairy and Cueball is now together to the right and Black Hat advances towards them arms stretched out. Hairy steps backwards away from him.] Black Hat: I wrap my rubber arms around your sticky bulk. Black Hat: Your neoprene base bonds instantly with my surface. Black Hat: Never to let go. [Zoom in on Black Hat's head. He is holding his arms up in front of him clapping them together. Hairy shouts from off panel.] Black Hat: You are glue. I am rubber. Black Hat: Staring at you with my dead, rubber eyes- Black Hat: Forever. Hairy (off-panel): Moooom!

Calendar of Meaningful Dates

Calendar of Meaningful Dates

https://www.xkcd.com/1140

https://www.explainxkcd.com/wiki/index.php/1140:_Calendar_of_Meaningful_Dates

Calendar of Meaningful Dates Each date's size represents how often it is referred to by name (e.g. "October 17th") in English-language books since 2000 (Source: Google ngrams corpus) [A regular Gregorian calendar laid out in a grid, Sunday first, on a leap year, with some numbers larger than others.]

The calendar used in the comic is the standard Gregorian calendar used by most of Western Civilization. The comic looks at the frequencies of which dates appear in English writings indexed in the Google Books Library Project , by using the Google Ngram Viewer ( link ). Some dates are more (or less) frequently mentioned because they have a special significance. Other dates have correlations for which there doesn't appear to be any obvious reasons. September 11th, which is noted in the title text for being popular before the 9/11 attack, has also been the date of 2 significant battles in the War of 1812, one where the British landed in what was George Washington's large plantation, which likely contributed to its search volume. The date mentioned in the sub-heading (October 17th) is Randall's birthday. The title text mystery is explained here . In summary, many occurrences of "11th" in the writings were actually misread by the Google Books Library Project's optical character recognition software and/or reCAPTCHA users, becoming one of these: IIth , Ilth , iith , lith , llth , 1lth , 1ith , l1th , nth . The first of each month is generally more mentioned than others, perhaps because such dates are markers of a new month and may be used as landmark dates or deadlines. Similarly, the final day of each month is commonly a deadline day. Other dates have a less mundane significance, for example: Calendar of Meaningful Dates Each date's size represents how often it is referred to by name (e.g. "October 17th") in English-language books since 2000 (Source: Google ngrams corpus) [A regular Gregorian calendar laid out in a grid, Sunday first, on a leap year, with some numbers larger than others.]

Two Years

Two Years

https://www.xkcd.com/1141

https://www.explainxkcd.com/wiki/index.php/1141:_Two_Years

[Randall and Randall's fiancée sit on a bed, Randall's fiancée is talking on the phone. The person she is talking to, a doctor holding a clipboard, is shown inset.] Randall's fiancée: Oh god. [Randall and Randall's fiancée sit together while Randall's fiancée, now bald, is receiving chemotherapy. They are both on their laptops.] IV pump: ... Beeep ... Beeep ... Beeep ... [Randall and Randall's fiancée (who is wearing a knit cap) are paddling a kayak against a scenic mountain backdrop.] [Randall and Randall's fiancée sit at a table, staring at a cell phone. There is a clock on the wall. Her head is stubbly.] Randall's fiancée: How long can it take to read a scan!? [Randall and Randall's fiancée are back at the hospital again, Randall's fiancée receiving chemo. They are playing Scrabble.] Randall: "Zarg" isn't a word. Randall's fiancée: But caaaancer. Randall: ...Ok, fine. [Randall and Randall's fiancée (wearing a knit cap) are listening to a Cueball-like friend. A large thought bubble is above their heads and it obscures the friends talk. The text below, split in three is the only part there can be no doubt about:] Friend: So next year you should come visit us up in the mounta a and Randall and Randall's fiancée (thinking): "Next year" [Randall and Randall's fiancée are getting married, with a heart above their heads. Randall's wife's hair is growing back.] [Randall and Randall's wife (wearing a knit cap) stand on a beach, watching a whale jump out of water.] Fwoosh [Randall's wife is sitting at a desk with her laptop standing on top of two books. Her hair has grown back a little more. Randall stands behind her.] Randall: Hey— Randall: you're doing science, Randall: and you're still alive. Randall's wife: Yeah! [Randall and Randall's wife sit under a tall tree on a hill.] Randall: It's really only been two years? Randall's wife: They were big years. [Randall and Randall's wife sit at a table in a fancy restaurant. Her hair has grown back even more. The waiter (Hairy) brings them a dish with a cover on it.] Waiter: Happy... Anniversary? Randall's wife: Biopsy-versary! Waiter: ...Eww. While it is known that Randall's wife has since survived more than two years past the date of the invitation in Panel 6, it is unknown whether the invitation was later accepted. The followup comic Seven Years does not seem to include a visit "up in the mountains" among its various other recreational activities, but the one after it, Ten Years , does. However, since it is possible that the invitation was made up for the comic in order to represent the worry over any invitation envisioning the future at that time, it is possible that it was never proposed as depicted in the comic. Therefore, the real life invitation(s) which inspired the inclusion of Panel 6 in the comic could perhaps have referred in real life to an activity that is actually depicted in Seven Years or Ten Years , or to some other activity, which then may or may not have been realized.

This comic marks the second year of Randall Munroe 's wife's battle with cancer, and appears to depict actual events from those two years. Randall is depicted as Cueball and his wife as Megan , as usual for both. This comic later became part of a series of comics directly continued in 1928: Seven Years and later continued in 2386: Ten Years . The first eight panels of this comic are included in the next two, although slightly grayed out. Explanations of the individual panels: The title text is referring to a possible side-effect of chemotherapy drugs , the inability to concentrate. It could also just be the fact that the chemo can make you feel just terrible. When whatever effect kicks in, she loses the rest of their Scrabble games for that day. However, as we see in panel 5, there is a reason why she wins all of the first half of their games. But this is not enough, or she even forgets to play on the cancer, when the drugs take effect. The use of the asterisk in the title text for "*dominated*" might be a reference to the 1999 game Unreal Tournament in which the game announcer voice would from time to time use the words "dominating" or "dominated" in a deep tone when a player is doing really well in the game (for example being on a multi-kill strike). Example sound here . Knit caps have only been used a few times in xkcd, most prominently on Knit Cap Girl in 1350: Lorenz , see her section for more details. [Randall and Randall's fiancée sit on a bed, Randall's fiancée is talking on the phone. The person she is talking to, a doctor holding a clipboard, is shown inset.] Randall's fiancée: Oh god. [Randall and Randall's fiancée sit together while Randall's fiancée, now bald, is receiving chemotherapy. They are both on their laptops.] IV pump: ... Beeep ... Beeep ... Beeep ... [Randall and Randall's fiancée (who is wearing a knit cap) are paddling a kayak against a scenic mountain backdrop.] [Randall and Randall's fiancée sit at a table, staring at a cell phone. There is a clock on the wall. Her head is stubbly.] Randall's fiancée: How long can it take to read a scan!? [Randall and Randall's fiancée are back at the hospital again, Randall's fiancée receiving chemo. They are playing Scrabble.] Randall: "Zarg" isn't a word. Randall's fiancée: But caaaancer. Randall: ...Ok, fine. [Randall and Randall's fiancée (wearing a knit cap) are listening to a Cueball-like friend. A large thought bubble is above their heads and it obscures the friends talk. The text below, split in three is the only part there can be no doubt about:] Friend: So next year you should come visit us up in the mounta a and Randall and Randall's fiancée (thinking): "Next year" [Randall and Randall's fiancée are getting married, with a heart above their heads. Randall's wife's hair is growing back.] [Randall and Randall's wife (wearing a knit cap) stand on a beach, watching a whale jump out of water.] Fwoosh [Randall's wife is sitting at a desk with her laptop standing on top of two books. Her hair has grown back a little more. Randall stands behind her.] Randall: Hey— Randall: you're doing science, Randall: and you're still alive. Randall's wife: Yeah! [Randall and Randall's wife sit under a tall tree on a hill.] Randall: It's really only been two years? Randall's wife: They were big years. [Randall and Randall's wife sit at a table in a fancy restaurant. Her hair has grown back even more. The waiter (Hairy) brings them a dish with a cover on it.] Waiter: Happy... Anniversary? Randall's wife: Biopsy-versary! Waiter: ...Eww. While it is known that Randall's wife has since survived more than two years past the date of the invitation in Panel 6, it is unknown whether the invitation was later accepted. The followup comic Seven Years does not seem to include a visit "up in the mountains" among its various other recreational activities, but the one after it, Ten Years , does. However, since it is possible that the invitation was made up for the comic in order to represent the worry over any invitation envisioning the future at that time, it is possible that it was never proposed as depicted in the comic. Therefore, the real life invitation(s) which inspired the inclusion of Panel 6 in the comic could perhaps have referred in real life to an activity that is actually depicted in Seven Years or Ten Years , or to some other activity, which then may or may not have been realized.

Coverage

Coverage

https://www.xkcd.com/1142

https://www.explainxkcd.com/wiki/index.php/1142:_Coverage

[Cueball is looking at a phone.] Cueball: Man, the coverage here is awfu— [Another man punches Cueball.] [Caption below the panel:] Faraday cagematch

The caption "faraday cagematch" is a portmanteau of "faraday cage" and "cagematch". A Faraday cage is a cage of conducting material that interferes and blocks out electromagnetic radiation like cell phone signals, provided the material is of the appropriate thickness and the gaps between the "bars" are significantly smaller than the wavelength of the radiation. A cage match is a type of professional wrestling match in which the participants fight in a ring enclosed by a metal cage. The comic caption is a play on the two terms, putting Cueball into a cage match in the Faraday cage that is blocking his reception. Also the fact that Cueball gets hit in the face immediately after stating that the coverage is awful might be a joke about the different meanings of the word cover, boxing for example the word cover-up is a defensive technique, while phone coverage refers to the connection quality of his phone to the mobile phone network. The fact that Cueball, obviously referring to his phone signal, complains about awful coverage (caused by the faraday cage) while his head is also badly or not at all covered (caused by himself), which allows his opponent to strike him, might be described as ironically comedic. The title text is a play on a rule in cage matches that states that a participant wins if they are first to escape the cage. Tunneling diodes are capable of fast operation, allowing a device to generate high frequency signals, which are more capable of penetrating the mesh openings in a Faraday cage. Randall uses Faraday cages again in Faraday Tour . [Cueball is looking at a phone.] Cueball: Man, the coverage here is awfu— [Another man punches Cueball.] [Caption below the panel:] Faraday cagematch

Location

Location

https://www.xkcd.com/1143

https://www.explainxkcd.com/wiki/index.php/1143:_Location

[Three people around a computer. One of them is typing.] Typing: Hey, party tonight? Typing: We'd all love to come see your new place! Reply (through monitor): Wait, what? [Cut to guy sitting at a laptop.] Reply (through the guy's monitor): We want to hang out! Guy typing: We're not, like, good friends. Reply (through the guy's monitor): I know, but we were thinking about it and we really like you! [Cut back to the three friends.] Typing: You should have us over tonight! Typing: For, like, an hour. Typing: It'll be fun! Reply (through monitor): Well, uh, sure. [Cut to color-inverted image of the guy's house. Four Enlightened-controlled Ingress portals are in the guy's back yard.] Friends (off-screen): YESSSS! Guy (from inside his house): I still don't get why you're suddenly so excited to hang out.

Ingress is an augmented reality location-based service game in which players have to visit certain real-world places marked by the game as containing in-game objectives called portals (much like in its far more well-known offspring Pokemon GO). The single guy in the comic owns a home surrounded by an abundance of portals, which makes it an attractive destination for the three friends who contact him via the computer. They are obviously not really friends of the guy, but just wish to come by because of the portals. The portals in the comic are controlled by the green "Enlightened" team (and have links and a field), making them valuable resource caches for the "Enlightened" team, and priority targets for the blue "Resistance" team. Foursquare , referenced in the title text, is another service that lets users check into places they visit for discounts in a similar way to how Ingress players visit portals for points. Unlike Foursquare places, which are businesses and public places such as parks, Ingress portals also include historic houses that are still private residences, as well as churches, so Ingress is more likely to reward people visiting a friend's house. "Space noises" refers to the ambient sounds when playing Ingress. [Three people around a computer. One of them is typing.] Typing: Hey, party tonight? Typing: We'd all love to come see your new place! Reply (through monitor): Wait, what? [Cut to guy sitting at a laptop.] Reply (through the guy's monitor): We want to hang out! Guy typing: We're not, like, good friends. Reply (through the guy's monitor): I know, but we were thinking about it and we really like you! [Cut back to the three friends.] Typing: You should have us over tonight! Typing: For, like, an hour. Typing: It'll be fun! Reply (through monitor): Well, uh, sure. [Cut to color-inverted image of the guy's house. Four Enlightened-controlled Ingress portals are in the guy's back yard.] Friends (off-screen): YESSSS! Guy (from inside his house): I still don't get why you're suddenly so excited to hang out.

Tags

Tags

https://www.xkcd.com/1144

https://www.explainxkcd.com/wiki/index.php/1144:_Tags

<div>Q: How do you annoy a web developer?</span>

HTML is a markup language used in web development, and is the subject of this comic. The comic employs multiple poor HTML practices while asking the rhetorical question of how best to annoy web developers, effectively answering the question that it poses. In HTML, all elements (except self-closing elements like <img> ) should consist of an open and close tag of the same type <div>Like this</div> . HTML (except in its formulation as an XML language—XHTML) has never been case-sensitive, but the practice of using uppercase tags for readability is long outmoded, and the mixing of cases in this example would definitely annoy a developer. Another basic idea of HTML is that all elements should be properly nested. That is, any element whose open tag occurs inside a div must be closed before the div is closed. NB: In practice, web browsers will error-correct nearly all these problems. The rules of proper nesting also put restrictions on which tags can be placed where — "block" elements, such as <div> cannot be placed inside "inline" elements, such as <span> , and inline elements must be placed inside a block element of some kind. Thus, <span><div> is forbidden, even if the tags are closed in the proper order. Further, web developers make a distinction between semantic and structural elements. Semantic elements contain a clue in their name as to what kind of an element they are — for example, an <article> tag contains an article, such as a blog post or news article, while an <ol> tag contains an o rdered l ist. (It's wise to note that this is not an absolute rule; it's possible to put non-article content in an <article> , it's just not recommended.) Semantic tags do not, however, indicate how their contents are to be displayed; your browser might display an <article> in the default font, layout, and placement, while mine, a screen reader , might ignore everything on the page except <article> s, and read <article> s in a soothing voice . Structural tags, on the other hand, give no clues as to what they contain; they just indicate how a web page is to be laid out. <span> and <div> are structural tags; they can contain anything. Their definitions in HTML simply indicate that <div> is a block tag (it can affect both what the text looks like and where it is on the page; by default, it is displayed in a separate block from the rest of the text in the page, and has at least one line break before and after its display) and <span> is an inline tag: it affects what its text looks like, but not where it is on the page. Without additional attributes, it's impossible for a browser to tell what's supposed to be inside a <div> or a <span> , which means that my screen reader can't just pluck out the blog posts and read those.

Sky Color

Sky Color

https://www.xkcd.com/1145

https://www.explainxkcd.com/wiki/index.php/1145:_Sky_Color

[Science Girl and her mother, Megan, but with her hair up. Megan is at a desk and facing the girl.] Science Girl: Mommy, why is the sky blue? Megan: Rayleigh scattering! Short wavelengths get scattered way more (proportional to 1/ λ 4 ). Blue light dominates because it's so short. Science Girl: Oh. Science Girl: So why isn't the sky violet? Megan: Well, because, uh... ...hmm. [Caption Below the panel:] My hobby: Teaching tricky questions to the children of my scientist friends.

The point of this comic is that often, curious children ask their parents simple questions about understanding how the world works. Often, although the question is simple, the answer is not. "Why is the sky blue?" is a common example, since most parents are not familiar with Rayleigh scattering , and thus are unable to answer the question. Randall 's hobby is to make those questions even harder, so that the parents who are familiar with the subject (scientists, for example) will be stumped. Another point of this comic is that we often think that we understand a scientific phenomenon (e.g. why is the sky blue?); however, a certain simple question (e.g. why isn't the sky violet?) can often uncover large gaps in our actual understanding. Rayleigh scattering is the phenomenon that explains the color of the sky, where light of every wavelength gets scattered in the air by the inverse quartic (fourth power) of its wavelength as given in the comic. In the visible spectrum , blue light has a wavelength of 450–495 nm while violet has a shorter wavelength of 380–450 nm. Violet light does indeed get scattered more than blue light, however the lower portion of the spectrum for sunlight consists of blue light and eyes are much more sensitive to blue light than violet light. Furthermore, the sunlight contains more blue than violet to begin with as a result of the surface temperature of the sun. This leaves the impression of a blue sky. A good explanation, including why blue and not violet, can be found in Usenet Physics FAQ :: Why is the sky blue? , but note that human color perception is more complicated than described there. The title text refers to a mirror image , and is discussed by the famous American theoretical physicist Richard Feynman in a famous BBC documentary [1] , as one of the problems which he used to have fun with first years (British English for first year student or freshman). A mirror image is a virtual image produced by the reflection of light on a mirror. It's common to think of images in mirrors as being reversed left-to-right, as any text held in front of us will appear flipped. This is actually an issue of perception. In a plane mirror, images are reflected directly: the left side of your body will be reflected in the left side of the mirror, and vice-versa. The source of confusion is that people tend to think of a mirror image the way we would think of a person facing us. When another person faces us, they turn around the vertical axis, placing their right hand on our left side, so seeing our left hand on our left side in a reflection seems like an inversion, even though it's a direct representation. By the same token, in order to hold text up to a mirror, we generally flip it around the vertical axis, so that the start of the text is on right, and the end on the left (in English, at least). When the mirror reflects this, we see the text as backward, but the mirror hasn't reversed it, we reverse it when we turn it toward a mirror. In other words, the vertical axis is only "special" because we're used to objects turning around it, so we come to expect that reversal, instead of a reflection. You can induce a mirror to reverse left and right only --- by standing next to it instead of in front of it, facing along the plane of the mirror itself. If you lift your right arm, you can clearly see your image's left arm raising, without having to adjust for frame of reference. Similarly, you can induce a mirror to reverse top and bottom only by holding it flat above your head or laying it flat on the ground and standing on it (or perhaps standing under a suitably equipped bedroom ceiling). See this video for a demonstration. [Science Girl and her mother, Megan, but with her hair up. Megan is at a desk and facing the girl.] Science Girl: Mommy, why is the sky blue? Megan: Rayleigh scattering! Short wavelengths get scattered way more (proportional to 1/ λ 4 ). Blue light dominates because it's so short. Science Girl: Oh. Science Girl: So why isn't the sky violet? Megan: Well, because, uh... ...hmm. [Caption Below the panel:] My hobby: Teaching tricky questions to the children of my scientist friends.

Honest

Honest

https://www.xkcd.com/1146

https://www.explainxkcd.com/wiki/index.php/1146:_Honest

[Two Cueballs are walking.] Cueball: I mean, let's be honest here- Friend: Ok. [The friend is talking with his palm out.] Friend: I don't understand why anything happens and I'm confused and scared and trying really hard all the time. [The two Cueballs look at each other.] Cueball: ...Too honest. Cueball: Scale it back. Friend: Sorry.

