Map Projections

Explanation:
Map projection , or how to represent the spherical Earth surface onto a flat support (paper, screen...) to have a usable map, is a long-time issue with very practical aspects (navigation, geographical shapes and masses visualization, etc.) as well as very scientific/mathematical ones, involving geometry or even abstract algebra among other things. There is no universal solution to this problem: Any 2D map projection will always distort in a way the spherical reality. Many projections have been proposed in various contexts, each intending to minimize distortions for specific uses (for nautical navigation, for aerial navigation, for landmass size comparisons, etc.) but having drawbacks from other points of view. Some of them are more frequently used than others in mass media and therefore more well-known than others, some are purely historical and now deprecated, some are very obscure, etc.
Randall suggests here the idea that someone's "favorite" map projection can reveal aspects of their personality, then goes through a series of them to show what they can mean.
He may actually believe that all map projections are in a way bad. This could be inferred from the fact that he much later began  publishing a series of Bad Map Projections .
The Mercator projection was introduced by Flemish cartographer Gerardus Mercator in 1569. The main purpose of this map is to preserve compass bearings; for example 13 degrees east of north will be 13 degrees clockwise from the ray pointing toward the top of the map, at every point.  A mathematical consequence is the mapping is conformal, i.e. if two roads meet at a certain angle on the surface of the Earth, they will meet at that same angle on the map.  It also follows that at every point the vertical and horizontal scales are the same, so locally i.e. considering only a small part of the map, geographical features (shapes, angles) are well represented, which helps a lot in recognizing them on-the-field, or for local navigation in that small part only. For this reason, that projection (or a close variant) is used in several online mapping services (such as Google Maps), which means that it is frequently encountered by the general public. A straight line on the map corresponds to a course of constant bearing (direction), which was very useful for nautical navigation in the past (and thus made that projection very well-known).
However, from a global point of view, this projection is radically incorrect in how it shows the size of landmasses (for instance, Antarctica and Greenland seem gigantic), and furthermore, it always excludes a small region around each pole (otherwise the map would be of infinite height), so it doesn't provide a complete solution for the problem of map projection. The comic implies that people who like that projection aren't very interested with map issues, and typically use what they are offered without thinking much about it.
The Van der Grinten projection is not much better than the Mercator. It was adopted by National Geographic in 1922 and was used until they updated to the Robinson projection in 1988.
The Van der Grinten projection is circular as opposed to the Mercator projection. The fictional person believes a circular map is more fitting to the real Earth's three-dimensional spherical nature because both are round. This belief fails to recognize that a two-dimensional circle has very little in common with the surface of a sphere, and thus this projection still causes a vast distortion of space and area.  Because of this, Randall implies the Van der Grinten enthusiast to be optimistic and childishly simple-minded (e.g. "you like circles").
The Robinson projection was developed by Arthur H. Robinson as a map that was supposed to look nice and is often used for classroom maps. National Geographic switched to this projection in 1988, and used it for ten years, switching to the Winkel-Tripel in 1998.
The Beatles was a rock band that enjoyed great commercial success in the 1960s, and are widely considered the best act ever in the genre of popular music. The Beatles, coffee, and running shoes are all things that are very commonly enjoyed and largely uncontroversial, as well as being comforting.  Liking these specific things suggests an ordinary, easygoing lifestyle paralleled by the projection.
Also called the Fuller Map, the Dymaxion map takes a sphere and projects it onto an icosahedron, that is a polyhedron with 20 triangular faces. It is far easier to unwrap an icosahedron than it is to unwrap a sphere into a 2D object and has very little skewing of the poles. Buckminster Fuller was an eccentric futurist who believed, for example, that world maps should allow no conception of "up" or "down". He was therefore more than happy to defy people's expectations about maps in the pursuit of mathematical accuracy.
Randall associates the projection to geek subculture and niche markets:

Proposed by Oswald Winkel in 1921, the Winkel tripel projection tried to reduce a set of three (German: Tripel) main problems with map projections: area, direction, and distance. The Kavrayskiy projection is very similar to the Winkel Tripel and was used by the USSR, but very few in the Western world know of it.
The comic links this projection to hipster subculture. The hipster stereotype is to avoid conforming to mainstream fashions. "Post-" refers to a variety of musical genres such as post-punk , post-grunge , post-minimalism , post-rock , etc. that branch off of other genres, and are generally considered less accessible than the genres that spawned them. Liking a genre just called "post-" implies that the listener prefers music that is less mainstream, and may have that as the only criterion for listening.
Trivia
The Goode homolosine projection takes a different approach to skewing a sphere into a roughly circular surface. An orange peel can be taken from an orange and flattened with fair success; this is roughly the procedure that John Paule Goode followed in creating this projection. Randall is suggesting that people who like this map also prefer relatively easy solutions to other things in life, despite those solutions having nuanced problems that are more difficult to address.
People often make arguments that if normal people ran the United States, then the US wouldn't be in the trouble it is. This is from the belief that career politicians are simply out to make money and will only act in the interest of their constituency when their continued easy life is threatened (usually around election time). While some form of this view is very common and probably pretty much correct, Randall is saying that someone who likes this map may take this to extremes.
Airline food is another, much maligned, problem. How do you store enough food to feed people on long airplane trips? What kind of food can be served in an enclosed, low-air-pressure environment? The common solution is to use some kind of prepackaged, reheated meal. Randall is saying that the people in favor of the Goode Homolosine wonder why the airlines don't simply order meals from the restaurants in the airport, store that food, and serve it, rather than using bland reheated food. However, this seemingly-obvious solution ignores how being in an airplane dulls your sense of taste. Airplane food is actually over seasoned for eating on the ground, meaning that if airlines switched to restaurant food it would probably taste even blander. There would also be issues with acquiring special meals (for example, vegetarian, Kosher, and Halal meals), especially if suitable restaurants were not in close range to the airport.
Older cars burned oil like mad fiends, and oil back then would become corrosive to the innards of an engine, so oil had to be changed often. But, with the introduction of synthetic motor oil and better designed engines, new cars only need their oil changed about every 10,000 to 15,000 miles. A common conspiracy theory is that modern automobile oil manufacturers still recommend that car owners change their oil every 3,000-5,000 miles to "drum" up more business, even though that frequency is unnecessary.
All of these references suggest that people who like the Goode Homolosine projection are fans of easy solutions to problems. However, the solutions would not necessarily work in practice. For instance: the restaurants might have trouble making enough food for the whole plane, and it could get cold before being served; the air conditions aboard planes can affect taste, so airlines say they optimize for this; there is no such thing as a "normal" person, and if there were, he/she would have virtually no chance at actually getting into government office and/or may not have prior political experience that would be helpful for congress; and the Goode Homolosine projection, while mostly resembling a flattened orange peel as suggested by the earlier analogy, does indeed cut down on distortion, but also has serious problems of its own, such as leaving huge gaps of nothingness between the continents, making distances across the oceans difficult to visualize.
The Hobo–Dyer projection was commissioned by Bob Abramms and Howard Bronstein and was drafted by Mick Dyer in 2002. It is a modified Behrmann projection . The goal was to be a more visually pleasing version of the Gall–Peters.
As is discussed in the Gall–Peters explanation, the Gall–Peters was developed to be equal area, so that economically disadvantaged areas can at least take comfort in the fact that their country is represented correctly by area on maps.
Randall associates the Hobo–Dyer projection to "crunchy granola" — a stereotype associated with vegetarianism, environmental activism, anti-war activism, liberal political leanings, and some traces of hippie culture.
With feminism becoming mainstream and alternative genders being more widely accepted, some have begun to invent gender-neutral pronouns so that when referring to a person whose gender is not known they cannot be offended by being referred to by the wrong pronouns. In Middle English 'they' and 'their' were accepted genderless pronouns that could replace 'he', 'she' as well as be used to represent a crowd, but this usage is considered by some to be grammatically incorrect because of the plural/singular debate ( stupid Victorian Grammarians! ). There have been many attempts at popularizing invented gender-neutral pronouns and they are beginning to achieve some degree of success in the mainstream.
Also known as the Equirectangular projection , it has apparently been in use since approximately 100 AD. The benefit of this projection is that latitude and longitude can be used as x,y coordinates. This makes it especially easy for computers to graph data on top of it.
According to the comic, the projection appeals to people who find much beauty in simplicity.
In any good discussion there has to be at least one smart-ass. [ citation needed ] This is a comic about map projections, that is, the science of taking a sphere and flattening it into 2 dimensions. The smart-ass believes that we shouldn't even try: a sphere is, tautologically, the perfect representation of a sphere.
To quote The Princess Bride : "Yes, you're very smart. Shut up."
A globe is, of course, the "map projection" used by Google Earth when zoomed out.
Similar to the Dymaxion, the Waterman butterfly projection turns a sphere into an octahedron, and then unfolds the net of the octahedron, which was devised by mathematician Steve Waterman based upon the work of Bernard J.S. Cahill .
Bernard Cahill published a butterfly map in 1909. Steve Waterman probably has the only extant "ready to go" map following the same general principles, though Gene Keys may not be far behind. Waterman has a poem with graphics in a similar vein to this xkcd comic that is worth reading. [1]
Polyhedral projections like Cahill, Dymaxion or Waterman typically offer better accuracy of size, shape and area than flat projections, at the expense of compass directionality, connectedness, and other complications.
The joke is that the person responding deeply understands map projections; anyone who knows of this projection is a person that Randall would like to get to know.
The Peirce quincuncial projection was devised by Charles Sanders Peirce in 1879 and uses complex analysis to make a conformal mapping of the Earth, that conforms except for four points which would make up the midpoints of sides and lie on equator (the equator is represented by a square and the corners connect the sides in the middle.)
Inception was a 2010 movie about meta lucid dreaming . It has a complex story that is difficult to follow and leaves the viewer with many questions at the end, and almost always needs to be watched multiple times to be understood.
The human brain is not well developed to deal with oddly obvious things. One example is that everyone has a skeleton, but everyone is surprised to see a part of their body represented by an X-ray. Another is the fascinating complexity of the human hand, a machine which is amazingly complex, driven by a complex interplay of electrical and chemical signals; yet is the size of the hand and so useful. A fascination with or fixation on such thoughts is often associated with an altered state of mind brought on by marijuana consumption. Therefore, Randall may be implying that this map would appeal to stoners.
The Gall–Peters projection is mired in controversy, surprisingly for a map. James Gall , a 19th-century clergyman, presented this projection in 1855 before the British Association for the Advancement of Science . In 1967, the filmmaker Arno Peters created the same projection and presented it to the world as a "new invention" that put poorer, less powerful countries into their rightful proportions (as opposed to the Mercator). Peters played the marketing game and got quite a few followers of his map by saying it had "absolute angle conformality," "no extreme distortions of form," and was "totally distance-factual" in an age when society was very concerned about social justice. All of these claims were in fact false. The Mercator projection distorts size in favor of shape, and Gall-Peters distorts shape in favor of size, being especially inaccurate at the equator and the poles.
The implication is that the fans of this map are pompously concerned with social justice, and willing either to lie or convey marketing mistruths to promote that cause. Alternatively Randall just dislikes this map projection so much due to the above mentioned inaccuracies, that he hates anyone who likes it.
The title text makes a joke that goes to the familiar meme from CSI: Miami , in which the star, David Caruso starts a sentence, then puts on his sunglasses and ends the sentence with a corny pun. In this case, the pun is on map projection and projection in psychology. Psychological projection is an unconscious defense mechanism wherein a person who is uncomfortable with their own impulses denies having them and attributes them to other people, and blames these people for these impulses. The Sunglasses internet meme has been used in other comics as well.
What your favorite Map Projection says about you [All of these are organized as Title, a copy of the particular projection underneath, and what it says about you under that.]
Mercator You're not really into maps. Van der Grinten You're not a complicated person. You love the Mercator projection; you just wish it weren't square. The Earth's not a square, it's a circle. You like circles. Today is gonna be a good day! Robinson You have a comfortable pair of running shoes that you wear everywhere. You like coffee and enjoy The Beatles. You think the Robinson is the best-looking projection, hands down. Dymaxion You like Isaac Asimov, XML, and shoes with toes. You think the Segway got a bad rap. You own 3D goggles, which you use to view rotating models of better 3D goggles. You type in Dvorak. Winkel-Tripel National Geographic adopted the Winkel-Tripel in 1998, but you've been a W-T fan since long before "Nat Geo" showed up. You're worried it's getting played out, and are thinking of switching to the Kavrayskiy. You once left a party in disgust when a guest showed up wearing shoes with toes. Your favorite musical genre is "Post–". Goode Homolosine They say mapping the Earth on a 2D surface is like flattening an orange peel, which seems enough to you. You like easy solutions.You think we wouldn't have so many problems if we'd just elect normal people to Congress instead of Politicians. You think airlines should just buy food from the restaurants near the gates and serve that on board. You change your car's oil, but secretly wonder if you really need to. Hobo-Dyer You want to avoid cultural imperialism, but you've heard bad things about Gall-Peters. You're conflict-averse and buy organic. You use a recently-invented set of gender-neutral pronouns and think that what the world needs is a revolution in consciousness. Plate Carrée (Equirectangular) You think this one is fine. You like how X and Y map to latitude and longitude. The other projections overcomplicate things. You want me to stop asking about maps so you can enjoy dinner. A Globe! Yes, you're very clever. Waterman Butterfly Really? You know the Waterman? Have you seen the 1909 Cahill Map it's based— ...You have a framed reproduction at home?! Whoa. ...Listen, forget these questions. Are you doing anything tonight? Peirce Quincuncial You think that when we look at a map, what we really see is ourselves. After you first saw Inception , you sat silent in the theater for six hours. It freaks you out to realize that everyone around you has a skeleton inside them. You have really looked at your hands. Gall-Peters I hate you.


