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Integration by Parts

Integration by Parts

https://www.xkcd.com/1201

https://www.explainxkcd.com/wiki/index.php/1201:_Integration_by_Parts

A Guide to Integration by Parts: Given a problem of the form: ∫f(x)g(x)dx=? Choose variables u and v such that u=f(x) dv=g(x)dx Now the expression becomes: ∫udv=? Which definitely looks easier. Anyway, I gotta run. But good luck!

Integration by parts is an integration strategy that is used to evaluate difficult integrals by trying to find simpler integrals derived from the original. It is commonly a source of confusion or irritation for students when they first learn it, due to the fact that there is really no way to accurately predict the proper u/dv separation just by looking at an integral. Integration by parts requires patience, trial and error, and experience. Randall shows a somewhat complicated math problem and, in an attempt to "help", simplifies it into a more compact integral. This is the first part of performing integration by parts, which involves the guessing. Having gotten it into integration by parts format, he then leaves without describing the actual solution. The general integral ∫ (u dv) is equal to uv - ∫ (v du) , and this is the more tedious part of the math and where problems will arise if you picked the wrong u and dv at the beginning. The narrator makes a point of leaving here, so we can't ask for help or complain if the choice of u and dv was wrong. The title text points out that if the integral of x can be divided so that u = x and dv = dx and implying v = x, then it leads to the result (1/2)x². This implies the original integral was just ∫x dx, and not needing integration by parts in the first place. Mathematics teachers and extreme math geeks will also cringe at this answer, however, since an indefinite integral requires an integration constant. The correct answer is actually (1/2)x² + C, as Randall hints. The +C symbolizes that an indefinite integral can be shifted by any constant and still gets the same answer on the reverse derivative . Definite integrals specify a range that they're valid on and thus there is no need to add this constant. A Guide to Integration by Parts: Given a problem of the form: ∫f(x)g(x)dx=? Choose variables u and v such that u=f(x) dv=g(x)dx Now the expression becomes: ∫udv=? Which definitely looks easier. Anyway, I gotta run. But good luck!

Girls and Boys

Girls and Boys

https://www.xkcd.com/1202

https://www.explainxkcd.com/wiki/index.php/1202:_Girls_and_Boys

[Megan facing left is sitting on a stool at a table while studying. She is bent over her paper writing on it, while her laptop is standing open on top of two books lying in front of her. In front of her, just inside the panel to the left is the back and neck of another student sitting on a chair visible, with only the rear leg and back of the chair shown. Behind her just inside the panel to the right is the front end of another table, one leg visible, and here lies a pile of paper, as tall as the two books. Two frames above Megan narrates the poem:] Girls go to college To get more knowledge [Cueball facing right, is sitting on a chair at a table also studying. He is holding a piece of paper up in one hand head turned toward it. His other hand holds a page, with text shown as thin lines, in the open book lying in front of him. His laptop is standing open behind the book. In front of him, just inside the panel to the right is the back and arms of another student sitting on a chair visible, with only the rear leg and back of the chair shown. Behind him just inside the panel to the left is the front end of another table, one leg visible, and here lies a pile of four books. Two frames above Cueball narrates the poem:] Boys go to college To get more knowledge [Space launch control room with Megan and Cueball standing in the middle of the room working together. Megan sitting behind a table with a rectangular item on top, holds a model of the capsule that goes on the top of a space craft in her hand pointing to it with the other hand while Cueball standing to the right gestures at the model as well. To the left sits Ponytail in an office chair, she is wearing a head-set and sits in front of screen, just inside the panel, she seems to be controlling something, but no keyboard is visitable. Above her is another screen attached to the wall (off-panel). The the right there sits a Cueball-like guy on a chair, who is also working on some screen, which is mainly off-panel as is the front of his head. On the wall behind there hangs two pictures. The first shows the curve of a white planet against black space, two continents or clouds visible. There is an insert in the top left corner with a small drawing, and some text or number (unreadable) in the top right corner. The other picture seems to show a space craft with two large solar panels, white on the black black background of space. Has some similarities to the international space station. There are four white lines representing text labels pointing to different parts. One frame at the top narrates the poem:] Girls and boys [A large gray rocket with two lifter rockets, one on each side, launch into the black night, rising up with white fire out the end on top of a huge pile of gray exhaust smoke, that billows out filling the entire width at the ground level, where gray lines stars out on the black ground. A white rectangle right above the tip of the rocket narrates the poem (which first ends in the title text):] Go to Jupiter Going to Jupiter was most famously explored in the film 2001 and its sequel 2010 , where a space ship lands on the moon Europa . The film Outland is set on a mining operation on Jupiter's moon Io .

This comic is a play on the popular school-yard taunt , "Girls go to college, to get more knowledge; boys go to Jupiter, to get more stupider," also commonly heard as "Boys go to Mars, to get more candy bars; girls go to Jupiter, to get more stupider." The words "boys" and "girls" may be interchanged, depending on the gender of the person chanting. The schoolyard taunt embodies the competitiveness and separation commonly seen between young boys and girls, and ideas about the superiority of one's gender. It should be noted that, historically, most higher education was preferentially or exclusively reserved for men, but that changed rapidly over the course of the 20th century. By the late 1970s more women than men were enrolling in college, and that trend has only increased, to the point where women make up nearly 60% of undergraduate students in American colleges and universities. This is an issue of substantial concern, because it reflects national trends in men failing to achieve academically. This comic may be pointing out that this gendered competition, which is often inculcated from an early age, is counter-productive, because it focuses on one gender succeeding at the expense of the other. In truth, human achievement is maximized when both men and women are given opportunities to gain skills and succeed. The comic subverts the original rhyme by having both girls ( Megan ) and boys ( Cueball ) go to college to gain knowledge, and then using that knowledge to go to Jupiter as part of a space program , working in cooperation with other men (another Cueball-like guy) and women ( Ponytail ). Going "to Jupiter, to get more stupider" is ironic considering that human beings have not yet even gone to Mars, so to go to Jupiter would take a huge amount of knowledge, investment, and further development of current technology. Likewise, people in space programs going to Jupiter would have advanced degrees, a great deal of knowledge, and a motivation to seek out more knowledge. Space programs and going to Jupiter would require the cooperation of many different people, men and women included, rather than the divisive atmosphere of the schoolyard. The title text points out that by going to Jupiter you would get more knowledge , which is generally the purpose of any space program; that is, the purpose is to advance science, and it wouldn't actually be dumb at all. Therefore, the task of going to Jupiter is absolutely dependent on going to college, cooperation, and getting more knowledge; entirely the opposite of what the schoolyard taunt suggests. [Megan facing left is sitting on a stool at a table while studying. She is bent over her paper writing on it, while her laptop is standing open on top of two books lying in front of her. In front of her, just inside the panel to the left is the back and neck of another student sitting on a chair visible, with only the rear leg and back of the chair shown. Behind her just inside the panel to the right is the front end of another table, one leg visible, and here lies a pile of paper, as tall as the two books. Two frames above Megan narrates the poem:] Girls go to college To get more knowledge [Cueball facing right, is sitting on a chair at a table also studying. He is holding a piece of paper up in one hand head turned toward it. His other hand holds a page, with text shown as thin lines, in the open book lying in front of him. His laptop is standing open behind the book. In front of him, just inside the panel to the right is the back and arms of another student sitting on a chair visible, with only the rear leg and back of the chair shown. Behind him just inside the panel to the left is the front end of another table, one leg visible, and here lies a pile of four books. Two frames above Cueball narrates the poem:] Boys go to college To get more knowledge [Space launch control room with Megan and Cueball standing in the middle of the room working together. Megan sitting behind a table with a rectangular item on top, holds a model of the capsule that goes on the top of a space craft in her hand pointing to it with the other hand while Cueball standing to the right gestures at the model as well. To the left sits Ponytail in an office chair, she is wearing a head-set and sits in front of screen, just inside the panel, she seems to be controlling something, but no keyboard is visitable. Above her is another screen attached to the wall (off-panel). The the right there sits a Cueball-like guy on a chair, who is also working on some screen, which is mainly off-panel as is the front of his head. On the wall behind there hangs two pictures. The first shows the curve of a white planet against black space, two continents or clouds visible. There is an insert in the top left corner with a small drawing, and some text or number (unreadable) in the top right corner. The other picture seems to show a space craft with two large solar panels, white on the black black background of space. Has some similarities to the international space station. There are four white lines representing text labels pointing to different parts. One frame at the top narrates the poem:] Girls and boys [A large gray rocket with two lifter rockets, one on each side, launch into the black night, rising up with white fire out the end on top of a huge pile of gray exhaust smoke, that billows out filling the entire width at the ground level, where gray lines stars out on the black ground. A white rectangle right above the tip of the rocket narrates the poem (which first ends in the title text):] Go to Jupiter Going to Jupiter was most famously explored in the film 2001 and its sequel 2010 , where a space ship lands on the moon Europa . The film Outland is set on a mining operation on Jupiter's moon Io .

Time Machines

Time Machines

https://www.xkcd.com/1203

https://www.explainxkcd.com/wiki/index.php/1203:_Time_Machines

[Small caption above the first panel:] The problem with time machines: [Cueball has his hands on the lever of a time machine.] [Cueball flips the switch from OFF to ON.] Switch: Click Time machine: E E E E E E EEEE Time machine: EEEE E E E E E E Switch: Click [Cueball flips the switch from ON to OFF.] [Cueball looks at his palms.] Cueball: ??? This comic's title is very similar to 716: Time Machine .

