Chemistry Nobel

Explanation:
The periodic table of the elements is a display which arranges all of the 118 ( currently ) known chemical elements by atomic number and sorts them into columns such that each column contains a group of elements displaying similar chemical properties. The original version of this table was developed by Russian chemist Dmitri Mendeleev in 1869, when he realized that certain properties repeated periodically as elements became more massive. Notably, this system left obvious gaps at the top of the table. Mendeleev correctly predicted that some of these gaps represented elements that had not been discovered yet, and even predicted their properties based on the patterns in the table. The later discovery of those elements (including germanium and gallium) helped validate Mendeleev's work. Other gaps, however, were not due to undiscovered elements, but merely resulted from the properties of electron orbitals in atoms: upper rows of the table represent orbitals with fewer possible electrons and hence fewer elements, so displaying the lower rows properly below the upper ones leaves gaps in the upper rows. In other words, elements could not actually exist in these spaces, spaces which only existed in the realm of human bookkeeping. The joke of this comic is that it treats these gaps as if they represented elements that hadn't been discovered yet. Ponytail and her team have won the Nobel Prize in Chemistry merely by looking for and finding these elements. She expresses surprise that no one else had thought of such a simple direction for research.
By definition, each element has one more proton than the previous element - so element 1, hydrogen, has one proton in the nucleus, while element 2, helium, has two protons in the nucleus. The periodic table represents elements in their atomic form, where there are an equal number of protons and electrons (as opposed to an ionized form where they are unequal), so the structure of the periodic table is based on the structure of the "orbitals" that electrons fall into.
The first row of the periodic table has elements whose electrons only have an "s orbital" (at least when the electrons are in their ground state, which is the non-excited state that they are normally in). There is only one s orbital in each row, and an s orbital only has room for two electrons, so there are only two elements in the first row. The Pauli exclusion principle, mentioned in xkcd 658, means that only two electrons can be in each orbital. The second row of the periodic table contains elements with only s and p orbitals. As mentioned, there is only one s orbital at each "level" of orbital, with each level basically corresponding to a row, but there are three p orbitals at each level, so there can be four total pairs of elements in the second row, for eight total elements in the second row. (You can see that level one has a total of 1^2 orbitals, or 1 orbital, while level two has 2^2 orbitals, or 4 orbitals.) After p orbitals, the next type of orbital that can exist at higher levels is a d orbital. For levels that have a d orbital, there are five d orbitals at each level. Beginning with the fourth row, you can see elements whose highest-energy electrons are in an s orbital (the first two columns), a p orbital (the last six columns), or a d orbital (the middle ten columns). The d orbitals for row four are actually classified as the 3d orbitals (meaning they belong to level three), but because they have higher energy than the 4s orbital, they are put on the fourth row. The "aufbau principle" says that electrons fill the lowest energy orbitals first, which means that level one orbitals get filled before level two orbitals, which get filled before level three orbitals, and that within each level the s orbitals get filled before the p orbitals. So, there are two columns on the periodic table for each orbital - although helium is put in the far right instead of in the second row with the other elements whose highest electron is the second one in an s orbital, because putting it on the far right shows that helium is stable like the other "noble gases" in the far right row.
The final type of orbital that exists as the ground state for a known element is the f orbital, but almost all periodic tables show the elements with their highest electrons in an f orbital - the lanthanides and actinides that are mentioned in the title text and described below - in rows below the table, to prevent the table from becoming too wide to print easily.
The comic is based on the joke that somehow every physicist and chemist for generations somehow missed that there are actually p and d orbitals at levels one and two, and so it shows the empty space in the columns corresponding to the p and d orbitals in level one and the d orbitals in level two being filled with undiscovered elements. In reality, there are no p or d orbitals at the first level and no d orbital at the second level, due to quantum mechanics (involving the possible values of something called the quantum n, l, m, and s numbers, where n is the level and l determines whether is an s, p, d, or f orbital). The comic also shows a line of d orbital elements in the third row, even though the 3d orbitals are already represented in the fourth row (where they are placed due to having higher energy than the level 4 s orbitals). The Pauli exclusion principle has been known since 1925, and Mendeleev (mentioned in xckd 965) developed the structure of the periodic table in 1863 to describe the structure of the known elements, so the idea that such a basic thing as more elements in the early rows that had never been discovered by any chemist ever would be quite surprising. In reality, the elements toward the top of the periodic table that are known to be naturally occurring were generally discovered earlier, while all the most recently discovered elements are higher-numbered elements lower down on the table that are very short-lived before they undergo radioactive decay to another element and have never been seen to be naturally occurring.
The lanthanides and actinides mentioned in the title text are series of elements with higher atomic numbers that have electrons in orbitals that no previous elements have, and thus occupy columns of the periodic table that don't exist for lower-numbered elements. Sometimes these elements are displayed in the table , a format that corresponds with their actual orbital structure; this format is too wide for most display media, thus the lanthanides and actinides are separated out and displayed "floating" beneath the rest of the periodic table. The title text jokes that these floating series of elements are actually surrounded by actual elements.
In real life, the 2019 Nobel Prize in Chemistry was awarded to John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino for their work in the development of lithium-ion batteries; it was announced on October 9, just a few days before this comic was published, so the chemistry Nobel Prize was in the news.
[Ponytail stands in front of an image with a white section in the shape of the 7 rows of the periodic table  of the elements, but without the two rows usually shown beneath with the lanthanides and actinides. The “empty” sections at the top of the table are filled with three rows of dotted boxes, 16 boxes in the top row and two rows with 10 boxes each, shifted one right from the top row. Ponytail points to this area with a pointer while she looks and gestures towards an off-panel audience.] Ponytail: I don't know why no one else thought to look here.
[Caption below the panel]: The 2019 Nobel Prize in Chemistry went to the team that discovered the elements in the big gap at the top of the periodic table.


FacultyStudent Ratio

Explanation:
Universities are often rated in various ways to help students/parents pick which one to attend. This comic satirizes the very real culture of schools modifying their actions to artificially inflate their ratings. One metric used in ratings is the ratio between the number of faculty members to the number of students . Typically this is expressed as the student-teacher ratio, which normally determines how much time teachers get to spend with individual students. The lower the ratio, i.e., the fewer students per teacher, the smaller classes teachers have to teach, and thus the more attention the teachers can give to each student. However, having many more teachers than student(s), as in this comic, is not very beneficial to the student(s). (For context for international readers, high student-teacher ratios are common and expected in the United States, Randall's home country, whereas some nations especially in Asia sometimes report much lower ratios, often close to 1:1 in some areas.)
Another metric commonly used to measure a college's exclusivity and therefore prestige is the college's rejection rate; more prestigious schools get more applicants, and since they can accept only a limited number, they must reject many. Less prestigious schools often accept a higher fraction of their applicants, but some schools will reject students whose test scores, résumé, etc. are much higher than average for the school since it's likely that college is a "safety school" and the student won't actually go there. This rejection can decrease the school's acceptance rate and make it appear more prestigious. However, if the above-average student does want to attend that school, they are unable to, even though it would be good for both the college and the student.
For-profit universities and diploma mills may use techniques like this to artificially boost their ratings or use fabricated metrics and accreditation mills to give an inflated appearance of value. Predatory publishers and conferences are other techniques used to inflate the perceived value of a school or to pad curriculum vitae.
In the title text, other metrics are skewed in the school's favor:
[Cueball is sitting hunched over a desk writing while ten people crowd around him, five on each side, all leaning towards him. On the left side, they are Hairbun, a Cueball-like man, Hairy, Megan - who speaks, and another Cueball-like man. On the right are Ponytail, a third Cueball-like man, another Megan-like woman, Blondie, and finally a fourth Cueball-like man.] Megan: How's the work going? Cueball: Can you all at least stand back a little?
[Caption below the panel]: My school tried to game the ratings by having a 30:1 faculty:student ratio


Percent Milkfat

Explanation:
While cow milk contains a variable amount of fat (about 4.2%), whole milk from the store generally contains about 3.5% milkfat by weight according to the comic and some sources; other sources list similar but not identical numbers such as 3.25%.
Dairies commonly sell whole milk as well as products with less fat produced by removing milkfat. In the United States , there are three common products with less fat: 2% or "reduced fat" milk, 1% or "lowfat" milk, and "fat-free" or "skim" milk with 0 to 0.5% milkfat.
Since whole milk is labeled as "whole" milk and not as "3.5% milk," one might naively assume that whole milk is 100% milkfat, although this is not the case; 100% would be a product which is entirely milkfat (also known as butterfat), such as clarified butter or ghee. In milk, the remainder is mainly water along with proteins, lactose (a sugar), and other substances.
The comic analogizes this difference to the fact that physicists believe that "ordinary" matter constitutes only 5% of the actual mass-energy of the universe. Scientists predict the existence of another kind of matter known as " dark matter ," invisible to our current instruments but exerting gravitational force on ordinary matter, which would constitute 85% of total matter and 27% of the universe's mass-energy, with the remainder an even less detectable and more mysterious " dark energy " accounting for the increasing speed of expansion of the universe .
Ponytail uses these quantities to "explain" the "missing" percentage in whole milk between the actual 3.5% and a potential 100% "whole." She actually uses the 27% as mentioned above for dark matter. She thus indicates that dark energy takes up the remaining 69.5% of the whole milk.
Ponytail is assuming that dark matter and dark energy are distributed uniformly throughout all pockets of the universe, no matter how small. This assumption is common in statistics and may have seemed appropriate since no one knows the proportion of dark matter or dark energy of an object as small as a milk carton (though a more sensible argument is that all matter is accounted for when considering the milk and the carton; no additional "dark" matter is necessary to explain the weight of the milk carton).
Cosmologists are working to better understand dark energy or another reason for the universe's accelerating expansion. The title text supposes that both cosmologists and the Food and Drug Administration (FDA), which regulates milk and other food items in the United States, are trying to understand the dark energy of the whole milk. In real life, the work of cosmologists and FDA scientists does not overlap at all. [ citation needed ]
Dark energy was recently mentioned in 2113: Physics Suppression , but before that milkfat and dark energy were actually mentioned in the same sentence in 2063: Carnot Cycle from almost a year before this comic, so the idea behind this comic is not new for Randall. Dark matter was mentioned back in 1758: Astrophysics .
[Ponytail, raising her palm, and Cueball are talking.] Ponytail: "2% milk" is 2% milkfat. But "whole milk" isn't 100% milkfat–it's 3.5%. Cueball: Weird. What's the rest of it? Ponytail: About 27% is dark matter. The remainder is dark energy.