The phrase "let's be honest here—" is often used to soften a statement that might otherwise seem crass. Before Cueball can finish his sentence, he is interrupted by his friend, who takes the opportunity to honestly state his deepest feelings. It is possible that Cueball's friend's last response, "Sorry," (which is on response to Cueball saying, "Too honest. Scale it back.") is insincere as a way of scaling his honesty back by not being honest in his next statement. The human condition is essentially terrifying, having to try to keep up appearances all the time. The title text could be a reference to angst , a word used in English to describe an intense feeling of panic — but the friend of Cueball proposes to work on a better understanding on his own fears. Randall has mentioned having ADD, such as in 1106: ADD . People with neurological or psychological problems such as ADD often express having trouble with things in everyday life that other people seem to find easy. [Two Cueballs are walking.] Cueball: I mean, let's be honest here- Friend: Ok. [The friend is talking with his palm out.] Friend: I don't understand why anything happens and I'm confused and scared and trying really hard all the time. [The two Cueballs look at each other.] Cueball: ...Too honest. Cueball: Scale it back. Friend: Sorry.

Evolving

Evolving

https://www.xkcd.com/1147

https://www.explainxkcd.com/wiki/index.php/1147:_Evolving

[Bacterial cell culture.] What? Staphylococcus aureus is evolving! ... Off-screen: Aww, crap. Staphylococcus aureus evolved into Methicillin-resistant Staphylococcus aureus!

In a Pokémon game, a player goes out in search for the eponymous creatures. Many Pokémon can be found directly in the wild, but there are also a lot of Pokémon that require training and growth, to cause them to "evolve" into new Pokémon. "Evolve," the game's term, is a misnomer which earned itself quite some controversy in the past; in reality, Pokémon "evolution" is more akin to puberty or metamorphosis, since instead of the entire species of Pokémon acquiring changes through an extended period of time, one specific member of the species grows instantly to the "higher stage." At that point in the game, the Pokémon glows before transforming into the new form, then stops glowing, and the very same text "What? XXX is evolving!" is used (see this video or those screenshots for instance). The changes of such a transformation can be quite dramatic ... or not. This comic depicts the "evolution" of bacteria as observed by a Biologist in the same format as the game Pokémon. Here we have Staphylococcus aureus , which is not a desirable bacterium (it causes Staph infections ) which evolves into "Methicillin-resistant Staphylococcus aureus " . Methicillin is an antibiotic. If the bacterium becomes resistant, it means the antibiotic will be less effective against it, making infections harder to treat. Thus the observer is not pleased with such an evolution. The title text references this by suggesting that biologists do not want bacteria to evolve in this way, as opposed to Pokémon where you put a Pokémon on the "front lines" as much as possible to gain it experience and hope it evolves. A point of irony is that Pokémon evolution can easily be prevented, by using an Everstone, or stopped, by pressing the B button in the game controller during evolution, especially if there are Pokémon that one does not want to evolve. The bit about the front lines is that, if a bacteria colony is exposed sufficiently to an antibiotic, those bacteria with any level of resistance to the antibiotic are less likely to be killed by the antibiotic, and are able to reproduce in spite of the antibiotic. Most future generations of bacteria now have this level of resistance instead of just a small subset. This makes the likelihood of future more resistant and harder to treat mutations even more likely. Staphylococcus aureus is a very common bacterium, that under an electron microscope looks like the xkcd drawing, and is the major cause of staph infections in the nostrils and skin. Hospitals are often plagued with outbreaks of Methicillin-resistant Staphylococcus aureus (MRSA), which is very difficult to treat as the typical antibiotics do not work on it. [Bacterial cell culture.] What? Staphylococcus aureus is evolving! ... Off-screen: Aww, crap. Staphylococcus aureus evolved into Methicillin-resistant Staphylococcus aureus!

Nothing to Offer

Nothing to Offer

https://www.xkcd.com/1148

https://www.explainxkcd.com/wiki/index.php/1148:_Nothing_to_Offer

[Radio on a dresser.] Radio: I have nothing to offer Radio: But Radio: Blood, toil, tears, sweat, Radio: spit, bile, vomit, urine, [Text is now bleeding through the background and gets obscured then cut off.] Radio: mucus, semen, earwax, lymph, gastric acid, sebum, pus, endolymph, intracellular fluid, blood plasma, vitreous humor, feces, pleural cavity fluid, chlye, synovial fluid, peritoneal fluid,

"I have nothing to offer but blood, toil, tears, and sweat " is a famous phrase in a speech given by Winston Churchill , which would be heard on the radio in the 1940s. The comic then goes on to list numerous other increasingly obscure bodily fluids , including through the title text, ending humorously with gin (which Churchill was partial to). The fluids in order: blood , tears , sweat , spit , bile , vomit , urine , mucus , semen , earwax , lymph , gastric acid , sebum , pus , endolymph , intracellular fluid , blood plasma , vitreous humor , feces , pleural cavity fluid , chyle , synovial fluid , peritoneal fluid , cerebrospinal fluid , pericardial fluid , sputum , aqueous humor , perilymph , chyme , hydatid fluid , interstitial fluid , and rheum . The partially obscured ones near the end are taken by process of elimination. CHLY- seems to be a typo for CHYL(E). [Replace 'gin' with 'tea' for all other Bri'ish people] [Radio on a dresser.] Radio: I have nothing to offer Radio: But Radio: Blood, toil, tears, sweat, Radio: spit, bile, vomit, urine, [Text is now bleeding through the background and gets obscured then cut off.] Radio: mucus, semen, earwax, lymph, gastric acid, sebum, pus, endolymph, intracellular fluid, blood plasma, vitreous humor, feces, pleural cavity fluid, chlye, synovial fluid, peritoneal fluid,

Broomstick

Broomstick

https://www.xkcd.com/1149

https://www.explainxkcd.com/wiki/index.php/1149:_Broomstick

[Megan wearing red shoes talking to somebody off-screen.] Off-screen: Bring me the broomstick of the Wicked Witch of the West and I'll take you home. Megan: Got it. [Megan wearing red shoes standing before steps.] Megan: You can have the slippers if you let me borrow your broom. Off-screen: Deal. [Megan carrying a broom and singing without wearing the red shoes.] [Megan flying in a balloon over three Wizard of Oz characters.] Megan: That was easy.

Megan plays the part of Dorothy , the protagonist of The Wonderful Wizard of Oz . Dorothy has been trapped in the Land of Oz due to extreme weather and must obtain transportation home. An off-screen character, presumably the Wizard of Oz himself, offers her a ride if she obtains the The Wicked Witch of the West 's magic broom. Megan wears Ruby Slippers and uses them as a bargaining chip to obtain the Witch's broom. The "little dog" offered in the title text is Dorothy's faithful companion Toto . The Wicked Witch of the West is a fictional character and the most significant antagonist in The Wizard of Oz , which is based on L. Frank Baum's children's book The Wonderful Wizard of Oz . In the 1939 version of The Wizard of Oz , the Wicked Witch flies on her broom over the Emerald City demanding Dorothy's surrender, and the Wizard demands the destruction of the Witch with her broom as proof, in exchange for granting the wishes of Dorothy and her companions. The point of the comic is to show how easily Dorothy could resolve the situation if she was willing to forsake both her traveling companions and her pet. She leaves Toto with the Witch; it is unclear whether she plans to retain possession of the broom and return it in order to collect him, or plans to abandon Toto as well. She will also leave Oz completely at the mercy of said witch by giving her the Ruby Slippers and leaving with the Wizard. It should be noted that this resolution defies the canon established in the movie, as nobody could remove the slippers as long as Dorothy lived , presumably including Dorothy herself. Additionally, it turns out that the Wizard was a fraud and was unable to take her home, and ironically it is the ruby slippers that did so. The Wizard of Oz was also referenced in Five-Minute Comics: Part 4 , and iOS Keyboard . [Megan wearing red shoes talking to somebody off-screen.] Off-screen: Bring me the broomstick of the Wicked Witch of the West and I'll take you home. Megan: Got it. [Megan wearing red shoes standing before steps.] Megan: You can have the slippers if you let me borrow your broom. Off-screen: Deal. [Megan carrying a broom and singing without wearing the red shoes.] [Megan flying in a balloon over three Wizard of Oz characters.] Megan: That was easy.

Instagram

Instagram

https://www.xkcd.com/1150

https://www.explainxkcd.com/wiki/index.php/1150:_Instagram

[Cueball, raising a hand, is talking to his Cueball-like friend who is sitting by his computer.] Cueball: I've been putting all my stuff in Chad's garage. Cueball: He has nice shelves. Cueball: And he lets me in to see it whenever I want. [In the next panel, without a frame, there is a close up of a note. Above the note is a small black frame with Cueballs comment:] Cueball (off-panel): But I got this note from him: [The note:] Dude In like a month im gonna Craigslist all that shit you left in my garage Just FYI -Chad [Zoom in on Cueball who lifts both hands palms up.] Cueball: It's an outrage! This is no way to run a storage business! Friend (off-panel): Are you paying him to look after your stuff? [Final frame almost like the first frame, but Cueball has taken his hands down.] Cueball: No. Friend: Then what he runs isn't a storage business. Cueball: Well, I'm this close to not giving him any more stuff. Friend: That'll teach him.

As indicated by the title, this comic is an allegory for a controversy over Instagram , a photo-sharing social network now owned by Facebook . In December 2012, Instagram changed their terms of use , allowing the network to sell user-uploaded images, without profit to the content generators. This infuriated many users, who closed their accounts or stopped uploading images. In the comic Cueball tells his Cueball-like friend about his problem with Chad, who just sent him a note telling him that he no longer wants to store all this stuff that Cueball has left in his garage. Cueball left it there because Chad has nice shelves and lets him in to see his stuff whenever he wishes, so that was really convenient. Chad's note tells Cueball that he has a month to move his shit — after that he will try to get rid of it by selling it on Craigslist . This is a website where individuals can contact others interested in buying or selling goods. As a verb, it means to sell something on Craigslist. ( FYI is an abbreviation of For Your Information ). Cueball is outraged, as this is not way to run a storage business . But when his friend asks him if he paid anything for this "storage business", it turns out that he did not. The friend then concludes that it is not a storage business. This is exactly the problem with Instagram (or its users). A user does not pay anything, but to create an account you have to sign a terms of service/end user license agreement. A user has thus effectively signed their consent to whatever Instagram has written. Instagram can then change these terms if they give a forewarning (as Chad has done here). However, most users don't read the terms before clicking the "I agree" option, so it can come as a shock when Instagram uses the data in a way the user hadn't anticipated. Instead of getting angry Cueball should thus just go and remove his stuff, but instead he is just going to almost (but not quite) stop giving Chad any more stuff. This is also making fun of those Instagram users that complain about the new way of using their data, but at the same time keep uploading more pictures. The users have often developed a kind of addiction, so they cannot just stop sharing their life (in pictures). In the title text Cueball continues with an idea of calling the cops. He thinks that Chad is a thief. He thus ignores that he left the stuff at Chad's house of his own accord. And after Chad has been arrested (which will of course never happen) he wishes to move all his stuff to another house, just to continue to get free storage. There are two major flaws in this logic - and it is the same with the logic of the disgruntled Instagram users. You cannot accuse Instagram of stealing because it was you who gave them the images in the first place, and it is irresponsible to assume that this will not happen if you give your photos to another free social networking service (e.g. Facebook ). These kind of issues (with Facebook as the evildoer) are also the subject of 743: Infrastructures and 1390: Research Ethics . [Cueball, raising a hand, is talking to his Cueball-like friend who is sitting by his computer.] Cueball: I've been putting all my stuff in Chad's garage. Cueball: He has nice shelves. Cueball: And he lets me in to see it whenever I want. [In the next panel, without a frame, there is a close up of a note. Above the note is a small black frame with Cueballs comment:] Cueball (off-panel): But I got this note from him: [The note:] Dude In like a month im gonna Craigslist all that shit you left in my garage Just FYI -Chad [Zoom in on Cueball who lifts both hands palms up.] Cueball: It's an outrage! This is no way to run a storage business! Friend (off-panel): Are you paying him to look after your stuff? [Final frame almost like the first frame, but Cueball has taken his hands down.] Cueball: No. Friend: Then what he runs isn't a storage business. Cueball: Well, I'm this close to not giving him any more stuff. Friend: That'll teach him.

Tests

Tests

https://www.xkcd.com/1151

https://www.explainxkcd.com/wiki/index.php/1151:_Tests

[Megan pouring a bucket of purple liquid on the presents at the base of a Christmas tree.] [Megan pouring a bucket of pink liquid on the presents at the base of a Christmas tree.] [Megan looking at the soaked presents.] Megan: All my presents appear to be Gram-negative. Cueball: I wish you hadn't opened the home bio lab kit first.

The first present Megan opened contained a home biology lab kit, including the equipment needed to perform a Gram stain. Gram staining is a technique used in microbiology to separate bacteria into two broad categories based on the structure of their cell walls. The sample is treated with two different dyes: first a purple dye, then secondly a pink one. When subsequently examined under a microscope, "Gram-positive" bacteria retain the purple color of the first dye, whereas "Gram-negative" bacteria do not, allowing the second pink stain to show. All Megan's presents have been stained pink, and are presumably therefore Gram-negative. In the process, she has damaged the other presents, hence Cueball's wish that she had opened another present first. The title text refers to two bacteria commonly used as controls to confirm that the technique has been correctly performed: Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Neither are bacteria you want to be coming into contact with in any substantial quantities [ citation needed ] , hence the need to stop accepting presents from " That Guy ". [Megan pouring a bucket of purple liquid on the presents at the base of a Christmas tree.] [Megan pouring a bucket of pink liquid on the presents at the base of a Christmas tree.] [Megan looking at the soaked presents.] Megan: All my presents appear to be Gram-negative. Cueball: I wish you hadn't opened the home bio lab kit first.

Communion

Communion

https://www.xkcd.com/1152

https://www.explainxkcd.com/wiki/index.php/1152:_Communion

[Cueball and Danish are taking a stroll.] Cueball: How was Christmas? Did you go to church? Danish: Yup. We celebrated the birth of a child, then we ate of his flesh and blood. [Silence from Cueball.] Danish: Seriously hope we got the right child this time.

This comic plays on the Christian doctrine that the Holy Communion bread and wine are Jesus' flesh and blood. It is based on the words of Jesus from the synoptic gospels and Paul's first epistle to the Corinthians during the Last Supper , today used by the priest as Words of Institution . According to the Roman Catholic doctrine of transubstantiation , as well as in the Eastern Christian tradition, the substance (using the Aristotelian concept that all things have an accident, or physical make-up, as well as a substance, or true nature/purpose) of the bread and wine change to Jesus' flesh and blood, while their accidents remains the same. Many people, including many Catholics, believe this concept means the bread and wine literally turn (i.e., their accidents changes) into Jesus' flesh and blood during the ceremony. Some Protestant denominations reject this doctrine, both its actual and misunderstood application, with some taking the words as wholly symbolic of Jesus' sacrificial death and others believing the bread and wine create a real spiritual connection to Christ but do not change their substance. In the second panel, Danish accurately describes what would happen at a traditional Christian Christmas service, though in such a way as to make it sound macabre. After walking and thinking in panel three, she makes it more macabre when worrying that they, again, may have gotten hold of the wrong child for the sacrifice needed to drink blood and eat flesh. The title text further spoofs the common understanding of the doctrine of transubstantiation and elaborates on Danish 's concern in the last panel by supposing that the act of taking a sip of wine during Holy Communion turns that wine into the blood, not of Jesus, but of a decades-old murder victim. Alternatively, the title text could be interpreted as saying that the wine actually acquires Jesus' DNA, and that Jesus was "killed" in the 1970s. The police, who investigated Jesus' 1970s death, would then have his DNA on file. It should be noted that saliva includes DNA, so the positive result may be the DNA from the person who spit the wine/blood out and does not necessarily mean that that person was murdered by the church in order to prepare the wine/blood. This could be a reference to the resurrection of Jesus. [Cueball and Danish are taking a stroll.] Cueball: How was Christmas? Did you go to church? Danish: Yup. We celebrated the birth of a child, then we ate of his flesh and blood. [Silence from Cueball.] Danish: Seriously hope we got the right child this time.

Proof

Proof

https://www.xkcd.com/1153

https://www.explainxkcd.com/wiki/index.php/1153:_Proof

Zeno: My client couldn't have killed anyone with this arrow, and I can prove it! Judge: I'd like to examine your proof, Zeno. You may approach the bench. Zeno: —But never reach it!

Zeno of Elea was an ancient Greek philosopher who devised several apparent paradoxes of motion called Zeno's paradoxes . Here are the two relevant to the comic: Arrow paradox: At any instant in time, an arrow suspended in mid-air is no different from an arrow in motion. How, then, can motion occur? (Answer: calculus [all objects have a velocity].) The lawyer presumably intends to use this argument to prove that his client could not have used the arrow to commit murder. Another possibility was that it is impossible to hit a person in motion. Dichotomy paradox: Suppose I need to go from point A to point B. First I must walk halfway there: half of the distance between A and B. Then I must walk half the remaining distance, which would bring me to three-quarters of the original distance; then I must again walk half the now-remaining distance to reach a point seven-eighths of the way from point A, and so on. Because I would have to take an infinite number of non-zero steps, I will never reach point B. By the same argument, the lawyer in the comic can get closer and closer to the judge's table, but never reach it. There are two possible law vs math/logic puns in the comic, on the words "approach" and "proof." " Approach the bench " is a legal term meaning to have a private conversation with the judge; approach in calculus means an infinite process where a function value gets closer and closer to a limit value that it never actually reaches, reminiscent of Zeno's paradoxes. "Proof" is also ambiguous, with a different meaning in formal mathematics than in jurisprudence . See Proof (truth) and Mathematical Proof , for example. Gottfried Leibniz is the co-inventor of calculus (along with Isaac Newton; see 626: Newton and Leibniz ). If Leibniz were to testify in this imaginary trial, he might argue that calculus invalidates Zeno's paradoxes, because the moving arrow has a different velocity than a stationary one (the function describing the motion has a nonzero derivative at the point), and the infinite series in the dichotomy paradox has a finite sum. Both Zeno and calculus assume a continuous, infinitely divisible, ideal spacetime (as does quantum mechanics ); a different solution would be available if spacetime turns out to be discrete. However, Zeno is arguably not concerned with actually calculating the correct answer. In the real world, Zeno can be trivially disproven simply by moving and reaching a desired target (it is said that Diogenes the Cynic reacted to the paradox by wordlessly walking to a destination, to demonstrate his contempt for it). It remains a question of debate whether a mathematical approach addresses the central points in Zeno's arguments. 994: Advent Calendar is also about Zeno. Zeno: My client couldn't have killed anyone with this arrow, and I can prove it! Judge: I'd like to examine your proof, Zeno. You may approach the bench. Zeno: —But never reach it!

Resolution

Resolution

https://www.xkcd.com/1154

https://www.explainxkcd.com/wiki/index.php/1154:_Resolution

Cueball: I'm scared of being stuck—thinking I'm fixing things about myself but never actually changing. Cueball: My 2013 resolution is to break out of loops. To recognize when I'm not making progress, stop yelling at myself, and try a different approach. Out of panel: Wasn't that also your resolution last year? Cueball: Yeah, but this year's gonna be different.

This New Year comic is a little reminder that it's the last day of 2012 , and it's time to make your New Year's resolutions ! Cueball wants to break a very common habit of resolving to do something (go on a diet, for example), not doing it, and then trying the same, dysfunctional plan again, thinking it will work "this year." This is another way of stating a common folk definition of insanity: to keep doing what you always do yet expecting different results. The irony is that Cueball resolved the same thing last year, and it is implied it didn't work, but he says it'll be different "this year." The title text is a parody of the saying "if at first you don't succeed: try, try, try again." Cueball: I'm scared of being stuck—thinking I'm fixing things about myself but never actually changing. Cueball: My 2013 resolution is to break out of loops. To recognize when I'm not making progress, stop yelling at myself, and try a different approach. Out of panel: Wasn't that also your resolution last year? Cueball: Yeah, but this year's gonna be different.