Cueball activates a time machine to go back into the past. The time machine rewinds time, but in the process rewinds the event where the time machine itself was turned on, turning the time machine off in the process. He is now a few seconds in the past, prior to having activated the time machine, but he is baffled that he does not seem to have accomplished anything and turned off the time machine unintentionally. It would seem that the time machine is the world's most technologically-advanced " useless machine " (a device whose only purpose is to switch itself off when it is switched on). The title text mimics a countdown to an event. "T minus 10," for example, means 10 seconds until the event. When the event is the activation of a time machine traveling back in time, after 10 seconds it will once again be "T minus 10," and a second later it will be "T minus 11," counting up rather than down. This casts doubt on the value of the countdown because, from the perspective of the time traveler, the event has already taken place. Cueball is only able to travel back in time a few seconds because in this comic time is seen as continuous and linear from Cueball's point of view, so he can only travel back in time to the moment he activated the machine (the first series of "E"s is the machine warming up and the second series of "E"s is that in reverse) the logic behind this is that because time appears to be continuous, Cueball's input was required for the machine to work. Since it does not appear to be a traveling vessel, it is also possible that Cueball could trap himself in the past by traveling to a time before the machine was created, and it would remain in the present. [Small caption above the first panel:] The problem with time machines: [Cueball has his hands on the lever of a time machine.] [Cueball flips the switch from OFF to ON.] Switch: Click Time machine: E E E E E E EEEE Time machine: EEEE E E E E E E Switch: Click [Cueball flips the switch from ON to OFF.] [Cueball looks at his palms.] Cueball: ??? This comic's title is very similar to 716: Time Machine .

Detail

Detail

https://www.xkcd.com/1204

https://www.explainxkcd.com/wiki/index.php/1204:_Detail

My Neighborhood's Resolution in: [A two-axis graph with years from 2000 to 2100 plotted on the x-axis and resolution from 1 meter to the Planck length plotted on a logarithmic scale on the y-axis. Three points in a line close to (~2010, 1 meter) are plotted at the bottom left of the graph; they have a strong positive correlation. Two trendlines are drawn on the graph; one is labeled "Earth" and remains constant at the Planck length over time; the other is labeled "Google Earth" and connects the aforementioned three points, extending upward in a straight line and approaching the Planck length around 2100. Both trendlines break up into question marks before the point they would intersect.]

Google Earth is a mapping software service provided by Google that allows people to view the Earth from above. If zoomed in to maximum magnification, one can obtain clear views of individual streets and homes. An image's resolution is the smallest length detectable in that image. In terms of Google Earth, this refers to the real-life distance corresponding to one pixel in an aerial image. Randall points out that the level of detail in Google Earth's images has been increasing exponentially since its introduction, as aerial imaging technology improves and better ways of collecting the data are found. Each tick in the scale represents a resolution improvement by 1000 times. In quantum mechanics , the Planck length is (in layman's terms) the smallest measurable distance, defined as approximately 1.6×10 −35 meters, or around 10 20 times smaller than the diameter of a proton. As the graph indicates, this may be called the "resolution" of the universe. Randall extrapolates the exponential trend of Google Earth's increasing resolution, 'revealing' that by the year 2120 or so, Google Earth's resolution will approach and even possibly exceed the Planck length, an obviously fanciful and impossible idea. Current laboratory instruments cannot even get close to measuring the Planck length, barely able to reach the level of the atom. (Which, by the chart's prediction, will be surpassed by Google Earth at around 2040.) Other comics exploring unwarranted extrapolation include 605: Extrapolating , 1007: Sustainable and 1281: Minifigs . The title text refers to controversy that Google received at one point regarding their use of vehicle-mounted Street View cameras to take images of streets and houses, and how such photography could constitute an invasion of privacy. Google defended itself by stating that the cameras can see nothing more than a pedestrian walking by. Given the trendline in this comic however, Google would need to produce resolution in the nanometer range by 2031, which (using today's technology) would require the use of scanning electron microscopes . The same 'invasion of privacy' defense would obviously not work here, as 1) current scanning electron microscopes in labs can only be used with small specimens at very close range, and are completely unsuitable for observing something as large as a house or for observations from a passing car, and 2) most pedestrians are not equipped with scanning electron microscopes. [ citation needed ] My Neighborhood's Resolution in: [A two-axis graph with years from 2000 to 2100 plotted on the x-axis and resolution from 1 meter to the Planck length plotted on a logarithmic scale on the y-axis. Three points in a line close to (~2010, 1 meter) are plotted at the bottom left of the graph; they have a strong positive correlation. Two trendlines are drawn on the graph; one is labeled "Earth" and remains constant at the Planck length over time; the other is labeled "Google Earth" and connects the aforementioned three points, extending upward in a straight line and approaching the Planck length around 2100. Both trendlines break up into question marks before the point they would intersect.]

Is It Worth the Time?

Is It Worth the Time?

https://www.xkcd.com/1205

https://www.explainxkcd.com/wiki/index.php/1205:_Is_It_Worth_the_Time%3F

[Above the frame is written the following text:] How long can you work on making a routine task more efficient before you're spending more time than you save? (across five years) [The rest of the the comic is given in a tabular format. At the top of the table is how often you do the task, with six time increments underneath, and then at the side is written How much time do you shave off at the leftmost part of the page, with 9 lengths of time to the left. The empty fields in the calendar are shaded dark gray.] [The first row is for 1 second, where the table values are 1 day (for 50 per day), 2 hours (for 5 per day), 30 minutes (for daily), 4 minutes (for weekly), 1 minute (for monthly), and 5 seconds (for yearly).] [The second row is for 5 seconds, where the table values are 5 days (for 50 per day), 12 hours (for 5 per day), 2 hours (for daily), 21 minutes (for weekly), 5 minutes (for monthly), and 25 seconds (for yearly).] [The third row is for 30 seconds, where the table values are 4 weeks (for 50 per day), 3 days (for 5 per day), 12 hours (for daily), 2 hours (for weekly), 30 minutes (for monthly), and 2 minutes (for yearly).] [The fourth row is for 1 minute, where the table values are 8 weeks (for 50 per day), 6 days (for 5 per day), 1 day (for daily), 4 hours (for weekly), 1 hour (for monthly), and 5 minutes (for yearly).] [The fifth row is for 5 minutes, where the table values are 9 months (for 50 per day), 4 weeks (for 5 per day), 6 days (for daily), 21 hours (for weekly), 5 hours (for monthly), and 25 minutes (for yearly).] [The sixth row is for 30 minutes, where the table values are greyed out (for 50 per day), 6 months (for 5 per day), 5 weeks (for daily), 5 days (for weekly), 1 day (for monthly), and 2 hours (for yearly).] [The seventh row is for 1 hour, where the table values are greyed out (for 50 per day), 10 months (for 5 per day), 2 months (for daily), 10 days (for weekly), 2 days (for monthly), and 5 hours (for yearly).] [The eighth row is for 6 hours, where the table values are greyed out (for 50 per day, 5 per day and daily), 2 months (for weekly), 2 weeks (for monthly), and 1 day (for yearly).] [The ninth and final row is for 1 day, where the table values are greyed out (for 50 per day, 5 per day, daily and weekly), 8 weeks (for monthly), and 5 days (for yearly).]

