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Instructions

Instructions

https://www.xkcd.com/2601

https://www.explainxkcd.com/wiki/index.php/2601:_Instructions

[The comic consists of one radio button, a small circle in the center of a large white panel. It is interactive. When pressing the radio button (selecting it), it turns blue. The second the radio button is pressed a more than 9-hour long audio file of coding instructions begins to play, and a mute button appears in the bottom right corner. It fades slowly into full opacity. Pressing this button will change it to a loudspeaker. It toggles whether there is sound playing or not. It is not possible to shut down the audio by pressing the radio button. Once selected it cannot be deselected as there is only this one option.] [Covered by the radio button is an image of a turtle crawling from left to right, with a dotted line trailing behind it, indicating its movement. This image can only be seen by looking in the place where images for xkcd are usually placed on xkcd.] [To read a transcript of the audio file go here: 2601: Instructions/Audio Transcript .] The image drawn by the Logo program is a depiction of Bob Ross standing in front of a canvas, on which he has painted "a happy little tree, holding up a happy little world". However, unlike his usual "happy little trees", the tree depicted is not a small pine, but rather a gargantuan World Tree growing from the back of a giant World Turtle , on which a Flat Earth rests. (The "happy little world" does bear several small pines more typical of his style.) Near the middle of the world, a Cueball sits while listening to the radio, perhaps tuning in to the same transmission that generated the image. Closer to the reader, a turtle is shown walking around, leaving dotted-line tracks behind it, suggestive of the Logo turtle. The dotted-line tracks spell out "TY", shorthand for "thank you". At the far left of the image, a robot and human are drawn next to a turtle which has flipped onto its back. The robot declares, "Poor thing!" while the human says "I'll help". This is a reference to the "empathy tests" employed to distinguish humans from androids in Do Androids Dream of Electric Sheep? and its film adaptation Blade Runner . As part of the test, the listener is asked to imagine being in the desert, flipping a tortoise onto its back, and refusing to turn it back over, while their eyes are monitored for signs of emotional response (or lack thereof). In this case, the robot expresses sympathy for the turtle and the human declares that he will turn it back over. (Although the robot is very clearly distinguishable from a human being.) [A man with large hair and a beard is holding an artist's palette with five patches of paint in one hand and a paintbrush in the other. He looks upon his canvas, where he has painted a large painting.] Painter: A Happy little tree Painter: Holding up a happy little world. [The painting contains lots of stuff. Among others, is a robot that sees Cueball bending down to lift a turtle that is on its back. They talk:] Robot: Poor thing" Cueball: I'll help [In the top right corner, there is a dotted line forming a semi-circle around the corner. Inside this are the words:] Vacuum decay [There are no other words in the image. The image includes:] In the sky: On top of the tree: Under the tree: [The rest just needs to be written out in detail...]

This is the 12th April fools' comic released by Randall . The previous April fools' comic was 2445: Checkbox , which was released on Thursday, April 1st, 2021. When loading the comic just a small dot is shown, a radio button (or option button). Usually, there would be more than one to give the user options. Once it has been selected it cannot be deselected. Once pressed the button turns blue and this starts the real part of this April fool's comic. The comic consists of an audio file . The speech is a mix of facts about turtles and coding instructions in LOGO . When executed, the instructions draw an xkcd comic. The audio file is 9 hours and 7 minutes long. Once the voice begins to describe the instructions (hence the title) it is possible to mute the audio by pressing a muted button at the bottom right of the screen. This fades into view when the radio button is pushed. Pressing it will change the button to a non muted loudspeaker . These were the same buttons that were in the previous April fool's comic 2445: Checkbox . That was the first xkcd comic with audio , and thus these were two April fools' comics with audio in a row, and these are the only comics with audio. In the Checkbox comic, the mute buttons meaning are reversed, so the sound is on when the loudspeaker is shown and muted when the mute button is shown. It could be another layer to the April fool's joke or just an error by Randall. The image originally displayed on this page was of a small turtle crawling in the center where the radio button is in the real comic. That was the image that would be downloaded by web crawlers like explain xkcd's bot, as it is what was placed here on xkcd: https://imgs.xkcd.com/comics/instructions_2x.png . This is of course not the real comic, which cannot be downloaded in that manner. The "turtle" is a key concept in Logo, a programming language especially designed to teach programming to children in an easy way. The turtle in the logo is the cursor. Programming commands move the turtle, drawing a line as it goes. Of course, listening to hours of instructions, including the speech-synthesized reading of source code, is not an easy way to code or draw a picture. [ citation needed ] In addition, at the end of the audio the voice says: The title text alludes to Bob Ross 's catchphrase "happy little trees" in The Joy of Painting , a PBS TV show in which Ross leads the viewer through the painting of a nature scene. The audio file itself is also presented in the style of The Joy of Painting ; it begins with greeting the viewer and introducing the color palette to be used (just one color, in this case, as Logo and all computer monitors of the time were monochrome). The speaker then reads out some helper functions to be used in programming the scene, which is more analogous to Ross's palette of paints (titanium white, carmine red, etc.) along with words of encouragement as each is completed. The functions are DIST, to calculate the Euclidean distance between two points, LERP, to perform linear interpolation , MIX to average two numbers (with LERP), and CUBIC to draw cubic Hermite splines . From there, the speaker alternates between sketching parts of the scene and offering more words of encouragement, mixed in with turtle facts. Transcribing the audio into text was organized as a project on github . This is not the first time that Randall made an interactive comic where turtles played a big part, see 1416: Pixels . In this, he jokes with the idea of turtles all the way down, which is also mentioned in the audio file. He also made a comic simply called 889: Turtles . This comic has a unique header text , see the details here . The header is: "Today's comic was created with Patrick , Amber , @chromakode , Michael , Kat , Conor , @zigdon , and Benjamin Staffin ." The header had not changed since the promotion of the new what if? 2 book. [The comic consists of one radio button, a small circle in the center of a large white panel. It is interactive. When pressing the radio button (selecting it), it turns blue. The second the radio button is pressed a more than 9-hour long audio file of coding instructions begins to play, and a mute button appears in the bottom right corner. It fades slowly into full opacity. Pressing this button will change it to a loudspeaker. It toggles whether there is sound playing or not. It is not possible to shut down the audio by pressing the radio button. Once selected it cannot be deselected as there is only this one option.] [Covered by the radio button is an image of a turtle crawling from left to right, with a dotted line trailing behind it, indicating its movement. This image can only be seen by looking in the place where images for xkcd are usually placed on xkcd.] [To read a transcript of the audio file go here: 2601: Instructions/Audio Transcript .] The image drawn by the Logo program is a depiction of Bob Ross standing in front of a canvas, on which he has painted "a happy little tree, holding up a happy little world". However, unlike his usual "happy little trees", the tree depicted is not a small pine, but rather a gargantuan World Tree growing from the back of a giant World Turtle , on which a Flat Earth rests. (The "happy little world" does bear several small pines more typical of his style.) Near the middle of the world, a Cueball sits while listening to the radio, perhaps tuning in to the same transmission that generated the image. Closer to the reader, a turtle is shown walking around, leaving dotted-line tracks behind it, suggestive of the Logo turtle. The dotted-line tracks spell out "TY", shorthand for "thank you". At the far left of the image, a robot and human are drawn next to a turtle which has flipped onto its back. The robot declares, "Poor thing!" while the human says "I'll help". This is a reference to the "empathy tests" employed to distinguish humans from androids in Do Androids Dream of Electric Sheep? and its film adaptation Blade Runner . As part of the test, the listener is asked to imagine being in the desert, flipping a tortoise onto its back, and refusing to turn it back over, while their eyes are monitored for signs of emotional response (or lack thereof). In this case, the robot expresses sympathy for the turtle and the human declares that he will turn it back over. (Although the robot is very clearly distinguishable from a human being.) [A man with large hair and a beard is holding an artist's palette with five patches of paint in one hand and a paintbrush in the other. He looks upon his canvas, where he has painted a large painting.] Painter: A Happy little tree Painter: Holding up a happy little world. [The painting contains lots of stuff. Among others, is a robot that sees Cueball bending down to lift a turtle that is on its back. They talk:] Robot: Poor thing" Cueball: I'll help [In the top right corner, there is a dotted line forming a semi-circle around the corner. Inside this are the words:] Vacuum decay [There are no other words in the image. The image includes:] In the sky: On top of the tree: Under the tree: [The rest just needs to be written out in detail...]

Linguistics Degree

Linguistics Degree

https://www.xkcd.com/2602

https://www.explainxkcd.com/wiki/index.php/2602:_Linguistics_Degree

[Megan, who is wearing a graduation cap, receives a degree which is handed to her by Hairbun. They are standing on a podium with Ponytail and Cueball standing below as onlookers.] Hairbun: Congratulations on the degree! Your word is "Bassoon." Ponytail: Oh nice! Not as cool as my "Jackalope," but still not bad. Cueball: You all are lucky. I'm stuck with "Slurp." [Caption below panel:] Every linguistics degree comes with one word that you're put in charge of.

Hairbun hands Megan a linguistics degree, and informs her she is now "in charge of" the word ' bassoon .' Watching this, Ponytail and Cueball compare the words they were assigned when they got their linguistics degrees, ' jackalope ' and ' slurp ' respectively. Ponytail thinks bassoon is a cool word but thinks her own is better, whereas Cueball is not satisfied with his word. A bassoon is a woodwind musical instrument with a double reed, while a jackalope is a mythical creature, a jackrabbit crossed with an antelope . It is never clarified what being "in charge of" a word entails. It could mean being in charge of keeping track of the word, or having actual authority over the use of the word, which is unlikely as normally language use cannot be dictated by a single person . Also, no specific university has control over all of linguistics as far as we know, so it would require every university capable of giving people linguistics degrees to co-operate, so nobody is assigned the same word. Any well-educated member of the linguistic community will know what is being suggested is impossible hence why they are the only ones aware of how important it is. The title text merely furthers how seemingly random the entire situation is. The word "linguistics" was assigned to a "random student in Ohio who barely graduated and then went into automotive marketing", who we can assume isn't very important to the field of linguistics. [ citation needed ] But this means that no one is actually taking care of this important word, since it must be assumed that the student is no longer interested in linguistics. The idea of individuals having a guardianship of an idea or concept has appeared in science fiction. For example, in Fahrenheit 451 characters have memorised books to save them from book-burning and... spoiler-stuff. It also exists in reality. Members of the Royal Spanish Academy , the institution that defines the official dictionary of the Spanish language, are symbolically put in charge of one letter of the dictionary each to take care of it. [Megan, who is wearing a graduation cap, receives a degree which is handed to her by Hairbun. They are standing on a podium with Ponytail and Cueball standing below as onlookers.] Hairbun: Congratulations on the degree! Your word is "Bassoon." Ponytail: Oh nice! Not as cool as my "Jackalope," but still not bad. Cueball: You all are lucky. I'm stuck with "Slurp." [Caption below panel:] Every linguistics degree comes with one word that you're put in charge of.

Childhood Toys

Childhood Toys

https://www.xkcd.com/2603

https://www.explainxkcd.com/wiki/index.php/2603:_Childhood_Toys

[Title:] Childhood Toys [Subtitle:] By Practicality for Commuting [Caption of the first box:] Practical [Cueball, wearing a helmet, drives by on an electric scooter, passing another Cueball and Hairbun, who is holding a briefcase.] Scooter Cueball: Hi, boss! [Caption of the second box:] Less Practical [Ponytail rides by White Hat on a unicycle.] Ponytail: Good Morning! [Caption of the third box:] Impractical [Cueball bounces past Megan on a pogo stick.] Pogo Stick: Boing boing Cueball: How's it going? [Caption of the fourth box:] Very Impractical [Cueball slides past Hairy(?) on a Slip 'N Slide.] Cueball: Wheeeee Cueball: Hi Boss!

This comic shows various objects, ranked by how practical they would be for long-distance transportation. The objects are described as childhood toys. The "Practical" panel shows objects designed for convenient transportation, namely bicycles and electric scooters . Most people know how to ride a bicycle, and can easily go several miles on it. Scooters (shown in the comic panel) are also relatively easy to use, and may have a motor allowing them to be used for significant distances — the one shown has the appearance of one with a battery unit rather than being 'leg-propelled', and is named as such in the list for which it has been depicted. These are not considered "toys" at adult size as they are widely used for transport, but children's bikes and scooters (particularly unpowered scooters) not used for transport would generally be considered toys. The practicality of bicycles and e-scooters tends to depend more on local infrastructure and amenities (i.e., the presence of a safe cycle route and the destination being within a sensible distance) than on the equipment itself. Bicycles can carry substantial loads . In some countries e-scooters are legally restricted or prohibited on public roads which may make commuting on them unviable. The "Less Practical" panel has objects designed for transportation, but which may be harder to use than the first panel. Skateboards and roller skates , while designed for transportation, don't work great over long distances or when carrying objects, and Big Wheels and unicycles (shown in the panel) are simply less practical bikes. In the "Impractical" panel are objects that are designed for transportation, but are very much not designed for convenience, especially over long distances. Stilts are long poles that one stands on to extend their legs; while they increase the user's stride length, it takes quite a bit of practice to use them, especially if they're very long. A jump rope is a rope that the user swings around their body while they jump over it whenever the rope passes below their feet; it doesn't actually provide any transportation by itself, the user is simply hopping to their destination, which is a very tiring way to travel (but very good exercise if you can do it). A wagon has no propulsion of its own, it has to be pulled by the user; parents sometimes use it to transport their children short distances (such as to a playground). Larger wagons are used commercially. A Pogo stick is a pole with a spring at the bottom and a platform for standing on, which can be used to bounce; while fun for bouncing a few yards (as shown in the panel), like the jump rope it would be tiring for long distances. The "Very Impractical" panel has objects that may be used for transportation, but to an incredibly limited degree. Slip 'N Slides (shown in the panel) only work (effectively) downhill, and only where they are placed down. Trampolines and Tire swings could let you go somewhere, but you'd need to set up multiple in a row leading to your destination beforehand. Hot Wheels cars could be put onto the bottom of shoes to create extremely ill-advised [ citation needed ] improvised rollerskates, but the car on its own has effectively no merit for transportation. The title text refers to tetherball , a game found in many playgrounds where a ball is attached to a pole by a long rope. This is also very impractical, as the rope just winds around a stationary pole. It's possible that he is swinging from the rope and letting go (which would explain the bruises and scrapes, as well as the torn rope), but there is no remotely practical way to use this to commute. [ citation needed ] Nevertheless, if you were able to swing quickly enough and cut the rope at exactly the right moment, you might be able to achieve a short commute to a nearby target. This method may have been inspired by NASA purchasing a launch via the SpinLaunch rocket system the same week as the comic appeared. [Title:] Childhood Toys [Subtitle:] By Practicality for Commuting [Caption of the first box:] Practical [Cueball, wearing a helmet, drives by on an electric scooter, passing another Cueball and Hairbun, who is holding a briefcase.] Scooter Cueball: Hi, boss! [Caption of the second box:] Less Practical [Ponytail rides by White Hat on a unicycle.] Ponytail: Good Morning! [Caption of the third box:] Impractical [Cueball bounces past Megan on a pogo stick.] Pogo Stick: Boing boing Cueball: How's it going? [Caption of the fourth box:] Very Impractical [Cueball slides past Hairy(?) on a Slip 'N Slide.] Cueball: Wheeeee Cueball: Hi Boss!

Frankenstein Captcha

Frankenstein Captcha

https://www.xkcd.com/2604

https://www.explainxkcd.com/wiki/index.php/2604:_Frankenstein_Captcha

[A captcha design, with a header and four rows of four pictures each below it. The header, in white lettering on a blue background, reads:] To continue, please click All squares containing Frankenstein [The pictures, all with gray backgrounds, are as follows, from left to right in each row:] Row 1 Monster: GRRR Row 2 Row 3 Frankenstein: It's alive! Girl: Monster! Row 4 [Caption below the panel]: Oh no.

