No, The Other One

Explanation:
This is a map of the United States, showing cities or towns with the same name as other more famous places. For example, the map has a dot for a relatively unknown place called Los Angeles, located in Texas, not to be confused with the very well known Los Angeles that is in California.
Few place names are unique, and there may be many places with the same name . Multiple American towns have been named after the same British town, famous person, or geographic feature.
However, names can become associated with specific places on a national level, where the best-known example is usually the biggest or otherwise the most significant. The name of this comic indicates the contextualization required to specify one of the less-famous exemplars of a given name. Someone might say they are from "Los Angeles" and would have to say "no, the other one" since the listener would assume they are from Los Angeles, California.
The title text references Key, West Virginia and Key West, Virginia , two places that, when spoken aloud, are only distinguishable by the pause (comma) location. Neither are to be confused with Key West, Florida , which is a location well-known nationally.
[A typical line-drawn map projection of the United States, with discontiguous Alaska and Hawaii moved into a convenient corner.] [Coastlines and national borders are in a firm half-tone.] [Non-coastal state boundaries are shown in a lighter tone and feature the standard two-letter abbreviations.] [Location dots and labels of the settlements they represent are overlaid in solid black.]
[Within each of the states, expanded here for readability, are the following placenames...] AK [Alaska] Houston AL [Alabama] Detroit Houston Jackson AR [Arkansas] Nashville AZ [Arizona] Miami Peoria CA [California] Beaumont Jamestown Lincoln Mesa Plymouth CO [Colorado] [An unlabelled dot, between text for Louisville, CO and Atlanta, NE; probably the actual Mesa, CO.] Louisville Mesa [Appears to be the incorrectly-labeled town of Orchard Mesa, CO.] CT [Connecticut] Salem DE [Delaware] Atlanta Newark FL [Florida] Bowling Green Houston GA [Georgia] Albany Columbus Dallas Roswell HI [Hawaii] Mountain View IA [Iowa] Indianapolis Knoxville ID [Idaho] Atlanta Princeton IL [Illinois] Beverly Hills Lincoln Plano IN [Indiana] Houston Plymouth KS [Kansas] Detroit Manhattan Ottawa KY [Kentucky] Anchorage New Haven LA [Louisiana] Alexandria MA [Massachusetts] Princeton MD [Maryland] Pasadena Phoenix ME [Maine] Lisbon Portland Vienna MI [Michigan] Atlanta Saint Louis MN [Minnesota] Albany Austin Bloomington Grand Rapids MO [Missouri] Boston Houston Savannah MS [Mississippi] Philadelphia MT [Montana] Lincoln Manhattan NC [North Carolina] Dallas Washington ND [North Dakota] Jamestown New England NE [Nebraska] Atlanta Cedar Rapids Memphis NH [New Hampshire] Lisbon NJ [New Jersey] Long Beach NM [New Mexico] Des Moines Las Vegas NV [Nevada] Dayton NY [New York] North Pole Philadelphia Texas [Further subtitled as...] (Texas, Mexico) OH [Ohio] Bowling Green Cambridge Gettysburg Houston OK [Oklahoma] Disney Orlando Saint Louis OR [Oregon] Dallas Oakland Phoenix PA [Pennsylvania] Jersey Shore RI [Rhode Island] Lincoln SC [South Carolina] Baton Rouge SD [South Dakota] Dallas Gettysburg TN [Tennessee] Fayetteville White House TX [Texas] Atlanta Beverly Hills Buffalo Los Angeles Miami New York Pasadena San Diego Santa Fe South Bend UT [Utah] Cleveland VA [Virginia] Key West VT [Vermont] Richmond WA [Washington] Des Moines WI [Wisconsin] Atlanta WV [West Virginia] Bridgeport WY [Wyoming] Albany Atlantic City Buffalo


1991 and 2021

Explanation:
This comic shows a Cueball from 2021 who is once again discussing the future's technology with White Hat, this time in 1991 instead of 2010. White Hat is awed by the advances in technology, but is not expecting that the law combating laser attacks on passenger aircraft is not the most important thing mentioned.
"Laser attacks on airliners" sounds dramatic and important, and White Hat probably thinks that laser weapons have been developed and used to attack aircraft. Given that "a [US] federal law" has been passed to combat such attacks, White Hat may be envisioning a future where US citizens have access to laser guns, and some reckless individuals have been firing them at airplanes. (If it were some other group like terrorists or foreign militaries, a federal law would be unlikely to dissuade them.)
In reality, the "lasers" in question are low-powered laser pointers, which some people aim at passenger airliners as a (dangerous) prank. When the beam hits the airplane, it cannot damage the plane itself, much less shoot it from the sky; [ citation needed ] it can, however, blind the pilot, which poses a threat to them and their passengers. A law ( 18 USC §39A ) was thus passed in 2012 to criminalize this.
The robot fighting TV shows mentioned include BattleBots , Robot Wars , and MegaBots , the earliest of which started in 1998. In them, machines armed with a variety of weapons fight in an arena. These are not technically robots or drones in the traditional sense of operating autonomously; for the most part, they are either remote controlled or piloted by humans, and have only rudimentary on board computer systems.  They are certainly not controlled by AI.  Also, while these shows have been popular enough to return to the air after periods of hiatus, they are not nearly as popular as sports involving humans.
In this comic, "cordless phone" may be meant literally, meaning any wireless phone without a cord. That's distinct from common parlance where "cordless phone" is distinct from a cellular phone, and is a wireless extension of a landline, typically of limited range, i.e. within a home. It seems likely that Cueball was using a term he believed a 1991 citizen would more easily relate to. Although cell phones had been in use for over a decade by 1991, they were most commonly depicted as a foible of a stereotypical "businessman", typically accompanied by displays of distraction, classism, & self-importance. The term "cell phone" was at that time frequently used to refer to older analog cellular networks, with many mobile users proud of their new CDMA or GSM " digital " phones, as distinct from true "cellular" systems which have been deprecated since that time (this distinction has since disappeared from common usage). A more general term used in modern parlance, such as "mobile phone" or "wireless phone" may have been less recognizable to the average person in 1991. Describing a cell phone as "a cordless phone [where you can] send news stories to your friends" would be a reasonable way of describing a cell phone to a person of that era.
Additionally, cellular phones today do not have much longer range than cellular phones of 1991 (in fact most have less range, due to their lower transmission power & use of higher frequencies, as well as indirectly due to increasing crowding on most wireless frequencies). Cordless phones reliant on a land-line, may exhibit somewhat longer range than they did in 1991, due to improvements in digital error correction & audio compression, although the effective range of a single transmission at a given power & frequency would otherwise be reduced by interference from the proliferation of other wireless devices outside functional range &\or operating independently. Satellite phones also offer more terrestrial range than cellular or cordless landline phones, however their functional range has not greatly increased since 1991 either (being already sufficient to reach a satellite within line-of-sight above). A possible explanation for a perceived "longer range" is that cellular phone towers are much more omnipresent than in 1991, granting cellular devices much greater functional area even though their functional range from one tower is typically less than in 1991.
Sharing on social media has distorted what news stories people encounter. Instead of a curated selection of important [ citation needed ] news fact-checked by a newspaper or tv/ radio broadcast from a large corporate media conglomerate , we see only what people similar to us found interesting.
By most reasonable measures, the most important technologies on the list could be seen as the rise of mobile phones, and the ability to easily share news stories (aside of course, from any perceived advent of high-powered laser weapons or televised robotic warfare). The first of these, mobile phone usage (& smartphones in particular) has led to a dramatic change in how people communicate, with a large amount of communication now remote, which was not as convenient in the 90s (requiring, for example, setting up roaming at the carrier's office before taking the phone to another city) and impossible for most people a few decades prior: Low frequency wireless for personal communication was relatively uncommon in the early '90s & remains so today. Sharing of news stories person-to-person is partly blamed for the spread of fake news ; misinformation has become more and more politically, legally, & socially significant in the past few years. While wireless communication has certainly had enormous & wide-ranging effects, the factuality of the data communicated is arguably of greater importance than the means of its communication. The joke is that the impact of a technology on society isn't really about how exciting or dangerous it might look at first glance.
The title text horrifies 90s White Hat , as it not only refers to a pandemic serious enough to induce lockdowns, but mentions it casually, in reference to the existence of computer webcams. COVID-19 is already a hugely impactful deadly disease, but by mentioning it without details, it leaves White Hat to guess as to the details. Cueball doesn't specify whether there have been one or more pandemics (the plural use of 'lockdowns' could be taken to imply that there were more than one), or how serious they were, how long-lasting, or how many lives were lost to them.  In consequence, White Hat could easily be assuming a dystopian future even worse than what really happened.
[Cueball (with an aura) is talking to White Hat.] White Hat: Welcome to 1991! White Hat: So you're from 2021?  What happens with technology over the next 30 years?
[Same scene, except Cueball has his palm out.] Cueball: We passed a federal law to combat laser attacks on airliners, and there are TV shows where robots battle. Cueball: Also, cordless phones are longer range now, and it's really easy to send news stories to your friends. White Hat: Wow, okay.
[Same scene.] Cueball: Now, try to guess which of those things turn out to be important. White Hat: ...is it not the lasers? Cueball: It is not the lasers.
On release, the title text was not actually included as such. It was instead included as the text of a "see also" link, which is often invisible to readers and is activated by clicking the comic. Such links have been used in the past for larger versions of the comic or for related information on other sites. Here, it linked back to the comic itself, and was evidently a mistake.


