Venus

Explanation:
Miss Lenhart is teaching a class on science about the planet Venus .
In the first panel, we see her teaching the history of Venus. Venus may have had water on its surface billions of years ago, but if that's true all hydrogen since then was eventually lost due to dissociation. However, there is no evidence that Venus ever had fields of flowers, or Venusians, or any other form of life.
The runaway greenhouse effect on the second panel is a play on words. While the term normally refers to a rapid rise in temperature caused by greenhouse gases, Miss Lenhart uses the term literally and claims the existence of sentient greenhouses that actually ran away. In reality, the effect caused Venus to develop a thick atmosphere of carbon dioxide, which raised its temperature above to approx. 460 °C (860 °F), hotter than daytime on Mercury. This eventually destroyed all evidence of anything that had been on the surface of Venus billions of years ago.
The third panel ties the previous distortion of Miss Lenhart into the very real historic reputation of the Netherlands as flower growers and as a further fabrication by Miss Lenhart the Dutch flower industry was in fact started by the Venusians.
In the final panel we learn that she is a month away from retirement and doesn't care about relaying accurate information anymore. She just wants to have a laugh at the expense of the naive school children. Although it is clear that Science Girl in the front row was not fooled.
The title text jokes about the butterfly effect , the idea that a butterfly flapping its wings in Japan can cause a Tornado in the U.S.. In this case the butterflies would just help pollinate the flowers. The butterfly effect is a term coined by Edward Norton Lorenz who had the comic 1350: Lorenz named after him due to its chaotic nature.
Although Miss Lenhart was supposed to retire a month after this comic she seems to return a year later for a math course at university level, in 1724: Proofs , where she continues the trend from this class.  It is probable that she retired from a primary or secondary school teaching position, likely to collect a pension, before taking a side job at a university/college level.
[Miss Lenhart is standing in front of an image depicting a section of a temperate Venus' surface, with greenhouses, grass, flowers and a river flowing into a sea.] Miss Lenhart: Venus was once temperate. It had seas and rivers, and Venusians cultivated vast fields of beautiful flowers.
[The image now shows the entirety of Venus, with continents and oceans. The greenhouses appear to be fleeing from Venus.] Miss Lenhart: Until their greenhouses fled the planet due to the runaway greenhouse effect.
[Miss Lenhart is shown to be standing in front of a classroom. Science Girl is sitting in the front row.] Miss Lenhart: The Venusians pursued their greenhouses to Earth, settling in the Netherlands and kickstarting the Dutch floral industry. Any questions?
Off-panel student (presumably Science Girl): Because you're retiring in a month, do you just not care what you say anymore? Miss Lenhart: What?! I ride the skies atop a screaming bird of truth! Also, yes, I do not.


Degree-Off

Explanation:
Cueball (physics), a grown-up Science Girl (biology), and Megan (chemistry) appear to be on a talk show called Degree-Off, hosted by Hairy , where representatives of different fields, try to explain why their field is the best and why to get a degree in their field. The title "Degree-Off" is a portmanteau of " degree ", as in the recognized completion of studies at a school or university,  and " face-off ", a direct confrontation between two people or groups. Since there are three participants, this is not a true face-off, unless Megan, who does not speak, is not counted.
The host asks the physicist Cueball to go first. He light-heartedly begins to tell what appears to be long story, beginning with a Richard Feynman anecdote. During the Manhattan Project in Los Alamos, Richard Feynman got bored because of the isolation and started learning lock picking on the secret documents safes. Using these new skills, he played lots of pranks on his colleagues, like leaving notes and spooking them into believing there was a spy among them (which, of course, there was ). He finishes his case with a quote from Ernest Rutherford , implying that his speech was quite long and winding. The quote communicates the idea that physics is the only fundamental framework, so that the job of chemists, biologists and other scientist simply is to catalog and systematize observations ("collect stamps") on phenomena too complicated to presently be fully described in terms of physics. This idea was earlier lampooned by Randall in 435: Purity (and is also stated in the title text of 1158: Rubber Sheet ).
The biologist goes next, showing with a graph (see below) that the field of biology has helped reduce disease. She then goes on to claim that the heroes in biology (the part known as Medicine) have even " slain " one of the Four Horsemen of the Apocalypse . Different traditions designate the Four Horsemen differently, but it is common for their number to include Plague or Pestilence.  Science Girl claims that the field of biology has eliminated widespread Pestilence - at the time of writing it was not readily apparent that the old dog still has some teeth (although the rate of death from infectious disease in 2020–21 is still less than 200 per 100 thousand, far lower than the early 20th century). The imagery of Pestilence being thwarted by modern medicine was also used in the book Good Omens , by Terry Pratchett (of whom Randall is a fan, see 1498: Terry Pratchett ) and Neil Gaiman , where Pestilence has retired after the discovery of Penicillin , and been replaced by Pollution .
The graph shows the death rate from infectious disease in the USA with the range of 1900-2000. The spike is attributable to the 1918 flu pandemic . It has been published in the paper Trends in Infectious Disease Mortality in the United States During the 20th Century .
Science Girl then goes on to directly accuse Cueball (i.e. physicists) of creating a new Horseman to replace the one slain by the biologists. She refers to the development of the atomic bomb , which was built and tested in the New Mexico desert . The new horseman is therefore the atomic bomb, or the various perils associated with it.
Science Girl's implied condemnation of the physics community has been echoed by some of the scientists involved in the project itself. After the test detonation of the first nuclear weapon on July 16, 1945, J. Robert Oppenheimer , the director of the Los Alamos National Laboratory , found himself quoting the Bhagavad Gita : "Now I am become Death, the destroyer of worlds."
This harsh moral judgement shocks Cueball, who exclaims "I thought this was supposed to be fun and lighthearted!" While the set-up is of a frivolous friendly competition, Science Girl's presentation is surprisingly dark. Her retort in the final panel reveals that she was angered by the off-hand dismissal of 'soft' sciences as "stamp-collecting", and turned the game from a light-hearted fun into something more serious.
In the title text the biologist goes on to declare in All caps that she is surprised a physicist isn't "harder", after all their condescending towards the "squishy" sciences. The use of 'hard' and 'squishy' is a play on the colloquial division between the so-called 'hard' sciences (such as physics and chemistry) and 'soft' sciences (such as biology and geology). 'Hard' sciences usually refer to the perception that in fields like physics, precisely repeatable experiments and measurements are possible, as opposed to 'soft' sciences seen as placing less emphasis on precisely quantifiable predictability - however Science Girl is extending 'hard' to its meaning of 'stoic', mocking Cueball for not being able to weather a personal moral attack. Again she is indicating that she's upset by directly referencing a mocking portrayal of other fields allegedly made by Cueball.
To be fair to Cueball, the outbreak of disease is more a topic for epidemiology, and biology has spawned multiple diseases, atrocities, and bad movies. However, the Manhattan Project marked the first time in history that humanity possessed the ability to destroy itself - and shortly thereafter humanity got perilously close to doing so .
In 520: Cuttlefish Randall shows that he personally respects biologists - or at least fears them.
Within a year Randall has made several other comics about nuclear weapons, this one was the first of these the second, 1539: Planning , came out just 1½ month after this one and after that these two were released early in 2016: 1626: Judgment Day and 1655: Doomsday Clock . Nuclear weapons are also mentioned twice in Thing Explainer , specifically they are explained in the explanation for Machine for burning cities about thermonuclear bombs , but they are also mentioned in Boat that goes under the sea about a submarine that carries nukes. All three comics and both explanations in the book, does like this comic, comment on how insane it is that we have created enough firepower to obliterate Earth several times (or at least scourge it for any human life).
[Hairy is acting as the host of a TV talk show, Degree-Off holding a microphone up. Cueball, a character who looks like a grown-up Science Girl, and Megan are acting as representatives of physics, biology and chemistry respectively. They each stand behind their own lectern with the respective subject label.] Hairy: Welcome to the Degree-Off , where we determine which field is the best! Physics, wanna go first? Cueball (Phys): Sure! I'd like to tell the story of Richard Feynman's Manhattan project lockpicking pranks... Labels: Phys Bio Chem
[Zoom in so Megan is no longer visible. Cueball lifts his hand] Cueball (Phys): ...and as he said, "all science is either physics or stamp collecting." Cueball (Phys): Thank you. Hairy: Great! Bio, you wanna go next? Grown-Up Science Girl (Bio): Okay. Labels: Phys Bio
[Zoom in on Grown-Up Science Girl so only she and her lectern are shown. A graph is shown above her. There us a label for the y-axis to the left of the axis which has four ticks with numbers. The x-axis is a timeline without ticks but three years indicating the start center and end of the axis. The graph shows a curve falling off, with one great spike up around 1920.] Y-axis label: Per 100,000 Y-axis: 800 600 400 200 X-axis: 1900 1950 2000 GUSG (Bio): This is a graph of the death rate from infectious disease in this country. Labels: Bio
[Zoom back to original scene with Hairy holding the microphone down and Grown-Up Science Girl raising her left hand, while Cueball looks at her.] GUSG (Bio): The heroes of my field have slain one of the four horsemen of the apocalypse. Labels: Phys Bio Chem
[Zoom in on only Cueball and Grown-Up Science Girl who is pointing aggressively at Cueball who leans away from her one hand on his lectern for support.] GUSG (Bio): While the heroes of your field gathered in the desert to create a new one. Labels: Phys Bio
[Zoom back to previous scene all are holding their hands down.] Cueball (Phys): ...Jeez, what the hell? I thought this was supposed to be fun and lighthearted! GUSG (Bio): You must have been thinking of stamp collecting. Labels: Phys Bio Chem


