Awful People

Explanation:
Megan and Cueball are having a conversation about social media. Cueball mentions that when responding to textual comments on a screen, it can be easy to forget these comments are made by thinking, feeling humans (a sentiment expressed before on XKCD ). Megan agrees, but also relates a negative comment she got from a stranger about her taste in movies. The twist is that it turns out the person criticizing her was a murderer. Although this does not inherently negate his taste in movies, it does free Megan from the burden of weighing his opinions equally to her own.
The title-text mentions the “LakeSlayer7” which is clearly a reference to the "Lake Slayer" in the comic. They mention, contrary to several other reviewers, that a burger joint in town is unsatisfactory, and that the reader should come to a place “by the lake” instead, which might be (and probably is) a plot to lure people to the lake and to be slain. [ citation needed ]
In many social and news sites there is a tendency to surface negative content . This can be editorial intent , naive algorithms , or both , attempting to induce rage to drive engagement. Review sites can exhibit a bias in either direction, with minutiae burying valid feedback.
[Cueball and Megan are having a conversation while walking.] Cueball: The Internet makes it easy to be a jerk and forget the person we're talking to is a human. Megan: Yeah... Megan: But it also makes us see messages from awful people and assume they come from normal peers.
[Closeup on Megan. Above Megan is a picture of a "reply" post from a man with sunglasses. The post has a title above it.] Megan: Recently I got a mean reply from a stranger. It was minor but it really got to me. Post title: Replies to "Favorite Movie" Post: Every group has one person who likes that movie, and it's the friend they all secretly hate.
[Blondie as a news anchor behind a desk. A "News4" logo is displayed on the desk. There is a picture of the man with sunglasses with "Arrested" under his name. His picture is next to a picture of a house with "Breaking" above it. Megan's dialogue appears above the picture, but she herself is not shown in this panel.] Megan: Then the next week I saw that guy on the news. He was an actual murderer!
[Megan and Cueball standing next to each other.] Megan: I can't believe I spent a week stressed out that my taste in movies wasn't shared by the East Valley Strangler. Cueball: Yeah, at least wait for a second opinion from the Lake Slayer.


Edge Cake

Explanation:
Megan —possibly an IERS (International Earth Rotation and Reference Systems) agent—wishes Emily, represented as Hairbun , Happy Birthday. This prompts a confused Cueball to ask if her birthday was sometime last month. Emily explains that she was born over the North Pole in a plane, meaning that she was born in every timezone at once. Technically though this is false, as there are some timezones (such as UTC+5:45 ) that are not represented at the north pole. Except for the one hour before it's midnight at the International Date Line, the date in eastern time zones is one day ahead of western time zones, so Emily would have been born on two days at once.
She also says that it was February 29th (presumably it was also February 28 or March 1 in some time zones). February 29th only happens at most once every four years in the Gregorian calendar, adding to the confusion - people born on February 29th often celebrate their non-leap-year birthdays on arbitrary days (or not at all ). Normally one could simply use the time zone of the city the airplane took off from , but the airline company was changing ownership from one country to another at the time, so this option has apparently been ruled out. This is not terribly logical, however, since contracts transferring ownership usually specify an exact time (commonly one minute before or after midnight in a specific time zone to avoid confusion on which day midnight is in) to come into effect.  Regardless of which time zone(s) she was in when she was born this is an absolute time and if she was born before it she would have been born in an aircraft of the first country and if after it in an aircraft of the second country. Alternately, the time zone of the city the aircraft took off from doesn't change even if the nationality of the plane changes in midair, so that should have still been an option.
The punchline is that rather than try to identify the correct birthday for Emily, the BIPM has decided to let her have birthdays whenever she wants.  This doesn't make much sense, however. As noted above even if she was born in every time zone at once it could only have been on one of two days (February 29th, plus either February 28th or March 1st). Since it is common for people born on February 29th to celebrate on February 28th in non-leap years, it would have been trivial to pick the non-leap day present in some of the time zones (either February 28th or March 1st) and declare it Emily's birthday. It's possible that Emily was told "You can choose when you want your birthday to be", and Emily decided to exploit the lack of specificity to the degree presented in the comic.
In real life researchers in the Arctic at or near the North Pole use Coordinated Universal Time as the local time standard by convention, to avoid this exact problem. Thus it could have been said that Emily was born on the date that it was at that time in UTC. Furthermore, it is extremely unlikely that she would have been born at the exact instant the plane was over the north pole, indeed, it is unlikely that the plane even traveled over the exact pole, as opposed to a few miles or even feet to either side of it. With modern positioning equipment such as GPS, it should have been possible to determine which time zone the plane was in when she was born. Even in the impossibly unlikely event that she was directly above the pole at the instant of her birth, at jetliner speeds the plane was traveling about ten miles per minute, so a reasonable delay of even seconds in declaring "time of birth" would have placed the plane and her clearly in one time zone.
Both the comic title and Cueball's final line are puns on " edge case ", an engineering term referring to situations or conditions that are unusual in a way likely to cause problems unless specifically accounted for. Edge pieces are generally only important with sheet goods (brownies, sheet cakes, etc), which are typically cut into pieces creating a difference between pieces originating on the edge and pieces originating from the center. Since the top and sides of a cake are often frosted, an edge piece has two faces covered in frosting and a corner piece has three, while a center piece only has one. Depending upon your relative preferences between the surface (often icing over marzipan) and core body of the cake (which can be fruitcake, or some variety of spongecake, etc, but not actually obvious which until the cake is cut), it being an edge-faced slice can be considered a bonus. Cueball certainly seems to appreciate this.
The title text states that the IERS sends Emily a cake every time they add or remove a leap second, out of superstition (perhaps Megan is delivering that cake). The International Earth Rotation and Reference Systems Service is in charge of global time standards. It occasionally adds one leap-second to Coordinated Universal Time to adjust for changes in the rotation speed of the Earth.
The comic might also be a modern version of the SS Warrimoo , a passenger liner that reportedly crossed the international date line at the equator on midnight Dec. 31, 1899. This would have placed her bow in the Southern Hemisphere on 1 January 1900, her stern in the Northern Hemisphere on 31 December 1899. She would therefore have been simultaneously in two different hemispheres, on two different days, in two different months, in two different years, in two different decades, and according to some definitions in two different seasons (northern winter and southern summer) and possibly in two different centuries.
[Megan is walking towards Cueball and Emily (who resembles Hairbun), holding a cake.] Megan: Happy birthday, Emily! Cueball: Wait, wasn't that last month? When's your birthday, anyway? Emily: It's complicated.
[A diagram of a flight path over the North Pole, with meridian lines radiating out from the center. Emily's dialogue appears above the diagram, but she herself does not appear in this panel.] Emily: My mom went into labor on an arctic international flight that diverted directly over the North Pole. Emily: I was born in every time zone at once.
[With Megan standing behind her, Emily holds out a plate of cake to Cueball.] Emily: It was also February 29th, and the airline was just changing ownership between countries. Emily: The International Bureau of Weights and Measures finally issued a declaration that it's my birthday whenever I want. Emily: Cake? Cueball: Nice, it's all edge pieces.


Webb

Explanation:
This comic depicts an advent calendar geared toward astronomers anticipating the launch of the James Webb Space Telescope .
At the time this comic was published, the James Webb Space Telescope (JWST) was scheduled to be launched on the 22nd of December, 2021 (after many prior delays ). Christmas would indeed have come early for astronomers if the launch had been successful and on time. By December 14, the launch date had been pushed back again to "no earlier than December 24", as NASA was working on resolving a communications issue between the observatory and its launch vehicle system. This was followed by another delay announced on December 21, when the launch date was pushed back to December 25, due to weather concerns. It was successfully launched from Kourou in French Guiana on December 25 at 09:20 FGT (12:20 UTC, 07:20 EST ), as hoped for in this comic: 2559: December 25th Launch .
A normal advent calendar marks the days until Christmas by allowing miniature doors to be opened, or other means of revealing some treat/picture. This is often from the 1st of the month until the 'big reveal' on the 24th or 25th, though other schemes may exist in other cultures. This particular calendar features 18 hexagonal features, intended to be sequentially accessed over several days, in the same layout as the 18 gold-beryllium mirror segments designed to fold out to form the JWST's primary mirror. The first door is on the 5th, two days after this comic's publication date, making the last on the 22nd, the 'Big Day'.
Cueball's question could be interpreted two ways: Cueball doesn't know about JWST, so he is asking why this advent calendar ends before Christmas (and possibly fearing this calendar is similar to the one in 1245: 10-Day Forecast ); or Cueball does know about JWST and its history of delays, so he is asking why the calendar ends on 22 when there is no certainty in that launch date (and also implying that he expects it to be delayed). [Note: two weeks after the comic was posted, the JWST was again delayed, this time to no earlier than Christmas Eve (and later finally to Christmas Day itself), making the expectation accurate. This would also make a traditional advent calendar serve equally well, were it not for the hexagon design.]
December 22 is also the day after the northern hemisphere winter solstice. The end of the world was famously predicted for the winter solstice in 2012 .
The title text references the fact that chocolates in advent calendars are often molded into different shapes, and the fact that the later numbers have a "pamphlet on managing anxiety" is probably supposed to quell the impeding fear that the launch could be delayed further or go wrong. The telescope's launch was initially planned for 2007, but due to various redesigns, financial issues, accidents, flaws, and the COVID-19 pandemic , the launch date was pushed back to 2011, then 2013, 2018, 2020, May 2021, October 2021, and finally to the current launch date in December 2021. It may also allude to post-launch concerns; even if the launch goes well, there will still be nervousness about the complex 160-day process in which the JWST reaches its intended observation point 930,000 miles from Earth, many subsystems are unfolded/deployed, and the instrument passes its final calibrations. There is effectively no way to rescue/repair this expensive piece of equipment should anything be amiss, unlike the Hubble Space Telescope , which was visited five times by Space Shuttles to remedy and enhance various features. (There exist issues with even Hubble that cannot currently be considered repairable without the Shuttles or any proven replacement, and the JWST will be located far beyond Hubble's operational orbit in a place much more difficult to get to.)
The JWST has been referenced previously in 1730: Starshade , 2014: JWST Delays and 2447: Hammer Incident , mentioned in 1461: Payloads as well as indirectly in 975: Occulting Telescope . After this comic it was referenced in 2559: December 25th Launch and 2564: Sunshield .
[Cueball and Ponytail are looking at an advent calendar hanging on a wall in front of them. The advent calendar is loosely tiled with 18 smaller hexagons, numbered from 5 to 22 in no clear order or pattern. They are regularly arranged into a larger hexagonal shape and of the five rows, there are three in the top and bottom ones, as also with each diagonal edge. There are four in each of the other rows, offset symmetrically, with a gap where a fifth could have been in the centre of the middle row.] Cueball: The hexagons are nice. Cueball: But why does it end at 22? Numbers:
[Caption below the panel:] Astronomer Advent Calendar