Indoor Socializing

Explanation:
Cueball is meeting White Hat , who is probably not in the same household. White Hat asks how Cueball is, which is normal small talk, but Cueball responds by expressing his anxiety that they're inhaling one another's "gross lung air". Cueball then repeats a common joke regarding how impossible it is to connect with people when our conversation norms discourage honest communication, switching to a more socially acceptable "fine".
"Gross" here may be a pun on the term gross anatomy (i.e. anatomy at the macroscopic level) and "gross" as a synonym for "disgusting."
A recurring theme in xkcd is characters expressing an uncomfortable awareness of realities that most people tend to ignore, particularly for experts in a particular field (examples include 2057: Internal Monologues , 913: Core , 203: Hallucinations , and 1839: Doctor Visit ).  In this strip, likely as a result of being primed by awareness of the COVID-19 pandemic , Cueball finds it difficult to be in the same building with other people without being aware of the fact that they're breathing the same air, meaning that particles of biological material are being freely exchanged. In an earlier era, such concerns might have been dismissed as being extreme, but the pandemic has demonstrated that there's very real reason to be concerned.  Even if everyone involved is vaccinated, that doesn't entirely remove the risk, nor does it protect against other diseases, which can spread in similar ways.
The title text reinforces the idea that knowing more about any subject increases the likelihood that you'll become disturbed by some constant and basic reality of life. In this case, studying biology tends to be disturbing, since the field involves in depth knowledge of our own bodies, as well as all other organisms we encounter, and which makes one uncomfortably aware of all the risks and flaws basic to being alive.
Normally, inhaling unfamiliar biological organisms from the bodies of others is one way the immune system learns its environment, to prepare for possible diseases like seasonal colds.  With the advent of common distant travel, culture has adapted to the onslaught of new organisms people are exposed to, giving us strong senses of hygiene to protect our health beyond the adaption of our immune systems.  Diverse cultures of hygiene have evolved deadly superbacteria, produced sets of people with very good hygiene and very weak immune systems, as well as saving millions of lives, providing for treatments like safe open surgery and normalising novel piercings.  Often learning of the realities of the pervasiveness of micro-organisms and the details of biology can clash with one's culture of hygiene.
[White Hat and Cueball are having a conversation.] White Hat: How are you? Cueball: Excruciatingly aware of how much of each other's gross lung air we're breathing. Cueball: I mean, fine!  How are you?


Linked List Interview Problem

Explanation:
This is another one of Randall's Tips , this time a Coding interview Tip.
In computer programming, a linked list is a type of data structure that stores data throughout memory accompanied with memory addresses of the next, and potentially previous data point, establishing a relative ordering for a collection of data. Several common software engineering interview questions involve manipulating or otherwise interacting with linked lists. Possibly because programmers in the current day rarely work with linked lists directly, Randall suggests that such structures belong in a "technology museum," and thinks it would be more beneficial to mankind to email the list to such a museum rather than perform any useful work with it.
A linked list is a way to store sequential data in computer memory. Each piece of data is stored with a pointer to the next piece. This makes it very easy to add new data in the middle, since only one existing pointer must change to point to the new data. The drawback of a naive implementation can be that finding data may require following the entire chain. Technical programming interviewers like to see if applicants are familiar with the structure and the computational complexity concept itself.
Linked lists are, historically, one of the two main data structures that represent sequential data, along with arrays. Unlike arrays, they have the theoretical advantage of O(1) insertions and deletions thanks to not needing to reallocate the entire structure, but have O(n) random access (see comparisons ). However, modern processors' cache structure favors data that are located next to each other, pre-fetching the adjacent items, and modern processors can perform bulk memory moves, making resize operations faster. Finally, using linked lists usually implies dynamic allocation of each list member as opposed to reserving memory for a bunch of items in a bulk and then using that memory once an item has to be added. Memory allocation tends to be slow on modern systems and adds overhead for managing the information, which byte is allocated for what item, which can be significant, particularly for smaller data items; many small allocations also tend to fragment memory, which can lead to it being wasted and unavailable to the app later, particularly in long-running processes such as web servers. These properties tend to make linked lists poorly suited for most system programming applications in which a programmer might write algorithms to manipulate data structures, instead of using existing libraries.
Modern programming languages usually provide abstractions (often named "array," "vector" or "list") which interact with the sequential data at the memory level, providing access to this data while using arrays, linked lists, hybrids of the aforementioned technologies, or other approaches, and the programmer doesn't necessarily need to care one way or another. Knowing the underlying concepts is still useful, however, when creating fast running code which scales well to large data, avoiding (e.g.) traversing the list over and over again, or performing particularly inefficient operations.
Cueball's code implements a routine whose name implies that it does a mundane task, specifically traversing a linked list, but in fact emails the contents of the list to a technology museum. This could reveal private data that might be stored in a linked list, such as bank account numbers, medical information, passwords, etc., and would thus be a terrible idea. This is why interviewers - presumably job interviewers - would "get really mad".
In the title text, a singly linked list contains pointers to traverse the list in only one direction; namely, from the head to the end. By contrast, each element in a doubly linked list contains pointers to both the "next" and "previous" elements, enabling traversal in either direction. Randall continues the implication that such lists are obsolete by implying that traversing such a list would be akin to time travel. Without the "previous element" pointers, Randall is concerned he would not be able to reverse the time travel, as he could not traverse the list in the reverse direction.
[Cueball is writing on a whiteboard with a blue pen with Ponytail looking over his shoulder. The text on the board is unreadable, but it is is written in blue above them. It is a piece of code and it reads:]
Ponytail: Hey.
[Caption beneath the panel:] Coding interview tip: Interviewers get really mad when you try to donate their linked lists to a technology museum.


H-alpha

Explanation:
Black Hat has acquired an H-alpha filter. This is a special kind of optical filter used for scientific observations of the Sun's chromosphere . It is different from an ordinary solar filter, which is used to protect one's eyes or camera, as looking at the Sun bare-eyed will do damage to one's eyes. A camera using an ordinary (not H-alpha) solar filter was seen in 1828: ISS Solar Transit , and the consequences of not using such a filter were explored in 2227: Transit of Mercury .
Black Hat points out that the filter can also be used to look at nebulae , but doesn't see much further use for it; since the filter only transmits a very narrow bandwidth of light, one generated by hot hydrogen, it is not useful for looking at much else. This gives him an idea, and he leaves.
WARNING!!! A deep sky nebula H-alpha filter has a wider bandwidth than a solar H-alpha filter and WILL hurt the eyes if used to observe the sun!
Upon returning, his hat looks damaged. He casually shares with Cueball three seemingly unrelated observations which suggest what he was up to in the meantime: that most modern blimps use helium to keep them aloft, that their household is out of fireworks, and that an advertising company (or several, going by the title text) is upset. Early in the 20th century, most airships such as blimps and zeppelins used hydrogen as the lifting gas.  There were several incidents in which this gas ignited while the ships were in flight, resulting in spectacular and catastrophic fireballs, most famously the Hindenburg disaster . Taken together, the implication is that Black Hat tried to set someone's advertising blimp alight using fireworks; so he could use his H-alpha filter to look at the burning hydrogen.
In modern times, one of the most well-known uses of airships is blimps for advertising, as they are an unusual and hence attention-getting sight in the sky, offer a large surface area that can be used to show a slogan or logo, and can stay aloft for a long time at comparatively little cost. Modern blimps almost exclusively use helium as a lifting gas. While helium is significantly more expensive than hydrogen (and a non-renewable resource), it has similar weight and therefore similar lifting power to hydrogen, but is not flammable. (In fact, as a noble gas, helium is totally non-reactive under normal conditions).  Any attempt to cause a hydrogen fireball would, therefore, be doomed to failure.  Nonetheless, if Black Hat managed to set off sufficiently powerful fireworks near the blimp, it could potentially damage the skin, risking a loss of helium and possibly putting people in danger, which is likely why the advertising company is "real mad".  The joke is that Black Hat would do something as destructive as attempting to destroy a blimp in flight, potentially killing people aboard or on the ground, merely to have the opportunity to use his H-alpha filter.
Cueball "responds" by holding whatever he's reading closer to his face, apparently hoping to avoid further conversation (or consequences).
The title text references the insurance company MetLife, which until 2016 used the cartoon character Snoopy as an advertising mascot. In the Peanuts comics, Snoopy would frequently imagine himself as a fighter pilot in World War I in an aerial battle with the Red Baron , a battle he would frequently lose. The detail that Black Hat "dressed up as the Red Baron" might help explain another point: advertising blimps typically fly higher than the effective range of most fireworks. It would be entirely consistent with Black Hat's history to modify the stolen triplane mentioned in 496: Secretary: Part 3 to allow him to launch fireworks from the air, in mockery of an old-fashioned dogfight.
This comic was published shortly before Independence Day 2021, a US holiday that is often commemorated with fireworks. This may explain why Black Hat and Cueball originally had some fireworks around.
[In a slim panel Black Hat is seen holding a small black device up in his left hand.] Black Hat: I got an H-Alpha filter for looking at the sun.
[In a broad frame-less panel Black Hat, holding the device down in his left hand while standing behind Cueball who is sitting in an armchair reading on his tablet.] Black Hat: It also works for nebulae. But that's about it. There just aren't that many hot blobs of hydrogen to look at, I guess.
[Back to a slim panel, Black Hat is seen holding his left hand to his chin, while he holds the device down in his right hand.] Black Hat: ...Unless...
[Another two slim panels follows. In the first Black Hat turns around and leaves, his head already partly outside the panel already, and he no longer holds the device in his hands. And then follows an empty beat panel.]
[In a broad panel Black Hat re-enters with the device held down in his hand. He is walking towards Cueball in his armchair. His black hat is somewhat out of shape. Cueball is still reading but is now hunched further forward and he has lifted his tablet so it is very close to his face.] Black Hat: Huh, did you know blimps all use helium now? You learn something new every day! By the way, we're out of fireworks. Black Hat: And some advertising company is real mad.


