Mars Landing Video

Explanation:
Three days before this comic was published, NASA successfully landed a new rover, Perseverance , on Mars. This was also the subject of the previous comic 2427: Perseverance Microphones .
This comic was published shortly before a NASA press briefing that showed, as mentioned in the comic, the first ever full-speed video of a Mars landing. This comic is set at that press briefing and was published shortly before NASA, either unaware of Randall's threat or recognizing that it was not serious, went ahead and hold the briefing in real life. "Full-speed" here means that the video was captured at a frame rate high enough that it looks continuous when played back, as opposed to low-frame-rate imagery that looks jerky when played back.
The comic plays on the fact that if there is only one of something in a set, that one thing is the most/least in that set by lack of comparison. As there is only one full speed video of a Mars landing, that makes the video the best one as well as the worst one. Randall , who has often been banned from conferences , has apparently also been banned from NASA's press briefings. So he decided to crash the conference (literally, see below) solely to ask the question, "Is this then not also the worst video ever", flouting his ban and embarrassing NASA (a prior case of the latter is possibly why the former is currently active).
He follows up with the question of whether NASA is planning to make a worse Mars landing video, which is silly because people generally don't intend to make something worse. [ citation needed ] However, because this video is the worst full-speed video of a Martian landing by virtue of being the only full-speed video of a Martian landing, it is likely that if enough full-speed videos of Martian landings are made in the future, this video will not be the worst forever. Although this is merely a consequence of the fact that it is the only full-speed video of a Martian landing so far, the fact that it is technically true, as well as the way that Randall phrases it, makes it look embarrassing for NASA. The tendency of Randall (the character, not the real-life person) to make rude, embarrassing, and otherwise unwelcome comments is probably why he has been banned from NASA's press briefings, as well as all those conferences.
Judging by the sound effects, Randall has chosen to literally crash his way through the roof, using a "skycrane" — a general term for aerial vehicles that can lower or raise objects similarly to standard cranes. Specifically, one of these was used to land the Perseverance rover three days before. On Earth one might use the Sikorsky S-64 Skycrane helicopter, while NASA used a custom-built skycrane delivery system for the Perseverance rover. Randall deems using a skycrane to crash a conference about a skycrane ironic, especially since NASA's security was totally unprepared to stop him from using this method - a method NASA developed - to crash the press-briefing.
The title text refers to the 11-minute communications delay (one-way; 23-minute delay round-trip) between Mars and Earth, due to the speed of light and the distance between the planets at the time of the rover's landing. The Perseverance mission control must wait this long before they can even begin to respond to anything that happens to the rover, which Randall here twists into an 11-minute period in which he can ask whatever questions he likes before NASA can respond. This would only make sense if the conference he was crashing was on Mars and they were waiting for his questions here on Earth, or vice versa and plays on the ambiguity of the expression "Mars briefing", which can mean both a briefing about Mars and a briefing taking place on Mars.
[Hairbun is standing, arms spread out,  on a podium in front of a lectern. There is a "Crash" on the top right of the panel with several lines around to indicate the position, and an off panel voice coming from there. As indicated in the caption below the voice is from Randall.] Hairbun: We're excited to share the first ever full-speed video of a Mars landing. Sound: Crash Randall (off-panel): Doesn't that mean it's also the worst ever full-speed video of a mars landing? Randall (off-panel):Do you expect that record to stand forever, or is NASA working on a worse one?
[Caption below the comic]: NASA tried to ban me from their press briefings, but ironically their security was totally unprepared to deal with a skycrane.


Exposure Models

Explanation:
This is another comic in a series related to the COVID-19 pandemic .
Cueball (or Randall ) created another COVID exposure model to help lower his risk of catching COVID-19 in the pandemic. Megan inquires about the model's result, to which Cueball admits that he's been sitting at his computer continuously debugging models, and draws the conclusion that debugging COVID-19 models lessens close contact with other people. This is similar to the premise of 1445: Efficiency and 1708: Dehydration , except with the situation reversed — where before, researching a situation made the situation worse, here Cueball's time "wasted" has actually benefited him.
By "model," Randall likely means a manually crafted model, since he describes debugging it, but he may also mean the form of automatically generated software that is used in modern machine learning.
Cueball is too busy making models to figure out how to actually lower his risk other than sitting around repeating the work of others and improving his model-building skill. He has also created a meta-model, reporting the number of models Cueball has to create to wait the pandemic out. The fact that Megan refers to having to wait for the time that it would take Cueball to create four more models as "so close" implies that Cueball goes through models quickly, which makes sense because he spends all of his time working on new ones.
In the title text Randall mentions that he is dangerously close to making a spreadsheet about how many spreadsheets about coronavirus he has made cumulative over time. This would be a recursive graph, a recurring theme on xkcd.
[Cueball is sitting in an office chair at a desk typing on his laptop as Megan walks in.] Cueball: I built another COVID exposure model to help me limit my risk.
[Megan stands behind Cueball, who has turned in his chair to face her. He is leaning his arm on the back of the chair.] Megan: Any new insights? Cueball: Yeah: "If you spend all day debugging models, you don't have close contact with a lot of people."
[Cueball turns away from Megan to type on his laptop again. The back of his chair has disappeared.] Megan: Well, I guess it worked. Cueball: According to my meta-model, the end of the pandemic is only four more models away. Megan: So close!


Post-Pandemic Hat

Explanation:
This is another comic in a series related to the COVID-19 pandemic .
During the COVID-19 pandemic, there was a significant shift from in-person to computer-mediated interactions for both recreational and professional activities. For many, the computer setup used for these interactions is a laptop with a webcam above the screen. As people have become accustomed to looking directly into the camera, i.e. above where the other people's faces are, to simulate eye contact for meetings, Randall implies that there will be issues returning to pre-COVID life. In response, he has designed a baseball cap with an image that resembles a laptop webcam that sits above the wearer's eyes and a message that humorously acknowledges that the reader is likely reverting to virtual meeting habits for in-person interactions and that reminds people that for in-person interactions, one must look the other person's face, not above it like there's a webcam there.
The cap in this strip likely references a tradition of novelty tee-shirts, intended to be worn by women, feature "my eyes are up here!" or similar words written across the chest, and an arrow pointing upwards. These shirts are designed to both tease and parody the tendency of heterosexual men to look at a woman's breasts, usually automatically and without conscious thought. The cap, as a result, compares the conditioned response of looking at a webcam with the instinctive response of looking at a woman's chest, both of which would result in failure to make eye contact during a conversation.
Actual shirt-based text (as in the Title Text) would represent where a video-conferencer is not staring at the screen-top camera to 'fake' eye contact on the other screen(s) but truly aimed at the image of the eyes. The view of such an 'honest' stare could look like a 'chest gaze'.
1889: xkcd Phone 6 'solved' all these problems by putting a camera in the middle of the screen.
[A ballcap with an image of a webcam lens and a message reading "Excuse me, my eyes are actually down here" above a downward-facing arrow] [Caption below the panel]: Hat for post-pandemic socializing


Leap Year 2021

Explanation:
Cueball , checking his phone, comments on how fast time goes, saying it is already March. (This comic was posted on March 1, 2021.) Black Hat overhears him and says that it's actually February 29.
February 29 exists in the Gregorian calendar and its predecessor, the Julian calendar , as a correction mechanism for the fact that one tropical year on Earth is not exactly 365 days long. It's closer to 365.2422, and to prevent the dates from precessing relative to the seasons, an extra day is added once every fourth year, also called a leap year. This is still not enough to completely match Earth's orbital period, and for that reason the Gregorian calendar changed the leap year rules to be as follows: Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. This makes the average year 365.2425 days long, which approximates the 365.2422 days in the tropical year.
Black Hat wants every year to have a February 29, for no clear reason. Cueball acknowledges that he could accomplish this, if he could convince enough people to go along with it. Calendar systems are all invented, and whatever date systems are commonly acknowledged become the "correct" date. Cueball initially considers the change minor, assuming that they would simply change March 1st to February 29th on non-leap years, which would merely rename a single day and skip "March 1st" by going directly from February 29th to March 2nd. Black Hat clarifies that he actually wants to add another day, and the day AFTER that will be March 1. This could still be a minor change, if March were changed to a 30 day month on non-leap years, but Black Hat apparently wants the changes to propagate throughout the year. This would result in a 366-day year, causing the months to drift out of alignment with the seasons over the course of years, needlessly complicating time-keeping. Black Hat is unconcerned with the effect this will have on the "people of the future", and, as in the past , people around him are much more concerned about the time problems he's creating than he is. This once happened in ancient Egypt, where the priests had leap years every three years instead of every four years, so ancient Egypt had to have no leap years for several decades afterwards in order to fix the calendar.
In the last frame, Black Hat states that if the those people cared about the problems he's causing, "they shouldn't have decided to live in the future." Of course, it is at present impossible to choose the time period in which you live, [ citation needed ] yet Black Hat intends on penalizing them for it. Any number of positions could be proposed as a motive for his actions (for example, he may envy them for having the technology or benefits of the future, and wants to counteract that), but it is most likely that he is simply honing his sociopathic tendencies on a defenseless target.
In the title text, Cueball responds that this change would also cause issues for him, who is "living in the present", and he should not be forced to "move into the future". Alternatively, viewing the quote as a continuation of Black Hat's text at the end of the comic, he could mean that the effect of his new calendar is placed mostly on future people, and since he literally lives in the present and doesn't intend on travelling to the future, he can do what he wants without many repercussions. In this second interpretation, the phrase "move now" can be taken to have a double meaning: not only does Black Hat not intend to move presently, he also does not intend to move where the present currently is (i.e., move the "now" into the future).
[Cueball checking his phone in a narrow panel.] Cueball: Can't believe it's already March. Black Hat (off-screen): Nah, it's February 29th.
[Cueball has put his phone away and is standing next to Black Hat.] Cueball: It's not a leap year. Black Hat: I decided to make it one. Every year deserves to leap. Cueball: Can you do that? Black Hat: Can anyone stop me?
[Zoom in on Cueball.] Cueball: I guess if you just encourage people to call March 1st "February 29th", they can go along with it if they want. Just a one-day renaming. Black Hat (off-screen): No, tomorrow will be March 1st.
[Cueball standing to Black Hat, who is walking off screen to the right, with his finger raised.] Cueball: So you're causing calendar drift for future generations. Black Hat: If they didn't want to experience consequences, they shouldn't have decided to live in the future.