The comic is a straightforward chart showing the amount of work (time) one can dedicate to making a task more efficient, in order not to spend more time optimizing the task than the total time saved. This may illustrate the fact that computer scientists often try to optimize tasks they are likely to perform again in the future - a common goal in their work - even though the work needed for that optimization can itself prove much longer than the time saved when doing the task again; this was previously referenced in 974: The General Problem . E.g. if you do some task every week once, and you are able to save 1 minute of time by doing some preparatory work (e.g. build or buy a tool), you can spend 4 hours doing this preparatory work, and you will, across five-years time, come even. Any less time spent doing the preparatory work, and you will profit from it. The calculation on which the chart is based, for this example: 5 years / 1 week = 260 occurrences of the task 260 occurrences × 1 saved minute = 260 saved minutes = 4.3 hours Therefore, 1 minute saved every week would, across five years, save over 4 hours of your time. Or, in algebraic form: Total time shaved off across 5 years = 5 × "How often you do the task every year" × "How much time you shave off" The grayed out areas represent times which are either impossible to save, or where, if you could save this much (say 6 hours on one day), it would almost be worth it no matter how long it takes. For instance it is impossible to shave 1 hour off a task if you perform it more than 24 times a day – the total time shaved off per day would amount to more than one day, and thus you could not have performed the task this many times in a day to begin with. On the other hand, 6 hours shaved off for one day is not impossible, but the net benefit would be so great, that it would very quickly earn itself back again almost no matter how long it takes. If the assumption is that a work day is 8 hours, then even if it took 2 years to do the improvement, you would already have earned it in after less than five years in total - both with the 2 years to make it and the time it takes to save 2 years (2.67 years in this case for at total of 4.67 years). The comic assumes that equal amounts of time have equal value, which is not necessarily true. For an extreme example, consider programming a telephone with speed dials to be used when there is a fire or to call an ambulance or the police. This may take longer than the time saved when the call is placed, but it is worthwhile to spend a large amount of free time to save any time during an emergency. Of course, all these conclusions presume you are the only one that benefits. If the savings can be easily adapted by others - for example, computer code for a program that automates a task for hundreds of people - then the amount of time that can be spent increases. Indeed, in some cases, when optimizing for others, spending far more time than they save can be worth it, if the people you're working for are paying you for the product and the time savings keep them happy and likely to keep paying you. And if what you're optimizing is a business process that's unlikely to go out of date with your employer's current tools or its current products, then you may have more than 5 years to amortize the improvement. The title text points out the time you spend studying this comic detracts from your overall efficiency, and concludes that maximizing efficiency would require optimal use of every second and finishes very philosophically by pointing out that every second you use counts towards your life total - also those you spend reading and/or editing a wiki about a web comic... The comic derives humor from the absurd conclusions of hyper-efficiency, which have been examined in What if? - Cost of Pennies , and also in 951: Working which is devoted to insufficient economy, where the money saved is compared to the time wasted while looking for a bargain. In 1319: Automation Randall investigates how bad it really goes when you decide to automate a program to save you time... See also the Time management category . [Above the frame is written the following text:] How long can you work on making a routine task more efficient before you're spending more time than you save? (across five years) [The rest of the the comic is given in a tabular format. At the top of the table is how often you do the task, with six time increments underneath, and then at the side is written How much time do you shave off at the leftmost part of the page, with 9 lengths of time to the left. The empty fields in the calendar are shaded dark gray.] [The first row is for 1 second, where the table values are 1 day (for 50 per day), 2 hours (for 5 per day), 30 minutes (for daily), 4 minutes (for weekly), 1 minute (for monthly), and 5 seconds (for yearly).] [The second row is for 5 seconds, where the table values are 5 days (for 50 per day), 12 hours (for 5 per day), 2 hours (for daily), 21 minutes (for weekly), 5 minutes (for monthly), and 25 seconds (for yearly).] [The third row is for 30 seconds, where the table values are 4 weeks (for 50 per day), 3 days (for 5 per day), 12 hours (for daily), 2 hours (for weekly), 30 minutes (for monthly), and 2 minutes (for yearly).] [The fourth row is for 1 minute, where the table values are 8 weeks (for 50 per day), 6 days (for 5 per day), 1 day (for daily), 4 hours (for weekly), 1 hour (for monthly), and 5 minutes (for yearly).] [The fifth row is for 5 minutes, where the table values are 9 months (for 50 per day), 4 weeks (for 5 per day), 6 days (for daily), 21 hours (for weekly), 5 hours (for monthly), and 25 minutes (for yearly).] [The sixth row is for 30 minutes, where the table values are greyed out (for 50 per day), 6 months (for 5 per day), 5 weeks (for daily), 5 days (for weekly), 1 day (for monthly), and 2 hours (for yearly).] [The seventh row is for 1 hour, where the table values are greyed out (for 50 per day), 10 months (for 5 per day), 2 months (for daily), 10 days (for weekly), 2 days (for monthly), and 5 hours (for yearly).] [The eighth row is for 6 hours, where the table values are greyed out (for 50 per day, 5 per day and daily), 2 months (for weekly), 2 weeks (for monthly), and 1 day (for yearly).] [The ninth and final row is for 1 day, where the table values are greyed out (for 50 per day, 5 per day, daily and weekly), 8 weeks (for monthly), and 5 days (for yearly).]

Einstein

Einstein

https://www.xkcd.com/1206

https://www.explainxkcd.com/wiki/index.php/1206:_Einstein

[Cueball and friend eating at a table.] Cueball: I'm currently conducting an experiment which may prove Einstein wrong! Friend: Ooh, exciting! 1947: [Einstein and Cueball walking.] Einstein: It's impossible to find a good sandwich in this town.

In this comic Randall is playing with the notion that since Einstein contributed so much to society, and many of his works have withstood testing, disproving Einstein must be a difficult task. This is proven false by taking a mundane declaration by Einstein and proving it false with a simple task. Nobel laureate and Time Person of the Century Albert Einstein is often considered one of the smartest and most influential people in world history. His theories have revolutionized our understanding of the universe and inspired generations of scientists. In this comic, Cueball indicates to a friend that he is working on an experiment that may disprove Einstein. The implication is that Cueball is conducting a serious scientific experiment which may disprove one of Einstein's scientific theories. The second frame, however, implies that the Einsteinian "theory" Cueball's experiment may disprove is an offhand (and subjective) remark by Einstein about the availability of good sandwiches; this is not to mention the possible changing in quality of said sandwiches over time. The experiment Cueball is "currently conducting" probably refers to the fact that he is currently eating a sandwich, and if that sandwich was indeed a good one, Einstein would be proved wrong. Part of the humor here is that Cueball's friend probably assumes that when Cueball says "currently," he means the experiment is part of Cueball's work, not what he is doing at that exact moment. In 947: Investing , Randall comments on how people put too much credence in a joke Einstein made in passing, and in 799: Stephen Hawking we see Stephen Hawking in a similar predicament, every word he says taken as a major declaration. The title text demonstrates the ability to "disprove" Einstein while not challenging his scientific work but rather one of his decisions in his capacity as a patent clerk at the Swiss Patent Office at the time he published his first major papers (previously alluded to in 1067: Pressures ). According to the Einstein FAQ on the Swiss Federal Institute of Intellectual Property's website, patent #39561 is one of several patents that "we can assume ... were personally examined by Einstein". A PDF of the patent, which was indeed a gravel sorter ( trommel ), can be found here in German. [Cueball and friend eating at a table.] Cueball: I'm currently conducting an experiment which may prove Einstein wrong! Friend: Ooh, exciting! 1947: [Einstein and Cueball walking.] Einstein: It's impossible to find a good sandwich in this town.

AirAware

AirAware

https://www.xkcd.com/1207

https://www.explainxkcd.com/wiki/index.php/1207:_AirAware

[Cueball and Black Hat looking at a remote-controlled flying object.] Cueball: What's that? Black Hat: It's a drone for my new business, AirAware . Black Hat (narrating): Our UAVs follow you and learn your schedule. If you miss a turn, forget an appointment, or give someone inaccurate information, they alert you. Megan (on phone): I'll be there in five. Booming voice from the sky: WRONG! Megan: Augh! Cueball: That sounds annoying. Who would pay for that? Black Hat: Huh? Nobody pays. I'm just making these and releasing them. Cueball: That's not a business. You're just yelling at strangers from the sky. Cueball: A business has to make money somehow. Booming voice from the sky: WRONG! Cueball: Augh!!

Upon being asked by Cueball , Black Hat reveals his new 'business', AirAware. He explains it uses a Quadrotor Unmanned Aerial Vehicle ( UAV ) that flies and records a person's daily schedule. If that person either deviates, forgets an appointment, or tells somebody incorrect information, the drone alerts the 'client' with an annoying "WRONG!". Cueball is skeptical of the 'business plan' and questions its potential. Black Hat expands, saying that his intention is not personal profit, and he is simply releasing them himself. Cueball starts to argue that it is not a business, since there is no monetary gain, before being abruptly interrupted by the AirAware drone, declaring that his previous sentence was incorrect. This implies that Black Hat's business is not for profit; it's just another one of his sadistic schemes to torture people, and Cueball is his latest victim. Although the Wikipedia page for business states that a business "may also be not-for-profit", this isn't really relevant, as 'making money' and 'making a profit' are different things. It would be better classified as a different type of organization, or even as a hobby . Google Now is software by Google, shipped with newer Android devices. It shows you important information when you need it, like traffic on your way to work or home and upcoming events from your calendar. It also reminds you when to leave in order to reach an appointment in time. In the title text, Black Hat has modified this to tell you when you're too late to get there, instead. It can also refer to a bug in Google Now , which is that Google Now incorrectly calculates the time you have to leave, and it always calculates that what it calculated will be 1 minute too late, so it shows "The transportation mode you selected will not let you arrive on time" almost always, unless you refresh. An alternate explanation for the pronouncement of "WRONG!" by the quadcopter in the last panel is that it is referring to the plethora of companies in the electronic era, and even today, that don't actually make much (or any) money, but are still considered successful businesses. [Cueball and Black Hat looking at a remote-controlled flying object.] Cueball: What's that? Black Hat: It's a drone for my new business, AirAware . Black Hat (narrating): Our UAVs follow you and learn your schedule. If you miss a turn, forget an appointment, or give someone inaccurate information, they alert you. Megan (on phone): I'll be there in five. Booming voice from the sky: WRONG! Megan: Augh! Cueball: That sounds annoying. Who would pay for that? Black Hat: Huh? Nobody pays. I'm just making these and releasing them. Cueball: That's not a business. You're just yelling at strangers from the sky. Cueball: A business has to make money somehow. Booming voice from the sky: WRONG! Cueball: Augh!!