Nightmare Code

Explanation:
Although the pandemic is not directly mentioned, this comic is another in a series of comics related to the COVID-19 pandemic .
A person using futuristic technology is giving a presentation or lecture. The content of his projected screen includes the names of the first four letters of the Greek alphabet , which he refers to as the Nightmare Code. The presenter expects that the list is familiar to his audience, but that it is novel information to them that it used to have a purpose other than providing arbitrary names to hurricanes, virus variants, and nanobot swarms.
The presenter refers to Greek as a language from Earth: this implies that the audience is mostly extraterrestrial - on Earth, everything is Earth implicitly. This may be the reason that they're unaware of the Greek language: the nightmare code may have spread beyond Earth, but a rather small Earth language may not be common knowledge.
Atlantic hurricanes and tropical storms are named once they have sustained wind speeds of 33 knots (61 km/h; 38 mph) or more. The names for these storms go from A-W each year (each letter has a name randomly chosen from a predefined list), with 21 names allocated each yearly period . When the 21 names are exhausted, Greek letters were once used to continue naming storms as needed, although the World Meteorological Organization decided not to use Greek letters when naming storms from 2021 onward. Perhaps in this vision of the future, the naming lists have given way to using the Greek alphabet exclusively.
Virus variants may also be given names once they are deemed sufficiently nightmarish. At the time of this writing, eleven variants of SARS-CoV-2 have been labeled with Greek letters.  Previously, variants were named informally for the region in which they were identified (as were many viruses themselves), but this practice has ceased due to risks of discrimination and the perverse incentive of countries to suppress health information for the sake of saving face. A place may become (in)famously known as the origin of a disease by such a name, even if it originated elsewhere; an example is Spanish flu , which was actually first observed in the US state of Kansas. Nowadays vague names such as 'bird flu' or partly-informed geographic names tend to be better referenced by their hemagglutinin and neuraminidase subtypes, such as "H1N1" and "H9N2". The more technical coronavirus identification system uses a term such as "lineage B.1.617.2", whose awkwardness makes it unlikely to replace better-known names such as the "Kent variant" or "Indian variant".
Another set of historic nightmares the audience clearly knows about, which are still in our own future, are nanobot swarms, presumably nanoengineering failures and/or deliberate misuses of nanotechnology of the Gray goo type. Significant recurring or sequential events have seemingly earned the need to differentiate their outbreaks, and Greek letters have been used to do this. One may even be tempted to speculate that the futuristic figure and his presentation equipment float in space because the Earth has been rendered uninhabitable as a result of one or more of said nanotechnology disasters.
The cultural forgetfulness about the neutral basis of the old letters, after perhaps who-knows-what nanobot disasters that may have scoured the Earth clean of all things Greek, has led to no other common use for them except for their use in identifying far too many crises. The words themselves thus are instantly associated to bad times for almost everyone.
The title text indicates that future people stopped using the term "alphabet" (which derives from the first two letters of the Greek alphabet, alpha and beta ) due to the negative associations of the words caused by them being used to describe nightmarish occurrences. The "alphabet" is now called "charset", for "character sets".
[A Cueball-like person is giving a presentation while wearing futuristic gear, including a visor with an antenna rising from it, a backpack-like appliance of some kind, and a futuristic pointer.  The audience is not pictured.  The presenter is floating rather than standing.  The presentation is projected from a small device near the bottom of the frame, and the appearance of the presentation suggests it is a hologram. The content of the slide shows the names of the first four letters of the Greek alphabet:] Alpha Beta Gamma Delta
Presenter: We all know the Nightmare Code , used to assign neutral names to scary ongoing lists, such as hurricanes, virus variants, and nanobot swarms. Presenter: But did you know it actually originated as the letters of an ancient Earth language?


Board Game Party Schedule

Explanation:
This comic shows a timeline of a gathering to play some sort of fairly complex board game.  These games often have many pages of rules, and a long setup time.  Often the very complex rules must be explained in detail, which can be extremely dull in a group environment.
Conversely, just beginning like at the time entry point "it will make sense once you play" without explanation often leads to new player frustration that, had they had a complete understanding, they would have made different choices and had a more reasonable chance at victory, or even worse, avoided constantly being informed of "illegal moves".
In addition, since it's a party, there are other activities that take place in addition to playing the game, notably ordering and eating food.
By the time you eat, prepare the game, and teach the new players, little time is left to actually play the game. This comic exaggerates this dynamic, for in the timeline, no one gets to play the game at all. Often during these gatherings the frustration with the factors above cause people to suggest settling on a simpler or more well known game.
The title text observes some of the guests supposedly playing a fictional [ citation needed ] board game, Meta Board Game Party – a game about board game parties. Because the quoted rule states that arguing in the "breakaway faction" is worth more victory points, it would be optimal strategy for them to do just that, for as long as possible. This seems to be a sarcastic explanation as to why they tried to get the whole group to play some other game and turned the ensuing debate into 45 minutes of bickering.
[Caption above:] Board Game Party Schedule
[A timeline is shown, from about 6PM at the top to about 11PM at the bottom. Events are displayed as white rectangles, labeled as follows:]
before 6PM: people filter in 6:00–6:25: small talk 6:25–6:55: debate which game to play 6:55: remember that you need to order food 6:55–7:15: debate where to order from 7:15: pick a place, order 7:15–7:40: pick a game and start setting up 7:40–8:20: explain rules to new people 8:20: food arrives 8:20–9:00: eat food 9:00–9:27: resume setting up 9:27–9:52: more explanation 9:52–10:13: restless faction tries to start simpler game 10:13–10:38: general debate 10:38–10:57: “It will make sense once you play” 10:57–11:10: finish setting up after 11:10 PM: people head home


Danger Mnemonic

Explanation:
The teacher Miss Lenhart warns two small kids using a danger mnemonic .
However, this is actually a mash-up of three different common danger mnemonics, each of which warn about different hazards.
This mnemonic is intended to help recognize a venomous coral snake , which has red, black, and yellow stripes, with the red and yellow stripes adjacent. Nonvenomous king snake species also have red, black, and yellow stripes, but the black stripes separate the red and yellow ones. Note that this identification is accurate only in eastern North America; coral snakes in other parts of the world sometimes have black stripes touching red stripes. The safest course of action is to avoid any snake with the warning colors of red, yellow/white, and black stripes. Another corruption of same warning features in 1604: Snakes .
This mnemonic is used to identify poison ivy and poison oak throughout much of North America. These plants both produce an oily surface resin called urushiol, which causes an allergic reaction in the majority of people. Touching either plant can result in contact dermatitis, which can be severely itchy or painful. If burned, the urushiol can be inhaled, causing lung irritation.  While rarely serious, these reactions are often severely unpleasant and can last for weeks, so avoiding the plants is well advised.  Both plants generally grow three leaves at the end of each branch, and grow berries that turn white when ripe.  The mnemonic helps in remembering this characteristic to distinguish them from similar-looking but harmless vines. See 443: Know Your Vines .
This mnemonic predicts bad/good weather conditions based on a particularly red sunrise/sunset. It is predictive at middle latitudes where the prevailing winds go from west to east.  Regions of higher air pressure will cause a particularly red sky at sunrise/sunset, so a red sky in the evening indicates a high pressure system is coming in from the west with its calmer weather, while a red sky in the morning indicates a low pressure front coming in (usually with rain and rougher weather). In some countries (such as the United Kingdom), the saying mentions shepherds rather than sailors. Randall actually wrote a newspaper article explaining this phenomenon.
Combining all three sayings sounds particularly ominous. It implies that a person is involved with a situation simultaneously involving coral snakes, poison ivy, and potentially nasty weather.  In such a case, Miss Lenhart advises the children to "just get out of there", implying that the situation is too dangerous to try to deal with.
The title text refers to another mnemonic: 'Beer before liquor, never been sicker; liquor before beer, you're in the clear.' Unlike the first three mnemonics, which are genuinely useful for avoiding danger, this one is largely a myth , as the order in which you drink alcohol is unlikely to impact how sick you become. However, whether the mnemonic is true or not, testing it would involve multiple drinks of alcohol, which would be ill-advised when facing a dangerous situation, particularly one as bizarre and complex as implied in this strip.
See also 2422: Vaccine Ordering for the previous time xkcd referenced the latter mnemonic.
See also 2038: Hazard Symbol for another combination of danger warnings.
[Miss Lenhart is holding a finger up in front of two children: a boy with spiky hair and Science Girl.]
Miss Lenhart: Now, remember: Miss Lenhart: If red touches yellow amid leaves of three under a red sky at morning, Miss Lenhart: You should probably just get out of there.


Board Game Argument Legacy

Explanation:
This comic continues the joke from comic 2486: Board Game Party Schedule , released the previous week, about the difficulty some gaming groups have actually playing any game at all once they get together.  In this scenario the group have leveraged the difficulty of choosing a game into a game itself.  It seems to be that each player has a certain number of votes, or tokens, that they can use to decide which game to play, with the added element that they permanently dispose of the losing game. This can lead to strategic play where a player might vote for a game, even if they don't want to play it that night, so that they could still play it at some future resolution of the choosing.
Once the voting is finished, the next phase of the game is to debate which expansion packs they should collectively buy for which game.
A legacy board game is one where players change the game itself in the course of play, such as by writing on certain cards and ripping up others, causing future sessions to be modified. A legacy game thus avoids the tendency of some games to become repetitive if they are played every week, which is a common tradition among friends or families. The meta-game this comic describes fits this definition, because the available pool of games (and expansion packs) changes based on the players' decisions. Randall refers to the “game” of choosing what to play having become repetitive. Although official legacy games are sold by the manufacturers of the original game, some players may create their own legacy versions of a game.
The title text refers to how many board and card game owners are bothered by legacy games because they destroy game pieces. A legacy game, of course, is meant to be permanently altered, but many players find it hard to perform destructive actions like cutting or tearing up cards. At an extreme, some owners wish to keep their games in as-new condition, going as far as refusing to shuffle cards in ways that bend them, or not punching tokens out of their cardboard frames. Even some games not classed as "legacy" games may have elements such as blank cards to be filled in by the players. For those who are reluctant to make changes, these items may remain blank forever. An additional layer of humour comes from the fact that it sounds like the speaker is chastising a game owner who does not want to engage with ordinary elements of the game, but instead urges them to pour soda on the game (something that would usually be an unfortunate accident). "2d6" is standard notation for games that involve rolling several different types of dice, where the first number refers to the number of dice to be rolled (in this case 2), and the second number referring to the style of dice (in this case 6-sided). That means that the player could end up pouring between 2 and 12 ounces of soda (inclusive) into their game box, depending on the total value rolled on the two 6-sided dice and assuming the dice roll directly translates to ounces.
The board game boxes visible in this comic are real board games (from left to right):
[White Hat, Megan, Ponytail, and Cueball are sitting around a table that is covered with board game boxes. White Hat is pointing at Ponytail. Both Ponytail and Cueball are holding boxes.] Ponytail: You may reallocate up to five tokens to your top choice from last week. Remember, the game with the least support tonight will go to the thrift store. Ponytail: Next, we'll resume the debate over ordering expansion packs.
[Caption beneath the panel:] We got tired of having the same repetitive arguments every week over which game to play, so we developed Board Game Argument: Legacy .