Citogenesis

Explanation:
This comic is calling into question the reliability of Wikipedia . This is a favorite pastime of librarians, teachers, and professional researchers, and not usually one of Randall 's. Wikipedia is a free and freely editable encyclopedia that aims to become a comprehensive, neutral compilation of verifiable and established facts .  Wikipedia aims to provide only facts backed by reliable sources . However, this comic strip details a process in which Wikipedia can not only spread misinformation but make said misinformation seem reliable through a process of "circular reporting".
The title of the comic is a play on the word cytogenesis . Cytogenesis is the formation of cells and their development. Citogenesis , on the other hand, is a portmanteau of 'Citation' and 'Genesis'. A Citation is a reference to a source, used to back up a specific claim, and genesis means the origin of something.  By extension, citogenesis is the creation of text in a reliable source that can be cited to back up a claim.
In the process described here, someone adds an untrue claim to an article in Wikipedia. A writer of some supposedly "reliable source" checks Wikipedia for information, and blindly relies on it, without checking for proper sources - the comic uses rushed writers, such as those responsible for news stories, as an example of someone who may do this. Eventually, someone notices the claim in the reliable source and cites it in the Wikipedia article. The citation now gives the claim credence, as readers don't realize that the official source was based on the Wikipedia article. Thanks to this citation, other reporters, slightly more cautious than the first, consider this bit of information to be reliable and then cite it in articles of their own. Those articles then get cited in Wikipedia, making the claim seem more reliable, encouraging even more reporters to believe it and repeat the claim. Eventually, a long list of citations is available, giving an impression of consensus, even though all of it originated with a single article, which was based on an uncited Wikipedia edit.
Four years before, Randall commented on Wikipedia about that process happening to him (on a minor detail), which probably indicates the inception of this comic:
In turn, Randall originated the untrue assertion in this comic that Steven Chu , a physicist, and at the time of the strip the U.S. Secretary of Energy, invented the Scroll lock key, a common button on computer keyboards. Since most people are aware of the scroll lock key but know little about its function or origins, this false information would make for an interesting piece of trivia that would likely spread very quickly.
Following this comic, the actual Scroll Lock and Steven Chu articles were both vandalized by "helpful" editors trying to project Randall's reality on Wikipedia. As of May 2022, the Wikipedia article on Citogenesis redirects to the " Circular reporting on Wikipedia " section on the article " Circular reporting ". The section credits the term "citogenesis" to Randall Munroe, with a citation linking to this comic. To make matters even more surreal, a Wikipedia editor once flagged the link to this xkcd comic as "Dubious - The material near this tag is possibly inaccurate or non-factual."!
We haven't seen a book like the one Randall describes in the title text.  But one example of the misuse of Wikipedia by "reliable sources" concerns the former German minister Karl-Theodor zu Guttenberg . His complete name contains fifteen names/words and reads: Karl-Theodor Maria Nikolaus Johann Jacob Philipp Franz Joseph Sylvester Freiherr von und zu Guttenberg. An anonymous user added one more ("Wilhelm") to the German Wikipedia, just the evening before Karl-Theodor zu Guttenberg was presented as the new Federal Minister of Economics and Technology on February 10, 2009. The next day many major German newspapers published this wrong name ( translation of bildblog.de ).
Where Citations Come From: Citogenesis Step #1 Through a convoluted process, a user's brain generates facts. These are typed into Wikipedia. [Hairy sits at a desk, typing on a laptop.] Hairy: (typing) The "scroll lock" key was was designed by future Energy Secretary Steven Chu in a college project.
Step #2 A rushed writer checks Wikipedia for a summary of their subject. [Ponytail sits at a desk, typing on a desktop.] Ponytail: (typing) US Energy Secretary Steven Chu, (Nobel Prizewinner and creator of the ubiquitous "scroll lock" key) testified before Congress today...
Step #3 Surprised readers check Wikipedia, see the claim, and flag it for review. A passing editor finds the piece and adds it as a citation. [Cueball sits on a couch with a laptop in his lap, typing.] Cueball: Google is your friend, people. (typing) <ref>{{cite web|url=
Step #4 Now that other writers have a real source, they repeat the fact. [A flow chart, with "Wikipedia citation" in the center. The word "Wikipedia" is in black, the word "citations" is white with a red background. [A black arrow leads from "brain" to "Wikipedia."] [A black arrow labeled "words" leads from "Wikipedia" to "careless writers," and a red arrow labeled "citations" leads back to "Wikipedia citations."] [A black & red arrow leads from "Wikipedia" to "cited facts" which leads to "slightly more careful writers," which leads to "more citations," which leads back to :"Wikipedia" (all black & red arrows).] References proliferate, completing the citogenesis process.


Wisdom of the Ancients

Explanation:
This comic refers to a common experience that those trying to solve tech problems have. Typically, people search on Google to try to find solutions to the problem. Sometimes the solution can be found on a software program's website, but the most helpful solutions frequently come from discussions on message boards, particularly for more obscure problems. This is because the odds are rather high that someone else, years ago, had the same problem you're having and resolved it.
However, in this comic, Cueball is unable to find any mention of the problem he's currently facing except for one forum post about it that did not include the problem's solution. This is akin to finding an FAQ with questions but no answers.
The title is a satirical reference to the notion that the "ancients," i.e. from thousands of years ago, possessed knowledge that has been lost to the centuries (such as exactly how Stonehenge was built), and that artifacts from those times do not fully divulge such knowledge. The fact that the "ancient" referred to in the comic is from 2003 (only 8 years before the comic was published) is an exaggeration of the feeling that the forum poster is lost to the sands of time, but in some sense this feeling is nonetheless true, since Cueball is unlikely to be able to contact them.
The title text is a suggestion to forums to be aware of the fact that people are likely going to come across such posts in the future and therefore to provide handy summaries of the most helpful conclusions of long threads for them, since combing through several false starts and failed attempts to resolve a problem can be quite tedious. Some forums do indeed follow this practice, pinning the solution or the most helpful approximation to one to the top under the original question.
In 1722: Debugging the title text also mentions googling an error message, explaining what it means if you get zero results. Sort of.
http://www.mirrorsoferis.com/forum/thread05232003a.html
[A poem is written outside and right justified along the left edge of the panel to the right.]
Never have I felt so close to another soul And yet so helplessly alone As when I Google an error And there's one result A thread by someone with the same problem And no answer Last posted to in 2003
[Cueball stands in front of his desk, having risen so the chair has moved away behind him. He is holding on to his computer's screen, looking at it while visibly shaking the screen and shouting at it.] Cueball: Who were you, DenverCoder9? Cueball: What did you see?!