53 Cards

Explanation:
In this comic, Cueball claims that he has found a way to manipulate a 52-card deck into a 53-card deck by shuffling and rearranging the cards, presenting a complex-looking diagram to support his claim. Ponytail naturally disputes the claim immediately, which Cueball counters by challenging Ponytail to prove that his math is wrong.
The comic is a satire of the way that conversations tend to go between physicists and perpetual motion enthusiasts (or cranks in general). Perpetual motion is the idea that it could be possible for a mechanical system to work indefinitely without any external input of energy. The laws of thermodynamics absolutely prohibit this, so the only way that this could be possible is if the laws of thermodynamics are wrong. Unfortunately, the laws of thermodynamics are some of the most foundational and well-tested laws in science, so perpetual motion is considered to be a pseudoscience , pursued only by ignorant or quixotic cranks.
One of the things that you could do with a perpetual motion machine is to violate the law of conservation of energy - that is, you could create free energy out of nothing, simply by building a mechanical device. This is likely what Randall is satirizing with the idea of a process that can generate an extra card out of nowhere - it makes no physical sense, but nonetheless Cueball is convinced that he has found a way to do it.
A common defense employed by pseudoscientists, when challenged on their ideas, is to issue a counter-challenge and demand people prove them wrong, as Cueball does in this comic. This is a fallacious line of argument, since the fact that Ponytail cannot prove Cueball wrong does not mean that he is right. Nonetheless, this aggressive defense often works to discourage argument, since it takes far less effort to make a claim than to refute it.
Possibly, Cueball's plan involves usage of the Banach-Tarski paradox , a mathematical theorem which describes a method of "dismantling" a solid sphere, rearranging the component pieces, and reassembling them into two solid spheres identical to the original. This is only possible in a mathematical ideal case, because the "component pieces" are actually collections of infinitely many disjoint points; such a procedure cannot be performed in physical reality. Cueball's operations of shuffling and rearranging are analogous to the operations used in the Banach-Tarski operation, which involves only moving and rotating the component pieces without changing their shape. The Banach-Tarski paradox was also referenced in 804: Pumpkin Carving .
In the title text, Ponytail responds to Cueball's challenge with snark, claiming that the most obvious error is the fact that the formula's result is "53". The implication is that his math results in the wrong answer , which is proof that the calculations must contain errors.  This, of course, starts with the assumption that Cueball's claimed result is impossible, rather than attempting to find the flaws in his specific method. Because most people would conclude, by basic physical reasoning, that merely shuffling and rearranging a deck of cards cannot increase the number of cards in the deck, that feels like a safe assumption. By analogy, increasing the amount of energy in a system only by moving and transferring energy should be equally impossible, on its face.
[Cueball and Ponytail are standing next to a flowchart, with Cueball gesturing to it.]: Cueball: I've found a way to turn a 52-card deck into 53 cards by shuffling and rearranging them. Ponytail: No, you haven't. Cueball: How do you know?! I challenge you to find an error in my math!
[The flow chart consist of 15 boxes of different sizes, connected with arrows. In four of them (top, bottom and two in the middle) a deck of card is shown. Next to the top and bottom a number is written, near the other two, which are the only round boxes, numbers are shown in one of the nearby boxes instead. Beneath the top box there are two boxes with readable text. The other 7 boxes, without numbers or card decks have unreadable text. From top to bottom are the readable content:] 52 Shuffle Cut 21 38 53
[Caption below the panel]: Every conversation between a physicist and a perpetual motion enthusiast.


Wardrobe

Explanation:
Megan leaves Cueball outside while she goes into a wardrobe to consult with Tumnus on the pressing question if Narnia is part of the EU. It turns out they have joined (some time after the UK joined), which makes Megan complain about another border to deal with. And Cueball waiting outside goes looking for a lock for the wardrobe door.
This comic references The Chronicles of Narnia , a series of children's fantasy books by C.S. Lewis (some of which were later made into movies , plays, and TV and radio shows) about a group of children from England who travel to a magical land called Narnia. In the first book of the series (by publication date), The Lion, the Witch, and the Wardrobe , Narnia is accessible through a wardrobe in a residence in the English countryside. Mr. Tumnus is a faun in Narnia and the first character that the first human visitor, Lucy Pevensie , meets on her first trip through the wardrobe portal. Referencing Narnia is a recurring theme in xkcd. Tumnus was depicted in the first comic to reference Narnia: 665: Prudence .
The comic also makes reference to membership in the European Union . The United Kingdom (UK) is a member of the EU at the time of this comic, but narrowly voted via public referendum in 2016 to exit the EU (a process commonly referred to as Brexit , portamanteau for Britain/British and exit), but working out the details of this separation has proven more complicated than the simple in/out vote implied.
Narnia applying to join the EU shortly after the UK, as referred to in the title text, would theoretically be possible, even if only The Lion, the Witch and the Wardrobe was considered, since the UK joined the EU in 1973, whereas the wardrobe entrance to Narnia was discovered during World War 2, therefore in the period between 1939 and 1945. However, they would most likely be rejected due to not technically existing in Europe and having a monarchy government (EU membership requires a stable democracy).
One of the major issues with Brexit was the border between Northern Ireland and the Republic of Ireland . The two countries share the island of Ireland , but Northern Ireland is part of the UK while the Republic is an independent country which remains part of the EU. If the UK exit the EU, it would have different customs regulations than the Republic of Ireland, and there would need to be some kind of customs border.  The most obvious solution would be to establish a controlled land border between the two countries, but this would raise some serious difficulties and dangers.
Northern Ireland has had a long history of civil unrest and ethno-nationalist conflict. The most recent period of conflict, commonly referred to as The Troubles , resulted in over 3000 deaths between 1969 and 1998. In 1998, the UK and Ireland entered into a treaty, known as the Good Friday Agreement (overwhelmingly approved by referendums in both parts of Ireland). This treaty was intended to resolve many of the issues that drove the conflict, and has largely been successful in putting a stop to the violence. One of the agreements in the treaty was a totally open border between the two parts of Ireland. As both were in the EU, this was easily done, because they already shared a customs union. Over the following two decades, the ease of transit created major trade links between the two areas, and many people lived in one country and worked in the other. In the UK Brexit referendum, a majority of Northern Ireland voters voted to remain in the EU. Placing a hard border between the two countries would create major economic disruptions, and serious hardships for people living near the border. It would also undermine the intent of the Good Friday Agreement, which could lead to terrorist attacks and the rekindling of hostilities. The Irish government raised this issue from the time Brexit was first proposed, but their warnings were not fully heeded.
The alternative to this border would be to maintain open borders between Northern Ireland and the Republic of Ireland, but institute customs checks between the island of Ireland and the United Kingdom.  In October 2019, Boris Johnson, British Prime Minister, negotiated a Brexit deal with the EU that included this arrangement
While the Northern Ireland/Republic of Ireland border issue has received the most attention, the UK has land borders with two other EU countries. The UK territory of Gibraltar shares a border with Spain. There are also two Sovereign Bases Areas that share a border with the Republic of Cyprus.
The portal in the wardrobe represents another border of the UK, namely the border between England and Narnia. This 'border', of course, exists only in fiction, but the joke here is that it must be dealt with in the Brexit negotiations, further complicating an already messy situation. [ citation needed ] A further source of implicit humor is the juxtaposition of a fantasy children's tale about the magical land of Narnia with the highly contentious, political, adult world of Brexit.
Cueball suggests solving the situation by simply locking the wardrobe (which was never very accessible, even in The Chronicles of Narnia ), effectively isolating the UK from Narnia and making the border problem moot. This wouldn't work even in the fictional world of the books, as new ways to enter Narnia pop up in every book, although most of them are accessible only to the kids from the first book and their friends.
The title text references the amount of time it has taken to complete the Brexit negotiations, currently three-plus years and counting. The negotiators have set a series of deadlines to complete the negotiations, but have repeatedly had to extend those deadlines because they haven't reached any agreement. The comic was posted roughly one week before the then-current Brexit deadline of Oct. 31, 2019.  However it was already expected that that deadline too would probably be extended . In The Chronicles of Narnia , time moves inconsistently in Narnia compared to Earth, usually passing more rapidly in Narnia than on Earth. Lucy Pevensie and her siblings enter the wardrobe as children, have extensive adventures in Narnia lasting many years, and then return to Earth to find that they are children again and that only a few minutes have passed. The suggestion here is that holding the slow, complex Brexit negotiations in Narnia would take relatively little time on Earth, and the whole affair could be completed in time for the deadline.
A punchline similar to the title text, where the slower passing of time was used to take on time-intensive real world problems, was also used for one of the comics in 821: Five-Minute Comics: Part 3 . The time difference was also mentioned in the title text of 1786: Trash .
[Megan is entering into an open wardrobe, while Cueball stands outside.] Megan: I'll go ask. Megan: You wait here.
[Cueball stands outside the now-closed wardrobe.]
[In a frame-less panel Cueball keeps standing outside the closed wardrobe with voices heard from inside the wardrobe. The characters talking are inferred from the context.] Mr. Tumnus (from inside wardrobe): Halt! Who goes there? Megan (from inside wardrobe): Hey Tumnus. Quick question. Mr. Tumnus (from inside wardrobe):  Yes?
[Cueball is walking away from the closed wardrobe. Voices can still be heard from inside the wardrobe.] Megan (from inside wardrobe):  Is Narnia in the E.U.? Mr. Tumnus (from inside wardrobe): Yes, we joined after you did. Megan (from inside wardrobe):  Oh great, another border to deal with. Cueball: I'll go find a lock for the door.