Footnote Labyrinths

Footnote Labyrinths

https://www.xkcd.com/1208

https://www.explainxkcd.com/wiki/index.php/1208:_Footnote_Labyrinths

[Excerpt from what appears to be an academic paper with footnotes.] experiments to observe this and we found no 1 2 evidence for it in our data. 1 Ignore this 2 Increment by 2 before following 3 Not true 3 2 4 Ibid. 5 True 2 6 3 6 Actually a 1 2 2

This is a logic puzzle where the reader has to follow a confusing network of footnotes to determine whether the word "no" is to be ignored or not. In the following solutions, "right-associative" means that the footnotes are evaluated from right to left or top to bottom, and left-associative from left to right or bottom to top (e.g. (2 6 ) 3 is left-associative, and 2 (6 3 ) is right-associative). The term "ibid." is short for "ibidem", or "at the same place", meaning the reference was noted on the same page just before. Interpreting nested footnotes as footnotes on footnotes, left-associative no 1 2 = (no 1 ) 2 = "ignore this" (it is meaningless to increment a phrase by 2), so the correct statement is "we found evidence for it in our data". Interpreting nested footnotes as footnotes on footnotes, right-associative "no 1 2 " = "no 1 + 2 " = "no 3 ". We turn to the definition of 3 , which is "not true 3 2 " = "not true 3 + 2 " = "not true 5 ". Now 5 is "true 2 6 3 ". The 6 says that the 2 footnote is really 1 2 2 = 1 (4. ibid.) = 1 3 , but the 3 tells us that the 6 is "not true 5 ", getting us into an infinite loop, meaning there is no solution. The title text suggests interpreting footnotes as exponents (minus one, modulo 6, plus 1). Because applying the operations "minus one, modulo 6, plus 1" to an integer always results in an integer between one and six (inclusive), no sequence of integer exponents will ever end up referencing a footnote that does not exist. In mathematics, nested exponents are exclusively right-associative. "no 1 2 " = "no 1 ", so we ignore the "no" and the correct statement is "we found evidence for the data." Meanwhile, 3 becomes "not true 3 ", an infinite recursion , and since 2 6 3 mod 6 = 4, we just get "ibid" and the 5 refers back to the 3. Footnote 6 is equivalent to 1 4 = 1 = "ignore this". The comic 1184: Circumference Formula is also playing on the typographical similarity between footnotes and exponents, as well as adding even more ridiculous rules. [Excerpt from what appears to be an academic paper with footnotes.] experiments to observe this and we found no 1 2 evidence for it in our data. 1 Ignore this 2 Increment by 2 before following 3 Not true 3 2 4 Ibid. 5 True 2 6 3 6 Actually a 1 2 2

Encoding

Encoding

https://www.xkcd.com/1209

https://www.explainxkcd.com/wiki/index.php/1209:_Encoding

[Cueball and Megan are both holding walkie-talkies. Cueball is talking into his, Megan is holding hers down. Both are looking up in the sky.] Cueball: No, the combining diacritics go over the interrobang! Megan: Oh jeez, I think he's lost control. [Caption below the panel:] The skywriter we hired has terrible Unicode support.

Skywriting is using an airplane to write words in the sky with controlled releases of smoke. Unicode is a standard for digitally encoding text which supports a huge variety of characters and modifiers. Cueball and Megan hired a skywriter to write some text which they provided in Unicode, but now they are dissatisfied with the result and Cueball is using one of their walkie-talkies to tell the pilot about his mistake—with the result that the pilot seems to lose control (presumably control of the plane, not the text). An interrobang (‽) is a combination question mark and exclamation mark. A diacritic is any symbol added to a character (for instance ´, ˘, ˇ, ¨), usually an accent mark added to a letter. In Unicode, combining diacritics are represented as separate characters, but computer programs that render text graphically treat them as modifications to the previous character. The request to modify the interrobang is strange, given that diacritics are supposed to modify letters , not punctuation marks, and given that an interrobang is already conceptually a character combination. On the other hand, combining diacritics can technically be used on any character, so the intended result will be something like: ‽̃ͦ̀̏͆̐̋̿ͣͭ́ͯ͒ The skywriter's errors and the phrase "Unicode support" play off the common issue of software rendering Unicode symbols incorrectly . But here the error does not seem to make the text unintelligible: all the skywriter has apparently done is put a diacritic underneath (or perhaps next to) the interrobang instead of above it. If this is the only problem with the text (which is likely, given that an interrobang would probably be at the end), then the comment that the skywriter has "terrible Unicode support" makes Cueball and Megan seem fastidious and unforgiving. The comic points up computer users' tendency to use hyperbole when describing minor problems, exaggerating their relative seriousness. Here Cueball and Megan seem concerned more about their incorrectly rendered text than about the skywriter's safety. The title text is presumably Cueball's reply, in which he appears to have misunderstood Megan: he is baffled as to how the pilot could have "lost" the Unicode control characters , which are the first 32 character codes in Unicode, but Megan was actually referring to the pilot losing control of the plane . Comic 1647: Diacritics also references an absurd use of diacritics. [Cueball and Megan are both holding walkie-talkies. Cueball is talking into his, Megan is holding hers down. Both are looking up in the sky.] Cueball: No, the combining diacritics go over the interrobang! Megan: Oh jeez, I think he's lost control. [Caption below the panel:] The skywriter we hired has terrible Unicode support.

I'm So Random

I'm So Random

https://www.xkcd.com/1210

https://www.explainxkcd.com/wiki/index.php/1210:_I%27m_So_Random

[Black Hat is sitting in an office chair at a desk when Hairy runs up behind him with his arms raised up.] Hairy: Monkey tacos! Hairy: I'm so random. [A frame-less panel pans to Black Hat and his desk, showing there is a computer on his desk and that he is actually typing on a keyboard in front of him on a lowered shelf.] Black Hat: Yeah, me too. [Black Hat swivels his chair around (as shown with a gray curved line beneath the chair at his feet) to face Hairy. He then emits from his mouth a massive speech bubble filled with random numbers in gray. This torrent of random numbers knocks Hairy to the ground as he shields his face with one arm while the other grasps for the floor to cushion his fall (it is notable that speech bubbles are not normally used in xkcd.) The numbers themselves are written deliberately haphazardly and in varying sizes, which makes it difficult to read them in any consistent manner; however, for reasons explained above, there is actually some order, and using that order they would appear like this:] Black Hat: 100973253376520135863467354 876809590911739292749453754 204805648947429624805240372 063610402002291665084226895 319645093032320902560159533 476435080336069901902529093 [With Hairy gone, Black Hat has turned back and resumed working at his computer.]

A child Hairy walks up to Black Hat , utters a nonsense phrase ("monkey tacos"), and then proclaims that he is "so random". This is a fairly common modern phenomenon in which children (hopefully only children) make "random" statements, and somehow imagine themselves to be funny and interesting because of this. Black Hat, never one to hesitate over bringing someone down, replies that he is also random. He then proves this by pouring forth a torrential stream of truly random numbers that overcomes poor Hairy. Black Hat then resumes his posture at the computer, as if nothing has happened. It is true that when brilliant and creative people speak passionately about a subject, they can make mental leaps and changes of context that might seem bewildering to an outsider. The conversation may even seem to be "random". However, simply vocalizing nonsense is not analogous, or even desirable; it is more likely a character trait of someone who is immature or has difficulty in following or adding to a normal human conversation. Black Hat's "random" numbers are actually quoted from the first lines of A Million Random Digits with 100,000 Normal Deviates making it both "officially random", but also essentially not. This book is also referenced in 1751: Movie Folder . See also: 221: Random Number . A side note is that "Monkey tacos" is a phrase that contains two trochees. A trochee is a metric foot with one stressed beat and one unstressed beat; it may be a reference to or an unconscious allusion to 856: Trochee Fixation . The title text deals with the connotations of the word "interesting" in different contexts. On one hand, children may be easily amused by behavior that lies outside of conventional social norms and defies expectations. Children may attempt to add whimsy to a situation they perceive as dull by interjecting words that have no significant meaning or relationship whatsoever to anything around them, merely to make things seem different and therefore "interesting" (at least to them.) There is some merit to this perspective: human social norms developed largely as a way to make social interaction more predictable and manageable and correspondingly less interesting, to free up our attention for other, more pressing matters. Someone who is indeed behaving "randomly" often does command interest and attention, if only because their unpredictability makes them potentially dangerous. However, to a child, social conventions may seem arbitrary and needlessly inhibitive, and they will often test the limits of such conventions by deliberately acting in violation of them and seeing what happens. "Random outbursts" of nonsense phrases are a fairly harmless way of doing this, and often do not incur sharply negative responses beyond annoyance (Hairy's experience being an exception), so children (including Randall in his youth) might do this very frequently until they mature out of it. However, "interesting" in information theory is quite a different matter. Information theory is " the mathematical treatment of the concepts, parameters and rules governing the transmission of messages through communication systems. " It is therefore very concerned with the meanings of the words and phrases people use to convey information, and it would regard something as "interesting" if it exhibited a notably consistent and predictable pattern that pointed towards greater significance. As such, "the opposite of interesting" would be expressions that hold no meaning, convey no information, and do not indicate any recognizable patterns or significance - such as the "random outbursts" that Randall once believed made him seem interesting as a child. He characterizes these interjections of random words as "lexical white noise," "lexical" meaning " relating to words or vocabulary of a language. " White noise is essentially random sound waves which, taken en masse, blend into audio static that takes on a macroscopically uniform sound experience despite their random nature. This can be used in some sleep or relaxation therapies, which foils well with the random assault experienced in the comic. There are also other colors of noise , and yes, people have strong opinions as to which one is better . [Black Hat is sitting in an office chair at a desk when Hairy runs up behind him with his arms raised up.] Hairy: Monkey tacos! Hairy: I'm so random. [A frame-less panel pans to Black Hat and his desk, showing there is a computer on his desk and that he is actually typing on a keyboard in front of him on a lowered shelf.] Black Hat: Yeah, me too. [Black Hat swivels his chair around (as shown with a gray curved line beneath the chair at his feet) to face Hairy. He then emits from his mouth a massive speech bubble filled with random numbers in gray. This torrent of random numbers knocks Hairy to the ground as he shields his face with one arm while the other grasps for the floor to cushion his fall (it is notable that speech bubbles are not normally used in xkcd.) The numbers themselves are written deliberately haphazardly and in varying sizes, which makes it difficult to read them in any consistent manner; however, for reasons explained above, there is actually some order, and using that order they would appear like this:] Black Hat: 100973253376520135863467354 876809590911739292749453754 204805648947429624805240372 063610402002291665084226895 319645093032320902560159533 476435080336069901902529093 [With Hairy gone, Black Hat has turned back and resumed working at his computer.]