Bad Map Projection The Greenland Special

Bad Map Projection: The Greenland Special

Explanation:
This is the fourth comic in the series of Bad Map Projections displaying Bad Map Projection #299: The Greenland Special. It came one and a half year after the third 2256: Bad Map Projection: South America (#358), and was followed about 10 months later by 2613: Bad Map Projection: Madagascator (#248).
Map projections are different methods of representing the curved surface of the Earth on a two-dimensional map. There's no perfect way to do so. Because the Earth is not flat, any 2D map projection of it will always distort in a way the spherical reality, and a map projection that is useful for one aspect (like navigation, geographical shapes and masses visualization, etc.) will not be so for all the others. Typically a projection can represent only distances, areas or angles correctly, or at best imperfectly compromise two of these. The map choice should reflect the purpose you need to put it to, as it will necessarily distort (perhaps by twisting, skewing and/or resizing) those aspects it was not designed to show intact.
One such projection is the Mercator projection , which is designed so that all north-south lines of longitude are parallel to each other and all rhumb lines are consistent, which is most important in the time of map-based navigation. In reality, apart from the direct east-west directions, all the imaginary straight lines eventually meet at the poles - even if they look parallel. The apparent distance between lines of latitude at the more extreme latitudes expands and the vicinity around each pole can never be drawn, as Mercator maps show geographic features plotted over ever larger map areas and distances than they should, for those nearer the poles, compared to those more equatorial. It is not possible to accurately compare the sizes of features across the globe using this projection, although the distortions can be effectively ignored for more local maps that do not plot a significant area of the globe (other than very close to the poles, historically not an issue) and along or between any given narrow strips of latitude away from the equator the comparison is between near equal scalings.
Greenland is a large [ citation needed ] island in the Arctic ocean and one of the nearest pieces of land to the north pole. The Mercator projection shows it to be significantly larger than it really is, compared to equator-straddling features such as Africa. It is therefore one of the most obvious inaccuracies of Mercator's map, if used (e.g.) in the classroom to teach physical geography (which perhaps would best use a representation that was consistent to area) rather than navigation.
The equal-area projections such as Mollweide or Tobler Hyperelliptical , the latter of which seems to extremely closely match the majority of the features evident upon the hand-drawn map, ensure that shapes contain the same relative  proportion of area as they would upon the original spherical (or slightly spheroidal ) surface, across all latitudes, but only by bending the directions and rescaling the distances ever more drastically the closer to the map edge (the anti-meridian to that the map is centred upon) you go. Unlike the Mercator projection, you can show the poles (as the extreme upper and lower limits of the rim) from an equatorially-centred view, and every point of the Earth is given one definite position (or two, where they lie exactly upon the crossing point between the left/right extremes of the map).
This comic's projection has retained this singular inaccuracy as a deliberate feature, though avoiding all other such inaccuracies of the Mercator projection by using a different projection elsewhere that is designed explicitly to avoid them. For example, a traditional Mercator map would show other polar areas such as Antarctica, southern South America, or even New Zealand as larger, but this map does not.
Although it may not be obvious, due to no land-masses being normally shown at/close-enough to the North Pole, the Mercatorish Greenland actually extends beyond the Elliptic map's northern limits into positions that do not even exist in reality - it does not even 'wrap around and over' the pole (like a bad toupée) but passes through it and the arbitrary back-edge meridian line and into purely imaginary space that does not exist upon the surface of the Earthly sphere. (For a flipped comparison, the lower 'curve' of Antarctica is not its coast, but merely the map's 'wrap-around' edge where a further step would have you stepping back onto the continent at a second point of this nominal edge. The true coast of Antarctica is only the rough upper edge, passing between the two points which each represent the one arbitrary 'wrap-around' coordinate that is opposite-but-adjacent on the map's oval edging, i.e. at ±180°E/W, but which otherwise has no particularly special quality 'on the ground'.)
The title text suggests that this map was created for people who believe Greenland should be larger. Whether these people believe it should be physically increased in size in some manner or should simply receive a greater share of the attention is unclear. One method for increasing its size would be to increase the coverage of its ice cap, which is currently decreasing in size due to increases in temperature. However, increasing Greenland's ice coverage to the size it appears on a Mercator map would involve covering the entire island and surrounding ocean with ice, which would be very problematic for Greenland's population [ citation needed ] .
Bad Map Projection #299: The Greenland Special Equal-area map preserves size everywhere except Greenland, which uses the Mercator projection. [A drawn world map, perhaps the Tobler hyperelliptical projection, except for Greenland which is of a typical Mercator appearance and sized at almost the size of Africa, to almost entirely fill the space between Canada and Iceland. It extends up well beyond the nominal location of the North Pole, while its southern tip has an apparent latitude comparable to that of Spain or the vicinity of Virginia.]


Pre-Pandemic Ketchup

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic .
Just like 2474: First Time Since Early 2020 , Randall compares the pre-pandemic life and the post-pandemic life in this comic. Life has changed dramatically due to the COVID-19 pandemic and the subsequent lockdowns and restrictions by governments around the world.
In this comic, Cueball bought a bottle of ketchup before the pandemic and they have not bought that kind of ketchup since, possibly due to supply chain disruptions or that brand not being available to order online. It may be a reference to the shortage of ketchup packets caused by an increase in takeout orders and restaurants replacing the ketchup bottle on the table with single serving units [ dubious ] . Cueball is now cleaning out his cupboard, perhaps as a form of "pandemic spring cleaning" to make way for the future, and considers throwing it away. An offscreen character encourages him to toss it.
In the title text, Cueball (or possibly Randall ) is wondering in which year he would discard the last weird food item that he bought online in early 2020.  If he's going for the Expiration Date High Score to beat 24.3, he should probably wait until 2045 or so.
[Cueball is standing in a kitchen, looking at bottle with label which he is holding in his hand. He is talking to a person off-panel behind him, who replies. There is a cupboard above him, with stuff protruding from the shelves. Below that is a counter, with a drawer and a cupboard. There is an  bottle with fluid, a can and a jar on top. Only the latter two has labels.] Cueball: Oh wow, pre-pandemic ketchup! Cueball: We haven't bought this kind since before. Cueball: I'm gonna toss it. (off-screen): Eww, yes.
[Caption below the panel:] Spring 2020 forms a weird dividing line in my kitchen.


Immune Factory

Explanation:
This comic is another entry in a series of comics related to the COVID-19 pandemic , specifically regarding the COVID-19 vaccine .
When Hairy received his first dose of a COVID-19 vaccine, his body began building a defense in the form of antibodies. He has now received his second shot, and is feeling even more unwell than the first time, since his body has ramped up the production of antibodies, as Cueball states. Hairy and Cueball then begins to make comments that metaphorically compare Hairy's immune system to a factory, hence the title Immune Factory.
Vaccines in general work by giving the body's immune system a chance to respond to a pathogen without actually being infected. The immune system responds by producing antibodies, proteins customised to attach to the pathogen, either disabling it directly or marking it for attack by immune cells. After the vaccine (or after an actual illness), the immune system remembers how to make the antibodies and can more quickly respond to future infections. This is why Hairy describes his body as an "antibody factory".
However, many common symptoms of illness (such as fever, soreness, diarrhea and nausea) are actually caused by the body's immune response rather than the infection itself. As a result, vaccines can result in similar symptoms to an illness, albeit milder and of shorter duration.
Hairy extends the "body as factory" metaphor by complaining that, since he feels unwell, the factory must be violating OSHA regulations—that is, rules that protect workers from unsafe work conditions. Hairy says his lymphatic system (a major component of the immune system) is protesting the "brutal" work of responding to the vaccine, as human workers might protest a dangerous workplace.
In real workplaces, one possible response to worker dissatisfaction is for them to unionize , forming an organization that can use their solidarity to bargain for improvements to working conditions. Hairy says that this is what his immune cells have done. It is not clear whether this corresponds to any actual part of the immune response, or whether it is simply a humorous expansion on the "factory" metaphor.
Cueball uses the "union" statement to set up a pun on two meanings of the word "scab". If unions make demands that an employer refuses, their workers may strike , or refuse to work. Employers may keep the workplace running by hiring strikebreakers , non-union workers (or union workers who break ranks with their colleagues). Union members may refer to strikebreakers by the pejorative term "scabs".
Another meaning of "scab" is the hard coating the body produces to cover a bleeding or seeping wound while it heals. Smallpox is a dangerous illness that causes ulcers upon the skin, leading to many small scabs forming as those ulcers heal. Prior to modern vaccination techniques, people were sometimes deliberately infected with smallpox—typically from a person with a mild case—while they were healthy. This process, now called variolation (after Variola , the virus that causes smallpox), could be done in various ways. Some methods used pus or fluid from smallpox ulcers, but others used scabs from the ulcers, dried and powdered. This powder might be rubbed into a cut in the skin, or insufflated (blown up the person's nose).
The pun therefore is that members of the immune system union would not like either kind of scab. Hairy finds the pun appalling, and tells Cueball to leave .
The title-text parodies the trend for recent incarnations of unions to rebrand or form anew with a descriptively apt name (possibly with a forced acronym, or styled as one for branding purposes), rather than the (Extended/ Very Extended /etc) Three Letter Acronyms of times past. In this case making a portmanteau of "immune union" - Immunion. The cleverness of this name apparently convinced some of Hairy's immune cells that were previously opposed to the union to change their minds.
[Cueball walks in from the left, hand held up in front of him, to where Hairy is sitting in an armchair facing away, sick from a second vaccination. Hairy is wrapped in a blanket and holding a steaming mug, and his hair is messy.] Cueball: I guess the first shot made your body build defenses, and now it's ramping up production. Hairy: So I've become an antibody factory.
[Cueball has walked around the chair and is now facing Hairy, whose mug continues to steam just as much.] Hairy: I don't feel great. I think my factory has some OSHA violations. Hairy: My lymphatic system is protesting brutal working conditions.
[In a frame-less panel, Cueball continues to stand in front of Hairy, whose mug is steaming less.] Hairy: Update: my immune cells have unionized. Cueball: Common side effect. Helps maintain a healthy balance.
[Cueball has raised a finger into the air, while Hairy is pointing in Cueball's direction. Hairy's mug is no longer steaming.] Cueball: Immune system unions are actually why we stopped doing variolation. Hairy: Oh? Why? Cueball: They don't like scabs. Hairy: Ugh. Leave.