Sword in the Stone

Explanation:
In this comic, Megan pulls a sword out of a stone. A flash of light comes down and music plays, and a heavenly voice tells her she has ascended to the throne of England . Megan then pulls out her phone and searches on Wikipedia for England . After having read for a while she begins, while reading on, to replace the sword into the rock.
The comic references the fables of King Arthur and the Knights of the Round Table . In Arthurian legend, whoever can remove The Sword in the Stone is the lawful king of Britain (although this comic, as some versions of the legend, refers incorrectly to England). Arthur is an orphan being raised in secret; he notices the sword, removes it, and is proclaimed king. The sword is sometimes identified as Excalibur , although in other versions Excalibur was acquired by King Arthur from the Lady of the Lake . The most familiar version of this story is The Sword in the Stone by T. H. White which is based on Le Morte d'Arthur by Sir Thomas Malory . The animated musical by Walt Disney is a well-known version of this fairytale based on White's book.
A key element in the joke is that as Megan begins to read about England, especially information concerning being an English ruler, she quickly thinks better of this and begins to put the sword back in its place. The punchline that Megan puts the sword back after reading about England suggests that the "gift" of being the leader of England is not worth the risk and/or work associate. British history is rife with monarchic strife, and a brief inquiry into their causes of death will show that almost one in three British rulers have died either in battle or from murder, etc. This would quickly lead most sane people to conclude that the risks associated with ruling England far outweigh the benefits.
The title text furthers this plot, having Megan comment on the hassle when the only thing she was interested in was the cool sword. Apparently, Megan is not enthusiastic about power, and her choice is made when she sees how problematic it could be to reign over the country of England. There is also a subtle play on the fact that in the T. H. White version, Arthur likewise is unaware of the significance of pulling the sword from the stone - he is simply looking for a sword to replace the one belonging to his step-brother Kay that was stolen under his watch, to avoid embarrassment and reproach.
From the time of the Roman Empire all the way up to Charles II's reclamation of the throne, the area now known as England has seen several migration waves, Viking raids, invasions and fierce power struggles among aristocratic families. Besides the constant threat of usurpation, as evidenced by the numerous wars for the crown, such as the Norman conquest and the War of the Roses , there were also constant difficulties in managing the frontier regions. This can be seen from Hadrian's Wall , a creation of the titular Roman Emperor designed to keep the ever difficult Scots out of the areas of Roman control (the Scots would be a constant problem for England up until the reign of King James VI and I ; think of the movie Braveheart for a good example of the regular headaches they caused, seen from the English point of view), as well as the Welsh uprisings that occurred with such consistency that you could set your watch by them.
It is worth emphasizing that the term "England" is anachronistic in this context. At the time Arthur supposedly existed, there was no England — England was formed by Germanic tribes who settled in Britain between the fifth and seventh centuries . In many of the stories, including the earliest, Arthur was in fact depicted as a leader of the native Romano-Britons in their attempts to repel these invaders. England would not exist had Arthur succeeded. The anachronism is not new; it entered Arthurian legend in the Middle Ages. (Thomas Malory's Le Morte d'Arthur , for example, refers to Arthur as King of England.) In Arthurian legend, it was stated that Arthur would return when needed (in some versions he was explicitly associated with the Mab Darogan , a Welsh Messianic figure who would finally drive the English out of Britain and reclaim it for the native Britons).  It is possible that Megan in this comic is a 21st-century reincarnation of Arthur.
The timing of this comic might relate to the birth of princess Charlotte Elizabeth Diana on May 2, 2015, just four days before this comic, and the burden of a royal of having a whole life in public shaking hands of strangers. Since 2013 the line of succession was changed to absolute primogeniture , meaning that she will keep her current position in the line (4th after her older brother ) even if she later gets baby brothers. Before this year, that would not have been the case, as the male gender took rank over birth order.
It is also probably not a coincidence that this comic was published the day before the UK General Election , occurring on May 7, 2015. This election decides the modern-day leader of the UK. And the problems they face today may even be more likely to cause Megan to give away the throne, than the risk of untimely death she would have faced in Arthur's days.
A similar Wikipedia gag appears in 911: Magic School Bus .
The sword in the stone also appears in 2578: Sword Pull .
[Megan walks up to a sword in a stone.]
[Megan attempts to pull the sword out of the stone.]
[A beam of light and music plays as she removes the sword.]
[While standing with the swords a voice from the sky speaks in gray shaky letters:] Celestial voice: The Throne of England is yours
[Megan takes out her smart phone and searches:] Wikipedia England
[Megan reads on her phone.]
[Megan starts to replace the sword back into the stone.]


Astronomy

Explanation:
For objects at a great distance one can achieve a better view by using a telescope as it is the typical method in Astronomy . Looking through a lens or a microscope in biology and other disciplines does magnify short distant objects. And a magnifying glass works more like a microscope when your eye lense is close to the focus of the magnifying glass, but when looking at distant objects you have to increase the distance between the glass and your eye where the focal length of your magnifying glass must be increased to meters instead of centimeters or less on a close view. But in general a Galilean Telescope works at the same principle as a magnifying glass together with your eye lens, the magnifying glass only has to have a long focal length which is optimized for far distances.
In the comic, the objects being viewed by Megan could be stars , galaxies and the planets of our Solar System . Megan is using a telescope. Beret Guy attempts to view them using a step-ladder to get closer to the stars, and then looking at them through his simple hand-held magnifying glass. This approach could be successful only if the stars were a few meters away, so that the ladder would take him within a few centimeters of the study object. In fact the visible stars are several light years away (typically 18-20 orders of magnitude further away) and getting two meters up on a ladder won't make any perceivable difference. [ citation needed ]
The title text assumes (for comic effect) that the only thing wrong with Beret Guy's strategy is the instability of the ladder endangering the expensive microscopes used by biologists for Astrobiology . Astrobiology is the study of life (or the possibility thereof) elsewhere in the universe, and here it would be either the planets and moons in our Solar System or exoplanets they needed to look at. This is the second comic related to studying exoplanets in two weeks, the first being 1517: Spectroscopy (see more references there).
Since we cannot go there, they do, of course, not use any microscopes in the direct studies. However, one typical magnifier in biology is the electron microscope , used to study microbiology , and they cost a lot and are very heavy. It is therefore inadvisable to carry one up a ladder, and it could possibly become very expensive if you did try it anyway.
[In front of a starry black sky, Megan looks at the stars through a telescope about twice her size, touching it at the base. She remains in the exact same position through all four panels.]
[Beret Guy enters the panel holding a ladder and a magnifying glass.]
[Beret Guy places the ladder next to Megan and her telescope. The ladder is stands like a triangle, is slightly larger than Megan, but smaller than the telescope.]
[Beret guy climbs to the top of the ladder, and looks at the stars through a magnifying glass.]
Usually, however, Beret Guy has strange powers , so it's quite possible that his method would yield similar or even better results than Megan's approach; see for instance 1490: Atoms . Given his naivety, it's also possible he just doesn't realize they should look any different. His naivety of astronomy is demonstrated in 811: Starlight .
The history of astronomy is filled with drastic misunderstanding of distances to celestial bodies, even up to the present day like Randall has covered in 1342: Ancient Stars . Thus, the comic could be in reference to the general overestimation of distances, albeit taken to the opposite extreme.


Microdrones

Explanation:
Amazon Prime Air is a conceptual drone -based delivery system currently in development by Amazon.com. While on one level he thinks the idea is cool, Cueball worries about living in a sci-fi dystopia, with those drones flying all around him, tracking his actions, etc. In the third panel, Megan suggests sending a message to Congress, suggesting a law for making the stealing of drones legal. This would alleviate the problem of drones flying around everywhere because if they did people would catch them to use for themselves. In the final panel Megan begins to search for butterfly nets so they are ready to catch the microdrones when the law to make it legal to steal the drones goes through.
This tactic may not work as well as planned; drones will likely simply fly higher or employ other security measures since there are no regulations on drone behavior.
The title text suggests one of five things:
Amazon drones is also the subject of the title text in 1625: Substitutions 2 and there are two quadcopters over the volcano lake in 1608: Hoverboard . Also, Cueball is abducted by seemly sentient drones in 1630: Quadcopter .
[Cueball is standing behind Megan who sits at a desk typing on her laptop.] Cueball: So how do we regulate all these micro drones? Cueball: I mean, Amazon delivery bots sound cool...
[Cueball stands alone surrounded by three micro drones.] Cueball: But I worry that overnight we'll realize we're surrounded by these things, no one will know who's controlling them, and then bam , sci-fi dystopia.
[Megan turns in her chair towards Cueball.] Megan: If you wanna slow it down, why not just remove all regulations, but then make drone theft legal?
[Cueball takes his hand to his chin and Megan turns back to type on the laptop.] Cueball: ...I like that. Megan: You write to congress. Megan: I'll stock up on butterfly nets.


Dimensions

Explanation:
This cartoon is a romantic musing about time, and how even though we may not always realize it the progression of time is one of the better things in life.
To accurately describe the world requires at minimum three spatial dimensions and the fourth dimension, time. The spatial dimensions don't necessarily have to be the familiar Cartesian system (Forward/backward, Right/Left, Up/Down), but can be described in many ways (like the spherical or cylindrical system). In spite of the fact that we are being pushed around the universe by being on Earth, we can exercise some control over these spatial dimensions by moving, and therefore our trajectory through these dimensions is not inexorable (impossible to stop). As we only can go one direction in time and have no way of changing the speed, we also are figuratively being pushed through time, and this movement is inexorable.
Cueball sits under a tree un-moving with Megan simply enjoying the passage of time and says, "Of the four dimensions I could have spent my life being pushed inexorably forward through, I guess "time" isn't the worst." All of this amounts to an unusually erudite way for Cueball to say he feels content with how his life has turned out, despite the natural doubts one has as they get older.
In the title text, Cueball then continues to muse about his favorite dimensions and places time in his top three dimensions. This means that one of the three spatial dimensions must be his least favorite. Though it is impossible to determine how he defines his favorite dimensions, as dimensions can be defined somewhat arbitrarily, they likely are length, height, and time as comics only use these three (time being represented by panels). Since rising steadily and digging downward are both pretty lethal, one could assume that Randall's least favorite dimension is up/down. (See also the one of my favorite halves comment in 1556: The Sky ) This could also be a reference to 1190: Time .
Previously Randall has made a comic about a man who was pushed sideways — so he was pushed both through time and fell sideways: 417: The Man Who Fell Sideways .
[Cueball is sitting up against a tree, Megan lies with her hands behind her neck in front him under the foliage of the tree.] Cueball: Of the four dimensions I could have spent my life being pushed inexorably forward through, I guess "time" isn't the worst.
Interestingly, Randall has already, back in the December 2014 issue of Wired magazine, published the xkcd guide to dimensions where the main part of this comic was already used in panel 9 out of 20. This issue of Wired magazine was about multiple dimensions, and Randall's section is about imagining higher dimension. The article is a mix of xkcd-style comics and captions explaining them.  The panel in question show Cueball saying, "Of all the dimensions I could have spent my life being pushed inexorably through, I guess "time" isn't the worst." (the only difference being that "all the" has been changed to "the four" in this comic). In panel 15 of the Wired comic series, Randall considers how dimensions can be represented in a two-dimensional comic strip: a character moving within a panel represents movement in space but movement from panel to panel represents movement in time.