Manage Your Preferences

Explanation:
This comic illustrates the complex dialogues often employed by webpage or software designers to hide settings from the user. Many pages provide controls to set privacy-related preferences but make those settings opaque in an attempt to dissuade users from using them. The idea is that a user will become impatient by the confusing options and select the defaults, which provide the site or software with more access or information. This situation is compared to Myst , a 1990s puzzle video game.
Companies which collect or process personal information are required by privacy legislation to give their users the option to withhold personal information, although regulations vary depending on the region-specific laws. The operators of such services usually want to collect as much personal data as they can in order to target advertisements or sell their information to someone else, and wish to incentivize their users not to activate those features. One tactic that is frequently used to accomplish this goal is to provide the user an option which enables all the data collection, but to make the process of disabling the collection time-consuming or difficult. This type of action is generally illegal under the same privacy legislation, but regulation of it has been lax so many companies still try it.
"Atrus" in the title text is the main non-player character in the Myst series. In the first game these people were imprisoned within books. Pages needed to be collected to complete the books, and it was incredibly hard to find a single page, involving extensive laborious navigation and exploration, and the finding and solving of hidden puzzles. In the Myst mythos, the books open portals to other worlds, a little like web hyperlinks. Some sites' privacy settings are similarly labyrinthine. For example, some sites will run scripts from a variety of providers but will only allow users to disable them one site at a time without an explanation of what each one does.
The black background possibly shows how many sites are providing tools to switch between light and dark backgrounds now. For a long time white backgrounds were the usual default style, and only people who understood esoteric browser configurations could redisplay many things with a black background - possibly to help with perceived eyestrain or power usage in certain displays. More recently, it is a fashionable setting for content providers to compose as a selectable option. It is out-of-place for Randall to show a black background, as many of his comics take place in technical computer systems that often have a black background anyway, as most computer terminals still do.
Some browsers and websites do have actual games embedded within their various configuration interfaces. Chrome , for example, has the famous dinosaur game .
[Cueball is sitting in an office chair at a desk in front of his laptop computer. A black zigzag line points to the screen, and above this is shown what is displayed on Cueball's screen. This is shown as a black rectangle, with a white box, with black frame, overlaid over the top of the black section, extending half way above it. The text in this white box is in gray font. Inside the black rectangle are two gray rectangles, with white borders and black text. A small rectangle at the top has "Manage your Preferences" inside it, and a large rectangle below has 6 lines of text.] Agree to whatever Transport me to an immersive Myst-like game where I click confusingly-labeled toggle switches, only some of which work, perhaps never to find my way back to the page I wanted.
The title-text originally said "Atrius" instead of "Atrus". A few hours after the comic's release, this was changed.


Mars Rovers

Explanation:
In this comic, Randall has made a scatter plot displaying 6 different Mars rovers on a cuteness versus capabilities chart. Only three rover pictures are shown in the main plot, as two of the four rovers are near identical to other rovers sent to Mars, and the last rover is displayed off the cuteness chart.
He finds the Curiosity and Perseverance rovers to be very capable / useful, but not very cute. Spirit and Opportunity are cuter than the first two, but less capable.
The recently launched Perseverance rover contains a drone helicopter, Ingenuity , which Randall finds pretty cute, but is unsure how exactly to grade for capability. The error bars make Ingenuity look like it's bobbing up and down, as helicopters sometimes do. It's debatable if a flying drone can be considered a Mars Rover, since a rover is usually something that drives over a surface, but the anticipated flight plan for Ingenuity is to cover some distance (by air) and then land on the ground again.
Finally, on the very right far off the cuteness chart is the Sojourner rover, launched in 1997. He considers this rover extremely cute, but ultimately not that capable. To indicate the extreme cuteness of Sojourner (previously mentioned in 1585: Similarities ), he has drawn it far outside the axis of the plot to indicate it falls off the chart.
In the title text, Randall is disappointed that there aren't many people who have modified their Roomba vacuums to look like (or act like?) the Sojourner rover. Roombas are a recurring theme on xkcd. Search results at the time of posting are mainly reports mentioning the iRobot company, makers of the Roomba line, since one of its founders worked on the Sojourner rover.
The end of the title text, "be the change," is a truncated form of the expression "be the change you want to see in the world"; basically, if there's something you want to see happen, be the one who makes it happen. This implies that Randall will be modifying his Roomba to look/act like Sojourner .
[A scatter plot is shown with two labeled axis, each with 5 ticks and ending in an arrow. Two types of Mars rovers are drawn in the top left part, at the top tick and the next highest tick. Each rover type has a label with two names. A third smaller drone is drawn in the lower right part close to the third tick on the Y-axis, with a single name label. It has two arrows pointing up and down to question marks, and two small lines of either side of the rotor blades, indicate movement. Far to the right, about twice the length of the drawn X-axis from the origin of the chart, and at the height of the lowest tick on the Y-axis, is a third type of rover, also with a single name label. The entire chart also has a label:] Mars Rovers Y-Axis: Capabilities X-Axis: Cuteness Curiosity & Perseverance Spirit & Opportunity Ingenuity Sojourner


Vaccine Guidance

Explanation:
This is another comic in a series related to the COVID-19 pandemic .
On the day this comic was published, the Centers for Disease Control and Prevention (CDC) released new guidelines relating to COVID-19, lifting many of the existing restrictions for people who have been fully vaccinated for two weeks. Megan , speaking as a CDC spokesperson, is introducing these new guidelines in a video press conference. However, the other participants in the press conference quickly start asking about actions that have little or nothing to do with the vaccine, some of which would be dangerous whether COVID-19 was a risk or not, similarly to 2238: Flu Shot . It's possible that they do not remember life before the pandemic very well, as in 2391: Life Before the Pandemic .
Blondie asks whether it would be okay to visit neighbors and drink milk directly from the carton. In most Western cultures, drinking directly from a container that could be shared with others (such as a milk carton) is considered unsafe, due to the risk of diseases being transmitted, and generally gross, as saliva and other biological material is passed that way. While these risks are arguably worse during the pandemic, it was unacceptable before the pandemic and will presumably be so afterward.
Science Girl asks whether it would be okay to ride a bike down the stairs of a family member's house, which has a severe risk of injury.
White Hat follows up asking whether he can get a horse, and whether it would help for him and/or the horse to wear masks. This has basically no relation to anything else that was said. In response, Megan gives up trying to answer the increasingly irrelevant questions and ends the call.
In the title text, Randall mentions that when he is fully vaccinated, he will be able to write messages in ALL CAPS . This is generally used to indicate shouting, an activity which could spread COVID-19 and cause infection if done in person.
[Megan's face is seen at the bottom of the panel with the CDC-logo slightly above her and to the left; it is a black rectangle with the letters in white, and with a white jiggly line to the left of the first C.] Megan: Our new guidance: Fully vaccinated people can gather privately with no masks or distancing, and can visit with unvaccinated low-risk people in one household. Megan: Any questions? Logo: CDC
[Blondie, Hairy and Megan are seen at the bottom of the panel in three separate rectangular panels with Blondie and Hairy's panels at the left above one another. Those panels are almost square and also smaller than Megan's, more rectangular panel to the right of theirs. This panel is centered at the middle of those two panels to the left, and the logo is still visible. It is also shown that Megan is standing behind a lectern. Blondie, above Hairy, is the one asking questions to Megan.] Blondie: If my neighbors and I are all vaccinated, can I visit them unmasked and drink milk straight from the jug in their fridge? Megan: I...You can visit, yes. Blondie: And the jug thing? Megan: ...Next question? Logo: CDC
[In a frame-less panel there are two panels at the bottom, with Science Girl in the largest to the left and Megan in the smaller to the right, with the logo still visible, but unreadable still the lectern is shown.] Science Girl: I'm fully vaccinated. Can I ride my bike in my sister-in-law's house? Megan: In her house? Science Girl: Like, down the stairs. Megan: I guess? You should at least wear a helmet. Science Girl: Even if she's not high-risk? Megan: Any other questions?
[White Hat is in a rectangular box at the bottom of the panel. Megan is replying from off-panel to the right from a star burst at the edge of the panel. At the bottom there is a message in a black rectangle with white text.] White Hat: I'm two weeks past my second dose. White Hat: Can I get a horse? Megan: Thank you all for coming. White Hat: What if I wear a mask? White Hat: What if the horse does? Message: Meeting ended by host.