Money

Explanation:
This is a chart comic - a type of comic that Randall does from time to time. He has for instance done maps of the Internet ( twice !) and other huge visualizations like this chart Radiation with a similar structure as this chart but with Radiation as the subject. The Radiation chart is most likely the inspiration for this much more comprehensive Money chart.
In the chart there are five boxes with items on different scales of monetary value. Each scale of dollar increments are different colors. One dollar increments are green - naturally, because American paper money is green. Thousands are Orange/Red. Millions are gray. Billions are yellow. Trillions are blue. This comic uses the short scale for naming large numbers (so a billion = 1000 millions = 10 9 rather than a million millions = 10 12 as in continental Europe).
Because the comic is so huge and complex the explanation has been split into several parts and also individual pages:
Below are five tables with explanation for some of the items. The transcript is (as is usually the case with huge comics) only given for the text that is visible on the picture shown here above. However the full transcript for all the text in the huge image has also been completed. Finally some tables with prices has been made (although they are not yet complete).
In the Billions box there is a vague term called the "Economic Vortex" as well as arrows that flow between different blocks of this box. This is to show where the money goes. Where it is collected from, and where it is distributed to.
Included in one frame is a small man with a red and white striped shirt, blue pants, a cane and a knit cap. He is known as Wally or Waldo (in the US) from the Where's Waldo books . To not give anything away for those who wish to search for him themselves there will be no spoiler here. But if someone needs a little help... Then by clicking this link you will be directed to the relevant section amongst the five sections where Waldo can be found. (The link will take you to that section of the full transcript page). If you still cannot find him (or give up in advance) then just search the transcript page for Wally or Waldo.
The title text is a reference to the phrase "Show me the money!" which originates from the film Jerry Maguire .
[This transcript is only reproducing text visible on the front page comic .] [Title panel at the top left has one large heading, and then it is possible to read the first and third out of five lines (but not for instance the second line which is just the word "almost"):] Money A chart of all of it [Below this there are 5 large panels, each with a series of plots, comparing the values of various things. The only clearly visible text is the title of each panel written in white on black background at the top of each panel] [The first section covers single coffees up to the hourly salaries of CEOs. It is located below the title panel and there are a lot of green groups marked by unreadable text.] Dollars [The next section discusses values from around $1000 to $1,000,000, including a dissection of the song If I had $1000000. It is located directly below the Dollars section and has mainly orange groups (but also some green) marked by unreadable text.] Thousands [The third section focuses on $1,000,000 to $1,000,000,000, with a large section on campaign contributions of American political presidential campaigns, values of expensive works of art, and J. K. Rowling. It is located to the right of the Thousands section below the Billions section and there are a lot of gray groups (but also some orange) marked by unreadable text.] Millions [The fourth section gets into larger scale finances, profits of various sectors, costs of natural disasters, and net worths of the richest people on the planet. Also, Donald Trump. It is located to the right of the Dollars section and above both the Millions and Trillions section and has mainly yellow groups (but also some gray and red) all marked by unreadable text. There are, however, a few large headings that can be read:] Billions Education The Economic (...?) US household income Federal budget [In the last panel global financial status is described. It discusses derivatives, liquid assets, public debt by nation and GDP by continent, culminating with the total economic production of the human race to date. It is located below the Billions section to the right of the Millions section and has mainly cyan groups (but also one yellow) all marked by unreadable text.] Trillions [ For the full transcript of the huge image see 980: Money/Transcript . ]


Porn Folder

Explanation:
Cueball seems to have found a porn folder. However, it contains a directory loop, set up by a person off-screen. It is possible to actually do this, but it is widely regarded as a very bad idea, as it can break the system in not-so-obvious ways (mostly by causing seemingly-trivial operations to infinite loop). The implication is that the folder does not need to contain pornographic images because the folder is the porn—its violation of the taboo against looping is something the off-screen character finds erotic.
link() is the Linux system call to create a hard link. In an unmodified Linux kernel, it will not allow directory hard links for this exact reason; the person who set up the porn folder apparently "forced" Linux to comply, with all of the sexual analogies that suggests.
[Cueball sits at a desk, looking at a laptop screen with one hand on his chin.] Cueball: So I thought I found your porn folder, in calendar/backup/PORN/ Friend (off screen): Don't open that!
[A wider shot of the person looking at the laptop.] Cueball: But it contains a bunch more folders, filled with more folders, and then... after 20 levels, somehow I'm back at the main folder? Friend (off screen): It's, uh, well hidden.
[Cueball has turned around in the chair, now with the laptop in his lap.] Cueball: I think there's no actual porn here. Cueball: You're just turned on by filesystems. Friend (off screen): It's a hardlinked directory loop - so taboo! Cueball: Now I feel dirty sharing a drive with you.


Set Theory

Explanation:
This comic is a pun on the phrase " Proof by Intimidation " which normally is a jocular term used mainly in mathematics. It refers to a style of presenting a purported mathematical proof by giving an argument loaded with jargon and appeals to obscure results, so that the audience is simply obliged to accept it, lest they have to admit to their ignorance and lack of understanding.
However, in this comic, "Proof by Intimidation" is taken to mean that by intimidating the elements within a set, they will conform to the proof (or, as the title text says, they will become "well-ordered"). This is accomplished by believing that the elements can be anthropomorphized such that they feel fear. The idea of executing as an example was discussed by Sun Tzu in the ancient book The Art Of War .
This interpretation of the term "Proof by Intimidation" bears great resemblance to argument from the stick , which is a fallacious form of reasoning of the form
1.  If not P, I will do you harm.
2.  Therefore, P.
This form of fallacy has the distinction, if properly applied, of never being called out as fallacious.  Ponytail, however, is threatening the proposition itself, rather than her audience, bringing a level of absurdity to the situation.
The axiom of choice (which has been referenced previously in 804: Pumpkin Carving ) says that given any collection of bins, each containing at least one object, it is possible to make a selection of exactly one object from each bin. It was later referenced in the title text of 1724: Proofs , another comic about a math class with a similar theme on how teachers teach their student mathematical proofs.
In the title text, the well-ordering theorem states that every set can be well-ordered. A set X is well-ordered by a strict total order if every non-empty subset of X has a least element under the ordering. This is also known as Zermelo's theorem and is equivalent to the Axiom of Choice. The woodchipper is a reference to the 1996 film Fargo , where a character uses one to dispose of a body.
[Miss Lenhart stands at a blackboard, facing away from it. She has a pointer in her hand, and written on the blackboard is some set theory math, although one of the set elements is being pointed into a guillotine.] Miss Lenhart: The axiom of choice allows you to select one element from each set in a collection Miss Lenhart: and have it executed as an example to the others.
[Caption below the panel:] My math teacher was a big believer in Proof by Intimidation.


Privacy

Explanation:
This comic is about Cueball and Megan attempting to find some privacy to "hook up", which is slang for engaging in sexual activity.
They start at a dormitory, which would offer some privacy. Unfortunately, the door is locked. They go to another dorm, but it is occupied by someone playing a MMORPG who is "in a raid ", which means that the gamer is teaming up with others to "raid" something, probably an enemy, and loot their items. This also pokes fun at the fact that some raids may take a very long time to execute, in this case apparently taking on the order of 24 hours. (This comic was published on a Monday morning.)
In the third frame, the two try to go to the library's rare book collection. Such a place would usually be deserted, making it usable for sexual activity. However, it is currently occupied by a visiting Nelson Mandela , who is on a tour of the school.
Moving on to more bizarre places, they next try an accelerator tunnel , another place that would be private. However, the particle accelerator is in use and the door is sealed tight. This would be a normal safety feature to protect researchers from being exposed to potentially dangerous ionizing radiation from the particle beam.
The couple then try a beaver lodge , which, despite being private, is too tiny to fit in, and the only entrance is underwater. What makes it more difficult to get in is that it is winter, and the ground is presumably frozen solid.
The last place they attempt to go to is hyperspace , science fiction jargon for an ‘alternate dimension’ that starships supposedly use to travel faster than light. The word is frequently used in the Star Wars movies. However, there is no evidence that anything like hyperspace exists in reality, and in fact current theories of physics do not allow it.
The caption is a parody of other laws of physics, such as "brightness is inversely proportional to distance from the source".
The title text indicates that the two eventually found privacy for sex in a laboratory, but inadvertently got Megan pregnant. This is a parody of news articles discussing whether scientists can create synthetic life in a lab. This eventual headline appears in a few 1037: Umwelt frames as "Scientists Create Life In Lab", with a similar secondary headline/caption as the punchline.
The comic 658: Orbitals is similar in nature to this comic.
Dorm: [Cueball and Megan holding hands in front of a door. Megan is attempting to turn the doorknob.] Locked
Other Dorm: [Cueball and Megan holding hands inside another dorm room. The roommate is sitting at a computer wearing a headset.] Roommate: I'll be done Tuesday. Roommate in raid
Library Rare Book Collection: [Cueball and Megan looking through a closed door. Inside Nelson Mandela and two university workers are talking amongst various items on display.] Occupied by tour for visiting Nelson Mandela
Accelerator Tunnel: [Cueball and Megan in silhouette in front of an imposing-looking door. The door is marked "NO ENTRY" with a radioactive trefoil symbol, and has a passcode scanner beside it.] Sealed while beam is in operation
Beaver Lodge: [Megan climbing on top of a dirt mound while Cueball stands on the ice beside it. A cross-section reveals a beaver inside the mound and a submerged entrance.] Frozen over for winter to keep out predators, only accessible via underwater entrance
Hyperspace: [Megan reading a textbook in front of a table piled with five other textbooks. Cueball looks over Megan's shoulder.] Cueball: Are you sure ? Ruled out by current understanding of physics
College Law #27: The availibility [sic] of private space is inversely proportional to the desirability of the hookup.