Emojic 8 Ball

Explanation:
Emojic 8 Ball is a parody of the Magic 8-Ball using emoji instead of words. "Emojic" is a portmanteau of "emoji" and "magic".
A real Magic 8 Ball is a toy designed to visually resemble a real pool ball , which responds to questions (posed as yes-or-no questions) asked of it, ostensibly by magic. The responses are provided through a window on one face that displays text phrases printed on a triangular shape as depicted in this comic. Vintage balls contained a die with multiple triangular facets suspended in a dark fluid, while modern balls feature an electronic screen.
The ball in this comic provides responses in the form of graphical Unicode "text" (which this comic is suggesting are emoji ).
It is possible that this may be commentary on the inclusion of such "meaningless" symbols into Unicode. Ask a question and get a meaningless reply, even more meaningless than the answers given by a Magic 8 Ball.
It could also be commentary about the ambiguous nature of advice from fortune tellers, horoscopes, etc.  Each emoji has an ambiguous meaning (for example, depending on context, the cow symbol 🐄 could refer to beef or farming). The interpretation has more to do with the person receiving the fortune than anything given by the so-called fortune reader.
With the default question being "How will I die?", this may also be partially a reference to " Machine of Death ". This book from 2010 is a collection of short stories edited by amongst other Ryan North (of Dinosaur Comics ) mentioned here since the idea was based on one of his comics . Since Randall Munroe wrote one of the stories the reference is very likely. All the stories are based around a device, the "Machine of Death", that can predict, with 100% accuracy though generally with extreme ambiguity, how people die from a drop of their blood. In many of the stories very unusual deaths are predicted, often in a very literal way, but not so you know when or where you will die. From the official home page the entire book can be downloaded for free as a PDF file (broken) 2020/06 archive.org copy . (Randall's story begins on page 421 - or page 218 of the two sided PDF file. It is simply called "?"). The "Machine of Death" may also have been referenced in the fourth panel of 1341: Types of Editors .
Emoji were previously referenced in 1513: Code Quality . Emoji has since then become a recurrent theme on xkcd. But this is the first one with Emoji in the title.
Note: if you see mostly squares (possibly with six numbers/letters inside) in the 8 Ball instead of actual symbols or pictures, it means your system doesn't have fonts that support the Emoji unicode characters.  Scroll down to the discussion section below for suggestions on how to get and install the right font for your system, as well as to see a list of emoji characters so you can easily see if they're working or not.
[An image of a shiny black ball with a white circle forming a black window at its center. Above the image is a title where the number 8 is written in a black circle, making it look like an 8-ball.] Emojic 8 Ball
[Below the title is an input field with a placeholder text in grayed out text:] How will I die?
[Below is a gray submit button.] Ask
[The Emojic 8 Ball is below the ask button. The text in the input field can be changed by the user before pressing the ask button. After the submit button is pressed, 1 to 3 emoji symbols appear in the black window, framed inside a light blue equilateral triangle with one end pointing straight up. Once this has been done once, then a link appears below the panel with this text: Permalink].


Placebo Blocker

Explanation:
This comic is a joke about the difficulty of testing a drug that is supposed to block the placebo effect.
A placebo experiment is used for testing a drug candidate. It has two groups: one that gets a real drug candidate, and one that gets a fake. The placebo effect describes the observation that the group that gets the fake often show signs of having received a working drug - though commonly weaker than in the group that gets an effective real drug.
Cueball states to Hairbun , with a citation from the real world, that his team created a Placebo Blocker, a drug designed to prevent the placebo effect. Cueball begins to design a test for this new drug. Following typical experimental design, patients would be split into two groups: a control group, and the group that receives the treatment.
Cueball knows that the treatment given to the control group is supposed to be designed so that it is not influenced by the variable trying to be isolated. As the placebo effect is the effect under investigation, a placebo can not be used as a control treatment as a comparison with a placebo blocker. Cueball tries to design around this. In his test, both groups would receive a placebo as a treatment for an unspecified condition (the Treatment Placebo ); in addition the test group would receive the Placebo Blocker drug, while the control group would get a placebo pill instead (the Placebo-Blocker Placebo ). If this works as expected, the Treatment Placebo would be blocked by the Placebo Blocker in the test group, while in the control group, the Placebo-Blocker Placebo may have a placebo effect in blocking the placebo effect of the Treatment Placebo , and the difference between these effects can be measured to test the effectiveness of the Placebo Blocker .
Cueball and Hairbun think about this trial until they both develop headache from frustration. Cueball then kindly offers Hairbun a sugar pill. While this might have helped cure the headache via the placebo effect had he told her it was a headache treatment, by revealing the pill as merely a sugar pill, it may reduce the effect (though it has been shown that placebos tend to work even if the subject is aware that they are placebos).
In the title text, Cueball mentions that his sugar pills against headache works even better together with the new experimental placebo boosters . Incidentally, he indicates that he keeps those in the same bottle with his sugar pills. Assuming someone believes placebo boosters are in the jar this would allow them to take the sugar pills and receive a greater placebo effect, as the placebo effect is based upon faith in the treatment, regardless of whether there are placebo boosters in the jar.
It is possible but unlikely that:
Questionable neuroscience research is also discussed in 1453: fMRI .
The placebo effect refers to the phenomenon in which patients given an inactive treatment such as a sugar pill can still show improvement relative to an untreated patient. The placebo effect is thus very important to consider when testing new drugs, since even ineffective drugs can have a positive effect on the patients due to the placebo effect. Modern drug experiments are hence conducted as double-blind trials , where the patients are randomly given either the treatment or a placebo without either they or the administering doctors knowing who receives the new drug and who received the placebo pill. (It is important that the doctor does not know, as if they did, it may affect the way they interact with the patient.)
Generally the patients need to believe that they are receiving an active treatment, but one study showed that the effect can occur even if the patients are told that they are receiving a placebo pill. The key factor seems to be that the patients must believe that a positive effect will occur. For example, (1) patients experience a greater effect if they believe that the treatment is expensive and (2) patients who know that they have not been given an active treatment will experience the effect if they are told that placebos can have a positive effect through the power of the mind. Furthermore, the placebo can increase the effectiveness of treatments which seem larger (this is why over-the-counter pain medication is often administered as two half-doses rather than just one full dose).
Several reasons for the placebo effect have been proposed, from study artifacts - such as under-reporting of negative outcomes by patients who think they are being treated, to neurological explanations for how mental state can translate into physical outcomes.
Placebo-blockers do actually already exist. A side-effect of the opiate antagonist Naloxone is that it blocks the placebo effect .
It should be noted that placebo does not actually improve the objective condition, only the patient's subjective perception of it (i.e. the patients do not get better more than they randomly would, but the placebo makes them think they do). [ citation needed ]
The placebo effect is one of the greatest mysteries in modern medicine. It is typically found that the placebo effect is an effective treatment in itself in addition to the effectiveness of drugs and other treatments, and it has been found to cause small improvements to cancer outcomes. In other cases such as pain relief, the placebo effect is claimed to be comparable with the effectiveness of the drug itself - but this is a misunderstanding: this is not evidence of placebo working, but of the drug not working .
The comic refers to the recent study by Kathryn T. Hall, Joseph Loscalzo, and Ted J. Kaptchuk. (2015) Genetics and the placebo effect: the placebome. Trends in Mol Medicine. Volume 21, Issue 5, May 2015, Pages 285–294 - however, bear in mind that one has to treat studies very carefully Kaptchuk vs Placebo
It is possible to test the placebo blocker using three groups: a test group who receive a placebo and a placebo blocker, a control group who receive a placebo but no blocker, and a second control group who receive no treatment whatsoever, as a lack of treatment is the variable that an actual placebo is designed to control for. Still it might be hard to determine if the pills are having a negative effect or blocking the placebo effect, so multiple trials with multiple illnesses may have to be carried out.
[Hairbun is standing in front of Cueball who does all the talking. Below them is a footnote.] Cueball: Some researchers* are starting to figure out the mechanism behind the placebo effect. Cueball: We've used their work to create a new drug: A placebo effect blocker . Footnote: * Hall et al, DOI: 10.1016/J.MOLMED.2015.02.009
[Zoom in on Cueball who now holds his arms out.] Cueball: Now we just need to run a trial! We'll get two groups, give them both placebos, then give one the real placebo blocker, and the other a... Cueball: ...wait.
[Hairbun holds her chin, while Cueball just stand there for a beat panel.]
[Hairbun looks again at Cueball who begins to take the lid off of a medicine bottle.] Hairbun: ...My head hurts. Cueball: Mine too. Cueball: Here, want a sugar pill?