Commonly Mispronounced Equations

Explanation:
This comic is a collection of very commonly used physics and mathematical equations, along with their "correct" pronunciations. Equations are normally voiced out loud either by their names ("mass-energy equivalence") or by saying the parts out loud using normal linguistic rules ("E equals m c squared"). This comic instead asserts that equations are meant to be said out loud like words, using their own set of phonic rules.
Though the premise may initially seem absurd, some nerds have both the trait of using equations as commonly as others might chat and that of finding it entertaining to coin amusing new words ("input", "pwn"). Saying the equations more rapidly can speed up work or make work seem more enjoyable.  This phenomenon is called clipping .
Using clipped or verbalized forms of equations is sometimes standard practice within a given field. The equation for continuously compounding interest A=Pe rt is commonly taught and discussed as the "pert" equation, while the definitions of the main trigonometric functions is similarly taught and discussed as SOH-CAH-TOA: sine = opposite/hypotenuse, cosine = adjacent/hypotenuse, and tangent = opposite/adjacent. These particular "corrections" are all nonstandard, however, occasionally conflicting with more normal readings like "pivnert" for the ideal gas law. The "corrections" are also internally inconsistent, with equal signs and exponents sometimes omitted and sometimes included and intermediate vowels.
[Each equation is bordered, with a pronunciation guide beneath.]
Commonly Mispronounced Equations
Row 1
F = G m₁m₂/r² FUH- JAM -ER
E = mc² EM -CAH-TOO
a² + b² = c² AT- BOOT -COOT
Row 2
A = πr² APP -ER-TOO
H = −Σpᵢlog pᵢ HA- SPLOG -PEE
PV = nrt PAV -NURT
Row 3
e iπ = −1 EYE -PIN
F = ma FEE -MAH
∂²u/(∂t²) = c ∂²u/(∂x²) DOOT CAH- DOOX
Row 4
f'(x) = lim h→0 f(x+h) − f(x) / h FAX -LIM-OH FAX -UH-FOX
x = −b ± √(b² − 4ac) / (2a) ZA- BO -BA FAK- TOH -AH


Dual USB-C

Explanation:
This comic was the first in what became a new series of Cursed Connectors and presents Cursed Connector #187: Dual USB-C. The series continued two comics later with 2495: Universal Seat Belt (#65) and was followed three weeks after that by 2503: Memo Spike Connector (#102).
Starting roughly around 2016, the word "cursed" has become slang for something that makes the user feel uncomfortable (unlike the classic definition, nothing supernatural needs to cause the discomfort).
USB-C connectors are the newest version of the USB standard , and Randall showcases a new type of connector which would see two USB-C plugs side-by-side able to be inserted simultaneously by housing them inside a NEMA 1-15P plug, more commonly known as a Type A plug, that is usually used in some countries to connect electrical devices to AC current. This does not seem to offer any advantages over the current implementation.
Further, the plug introduces several disadvantages, including, but not limited to
The connector therefore is considered cursed.
Notably, there's an existing dual USB-C plug in use for Macbook-compatible high-performance dongles, among other things, which is remarkably similar but avoids all the above disadvantages. It instead invites confusion with the NEMA 6-15 connectors.
The title text indicates that an equivalent for the 3-pronged NEMA 5-15P plug (a.k.a the Type B plug) for AC current could be created easily by incorporating a USB-B plug, which are small and square-shaped and could therefore function as the ground prong. There appears to be no reason to do this other than because both names contain the letter 'B'.
Unconventional uses for electric plugs are a recurring topic in xkcd (see 1293: Job Interview and 1395: Power Cord ). Combining them with USB was previously explored in 1406: Universal Converter Box among other combinations.
[A power cord like plug with two prongs is shown, but each prong is in the shape of USB-C connectors. Above is a title and below is a label.] Cursed Connectors #187 Dual USB-C


Flawed Data

Explanation:
This is another comic about what is the right or wrong way to perform research when data is not adequate.
In the first frame, Cueball presents a report on a poster (two graphs with data points and possible fitted curves), admitting that all of the data is actually flawed. He doesn't explain if it's contrary to some outcome or revelation, or perhaps a systematic error in the data-gathering process.
From there, three different reactions to this is displayed in order of how good a decision they make based on this realization.
Good
In the first scenario Cueball states they are no longer sure about the conclusions they had drawn from the flawed data. This is, of course, the scientifically appropriate decision. The less reliable data is, the less reliable the conclusions that can be drawn. Ideally, flawed data would be discarded altogether, but there are situations in which better data is not available, so a compromise may be to draw tentative conclusions, but make clear that those are uncertain, due to issues with the data.
Bad
In the second scenario Cueball then explains that after heavy manipulation ("doing a lot of math") of their flawed data, they decided they were actually fine. There are a number of methods that can be used to manipulate or "clean" data, with varying levels of complexity and reliability. Some of these methods may be valid in certain situations, but applying them after the initial analysis failed is highly suspect.  The likelihood, in such a case, is that the researchers tried different methods of data manipulation, one after another, until they found one that gave the results they wanted. This is clearly highly subject to the biases of the researchers (both conscious and unconscious) and is much less likely to result in accurate conclusions. Hence, this approach occurs in research more often than it should, and Randall is making clear that it's "bad".
Very bad
In the third and final scenario, Cueball explains that they scrapped all the flawed data. However, instead of trying to make some new data by correctly redoing research/measurements/tests, they instead trained an Artificial Intelligence (AI) to generate better data from nothing but a desire to match a target outcome. This is of course not real data, but just a simulation of data, selectively sieving statistical noise for desirable qualities. And since they are probably looking for a specific result, they are training the AI to generate data that supports this. This approach is "very bad", as it not only produces no useful science, but means that future researchers will be working from entirely artificial data. Doing so would be destructive to science and would be considered incredibly unethical in any research body or association. The only purpose of such a method would be to convince others that you'd proven something interesting, rather than determining what's true (and possibly gain some experience in AI programming). AI is a recurring theme on xkcd.
In the title text, the results from the very bad approach are mentioned and the fact that they got the data they were looking for is made clear when they state that We trained it to produce data that looked convincing, and we have to admit, the results look convincing! The AI was of course trained to provide data that looks convincing, which is why they are so convinced of the results.
[Cueball is pointing a stick at a poster hanging behind him while addressing an unseen audience. There are two graphs on the poster with data points and fitting curves.] Cueball: We realized all our data is flawed.
[The three next panels all have a label in a frame going over the top of each panels frame. The poster can no longer be seen in the rest of the panels. Cueball has taken the stick down.] Label: Good Cueball: ...So we're not sure about our conclusions.
[Cueball holds the pointer almost as in the first panel.] Label: Bad Cueball: ...So we did lots of math and then decided our data is actually fine.
[Cueball holds the pointer so it point upwards. Also he lifts his other hand a bit up.] Label: Very bad Cueball: ...So we trained an AI to generate better data.


Universal Seat Belt

Explanation:
This became the second installment in the series of Cursed Connectors and presents Cursed Connectors #65: The Universal Seat Belt. The series began two comics earlier with 2493: Dual USB-C (#187) and was followed three weeks later by 2503: Memo Spike Connector (#102).
The comic shows another of Randall's "Cursed Connectors", the "Universal Seat Belt " — a pun on the Universal Serial Bus ( USB ) connector — which would have the same abbreviation of USB.
USB connectors are mostly designed for free and unrestricted insertion and removal. There may be a slight use of the internal and external bumps and dimples to provide a tactile indication of being engaged or disengaged, but there are usually no facilities to prevent a connector being easily pulled out of even a port being actively used - the OS can do no more than complain that a device has been removed without first ensuring proper logical unmapping of the resource (which in turn may have to await a current session of data transfer being completed or aborted) or warn that a "delayed write" has failed.	 Anyone who has used USB in a frequently-jostled environment knows the connectors can't withstand much jerking around without their connection to their mainboard permanently failing.
Car seat-buckles, on the other hand, have very definite requirements to not come loose unless intentionally and mechanically released, in order to keep the passenger safely anchored to the seat.
The title text claims that the seat belt is secure in the case of a crash. This is another pun, as seat belts protect passengers in a car crash while USB standard is designed to protect the computer in the event of a device hardware malfunction.
Another similarity between seat-belts (especially on back seats) and USB-plugs is that they can be a bit fiddly to insert. A seat-belt lock with the asymmetric design of a USB-A plug would be even more fiddly and thus "cursed".
One possible use for the USB data connector might be to give a certain degree of 'proof' that the belt is plugged in, although that functionality is fairly well covered by current anchor-point sensors that (combined with seat-occupancy sensors that may respond to the weight of a seated person) can trigger dashboard lights and possibly warning sounds in vehicles as necessary to prompt correct usage of restraining belts. That system does not usually need an electronic data connection between anchor and belt, an anchor-side switch should suffice, and it would still require a mechanical gripping/hooking method to make it of any use to be engaged in the first place.
The USB specification is designed such that USB connectors fit snugly from pressure.  This means they usually need no button, like seatbelts have, to lock them in place.  If one hacks a USB connection to increase the tightness, so that it can withstand more force applied to it and still hold its function, it becomes much harder, or even impossible, to insert and remove.  Randall has removed the button, such that the connectors are a "cursed" misleading and dangerous use of similar form.
[The two ends of a seatbelt are shown next to each other, but the seatbelt connectors are replaced with a USB-A plug and port. Above is a title and below is a label.] Cursed Connectors #65 the Universal Seat Belt