Space Launch System

Explanation:
SLS, which stands for Space Launch System , is the new launch program being designed by NASA to replace the retired Space Shuttle launch system. In the first frame, Cueball is showing Black Hat something about the SLS, possibly a video on his phone or other portable electronic device.
As usual with his appearances, Black Hat is causing trouble. Specifically he asks if Nazi scientists are going to build NASA's new SLS program. Specifically he mentions the former Nazi party member Wernher von Braun , who was one of the developers of the Saturn V launch vehicle, who came over to America (from Germany ) as part of Operation Paperclip and helped develop NASA's space program. The unfortunate reality of Operation Paperclip, and one that Black Hat aims to make people uncomfortable with, is that a significant number of ex-German personnel were Nazi party true-believers, and their defection to America effectively granted them amnesty of any war crimes.
Black Hat extrapolates this sad reality into an obvious troll attempt: that putting actual Nazis in charge will get you results. This assumption is obviously a bridge too far (which is the comic's punchline), but he gets his desired reaction out of Cueball, who is hanging his head (or staring him down- Randall has left no details to distinguish). First he makes it clear that the lesson is that you should put the Nazis in charge (and we saw from World War Two what that could lead to). Then when Cueball states this is a terrible lesson, Black Hat puts salt in his wound by suggesting that the only way to find a better lesson is to ask a Nazi for a better one - a consistent move if you apply his lesson, but a logic bomb because he suggests to put a Nazi in charge of finding another lesson other than "put a Nazi in charge".
The title text is a reference to Shania Twain 's song " That Don't Impress Me Much ". Twain's lyrics include the line "Okay, so you're a rocket scientist / That don't impress me much". But, the title text argues that if she stood under the new SLS prototype, she would admit it was in fact, impressive. And it is thus the SLS head engineer (Garry Lyles) plans to invite Shania to do just that. Although he could still understand if she did not wish to date him, he would be surprised if she was still unimpressed.
[Cueball, is holding something up to show it to Black Hat. It is small and rectangular with a black line in the middle (possible a rocket).] Cueball: Check out the SLS — 130 tons to orbit. Finally, rockets that improve on the ones we had 40 years ago. Black Hat: Are we getting Nazis to build those ones, too?
[Text is written between two frames, with two smaller frames below. A line comes up to Cueballs first comment, showing that it is still the two from the first frame talking, but off-panel.] Cueball (off-panel): What? Black Hat (off-panel): When we first captured von Braun and his team, we had our engineers interview them, then we built the rockets. Black Hat (off-panel): But our rockets kept exploding. [First small panel below the above text: A soldier with helmet and a machine gun is guarding von Braun who is tied to a chair, while being interviewed by an almost bald scientist (hair along the back of his head), who takes notes on a piece of paper.] [Second small panel below the above text: The same scientist standing with the paper, watches as a launching rocket explodes. The landscape behind shows a hill.]
[A black frame with white text above the white Saturn V rocket flying through space.] Black Hat (off-panel): Eventually we gave up and had the German teams do it, and they built us the Saturn V Moon rocket.
[Cueball is looking down, his hand with the thing he showed to Black Hat in the first panel hanging down. Black Hat looks at Cueball.] Cueball: I'm… not sure what lesson to take from that. Black Hat: "If you want something done right, learning from the Nazis isn't enough. You have to actually put them in charge." Cueball: That's a terrible lesson. Black Hat: Then I guess you should get a Nazi to come up with a better one.


Percentage Points

Explanation:
Senator Grayton is a fictional character, made up for this comic; which is unusual for xkcd, as it typically uses real-world references.
The issues that Grayton supports:
The term percentage point is used to overcome an ambiguity when comparing two percentages.
Reduction of a stated number by a percentage
When the original value is given as a number, there is no ambiguity. In the statement below the only possible conclusion is that now only 162,000 people approve of Grayton. Previously 200,000 people approved of Senator Grayton, and then his approval rating dropped by 19%.
Reduction of a percentage by a percentage
When the original approval rating is given as a percentage (20% in the comic), then a reduction of 19% has two possible meanings: 1) Of the 20% who previously approved (200,000 people), 19% no longer approve. In this case the result is 162,000 as in the above example. 2) Compared to the original results, 19% fewer of the entire original sample of 1 million people approve. In this case only 1% of the original 1 million approve, equal to 10,000 people.
If using the second method of comparing percentages, the approvals rating should be described as having dropped by 19 percentage points. In reality, the distinction between the two methods is often overlooked, leading to confusion.
The caption's issue with "percentage" versus "percentage points" is that if Grayton's 20% approval rating drops by 19%, that means that his support has only dropped 3.8 percentage points since 19% of 20% is only 3.8%. That would mean that even after all his outrageous statements, his support dropped only from 20% to 16.2%. However, if the news reports that his 20% approval rating dropped 19 percentage points , that means his support has dropped to 1%, which appears to be more accurate given Grayton's egregious policy decisions and the description of his campaign as having "imploded."
The punchline to all this is that Randall is more bothered by the "percent" ambiguity than by Grayton's appalling policy plans.
References in the title text:
[Cueball is sitting in an armchair watching TV while listening to a news report coming from the TV as shown by a zigzag line.] Voice from TV: Senator Grayton's campaign has imploded following the candidate's promise to give tax breaks to drunk drivers and to authorize the use of unmanned Predator drones in the War On Christmas. Grayton had been polling at 20%, but his support has since plunged by 19%.
[Caption below the panel:] I hate the ambiguity created when people don't distinguish between percentages and percentage points.


Drinking Fountains

Explanation:
Here, we see Cueball using the restroom; as the title text indicates, he is eliminating the liquid waste from his body, or peeing. Some people feel a brief compulsion to urinate after drinking, even if they don't actually need to. Cueball says that he avoids the use of the drinking fountain right after peeing, because he is apparently one of these people and he is afraid that he will be forced into immediately peeing again. And as in the image above, he would be stuck in a loop. A loop is a computer science term, but also used elsewhere, to indicates going through the same steps over and over again. In this case, the bathroom and drinking fountain form an infinite loop, which, when used about computers, refers to a loop which never ends, [ citation needed ] eventually crashing (or hanging, which might actually be worse) the computer, which is therefore a situation to be avoided at all costs.
The title text says Cueball/ Randall would be embarrassed in trying to explain his experiment to someone, as an experiment of this nature seems interesting to geeks but gross to non geeks (and to geeks too, if we're being honest), and he wouldn't be able to lie about what he was doing if called by someone.
A thread on yahoo answers [1] with a (purported) Biology major concluded that drinking from a hose and peeing at the same time would not work: the kidneys can only process so much pee at a time, and the majority of it is re-used. But since the experiment doesn't put a lower boundary on the flow that would be regarded as an ongoing pee, this objection is invalid. Constantly sipping and dripping might be possible.
[Cueball leaving a public bathroom. A water fountain is next to the bathroom door. An arrow points to the next panel.]
[Cueball drinking from the water fountain. An arrow points to the next panel.]
[Cueball reenters the bathroom. An arrow points back to the first panel.]
I avoid drinking fountains outside bathrooms because I'm afraid of getting trapped in a loop.


Potential

Explanation:
This comic jokes about the common rant by teachers when they are annoyed by lazy or ignorant kids. They commonly say that the kids are not working up to their "full potential" and they need to work harder. The comic comforts the kids who were subject to this — by telling the students if they did reach their full potential, they could, instead of providing better essays and science fair projects, possibly create a monster robot with 6 mechanical legs apparently able to pick up and throw cars, and use machine-guns and force-fields. This is definitely not what they wanted when they said to work to your full potential. [ citation needed ]
Note that such a huge and complex machine is usually seen in sci-fi books or movies. Generally, it is the main antagonist that creates them.
The title text describes a parallel to the example in the strip, using philosophy rather than engineering. Randall expresses frustration when his teaching gives underprivileged kids the intellectual skills needed to raise existential questions that bug him. His extremely destructive solution is to turn the students onto drugs and crime, where they won't have time or peace of mind to think about philosophy.
Narrator: When teachers complain, "You're not working at your full potential!" [Explosion in background.]
Narrator: Don't take it too hard. [Car casually spirals through the air while a crash is heard in the background.]
Narrator: They complain way more when you do. [A mechanized, 6-tentacled robot rampages around, picking up cars and creating a small warzone before the student inside while the lamentations of people and the building of military forces are in the background.] Throughout the third frame: AAAAAAAAAAAAAAAAAAAAAAAAAAA! In the control center of the robot: Click, beep, whirr Out-of-frame: It's headed this way! Ponytail: Somebody stop him!


Tradition

Explanation:
This comic uses the source of the American Society of Composers, Authors and Publishers to say that the 20 most played Christmas songs in the US between 2000 and 2009 were all released between the 1930s and 1970s. It conspicuously excludes a number of more modern songs that seem ubiquitous, but this is because those songs do not appear on the ASCAP list.
"Popular release" in this context means release to the general public, not the version of the song which is most popular.
The Baby Boomers were born in a period of time after the second World War after the troops came home and, thankful for their lives, went on to produce lots of children.
The data appears to come from an ASCAP survey conducted in 2009 .
The title text points out that many "traditions" actually have no historical precedent, they're just routines that have been spread by lots of people. The Baby Boomers, since they made up a huge fraction of the US population, were able to accidentally ground many "traditions" that their parents made up in American society just by consensus among themselves.
The 20 most-played Christmas songs (2000-2009 radio airplay) by decade of popular release [A bar chart labeled on the X-axis with the decades "1900s" through "2000s" labeled. Each bar has, as one unit, a labeled song. "1900s", "1910s", "1920s", "1980s", "1990s", and "2000s" are empty. "1930s" has "Santa Claus is Coming to Town". "1940s" has "Rudolph the Red-Nosed Reindeer", "Winter Wonderland", "Chestnuts Roasting on an Open Fire", "Let it Snow", "Have Yourself a Merry Little Christmas", "I'll be Home for Christmas", and "White Christmas". "1950s" has "Rockin' Around the Christmas Tree", "Jingle Bell Rock", "Blue Christmas", "Little Drummer Boy", "I Saw Mommy Kissing Santa Claus", "Silver Bells", "It's Beginning to Look a Lot Like Christmas", "Sleigh Ride", and "Frosty the Snowman" "1960s" has "Holly Jolly Christmas" and "It's the Most Wonderful Time of the Year" "1970s" has "Feliz Navidad"] Every year, American culture embarks on a massive project to carefully recreate the Christmases of Baby Boomers' childhoods.