Humans

Explanation:
The comic is set in the future, with two hovering robots discussing ancient history, in particular the clothing styles of kings and queens of the now extinct human species. It appears that robot archeologists have long ago unearthed remains from one or more human civilizations, providing evidence to build a concept of what humans must have looked, acted and even sounded like. Recently they must have discovered or determined new evidence, which presumably indicates the wearing of colorful clothing by human monarchs. Until this occurred they had very little if any reason to believe that any humans wore clothing. Noting the previous knowledge that some humans had metal rings around their heads, they have drawn the conclusion that these formed a separate species "Human Kings" and the crown is a natural outgrowth of the skeleton. Alternatively, the narrative of the fictional, horned Star Wars villain Darth Maul may have somehow survived into the era of robot film and misinterpreted as describing a human, though Maul's skin is red, not pink.
When dinosaur bones were first dug up, the idea that dinosaurs were scaly, reptilian-like creatures was developed with the information available at the time. In recent times, it's been discovered that most dinosaurs actually had feathers , and in well preserved specimens, often from the Jiufotang Formation in Northern China, feathers of various forms are clearly visible.
As this runs counter to the widespread and long-held image of dinosaurs as dramatic reptiles, the public has been reluctant to accept this new discovery, especially as the addition of feathers often conjures up the image of a giant chicken. (See 1104: Feathers ). Had it been discovered that dinosaurs were in fact covered with 6-inch long razor tipped spikes, people may have accepted this immediately as it conforms to the stereotype of dinosaurs as killing machines.
In the same way, the new information on kings and queens being covered in fabric runs counter to the movie inspired image that the robot on the right had about humans, picturing them as being pink warriors that could grow metal out of their heads. The head-metal image may have been inspired by the discovery of kings and queens buried or entombed with their crowns lying on top of their skulls - for example the Electress Palatine Anna Maria de'Medici . If the robot beings in this comic don't know enough about human anatomy, they may assume that the metal crown is a specialized part of the human skeleton.
Shown at least some evidence pointing to the truth - that humans typically wore clothing, and that a monarch's crown is only a symbol worn atop the head and not part of their body - the robot is predictably disappointed. Humans wearing clothing reduces them, in its opinion, to "big pillows," much like dinosaurs with feathers reduces them from primal beasts to "big chickens." Something made of cloth (or covered in it), at least in this robot's mind, cannot be a significant actor in history.
The robot fails to reason that, among other things, history was what it was, and its wanting things to have been a certain way does not make it so. In addition, just as the clothing-wearing human is more than a mere pillow, and would have held much fearsome power over the world, a feathered dinosaur is not necessarily merely a giant chicken, but is still a powerful killing machine.
The title text references our failure to change the popular image of dinosaurs to reflect the way they truthfully once were. Randall jokingly suggests that we should apply the same "featherless is cooler" logic to popular images of bald eagles ( since they are modern dinosaurs ), and remove their feathers (only in depictions of them, presumably), leaving them entirely bald. He appears hopeful that such a direct comparison, using the national symbol of the US no less, would provoke the public to change its mind about how dinosaurs are viewed, since modern raptors (birds of prey) are typically viewed with awe and respect, and are not often associated with the "chicken" stereotype mentioned above.
[Two robots are hovering in mid-air in the comic; what appear to be their optical arrays are facing each other.] Robot 1: You know, new research suggests ancient human kings and queens were covered in colorful fabric. Robot 2: Ugh, I like movie humans more. Screaming pink warriors with metal crowns poking through the skin on their heads! Robot 2: Now they're, what, big pillows? Robot 2: Science ruins everything.
It is worth noting that this comic was released a few weeks before the scheduled release of Jurassic World , a reboot of the Jurassic Park movie franchise. This new movie, while supposedly aware of recent advances in dinosaur research, still depicts dinosaurs as giant lizards without feathers. It seems likely that the robot's comment about "pink humans" is targeted at this movie, especially given Randall's many earlier references to Jurassic Park and his fear of velociraptors .


Vodka

Explanation:
Vodka is a distilled beverage composed primarily of water and ethanol, sometimes with traces of impurities and flavorings. Traditionally, vodka is made by the distillation of fermented cereal grains or potatoes , though some modern brands use other substances, such as fruits or sugar.
When people use the phrase "maybe it's the [type of alcohol] talking", they usually mean that they are speaking under the influence of alcohol and are saying things they probably wouldn't say when sober . This is similar to the Latin saying " in vino veritas " - in wine there is truth. However, in this comic, it appears that the vodka itself is literally speaking through Ponytail to discuss its origin, potatoes in this case. Other comics in which things have been taken too literally include 1099: Tuesdays and 1364: Like I'm Five .
In the title text the vodka is implying it can be made from many other things beside potatoes. Vodka can be manufactured from potatoes, grain, and most other plants. Most illegal distilled vodka is often made with whatever one has on hand. However, vodkas are often repeatedly distilled to remove the "foreshots" (the first few ounces of alcohol that drip from the condenser), the "heads" (the higher alcohols which are first to condense during distillation) and the "tails" (the lower fusel oils which are last to be distilled). Removal of these leaves a clear solution consisting almost entirely of ethanol and water. This is in contrast to other distilled beverages like whiskey , brandy and rum .
In 1541: Voice Ponytail is again possessed by a non-human entity , or maybe she is just making pranks with Megan in both cases.
[Ponytail and Megan sit together at a table with two small shot glasses on the table. Ponytail is imbibing from a large bottle, while Megan is cradling a relatively large glass.]
Ponytail: Maybe this is the vodka talking, but: Ponytail: Hi! I'm made from potatoes!


Bracket

Explanation:
A tournament bracket shows the planned series of matchups in a tournament. In this comic Randall has shown a plan for a tournament between a wide range of cultural icons, both real and fictional, based mostly on similarities in their names. Various Internet groups have speculated on who would win in a fight between characters from different films. It may be relevant that the film Batman v Superman: Dawn of Justice was soon to be released at the time the comic was made where the two eponymous superheroes , Batman and Superman , fight against each other.
The individual starting pairings are generally based on common or similar given names or surnames. Some adjacent brackets are "segued" by someone like Jeff Daniels, who segues from a bracket of "Jeff"s into a bracket of "Daniels"es. The bracket itself is fairly arbitrary. Most initial matchups are pairs, although several are trios and there's a quadruplet in the Russels group, while a single entry, Beyoncé , is given a first- and second-round bye . Most of the participants in the tournament are people, with a few exceptions. Shallots (small onions), scallops (bivalve mollusks), and scallions (green onions) are similar sounding foods, therefore may be confusing for some individuals (perhaps including Randall ). The final grouping on the lower right of the bracket features a several retail stores and a film.
The title text possibly refers to Dr. Dre , particularly as a reference to his 2001 song " Forgot About Dre ". Alternatively, the title text could simply be a reference to the large number of pop culture personas that include the word "Doctor", such as Doctor House , Dr. Oz , Dr. Phil , Dr. Watson , "Doc" Brown , Dr. Seuss , Dr Pepper , Doctor Doom , Dr. Zoidberg , Dr. Horrible 's Sing-Along Blog and many others . Another simpler explanation is that it would cause the reader to question "Doctor Who?" answering their own question, although this answer would be incorrect because The Doctor is already present. It could also be a reference to the dual meaning of "The Doctor," either he meant to include Time Lord from Doctor Who and forgot about the EMH from Voyager, or he remembered the EMH and forgot the Time Lord.
The incentive for the comic may have been the French Open 2015 , which started on the day of the publication.
The comic inspired several groups to play out versions of the bracket.  One user-voting based match-up on twitter, XKCD Bracket , was featured by Randall on the xkcd home page, with a link at at the top of the website, although the account was not created by Randall. (The link was part of a "news" flash, the other was regarding his book based on 1133: Up Goer Five . See more on this news in that comics explanation). In the final match on July 29, Neil Armstrong defeated Mister Spock (see the complete bracket ). The link was removed sometimes before Monday, 10 August 2015, within two weeks of the final result being revealed.
Later Randall has made one smaller but similar bracket in 1819: Sweet 16 , and then an interactive April fools' comics in 2019, with an even larger bracket for determining the best emoji in 2131: Emojidome . The bracket for this comic was shown with links from the comic during the matches.
[A tournament bracket. With the names listed in groups on the left-hand side and right-hand side as shown below. Within individual groups the names are ordered in match-ups, two, three or even four in the first match. The last name on the right, Beyoncé, is not even matched for first round. The winners goes on to the next match, but there are many that skips some of the matches up until the quarterfinals, so some need to win 5 matches to reach the quarterfinals, others only need to win 4 of 3, and Beyoncé only 2. After the first level, the match-ups are always between two names. The two sides join up in a final in the middle, where the winner of the left side has a place for the name below and the winner of the right a place for the name above a central rectangular frame with place for the winners name. Below the pairing in the first round matches are mentioned above each of the clear groupings of the bracket.]
[These are paired two and two.] Louis Armstrong Neil Armstrong Lance Armstrong Stretch Armstrong [These are paired two and two.] Jeff Gordan Jeff Bridges Jeff Daniels Jack Daniels [These are paired two and two.] Orson Welles H.G. Wells George Orwell Wells Fargo [The first four, two, three and two are paired.] Kurt Russell Russell Brand Russell Crowe Russell Simmons Richard Simmons Gene Simmons Gene Hackman Hugh Jackman Alan Rickman Alan Parsons Alan Partridge [The first four, three and two are paired.] Jenny McCarthy Joseph McCarthy Eugene McCarthy Eugene V. Debs Gene Wilder Olivia Wilde Oscar Wilde Oscar De La Renta Oscar De La Hoya [These are paired two and two.] Jack Nicklaus Jack Nicholson Phil Mickelson Nicholas Nickelby [These are paired.] Ryan Adams Bryan Adams [These are paired.] Chubby Checker Fats Domino [These are paired two and two.] Colin Firth Colin Farrell Will Ferrell The Farrelly Brothers [These are paired.] Joseph Gordon-Levitt Jennifer Love Hewitt [These are paired two and two.] Danny Glover Donald Glover Donnie Wahlberg Mark Wahlberg Mark Ruffalo Mark Shuttleworth [The first three and two are paired.] Philip Pullman Bill Pullman Bill Paxton Bill Murray Dan Aykroyd [The first two, and then three times three are paired.] Ginger Rogers Fred Rogers|Mister/Fred Astaire/Rogers Mister Spock Doctor Spock Doctor Octopus Doctor Manhattan Doctor Strangelove Doctor Strange Dr. No The Doctor Cory Doctorow [These are paired two and two.] Jerry Lee Lewis Jerry Lewis Jenny Lewis Xeni Jardin [These are paired two and two.] Chris Evans Chris Hemsworth Chris Pine Chris Pratt [These are paired.] Shallots Scallops Scallions [These are paired.] Siouxie Sioux Suzanne Vega [These are paired.] Tom Arnold Arnold Palmer Amanda Palmer [These are paired two and two.] Wes Craven Wes Anderson Paul Thomas Anderson Poul Anderson [These are paired two and two.] Sir Walter Scott Sir Walter Raleigh Sir Francis Drake Frank Drake [The first three, two and two are paired.] Van Halen Van Morrison Van Wilder Robert Van Winkle Rip Van Winkle Rip Torn Natalie Imbruglia [The first four are paired two and two the last is the only one not paired.] The Body Shop Bath and Body Works Bed Bath and Beyond Beyond Thunderdome Beyoncé