Debunking

Explanation:
When writing a news article that "debunks" a claim (shows why it is false), writing its headline in the form "X is false" is discouraged . The reason is that just repeatedly seeing "X", even if negated or followed by "is false", can make readers subconsciously believe it.
To avoid this, Randall as a journalist has worded his debunking articles in a positive sense. This makes for a confusing read if the reader has not heard of the original claim. The "original claims" allegedly being debunked here don't actually appear to have been made anywhere, and can only be inferred from the debunking.
Much of the debunking relies on setting simple facts straight, making for bizarrely banal headlines.
[Several news headlines are shown in boxes.] [Box 1] AP photos show Dr. Fauci's office contains a normal number of microwaves [Box 2] Fact check: singer Billie Eilish was born years after the TWA Flight 800 explosion [Box 3] Vaccinated people can remove their hats without trouble by tugging upward, say doctors [Box 4] Physicists say Dorito powder is affected by gravity [Box 5] Steering wheels will work normally on Dec 12th; make left and right turns as usual [Box 6] CNN investigation: Santa's skin is dry and healthy this year, with the same amount of oil as before [Caption below the panel:] I don't know whether the "Don't repeat the claim in the headline debunking it" thing works or not, but it definitely makes reading the news weird.


The Last Molecule

Explanation:
This comic jokingly proposes a situation in which chemists have discovered and catalogued every single possible molecule. Thus they declare they have "completed chemistry."  As deep learning algorithms can now predict chemical properties of proteins in advance of measurement, this situation may be looming closer.
Like comic 2268 , this may be a reference to a quote from around 1900, often attributed to Lord Kelvin or Albert Michelson: "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement." More likely, this is a reference to attempts by Frege and by Russell and Whitehead a century ago to prove using symbolic logic the completeness of arithmetic. This turned out to be impossible since Kurt Goedel's famous Incompleteness Theorem proved that at least one proposition could neither be proved true or false. Against this background, the idea that natural sciences could be 90+% complete is humorously exaggerated.
In real life the number of ways to arrange atoms into molecules grows combinatorically with the number of atoms in a molecule. Since molecules can be extremely large (up until the point where gravity takes over and initiates nuclear fusion), the number of possible combinations is much much larger than the number of particles in the observable universe, making the full cataloging of all molecules impossible. Thus, a "final molecule" cannot be reached. In addition, chemistry is the study of the interaction and changing states of atoms and molecules, not simply the cataloging of all specimens of molecule. Even if we did have a list of every molecule, there are a far greater number of ways to continue studying them, so the field would still be nowhere near completed.
This is reminiscent of biology's focus in previous centuries on simply cataloging the species on Earth, or Mathematics' classification of finite simple groups (only the latter was, surprisingly, actually completed successfully).
Further, the goal of science is not to "complete" a field, but to understand it better and better (finite order group theory did not shutter its doors after all finite simple groups were classified).  No scientific field is considered fully understood (or rather, it is then considered a specialisation of a wider field). As readers are aware of this, part of the humor comes from the very high percentages given to the different fields. Putting Biology at 93% and Physics at 98% is patently absurd. Another part of the humor is the precision. As mentioned in the title text, we can't even give a definitive answer to changing-target yet deceptively simple questions like "How many kinds of ants are there?"
If biology were simply a matter of cataloging species, we are currently at around 10-20%. And yes many of them are ants; when J.B.S Haldane, founder of the field of population genetics, was asked what he learned about God from studying creation, he reportedly said "God is incredibly fond of beetles" . Counting species aside, fundamental and important problems such as what genes promote which traits, the nature of cognition, and the mechanism behind several diseases remain complete mysteries. We know less about our own ocean floor than we do about the surface of Mars.
As for Physics, all the elementary particles of the Standard Model of particle physics have been experimentally detected, culminating in the 2012 detection of the Higgs Boson . But questions such as "what is dark matter?", "how do we unify the four fundamental forces?", "how do we make nuclear fusion possible on earth?", "is the speed of light symmetrical?", and "how many dimensions does the universe have?" make it clear that the field still has a long, long way to go.
The title text in particular makes fun of Biology lagging behind due to the inherent difficulty of cataloging all species. Species are being constantly created and recategorized, so even if it were possible to know exactly what animals were alive on Earth at any one time, and which could interbreed, there would still be no agreement on the number of species they constituted, and that's without even getting into historic species, such as the contentious question of whether Neanderthals are considered a subspecies of homo sapiens, or a whole separate species.
[Ponytail is presenting on a stage. To the top-center of the slide which Ponytail is pointing to, there is a circled "100% complete" under "Chemistry", then to the left is "Biology" which is at "93% complete" and to the right is "Physics" which is at "98% complete". The bottom of the slide shows the structural formula of a molecule which is captioned "The Last One", along with a few smaller captions around it drawn as squiggles.]
Ponytail: With the discovery of the last molecule, I'm pleased to announce that chemistry is finally complete. Ponytail: Best of luck to our competitors in their race for second place.


Incident Report

Explanation:
An incident report describes the sequence of events when something goes wrong, including the lead-up as well as the aftermath. This usually involves describing at what time related events happen. In this comic, a report at a nuclear power plant on the day of the comic's publishing starts with particularly vague timestamps (that a package of fireworks arrived "roughly 18 hours prior" to it), then uses approximate minute-level precision ("14:00" and "14:20", which could reasonably be five minutes off in either direction), then minute-level precision ("14:28"), then second-level precision ("14:29:22" and "14:29:26").
This suggests that the clock time is really a proxy for the amount of time before one specific moment where everything falls apart, and when seconds start appearing, it implies that the recollection is within a few minutes of the disaster. Normally the increased level of precision reflects close monitoring capabilities of the affected systems, reviewing monitoring equipment, such as surveillance camera and microphone recordings, and/or detailed analysis by incident investigators. It may have been sufficient for the resulting inquiry to merely note the prior arrival of the original package, and possibly then read off (whatever remains of) the signing-in logs for the approximate times each member of staff arrives on the scene. At some point, though, the investigation will refer to fully timestamped security recordings, perhaps even eventually frame-by-frame with particular interest in exactly which things touched exactly what other things, in sequence, in order to hopefully learn all the necessary lessons about the incident.
Synchronization of events is important in incident investigations , so often systems are required to take input from common, relatively precise time references, such as GPS , WWV broadcast , or cellular telephone systems. For example, an aircraft crash needs radar positioning data synced with voice communications and flight recorder data .  Lack of correlation between these is a potential source of conspiracy theories, for example one of the hijacked planes on 9/11 crashed into Pennsylvania either at 10:03 or 10:06 depending on two different information sources.
In many situations, incident reports are anonymized as shown to protect the identities of those people involved in the incidents. This is often done to prevent unnecessary blaming of certain individuals, particularly when it hasn't yet been determined whether the incident was negligence or just an accident.
Examples of real-life incident reports with second-level precision timestamps showing the increasing precision around critical moments include:
The report shown cuts off before reaching the actual incident, leaving it to the reader to imagine what happened next. If the birthday cake has lit candles, one possible sequence of events is that a dropped or badly thrown juggling pin could have hit one of them and then rolled over to the fireworks package, thus igniting the package. This would have caused the fireworks to go off underneath the reactor control's console.
Although the comic refers to juggling "pins" , jugglers commonly call those props "clubs." It is possible Randall is confusing the similarly shaped objects in 10-pin bowling to juggling clubs. "Pins" are another name for a component of Uranium Carbide type nuclear fuel rods , which are involved in the safe control of the nuclear reaction within a nuclear power plant. No sane reactor staff would juggle these complex, heavy and expensive pieces of equipment. [ citation needed ]
The title text refers to the theme music from the 1975 film Jaws , which has come to represent impending danger. Movies use music to create the correct emotional tone; suspenseful music indicates that something bad is about to happen. The Jaws theme is an iconic example, famously used to create a sense of foreboding, then uses increasingly rapid tempo to build a sense of imminent danger, culminating in a dramatic moment of disaster (a shark attack, in the film). As with the increasing tempo of this theme, the increasing precision with which events are recorded in an incident report build the increasing sense that something terrible is imminent.
9603120071 is an actual accession number for an incident at San Onofre Nuclear Generating Station in 1996. Four slightly contaminated stray kittens were found, cleaned, and adopted. No clock times were mentioned in the report.
Real-world nuclear power stations have strictly regulated control rooms which would prevent the simultaneous presence of fireworks, juggling and birthday celebrations. [1] [2] There is no East Valley nuclear power plant, but there are two reactor units at the nuclear power plant in Beaver Valley, Pennsylvania.
Facility: East Valley Nuclear Plant Date: 12/10/2021 Report ID: 9603120071 Event description: Roughly 18 hours prior to the incident, an Amazon package containing fireworks was mistakenly delivered to the reactor control room and left under the console. The next day, at approximately 14:00 , Technician A arrived at the facility with a bag containing four juggling pins. At 14:20 , Technician A entered the control room, and joined Technician B at the console. At 14:28 , Technician C exited the elevator and approached the control room holding a birthday cake intended for Technician B. At 14:29:22 , Technician A said "Hey [Technician B], check out this cool trick I learned" while taking out the juggling pins. Technician B turned to look just as, at 14:29:26 , Technician C entered holding the cake.
[Caption below the panel]: You know things are about to get bad when the incident report starts including seconds in the timestamps.