Cryogenics

Explanation:
Megan , holding a smartphone , tells White Hat that everyone now carries a computer in their pocket, and refers to how it is always on-line (connected) and is full of sensors (like orientation, vibration and GPS etc.). This is actually amazing and White Hat assumes she is overwhelmed and ask her if the development is changing too fast for her.
But it turns out that Megan is actually disappointed about the pace of technology's improvement, that it goes too slowly . (Who isn't disappointed? From old sci-fi movies' predictions, we should by this point have flying cars and the flying skateboard like in Back to the Future 2 or a hyper technological future like in Blade Runner ). She tells White Hat that she has decided to cryogenically freeze herself now that she has developed cryogenics (hence the title) far enough for humans to survive such a deep freeze, and then she climbs into her homemade chamber and plans to skip 30 years ahead in time. (Actually, this should be called "cryonics", preserving humans, not "Cryogenics", which is just science at low temperatures)
Cryonic freezing is the ability to freeze oneself, so that one does not age and doesn't experience the passage of time. It is common in fiction as a useful technology for long space flights or other necessary preservation (like in the book 2001 ). Also people who are terminally ill or beyond current technology to save sometimes go through companies such as the Cryonics Institute in hope that future technology can cure them.
However, to Megan's chagrin, when she wakes up, she is told by Cueball ( who is not Terry !) that all the other scientists and engineers that were fascinated about the future had also frozen themselves using her technology, even building their freezing chambers in a line to either side of her chamber, so nothing had been invented while she was frozen.
But as Cueball tells her in the final panel, they are all waking up now, implying that finally something new can be invented! But Megan then immediately decides to freeze herself again to see what happens next, hoping the situation 30 years later will be different. But then the guy in one of the nearby chambers gets the same idea as she did (again). However, if everyone does the same thing again, the situation will repeat itself and nothing will ever change again, as they can continue this process in 30 year steps. (Note that this is not time travel , but still related to this recurring theme in xkcd, and similar methods have been called time travel in xkcd before, like in 630: Time Travel and especially 1617: Time Capsule .)
It seems, however, that the engineer in the nearest chamber, to Megan's right, spots this problem and tries to stop all the other engineers from freezing down again, as he says Wait, guys .
The moral of the comic is: Don't freeze yourself, engineers and scientists! We need your help!
The title text refers to tech startups, (and existing tech companies) who often use bold marketing techniques, proclaiming that they are going to "revolutionize" not only a particular product or service, but every facet of a user's life. One of the cliché phrases used in presentations is "Welcome to the future", implying that their product is the only way forwards, and all others are rendered obsolete.
In the title text this cliché is turned on its head, when Randall tells about a very short lived tech startup he tried to get going. The reason for the short life of the company was that it admitted that nothing changed with its slogan: "Welcome to the future! Nothing's changed."
Technology by its nature tends to evolve and improve, and thus a tech company which doesn't change will fall further and further behind their competitors, likely ending up going bust. Which was the case with Randall's (fake) tech startup.
[Megan staring down at a smartphone in her hand while talking to White Hat.] Megan: Everyone's carrying sensor-packed, always-connected computers everywhere. That wasn't true ten years ago. White Hat: It's all changing too fast, huh? Megan: No, too slowly.
[Zoom in on Megan's upper part as she holds up the smartphone showing its screen.] Megan: There's so much potential here. These clumsy, poorly-designed toys are nothing compared to what lies ahead.
[Megan climbs into a cryogenic chamber which stands on a base where a small box at the end of the chamber is connected to it through a bend tube. She leaves the smartphone on the floor in front of White Hat.] Megan: That's why I've worked to develop cryogenic freezing. Megan: I'm gonna skip forward 30 years and use this stuff when it's good .
[Cueball is greeting Megan holding a fist up in front of him, as Megan with morning hair rises up from the open cryogenic chamber.] 30 years later... Cueball: Welcome to the future! Nothing's changed. Megan: What? Megan: Why??
[Cueball still stands in front of Megan in the chamber, but the scene has rotated revealing a row of other cryogenic chambers behind. The chamber after Megan's is still closed, but the others are open and people emerging.] Cueball: When cryogenic freezing was invented, all the engineers who were excited about the future froze themselves. So there's been no one building anything new.
[The scene has rotated to look straight in on the long side of Megan's chamber, Cueball is standing to the left of the chamber. She holds the cover ready to close it again. Two voices comes from off-panel to the right.] Cueball: But they're all waking up now! Megan: Sweet! I'm gonna jump forward to see what they do! Engineer 1 (off-panel): Me too! Engineer 2 (off-panel): Wait, uh, guys?


Plastic Bags

Explanation:
This is another comic with one of Randall's fun facts .
In the United States, at the time this comic was written, most grocery stores used to provide plastic bags free; as well as a "bagger," whose only job is to bag the groceries — although sometimes this function is performed by the cashier. An exception to this rule might be "extreme discount" stores, such as Aldi . Customers are rarely, if ever, expected to bag their own groceries, even if they bring a reusable bag. It follows that sometimes a bagger might become a bit overzealous and use too many bags for too few products. This comic is mocking this tendency to go overboard, which is incredibly wasteful. The last frame takes this practice to its absurd and frustrating end, showing a reusable bag that has been double bagged with plastic bags. Exactly why bags are provided is probably a topic best left to academic discussion, but suffice to say that it is the state of the industry in the U.S. Perhaps grocery chains are concerned that if they did not provide free plastic bags, customers would defect, instead, to a competitor. Most shoppers view plastic bags and bagging by the store as givens.
Relatively recently, some U.S. jurisdictions have begun to join more and more governments world-wide to either ban plastic bags, charge customers for them, or generate taxes on each sold bag. Using Washington, DC ( Randall 's home turf) example, as of 2010 customers are charged a $0.05 tax (again, by the local government and NOT by the grocery store) for each plastic bag, and receive an equivalent rebate for each reusable bag. While today it is accepted as a fact of life, the tax angered many at its adoption, even spurring some to claim that they would do their shopping in the next state over (in this case, Virginia), driving 5 or 10 miles to save 5 or 10 cents (this would address the theme of wasting money to save a trivial amount, addressed by Randall in 951: Working ). The tax has since become accepted as a fact of life, and has been quite successful at its initial goal of reducing the amount of bags discarded in area rivers and streams.
The title text refers to the idea that while many attempt to make the environmentally-conscious decision to bag their groceries with reusable bags, thereby keeping plastic bags out of landfills, sometimes they forget to bring their bags with them from the car, or even leave the bags at home altogether. Randall is commenting on the sense of euphoria he derives from a relatively simple task: remembering to bring the reusable bags to the grocery store and taking them into the store, rather than the good feeling from helping clean up the environment.
Fun Fact: Stores have a competition to see who can spread your items across the most plastic shopping bags.
[5 items placed in a single bag; heaviest item placed at the bottom.] Bag Packer: Here you go! Shopper: Thanks!
[Same items; heaviest item now placed in separate bag.] Bag Packer: Here you go! Shopper: Oh, that's easier to carry.
[Heavy item is now double bagged.] Bag Packer: Here you go! Shopper: Double-bagging the big stuff makes sense...
[The other 4 items are now split into 2 separate bags.] Bag Packer: Here you go! Shopper: That's a bit wasteful...
[The 2 separate bags are now double bagged.] Bag Packer: Here you go! Shopper: You just put five items in six bags.
[Every item is now in its own, double-bagged bag.] Bag Packer: Here you go! Shopper: OK! I give up! I'll buy a reusable bag!
[Reusable bag is double-bagged.] Bag Packer: Here you go! Shopper: Augh!


Phantom Menace

Explanation:
Cueball is waiting outside a building with an unidentified character, who is dressed as Darth Maul , a character from Star Wars: The Phantom Menace . Before its release in May 1999, The Phantom Menace was one of the most anticipated movies of all time, with fans camped in lines outside of movie theaters as much as a full month in advance of ticket sales. In this comic, Cueball and his friend are apparently still waiting to see the movie, not having realized that they are waiting outside of a building that is not a movie theater. More importantly, they have been waiting for thirteen years, which should be long enough to realize their error.
Darth Maul, the source of Cueball's friend's costume, is a Sith apprentice in the film. The Sith are the group of characters in the Star Wars universe who embrace the dark side of the Force and are the enemies throughout the series. Cueball is holding a cheap replica of a lightsaber , which is the weapon used by the Jedi and the Sith.
This comic seems to be poking fun at those people who are willing to wait long in advance for the release of some product or the first theatrical release of a movie. The title text expands upon this when one of the characters states that going to a theater across town may be better, but he is worried about taking the chance due to the possibility of losing their place in this line, a misplaced sense of priorities if the line goes nowhere, and they are presently the only two in it.
[Cueball, holding a lightsaber, and another stick figure character in a Darth Maul mask stand on the sidewalk outside of a brick building in an urban area. Each is holding money in his or her hand. There is a broken window on the building.]
[Beat panel. They continue to stand there.]
[Beat panel. They continue to stand there.]
[Darth Maul turns to Cueball.] Darth Maul: Are you sure this place is a theater? Cueball: Let's give it one more month.