Keyboard Mash

Explanation:
Cueball is chatting with White Hat , who says he is frustrated because a barking dog is preventing him from sleeping and White Hat mashes the keyboard to show his frustration. Keyboard mashing is often used in this way where the user makes their hands spasm across the keyboard, creating a line of text that can be compared to an angry groan in real life. Cueball is about to give some advice, but is confused by a quirk in what White Hat typed. All the characters he typed (except one) were on the home row of the QWERTY keyboard, the row starting with the letters A, S, D, and F, in the middle of the keyboard. The letters A, S, D, F, J, K, and L (all from the home row) are scattered throughout the text, but there is a 7 (which comes from the numbers row, on top of the keyboard) in the middle of this text. Cueball, wonders how White Hat put a seven in there, because if White Hat was keyboard mashing and touched the 7 key, he likely would have hit any of the QWERTY row keys because of keyboard mashing hand spasms, but he didn't. All the other characters were on the home row. White Hat berates Cueball for always focusing on strange, tiny details. When the final panel shows what's going on where White Hat is, we see that a giant spider has imprisoned him in a web and is talking to Cueball, which explains how the keyboard mashing "White Hat" did was strange.
The reason the dog was barking appears to be because the giant spider was lurking nearby. Little did White Hat know that the dog was alerting him of the spider. When the spider notices that White Hat mentions the barking dog to Cueball, the spider apparently restrains White Hat and takes over typing. Another possibility is that the "dog" barking is actually White Hat, as he is seen making grunts from beneath the spider's silk. It can be seen in the last panel that the spider is typing with 3 legs, which explains how the 7 key would have been pressed.
The statement "I am a normal human typing with my human hands" is an oddly specific assertion from the giant spider that it is actually a human, a claim that would normally be taken for granted and had not really been cast into doubt by Cueball's inquiries about how "7" got into a string of home-row keystrokes.
The title text invitation ends with a similar statement, suggesting that they "...CHAT ABOUT OUR INTERNAL SKELETONS", which spiders (unlike humans) do not possess and which are not a common conversation point among humans, helping to demonstrate (along with the spider's suspiciously specific denial and using the phrase cook bread instead of bake bread) that the spider is not very good at blending in as a human. This implies that the spider also wants to trap and possibly eat Cueball as well, or actually hang out with him in an attempt to make friends or to find out how humans talk so the spider will be able to blend in better in the future. "...HANG OUT INSIDE MY HOUSE" may also have a double meaning, as White Hat and the spider are actually "hanging" from the ceiling inside White Hat's house. Also another oddity is that the spider asks Cueball to cook bread, although bread is actually baked, and in any case this isn't a common pastime during the night (the spider could also mean make toast). The final oddity is that the title text is written in all caps which is usually interpreted as shouting and would not be used in a casual invitation, although the title text should just be imitating the fact that the rest of the text messages use a font that make them look like they are in all caps.
The central theme of the comic is a vindication of Cueball's world-view, wherein tiny oddities such as the appearance of a numeral in a keyboard mash merit investigation. In the real world, the appearance of a "7" in the middle of a home row keyboard mash is more likely attributable to key ghosting .
Alternatively, the fact that Cueball uses the phrase "all your hands" instead of "both your hands" or "both of your hands" could indicate that Cueball (and likely other people as part of a coordinated uprising of giant spiders) has also been taken hostage by a spider, and the spider behind Cueball's profile picture knows that the organism behind White Hat's profile picture is a spider, not a human. This would also explain why the spider behind White Hat's profile picture feels that the spider behind Cueball's profile picture pointing out the usage of a numeral among home row keys is weird; spiders know that other spiders have many legs and that these legs do not have to be in the same section of the keyboard.
In the title text of 1541: Voice there is again a reference to a sentence that could be uttered correctly by a human, but would never be used in real life. But a non-human entity that tries to blend in as a human, may inadvertently use such a "wrong" sentence to try to ensure other people think they are indeed humans. It is a direct reference to the type of sentence used in the title text here.
This comic is somewhat unusual in that the panels are read from top to bottom instead of being read from left to right in more than one row. This may be in order to accommodate the second panel, which must be tall due to containing a text conversation, without making the comic look weird due to the second panel being much taller than the first panel.
[Cueball approaches his desktop computer, which has emitted a message seemingly from White Hat as it displays a picture of him.] New chat message
[Below the chat log is shown with White Hat's comments on the left in gray frames and Cueball's comments to the right in white frames. The first post in a row from each person is labeled with their picture at the end of a small arrow in the frame]: White Hat: Can't sleep. Stupid dog keeps barking. White Hat: So frustrating. FJAFJKLDSKF7JKFDJ Cueball: Ugh, I'm sorry. Maybe you could... Cueball: ... Okay, wait. I have to ask. Cueball: How did you hit a "7" in the middle there? White Hat: Huh? White Hat: I was just randomly keyboard mashing. Cueball: Sorry, Right. White Hat: Anyway, Cueball: I know this is silly, but like... All your hands were clearly right on the home row. Cueball: I don't get how one finger could have stretched up to the "7". White Hat: Why do you always fixate on these bizarre details? Cueball: I don't know. Cueball: Sorry. White Hat: It's weird, is all.
[Chat transcript continues above White Hat's laptop, as it started in the first panel over Cueball's computer. But now we see a human-sized spider suspended from the ceiling by web is using three of its legs to type on the laptop. Behind the spider, White Hat is suspended from the ceiling upside down, almost totally encased in spider web. He tries to speak. Between them, a chair has been knocked over onto its back.] Spider (as White Hat in the chat): I am a normal human typing with my human hands. Cueball (chat): Yeah, of course. I know. White Hat (speaking): Mmm!! Mmph!!!


The BDLPSWDKS Effect

Explanation:
The BDLPSWDKS Effect in the title is an acronym for Bernoulli-Doppler-Leidenfrost-Peltzman-Sapir-Whorf-Dunning-Kruger-Stroop Effect, as explained by Ponytail in the comic. She stands in front of a slide that shows Cueball being subjected to this effect.
The effect mentioned appears to be a mashup of seven scientific principles (with nine scientists' names included) from physics and social sciences, with elements from each principle appearing in the resulting description of the effect:
This comic is probably a comment on the "replication crisis" in social psychology which has been in the news recently . For example, studies finding that merely thinking about intelligent people (e.g., writing down the attributes of a professor) will actually improve performance on math tests were once widely believed, and this "intelligence priming" effect is even included in textbooks. However, recent attempts to reproduce these effects have mostly failed and this failure to replicate is true of many social priming effects as well as other experiments in social psychology. Randall is also mocking the complicated, or even convoluted, setups often used in these experiments.
Usually, for an effect to be considered real, the scientific method requires the effect to be replicated by different experimenters in different times and places. It is hard to imagine several scientists in different parts of the world creating the setup to replicate this effect; however the title text mentions, sarcastically, that it has been done countless times.
Many other xkcd strips have commented on the ease with which surprising and novel, but false, results can be published in the scientific literature, such as 1478: P-Values and 882: Significant .
[Ponytail stands next to a screen displaying a firetruck hurtling toward Cueball on what appears to be a layer of gas.]
Ponytail: The Bernoulli-Doppler-Leidenfrost-Peltzman-Sapir-Whorf-Dunning-Kruger-Stroop Effect states that if a speeding fire truck lifts off and hurtles towards you on a layer of superheated gas, you'll dive out of the way faster if the driver screams "red!" in a non -tonal language that has a word for "firefighter" than if they scream "green!" in a tonal language with no word for "firefighter" which you think you're fluent in but aren't .