This comic strip is a play on the meanings (and misunderstanding) of the name "Frankenstein". Frankenstein; or, the Modern Prometheus is an 1818 novel by Mary Shelley about a medical student named Victor Frankenstein who creates an artificial life-form. The man he creates once describes himself as "the Adam of [Frankenstein's] labour" in the book, and strictly speaking is properly known as "Frankenstein's monster " (or perhaps "creation" or "son"), but is often erroneously called "Frankenstein" himself. This has been fertile ground for many, many debates about whether the monster could also properly be called "Frankenstein," either as a family name, an honorific, or simply because it's more recognizable and convenient. Randall has weighed in on the debate himself in a previous comic, 1589: Frankenstein . The CAPTCHA shown in the comic instructs the user to select all tiles containing Frankenstein. The tiles include both a reanimated corpse resembling Frankenstein's monster and a scientist yelling, "It's alive!” who is clearly intended to be Victor Frankenstein. The problem arises from the contrast between various definitions of the term Frankenstein. Going just off the book's text, the monster has no name, so the correct answer to the CAPTCHA is just the left square of the third row. However, the character depicted there is clearly Henry Frankenstein from the famous 1931 film adaptation (Victor Frankenstein never said the words "it's alive!" in the book), and likewise the creature depicted is clearly inspired by Boris Karloff 's iconic portrayal in that film and its sequels. If the images are captured from that film, then all four of them could be said to be "containing (a subset of) Frankenstein (the 1931 film)". Some CAPTCHAs - especially Google's widely spread reCAPTCHA - nowadays serve a dual purpose: (1) to separate human users from bots by way of intelligent interaction, and (2) to train a neural network, hence the "correct answer" to image recognition CAPTCHAs is not known ahead of time and is merely based on the most commonly-chosen tiles. Thus, a user who knows that "Frankenstein" refers only to the scientist would face this CAPTCHA with dread, uttering "Oh No" as they realize that they must select the tiles containing the monster, and possibly not even be allowed to select the tile containing the actual scientist Victor Frankenstein if they want to pass the CAPTCHA. Alternatively, this comic strip with its "Oh No" caption could be referencing 1897 , which would imply that someone had actually created a Frankenstein's monster which needs to be located as soon as possible. Many of the other tiles appear to be pictures of entities that inspire similar pedantry. For example, there is a picture of a turtle (or possibly a tortoise, or a reference to the Voight-Kampff test used in a manner analogous to CAPTCHA), a ship (or possibly a boat), Link (the name given to each of several protagonists that appear across generations and timelines, throughout the Legend of Zelda video games, who many erroneously refer to as Zelda), a pond (or possibly a lake, a puddle, or a mirage ), a squash or pumpkin (often subject to the fruit or vegetable debate), an erupting volcano (with lava, or is it magma?), and the planet Pluto (or is it a dwarf planet?). Other tiles seem to be inspired by images that commonly occur in actual captchas, like the STOP sign or the traffic light. However, at least some of these may also be meant to fall into the category of entities that inspire pedantry, for example: because traffic lights can also be called traffic signals or stoplights; many people thinking that the shape of a stop sign is a hexagon, not an octagon; and the definition of a sandwich (previously discussed as a “random semi-ironic obsession” in 1835 ). The title text refers to one of the methods used to distinguish a ship from a boat. When making a turn, if the vessel leans towards the inside of the turn circle then it is considered a boat, whereas if the vessel leans away from the turn circle it is considered a ship [1] . Since the vessel generates a wake as it moves, checking whether it is a boat or a ship can be done while it is literally drawing a line on the water (the wake). The phrase "a line drawn in water" is also an idiom for something ephemeral. Ironically, it has persisted for a long time and dates back at least to the early Buddhists. (e.g. AN 3.132 & AN 7.74 ). The distinction between a ship and a boat is also unclear, having changed over time, with no universally accepted rule to distinguish between the two . The title text is also a pun on the common idiom "drawing a line in the sand." The title text could also be referencing the image of a boat or ship that appears as one of the CAPTCHA tiles in the comic, where Randall has drawn a squiggly line often used in crude drawings to represent a waterline. [A captcha design, with a header and four rows of four pictures each below it. The header, in white lettering on a blue background, reads:] To continue, please click All squares containing Frankenstein [The pictures, all with gray backgrounds, are as follows, from left to right in each row:] Row 1 Monster: GRRR Row 2 Row 3 Frankenstein: It's alive! Girl: Monster! Row 4 [Caption below the panel]: Oh no.

Taylor Series

Taylor Series

https://www.xkcd.com/2605

https://www.explainxkcd.com/wiki/index.php/2605:_Taylor_Series

[Miss Lenhart pointing a stick at a whiteboard, which has some scribbled text written on it and one line is circled.] Miss Lenhart: At this point, you're probably thinking, "I love this equation and wish it would never end!" Miss Lenhart: Well, good news! [Caption below the panel:] Taylor series expansion is the worst.

In mathematics, a Taylor series expansion is a polynomial power series approximation of a function [1] around a given point, composed of an infinite sum of the function's derivatives , each both divided by successive factorials and multiplied by the incrementally increasing power of the distance from the given point. Such expansions usually continue without end. Beyond approximation of functions, Taylor series are also useful for deriving numerical approximations of irrational values, such as π , as well as symbolic forms to make functions easier to integrate or otherwise manipulate with calculus. [2] However, because they involve difficult calculus operations, and can be annoyingly tedious to calculate by hand , they are often not loved by math students. [3] Miss Lenhart appears to be teaching a class about how to use a Taylor series. She presumes her students want to keep learning about the series, in that they, "wish it would never end." She then says "Good news!" because the series does not end. The cartoon's humor is based on the contrast between wishing the series won't end, ordinarily desired of sequences of enjoyable events, and the infinite nature of the Taylor series, which is less likely appreciated by her students struggling to understand why the sums converge to their resulting value. The title text is a reference to the common practice among physicists and engineers of abbreviating the Taylor series to only the first few terms, typically one or two, in order to simplify the mathematics of their models. The title text is also a pun on the use of the word "series" to refer to a television program. It symbolizes the terms of the mathematical series as a metaphor with a television season, suggesting that only the first term is useful. It makes fun of the common sentiment against bad screenwriting of a series by saying that, "The series should have been cancelled after the first season," replacing "season" with "term." (Notably, both "term" and "season" are used to refer to a stretch of time during which a program is airing—generally, a television or scholastic program, respectively.) Also note that US President Zachary Taylor died during his first term. In a way, his presidency was cancelled during his first term. [Miss Lenhart pointing a stick at a whiteboard, which has some scribbled text written on it and one line is circled.] Miss Lenhart: At this point, you're probably thinking, "I love this equation and wish it would never end!" Miss Lenhart: Well, good news! [Caption below the panel:] Taylor series expansion is the worst.

Weird Unicode Math Symbols

Weird Unicode Math Symbols

https://www.xkcd.com/2606

https://www.explainxkcd.com/wiki/index.php/2606:_Weird_Unicode_Math_Symbols

Weird Unicode Math Symbols And their meanings

This comic proposes joke explanations for various unicode symbols with obscure or no known uses. This comic may have been inspired by this blog post , which went viral (in a limited sense) the same day the comic was published. Weird Unicode Math Symbols And their meanings

Geiger Counter

Geiger Counter

https://www.xkcd.com/2607

https://www.explainxkcd.com/wiki/index.php/2607:_Geiger_Counter

[Cueball and Ponytail are wearing hard hats and standing in what looks to be some sort of desert or rocky area. Cueball is holding a Geiger counter in his hands. Ponytail is holding a clipboard.] Cueball: At first I was confused about why they wanted me to carry a Geiger counter here, but then it clicked.

This comic is a simple pun . Cueball and Ponytail are standing in what looks to be a desert, and Cueball is holding a Geiger counter in his hand. Cueball remarks that he did not understand why he was asked to carry a Geiger counter, but that it then "clicked" with him. Geiger counters are devices used to measure the amount of radiation in an area. When a particle of ionizing radiation hits the sensor of a Geiger counter, it will give off a distinct "clicking" noise. "Click" can also be a slang term for the Eureka effect , a sudden moment of understanding. The pun in this comic insinuates that Cueball realized why he was asked to bring the Geiger counter when it clicked, indicating radiation nearby. In radioactive areas, it is usually a good idea to carry around some sort of radiation detector for safety reasons . [ citation needed ] This is likely a parody of a fairly well-known pun that takes advantage of a similar double meaning: "I wondered why the baseball was getting bigger. Then it hit me." Just as that pun uses "hit me" to mean both the action of the ball and to understand, this comic uses the "clicking" to mean both the action of the Geiger counter and to understand. A related variety of pun, told in the third person , is the Tom Swifty . The title text is also a pun, with the implication being the narrator "understood" once they "stood under" the birds that were perched on the wire (who may have then pooped on the narrator to bring them to their understanding [in the "realization" sense]). [Cueball and Ponytail are wearing hard hats and standing in what looks to be some sort of desert or rocky area. Cueball is holding a Geiger counter in his hands. Ponytail is holding a clipboard.] Cueball: At first I was confused about why they wanted me to carry a Geiger counter here, but then it clicked.

Family Reunion

Family Reunion

https://www.xkcd.com/2608

https://www.explainxkcd.com/wiki/index.php/2608:_Family_Reunion

[Megan, White Hat, Cueball, Hairy, Danish, a white cat with black patches on its back, Hairbun, a chair with a half-full wine-glass on the seat, and a potted plant on a cabinet are "standing" in a line. White Hat is holding a glass and Hairy has his hands to the side in a "shrug" position. Megan and Cueball are facing right and everything/one else is facing left (except for the potted plant, which is not facing any direction). There are arrows pointing to each of the living creatures.] 14th cousin [Megan] 2nd cousin [White Hat] Me [Cueball] 12th cousin [Hairy] 35th cousin [Danish] 17,000,000th cousin [cat] 9th cousin [Hairbun] 50,000,000,000th cousin [potted plant] [Caption below the panel:] Really, every gathering is a family reunion.

Because all humans are descended from a common ancestor , every human is, at some point, related to every other human, albeit distantly. Similarly, all life forms on Earth are presumed (with good reasons) to be descended from a single even more distant relative whose ultimate lineage became more relevant than any from its own 'cousins' at the time, and thus all life forms are distantly related. This makes every interaction with another life-form, technically, a family reunion, if not in the traditional sense. The general English definition of a cousin , which is a person sharing an ancestor who is not a direct parent of either party, can be qualified by two numbers. There is the n th-ness of the relationship (the fewest generations you need to go beyond one's parentage, "a first cousin" implies that a grandparent is the key link) - for example, this Cueball's relation to White Hat is via a great-grandparent, whilst that with Hairbun is through a great-great-great-great-great-great-great-great-grandparent. A "removed" number is any difference in this number between the two individuals, such that a child of a direct cousin invokes a "once removed" relationship between the two (without individually qualifying who is the 'senior' generation, from whom the 'nth' count is determined). You would normally only qualify "first cousin" if this fact is considered important, and "zero times removed" would also be considered implicit. As pointed out in the title text, cat lifespans (or, more importantly, inter-generational breeding cycles) are somewhat different from those of humans. Although they would have still been very similar immediately after the divergence from the appropriate most recent common ancestor (MRCA), the differences will have built up to a generational-count displacement of a similarly extreme nature. i.e. that while the shared ancestor is Cueball's 17-million-or-so-Great Grandparent, the cat is in turn the 31-million-or-so-Great Grandchild. Exactly how accurate, or even precise, Randall considers these numbers is unknown, but it is the kind of fact that we know he likes to research and use expert opinion for. According to this Quora page , there have been about 13,000 generations of modern humans, so the people at this party would be quite closely related, all things considered. The Evogeneao Tree of Life diagram indicates that humans and cats diverged around 90 million years ago and humans and plants diverged around 1.8 billion years ago. If we presume that generations of humans (including proto-humans, pre-humans, etc) since the divergence from cathood (including proto-cats, pre-cats, and the rest, back to the common ancestral form) have averaged around 5 years, then a 17 millionth cousin may be about right. Many of our (and cats') early ancestors will have necessarily been small burrowing mammals — to have been amongst the ones who survived the asteroid around 66 million years ago that killed off most of the dinosaurs — with contemporary equivalents having breeding cycles in terms of a year at the most. But we currently have a large feasible range of generational cycle (15-50 years, very roughly, with or without technical/social help or hinderances), that may have started to drag our long-term average upwards since at least the age of the early hominids, if not the age of our primate forebears or earlier. To get a 50 billionth cousin from the potted plant, then the generations of (eventually) humans since we were of the same form as that time's ancestral plants (or vice-versa) would need to average two weeks. This is possible, but difficult to be precise about due to the lack of much of the required evidence in the known fossilized remains. Any reasonable estimate, however, should be heavily weighted towards generation spans common for unicellular eukaryotes, rather than the longer generations common for multicellular eukaryotes: the general consensus on the most recent common ancestor for of animals and plants identifies it as a unicellular eukaryote. Given the above analysis of eukaryotes as cousins one wonders why Randal Monroe didn't include that every lack of gathering is also a family reunion. [Megan, White Hat, Cueball, Hairy, Danish, a white cat with black patches on its back, Hairbun, a chair with a half-full wine-glass on the seat, and a potted plant on a cabinet are "standing" in a line. White Hat is holding a glass and Hairy has his hands to the side in a "shrug" position. Megan and Cueball are facing right and everything/one else is facing left (except for the potted plant, which is not facing any direction). There are arrows pointing to each of the living creatures.] 14th cousin [Megan] 2nd cousin [White Hat] Me [Cueball] 12th cousin [Hairy] 35th cousin [Danish] 17,000,000th cousin [cat] 9th cousin [Hairbun] 50,000,000,000th cousin [potted plant] [Caption below the panel:] Really, every gathering is a family reunion.

Entwives

Entwives

https://www.xkcd.com/2609

https://www.explainxkcd.com/wiki/index.php/2609:_Entwives

[A large treelike person (an Ent, maybe Treebeard) is holding one of his arms out towards six characters that are all looking at him. A man (Aragorn) with beard stubble and long hair, a dwarf (Gimli) with a helmet and a very large beard, an elf (Legolas) with long blonde hair (holding a bow down), and three short persons, hobbits, two with dark hair, and the middle one with blonde hair.] Ent: Alas, there are no Ent women. The Entwives all vanished in the second age, during Sauron's war. Aragorn: I'm so sorry. Ent: And what about you all? Same story, I assume? Aragorn: Huh? No, what do you mean?