Geothmetic Meandian

Explanation:
There are a number of different ways to identify the " average " value of a series of values, the most common unweighted methods being the median (take the central value from the ordered list of values if there are an odd number - or the value half-way between the two that straddle the divide between two halves if there are an even number) and the arithmetic mean (add all the numbers up, divide by the number of numbers). The geometric mean is less well-known but works similarly to the arithmetic mean. The geometric mean of n positive numbers is the n th root of the product of those numbers. If all of the numbers in a sequence are identical, then its arithmetic mean, geometric mean and median will be identical, since they would all be equal to the common value of the terms of the sequence. However, if the sequence is not constant, then the arithmetic mean will be greater than the geometric mean , and the median may be different than either of those means.
The geometric mean, arithmetic mean and harmonic mean (not shown) are collectively known as the Pythagorean means , as specific modes of a greater and more generalized mean formula that extends arbitrarily to various other possible nuances of mean-value rationisations (cubic, etc.).
Outliers and internal biases within the original sample can make boiling down a set of values into a single 'average' sometimes overly biased by flaws in the data, with your choice of which method to use perhaps resulting in a value that is misleading, exaggerating or suppressing the significance of any blips.
In this depiction, the three named methods of averaging are embedded within a single function that produces a sequence of three values - one output for each of the methods. Being a series of values, Randall suggests that this is ideally suited to being itself subjected to the comparative 'averaging' method. Not just once, but as many times as it takes to narrow down to a sequence of three values that are very close to one another.
It can be shown that the xkcd value of 2.089 for GMDN(1,1,2,3,5) is validated:
The function GMDN in the comic is properly defined in the second row since F acts on a vector to produce another three vector, however GMDN in the last line is shown to produce a single real number rather than a vector and is thus missing a final operation of returning a single component. Each row in this table shows the set Fn(..) composed of the average, geomean and median computed on the previous row, with the sequence {1,1,2,3,5} as the initial F0. While GMDN is not differentiable, due to the median, this can be interpreted as somewhat similar to a heat equation which approaches equilibrium through averaging. Interestingly, the maximum value alternates between the average and the median (highlighted in bold in the table), while the minimum value alternates between the geomean and the median. This holds for many inputs thus providing the basis for a possible proof-by-induction of convergence on the range (see discussions).
The comment in the title text about suggests that this will save you the trouble of committing to the 'wrong' analysis as it gradually shaves down any 'outlier average' that is unduly affected by anomalies in the original inputs. It is a method without any danger of divergence of values, since all three averaging methods stay within the interval covering the input values (and two of them will stay strictly within that interval).
The title text may also be a sly reference to an actual mathematical theorem, namely that if one performs this procedure only using the arithmetic mean and the harmonic mean, the result will converge to the geometric mean. Randall suggests that the (non-Pythagorean) median, which does not have such good mathematical properties with relation to convergence, is, in fact, the secret sauce in his definition.
The question of being unsure of which mean to use is especially relevant for the arithmetic and harmonic means in following example.
Cueball and Megan decide to complete the exchange between themselves in order to save the Bid-ask spread of the Exchange rate which is the cost the bank imposes on Cueball and Megan for its service as a Market maker .
In one direction (€/$), Cueball is using the arithmetic mean but Megan is using the harmonic mean while in the other direction ($/€), Megan is using the arithmetic mean but Cueball is using the harmonic mean. This creates two new exchange rates which are closer than the orginal rates, but the new rates are still different for each other. Megan and Cueball can then iterate this process and the rates will converge to the geometric mean of the original rates, namely:
There does exist an arithmetic-geometric mean , which is defined identically to this except with the arithmetic and geometric means, and sees some use in calculus.  In some ways it's also philosophically similar to the truncated mean (extremities of the value range, e.g. the highest and lowest 10%s, are ignored as not acceptable and not counted) or Winsorized mean (instead of ignored, the values are readjusted to be the chosen floor/ceiling values that they lie beyond, to still effectively be counted as "edge" conditions), only with a strange dilution-and-compromise method rather than one where quantities can be culled or neutered just for being unexpectedly different from most of the other data.
The input sequence of numbers (1, 1, 2, 3, 5) chosen by Randall is also the opening of the Fibonacci sequence .  This may have been selected because the Fibonacci sequence also has a convergent property: the ratio of two adjacent numbers in the sequence approaches the golden ratio as the length of the sequence approaches infinity.
Here is a table of averages classified by the various methods referenced:
F(x1,x2,...xn)=({x1+x2+...+xn/n [bracket: arithmetic mean]},{nx,x2...xn, [bracket: geometric mean]} {x n+1/2 [bracket: median]})
Gmdn(x1,x2,...xn)={F(F(F(...F(x1,x2,...xn)...)))[bracket: geothmetic meandian]}
Gmdn(1,1,2,3,5) [equals about sign] 2.089
Caption: Stats tip: If you aren't sure whether to use the mean, median, or geometric mean, just calculate all three, then repeat until it converges
Geothm means "counting earths" (From Ancient Greek γεω- (geō-), combining form of γῆ (gê, “earth”) and ἀριθμός arithmos, 'counting').  Geothmetic means "art of Geothming" based on the etymology of Arithmetic (from Ancient Greek ἀριθμητική (τέχνη) (arithmētikḗ (tékhnē), “(art of) counting”).  This is an exciting new terminology that is eminently suitable for modern cosmology & high energy physics - particularly when doing math on the multiverse.  However, it is unlikely this etymology is related to the term "geothmetic meandian" as coined by Randall, as it can be more simply explained as a portmanteau of the three averages in its construction: geo metric mean, ari thmetic mean , and me dian .
The following Python code (inefficiently) implements the above algorithm:
Here is a slightly more efficient version of the Python code:
And here is an implementation of the Gmdn function in R:


Circles

Explanation:
The comic depicts five overlapping circles, themselves encircled by circles of various sizes which enclose two, four, or all five of the smaller overlapping circles, as in an Euler diagram . Several well-known logos consist of overlapping circles, and the larger circles reference these logos. These are: Mastercard , which consists of two side-by-side overlapping circles (technically, disks, since they're filled in); Audi , which is four side-by-side overlapping circles, and the Olympic rings , which are five topologically linked rings in a "W" shaped pattern.
To indicate that the Mastercard logo comprises two overlapping circles, the diagram draws a larger circle around the first two circles, inscribed with a label. Other than its size and the label, this new circle is identical to the five smaller circles.
Similarly, to indicate that the Audi logo comprises four overlapping circles, the diagram again provides a larger circle, this time encompassing the first four smaller circles, inscribed with a label. The "Audi" circle completely encloses the "Mastercard" circle, indicating that the four circles of the "Audi" logo include the two circles of the "Mastercard" logo.
Finally, an even larger circle, enclosing all of the other circles, indicates that the Olympic Rings use all five original circles.
The comic was released only about four months before the postponed 2020 Summer Olympics was scheduled to start on 23 July 2021. It was postponed because of the COVID-19 pandemic , which has spawned a series of comics on xkcd.
The title text is a textual representation of the Mastercard name as a Venn diagram containing the letters in the words "master" and "card" — A and R are shared by both, while MSTE and CD are unique to their respective elements.
[Five small circles, looped together in the style of the Olympics logo is drawn in the center. On the left, a larger circle surrounds two of the prior ones, incidentally overlapping a third circle. A larger circle surrounds four of the small circles, thus also the previous mentioned circle, cutting over the last of the five circles. Finally a very large circle fully contains all the other circles. The three larger circles have labels, with the small ones label above, and with a small clarifying line from the label towards the top of this circle. The middle sized circle has the label standing on a break in the circle at it's bottom, and the largest circle has the label just beneath it. From smallest to largest of the circles the labels are:] Mastercard Audi Olympics


Post-Vaccine Party

Explanation:
This is another comic in a series related to the COVID-19 pandemic .
As more and more people are getting vaccinated against COVID-19, and as the CDC has released guidelines suggesting vaccinated people can start gathering in larger groups, there is increasing excitement about the possibility to resume get-togethers, and have a party. However, being very cautious, Randall is cutting down the scope for his first "post-pandemic" party from that of a normal party. Not all of the scope reductions make sense. [ citation needed ]
The title text mentions that in the end, despite Randall's efforts, even the incredibly mild disruption of an M&M's falling into a cup of water caused the party-goers to panic and flee, much as Cueball and Ponytail did in a similar situation .
[The comic consists of four underlined headings, two by two grid, with three or four lines of text beneath each. Almost all of the original lines of text have been fully or partially crossed out (marked with <del> below), and five new items have been added (marked with <ins> below), plus some brackets and one arrow. Even one of the added items has been modified.] Drinks Soda Wine Beer Cocktails Small cups of ice water
Food Pizza Nachos Various snacks Three M&Ms and a saltine per person
Entertainment Music (ambient) Karaoke Big screen TV showing sports Bob Ross
Activities Board games 52-card pickup [The "52" is then stricken out and replaced with "3"] Video Games Ping ( Pong ) [A red arrow points from "Video Games" to "(Pong)"] Good conversation
[Caption below the panel:] We're planning our first post-vaccine party, but we want to start slow.