Kolmogorov Directions

Kolmogorov Directions

https://www.xkcd.com/1155

https://www.explainxkcd.com/wiki/index.php/1155:_Kolmogorov_Directions

[Cueball on the phone.] Phone: How do I get to your place from Lexington? Cueball: Hmm... Cueball: Ok, starting from your driveway, take every left turn that doesn't put you on a prime-numbered highway or street named for a president. [Caption below the panel:] When people ask for step-by-step directions, I worry that there will be too many steps to remember, so I try to put them in minimal form.

Andrey Kolmogorov was a mathematician who worked, among other things, on defining computational complexity. Roughly speaking, the Kolmogorov complexity of a string (of bits, words, symbols, etc.) is the shortest description that allows an accurate reconstruction — or, in some variants, the length of the smallest program which will output the original string. Cueball 's method of giving directions is very reminiscent of Kolmogorov's method of determining complexity. However, it is unlikely they know all the presidents, nor can calculate prime numbers in their heads, and so will have trouble with certain parts. These directions may have minimal Kolmogorov complexity, but they are non-intuitive and are likely not the shortest or quickest way to get there, considering that they consist mostly of left turns. This is not the first time Cueball has had difficulties with directions, and here we see he hates giving directions as much as he hates receiving them. The joke in the title text is that Cueball just sent his friend to a store to buy a GPS device to give him the correct directions. (By the time this comic was published, GPS-enabled smartphones had already largely displaced dedicated GPS devices, [1] but Cueball could be talking to a person who does not wish to own a smartphone.) [Cueball on the phone.] Phone: How do I get to your place from Lexington? Cueball: Hmm... Cueball: Ok, starting from your driveway, take every left turn that doesn't put you on a prime-numbered highway or street named for a president. [Caption below the panel:] When people ask for step-by-step directions, I worry that there will be too many steps to remember, so I try to put them in minimal form.

Conditioning

Conditioning

https://www.xkcd.com/1156

https://www.explainxkcd.com/wiki/index.php/1156:_Conditioning

Every few hours, subwoofer plays throbbing bass for 10 seconds... [With arrow pointing to subwoofer.] ...then bread crumbs are dispensed into box [With arrow pointing to bread feeder machine.] Opening [With arrow pointing to feeder opening shaped like a driver side car window.] Local wildlife [With arrows pointing to birds and a squirrel.] Protip: Leave this device in your yard for a week, then watch as the problem of loud music from passing cars solves itself.

Herein, the author devises a method of addressing the issue of drivers who turn up their music to irritating levels which usually results in a lot of bass coming from the car — the low frequencies being the ones that most easily penetrate the car and travel farther, thus being more audible to those around the car. As the title suggests, the idea is to condition animals to respond to a thumping bass. The machine is described as working as follows: every few hours, the bass would turn on, and the box would dispense food behind an opening designed to look like an open car window. Over time, local wildlife would flock to the box to get the food from inside, and would become trained that the sound of a subwoofer means that they can get food by flying through a car window.. Eventually, the animals would respond to any low music, including that played by cars. The end result would be that the local wildlife would approach, and presumably attempt to enter, any car that has that same thumping bass. Drivers, in turn, would cease to turn up their music in order to prevent the groups of animals from chasing after their cars, thus solving the problem of annoyingly loud bass. This behavior modification can itself be seen as a somewhat different form of conditioning . Although this plan may seem far-fetched, a similar scheme was seriously proposed in the United Kingdom during World War I to condition seagulls to associate a submarine's periscope with food, which would give away the locations of enemy submarines as the gulls flocked to their periscopes being raised. The title text is a dialogue about using a similar method of conditioning to send animals after a visiting Pope . Why someone would want that to happen is left to the reader's imagination, although papal visitations usually disrupt the local communities with onerous traffic and special and ostentatious ceremonies, and do attract huge crowds of dignitaries, celebrities, the faithful, the curious, and attending purveyors of foodstuffs and trinkets. Not to mention the impact to the local AirBnB market. Or it could just be Black Hat, who would not need any particular reason for this sort of behavior, and might choose the Pope because of his highly recognizable outfit. Every few hours, subwoofer plays throbbing bass for 10 seconds... [With arrow pointing to subwoofer.] ...then bread crumbs are dispensed into box [With arrow pointing to bread feeder machine.] Opening [With arrow pointing to feeder opening shaped like a driver side car window.] Local wildlife [With arrows pointing to birds and a squirrel.] Protip: Leave this device in your yard for a week, then watch as the problem of loud music from passing cars solves itself.

Sick Day

Sick Day

https://www.xkcd.com/1157

https://www.explainxkcd.com/wiki/index.php/1157:_Sick_Day

[This comic shows a pie chart with 5 slices, each with a label and a line pointing to these five different sized slices. There is a caption above the chart:] Activities while sick: [The labels on each slice is given in clockwise order starting from the top. The percentages are estimated from the image and are noted in the square brackets before the transcript:] [54%] - Shifting around in bed feeling my skin crawl [24%] - Wiping various face holes [5%] - Staring at a news site but not reading it [14%] - Thinking about how cool it is that I'm partly made of an army of critters that patrol my body ruthlessly dispatching anything they find trying to prey on me. [3%] - Pondering hooking an aquarium pump up to my sinuses

This pie chart for the most part reflects the usual experience of being sick — tossing and turning in bed and cleaning up mucus and other bodily fluids from facial orifices— in addition to a few ponderings of a rather more scientific bent. The "army of critters that patrol my body" would appear to refer to the human immune system , which is made up of various cells and processes that actively fight infections and pathogens. The punchline appears to be "pondering hooking an aquarium pump to my sinuses," which indicates that Randall 's sinuses were completely clogged with mucus, which made him wonder whether hooking up an aquarium pump would help clear them out, perhaps akin to a Neti pot . Studies on nasal irrigation, however, have had mixed results, and the practice may not in fact be beneficial. Randall's Wikipedia path: Virus →‎ Immune system →‎ Innate immune system →‎ Parasites →‎ List of parasites of humans →‎ Naegleria fowleri →‎ Primary amoebic meningoencephalitis . Naegleria fowleri is known as the brain-eating amoeba. It is found in warm bodies of stagnant fresh water and causes the disease primary amoebic meningoencephalitis, a rare but highly lethal condition. Although N. fowleri are not commonly found in aquariums, Randall's Wikipedia wanderings force him to conclude that attempting to clear out his sinuses with an aquarium pump is too risky. Since this danger would presumably not be present at all with an unused, sterilized aquarium pump, the comic may be referring to a particular pump currently in use and close at hand. [This comic shows a pie chart with 5 slices, each with a label and a line pointing to these five different sized slices. There is a caption above the chart:] Activities while sick: [The labels on each slice is given in clockwise order starting from the top. The percentages are estimated from the image and are noted in the square brackets before the transcript:] [54%] - Shifting around in bed feeling my skin crawl [24%] - Wiping various face holes [5%] - Staring at a news site but not reading it [14%] - Thinking about how cool it is that I'm partly made of an army of critters that patrol my body ruthlessly dispatching anything they find trying to prey on me. [3%] - Pondering hooking an aquarium pump up to my sinuses

Rubber Sheet

Rubber Sheet

https://www.xkcd.com/1158

https://www.explainxkcd.com/wiki/index.php/1158:_Rubber_Sheet

[Beret guy is standing on a giant bowling ball on a rubber sheet. Megan is watching.] Beret Guy: Imagine a giant bowling ball on a rubber sheet. Beret Guy: The ball's weight makes a dent in the sheet. [A rope is pulling the ball down into the sheet.] Beret Guy: Now imagine a rope that pulls the ball down even further. Beret Guy: ...Annnnd... [Rope lets go. Ball is catapulted with Beret Guy on it.] BOOOIING Beret Guy: Wheee [Beret guy and ball are falling back down.] Megan: ...Oh. I thought this was about physics. Beret Guy: Imagining is fun!

This comic refers to a common analogy used to explain how mass distorts space-time — a bowling ball resting on a sheet of rubber distorts the sheet due to its weight. The system has some qualitative features in common with gravity; it's often misused to show that "mass warps spacetime" ( 895: Teaching Physics ). The next part of the original analogy explains a black hole: the slope of the sheet becomes so deep that you can't climb out from the bottom any more, similar to a black hole, which even light can't escape from. However, the comic subverts the analogy, and the sheet becomes a trampoline instead. Reading onwards, it seems that Beret Guy is just messing about with the scenario. The line "Imagining is fun! " is also a homage to Richard P. Feynman 's "Fun to Imagine" Series of Interviews. The power of Beret Guy's imagination—so that he can physically experience what he imagines—is reminiscent of 248 . The title text also states that the rubber sheet, broken rope and trampoline are still all about physics (see also 435: Purity ). [Beret guy is standing on a giant bowling ball on a rubber sheet. Megan is watching.] Beret Guy: Imagine a giant bowling ball on a rubber sheet. Beret Guy: The ball's weight makes a dent in the sheet. [A rope is pulling the ball down into the sheet.] Beret Guy: Now imagine a rope that pulls the ball down even further. Beret Guy: ...Annnnd... [Rope lets go. Ball is catapulted with Beret Guy on it.] BOOOIING Beret Guy: Wheee [Beret guy and ball are falling back down.] Megan: ...Oh. I thought this was about physics. Beret Guy: Imagining is fun!

Countdown

Countdown

https://www.xkcd.com/1159

https://www.explainxkcd.com/wiki/index.php/1159:_Countdown

[Black Hat is sitting with his laptop on a desk when Cueball, standing behind him, looks up on the wall and asks him about the large digital countdown timer with red numbers which is hanging high up on the wall. It has a white frame around the black display with the red numbers. Most of the left part of the counter is covered by a framed picture that hangs on a string attached to a nail above the counter. The picture depicts either a setting sun reflecting in an ocean or an exploding volcano with lava flowing away from it. The picture does not block the left-most part of the frame around the counter, and it is also possible to see the two left-most lines of the first digit on the countdown, so they are both turned on. This proves that the numbers go all the way to the left end. The next five digits are covered by the picture. Then one digit is only partly covered, as only the two most left lines are not visible. From the visible lines, it is though clear that this digit shows a 0. The next seven digits are fully visible, giving eight discernible digits.] 00002409 Cueball: What's that? Black Hat: Countdown. [Same picture, but Cueball is looking at Black Hat. The counter counts down.] 00002400 Cueball: To what? Black Hat: Supervolcano, I think. I forget which one. [Cueball looks up again for about 18s (between 2nd and fourth image) - beat panel.] 00002396 [Cueball looks at Black Hat again.] 00002382 Cueball: Maybe we should move that picture? Black Hat: Too hard to reach. It's probably fine.

The comic shows a seven segment display (aka calculator-style numbers ) with a countdown. Black Hat explains that it is a countdown, maybe to a supervolcano eruption. However, an unfortunately placed picture blocks view of the full display. Due to the form of a seven-segment display, the first digit could be 0, 6, or 8, and five digits are completely blocked by the picture. Cueball is worried and asks him to move the picture, but Black Hat lazily or teasingly refuses to move it. He has already teased that he doesn't know what the countdown is for. His reply can either be understood as if he does not know which one of the ( seven potential ) supervolcanos it is counting down to, or to which other cataclysmic event it is a countdown for (such as a meteor strike or global nuclear war for instance - it could also just be a general Doomsday Clock ). Since it seems to be Black Hat's countdown, it is safe to assume that he knows both what it counts down to and when it stops, but he just likes to mess with peoples' minds. The fully visible part starts at 2409, and based on the pace of the scene, it seems to be in seconds. Thus, it is unclear when the eruption might occur. If the obscured digits are all 0s, it could be as soon as 40 minutes. On the other hand, if the obscured digits are '899 999', there's another 2.85 million years to go; if they are '000 001', we have a little more than 3 years. The choice of the picture is probably also interesting. The image is distorted enough that you can imagine it as being two very different images. In either case, it could make sense. If it is a volcano, the supervolcano clock makes sense. On the other hand, we are talking about the possible end of the world as we know it, so the sun setting upon humanity could be a great metaphor. The title text: "For all we know, the odds are in our favor" could imply the assumption that since we can't see the digits behind the picture, we can treat them as random. If so, chances are only 1 in 300 000 they are all zeros. However, because of statistical principles such as Benford's law , the digits are not entirely random, and the odds are higher than 1/299 999 for all the digits to be zero since the middle 4 digits are zero. In an alternative view, the strip is not about pondering at distributions of digits on an oracle countdown. It's more of a grim view of our natural disaster prediction capabilities. As they say – the question is not if it will happen but when it will happen. "Move the picture" would mean investing in research and warning systems - that would correspond to shifting the picture to the left. If we disregard the 40 minutes, but instead think of it as an arbitrary interval of interests, minuscule as we folks have them, say - one's lifetime; or grimmer yet - some term of office . Because, hey, year after year passes and no apocalypse has been observed - the empirical odds are low indeed. An interesting question is what we would use the knowledge of the timing of our impending doom, if it is an event we can do nothing about, such as stopping a supervolcanic eruption or a large asteroid with a direct impact course on Earth. Would we not have lives more happily for our remaining years, how few that might be, while not knowing... On the other hand, if the event is something we might prevent given enough time to plan (and the funding resources such knowledge would ensure), then it may have saved us if we moved the picture just in time! Using a countdown theme for comic #1159 could be a subtle joke, as 11:59/23:59 is one minute to midnight (on the Doomsday clock!). Supervolcanos were also referenced in the title text of 1053: Ten Thousand and it is the subject of in 1611: Baking Soda and Vinegar . [Black Hat is sitting with his laptop on a desk when Cueball, standing behind him, looks up on the wall and asks him about the large digital countdown timer with red numbers which is hanging high up on the wall. It has a white frame around the black display with the red numbers. Most of the left part of the counter is covered by a framed picture that hangs on a string attached to a nail above the counter. The picture depicts either a setting sun reflecting in an ocean or an exploding volcano with lava flowing away from it. The picture does not block the left-most part of the frame around the counter, and it is also possible to see the two left-most lines of the first digit on the countdown, so they are both turned on. This proves that the numbers go all the way to the left end. The next five digits are covered by the picture. Then one digit is only partly covered, as only the two most left lines are not visible. From the visible lines, it is though clear that this digit shows a 0. The next seven digits are fully visible, giving eight discernible digits.] 00002409 Cueball: What's that? Black Hat: Countdown. [Same picture, but Cueball is looking at Black Hat. The counter counts down.] 00002400 Cueball: To what? Black Hat: Supervolcano, I think. I forget which one. [Cueball looks up again for about 18s (between 2nd and fourth image) - beat panel.] 00002396 [Cueball looks at Black Hat again.] 00002382 Cueball: Maybe we should move that picture? Black Hat: Too hard to reach. It's probably fine.

Drop Those Pounds

Drop Those Pounds

https://www.xkcd.com/1160

https://www.explainxkcd.com/wiki/index.php/1160:_Drop_Those_Pounds

[We see a poster taped to a wall. It has Megan and Cueball in the bottom left, a silhouetted crenelated tower in the bottom right, and a thin arc between them. It reads:] Struggling with those 2013 resolutions? We'll help you hit your target By dropping thirty pounds fast [Small print.] WEB: http://[illegible].com CALL: [illegible] The flyer for our trebuchet–building club may have been too subtle.

The comic presents a flyer with text typical of a ubiquitous advertisement for a "Weight Loss Program". However, the image at the bottom of the flyer and the text below the flyer make it clear that the flyer is actually an advertisement for a trebuchet club. This unexpected meaning is meant to highlight the ambiguity of the flyer's content. A counterweight trebuchet is typically a gravity powered siege engine, which was originally used to attack fortifications. It works by dropping a raised counter weight to rotate a throwing arm, launching a projectile on a ballistic path. The phrase "We'll help you hit your target by dropping 30 pounds FAST" is where the ambiguity is produced. In the context of a weight loss ad, the "target" would be a rhetorical device referring to the weight which one wishes to achieve. In the context of a trebuchet club, the target is a literal location which one is trying to hit with a projectile. Likewise, a weight loss ad may indicate that a client could quickly lose 30 pounds (~13.6 kg). However, in this context, the 30 pounds being dropped is either the counter-weight - which is dropped to provide a trebuchet with its power, implying a rather small trebuchet - or the projectile itself being dropped at the target - it will be slower than the counter-weight but definitely still much faster than any weight loss program. The only hint that the flyer advertises a trebuchet club is in the drawing at the bottom of the flyer, which appears to show two individuals pondering a ballistic path towards a castle tower, though no trebuchet is shown. The text below indicates that this flyer "may have been too subtle". The title text suggests that, if the flyer is indeed too subtle a form of advertisement, they will use the LEAST subtle options of announcing their club's existence — likely by using their trebuchet to attack the town.That would certainly get the club some attention! See also 382: Trebuchet . [We see a poster taped to a wall. It has Megan and Cueball in the bottom left, a silhouetted crenelated tower in the bottom right, and a thin arc between them. It reads:] Struggling with those 2013 resolutions? We'll help you hit your target By dropping thirty pounds fast [Small print.] WEB: http://[illegible].com CALL: [illegible] The flyer for our trebuchet–building club may have been too subtle.

Hand Sanitizer

Hand Sanitizer

https://www.xkcd.com/1161

https://www.explainxkcd.com/wiki/index.php/1161:_Hand_Sanitizer

[Cueball looks at a poster while holding a bottle.] Poster: An invisible sneeze droplet can contain 200 million germs! [Same scene, except Cueball is looking at the bottle.] Product label: Our hand sanitizer kills 99.99% of germs! [Cueball types on a calculator while still holding the product.] Cueball (typing on calculator): 200 000 000 × 0.01% = [Cueball holds down his calculator.] Cueball: Ew.

The number of germs that would be left after using the hand sanitizer is 200 million times 0.01%. 0.01% is equivalent to 0.0001 in decimal, so the multiplication is 200 000 000 × 0.0001. That is 20 thousand germs, which is still a surprisingly large number of germs. Recently, scientists have shown that it only takes 20 virus particles to infect someone (with analyzed virus; not all germs are equally effective). However, they have also previously noted that the effectiveness of hand sanitizer is actually higher than 99.99%, but it's a bit awkward to print a more precise decimal in an advertising slogan. (Several brands actually kill near 100%, but don't want to risk going to court for false advertising because a few germs got past.) "Hipster CDC" is a combination of the acronym for the Centers for Disease Control and Prevention , an organization dedicated to studying infectious diseases and limiting their spread, with the label hipster . Hipsters form a cultural group associated with a distaste for popular culture; they stereotypically talk about how bands, authors, etc. were better before they "went mainstream" and proclaim that they liked a certain thing "before it was cool." The title text extends this sensibility to the flu, which in fact did peak years ago, such as in 1918, when a world-wide flu epidemic killed tens of millions. The humor lies in the notion that the "Hipster CDC" apparently approves of the time when the flu was more widespread and fatal, while most people consider the diminishment of the flu is a good thing. This could be a jab at hipsters' common insistence on liking things before they "go mainstream": many things, before they go mainstream, just aren't very good, and therefore hipsters' taste in things is highly questionable. [Cueball looks at a poster while holding a bottle.] Poster: An invisible sneeze droplet can contain 200 million germs! [Same scene, except Cueball is looking at the bottle.] Product label: Our hand sanitizer kills 99.99% of germs! [Cueball types on a calculator while still holding the product.] Cueball (typing on calculator): 200 000 000 × 0.01% = [Cueball holds down his calculator.] Cueball: Ew.

Log Scale

Log Scale

https://www.xkcd.com/1162

https://www.explainxkcd.com/wiki/index.php/1162:_Log_Scale

[A bar chart on a piece of paper, with a second piece of paper attached to it.] [Title of the bar chart] fuel energy density of different materials in megajoules/kg [Values of the first 4 bars on the paper] 19 24 39 46 [The different bars for Sugar, Coal Fat and Gasoline and Uranium on a linear scale with the bar for Uranium exceeding on the attached stack of paper] [Labels of the 5 bars on the paper] Sugar Coal Fat Gasoline Uranium [The uranium bar on the chart goes off the page onto a huge strip of paper folded up into a stack slightly taller than Cueball.] [Value on the top end of the paper strip] 76 000 000 [Caption below the panel:] Science Tip: Log scales are for quitters who can't find enough paper to make their point properly . This comic was seen in the What If? book, taken from "a certain webcomic".