In The Lord of the Rings , the Ents are a species of tree-like humanoids, such as the one depicted in this comic. The comic shows an Ent, presumably Treebeard , meeting with some of the nine from the Fellowship of the Ring . The image is inaccurate inasmuch as it shows three hobbits : during the Ents' interactions with the Fellowship, two of the four hobbits ( Frodo and Sam ) were elsewhere in Middle Earth , so it was only Merry and Pippin who met the ents. The other three in the image are the human Aragorn , the Dwarf Gimli and the Elf Legolas . The last two of the nine, not depicted, were the wizard Gandalf and the human Boromir . Part of the backstory of the Ents is that all the females of their species (the Entwives that this comic is named for) had disappeared thousands of years before during Sauron 's war of the second age . The Ents and the Entwives lived in separate locations, and eventually, when the Ents went to visit the Entwives, the latter were seemingly nowhere to be found. The Ents have been searching for their lost mates ever since. The loneliness of the Ents' all-male society is considered a great tragedy in their culture. It is several thousands years ago in the time of the Lord of the Rings trilogy, and the Ents have all but forgotten how the Entwives even looked. They live for many thousands of years. This comic uses that backstory to satirically comment on the extreme gender imbalance of the protagonists of Lord of the Rings; when presented with the all-male Fellowship, the Ent assumes that they must come from a race afflicted by a similar tragedy. In a broader sense, this can be read as a commentary on how few female characters there are in the trilogy overall. In reality, the general lore presents, or at least mentions, the existence of at least multiple (if not numerous) female characters of almost all races that make up the fellowship (dwarf, man, elf, hobbit), and does not suggest that what happened with the Ents and their Entwives happened to any other race. The clickable link on the image leads to the satirical video Lord of the Rings Trilogy but it's EVERY scene where two female characters interact . The creator claims that this shows all the scenes from the trilogy where two female characters interact (but later admits in the Youtube comments that there are indeed a few more). There is only one 3 second long scene, which only emphasizes how few female characters there are in the trilogy. The inclusion of this clip may be a reference to the Bechdel test , a baseline indicator of the representation of women in a piece of media that requires two women to have a conversation about something other than a man. Whether this three-and-a-half-word exchange is sufficient to pass the test is debatable. Later versions of the test suggest that the two women should be named (i.e. not just two incidental characters that have very few lines), whereas this scene is between Éowyn and an unnamed girl. There is debate as to if there are other scenes with women speaking with women, and if we are only talking about human women, or if other races females would also count. There are at least three important female characters, but they do not meet/speak much if at all. But they have several scenes where they talk, even a long monologue... But if they speak to someone it is male characters. The title text most likely refers to the character of Arwen , an elf woman and, later, wife of Aragorn; while somewhat important to the story, she is nowhere near as significant as the males of the Fellowship, despite being used more prominently in the movies than in the books. Even if she were part of the Fellowship, a single important woman wouldn't counterbalance the heavily male-centric storytelling. The way that the title text is phrased is a reference to the proverbial (and implicitly imaginary) " Girlfriend in Canada ," a trope in which a single American character claims to have a girlfriend that their friends wouldn't know "because she lives in Canada" (or some other sufficient separation such as "goes to another school"), when in reality the reason that nobody else has met her is because she doesn't exist (with an implication that the character is either a closeted gay or an incel ). Canada is one of only two countries with which the United States has land borders, making it a potentially plausible place for some American's long-distance girlfriend to live, and presumably the Fellowship consider the Elf kingdom of Rivendell to be sufficiently distant to allow the Ent to accept the plausibility of the statement without any further delving into potentially awkward details. [A large treelike person (an Ent, maybe Treebeard) is holding one of his arms out towards six characters that are all looking at him. A man (Aragorn) with beard stubble and long hair, a dwarf (Gimli) with a helmet and a very large beard, an elf (Legolas) with long blonde hair (holding a bow down), and three short persons, hobbits, two with dark hair, and the middle one with blonde hair.] Ent: Alas, there are no Ent women. The Entwives all vanished in the second age, during Sauron's war. Aragorn: I'm so sorry. Ent: And what about you all? Same story, I assume? Aragorn: Huh? No, what do you mean?

Assigning Numbers

Assigning Numbers

https://www.xkcd.com/2610

https://www.explainxkcd.com/wiki/index.php/2610:_Assigning_Numbers

[Cueball holds a hand up to his chin while he ponders the contents of what may be a whiteboard. There are five general lines of unreadable scribbling on the board, and between the two bottom lines, there is a square frame to the right with another scribble to the left. Cueball's thoughts are shown above him in a large thought bubble.] Cueball's thinking: If I assign numbers to each of these things, then it becomes data , and I can do math on it! [Caption beneath the panel:] The same basic idea underlies Gödel's Incompleteness Theorem and all bad data science.

This explanation is by mathematical necessity either incomplete or incorrect. Cueball is falling into a common trap, because a little knowledge is a dangerous thing. Faced with some sort of information, of an unknown kind but seemingly not intrinsically mathematical in nature, he has decided that one possible way to proceed is to somehow translate everything into values which can be combined and compared numerically. This is a very common thing to do, in fields as diverse as computational linguistics or sports analytics , and can be a powerful tool for understanding and learning new things about a subject as Data science tries to extract knowledge and insights from potentially noisy and disordered facts. But it is also used to implement bad science by using incorrect or misguided ideas about how to represent the source material. While it's possible to casually assign numeric values to random pieces of data, these numbers are generally not meaningful enough to compute with and draw any useful inferences from. It is generally possible to perform statistical analysis only on actual measurements, not on what may effectively be arbitrarily-assigned values. Machine learning algorithms, which are commonly used by data scientists, typically require all their inputs to be numerical. However, most datasets contains categorical features (e.g. the description of a piece of furniture: chair, table, ...). Data scientists therefore use encoding techniques to convert these categorical features to a numerical form so they can be used as inputs to a machine learning model. For instance, label encoding consists of arbitrarily assigning an integer to a category (chair=0, table=1, ...) which may appear meaningless to most observers. In various cases, they may be right. So, as well as being the mechanism that underlies one of the most profound theorems of 20th century mathematics, it can be mis-used for all kinds of bad or misguided science. From Cueball's attitude, it is far from clear that his attempt will reliably translate his project into a numerical system, nor that his attempt to "do math on it!" will be any more competent. One of the major characters who looked at the concept is Kurt Gödel. He introduced the idea of Gödel numbering with his landmark incompleteness theorems . In it a unique natural number is assigned to each axiom, statement, and proof, which might otherwise be difficult to accurately process in any other kind of approach. Instead, it is now possible to create metamathematical statements in the language of mathematics. This allowed Gödel to make the statement "This statement cannot be proven based on the axioms provided" in a mathematically rigorous way. A simple proof by contradiction shows that the statement cannot be false, and therefore (in most logical systems) must be true. The proof goes as follows: 1. Assume that "This statement cannot be proven from the axioms" (Call this statement G) is false. [1] 2. Therefore G can be proven from the axioms. [2] 3. The axioms exist. [3] 4. Therefore, G is true. [4] 5. Therefore, G and also not G. [5] 6. This is a contradiction, and therefore A (that is, 'not G') or B (ZFC) must be wrong. We are not willing to sacrifice assumption B, so we must conclude that A is false, given B. [6] 7. Therefore, G. Notice that the truth of Gödel's statement does not depend on any particular set of axioms, and adding axioms (such as "Gödel's particular statement is true") only opens up new iterations of the statement which cannot be proven based on the expanded set of axioms (A statement such as "All statements of a similar nature to Gödel's particular statement" is not precise enough to serve as an axiom.). As such, with a little more legwork, it can be proven that any logical system robust enough to accommodate arithmetic must necessarily contain facts that are true within the system but cannot be proven or disproven within the system. The importance of this result cannot be understated, as it upended the entire philosophy of mathematics. David Hilbert 's famous proclamation "We must know, we will know" is simply incorrect. ... Either that, or (ironically) Gödel used an "inconsistent" or "incomplete" system to produce his result. The title text suggests that Gödel should perform such an analysis on different branches of mathematics, by calculating the average of all the fields' theorems' Gödel numbers. This is nonsensical for a number of reasons: 1) Gödel is long dead, and dead people can't write articles; [ dubious ] - see 599: Apocalypse 2) Gödel numbers grow very large very quickly, and depend heavily on the specific values assigned to each logical operator. Therefore the results could be manipulated simply by changing the numbering order of each operator; 3) It may be very hard to gather all theorems in a field, or even a representative sample; 4) Different fields of science, like biology or human behaviour, may not be able to write their theorems in the mathematical language of Gödel's incompleteness theorem If anyone were to attempt this form of analysis, it would be an example of the bad data science described in the caption. [Cueball holds a hand up to his chin while he ponders the contents of what may be a whiteboard. There are five general lines of unreadable scribbling on the board, and between the two bottom lines, there is a square frame to the right with another scribble to the left. Cueball's thoughts are shown above him in a large thought bubble.] Cueball's thinking: If I assign numbers to each of these things, then it becomes data , and I can do math on it! [Caption beneath the panel:] The same basic idea underlies Gödel's Incompleteness Theorem and all bad data science.

Cutest-Sounding Scientific Effects

Cutest-Sounding Scientific Effects

https://www.xkcd.com/2611

https://www.explainxkcd.com/wiki/index.php/2611:_Cutest-Sounding_Scientific_Effects

[A tournament bracket tree is shown with 16 scientific effect names, with 8 on the left and 8 on the right side. From both sides toward the middle the brackets reduce from eight to four, to two, then to one line where the latter join to a rectangle in the middle for the winners name of the final match. Above the bracket there is a title:] Cutest-Sounding Scientific Effects [Left side:] YORP effect Nocebo effect Woozle effect Stroop effect Pockels effect Cheerios effect Hot chocolate effect Perky effect [Right side:] Bouba/kiki effect Cutaneous rabbit effect Small firm effect Little Parks effect Dr. Fox effect Oddity effect Butterfly effect Popcorn effect The first wave ran from April 25, 2022 at 5:19pm ET to the next day at 5:42pm ET. The second wave started on April 26, 2022 at 5:56pm ET and ended around 11:56am ET. The third wave started on April 27, 2022 at 6:54pm ET and ended around 12:54pm ET. The fourth wave started on April 28, 2022 at 4:30pm ET and ended around 10:30pm ET.

Randall has compiled yet another single-elimination tournament bracket for a knock-out competition, by public vote, between 16 different scientific effect names that he seems to consider worthy of being cute-sounding. As of the release day, he is determining the result in a series of Twitter polls . These results are shown here . See below for explanations for what each of the 16 effects are. Several unrelated scientific effects were previously combined in 1531: The BDLPSWDKS Effect , which also included the Stroop effect (the last S). In the title text, Randall coins the term "Stroop-YORP number" as a count of how many 'casual' references a future publication can sneak into it from the 16 finalist names for cutest effect. It specifies that it should be without the word effect after the words (sans 'effect'). Tongue-in-cheek 'counting scores' are familiar in the likes of the Erdős and Bacon numbers, both of which are referenced by 599: Apocalypse (the latter only in the title text). In these cases the ideal is to get the lowest number, whereas here higher is better. The cross-field hybrid Erdős–Bacon number is one in which the desired score is the lowest sum of both values (neither being undefinable) by dint of having participated in both arenas of respective achievement, but not necessarily (or practically) in a single combined presentation. For instance the Stroop-YORP number could be high for a wildlife paper. That could possibly use "butterfly" and "rabbit" (possibly needing the latter to be specifically 'cutaneous', to count), which may both be found in "little parks" with some "popcorn" seen littered around without too much "oddity"; and of course a (Dr.?) "fox" could be in the area, getting a score of 6. But other words may be a stretch, with an imaginative reference to a "woozle" possibly easier to employ than to evoke anything of the "nocebo". On the other hand, for a space-science paper there may be more obvious (mis)uses for physics-related terms, and mentioning YORP might well be expected. But it may need creative thinking to introduce the rabbit or the more psychological idea of Stroopicity, etc, without reason to discuss the responses of animal or human payloads being sent there. It is not actually obvious whether Randall intends the score to only be valid if the insertions are off-field and/or undetected, such as when someone is wagered that they can slip unrelated song lyrics or a 'hello' to Jason Isaacs into a public speech without the rest of the audience twigging. A search of google scholar indicates many articles with a score of 2 (e.g. this paper , which refers to butterfly shaped popcorn), but 3 or more seems to not be attested. YORP effect The YORP effect is the effect of sunlight on an asteroid with variations of shape and/or albedo, which can increase its rotation rate and/or modify its axis of rotation. It can cause objects to eventually spin apart or drastically change their orbit. It is an acronym of the names Yarkovsky, O’Keefe, Radzievskii and Paddack, who were instrumental in its discovery. More than a century ago, Yarkovsky determined that heat applied to a symmetrical rotating body would be asymmetrically re-emitted and apply a small but continuous thrust, and this was added to by considering the forces to non-symmetrical bodies. Nocebo effect An effect in which a recipient of medication who believes that it will have negative side-effects is more likely to experience those negative side-effects, whether they can be really caused by the medication or not. Opposite of the placebo effect , which focuses on positive side-effects that arise beyond the true efficacy of a given treatment. Nocēbō is Latin for “I shall harm”, coined to oppose placēbō , “I shall please”. Woozle effect If a study gets repeatedly cited and otherwise disseminated, then people will start to believe it regardless of whether it has any evidence behind it. And if there is not any evidence, it becomes an urban myth. Named after a Winnie-the-Pooh story in which Winnie-the-Pooh and Piglet try to catch an imaginary animal called a woozle, and accidentally follow their own tracks in circles. A similar effect was discussed in 978: Citogenesis , wherein a sourceless statement on Wikipedia can become apparently credible via simple repetition. Stroop effect The Stroop effect (referenced in 1531: The BDLPSWDKS Effect ) is a psychological phenomenon in which it is easier to name the visual color of a word when the word refers to its own color, than when the word refers to a different color; i.e. the fact that saying that Red is red is easier than to say that Blue is green. Named after John Ridley Stroop . Pockels effect A phenomenon where an electric field passed through a medium can cause the medium's refractive index to depend upon the polarization and propagation direction of the refracted light, a property known as birefringence . Named after Friedrich Carl Alwin Pockels . Cheerios effect A phenomenon where objects floating in a liquid appear to attract or repel each other. Named after the cereal Cheerios, which are an everyday demonstration of this phenomenon because many eat Cheerios in a bowl of milk. Hot chocolate effect A phenomenon where the sound created by tapping a cup of hot liquid rises in pitch as a soluble powder is added. Perky effect An experiment in which participants were asked to visualize an object while staring at a screen on which the outline of that object was subtly projected. Participants believed the projected shape to be only a product of their imaginations. Named after Cheves Perky . Bouba/kiki effect An observation that people, despite different native languages, will relatively consistently assign names with certain sounds to blobby or spiky shapes, suggesting the association of sound and shape is non-arbitrary. Bouba and kiki were two of the words used in the experiment. Cutaneous rabbit effect A phenomenon where, when tapped on one part of the body in rapid succession and then switching to another, the subject feels the tapping at locations in between the two. For example, if rapidly tapping the wrist then switching to the elbow, the subject will subjectively feel as if they are being tapped at progressive intervals between the wrist and elbow, when they are not. Small firm effect An economic theory that small firms usually perform better than larger ones Little–Parks effect A phenomenon where a fluctuating magnetic field passed through a superconductor can slightly suppress its superconductivity, inducing small fluctuations in its electrical resistance. When juxtaposed against the "small firm effect", as in the bracket, one might get the impression that it is somehow related to urban architecture or civil engineering. Dr. Fox effect A disputed theory that student evaluations of their teachers are likely unreliable, because they are largely based on the teacher's charisma instead of the quality of their content. Oddity effect A theory that when fish assemble in shoals (large social groups), any that stand out appearance-wise will be attacked by a predator, explaining why shoals tend to have similar-looking members. Butterfly effect The butterfly effect is the sensitivity of chaotic systems to small changes in initial conditions. The weather system of Earth is chaotic, and so an arbitrarily small change in air patterns (such as could be caused by the flapping of a butterfly's wing) could ultimately change the weather for the whole world. Popcorn effect A phenomenon exhibited by crushed ore placed on a vibrating screen for separation in mineral processing, in which larger particles tend to bounce higher than smaller particles. [A tournament bracket tree is shown with 16 scientific effect names, with 8 on the left and 8 on the right side. From both sides toward the middle the brackets reduce from eight to four, to two, then to one line where the latter join to a rectangle in the middle for the winners name of the final match. Above the bracket there is a title:] Cutest-Sounding Scientific Effects [Left side:] YORP effect Nocebo effect Woozle effect Stroop effect Pockels effect Cheerios effect Hot chocolate effect Perky effect [Right side:] Bouba/kiki effect Cutaneous rabbit effect Small firm effect Little Parks effect Dr. Fox effect Oddity effect Butterfly effect Popcorn effect The first wave ran from April 25, 2022 at 5:19pm ET to the next day at 5:42pm ET. The second wave started on April 26, 2022 at 5:56pm ET and ended around 11:56am ET. The third wave started on April 27, 2022 at 6:54pm ET and ended around 12:54pm ET. The fourth wave started on April 28, 2022 at 4:30pm ET and ended around 10:30pm ET.