Mine Captcha

Explanation:
This comic, like 1897: Self Driving , references the approach of using human-entered CAPTCHA inputs to solve machine learning problems, particularly those involving image classification.
In order to prevent automated programs from using web services, Google offers a protection called reCAPTCHA , which performs various tests to see if a user is human or machine. (One of these tests is a "I'm not a robot" checkbox which must be checked in order to proceed, although ticking the box is merely a formality, and later versions of reCAPTCHA can simply perform the tests quietly in the background without needing user consent).
If the reCAPTCHA system suspects that the user may be an automated bot, it presents an image recognition challenge that only humans should be able to pass. This has the desired effect of denying access to robots, but it also has a side benefit that the human input can be used to train Google's image recognition software. The challenge usually features a square grid of images, typically things one might see while driving - eg. "check all squares containing a STOP SIGN". If the user clicks the correct squares, they are permitted to continue.
Minesweeper , on the other hand, is a logic puzzle game in which the player is presented with a grid of unrevealed squares, and must deduce the location of mines that have been secretly hidden on random squares. The game provides clues by marking some squares with the number of mines (up to a maximum of 8) that are adjacent to that square; by carefully considering the possibilities, a player can deduce which squares must contain mines, and mark them with flags to avoid clicking on them. Revealing a mine loses the game.
In this comic, Randall combines the two concepts to create a "Mine Captcha", which is presented in the form of a reCAPTCHA challenge but actually appears to be a mini game of Minesweeper. (To be more precise, it is actually the opposite of regular Minesweeper, since the challenge invites the user to click on the mines - in Minesweeper, you are supposed to not click the mines. Furthermore, on its own terms it is unsolveable as a reCAPTCHA, since the user is asked to click on all pictures of mines. However, as in the real Minesweeper, there are no pictures of mines displayed (in Minesweeper, these only appear when the game is over). Taking the game as playable, however, in both cases you still need to know where the mines are, so it is still solved the same way).
A real-world Mine Captcha would be somewhat ineffective for a variety of reasons. Firstly, not every human would recognize a game of Minesweeper and therefore wouldn't understand what they are being asked to do. Even if they do recognize the game, they may not know the logical method for deducing the locations of mines. Additionally, even for skilled players, there is a trap in that the Captcha's objective is the reverse of regular Minesweeper; they might therefore get tripped up by muscle memory and click on something that is not a mine, which would fail the challenge.
Another issue is that games of Minesweeper can sometimes involve a degree of luck, as it is possible to generate a puzzle which does not give sufficient information to unambiguously deduce the location of every mine (Though this may not be a problem since Randall's Minesweeper is only a 4x4 grid). In these situations, the most a player can do is click the uncertain square and hope for the best. If the Mine Captcha is poorly implemented in this way, this would increase false negatives in human detection due to some humans failing the captcha purely due to bad luck. (Some variants attempt to eliminate this problem: Mine Detector , for example, is a variant game which provides better information, such that it's almost always solvable without guessing except at the highest difficulty level).
Finally, a Mine Captcha would actually be fairly easy for an artificial intelligence (AI) to solve, since it is a logic puzzle - as long as the AI can read the numbers, it can simply use an algorithm to eliminate all impossibilities until it has the correct answer. (Indeed, for a 4x4 grid, it's even easier than that; a computer could quickly brute-force the problem by trying every possible arrangement of mines until it has the correct one).
It seems that Randall predicted that an AI might try to solve the captcha itself, as he rendered each numeral in a different style; this is similar to obfuscation methods used in text-based captchas to prevent automatic text recognition software from reading the captcha. However, it would not be very effective in this case as the same numbers have the same color; an AI could simply recognize the color instead, which is even easier for an AI than trying to read a number.
The title text is similar to 1897: Self Driving where the CAPTCHA solver is asked to answer quickly, implying that the training data is actually a real-world situation being experienced by a self-driving vehicle at that very moment. The joke here is that real-life minefields do not have large numbers indicating which of the surrounding land contains mines [ citation needed ] .
Assuming that columns are denoted by letters A, B, C, D, left to right, and rows are denoted by 1, 2, 3, 4, top to bottom, one way to solve the captcha is as follows:
The leftmost red 3 at A3 is surrounded by four squares (A2, B2, B3, A4), of which we know three are mines. Therefore, one of these squares is not a mine. However, because of the blue 1 at B4, we know that only one of B3 and A4 can be a mine, otherwise, there would be more than one mine adjacent to B4; therefore, A2 and B2 must be mines. Otherwise, there could only be two total mines adjacent to A3.
Since A1 is a green 2 and is adjacent to two squares that we now know are mines (A2 and B2), this means that B1 is not a mine. If it was, there would be 3 adjacent mines to A1. Furthermore, since there is a blue 1 at C1, and we know that the adjacent B2 is a mine, this means that D1 and D2 are also not mines, since if any of them were, there would be more than one mine adjacent to C1.
We also know that C3 and C4 are not mines, since we already know that the blue 1 at B4 is next to exactly one mine (on either B3 or A4). Since this eliminates two of the three possible neighbors of the blue 1 at D4, this means that D3 must be a mine.
Finally, since we now know the locations of two of the mines around the red 3 at C2, and we have eliminated all other possibilities, B3 must be a mine. Therefore, the mines are at A2 , B2 , B3 , and D3 . This solves the puzzle.
[A Minesweeper game in a 4x4 grid is shown beneath a blue rectangle. There is an explanation in white text in the blue field:] To proceed, click all the pictures of Mines
[The Minesweeper field has six cells with revealed numbers on a light gray background. The other 10 fields are empty and dark gray. The three ones are blue, the single two are green and the two threes are red. On top of this each number is drawn in a different font/style. The ones changes how bold they are. The two is drawn in a 3D format, the one three is very thin and the other is drawn with two lines and no filling in between (hollow). The grid looks like this:]


Logic Gates

Explanation:
The comic lists logic gates . The first six are real but the last six are made up and get increasingly absurd. The names for these last six use the same letters and syllables as the first six so as to appear at a glance to be consistent with their naming conventions.
Some of the ways the gate parts are combined seemingly-impossibly can raise ideas in the mind of the reader of how quantum computing involves processing multiple possibilities at once, or how machine learning involves solving systems backward from their outputs to their inputs.  The names ring of calling more and more profoundly to some mythological catastrophe.
The only real-life logic gate that was omitted is the XNOR gate (short for "eXclusive Not OR"; it compares the inputs, and if and only if they are equal, it outputs true). Note that the "NORG XORT" gate would be logically equivalent to it, if it were tipped to match its uniquely XOR-style tail, since it would then be an XNOR gate with NOT on both inputs, a modification that has no ultimate effect on the logic as it merely switches the case of which exclusivity it needs to be, and does not care which version of same-input it might be responding to.
A double-NOT on an input would produce the identical output again (...if the input is not not true). Two NOTs preapplied to a (N)AND or (N)OR would produce the same output as a (further-)NOTed version of the (N)OR or (N)AND, conversely (...if not -1 and not -2 then this also means that neither 1 nor 2). Normally this would be shown, if necessary, as full NOT gates on the lead-in inputs but (see Transcript, below, and the NORG XORT description above) the shortcut element is occasionally used in further mix'n'match symbology (together with reinterpreting connectivity lines as partial shape-edges and vice-versa) in 'understandable' but definitely non-standard ways.
Along with the deliberate confusion of connector and shape-edge lines, directionality is also played with in several cases, with input 'ends' perhaps also at the (implied) output end and reversed sub-symbols implying a composite gate with substructural feedback or perhaps diode-rectification upon a bidirectional logic path.
Much like 2360: Common Star Types , as the list progresses, the names start to sound more like mythical creatures, closing with the "Norxondor gorgonax". As with the symbology, the names appear to be nonsensical recombinations of the standard ones (perhaps with off-subject inspirations, in some cases) but often do not match up with the symbolic (mis)use, such as an X in the name not implying/being implied by an XOR's unique drawn feature.
In the title text Randall claims that in the programming language C the multiocular O (ꙮ) character, an exotic glyph variant of the Cyrillic letter O, is used to represent the bitwise version of the last operator Norxondor gorgonax (presumably ꙮꙮ represents the non-bitwise version), fitting as the multiocular O is used to refer to "many-eyed seraphim " (angels) in some religious literature. Gorgons ( beige or otherwise) have heads covered with snakes instead of hair, and so possess multiple eyes, the most famous was known as Medusa (she was depicted in 1608: Hoverboard ).  The ꙮ character abstractly inspires ideas of great otherworldly demons like those of the Cthulhu mythos.
C is a low-level programming language, and as such, it has many operations that correspond to logical (i.e. bitwise) operations.  These contrast with operations that work in a non-bitwise way.  For example, "&&" is the non-bitwise "AND" operator that takes the operands as a whole, while "&" is the bitwise "AND" that combines the respective bits of its two inputs independently before spitting out the new single composite value the output bits represent. In non-bitwise operations, 0 always represents "FALSE", while any non-zero value means "TRUE" for inputs, and 1 is used to represent TRUE for outputs.  Thus, "14 && 3" gives the result 1: TRUE AND TRUE -> TRUE.  In the bitwise operation, using the same values, the decimal value 14 has the binary value 1110 and the decimal value 3 has the binary value 0011, and for this example we get:
[The comic shows a chart with twelve electronic logic gates arranged in three rows of four. Each gate is depicted as a schematic symbol, with a label underneath. Above them is a header:] Common logic gate symbols
[Here below follows a description of the 12 gates in the three rows, with their label given beneath each description:]
[A standard gate symbol used in real life. Two inputs on the left lead to the vertical left edge of a solid D-shaped symbol. From the right side of the D there is one output.] AND gate
[A standard gate symbol used in real life. Two inputs on the left lead to a convex-crescent left edge of a crescent-shaped symbol. The right side of the crescent symbol's shape forms a point at its output. From the right side of the crescent there is one output.] OR gate
[A standard gate symbol used in real life. One input leads to a triangular symbol pointing to the right. There is a small bubble symbol connected to the triangle on the output, which leads right.] NOT gate
[A standard gate symbol used in real life. This is identical to the OR GATE, except the output has a bubble attached, like the NOT GATE's output.) NOR gate
[A standard gate symbol used in real life. This is identical to the OR GATE, except the left-hand arc at the input has a double-stroked line.] XOR gate
[A standard gate symbol used in real life. This is identical to the AND GATE, except the output has a bubble attached, like the NOT GATE's output.] NAND gate
[An unusual symbol. This symbol has one input on the left leading to a convex-crescent left edge, like the OR GATE. The output side as a smooth crescent like the AND GATE but has two outputs.] NORX gate
[An unusual symbol. This symbol has two inputs on the left leading to a vertical left edge input, like the AND GATE. The output side has a convex-crescent double-stroked output like the mirror image of the XOR GATE's input. There are two outputs.] GAND ate
[An unusual symbol. This resembles the NOT GATE except there are two inputs instead of one leading into the left side.] XAND gort
[An unusual symbol. This has a double-stroked convex-crescent input like the XOR GATE, but the two inputs have bubbles attached. The single output has a smooth crescent shape with a bubble, like a NAND GATE.] NORG xort
[An unusual symbol. Two inputs lead to a convex-crescent edge, and the two lines of this symbol now enter a double-stroked convex-crescent input like the XOR GATE. The two lines of -this- symbol have bubbles placed half way across their horizontal length, and are presumably the outputs.] ANDORX gant
[An unusual symbol. The symbol is identical to the NOR GATE, except the upper and lower horizontal parts of the symbols hull have a NOT GATE placed on them - one pointing to the left on the upper line, and to the right on the lower line. There is one output to the symbol, with a bubble attached.] NORXONDOR gorgonax