Gift Exchange

Explanation:
In December, white elephant gift exchange parties are popular, in which party-goers bring and exchange presents, via a variety of procedures which often involve individuals taking turns to pick a present. Usually they can either pick a wrapped present and open it, or take a present that someone else has opened already.
Many political scientists think that creating a fair gift exchange is a really tricky problem, since it involves different valuation of various goods (one person might like socks while another person would not), a possible incentive to misrepresent how much you value things ("You're going to have to offer me a LOT to give up these socks, because I really like them"), arbitrary order effects (who goes first matters), and more. These problems have a lot of political analogues in the political science topics of social choice theory and mechanism design , and many political scientists dedicate years of their life to figuring out the best solutions. Therefore, a political scientist would enjoy the challenge of creating a fair gift exchange; it is the best gift that Ponytail could have given them.
The scenario Ponytail presents is formally known as a fair item allocation problem, for which there are various approaches to how to define fair , and various proposed allocation algorithms, some of which are computationally intractable even for small numbers of participants.
The fact that the family loves surveys implies that a favourite method of political scientists, surveying the electorate, would be greatly appreciated. The "It's okay if it's complicated" line is funny because many of the theoretically best solutions a political scientist might come up with would be very complicated--far more so than the typical person would want to think about.
In the title text, having well-formatted budgets makes a scientist's job much easier since it is better for data manipulation. In the same way, expressing preferences on a well-calibrated numerical scale makes data manipulation simple and straightforward. Therefore, Ponytail's scenario is an excellent gift for the political scientist. It also extends the humorous scenario of the nerdy family who enjoy filling in complex surveys - the same family would be likely to enjoy a well-formatted budget spreadsheet.
[Ponytail is talking to Cueball.] Ponytail: Ugh, I have to organize a fair gift exchange for my survey-loving family. Ponytail: Do you want to help? Ponytail: They said it's "okay if it's complicated."
[Caption below the panel:] The perfect gift for a political scientist


Notifications

Explanation:
Many devices will notify the user when something of possible interest occurs (e.g., a new phone call is received, a load of laundry is done).  Some, such as the instant messaging software Slack , allows you to turn notifications off while you're offline or away (or just don't want to be disturbed). Such a function would be desirable in real life, as illustrated here.  The sender can sometimes override this and notify the user anyway.
White Hat is telling Cueball and Megan about "another thing that annoys [him] about people," which means that either the strip begins after he has already vented a long series of gripes, or he is prone to spontaneously airing one of his many grievances non sequitur .  (Both of those traits could be something that annoys Cueball about people.) Cueball responds by "turning off his notifications" from White Hat. White Hat immediately falls silent, sparing Megan and Cueball from further boring "conversation". Maybe Cueball has picked up the "Commented" trick , White Hat is thrown off by the unusual statement, or it could be that he just naively takes Cueball at his word.  Either way, now that he "knows" that he will not receive any further immediate engagement from Cueball, he thus gives up, for the time being, talking at Megan and Cueball about his annoyance(s). If he believes the premise, he might recite the rest of his conversation as soon as Cueball supposedly turns notifications back on. His behavior is reminiscent of a user who is logged into a chat server but is "away from keyboard" and totally disengaged.
Megan starts to ask Cueball what he's doing, but Cueball shushes her to let it 'keep working' -- presumably, if Megan speaks up, she might alert White Hat that Cueball is still listening and draw him back into conversation.
In the title text, this is taken even further by combining this with a standard real-life reason (or excuse) to leave a social situation: that the person has to leave because it is getting late. It is often used when someone really has a thing early the next day and wants to get home early to get enough sleep to be prepared for the "thing", but the vagueness of the thing suggests that they just want to get out of uncomfortable company or situations.
The specific time, 10:34 pm, informs the messenger (who could be anywhere) of the user's time zone, and tells the one that wishes to notify that it is past the normal bedtime in the user's time zone. And this is why the program would normally ask if they still really wish to notify them, since they would risk waking the recipient up. This could cause annoyance if the message is not urgent and important. In this case, however, it is clear he is awake and wants to leave the social situation, supposedly because of a thing he has the next day. In this situation, it is funny because apparently it's Cueball talking about himself in the third person to another person who knows they are in the same time zone, and unless all of the characters are out really late it's unlikely that it's actually that late at night in "Cueball's time zone" at the moment.
An alternate explanation is that the comic highlights how strange it is that the "This user has notifications off, Notify anyway?" pop-up can sometimes leave one paralyzed with indecision, despite the fact that it does literally nothing to stop you from sending the text as normal. If it pops up when you send a text, now you have to decide whether your text is important enough to notify the person you have texted, even though they have notifications off. It's the same situation as if you're told that your boss is doing something important. You could be paralyzed, trying to figure out whether "the machine ran out of batteries" is more important than whatever generic "important thing" the other person is doing. Plus, now you have to factor in things like whether your interruption will cause more harm than help, how long it'll take, etc.
If Cueball just "Blocked" notifications from white hat, White Hat would simply be annoyed and just keep talking (because blocking implies that you just don't want to talk anymore.) However, by giving White Hat the option to "Notify anyway", Cueball paralyzes White Hat with indecision, as shown by him not doing anything for multiple panels.
This is ironic, as when users are given the option to "Notify anyway", it basically renders the action of turning off notifications useless because anyone can bypass the system. However, it still works to stop most message notifications, because no one wants to bypass the filter and risk annoying the person who turned off notifications. This may be why Cueball shushes Megan to let it 'keep working'; If Megan speaks up, White Hat might realize that Cueball's 'filter' does literally nothing to stop his messages, and White Hat would resume his rant.
[White Hat, Megan and Cueball are standing next to each other. White Hat is separated from the other two figures by a small margin.] White Hat: And another thing that annoys me about people is... Cueball: This user has notifications turned off.
[The camera zooms in on Megan and Cueball. Megan turns to look at Cueball.] Cueball: They will see your messages when they're back. Cueball: Notify anyway?
[The camera zooms outward to show White Hat. Megan turns back to look at White Hat. All three figures are standing silently.]
[Megan turns to look at Cueball again.] Megan: What are you-- Cueball: Shhh- It's working.