Lightsabers

Lightsabers

https://www.xkcd.com/2612

https://www.explainxkcd.com/wiki/index.php/2612:_Lightsabers

[Two Cueball like Jedi are engaging each other in a duel using lightsabers over 12 panels of equal size, with sound effects as the only sound. In the first panel the left Jedi has his lightsaber extended holding it in both hand pointing towards the other, who at this time is just turning his lightsaber on.] Tssssss Click [Almost same position of the Jedi, but the right Jedi's lightsaber has now extended, making a sound. He is holding it up near his head in both hands] Tsss [Then they run towards each other and swing their lightsabers towards each other, two small arcs indicating the swing of the lightsabers.] [The two beams hit each other and connects at the middle in a big bloop of light, with drops of "light" jumping off both above and below the connected lightsabers. Both Jedi still holds on to their handles with both hands. A loud sound comes out of the connection:] Bloop [The Jedi stands still holding their handles. The beam is now forming a bow between the two handles.] [The left Jedi violently shakes his handle causing a wave to travel down the beam towards the right Jedi.] Shake shake [The right Jedi shakes his handle and well and another wave travels the opposite direction towards the left Jedi.] Shake shake [Back to the bow of light between them, but the beam is visibly still shaking, but no wave is traveling any longer.] [Same setting but the shaking has stopped. The right Jedi turns his lightsaber off on his handle with a sound:] Click [The beam of light is retracted quickly into the handle of the Jedi turning his lightsaber off. So quickly that the two Jedi, still holding on to their handles are pulled up in the air and towards each other as the sound of the beam turning off is heard. Lines indicate their movement and shadows on the ground beneath them indicate they are in the air.] Zhhhiiiip [When the beam is completely retracted the two handles collide and so do the heads of the two Jedi with a loud sound. They still hold on to their handles with both hands. They still hang in the air with shadows on the ground beneath them.] Bonk [In the final panel the two Jedi lie unconscious on the ground with their heads towards each other and with their arms stretched out towards each other. The connected handles lie between them.]

Bad Map Projection Madagascator

Bad Map Projection: Madagascator

https://www.xkcd.com/2613

https://www.explainxkcd.com/wiki/index.php/2613:_Bad_Map_Projection:_Madagascator

Bad map projection #248: Madagascator Mercator projection but with the North Pole in the Indian Ocean so it exaggerates the size of Madagascar instead of Greenland. Various countries and oceans are labeled, and country borders are shown.

This is the fifth comic in the series of Bad Map Projections displaying Bad Map Projection #248: Madagascator. It came about 10 months after the fourth 2489: Bad Map Projection: The Greenland Special (#299). This time, Randall used the classic Mercator projection but instead of placing the North Pole on top and the South Pole on the bottom it is oriented so that the top is the island of Mahé . The map projection is technically a Oblique Mercator projection , with an unusual choice of the cylinder's axis. Since the Mercator projection tends to visually distort areas near the top and bottom of the resulting map, this gives some areas, notably Madagascar, very unusual shapes, hence the name the Madagascator — a portmanteau of "Madagascar" and "Mercator"! The Mercator projection became the standard projection for world maps during the 1800s, because a straight line (or rhumb line ) in a Mercator map represents a constant bearing relative to true north. Historically, when navigation was performed by compass, this was a very valuable feature, since one (adjusting for the differences between true and magnetic north) could plot a constant-bearing course between two locations by simply looking at their relative direction on the map. However, in the mid-20th century, the Mercator was criticized because it causes distortion near the north and south poles of the map, giving an inaccurate impression of relative sizes. The most commonly given example of this is the size of Greenland — although on the Mercator it appears to be larger than Africa in area, Africa in reality covers an area 14 times that of Greenland. Randall turns this example on its head by making Madagascar, rather than Greenland, appear larger in the Madagascator than in reality. By contrast with Greenland, the world's largest non-continent island, Madagascar is only the fourth-largest island in the world, behind Greenland, New Guinea, and Borneo. To accomplish this, instead of placing the north pole of the map at the geographic North Pole, Randall places the north pole of the map on the island of Mahé in Seychelles. As Madagascar is relatively close to Mahé (around 650 mi (1050 km) distant), placing the north pole of the Mercator projection at Mahé significantly distorts the size of Madagascar, making it appear comparable in size to Europe on the map. But this distortion is even more pronounced when it comes to the island of Mahé itself, as Randall notes in the title text. Although Mahé, the largest island in Seychelles with an area of 60.7 square mi (157.2 square km), is minuscule even compared to Madagascar, the claim in the title text that it appears "larger than the rest of the Earth's land area combined" is an understatement. No part of Mahé is visible in the comic, but clicking on the actual comic will open a website that displays Mercator projections with a pole in any chosen location, with the location of the one opened set to Mahé. The chosen pole is (infinitely far to) the right of the screen, while its antipode is on the left. With this, it is possible to see that the island is indeed larger than the rest of the map's land area combined. A single national park within the island rivals Africa in size, and the narrow dirt road closest to the pole appears thicker than Panama. This also reveals that the location of the map's north pole (the "small lake" mentioned by Randall) is the lake impounded by the Rochon Dam, a popular tourist location in Mahé. Unlike previous Bad Map Projections, Morocco and Western Sahara are drawn as one unlabelled country. Bad map projection #248: Madagascator Mercator projection but with the North Pole in the Indian Ocean so it exaggerates the size of Madagascar instead of Greenland. Various countries and oceans are labeled, and country borders are shown.

2

2

https://www.xkcd.com/2614

https://www.explainxkcd.com/wiki/index.php/2614:_2

[An apparent generalisation of a scientific expression consisting of a dotted rectangular 'box' outline, left empty, and various commonly-themed symbology around it:] [as normal text, to the left of all the rest:] 2 [superscript to the immediate left of the box:] 2 [subscript also to the immediate left of the box:] 2 [superscript to the immediate right of the box:] 2 [subscript also to the immediate right of the box:] 2;2 [i.e. separated by a semicolon] [as normal text, to the right of almost all the rest:] (2) [i.e. enclosed in standard parentheses] [smaller subscript, centered immediately beneath the 2 within the parentheses:] 2 [Further details are drawn in grey tone, around or near various of the elements of the expression:] [Captions above the numbers] [with an arrow pointing to the leftmost 2:] Regular Math [with an arrow pointing to the leftwards superscript 2:] Physics [with an arrow pointing to the rightwards superscript 2:] Regular math or footnotes [with an arrow pointing to the parenthetical 2 at the right:] Either high school math functions or incomprehensible group theory [Captions below the numbers] [with an arrow pointing to the leftwards subscript 2:] Chemical Physics [with an arrow pointing to just the rightwards subscript 2:] Chemistry [with an arrow pointing to a distorted grey ring snaking around only the comma of the semicolon and the following 2 of the rightmost subscript:] Matrices! [with an arrow pointing to a larger grey ring that passes fully around the whole semicolon and final 2 of the rightmost subscript:] The physicists are at it again [with an arrow pointing to the small 2 placed below the parenthetical 2:] Oh no. Whatever this is, it's cursed.

This demonstrates the different ways in which the number 2 can be typeset in various scientific fields. While these ways of typesetting are used with any number, using the number 2 in this instance provides a clear illustration how adding numbers can significantly alter a feature of a concept (such as the number of electrons in an atom) or perform a mathematical operation on it (such as raising a value to its second power). The dotted box represents any character (a number, letter, or bigram of letters, as appropriate to the various signifiers). All the other notation consists only of the digit 2, with occasional additional punctuation, in various locations in relation to this character. Each of these is labelled as to what its 'purpose' might normally be with respect to the general term: Regular Math Precedes the term. "2x" indicates two times the value of x in normal algebraic use that should be familiar for many people. Physics A preceding superscript. " 2 H" would indicate the particular isotope of hydrogen with the atomic weight of two, namely deuterium, which is most often encountered when working with the atomic level of matter where the total number of neutrons and protons in the atom is important. It can also represent tetration , which is iterated exponentiation. Chemical Physics A preceding subscript, as in " 2 He", indicates the atomic number of an atom, which is the number of protons it contains. It is thus a guide to the number of electrons its unionised form usually has and hence is meaningful for its potential chemical interactions with other atoms. This number of protons should be invariant for any particular named element, but is usually given simultaneously with the presuperscripted mass number for which it can indicate the applicable nuclear physics. Chemical physics is a subdiscipline of physics and chemistry. It can also represent pentation , which is iterated tetration. Regular Math or Footnotes A trailing superscript is typical of a power value ; in this case "x²" would be x multiplied by itself - a common mathematical standard. Additionally, superscripted numbers are one common way to mark words in a line of text in a way to refer to a footnote , typically placed at the bottom of the page and containing additional information that would distract from the main text itself. The ambiguity between footnotes and exponents was used in 1184: Circumference Formula . Chemistry A trailing subscript is used in chemistry to indicate a multiple of the element (or group of elements, in brackets) in a chemical formula . "H 2 O" indicates two hydrogen atoms bond with a single oxygen atom in a molecule of water. Matrices! ("2,2") Extending the trailing subscript with a comma-separated value usually indicates a multidimensional array (e.g., establishing a 2-by-2 square of numbers, or this particular position in such an array), which is in the realm of matrix mathematics . This is a little bit beyond 'everyday algebra' for many people, as seemingly indicated by the exclamation of the mere mention of matrices. The Physicists Are At It Again ("2;2") This label encompasses a mark that turns the prior comma into a semicolon, as part of the trailing subscript. This is a common notation for the Covariant derivative of a tensor field, which is commonly used in the mathematics of general relativity. Either High School Math Function or Incomprehensible Group Theory The number 2 in parentheses that follow a term would normally be the argument to a function . For example, "f(2)" means that you should take the value 2, and find the result if manipulated by the predefined function f . It is generally taught as part of algebraic mathematics in high school . In group theory , however, the number 2 in parentheses could indicate a special kind of group, such as an an element of a symmetry group that keeps 2 fixed, or some kind of group of 2x2 matrices. For instance, SU(2) is a 3-dimensional Lie group of unitary matrices . These concepts are taught in graduate or advanced undergraduate mathematics courses. Oh no. Whatever this is, it's cursed. A symbol centered underneath another larger symbol is normally reserved for doing summations or products, where the big symbol is Σ or Π, or some other operation applied to a sequence of numbers. It does not make sense to have a single number on top of a smaller one. As with other things where something appears to have gone wrong in Randall's comic universe, the explanation for this particular anomaly is that it is 'Cursed'. Two numbers may be stacked directly on top of one another in parentheses as binomial coefficients : ( 2 2 ), but those are always the same size, denoting a combination . In this case, 2 choose 2 is equal to one combination. The usage mentioned in the alt text is an operation (e.g. Σ for summation) over a variable, usually indicated by a letter such as i, where the operation is performed over all values of the variable (i.e., you Σ (sum) the argument over all values of i). In the "2" case, the alt text says "you 2 the argument over all values of 2" (i.e., the Σ operation has been replaced by the "2" operation and the i variable has been replaced by the "2" variable). 2 is usually not an operation, though the definition of 2 under Church encoding is a function that takes in and produces functions. 2 applied to 2 in the church encoding is 4. However, the title text implies that 2 is treated like a variable,which it is not (and it's definitely not a operator and variable at the same time). Things being cursed is a common trope within recent xkcd comics, which have mentioned items including Cursed chairs and cursed connectors . This notation is one of the few occasions where the supernatural has demonstrable implications for science and mathematics for those foolhardy enough to use it. [An apparent generalisation of a scientific expression consisting of a dotted rectangular 'box' outline, left empty, and various commonly-themed symbology around it:] [as normal text, to the left of all the rest:] 2 [superscript to the immediate left of the box:] 2 [subscript also to the immediate left of the box:] 2 [superscript to the immediate right of the box:] 2 [subscript also to the immediate right of the box:] 2;2 [i.e. separated by a semicolon] [as normal text, to the right of almost all the rest:] (2) [i.e. enclosed in standard parentheses] [smaller subscript, centered immediately beneath the 2 within the parentheses:] 2 [Further details are drawn in grey tone, around or near various of the elements of the expression:] [Captions above the numbers] [with an arrow pointing to the leftmost 2:] Regular Math [with an arrow pointing to the leftwards superscript 2:] Physics [with an arrow pointing to the rightwards superscript 2:] Regular math or footnotes [with an arrow pointing to the parenthetical 2 at the right:] Either high school math functions or incomprehensible group theory [Captions below the numbers] [with an arrow pointing to the leftwards subscript 2:] Chemical Physics [with an arrow pointing to just the rightwards subscript 2:] Chemistry [with an arrow pointing to a distorted grey ring snaking around only the comma of the semicolon and the following 2 of the rightmost subscript:] Matrices! [with an arrow pointing to a larger grey ring that passes fully around the whole semicolon and final 2 of the rightmost subscript:] The physicists are at it again [with an arrow pointing to the small 2 placed below the parenthetical 2:] Oh no. Whatever this is, it's cursed.

Welcome Back

Welcome Back

https://www.xkcd.com/2615

https://www.explainxkcd.com/wiki/index.php/2615:_Welcome_Back

[A large cloud fills the upper 3/4 of the panel. That it is a cloud is indicated by curved lines at the bottom of the cloud. Below the cloud lines is a tornado in the right part of the background. It is throwing up dust on or near the mid-distance horizon and creating an active debris cloud. In the foreground Cueball is standing holding his phone up in one hand, looking at the screen, which is on as indicated by five "light lines" coming of his display. Three paragraphs of text fills most of the white cloud space above Cueball, they are connected by lines, with the last leading down to the top of Cueball's phone. There are two rounded boxes to the right and below the first two paragraphs with text. They represents buttons Cueball presses on the screen to get to the next text message.] Hi! The TornadoGuard™ team is proud to announce a big update! We've added- Okay Note to users of sentinel mode: We've heard your feedback, and the controls are now- Got it The TornadoGuard™ team saw this cool leaf shaped like a spider; do you want to see... [Caption below the panel:] When you open an app for the first time in a while, you have to wait around while it tells you about all the cool adventures it's had.

Cueball is opening an app called TornadoGuard, a reference to comic 937: TornadoGuard . In that comic the app is described to have a function so it "plays a loud alert sound when there is a tornado warning for your area". Tornadoes are a recurring theme on xkcd. In the background, a tornado is approaching, so presumably a loud alert sound has just played and Cueball has opened the app. It is also possible that the app didn't play any alert (see reviews of the app in 937 ), but Cueball saw the Tornado and thus opened the app to check whether it had any news. However, before he can interact with the app and learn more about the tornado, he has to click through various old messages from the app, since he hasn't opened the app in a while. This is feasible because May, which is the month in which this comic was published and typically the most active month for tornadoes, had seen fewer-than-average tornadoes in the previous two years but not during this year – see this Tornado Central story . So Cueball would have been more likely to have to worry about tornadoes this year than in the previous two years. The comic is poking fun at the obtrusiveness of these kind of messages by presenting a scenario where they cause a significant delay before Cueball would be able to read the very urgent information about current tornadoes. The messages include a description of a big update, a response to user feedback about one specific feature, and a social post seemingly unrelated to the app. This continues in the title text where there are two more messages that refer to specific world events and can therefore be dated: The fire that damaged the church of Notre Dame in Paris April 15th 2019; and the early attempts to limit the spread of Covid-19 disease, which was declared a pandemic on March 11th 2020. It has been a while since the last reference to the pandemic , actually the previous comic about this, 2563: Throat and Nasal Passages , was released almost exactly 4 months prior to this one. The two mentioned news stories were relevant about three and two years before this comic was published, respectively. Neither of these are important to know right now, whereas an announcement about an update that changes its functionality could be important to know about . Although it is possible that there are no more messages to click through if nothing of significance has happened subsequent to the title text ones , the reader can easily imagine that the development team has posted further 'real time' messages that Cueball will still have to scroll through and/or dismiss, with very little immediate importance compared with the imminent proximity of an actual funnel-cloud. [A large cloud fills the upper 3/4 of the panel. That it is a cloud is indicated by curved lines at the bottom of the cloud. Below the cloud lines is a tornado in the right part of the background. It is throwing up dust on or near the mid-distance horizon and creating an active debris cloud. In the foreground Cueball is standing holding his phone up in one hand, looking at the screen, which is on as indicated by five "light lines" coming of his display. Three paragraphs of text fills most of the white cloud space above Cueball, they are connected by lines, with the last leading down to the top of Cueball's phone. There are two rounded boxes to the right and below the first two paragraphs with text. They represents buttons Cueball presses on the screen to get to the next text message.] Hi! The TornadoGuard™ team is proud to announce a big update! We've added- Okay Note to users of sentinel mode: We've heard your feedback, and the controls are now- Got it The TornadoGuard™ team saw this cool leaf shaped like a spider; do you want to see... [Caption below the panel:] When you open an app for the first time in a while, you have to wait around while it tells you about all the cool adventures it's had.