Birds and Dinosaurs

Birds and Dinosaurs

https://www.xkcd.com/1211

https://www.explainxkcd.com/wiki/index.php/1211:_Birds_and_Dinosaurs

By any reasonable definition, T. rex is more closely related to sparrows than to Stegosaurus . [Diagram showing that Stegosaurus came earlier than T. rex , along with it showing that T. rex came closer in time to sparrows. Evaluation criteria "separation by time", "phylogenetic distance" and "physical similarity" are highlighted in red.] Birds aren't descended from dinosaurs, they are dinosaurs. Which means that the fastest animal alive today is a small carnivorous dinosaur, Falco peregrinus . [A picture of two birds is shown.] It preys mainly on other dinosaurs, which it strikes and kills in midair with its claws. [In red:] This is a good world.

Birds are commonly considered to be a separate class of tetrapods . However, this classification is false according to phylogenetic taxonomy . Taking into account that birds developed around 150 million years ago out of small theropod dinosaurs, birds along with crocodiles are indeed the remaining representatives of the archosaur clade . This premise appeared also in comic 867: Herpetology . This relation between birds and dinosaurs is depicted in the comic in a cladogram which shows that Tyrannosaurus rex is more closely related to the common sparrow than to Stegosaurus . Not only do the former share a phylogenetic branch, but T. rex also lived around 80 million years after Stegosaurus . The concurrence of both species in popular culture is a widespread error. T. rex is also much more alike to modern birds than to other dinosaurs in terms of anatomy. This relationship was pointed out on the Science journal the week of the comic. The comic draws the conclusion that if birds must in fact be considered modern dinosaurs, the hunting practice of birds of prey (specifically, the Peregrine Falcon ) is consequently a dinosaur fight. For an inveterate dinosaur aficionado like Randall , this fact must make the modern world much more attractive. The line "This is a good world." could also possibly refer to a famous scene from the pilot episode of the television series Firefly featuring two plastic dinosaurs in a somewhat philosophic dialogue. Randall is known to be a fan of the series . The title text is a sidesweep to the webcomic Dinosaur Comics drawn by Ryan North , who stands 6'6.5" (199 cm) tall. At that page the title text of the comic strip from the same day refers to Randall and xkcd . The conclusion of this comic is referenced in the title text of the last image in the Plastic Dinosaurs What if? By any reasonable definition, T. rex is more closely related to sparrows than to Stegosaurus . [Diagram showing that Stegosaurus came earlier than T. rex , along with it showing that T. rex came closer in time to sparrows. Evaluation criteria "separation by time", "phylogenetic distance" and "physical similarity" are highlighted in red.] Birds aren't descended from dinosaurs, they are dinosaurs. Which means that the fastest animal alive today is a small carnivorous dinosaur, Falco peregrinus . [A picture of two birds is shown.] It preys mainly on other dinosaurs, which it strikes and kills in midair with its claws. [In red:] This is a good world.

Interstellar Memes

Interstellar Memes

https://www.xkcd.com/1212

https://www.explainxkcd.com/wiki/index.php/1212:_Interstellar_Memes

[On a black background yellow circles and white bubbles are shown. Caption above the picture:] If other star systems are listening in on our pop culture, given the speed-of-light delay, these are the jokes and catchphrases they just learned about and are currently repeating way too much: [On a black background a map of star systems in relation to the Sun, which is roughly in the center, sending out radio waves is shown. Each star is a yellow circle of differing sizes, with a speech bubble (or more). The list is ordered from closest to furthest.] Proxima Centauri: I'm on a boat! Alpha Centauri A B: The cake is a lie! – ♪ Never gonna give you up ♫ Luhman 16: I can haz? Barnard's star: Leave Britney alone! – ♫ Chocolate Raaaiiin ♫ Wolf 359: Chuck Norris doesn't sleep. He waits. Lalande 21185: ♬ Numa numa ♪ Sirius: I still can't believe Bellatrix– – Dude, get over it. Gliese 65: INTERNETS! Epsilon Eridani: Ninjas fight all the time! Procyon: ...God kills a kitten! – A what? Epsilon Indi: You're the man now, dog! Tau Ceti: All your base are belong to us. Luyten's Star: Peanut Butter Jelly Time! Kapteyn's star: My spoon is too big! Kruger 60: MORE COWBELL! Gliese 1: Look at the tiny dancing Earth mammals! Van Maanen's star: WASSSUUP!?! Ad Leonis: Oh my God, they killed Kenny! – You bastards! 70 Ophiuchi: Welcome to Good Burger, home of the Good Burger. – What's a burger? – I don't know. Altair: Mr. T ate my balls! Sigma Draconis: Oh ... my ... gaawd. Delta Pavonis: I want the truth. – You can't handle the truth! Gliese 892: Hasta la vista, baby. Xi Boötis: Did I do that? HR 753: D'oh! Beta Hydri: Yippie-ki-yay, motherfucker. Vega: Resistance is futile. Zeta Tucanae: Let's get ready to ruuumble! HR 1614: Where's the beef? Groombridge 1830: I pity the fool! Delta Trianguli: May the Force be with you. Beta Virginis: Nobody expects the Spanish Inquisition! Arcturus: You talkin' to me ? Beta Trianguli Australis: I'm going to make him an offer he can't refuse. Lamda Aurigae: You've got to ask yourself one question: 'Do I feel lucky?' Capella: And now for something completely different. HD 211415: Live long and prosper. – Ok. Alderamin: EXTERMINATE! 51 Pegasi: Name's bond. James Bond. Caph: Take me to your leader! – No, Steve. Kappa Reticuli: Here's lookin' at you, kid. Alpha Hydri: Rosebud. Gienah: Ehh, what's up doc? Alpha Serpentis: Frankly, my dear, I don't give a damn.

Randall highlights various memes from popular culture. A meme is a phenomenon, often in this scenario in the form of a movie quote, a musical reference, a catchphrase or other notable saying that spreads quickly by word-of-mouth. Memes become popular because people hear about them and repeat them to others. Randall points out that if the assumed intelligent life from other star systems were listening to the things we said, then they would just now be hearing and popularizing memes started years ago on earth. The delay is due to the time that it takes for expressions of the meme to travel (presumably via radio waves) to distant star systems. Our solar system, from where the electromagnetic waves are emitted, is located just left of the center of the picture. The other star systems are arranged roughly according to their distance from the sun, while their size corresponds to the size of the star compared with that of the sun. The meme for Sirius is a pun; it refers to Harry Potter and the Order of the Phoenix, in which Bellatrix Lestrange kills Sirius Black. Radio waves travel at the speed of light . The title text jokes that these memes are so annoying that it would give us further incentive to develop the technology to travel faster than light , just simply to be able to outrun the radio waves, reach a distant star system, and apologize in advance to the "residents" about the memes, before the memes arrive. The table below lists all the memes described, and the star at which the comics states those memes should be heard by the time when the comic was released in 2013. The year of the meme plus the number of light years to the star should end up close to 2013. Most end up within the range 2011-2013 which may indicate the meme became popular one or two years later (on Earth or at the distant star system.) Two memes reach the targets in 2014. Some of those errors may be caused by the inaccuracy of the distances. The The Spanish Inquisition from Monty Python would have reached its destination in 2006. Because they're still watching Monty Python's Flying Circus in 2013 it must be very popular or maybe it took seven years to decipher that British humour . [On a black background yellow circles and white bubbles are shown. Caption above the picture:] If other star systems are listening in on our pop culture, given the speed-of-light delay, these are the jokes and catchphrases they just learned about and are currently repeating way too much: [On a black background a map of star systems in relation to the Sun, which is roughly in the center, sending out radio waves is shown. Each star is a yellow circle of differing sizes, with a speech bubble (or more). The list is ordered from closest to furthest.] Proxima Centauri: I'm on a boat! Alpha Centauri A B: The cake is a lie! – ♪ Never gonna give you up ♫ Luhman 16: I can haz? Barnard's star: Leave Britney alone! – ♫ Chocolate Raaaiiin ♫ Wolf 359: Chuck Norris doesn't sleep. He waits. Lalande 21185: ♬ Numa numa ♪ Sirius: I still can't believe Bellatrix– – Dude, get over it. Gliese 65: INTERNETS! Epsilon Eridani: Ninjas fight all the time! Procyon: ...God kills a kitten! – A what? Epsilon Indi: You're the man now, dog! Tau Ceti: All your base are belong to us. Luyten's Star: Peanut Butter Jelly Time! Kapteyn's star: My spoon is too big! Kruger 60: MORE COWBELL! Gliese 1: Look at the tiny dancing Earth mammals! Van Maanen's star: WASSSUUP!?! Ad Leonis: Oh my God, they killed Kenny! – You bastards! 70 Ophiuchi: Welcome to Good Burger, home of the Good Burger. – What's a burger? – I don't know. Altair: Mr. T ate my balls! Sigma Draconis: Oh ... my ... gaawd. Delta Pavonis: I want the truth. – You can't handle the truth! Gliese 892: Hasta la vista, baby. Xi Boötis: Did I do that? HR 753: D'oh! Beta Hydri: Yippie-ki-yay, motherfucker. Vega: Resistance is futile. Zeta Tucanae: Let's get ready to ruuumble! HR 1614: Where's the beef? Groombridge 1830: I pity the fool! Delta Trianguli: May the Force be with you. Beta Virginis: Nobody expects the Spanish Inquisition! Arcturus: You talkin' to me ? Beta Trianguli Australis: I'm going to make him an offer he can't refuse. Lamda Aurigae: You've got to ask yourself one question: 'Do I feel lucky?' Capella: And now for something completely different. HD 211415: Live long and prosper. – Ok. Alderamin: EXTERMINATE! 51 Pegasi: Name's bond. James Bond. Caph: Take me to your leader! – No, Steve. Kappa Reticuli: Here's lookin' at you, kid. Alpha Hydri: Rosebud. Gienah: Ehh, what's up doc? Alpha Serpentis: Frankly, my dear, I don't give a damn.