Mnemonics

Explanation:
A mnemonic is a trick that makes memorization easier. To memorize a sequence of names, a common type of mnemonic uses the beginning letters of the names in the sequence and invents another phrase using different words that start with the same letters. For example, the order of operations goes P arentheses, E xponentiation, M ultiplication and D ivision, A ddition and S ubtraction, and the traditional mnemonic goes P lease E xcuse M y D ear A unt S ally, or in Britain: B rackets, I ndices, M ultiplication, D ivision, A ddition and S ubtraction: there is no mnemonic, just the word "BIMDAS" to remember. To make them more memorable, mnemonics are usually quite silly and often vulgar. In this comic, Randall invents various scientific mnemonics, some of them as suggested replacements for traditional ones.
The category is listed at the top of the box, the members are listed below that. Then there is the traditional mnemonic that children are usually taught in school to help them remember. Below the comic is one or two options for new mnemonics suggested by Randall. The top one is illustrated in the frame.
XKCD Presents: Some New Science Mnemonics
(Pattern goes: Subject Elements Traditional mnemonic Contents of frame New mnemonics)
Order of Operations Parentheses, Exponents, Division & Multiplication, Addition & Subtraction Traditional: Please Excuse My Dear Aunt Sally [Person having a shark delivered to his laptop.] Please Email My Dad A Shark or People Expect More Drugs And Sex
SI Prefixes Big: Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, (Yotta) Milli, Micro, Nano, Pico, Femto, Atto, Zepto, (Yocto) Traditional: [I never learned one.] [Graph of the declining profits of the Zune.] [Karl Marx delivering a number of zeppelins to a bunch of confused proletarians.] Proletarians (off-screen): Er. What do we do with them? Karl Marx: Rise! Big: Karl Marx Gave The Proletariat Eleven Zeppelins(, Yo) Small: Microsoft Made No Profit From Anyone's Zunes(, Yo)
Taxonomy Kingdom, Phylum, Class, Order, Family, Genus, Species Traditional: King Philip Came Over For Good Sex Katy Perry: I'm not sure who doubts this, really. Katy Perry Claims Orgasms Feel Good Sometimes or Kernel Panics Crash Our Family Game System.
Geologic Periods (Precambrian), Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene Traditional: [I never learned one.] [A month's set of birth control pills.] PolyCystic Ovarian Syndrome Does Cause Problems That Judicious Contraceptves [sic] Partially Negate
Resistor Color Codes Black Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White Traditional: [none I care for] [Glenn Beck holding the traditional "Nanobot Vaccine Chemtrail 9/11" sign.] "Big Brother Reptilian Overlords", yelled Glenn, "Brainwashing Via Ground water!!"; or Be Bold, Respect Others; You'll Gradually Become Versatile, Great Wikipedians!
Planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune Traditional: My Very Excellent Mother Just Served Us Nachos [A pregnant Mary attempting to explain things to an incredulous Joseph with black hair and full beard] Mary's "Virgin" Explanation Made Joseph Suspect Upstairs Neighbor.


Brand Identity

Explanation:
This comic presents Randall 's idea for a line of food products all with clear black font on a white background. The products with black block lettering and white background stand out from the other items in this comic. The irony is that even though the branding isn't terribly creative, the lack of complexity is what causes the products to stand out. These product packaging styles resemble no-frills products and generic brands . For example, in Canada, the " No Name " generic brand of low-cost products sold by Loblaws general features a plain yellow label with the description of the product in bold black text, and occasionally an image of the product. The brand name is minimalized as are other legally-required elements (e.g. the weight of the product). Another of Loblaws' generic brands, President's Choice (PC) currently has a plain white background with black bold text for the labels on most of its products (usually with an image of the product as well as the brand name), although more recently, text in accent colours has been introduced.
The style of packaging might be a reference to The Prisoner TV series from the '60s, a dystopia set in a village (actually, "the village") locked out from the outside world. The shops here only sell "village food". See this photo for an example.
It might also be a reference to Portal’s bean cans.
In the title text, the lack of a listed URL relates to the lack of branding on the package. It is possible that omitting the URL the consumer's curiosity will be aroused, and they will spend time on the internet hunting for the actual site.

[The incredibly varied shelf of a supermarket aisle. There are many different types of products on this shelf. Each type has numerous different brands, all surrounding a very plain brand that has, as its only label, the type of product. A plain bag, labeled in plain black letters, says "Potato Chips" and is surrounded by all the other various brands of potato chips. The same exists for tissues, crackers, matches, peanuts, hot sauce, sugar, milk, pasta, coffee, black beans, lima beans, mayo, ketchup, tea, and bread. There is a stark contrast between the incredibly noisy and complex labeling of every other brand and this simple one.]
[Caption below:] If I ever sold a line of supermarket goods, this is how I'd build a brand identity overnight.


Advent Calendar

Explanation:
An Advent calendar is a special calendar used to count or celebrate the days in anticipation of Christmas. They come in a multitude of forms, from a simple paper calendar with flaps covering each of the days, to fabric pockets on a background scene, to painted wooden boxes with cubby holes for small items. Advent calendars typically take the form of a large rectangular card with "windows", of which there are usually 24: one for each day of December leading up to and including Christmas Eve (December 24). Consecutive doors are opened every day leading up to Christmas, beginning on December 1. The calendar windows open to reveal an image, a poem, a portion of a story (such as the story of the Nativity of Jesus), or a small gift, such as a toy or a chocolate item.
This comic, however, depicts an Advent calendar which has a chocolate every time they get halfway to Christmas. This is a joke because of Zeno's paradox , which said "Before a moving object can travel a certain distance, it must travel half that distance. Before it can travel half the distance it must travel 1/4 the distance, etc. This sequence goes on forever. Therefore, it seems that the original distance cannot be travelled, and motion is impossible." This means that eating chocolates at diminishing intervals will make it so Christmas never happens.
The title text says that when you get close to midnight, it gets physically impossible to eat the chocolates fast enough to keep up, but you could get to the one-second-away mark with a chocolate liquefier and feeder tube.
Going from the second to the last of the visible time stamps it goes like this: At 11:57:11.25 PM there is still remaining 00:02:48.75 (2 minutes 48 seconds and 75 hundredth of a second.) Half of this time period will then progress before the next windows time stamp, that is 00:01:24.375 (1 minute and 24.375 s). This will then give the next time stamp by adding to the previous and we get: 11:58:35.625 PM. This has been rounded to 35.63 s in the comic. Similarly the time stamp for the next four windows, whose top are visible below, can be calculated starting from the fact that there is now only 00:01:24.375 left of the day.
It would take three more windows before crossing the 11:59:59 line with less than one second to go. At the 19th window there would only be 0.6591796875 seconds left of the day for a time-stamp of 11:59:59.3408203125. So that would be a window another line further down, even below the green window (no. 15) that is just visible at the button of the panel. And you would have to eat four chocolates in less than five seconds from window no. 16 to fulfill Randall's prediction.
When reaching the 24th window there would be 0.0206 s left, so that is 6 chocolates in 0.638 s. That may be a good place to stop, but of course you could continue at least until reaching the Planck time of 5.39 x 10 -44 s. That limit will not be reached before window 162, so there are still 138 chocolates left for those last two hundredths of a second.
1153: Proof is also about Zeno, and 1577: Advent is a very different longer running Advent calendar (but with only a finite number of windows). [ citation needed ]
[A portion of an advent calendar shows 12 windows where the date can be seen below. The top row is cut off so you cannot see the very top of the window At the bottom there are four more windows, but only the top part can be seen, and there is no decoration visible. All the other windows have a decoration, although, you cannot see the one on the second window as it is opened more than 90 degree. The first is also opened, but not more than you can see there is a decoration. The 3rd is also open. The rest is still closed.] [A green mistletoe on red, partially open.] December 23 rd
[A fully open window.] December 24 th 12:00 AM
[A red and white Santa hat on green just opened.] December 24 th Noon
[Two crossed red and white candy canes on white. From here all windows are closed.] December 24 th 6:00 PM
[A red Christmas ball on white.] December 24 th 9:00 PM
[A white Christmas star on red.] December 24 th 10:30 PM
[A red Christmas heart on gren.] December 24 th 11:15 PM
[A red Santa sleigh on white.] December 24 th 11:37:30 PM
[A red and white Christmas sock on green.] December 24 th 11:48:45 PM
[A green Christmas tree on red.] December 24 th 11:54:22.5 PM
[A red and green Christmas wreath on white] December 24 th 11:57:11.25 PM
[A red and white Christmas gift on green] December 24 th 11:58:35.63 PM
[Below the top of four more windows where only the background colors can be seen red, white, green and then red again.]
[Caption below the panel:] Zeno's Advent Calendar


Coinstar

Explanation:
This is another one of Randall's Tips , this time a Holiday Tip.
Chocolate coins are a popular holiday candy, and thus this is another Christmas comic . These candies are usually plain chocolate formed in the shape of coins and covered in metallic foil wrappers.
Coinstar machines accept all your loose coins, sort them, count them, and then give you the same amount of money in paper currency, around 9% less as it says in the title text. You may find similar machines in grocery stores and shopping malls around the US and Canada.
These machines work by vibrating a box with a series of slots along one side, which each corresponding to the sizes of standard accepted coins. The vibrations move the coins along the different slots. If they pass through the slots the coins are then fed into a mechanism with a counterweight that's balanced to test the weight to ensure that it has captured the appropriate coin. Coins of the right size but wrong weight (such as similarly sized coins of different currencies) are dropped back out into a reject chute to be retrieved by the customer. Coins that do not fit the standard sizes also get rejected in the same way. There are also various anti-theft mechanisms that prevent coins from being counted and then retrieved. Coins that meet the programmed criteria are funneled into internal repositories and are counted towards the total.
The chocolate coins in the comic appear to have damaged the machine. As the only property that the candies share with actual currency may be its appearance the machine would not be designed to handle the softer material causing the machine to malfunction and create the unusual noises presented. The chocolate may have fouled the initial vibrating tabulator; it may be that the coins are getting caught in the reject chute or are fouling the scales. In any case, the anti-theft system is being triggered, causing the machine to shut down (preventing false totals from registering) and an alarm to sound.
The title text suggests that the machine would take its customary 9% from the total of the chocolate coins which is ironic since the reader knows that their candy has insignificant monetary value.
[A mischievous Cueball empties a small bag into a machine.] whirrrrrrr bzzt [Machine makes progressively less happy noises.] kachunk tshhhhhhhhhh clickclickclickclick GRIND [Machine malfunctions and shuts down.] pop beeeeeeeeeeeep! [Text below frame] Holiday tip: Coinstar does not handle chocolate coins well.