Deep End

Deep End

https://www.xkcd.com/2616

https://www.explainxkcd.com/wiki/index.php/2616:_Deep_End

[Caption above the scene] How deep ends form in pools [On the left of the image is the shallowest water in the pool, about the height of Megan. All the water in the image is grey. She is swimming in the water, and a duck floatie and a beach ball are floating to the left of her. It is labeled] Shallow End [Underneath, a thick layer is labeled] Pool Floor [Going to the right from there, the pool floor begins to curve downwards. As the floor goes down, the water gets deeper. In the deepest area, it is labeled] Deep End [At the bottom of the deep end, there is a curve and a deposit on the pool floor. Within the sediment and pool floor, there are some small pools of trapped water, labeled with three arrows] Trapped Water [On the pool floor an arrow indicates that the oceanic plate is moving left-to-right across the image, which is labeled] Subduction [Some of the water pools are dragged along by the pool floor, while others float up through the ground. The latter are accompanied by several arrows pointing up to indicate upwards movement. These are labeled:] Upward Migration [At the surface there is an area, which is labeled] Splash zone [The water erupts in two geysers, the left slightly larger than the other. Several children (small versions of Ponytail, Hairy, and Science Girl as herself) are playing there. Science Girl is sitting with her arms in the air facing the geysers, and Ponytail and Hairy are running towards the right geyser, Hairy with his arms in the air. The area is labeled] Splash Zone [To the left of the splash zone is the edge of the pool, where a Cueball figure is in mid-air after jumping off the diving board, with his arms outstretched. This is labeled] Pool Deck

Pools, like oceans, contain water. This comic produces a schematic for the former, derived from science about the latter. On Earth, the surface consists of tectonic plates which move around. In this comic, Randall equates swimming pools with plate tectonics , to explain how deep ends form in said pools. In actuality, swimming pools aren't formed by plate tectonics (at least, not the ones made by people; we can't be sure about the others). A swimming pool is a pool of water, typically used for swimming. Most of these have a deep end and a shallow end. This is intentional, usually to allow less confident swimmers to have somewhere to stand up when needed, while also accommodating activities (such as diving, underwater swimming, rescue practice, etc.) which would not be possible in shallower water. Subduction , a geological process in which one plate slips beneath another and is forced down into the mantle, is shown here as the reason swimming pools have deep ends. This usually takes place between continental plates and oceanic plates, although it could happen with two oceanic plates. The comic depicts the former, an oceanic plate subducting under a continental one. With tectonic plates, this often results in a deep oceanic trench where one plate slides beneath the other, as well as a chain of volcanoes above areas farther along the subducting plate, where rock that has liquefied from the subduction comes toward the surface as magma and erupts in volcanoes. An example is the Cascadia Subduction Zone in which the Juan de Fuca Plate is subducting beneath the North American Plate , creating the volcanic Cascade Range . A splash zone is an area of a waterpark with water being sprayed around, allowing people to get wet without the need to get into the pool. It is not a geological term, but splash zone can mean the area next to a coastline that gets splashed by waves. In this comic, the splash zone consists of natural geysers, fed by the bubbles of water that return upwards from the subducted plate. The title text refers to back-arc basins , zones of depression that sometimes occur slightly beyond volcanic arcs due to a rift in the tectonic plate. The ban on running in this area likely has more to do with its proximity to the pool area than any danger intrinsic to back-arc basins. A typical safety rule around swimming pools is to avoid running on the pool deck to prevent injuries due to slipping and falling on the hard deck. Other comics that mention unusual tectonic plate motion include 1388: Subduction License and 1874: Geologic Faults . [Caption above the scene] How deep ends form in pools [On the left of the image is the shallowest water in the pool, about the height of Megan. All the water in the image is grey. She is swimming in the water, and a duck floatie and a beach ball are floating to the left of her. It is labeled] Shallow End [Underneath, a thick layer is labeled] Pool Floor [Going to the right from there, the pool floor begins to curve downwards. As the floor goes down, the water gets deeper. In the deepest area, it is labeled] Deep End [At the bottom of the deep end, there is a curve and a deposit on the pool floor. Within the sediment and pool floor, there are some small pools of trapped water, labeled with three arrows] Trapped Water [On the pool floor an arrow indicates that the oceanic plate is moving left-to-right across the image, which is labeled] Subduction [Some of the water pools are dragged along by the pool floor, while others float up through the ground. The latter are accompanied by several arrows pointing up to indicate upwards movement. These are labeled:] Upward Migration [At the surface there is an area, which is labeled] Splash zone [The water erupts in two geysers, the left slightly larger than the other. Several children (small versions of Ponytail, Hairy, and Science Girl as herself) are playing there. Science Girl is sitting with her arms in the air facing the geysers, and Ponytail and Hairy are running towards the right geyser, Hairy with his arms in the air. The area is labeled] Splash Zone [To the left of the splash zone is the edge of the pool, where a Cueball figure is in mid-air after jumping off the diving board, with his arms outstretched. This is labeled] Pool Deck

Maps

Maps

https://www.xkcd.com/2617

https://www.explainxkcd.com/wiki/index.php/2617:_Maps

[Cueball is holding his hands up and is staring down at his open palms. Megan and White hat is looking at him.] Cueball: You look around one day and realize the things you assumed were immutable constants of the universe have changed. Cueball: The foundations of our reality are shifting beneath our feet. Cueball: We live in a house built on sand. [Caption below panel] The day I discovered that Apple Maps is kind of good now

The term "map" carries a double meaning within this comic. While it refers to an actual map, it also refers to the concept of "map and territory," where your map is your model of the universe, and the territory is the universe itself. Cueball has a map of the universe where Apple Maps is bad, and is surprised to discover that the map no longer fits the territory, and thus has to update his map. The title text mentions OpenStreetMap , an open-data crowd sourced geodatabase, which has also improved since Randall has last checked, potentially moving it from a "pretty good" score to a "really good" score. He also adds two examples on how the Apple Maps service has improved: zooming in on cities, like London or New York you can see features like trees and road markings, the latter usually not visible on other mapping services at all. He marvels at the number of "good" mapping options now! Google Maps itself, and especially its satellite coverage outside the US, was considered quite bad when it launched in 2005. The maps displayed back then led to mockery among "real" cartographers that the service couldn't really be considered a map, either: It was called "map-like", with casual digital maps being so new at the time. However, Google's popular mapping approach revolutionized how maps were perceived all over the world. The approaches Google uses are explained in How Google Maps is Made . This approach blurs the lines between traditional paper maps, GIS (geo-informational systems) and digitally rendered maps on screen. The process of "mapping" - as it is referenced here - has since moved significantly into the digital realm. [Cueball is holding his hands up and is staring down at his open palms. Megan and White hat is looking at him.] Cueball: You look around one day and realize the things you assumed were immutable constants of the universe have changed. Cueball: The foundations of our reality are shifting beneath our feet. Cueball: We live in a house built on sand. [Caption below panel] The day I discovered that Apple Maps is kind of good now

Selection Bias

Selection Bias

https://www.xkcd.com/2618

https://www.explainxkcd.com/wiki/index.php/2618:_Selection_Bias

[Blondie is standing on a podium behind a lectern with a microphone. She is standing under a hanging sign with large text. In front of the podium is an audience of five seated persons all with their hands raised above their heads. The audience includes two guys that look like Cueball, Hairbun, and two other persons with dark and blonde hair.] Sign: Statistics conference 2022 Blondie: Raise your hand if you’re familiar with selection bias. Blondie: As you can see, it’s a term most people know...

Selection bias is when a survey or poll of some sort comes up with incorrect results due to those who were asked. For example, if you asked a group of people how many acres of land they own, your average number will be higher if you ask a group of farmers rather than a group of city residents. The joke is that she is thus falling for the very thing she's trying to explain. A statistics conference is likely to have an audience consisting of professional statisticians, or at least people interested in the subject, and it is expected that most of them would thus be familiar with any mainstream statistical term, like selection bias. Had she asked a random sample of people in the street, many of them would likely not be sure what selection bias is. This effect is also the subject of 2357: Polls vs the Street . This joke also ties into how statistics as a whole can be highly counter-intuitive and sometimes almost paradoxical, where things like the Monty Hall problem and survivorship bias lead people into thinking the answer to a problem is definitely in a place it's not. That Blondie, presumably a statistician herself, made this kind of (potentially deliberate) error is professionally embarrassing but not unprecedented. The title text refers to Acquiescence bias , which is the tendency of people to respond positively to positive questions, for example, "Are you familiar with the famous webcomic xkcd ?" is more likely to generate the answer yes than "Are you familiar with that webcomic for engineers that nobody else understands until they go to Explain xkcd ?" Acquiescence bias is not a widely known concept, [ citation needed ] making the results of this poll suspect; similar to the selection bias example above, the reason that the general public seems familiar with acquiescence bias may be because the surveyor themself fell victim to promoting acquiescence bias. [Blondie is standing on a podium behind a lectern with a microphone. She is standing under a hanging sign with large text. In front of the podium is an audience of five seated persons all with their hands raised above their heads. The audience includes two guys that look like Cueball, Hairbun, and two other persons with dark and blonde hair.] Sign: Statistics conference 2022 Blondie: Raise your hand if you’re familiar with selection bias. Blondie: As you can see, it’s a term most people know...

Crêpe

Crêpe

https://www.xkcd.com/2619

https://www.explainxkcd.com/wiki/index.php/2619:_Cr%C3%AApe

[Cueball is holding a plate up in both hand, showing Megan the crepe lying on the plate. His word for crêpe has a different diacritic over the "e" than the normal circumflex (^). Instead it looks more like an open arrow head.] Cueball: Check out this crêpe I made! Megan: Weird circumflex, but okay.

Cueball has made a crêpe , a thin pancake known for its legendary status in French cuisine, which he proudly announces. However, the circumflex (the accent above the e) is written strangely. Instead of the usual simple angle (^), it looks more like the outline of a flattened arrowhead ( ⮝ ). Megan , who can apparently hear the orthography of spoken text, comments on the odd shape with an appropriate pun. Megan's response, "Weird circumflex but okay" is a play on the recent expression Weird flex, but ok . A "flex" is bragging about something. A "weird flex" is used when the speaker acknowledges (perhaps ironically) that the first person is attempting to brag about something, but doesn't recognise the thing as brag-worthy. Her answer could also be applied to the shape of the crêpe, as circumflex means "bent around". In some dialects of English (e.g. British English), and in the original French pronunciation, "crêpe" is said so that the ê is pronounced as in "get" (i.e. "cr-eh-p"), but American English speakers pronounce it like an "A" (i.e. "cr-ay-p"). The title text continues the wordplay by saying that "A medicine that makes you put two dots over your letters more often is a diäretic". The word diäretic is a pun on diuretic (a substance promoting increased urine production), diaeresis (a symbol in the form of two dots placed above a vowel, as the ä in the made up word diäretic; the adjective form of diaeresis can be spelled " dieretic ") and diacritic (a glyph added to a letter to distinguish its sound from the normal version, what both the circumflex and the diaeresis are). See also the comic 1647: Diacritics about the use of these. Taking a diäretic medicine would supposedly cause you to use diaeresis (also known as umlaut) över möre lëtters thän wöuld üsuallÿ bë thë cäse. Diacritics are rarely used in English, potentially because of the diverse set of origin languages it developed from, or the wide variation of pronunciations within a same nation, but are a common feature of other languages. In English, they are normally only seen in specific loanwords (such as crêpe) or used for emphasis or decoration (for example the metal umlaut seen in rock bands like Motörhead , Mötley Crüe , Queensrÿche , or Spın̈al Tap ). The exception to this is the diaresis, which when it is used at all, is placed over the second vowel in a double-vowel word to indicate a morphological break between them as opposed to a diphthong (e.g. naïve or coöperation). The diaresis is optional, and, especially with words beginning with the co- prefix (e.g. cooperation, coevolution, or coincidence), rarely used. The New Yorker magazine is a famous outlier, advising consistent use of the diaresis in its style guide . [Cueball is holding a plate up in both hand, showing Megan the crepe lying on the plate. His word for crêpe has a different diacritic over the "e" than the normal circumflex (^). Instead it looks more like an open arrow head.] Cueball: Check out this crêpe I made! Megan: Weird circumflex, but okay.

Health Data

Health Data

https://www.xkcd.com/2620

https://www.explainxkcd.com/wiki/index.php/2620:_Health_Data

[Cueball and Doctor Ponytail are talking to each other. Cueball is sitting on an examination table and Doctor Ponytail, in a doctor's coat, is looking down and reading from a clipboard with some illegible writing on it.] Doctor Ponytail: I'm taking a look at your numbers, and it doesn't look good. Doctor Ponytail: You have a lot of measurements. Quite a few variables. [Same setting but Doctor Ponytail looks up at Cueball.] Cueball: Is that... bad? Doctor Ponytail: Variables are the #1 risk factor for outcomes. Doctor Ponytail: The past is a big contributor to the future. [Same setting but Doctor Ponytail puts her arm with the clipboard down.] Cueball: Isn't that just causality? Doctor Ponytail: Causality is the leading cause of death in this country. [Same setting.] Cueball: So what are my odds? Doctor Ponytail: Do you have a family history? Cueball: Of what? Doctor Ponytail: Just, in general. Cueball: ...Yes? Doctor Ponytail: Oh no.

Cueball tries to cut to the root of the issue by asking his chances of survival. Ponytail asks whether Cueball has a family history, but rather than asking for a history of specific illnesses, she is merely asking whether he has any family history at all. Her apparent concern on discovering that he does is presumably due to the fact that everyone who has a family history dies, and therefore she sees this as negative. However, this is not medically informative, since everyone has some kind of family history (whether they personally know anything of it or not) and everyone eventually dies. [ citation needed ] The comic is likely a comment on the impenetrability of some medical diagnoses, where high levels of jargon and non-contextualized statistics, combined with a lot of hedging language, can leave patients none the wiser about their prospects or the relative merits of various courses of treatment. Similarly, it could be reflecting on the effects of availability bias and the base rate fallacy when medical practitioners are deriving diagnoses, treatment options, and similar conclusions from medical records designed to highlight the information necessary to diagnose specific well-understood illnesses. It may also be making fun of poorly defined health statistics: statistics for the leading causes of accidental death in the United States , for example, typically cite 'poisoning' as the number one cause, even though poisoning other than drug overdoses is actually quite rare. The comic takes vague statistics to the extreme, citing 'causality' as the leading cause of death. The title text continues the joke, suggesting that researchers are searching for a cure for causality, which is absurd and inconceivable. The comic as a whole is reminiscent of 830: Genetic Analysis and 1840: Genetic Testing Results (particularly the title text of the latter), as the information given by the doctor in all three is self-evident and useless as a result. [Cueball and Doctor Ponytail are talking to each other. Cueball is sitting on an examination table and Doctor Ponytail, in a doctor's coat, is looking down and reading from a clipboard with some illegible writing on it.] Doctor Ponytail: I'm taking a look at your numbers, and it doesn't look good. Doctor Ponytail: You have a lot of measurements. Quite a few variables. [Same setting but Doctor Ponytail looks up at Cueball.] Cueball: Is that... bad? Doctor Ponytail: Variables are the #1 risk factor for outcomes. Doctor Ponytail: The past is a big contributor to the future. [Same setting but Doctor Ponytail puts her arm with the clipboard down.] Cueball: Isn't that just causality? Doctor Ponytail: Causality is the leading cause of death in this country. [Same setting.] Cueball: So what are my odds? Doctor Ponytail: Do you have a family history? Cueball: Of what? Doctor Ponytail: Just, in general. Cueball: ...Yes? Doctor Ponytail: Oh no.