Combination Vision Test

Combination Vision Test

https://www.xkcd.com/1213

https://www.explainxkcd.com/wiki/index.php/1213:_Combination_Vision_Test

[Caption above the drawing:] Combination Vision Test [Below the caption is a circle formed by several hundred numeric digits from 0-9.] [Caption below the panel:] If you can see one big number but not the other, you have synesthesia and colorblindness.

Synesthesia is a condition in which perception in one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. Common examples are experiencing colors when seeing numbers or words ( Grapheme-color synesthesia ), hearing tones or music while reading words or text, seeing sequences of numbers or month names in a distinct and fixed shape ( Number form ), etc. In 1608: Hoverboard Megan stands at the end of the Star Destroyer and wishes she had synesthesia so bad she can taste it... Color-blindness is one of a number of conditions in which a person cannot distinguish certain pairs of colors that other people without color-blindness might find easy to distinguish. There are many different forms of color-blindness; the most common is an inability to separate the colors red and green. There are two numbers embedded in the big circle of numbers, in a similar way to a common color perception test . But this test can not work for colors because it is just a black-and-white picture. Nobody can see it. However, the joke lies in the fact that those with one common form of synesthesia see colors associated with numbers. Randall implies that a synesthete will see colors connected to each number, and thus a color perception test will work after all - thus distinguishing synesthetes with color-blindness from those with normal color perception. The comic playfully suggests that if you have synesthesia as well as colorblindness , then some of the colors might appear identical and so one number would not be visible, only leaving the other number. The title text brings in two more conditions: diplopia , or double vision, and myopia , or near-sightedness. Those who are near-sighted sometimes see distant objects more clearly while squinting. Then they would be able to see the one large number still visible from the synesthesia/colorblindness combination, but because of double vision they see a second copy of it, hence two numbers that are the same. If we color the numbers in the circle in a consistent way (and leave the 2, 3, 5, 7 and 9s black) we can reveal the large numbers: The numbers are four and two, forming the number 42 , which is the famous " Answer to the Ultimate Question of Life, the Universe, and Everything ", according to the book The Hitchhiker's Guide to the Galaxy . The number 4 is formed by digits 2, 3, 5 and 7 (the single digit primes) while the number 2 is formed by digits 3, 5, 7 and 9 (the single digit odds, excluding 1). For Randall's test to work (i.e. for either the large 4 or the large 2 in '42' to get lost in the noise to those with a given color-blindness), either the little number 2 or the little number 9 would have to be lost in the background noise. So, for example, if the background appeared in shades of red and the little number 2 was a shade of green, then the large number 4 would be less visible to those with red-green color-blindness than to others. While it makes for a good joke, there are three reasons this kind of test wouldn't work in real life. The first is that there is no one set of color-number associations seen by all synesthetes. So while some synesthete might see '2' as green and '0' as red (so a red-green color-blind person would lose anything made up of '2's against a background of '0's), others might see '2' as yellow and '0' as blue, or any other association imaginable. The second reason it wouldn't work is that synesthetes do not (always) automatically see a 1:1 overlay of color on top of a number - they still need to read the number legibly. Randall's circle is very chaotic, so one wouldn't intuitively identify each single number. For a synesthete the color is produced after the number is recognized by the brain and lost when the focus shifts to the next number. However, some synesthetes may find if they pay attention to the numbers one by one they can make something out. However, as noted by a user in the discussion, who states that he has a type of synesthesia, he did indeed see the numbers ! Furthermore, in his blog's discussion section, one person commented they could see the large '2' but not the large '4' ! This was not because the person was colorblind, but because the '4' was mostly composed of numbers ('2's and '7's) whose colors blended in with the background, while the '2' contained an even mix of numbers, some of which (presumably '3's, '5's, and '9's) starkly stood out, making the large '2' easily visible. However, one could easily imagine this scenario pertaining to colorblindness: for example, a colorblind synesthete, in theory (although the third reason makes it clear why this would be extremely unlikely), might perceive most of the background numbers as shades of green (similar to the picture below) and see the '2's and '7's in shades of red, which would make it difficult to differentiate between the giant reddish '4' and the greenish background. The third reason the test would not work is that color-blindness is an inability to distinguish colors of light hitting the retina, it's nonsensical to imagine a synesthete would perceive two separate colors that they cannot normally separate anyway. But again in the above mentioned link this particular person did see the colors in a way where people with red/green color-blindness might have a harder time seeing the 4 than the 2 in 42. The next image shows all of the numbers, including 2, 3, 5, 7 and 9, colored in, in such a way as to ensure the number 42 is clearly visible to those with no particular blue-yellow color-blindness: The "real problem" is actually that if a synesthete does indeed see the digits as colors that resolve into either one or two numbers, then what color would these new "color-numbers" then appear to be? If a synesthete could see both large numbers AND they appeared as the same color as the small numbers as soon the synesthete perceived the numbers, then what would this meta-synesthete see? The '4' would blend in with the background '4's, while the '2' would stand out (as '2' was not used in the background). Would that mean that as soon as they noticed the giant '4', it would suddenly disappear into the background? Is this sort of layered synesthesia even possible? Keep in mind, as noted above, that synesthetes do not all see the same color-number associations. They also do not necessarily see every number in a different color, as depicted here, and may even see some numbers as purely black. [Caption above the drawing:] Combination Vision Test [Below the caption is a circle formed by several hundred numeric digits from 0-9.] [Caption below the panel:] If you can see one big number but not the other, you have synesthesia and colorblindness.

Geoguessr

Geoguessr

https://www.xkcd.com/1214

https://www.explainxkcd.com/wiki/index.php/1214:_Geoguessr

[Cueball is using a laptop, playing a game.] Cueball: This one's easy; There's the Parthenon. Athens. * CLICK * Cueball: What!? Why the hell is there a Parthenon in Nashville ? * CLICK * Cueball: OK, I'm clearly in Germany. * CLICK * Cueball: Dammit, Germany Pavilion at Epcot. [Caption below the panel:] My scores in Geoguessr would be higher if people quit building replicas of everything.

Geoguessr is a game in which the player is given a location in Google Street View and asked to guess precisely where in the world they are, by clicking on a map of the world, based only on the 360-degree view in the Street View display. Cueball is upset because he keeps making his guesses based on landmarks and his guesses end up being wrong. After all, the landmark he based his guess off of was a replica of the real one (the Parthenon in Nashville , which is more than 9000 kilometers or 5600 miles away from the Greek original ). Of course, from a statistical perspective, this makes sense. For every famous object, there are countless replicas; however, most people will be familiar with the specific location of the original object, and the vast majority of famous objects (except a few notable works of art) exist in only one place in the world. Take the Statue of Liberty , for instance — although the original is based in New York (well, actually, the original maquette is in Paris ...), it has hundreds of replicas all over the planet . Epcot is a Disney theme park in Florida which among other attractions includes pavilions of various countries, including Germany , which are built to resemble the typical style (architecture, vegetation, etc.) of the countries. Therefore, similarly to the replicas of landmarks, in this specific case, recognizing classic German architecture would put you on the wrong continent. However, as the title text alludes to, you're far more likely to find a dirt road than to find anything recognizable, since Google Street View maps roads more than anything else (hence its name). Becoming a connoisseur of such a mundane thing bears similarity to 915: Connoisseur . Anyone who's ever played with Geoguessr knows, also, that seemingly helpful clues can sometimes be useless. For instance, if you recognize the Cyrillic script on a sign, the countries using the Cyrillic script such as Bulgaria, Mongolia, Belarus, Ukraine, and Russia encompasses an enormous area, so unless you can recognize a specific region, there's no obvious place to guess where you can hope to get high points. Unlike somewhere like England, where guessing London is guaranteed to put you within a reasonable distance from a global perspective. Legoland is a good example of this: If you can't tell if you're in Denmark or California (or any of the other locations ), it's not like you can just guess halfway between and do well. [Cueball is using a laptop, playing a game.] Cueball: This one's easy; There's the Parthenon. Athens. * CLICK * Cueball: What!? Why the hell is there a Parthenon in Nashville ? * CLICK * Cueball: OK, I'm clearly in Germany. * CLICK * Cueball: Dammit, Germany Pavilion at Epcot. [Caption below the panel:] My scores in Geoguessr would be higher if people quit building replicas of everything.