Turing Complete

Explanation:
A Turing machine is a theoretical computer that has an infinite tape of symbols.   It can read and change the symbols on the tape as it moves up and down this tape according to a set of instructions (program).
This very simple machine can be shown to do every computational task that what we think of as a "computer" can do, given the right program and enough time. Something that is Turing complete is able to act as a Turing machine, though generally physical examples are limited to having a finite tape, [ citation needed ] and this means it is also able to do basically every computational task.
Many pieces of hardware and software are supposed to be Turing complete (even Excel, as previously pointed out in 2453: Excel Lambda ).  Some other things turn out to be Turing complete, even if they weren't designed for it (for instance, the tabletop game Magic: The Gathering or, at least within xkcd meta-reality, rocks in a desert ). Whatever Ponytail has been referring to is not shown, but it seems to be an anecdote about how something seemingly too simple and/or specialised to exhibit such a computational equivalence has been discovered to actually be that capable. Ponytail may refer to the recent articles about the background of the NSO zero click exploit for iPhones, e.g. this .
Mario is the lead character in a long running series of video games including Donkey Kong , Super Mario Bros and Mario Kart .  Running video games, such as Doom , is one common way of demonstrating the ability to run arbitrary programs on devices that were not intended as general purpose computers.  With complex processors being installed in more and more devices, it's plausible that someone could get a dishwasher to play Mario.
However, another reason to make a device run arbitrary code is to breach security. If the owner of a system assumes that it can only do one specific thing, like operate a dishwasher, they may not take precautions against hacking.  But if the system is actually Turing-complete, a hacker could potentially make it do something else, like become part of a botnet .  Therefore, "this is actually Turing-complete" could be the prelude to a complicated hacking attempt.  Sophisticated hacking attacks are often the work of hackers that have the support of a government, or nation-state .
The ForcedEntry exploit is a way that was developed to allow PDF files to force malware onto various devices. PDF files are normally used to present documents.  The exploit uses a  PDF's ability to do logic operations on pixels to implement a simple virtual CPU within one of the PDF renderer's decompression functions. Constructing a CPU in this way is similar to how a hardware CPU is made of individual logic gates.  ForcedEntry was publicized a few days before this comic came out.
In the title-text it is suggested that this mechanism can be used for what might be more legal and practical purposes, although this might be up to some interpretation depending upon who has the right (and permission) to do what.
A tech stack is one shorthand way of describing the way an integrated grouping of communicating software packages provides everything from the deepest data handling (even as low-level as an operating system itself) to the user interface. All of these will normally be on a computer (or possibly many of them, whether locally or distributed worldwide) and if a sufficiently functional surrogate system is capable of emulating this (computing what the original computer(s) would do) then it can be considered to effectively be the same stack of technology and duplicate or replace the originals.
[Ponytail has raised her hand, palm up, as she addresses Cueball.] Ponytail: ...Now, it turns out this is actually Turing-Complete...
[Caption below the panel:] This phrase either means someone spent six months getting their dishwasher to play Mario or you're under attack by a nation-state.


Immunity

Explanation:
This comic is, although not specifically referenced, another entry in a series of comics related to the COVID-19 pandemic .
A common issue posited by people opposed to vaccination , especially during the COVID-19 pandemic, is that there are other ways to become immune to diseases caused by viruses or bacteria — most notably, contracting the disease "naturally".
Cueball , by way of questioning, points out to White Hat that this makes no sense. Contracting the natural disease is the thing people are trying to prevent . Diseases are bad. [ citation needed ]
Although there are plenty of instances where someone has already recovered, and therefore is in possession of natural immunity , it would be better to have that immunity without getting sick at all. Especially with a disease like COVID that can cause permanent damage even to those who eventually clear the virus. Vaccination provides similar immunity without the negative effects of infection. While explaining that getting infected is the best way to avoid getting infected, White Hat thus realizes the circular logic presented by anti-vaxxers , and thus stops mid sentence.
The title text elaborates on this by pointing out that people with no understanding of the immune system will understand that contracting a disease to avoid contracting a disease is a bad idea, and that people with a strong understanding of the immune system will understand the specific ways it can fail (and that vaccines provide a greater benefit for less risk). It is thus only people with a limited understanding of the immune system, who know that infection can provide immunity but haven't thought out the disadvantages of catching the disease, who would make a claim such as White Hat does.
The comic does not specifically reference vaccines and anti-vaxxers. It could also be about people who refuse to wear masks and social distance during the pandemic, who do not understand how much they are putting other people at risk. White Hat may even be fumbling an explanation of his previous 2515: Vaccine Research into why vaccines are good.
Older folks may be familiar with the "infection gives you immunity" trope due to their experience with so-called "childhood diseases". Before there were vaccines for e.g. measles , mumps , and chickenpox , it was seen as preferable for young children to contract these diseases, because the risk of serious illness is greater for those who get "first infections" later in life. Children run a comparatively smaller risk of serious illness in return for (usually) life-long immunity. Note that this only ever made sense for children whose immune system is still flexible enough to adapt, and not for 30 something fitness bros. Furthermore, the trope has outlived its context. Small as the risk to children of serious illness from measles, mumps, and chickenpox might be, vaccines all but eliminate the risk of contracting serious symptoms at all, so there is no sensible reason to subject oneself to infection.
The trope, moreover, is misapplied to COVID-19, because, on present evidence, immunity from infection is short-lived (which, at least at the time of this comic, was exacerbated by the fact that variants with sufficiently different spike proteins to at least partially evade natural immunity (such as beta, delta, and omicron) were arising at a rate of multiple per year), so there is no benefit to be gained by running the risk of winding up in the hospital - or the morgue. The better comparison is to influenza , which people get vaccinated against every year. Instead of childhood diseases, think of diseases that had a high probability of serious illness at any age, such as poliomyelitis and smallpox , for which few accepted the "infection gives you immunity" trope (even though, for those diseases, infection typically yielded life-long immunity), and there was far less resistance to effective vaccines once these became available.
[White Hat has raised his hand, palm up, as he addresses Cueball.] White Hat: See, it's good to get infected, because it gives you immunity.
[White Hat has lowered his arm.] Cueball: Why would I want immunity?
[Same setting.] White Hat: To protect you from getting inf... White Hat: ...wait.


Rapid Test Results

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic .
This comic is a joke about COVID-19 rapid lateral flow test results. These devices are used in many countries for individuals to test their own nasal and oropharynx fluid for evidence of COVID-19 virus to detect asymptomatic infection.  These tests have two indicator strips - a test line for covid-19 and a control line to check the device is working correctly.  Where a control line is not present, the test should be ignored and repeated. Until comparatively recently pregnancy was the occasion most familiar for requiring this form of test)
The first 2 answers are the standard indicators for a negative and positive result, but Randall takes this to absurdity, see below in the table .
The title text interprets the hyphen in "Covid-19" as a negative sign to make a mathematical joke (or possibly a reference to antimatter , which in reality mutually annihilates when coming into contact with regular matter). Here Randall postulates a counterpart virus to Covid-19, resulting in a test with inverted colors, which he names Covid+19. When combined this anti-coronavirus exactly matches the original one and results in zero Covid, curing those who had previously been infected.
This was the last comic before this year's Christmas comic . It was about Covid-19 testing. The last comic before the 2020 Christmas comic, 2402: Into My Veins , was about the Covid-19 vaccine.
[Header above the comic:] Interpreting Rapid Test Results
[What follows is a set of 8 possible rapid test results for COVID-19.]
[One line on the "C".] Negative
[Two lines, one on the "C" and one on the "T".] Positive
[Two curvy lines on the "C" and the "T", resembling the "approximately equal" sign.] Approximately positive
[Two lines, not on the "C" or the "T", but they are instead closer together.] Positive (college ruled)
[Five lines resembling a cell signal symbol.] Good cell signal
[Two straight lines, on the "C" and "T", with lines going outward from the centre, giving an illusion of the lines being curved.] Did you know these lines are actually parallel?
[One line on the "C", and two lines in a cross with one line sticking upward of the center of the cross.] The Blair Witch is near
[Three lines, with one on the "C", one on the "T", and one in the middle of the "C" and "T".] Click to expand Covid menu


December 25th Launch

Explanation:
The James Webb Space Telescope (JWST) is a space telescope jointly developed by NASA, the European Space Agency, and the Canadian Space Agency. It has suffered many, many delays over its development period (as previously referenced in 2014: JWST Delays ), but it finally launched on Christmas day, December 25, 2021.
This was about 7 hours after this comic appeared. The release day of this comic was Christmas Eve the 24th of December. As can be seen from when this page was created 05:02:00, 25 December 2021 (UTC), the comic came out at least 7 hours before launch which was 12:20:00, 25 December 2021 (UTC). Since Boston ( Randall's home town) is 5 hours after UTC then the comic must have released close to midnight on the 24th for Randall, and clearly before midnight for the rest of the time zones in the US.
Web comics are usually drawn some time in advance. When this comic was drawn and scheduled for publication, it is possible NASA had not yet announced that the launch of JWST was slipping from Christmas Eve to Christmas Day.
The launch was probably three days after Randall opened the last number in his Webb advent calendar. (Thus this is the second Christmas comic this year referring to the telescope).
In this comic, the James Webb Space Telescope is finally ready to take off. However, an unfortunate circumstance occurs: Santa Claus himself, presumably on his way to or from delivering presents to children, crosses into the path of the launch rocket. The joke is the implication that, right on the brink of success, this extraordinarily unlucky incident will either destroy the telescope, harm Santa, or cause yet another delay, much to Cueball 's horror.
Real launch aborts have occurred with fewer than 2 seconds left in the countdown, causing delays of over a month.
According to the title text, the range safety officer has made the decision to shoot down Santa Claus's sleigh, in order to clear the sky above, protecting the launch window. This seems to demonstrate that they are determined not to let anything delay the launch any further (or that given a choice between destroying the telescope or destroying Santa, the range safety officer chooses the latter). "Range Safety Officer" is the job title of a person in charge of the safety of a launch.
Airspace is normally closed to air traffic to avoid collisions between aircraft and rocket launches.  While Santa might not know about such restrictions, he already knows about this particular launch because thousands of astronomy geeks have asked for a new space telescope as a Christmas present in their letters to Santa, and the easiest way for Santa to deliver such a present is just keeping a safe distance from the launch pad. Moreover NORAD tracks Santa 's flying around the world and would be able to give sufficient warning to both Santa and Ground Control to prevent such a close encounter of a festive kind; as well as to prevent accidental global thermonuclear war by confusing a pack of flying reindeer with a first-strike attack by a foreign power. Finally, Santa Claus performs deliveries overnight, while the launch is scheduled for morning local time , so the timing of such a collision would not occur.
The JWST has been referenced previously in 1730: Starshade , 2014: JWST Delays , 2447: Hammer Incident and 2550: Webb , is on the list of payloads in 1461: Payloads and its planned use was indirectly referenced in 975: Occulting Telescope .  Santa is known to maintain a list of humans responsible for technological incidents and to have suitable punishment for offenders. 12 days after launch it was referenced again in 2564: Sunshield .
[Close-up of the top of the James Webb Space Telescope launch rocket. A "Webb" logo can be seen alongside other indistinct logos. Some clouds and birds are visible in the background.] Caption: T-minus 10...9...8...
[Zoom-out to show the complete rocket and the ground below. The rocket takes up the bottom-left corner. At the top-right, Santa Claus and a line of reindeer are flying in towards the left.] Santa: Ho ho ho! Santa: Merry Christmas!
[Ponytail and Cueball sitting at mission control consoles.] Cueball: Oh no.