Earthquake Early Warnings

Explanation:
A week before this comic, on October 17th, California introduced an earthquake warning system in the form of an app for smartphones called MyShake .
The system works through a network of sensors across the state that can detect P-waves from an earthquake , which move faster than the S-waves , which cause most of the damage. In addition, the sensors send the warning electronically - at a significant fraction of the speed of light - much faster than either P-waves or S-waves. Because of these differences in speed, the network can send warnings through the app about 5-20 seconds before major shaking occurs, enough time for people to take cover under tables, run outside, etc. The farther you are away from the epicenter, the more warning time you have.
In the comic Megan talks about the app, suggesting how cool it is, but Cueball is upset.  He seems to think that prediction of the earthquake coming is like a spoiler that ruins the experience of how an earthquake should be experienced.  Apparently he prefers to simply be taken by surprise like most people are when an earthquake large enough to feel hits.
He also personifies the tectonic plates (whose shifting positions causes the quake), saying that we should all feel the shaking the way the tectonic plate intended. The statement is usually one regarding to arts, such as a music lover might prefer to listen to older music from vinyl (including cracking sounds, etc.) instead of a remastered digital version, as it is, as the artist intended.
In the title text Cueball mentions that he was fired from the National Weather Service five minutes after they hired him because the first thing he did was to rename tornado warnings as tornado spoiler alerts. A spoiler alert is something used, for instance, when talking about a plot twist of a new movie, so that people who haven't seen the movie can avoid learning important details that would spoil the experience of seeing the movie. Cueball seems to genuinely wish to be surprised by these potentially lethal phenomena for which just minutes of warning may make the difference between life and death.
Earthquake warnings, on a smartphone but not as an app, were the topic of 723: Seismic Waves , and shortly before that a protip for an alternative seismograph was mentioned in 711: Seismograph . An app for warning about tornadoes was the topic of 937: TornadoGuard . Warnings in general by the NWS were the subject in 2179: NWS Warnings , which mentioned tornadoes, volcanoes, tsunamis, and many other hazards. Tsunamis are often caused by earthquakes, though earthquakes were not specifically mentioned.
[Megan is looking at her phone while standing next to Cueball] Megan: Ooh, California has a new earthquake early warning app. Cueball: Yeah, I'm so mad about it.
[Megan puts her phone down and looks at Cueball who throws his arms up in the air.] Megan: What, why? Cueball: It ruins the experience of trying to recognize the p-waves before the obvious main waves hit.
[Megan still looks at Cueball who has taken his arms down.] Megan: So you're mad about earthquake spoilers? Cueball: I just want to experience the shaking the way the tectonic plate intended!


Imagine Going Back in Time

Explanation:
Cueball is checking his Pokémon Go app to check on the status of a Pokémon he had previously left in a gym (to defend it against the other two teams in the game). In the gym he sees that another player named "Reelect Trump 2020" has left a frog Pokémon, which is now standing next to his. Cueball, evidently not a fan of President Trump or his supporters, finds it distasteful to be indirectly associated with someone whose political views he finds unpleasant. Alternatively, it may simply be that Cueball doesn't want politics injected into a game that he plays for fun.
When he remarks on this to Megan , she observes how strange that remark would sound if he said it to his younger self from 20 years ago. Normally when people say "imagine going back in time", they are merely constructing a hypothetical scenario to illustrate how rapidly society has changed over the years. Megan is likely pointing out that the idea of Donald Trump becoming the President of the United States (let alone coming up for re-election) would have seemed very farfetch'd just 20 years ago.
However, it turns out that Cueball somehow actually does have the time-travel technology required to pull this off, and so he takes Megan's suggestion literally and goes back in time 20 years to do exactly what she suggested: he repeats the statement to his younger self to see what his reaction will be.
Unfortunately, past Cueball (in the year 1999) chooses to focus on a completely different aspect of the statement: the fact that Pokémon - a game that past Cueball sees as a children's game - will still somehow be popular in 20 years, and that his adult self is still playing it. These observations make Cueball feel uncomfortable, as they highlight the fact that he is spending time on pursuits that his younger self sees as frivolous or childish. He gets defensive and starts to argue with his younger self.
When his younger self begins to call it a sobering and cautionary tale, it may dawn upon present Cueball that he may just have changed how his former self will behave. (Could he, in the new iteration, never even begin playing Pokémon Go, and thus present Cueball may disappear and a different version of himself will exist 20 years later? Or could he have seeded encouragement for himself being more readily connected to all things Pokémon in the intervening years, putting himself further ahead of the resurgence in its popularity?) Or else future-Cueball is just frustrated at how past-Cueball is failing to notice his intended revelation — and in turn is failing to appreciate past-Cueball's own naive but still insightful interpretation.
Pokémon is a media franchise that debuted in 1996 in Japan as both a video game and a trading card game. It was originally designed for and marketed to younger children (the tie-in cartoon series constantly emphasizes its main characters are ten years old), with a design, aesthetic and gameplay that were optimized for a younger audience. Since then, and up to 2019, there have been a total of eight generations of video games on consoles. As the franchise continued to thrive and evolve, it's gone through multiple generations, including Pokémon Go , an augmented reality game for smartphones. These latest versions, in particular, have become popular with (and marketed to) adults, some of whom grew up playing the earlier generations.
In 1999 in North America, only the first generation of Pokémon video games had been released, consisting of Pokémon Blue and Pokémon Red for the Nintendo Gameboy. The second generation of Pokémon video games would not even be announced in Japan until November 1999 , and advertising for the North American release would begin in December of 1999.  A person living in 1999, who has only seen the first generation, with no official confirmation that a second generation was even being considered, and unable to predict the nostalgia market that would appear later, would quite plausibly wonder about its popularity 20 years later.
Donald J. Trump was the president of the United States at the time of publishing, elected in 2016. Even during his campaign, the idea of his election was considered absurd in many circles, as he had never held any kind of public office, and had no background that would lend itself to expertise in government or public policy. Prior to his election, he was primarily known as a New York real estate mogul and host of the 2003 reality television show The Apprentice .  While he'd been teasing the idea of a presidential run since the 1980s, and indeed was seeking the Reform Party candidacy in 1999 (at the advice of then-Governor of Minnesota Jesse Ventura , another actor-turned-politician), most people did not take the idea seriously, and the concept of him actually being President of the United States would have been hugely unexpected to most Americans in an earlier era.  1999 Cueball might regard the name "Reelect Trump 2020" as an ironic joke, like a campaign button for Vermin Supreme or the Sweet Meteor Of Death . That Randall is not a fan of Donald Trump became clear in 1756: I'm With Her and many comics that followed it, now including this.
Randall released a comic about Pokémon Go less than a week after its release back in July 2016: 1705: Pokémon Go . But Pokémon in general has been a recurring theme in xkcd long before Pokémon Go was released.
Pepe the Frog is an internet meme that has become associated with Donald Trump after his use of it during his presidential campaign. The use of a frog Pokémon, therefore, is a callback to this internet phenomenon.
The Pokémon left in the gym is most likely Politoed , the only official frog Pokémon released in the game at the time of publication. It comes from the tadpole series with Poliwag that evolves into Poliwhirl which by using a King's Rock can be evolved to Politoed (instead of to Poliwrath ). There are other frog-like Pokémon in the game which are scheduled to be added to Pokémon Go, but where people who dislike Trump might have chosen Toxicroak , it seems an unlikely choice by a fan that hopes Trump is reelected!
This comic's joke is similar to one used in the 1985 science-fiction film Back to the Future , in which Doc Brown (of 1955) is shocked to learn that Ronald Reagan would be the President of the United States in thirty years' time, when in 1955 Reagan was a TV actor.
Digimon , as mentioned in the title text, is another media franchise which is similar to Pokémon in some ways, though it is sometimes perceived as more "cool" and "adult" oriented.  Its popularity in North America rose around 1999 with the airing of its anime series, but never became as popular as Pokémon .
This was the first of two time travel comics in less than a week, as the one two comics after this one, 2222: Terminator: Dark Fate , also had future Cueballs travel back to visit their past self.
[Cueball talks to Megan while looking at his smart phone.] Cueball: Ugh. A player named "Reelect Trump 2020" put a frog Pokemon in the gym next to mine.
[Megan puts her hand to her face. Cueball is holding a device in his hand with an antenna. He uses the other hand to move a stick on the device.] Megan: Imagine going back in time and saying that to yourself 20 years ago. Cueball: Oh, I have a time machine! I'll try that.
[A sound effect between panels, likely the sound of Cueball's time machine.] Bzzzzt
[Two Cueballs standing, facing each other. The one on the right is holding the handheld device, and is thus Cueball from 2019.  He is apparently repeating his statement to the other Cueball from 1999, with only the last 3 words shown. He gestures towards the left Cueball. Above the left Cueball there is a frame with a caption:] 1999 Cueball from 2019: ...next to mine.
[Cueball from 1999 is shown, with Cueball from 2019 speaking off panel.] Cueball from 1999: I see. Cueball from 1999: Pokemon is still popular in 2019? Cueball from 2019: Yeah.
[Cueball from 2019 is holding a finger up in front of Cueball from 1999.] Cueball from 1999: And it's cool for people your age to play it? Cueball from 2019: OK, I did not come here to be mocked. Cueball from 1999: This is a sobering cautionary tale. Cueball from 2019: Listen, self...