Forest Walk

Explanation:
Megan is walking through a wide landscape with Beret Guy who owns a big part of it. Megan is surprised that he owns such a big property, however, Beret Guy is known for his inexplicable businesses such as in 1493: Meeting and from 1032: Networking ; we know he probably has enough resources to be able to buy it. Alternatively, he might have simply inherited it from his mom (see 502: Dark Flow ), or may not understand the concept of owning it. Nevertheless, he walks here every day, and from the context of the comic, it seems pretty much no one else comes here.
They meet a rather disheveled-looking bearded man hanging from a parachute caught in a tree. The man shakes a stick at them and demands to be helped down to the ground. Beret Guy simply addresses him as "Mister Cooper" and asks if he promises to return the money he took. The man angrily refuses, and Beret Guy casually says he'll see him again tomorrow, suggesting that this conversation has become a daily routine.
Megan asks if the man was D. B. Cooper, which Beret Guy immediately confirms. He then comments on an owl nest as another bit of "neat stuff" found on his land, suggesting that he finds Cooper's presence to be just another mildly interesting part of this land.
D. B. Cooper is the identity given to a man who hijacked a Boeing 727 aircraft in 1971. He collected a $200,000 ransom (equivalent to $1,250,000 in 2020) and famously donned a parachute and jumped from the plane over the state of Washington. He was never seen or heard from again. Despite lengthy FBI investigations and nationwide publicity, the hijacker was never identified. A few thousand dollars of the ransom money was found in a river, nearly 10 years after the hijacking, but the remainder has never been recovered. The only things known about him are a police composite drawing and the name "Dan Cooper", under which he had purchased his airline ticket (he was called "D.B." as a result of a miscommunication with the media, and the name stuck).
The high-profile case followed by the never-solved mystery has led to a massive amount of speculation as to his identity, background, and what became of him. Many consider the most likely scenario to be that he didn't survive the parachute jump, and simply crashed somewhere that his body was never found. Others imagine that he escaped with the money and simply managed to evade capture.
The comic is insinuating that, after leaping from the plane, he got entangled in a tree in Beret Guy's land, and has been there ever since.
Uncanny situations are nothing new to Beret Guy since he possesses many strange powers . Hence, the concept of a famous criminal hanging from a tree for nearly 50 years doesn't seem any more interesting to him than an owl's nest. In keeping with the typical bizarre-ness of Beret Guy's life, it isn't explained how a man could survive for half a century hanging from a tree, why he'd choose to remain trapped there for his entire life rather than return money that he's in no position to spend, or why Beret Guy wouldn't simply report his whereabouts to the police.  All of these are simply accepted as unremarkable realities of life, for him.
D. B. Cooper was already referenced by Randall in 1400: D.B. Cooper , 1501: Mysteries and 2452: Aviation Firsts .
The title text may refer to the linguist from 2390: Linguists who is more interested in the linguistic nuances that people use than in actually responding to their call for assistance. It is not known how many others have walked through Beret Guy's land, in the interim, or whether it is their nature or the general aura from Beret Guy, but the linguist did not much more than ponder the phrase "help me down". Megan also seems in no particular hurry to intervene.
[Megan and Beret Guy are walking through a landscape with spread-out trees and grass and puddles on the ground.] Megan: Wow, this is all yours? Beret Guy: Yeah! All the way back to the river! Beret Guy: I walk here every day.
[Megan still walks towards Beret Guy who has now stopped and is looking up while speaking to a man hanging in a tree in front of them. The man has long wild hair and a large beard. He hangs from his parachute which has been folded around a large branch sticking out from beneath the top of the tree. He is holding a long stick of some sort, seemingly attempting to threaten Beret Guy, as the stick and his legs are vibrating as indicated with small lines.] Beret Guy: Morning, Mister Cooper! Cooper: You help me down this instant!
[Pan down to show only Beret Guy and nothing else. Cooper replies from off-panel from the top corner.] Beret Guy: Do you promise to give back all the money you took? Cooper [off-panel]: Never! Beret Guy: Okay! See you tomorrow!
[Megan and Beret Guy continue walking through the landscape with three small trees behind them, as well as grass, rocks, and a small puddle. Megan looks back over her shoulder towards where Cooper is hanging.] Megan: Was that D.B. Cooper? Beret Guy: Yeah, and up ahead there's an owl nest! Beret Guy: There's so much neat stuff here.


Abandonment Function

Explanation:
This is another one of Randall's Tips , this time a Tech Tip.
Pet abandonment is a situation of concern among biological pets, and is part of the reason there are animal rescue organizations providing for adoption in most regions.  Since drones are automated, they can be programmed to have an automatic abandonment function.
In reality, this "abandonment function" is the norm that things left outside homes are often considered gifts for any passersby who would like them.  Hence, following the instructions in the webcomic may result in one's drone disappearing for a new owner, but not for the reason depicted.
With the drone responsible for flying to find its own new owner, one can possibly imagine it becoming more and more "fervent" as its charge runs down, to prevent the accumulation of derelict drones in the streets.
Triggering abandonment based on extended close proximity to the device's own controller could produce issues such as accidental activation, or malicious activation by a party who could send the proximity signal from a great distance, possibly to many drones at once, via software defined radio . It is, however, more likely that being left consciously uncontrolled for an extended period is the actual trigger, with the attachment of the controller being more a direct courtesy to the next adoptive-owner, and/or preventing the loss of carrier signal that would instead activate whatever auto-homing (i.e. return-to-launch-point) behavior the more sophisticated drones may use if ever beyond their pre-programmed flight parameters.
The concept of there being "wild" vs "domesticated" drones rings again both of wildlife and pets, and of new intelligent software providing for drones acting on their own.  In the latter case, protection for "wild" drones could imply many things about the role of artificial intelligence in society.  Did we organize the wild drones to obey our laws, or are we protecting them in fear of being punished by their superior power? A foreign military drone could also be considered a wild drone.
But more likely Randall is imagining flocks of abandoned drones, fending for themselves, traveling distances as they survive off of seasonally-dependent charging resources.  This is similar to the behavior of birds, which are protected (in the U.S.) by the real-world Migratory Bird Treaty Act of 1918 . Aggressive flocks of drones was used in 1630: Quadcopter and drones has become a recurring theme on xkcd, where also training of drones as a pet has been the subject in 1881: Drone Training .
This idea of protecting drones is analogous to the anomaly that misbehaving drones have not been well tracked by law enforcement: https://observer.com/2020/01/drone-flock-mystery-baffling-authorities/ .  If computer viruses continue to evolve, wild drones could indeed evolve too, as they are directed by software, but usually a human being or organization is considered to be somewhere at the helm (separately) of both computer viruses and drones.
The idea that a drone may choose of its own volition whether to find a new owner or join a wild flock is a little similar to the situation for abandoned pets.
[A multi-Rotor drone is seen flying though the air from left to right. Tied below the drones main body is the drone's own remote controller. Movement lines behind drone indicate a wavery flight path. A voice emanates from the drone:] Drone: Hi, I'm yours now! Please charge me! Drone: Hi, I'm yours now! Please charge me!
[Caption below the panel:] Tech Tip: If you ever get tired of a toy drone, tie the controller to it and set it outside. Its abandonment function will activate and it will find a new home.