Confounding Variables

Explanation:
In statistics, a confounding variable is a third variable that's related to the independent variable, and also causally related to the dependent variable. An example is that you see a correlation between sunburn rates and ice cream consumption; the confounding variable is temperature: high temperatures cause people go out in the sun and get burned more, and also eat more ice cream.
One way to control for a confounding variable by restricting your data-set to samples with the same value of the confounding variable. But if you do this too much, your choice of that "same value" can produce results that don't generalize. Common examples of this in medical testing are using subjects of the same sex or race -- the results may only be valid for that sex/race, not for all subjects.
There can also often be multiple confounding variables. It may be difficult to control for all of them without narrowing down your data-set so much that it's not useful. So you have to choose which variables to control for, and this choice biases your results.
In the final panel, Miss Lenhart suggests a sweet spot in the middle, where both confounding variables and your control impact the end result, thus making you "doubly wrong". "Doubly wrong" result would simultaneously display wrong correlations (not enough of controlled variables) and be too narrow to be useful (too many controlled variables), thus the 'worst of both worlds'.
Finally she admits that no matter what you do the results will be misleading, so statistics are useless. This would seem to be an unexpected declaration from someone supposedly trying to actually teach statistics [ citation needed ] , and expecting her students to continue the course. Though there is a possibility that she is not there to purely educate this subject, but is instead running a course with a different purpose and it just happens that this week concluded with this particular targeted critique.
In the title text, the residual refers to the difference between any particular data point and the graph that's supposed to describe the overall relationship. The collection of all residuals is used to determine how well the line fits the data. If you control for this by including a variable that perfectly matches the discrepancies between the predicted and actual outcomes, you would have a perfectly-fitting model:  however, it is nigh impossible (especially in the social and behavioral sciences) to find a "final variable" that perfectly provides all the "missing pieces" of the prediction model.
[Miss Lenhart is holding a pointer and pointing at a board with the a large heading with some unreadable text beneath it. Below this there are two graphs with scattered points. In the top graph the points are almost on a straight increasing line. In the bottom the data points seem to be more random. Mrs Lenhart covers most of the right side of the board, but there is more unreadable text to the right of her.] Miss Lenhart: If you don't control for confounding variables, they'll mask the real effect and mislead you. Heading: Statistics
[Miss Lenhart is holding the pointer down in one hand while she holds a finger in the air with the other hand. The board is no longer shown.] Miss Lenhart: But if you control for too many variables, your choices will shape the data and you'll mislead yourself.
[Miss Lenhart is holding both arms down, still with the pointer in her hand.] Miss Lenhart: Somewhere in the middle is the sweet spot where you do both, making you doubly wrong. Miss Lenhart: Stats are a farce and truth is unknowable. See you next week!


Moonfall

Explanation:
Megan asks Cueball if he is excited for the release of the movie Moonfall .
Moonfall was released in February 2022, a couple of months after this comic. Its director, Roland Emmerich , is known for blowing up things in his movies (see for instance the Roland Emmerich Supercut ), as well as for factual inaccuracies in his work (mainly the scientific implausibility of his many disaster movies like Independence Day , The Day After Tomorrow and 2012 ).
The plot of Moonfall is scientifically preposterous, making it potentially "cringe-worthy" for someone who enjoys "hard" science fiction, like Cueball.
For the moon to fall from the sky, it would have to stop orbiting. Most forces applied it to will simply change the way in which it is orbiting, making the orbit more elliptical, larger or smaller. To stop it from orbiting entirely, a 'braking' force would need to be applied in the opposite direction of its travel, to halt it.
The moon's mass is about 7.34767×10 22 kg and its speed about 1.022 km/s, so the energy needed to stop it is ½ mv 2 or about 3.8364×10 28 joules. That's about the energy of 1 trillion large nuclear explosions, centered on the leading-most point of the moon's surface. A precisely-oriented stellar body could strike the moon to do this, like a billiard ball colliding with tons of interstellar moon shrapnel instead of dust.
Less counteractive energy could make the Moon change orbit to one with a perigee below the surface of the Earth, close enough to (partially) enter the atmosphere or merely bring it down beneath the applicable Roche limit . These scenarios would be only technically less catastrophic, and whether the Moon fragments from the initially applied force, the stresses of its nearest (non-contact) distance to Earth or actually survives largely intact until there is a more direct physical interaction, the precise degree of the effect might be practically academic.
Cueball explains to Megan that he usually likes it when stories are based on good science. Maybe only bending it a bit to create the story, to expand our ideas of what is possible. But then he goes on to state that he supports giving Roland Emmerich as much money as he wants, to make cool spaceship noises and smash moons into things. In the movie it is only a moon (the Moon , presumably, see the plot below). But in general Roland often uses huge explosions in his movies, something also previously said about other similarly-styled directors like Michael Bay .
Megan sums the situation for Cueball up, stating that he is excited to expand our ideas of how much stuff can explode at once.
In the title text Cueball continues by explaining that while novel ideas and explosions are good, what he really want from a movie is novel ideas about cool explosions. So new ways to explode things, or ideas about exploding more things at once. Or both.
In 1536: The Martian a similar discussion of an upcoming movie is made for The Martian . But in that case it is the scientific accuracy that is the subject, and the lack of huge explosion that makes it hard to believe it could become a big budget movie! It is very rare that Randall makes a movie review like in those two comics.
Spoiler Alert
In Moonfall, a mysterious force knocks the Moon from its orbit around Earth and sends it hurtling on a collision course with life as we know it. With mere weeks before impact and the world on the brink of annihilation, NASA executive and former astronaut Jo Fowler is convinced she has the key to saving us all - but only one astronaut from her past, Brian Harper[,] and a conspiracy theorist K.C. Houseman believe her. These unlikely heroes will mount an impossible last-ditch mission into space, leaving behind everyone they love, only to find out that our Moon is not what we think it is. —Centropolis Entertainment, quoted at IMDB
[Cueball and Megan walking to the right] Megan: Are you excited for Moonfall ? Megan: Or cringing? Cueball: Well...
[Closeup on Cueball] Cueball: I like when stories are grounded in good science because it's exciting to expand our ideas of what's possible.
[Zoomed back out to Cueball and Megan walking to the right. Cueball has his palms raised] Cueball: But I also support giving Roland Emmerich as much money as he wants to make cool spaceship noises and smash moons into things. Megan: Excited to expand our ideas of how much stuff can explode at once.