Emulation

Explanation:
Here Cueball is speaking with a fictitious example of artificially intelligent software similar to the type popularized in the 1980's when personal computers had just become mainstream.  Although modern computing platforms might still be backwards-compatible with 8-bit era software, it is more likely that the old applications will need to be run within an emulator that can simulate the necessary hardware components required by the application.
In this case the "8-bit AI" is having a conversation with Cueball as it carries out tasks common to the era, specifically asking the user to insert a floppy disk into drive "A:" (A: traditionally being the first floppy drive on IBM-compatible PCs).  At the time internal storage like a hard disk was an expensive luxury item and most applications were stored on removable media.  An application that could not fit on a single floppy disk would be programmed to prompt the user to insert successive floppies which held the required data.  However, the speed at which data could be loaded from such devices was very slow , requiring anywhere from ten seconds to ten minutes to load a level or an advanced dialog box. Sometimes the software would even incorporate feedback mechanisms like loading screens to let the user know the program was proceeding as intended and had not crashed.
When software operating under an emulator such as DOSBox makes a request to access disc storage, the emulator will often map the command to a file or file system on the enveloping computing environment which can now contain hundreds or thousands of gigabytes of storage.  Depending on the configuration, this may require a user action to complete the virtual operation (Cueball's click). The speed of modern hardware allows the data to be transferred at speeds several orders of magnitude higher than what was possible in the past. The 8-bit AI notices this and makes a comment about the transfer speed.
Here we begin to see the consequences of emulation upon the anthropomorphized software application. Because the emulator is constructing the application's entire reality, the 8-bit AI has no reason to believe it is anywhere other than a 1980's computing platform for which it was designed.  While the application does notice the abnormally fast load time, Cueball decides to not burst his anthropomorphized program's bubble and responds that the file loaded quickly because of a new floppy disk from Memorex , which was a well-known manufacturer of premium magnetic recording media in the 1980s.  Memorex was also known for a famous series of commercials with the tagline, "Is it live? Or is it Memorex?"—tying into the comic's theme of a lack of unawareness that something is being digitally duplicated.
To compound the problem, computers of the era often lacked a real-time clock or would have an inability to process dates beyond 1999 , and therefore the software application in this comic still believes that it is running at the time of its creation - the 1980's. To this end the program casually asks how President Reagan is doing, as Ronald Reagan was the President of the United States from 1981-1989 when early PCs were on the rise. He died in 2004, 15 years before the publication of the comic. This is why Cueball seems slightly uncomfortable with noncommittally telling the software Reagan is "fine."
In the title text, Cueball references the living in a simulation trope, mentioning that it is not fully clear that he is actually living in 2019. This has been a theme in science fiction such as The Matrix , which has been referenced several times in xkcd. That we are living in a simulation was also the subject of the comic 505: A Bunch of Rocks .
[Cueball sits in an office chair at a desk typing on a laptop computer. The computers response to his typing is shown emanating from a starburst on the screen with zigzag lines between different sentences.] Laptop: Loading... please insert disk into drive A: Cueball: *click* There you go. Laptop: Thank you. Wow, this disk is incredibly fast! Cueball: Yeah, uh, it's the new model from Memorex. Laptop: Amazing. And how is President Reagan? Cueball: He's... He's fine.
[Caption under the panel] I feel weird using old software that doesn't know it's being emulated.


Terminator Dark Fate

Explanation:
Cueball is on his way to see the new Terminator movie; Terminator: Dark Fate , when Cueball's future self comes back to stop him, trying to convince him that, as always, he will be disappointed by sequels. (This was, for instance, the main joke in the last part of 566: Matrix Revisited .)
Future Cueball (who we shall call Cueball-2) almost succeeds in convincing present-day Cueball (who we shall call Cueball-1) not to go see the movie in spite of good reviews and the fact that the original star Linda Hamilton is back after several movies without her. Due to the nature of time travel, Terminator: Dark Fate actually negates any movie that came after the first two ( The Terminator and Terminator 2: Judgment Day ). However, they are interrupted by a second Future Cueball, Cueball-3, who states that in his timeline he hadn't seen it but wished he had, making present-day Cueball exclaim that they should go see it together.
Cueballs 1, 2, and 3 are interrupted again by the appearance of two more Cueballs, presumably Cueball-1 and Cueball-3 who have seen the movie, regretted it as Cueball-2 did, and travel back in time to stop themselves from seeing it. In the next panel another 5 Cueballs appear, however, their reasons for coming back have degraded, with the last one stating that he came back simply because, at the time he came from, the theater sold out of tickets because all the time-traveling Cueballs purchased all of them.
A common trope in science fiction is to Set Right What Once Went Wrong , where characters travel in time in order to stop a particular event from happening so as to prevent an undesirable timeline. The Terminator series film series is famous for this time travel trope. The initial 3 films feature a time-traveling robot sent from the dystopian future to kill a particular human, with the future resistance in turn sending a protector to ensure the human's survival. However, the series has never been consistent on even the broadest rules of how time travel affects the timeline, with each movie exploring different possibilities. This is another point of spoof for the comic, featuring multiple recursive time loops until it becomes a jumbled mess.
The final panel also invokes the "killing Hitler" trope. Adolf Hitler was the leader of Nazi Germany during World War II, and it has been a common plot idea to "go back in time to kill Hitler" such as in 1063: Kill Hitler , by presuming that the world would be better if World War II and The Holocaust had never happened. There are also works that postulate that such a killing would have unintended consequences, making things worse (for example, if Hitler had been replaced by a more competent leader, the Axis power might have won the war). In any case, this Cueball is over 70 years too late to kill Hitler, as Hitler is now dead. [ citation needed ]
The title text is what is said by the next Cueball-11 (the 10th time-traveler), with each link in the chain relating to the Terminator movies. Except at the end where the initial "dangerous robot" turns out to be a robot sent to vacuum the floor. Robotic vacuums, such as the Roomba , are a recurring theme on xkcd.
The title text split up:
Thus Cueball-11 tries to stop the person that needs to destroy the Roomba by stopping his protector's protector, presumably so that the floor will be cleaned in his timeline.  It's strange that Cueball would rather execute a complicated time-travel plot than just clean the floor himself, but we've seen him make extreme versions of mundane activities before (e.g. 1017: Backward in Time , which is not actually related to time travel despite the name).
This was the second time travel comic in less than a week, as the comic two comics before this one, 2220: Imagine Going Back in Time , also had Cueball travel back to visit his past self.
[Cueball is walking to the right. Another Cueball, Cueball-2, appears behind him in a bubble of energy that appears with a loud sound. The bubble floats in the air behind the walking Cueball, with Cueball-2 inside holding his arms out to the side and having his legs bend.] Zap!
[Cueball-2 from the sphere is standing to the left of Cueball, pointing at him. Cueball has stopped and is looking back over his shoulder] Cueball-2: I've traveled back in time to stop you from seeing Terminator: Dark Fate !
[Cueball-2 is looking at Cueball who has turned around and holds his arm a bit out to the sides.] Cueball: But it looks so good! Reviews are actually decent! Mackenzie Davis! Linda Hamilton is back!
[Cueball-2 is holding both arms up, hands held down as Cueball stands normally.] Cueball-2: I know, but you always think this, and you're always disappointed. Cueball: I guess ...
[Zoom out as another Cueball, Cueball-3, appears to the left in a similar bubble of energy and noise as in the first panel, his arms are out to the sides and his legs are bent. Cueball-2 is holding a hand in front of his mouth, while Cueball throws his arms out to the side.] Zap! Cueball-3: Hi, I'm from the future where you didn't watch it and I realize I still kind of want to see it. Cueball: Let's go together!
[Another bubble appears from the right of the three Cueballs, the one in the middle (Cueball-2) holding his arms out. This new bubble contains two Cueballs. The first, Cueball-4, throws up his arms over his head, while Cueball-5 has one arm out in front of him. Both have their legs bent.] Cueball-4: No! We're both of you from the future! We're here to stop you!
[In a large panel, five more individual energy bubbles with five Cueballs appear. Two of the bubbles float over the now five Cueballs on the ground. The other three are a bit lower and in line to the right. Cueball-6 to 10 are in different poses, all with their legs bent, all the way to sitting on the knees in one case and most of them throw their arms out to the side. All look down at the five regardless of their bubble's position. Their text is alternating between being up and down, so the text goes over or below the other text, making it hard to decide which comes first. This may be intentional. But here they are in the order of Cueballs as they come from left to right:] Cueball-6: I'm here to stop you! Cueball-7: I'm here to stop the robot sent to stop you! Cueball-8: I'm here to protect you from...you? I lost track. Cueball-9: I'm here to kill Hitler. Did I get the right year? Cueball-10: I'm here to get tickets because in like 20 minutes you people buy them all.