New Horizons

Explanation:
New Horizons is a NASA mission launched in 2006 to study the dwarf planet Pluto and its moons. Its closest approach to Pluto was on July 14, 2015 ( NASA countdown clock ), two weeks after the publication of this comic. In April and May 2015, it captured the first images of Pluto with enough resolution to see some details on Pluto's surface ( NASA photos from 12 April to 12 May ). These images are similar to the second panel of the comic, with Pluto shown as a gray dot only a few pixels wide. Dawn is a NASA mission launched in September 2007 to study the asteroid Vesta and dwarf planet Ceres . Its closest approach to Vesta began on July 16, 2011 by the Vesta approach , and entered orbit around Ceres on 6 March 2015. And in fact the pictures of Ceres are still in a much better resolution like in this comic 1476: Ceres , but these images are also still mysterious.
On the day this comic was published, New Horizons was at 0.34 AU from Pluto and 32.55 AU from the Sun ( Johns Hopkins University's New Horizons page ). One Astronomical unit (AU) is the approximate distance of Earth from the Sun, or about 150 million kilometers.
Distances from the Sun by semi-major axis : Vesta 2.36 AU; Ceres 2.77 AU; Jupiter 5.20 AU; Pluto 39.26 AU.
A slingshot maneuver is a technique where a spacecraft is maneuvered or accelerated with the help of a gravitational field.  In the comic, presumably someone named Steve made the calculations for the New Horizons spacecraft to accelerate toward Pluto using Jupiter 's gravity.
In the first panel we see Cueball and Ponytail standing in front of a computer monitor and observing a series of images sent back from New Horizons as it approaches the planet. They are about to see the dwarf planet Pluto with the highest resolution ever.
As the spacecraft gets closer, the images return... Earth . Steve had miscalculated the gravity assist and the spacecraft was about to crash into Earth.
Because the spacecraft carries 10.9 kg (24 lb) of radioactive plutonium-238, a crash on Earth is extremely dangerous.  It was estimated that a worst-case scenario of total dispersal of on-board plutonium during the launch would spread the equivalent radiation of 80% the average annual dosage in North America from background radiation over an area with a radius of 105 km (65 miles) ( Draft Environmental Impact Statement for the New Horizons Mission ).  Because of decay during the flight, the situation would be slightly less dire if it crashed years later, but still a major disaster.
Less importantly, this is a huge embarrassment, especially in front of the successful Dawn team, who were the first to get a probe to visit a dwarf planet. Part of the joke is the utter implausibility of such an error being made, and then not being detected.
The title text suggests the team is considering crashing the probe into Steve's house as punishment for his errors.  However, doing so would expose Steve's neighbors to potentially lethal levels of radiation.  Therefore, the team would most likely have to crash the probe into an unpopulated area or the sea, to minimize human exposure. Randall described what might happen if New Horizons crashed into one's car in his what if? blog [1] , and assuming the car was parked in the driveway the house would be similarly affected by the blast.
Luckily this was not what happened and when New Horizons reached Pluto 1½ month later Randall made this tribute to the achievement: 1551: Pluto and also on that day he released the first what if? in over three months, and it was called New Horizons .
Randall has used a Steve in a similar context in 809: Los Alamos (set in 1945). If this is the same person, then 'Steve' would be at least 90 years old in 2015. A person named Steve also comes up with an inappropriate suggestion in 1672: Women on 20s .
[Cueball and Ponytail are standing in front of a large computer console. Cueball's hands are on the keyboard; both are looking at the screen.] Cueball: We made it! After all these years, New Horizons is finally revealing the surface of Pluto! Ponytail: Take that , Dawn team.
[In the next four frames, we see photos, entirely black except for a circle in the middle. The circle is initially small, indistinct and appears in shades of grey. Successive circles are larger showing more color and shade variation. In the last, we see a blurry but recognizable outline of Africa, the Middle East and part of Western Asia, along with some clouds. The lighting pattern suggests that it is daytime in Africa, sometime in the northern summer.]
[A close-up of the two at the console.] Cueball: OK, who did the calculations for the Jupiter slingshot maneuver? Ponytail: (facing away from the computer console) Dammit, Steve...


Antique Factory

Explanation:
Beret Guy has a new job with a paradoxical premise. When asked where he works, he says " Antique factory!" which is an oxymoron since one cannot build an antique object directly in a factory: Only when the item is old enough to be worth more than its original price (and will often have to have been in use during this time period), can it be called an antique.
At the "factory", Beret Guy walks up to a chair, a table, and a small cabinet, then simply sits down in the chair and does nothing else. Of course, one does not simply make or manufacture antiques - instead, one must wait. Beret Guy appears to be doing exactly this. The implication is that the "antique factory" is simply a place where furniture is stored until it becomes old enough to be considered "antique", and that Beret Guy doesn't perform any useful function (except perhaps using the items to make them look old and worn, or keeping an eye on the inventory so it won't be stolen).
The title text refers to allergy warning labels saying May contain nuts . More specifically, they may say "Manufactured in a facility which also processes nuts", "Manufactured on equipment that also processes nuts", or similar. These warnings indicate that bits of powder and oil from nuts may have been mixed into the product, creating a hazard to people with nut allergies. Sometimes these warnings are used for allergens besides nuts, but nuts are likely the most common.
The joke here is that of course the time that has passed for a specific item to become an antique will be the same time that has also passed while elsewhere nuts have grown. Thus the time that has inexorably passed to make a specific item antique will also have processed nuts.
Beret Guy has previously "traveled" into the future in 209: Kayak . He has also previously waited for a long amount of time in 1088: Five Years .
[Beret Guy is leaving with a briefcase in hand.] Beret Guy: Gotta go - I'm late for work. Off-screen voice: Oh, where are you working now? Beret Guy: Antique factory!
[Beret Guy arrives in a room with a chair, a table, and a small cabinet. He pulls out the chair.]
[Beret Guy sits in the chair. He has placed the briefcase behind the chair.]
[Beat panel.]


Beer

Explanation:
Hairy offers Cueball some beer from his fridge, and Cueball takes the opportunity to suggest that people should admit that beer tastes bad and stop pretending to like it. Hairy berates Cueball for making such an affirmation, and Cueball admits defeat, deciding to drink the beer anyway and pretend to like it to play his part in what he perceives to be a mass delusion.
There are two possible interpretations of this comic. One is that Cueball is right and that no one really likes beer, and everyone is just pretending in order to fit in. The other is that Hairy actually likes beer, but Cueball fails to recognize that possibility, assumes Hairy is faking it, and plays along.
In the case where Cueball is correct, the comic would imply that beer doesn't actually taste good, and people instead pretend to like beer to conform to social norms. The theory is that this pretense is perpetuated by advertising and peer pressure , which present beer as a naturally pleasant beverage. In this interpretation, Cueball, having failed to break the mutual knowledge barrier , admits defeat and joins Hairy in pretending to enjoy beer.
The second case would mean that Cueball mistaken in assuming that nobody likes beer, either because he fails to empathize with those who have a different experience than his, or because he's heard from other people who also admitted not to like beer, and extrapolated that opinion to everyone (perhaps assuming that such admissions are underrepresented due to the cultural bias in favor of drinking ).
The title text expands on Cueball's perspective, stating ( sarcastically ) that he feels no peer pressure to like beer. The pressure to drink beer or other alcoholic drinks is a well-known phenomenon, especially among adolescents and young adults .
[Cueball and Hairy standing in front of a fridge.] Hairy: What do you drink? Stouts? Lagers? Cueball: Uh, anything's fine.
[Cueball and Hairy holding beers and Hairy is drinking.] Cueball: ...do you ever think maybe we should just admit that all beer tastes kind of bad and everyone's just pretending?
[Now Cueball drinks.] Hairy: Man, you are no fun at all. Cueball: Ok, got it. Not a word. Hairy: Dude, if you don't like it, don't drink it. Cueball: No, no, gotta do my part! Mmmmm!!!


Words for Pets

Explanation:
The comic shows four similar Euler diagrams , one for each of the first four years of living with a pet . The diagrams depict sets of words which have varying efficacy in actually identifying the pet, and each one shows how the words used by Randall to refer to his pet change year by year and becoming less and less specific as time goes on.
In the first year it is dominated by the actual name of the pet or words closely related. For example, a dog named Lassie might be called either " Lassie ", "dog", "collie" or "boy/girl".
Moving on to the second year, these related words like "dog" and "collie" get more abundant while the actual name is seldom used. Phrases such as "good dog" or "here, boy" are likely common. Giving a dog the name "Dog" is so common that there is a trope about that.
In the third year, the pet's name is no longer used at all and the owner probably uses simple phrases like "come" or "come here" to call the pet, omitting the name. This is also probably referring to expletives.
The fourth year entails the use of just any sound, not coherent words . This may be referring to something like baby talk , attempted mimicry of the pet's vocalizations, or whatever random sounds the owner has discovered that get a response from the pet.
This development can be attributed to the fact that some animals don't listen to their own name but rather react to the sound of the voice of their owner. It could also refer to the growing bond between owner and the pet, as well as the effect described in 231: Cat Proximity .
The title text suggests that the inevitable result of this continuing pattern is that by the seventh year, Randall will be communicating with the pet in its own language. This might refer to the tendency of some pet owners to mimic or imitate their pets' vocalizations, as if speaking to them. Alternatively, this could be interpreted as a joke that pets don't have proper language and the owner has degenerated to a lack of language themselves as time goes on.
The title text and the caption makes it a little difficult to be certain if the comic refers to when you talk about your pet to other people ("my dog is always hungry") or when you call at it, which would be the only time it would make sense to use coherent words in the animal's own language - "Woof" = come here.
[Caption above the frame:] Words I use to refer to a pet over the years I live with it:
[Inside the box are four diagrams. Each diagram contains three elliptical sections containing the previous one, each section is drawn identical from diagram to diagram and they are labeled the same way from diagram to diagram. A fourth section (a red ellipse) moves from diagram to diagram and its label changes from diagram to diagram.]
[The red section of the first diagram mainly overlaps the innermost section, but about a third of it is in the second section. The labels are written above the three white sections and then inside the red section. The labels from inside and out and last the label of the red section:] The pet's name Words related to the pet Coherent words of any kind First year
[The red section of the second diagram mainly overlaps the right part of the second section, but it just touches both the first and the third section. The labels are written above the three white sections and then inside the red section. The labels from inside and out and last the label of the red section:] The pet's name Words related to the pet Coherent words of any kind Second year
[The red section of the third diagram mainly overlaps the right part of the third section, but about a third of it is inside the second section and a small part is outside of the third section. The labels are written above the three white sections and then inside the red section. The labels from inside and out and last the label of the red section:] The pet's name Words related to the pet Coherent words of any kind Third year
[The red section of the fourth diagram is completely outside the third section and has to be so far to the right, that the other sections has been moved from the center of the frame to the left. The labels are written above the three white sections and then inside the red section. The labels from inside and out and last the label of the red section:] The pet's name Words related to the pet Coherent words of any kind Fourth year onward