Mainly Known For

Mainly Known For

https://www.xkcd.com/2621

https://www.explainxkcd.com/wiki/index.php/2621:_Mainly_Known_For

[Megan holds her hand palm up towards Cueball.] Megan: ...And her dad looks exactly like the Pixar guy. Steve what's-his-name? Jobs? Cueball: "Pixar guy"? Cueball: You always know famous people for such weird reasons. [Megan puts her hand down.] Megan: What do you mean? Cueball: Who is John Lennon? Megan: Wasn't he in a band? With Ringo from Shining Time Station . Cueball: How is that your main association? [In a frameless panel Megan holds a finger up in front of Cueball.] Megan: I also know he once did a song with the guy from Labyrinth! Cueball: You mean David Bowie? I think he's famous for some other stuff, too. [Megan puts her hand down while Cueball facepalms. The line connecting his is curved.] Megan: Oh yeah, he was also in Zoolander! Megan: I forgot that movie, it came out back when Jenna Bush's dad was president. Cueball: *Sigh*

Frequently, when people can't remember a celebrity's name, they will point out other works they are known for in hopes someone else will recognize them from that and remind them of the name. The comic, for its demographic of nerds, is joking on how it can come across to have lived a life separate from popular culture, where one learns things for different reasons than most people do. Cueball points out that Megan's tendency to avoid the "main" association and instead go with a much more secondary one is weird, which confuses her. To demonstrate how weird her associations are, Cueball asks her, "Who is John Lennon ?" Lennon was a founding member of The Beatles , which is one of the most famous bands of all time. Megan recognizes Lennon as a musical artist, but is unable to remember the name of The Beatles. Bizarrely she does remember the name of Lennon's bandmate Ringo Starr . Even stranger, Megan still fails to associate Ringo with The Beatles, but rather remembers him as Mr. Conductor from the first season of the 1989 children's television show Shining Time Station . Starr was never particularly well-known for his acting career, and even among his acting roles Shining Time Station was a minor and obscure example. Hoping to show that she really does know Lennon and that her associations aren't weird, she points out that she remembers John doing a song with David Bowie . But she cannot remember the name of the song (" Fame ") or even Bowie's name, recognizing him instead for his acting role in Labyrinth . When Cueball states Bowie's name and adds, presumably sarcastically, that he think he is famous for "other stuff", she also remembers Zoolander which is a less prominent film in which Bowie had a cameo. Bowie is primarily famous for his famous musical career (such as his smash hits " Space Oddity " or " Let's Dance "). Sensing Cueball's annoyance, but failing to understand it, she attempts to excuse herself for not remembering Zoolander to begin with, because it came out a long time ago, during the Presidency of George W. Bush . Zoolander was indeed released in 2001. Apparently unable, again, to remember the president's name, she identifies him as " Jenna Bush 's dad". Jenna Bush is a minor TV personality and is far less well known than her father.. While the kind of associations people make, like Megan in this comic, are often prone to the Mandela effect , Megan's information about all the celebrities is, in fact, correct, but apparently they are never what those people are best known for. The oddness of having such obscure knowledge about celebrities and popular culture, but apparently missing far more common knowledge, is frustrating to Cueball, but there's nothing he can point to that she's wrong about. There may also be some overlap with the Streisand effect , named after a woman widely known for owning an overly lavish mansion on the coast of a state north of Mexico. In the title text, Megan stacks her unusual references and takes them to extremes. She refers to " Keira Knightly " [ sic -- her surname is spelled Knightley], who is probably best known for her roles in the Pirates of the Caribbean films and the 2005 Pride and Prejudice film , by referencing her small role in Star Wars: Episode I – The Phantom Menace (as Sabé, who funnily enough is a handmaiden and decoy for Queen Padmé Amidala, a main character played by Natalie Portman). "Star Wars" is one of the most famous film franchises in history, but Megan seems not to know the name of the series, or the film, referring to it as the "first movie" (it was the first in the plotline, but the fourth one made) in "that series by The Land Before Time producer". ( George Lucas is famous as the creator of Star Wars but was also one of the executive producers of the 1988 animated film The Land Before Time .) In addition to George Lucas, she identifies another actor in the Star Wars series, Samuel L. Jackson , by his roles in Jurassic Park (an extremely successful film, but one in which Jackson had a relatively small role) and the PBS children's series Ghostwriter (in which Jackson appeared in only a few episodes). In addition, Megan mentions that the Star Wars series had "script work by Billie Lourd 's mom", referring to Carrie Fisher . Fisher came to fame playing the major role of Princess Leia Organa in the original "Star Wars" film, and reprising her role in multiple sequels, but she also contributed uncredited script-doctoring work to the franchise. Ghostwriter was previously featured in 130: Julia Stiles , which described a scene from the show as "the best thing ever to appear on TV". [Megan holds her hand palm up towards Cueball.] Megan: ...And her dad looks exactly like the Pixar guy. Steve what's-his-name? Jobs? Cueball: "Pixar guy"? Cueball: You always know famous people for such weird reasons. [Megan puts her hand down.] Megan: What do you mean? Cueball: Who is John Lennon? Megan: Wasn't he in a band? With Ringo from Shining Time Station . Cueball: How is that your main association? [In a frameless panel Megan holds a finger up in front of Cueball.] Megan: I also know he once did a song with the guy from Labyrinth! Cueball: You mean David Bowie? I think he's famous for some other stuff, too. [Megan puts her hand down while Cueball facepalms. The line connecting his is curved.] Megan: Oh yeah, he was also in Zoolander! Megan: I forgot that movie, it came out back when Jenna Bush's dad was president. Cueball: *Sigh*

Angular Diameter Turnaround

Angular Diameter Turnaround

https://www.xkcd.com/2622

https://www.explainxkcd.com/wiki/index.php/2622:_Angular_Diameter_Turnaround

[Cueball and a row of 7 spiral galaxies, the first 5 growing sequentially smaller and the last 2 growing larger] Angular Diameter Turnaround [A spiral galaxy emitting light and Cueball in a small circle with closely spaced grid lines, captioned "T=1b yr."] [A stretched truncated circle with widely spaced gridlines, with the galaxy at one side and Cueball on the other, and light following a curved path through the stretched space to Cueball, captioned "Now (T=13.8b yr.)". Cueball is thinking "Big!"] Illustrated using phones instead of galaxies (Brightness and redshift adjusted to keep phones visible) Things that are far away look smaller, but things that are really far away look bigger , because when their light was emitted, the universe was small and they were close to us. [numerous iPhones scattered in space, with numbers visible on their lockscreen. The closest is brightly lit and says "13 billion years after the Big Bang" on the screen. Subsequent phones behind this one are smaller, fainter and more red, until they reach "3" (the rest of the text is too small to read). From this point, the phones grow larger, although they continue to get fainter and redder. Subsequent phones show "2", "1", "500 million", "200 million", "50 million", "20 million" (which is larger than the original "13 billion years after the Big Bang" phone) and a very large, faint phone so big that only the word "thousand" is visible, with the rest of the screen obscured behind other phones or so large it extends off the panel]

This comic references multiple physics and maths concepts, including Angular diameter , Angular diameter distance , Redshift , and mobile phones , although mobile phones are not a core science at this time. [ citation needed ] The comic shows the galaxies of the universe as Samsung Galaxy mobile phones, pairing the age we see them at from earth, the degree they are redshifted, and how much of the sky they take up, known as their angular diameter. The mobile phones that are closer and older have depleted batteries, whereas the batteries are full for those phones from which the light is still only beginning to reach us. This is how galaxies appear in the sky if they were phones that had batteries lasting billions of years, the light reaching us from deeper into the past as it comes from objects that are farther away. Phones at a low battery may be a reference to 1373: Screenshot , where Randall commented that it is hard to pay attention to any phone with a low battery as the need to charge it is so urgent. An important takeaway from this comic is that the events that occurred at the very start of our universe are etched in our sky as if they are still happening now , in a detailed faint timeline, that we are still learning more and more from. Using the mobile phone metaphor helps as, when the technology space was young and smaller there were mobile phones , such as the original iPhone , which one might still remember despite there being many more recent and better ones in a more crowded market space. Randall's intent appears to be to highlight how just a few very distant galaxies occupy incredibly large proportions of the sky and are seen as they were at a very young age. Mobile phones have this similarity, of massive presence, relatively early stages of new technology, and bringing information from far away. The large galaxies can be seen in dark red in the background as if the unimaginably ancient child galactic bodies are looming forebodingly behind everything else. The title text refers to galaxies falling into a pool of dilute blood as if the void beyond were hell. This completely misses the point as to what redshift is, being an effect on the wavelength of light, rather than light being filtered through regions of infernal suffering or far galaxies being stained by the blood of the enemies of Android phones. This physical concept has a lot of juxtaposition of things that usually contradict, and Randall has put energy into attempting to highlight that. Katie Mack tweet: https://twitter.com/AstroKatie/status/1516548836709343238 Spacetime diagram possibly has reasonable visualizations of the kinds of relations bodies have when they are moving this far apart, including angular diameter distance. Simultaneity no longer exists at such distances. Distance is debated too, although that would be a different article. [Cueball and a row of 7 spiral galaxies, the first 5 growing sequentially smaller and the last 2 growing larger] Angular Diameter Turnaround [A spiral galaxy emitting light and Cueball in a small circle with closely spaced grid lines, captioned "T=1b yr."] [A stretched truncated circle with widely spaced gridlines, with the galaxy at one side and Cueball on the other, and light following a curved path through the stretched space to Cueball, captioned "Now (T=13.8b yr.)". Cueball is thinking "Big!"] Illustrated using phones instead of galaxies (Brightness and redshift adjusted to keep phones visible) Things that are far away look smaller, but things that are really far away look bigger , because when their light was emitted, the universe was small and they were close to us. [numerous iPhones scattered in space, with numbers visible on their lockscreen. The closest is brightly lit and says "13 billion years after the Big Bang" on the screen. Subsequent phones behind this one are smaller, fainter and more red, until they reach "3" (the rest of the text is too small to read). From this point, the phones grow larger, although they continue to get fainter and redder. Subsequent phones show "2", "1", "500 million", "200 million", "50 million", "20 million" (which is larger than the original "13 billion years after the Big Bang" phone) and a very large, faint phone so big that only the word "thousand" is visible, with the rest of the screen obscured behind other phones or so large it extends off the panel]

Goofs

Goofs

https://www.xkcd.com/2623

https://www.explainxkcd.com/wiki/index.php/2623:_Goofs

[An excerpt from an Internet Movie Database web page showing a list of goofs from a film. Each item has some small illegible text below it, which on the real IMDb would say something like "7 of 72 found this interesting | Share this". The first and third items have a faint yellow-tinted background. The third item is only partially visible at the bottom of the "screen".] [Heading:] Goofs (78) [List:] The space detective's office is on Chestnut Ave, but Lower Manhattan has no street by that name. Agent Glennifer pursues the cybernetic dog onto what is clearly Ludlow Street. The agents destroy the blimp drones in Union Square with harpoons from a store display rack. The nearest harpoon store is several blocks away and has no outdoor displays. The apartment in the background of the hologram kissing scene actually exists in downtown Vancouver. We called the owners, who confirmed they had no residents named [...] [Caption below the panel:] Sometimes the IMDB "Goofs" section really seems to struggle with the whole premise of fiction.

IMDb is the Internet Movie Database , a website that contains detailed, user-contributed information about movies and TV shows. One of the sections in many entries is " Goofs ". This may list bloopers, inconsistencies, implausible actions, anachronisms, etc. in the movie. While some people find enjoyment in searching for these errors, to others, the entries listed can often be overly pedantic and missing the point [ citation needed ] (a problem that can often afflict sites that rely on users to provide their content [Hey! Who you calling a pedant?]). The comic makes fun of this with several goofs that simply point out differences between something in the movie and reality; but since the movie is fiction (in this case, a science fiction film that includes a space detective, a cybernetic dog, blimp drones, and a hologram kissing scene), one can say that these "goofs" might simply be more differences between the movie world and our own. In the first goof, a named street doesn't actually exist in the city in which the movie is set. Unless the address is important to the plot (Manhattan has a number of streets with well-known characters - for example, the main theatre district is on Broadway, Fifth Avenue is a major shopping district, and Wall Street is known for large financial institutions), screenwriters can and do make up street names. It might actually be expedient to 'rename' a setting in many cases, to avoid issues such as fans showing up at said street and harassing the residents. In the second example, they point out that there's no harpoon store at the location where the characters obtain a harpoon in the movie, and the nearest actual harpoon store doesn't have a display window. Movies take liberties with details like this for plot expediency, and is not considered a goof. Manhattan does not appear to have any notable harpoon stores, [ citation needed ] with or without the kind of frontage described. In the third example, the background of a scene is of an apartment in Downtown Vancouver (a cheap and popular filming location that frequently stands in for other cities). The goof points out that the real-life apartment does not belong to the character who supposedly lives in it. Fictional movie characters do not exist in reality, [ citation needed ] and many scenes are set in fictional locations that are completely separate from their real-life filming locations. As such, this is only a "goof" if the scene is taken entirely literally. The title text describes an actual anachronism. The film is set in 2018, but there's a billboard for the movie Avengers: Age of Ultron , which came out in 2015, while the next Avengers film, Avengers: Infinity War , came out in 2018. Assuming the movie was filmed before 2018, the filmmakers wouldn't have known what films would be current at the time it would be released, and certainly not the artwork they'd be using to promote them. They could have chosen to set it during the time of initial filming, but again, unless the specific date is significant to the plot, it's common to set (or rather, assume) a film takes place about the same time it's released. Generic advertisements for fictional (or parody ) films might be put over egregiously obvious existing material, physically or in post-production editing, as might references to major brands – perhaps replaced by those agreed with from product placement partners. The title text also mentions the possibility of a self-reference – the billboard could be for this film itself since it's being released at the same time it's set. This assertion that in-universe self-reference is plausible for a movie production is likely another example of the goof's writer failing to understand the basic "premise of fiction". Most movies do not exist within the fictional world they portray, [ citation needed ] and many audiences would find self-reference to be a far greater obstacle to suspending disbelief than an ad for the wrong Avengers movie. [An excerpt from an Internet Movie Database web page showing a list of goofs from a film. Each item has some small illegible text below it, which on the real IMDb would say something like "7 of 72 found this interesting | Share this". The first and third items have a faint yellow-tinted background. The third item is only partially visible at the bottom of the "screen".] [Heading:] Goofs (78) [List:] The space detective's office is on Chestnut Ave, but Lower Manhattan has no street by that name. Agent Glennifer pursues the cybernetic dog onto what is clearly Ludlow Street. The agents destroy the blimp drones in Union Square with harpoons from a store display rack. The nearest harpoon store is several blocks away and has no outdoor displays. The apartment in the background of the hologram kissing scene actually exists in downtown Vancouver. We called the owners, who confirmed they had no residents named [...] [Caption below the panel:] Sometimes the IMDB "Goofs" section really seems to struggle with the whole premise of fiction.

Voyager Wires

Voyager Wires

https://www.xkcd.com/2624

https://www.explainxkcd.com/wiki/index.php/2624:_Voyager_Wires

[In the bottom right corner is a space probe, with large satellite dish and long antenna. Behind it runs a long wire, that makes three loops before it is connected to North America on the Earth in the top left corner. To the left of the Earth there is a second wire, which goes off-panel to the left.] [Caption below the panel:] Sad news: Due to high copper prices and budget constraints, NASA may finally have to cut the wires that they've been spooling out to communicate with Voyager 1 and 2.