Screen Time

Explanation:
Cueball is reading the report from a smartphone app showing the average time each day that he was NOT looking at his phone during the hours he was awake this last week.  This is a reversal of the more expected behavior for a screen-time app, which would normally report the amount of time spent looking at the screen. The point is that as mobile phone usage becomes more prevalent, it may be easier to comprehend to report non-screen time.
People in the US spent an average of 24 hours of non-work/education screen time per week in 2015, compared to 10 hours of active leisure, according to one estimate.[ How free time became screen time ]  Averaged per day that comes to 3.4 hours screen time and 1.4 hours active leisure.
Screen time may be associated with various undesirable conditions, such as mental health difficulties like depression, decreased activity, reduced sleep quality and quantity.
In Cueball's particular case, if we assume that he is awake 17 hours a day (the average for most people in USA), then his non-screen time average of 2 hours 48 minutes means that he spent more than 84% of his awake time last week looking at a screen. This means that while his 6% improvement is positive, he still has quite a significant habit. His previous non-screen-time would have been 2 hours 38 minutes, so he has managed to shave 10 minutes off.  Increased screen time often comes at the expense of decreased sleep time, so it may not be fair to assume a constant amount of sleep. [1] [2]
Ironically, in order for Cueball to use the app, he has to be looking at his mobile screen. The increasing use of mobile devices in modern society has been a cause for concern, with many people arguing this leads to addiction, other health risks, or people simply not talking to each other.
The title text parodies the idea of a screen time app by describing a "shoe time" app, which would track the amount of time a person spends wearing shoes. It's unclear what the practical use for this would be, as there is little controversy about the prevalence of shoes in our society. Possibly an app that tracks the amount of time wearing specific shoes could be useful; for example, a person suffering medical problems from wearing the wrong footwear could track the amount of time they spend wearing particular shoes, and correlate this with their health to figure out which ones are causing problems.
Possibly, the point being made is that use of phones have become so constant in our lives that using them for many hours a day is as unremarkable as using shoes for many hours a day. Or, since it's the socks that are Bluetooth-enabled, they may be reporting negatively about almost constant obstruction by shoes, whereas the socks would prefer to report a much lower "Shoe Time" score.
Some cultures have the custom of taking shoes off when in the house, so those people would boast lower (and presumably more favorable) "Shoe Time" scores.  It may also be a reference to the " shoe phone " on the television show Get Smart . (If Maxwell Smart wore these socks, they could track his phone usage, because his phone was in his shoe).
[Cueball  is looking down at his phone. The text is what he reads on the screen, as shown by a zigzag line emanating from a starburst at the top of the phone.] Phone: Screen time report: Phone: While awake, you averaged 2 H 48 M per day looking at things other than your phone. That's up 6% from last week!
[Caption below the panel] At some point, it starts making more sense to track non -screen time.


Software Updates

Explanation:
As time passes, upgrades to most products are inevitable, with software being no exception.
However, as many updates create multiple versions, support for all of them can become a bit of a hassle for the company that creates them, so old versions frequently become unsupported after some years, or in some cases even months, of their releases.
Software as a Service (SaaS) is a software licensing and delivery model in which software runs on the vendor's computers (servers), accessed by customers remotely. The software is said to run "in the cloud" as "cloud applications". Customers purchase subscription licenses. Since the only copy of the software is that which the vendor runs on their own computers, all customers use the one latest version of the software, which is upgraded whenever the vendor chooses to.
The benefits of SaaS is that the customer mostly does not have to worry about whether their machine is able to run the software, and both the vendor and customer only have to concern with managing one version instead of being familiar with multiple ones. The downside of SaaS, however, is that if the vendor alters or removes a feature that the customer prefers or requires, or introduces a bug, the customer has no ability to remain with an older version, losing a feature of the software that they depend on, or get impacted by a new bug that is introduced by an upgrade to the software with no ability to run the older version.
This downside of SaaS is frequently pointed out by skeptics of SaaS, who like to argue that the traditional purchase model allows the consumer to theoretically able to operate that version indefinitely; there is no obligation to pay ongoing fees or to upgrade to later versions. Indeed, some users do stay on old editions because of unfavorable changes in the newer versions, which is not something SaaS customers can do.
Randall argues that in reality, though, because even these traditional pieces of software have versions and are equally susceptible to having a feature axed by the developer, as well as the problems of running increasingly old software - mainly concering bugs and later-discovered security vulnerabilities that would only be patched via upgrades, the practical upshot of these trends is that it's rarely plausible to buy a single copy of software and continue to run it indefinitely. Almost all consumers who continue to use a particular piece of software will eventually need to upgrade to and pay for new versions. While this isn't precisely the same as paying regular licensing fees and running software that automatically updates, it's an effectively similar model. In that sense, "All software is Software as a Service".
The title text refers to a different aspect of cloud applications. Since they run "in the cloud" on remote computers, they are subject to the limitations of network speed to the servers. The time for data to be sent to a server and a response to be received back is called the "ping time".
Since a "cloud server" is just a computer, there is no fundamental difference between software running remotely and software running locally on a user's computer. The biggest difference is that software running locally will respond almost instantly to user input, whereas software running remotely may take longer to respond, since the data first needs to be sent over a network (the internet), processed, and then sent back to the user's computer. In addition, the chance of data loss (packet loss) may cause the response to be even slower, as data has to be re-sent, or often result in no response at all. Hence, in practice, this can have an enormous impact on the experience of using remote software vs software that runs locally (as anyone who has tried online gaming on a laggy server can attest).
However, technically speaking, there is a nonzero time taken for the data to travel from the user's keyboard onto the computer, across the various circuitry, and back to the monitor. Hence there is a "ping" time even for a local computer (in fact, many "gaming" monitors advertise low input lag, in the order of 1-5 milliseconds, as a feature). Therefore, you could technically say that all applications are cloud applications, just that some (local computers) have very fast ping times whereas for others (servers on another continent) it may be quite slow.
This ignores the fact that being a "cloud application" implies that it runs on a server in a remote location. The joke is similar to the one that claims everyone commutes to work - including those that "work from home" - but their commute times just vary a lot. For example, consider the "commute" from your bedroom to your home office.
[A graph with two axes. Over and right of the axes are two labeled arrows pointing along the two axes:] X-axis: Time Y-axis: Software Version Number
[The graph consists of three lines. Two gray lines moves in upwards step from left to right. The upper line begins a bit up the Y-axis, the bottom line begins somewhat down the X-axis. From there both lines move upwards in steps of different height. The distance between them stays on average about the same for the entire graph, but moves from bottom to top of the graph. Labeled arrows point to the top and the bottom gray line. The area between them is shaded light gray and has a gray label written in the middle. The third line is black. It begins from a dot just under the second step in the upper gray line. This line also makes steps, keeping close to the upper line, although it makes fewer steps than that line. But a bit over halfway to the top, it stops stepping, staying on the same level for the rest of the graph; thus eventually it falls outside of the light gray area between the other two lines, where it had been until the bottom line stepped above it. This black line is also labeled, with normal black text written beneath the first full step inside the gray area. There is one other point labeled on the black line: a dot just after the final step, under the next large step in the upper gray line. At the end of the black line there are question marks with an arrow beneath pointing right. The arrow has a label to the left.] Upper gray line: Newest Version Bottom gray line: Oldest Supported Version Light gray area: Support Zone Black line: My current version Start dot: First Install Second dot: An update finally breaks a feature I'm unwilling to lose End of black line: ??? Arrow label: The Abyss
[Caption below the chart]: All software is Software as a Service.