Formatting Meeting

Explanation:
In the United States , it's common to write dates numerically in the format month / day / year -- 2/3/22 means February 3, 2022 (the century is often omitted when it's obvious that the date is around the current time). In Europe, the usual order is day/month/year - so 2/3/22 is 2nd March, 2022.
" Localization " is the technique used in software to make it accept input and display output in the formats most natural to users in their locations. For example, in the United States numbers use commas "," to separate thousands and a decimal point "." to separate the decimal values, while in large areas of the EU it is the reverse .  And the textual output will be translated to the local language. Naturally, this also includes displaying dates in the local format, as described above. Localization may also include the adoption of the tax law to the location, for instance when adopting tax software made for the US to the UK.
The joke in this comic is that two dates are shown, on the same display , relating to meetings regarding localization. The date of the meeting of the US team is localized in the US format while the EU team's meeting is localized in the European format, and these two dates (about a month apart) happen to be formatted the same (there are 64 such pairings of dates, as long as the day of the month of one is between 1 and 12 and not equal to the presumed month of the other). Cueball needs to explain that the European meeting will be a month later than the US meeting to avoid any confusion due to the ambiguity. Which is ironic , since the aim of localization is to reduce such confusion .
A further interpretation, which extends also into the title text, is that these groups may have been supposed to meet on the same day. But even the committee that was supposed to fix these problems messed this up. Cueball may be 'explaining' the staggered approach to cover up that the two groups are already reading the date(s) for the meeting quite differently.
ISO-8601 (that is, standard number 8601 as promulgated by the International Organization for Standardization since 1988) specifies a date format of YYYY-MM-DD (e.g., 2021-12-31), which results in dates being listed in chronological order when sorted stringwise. The ISO format is called " big-endian ", which refers to the fact that the most significant unit in the date (the year) comes first. The European format is instead " little-endian ", as the front-end value represents the finest possible distinction the date can convey - the particular day. The American format is " middle-endian ", or occasionally "mixed-endian", since the value given first is the one which is neither the one with greatest significance nor the most precise.
In the above, the 'value groups' are not usually internally checked for ' endianness ', but regular numerals are also usually written with the largest place values on the left – for example, the first 2 in 2021 is the thousands place – though whether this convention is big-endian or little-endian depends on whether the writing system of such numbers is in the context of left-to-right or right-to-left text. The concept of endianness is most often used in reference to the storage order, whether of indivisible binary bits or of values built up of successive value groups. Pairs of hexadecimal values are individually usually represented in big-endian 'numeric' order, where bitwise distinctions are not necessary, but it is useful to know if a system stores a multibyte value in big-endan or little-endian packing, i.e., whether the value 0x01 0x02 (values 1 and 2, on their own) is treated as a value of 258 (0x01*256 + 0x02*1) or 513 (0x01*1 + 0x02*256). (The term was taken in inspiration from a Jonathan Swift story about a war over which end of a boiled egg one should cut into, a useful metaphor for many other situations where diametrically opposed self-justifications for one or another practice may lead to standing by vague principles rather than agreeing upon a unifying resolution.) This standard was also mentioned in 1179: ISO 8601 and used in 1340: Unique Date .
The joke in the title text is that it appears some people attempted to interpret the improperly formatted date as if it were expressed in the more ISO-8601 style of format of "Y/M/D". They read the date as 20 02, March 22, so they already went to their meeting almost 20 years ago. Unless the announcement of the meetings was made 2 decades in advance, there's a paradox that these participants would have taken the date from an announcement in the far future. However, a strict interpretation of the date would make this incorrect: ISO-8601 format specifies four-digit years (which also avoids having to assume the century), two-digit months, and two-digit days. Therefore "2/3/22” can by specification not be an ISO-8601 date, as "2" can only be rendered as "0002", and "3" must be "03". Even if the leading zeroes were omitted in violation of ISO-8601, the year would become Year 2 , not Year 2002. Since the standard always uses a 4 digit 'YYYY' format in the first field, and no common formatting uses YYYY-DD-MM, any date written in ISO-8601 is easily recognized and (comparatively) unambiguously interpretable as YYYY-MM-DD. Dates written as if Y-M-DD or other distortions should be considered formatted improperly, and unwisely.
[A screen is shown which displays five rows of text, the top three above a dividing line. To the right of the screen the upper part of Cueball is visible as he delivers a message concerning the text on the screen:] Localization working group Upcoming meetings ----------------- US Team: 2/3/22 EU Team: 2/3/22
Cueball: And the European formatting and localization team will meet a month later...


Throat and Nasal Passages

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic .  This comic became the last to reference the pandemic for a long time. The next reference to COVID-19 came four months later and in 2615: Welcome Back it was just briefly mentioned in the title text.
In the graph a black solid line displays how much he has been thinking about his throat and nose since 2000 and up until 2022. The first 20 years the graph oscillate up and down once every year, and every spike represents the common cold and flu season. Autumn and winter causes the spike, while spring and summer clearly drops. Perhaps this is indicating no tendency to suffer from hayfever , which might at least produce mini-spikes at the times of of maximum grass-pollen, tree-pollen and/or other similar atmospheric flotsam. There is basically a spike for every year, although some years it looks a bit different which could be variations induced by complex sociological or meteorological drivers - meeting more or fewer people inside stuffy buildings rather than in the open air. But all in all the peaks seem low, especially when compared to how much time he has thought about it since the COVID-19 pandemic broke out around March 2020. Each summer since there has been a dip, but not anywhere close to the tops of the previous years, and around New Year 2022 the graph peaks (likely due to the Omicron variant ).
The peaks in 2020 and 2021 (2022) are about 6 times higher than those the year before 2020. So if the Y-axis begins at zero, this is how much more he thinks of his throat now than during the times when he actually had a cold.
There seems to be no way of knowing if Randall has had COVID-19, but from his comics it seems safe to assume he is fully vaccinated. At the time of release the Omicron variant of COVID-19 seems to by-pass the protections given by vaccines for about 50% of those vaccinated, although vaccinated people generally do not experience severe symptoms.
The joke is in the dotted line at the very bottom of the graph which either is just above zero, or is actually supposed to be the zero line (which would not change the above assumption about 6 times more thinking). This line reflects how much time he actually wishes to think about them, which is probably not at all. But even before corona Randall seems to have spent way too much time pondering his sore throat.
In the title text Randall references the trick known as "You are now aware of your tongue", which is a self-fulfilling prophecy because it will make anyone hearing it involuntarily think and be aware of their tongue. In a much earlier comic, 972: November , this trick was the topic, see more about it there.
Randall sarcastically remarks that the tongue trick needed an element of mortal peril to be truly enjoyable, as with the corona pandemic making him aware of his throat and nasal passages. His actual opinion is probably the opposite, that it was annoying before and that it only became worse now that it contains the danger of death. Being aware of your tongue is annoying, but not dangerous. Being aware of your throat during the COVID-19 pandemic may leave you fearing for your life, even if there is nothing wrong with your throat.
Randall has before the corona pandemic complained about a sore throat caused by the common cold, see 1612: Colds , more than once just a few weeks apart, see 1618: Cold Medicine . See also 1896: Active Ingredients Only .
[A graph with two curves are shown. The Y-axis ends in an arrow, but has no units or ticks. The X-axis has no arrow but has 23 ticks with every fifth longer and every tenth labeled. The first tick extends the Y-axis below the X-axis. Both curves start over the second tick and end over the last tick. One curve is a dotted straight line running along the bottom of the graph just above the X-axis. The other start a bit higher and oscillate a bit up and down with 19 sharp peaks and 19 troughs, where some of the troughs have extra features, and not all are equidistant. After this a 20th small peak just starts to drop down again, before the curve goes in to a very steep rise almost all the way to the top of the graph. There is a small dip on the way before it reaches a maximum. Then a deep drop followed by a smaller rise before an even deeper drop. But then at the end, the graph rises almost vertically to the highest point where the graph stops over the last tick. At the top left of the graph the two lines are explained showing a solid and a dotted line with text to their right. Below this, above the solid curve midway between the first two labels on the X-axis, is a label from which 5 arrows points to 5 consecutive peaks.] - How much Time I have spent thinking about my throat and nasal passages, over time ┅ How much I want to think about them Label:Cold/Flu Season X-axis: 2000 2010 2020


Sunshield

Explanation:
This is another comic with a Fact , though not a Fun fact - this time an Astronomy fact. The next comic with a fact, namely 2596: Galaxies , was also with an Astronomy fact. This is the first time that the field that a fact pertains to has been immediately repeated.
JWST stands for James Webb Space Telescope , a space telescope that was launched 12 days prior to publication of this comic, see more details here 2559: December 25th Launch .
It has a sunshield to protect its instruments from the heat of the sun and to keep them below 40 K (-233 °C/-388 °F). Deployment of the sunshield was completed the day before the comic was published. The JWST has to undergo a complex sequence of deployment steps to unfold parts that had to be packed tightly for launch. This sequence has 344 possible points of failure that would render the very expensive space telescope useless; 75% of them led up to the successful full deployment of the sunshield. Thus successful steps are widely celebrated, with this comic an example of such a celebration.
Ordinary cameras use a flash to take pictures in low-light situations. Outer space is very dark [ citation needed ] (one of the JWST's mission objectives will help astronomers calculate exactly how dark ), so this comic posits that the JWST has a very powerful flash to compensate for this. Most astronomical cameras don't use flash photography [ citation needed ] -- they depend on the light either emitted by objects themselves (e.g., stars) or from nearby very bright objects (e.g., Solar System planets will reflect the Sun's light, while distant clouds of gas and dust may be largely illuminated by the light of supernovae or recently formed stars within or near them). A flash generally doesn't work for many reasons:
There are some examples of astronomical research done using things similar to a flash. Radar astronomy involves emitting radio waves (microwaves) that bounce off distant planets, asteroids, comets, etc., and analyzing the returned waves. The Lunar Laser Ranging experiment uses lasers, which are loosely related to flashes for photography, to measure the distance between Earth and Moon. The outward light is concentrated upon the approximate area of the lunar target, which employs an optical trick to send most of that which actually struck it back to the approximate area of the source equipment.
The comic assigns the sunshield a new, comical purpose of shielding the Sun (and Earth ,which is roughly in the same direction as the Sun, due to the deployment at the L2 Lagrange point ) from this flash, rather than the other way around. When the camera is taking a picture, the comic shows space in front of the shield lit up while there is a totally dark shadow behind the shield (in the direction of Earth and Sun).
The comic also has the camera making a "click" sound. In traditional mechanical cameras without a mirror, this sound comes from the shutter opening and closing, and mirror-less digital cameras mimic this sound so the user (and subject, when human) knows when the picture is being taken. JWST won't actually click -- it doesn't have a shutter, as it takes long-exposure digital images, and in space no one can hear you click .
The telescope also tells the universe to smile for the picture. The universe doesn't have a mouth to smile with [ citation needed ] , although there are a number of features both on Solar System objects and in deep space that look like faces; this is a phenomenon called pareidolia . The most well known is the Man in the Moon , but there are numerous others both in the Solar system , most famous is probably the Face on Mars and out among the galaxies, like the Cheshire Cat galaxy group named after the Cheshire Cat from Alice in Wonderland .
The title text suggests that, due to the sunshield not being angled to shield Mars, Mars's surface has been badly scarred by the flash. This implies incredible strength of the flash, perhaps to ensure the light can return from its destinations, comparable to death-ray satellites in fiction.
[The James Webb Space Telescope (JWST) is floating through space, shown in white on a pitch black background. The two mirrors are seen in front of the sunshield, which is kite shaped. A white line goes from the telescope up to two lines of white text, connected with a small white line.] JWST: Okay, universe- JWST: Smile!
[Same setting, but now only a small thin white line goes up to a line of white text representing a sound made by the telescope.] JWST: Click
[Same setting, but now it turns out that a small bulb on the front of the telescope is a flash light. A bright flash glows from the bulb, turning most of the panel white. A cone on the left side is blocked and kept pitch black by the telescope's sunshield. The light fades a bit towards the edges of the picture, giving the light cone a rounded appearance. Thus the image actually looks a lot like Pac-Man in the process of eating the telescope.]
[Caption below the panel:] Astronomy fact: The purpose of the JWST sunshield is to protect the Sun and the Earth from the telescope's powerful flash.