Global Temperature Over My Lifetime

Explanation:
This is Randall Munroe in his role as a meticulous, conscientious presenter of scientific data.  The activities shown in Randall's lifeline, whether learning to ride a bike or even getting married, pale into insignificance when the consequences of unprecedented global average temperature rise are understood and accepted.  In particular, he shows that back in 1982, two years before Randall was born, Exxon wrote an internal report predicting the rise of global temperatures due to fossil fuel use, and 40 years later their prediction (shown as the X in a circle at the top-right) is being shown to be right on track. Unfortunately, that report was hidden and not seen until much later, and the world has been slow to respond with the urgency needed to reverse the damage being done to the planet.
The Wikipedia article global temperature record has some telling graphs to supplement Randall's.  This one: Global Average Temperature is the global average temperature change for the modern era, since data started being collected regularly in 1850.  This one: 2000 Year Temperature Comparison reconstructs 2000 years of temperatures.
And this comic is a small segment of another comic 1732: Earth Temperature Timeline .
The comic itself links to the referenced Exxon document about CO2 emissions .
The comic was published on the same day that the U.N. Intergovernmental Panel on Climate Change released its 2021 Assessment Report
One of the entries is I somehow graduate despite spending most of my time playing Mario Kart. Mario Kart is a popular video game series developed by Nintendo , and has been a recurring theme on xkcd. Hewing close to the comic's timeline, 127: The Fast and the Furious , which contains an early Mario Kart joke, was released in July 2006.
The title text refers to the fact that Exxon, being a fossil fuel company, is likely to make better predictions on fossil fuel use as they are involved in fossil fuel production themselves.
Graph of temperature over time, titled:
"Global average temperature
Over my lifetime
(60-month running june average, NOAA NCEI time series)"
The X axis is in years, going from 1980 to a little after 2020. Each decade is marked.
The Y axis in in °C, with the "20th century average" at the bottom, up to +1°C (from the average), labelled every 0.2°C.
Certain points and periods on the graph are marked and contain descriptions of events and actions that occurred in Randall's life.

November 1982 Exxon International report predicts that fossil fuel use will raise global temperatures to about 1°C above their normal levels within 40 years October 1984 I’m born in Easton, PA Summer 1991 I learn to ride a bike Spring 1992 My elementary school celebrates Earth Day and I learn about the greenhouse effect 1993-1996 I get very into Star Wars and Animorphs Fall 1996 I stand around awkwardly at my first middle school dance Spring 2002 I get accepted into college Spring 2006 I somehow graduate despite spending most of my time playing Mario Kart Summer 2006 I see An Inconvenient Truth in the theater and feel anxious Fall 2011 I get married Summer 2012 I read headlines about a global warning “pause” and hope that maybe things aren’t so bad 2013-2021 I read more about climate science and get steadily more alarmed Spring 2016 I read the 1982 Exxon report June 2020 Global 60-month average reaches +0.94°C, Easton, PA is 2°C hotter than normal for the fifth year in a row Today (no description) 2022 (near future) [Large X within a circle] 1982 Exxon Prediction


Average Familiarity

Explanation:
This comic claims that experts vastly overestimate how familiar other people are with their own field of study. As an example, Randall shows a conversation between Ponytail and Cueball as two geochemists specializing in silicate chemistry. Although the two scientists understand that the layman does not know all that they know about silicates, they are still under the impression that other people at least know the chemical makeup of olivine and some feldspars . Cueball also mentions quartz , an even simpler mineral taken for granted by Ponytail.
In truth, the average person can't be expected to know the chemical makeup of any arbitrarily-chosen substance reliably (or any material at all), if that average person's job and hobby do not involve chemistry — aside from the few that made their way into common knowledge , like NaCl for salt [1] (sodium chloride or halite in mineral form), H 2 O for water (facetiously known as dihydrogen monoxide, ice in mineral form), or CO 2 for carbon dioxide (while most people are more familiar with its gaseous form, it is also used in mineral form as dry ice ), and may not even know the definition of "feldspar" beyond "a mineral", if at all.
It even goes so far as to initially gloss over the 'everyday' knowledge of quartz... until prompted by the slightly-less-overestimating partner in the conversation. Perhaps like a gardener forgetting to mention the lawn he maintains (along with the 'actual' plants in the borders or vegetable patches), there seemed no need to include such a common mineral as a subject of silicate chemistry. Quartz is a basic silicon oxide (SiO 2 ) that many non-chemists have heard of because it is common and has a variety of uses, though they would not know its chemical structure. Quartz can be found as distinct large-scale crystals (probably obvious to the layman, as an ice-cube is in a drink) but also features as a hard-wearing micro-constituent of many rocks. Quartz is a major component of most sand (except for coral sands, which are calcium carbonates).  Quartz crystals are sometimes made into jewelry and other decorative objects. Most modern clocks use the resonance frequency of quartz to keep time.
Minerals like feldspars and olivine generally exist as a continuum of varying chemical formulas, represented as a mixture of "endmembers" that have some pure composition. Feldspars are a category of aluminum-containing silicate minerals that account for the most of the rock in the earth's crust by mass. They are composed of a silicon-aluminum-oxygen lattice filled with sodium, potassium, or calcium ions. The major varieties are CaAl 2 Si 2 O 8 (anorthite), NaAlSi 3 O 8 (albite), and KAlSi 3 O 8 (potassium feldspar). Olivine is most notable as being the primary constituent of the upper mantle and commonly found in stony meteorites, and has the formula X 2+ 2 SiO 4 , where X is any iron or magnesium ion. The ends of the spectrum are Mg 2 SiO 4 ( forsterite ) and Fe 2 SiO 4 ( fayalite ).
In the title text the two geologists express belief that the average person should be more familiar with silicates because of how ubiquitous they are. Their somewhat-exasperated statement plays on the phrase "you can't throw a rock without hitting one," a standard hyperbole about how common something is. Indeed, silicate rocks are extremely common on Earth — not only would a rock thrown in a random direction stand a decent chance of striking a silicate mineral rock, but the rock being thrown also has a very high chance of being a silicate mineral rock. With the exception of a few carbonate deposits, rocks found in large deposits on Earth's surface nearly all have silica in them, even extraterrestrial rocks. The Earth's crust is about 60% silica by weight. [2]
[Ponytail and Cueball are talking. Ponytail has her hand raised, palm up, towards Cueball.] Ponytail: Silicate chemistry is second nature to us geochemists, so it's easy to forget that the average person probably only knows the formulas for olivine and one or two feldspars. Cueball: And quartz, of course. Ponytail: Of course.
[Caption below the panel] Even when they're trying to compensate for it, experts in anything wildly overestimate the average person's familiarity with their field.


Every Data Table

Explanation:
This comic is another entry in a series of comics related to the COVID-19 pandemic .
It shows a future data table with one entry for each year from 2017 to 2024, so this table is made at least three years after publication of the comic (presuming it does not depict some form of advanced estimation of trends). The only discernable differences across the eight years are that two years have footnotes as in 2020* and 2021 † , whereas the other six years have not.
Sometimes a symbol such as an asterisk (*) or a dagger (†, also called an obelus or obelisk) is used to denote an unusual entry in a table to be explained in a footnote with a matching symbol.
The COVID pandemic has had a large impact on the entire world and one way this can be seen is through strange stats resulting from the effects of the pandemic, at least in 2020 and 2021, the years marked with footnote in the data table. Various statistics such as employment statistics, spending power, holiday miles, pet ownership, births (or at least conceptions), and — naturally — deaths may have been either grossly suppressed/increased for the majority of 2020, and for 2021 may have hardly recovered, partially recovered, renormalized, bounced back with a vengeance or be over-compensated for in the effort to catch up.
Thus Randall concludes that every data table will look like this one from now on, hence the title of the comic.
In the title text Randall states that he hopes 2022 is relatively normal. Comically, he doesn't mainly hope for this because he wants the Covid-19 pandemic to end, but rather because he doesn't know what symbol is used after the asterisk and the cross.
It is hard to know what 2022 might be like. Nothing (at the time of this comic being published in August 2021) is exactly back to normal and proper recovery or the resulting compensatory readjustment may not have concluded in time for 2022 to reflect the trends expected based upon pre-2020 figures, and the additional further years that future statistics will record.
Common symbols that are used if the first two are taken include multiple symbols (such as †† or ***), or a series of further single-symbols such as the convention to use a double dagger (‡), the section symbol/silcrow (§), the parallel/double-pipe (‖) and the paragraph symbol/pilcrow (¶). Alternately you could just start and continue the series with superscript numbers (¹, ², ³ ...), especially when you discover a need to frequently clarify multiple and/or nested footnotes on each page, or save up a whole chapter of many such references to present them as 'endnotes', upon entirely different pages from the text being referenced.
Unrelated to the usage as English footnote characters, the asterisk and dagger symbol are used in German mainly as the shorthand genealogic signs to express "born" and "died" respectively (e.g. in encyclopaedias, as the German terms are three-syllable words for both and need to be shortened), so a person that is 2020(*) and 2021(†) would have been alive for only about a year, depending on the months. This symbology is also used on some tomb stones. An optimistic view is the "birth" and "death" of the Coronavirus itself, which would also understandably result in uncertainty on the next symbol in this order, for 2022. Pessimists in this context might suggest to use ∞, which is the symbol for infinity.
Similarly, in biology, species (or genus, etc...) that are possibly extinct are indicated with an asterisk and dagger is used to note the possible extinction (double asterisks indicate taxa believed to be extinct in the wild but known to be extant in cultivation). This of course do not fit well with the Covid-19, which is not close to extinction, and it is also not about to cause the extinction of humans.
Randall, however, seems to have forgotten the potential monkey's paw nature of his wish. 'Relative' requires a comparison between things. It could well be that the whole fall-out of the pandemic becomes the new normal, and future years have no necessity to use symbols to explain how those years come to be like everyone knows they are, while dates before 2020 will be entirely understood as the old-normal. Only 2020 and 2021 may need contextual clarifying, due to the necessary transition/limbo between the earlier unaffected and later fully-adapted scenarios.
[A data table is shown with eight years given. After each year is seven dots. At the end of these dots are unreadable text/scribbles. The table is slanted compared to the panel, so the top year is in the top left corner, partly obscured by the panel, and the dots end at the edge of the panel, so only very small part of the scribles are seen (resembling an eight dot). And at the bottom the year is close to the middle of the panel, but most of the year is below the panel, and only the last three dots are visible. Two years have symbols indicating an unseen footnote.] 2017....... 2018....... 2019....... 2020*...... 2021 † ....... 2022....... 2023....... 2024.......
[Caption below the panel:] Every data table from now on