Voting Referendum

Explanation:
The day before this comic's publication was an election day throughout the United States , primarily for local and state issues (normal elections for federal offices of the President, Senate, and House of Representatives are always in even years). The topic of today's comic highlights many different methods for conducting elections and counting votes. While elections are primarily used to allow voters to select from candidates for public offices, election ballots also frequently present questions for voters to directly voice their support or opposition to some change in a process or law - commonly called a referendum .  The comic depicts an election ballot referendum for voters to select the method to be used in future elections.  While the referendum is asking voters to select a method from a long list of methods, a referendum is usually presented as a specific proposal which requires a simple Yes or No vote.
As an example, the ballot in New York City included a referendum ( which passed ) on whether to use a different method, ranked choice voting (another name for instant-runoff voting as described below).
A common issue with such referenda is what method to use to conduct the referendum itself. Here, the method of marking each choice on the ballot reflects the marking method which would be used if it were the winner. Moreover, each item is listed in a way which is suggestive of what it means (e.g., "First past the post" is the first one, "Top-two" is among the top two, and "Multiple non-transferable vote" is selected among numerous other ones). A few of the methods allow for multiple winners, which can often be good when electing councils and representatives, but it is unclear what it would mean to have several of these voting methods all win.
The aim of political elections in first-past-the-post is to determine which of the candidates standing for election is most preferred by the most voters. In a simple two-person contest, this process is quite effective, since whichever candidate receives the most votes will be the one that the majority of voters prefer. This system works well for simple cases, but for elections with more than two candidates this system may result in a candidate being elected who less than 50% of the voters would prefer.
For example, in a contest with three candidates, A, B and C, in which candidate A receives 43% of the vote, candidate B 38%, and candidate C 19%, candidate A will be elected, even though some of the voters who chose candidate C might have preferred candidate B as their second choice instead of candidate A, leading to a result which pleases less than half of the population. For example, the above distribution of votes happened in the 2000 United States presidential election in Florida , where George W. Bush beat Al Gore by less than 1000 votes largely because of the third-party candidacy Ralph Nader, whose 100,000 voters would mostly have otherwise gone to Gore.
Additionally, in election of multiple candidates across a country (or region etc.), first past the post does not lead to a distribution of elected representatives proportional to the total number of votes, only electing the lead candidate in each case. For example, imagine a country with 100 representatives to be elected, with each seat having the same distribution as described in the example above. Under first past the post, 100 representatives will be elected representing party A, and none for party B or C.
Despite these drawbacks, First Past the Post voting continues to be used for political elections in many countries including the US and UK, which historically have both had two main parties receiving the majority of votes. The First Past the Post system has received much criticism, particularly from smaller parties who may lose out; however, supporters promote the simplicity of the system compared to other methods.
This system is shown with a radio button , the classic computer metaphor for being allowed one choice out of a set.
This method is used in California and Washington to select candidates for the US House of Representatives. In most states' primary-election systems, each party votes separately to select one candidate to continue to a first-past-the-post general election ballot. In these two states, on the other hand, candidates from all parties, as well as "independent" candidates from no party, run in a single race, and the top two finishers then contest the general election, even if both are from the same party (a common occurrence in heavily-Democratic California), and even if one candidate has a clear majority of the vote. (In an older version, a majority winner in the primary was immediately declared elected. This was held to be in violation of federal law, by effectively setting an "election day" before the national Election Day in November.) This is a form of the two-round system , a system for selecting elected officials most notably used to elect the President of France
This system is almost identical to the top-two primary, but with two differences. First, the open-to-all ballot is held on the national Election Day, instead of on the state's primary day. (This avoids the conflict with Federal law described above.) Also, the second round of the election is not held if one candidate has a clear majority (more than 50%) of the votes in the first round. Like the top-two primary and the first-past-the post system, the comic represents this system with a radio button, except this one has been marked, indicating the vote.
In cumulative voting, voters get as many votes as there are seats to be filled, and may distribute them as they choose. This system's most common use is in selecting corporate boards of directors. It is also used in some areas to allow a minority bloc within an electorate to elect some of its preferred candidates without imposing a system of separate districts.
The comic illustrates this with multiple radio buttons, each row representing an option/candidate and each (implied) column one vote. On the ballot the first 2 radio buttons are marked, as they are each the only radio buttons in their column and cannot be unmarked.
In this system, each candidate is listed as a yes/no choice, where the voters can choose which candidates they approve of winning the election, and which ones they do not approve of.  The winner of the election is the candidate with the highest approval rate.
This type of voting system can be used as a vetting process to filter out undesirable candidates before the final vote; for example, the United Nations uses a series of "straw polls" to filter out candidates for the Secretary General before the Security Council makes a final vote.  In 2018, Fargo, North Dakota switched to using approval voting to elect local politicians, making it the only jurisdiction in the United States to use this system.
In the xkcd ballot, the approval option is presented as a checkbox, where a check in the box is "approve" or an empty box is "disapprove". Checkboxes are distinct from radio buttons in that several can be marked in the same field, and can also be unmarked without marking another.
This system for electing multiple members to a ruling body is also known as plurality-at-large voting or block vote. It is commonly used in the US for city council elections, and simply limits the number of votes per voter to the number of winners. It allows a cohesive plurality of the electorate to claim all of the seats, denying other voters any representation whatsoever.
In 2019, the Justice Department required Eastpointe, Michigan to run at least the next two elections via single transferable vote because their existing plurality-at-large system was disenfranchising black citizens.
This system is also shown as a checkbox, as each candidate gets either 0 or 1 votes from each voter.
In this system, people vote for all the candidates, or perhaps their favorite three, but assign different preferences to each candidate they vote for, as in 1 for their first choice, 2 for the second, 3 for their third, etc.  If at least 50% of voters vote for a candidate as their first choice, that candidate wins.  If not, the person with the least votes gets eliminated, and anyone who voted for that person has their next (slightly less favorable) choice automatically move up a rung.  The 50% mark is again checked, and if there is no winner, another lowest-voted candidate is eliminated.  Eventually one candidate will emerge victorious. The advantages of this system are that there is rarely a need to have another election if things are close (the information is already there to "instantly" recalculate the vote based on additional voter preferences), and "spoiler" candidates only cause problems when they become competitive. And as Arrow's impossibility theorem shows, as with all ranking methods, sometimes voters can hurt a candidate by ranking them more favorably .
On this weird xkcd ballot, we see this type of ranking between this type of voting ( Instant runoff voting ) and the two that follow ( Single transferable vote and Borda count ), all of which allow multiple ranked votes.  It appears that between these three, Randall has voted for Single transferable vote as his top choice, Borda count for his second choice, with Instant runoff voting as his third choice.
This system extends the instant runoff to multiple-winner elections. Specifically, the election threshold is set not at 50%, but at 100%/( k +1) where k candidates will win (in other words, just high enough to prevent more candidates from reaching it than there are seats). The bottom candidates are eliminated as in instant-runoff and their votes redistributed. In addition, if a candidate wins with more than enough votes, the extra votes (either a fraction of each vote, or some subset of the ballots) are also redistributed. This procedure continues until the requisite number of winners is reached.
Each ballot is counted as 1 point for the last choice, 2 for next-to-last, and so on up to n for the first choice among n candidates. The highest point-earner(s) win. This system may also be calculated as 1 point for first choice, 2 for second, etc., with the lowest total winning; this variant, called the "cross-country vote" (due to its resemblance to the scoring system of the sport of cross-country running), is used by the NCAA's various selection committee as one step in choosing championship tournament fields.
The title text refers to the inventor of the Borda count, Jean-Charles de Borda (for whom it is named), implying that the use of the system implies the inclusion of a ballot in which he gets one point in the counting. This "1 point" would be quickly drowned out by any sensible quantity of actual votes. This also humorously suggests that if no one were to vote at all, Borda would win by default.
For each candidate, the voter selects a value within a fixed range (the xkcd voter sees this choice presented as a slider) for each candidate, independent of the values given to other candidates. The highest total wins. (If the range is restricted to two values, this becomes the approval system.)
The punchline for the comic is that the whole referendum is a chicken-and-egg problem: in order to accomplish the purpose of a referendum, one needs to know how the votes will be translated into a result, but in this case, determining that rule is the purpose of the referendum. Additionally this xkcd demonstrates one of the mechanisms that makes it hard to change the currently-used voting system in any state: Each voting system in fact votes for itself as the ones who are able to decide upon the voting system being in use have been elected using the current voting system and therefore are likely to profit from it.
[A voting ballot is shown with an underlined header and 10 different options below with different boxes/buttons next to each choice.  Some are empty, some are marked/checked or numbered.] Which voting system should we use?
[Empty radio button]: First past the post [Empty radio button]: Top-two primary [Filled radio button]: Louisiana primary [Three radio buttons in a row, first two filled]: Cumulative voting [Checked box]: Approval voting [Checked box]: Multiple non-transferrable vote [Box marked]: 3: Instant runoff voting [box marked]: 1: Single transferrable vote [box marked]: 2: Borda count [Slider with value slightly below half]: Range voting
[Caption below the panel:] The referendum went well, but we can't figure out how to count the ballots.


Recombination And Reionization

Explanation:
The hydrogen line is a spectral line of neutral (un-ionized) hydrogen atoms. The electrons in an atom have a property called spin, equal to either 1/2 or -1/2, and one "spin state" of the electron in neutral hydrogen has slightly more energy than the other spin state. This means that when the electron in a hydrogen atom spontaneously switches its spin state, it releases a photon at a certain frequency called the hydrogen line. This line falls in the microwave region of the electromagnetic spectrum, with a frequency of ~1.42 gigahertz (GHz). The wavelength corresponding to this frequency is about 21.1 centimeters, giving it the common name of the 21-centimeter line. In this comic, Ponytail is attempting to detect the signal of this emission line from the ancient universe, although due to redshift , the line's frequency has decreased from 1.4 GHz to only ~100 megahertz (MHz), putting it in the current FM broadcast band . In most parts of the world, FM radio makes use of frequencies from 87.5 to 108 MHz.
The problem that FM radio and the signal for which Ponytail is searching overlap in frequency quickly becomes apparent when tuning to the frequency detects a local radio station rather than the desired signal. The radio station is called Hot 92.7: The Vibe; this indicates that Ponytail is searching for a signal at 92.7 MHz, but there is a radio station interfering with it. She demonstrates this to Cueball by playing the live signal for him, but says that once the radio DJ stops talking, their research will result in a Nobel Prize . This is unlikely, as most radio stations broadcast 24 hours a day without ever stopping (except in cases of power failure, which would also affect Ponytail's radio telescope). An unstated joke is that Ponytail's observational setup receives the FM radio signal at all; any actual radio telescope would have incorporated methods from its inception to exclude local sources of radio signals such as FM radio.
Cueball points out that perhaps the signal is what the supposed primordial hydrogen line actually sounds like during the phase of universe formation called reionization . Ponytail jokes back that the primordial universe must enjoy playing popular singer Selena Gomez . Although it is theoretically possible that a naturally occurring radio transmission might sound like music to humans, it would not contain clearly understandable coherent sentences in a language that did not exist when the transmission was created. [ citation needed ]
The title text refers to the signal Ponytail is detecting, claiming that it originates from before the formation of the first stars in the universe (which took place approximately 150 to 200 million years after the Big Bang ), but is additionally post-Malone. " Post Malone " is the stage name of a popular hip hop musician and singer, so this is a play on words, as the "Post" in his stage name isn't referring to "after" something, but is simply his (real) last name, and perhaps a play on the expression "a star is born" for an artist becoming a famous celebrity.
[Panel showing Ponytail sitting working at some type of console, possibly in her laboratory. Cueball is standing on the other side of the console, facing her.] Ponytail: Our lab is trying to pick up the spin line of neutral hydrogen. It's the only radiation from the era before the first stars formed.
[Panel showing Ponytail and Cueball.  Ponytail has paused working, with one hand raised off the console.] Ponytail: It was 1.4 GHz at first, but by now it's redshifted to the 100-MHz range. Cueball: Isn't that also where FM radio broadcasts?
[Frameless panel showing Ponytail and Cueball.  Ponytail is pressing a key on the console to enable and disable a live signal from her lab's equipment.] Ponytail: Yeah. That's the problem.  Listen: Sound of switch on console: *Click* Audio signal from console: You're tuned to Hot 92.7: the Vibe! Coming up next... Sound of switch on console: *Click*
[Panel showing Ponytail and Cueball.  Ponytail has resumed working at the console, and Cueball has raised a hand to his chin.] Ponytail: But once this guy stops talking, that Nobel Prize will be ours . Cueball: Maybe that's not a station – maybe that's just what reionization sounds like. Ponytail: Reionization plays a lot of Selena Gomez.