Insight

Insight

https://www.xkcd.com/1215

https://www.explainxkcd.com/wiki/index.php/1215:_Insight

[White Hat is holding a finger up while talking to Cueball.] White Hat: Maybe before we rush to adopt < Google Glass > we should stop to consider the consequences of blithely giving this technology such a central position in our lives. [Caption below the panel:] Don't have any insights about a new technology? Just use this sentence! It makes you sound wise and you can say it about virtually anything.

White Hat is giving a profound insight into <Google Glass>. This insight, however, can be given, sounding just as profound, for any other new technology that comes around—hence the angled brackets around Google Glass , indicating that "Google Glass" is a placeholder. This, of course, means it is not profound at all, as it has no actual insight into Google Glass (or any other technology). The title text highlights a common trait of human listeners. The above sentence is constructed in such a way as to trigger the listener's reservations about the new technology. The sentence sounds profound, not because it has any actual insights, but because it causes the listener to fill in the missing insights with his own pre-existing thoughts on the matter. This is a typical effect of Confirmation bias . Not only does this cause Cueball to regard White Hat as insightful, but it also causes Cueball to think that White Hat agrees with whatever it is that Cueball fears <Google Glass> for. It seems no coincidence that Randall chose Google Glass as the placeholder. It seems generally that he is no fan of these, which was shown soon after in 1251: Anti-Glass and later again in 1304: Glass Trolling . This was the first time Google Glass was directly mentioned but since this comic Google Glass has become a recurring theme in xkcd. The caption is reminiscent of Randall's tips , but since the word tip is left out, it is not itself a tip comic. [White Hat is holding a finger up while talking to Cueball.] White Hat: Maybe before we rush to adopt < Google Glass > we should stop to consider the consequences of blithely giving this technology such a central position in our lives. [Caption below the panel:] Don't have any insights about a new technology? Just use this sentence! It makes you sound wise and you can say it about virtually anything.

Sticks and Stones

Sticks and Stones

https://www.xkcd.com/1216

https://www.explainxkcd.com/wiki/index.php/1216:_Sticks_and_Stones

[A child, who looks like a miniature Cueball, is running with arms outstretched toward Cueball.] Child: Did you hear what he said about me!? Cueball: Well, remember: sticks and stones may break my bones, but words— Child: —can make someone else feel happy or sad, which is literally the only thing that matters in this stupid world? [Brief pause.] Child: Right? Cueball: The world isn't that bad. Child: Explain the line about sticks and stones? Cueball: ...OK, maybe it's kind of horrific.

Sticks and Stones is a nursery rhyme, which goes as follows: The nursery rhyme often by parents and with some variation, to persuade an individual, usually a child, to ignore any name calling or mean taunts that were said by others in an attempt to hurt the individual's feelings. The comic challenges this sentiment when the child responds that, although words can't harm you physically, they can change how you feel, and isn't that the most important thing of all? Cueball obviously sees the simple truth in this, but tries to deflect by claiming that the world really isn't that bad. The child refers again to the rhyme, observing that the physical world can be harsh enough, because there are things like sticks and stones that break your bones and presumably people who use them as weapons to do so. Or yet worse, that someone would think up such a gruesome saying in the first place. Upon reflection, Cueball agrees that this image is actually horrific. The title text is rather dark, and is probably a reference to the currently active bullying and shaming culture. None of us deserves to be beaten or stoned, but words are powerful enough to make us think that we do. In the long tradition of the science of the obvious, recent studies (for example: Social rejection shares somatosensory representations with physical pain ) have shown that, in fact, the brain's reactions to physical pain and emotional rejection are somewhat similar and even feed into each other. [A child, who looks like a miniature Cueball, is running with arms outstretched toward Cueball.] Child: Did you hear what he said about me!? Cueball: Well, remember: sticks and stones may break my bones, but words— Child: —can make someone else feel happy or sad, which is literally the only thing that matters in this stupid world? [Brief pause.] Child: Right? Cueball: The world isn't that bad. Child: Explain the line about sticks and stones? Cueball: ...OK, maybe it's kind of horrific.

Cells

Cells

https://www.xkcd.com/1217

https://www.explainxkcd.com/wiki/index.php/1217:_Cells

[Caption above the panel:] When you see a claim that a common drug or vitamin "kills cancer cells in a petri dish," Keep in mind: [Cueball in a lab coat stands on a chair next to a desk, pointing a gun at a petri dish. There is a microscope on the desk.] [Caption below the panel:] So does a handgun.

Cancer is one of the most feared group of illnesses due to high mortality and a topic visited by Randall in past comics . Whenever a study finds a hint of a cure, it is hyped up in media as major breakthrough. However, because research is done in a laboratory using cultivated cancer cell assays in petri dishes or well plates, it typically does not take interactions with other parts of a body into consideration, which is ultimately necessary for a patient to survive treatment without harmful side-effects. In order for a cancer treatment to be viable, it would have to primarily target only cancer cells; not healthy ones. Added to this is the issue that major cancer in the body quickly evolves resistance to most treatments, most treatments end up either unused or used as just one in a cocktail of cancer fighting drugs. Here, Randall reminds us that there's no need to get excited upon hearing about a drug that kills cancer cells because it may very well harm healthy cells as well, just as a bullet fired from a handgun would. Alternatively, one could interpret the message that, since something as mundane as a handgun is capable of destroying cancer cells, it really is not too impressive for a drug to make that claim. The title text suggests that even if a drug did only kill cancer cells while leaving healthy cells alone, the human body still has many other complex processes that may render a drug that works in a petri dish insufficient. For instance, a drug that kills cancer cells in a petri dish may not be able to get at cancer cells deep within a human body. It is a long way from the laboratory to the pharmacy. A more humorous interpretation of the title text is that it will only kill cancer cells if they are in petri dishes, and not anywhere else. The naming convention here is similar to "lung cancer", breast cancer", etc., but of course, petri dishes are not normally a part of human organism [ citation needed ] . Less probably, it might be about cancer cells that originated from, but are not necessarily located within, petri dishes, making the scenario even more oddly specific. [Caption above the panel:] When you see a claim that a common drug or vitamin "kills cancer cells in a petri dish," Keep in mind: [Cueball in a lab coat stands on a chair next to a desk, pointing a gun at a petri dish. There is a microscope on the desk.] [Caption below the panel:] So does a handgun.

Doors of Durin

Doors of Durin

https://www.xkcd.com/1218

https://www.explainxkcd.com/wiki/index.php/1218:_Doors_of_Durin

[White Hat, Megan, and Cueball stand. Megan has her finger up.] Megan: I've got it! Megan: What's the elvish word for friend? Cueball: Mellon. [The trio stand. A off-panel door opens.] RUMBLE [White Hat has his palm out, while Cueball has his palm on his chin.] White Hat: So what's the elvish word for "frenemy"? Cueball: ...Mellogoth? SLAM!!

The comic is based on the Lord of the Rings , specifically a scene from The Lord of the Rings: The Fellowship of the Ring , where the eponymous fellowship is trapped outside the door to the Mines of Moria . There's a spoken password to open the doors, an Elvish inscription on them provides a clue: "Speak friend, and enter". The party leader ( Gandalf ) initially interprets this to mean that a friend could speak the password and enter. Only after many unsuccessful efforts does Gandalf realize it is actually a very simple riddle: The password is the Elvish word for "friend" ("mellon"), and the inscription should in fact be interpreted as "Speak [out loud the word] mellon [(the Elvish word for friend )], and [you will be able to] enter". See the Wikipedia article Use–mention distinction . In this comic, Cueball, White Hat, and Megan reenact the scene, with Cueball taking the role of Gandalf. The doors apparently open off-panel when the password is spoken. White Hat then wonders aloud what the Elvish word for "frenemy" is, and Cueball postulates "mellogoth". This is a portmanteau of "mellon" and "goth", much like how "frenemy" is a portmanteau of "friend" and "enemy". The Elvish word-root goth is best known as part of the name of Morgoth (literally, "Black Enemy") of the Silmarillion . The doors apparently immediately slam shut the moment Cueball says mellogoth . It is unclear whether this is because the opposite of the password has been spoken, or because the doors take offense to the word/concept frenemy , of which xkcd has previously made fun in 919: Tween Bromance . The title text ponders what would occur if the Sirannon, a stream running adjacent to the path leading to the doors, were to be completely blocked with the doors left open. The already partially blocked Sirannon had formed a pool before the doors; which contained some sort of monstrous horror from the depths of the Earth, referred to as the Watcher in the Water . Randall seems to think that the pond draining into the mines would connect the Watcher with another horror within: the Balrog (a high-level servant of Morgoth) living within the depths of the mines. Balrogs are primarily creatures of fire and shadow, so having a bunch of water dumped on it is unlikely to please it but may weaken it. He then goes on to wonder about the outcome of a battle between the two monsters. [White Hat, Megan, and Cueball stand. Megan has her finger up.] Megan: I've got it! Megan: What's the elvish word for friend? Cueball: Mellon. [The trio stand. A off-panel door opens.] RUMBLE [White Hat has his palm out, while Cueball has his palm on his chin.] White Hat: So what's the elvish word for "frenemy"? Cueball: ...Mellogoth? SLAM!!