Siri

Explanation:
Science Girl thanks Siri on her smartphone for setting an alarm. In the next panel, she asks Cueball , "Is Siri alive?", since AI assistants can seem to be almost human on a very superficial level. Cueball answers "No," since Siri is entirely software, and we don't generally attribute life to computer programs (the closest might be computer viruses , since they replicate).
Science Girl then asks "How did she die?" She may have already been treating Siri as alive because she could talk to 'her,' and treats this lack-of-life as a new state of being. So rather than interpreting the answer in a philosophical sense of whether Siri is something that ever can be alive, which might normally have been presupposed, she treats it as meaning that Siri had (just) expired. This may require a credulous certainty of 'facts' taken literally - it is not clear what could then be understood if Siri were 'proven' to be alive and talking again, afterwards.
Or perhaps she thinks that the software Siri is a software embodiment of an actual person (or possibly ghost of actual person), and Cueball was talking about the original person. We don't currently have the technology to upload a person's personality into a computer , [ citation needed ] but it's a popular science fiction trope and many scientists think we will eventually be able to do this .
Another explanation could be that she associates everything into two categories, 'alive' and 'dead', without considering any intermediate or altogether separate categories, such as 'was never alive' or 'was programmed by people who are/were alive, but is not itself alive'. This false dichotomy causes Science Girl to misinterpret Cueball's answer of Siri not being alive as "Siri is dead."
Finally, she could have actually been asking about Susan Bennett , the voice actress that recorded the base sounds for the synthesizer, perhaps thinking she recorded the full line rather than just base sounds for the software to synthesize. Assuming Science Girl meant the default voice, Bennett is very much alive, and Science Girl simply asked her question wrongly.
The title text explains that, contrary to the above explanations, Siri actually died in a battle with Alexa , another personal assistant, hinging on their abilities to set multiple timers. Siri can set multiple timers, but this feature must be enabled via shortcuts. Alexa's ability to do so is much simpler and more user friendly. Of the many actions that these programs are able to perform, this is probably one of the more trivial, so it's not very comprehensible, at least to those not themselves living as digital assistants, that it would be the chosen method for a duel to the death. One possible explanation is that Alexa itself led the battle to that arena, where she knew she could win thanks to her superiority.
[Science Girl is holding her phone up in one hand looking at the screen. A starburst from the phone indicates the voice coming from the phone] Phone: Your timer is set. Science Girl: Thanks
[The picture broadens and shows that Science Girl, with the phone now held down, is standing in front of a desk, where Cueball, facing her, is sitting in an office chair using a laptop.] Science Girl: Is Siri alive? Cueball: No.
[Back to only showing Science Girl, her phone and arm still held down at her side.] Science Girl: Oh, ok.
[Same setting but Science Girl has raised her arm with the phone, looking at it again.] Science Girl: How did she die?


Solar System Cartogram

Explanation:
In this comic, Randall has made a cartogram showing the planets in the solar system . Cartograms are a type of map in which geographic area is displayed proportionately to some secondary characteristic - in this case, population. From the title text it is clear that the population in question is human (persons) (but even if all life forms where counted it it wouldn't matter, since the only confirmed life in the Solar System is on Earth). Thus the other planets have a population of 0 and are shown as nothing more than dots.
This comic is a joke about cartograms, which are used, for instance, to show electoral representation. A standard American electoral map is very misleading. Though the split between the two major parties, Democrats and Republicans, is about 50-50, most of the area of the U.S. map is shown in the color associated with the Republican Party, red. That's because many Democrats live in densely packed districts occupying little land area, while many Republicans live in rural districts with large land area but few people. This has led to the rise of electoral cartograms in which district areas are shown in proportion to population, correcting the misimpression that most of America is conservative.
Solar system diagrams are likely also to be misleading. Illustrators are overwhelmingly forced to use a far more scaled-down spacing between planets, compared to their scaled sizes, even if they can (or care to) maintain consistency in the relative distances and/or radii on linear scales. (The huge factors of difference involved instead may lend themselves to being physically modeled to better give some sense of the spacing and sizing differences.) Here, Randall has intentionally applied the wrong solution to the problem.
Interestingly, the side of the Earth shown includes China and India, two countries that alone account for over a quarter of all humans on Earth.
The title text states that even though Randall counts every active Mars rover as a person (for sentimental reasons), they are almost nothing compared to Earth's roughly 7,900,000,000 persons. Mars therefore is still nothing more than a dot compared to the Earth. There are a total of five rovers at the time of the comic's publication; in chronological order, they are Sojourner, Spirit and Opportunity, Curiosity, and Perseverance. Only the latter two were functional at the time of the comic's publication, giving Mars a rover population of two. A third rover, China's Tianwen-1 , landed on Mars on 2021 May 14, making for an all-time high of three active rovers.
Mars rovers are a recurring theme on xkcd and only a few weeks earlier, a comic named 2433: Mars Rovers was released. This is the fourth comic this year to reference Mars Rovers.
[Above a chart are two paragraphs with explanation:] Most solar system diagrams are misleading. This chart offers a more accurate view by showing the planets sized by population.
[Below the explanation is a list of the eight planets in the solar system. They are shown in order with labels. All but Earth show up only as dots. Earth is large and clearly drawn, with a view approximately centered on Indonesia. The spacing between the dots is equal, and the same distance as from those closest dots to Earth to Earths surface. Earth's label floats below it, while the other planets' labels connect to their respective dots with lines, with text either above or below the line of planets:] Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune


Epistemic Uncertainty

Explanation:
This comic is a comparison of two different research studies. One of these studies shows "regular uncertainty". One of these studies shows "epistemic uncertainty." In both panels, the core data is the same. The drug in question is 74% effective. However, the uncertainty qualities are different. The first is straightforward. The confidence interval (the error bars on the chart) is from 63 to 81%. The second panel includes the additional wrinkle of "George the Data Tamperer, whose whims are unpredictable."
In statistics, a confidence interval is an estimate which provides a range of values. These values are based on the statistical probability that the data collected represents a certain result. The confidence interval is a reflection on the uncertainty imposed by the limits of study sample sizes. No study will ever have an infinite data set. [ citation needed ] As a result, it is possible for different studies to give slightly different results.  Averaging the results of multiple studies can give a result that is probably more accurate. The result given may still be skewed. A small skew is more probable than a large one, though. For example, if a drug was 80% effective it would be possible for several small studies to show a spread of different results with an average of 74% effectiveness. If the drug was 99% effective it would still be possible to randomly end up with the same data. However, this would be highly unlikely. This gives us a spread of "likely" predictions. Predictions outside a certain interval are considered too unlikely to be realistic.
George the Tamperer and Evangeline the Adulterator (from the title text) are analogous to the characters from Alice and Bob cryptography thought experiments. In the most basic examples, Alice and Bob are communicating. A third party, Eve the Eavesdropper, is spying on them. Both George and Evangeline have the ability to alter the study's results. George and Evangeline add uncertainty to the final data product. Specifically, they add epistemic uncertainty.
Epistemology – unlike epidemiology – is the branch of philosophy related to knowledge. Thus epistemic uncertainty is the ultimate impossibility to be sure that what we know is accurate. We are not unsure what is accurate beause of failures in measurement. We are unsure what is accurate because of the intrinsic limits of knowledge. It seems that the "epistemic uncertainty" data has a 25% chance of data tampering by George. In  the previous study, the data is known but its reflection of the general case is uncertain to an extent. In contrast, in this study even the knowledge of whether any single data point is correct is uncertain. Thus, their data has a 25% chance of being incorrect. There is no possible statement about how incorrect it may be.
The title text mentions an individual called "Evangeline the Adulterator." She adulterates their drug doses. If this happened, the researchers would not even be sure the patients received the dosages (or exacting medicines/placebos) as prescribed. The study methodology itself would be in doubt.
[Two panels are shown with labels above them.] Regular Uncertainty Epistemic Uncertainty
[In both panels Megan stands in front of a data presentation on a slide behind her. She is pointing at the slide with a stick.]
[In the left panel titled 'Regular Uncertainty'. Megan standing in front of a presentation of a graph showing, from top to bottom, the number 74%, a horizontal line with a small black diamond near the middle representing an average with error bars, and a line of dots representing data in a horizontal scatter plot.] Megan: Our study found the drug was 74% effective, with a confidence interval from 63% to 81%. 74%
[In the right panel titled 'Epistemic Uncertainty'. Megan stands in front of a presentation of data with a silhouette of a man with a hat labelled with a white question mark. Above this are three guesses of the "real" result and its relation to the study result.] Megan: Our study found the drug to be 74% effective. Megan: However, there is a 1 in 4 chance that our study was modified by George the Data Tamperer, whose whims are unpredictable. 73 -> 74?? 47 -> 74?? 0 -> 74?? ?


IMDb Vaccines

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic .
This is another entry in the My Hobby series. Cueball is evaluating movies on IMDb (the Internet Movie Database ), based on how many people would need to be vaccinated for COVID-19 , in order for them to follow the CDC's most recent guidelines. The guidelines tell how fully vaccinated people should act ( at time of posting ). The evaluation assumes that the COVID-19 pandemic spread to the universes where the movies take place by the time at which they take place. This is part of a continuing pattern of comics . In these comics Randall applies COVID-19 safety standards to pre- or post-COVID situations.
At the moment, Cueball is viewing the final confrontation between Luke Skywalker, Darth Vader (formerly Anakin Skywalker), and Emperor Sheev Palpatine. This confrontation takes place on the second Death Star in Return of the Jedi . Darth Vader wears a breathing apparatus in a mask that fully covers his face. Vader wears this because he sustained massive respiratory damage several movies earlier. During the confrontation, the Emperor is killed. Then Luke removes Vader's mask to see his face. (It is revealed in a previous film that Vader is Luke's father.) COVID-19 would be impossible for the Star Wars movies. It would be impossible because the Star Wars movies take place "a long time ago in a galaxy far, far away". This time was well before COVID-19 existed. [ citation needed ]
Cueball notes that if only Luke had been vaccinated, he would still be a possible risk to Vader. The various vaccines seem to do well to protect recipients from the harsher outcomes of the virus. The vaccines may not completely prevent them from mild infection and potentially then passing it onwards. Luke is young and healthy. Luke is probably less susceptible, if Luke were to be exposed to the virus at any point. Vader's health issues mean that Vader would be in much greater danger from such a respiratory disease without Vader's own personal inoculation. The Emperor is elderly, but probably not at as great of a risk as Vader is. However, the Emperor, too is susceptible if the Emperor were infected.
Cueball judges that Darth Vader's mask and breathing apparatus would protect Vader from the virus, a topic that was previously considered in 2367: Masks . The protection is at least to a limited extent. This is not an unreasonable assumption. Vader's suit has allowed Vader to survive the vacuum of space for short periods of time . Cueball concludes that all the characters in this fight need to be vaccinated in order to prevent the spread of the virus. This will be true until the Emperor dies. After the Emperor dies, only Vader needs to be vaccinated.
The title text refers to two separate CDC recommendations. If you are visiting with people from a single household when vaccinated, all at low risk of serious complications from COVID-19, you do not have to take precautions. The precaution that you do not have to take include physical distancing or masks. If you are visiting with people from multiple households, then it is recommended that you take precautions against the spread of the disease regardless. Cueball is unsure whether or not Darth Vader and the Emperor live in close enough proximity to count as a single household. Whether Vader and the Emperor live in a single household would change how Cueball decides who should and should not be vaccinated. It is unknown, based on the Original Trilogy of Star Wars movies alone, how much time Vader and the Emperor spend in proximity. The "weird black egg thing" refers to Darth Vader's meditation chamber . The meditation chamber first seen in The Empire Strikes Back , which allows Vader to spend some time outside of his suit.
[Cueball is sitting in an office chair at a desk typing on a laptop. There is a large thought bubble of his thoughts above his head, and his typing on the laptop makes sounds.] Cueball's thoughts: For the throne room scene, I think it's all three until the Emperor dies, then Vader only. It can't be Luke only, since he's visiting Vader, who is clearly at elevated respiratory risk. Plus, he removes Vader's mask! Keyboard: Type type.
[Caption below the panel]: My Hobby: Editing IMDb to note the minimum set of people who need to be vaccinated in each scene for it to pass muster under current CDC guidance.