This comic strip is a tip , specifically the first science tip . As with most of Randall's tips, it is technically interesting for some applications but not very practical. Uranium is stated to have 76 million MJ/kg, while the next highest material shown on the graph (gasoline) has 46 MJ/kg. Thus the uranium graph should be taller by a factor of 76,000,000/46 = 1.652 million. So, if the gasoline graph were 9mm in height, the uranium graph should be a bit more than 14.868 million mm tall, or nearly 15 km (9.2 miles) tall. Thus the need to fold the paper. It should be noted that the method of extracting energy from the first 4 materials ( combustion ) is completely different from the method used with uranium ( nuclear fission ). If the technology existed to use nuclear fusion , then the first 4 materials would yield a higher energy density than uranium. A log scale is a way of showing largely unequal data sizes in a comprehensible way, using an exponential function between each notch on the y axis of a graph. So for example the first on a Y axis of a graph using a log-10-scale would be 1, then 10, then 100 and 1000 for the fourth. A log/logarithmic function is the inverse of a corresponding exponential function . A log-scale version of the chart in the comic would look like this: The log scale can also be abused to make data look more uniform than it really is. On a log scale the energy density of uranium looks larger than that of the other materials, but not dramatically so. The joke is that if one wanted to make their point "properly," they would go ahead and use ridiculous amounts of paper to show the difference between bars using a linear scale; this method would focus more on the shock factor of the differences in question, and less on actual communication/representation of data. Cueball seems to be passionate about the MJ/kg of uranium, so he would rather demonstrate the grandeur of the data than use a more efficient scale. See these examples for well known day-to-day measurements which are measured on a log-scale. The title text mentions computer scientist Donald Knuth ; the fictional notation is a parody of Knuth's up-arrow notation . Using paper thickness as the basis for a log scale would probably give the exponential function a very large base. However, it can be noted that Knuth's up-arrow notation can handle numbers far, far larger than this paper stack notation; for example the number 3↑↑↑3, also known as Tritri [1] , very compact in up-arrow notation, would require a number of iterations pinned to the stack on the order of several trillion. 3↑↑↑↑3 , also known as Grahal [2] , would require a number of iterations that is not only too large to write down, but attempting to write that number using the same paper stack notation would require printing off a second stack of several trillion iterations just to hold the number pinned to the first stack. By repeating this multi-stack repetition, you reach the limit of up-arrow notation. It should be noted that Randall has used log scales in past comics. [A bar chart on a piece of paper, with a second piece of paper attached to it.] [Title of the bar chart] fuel energy density of different materials in megajoules/kg [Values of the first 4 bars on the paper] 19 24 39 46 [The different bars for Sugar, Coal Fat and Gasoline and Uranium on a linear scale with the bar for Uranium exceeding on the attached stack of paper] [Labels of the 5 bars on the paper] Sugar Coal Fat Gasoline Uranium [The uranium bar on the chart goes off the page onto a huge strip of paper folded up into a stack slightly taller than Cueball.] [Value on the top end of the paper strip] 76 000 000 [Caption below the panel:] Science Tip: Log scales are for quitters who can't find enough paper to make their point properly . This comic was seen in the What If? book, taken from "a certain webcomic".

Debugger

Debugger

https://www.xkcd.com/1163

https://www.explainxkcd.com/wiki/index.php/1163:_Debugger

[Megan and Cueball are at the top of a grassy hill, rendered in silhouette. Megan is lying down on the grass while Cueball is sitting.] Cueball: I don't understand how my brain works. [A close-up of the two characters. Megan lifts her head slightly.] Cueball: But my brain is what I rely on to understand how things work. [The shot zooms out again.] Megan: Is that a problem? Cueball: I'm not sure how to tell.

Cueball mentions to Megan that he can't understand how his mind works, the same mind he uses to understand how things work, and he's not sure if this is a problem. In other words, if he can't understand how his mind works, then how can he tell that it does in fact work and that his perception of reality is accurate? Ordinarily he would use his mind to figure it out, but if his mind really doesn't work, then he'll probably never determine that his mind doesn't work. Not only that, he can't even trust his brain to tell him if his inability to understand his own brain is an issue. Understandably, he's a little unsure of how he should feel about this. Per the comic title, a debugger is a piece of software used by programmers to find bugs in the applications they are making. The title is an allusion to that debuggers are very much like our brains in the aspect described above - most programmers don't understand how debuggers internally work, and they can't be sure that debugger is bug-free - if there is a bug in the debugger itself, it can't be accurately used to find bugs. The title text alludes to the above problem, in that if a website's "report a bug" page is buggy to a degree that it prevents the actual reporting of a bug, then users cannot use the form to report that the form itself is broken. Thus it can take quite some time before the site administrators realize this error, if they do at all, as unless they test it themselves, the administrators are likely relying on users to report problems they find, which they can't, making it appear as if there are no problems. This is somewhat analogous to the "brain" dilemma in the main comic, where the usual problem-pondering and resolving method itself can have a problem, but there is no straightforward way to tell. [Megan and Cueball are at the top of a grassy hill, rendered in silhouette. Megan is lying down on the grass while Cueball is sitting.] Cueball: I don't understand how my brain works. [A close-up of the two characters. Megan lifts her head slightly.] Cueball: But my brain is what I rely on to understand how things work. [The shot zooms out again.] Megan: Is that a problem? Cueball: I'm not sure how to tell.

Home Alone

Home Alone

https://www.xkcd.com/1164

https://www.explainxkcd.com/wiki/index.php/1164:_Home_Alone

[Aged man standing at the head of a flight of stairs. A paint can on a rope is swinging into a child at the foot of the stairs. A child on the floor is in a semi-fetal position and crying.] Child: Ow!! Child on floor: Waaaaaaaaa! Rejected movie ideas: Age-reversed Home Alone reboot.

Home Alone is a popular 1990 film in which the child protagonist Kevin McCallister (portrayed by Macaulay Culkin ) is accidentally left alone in his house when his family goes on vacation, and has to thwart a burglary all by himself. In the movie, McCallister comes up with a variety of ingenious traps and schemes (usually involving jury-rigged toys and household items) to harass, injure and eventually incapacitate the burglars, which was the film's defining feature. On a more general level, the films revolve around the classical trope with an underdog defeating a much stronger opponent (the burglars), through his own ingenuity. The film spawned a series of sequels (4 as of 2012, the first of which also starred Culkin) all with a similar premise to the original. This strip, however, proposes a reboot of the franchise, with the main change to the film being that of an age-reversal, so the story is now about an adult man setting needlessly harmful traps to hurt defenseless children breaking into his house. This would likely be seen as distasteful at the very least, and would probably lead to a negative reputation for the film. The title text adds another punchline when it is revealed that the reboot also stars Macaulay Culkin in the same role. This may suggest that the age-reversal gimmick was done to allow for him to star in the film as the same character despite growing up since the beginning of the franchise. This would be a rather misguided attempt to revive his career, and would probably just prevent any further success. The scene depicted in the strip is an adaptation of an iconic scene from the first movie (used heavily in advertising) where McCallister hangs two paint cans in strings above the staircase, and let them swing down to hit the burglars in the face. [Aged man standing at the head of a flight of stairs. A paint can on a rope is swinging into a child at the foot of the stairs. A child on the floor is in a semi-fetal position and crying.] Child: Ow!! Child on floor: Waaaaaaaaa! Rejected movie ideas: Age-reversed Home Alone reboot.

Amazon

Amazon

https://www.xkcd.com/1165

https://www.explainxkcd.com/wiki/index.php/1165:_Amazon

Round 14 Estimated outflow volume in cubic meters per second [A cube of water representing the outflow of the Amazon, with various marine life in it and people standing around it.] Amazon 220,000 [A pile of boxes representing the outflow of Amazon.com, dwarfed by the large cube of water next to it.] Amazon.com 0.9 Advantage: Amazon

The Amazon River in South America is the second longest river in the world and by far the largest by waterflow. Amazon.com is a website that specializes in commerce and selling goods over the internet. The "round 14" suggest they are being compared in different criteria in a sort of competition. With such different systems, we can assume that most of those comparisons were similarly funny. The title text mentions two other criteria of comparison. The measure of flow for the Amazon river (cubic meters per second) indicates the volume of water that passes a given area in the river at any second. To illustrate how much 220,000 cubic meters is, the comic shows a car parked next to 220,000 cubic meters of water. 220,000 cubic meters equals a cube with an edge span of 60.4 meters. By comparison the 0.9 cubic meters (900 l) of goods that are shipped by Amazon.com seems very small (note that 900 liters of goods per second is still a lot). To illustrate this size, the comic shows an Amazonian fish (or possibly an Amazon river dolphin ) investigating the packages. Iquitos and Manaus are cities near the source and middle respectively of the river; the title text suggests that it is shorter to have a package shipped between the two than let it drift downstream. "Minutes to skeletonize a cow" refers to piranha , an Amazonian predatory fish with a popular reputation of being capable of the mentioned act when hunting in groups. (It should be noted that, while not fictional per se, the legendary cow-killing piranhas had been starved beforehand by local humans.) In 1599: Water Delivery Amazon.com takes the fight against the Amazon to a new level by delivering water within one hour; however, the Amazon River is not mentioned in that comic. Round 14 Estimated outflow volume in cubic meters per second [A cube of water representing the outflow of the Amazon, with various marine life in it and people standing around it.] Amazon 220,000 [A pile of boxes representing the outflow of Amazon.com, dwarfed by the large cube of water next to it.] Amazon.com 0.9 Advantage: Amazon

Argument

Argument

https://www.xkcd.com/1166

https://www.explainxkcd.com/wiki/index.php/1166:_Argument

[A page from a very long thread on " FREE Energy ~Forum~."] Thread: You're all crackpots who don't understand thermodynamics. [A bar above the comments:] Page 547 of 547 <<First <Prev 1 2 3 ... 545 546 547 Poster 1 [Default face icon]: No, idiot, only the north end of a magnet increases entropy. The south end decreases it. Poster 2 [Power strip plugged into itself icon]: I wiki'd this "First Law" and I don't see the issue. My device isn't a robot and doesn't harm humans. Poster 3 [Person with a large structure behind them icon]: What if we trick the government into only suppressing the left side of the flywheel? Ironically, the argument I started on a perpetual motion forum in 2004 shows no signs of slowing down.

A perpetual motion machine is a hypothetical device that is supposed to move infinitely with no external forces helping it, thus providing an unlimited source of energy. The existence of such an object would contradict the laws of thermodynamics, so perpetual motion machines are known to be impossible. A conspiracy theory called Free energy suppression asserts that it really is possible to get infinite energy and special interest groups have worked to hide it. In the comic, Randall says that he posted to a forum dedicated to the idea back in 2004, and the thread is still active — it kept on going forever, like the perpetual motion machine they desire (in contrast with real attempts to build such a machine, which all stop quite soon). Of course, the reason the thread continues is that its advocates continue to add energy to it, in the form of comments. "Hot air", if you will. The second law of thermodynamics states that the entropy of an isolated system never decreases. See this video about entropy . Thus, even if you could build a perpetual motion machine, you wouldn't be able to use it to produce energy that could be consumed by another device. The three supposed comments show humorous forms of scientific ignorance : Furthermore, the avatar being used by the second poster is that of a power strip plugged into itself, which is often jokingly thought of as a perpetual motion machine. The title text refers to the fact that inventors have been trying to create perpetual motion machines, but have all failed to succeed. But given the fact that they all failed, each attempted perpetual motion machine stopped running at some point, while the search has never stopped. [A page from a very long thread on " FREE Energy ~Forum~."] Thread: You're all crackpots who don't understand thermodynamics. [A bar above the comments:] Page 547 of 547 <<First <Prev 1 2 3 ... 545 546 547 Poster 1 [Default face icon]: No, idiot, only the north end of a magnet increases entropy. The south end decreases it. Poster 2 [Power strip plugged into itself icon]: I wiki'd this "First Law" and I don't see the issue. My device isn't a robot and doesn't harm humans. Poster 3 [Person with a large structure behind them icon]: What if we trick the government into only suppressing the left side of the flywheel? Ironically, the argument I started on a perpetual motion forum in 2004 shows no signs of slowing down.

Star Trek into Darkness

Star Trek into Darkness

https://www.xkcd.com/1167

https://www.explainxkcd.com/wiki/index.php/1167:_Star_Trek_into_Darkness

[Cueball staring at computer screen.] Cueball: Oh, wow. Look at Wikipedia's Talk page for Star Trek into Darkness. I have a new favorite edit war. Megan (off-panel): Oh? Cueball: Forty thousand words of debate over whether to capitalize "into" in the movie's title. Still no consensus. Megan: That's magnificent . Cueball: It's breathtaking. Megan: They should have sent a poet. Cueball: Well, I'm making an executive decision. I hope both sides accept this as a fair compromise. [A Wikipedia page titled " ~*~ StAr TrEk InTo DaRkNeSs ~*~ "] After the publication of the comic, the debate continued with full force, complete with a section of xkcd-inspired suggestions . The article itself was soon protected, so that only administrators could edit it. A day later, the title was changed to one including a capital "Into" by the administrator Mackensen . (The debate continued on his talk page .) https://en.wikipedia.org/wiki/~*~_StAr_TrEk_InTo_DaRkNeSs_~*~ was a valid redirect link for quite some time, having not been deleted when requested in 2015 , but 2016 . The Independent published an article about the " grammatical tizzy ", and the affair as a whole was added to Wikipedia's humorous list of the lamest edit wars .

The talk page of a Wikipedia article is used to discuss changes to the article. An edit war is a dispute about a specific edit to an article, manifesting as a series of edits alternating between making and reverting the change, and usually accompanied by a more-or-less heated debate on the talk page. Here, Randall is referring to a dispute on the Wikipedia article about Star Trek Into Darkness (an upcoming Star Trek film at the time of the comic's posting). On the day before the comic was published, the article name had a lowercase "into", and the talk page looked like this (rounded off in a friendly way, with the posting of a summary of the arguments , and an exchange of virtual hugs). In summary, the debate centers around whether "Into Darkness" should be treated as a prepositional phrase (as in "Star Trek[king] Into Darkness") or an unpunctuated subtitle (as in "Star Trek[:] Into Darkness"), whether compound prepositions like "into" should be capitalized in titles, and whether the capitalization of the title in the movie's official promotional material is relevant. The intensity and multiple facets of a debate over one tiny letter is apparently entertaining to Randall. Cueball changes the title so that every other letter is capitalized, and adds framing tildes and asterisks (a common, but childish and ugly way of emphasizing titles online). The title text indicates Randall's belief that such arguments are perpetual and will always arise. He suggests that the edit to the Wikipedia page will result in a dispute over variants of Cueballs "compromise" . One new alternative has the letter cases switched (or shifted, depending on your perspective), one uses a different set of "bracketing" characters (xX_[...]_Xx instead of ~*~[...]~*~), and one uses the original title, but with a lowercase "L" instead of a capital "I" (which appear similar in many fonts). Alternating-case text later caught on as an internet meme in 2017 (four years after this comic strip was published) for representing a mocking tone. Megan's line of "They should have sent a poet." is a quote from the film Contact . The quote is also referenced in 482: Height . In the movie, the line was meant to convey that only a poet could adequately capture the beauty seen; here, it indicates that prose is insufficient to capture the ironic beauty of the edit war. The old "favorite edit war" might be the one referenced in the title text of 878: Model Rail or the one resulting from the addition of the 739: Malamanteau article to Wikipedia [Cueball staring at computer screen.] Cueball: Oh, wow. Look at Wikipedia's Talk page for Star Trek into Darkness. I have a new favorite edit war. Megan (off-panel): Oh? Cueball: Forty thousand words of debate over whether to capitalize "into" in the movie's title. Still no consensus. Megan: That's magnificent . Cueball: It's breathtaking. Megan: They should have sent a poet. Cueball: Well, I'm making an executive decision. I hope both sides accept this as a fair compromise. [A Wikipedia page titled " ~*~ StAr TrEk InTo DaRkNeSs ~*~ "] After the publication of the comic, the debate continued with full force, complete with a section of xkcd-inspired suggestions . The article itself was soon protected, so that only administrators could edit it. A day later, the title was changed to one including a capital "Into" by the administrator Mackensen . (The debate continued on his talk page .) https://en.wikipedia.org/wiki/~*~_StAr_TrEk_InTo_DaRkNeSs_~*~ was a valid redirect link for quite some time, having not been deleted when requested in 2015 , but 2016 . The Independent published an article about the " grammatical tizzy ", and the affair as a whole was added to Wikipedia's humorous list of the lamest edit wars .

tar

tar

https://www.xkcd.com/1168

https://www.explainxkcd.com/wiki/index.php/1168:_tar

[Megan and White Hat stand next to a nuclear bomb. The bomb has a hatch open on top, and a small blinking screen. The two people are shouting off-screen.] Megan: Rob! You use Unix! White Hat: Come quick! [Megan, White Hat, and Rob look at the screen on the bomb. Rob peers closely. The screen is on the bomb, but is shown at the top of the panel in black with white letters, except "tar" and the last underscore which is in gray and "ten" which is black but written in a white box. The text reads:] [They all stand in the same position, but without the text displayed. Beat panel.] [Still in the same position but White Hat becomes impatient.] White Hat: ...Rob? Rob: I'm so sorry.

tar ("tape archive") is a Unix application that creates (and extracts) archives in the ".tar" format. It is typically used through the text-based terminal, using cryptic single-letter arguments such as " tar -cvf archive.tar * ". The comic alludes to the fact that despite years of use of the command, it's still hard to remember the arguments without searching for them, such as with Google. The joke here is that a "tar" command with perfect syntax on the first try without outside help is such a daunting task that even Rob can't overcome it with confidence, and apologizes for not being able to prevent their imminent death. The fact that Megan and White Hat assume that Rob can disarm the nuclear bomb because he uses Unix can be referring to an over-generalization fallacy that a partaker in a practice is an expert of a practice. Not all people who use Unix necessarily know how to use tar commands. Then again, since he's the only person nearby who knows any Unix and thus their only hope, their fallacy is pretty justified. The title text points out that while much of computing changes very quickly, the tar program, which is very old (originating ca. 1975), is still around and heavily used. And yet, Randall complains he still cannot type out a line of tar command with correct flags without having to look the flags up. Tar is a very common command that Unix users will come across regularly, much like Windows users will come across .zip files. Depending on the flavor of Unix, the order of the flags, or the lack or inclusion of a '-' could render the command incorrect. Most true Unixes (AIX, HPUX, Solaris) not using the GNU utilities would give an error on the above tar example. For such a simple command, it is one that most people need to look up references to use. There is probably also a pun on " tarbomb ," a poorly created tar archive that, when extracted, dumps a load of files into the current directory that the user has to clean up. And although the bomb looks more like Fat Man , the type of bomb that was used over Nagasaki , at least size-wise, it may also be a pun on the name of the largest ever hydrogen bomb which was called the Tsar Bomba (translation: "emperor bomb"). In 208: Regular Expressions Cueball saves the day by knowing regular expressions , although in the title text it is alluded to how easy these may also miss a character. Rob may refer to Rob Pike , who was a member of the team at AT&T who created Unix. [Megan and White Hat stand next to a nuclear bomb. The bomb has a hatch open on top, and a small blinking screen. The two people are shouting off-screen.] Megan: Rob! You use Unix! White Hat: Come quick! [Megan, White Hat, and Rob look at the screen on the bomb. Rob peers closely. The screen is on the bomb, but is shown at the top of the panel in black with white letters, except "tar" and the last underscore which is in gray and "ten" which is black but written in a white box. The text reads:] [They all stand in the same position, but without the text displayed. Beat panel.] [Still in the same position but White Hat becomes impatient.] White Hat: ...Rob? Rob: I'm so sorry.