Making Things Difficult

Explanation:
This comic is a reference to the breast cancer surgery that Randall 's fiancee/wife underwent, and is one of many comics about cancer he made because of this.
This comic is the follow up appointment after the surgery. When doctor Ponytail asks Megan to take her shirt off, she refuses until Ponytail gives her a necklace of purple beads. Younger and more boorish Mardi Gras tourists sometimes offer necklaces like this in exchange for the exposure of a person's breasts.
Megan's line "You know the rules" implies that Megan has stipulated that every time she takes off her shirt for the doctor, a necklace of beads must be exchanged.
In the official transcript the doctor is described as an Oncologist , a doctor who works with cancer patients, and Megan/Randall's wife is described as a Delightfully Awesome Person . It is also stated that the oncologist fake-annoyedly searches for something in pockets and that it is a Mardi Gras bead necklace she takes out.
Below the xkcd logo in the header at the top of the comic page there is the following text: "Some context for the cancer comics:" and below that a link to a blag posting regarding family-illness that talked about the real world events leading up to this comic.
The title text refers to a mastectomy , the surgical removal of one or both breasts. One possible treatment for breast cancer is to surgically remove the breast. After this procedure a false or prosthetic breast is often added to retain the prior physical appearance. The title text suggests this prosthesis could serve as a charging station by including the following features: a spare battery inside the prosthesis, a USB port where the nipple would normally be, and a ring of lights showing the charge level of the battery arranged around the areola (the darker circle of skin around the nipple).
This is one of the few comics where a character wears regular clothes, but doctor Ponytail has been seen before in 883: Pain Rating and later in 1713: 50 ccs . Megan is in both, and Cueball also in the latter.
[Ponytail in a doctor's coat is carrying a clipboard with lines indicating text, consulting it while Megan is sitting on a high medical table with a full body gown on. At the top there is a frame crossing over the top of the first panel with a caption:] Caption: Breast Cancer Surgery Follow-Up... Ponytail: You're looking great! Remove your top so I can check how the incision is healing. Megan: Nuh-uh.
[Ponytail has taken her arm with the clipboard down, while Megan is holding her hand with a thumb up.] Ponytail: *Sigh* Ponytail: Do we have to do this every time? Megan: You know the rules.
[In a frame-less panel showing only Ponytail, she searches for something in both her pockets, three sets of two small lines indicate how she moves her hands around inside them.] Ponytail (Mumbling to herself, in smaller text): This is so ridiculous...
[Ponytail holds a purple bead necklace up in an outstretched arm. Megan begins to disrobe, opening the dress at her neck pulling with both arms as shown with three sets of two small lines.] Ponytail: Here. Megan: Woooo!


Wait Wait

Explanation:
Wait Wait... Don't Tell Me is an hour-long weekly radio news panel game show produced by Chicago Public Radio and National Public Radio . The show is hosted by playwright and actor Peter Sagal . Each episode ends with the panelists making up a potential future news story, usually with implausible "facts". This comic is making puns on the title of the show based on what Peter Sagal might have done that was newsworthy.
Carl Kasell , who also served as the news anchor on Morning Edition , was the show's official judge and scorekeeper until May 2014 (after this comic was published), when he retired and was replaced by Bill Kurtis.
The 1st row, 4th paper may refer to the Laugh Factory Incident of 2006.
In the 3rd row, first paper, Lakshmi Singh is NPR's national midday newscaster.  This paper leads to the second paper on the third row, in which Sagal's wife divorces him over his affair with Singh.
In the 3rd row, 3rd paper is a reference to a protest at UC Davis (on the campus of University of California, Davis) protests in early 2012 in which sitting, peaceful protesters were calmly pepper-sprayed in their faces by a police officer. That spawned an internet meme of epic proportions .
In the 4th row, 2nd paper is a reference to the movie, Ghostbusters .
In the 4th row, 3rd paper is a reference to Granny Weatherwax of Terry Pratchett's Discworld novels; Granny Weatherwax is a witch who carries a sign saying " I ATEN'T DED "(sic) when having out-of-body experiences.
In the 5th row, 2nd paper is a reference to another internet meme in where someone leaves out the verb in the sentence. The implication is that the verb is something bad, but which bad thing is left as an exercise to stew in the reader's mind. See the I Accidentally ___ meme for more information.
In the 5th row, 3rd paper is a reference to the Eldritch abomination Cthulhu, from " The Call of Cthulhu " by H.P. Lovecraft . He is one of the Old Ones, the Elder Gods, and is awakened by his worshipers chanting, "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" ("In his house at R'lyeh, dead Cthulhu waits dreaming.") Hence the title, "Wait, Wait, Don't speak its name."
Two years later another New Years comic, 1311: 2014 , took a similar look at what could happen in 2014, just as this does for 2012. Interesting enough the title of that comic (just the year it was looking at) is more related to the title of the next comic after this one, which is also a New Year comic, and the title is also just the number of the year: 998: 2012 .
Headlines!
Stockpiled in case Peter Sagal, host of NPR's Wait Wait Don't Tell Me , does something newsworthy in 2012.
[Series of above-the-fold newspapers follows; Each has a headline, picture in most of them, and an explanation.]
[First row, first paper.] Wait Wait Don't Shoot Me [A fierce Peter Sagal in a balaclava brandishes a gun in a supermarket.] NPR's Sagal in Whole Foods hostage standoff.
[First row, second paper.] Wait Wait Don't Vote For Me Peter Sagal quits race for GOP top spot [A sullen and defeated Peter Sagal surrounded by supporters admits defeat.]
[First row, third paper.] Wait Wait Don't Judge Me Sagal opens up about his Kermit fantasy. [Stock profile images of Peter Sagal and Kermit the Frog.]
[First row, fourth paper.] Wait Wait Don't Fire Me [Stock profile image of Peter Sagal.] Peter Sagal let go after racist tirade.
[Second row, first paper.] Wait Wait Don't Cancel Me NPR axing news quiz. [NPR spokesperson delivering announcement.]
[Second row, second paper.] Wait Wait Don't Interrupt Me Sagal stabs Carl Kasell in on-air dispute. [Peter Sagal mid-attack with a knife.]
[Second row, third paper.] Wait Wait Don't Look At Me [Peter Sagal with a skin condition.] Peter Sagal's Poison Ivy Ordeal Peter Sagal: "My 'Nam"
[Second row, fourth paper.] Wait Wait Don't Friend Me Peter Sagal deletes his Facebook account. [Person holding up a laptop with an "Facebook account not found" screen.]
[Third row, first paper.] Wait Wait Don't Seduce Me How Lakshmi Singh stole Sagal's Heart. [A wistful Lakshmi Singh being left by a sullen Peter Sagal.]
[Third row, second paper.] Wait Wait Don't Leave Me [A wistful Peter Sagal being left by a furious Beth Sagal.] Sagal's wife out after affair
[Third row, third paper.] Wait Wait Don't Spray Me Police Raid Sagal's Occupy NPR protest [Scummy policeman in riot gear spraying Peter Sagal in the face point blank.]
[Third row, fourth paper.] Wait Wait Don't Indict Me Sagal, five others named in cash-for-tote-bags scandal [Peter Sagal doing a perp walk.]
[Fourth row, first paper.] Wait Wait Don't Clone Me Peter Sagal 'Outraged' over DNA harvesting. [Fiery Peter Sagal, missing a small amount of DNA, at a lectern.]
[Fourth row, second paper.] Wait Wait Don't Bust Me Peter Sagal's ghost captured [Ghostbusters, careful not to cross the streams, capture the ghost of Peter Sagal.]
[Fourth row, third paper.] Wait Wait Don't Dissect Me Snoozing Sagal nearly snuffed in autopsy snafu [Peter Sagal running away from from a very surprised pathologist.] Peter Sagal: "I aten't dead"
[Fourth row, fourth  paper.] Wait Wait Don't Objectify Me Peter Sagal is more than just a piece of meat
[Fifth row, first paper.] Wait Wait Don't Beatify Me [Peter Sagal shakes his fist at a picture of the pope.] Peter Sagal Rebukes Pope
[Fifth row, second paper.] Wait Wait Don't Me Peter Sagal Accidentally [Peter Sagal in a blank vacant.]
[Fifth row, third  paper.] Wait Wait Don't Speak Its Name [eyes... Eyes... AAAHHH.] Peter Sagal wakes Eldritch terror Peter Sagal:"AAAAAAAA"
[Fifth row, fourth paper.] Wait Wait Even For NPR This Is A Bit Much This American Life to document the road to recovery for those who suffer the trauma of losing on Wait Wait


2012

Explanation:
This New Year comic is in reference to the fact that the Mayans , an ancient civilization in the Americas , created a calendar that ends (or, more accurately: restarts) on December 21, 2012. This date is regarded as the end-date of a 5,125-year-long cycle in the calendar used by the Mayan culture. Knowing this, some thought that the world was going to end on that date.
Consequently, a lot of people were talking about the Mayans, concerned that the world might end. After December 21, 2012 passed uneventfully, everyone was less concerned about the Mayans, because the world didn't end [ citation needed ] . It is worthy of note that this comic was published nearly a year before the "significant" date and that Randall predicted both the hype and the aftermath perfectly.
There is a measure of irony to be had in how the Mayans who still exist today were largely ignored by the doomsayers. "Or acknowledging that huge city-building ancient American civilizations existed at all."
In the final frame, Megan parodies the phrase, "Those who fail to learn from history are doomed to repeat it," applying a twist to suggest an academic context. In most American schools, a Grade Point Average is computed by assigning numeric value to each letter grade: A=4, B=3, C=2, D=1, and F=0; receiving high marks (all A's) thus yields a 4.0 GPA. However, if you "Fail to learn from History" — that is, get a failing grade, F, and had at least 3 other classes (not an unusual course load) — you would still get a 3.0 with A's in those other classes. With a more common workload of eight courses per year, GPA as high as 3.5 can actually be reached in those circumstances. She is making the callous — if roundabout — observation that failing to grasp history, while no doubt troubling, isn't an academic show-stopper. Her comment may also be taken to suggest that people who feared the Mayan "prediction" of the end of the world would come to pass had failed to appropriately extrapolate from the numerous other faulty predictions of the end of the world . In fact the Mayans never actually predicted the end of the world with their calendar, those who failed to learn from history jumped to conclusions yet again.
The title text jokes that to make up for the lack of Mayan discussion, Randall plans to spend 2013 talking solely about Mayans. For obvious reasons [ citation needed ] , people would probably get sick of this very quickly, hence his comment that his relationships might not fare well. Thankfully, as of 2014, not a single published xkcd comic of 2013 featured any Mayans, so we're pretty sure this promise wasn't kept.
[Cueball and Megan are talking.] Cueball: Well, it's 2012.
[Cueball and Megan in frameless panel.] Megan: Yup. Megan: Only 354 days left until everybody abruptly stops talking about Mayans.
[Cueball and Megan in wide panel to fit longer text content.] Cueball: Or thinking about Mayans. Cueball: Or acknowledging that huge city-building ancient American civilizations existed at all. Megan: You know what they say — those who fail to learn from history can still manage a 3.0 if they ace their other subjects.