Latency

Explanation:
This comic is about the time it takes for a request to be processed; a total of 1 second is devoted to automated processes, but 2-15 minutes or longer are devoted to a not-yet-automated process that is performed by a human.
Part of the humor comes from the fact that most, if not all, instances of a person copying and pasting data from one place to another could be trivially automated and included as part of the automated steps, if only a programmer could take the time to program the process. Having a human take several minutes to move data that a computer could move in fractions of a second is incredibly inefficient, and reflects the humorously poor optimization present in many routine processes.
The title text refers to SCAPDFATIAT, which is defined in the comic as Someone Copies and Pastes Data From a Thing Into Another Thing.
Because it requires a human worker to fully accomplish, in-between various other work commitments as well as possibly personal/non-work activities, it is plausible that (even if the copying was started promptly enough) the person involved will not have pasted onwards by the time their effective working day ends. It might be reasonable to assume that a job that ought to take no more than a few actual minutes thus is only 'guaranteed' to be concluded at some point the following working day (which may be a whole long weekend away, possibly including public holidays). The business will therefore state (e.g. in contractual service agreements) that the guaranteed response times are of the order of "within one working day". Even if they hope and expect that any request passed to their staff is handled within a much shorter timescale. If reliably capable of being fully automated (e.g. with a resilient and continually maintained server infrastructure), could be fulfilled almost instantly at any time of day or night. But it may be the need to keep an 'intelligent' human in the loop (as well as to "under-promise and over-deliver", rather than the reverse) that makes the concept of "next-working-day" a more attractive commitment to make.
[Caption above a graph showing a bar with 6 lines between the two ends:] Typical process latency:
[The bar is split in two small regions at either end with two times two lines close to each other at the left and only one of those pairs of lines near the right. In between is a very long white area with no features. Above the two small segments at either end, there are small brackets of this type "{" lying down so the tip points up towards a curved line that then goes up to two labels.] Left: Automated steps: 800 ms Right: Automated steps: 200 ms
[A similar, but very long, bracket is below the bar indicating the long white area in the middle. The tip points down to a label:] Someone copies and pastes data from a thing into another thing: 2-15 minutes (More if the person on call is busy)


Decorative Constants

Explanation:
This is another one of Randall's Tips , this time a Math Tip.
Randall gives an example of a complex looking equation labeled 4-15:
T = 𝔻m 0 (r out − r in ) μ̅
But since 𝔻 and μ̅ are "decorative", the equation can be reduced to
T = m 0 (r out − r in )
Here T is the net rate, m 0 the unit mass and (r out − r in ) the flow balance.
The decorative symbols can be interpreted as constants 𝔻 = μ̅ = 1, in which case the implied operations of multiplication and exponentiation make sense. The 𝔻 is double-struck ("blackboard bold", thus in the comic only the vertical line is double). Mathematicians, who are always searching for more symbols [ citation needed ] , have taken to distinguishing things represented by the same letter by using different fonts, such as 𝑑, 𝐝, 𝒅, 𝐷, 𝐃, 𝑫, 𝒹, 𝒟, 𝖉, 𝕯, ∂, 𝕕, and 𝔻. The double-struck font is easier to write on a blackboard than a proper bold letter and often represents a set, such as ℝ for the set of real numbers or ℂ for the set of complex numbers. 𝔻 can represent the unit disk in the complex plane, the set of decimal fractions, or the set of split-complex numbers.
μ is the Greek lowercase mu and has many uses in mathematics and science. Here it has a bar, μ̅, which could indicate a number of things, including the complex conjugate. Intriguingly, μ is the symbol in statistics for the population mean, and the overbar represents the sample mean, so this could represent a random variable which is the average of a sample of means μ i of different populations in some larger ensemble of populations.
Using a special version both of D and μ to even further spice up the formula all leads up to the math tip:
If one of your equations ever looks too simple, try adding some purely decorative constants.
Other examples of well known equations that are profound but look simple include
E = mc 2 ( Special Relativity ), PV = nRT (the Ideal Gas Law ), F = ma ( Newton's Second Law ), V = IR ( Ohm's Law ), and G μν + Λ g μν = κT μν ( Einstein field equations ), and e πi +1 = 0 ( Euler's Identity ).
Of these, only the Einstein field equations have been spiced up with decorative indices (which actually hide a system of ten nonlinear partial differential equations).
In the title text Randall mentions the Drag equation , which is attributed to Lord Rayleigh . In fluid dynamics , the drag equation is a formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid. The equation is F d = ½ ρu 2 c d A . Here F d is the drag force, ρ the mass density of the fluid, u the relative flow velocity, c d the drag coefficient and A is the area.
Randall jokes that the factor of ½ in the equation is meaningless and purely decorative, since the drag coefficients, c d , are already unitless and could just as easily be half as big thus leaving out the ½ in front of the equation. The ½ is thus just an example of a "decorative constant." The usual reason for including the factor of ½ is that it is part of the formula for kinetic energy that appears in the derivation of the drag equation, i.e. ½ ρu 2 . However, modern treatments are so condensed that this factor of ½ is often smuggled in with no explanation.
Since we can choose the constants to be whatever we want, it could be possible to absorb the ½ into the drag coefficient c d , but that does not mean it is unmotivated, since it comes from the kinetic energy. Still, Randall quotes Frank White's Fluid Mechanics textbook, which two times calls it "a traditional tribute to Euler and Bernoulli." According to White, the factor of ½ rather comes from the calculation of the projected area of the object being dragged. Randall has brought up this point before, in his book, " How To "
The line from White probably refers to renowned mathematicians Leonhard Euler and Daniel Bernoulli . Euler who is held to be one of the greatest mathematicians in history worked directly with Daniel and was a friend of the Bernoulli family , that produced eight mathematically gifted academics.
Daniel Bernoulli is known for modifying the definition of vis viva (what we now call kinetic energy) from mv 2 to ½ mv 2 , as motivated by the derivation from the impulse equation. In 1741, he wrote
[Define vis viva ] esse ½ mvv = ∫ pdx .
That is, "define vis viva to be ½ mv 2 = ∫ p d x ," where p is the force (from pressione ) and d x is the differential of position (infinitesimal displacement). Today, this equation says that the kinetic energy imparted to an object at rest equals the work done on it.
In the drag equation ½ ρu 2 represents the dynamic pressure due to the kinetic energy of the fluid, and hence the 1/2 makes sense to keep in the equation, and could thus easily be argued not to represent a decorative constant.
The title text is pretty much word-for-word a repeat from Randall's book How To . In Chapter 11: How to Play Football , he misuses the drag equation, and mentions this fact in more depth, in a footnote.
[A small panel only with text. Written as an excerpt from a mathematical text book. Begins with a number for an equation, then follows the equation written in larger letters and symbols. And below are explanations of each term in the equation. The μ has a bar over the top and the D has a double vertical line.] Eq. 4-15 T = 𝔻m 0 (r out - r in ) μ̅ T: Net rate m 0 : Unit mass (r out -r in ): Flow balance 𝔻, μ̅: Decorative
[Caption below the panel:] Math tip: If one of your equations ever looks too simple, try adding some purely decorative constants.