Expedition

Expedition

https://www.xkcd.com/1169

https://www.explainxkcd.com/wiki/index.php/1169:_Expedition

[Cueball is at a computer.] February 4th: Departed the mouth of the Lena River, heading south. It has been nearly half an hour and still no sign of civilization. The scroll wheel tempts me, but I will not cheat. Click click click [Caption below the panel:] My hobby: Getting lost on Google Maps satellite

Google Maps is a service provided by Google that offers a map of the world including satellite and aerial imagery for free. Using the scroll wheel , the user can zoom out to see a larger area. Lena River is a river in Russia, flowing into the Arctic Ocean (with a large delta ). Clicking on the comic leads to an online Google Maps page showing the satellite imagery of the Lena Delta . Travelling south up the river will lead to the city of Yakutsk and eventually to Lake Baikal . It appears that Cueball is simply trying to explore the world without leaving his laptop or purchasing an expensive game. Alternatively, he may be playing Mapcrunch , this 'game' randomizes a street view location with the goal of finding the airport. The title text states that he apparently somewhat still treats it as a game and that he has been on it for at least a decade. In the years since, a game called GeoGuessr has been released, with the user being put into a random location in Google Street View and asked to guess where they are in the world by analyzing clues in their environment. This often necessitates the user making their way from the middle of the wilderness to some manner of civilization, exactly as in the comic. [Cueball is at a computer.] February 4th: Departed the mouth of the Lena River, heading south. It has been nearly half an hour and still no sign of civilization. The scroll wheel tempts me, but I will not cheat. Click click click [Caption below the panel:] My hobby: Getting lost on Google Maps satellite

Bridge

Bridge

https://www.xkcd.com/1170

https://www.explainxkcd.com/wiki/index.php/1170:_Bridge

[A youthful Cueball talking to an unseen parent.] Parent: No, you can't go. Cueball: But all my friends— Parent: If all your friends jumped off a bridge, would you jump too? Cueball: Oh, jeez. Probably. Parent: What!? Why!? Cueball: Because all my friends did. Cueball: Think about it — which scenario is more likely: Cueball: Every single person I know, many of them levelheaded and afraid of heights, abruptly went crazy at exactly the same time... Cueball: ...or the bridge is on fire? Parent: ...I, uh...hmm. Cueball: Imagine reading this on CNN: " Many fled their vehicles and jumped from the bridge. Those who stayed behind... " Cueball: Is something good about to happen to those people? Parent: Maybe they'll find cookies? Cueball: OK, you stay. I'm jumping.

"If all your friends jumped off a bridge, would you jump too?" This is a common question, used to challenge a decision based on the bandwagon effect . It challenges someone to consider whether something is really a good idea, even if everyone else does it (in this case, friends). The sentence is, upon closer analysis, a straw man attack that over-extrapolates the bandwagon effect. Cueball responds by assuming that if all of his friends jumped off a bridge, there must have been some extreme circumstance that made it logical to do so; for example, that the bridge is on fire. This points out a logical fallacy with the question: if they really are jumping off a bridge, they're probably motivated by something serious as opposed to an idiotic risk. So the humor of this comic is in all the different ways the question can be turned on its head, and made to mean something the unseen speaker probably never intended. The title text suggests that, even if there is nothing wrong with the bridge, the person asking the question is not acting right. The proper reaction would be concern about the mental (or physical, they could be injured) state of the people jumping off for no valid reason, and not just brushing them off as unworthy of attention. This is so especially when these people are described as "all my friends", so they have presumably always behaved correctly until they decided to jump off the bridge. [A youthful Cueball talking to an unseen parent.] Parent: No, you can't go. Cueball: But all my friends— Parent: If all your friends jumped off a bridge, would you jump too? Cueball: Oh, jeez. Probably. Parent: What!? Why!? Cueball: Because all my friends did. Cueball: Think about it — which scenario is more likely: Cueball: Every single person I know, many of them levelheaded and afraid of heights, abruptly went crazy at exactly the same time... Cueball: ...or the bridge is on fire? Parent: ...I, uh...hmm. Cueball: Imagine reading this on CNN: " Many fled their vehicles and jumped from the bridge. Those who stayed behind... " Cueball: Is something good about to happen to those people? Parent: Maybe they'll find cookies? Cueball: OK, you stay. I'm jumping.

Perl Problems

Perl Problems

https://www.xkcd.com/1171

https://www.explainxkcd.com/wiki/index.php/1171:_Perl_Problems

[Man with sunglasses talking (or, alternatively, rapping) to Cueball.] Sunglasses: If you're havin' perl problems I feel bad for you, son- Sunglasses: I got 99 problems, Sunglasses: So I used regular expressions. Sunglasses: Now I have 100 problems.

Perl is a scripting language that makes heavy use of regular expressions , which are good for dealing with large amounts of text quickly. In the comic, the man wearing sunglasses parodies the song " 99 Problems " in which the rapper Jay-Z says: If you're havin' girl problems I feel bad for you, son- I got 99 problems, But a bitch ain't one. In the comic however, the rapper tries to solve his problems with Perl's regular expressions, and ends up only creating another problem for himself, which is a reference to a famous quote by Jamie Zawinski (whose name could also be shortened to "Jay-Z"): "Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems." (This quote was revisited in 1313: Regex Golf .) "program --help" is a common way, originating with the GNU project, to ask a program to show documentation on its usage and supported parameters; which, for some program, could include a "-z" command-line argument ("flag"), so the command would read "jay -z". In this case, it is just an obvious play on the rapper's name. jay is also an actual C program that is a compiler-compiler for java, but it doesn't have a "-z" flag. This sort of problematically recursive self-reference is reminiscent of comic 927: Standards , and 1739: Fixing Problems . [Man with sunglasses talking (or, alternatively, rapping) to Cueball.] Sunglasses: If you're havin' perl problems I feel bad for you, son- Sunglasses: I got 99 problems, Sunglasses: So I used regular expressions. Sunglasses: Now I have 100 problems.

Workflow

Workflow

https://www.xkcd.com/1172

https://www.explainxkcd.com/wiki/index.php/1172:_Workflow

[Changelog for version 10.17 of a piece of software.] One change listed: "The CPU no longer overheats when you hold down the spacebar" Comments: LongtimeUser4 writes: This update broke my workflow! My control key is hard to reach, so I hold spacebar instead, and I configured Emacs to interpret a rapid temperature rise as "control". Admin writes: That's horrifying. LongtimeUser4 writes: Look, my setup works for me. Just add an option to reenable spacebar heating. Every change breaks someone's workflow.

Users will often try to work around bugs in software, and are sometimes able to get used to having the bugs around. Some bugs are even interpreted as features and users complain when the software authors fix them. This phenomenon has been named Hyrum's law : the law states that whatever the official feature list actually says, if a program has enough users, eventually every feature (whether intentional, unintentional, or a bug) will be relied upon by someone. A similar effect may be caused by other improvements, particularly those which involve changes in the user interface . This comic shows a somewhat extreme example. An unnamed application had a bug causing the CPU to overheat whenever the spacebar was held down too long. In version 10.17, this bug was fixed. Soon, LongtimeUser4 complained that they relied on the fact that the CPU overheats if the spacebar is held down. They had stumbled across this "feature" (which is, again, weirder than usual) and took advantage of it to streamline their workflow, and they wanted an option to re-enable it. Emacs (name originally derived from E ditor MAC ro S ) is a text editor originally written at MIT in 1976 and adopted into the GNU project in 1984. The control key sees extensive use in Emacs, and since it's hard to reach, users often remap it to Caps Lock or some other key. LongtimeUser4 fixed the problem very clumsily ("horrifying," as the admin puts it) and is annoyed that their kludge no longer works. The moral of the story is that you can't please everyone. Examples of real life changes in software which, though often acclaimed by critics, caused great annoyance among the existing user base include ribbons introduced in Microsoft Office 2007 and the Start screens of both Windows 8 and Unity desktop manager bundled with Ubuntu from versions 11.10 through 17.04. In the latter case, developers included an option to use the older interface; for the rest, applications emulating old behavior were developed by third parties. The title text makes a hyperbole to humorous effect; children will freeze to death during the winter because they won't be warmed by a rather unconventional heater. Making (or creating an illusion of) a connection between one's opinion and care for children's welfare is a common method of gaining public support, as such arguments are hard to deflect without sounding cruel and uncaring. "holding down spacebar to stay warm" could also be a reference to space heaters . [Changelog for version 10.17 of a piece of software.] One change listed: "The CPU no longer overheats when you hold down the spacebar" Comments: LongtimeUser4 writes: This update broke my workflow! My control key is hard to reach, so I hold spacebar instead, and I configured Emacs to interpret a rapid temperature rise as "control". Admin writes: That's horrifying. LongtimeUser4 writes: Look, my setup works for me. Just add an option to reenable spacebar heating. Every change breaks someone's workflow.

Steroids

Steroids

https://www.xkcd.com/1173

https://www.explainxkcd.com/wiki/index.php/1173:_Steroids

[Megan is walking while an energy sphere (Sphere) floats behind her and talks to her. The sphere is black but surrounded by six outwardly-curved segments that are shaded gray. The white parts in between makes it look like it irradiates light out along these lines.] Sphere: Explain to me this "steroid scandal." [Zoom in on Megan's face while she holds a hand to her chin.] Megan: Well, uh... Megan: We humans are sacks of chemicals which stay alive by finding other chemicals and putting them inside us. [Megan has turned around facing towards the Sphere to the left. She holds up one hand palm up.] Megan: We hold contests to see which humans are fastest and strongest. Megan: But some humans eat chemicals that make them too fast and strong. [Megan still facing the Sphere holds her arms out.] Megan: And they win contests! Sphere: That does sound bad. Megan: It's awful!

This comic is about steroid usage to enhance humans performance ; it is likely inspired by Lance Armstrong 's then-recent confession to blood doping in a televised interview with Oprah Winfrey (although Armstrong's confessions did not itself include anabolic steroid use; "steroids" is a common catch-all phrase often misused to reference other forms of doping ). This comic is making the point of the opinion that the criterion about which chemicals (steroids) humans may or may not take in to be considered the strongest or fastest is an artificial criterion. This is demonstrated by Megan explaining the whole concept to an energy sphere representing a non-humanoid intelligence; when framed the way Megan explains it, the explanation sounds rather trivial and silly. A better explanation would be to say that some chemicals make humans faster and stronger but also damage the human body, so these chemicals are banned so the competitors won't destroy themselves. Another point Megan has missed is that the competitions aren't unrestricted, they're designed around specific rules and structures, to which all participants agree. The chemicals in question are a violation of those rules, and so are both dishonest and subvert the entire purpose of the competition. This comic is one of many instances where Randall attempts to trivialize sports. The title text changes the perspective again by suggesting that humanity itself is trivial in the grand scheme of things and that really all we are is a "transition" state between old dust and new dust, with a bunch of emailing in between. This is a version of the saying that the Universe is just trying to turn itself into Iron, which is the atom with least energy, and it can thus neither be fused in stars or decay radioactively. The comic was published on Ash Wednesday (Western liturgical start of Lent). The dust to dust reference calls to mind the charge, "Remember man that thou art dust and unto dust you shall return," which is traditionally spoken by priests as they place ashes on the foreheads of observers on Ash Wednesday, in addition to the idea that all atoms in the universe other than Hydrogen, Helium, and some Lithium, were created after the big-bang via Stellar nucleosynthesis , with further production and dispersal via Supernova nucleosynthesis . Thus the reference by Joni Mitchell in the song Woodstock : "We are stardust..."; and echoed by Carl Sagan : "We are star stuff." Similar talking floating energy spheres have been used later in 1450: AI-Box Experiment , where it was clearly a different sphere and then in the Time traveling Sphere series. There is no indication of it here, but the sphere here could be another time traveler as well, back to try and understand humanity. [Megan is walking while an energy sphere (Sphere) floats behind her and talks to her. The sphere is black but surrounded by six outwardly-curved segments that are shaded gray. The white parts in between makes it look like it irradiates light out along these lines.] Sphere: Explain to me this "steroid scandal." [Zoom in on Megan's face while she holds a hand to her chin.] Megan: Well, uh... Megan: We humans are sacks of chemicals which stay alive by finding other chemicals and putting them inside us. [Megan has turned around facing towards the Sphere to the left. She holds up one hand palm up.] Megan: We hold contests to see which humans are fastest and strongest. Megan: But some humans eat chemicals that make them too fast and strong. [Megan still facing the Sphere holds her arms out.] Megan: And they win contests! Sphere: That does sound bad. Megan: It's awful!

App

App

https://www.xkcd.com/1174

https://www.explainxkcd.com/wiki/index.php/1174:_App

[A popup window on top of a webpage displayed in a smartphone browser that looks like Safari.] Want to visit an incomplete version of our website where you can't zoom? Download our app! [OK] [No, but ask me again every time]

Some websites have a mobile app designed for use on mobile devices such as smartphones and tablets. In theory this is because the main website will be more difficult to navigate on the small screen of a mobile, or some features won't work. In practice, this alternative is frequently worse than simply viewing the standard web page, for reasons offered in the comic: The comic offers a brutally honest version of such a promotional popup. Compounding the frustration is that some sites aggressively promote their app/mobile version with a popup message that repeats the suggestion on every visit to the site, and as the title text notes, if you reject the popup, you end up on the site's homepage, rather than the subpage you may have been trying to reach via a web search. A similar effect (where the mobile version will only load the site's main page) is described in more detail in 869: Server Attention Span . [A popup window on top of a webpage displayed in a smartphone browser that looks like Safari.] Want to visit an incomplete version of our website where you can't zoom? Download our app! [OK] [No, but ask me again every time]

Moving Sidewalks

Moving Sidewalks

https://www.xkcd.com/1175

https://www.explainxkcd.com/wiki/index.php/1175:_Moving_Sidewalks

[Cueball and Megan on the opposite far ends of a bidirectional moving sidewalk. Arrows indicate that one half will carry Cueball from left to right, while the other half will carry Megan from right to left. In each direction, the sidewalk is made up of a series of individual conveyors.] Cueball: Ready? [A diagram labels various individual conveyors as follows.] [Outermost conveyors:] Moving Sidewalk [Second and second-last conveyors:] Moving Sidewalk (2x Speed) [Next conveyors:] 3x Speed [Next conveyors:] 4x Speed [Innermost conveyors:] 5x Speed [Spot between the two sidewalks, directly in the center:] High-Five Location Megan: Ready. This comic was originally uploaded with all the arrows facing in the opposite direction, before Randall updated it with the current image.

Cueball and Megan are getting ready to ride an array of mini-conveyor belts, each going at a speed multiple of the first ones. Assuming they both take the one in front of them, each conveyor belt will speed them up a little bit more with little effort on their part, ultimately reaching a point where they are going very fast and are close enough to be able to high-five each other. The average moving walkway speed globally is 3 feet/second (~1m/sec), so Cueball and Megan would only be travelling about 2/3 average human running speed by the time they meet. Even with the opposing forces added to their high five, it would be very unlikely for them to injure each other (though the slap would more than likely be painful). The title text may be a reference to a music video made by OK Go, "Here It Goes Again", in which the band jumps on and off of various treadmills in a similar fashion. A series of parallel accelerating conveyor belts is also a long distance travel mechanism used in Robert A. Heinlein's The Roads Must Roll and in Isaac Asimov's Robot Detective novels. [Cueball and Megan on the opposite far ends of a bidirectional moving sidewalk. Arrows indicate that one half will carry Cueball from left to right, while the other half will carry Megan from right to left. In each direction, the sidewalk is made up of a series of individual conveyors.] Cueball: Ready? [A diagram labels various individual conveyors as follows.] [Outermost conveyors:] Moving Sidewalk [Second and second-last conveyors:] Moving Sidewalk (2x Speed) [Next conveyors:] 3x Speed [Next conveyors:] 4x Speed [Innermost conveyors:] 5x Speed [Spot between the two sidewalks, directly in the center:] High-Five Location Megan: Ready. This comic was originally uploaded with all the arrows facing in the opposite direction, before Randall updated it with the current image.

Those Not Present

Those Not Present

https://www.xkcd.com/1176

https://www.explainxkcd.com/wiki/index.php/1176:_Those_Not_Present

Every time someone says something negative about a person who's not in the room, I scoot my chair back a few inches. [Cueball, Ponytail and two other people are sitting at a table drinking.] Person: He's not so bad, but his friends ... [Cueball scoots away from table.] Scoot scoot Ponytail: His band is never gonna take off if... [Cueball scoots further away.] Scoot scoot [Megan, Beret Guy, and Hairy come into view.] Off-screen: Yeah, his sister is even weirder . Off-screen: Did you see she had... Scoot scoot Beret Guy: ...and there's a video, but it's blurry... [Cueball turns around and leans his arm on his chair.] Cueball: What're you talking about? Hairy: Giant squid! Cueball: Mind if I join you?

Cueball (likely representing Randall ), has decided to leave conversations deemed toxic, by scooting a little bit away any time somebody badmouths someone not present. In each panel, he scoots progressively further away until he reaches an area with Megan , Hairy , and Beret Guy , discussing giant squids . He decides to join them, as this conversation is far more interesting to him than one criticizing people behind their backs. The title text jokes that the second group, is, in fact, dissing the giant squid rather than discussing how cool it is. As the squid is not present, Cueball scoots back. Every time someone says something negative about a person who's not in the room, I scoot my chair back a few inches. [Cueball, Ponytail and two other people are sitting at a table drinking.] Person: He's not so bad, but his friends ... [Cueball scoots away from table.] Scoot scoot Ponytail: His band is never gonna take off if... [Cueball scoots further away.] Scoot scoot [Megan, Beret Guy, and Hairy come into view.] Off-screen: Yeah, his sister is even weirder . Off-screen: Did you see she had... Scoot scoot Beret Guy: ...and there's a video, but it's blurry... [Cueball turns around and leans his arm on his chair.] Cueball: What're you talking about? Hairy: Giant squid! Cueball: Mind if I join you?

Time Robot

Time Robot

https://www.xkcd.com/1177

https://www.explainxkcd.com/wiki/index.php/1177:_Time_Robot

[Cueball runs towards Megan with a shotgun in hand.] Cueball: I'm from the future! Cueball: You're being stalked by an unstoppable robotic assassin! [Close up of Cueball's head.] Cueball: Of course, in a sense, we're all being stalked by an unstoppable robot. Cueball: A robot called time . [Cueball looking at a clock.] Cueball: I see it in the mirror. I see wrinkles, grey hairs. Cueball: I hear its metallic footsteps in the relentless rhythm of the ticking clock. [Cueball reaches out to Megan.] Cueball: Anyway, uhh - come with me if you want to live for a while. Cueball: You'll still die eventually. Cueball: We all will.