Transit of Mercury

Explanation:
This comic is in reference to the transit of the planet Mercury across the Sun on November 11, 2019 (the date of the publication of this comic), which appeared from Earth as a small black dot moving against the background of the Sun. Randall has made comics about solar transits before, albeit about the transit of the International Space Station, in 1828: ISS Solar Transit and 1830: ISS Solar Transit 2 . Viewing a solar transit requires a special lens filter to prevent the intense light from the Sun from burning out a telescope's imaging sensor.
The hashtag #nofilter is typically used on photo sharing sites, especially Instagram, to humblebrag about having encountered situations so photogenic that no further image enhancement (" filter ") is required to prepare them for general advertisement. In this comic, the hashtag is instead used to cap off an image about the predicament of the poster, where the lack of a proper astronomic filter has led to damage of personal property. The image shown on the comic is quite bright and blown out , and though the poster did manage to get a picture of Mercury, the sun's bright light permanently damaged their telescope.
The title text refers to a still different meaning of the word "filter"; it imagines a swimming pool growing green scum in the absence of a water filter , as opposed to a photographic or astronomic filter.
Although not directly referred to in this comic (although a variant was used in 1911: Defensive Profile , a third common variation of "No filter" is possibly alluded to here and can refer to someone who makes, or posts, tactlessly candid comments. While often this means comments that reflect the individual's actual views which are potentially offensive or socially unacceptable, it could also refer to someone who posts every mundane detail of their lives, such as what is growing in their swimming pool (as is shown in the title text). Multiple layers of meaning makes this pretty clever word play.
[Panel showing the sun partially obscured by clouds with faded gray blue sky around the sun, mainly upper right, as there are clouds in the lower left part. The image is very bright and blown out at the bottom left, obscuring most of the surface detail of the sun.  A small black dot is visible in the upper-right part of the sun's image.]
[Caption below panel, with a yellow unhappy smiley before the hash tag:] This photo of the transit of Mercury fried my telescope's imaging sensor 🙁 #NoFilter


Machine Learning Captcha

Explanation:
All websites other than explain xkcd have difficulties with spambots, which are automated entities created in order to log onto a website and spam or otherwise wreak havoc upon it. (This never happens to explain xkcd.) To guard against this eventuality, websites have implemented CAPTCHAs , a challenge used to prove the user is a human and not an automated program. A typical CAPTCHA might distort a random sequence of letters and numbers and put it in a strange and/or mixed font and ask a user to type it, or it might show a set of pictures and ask the user which ones contain fire hydrants; these tasks are meant to be easy for humans but obscenely difficult for computers. CAPTCHAs are a recurring theme on xkcd.
CAPTCHAs run by Google are also used to train artificial intelligences to get better at these difficult tasks, such as reading poorly-scanned text or identifying objects of interest on the road (the latter being the subject of 1897: Self Driving ).
This comic jokes about a malicious CAPTCHA which is being used to train an AI to dominate the world. In order to prevent people from taking shelter, the AI uses the CAPTCHA to ask humans like Cueball to tell it places where they would hide. The implication is that during a robot uprising, the AI, on the side of the robots, would then be able to track down humans much more easily.  The choices presented are (left to right, top to bottom):
House Sometimes, the best (or least-worst) response to a disaster is to "shelter in place" until the danger is passed, rather than risk getting caught in the open or in traffic.  This is commonly advised in response to biological, chemical, or radiological hazards, or in the case of a violent act committed in the community.  If the robot uprising is localized, then sheltering at home would be a fine response, because traveling to the other locations would increase the risk of being spotted and attacked by self-driving cars or aerial drones.  On the other hand, most homes contain a multitude of internet-connected devices, some of which may control vital electrical or heating systems, so if the robot uprising is widespread, then the home would not be a safe shelter. Tree or forest If there is a robot uprising, then traveling to a forest or other nature reserve, far away from developed cities and towns, would reduce the risk of being near a hostile piece of technology.  However, it also comes with limited resources for sustaining human life, unless the forest abuts meadows or farmland. Bunker or bomb shelter If the robot uprising includes the use of weapons of mass destruction (as in the Terminator franchise, or as was threatened in WarGames ), then only a hardened military structure is likely to survive. Car Cars offer some shelter and, more importantly, mobility in one convenient package.  Most families own at least one, and they are widespread in human-occupied areas, so even if the car is not as suitable as a long-term shelter (depending on how the road and gasoline/power networks survive the uprising) it makes a fine first step in evacuating to a more permanent hiding place.  This is of course assuming that the car is not self-driving and that hostile self-driving cars are not widespread. City Cities offer thorough selections of supplies and tools that may be harder to come by in more rural areas, but they are also home to lots of robots and automated systems that may participate in the uprising, not to mention humans who may be prime targets for the machines.  It may be necessary to visit the city to stock up on supplies in a post-apocalyptic scenario, but in the early stages of a robot uprising, it is best to leave them as quickly as possible. Sidewalk The sidewalk is exposed and presumably falls within a built-up area that is readily accessible to the machines; it is not at all suitable as shelter. Lean-to The log with a board leaning on it is an example of an improvised shelter.  Such a shelter could be constructed anywhere with local materials, and would not be marked on any map known to the robots, which are both positives for surviving the onset of the uprising.  However, it is lacking in insulation and protection, which makes it less suitable for longer stays. Mailbox Only a very young infant could fit in this mailbox.  This is not a viable shelter. A hole in the ground Like the improvised shelter, this option can be made almost anywhere and is easy to camouflage, and it offers additional insulation from weather and weapons of mass destruction.  It's a fine option if you happen to already have one or know where to find one, but it will be difficult to create a suitable one after the uprising begins.
Some of these choices may be Cow Tools , that is, presented not as serious options but to be funny because they are nonsensical.
The title text imagines a different malicious CAPTCHA which Randall says is "more likely" than the robot-uprising scenario, in which a company or government asks users to identify "disloyal" members of society. Presumably the company or government would then use this information to eliminate such "disloyal" members, either by firing them (company) or jailing, expelling, or executing them (government). This follows a theme of previous comic strips (e.g. 1968: Robot Future ) in which Randall expresses that he is more concerned about humans using AI for evil ends than he is about AI being evil in itself.
[Cueball is sitting in an office chair at his desk with one hand in his lap and the other poised over the keyboard of his computer. A zigzag line is drawn from a starburst on the computer screen going above the computer to where it is shown what is displayed on the screen. At the top there is the following text:] Computer: To prove you're a human, click on all the photos that show places you would run for shelter during a robot uprising.
[Below the text there are nine images arranged in a 3 by 3 square. In reading order they are: A house, possibly with an open carport; a large tree with two trees in the background; a bunker/bomb shelter; a car; a city skyline with several sky scrapers; a sidewalk with road on the left, grass on the right; a log with a board leaning up on the log; a mailbox; and a hole in the ground.]


Rey and Kylo

Explanation:
Rey and Kylo Ren , from the latest trilogy of the Star Wars series, are engaging in a lightsaber duel. Rey tells Kylo that they should not fight, but work together on cosmology , the study of the origins of the universe. Specifically she wants to study the expansion rate of the universe; scientists believe that the universe is expanding, and that the expansion rate is accelerating, but aren't sure of the exact rate, what the rate was in the past, or if it varies depending on location. Since the Star Wars movies take place "a long time ago in a galaxy far, far away", if Rey and Kylo presented their findings in the movie, it would theoretically give scientists more data points.  Although it is unlikely that modern scientists would use cosmological data from a movie generally considered fictional [ citation needed ] , especially as said time long ago and distance far, far away are never quantified, some movies and TV shows have spurred scientific innovations due to their subject matter (see below).
The caption, besides explaining the obvious nerd cred this turn of events would earn if it actually occurred in the movies, might also be a play on accusations against the Disney-owned franchise that it has begun pandering to progressives, with the complainers citing its racially diverse cast, powerful (in their eyes overpowered, and Mary Sue-ish) female protagonist, and a willingness to sacrifice sensible plot for perceived progressive talking points (e.g. Vice Admiral Holdo's plan and failure to communicate it).
The title text is Randall 's complaint that the Star Wars movies have been more focused on the Wars aspect than the Star aspect. It seems he would want a film about stars. It's worth noting that, with a half-width  space, "Star " and " Wars" are the same number of letters long, and are therefore perfect halves of the title.
Kylo Ren and Rey, though enemies in the films, have been shipped in fanfictions and fan theories, so their joining together in this comic may also be a play on that desired relationship.
Star Wars is a recurring topic on xkcd.
As far as we can tell, the stars of Star Wars (that is, the celestial bodies, not the actors) seem to be much the same as ours.  The "galaxy far, far away" has had various depictions over the years, but all sources agree that it is a spiral galaxy approximately the same size as our Milky Way galaxy, albeit with a less prominent bar than the Milky Way has.  We don't ever hear what name, if any, the Star Wars characters have for the galaxy, or why they call it a "galaxy" when the word comes from a Latin phrase, "Via Galactica" or "Milky Way" -- a question that Randall has brought up in 890: Etymology .
Light is known to have a speed, although we are not told what that speed is, or if it is constant for all observers in all reference frames.  That speed is an upper bound on the speed that objects can travel in real-space, as in our universe, but in Star Wars , ships can travel faster than that speed by "jumping" into a parallel dimension called "hyperspace".  This allows them to cross the galaxy in a matter of hours rather than tens of thousands of years.  According to our understanding of relativity, transmitting information faster than light is equivalent in some reference frames to transmitting information backwards in time (cf. the tachyonic antitelephone ), but such temporal paradoxes are not known to occur in the Star Wars universe.  The only known examples of information transmitted backwards in time come from the Force, such as limited precognition of incoming dangers or vague, prophetic visions of possible futures.  Speaking of which, "the Force" is said to be "an energy field, created by all living things" which "binds the galaxy together".  It's not clear if the Force is a fifth fundamental force or "merely" a manipulation of the fundamental forces by focused will, but powerful Force-users have been known to raise and move heavy objects, conjure lightning, and manipulate minds.
It is not known if the universe of Star Wars is expanding, contracting, or steady-state, although prior to Lucasfilm's acquisition by Disney, the officially-published non-film Star Wars media were collectively known as the "Star Wars Expanded Universe".
In addition to the usual stellar evolution process, stars in Star Wars are subject to premature destruction or spontaneous creation by various superweapons, such as the Sun Crusher and Star Forge.
Many of the planets of Star Wars are dominated by one or two biomes, rather than the dozens into which our homeworld is divided.  Some of these are reasonable enough (a planet could certainly be covered in desert or ice or lava depending on its water content and proximity to a star), but others require some novel climate patterns not exhibited on Earth (the same atmospheric pattern that gives rise to Earth's tropical rainforests also produces the Sahara Desert).
[Rey, on the left, and Kylo Ren, on the right, from the Star Wars series, are facing one another and wielding lightsabers:]
Rey: Kylo, we shouldn't fight! Let's set aside our differences and work together to measure the local properties of space, just in case someone in the far future is watching from another galaxy and wants our help to constrain the expansion rate!
[Caption below the panel:] The new Star Wars totally panders to cosmologists.