Cougars

Explanation:
Randall is giving reason number 58 why he should not have children. We see fictitious "father Cueball " talking about the Wikipedia entry for " List of fatal cougar attacks in North America ". As stated, many of the victims were young children near their home.
If you tell a child about something dangerous, but without giving them necessary context to feel protected from it, you are likely to cause nightmares, sleeplessness, or other fear-related issues [ citation needed ] . In most, if not all, cases this would be considered bad parenting, hence a person who enjoys doing so should perhaps not have children.
The title text demonstrates that not only is Cueball sharing factual information, he is intentionally adding hypothetical detail (e.g. "yellow eyes glinting in your window") to make the danger seem even worse. The child is unlikely to agree that learning this is fun. Incidentally, a panther is not an actual species but rather a term for either leopards or jaguars with melanistic conditions. Mountain lions themselves are rarely called panthers.
[Cueball is sitting at a computer; a child is standing behind.] Cueball: Whoa, ever seen Wikipedia's list of people who were attacked and killed by cougars? Cueball: Crazy how many of them were kids who were just playing outside their houses.
[Caption below the panel:] Reason #58 I should never have children: My love of learning and sharing knowledge about the world.


1000 Comics

Explanation:
This comic is the 1000th comic shown on xkcd containing 1000 characters from previous comics arranged in the shape of the number "1000". Megan is clearly excited as she screams "Woooo!", but Cueball , in true nerd fashion, thinks in base-2, saying that there are just 24 to go until a "big round-number milestone". The joke is that during programming, base-2 is used more often than base-10, making milestones powers of two rather than powers of 10. Where 1000 is a round number in base 10 (10 3 ), 1024 is a round number in base 2 (2 10 ). Binary is also referenced in the "Connect the Dots" puzzle, explained below.
In the 1000 comic Randall included 404: Not Found , see why in the explanation for this comic. This comic strengthens the fact that Randall did indeed count 404 as a "real" comic.
Each of the characters/drawings is numbered on this page:
About 2/3rds are described on this page:
There is a "Connect the Dots" puzzle hidden within the comic. However, rather than using the conventional decimal system numbering which would start with 1 and count up, 2, 3, 4, 5, ...  This "Connect the Dots" puzzle starts with 0 as a programmer would do and counts up in binary numerical order - 0,1,10,11,100,101,110,111,1000,1001 and back to 0. The revealed image forms the shape of a heart. This fits well with the title text where feeling less alone can equate to feeling loved.

[1000 characters, numerous of which have appeared previously in other comics, are arranged to create the number "1000". Two more people stand in the foreground commenting on the formation. There are several comments amongst these 1000 but here are only written the text that can be read from the small version shown above.] 1000 Megan: Woooo! Cueball: Wow—Just 24 to go until a big round-number milestone!


AAAAAA

Explanation:
Megan and Cueball get the idea to build a rotating bed from a TV show like Cribs , which documents the decadent homes of the wealthy.
Rotating beds are typically used for sexual activity and variety, but Cueball and Megan have made theirs rotate far too fast, like a merry-go-round , to be useful for this purpose.
The last panel is a flashback to earlier that day, when they see a rotating bed on television. Megan comments that a rotating bed does not seem difficult to build.
The title text implies that the high speed of rotation is not accidental as we may have assumed from the comic, but intentional, due to Megan and Cueball's erroneous belief that the rotation itself is supposed to turn them on, not the sexual activity they would engage in on the moving bed. A turning bed is also a pun with "turned-on."
[Cueball clinging onto bed sheets while being dragged away by centrifugal force.] Cueball: AAAAAAAA
[Megan similarly clinging on.] Megan: AAAAAAAA
[Overhead shot of both spinning around a plain white circle in a room with other accoutrements.] Both: AAAAAAAAAAAAAAA
[Cueball is sitting on a couch watching TV and Megan is standing behind the couch, with a frame overlapping the top of the panel containing a heading.] Heading: Earlier that day... Cueball: Haha, check it out–This guy's mansion has an actual rotating bed. Megan: You know, I bet it wouldn't be too hard to build one of those...


Game AIs

Explanation:
To understand the comic, you have to understand what the games are, so let's go (but first, the years in parenthesis in the comic are the year that the game was mastered by a computer):
These games are considered "solved", meaning the ideal maneuver for each game state (Tic-Tac-Toe, Connect Four) or each of the limited starting positions (Checkers) has already been calculated. Computers aren't so much playing as they are recalculating the list of ideal maneuvers. The same could be said for the computer's human opponent, just at a slower pace.
Black plays first, and players alternate in placing a stone of their color on an empty intersection. The winner is the first player to get an unbroken row of five stones horizontally, vertically, or diagonally.
The below games have not been "solved". Some of them may be solved some day, but the large number of possible moves has so far prevented this from being done. Others cannot be "solved" due to the influence of randomness or the existence of multiple "ideal" maneuvers for each position. That said, a computer's faster reaction time, higher degree of consistency in making the right decision, and reduced risk of user error make the computer objectively better than the human opponent in nearly all situations.
Here's the video of the University of Illinois robot mentioned in the comic.
The note mentions "the first game to be won by a chess-playing computer against a reigning world champion under normal chess tournament conditions", in the Deep Blue versus Garry Kasparov match on February 10, 1996, and the Ponomariov vs Fritz game in the Man vs Machine World Team Championship on November 21, 2005, considered the "last win by a human against top computer".
Ken Jennings, mentioned in the title text, is a famous Jeopardy champion who was beaten by Watson , an IBM computer. This was an exhibition match featuring Jennings, Brad Rutter, and Watson that took place in February 2011.
The below games are incredibly difficult to "solve" due to the near-infinite number of possible positions. Computers built in the early 21st century would take years to calculate a single "ideal" move. Worse, the human opponent has the ability to "bluff"; that is, to make a bad move, thus baiting the computer into a trap. Complex algorithms have been devised to make moves in a reasonable timeframe, but so far they are all highly vulnerable to bluffing. As mentioned in the comic, focused research and development is working on refining these algorithms to play the games better.
As the game is focused on human interaction, there's not a whole lot a modern computer can do in the closet. It would need some kind of robotic body in order to interact with its human partner, and emotion engines that could feel pleasure and displeasure in order to make decisions. The title text claims that Honda Motor Company has invented a " RealDoll " (sex toy shaped like a mannequin) with rudimentary Seven Minutes in Heaven capabilities, but they pale in comparison to a human's (specifically, Jeopardy champion Ken Jennings).
And finally
Calvinball is a game played by Calvin and Hobbes as a rebellion against organized team sports; according to Hobbes, "No sport is less organized than Calvinball!" Calvinball was first introduced to the readers at the end of a 1990 storyline involving Calvin reluctantly joining recess baseball. It quickly became a staple of the comic afterwards. The only hint at the true creation of the game ironically comes from the last Calvinball strip, in which a game of football quickly devolves into a game of Calvinball. Calvin remarks that "sooner or later, all our games turn into Calvinball," suggesting a similar scenario that directly led to the creation of the sport. Calvin and Hobbes usually play by themselves, although in one storyline Rosalyn (Calvin's baby-sitter) plays in return for Calvin doing his homework, and plays very well once she realizes that the rules are made up on the spot. The only consistent rules state that Calvinball may never be played with the same rules twice, and you need to wear a mask, no questions asked. Scoring is also arbitrary, with Hobbes at times reporting scores of "Q to 12" and "oogy to boogy." The only recognizable sports Calvinball resembles are the ones it emulates (i.e., a cross between croquet, polo, badminton, capture the flag, and volleyball.) Long story short, the game is a manifestation of pure chaos and the human imagination, far beyond the meager capabilities of silicon and circuitry, at least so far. The closest thing you could possibly get is having an AI automatically generate rules on the fly, similar to something like the currently-existent AI Dungeon or a similarly robust text algorithm; but even still, the computer would be unable to act upon these new rules in that state.
[A diagram with a caption above the diagram. The left column describes various levels of skill for the most capable computers in decreasing performance against humans.  The right side lists games in each particular section, in increasing game difficulty.  There are labels denoting the hard and easy ends of the diagram.]
Caption: Difficulty of Various Games for Computers
Top of Diagram: Easy
Solved Computers can play perfectly
Solved for all possible positions
Tic-tac-toe Nim Ghost (1989) Connect Four (1995)
Solved for starting positions
Gomoku Checkers (2007)
Computers can beat top humans
Scrabble CounterStrike Beer Pong (UIUC robot) Reversi Chess
February 10, 1996: First win by computer against top human November 21, 2005: Last win by human against top computer
Jeopardy
Computers still lose to top humans (but focused R&D could change this)
StarCraft Poker Arimaa Go
Computers may never outplay humans
Snakes and Ladders Mao Seven Minutes in Heaven Calvinball
Bottom of Diagram: Hard


Adam and Eve

Explanation:
This comic is a take on the anti-homosexual refrain, used often at those sorts of rallies "It was Adam and Eve, not Adam and Steve". This refrain is used to support the definition of marriage as between a man and a woman because in the Old Testament God created a man and a woman to start the human race. Adam and Eve are in the story in the Bible of the creation ( Book of Genesis ), and are the first pair of humans, created by God.
Adam walks in on Eve having sexual relations with Abel , who is Adam's son, which turns the joke from a homosexual one into an incest one.
In the title text, Adam continues that he would have preferred walking in on Abel and Steve. As well as probably no longer needing to be irked at the surprise involvement of his presumed spouse, and mother to his son, Adam seems not to have a homophobic prejudice (or less of one). Unlike those who use the contemporary version of the phrase. What's more, he doesn't personally dislike Steve in general and possibly considers him one of the better partners available at this time.
[Adam, portrayed as Cueball, has his palms out.] Adam: It's Adam and Eve , not Abel and Eve!!
[Caption below panel:] Adam was freaked out by what he'd just walked in on.