The comic starts with a scene similar to one in the 1984 science fiction action film The Terminator . In the movie a killing robot (played by Arnold Schwarzenegger ) is sent back in time to kill Sarah Connor, the main female protagonist of the movie. A human, Kyle Reese, also travels back in time to protect her (and he acquires a sawed-off shotgun which Cueball holds in the strip). However, in the following panels, Cueball explains that, even if he succeeds protecting Megan from the killing robot, we all are hunted by an unstoppable enemy trying to kill us – time. He goes on to point to the similarities between the time and a Terminator. The clock visible in the third panel features a red light in the place of a 3-hour marker, which is a reference to glowing red eyes of a Terminator. In the final panel, "come with me if you want to live" is a famous phrase from the movie , but in this case, amended with the facts about the inevitability of eventual death. Also, the title text is a play on a quote from The Terminator , where Sarah Connor starts to believe that " There's no fate but what we make for ourselves. ". It is also a reference to the character " Death " in Terry Pratchett 's Discworld novels. In the Discworld novels, Death's voice is always depicted in small caps and he is often caught making sometimes bizarre philosophical statements about life and death. 652: More Accurate is also riffing on Kyle Reese's introductory "Come with me if you want to live" line to Sarah Connor. The theme of the inevitability of the ravages of time is underlying 926: Time Vulture . [Cueball runs towards Megan with a shotgun in hand.] Cueball: I'm from the future! Cueball: You're being stalked by an unstoppable robotic assassin! [Close up of Cueball's head.] Cueball: Of course, in a sense, we're all being stalked by an unstoppable robot. Cueball: A robot called time . [Cueball looking at a clock.] Cueball: I see it in the mirror. I see wrinkles, grey hairs. Cueball: I hear its metallic footsteps in the relentless rhythm of the ticking clock. [Cueball reaches out to Megan.] Cueball: Anyway, uhh - come with me if you want to live for a while. Cueball: You'll still die eventually. Cueball: We all will.

Pickup Artists

Pickup Artists

https://www.xkcd.com/1178

https://www.explainxkcd.com/wiki/index.php/1178:_Pickup_Artists

[Beret Guy is talking with Hairy.] Beret Guy: What've you been up to lately? Hairy: I've been hanging out with some pickup artists. Hairy: I'm learning a lot! Beret Guy: Oh, that sounds like fun! [Caption below the panel:] The world seems like a happier place if you think "pickup artist" is like "pickup basketball player". This comic is one of a small set of comics with the same or almost the same title as another comic (the only difference being the use of the plural form of "artist").

A pickup artist is a person who considers himself skilled at picking up (finding, attracting and seducing) women (or men), through various psychological tactics and tricks. The term " pickup " in "pickup basketball" means informal and spontaneous. In pickup basketball the players are not part of an organized league or team but rather are just people who are available to play at that time and location. Beret Guy thinks (or wants to think) that what pickup artists really do is gather spontaneously to practice artistry , like the visual arts . This makes the world seem a happier place, especially considering his own disposition for (eccentric) art, and generally ability to always see the best in every situation. Randall does not believe that pick-up artists have healthy attitudes towards women and has elaborated on this previously in 1027: Pickup Artist (also featuring Hairy ) and in 800: Beautiful Dream . The title text also shows Beret Guy's belief that the " friend zone " is a physical place. The "friend zone" refers to the state of a relationship in which one party has romantic interests, but the other person only wants to be friends. Once the friend zone is established, it is said to be difficult to try to move beyond that point into a romantic relationship. Beret Guy however believes (perhaps intentionally, like with pickup artist) that a physical place filled with his friends should be a fun place to visit. Randall previously expressed criticism towards trying to just slip into a romantic relationship from the friend zone in 513: Friends . [Beret Guy is talking with Hairy.] Beret Guy: What've you been up to lately? Hairy: I've been hanging out with some pickup artists. Hairy: I'm learning a lot! Beret Guy: Oh, that sounds like fun! [Caption below the panel:] The world seems like a happier place if you think "pickup artist" is like "pickup basketball player". This comic is one of a small set of comics with the same or almost the same title as another comic (the only difference being the use of the plural form of "artist").

ISO 8601

ISO 8601

https://www.xkcd.com/1179

https://www.explainxkcd.com/wiki/index.php/1179:_ISO_8601

Public Service Announcement: Our different ways of writing dates as numbers can lead to online confusion. That's why in 1988 ISO set a global standard numeric date format. This is the correct way to write numeric dates: 2013-02-27 The following formats are therefore discouraged: 02/27/2013 02/27/13 27/02/2013 27/02/13 20130227 2013.02.27 27.02.13 27-02-13 27.2.13 2013. II. 27. 27 ⁄ 2 -13 2013.158904109 MMXIII-II-XXVII MMXIII LVII ⁄ CCCLXV 1330300800 ((3+3)×(111+1)-1)×3/3-1/3 3 2 27 2013 [the numbers 2013, 02, and 27 written overlapping each other] 10/11011/1101 02/27/20/13 2 0 5 3 1 1 2 67 4 37 8 [A black cat with 2-27-13 scrawled across its body in dripping white paint.] Cat: Hissss

When abbreviating the date into numerical form, various areas of the world tend to list the year, month, and day in different orders (as well as with different delimiting symbols), which can cause confusion particularly when the day value is 12 or lower allowing it to be easily interpreted as the month and vice versa. As a public service announcement , this comic states that there is in fact one international standard for writing numeric dates, set by the International Organization for Standardization in its ISO 8601 standard: YYYY-MM-DD. The comic then proceeds to list several discouraged ways of writing out the date of the comic's publication, as they do not match the standard. It begins with several commonly used ones in countries around the world, but then begins to list increasingly uncommon ways, ranging from strange (Roman numerals) to quirky (binary, Unix time) to essentially impossible (painting the numbers onto a black cat). The title text provides a perfect example of the kind of ambiguity that can arise when non-standard formats are used. The ISO standard was in fact published on 1988-06-05 and amended on 2004-12-01. This is mentioned in the title text in MM/DD/YY format; however, there is no way to naturally figure this out, particularly with the second date. With the year truncated to two digits and all three numbers at 12 or lower, the date referring to December 1, 2004 (the digits pairs 12, 01 and 04) has a number of misinterpretations. Usually 12 th Jan '04 (if written as US-style but read as European, or vice-versa) but with ISO-influenced "YY MM DD" ordering as one side or other of the misunderstanding it can easily become the 12 th day of April 2001, the 4 th day of December 2001 and the 4 th of January 2012. It takes two such communication errors to 'become' the 1 st day of April 2012. Date formats were again the subject in 1340: Unique Date and 2562: Formatting Meeting . The other mentioned formats are: Public Service Announcement: Our different ways of writing dates as numbers can lead to online confusion. That's why in 1988 ISO set a global standard numeric date format. This is the correct way to write numeric dates: 2013-02-27 The following formats are therefore discouraged: 02/27/2013 02/27/13 27/02/2013 27/02/13 20130227 2013.02.27 27.02.13 27-02-13 27.2.13 2013. II. 27. 27 ⁄ 2 -13 2013.158904109 MMXIII-II-XXVII MMXIII LVII ⁄ CCCLXV 1330300800 ((3+3)×(111+1)-1)×3/3-1/3 3 2 27 2013 [the numbers 2013, 02, and 27 written overlapping each other] 10/11011/1101 02/27/20/13 2 0 5 3 1 1 2 67 4 37 8 [A black cat with 2-27-13 scrawled across its body in dripping white paint.] Cat: Hissss

Virus Venn Diagram

Virus Venn Diagram

https://www.xkcd.com/1180

https://www.explainxkcd.com/wiki/index.php/1180:_Virus_Venn_Diagram

[Euler diagram with two circles that don't intersect. One circle is green, while the other is slight dark blue.] Green circle: Computer problems that make people say "Maybe it has a virus?" Blue circle: Computer problems caused by viruses

Randall uses an Euler diagram (technically not a Venn diagram ) to make fun of clueless computer users. The circles in the diagram don't overlap, meaning problems that people suspect are caused by viruses are never really caused by viruses, and problems that are actually caused by viruses are never suspected by people to be caused by a virus. When computers don't function as expected, a common response from ordinary users is "Maybe it has a virus ?". However, most of these situations can be explained by faulty hardware (freezing, blue screen, etc.) or software (crashes, errors, apparent lack of response to input, etc.), a general lack of maintenance (too slow to start up, too much clutter on screen, etc.), or user error. A virus can potentially cause those symptoms, but it's much more common for them either to cause immediate and massive damage (rendering the computer completely unusable, wipe the disk, display obvious propaganda, etc.), or to remain stealthy with no obvious symptoms (logging keystrokes, exfiltrating sensitive information, receiving commands in the background, etc.). Of course there is no clear separation and there is always some overlap between the two scenarios, so the diagram is not meant to be taken literally. The title text refers to the technological singularity , a hypothetical point in the future when superintelligence emerges in computers, so that they can build new computers with ever increasing intelligence. It is seen as impossible to predict what would happen beyond this point; hence the term "singularity". 1084: Server Problem makes a joke on this. "Defragging" is short for disk defragmentation , an easy, user-friendly action that PC users can undertake to supposedly make their computers run faster. It is therefore a common all-round recommendation to do this, regardless of the problem. Randall suggests the same clueless users would encounter the singularity and attempt defragging. It probably won't help much. [Euler diagram with two circles that don't intersect. One circle is green, while the other is slight dark blue.] Green circle: Computer problems that make people say "Maybe it has a virus?" Blue circle: Computer problems caused by viruses

PGP

PGP

https://www.xkcd.com/1181

https://www.explainxkcd.com/wiki/index.php/1181:_PGP

How to use PGP to verify that an email is authentic: Look for this text at the top [In mail header, light grey.] Reply [Highlighted, with arrow pointing to it from the text "Look for this text at the top" above.] -----BEGIN PGP SIGNED MESSAGE----- [In mail message, light grey.] HASH: SHA256 Hey, First of all, thanks for taking care of [After mail message.] If it's there, the email is probably fine

PGP (Pretty Good Privacy) is a program which can be used to encrypt and/or sign data, including messages sent as emails. Encrypting means encoding data in a way that requires a secret key to decrypt and read; signing means that there is a code included in the data which can be used to verify the identify of the sender and that the data has not been altered in transit. In the case of the email in this comic, it has only been signed; not encrypted (hence, the top of the first line of text can be seen and is legible in normal English). This is more common than encryption, as reading an encrypted message would require the recipient to already be a PGP user. In fact, the use of PGP even to sign email messages is so rare that most people have probably never seen a signed message. Because a signed email is so rare, and because it is already legible and unencrypted, Randall is making the tongue-in-cheek observation that few users, technical or otherwise, actually know how to use the signature to verify the authenticity of the sender using the PGP signature, and that such users can safely assume that since there is a signature, that is good enough evidence that the message is authentic. Further, because PGP signatures are so rare and probably ignored by most recipients, he suggests one would not expect anyone to even bother creating a false PGP signature; therefore the mere existence of a PGP header would suggest authenticity. The title text extends the joke by suggesting you confirm there's a bunch of random characters in the footer (this is the actual signature that PGP generates which can be used to verify the authenticity of the email). Again, Randall is humorously suggesting that the existence of the block is itself sure evidence of authenticity. How to use PGP to verify that an email is authentic: Look for this text at the top [In mail header, light grey.] Reply [Highlighted, with arrow pointing to it from the text "Look for this text at the top" above.] -----BEGIN PGP SIGNED MESSAGE----- [In mail message, light grey.] HASH: SHA256 Hey, First of all, thanks for taking care of [After mail message.] If it's there, the email is probably fine

Rembrandt Photo

Rembrandt Photo

https://www.xkcd.com/1182

https://www.explainxkcd.com/wiki/index.php/1182:_Rembrandt_Photo

[Megan is holding a laptop. Cueball is sitting at a desk and turned around to face Megan.] Megan: Hey, look - Rembrandt's parents having sex! Cueball: Waugh! Why do you- Cueball: ...Wait, how can there be a photo of that? Megan: It's an artist's conception.

Rembrandt was a 17th-century Dutch artist. Megan shows Cueball an alleged photo of Rembrandt's parents at the time that his mother became pregnant; his conception . Since photography wasn't invented until the 19th century, it can't be a real photo. Megan responds to Cueball's disbelief by stating that it is an artist's conception: an artistic imagination and depiction of an event. The joke thus is a pun on the phrase 'artist's conception' that can mean two different things: one, Rembrandt's mother becoming pregnant with him and two, the creation of the image. The title text refers to James McNeill Whistler who painted a portrait of his mother, known to Whistler himself as "Arrangement in Grey and Black No1" but more commonly known as " Whistler's Mother ". As a joke on this, Megan seems to want to show a photo of Whistler's mother, which would probably be pornographic or at least different from the famous portrait. The ::click:: is Megan switching to that picture on her laptop. [Megan is holding a laptop. Cueball is sitting at a desk and turned around to face Megan.] Megan: Hey, look - Rembrandt's parents having sex! Cueball: Waugh! Why do you- Cueball: ...Wait, how can there be a photo of that? Megan: It's an artist's conception.

Rose Petals

Rose Petals

https://www.xkcd.com/1183

https://www.explainxkcd.com/wiki/index.php/1183:_Rose_Petals

[Cueball enters a living room, to see a line of red rose petals on the floor.] [Cueball follows the line of rose petals.] [Cueball observes that the line of rose petals leads out the front door, down the driveway, and along the sidewalk.] [The rose petals leads up to a table fan behind what appears to be an inverted mailbox filled with rose petals with its back removed. Both are sitting on a Roomba which is motoring down the sidewalk. The fan is on, and is blowing the rose petals out the slit in the front of the mailbox. The contraption is making a sound and the Roomba has its brand written on it] Whirrrrrr Roomba

This comic strip is playing with romantic movies and gestures used in them. In such movies, one often used romantic gesture is spreading rose petals in the house or apartment , making a way towards the bedroom in which a romantic interest/lover is waiting surrounded by roses for a love-making session. The joke is that these petals don't lead from the front door to the bedroom and Cueball 's lover, but in the opposite direction instead from the bedroom out onto the street. It appears that someone has set up a box of rose petals and an electric fan atop a Roomba (an autonomous robotic vacuum cleaner) as a method of automatically creating such a trail. The title text suggests that despite the other party's intentions of setting this up as a joke to trick Cueball, Cueball ended up having a lovely time with the Roomba. [Cueball enters a living room, to see a line of red rose petals on the floor.] [Cueball follows the line of rose petals.] [Cueball observes that the line of rose petals leads out the front door, down the driveway, and along the sidewalk.] [The rose petals leads up to a table fan behind what appears to be an inverted mailbox filled with rose petals with its back removed. Both are sitting on a Roomba which is motoring down the sidewalk. The fan is on, and is blowing the rose petals out the slit in the front of the mailbox. The contraption is making a sound and the Roomba has its brand written on it] Whirrrrrr Roomba

Circumference Formula

Circumference Formula

https://www.xkcd.com/1184

https://www.explainxkcd.com/wiki/index.php/1184:_Circumference_Formula

Circumference of a circle: 2πr 2 2 The circle's radius

The circumference C of a circle is 2 π r , where r is the radius of the circle. Randall then makes a footnote about r , using 2 . This creates a typographical ambiguity, since a superscript 2 can also be an exponent (as in x 2 ). The comical purpose of this ambiguity is that the formula initially makes an appearance of a mistake and confusion with the formula for the area of the circle: A = π r 2 . If and only if the reader realizes that the superscript text is a reference to a footnote will they understand that the author has in fact supplied the correct formula. The title text makes a related joke. Randall has used r' (r- prime ) and r" (r-prime-prime, typically pronounced as r double prime ). The title text can be explained thusly: Like many symbols, prime has widely differing meanings depending on context. In mathematics prime is often employed to distinguish corresponding components in analogous systems. For example, in a description of a basic physical system, if the velocity of an object is denoted with the variable v , the velocity of that object at time=0 may be denoted with v′ . Playing off this use of prime, Randall has selected the radius of Earth Prime , a concept used in speculative fiction with parallel universes and multiple Earths. Earth Prime is our Earth (or at least the Earth from which the protagonists originate). However, other disciplines use prime to mean other things. In timekeeping and navigations ' denotes minutes (fractions of hours or degrees, respectively) and " denotes seconds (fractions of minutes). In the United States and some other places not using meters to measure distance, ' denotes feet and " denotes inches . The suggestion of using r' or r" does not cause any mathematical confusion, but using the former to denote the radius of a specific object and the latter to denote a radius using a specific unit of measurement would be highly esoteric. Furthermore, r' and r" can be used in calculus as a method of denoting, respectively, a first derivative and a second derivative. For someone attempting to use the formula and some derivative representing a circle's radius, trouble could result quite easily. 2 These are not intended to indicate the presence of a footn... oh, never mind. Circumference of a circle: 2πr 2 2 The circle's radius

Ineffective Sorts

Ineffective Sorts

https://www.xkcd.com/1185

https://www.explainxkcd.com/wiki/index.php/1185:_Ineffective_Sorts

Ineffective sorts

The comic gives examples of four non-functional sorting algorithms written in pseudo - Python . The first sort is an unfinished merge sort . The merge sort works recursively by dividing a list in half and performing a merge sort to each half. After the two halves are sorted, they are merged, taking advantage of the fact that the two halves are now in correct order and thus the merge can be done efficiently. The author of the merge sort in the comic appears to have given up on writing the sorted-merge part of the sort, which is why it's a half-hearted merge sort, but instead concatenates the halves without sorting. In its current state, the sort would divide the list into elements of size one, then recombine them in their original unsorted order, but in nested lists - making the original data more difficult to work with. The author acknowledges this failing with the comment "Ummmmm... Here. Sorry." The second sort is an "optimized" variant of bogosort . A standard bogosort works by randomly shuffling the elements in the list until they are sorted. In a comment, the author points out that this variant of bogosort runs in O(n log(n)), whereas standard bogosorts actually have an expected runtime of O(n·n!) but may never finish. This variant of bogosort finishes so much faster because in most cases it does not actually sort the list, instead reporting a fictitious error in the operating system (a "kernel page fault") if the list isn't ordered after shuffling log(n) times. The bogosort is "optimized" because no comparison sort algorithm can possibly do better than O(n log(n)) in the worst case. The third sort parodies a programmer explaining a quicksort during a job interview. The quicksort works by choosing an index as a pivot value and sorting all elements less than the pivot before the pivot and all the elements greater than the pivot after the pivot. It then does a quicksort to the section less than the pivot and the section greater than the pivot until the whole list is sorted. The interviewee flounders for a little while, then asks whether they can use the standard libraries to call a quicksort. The joke being, the standard library contains a quicksort, and the programmer would rather rely on that (possibly even pass it off as his own work) than his own example of quicksort. While it's commonly a good idea in real projects, this would surely count as a failure on interview. The final sort is just a mess. First it checks to see if the list is sorted, and exits if it is. Then it rotates the list by a random amount 10,000 times (as if cutting a deck of cards) and exits if the list is ever sorted. Next, in desperation, it checks if the list is sorted three times. Finally, realizing that they have no chance of success, the author performs the computer equivalent of a Rage Quit and attempts to destroy the computer rather than admit defeat. First, the program attempts to schedule a shutdown of the computer in five seconds, then attempts to delete the current directory, then attempts to delete the user's home directory (presumably the grader's files), and finally all the files on the computer. rm is a POSIX command; the -r and -f flags mean that the remove command will remove all contents of the specified directories and will not prompt the user beforehand. Under the guise of " portability ", the program runs the equivalent Windows rd command with switches to delete all files from the "C:" drive without prompting. Finally, the program returns a list containing the numbers one through five in order. In the title text, StackOverflow ( link ) is a question-and-answer site where programmers can ask and answer questions on programming. The author of this code takes advantage of the hopes that someone on StackOverflow knows what they are doing and has posted code to sort a list... and somebody implemented stacksort ; well, sort of. Ineffective sorts

Bumblebees

Bumblebees

https://www.xkcd.com/1186

https://www.explainxkcd.com/wiki/index.php/1186:_Bumblebees

[Caption above the panel:] Science fact: [A black and yellow bumblebee sits on the control column in the cockpit of an airplane. With lots of instruments and buttons in front of it. There is a caption below the panel:] Physicists still can't explain how bumblebees can fly airplanes.