The Martian

Explanation:
Cueball is very excited about seeing that the trailer for The Martian is finally released, because he really liked the book. Cueball most likely represents Randall himself in this comic.
This trailer for The Martian was released on Monday, June 8, 2015, two days before this comic, although a teaser "viral" trailer had been released the previous day. The film, starring Matt Damon ( The Bourne Identity ), is directed by Ridley Scott ( Alien ). It was released in the United States on October 2, 2015.
The Martian is based on a book of the same name by Andy Weir . The book is very popular among nerds. The plot is a cross between the film Apollo 13 and the plot of the novel Robinson Crusoe — but just on Mars .
Cueball is telling White Hat about this trailer and the book, thus White Hat asks if he should read it. Cueball then describes a scene from Apollo 13: You know the scene in Apollo 13 where the guy says "we have to figure out how to connect this thing to this thing using this table full of parts or the astronauts will all die?" And he then tells White Hat that The Martian is like that the whole way through. What is actually said in the mentioned scene is: We gotta find a way to make this fit into the hole for this using nothing but that. The first part being a large square box and the other a smaller cylinder.
The film Apollo 13 is based on the true historical event of the Apollo 13 incident where the astronauts find themselves in a damaged spacecraft. They evacuated from the Apollo Command Module , losing all its life support systems, to the Lunar Module which was designed only for two people for two days instead of three people for four days. One issue the crew faced was a buildup of carbon dioxide. In order to resolve the issue, the crew needed to find a way to attach a square-shaped air-cleaning cartridge from the command module to the circular receptacle of the lunar module: literally fitting a square peg into a round hole. In one brief scene , the Mission Control staff gather together a box of items equivalent to what the crew would also have on-board and sit down with the mandate to figure out how the astronauts can connect the two with the items available to them. In that case, the ground crew took on the task of trial and error given the availability of backup supplies in case they damaged or destroyed some of the supplies. Once a working solution was devised, specific instructions were relayed to the astronauts. Cueball suggests that The Martian essentially consists primarily of the type of problem-solving shown in that scene (as was suggested by the author, Andy Weir, in this interview). The Apollo 13 scene is actually referenced in the book, when the Matt Damon character says "CO2 isn't a problem. (...) All systems use standard filters (Apollo 13 taught us important lessons)."
In the final panel, White Hat, who probably would not be so interested in this kind of story, wonders how a novel based on that kind of seemingly cerebral and procedural problem-solving became a big-budget film starring Damon. Big-budget films are generally films with a great deal of special effects and often also action sequences likely to draw big audiences — and to gain big returns. Matt Damon has become a high-profile big-budget star known for action films like the Bourne film series .
On the day the movie was released in the US, Randall went to see it and released this comic about it: 1585: Similarities .
In 2561: Moonfall a similar discussion of an upcoming movie is made for Moonfall . But in that case it is the scientific inaccuracy that is the subject, and the huge explosion that makes it worth seeing anyway... maybe?
Spoiler alert: The title text references a particular part of The Martian' s story: The astronaut stranded on Mars has previously established communications with Earth by repurposing the Pathfinder space probe that NASA landed on Mars in 1997. While working on another piece of equipment, he accidentally subjects the probe to an electrical short-circuit, destroying its electronics and "bricking" it. " Bricking " is a term in consumer electronics which essentially means to cause an electronic device to become non-functional and essentially no more useful than a "brick". The term is commonly used in respect of an unrecoverable failure of software and often a corruption of firmware . An unexpected "bricking" can be very surprising, and in a case where the item is critical, could be devastating.  This bricking scene from the book was left out of the movie.
[Cueball is sitting at a desk using a computer and White Hat walks in.] Cueball: Ooh, trailer for The Martian! White Hat: What's that? Cueball: Movie of a book I liked. White Hat: Should I read it?
[Cueball pivots on chair and turns away from computer to face White Hat.] Cueball: Depends. You know the scene in Apollo 13 where the guy says "we have to figure out how to connect this thing to this thing using this table full of parts or the astronauts will all die? White Hat: Yeah?
[Cueball pivots on chair again and resumes using computer while talking. White Hat looks at his smart phone.] Cueball: The Martian is for people who wish the whole movie had just been more of that scene. White Hat: How on earth did that become a big-budget thing with Matt Damon? Cueball: No idea, but I'm so excited.
In a video interview by Adam Savage with Andy Weir the author of The Martian says that his goal was to make the whole book like the mentioned scene from Apollo 13 - exactly what the comic is saying. The video was posted on YouTube the day after the xkcd comic.
In the end, The Martian likely didn't disappoint the big-budget movie makers, grossing more than $630 million against a budget of $108 million.


Types

Explanation:
This comic is a series of programming jokes about a ridiculous new programming language, perhaps inspired by Mathematica and Wolfram Language — the latter was used by Randall many times before. Maybe it's also inspired by Gary Bernhardt's CodeMash 2012 lightning talk on JavaScript's unpredictable typing. In the talk, the highly technical audience was unable to correctly guess the results of adding various JavaScript types and roared with laughter when they were revealed. The programming language shown in this comic has types even more unpredictable than JavaScript.
Most regular programming languages distinguish types, e.g. integers, strings, lists… all of which have different behaviours. But for instance, the operation "+" is usually conventionally defined over more than one of these types. Applied to two integers, it returns their sum.  Applied to two strings (denoted by being enclosed in quotes) it concatenates them:
While these behaviours are standard, conventional, and intuitive, there is a huge amount of variation among programming languages when you apply an operation like "+" to different types. One logical approach is to always return an error in all cases of type mixing, but it is often practical to allow some case mixing, since it can hugely simplify expressions. Variation and lack of a clearly more intuitive behaviour leads some languages to have weird results when you mix types.
Weird results abound in the new XKCD programming language:
The title text contains three further examples relating to color. color.rgb("blue") returns the hexadecimal code for pure blue (as would be used in HTML, for example), which is how a real programming language might work. The lookup for "yellowish blue" returns "NaN" (Not a Number) again, which makes sense at one level because there is no such color as "yellowish blue" (yellow and blue are opposites on the RGB color triangle , making yellowish-blue an impossible colour , which can only be perceived with great difficulty through contrived figures). However a more typical result would have been a failure indicating that the color database does not include the name, in the same way that a typo such as "bluw" would. (Note that HTML does explicitly attempt to handle all "color names". For the record, "yellowish blue" is a dark blue with an imperceptible amount of red — #0E00B0 .) Similarly sorting the colors would normally produce some defined ordering, such as alphabetical, but in this language it generates the string "rainbow". It seems that Randall's new language understands color theory in an unusually deep way.
[Caption above the black part of the comic:] My new language is great, but it has a few quirks regarding type:
[The rest of the comic is written in a black rectangle. All text to the left of ">" is written in gray. Text to the right of the ">" on the lines with numbers are in white, and then gray text on the other lines. There seems to be a missing ">" after line no. 3.] [1]> 2+"2" => "4" [2]> "2"+[] => "[2]" [3] (2/0) = > NaN [4]> (2/0)+2 = > NaP [5]> "" + "" = > ' "+" ' [6]> [1,2,3]+2 = > False [7]> [1,2,3]+4 = > True [8]> 2/(2-(3/2+1/2)) = > NaN.000000000000013 [9]> Range("   ") = > (' " ',"! "," ","!",' " ') [10]> + 2 = > 12 [11]> 2+2 = > Done [14]> Range(1,5) = > (1,4,3,4,5) [13]> Floor(10.5) = > | = > | = > | = > |_ _ _10.5_ _ _