Mask Opinions

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic .
Cueball and White Hat are having a conversation about face masks, which have become everyday essentials during the COVID-19 pandemic. Cueball has become exasperated with the weight of mask-related knowledge on his mind at all times, citing examples of instances of conversation in which he irritably divulges his knowledge of face masks. White Hat tries to placate him with the idea that this won't go on forever. He suggests thinking and talking about other things, but given Cueball's obsessive tendencies in the past, this is unlikely to occur. The final words of the comic, "Well. Soon." may be a pun on the phrase "Get Well Soon", commonly said as an expression of sympathy for someone who is sick or injured. In this case, White Hat hopes that Cueball will be able to stop talking about masks soon, which in turn means that he hopes for an end to the coronavirus pandemic.  (It is not stated whether he hopes for an end to the coronavirus pandemic simply so that he can stop hearing Cueball talk about masks or because of the lives that would be lost if the pandemic continued.)
In the title text, Randall implicitly endorses White Hat's hope, while suggesting that the new norm of wearing a mask when you feel sick will still be useful after the pandemic ends. Given that masks lower the transmission rates of many viral infections, including the common cold, this could be a wise strategy for avoiding illnesses in the future. Such a practice has been present for some time before the pandemic in other countries, Japan among them, where the habit of masks is the result of the last big pandemic (Spanish Flu, 1919/1920), but in North America the practice began (and may end) with COVID-19. Eliminating the common cold through masks, in this case via hazmat suits, has been examined in the What If? chapter 'Common Cold'.
[Cueball and White Hat are standing and talking. Both are wearing masks.] Cueball: I am so excited not to have so many opinions about different kinds of masks at the forefront of my brain at all times. White Hat: Seriously.
[The panel is zoomed in on Cueball's upper body. His hands are raised.] Cueball: "Do you know any tricks for getting a good seal around the bridge of your nose?" Cueball: I do, and I want to stop knowing them.
[Cueball is walking away from White Hat with his hands raised above his head.] White Hat: You could always try talking about something else. Cueball: Honestly not sure I can! White Hat: Well. White Hat: Soon.


Immune Response

Explanation:
This is another comic in a series related to the COVID-19 pandemic .
As with a number of previous strips , Randall has a tendency to anthropomorphize both pathogens and the immune system, envisioning the process of infection and immune response as an epic battle . In this case, he treats his immune system as he would a child trying to accomplish something difficult, and worries about its emotional reaction.
The COVID-19 vaccines (like all viral inoculations) work by introducing viral proteins into the body, causing the immune system to react as if the actual virus were present, creating the antibodies to fight it. As a result, if the actual virus is introduced, the immune system will have the capacity to quickly eliminate it.
In this comic, Cueball has just received the COVID-19 vaccine and anthropomorphizes this process. He worries that his immune system is "freaking out", as the vaccine causes the body to 'think' it's under attack and respond as it would to a deadly threat. Cueball accordingly tries to reassure his immune system that the threat isn't real. However, Megan reminds him that the "panic" is the entire point, as that's what causes the body to build defenses, which will allow it to handle the real virus. Cueball then switches tactics, melodramatically announcing that the virus is about to kill him, and encouraging his "heroic immune cells" to save the day. The joke is that the basic elements of their response is accurate: the vaccine is essentially a ruse intended to "trick" the immune system into developing antibodies. However, the immune system obviously lacks a separate consciousness, and can neither hear nor understand their comments, [ citation needed ] making both reassurance and encouragement entirely moot.
In the title text, Cueball continues to treat his immune system like a conscious entity. Specifically, all of his communications sound like a parent, or other adult, trying to encourage a child who was trying to win a game: giving it a pep talk about how he doesn't care if it wins or loses as long as it has fun. This is a common refrain when parents or other adults try to reassure children in contexts where victory isn't especially important, and where enjoyment is the real goal. Cueball then remembers that this particular event is much more consequential. If his immune system were to 'lose' to the vaccine, that would presumably mean it was incapable of responding properly to the viral threat, meaning he'd be in serious risk of death if he contracted the actual virus. As a result, he corrects himself and states that winning, in this case, is "very important".
[Megan is walking toward Cueball, who is holding his arm.] Megan: How you feeling? Cueball: Not bad. Tired. A little sore.
[Zoom in on Cueball. He looks down at his arms, which are held out.] Cueball: I feel bad for my immune system. It doesn't know this isn't a real virus. It must be freaking out. Cueball: Hey buddy, don't worry! We're going to be fine. This is just practice!
[Zoom out. Megan gestures at Cueball, as he holds his arm.] Megan: No, don't tell it that . You want it to panic and build defenses that will be able to handle the real thing. Cueball: I guess. Cueball: Okay, let me try that again. Cueball: *ahem*
[Cueball dramatically clutches at his chest.] Cueball: Woe! My arm is stricken by a dreadful plague! Cueball: I feel death draw near! My only hope is those heroic immune cells! Megan: Perfect. Cueball: Psst - you're doing great! I'm so proud of you.


Ingenuity

Explanation:
Ingenuity is a drone-like helicopter deployed to the surface of Mars. It rode on the underside of the Perseverance rover and at the time of publication its protective housing had been released from the rover and it was being prepared for a flight in early April. The helicopter is supposed to take off after the rover fully releases it and clears its takeoff trajectory.
The comic projects what might happen if the mission controllers activated the helicopter early. In this case, the process is approaching the point of detaching the part-deployed Ingenuity. Ponytail and Cueball are present in mission control when Cueball trips and hits a button that clearly triggers the Ingenuity drone to take off. Perserverance, still firmly above/attached is seen to easily ride atop it. The rover exclaims "Wheee!", presumably from excitement or happiness.
In the title text, some character discovers powered flight is easier on Mars, which contradicts our current understanding that powered flight is very difficult on Mars . Mars may have less gravity, but Mars's atmosphere is 1% the density of Earth's. It's so thin that you couldn't move a feather with a fan. This is why the character mumbles his explanation of the science, because they know any explanation doesn't actually make sense.
The total mass of the two vehicles is about 556 times that of the helicopter alone, meaning the unexpected lift effect 'described' would have to be several hundred times more effective than that anticipated, depending upon the factor of overdesign already built in to avoid an expensive marginal failure. It also seems to be trivially easy to balance the extremely top-heavy loading upon the small solar-panel that tops out the counter-rotating coaxial blades, which adds yet more questions of both the dynamic and structural performance, never mind questions about the available power to accomplish this and the later possibilities to recharge.
It is not the first time that we have seen a Mars vehicle vastly exceed expectations in these pages.
It is also not the first time a character has caused an incident by tripping and hitting a control panel .
[Ingenuity/Perseverance is on the surface of Mars.] Perseverance: Ingenuity helicopter has been lowered. Perseverance: Preparing to release it onto the surface.
[A cut to mission control on Earth. Cueball trips and clicks on a key on his workstation, while Ponytail stands nearby.] Cueball: Oops Control panel: Click Trip
[Back on Mars, Ingenuity's rotor blades start spinning.] Ingenuity: Bzzzzzz
[Perseverance is being lifted into the air atop Ingenuity.] Perseverance: Wheeee! Ingenuity: Bzzzzzz