This is the first comic using a fact that is not a Fun fact . Instead it is a Science Fact. There is an often repeated legend that according to the laws of aerodynamics, bumblebees cannot fly. No theories of aerodynamics or mechanics have ever claimed such a thing, and the legend likely originates from a mathematical error that appeared in a 1934 book, written by a scientist who acknowledged that the conclusion was probably wrong. Here, Randall makes fun of the urban legend with some wordplay. "Fly" in English can refer to both flying under one's own power and the act of piloting a flying vehicle. The comic puts a bumblebee on top of a control column inside of an airplane and lets it fly the entire plane. But physicists are still confused and don't know how the bees are able accomplish this. The strip also creates a fallacy that when experts can't explain something, they must not be able to understand it. In this particular case, experts are unable to explain why bees can fly airplanes because they can't fly airplanes. [ citation needed ] This strip could be a reference to Bee Movie , in which the main character, Barry B. Benson, enlists the help of other bees to land a plane with the last reserves of pollen on Earth. The opening quote of the movie repeats the Bumblebee legend, followed by saying, "The bee, of course, flies anyway, because bees don't care what humans think is impossible." The title text mentions that sociologists are also unable to explain why many people repeat this obviously wrong urban legend . [Caption above the panel:] Science fact: [A black and yellow bumblebee sits on the control column in the cockpit of an airplane. With lots of instruments and buttons in front of it. There is a caption below the panel:] Physicists still can't explain how bumblebees can fly airplanes.

Aspect Ratio

Aspect Ratio

https://www.xkcd.com/1187

https://www.explainxkcd.com/wiki/index.php/1187:_Aspect_Ratio

[A gray car is crushed in a large black clamp.] Whenever someone uploads a letterboxed 16:9 video rescaled to 4:3, I do this to their car.

Aspect ratio is the relationship between the width and height of an image (and in this case, a video) and is denoted in a ratio of <width>:<height> - usually either in lowest common denominator, or with a decimal width to a height of "1". Up until the 1990s, all televisions and most computer monitors (CRT tube and LCD) were in the standard 4:3 aspect ratio, called "fullscreen" (meaning the width is 4/3 or 1.33... times the height). When HDTV was developed, the standard for television screens changed to 16:9 (width being 16/9 or 1.77... times the height), called "widescreen" (although widescreen can also refer to a number of even wider ratios used in feature films). Computer monitors are now available in widescreen ratios, though fullscreen remains common as well. Letterboxing is a process whereby an image which does not fully fill a screen is expanded to fill the screen by the addition of further material (mattes). Usually this is done with the addition of black bars in the empty space. One example of why this was necessary was widescreen films on VHS cassette. VHS could only record and play back 4:3 images. Thus, in order to display a widescreen film, the rest of the VHS's 4:3 image had to be filled with horizontal black bars at the top and bottom of the image. Those bars were part of the video information recorded on the cassette. When DVDs were introduced, many DVDs also had letterbox bars on the DVD's full screen image. With the increased popularity of widescreen televisions, DVD players were improved to offer anamorphic widescreen , in which the full widescreen image is horizontally rescaled (shrunk) into a 4:3 size, which the player then was able to display stretched horizontally back to the proper widescreen aspect. With the advent of Blu-ray, video is generally encoded in whatever its proper aspect ratio is intended to be, and the player itself is left to appropriately matte the image. The problem with letterboxed video (such as a 16:9 video letterboxed for 4:3) is that if one tries to watch the video on a 16:9 widescreen, where the image should fill the whole screen, instead the 4:3 letterboxed image fills part of the screen with further vertical mattes on the left and right of the image, thus producing an image much smaller than it needs to be, with mattes on all four sides. Some TVs or media players can zoom to help resolve the issue, although the video resolution usually suffers. By encoding only the video itself and allowing the player to do the matting, the video can be seen as large as possible on any given screen. Animorphs is a late-90's to early-00's young adult book series about shape-shifting teens who turn into animals to fight body-snatching aliens. Sony held the rights to create a film, but never made use of them, beyond creating URLs for a proposed movie on December 11, 2012. Animorphs has since been mentioned in the title text of 1360: Old Files as well as being the main joke in 1380: Manual for Civilization and 1817: Incognito Mode . In this comic, Randall appears to be complaining about the issue of widescreen videos which have been rescaled to 4:3 by "squashing" the video horizontally to make it narrower, and in the process causing everything to appear thinner/taller than it really is, causing an unpleasant experience. This is akin to crushing a car to the 3:4 ratio while putting black bars on both sides, which Randall uses as disproportionate retribution . A note is that, if someone managed to "expand" the car, the car would not be "un-crushed" and probably even destroyed even more, referencing the bigger damage done when "squashed" video is attempted to be "expanded" to its original ratio, distorting the video quality. When an image is converted to 3:4, the pixels are resized to squares. When resized to 16:9, the pixels therefore have a longer side and a shorter side. [A gray car is crushed in a large black clamp.] Whenever someone uploads a letterboxed 16:9 video rescaled to 4:3, I do this to their car.

Bonding

Bonding

https://www.xkcd.com/1188

https://www.explainxkcd.com/wiki/index.php/1188:_Bonding

This is source code written in the Java programming language which models a parent and a child playing a game of catch . Normally this game is played with the parent throwing a ball to their child, who catches it and throws it back, and repeated back-and-forth. The comic title "Bonding" refers to the building of relationship between the parent and the child. The joke lies in the puns using the words try , throw , catch , and Throwable . These can refer to actions in the real-life game, but are also keywords in the Java language that are used for exception handling , a method of signaling error conditions and responding to them. Also, the terms "parent" and "child" are usually interpreted more abstractly in programming, as generic terms used in hierarchical data structures . The program, as written, will recursively call the aim method alternately on the parent and the child indefinitely, causing each to take turns throwing and catching the Ball object. Note that unlike the real game, this program actually has the same person both throwing and catch the same ball on their turn. The ball is passed onto the other person by aiming it at them, which causes the person to both throw and catch the ball, and aim it back, perpetuating the cycle. This program will also eventually crash with a stack overflow error. The title text refers to the Eclipse IDE , which is a tool commonly used to develop software in Java. "Building character" is something that you would expect a parent to do, in order to instill in his child positive traits, such as confidence and athleticism. This is possibly a reference to Calvin and Hobbes , where Calvin's dad often encourages him to build character in a number of ways, including playing baseball. This is made more likely by other references combining technology with Calvin and Hobbes, such as xkcd comics 409: Electric Skateboard (Double Comic) , 702: Snow Tracking and 1002: Game AIs . However, here, "build" might also be a play on the term of " building " a program, while " character " refers to a data type in programming languages. It may also refer to the common notion that programming in C++ or Java builds character due to their powerful but sometimes finicky libraries. To compile this Java source code, the two classes would need to be in a .java file. The program defines two classes (types of objects): The program executes in the following order:

Voyager 1

Voyager 1

https://www.xkcd.com/1189

https://www.explainxkcd.com/wiki/index.php/1189:_Voyager_1

[A heading at the top of a white panel, then a line and below this 22 tally marks in two rows, four times five (three of these at the top) and then two extra.] Number of times Voyager 1 has left the Solar System

Voyager 1 is a U.S. space probe launched in 1977 to study the outer reaches of the Solar System and beyond. Popular press has on several occasions announced that it "has left the solar system" at each point when a boundary has been confirmed or a major event has taken place. This underscores the fact that there is no strictly defined and recognizable boundary of the solar system, or at least we haven't found one yet. On the day of this comics release (2013-03-22) it was announced that Voyager 1 had entered a new region of space . At this point Voyager 1 had passed through the Heliopause and entered the Interstellar medium , although this latter was first confirmed about half a year later in September 2013. The chart shows that Voyager 1 has left the Solar System 22 times, but in the title text only 16 are mentioned. The title text lists several such possible boundaries, (and how many times Voyager 1 has passed them) together with fictive humorous ones: See also Voyager over the “heliocliff,” but Solar System transition mysterious on Ars Technica. About eight years later, Voyager 1 leaving the solar system was brought up again in 2414: Solar System Compression Artifacts . [A heading at the top of a white panel, then a line and below this 22 tally marks in two rows, four times five (three of these at the top) and then two extra.] Number of times Voyager 1 has left the Solar System

Time

Time

https://www.xkcd.com/1190

https://www.explainxkcd.com/wiki/index.php/1190:_Time

The Past

The Past

https://www.xkcd.com/1191

https://www.explainxkcd.com/wiki/index.php/1191:_The_Past

[Cueball and Black Hat talking.] Cueball: Well, you know what they say. The past is a foreign country- Black Hat: -With an outdated military and huge oil reserves! Black Hat: Hmmm...

"The past is a foreign country, they do things differently there" is the opening line of " The Go-Between ", a novel by Leslie Poles Hartley (1895–1972), published in London in 1953. Black Hat notes that a country's past military tends to be less advanced than its current one, and that countries in the past had larger oil reserves as they had consumed less oil then. If a country from the past existed in its old state today, other countries would likely leap at the opportunity to exploit its oil reserves. Or: Black Hat could be considering sending the modern troops of a country from today back in time to rob the oil from the countries in the past. It could be profitable to invent a time machine for just that. "Mozart in Mirrorshades" is a short story by Bruce Sterling and Lewis Shiner, which features the use of time travel to exploit earlier eras' natural resources. Also, in the Hitchhiker's Guide to the Galaxy series, time has been exploited to use as energy. They say: "The Past is like a foreign country. They do things exactly the same there." The "If history has taught us anything" phrase is used to start several quotes: "If history has taught us anything, Arthur muses, it is that men with mustaches must never achieve positions of power." - Tom Rachman, The Imperfectionists "If anything in this life is certain, if history has taught us anything, it is that you can kill anyone." - Michael Corleone, The Godfather The title text starts by fitting the usual pattern of this phrase, but in the second half humorously subverts it. It extends the "past as a foreign country" metaphor by implying that lessons learned from history can count as military intelligence to use against it. A more recent movie, Christopher Nolan's Tenet (film) , also deals with destroying the past. [Cueball and Black Hat talking.] Cueball: Well, you know what they say. The past is a foreign country- Black Hat: -With an outdated military and huge oil reserves! Black Hat: Hmmm...

Humming

Humming

https://www.xkcd.com/1192

https://www.explainxkcd.com/wiki/index.php/1192:_Humming

[Megan is humming a tune.] Cueball: Hey. Cueball: What's that? [Megan is still humming the same tune.] Cueball: What are you humming? Cueball: Should I know the tune? Cueball: ...Hmm... [Cueball gets out his phone and opens up a music recognition program.] Phone: Identify song Phone: Recorded Phone: > Live [beta] Phone: Identifying... [A zoom in on the phone screen. An album cover with a picture of Megan on it.] Positive match: Check it out! By I hacked the audio fingerprint database Feat. MEEEEEE Track: We're out of cat food (pick some up?)

Services like MusicBrainz and SoundHound can detect a recorded song's acoustic fingerprint and match it with an existing song. This lets them identify the title and artist of an unnamed recorded musical extract. In this comic, Megan hacks the acoustic fingerprint database to add her own entry with a message to Cueball , in which she asks him to buy cat food . HTTP error code 406 means Not Acceptable. When a client requests data from a server, the client lists the data formats that it can accept. If a server is unable to provide data in any format that the client accepts, the server returns error 406 Not Acceptable. For example, this can occur if a client requests XML but the server supports only JSON. In the title text, the standard meaning of the error message is ignored and the text "Not Acceptable" is taken literally: The server is offended by Randall 's humming. [Megan is humming a tune.] Cueball: Hey. Cueball: What's that? [Megan is still humming the same tune.] Cueball: What are you humming? Cueball: Should I know the tune? Cueball: ...Hmm... [Cueball gets out his phone and opens up a music recognition program.] Phone: Identify song Phone: Recorded Phone: > Live [beta] Phone: Identifying... [A zoom in on the phone screen. An album cover with a picture of Megan on it.] Positive match: Check it out! By I hacked the audio fingerprint database Feat. MEEEEEE Track: We're out of cat food (pick some up?)

Externalities

Externalities

https://www.xkcd.com/1193

https://www.explainxkcd.com/wiki/index.php/1193:_Externalities

[This was a dynamic image where the text changed during April 1st. The main title text also changed after the dynamic part was finished, and there are even different title text for different part of the comic. This transcript is of the final version of the comic, (no longer dynamic or changing), as displayed at present on xkcd, there are still four different title texts for specific panels. These four title text are for that reason included here in the transcript.] [The basic title text for the entire comic is: "This comic went up on April 1st, and the panels changed throughout the day in response to readers doing things like breaking hashes, edited a rapidly-shuffling set of target Wikipedia articles, and donating to Wikimedia Foundation. (The vandalism is over now and CMU won the hashing contest.)" The other three title text are only active over certain panels.] [The first panel with the caption and Megan below has it's own title text. A part of that panel is a link, and in the section where this link is active there is no title text at all. The title text for the rest of the first panel is: "Happy April 1st, everyone!"] [A panel with only text is above the first drawing. There is a link on the top part of the text to http://almamater.xkcd.com/ (the link is now broken).] Ahoy, carnegie melonites! Come find your future at Baidu. [Below, not in a frame, is Megan.] Megan: But nothing about Tiananmen Square. [Caption floating above the frame of the next panel:] It takes great minds to stifle other great minds. [Ponytail sits at a desk, hand to her chin, with two Cueball-like guys with their hands on the table.] Ponytail: Let's block Canada Cueball-like guys: Sounds good. [Ponytail crouches on a moving Roomba (labeled) with a steaming mug of coffee in one hand and a smartphone in the other. Above her is a caption. The Roomba makes a noice] We're a convenient four hour drive from New York City (15,000 hours by Roomba.) Whirrrrrrr Roomba [Ponytail and Hairy corners Cueball as he walks out of a door, and a black haired ponytailed girl is moving towards him wielding a giant butterfly net. There is a caption above them:] Our recruiters are on the hunt for unaware CMU graduates [The fifth panel has it's own title text only active within (or very close to) the frame. It is: "uic has the third best hash. See the full standings at http://almamater.xkcd.com/best.csv" (The link is now broken)] [There is a caption above a website application. There is three fields to be filled, with each their caption and text:] or uic graduates, provied any of them manage to fill out the application correctly. Name which one Email forget it Education Riding the L all night long [Caption floating above the frame of the next panel:] At Baidu, Inc., you'll have the opportunity to work on cutting-edge projects. [Cueball sits at a computer.] Cueball: What does "make dog" do? Off-screen voice: Experimental dog generator. Don't click on it; the default size isn't set, so- *click* [The last three panels has their own title text, only active within a frame that could contain all three panel. Outside that "frame" (all the way around) is the other title text. Within the title text is: "The dog gains a pound for every $10 donated to the Wikimedia Foundation via this link. Currently at $51135.33."] [Small insert panel, going in above the next larger panel: Cueball stares at the screen.] Kzzzt *bip* Off-screen voice: Uh oh. [A giant dog looks down at the desk where the computer once was, now only the wires are left. Cueball, leaning way back in his office chair, holding his hand to his mouth, stares up at it.] [Again a smaller insert panel above the large one with the dog. A graphic showing two sliders and a dog (similar to the one in the previous panel). Next to the dog with arrows pointing to it are a thermometer graphic and an equation. Below is an e-mail type text and finally a caption. There are arrows over and under "God" and "dogs" between the g and d's.] d(x)=R [email protected] , Inc. Play God with dogs. TM

This was the fourth April fools' comic released by Randall . The previous fools comic was 1037: Umwelt from Sunday April 1st 2012. The next was 1350: Lorenz released on Tuesday April 1st 2014. This comic isn't a static image - even the title text changes depending on which part of the image you're hovering over. It presented a competition for students to see who could come closest to breaking a Skein hash but also an aid appeal for the Wikimedia Foundation. There are quite a few references in the comic to Baidu . Baidu is a large Chinese Internet services company that employs thousands, whose shares are publicly traded on world stock exchanges. It's the predominant Internet search provider of China, and is sometimes called the "Google of China". It offers parallels for the Chinese market of many of the services that Google provides and offers its own encyclopedic wiki with a restricted edit policy to serve as a replacement for Wikipedia. Wikipedia reports that Baidu's search engine handled 56% of Chinese internet search queries in Q4 2010. and that in October 2012, Baidu ranked 5th overall in the Alexa Internet rankings. Given that explanation for the Baidu references in #1193 is still solicited for explainxkcd, Baidu apparently is not well known yet among savvy XKCD readers. Baidu Search results reputedly follow the censorship dictates of the Chinese authorities, causing it to return censored responses to searches for politically sensitive terms like "Tianamen Square massacre" or "Falun Gong" when executed by web browsers that are connected via Chinese ISPs. When you execute such searches via Baidu in the US, the top links returned for these topics do seem to reflect Chinese government sensibilities although the uncensored English language Wikipedia articles for these topics are listed high in the query results. Baidu's reputation for censorship provides background for Megan's reply "but nothing about Tianamen Square" in response to the "Come and find your future at Baidu" employment enticement of panel one and also provides the background to understand the "It takes great minds to stifle other great minds" slogan of the second panel. The blank regions in the above image are dynamically generated from various sources. For the two days until comic 1194 appeared, a competition was underway to see who could come closest to breaking a Skein hash . The first text line of the first panel contains a link to http://almamater.xkcd.com . This page contained the text: Currently looking for Skein 1024 1024 input matching On this page, users were invited to enter "Your school's domain name" — presumably intended to be their college alma mater. (At least in the beginning, only a few top-level domains were accepted.) If the user entered an acceptable domain (by xkcd's rules, which apparently changed during the 48 hours of the competition), they could then enter data values one at a time. For each data value entered, xkcd returned a hash value and the number of bits by which it differed from the target value. The object was to achieve the lowest possible number of differing bits, ideally zero. A ranking page showed the lowest value achieved for each domain name entered, but not the data that achieved it. The first name on the list was substituted in various panels, and the third-place school showed in panel five. No data values were reported by xkcd, but various results were posted by users of the xkcd forums and on other websites, leading to copycat submissions, so that occasionally large numbers of institutions would show the same moderately low value. After the end of the contest, the data submission page vanished, replaced by the final list of rankings, which shows that Carnegie Mellon University achieved the best score with 384 bits incorrect out of 1024. The rankings only show a few hundred out of the several thousand domains submitted—presumably Randall chose to chop the copycat submissions off the end of the list, retaining only honestly obtained results. In some cases, Megan's reply seems to correspond to the company. The text in the second panel is based on the company in the first panel: The text in the form varies independently of the text at the top, sometimes related to the organization in 3rd place: The title text documents the different sources of data in the comic. The different title texts are: [This was a dynamic image where the text changed during April 1st. The main title text also changed after the dynamic part was finished, and there are even different title text for different part of the comic. This transcript is of the final version of the comic, (no longer dynamic or changing), as displayed at present on xkcd, there are still four different title texts for specific panels. These four title text are for that reason included here in the transcript.] [The basic title text for the entire comic is: "This comic went up on April 1st, and the panels changed throughout the day in response to readers doing things like breaking hashes, edited a rapidly-shuffling set of target Wikipedia articles, and donating to Wikimedia Foundation. (The vandalism is over now and CMU won the hashing contest.)" The other three title text are only active over certain panels.] [The first panel with the caption and Megan below has it's own title text. A part of that panel is a link, and in the section where this link is active there is no title text at all. The title text for the rest of the first panel is: "Happy April 1st, everyone!"] [A panel with only text is above the first drawing. There is a link on the top part of the text to http://almamater.xkcd.com/ (the link is now broken).] Ahoy, carnegie melonites! Come find your future at Baidu. [Below, not in a frame, is Megan.] Megan: But nothing about Tiananmen Square. [Caption floating above the frame of the next panel:] It takes great minds to stifle other great minds. [Ponytail sits at a desk, hand to her chin, with two Cueball-like guys with their hands on the table.] Ponytail: Let's block Canada Cueball-like guys: Sounds good. [Ponytail crouches on a moving Roomba (labeled) with a steaming mug of coffee in one hand and a smartphone in the other. Above her is a caption. The Roomba makes a noice] We're a convenient four hour drive from New York City (15,000 hours by Roomba.) Whirrrrrrr Roomba [Ponytail and Hairy corners Cueball as he walks out of a door, and a black haired ponytailed girl is moving towards him wielding a giant butterfly net. There is a caption above them:] Our recruiters are on the hunt for unaware CMU graduates [The fifth panel has it's own title text only active within (or very close to) the frame. It is: "uic has the third best hash. See the full standings at http://almamater.xkcd.com/best.csv" (The link is now broken)] [There is a caption above a website application. There is three fields to be filled, with each their caption and text:] or uic graduates, provied any of them manage to fill out the application correctly. Name which one Email forget it Education Riding the L all night long [Caption floating above the frame of the next panel:] At Baidu, Inc., you'll have the opportunity to work on cutting-edge projects. [Cueball sits at a computer.] Cueball: What does "make dog" do? Off-screen voice: Experimental dog generator. Don't click on it; the default size isn't set, so- *click* [The last three panels has their own title text, only active within a frame that could contain all three panel. Outside that "frame" (all the way around) is the other title text. Within the title text is: "The dog gains a pound for every $10 donated to the Wikimedia Foundation via this link. Currently at $51135.33."] [Small insert panel, going in above the next larger panel: Cueball stares at the screen.] Kzzzt *bip* Off-screen voice: Uh oh. [A giant dog looks down at the desk where the computer once was, now only the wires are left. Cueball, leaning way back in his office chair, holding his hand to his mouth, stares up at it.] [Again a smaller insert panel above the large one with the dog. A graphic showing two sliders and a dog (similar to the one in the previous panel). Next to the dog with arrows pointing to it are a thermometer graphic and an equation. Below is an e-mail type text and finally a caption. There are arrows over and under "God" and "dogs" between the g and d's.] d(x)=R [email protected] , Inc. Play God with dogs. TM