Lyrics

Explanation:
For some modern songs, the vocalist chooses to perform the track in a way that emphasizes emotion, accent or style over clear pronunciation of the lyrics. Some forms of music, for example the Jazz style Scat, use purely nonsensical lyrics while some styles of dance music use a single line of lyrics repeated throughout the track.
There are also certain types of people that may describe themselves as "lyric deaf", which is sort of the lyrical equivalent to being tone deaf , although it doesn't have an underlying medical understanding. Some people that describe themselves as tone deaf are even quite musically capable.
The comic is illustrating (in text form) how listening to such a song feels before you have learned what the actual lyrics are. The lyrics are represented in an indecipherable way, with a few mildly recognizable words. This represents the auditory experience of being able to hear and understand some words (perhaps incorrectly), but not all of them.
Another example of this experience can be seen in this British TV commercial from the 1980s, showing someone who has misheard Desmond Dekker song Israelites so for instance the line Poor me Israelites becomes Oh-oh my ears are alight . See more details in the trivia section.
This experience is similar to that shown by the character Havelock Vetinari the Patrician of Ankh-Morpork , in Terry Pratchett 's Discworld book Soul Music (see part of book here ). Rather than listening to music, he preferred to read the printed sheet music:
In fact the kind of music he really liked was the kind that never got played. It ruined music, in his opinion, to torment it by involving it on dried skins, bits of dead cat and lumps of metal hammered into wires and tubes. It ought to stay written down, on the page, in rows of little dots and crotchets, all neatly caught between lines. Only there was it pure. It was when people started doing things with it that the rot set in. Much better to sit quietly in a room and read the sheets, with nothing between yourself and the mind of the composer but a scribble of ink. Having it played by sweaty fat men and people with hair in their ears and spit dribbling out of the end of their oboe... well, the idea made him shudder.
For a related experience see Mondegreen .
The title text elaborates on the fact that Randall has the same experience when trying to understand song lyrics as when he sees text in his dreams. The last part of the title text is written in strange scripts to illustrate how he feels when seeing text in his dreams. Translated it says: it's hard to read and I can't focus.
Note that it looks like the song lyrics were written by drawing in a tool, like MS Paint, and then cutting out pieces and shifting them slightly.
The closest guess on the lyrics is this:
I can't even tell her Anything she wanna Had outstanding skill Beautiful Forgetting love.
(Note that the first line also might be I can't even help her .)
It is very likely that Randall completely made up these lyrics himself and if any song coincidentally share some part of them it only happens because Randall has chosen some very cliché lyrics, that would thus be likely to occur in some pop songs.
Nevertheless, here below are some possible song references, in which the exact line from above occurs:
Joe Budden 's song More of Me From the lyrics : World keeps spinning, learned sinners keep sinning And I can't even tell her some fights ain't fight worthy Cause my pops got 20 years clean, but her pops got 20 years dirty
Bill Anderson's song Baby's Blue Again From the lyrics : Oh Lord, and I can't even help her All I can do is just wait Until the clouds are all blown away
Johnny Cinco's song She Wanna From the lyrics : Buy here anything she wanna Fly in anything she wanna Try on anything she wanna
Chino Brown's song Love Again From the lyrics : I was at a point in my life Of just forgetting love Until the day you touched me
[Cueball sits in a chair holding something. A speaker on a counter behind him is transmitting music. Four lines of wavy undecipherable lyrics emanate from the speaker. The lyrics are surrounded by musical notes. Below is the best attempt to write this down in text, also using capitals when they are clearly there in the comic.] I CANT₣∇EN +ELҼ ⊤HER A|N⊃Г⊕N6 ƒHE W(AN NAp. HADβE Aūτ|ƒA!NNNG∩fҠILL... FOR♡ITiNn⊣GLOOOO!VEEE ?.-
[Caption below the frame:] Sometimes I wonder what it would be like to be able to understand song lyrics without looking them up.
Get up in the morning Get up in the morning slaving for bread, sir sleeping for for bread, sir So that every mouth Sold out to every monk can be fed and beef-head Poor oh-oh me Israelites me ears are alight
My wife an' my kids Why find my kids? them a pack up an' a leave me They buck up and a-leave me Darlin' she said, Darling Cheese head I was yours to be seen I was yards too greasy Poor oh-oh me Israelites me ears are alight
I think that's what he says But I need to hear it on a Maxell (There is a picture of a cassette tape below that last line of text.)


Planning

Explanation:
Big companies have always tried to get the greatest amount of information from their customers, because that translates into more money earned. However, ability to gather, store and process such information is limited by the technology available. With the recent development of computers, this ability has grown far more than anyone could have suspected just 20 years ago; to the point that companies like Google or Facebook get almost unimaginable amounts of data from their users; and this data is gathered and stored automatically and can be efficiently accessed.
This data is routinely used to, for example, tailor online ads to the browsing history of the user seeing the ad. They could potentially be used for more evil purposes, like selling the medical history of users to insurance companies. Many users don't feel that they're giving out so much information, and in fact that few of them have given Google or Facebook their medical history. However some leaks have proven quite the opposite. In the AOL leak referenced in 155: Search History , searches for "how does a male's cocaine use affect a fetus", "hysterectomy" or "8 alcohol drinks a day", surely would be interesting for a medical insurance company to know.
In the comic, Ponytail is puzzled because people are not worried about Google or Facebook using their information in evil ways; however Megan raises a quite fair point, namely that the huge amount of nuclear weapons in existence is much scarier, and that was worrying to the general public in the 1980s, however people have grown tired of that and now concerns have moved to internet privacy only because it's "new". What is perceived as dangerous or worrying follows trends and fashions not directly related to real danger (i.e. "happen on auto-pilot"). The point Megan is making is that maybe it's better to just accept that things work in this way and go with the flow. This is very similar to what happens in 1480: Super Bowl or 1534: Beer .
The title text hypothesizes a similar conversation being held ten years later (presumably in 2025, ten years after the comic was published), in which the two aspects of the above have been inexplicably mixed. A future equivalent to Ponytail asks why we all think it is OK to hand over the control of our nuclear weapons to Google and Facebook, which would certainly be a nonsensical (and deeply troubling) route to take. This could also be seen as another step toward the singularity , from which perspective handing over control of nuclear weapons could be desirable, catastrophic, implicit and/or unavoidable.
This comic was posted on the day after Vladimir Putin had announced that Russia would add 40 new intercontinental ballistic missiles to its nuclear stockpile within the year.
Within a year Randall has made several other comics about nuclear weapons, the first of these, 1520: Degree-Off , came just 1½ month before this one. Later  these two comics were released early in 2016: 1626: Judgment Day and 1655: Doomsday Clock . Nuclear weapons are also mentioned twice in Thing Explainer , specifically they are explained in the explanation for Machine for burning cities about thermonuclear bombs , but they are also mentioned in Boat that goes under the sea about a submarine that carries nukes. All three comics and both explanations in the book, does like this comic, comment on how crazy it is that we have created enough firepower to obliterate Earth several times (or at least scourge it for any human life) [ citation needed ] .
[Megan and Ponytail are walking] Ponytail: Why are people so comfortable handing Google and Facebook all this control over our lives? Megan: I dunno. Megan: Our species built thousands of nuclear weapons, scattered them around the planet, and then moved on to other things. Megan: Maybe it's best to accept that some of this big-picture planning is just happening on autopilot.


Hemingway

Explanation:
This comic is a reference to the six-word short story For sale: baby shoes, never worn , which has been commonly attributed to famous author Ernest Hemingway (the disputed authorship of the story is referenced several times in the comic).
The comic plays on the fact that the original story takes the form of a short advertisement that might have been seen in a newspaper, and makes up alternate versions that use various modern 'standards' that did not exist in Hemingway's time. In keeping with the original, each example remains six words long. The title text obeys this rule, too. Many of the drafts poke fun at the tragedy that the original story suggests. With the original ("For Sale: Baby shoes, never worn"), readers could infer that the baby who would have worn the shoes must have died. Randall tries to make the reader infer other, more absurd things instead.
The comic also alludes to Hemingway's practice of repeatedly re-working drafts of his novels before publication. For example, he is reported to have rewritten the final passage of A Farewell To Arms 39 times. Later editions of his works include these rough drafts, allowing the devoted reader to understand how the work developed.
The following are the various drafts offered in the comic.
The title text continues the reference to 325: A-Minus-Minus , but inverts the situation.  Rather than unexpectedly receiving a bobcat by package, this time the package contains a regular item instead of the expected bobcat. In keeping with the theme of the comic, the review is written in only six words.
Hemingway's Rough Drafts
[A list of rough draft stories.] For sale: This Gullible Baby's Shoes Baby Shoes For Sale By Owner Actually, there's no evidence Hemingway wrote Free Shoes, Provided You Overpower Baby For Sale: Weird Baby's Toe Shoes For Sale: Baby Shoes ✓ Prime eligible Though popularly attributed to Hemingway, the This Weird Trick Covers Baby Feet! For Sale: Baby Shoes, Just Hatched Sale: Seven-League Boots (Expedited Shipping) Complete this survey for free shoes! Shoes , by Ernest Hemingway [ citation needed ] This is my greatest short story. For sale: Baby shoes (-1) [cursed] <blink><marquee> Baby Shoes! </marquee></blink> For Sale: Baby-sized Saddle, Bobcat Hemingway Busted for Craigslist Shoe Scam


Voice

Explanation:
During a casual talk with Megan , Ponytail suddenly interrupts her normal speech stating that she is for some reason only capable of controlling her own voice once every six years. Apparently only for a very brief time since she immediately returns to the casual talk, continuing her previous sentence mid-word before being able to tell Megan how she could help her. Upon Megan's confused request, she denies knowledge of the occurrence, although in a somewhat suspicious way, using possibly fake laughter.
It could be this was just a prank by Ponytail, to tease Megan, but given her fake laughter reply to Megan's inquiry and the continuing comment in the title text it seems most likely that Ponytail is indeed possessed by some sort of entity that prevents her from expressing her own thoughts, except for a very short time every six years. Of course this may just be her way of continuing with the prank; see a previous case of such a prank below .
In case it is not a prank it would thus appear that Ponytail's usual "self" is indeed this possessing entity. Whether this entity is actually aware that the "real" Ponytail did speak, or if it actually does not know that it was interrupted (since it continued mid-word) is not clear from the last response to Megan.
The title text suggests that Ponytail is possessed by some sort of inhuman entity , most likely an alien or AI , unfamiliar with movies and eating. See below for related comics .
The comic, 1530: Keyboard Mash , also revolves around the same theme of a non-human entity trying to convince other humans that it is in fact a human. This is most clearly referenced in the title text of this comic. In Keyboard Mash, it is a spider that tries to chat like it was a human, making statements that are true if you are human, but which humans would never utter in a conversation like here - put some food in our normal mouths! However, the pretended 'human' being (the spider) is not seen by the other person in this comic. As opposed to this one where Megan speaks directly with Ponytail.
It has already been established recently, in 1528: Vodka , that Ponytail's voice can be hijacked by non-human entities. That time it was the vodka she was drinking that took over. It is possible that this is continuing or caused by the same openness to possession as shown here. It is also possible that she simply thinks possession jokes are funny and once again jokes with Megan.
Six years ago today, which according to this comic was the last time Ponytail had control of her own voice, this comic 600: Android Boyfriend was posted. Ponytail acquired an android boyfriend. It seems unlikely that this older comic has any relation with this particular episode - except that this comic mentions a six-year period and Ponytail is also in that comic.
Ponytail is mainly a filler character, showing up when two females are needed or when a large group of people are present.
It is important to note that Ponytail , like most xkcd stick figures , usually does not represent the same character in each comic. This Ponytail is likely unrelated to other instances of Ponytail.
[Megan and Ponytail are walking.] Megan: Are you doing anything later? Ponytail: I was th- I can only control my voice once every six years. Please, you have to -inking of going out, but no real plans. Megan: ...What was that? Ponytail: Haha, what?