Checkbox

Explanation:
This was the 11th April fools' comic released by Randall . The previous fools comic was 2288: Collector's Edition , which was delayed two days and released on Friday April 3, 2020. The next became 2601: Instructions released on Friday April 1, 2022 (a regular release day).
The comic looks similar to a loading screen. The actual comic (this “loading screen”) consists of an animated gif of a checkbox (hence the name).
The frame is replaced with an interactive panel. In the center is a check box, which clears itself immediately when checked. In the bottom right is a mute button, which begins muted. By unmuting, and changing it to a loudspeaker, sounds are played when the check box is checked. This was the first comic with audio on xkcd. But the very similar Fool's comic from the next year, 2601: Instructions , used audio as the main part of the joke. This comic and also has a mute button (but here the sound was on when the mute button is shown, seems like an error). This comic is also very similar to this one, as it only has one thing in the center, but not a check box, but a radio button .
Under the checkbox is a scrolling visual representation of the timing and duration of clicks in the check box, which also produce matching beeping sounds when unmuted. The representation consists of a dot for a short press, or a bar for a longer press. All long presses are represented by a bar of a pre-determined length; in other words, a longer press does not result in a longer bar.
By varying between brief and long presses, and brief and long intervals between presses, it is possible to enter characters in Morse Code.
The check box then begins operating by itself, producing sounds which can be decoded as Morse Code. These responses are also printed in the browser's JavaScript console in both plain text and a textual representation of Morse code. If left without any initial input for 30 seconds it would send the message CQ (meaning "Seek You").
The title text hints at the use of Morse Code in the comic; interpreting the "check" as a Morse Code dot and the "chhecck" (a long check) as a Morse Code dash gives ...---..., which is the Morse Code for "SOS", the international distress signal. Incidentally, inputting the SOS signal gives "YOU TOO?".
For the majority of inputs, the check box responds with a random selection from the following list:
Some keywords, however, have special responses .
This comic has a unique header text , see the details here . The header is:
"This comic was put together by Max Goodhart, Patrick, Amber, Benjamin Staffin, Kevin Cotrone, and Michael Leuchtenburg."
Read Max's blog post on development of the comic.
[. represents a short signal, - represents a long signal, and / represents pauses between words. Sojourner is a Mars rover which has been referenced by Randall in the past and is the entity operating the morse code device.]
See also QRS and QRQ.
An explanation of Q codes can be found here .
Steps to complete (directions can be abbreviated as their first letter):
After successfully repairing and rebooting Sojourner, a comic is opened which depicts it seeking out and finding its friends, Spirit, Opportunity, Curiosity, Perseverance, and Ingenuity. Curiosity and Perseverance are locked in a swordfight, and either Spirit or Opportunity is carried off by Ingenuity while the other speeds off a small mound of dirt. Ingenuity carrying a rover is a reference to the previous comic.
The page's JavaScript creates a global object morse with encode and decode methods.  From the developer console, it is possible to write morse.encode("A PHRASE") , which will print the Morse code corresponding to the text provided, or morse.decode("... --- ...") which will translate the Morse code to text.
BeepComic.hurryUp() to get the reply immediately in the console. BeepComic.send(...) to send directly to SOJOURNER.
[A small box is in the middle of a large white frame. The box can have a check-mark, but it is alternating between being checked or unchecked. At the bottom right there is a muted speaker (which can be unmuted). If the user press the checkbox gray dots or lines will appear below depending on the length of the press. These will move from right to left and then disappear.]


Spike Proteins

Explanation:
This is another comic in the COVID-19 series related to the COVID-19 pandemic .
This is also another comic about the current vaccine against COVID-19 . A vaccine is designed to provoke an immune response from the body of the recipient, which "trains" the immune system to attack actual viruses (or bacteria). For COVID-19, the spike protein , necessary for the virus to bind a receptor on human cells and invade them, is the key protein for an immune response. Almost all vaccines approved for human use pre-COVID actually contain either inactivated pathogen (e.g., flu vaccine), live but safe pathogen variants (e.g., measles), or some protein from the pathogen that the immune system can respond to (e.g., pertussis).  The four COVID-19 vaccines approved in the United States or the European Union as of the date of this comic, however, are all a relatively new type of vaccine that instead cause human cells to temporarily produce spike proteins, which the immune system then "learns" to attack. The Oxford-AstraZeneca and Johnson & Johnson ’s Janssen vaccine use a technique first approved for the July 2020 Ebola vaccine, in which a genetically modified adenovirus is used to deliver DNA to the nuclei of the vaccine recipients' cells, which convert the DNA to Messenger RNA (mRNA). The recipients' cells then use the mRNA as instructions to produce spike proteins. The Pfizer BioNTech and Moderna vaccines are of an even newer type: m RNA vaccines , which directly inject the mRNA into the body for the cells to use, and never have to enter the cell nuclei.
Beret Guy , in his usual fashion , misunderstands how reality works, then reality alters to fit his view of it.
After receiving the vaccine, as he informs Cueball and Megan , he claims he will now go away to make spike proteins. For him, this literally means that he (not his cells) will build them, by unexplained means. When he returns he is carrying his constructed protein, which is roughly 8 orders of magnitude larger than the normal version, and also appears to be dripping. He then drops it on the desk, where a laptop is being used. Cueball part-closes his screen to try to prevent the mass from landing on it - though he's only partially successful.
When a normal living body is coerced into making a spike protein, they are microscopic particles that distribute internally around the body to provoke an immune response. Beret Guy's macroscopic version provokes an understandable response of both disgust and confusion from both Cueball and Megan, who choose to ask why it is so wet. Proteins are highly hydrated molecules where water — through the moderation of its presence and absence in specific locations — plays a central role in shaping the structure and function of the protein (although it is not clear how Beret Guy knows that the spike protein should be hydrated since this is his first try). Though, of the many questions that might have been asked, it is not an entirely unreasonable snap reaction.
Beret Guy remains typically oblivious to the fuss he causes. His enthusiastic intention, apparently, is to leave his first proud creation there as he departs to construct further examples. They will likely be no less unwelcome.
Anything damp and squidgy (as this creation seems to be) would not be welcome around a laptop, for a number of reasons, and Beret Guy seems to have made a particularly messy contact with the part of the case where most such devices are likely to have clusters of heat vents or unruggedised ports/connections that may not react well to the ingress of liquids.
The title text is a pun on Acer, ACER2, and ACE2. Acer is a brand of computers including laptops. The ACE2 receptor , is an entry point on a cell to which the SARS-COV-2 virus attaches during the process of entering the cell. ACER2 is a real enzyme in humans which, although unrelated to ACE2 or SARS-COV-2, may also help bind the pun together.
[Cueball is sitting in an office chair at a desk with an open laptop in front of him. Megan stands behind him looking over his shoulder. Beret Guy is in front of the desk, walking away and looking back at the two while holding a hand to his shoulder, where he got the vaccine shot.] Beret Guy: Got the vaccine! Megan: Congrats! Beret Guy: Time to go make spike proteins.
[Cueball continues to work on his laptop while Megan is looking on.]
[In a frameless, narrow panel, Beret Guy walks back carrying a large object in his arms that looks like a spike protein. But it is about half as long as he is tall, fluffy and dripping wet, flexing slightly along its length, with the Y-shaped head pointed forwards, away from Beret Guy] Beret Guy: OK! Beret Guy: Here's my first try.
[Beret Guy drops the spike protein onto Cueball's desk with the Y-shaped end on the desk up against the back of Cueball's laptop. The movement is shown with several lines and a sound follows when it hits the desk. The head of it takes up the entire desk area not covered by the laptop, while the tail  overhangs the desk. Cueball is grabbing the lid and base of his laptop with both hands, pulling it partially closed and away from the spike protein, and Megan reflexively leans away.] Spike Protein: Plop
[Beret Guy turns to leave, with an outstretched finger pointing skyward. The overhanging part of the spike protein has sagged, and it is dripping some wet material over both the floor and desk. Cueball is sitting with his hands on the partially closed laptop, Megan stands normally again.] Beret Guy: More! Cueball: Ewww. Megan: Why is it so wet??


Hammer Incident

Explanation:
The James Webb Space Telescope (JWST) is a space telescope created to be the successor of the Hubble Space Telescope under construction at time of publishing and launched December 25, 2021, though in 2014: JWST Delays , xkcd predicted its launch would actually occur during late 2026.
It's implied that Cueball dropped a hammer on the mirror of the JWST and broke it. In superstition, breaking a mirror causes seven years of bad luck. The cost estimate for the JWST is currently US$10 billion, and Cueball is at a NASA official hearing for breaking this very expensive piece of equipment, no doubt costing NASA (and thus the nation) hundreds of millions of dollars more for repair work. However, Cueball is more concerned about personally experiencing seven years of bad luck.
In actuality the mirror panel is not made of glass, so it's likely that a dropped hammer would dent and distort the panel rather than shattering it. Presumably Cueball's hammer drop would damage or destroy only one mirror panel out of the JWST's eighteen panels. (If he had destroyed the entire telescope, he would have been facing 7×18=126 years of bad luck, and the damage costs would be much higher. Then again, this depends on the altitude that the destruction happened. ) Even breaking a single panel would likely be very expensive because it would require extremely accurate machinery and extensive calibration tests to make and install a replacement panel, especially because the back of JWST's mirrors are made of beryllium. Beryllium is expensive to purchase, since it is relatively scarce, and is very hard and abrasive, so making things out of it is difficult (and expensive due to the specialized machinery required and the precautions necessary to prevent inhalation). Breaking a beryllium mirror would lead to dust formation; single exposures to beryllium dust can cause acute beryllium poisoning and massively increase the risk of lung cancer, which is very bad luck on behalf of Cueball. In addition to the property damage, Cueball is probably liable for injuring his coworkers, which is probably the main reason why the NASA workers are so angry at him because human lives are more valuable than mere money. [ citation needed ]
The title text refers to the Cold Stone Creamery , a chain that mixes ice cream with various other ingredients, such as fruit or candy, in front of the customer before serving it. The usual surface for mixing is a piece of granite which is kept cold (about -10°C). It's implied that Cueball had tried mixing his ice cream and flavorings in the style of Cold Stone Creamery on the JWST mirror, which is also kept cold -- in fact much colder, as it's cooled to as low as 7 K (-266°C, or -447°F). If Cueball had mixed ice cream this way on the JWST, he would likely have scratched and/or stained the surfaces on the telescope and perhaps have gotten gunk into the instrumentation, and possibly, due to the localized temperature differential from ice cream hundreds of degrees warmer than the material, promoted damaging distortions or fractures -- hardly the 'good idea' mentioned in the title text.  (It also would not have worked: at sufficiently low temperatures, ice cream hardens and cannot be mixed.)
The bad luck from breaking a mirror is also referenced in 1136: Broken Mirror .
[Cueball, holding a palm up in front of him, stands before a long desk, behind which is a seated panel of four people, consisting of Ponytail, Hairy, a Cueball-like guy and Hairbun. Hairy is the only one to have one arm on the desk, all other arms are held down with hands below the desk.] Cueball: Yes, I know you're mad that I dropped that hammer. Cueball: But think about me— Cueball: Seven years of bad luck!
[Caption below the panel]: Man, NASA is really on my case about the James Webb Space Telescope.