This comic claims that the Voyager probes communicate with NASA though ridiculously long copper wires. These wires would have to be continuously lengthened as the probes travel away from Earth. Supposedly, because of "high copper prices and budget constraints," they may not be able to afford to lengthen the wires much longer. If this occurred, they would have to either cut the wires or let them break, which would prevent any further communication with the probes. In reality they use radio waves , not long copper wires, so this will not actually happen. If copper wires were dragged by the Voyager probes, assuming a 1mm² thick cable, 550 tons of copper would be needed per hour and it would add 1 million Ohm per hour to the cable resistance. At $8,560/ton , this would cost $41 billion dollars/year, which would be nearly twice NASA's entire annual budget . The resulting wire would slow down the probes by drag unless the wire itself was actively suspended (i.e. accelerated) continuously as it was fed. The wire could not be used for any other mechanical purpose such as a space elevator for this reason. Since the Earth spins, the wires would also spool around the Earth, slowing the probes down even further. Clearly, this is not a good idea. This problem might be avoided if the wires reached earth at one of the poles. Or perhaps they could go to an airplane that flies around earth at exactly 15 degrees of longitude per hour, with periodic air-to-air refueling, so that it is always on the side of the earth facing the probe. Because the Voyager probes aren't in the plane of the earth's orbit around the sun, the Earth would not, in its rotation around the sun, drag these copper wires through the sun. If it did, the wires would melt. The title text references the phenomenon seen with self-retracting cables, such as are commonly found on vacuum cleaners, where the free end of the cable, where the plug is, oscillates more and more wildly as the cable approaches full retraction, leading to the danger of a painful rap on the hand if it is not withdrawn in time. A planet-sized impact of this kind could cause severe damage. A few days before this comic was released, NASA had reported receiving corrupted data from the Voyager 1 probe. The fact that they are receiving any data at all means that the attitude control system must be working (or else the antenna would not point at Earth), but they continue to investigate how that data could be corrupted after that point. Spoiler alert The consequence of a cable between a craft in space and a planetary location being suddenly retracted was recently imagined in the first episode of the Apple TV+ series Foundation , wherein a space elevator tether was severed. It didn't end well for anyone other than the terrorists who won the freedom of thousands of inhabited worlds which had formerly suffered under the jackbooted oppression of Trantor 's fascist galactic Empire regime. Another illustration in fiction of a severed space elevator is in Red Mars, part of the Mars Trilogy by Kim Stanley Robinson. [In the bottom right corner is a space probe, with large satellite dish and long antenna. Behind it runs a long wire, that makes three loops before it is connected to North America on the Earth in the top left corner. To the left of the Earth there is a second wire, which goes off-panel to the left.] [Caption below the panel:] Sad news: Due to high copper prices and budget constraints, NASA may finally have to cut the wires that they've been spooling out to communicate with Voyager 1 and 2.

Field Topology

Field Topology

https://www.xkcd.com/2625

https://www.explainxkcd.com/wiki/index.php/2625:_Field_Topology

[A row of four signs, each held up by two posts, followed by a row of four rounded lozenge shapes, one for each sign. The signs and lozenge shapes are shaded as if three-dimensional objects, all being flattish with a small third dimension; the four lozenge shapes each have one pair of sides horizontal and the other pair at a slight angle from vertical, denoting a horizontal plane perpendicular to the signs extending "out" towards the viewer, which places each shape "in front" of its sign. All but the first lozenge shape have various numbers of ellipses within the shape - ovoids shaded to denote holes piercing through the objects.] [Leftmost sign:] Baseball Soccer Tetherball [The shape below this sign contains no ellipses.] [Second sign from left:] Volleyball Badminton High jump [This shape has one large ellipse in the center.] [Third sign:] Basketball Football Parallel bars [This shape has two large ellipses - one in the top half and one in the bottom half.] [Fourth and rightmost sign:] Olympic swimming Croquet [This shape has nine small ellipses - eight arranged symmetrically towards the edges of the shape and one in the center.] [Caption underneath the signs and shapes:] No one ever wants to use the topology department's athletic fields.

Field Topology is a subject in mathematics , but in this comic, Randall is instead examining the topology of playing fields used for various sports. The comic strip depicts a situation in which the common practice of multi-use athletic facilities has been organized by the "topology department" and constructed to be shared by all sports whose normal playing fields are topologically equivalent . One key assumption in topology is that you can ignore the specificities of shape, size and material of the objects concerned. This presents an amusing contrast as the "equivalent" topology department playing fields are actually not very appropriate for the activities listed in the comic, as the standard positioning, size and shape of hoops, nets and bars and the material of the field itself are not equivalent to the real playing fields used for those activities. (Not to be confused with mathematical fields , or the Fields Medal prize -- although the concept is likely a further pun in the comic, as math (including topology), and most things once can imagine really, are mostly performed ("played") within mathematical fields.) In topology, shapes which can be smoothly deformed into one another without adding or removing holes are considered equivalent. A topological hole is an area of the nominal space (or area, or other manifold) through which nothing restricted to this topology can pass. A loop is a path across the allowable territory of a topology (or a viable circuit to make through the world it describes) that end up where it started. For example, when describing the space taken up by a solid object such as a coffee mug, the handle forms a loop with a hole through it. If a loop cannot be tightened (ultimately adjusted to take a shorter path) down to a single point, then it must be wrapped around at least one "topological hole", and you have separately unique paths (or points, i.e., on different disconnected topologies) where you cannot adjust one loop to take the route of another without severing a looped path and reconnecting it. When describing a negative space, such as the space around an archway, the 'hole' would be the material of the arch itself. This is because a loop formed by a ring around any part of the arch material can only be shortened to a finite length, not to a point; the 'hole' is the arch-shaped obstruction which forces the existence of these loops. A basketball hoop connected to the ground forms a similar obstruction with a loop through it, so the space around the hoop contains an equivalent hole. In this comic the topology department has analysed the spaces where various sports are played by the number of such obstructions in the playing area. Each space depicted in the comic is then signposted with the sports which are played on a field with that number of holes. Baseball , tetherball and soccer are played on fields which are continuous in three-dimensional space. This means it is possible to traverse any path around or over any of the structures defining the field, while there are no obstructions which can be traversed through in a loop around them. The goals on a soccer field presumably do not create holes because the goalposts and crossbar are connected to the field by the net; Randall apparently considers these to form continuous surfaces which do not allow loops through them. Volleyball and badminton are played using a net suspended from poles, and the high jump has a bar that contestants jump over. The structure formed by the net or bar and the supporting poles can be considered to be a "hole" through the playing field, as a path over and under the net/bar forming a loop cannot be contracted to a single point, so their playing fields in the comic all have one "hole". A basketball court has two hoops. Parallel bars can be thought of as two archways. Both have opportunities to pass through either (or both) structures, and so the material of the structures define a hole in the topological abstract of the playing 'space'. Since we are told that these sports fields belong to the Topology Department - and are not necessarily generalized to all sports fields - we might assume that their "football" field is either for rugby or for American football using H-shaped uprights . An Olympic-sized swimming pool has ten lanes, and thus nine lane dividers which are fastened to the walls of the pool at each end, creating topological holes through the play area. Each hoop in croquet is similarly a hole through the space; while most versions of croquet use six hoops, nine hoops are used for "backyard croquet" which is played recreationally in the United States and Canada. The fact that the space in a swimming pool is typically filled with water [ citation needed ] has been overlooked by the topology department. As mentioned in the title text, this last configuration is also homeomorphic to a foosball table (with each rod sustaining the player figures above the table defining a hole) or a Skee-Ball lane (which is even more straightforward, as it is just a plane with several holes in which to throw balls). These "fields" don't actually have the same number of holes, but are apparently lumped together by the Topology Department as having "many" holes. Unfortunately, the Topology Department does not seem to have a field for hurdling events. [A row of four signs, each held up by two posts, followed by a row of four rounded lozenge shapes, one for each sign. The signs and lozenge shapes are shaded as if three-dimensional objects, all being flattish with a small third dimension; the four lozenge shapes each have one pair of sides horizontal and the other pair at a slight angle from vertical, denoting a horizontal plane perpendicular to the signs extending "out" towards the viewer, which places each shape "in front" of its sign. All but the first lozenge shape have various numbers of ellipses within the shape - ovoids shaded to denote holes piercing through the objects.] [Leftmost sign:] Baseball Soccer Tetherball [The shape below this sign contains no ellipses.] [Second sign from left:] Volleyball Badminton High jump [This shape has one large ellipse in the center.] [Third sign:] Basketball Football Parallel bars [This shape has two large ellipses - one in the top half and one in the bottom half.] [Fourth and rightmost sign:] Olympic swimming Croquet [This shape has nine small ellipses - eight arranged symmetrically towards the edges of the shape and one in the center.] [Caption underneath the signs and shapes:] No one ever wants to use the topology department's athletic fields.

d65536

d65536

https://www.xkcd.com/2626

https://www.explainxkcd.com/wiki/index.php/2626:_d65536

[A large sphere with a several lines, and in some places grids, are shown. Cueball, standing next to it, is dwarfed by its size, as it is at least seven times as tall as he is. The sphere has many lines following various great circles or parallel lesser circles around the curve of the sphere, and some patches of cross hatching to suggest further texturing along these lines hovering just below the degree of most of the illustrative detailing. The lines and grids cover the sphere in three layers of parallel axes, angled sixty degrees from each other, implying a huge mesh of equilateral triangles or hexagons. In the top right part of the ball is a black circle. An arrow points to this circle, and the end of the arrow goes to a larger circle that partly obscures the rightmost part of the sphere. The circle shows a zoom in on the surface in the black circle on the sphere. The zoom shows a small portion of the sphere's surface, showing that the grid comes along because the sphere is divided into elongated hexagonal faces with numbers up to at least five-digits. Seven numbers can be fully seen, but there are nine other faces partly shown, five of these with part of their numbers visible, one of these clearly only have four digits. One of the empty faces must also have a number with only 1-3 digits, as no numbers are visible although a significant part of the face is visible.] [Here follows the numbers in the zoomed in part of the sphere, with "..." represents numbers being cut off. The numbers are read in lines left to right, even though the numbers are tilted from down towards the right, which could have suggested a different reading order.] 30827 16[bottom part of a cut-off line][small cut-off circle] ...38 11875 25444 ...[top part of a cut-off line]5 12082 28525 3 [left part of a cut-off line]... 13359 13874 [Two cut-off lines, likely the start of the number 2]... [Caption below the image:] The hardest part of securely generating random 16-bit numbers is rolling the d65536.

In binary computing, 16 bit unsigned numbers range from 0 to 65535, for a total of 65536 unique numbers, a number which is hence well-known to software engineers. Generating large numbers in a manner that is truly random is a recurring problem in cryptography, required to send private messages to another party. People today still use dierolls to generate private random numbers. In role-playing games (and occasionally in other tabletop games), multiple shapes of dice are often used to generate random numbers in specific ranges. By convention, these are referred to as d n according to their number of faces. A traditional six-faced die would be a d6, and many popular pen-and-paper role-playing games use dice ranging between d4 and d20. While there are larger dice used in tabletop games (most commonly d100), these are usually split into multiple smaller ones. For example, a d100 is often two d10s rolled together, with one die providing the first digit and the other die giving the second digit — the total number of possible combinations (100) is the product of the number of faces of the two dice (10 * 10). While "real" d100s and other large-numbered dice do exist, most people consider them to be impractical: they need to be either impractically large or have very small faces (resulting in small print for the numbers), they're close enough to being spheres that it's difficult to get them into a stable resting position, and even if they are stationary, determining which face is "on top" is difficult to do by eye. The Zocchihedron (d100) die is also difficult to ensure as unbiased because of geometry requiring dissimilar faces and therefore a different mixture of 'stopping factors' for each face it could land upon. The largest unbiased die is a d120 (excluding the bipyramids, which can theoretically be made with arbitrarily many sides), so it is very likely that Cueball's d65536 die is also biased. Here, Cueball has constructed a d65536 for generating random 16 bit numbers. It may have solved the problem of generating large random numbers with fewer die rolls, but it magnifies all of the problems with large-numbered dice to ludicrous extremes. In order for the faces to be readable, the die is ridiculously huge, dwarfing the human standing next to it. Rolling such a die is not only physically challenging, but it would also need a huge space in which to roll if the result is to be random, and that space would need to have an extremely flat and rigid surface in order for the die to come to rest. And even if those problems were solved, simply getting to a vantage point to see the top of the die would be a major challenge, and determining which number was truly on top would be near impossible to do by eye. If one really wished to use dice, it would be much easier to simply use multiple dice rolls. For instance, one could roll eight d4 dice (or use 16 coin flips), and convert the result into binary. This has the same randomness as a single die roll [ citation needed ] ?, but can take much longer, so people do purchase d16s to simplify it and speed it up. The closest regular shape similar to the depicted in the comic could be a Goldberg polyhedron . However, no such polyhedron exists with exactly 65536 hexagonal faces. The closest Goldberg Polyhedron has a mixture of 65520 hexagons and 12 pentagons, totaling 65532 faces. It is possible to construct a fair die without a matching regular shape by limiting the sides which it could land on and designing those sides to be fair (for instance, a prism with rectangular facets that extend its entire length, and rounded ends to ensure it doesn't balance on end). The title text references how cryptographic systems (especially RSA and other factoring-is-hard based systems) are vulnerable to quantum attacks as quantum computing technology develops. The title text is essentially punning on the idea of a "large" quantum system. "Large" in the quantum computing sense would be on the order of 64 qubits each of which would be an atom or two at most. This would still be microscopic and will never be as large as the giant die the comic is centered on; but for a well-observed environment and human rolling without sufficient entropy (consider somebody obsessed with a certain number dropping the die on something soft), a conventional computer could predict some rolls. See also 538 for non-mathematical paths of cryptography. [A large sphere with a several lines, and in some places grids, are shown. Cueball, standing next to it, is dwarfed by its size, as it is at least seven times as tall as he is. The sphere has many lines following various great circles or parallel lesser circles around the curve of the sphere, and some patches of cross hatching to suggest further texturing along these lines hovering just below the degree of most of the illustrative detailing. The lines and grids cover the sphere in three layers of parallel axes, angled sixty degrees from each other, implying a huge mesh of equilateral triangles or hexagons. In the top right part of the ball is a black circle. An arrow points to this circle, and the end of the arrow goes to a larger circle that partly obscures the rightmost part of the sphere. The circle shows a zoom in on the surface in the black circle on the sphere. The zoom shows a small portion of the sphere's surface, showing that the grid comes along because the sphere is divided into elongated hexagonal faces with numbers up to at least five-digits. Seven numbers can be fully seen, but there are nine other faces partly shown, five of these with part of their numbers visible, one of these clearly only have four digits. One of the empty faces must also have a number with only 1-3 digits, as no numbers are visible although a significant part of the face is visible.] [Here follows the numbers in the zoomed in part of the sphere, with "..." represents numbers being cut off. The numbers are read in lines left to right, even though the numbers are tilted from down towards the right, which could have suggested a different reading order.] 30827 16[bottom part of a cut-off line][small cut-off circle] ...38 11875 25444 ...[top part of a cut-off line]5 12082 28525 3 [left part of a cut-off line]... 13359 13874 [Two cut-off lines, likely the start of the number 2]... [Caption below the image:] The hardest part of securely generating random 16-bit numbers is rolling the d65536.