Stratigraphic Record

Stratigraphic Record

https://www.xkcd.com/1194

https://www.explainxkcd.com/wiki/index.php/1194:_Stratigraphic_Record

[Image of the Earth in color as seen from far off in space with pitch black around the Earth. Two blocks of text are above and below the Earth in white rectangles:] Nearly 4.5 billion years ago, Earth had liquid water. But all the crust older than 3.5 billion years has been recycled into the mantle by subduction. [Same image of Earth, but now with only the middle of the panel black. Above and below is white sections (without a frame) with text:] A billion years of the stratigraphic record, the memory of the hills, is forever lost to us. What was it like here, four billion years ago? [A slimmer panel as the first, with two smaller white rectangles with text above and below:] Earth, What secrets do you have? [Similar panel, but now without the white rectangles. Instead a line comes up from the Earth as it speaks with white text, and in small letters, unlike normal xkcd text:] Earth: come closer [Zoom in on the Earth so it now fills almost the entire panel from left to right.] [Further zoom in on the Earth so now only part of the Earth can be seen in the panel. There is still black above, but not on the other three sides of the panel, which is filled with the Earth. It shows the northern part of the Earth with Alaska, Canada and some of mainland USA with one of the great lakes visible at the top right. The sea ice at the North Pole is also visible as are a small part of Russia near Alaska. Again the Earth speaks as in the first panel:] Earth: i'll never tell.

We have no rock formations on Earth older than about 3.5 billion years, as the comic points out, because everything solid from before that time has been subducted down into the Earth's mantle , by tectonic movement . The title text hints at the cooler Moon which stopped re-melting its surface much sooner, so we theoretically could learn something about Earth's history from examining our Moon's surface and makeup. Zircons are a type of mineral found in the Earth's crust , some of which have been estimated to be as old as 4.4 billion years, older than any other mineral. Anyways, here the Earth is anthropomorphized and actively teases the narrator; first it asks the narrator to draw in closer, as if it's about to tell us a secret, but then it whispers "I'll never tell". [Image of the Earth in color as seen from far off in space with pitch black around the Earth. Two blocks of text are above and below the Earth in white rectangles:] Nearly 4.5 billion years ago, Earth had liquid water. But all the crust older than 3.5 billion years has been recycled into the mantle by subduction. [Same image of Earth, but now with only the middle of the panel black. Above and below is white sections (without a frame) with text:] A billion years of the stratigraphic record, the memory of the hills, is forever lost to us. What was it like here, four billion years ago? [A slimmer panel as the first, with two smaller white rectangles with text above and below:] Earth, What secrets do you have? [Similar panel, but now without the white rectangles. Instead a line comes up from the Earth as it speaks with white text, and in small letters, unlike normal xkcd text:] Earth: come closer [Zoom in on the Earth so it now fills almost the entire panel from left to right.] [Further zoom in on the Earth so now only part of the Earth can be seen in the panel. There is still black above, but not on the other three sides of the panel, which is filled with the Earth. It shows the northern part of the Earth with Alaska, Canada and some of mainland USA with one of the great lakes visible at the top right. The sea ice at the North Pole is also visible as are a small part of Russia near Alaska. Again the Earth speaks as in the first panel:] Earth: i'll never tell.

Flowchart

Flowchart

https://www.xkcd.com/1195

https://www.explainxkcd.com/wiki/index.php/1195:_Flowchart

[A flow chart is shown with two boxes and two arrows. The first box rectangular:] Start [From the first box there is a short arrow straight down to a diamond shaped box:] Hey, wait, this flowchart is a trap! [An arrow continues down below from the bottom corner of the diamond box, where there is labeled, and quickly it turns left (in the direction of the arrow), going out under the diamond and then turns left two more times to end up on the right corner of the same box where the arrow points back again.] Yes

Flowcharts are diagrams used to show the logical flow of an algorithm , process, or program. Flowcharts are a recurring theme in xkcd . In this comic, Randall uses the fact that flowcharts can indeed be used to show a loop in the procedure: in this case, the reader will theoretically become trapped in a loop of reading the text in the diamond, following the line marked "YES," and ending back up in the diamond. Those familiar with flowcharts will notice though that, while diamonds usually contain decision questions (which can be answered multiple ways), the diamond here actually includes a statement instead. The title text contains a suggested solution to the loop: the way to escape the loop is to use a marker and add an additional "NO" arrow proceeding from the diamond to a rounded box labelled "END" before you start the algorithm at "START." This suggests that the decision question in the diamond could more properly be phrased as "Is this flowchart a trap?" However, to follow this suggestion, you would need to actually have the marker that you are about to write instructions to go get. Thus, you must also add the instruction "get a marker" somewhere before the flowchart actually begins (before "START"), so that you actually have the marker by the time you get to the flowchart in the comic. And since you did not have a marker and could thus not write this way out, you are still trapped! Of course, the reader could disregard the algorithm, but this would break the conventions of following the flowchart. This is perhaps part the comic's purpose - to suggest that a problem cannot be solved from within the confines of its own conventions. Randall has made use of flowcharts before, and previously released another comic named 518: Flow Charts . [A flow chart is shown with two boxes and two arrows. The first box rectangular:] Start [From the first box there is a short arrow straight down to a diamond shaped box:] Hey, wait, this flowchart is a trap! [An arrow continues down below from the bottom corner of the diamond box, where there is labeled, and quickly it turns left (in the direction of the arrow), going out under the diamond and then turns left two more times to end up on the right corner of the same box where the arrow points back again.] Yes

Subways

Subways

https://www.xkcd.com/1196

https://www.explainxkcd.com/wiki/index.php/1196:_Subways

Subways of North America [A subway-line style (bold colored, 45-degree aligned lines with white bars indicating stations) map has been constructed by combining and linking various parts of the subway maps from many different cities, as if all of the transit systems were connected directly. The cities include (from top to bottom, left to right) Vancouver, Montreal, San Francisco, Toronto, Boston, Chicago, Los Angeles, Cleveland, New York City, Philadelphia, Baltimore, Washington DC, Miami, Atlanta, Monterrey, San Juan, Santo Domingo, and Mexico City.]

The comic shows the maps of all North American subway networks. In reality, none of these systems are interconnected, but in the diagram subways from different cities that have the same color on the official subway map have whimsically named connections, such as the "Ohio-California Tunnel" connecting the Green Lines of Cleveland and Los Angeles, or the "Rocky Mountain Tunnel" connecting the Blue Lines of Chicago and San Francisco. Vancouver and San Francisco are connected through a station called Richmond, which appears to double as Richmond, British Columbia and Richmond, California . The "Springfield Monorail" is fictional, from the animated series The Simpsons (see Marge vs. the Monorail ), but its approximate location on this map would suggest the Seattle Monorail , or perhaps Springfield, Oregon, which Matt Groening revealed was the inspiration for the Simpsons' hometown . The Urban Mass Transit Systems of North America map (right) created by Yale Professor Bill Rankin on his web site Radical Cartography in 2006 presents all of the subway systems in North America at the same scale using geographic, instead of topological, layout. The networks on xkcd's map are displayed with absolutely no consideration to geographic position, in order to connect like-colored routes together. While Vancouver is the most North-West, Mexico City being the most South, and San Francisco the most west, distances are not accurate (in reality, Vancouver is closer to Chicago than to Toronto for example) and cities are often arranged in the wrong direction from one another: The map's design is modeled after the system map of the Massachusetts Bay Transportation Authority in Boston where Randall is from. Not all cities with a subway are shown on the map. Missing from the map: Subways of North America [A subway-line style (bold colored, 45-degree aligned lines with white bars indicating stations) map has been constructed by combining and linking various parts of the subway maps from many different cities, as if all of the transit systems were connected directly. The cities include (from top to bottom, left to right) Vancouver, Montreal, San Francisco, Toronto, Boston, Chicago, Los Angeles, Cleveland, New York City, Philadelphia, Baltimore, Washington DC, Miami, Atlanta, Monterrey, San Juan, Santo Domingo, and Mexico City.]

All Adobe Updates

All Adobe Updates

https://www.xkcd.com/1197

https://www.explainxkcd.com/wiki/index.php/1197:_All_Adobe_Updates

[Cueball is sitting at a laptop with a window with a red title bar floating over his head.] Adobe Update There is an update for: Adobe Download Manager This update will allow you to download the new updates to the Adobe Update Downloader. [OK] [Download]

This comic was probably a reaction to the installation service Ninite removing Adobe Flash Player from their free version the previous day. The comic makes fun of Adobe Systems software that delivers new versions of Adobe products to users' computers, such as Adobe Updater (which replaced Adobe Update Manager ) and Adobe Download Manager (which replaced Akamai ). These software increments might either be technical (to fix compatibility or security issues), or they might add new features that would go unnoticed. In addition, these updates are downloaded automatically by default, but the operating system might install them only if a user allows it to. The frequency of software changes (and changes in the way Adobe allows users to download new software) could result in confused users. In this case, the comic is saying that you must update the program before it can actually check for updates, something it already seems to be doing. There is an actual message that a specific version of these updaters display: The Adobe Updater must update itself before it can check for updates. Would you like to update the Adobe Updater now? In fact, the general necessity of such update managers has often been questioned, as they require the user to "download software in order to download other software". Other notable examples of companies who use update managers include Google and Sun / Oracle , with the latter being also mentioned in the title text. The two buttons 'OK' and 'Download' are implied to have the same effect, indicating the user has no real choice. Or, alternatively, 'OK' may simply just close the dialog without taking any action, as that is common in informational popups in many pieces of software. In that case, the placement of the 'OK' button implies that it is the default action, meaning most users will just ignore the update. Given the extreme frequency and perceived lack of changes (to your average end user), this anecdotally seems to be what most people do. Statistics for the high rate of un-patched systems in the wild support the anecdotal evidence. The language of the message also plays with repeated up and down , as in "there is an up date for the Adobe down load manager..." to give the whole process a feel of preposterousness verging on Carrollian literary nonsense . The title text also suggests that using update helper software which in turn must be updated bears the risk of creating a dependency hell . The "version 21.1.2 of the Oracle..." may refer to the Rush suite 2112 , where moment V is titled Oracle and contains the lyrics "I stand atop a spiral stair, An oracle confronts me there." [Cueball is sitting at a laptop with a window with a red title bar floating over his head.] Adobe Update There is an update for: Adobe Download Manager This update will allow you to download the new updates to the Adobe Update Downloader. [OK] [Download]

Geologist

Geologist

https://www.xkcd.com/1198

https://www.explainxkcd.com/wiki/index.php/1198:_Geologist

[Cueball, wearing earmuffs and goggles and holding a gun and a rock hammer in his hands, is walking away from his van in the background towards a group of rocks. The largest of these rocks is almost as tall as Cueball, but five smaller rocks are scattered on the ground, with a bit of grass growing at their bases. The van has text on its side:] Dept. of Geology [Zoom in on Cueball close to the base of the largest rock. He has put the rock hammer on the ground next to him and aims his gun at the ground and shoots three holes in the earth, the last hole is just forming, as smoke comes out of the end of the gun.] Blam Blam Blam [Zoom out again with Cueball hacking away at the top of tallest rock formation with his rock hammer. The gun has been left near the three holes in the ground. The van can again be seen as can most of the text.] Clink Clink ept. of ology [Cueball, without his head gear, sits at his desk in his office reading a piece of paper he holds in his hands. Three other papers are lying on the otherwise empty desk. Behind him various items hangs on the wall most likely images and diplomas etc. One of them is blank, two looks like images, and four has unreadable text. The last item is the top of the rock that he just chipped off in the previous frame. It has been attached to a mount as a hunting trophy. Above and below there are labels:] Earth 4,500,000,000 BCE - April 12, 2013

Geology is the study of the physical and chemical makeup of the Earth and geologists are sometimes called rock hunters, sometimes derisively. Hunters, after killing an especially difficult or rare beast, sometimes remove its head and hang it up on a wall as a trophy . Cueball , as a geologist, "kills the Earth" by shooting at it. He removes its "head," a chunk of rock, and hangs it up on his office wall. Above the trophy it says Earth, and below it gives it lifespan from 4,500,000,000 BCE (Before Common Era )), which is the current age of the Earth, and then until the day where he shot Earth, which is also the day this comic was released 2013-04-12. The topic of hunting things that are not usually hunted is also in 640: Tornado Hunter The title text is probably a reference to a chicken running around with its head cut off. A few billion years (7,600,000,000 years) is also about how much longer the Earth is expected to last, assuming it gets swallowed up by the expanding Sun at the end of the Sun's life . [Cueball, wearing earmuffs and goggles and holding a gun and a rock hammer in his hands, is walking away from his van in the background towards a group of rocks. The largest of these rocks is almost as tall as Cueball, but five smaller rocks are scattered on the ground, with a bit of grass growing at their bases. The van has text on its side:] Dept. of Geology [Zoom in on Cueball close to the base of the largest rock. He has put the rock hammer on the ground next to him and aims his gun at the ground and shoots three holes in the earth, the last hole is just forming, as smoke comes out of the end of the gun.] Blam Blam Blam [Zoom out again with Cueball hacking away at the top of tallest rock formation with his rock hammer. The gun has been left near the three holes in the ground. The van can again be seen as can most of the text.] Clink Clink ept. of ology [Cueball, without his head gear, sits at his desk in his office reading a piece of paper he holds in his hands. Three other papers are lying on the otherwise empty desk. Behind him various items hangs on the wall most likely images and diplomas etc. One of them is blank, two looks like images, and four has unreadable text. The last item is the top of the rock that he just chipped off in the previous frame. It has been attached to a mount as a hunting trophy. Above and below there are labels:] Earth 4,500,000,000 BCE - April 12, 2013

Silence

Silence

https://www.xkcd.com/1199

https://www.explainxkcd.com/wiki/index.php/1199:_Silence

[Megan is walking with a phone in her hand.] [Megan stops.] [Megan raises her phone.] Phone: Identify song recorded Phone: > LIVE [Beta] [Megan is in an empty room.] Phone: Listening... [The phone screen.] Positive match: 4'33" John Cage

4'33" is a 1952 composition by American avant-garde composer John Cage consisting of four minutes and thirty-three seconds of silence. More specifically, 4'33" consists entirely of faint ambient sounds coming from the environment, while all the players silently hold their instruments. The noise of the audience is considered part of the composition. It is Cage's most famous work, and the subject of many music jokes. Note that John Cage wrote plenty of other non-silent things. Megan is using an app on her smartphone that analyzes music that is playing and uses an online database to figure out what it is; popular real-world examples include Shazam and SoundHound . She does this in an empty room, correctly matching 4'33" . Cueball attempted to use the same app in 1192: Humming , but Megan hacked it there. The title text refers to the fact that since 4'33" is composed of the ambient sounds in an environment, if that environment is a recording studio, live music venue etc. the ambient sound is a band playing another song. [Megan is walking with a phone in her hand.] [Megan stops.] [Megan raises her phone.] Phone: Identify song recorded Phone: > LIVE [Beta] [Megan is in an empty room.] Phone: Listening... [The phone screen.] Positive match: 4'33" John Cage

Authorization

Authorization

https://www.xkcd.com/1200

https://www.explainxkcd.com/wiki/index.php/1200:_Authorization

[Diagram showing several connected bubbles. One in the center says "User account on my laptop," surrounded by "Dropbox," "Photos & files," "Facebook," "Gmail," "PayPal," and "Bank," which are connected to the middle bubbles and to each other. Below the middle bubble is one labeled "Admin account," which is covered in spikes, and has a "door" to the bubble above it.] If someone steals my laptop while I'm logged in, they can read my email, take my money, and impersonate me to my friends, but at least they can't install drivers without my permission.

Computer operating systems were initially written for the business environment. Thus they were made to be accessible to multiple employees, or users , but only fully accessible to administrators (or admins). Regular users can access and use programs on the computer, but only the admin is allowed to make changes to how the computer runs. This same split level of security continues to this day, even in privately owned, or "home", computers. The joke here is that the most important things on a computer are no longer the programs that it runs, but the private personal data it accesses (usually online). Anyone who wished to do real mischief on an active computer could do considerable damage without ever caring what the admin password was. The admin password, in effect, now guards a vault no one cares about. This comic pokes fun at the authorization mechanisms surrounding most operating systems' administrator accounts. It makes the argument that the user's data is more valuable than the integrity of the system. This is arguably true for most personal systems, although it is probably not true in a shared-server setup, where a system compromise could lead to the exposure of many users' data. Essentially, once a user is logged in , they can typically access all of their data without any further restriction. Modifying the operating system (for example, to install drivers ) requires a separate password. In fact, this password protection also hinders installation of malware , which is otherwise possible even remotely, with the malware then being able to e.g. steal passwords, enabling a hacker anywhere in the world to access your accounts without ever needing to touch your computer. So having your computer set up to not to ask you for an administrator's password arguably implies a bigger risk of identity theft than allowing others to access your system physically while being logged in does. The title text alludes to the security practice where computers automatically lock the user out after a few minutes, requiring a password from the user in order to continue using it. Instead, Randall's computer automatically switches to his brother's account, presumably compromising his data instead of Randall's. The fact that Randall's brother has an account on Randall's computer even though Randall does not live with his childhood family (so his brother would not need to use his computer often) could be because Randall does not want his brother to be able to access his files, PayPal, etc… when he uses his computer, which would indicate that either Randall is cynical, his brother is not trustworthy, or Randall is simply following the principle of least privilege . [Diagram showing several connected bubbles. One in the center says "User account on my laptop," surrounded by "Dropbox," "Photos & files," "Facebook," "Gmail," "PayPal," and "Bank," which are connected to the middle bubbles and to each other. Below the middle bubble is one labeled "Admin account," which is covered in spikes, and has a "door" to the bubble above it.] If someone steals my laptop while I'm logged in, they can read my email, take my money, and impersonate me to my friends, but at least they can't install drivers without my permission.