Versus Bracket

Explanation:
This comic shows a tournament bracket in which the initial matches represent works of fiction or non-fiction with "versus" (represented as versus , vs. , v , etc) in their names (e.g. Batman is initially matched against Superman in reference to Batman v Superman: Dawn of Justice ).  The list includes 13 movies, 2 video games, and one television episode.  The works referenced are:
Assuming the tournament bracket reflects the results of each original work, the second round would result as follows:
The title text refers to the 2002 action film Ballistic: Ecks vs. Sever , which is qualified to be in this tournament by virtue of having the word "vs." in its title, but as the film is regarded as one of the worst movies ever made , it has been defeated in a pre-entry match vs. "the passage of time" - it is thus not considered worthy of entry in the tournament.
Tournament brackets is a recurring subject on xkcd, most recently used in 2131: Emojidome and 2037: Supreme Court Bracket . The latter is especially similar to this comic, considering that it also extends normal "versus" situations to a second round. The first bracket comic, 1529: Bracket , prompted people to create a series of polls to determine the end results, much like Randall later did himself with Emojidome. Randall even made a reference to one of those polls in the xkcd Header text .
[A tournament bracket tree is shown with 16 participants each on the left and right side. From both sides toward the middle the brackets reduce to eight, then four, two, and one line where the latter join to a rectangle in the middle.]
[Left side:] Kramer - Kramer Ford - Ferrari The People - Larry Flint Joe - The Volcano King Kong - Godzilla Freddy - Jason Dracula - Frankenstein Alien - Predator
[Right side:] Marvel - Capcom Marge - The Monorail Justice League - Teen Titans Asterix - Caesar Batman - Superman Scott Pilgrim - The World Mega Shark - Giant Octopus Plants - Zombies


The Time Before and After Land

Explanation:
This comic indulges in some wordplay on the title of the 1988 animated movie The Land Before Time , which takes place millions of years ago in the time of dinosaurs.
The comic shows a timeline of the history of the universe from the Big Bang to the present day, with The Land Before Time placed at the point in the timeline where the movie is set, as well as other seemingly arbitrary events such as the formation of rocky planets and the evolution of ground-nesting bees. The joke is that Randall has contrived several periods of universal history that sound like funny permutations of "The Land Before Time" due to certain words being homophones , such as "time" and "thyme", or homonyms, such as the noun "land" (ground) and the verb "land" (to alight). He also split the word "before" into "bee" and "for".
The title text is for the phrase "the time for Beeland" and lists 2 places (that Randall found on Google) with the name "Beeland": a market in Spillimacheen, British Columbia or a chalet in Slovenia .
Bees are a recurring topic on xkcd.
[Caption at top of panel:] (Timeline not to scale)
[A timeline is shown with two endpoints and five other points. The points are labeled:] Big Bang Rocky planets form Earth forms Ground-nesting bees evolve The Land Before Time Thymus genus diverges Now
[Below the timeline are five overlapping time periods in three rows. The text is between two thick black bars. The time periods all start and end at two different points.]
[Big Bang to Rocky Planets Form:] The Time Before Land
[Big Bang to Ground-Nesting Bees Evolve:] The Time Before bees
[Rocky Planets Form to Thymus Genus Diverges:] The Land Before Thyme
[Ground-Nesting Bees evolve to Now:] Time for Land Bees!
[Thymus Genus Diverges to Now:] Bees Land on Thyme


Hotel Room Party

Explanation:
It is a common trope that really wild parties in hotel rooms, particularly by rock bands on tour, end up trashing that hotel room as crazy party goers break and spill things.  Such parties are widely perceived to be very fun, because they got so out of control.  In this comic, Cueball (together with Hairy , Ponytail , White Hat , Megan , and Blondie ) is misunderstanding cause and effect as he plans to throw a party where you trash a hotel room.  Instead of planning a wild party, he is planning to calmly and deliberately trash the hotel room by assigning people to do damage.  Unlike a real wild party, this is unlikely to be fun [ citation needed ] to anyone but hardcore geeks. Also, because Cueball is so organized, he is also planning for maintenance and cleaning services to undo the damage, or at least make it easier to dispose of.  Since what is shown of such parties is the aftermath, one could argue that leaving the damage is part of the point.
In actual trash-a-hotel-room parties the party goers are so hungover or tired afterward that they don't clean up but leave the damage.  This often results in rock bands being charged large amounts of money after the fact for the hotel to do the repairs.  For this reason, one would probably like the hotel to take as long as possible to find out, definitely not calling the manager to check that the room has been trashed appropriately as indicated in the title text.
In addition to rock bands, trashing of hotel rooms occurred in real life in the Tailhook scandal of 1991, where it was revealed at an earlier party naval officers cut down a wall between two hotel suites with a chainsaw . Trashing a home during a teenage party while parents are away, and the mad rush to clean up the damage/evidence before the parents return, is a common trope in teen movies.
[Hairy, Ponytail, Cueball, White Hat, Megan, and Blondie are standing in a line. Cueball is raising his left hand with his pointer finger extended and is facing his left. He is also pointing to the right. The other five are facing Cueball.] Cueball: OK everyone, let's break into teams. Cueball: Katie, get the wire cutters and start disassembling the TV. You two can strip the wallpaper. Mike and I will work on shredding the mattress. Cueball: You, start shopping for maintenance and cleaning services. We don't want to leave the staff to deal with this.
[Caption below the panel]: It's my first time throwing one of those parties where you trash a hotel room and I want to make sure I get it right.


Aurora Meaning

Explanation:
The phenomenon of an atmospheric aurora (known as aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere) occurs as a result of charged particles emitted by the sun interacting with the Earth's magnetic field. The magnetic field funnels the charged particles towards the polar regions of the earth. At some point, the flow of particles hits the atmosphere, where the particles interact with the molecules of the gases which make up the atmosphere and add to those molecules' energy. Those molecules subsequently release the added energy in the form of light, which is observed as an aurora.
Where in the atmosphere the aurora occurs is related to the quantity and energy of the particles being emitted by the sun. Under normal circumstances, this occurs in high latitudes relatively close to the poles. In less common circumstances of more intense solar activity such as a a solar flare or coronal mass ejection (CME), the charged particles are traveling faster and get diverted less by the Earth's magnetic field, so auroras will occur at lower latitudes. This comic indicates both the rarity with which this would occur and the impact it would have on people.
Polar latitudes: Normal; auroras typically can be seen in these high latitudes.
Subpolar latitudes: (e.g., southern Canada/northern US, most of northern Europe, northern half of Asia, and numerous small islands in the southern hemisphere) Happens frequently enough to be unconcerned but uncommon enough to be notable and interesting. About a week before the publication of this comic, on Wednesday, November 20, 2019, aurora activity was visible in the northern United States and southern Canada.
Subtropical/Tropical latitudes: Charged particles of sufficient energy to cause auroras at this latitude are very rare and have happened on only a few occasions in recorded history, and not during the space age. A particularly strong one was the solar storm of 1859 , which caused failure of telegraph systems all over Europe and North America and in some cases gave telegraph operators electric shocks. An event of that magnitude today would likely interfere with the functioning of electronic systems in orbit, possibly to the point of disabling them entirely, and would cause widespread damage to our now highly electrified world.
Equatorial latitudes: Auroras have never been recorded here, so all scientific inquiry into what the effect would be on the Earth in general, and on life itself, is purely theoretical. Were this to actually occur, those theories could be proven or disproven based on actual observations (presuming all observers have not been incapacitated or otherwise occupied by the complete breakdown of all electrical and electronic systems as the charged particles induce electric currents in conducting objects). An event powerful enough to have auroras at equatorial latitudes would be extremely energetic and would probably cause very high levels of damage on Earth.
The title text comments on what would happen if auroras were seen in the equatorial band. arXiv.org is an electronic database of unreviewed, pre-print research papers. The astro-ph.SR sublist is a list of papers in the "Solar and Stellar Astrophysics" topic. So if auroras were seen in the middlemost band, there would be many requests to upload electronic publications on the subject, as well as actual electrical interference to the servers of the website. Randall may have been consulting this server for research on the comic, prompting this specific observation.
[A drawing of a circle with six dashed lines dividing it into 7 segments with different width. Those at equal distance above and below the broadest middle segments have the same width. Each segment has a label. Above the circle there is a caption:] What it means if you see an aurora, by latitude.
[The labels of the seven segments:] Normal Cool and exciting Someone should go check on our satellites A bunch of open questions in solar-terrestrial physics are about to be answered Someone should go check on our satellites Cool and exciting Normal