Types of Scopes

Types of Scopes

https://www.xkcd.com/2627

https://www.explainxkcd.com/wiki/index.php/2627:_Types_of_Scopes

Content is a table, with column headings "Regular Blank Scope", "Electron Blank Scope", and "Radio Blank Scope". Row headings are "Micro", "Tele", "Peri", "Stetho", "Kaleido", "Gyro", and "Horo". Regular Microscope Look at small stuff Electron Microscope Look at really small stuff Radio Microscope Figure out why your radio broke Regular Telescope Look at stuff that's far away Electron Telescope Detect cosmic rays Radio Telescope Look at distant high-energy stuff Regular Periscope Look for enemy ships Electron Periscope Examine the hull of an enemy ship for structural flaws Radio Periscope Let the crew of your submarine listen to NPR Regular Stethoscope Listen to a patient's chest Electron Stethoscope Burn a patient's skin Radio Stethoscope Play the noises from a patient's chest on NPR Regular Kaleidoscope See cool shapes and colors Electron Kaleidoscope See cool Bremsstrahlung Radio Kaleidoscope Another word for the "Scan" button Regular Gyroscope Balance by spinning Electron Gyroscope Another word for electromagnet Radio Gyroscope Another word for turntable Regular Horoscope Get random life advice Electron Horoscope Predict a particle's quantum state Radio Horoscope Get random life advice from exploding galaxies

Electron microscopes , electron telescopes and radio telescopes are special forms of microscopes and telescopes , respectively. This comic explores what you could do with a hypothetical "electron ___-scope" and "radio ___-scope" for other "regular" items whose name also ends in -scope (namely: periscope , stethoscope , kaleidoscope , gyroscope and horoscope ). The third column with "radio" often plays on different meanings of the word radio: 1) related to radiation and 2) a device for receiving radio communication or broadcasts. The title text makes a pun on "gyroscope" and a middle-eastern pita wrap called a " gyros ". Content is a table, with column headings "Regular Blank Scope", "Electron Blank Scope", and "Radio Blank Scope". Row headings are "Micro", "Tele", "Peri", "Stetho", "Kaleido", "Gyro", and "Horo". Regular Microscope Look at small stuff Electron Microscope Look at really small stuff Radio Microscope Figure out why your radio broke Regular Telescope Look at stuff that's far away Electron Telescope Detect cosmic rays Radio Telescope Look at distant high-energy stuff Regular Periscope Look for enemy ships Electron Periscope Examine the hull of an enemy ship for structural flaws Radio Periscope Let the crew of your submarine listen to NPR Regular Stethoscope Listen to a patient's chest Electron Stethoscope Burn a patient's skin Radio Stethoscope Play the noises from a patient's chest on NPR Regular Kaleidoscope See cool shapes and colors Electron Kaleidoscope See cool Bremsstrahlung Radio Kaleidoscope Another word for the "Scan" button Regular Gyroscope Balance by spinning Electron Gyroscope Another word for electromagnet Radio Gyroscope Another word for turntable Regular Horoscope Get random life advice Electron Horoscope Predict a particle's quantum state Radio Horoscope Get random life advice from exploding galaxies

Motion Blur

Motion Blur

https://www.xkcd.com/2628

https://www.explainxkcd.com/wiki/index.php/2628:_Motion_Blur

[White Hat is holding a camera up to his face looking to the left away from Cueball and Ponytail standing to his right. Cueball is holding one hand, with a balled up fist, up towards White Hat] White Hat: Okay, I'm going to pan around. Cueball: No, wait, your shutter speed is too fast, it will look choppy if— [White Hat turns clockwise towards Cueball and Ponytail, with the camera held up partly behind his head, so it points in the panel. Cueball clenches both his fists, held down now, and hunches his shoulders. Ponytail stands as before next to him.] Cueball: Hnnnnngh [White Hat has turned around and is now pointing the camera towards Cueball and Ponytail. Cueball now appears blurry while Ponytail looks normal.] [Caption below panel:] Expert photographers can learn to generate their own motion blur to compensate for other people's bad camera settings. This comic remained on xkcd's front page even after the midnight between Monday and Tuesday (in Eastern Time), which is a rare instance that Randall has missed a midnight deadline.

This is analogous to something much more common that people do, by practicing moving their bodies relative to the motion of the camera: reducing blur when the shutter speed is too low. The title text refers to the fact that only one object - in this case, Cueball - appearing blurry while everything else in the frame is sharp is even more exotic. It can also be seen as a celebration and sarcasm regarding the rare experience of valuing having exotic knowledge and skills. It seems likely Randall has practiced reducing blur, but not succeeded at increasing it, and was possibly exposed to somebody saying "high" shutter speed when they meant "low" shutter speed, but this is presently unverified. This is somewhat similar to a trick 'used' by some fictional characters who have the power to make themselves unclear to observers or cameras alike. In real-life it is the difference between "stop motion" and "go motion" tricks. When light hits a human's retina, it is perceived for a short while even after the light has ceased. This means that objects moving across a human's field of vision at a sufficient speed will naturally appear blurry – in our perception, the light arriving right now from the trailing part of the object will mix with the light that arrived a moment earlier, from the leading part of the object. A camera's shutter speed is the amount of time that the shutter is open for each frame, allowing the image sensor to capture light. If the shutter speed is too high (relative to the frame-rate), this blurring will not occur, and the motion will look unnaturally crisp – if something is too small and/or too quick, the illusion of motion may disappear altogether; the object instead will appear as a brief flash of multiple objects standing still, like in the case of a fast-moving mouse cursor on a screen. See for instance this Videography - Slow Shutter Speed vs. Fast Shutter Speed Comparison . In cinema, the shutter speed is generally set to double the frame-rate, e.g. 1/48 s for footage shot at 24 fps (one of the lowest standard frame-rates, a remnant from the age of mechanical motion picture cameras and film projectors). An opposing problem is that of a camera not sufficiently matching the relative motion of a moving object, with a shutter speed that is too slow (and may need to be, given the choice of aperture and lighting conditions). Sports photographers must learn how to scan-and-pan their subjects (runners, horses, vehicles, etc) with enough synchronicity to capture them sharply, and possibly seemingly hanging frozen in mid-air against an artistically-blurred background. It is unclear how Cueball makes the motion blur include both his feet, as the friction with the ground should hinder them from vibrating horizontally in the manner that may cause for motion blur. Additionally, creating the kind of motion blur he does (with evenly distributed horizontal blur) requires extreme acceleration at both ends of the movement. [White Hat is holding a camera up to his face looking to the left away from Cueball and Ponytail standing to his right. Cueball is holding one hand, with a balled up fist, up towards White Hat] White Hat: Okay, I'm going to pan around. Cueball: No, wait, your shutter speed is too fast, it will look choppy if— [White Hat turns clockwise towards Cueball and Ponytail, with the camera held up partly behind his head, so it points in the panel. Cueball clenches both his fists, held down now, and hunches his shoulders. Ponytail stands as before next to him.] Cueball: Hnnnnngh [White Hat has turned around and is now pointing the camera towards Cueball and Ponytail. Cueball now appears blurry while Ponytail looks normal.] [Caption below panel:] Expert photographers can learn to generate their own motion blur to compensate for other people's bad camera settings. This comic remained on xkcd's front page even after the midnight between Monday and Tuesday (in Eastern Time), which is a rare instance that Randall has missed a midnight deadline.

Or Whatever

Or Whatever

https://www.xkcd.com/2629

https://www.explainxkcd.com/wiki/index.php/2629:_Or_Whatever

[White Hat and Cueball are looking out on a skyline with six smaller skyscrapers and one much taller. The tall building has three plateaus, where it gets thinner before the top. On the top there are also two tall antennas, one twice as high as the other. Around the buldings therare 7 small clouds and two distant birds flying next tot he top of the tallest building. The two are standing on a ground behind a fence, maybe a viewing point, for looking in over the city skyline. They are looking toward the tallest bulding.] White Hat: You know, back in the 90s, the Sears Tower was the world's tallest tower. Cueball: Yeah! Or "building." The CN Tower and the KVLY-TV Antenna were taller, but the CN Tower isn't always considered a building and the antenna is supported by guy wires or whatever. [Caption below the panel]: Whenever I get self-conscious about how obsessive I sound about some random topic, I panic and tack on "or whatever."

The Willis Tower (formerly the Sears Tower) is a 108-story, 442.1 meter skyscraper in Chicago. It is currently the third tallest building in North America, and was indeed the tallest building in the world for 25 years, surpassing the World Trade Center upon opening in 1973, and being surpassed by the Petronas Towers upon their opening in 1998. White Hat conveys some interesting historical trivia to Cueball , regarding the Sears Tower . Cueball then sets the record straight by correcting White Hat's use of the word tower: In the category of 'tower', the Willis Tower was never the tallest. Cueball then realizes he just one-upped White Hat with what he knows about tall structures in general, which might make him sound obsessive, so he tags on the meaningless caveat of "or whatever". This is meant to diffuse the tension he may have added by his well-meaning contradiction, but could also be taken as a passive-aggressive behaviour by interlocutors who may already be touchy about the original 'correction'. In the title-text, being already self-conscious that he has overstepped the mark for polite smalltalk, he then hypercorrects the self-perceived tone of his response by explicitly denying that he knows far more about the tower, but only by providing the very facts that he is trying to claim not to know. Alternately, this could be White Hat responding to something else Cueball said, as an annoyed way to either get Cueball to stop, or to make a point that Cueball knows more than is "normal" about skyscrapers. This comic hinges on the debate about the tallest structure vs tallest building . A building is generally defined as a human-built structure fit for human habitation when it is fit for human habitation, while a structure is generally defined as anything humans make. (Or in some cases, anything an animal makes, like crab shells. ) It is far from unusual for the tallest building (habitable) to be shorter than the tallest structure (uninhabitable), such as in 1974 when the tallest structure was the Warsaw radio mast at 646.38 meters. The radio mast was uninhabitable, [ citation needed ] so the tallest building was (sort-of coincidentally) the Sears Tower at 442.1 meters. The Warsaw tower collapsed in 1991, so it was not the tallest structure for the majority of the '90s. After the Warsaw Tower's demise, the KVLY-TV mast , which stood at 629 meters, held the record of tallest structure until either 2000 or 2010, with the opening of the Petronius platform and Burj Khalifa respectively. (The date depends on whether you count underwater towers, as the Petronius platform is an oil rig and only 75 meters of the platform are above water). It was also the tallest Guyed mast up until 2019, when it was reduced to 605.6 meters, giving the KRDK-TV mast the record. The CN tower stands at 553.3 meters (Measured from top of spire), which is higher than the Sears/Willis tower but shorter than the KVLT-TV mast. It is mentioned as is has some habitable space but not much, causing debate about whether it is a building (Referenced below). It was never the tallest structure, but if it's a building it would have been the tallest in the world from it's opening in 1976 until the Canton Tower 's in 2009. It is currently the 9th tallest building. The debate surrounding the tallest building does not stop at building vs structure. Architects have long argued about what the height definition of a building should be. Should it include antennas sitting at the top of the building? How about spires that form part of the architectural design of the building but are not part of the habitable space? Should we focus instead on the highest habitable floor? The debate has historically had relevance every time a new record is claimed by developers eager to reach new heights using any means possible ( Size Does Matter, At Least In The Tallest Building Debate ). There is yet more debate about what counts as a building vs a structure. While some people would say that any structure with any habitable space is a building, most people in the field agree that there is a certain threshold of habitable space, below which there is not enough habitable space to count as a "building", even if there is some. A main point in this debate are TV towers , which are often tall towers with little habitable space in them, but with an observation deck at the top. Examples include the Tokyo Skytree , Fernsehturm Stuttgart , and CN tower. A similar structure is the Dubai Creek Tower , a tower under construction in Dubai, set to become the world's tallest structure. (The Dubai Creek Tower will not, however, broadcast tv signals). TV towers are sometimes counted as buildings as they do have some habitable space. However, they are often not as they are commonly considered to not have enough habitable space to be buildings, hence Cueball's line "The CN tower isn't always considered a building" Wikipedia lists the tallest structures, and this YouTube video explains a bit more about tall buildings/structures. Since 2010 the Burj Khalifa has been both the tallest structure and the tallest building in the world. [White Hat and Cueball are looking out on a skyline with six smaller skyscrapers and one much taller. The tall building has three plateaus, where it gets thinner before the top. On the top there are also two tall antennas, one twice as high as the other. Around the buldings therare 7 small clouds and two distant birds flying next tot he top of the tallest building. The two are standing on a ground behind a fence, maybe a viewing point, for looking in over the city skyline. They are looking toward the tallest bulding.] White Hat: You know, back in the 90s, the Sears Tower was the world's tallest tower. Cueball: Yeah! Or "building." The CN Tower and the KVLY-TV Antenna were taller, but the CN Tower isn't always considered a building and the antenna is supported by guy wires or whatever. [Caption below the panel]: Whenever I get self-conscious about how obsessive I sound about some random topic, I panic and tack on "or whatever."

Shuttle Skeleton

Shuttle Skeleton

https://www.xkcd.com/2630

https://www.explainxkcd.com/wiki/index.php/2630:_Shuttle_Skeleton

[In the upper right part of the panel there is a small drawing of the Space Shuttle as seen from above. Beneath it, and to its left, is a much larger drawing with the same outline as the Shuttle. But this time the outer layers have been removed to reveal the inside. This has revealed a skeleton taking up the entire space inside. The head is in the front, and legs and tail at the rear, with arms and fingers in the wings, looking somewhat like a bat's "hand/wings". The bones are white with the frame of the shuttle gray or black. Some of the lines outlining the design of the shuttle are both on the small and the large drawing, along the wings and rear engines. Both feet and arms have five fingers/toes. There seem to be 24 ribs in the very long rib-cage.] [Caption beneath the panel:] The Space Shuttle was long assumed to be a type of fish or shark, but after it was decommissioned in 2011, analysis of its skeleton determined that it was actually a mammal.

The Space Shuttle was a reusable spacecraft system used by NASA from 1981 to 2011, after which it was decommissioned. In this comic, Randall suggests that the nature of the shuttle was in doubt or misunderstood until either an intact 'specimen' (of which there are four) had been dissected, or possibly the remains were reassembled from the two that were lost in accidents . With its shape, shown in the small image, and the tail fin, it looks a bit like a bony fish or ray . The joke is that after the shuttle was taken out of use, its skeleton was analyzed, and as shown in the comic, was found to have a skeleton typical of a mammal, with details such as the pentadactyl quadripedal bodyform hidden beneath its aerodynamic sweep, as well as having bones (i.e., not primarily cartilage). This morphology is similar to that possessed by a whale. Of course, the skeleton of a spacecraft is not made of bones, but rather of metal and other manufactured materials. [ citation needed ] As the understanding of the natural world developed, many taxonomic misconceptions were overturned, or at least the scientific terminology was tightened. For instance, it was found that dolphins and whales were mammals, not fish. [ cetacean needed ] Because of convergent evolution – the tendency for distantly-related species to adapt similarly to a given environment – it is often not easy to properly classify organisms merely by observing their exterior. For example, whales and fish have very similar body shapes, as did the extinct plesiosaurs, because life as a swimming vertebrate favors the same adaptations. In lieu of genetic analysis, or even of sufficient observation of them in the wild, the main progress in understanding differences among marine animals was often in dissecting the corpses of creatures found stranded or caught in nets, or reconstructing them from skeletal remains. Together with fossil evidence, insights were developed about their origins and differences from others' origins. The title text conflates the now-extinct Steller's sea cow , an aquatic mammal related to manatees and named after explorer/zoologist Georg Steller (also extinct), with the adjective "stellar", which means being of a star or stars, such as inter-stellar space or stellar masses. One might expect that the idea for this comic may have come from the recent California Supreme Court ruling that bumblebees are considered fish under a law which categorized several other invertebrates as part of a broad colloquial category of fish (as in "Fish and Game Department" designations.) However, given the short time between the ruling and the comic's release, it is likely that this was a coincidence. [In the upper right part of the panel there is a small drawing of the Space Shuttle as seen from above. Beneath it, and to its left, is a much larger drawing with the same outline as the Shuttle. But this time the outer layers have been removed to reveal the inside. This has revealed a skeleton taking up the entire space inside. The head is in the front, and legs and tail at the rear, with arms and fingers in the wings, looking somewhat like a bat's "hand/wings". The bones are white with the frame of the shuttle gray or black. Some of the lines outlining the design of the shuttle are both on the small and the large drawing, along the wings and rear engines. Both feet and arms have five fingers/toes. There seem to be 24 ribs in the very long rib-cage.] [Caption beneath the panel:] The Space Shuttle was long assumed to be a type of fish or shark, but after it was decommissioned in 2011, analysis of its skeleton determined that it was actually a mammal.