Language Development

Explanation:
Megan and Cueball are having what could appear to be a typical conversation about her child's ability to learn languages really fast. But the comic mixes up the concept of learning a language and the development of languages over time. The joke comes from the a conflation of two different things.
The conventional meaning of language development is the process by which infants begin to talk, that is to understand and produce intelligible speech. The field of language acquisition (sometimes called... language development) seeks to understand how baby humans are able to rapidly comprehend, internalize, and begin producing a new language so rapidly.
Instead of starting with babbling , the first stage of normal language development, this baby's form of "language development" seems to be the linguistic form: going through all of the theoretical stages of the evolution of the English language, from Proto-Indo-European to Germanic to Old English.
In comparative linguistics and historical linguistics , Proto-Indo-European is a theorized common ancestor of the Indo-European language family. Proto-Germanic is a reconstructed language formerly spoken in Iron Age Scandinavia. It developed out of Proto-Indo-European and is the proposed common ancestor for all Germanic languages . Old English would have developed out of Proto-Germanic. Modern English developed out of Old English with many additions from French (which comes from a different branch of the Indo-European language family). This parody of language development parallels the discredited theory of recapitulation in embryo development, sometimes expressed as "ontogeny recapitulates phylogeny", in which a developing animal embryo (ontogeny) was once thought to go through stages resembling successive adult stages in the evolution of the animal's remote ancestors (phylogeny).
In linguistics, reconstructed words from proto-languages are commonly marked with an asterisk (*) to show that the word forms are not attested by any historical sources but created as a proposed ancestor word. The baby says the Proto-Indo-European roots that the words "milk" and "please" are derived from. Obviously, the speakers of Proto-Indo-European did not speak in roots, but used words made from the roots, so the way the baby talks does not reflect any stage of development of the proto-language.
Some sounds babies make are hard to interpret. [ citation needed ] However, humans have a tendency to recognize known things and patterns. They see what they want to see and hear what they want to hear. Thus, a parent familiar with Proto-Indo-European may falsely hear their baby speak Proto-Indo-European by misinterpreting unintelligible sounds.
Perhaps this is an alternate universe where every baby has to gradually develop their language skills along a historical path rather than a child-developmental one, until they reach the ultimately developed modern language of their parents (in this case Modern English).
There have been alleged language deprivation experiments where newborn infants were not exposed to any spoken language in order to find the "natural human language", in the days before ethics review boards would have forbidden such cruel treatments. Such experiments are known today to be a source for psychological problems at least. Alleged outcomes in the apocryphal sources range from the deprived children imitating other sounds in their environment, to them dying.
In the title text, Randall describes a 2-year-old child as speaking in iambic pentameter and in Elizabethan English, a meter and dialect of modern English used by Shakespeare more than 400 years ago. The Terrible Twos are a colloquialism referring to the developmental tendency of two-year-olds to have more temperamental behavior, as the child's developing assertion of autonomy and self-identity clash with other expectations of behaviour, before hopefully acceptably balancing their assertiveness with social normatism. The toddler's quote of "forsooth, to bed thou shalt not take me, cur!" would roughly be equivalent to "Indeed, you shall not take me to bed, you dog!" in less archaic English.
[Megan and Cueball are looking to the left at a baby with dark hair. The baby sits on the left side of a table in an elevated baby chair.] Megan: He's only 1, so he still mostly speaks proto-Indo-European. Megan: But we've heard a few Germanic words already, so Old English can't be far off. Baby: *Melg- Baby: *Pl(e)hk- Cueball: They progress so fast!


Spinthariscope

Explanation:
This is another comic with one of Randall's fun facts .
As stated in the comic, a spinthariscope is a device with a small amount of radioactive material ( americium or thorium ) and a screen. When one of the radioactive atoms decays, it emits an alpha particle , which strikes the screen, which emits a small flash of light. You can see these flashes by looking through a lens.
It was invented in 1903 initially as a scientific instrument, but was soon replaced by more accurate and quantitative devices. But the original device was still popular for some time as an educational toy for children, and you can still get them today.
The joke in the comic is that most people have little understanding of radiation, and overreact to any mention that something is radioactive. So when Cueball tells Megan, White Hat, and Ponytail that the toy contains radioactive material, they're shocked and scared. But the amount of radioactive material in the toy is very tiny and the radiation is itself so trivially contained that there's practically no risk from it. The short-ranged alpha particles are likely stopped by the lens through which the harmless flashes of light (from particles that instead hit and neutralise in the internal screen element) are seen. Alpha decay always leads to an unstable decay product, which results in further decay (always gamma decay, and sometimes beta decay as well) which are less easily blocked, but the amount of such radiation from these decay products is negligible.
The fun fact in the caption says that Spinthariscopes have the highest ratio of "that can't possibly be safe and legal" to actual safety and legality of any known toy. When people hear about Spinthariscopes for the first time, they often assume, due to the radioactive material inside, that they must be very dangerous. They thus also question if such a toy is at all legal to make or own in the first place. But the fact is that Spinthariscopes are both safe and legal to make, sell and own.  So, the perceived danger and presumption that it must be illegal is at a very high number, and the actual danger and the actual illegality results in a very low number on the same scale. It is this ratio between perceived and actual danger and illegality that are the highest for Spinthariscopes, higher than for any other known toy.
The formulation, however, causes some confusion, because the caption uses actual safety and legality (high) instead of actual danger and illegality (low). Instead of a high ratio between perceived danger and actual danger, the result is an even ratio between perceived danger and actual safety, which are both high. The ratios for the other mentioned toys would also be even, as they have low perceived danger and low actual safety. This is obviously not the intended meaning, as the other toys are said to be toward the other end of the scale.
The title text mentions some other materials/toys that sound dangerous but aren't. Gallium is a metallic element with a low melting point of 29.76°C (85.568°F) so it will melt in your hand. Additionally, gallium has strange properties when it interacts with aluminum, causing aluminum to "melt" or become brittle. Tritium is a radioactive isotope of hydrogen, but can be used to create glowsticks and other lighted objects. Though these two toys might seem dangerous, they are actually typically used perfectly safely.
At the opposite end of the spectrum is lawn darts , a toy containing large darts that are thrown into the air to fall back down onto a target that's placed or marked upon the ground quite near the players' positions. Unlike the spinthariscope, which sounds dangerous but is actually harmless, lawn darts sound relatively innocent but can cause severe injury if you accidentally hit a person (and a few children were even killed ), so they were banned in the US and Canada in the 1980s. When sharpened, these toys even compare quite favorably to weapons of war .
Today many houses have smoke detectors using ionization caused by radioactive decay of Americium-241 to detect the smoke. So having something with radioactive material in your house is quite common, and in this case increases the safety level for those houses.
[Cueball is holding a small item up in on hand in front of his three friends. Megan has her arms lifted and bent in front of her, White Hat has his arms raised over his head and Ponytail is pointing at Cueball while her other hand, held down behind her, is balled into a fist.] Cueball: It's a spinthariscope, a 1940s toy with a radioactive isotope inside. If you let your eyes adjust to total darkness and look into the lens, you can see the flashes of individual atoms decaying. Megan: What?? White Hat: Aaaaa! Ponytail: Get it away!
[Caption below the panel:] Fun fact: Spinthariscopes have the highest ratio of "that can't possibly be safe and legal" to actual safety and legality of any known toy.


Hypothesis Generation

Explanation:
Miss Lenhart is teaching a science class and starts by formulating the fact that to perform any science you need to generate a hypothesis in order to test it.
The front row student, Cueball (presumably the rest of the students in the class are off panel), is thus prompted to ask the salient question of how one finds an original hypothesis. By using a clever prompting question in reply, Miss Lenhart allows the student to discover the answer himself. In typical Miss Lenhart fashion she is a bit rude, interrupting him before he can even formulate his thoughts. But the idea that he even has gotten an idea to share is proof that he has made a hypothesis about how to generate a hypothesis. This does not, however, answer how he did it, but now he knows he can do it.
This approach may not have worked with less eager/capable students, so it highlights the strengths of both the student and the teacher - and that she had a good understanding of the student's ability to reason this out with just the barest of guidance. Or perhaps it is just another prank by Miss Lenhart .
The key aspect being conveyed in this simple exchange is that one of the many good practices in science (no matter the aspect, though the specifics may change according to the precise field of study) is that one should first have an idea of what you can test and then perform the test to confirm (or rule out) your idea.
In the title text the joke is that it is thus very easy to make hypotheses and thus everyone makes them all the time, so there are numerous ones to test. And the now frazzled scientists that are trying to work their way through them request that everyone stop making new hypotheses until they have worked their way through the huge backlog of untested hypotheses already made.
[Miss Lenhart stands in front of a blackboard with various unreadable scribbles, gesturing towards it with a pointer.] Miss Lenhart: To do science, you generate a hypothesis, then test it.
[Cueball is sitting at a desk, raising his hand.] Cueball: But how do you generate a hypothesis?
[Miss Lenhart now stands in front of Cueball's desk, she is holding down the pointer and Cueball has his hands on his legs.] Miss Lenhart: Great question. How do you think you do it? Cueball: Well, maybe you - Miss Lenhart: And there you have it!