Eradication

Explanation:
This is another comic in the COVID-19 series related to the COVID-19 pandemic .
Megan and Cueball are discussing the possibility of SARS-CoV-2 eventually becoming "another circulating common cold virus".  This is considered to be a serious possibility , as a combination and vaccines and acquired immunity cause most people to have some degree of immunity as they age. This is particularly likely because SARS-CoV-2 poses little risk to small children, and if most people are infected with it in childhood, they'll likely be immune as adults. Multiple other coronaviruses are common in the human population, and fall under the category of "the common cold", causing only minor and temporary symptoms, with little serious risk for most people.
If SARS-CoV-2 does transition to being a minor disease, there will be little reason to continue focused eradication efforts, because the ongoing harm will be too little to justify such efforts.  It's extremely difficult to wipe out a virus altogether, as it requires every human population to be either isolated from the disease, or vaccinated until herd immunity is achieved.  There are only two viruses which have been totally eliminated in the wild: Smallpox and rinderpest , and rinderpest infects only cattle and other ruminants, not humans. The elimination of smallpox was one of the greatest public health accomplishments of the 20th century, and resulted from an aggressive and ambitious global vaccination effort. Smallpox is now considered to be extinct in the wild, with only a small number of samples still preserved in government labs.
Where diseases continue to be dangerous, ongoing global efforts are made to eliminate them entirely (polio, measles and rubella are currently targets of such programs).  If a disease ultimately becomes more or less harmless, its elimination is less of a priority.
The joke of this strip is that, in the aftermath of the COVID-19 pandemic, Megan feels so much rage and ill-will toward the disease that vaccination efforts are no longer only a matter of protecting health, but an expression of hostility toward the virus. Her argument is that, even if global elimination efforts are no longer justified by the danger of the virus, they should be pursued "out of spite". Like many other strips in this series, the characters tend to anthropomorphize the virus, treating it as an intelligent and sentient enemy, rather than mere force of nature. Given that mindset, the idea that the virus could cause so many deaths and so much disruption, and then continue to exist without consequence, would upset many people. Cueball agrees with her perspective, approvingly referring to it as "revenge". Cueball has also previously shown a merciless attitude towards endemic infections , even those that aren't particularly deadly, and so the idea of eliminating one entirely would probably appeal to him on its own merits.
The title text refers to the aforementioned extinction (in the wild) of smallpox. This is the type of line one might see in fiction , delivered to someone who is about to be killed, taunting them about the death of one of their friends or associates. The line treats the virus like a villain in an action movie, and revelling in the fact that we're finally going to kill it.
[Megan holding a hand up, palm held out, is walking with Cueball.] Megan: Even if the threat eventually fades, thanks to vaccines and stuff,
[They walk on, both with their arms down.] Megan: And it becomes just another circulating common cold virus,
[Megan holds her hand up in a fist, while Cueball hold his hand to his chin as they walk on.] Megan: I think we should pursue global eradication of SARS-CoV-2 out of spite . Cueball: Revenge-based public health policy. I like it.


ISS Vaccine

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic , specifically regarding the COVID-19 vaccine .
Megan has just realized that the astronauts on the ISS (the International Space Station ) probably can't get a vaccine against COVID-19 before they land. That is, it will not get shipped up to them.
This can be a concern because their immune system is impacted by extended stays in space. So when they come down again they may need to stay in quarantine longer, as the vaccine is not fully effective the first few weeks after administration. There could of course also be concern about getting COVID-19 while in space, but this is very unlikely due to the quarantine measures and other security measures taken by NASA and their Russian counterpart, Roscosmos . See this article with more details on these facts: What NASA is doing to keep COVID-19 off the space station .
Cueball 's reply, "NASA's good at orbital injections", is a pun on "orbital injection", also called orbital insertion , which is the adjustment of a spacecraft’s momentum that puts it into a stable orbit around a planet, moon, or other celestial body. Space agencies like NASA do this routinely on spaceflight missions. Getting an injection of a COVID-19 vaccine while in orbit aboard the ISS could also be called orbital injection, hence the pun.
The title text refers to the fact that, because the ISS orbits the Earth every 90 minutes, the people aboard it experience a day in that time, seeing a sunrise and sunset and crossing the International Date Line on the ground. One interpretation of this might be that 90 minutes on the ISS are equivalent to a day on the ground, making the people on board due for the second dose of the Pfizer vaccine (normally 21 days) or the Moderna vaccine (normally 28 days) after 31.5 or 42 hours, respectively, which Randall rounds to 30 or 40 hours. In reality, rather than tracking the local time of the territories it passes above, the ISS follows Coordinated Universal Time .
[Megan and Cueball are standing talking to each other.] Megan: I just realized— Megan: The astronauts on the ISS probably can't get the vaccine until they land. Cueball: Sure they can. Cueball: NASA's good at orbital injections.


Post Vaccine Social Scheduling

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic , specifically regarding the COVID-19 vaccine .
The comic shows a timeline of a multitude of (presumably) friends and acquaintances getting two doses of the SARS-CoV-2 vaccine.  Due to the recommended delay between shots, as well as the few weeks needed to build antibodies after the second shot, planning get-togethers becomes complicated by who is free to meet, or not yet.
The diagram is some form of Scheduling Diagram, maybe akin to a Gantt chart , which helps to coordinate the status of several individual 'processes' (personal vaccination schedules) and demonstrate where dependent activities (meet-ups) are mutually possible.
Eventually, everyone can start getting together, but during the time where some people have only received one, neither, or only got the second recently, the scheduling is complicated.  The complication is increased by the fact that people who have received one or two doses of vaccine, but haven't gone through the whole waiting period, can be expected to have some protection, but possibly not full protection (as represented by the dashed line).  In that case, there's the added question of how important it is that the person is at an event, and how much risk the people involved are willing to tolerate. This may be the reason for the "movie" set, in which all participants will have received both doses, but one will not have completed the final waiting period.
The title text references NP-hardness, a theme that has come up in past comics. NP-hardness describes a particular level of computational difficulty. Scheduling problems are normally NP-hard. But when extra challenges such as having to deal with whether or not people are vaccinated they become even more difficult.
In this case though, Critical Path dependencies seem trivial enough. Events (vertical lozenges across the dot-marked timelines of those included) are as trivial to validate as possible for those selected to attend. Fixed events in time can be scanned to show all those allowed to participate at that moment. Movable events can be rescheduled until (enough of) those hoped to be included are 'valid'. Complications may arise for those whose presence relies upon the status of others potentially attending, or the need to maintain time between two events (in either order) with part-shared attendees as a precautionary 'cool-down' isolation. It is not obvious that either of these issues factor in, any more than basic scheduling conflicts would.
The third person is scheduled for a movie before being fully vaccinated may be a direct reference to 2441: IMDb Vaccines , discussing the number of people that needs to be vaccinated to record a particular scene. Other than each line's identifying portrait (which are not of the Throne Room characters) no explicit age/vulnerability information is given to justify this, presumably the chart's users are aware of the specifics.
The third person in the table is included in a movie viewing (for which masks could be worn) shortly after their second immunization, but not included in the dinner group until the full benefit of the vaccine takes hold.  CDC guidelines permit vaccinated individuals to visit inside a home or private setting without a mask with one household of unvaccinated people who are not at risk for severe illness. Therefore the movie gathering conforms to CDC recommendations provided that the single unvaccinated person is not at increased risk of severe illness and the movie is in a home or private setting.
The third person in the table appears to have received the second shot twice.  This is possibly a reference to 2422: Vaccine Ordering . Another interpretation is that she lied about her first dose being her second dose to be invited to the movie.
[From top to bottom, eleven people are standing on the left side of the image: Danish, Cueball #1, Hairbun, Black Hat, Ponytail, Science Girl, White Hat, Hairy, Blondie, Cueball #2, and Megan, with even-numbered characters standing slightly further to the left. Each character’s first and second doses of the vaccine are labeled ① and ②, respectively. The time before each character’s first dose is drawn with a grey solid line; the time between their first dose and after they are fully vaccinated (two weeks after their second dose) is drawn with a grey dashed line; the time after they are fully vaccinated is drawn with a black solid line. Black Hat, Science Girl, Blondie, Cueball #2, and Megan have all received their first doses before the comic’s time frame. Social activities are drawn with an ellipse around the top and bottom members, and each participating character is identified with a large filled-in circle on their timeline. The ellipses are labeled :] DINNER   GAMES   MOVIE   BIRTHDAY   DINNER   CABIN
[The events that happen, in chronological order (from left to right), are:
[Caption below the panel:] Post-Vaccine Social Scheduling


AI Methodology

Explanation:
The joke in this comic is that the people are using artificial intelligence (AI) without understanding how to, and that by doing this the research concerned is at best unreliable and possibly deliberately compromised. The researchers acknowledge that their approach is risky and requires extra verification, but repeatedly use equally or more unreliable AI-based solutions to these problems. Therefore, their problems are likely as bad as they ever were and any other team using one of their verification tools is likely to experience similar unreliability. For an introduction to machine learning, you can visit https://fast.ai/ .
The first comment, that "some have questioned our AI-based methodology", refers to difficulty verifying the correctness of AI-based processing. A model (a program which solves a problem with AI-based statistical analysis) may appear reliable when it is instead insufficiently tested. Models are liable to experience issues due to lingering influences from its training data or a bad algorithm reducing the quality of the investigation. It is therefore necessary for research using such models to demonstrate that those models have been tested well enough that their results are likely to be useful. Frequently, additional tests are performed after training to confirm that the model can handle data collected in a different way to the data used to train it.
Cueball seeks to reassure his audience by quantifying the quality of his methodology. He does this by creating yet another AI to rank methodologies. This approach is unlikely to instill confidence for a variety of reasons:
While there are many red flags in the original AI and quality AI, it is theoretically possible that they operate as Cueball claims. The title text's comments about spacing and diacritics prove that this is not the case and that the quality AI, at least, is completely broken. AI models are given input in various complex ways and determine based on statistical analysis which details are important. Such models can easily find details in the training data which correlate with correct answers but make the resulting model useless.
For example, a research team once created a model which was given medical information to determine how likely a patient was to have cancer. The model was trained on existing patient records and the team planned to use it on new patients. However, the original model did not use the medical information but instead simply checked the name of the hospital--a patient at a hospital with "cancer center" in the name was likely to have cancer. The model had identified a data point which correlated with the desired answer, but this correlation was not useful for the intended purpose. The model concerned was discarded and a new one created without the hospital name.
In this case, the methodology sections are text written by humans, which can contain various artifacts of the writing process. These can include details like how the user chose to insert spaces, word usage, spelling, or diacritic marks which are optional in English (e.g. naive versus naïve). It appears that the training information identifies certain patterns which correlate with "good" methodologies. This indicates a few more problems for this research team:
[Cueball is standing on a podium in front of a projection on a screen and points with a stick to a bar chart histogram with a bell curve to the left and a single bar to the far right marked with an arrow.] Cueball: Despite our great research results, some have questioned our AI-based methodology. Cueball: But we trained a classifier on a collection of good and bad methodology sections, and it says ours is fine.


Aviation Firsts

Explanation:
This comic reflects the Ingenuity probe's first flight on Mars . Now that Ingenuity has completed its first flight, Mars can be counted among planets with controlled powered flight. The preceding milestones in this list were completed by the first space probes to reach and then land on Mars. Flight, landing and controlled landing were variously achieved by some or all of the prior landers, depending upon your definition of flight, but certainly by the Skycrane element used in landing both Curiosity and Perseverance rovers. These may not have qualified as controlled powered flight as they only used their power to control the landing, before flying off again under power without any more precise control than that needed to intentionally crash elsewhere.
The remaining milestones have only been completed on Earth, if at all, and also grow more bizarre and more specific further down the comic and extending into the title text.
[A chart is shown with nine items. To the right of each item there are two check boxes. Above the top row of check boxes are two underlined labels for the two columns. The first four rows have both boxes checked, and the last five have only the first box checked. The last two items are so long that they take up three and four rows of text. The first seven items are written on one line each.]


Excel Lambda

Explanation:
Cueball is computing and Ponytail criticizes him in a way that is reminiscent of the Code Quality series , although not as harsh. Cueball has lots of strange computer problems , and this will most likely result in another one.
The comic begins with Ponytail finding out that Microsoft Excel is adding a lambda function to their function library. This was announced by Microsoft for Beta users in December of 2020. A lambda function is a fundamental mathematical structure that can be used to define all possible computations, in what is known as lambda calculus . They are commonly found in programming languages such as Lisp , Python , and many others. A lambda function is also called an anonymous function because in most languages it can be passed to other functions (including another lambda function) without needing to be given any formal name.
Finding that Excel is adding a lambda function pleases Ponytail. Cueball claims that the lambda function is unnecessary, as when he needs arbitrary computation he just adds a block of columns to the side of his sheet and has a Turing machine process it. This would technically work as lambda calculus is formally equivalent to Turing machines. People have created Turing machines in Excel , although not for practical purposes.
Ponytail finds his solution absurd and is convinced Cueball is "doing computing wrong". But he claims that all computing is equally wrong, citing the Church-Turing thesis , a hypothesis which says that a function can be computed by executing a series of instructions if and only if that function is computable by a Turing machine. A classical Turing machine uses an infinitely long strip of tape as its memory; for Cueball, the large Excel column acts as the "tape". All ways of computing are "equally wrong" since, according to this thesis, they can all be translated to or from a Turing machine.
Ponytail and Cueball appear to have different ideas of 'computing'. Ponytail, like most programmers, probably includes efficiency and readability as important characteristics of 'doing computing right'. Cueball appears interested only in computability , a more theoretical point of view than Ponytail's.
Ponytail then says that Turing would change his mind if he saw Cueball's spreadsheet, presumably because of the extreme complexity of Cueball's code in the spreadsheet. Cueball's final statement is that Turing could ask him to stop, but would not be able to prove if he actually will stop.
Cueball's final statement is a reference to the halting problem mentioned in the title text. It is the problem of determining whether a given Turing machine will halt. The problem has been shown to be undecidable, i.e., it is impossible to build an algorithm that computes whether any arbitrary Turing machine will halt or not. Because of the way Cueball has behaved, he has been specifically mentioned in Turing's later formulations of the halting problem. Cueball finds this very rude. This is of course a joke, since Turing has been dead since 1954, presumably long before Cueball was born. But it would be crazy indeed if a scientist became so mad at a person that they would mention this person by name in their formulation of a serious problem.
Over-complicated spreadsheets were also mentioned in 2180: Spreadsheets .
[In a narrow panel, Ponytail is walking in from the left, looking down at her phone] Ponytail: Oh cool, Excel is adding a lambda function, so you can recursively define functions.
[Ponytail, holding her phone to her side stands behind Cueball, who is sitting in an office chair with a hand on a laptop standing on his desk. He has turned around to face her, leaning with the other arm on the back of the chair.] Cueball: Seems unnecessary. Cueball: When I need to do arbitrary computation, I just add a giant block of columns to the side of my sheet and have a Turing machine traverse down it.
[In a frame-less panel Ponytail is standing in he same position behind Cueball, who has resumed working on his laptop with both hands on the keyboard.] Ponytail: I think you're doing computing wrong. Cueball: The Church-Turing thesis says that all ways of computing are equally wrong.
[Ponytail is still behind Cueball, who has a finger raised in the air, and the other hand is on the desk. Cueball's head has a visible sketch layer which has not been erased.] Ponytail: I think if Turing saw your spreadsheets, he'd change his mind. Cueball: He can ask me to stop making them, but not prove whether I will!


Fully Vaccinated

Explanation:
This comic is another in a series of comics related to the COVID-19 pandemic , specifically regarding the COVID-19 vaccine .
The Centers for Disease Control and Prevention (CDC) has stated that once people are fully vaccinated, they are able to visit other people's houses (and not risk spreading/catching coronavirus). The implication, of course, is that you can visit people that you would also have visited before the outbreak. The humor in this comic comes from Megan who is just going to visit a random stranger's house. She explains this is okay because she is fully vaccinated, telling the person in the house that she is two weeks past her second dose. This was part of the topic of the last vaccine comic 2450: Post Vaccine Social Scheduling .
Restrictions to socializing, brought in as various governments reacted to the emergent COVID-19 pandemic, often disallowed or discouraged visiting family, friends, etc, beyond a mutually isolating 'support bubble', which meant that many house visits that might have occurred beforehand were no longer advisable. With the development and distribution of vaccines, and the eventual receiving of a second dose as applicable, the rules have been modified to allow those vaccinated to once again resume some degree of their prior outgoing behavior where the risks have been mitigated.
In this instance, though, Megan has taken the advice even further. Rather than opening back up to a situation closer to the 'old normal', she has taken it as an official sanction to exceed the old social limits and pester complete strangers. Alternately, this is what she always used to do, and only stopped 'for the duration', this unlucky householder being (one of) the first to be subjected to this 'guerilla visiting' now that there seems to be no reason not to continue.
In the title text, the owner of the house explains to Megan that just because she has been vaccinated she just can't enter into someone's house without being invited — a commonly understood form of property law.
But due to the vaccine type Megan thinks the owner has mixed this up with a commonly understood element of vampire lore, that vampires must be invited into a home before they can pass through the doorway.
In vampire lore, vampires are often able to transform into bats, and these two are thematically associated with each other. Since the coronavirus is likely a bat virome that has entered into humans, Megan misunderstands the owner's objection to her entry, believing that the homeowner thinks that she has become a vampire. (The virus, and thus elements of the vaccine, having ultimately originated in bats and therefore 'possibly' actual vampire stock.)
Megan thus begins to explain that the vaccine works on a bat virus and has nothing to do with bats. And since she is thus not a vampire she has no problems entering a doorway uninvited, and further explains that she is also not repelled by garlic or other classic weakness of vampires. Vampire lore states that they are repelled by garlic , crosses, holy water, sunlight, and wooden stakes through the heart (the last being a problem for humans in general, vampiric or otherwise).
The owner is attempting to explain that Megan does not have the legal or moral right to enter simply because she is vaccinated, but this seems to not register with Megan .
Doing ridiculous things that were never allowed, even normally, after being vaccinated or low-risk, was also the theme of 2434: Vaccine Guidance . 2391: Life Before the Pandemic also dealt with a similar theme, with Cueball and Megan reminiscing about activities they missed doing but which had not been allowed or possible before the pandemic.
[Megan is standing in front of a three-step stair leading up to an open door. She has one hand in the air while talking to someone inside the house, who replies. The ground outside has small tufts of grass.] Megan: Hi, I'm here to visit! Voice, from inside the house: Do I know you? Megan: No, it's cool, I'm two weeks past my second dose.
[Caption below the panel:] Remember, once you're fully vaccinated, the CDC says you're free to visit other people's houses.