Reports

Reports

https://www.xkcd.com/1219

https://www.explainxkcd.com/wiki/index.php/1219:_Reports

How to make boring technical reports more fun to read: Imagine they were written and sent in, unsolicited, by the estranged spouse of the head of the project. [Cueball is crouching alone over his computer in an empty room, typing on a laptop. He is surrounded by papers and books, apparently related to whatever project is working on. The laptop has a message on it, the text of which is displayed above the computer.] Computer: Six guard rails have erratic reflector placement, and one even lacks reflectors entirely, despite rule G31.02(b) clearly mandating consistent usage. Cueball: ...Sharon! Originally the title text proposed a speed limit of 2,500 miles per hour, which would mean the original message is about a ridiculously low speed limit of 2.5 mph. This was later corrected.

The quoted text of the report could (and indeed probably would , given the apparent contents) be stereotypically read out loud by the author, or internally by the reader, in an essentially monotonal manner, as exhibited by any number of popularised film and TV characters such as 'Arthur Pewtey' from the Monty Python sketch . But this comic asks us to imagine it instead voiced in the voice of an upset (soon-to-be-'ex-'?) spouse, presumably berating the project leader on various real or imagined infractions, and it works just as well. The jagged nature of the speech bubble indicates that the report has typed out on the computer's screen, but also helps to re-enforce the nagging internal voice. The title text joke relates to an alternative plan, namely to proportionally exaggerate everything you read. What would have been one serious accident that would have been prevented in the previous month had the speed limit been 25 mph, out of the three that actually occurred under the current limit, now becomes one thousand people saved! And all those lives would have been saved by reducing the speed limit to a 'mere' 25,000 miles per hour. Of course, around 2000 accidents would not have been prevented because people still try to mess with vehicles that are moving at hypersonic velocities. Note that the title text is inconsistent; if every number were to be multiplied by a thousand, then the speed limit would apply to 2000th Street. Somewhat surprisingly, there do exist streets of this name, mainly in Illinois. Although unlikely, the street may be 0.002th street, giving us 2 when multiplied per the title text. Though in this case 2nd St is a proper noun and thus should not be modified. How to make boring technical reports more fun to read: Imagine they were written and sent in, unsolicited, by the estranged spouse of the head of the project. [Cueball is crouching alone over his computer in an empty room, typing on a laptop. He is surrounded by papers and books, apparently related to whatever project is working on. The laptop has a message on it, the text of which is displayed above the computer.] Computer: Six guard rails have erratic reflector placement, and one even lacks reflectors entirely, despite rule G31.02(b) clearly mandating consistent usage. Cueball: ...Sharon! Originally the title text proposed a speed limit of 2,500 miles per hour, which would mean the original message is about a ridiculously low speed limit of 2.5 mph. This was later corrected.

Hipsters

Hipsters

https://www.xkcd.com/1220

https://www.explainxkcd.com/wiki/index.php/1220:_Hipsters

The layout is a chart with a series of plots reaching a stable equilibrium one after another, with the shape characteristic of a predator-prey model. In order, the labels are. How often I see... Hipsters --> Complaints about hipsters --> Complaints about the constant use and discussion of the word "hipster" --> Complaints that every level of meta-opinion on hipsters represents the same tedious navel-gazing by insecure people --> graphs making it all worse --> Now [The horizontal axis is labeled time. Where the final curve rises is marked 'now'.] This comic has been featured on Cheezburger.

The word "hipster" originally referred to counter-cultural youth and jazz aficionados in the 1940s and 1950s before the Hippie culture developed in the mid '60s. Recently, however, "hipster" has come to refer to, in Wikipedia's terms, "a subculture of young, urban middle class adults and older teenagers that appeared in the 1990s. The subculture is associated with independent music, a varied non-mainstream fashion sensibility, progressive or independent political views, alternative spirituality or atheism/agnosticism, and alternative lifestyles." Following the hipster resurgence, it became popular in many circles to hold hipsters in contempt, citing their conformity to a subculture by rejecting "mainstream" culture and deliberate (i.e. ironic) indulgence in obnoxious things like moustaches and bad movies. Randall continues the arguably hypocritical meta-complaining by showing more s-curves that represent subsequent, smaller backlashes, self-referentially including his own comic in that meta-complaining. There is a possible double meaning in the phrase "tedious navel-gazing by insecure people": the word "hipster" also refers to low-rise leg wear that sits at or below the hips, often in conjunction with revealing shirts, thereby exposing one's bellybutton. The title text reveals Randall 's awareness that he's only perpetuating the meta-complaining he's complaining about, but he bats away this criticism by pointing out the facts of the situation: the reader is not communicating with Randall but rather most likely in an empty room while browsing the Internet. That is, the criticising reader is experiencing a retreat into ironic detachment while still clearly participating in the thing in question, i. e. the graph. The title text may be a reference to a previous comic, 525: I Know You're Listening . The layout is a chart with a series of plots reaching a stable equilibrium one after another, with the shape characteristic of a predator-prey model. In order, the labels are. How often I see... Hipsters --> Complaints about hipsters --> Complaints about the constant use and discussion of the word "hipster" --> Complaints that every level of meta-opinion on hipsters represents the same tedious navel-gazing by insecure people --> graphs making it all worse --> Now [The horizontal axis is labeled time. Where the final curve rises is marked 'now'.] This comic has been featured on Cheezburger.

Nomenclature

Nomenclature

https://www.xkcd.com/1221

https://www.explainxkcd.com/wiki/index.php/1221:_Nomenclature

[Mrs. Whatsit, a woman drawn as Megan, holds her hand out and talks to Abbott (a tall guy with a baseball cap) and Costello (a short guy wearing a round brimmed hat and holding a baseball bat in his right hand.)] Mrs. Whatsit: You're both confused. Mrs. Whatsit: He's just "The Doctor". The names are from the original transcript .

Nomenclature can be defined as the devising or choosing of names for things. Here Randall connects three pop culture references that each contain one or more instances of ambiguous nomenclature based on pronouns: the " Who's on First? " skit, the " Doctor Who " television series, and in the title text also the novel " A Wrinkle in Time " by Madeleine L'Engle . The comic references the famous " Who's on First? " skit by the American comedy duo Abbott and Costello in the 1930s. This video is one of the original performances. Costello is the shorter character, with a round brimmed hat and baseball bat, while Abbott is taller and wearing a baseball cap. This reflects the most common image associated with the skit. In the routine, Costello is confused by the nicknames the ball players go by. The man playing first base goes by the name "Who", the man on second base goes by "What", and the one on third calls himself "I Don't Know". Costello asks "Who's on first?", inquiring the name of the first-baseman, and Abbott replies "that's right", affirming that the first-baseman's name is Who. Both parties become confused within a matter of seconds. The Doctor from the long-running British television series Doctor Who is often referred to as "Doctor Who" by people who think the series' name and their name are the same (although it should be noted that the name "Doctor Who" is not entirely incorrect; the character was referred to as such in the end credits for several seasons , as well as in the spin-off theatrical films starring Peter Cushing). In-universe, the character often introduces themself as "The Doctor", which elicits the response " Doctor who? ". Their response to this question is: "Just 'The Doctor'". Mrs. Whatsit appears to have interrupted the "Who's on First?" skit to clarify the confusion that the person on first is not called "Who", but just "The Doctor". The title text references the Madeleine L'Engle novel A Wrinkle in Time , which has characters with similarly ambiguous names. The book's Mrs. Whatsit appears to be on second base. "Aunt Beast" is a minor character in the novel from the planet of Ixchel. And they are playing a real baseball game. "Aunt Beast" is the batter and hits a pop fly high in the air towards second base while "Mrs. Whatsit" (presumably playing second base, in place of "What") is being encouraged to dive to catch the ball before it hits the ground, to get the batter out. So both the players "Who" and "What" have been exchanged with other characters going under similar names. [Mrs. Whatsit, a woman drawn as Megan, holds her hand out and talks to Abbott (a tall guy with a baseball cap) and Costello (a short guy wearing a round brimmed hat and holding a baseball bat in his right hand.)] Mrs. Whatsit: You're both confused. Mrs. Whatsit: He's just "The Doctor". The names are from the original transcript .

Pastime

Pastime

https://www.xkcd.com/1222

https://www.explainxkcd.com/wiki/index.php/1222:_Pastime

[Megan and Cueball are chatting. She has hair.] Megan: What've you been up to? Cueball: Definitely not spending every day consumed with worry over stupid things I never talk to anyone about. Megan: Oh, yeah, me neither. Cueball: That's good. Megan: Yeah. [The final panel is silent.]

When asked by Megan what he's been up to, Cueball responds with the suspiciously specific denial , "Definitely not spending every day consumed with worry over stupid things I never talk to anyone about.", which suggests that that is exactly what he's been spending every day doing, but he is hiding it from her and everyone else. Megan's response "Oh, yeah, me neither" suggests she too is worrying over stupid things but isn't admitting it. Instead of discussing their mutual worry and possibly making each other feel better, they instead continue to "not talk to anyone about it" and stand in awkward silence . The title text continues the irony suggesting it's good that they're too smart to spend all day being uselessly frustrated with themselves, but that's apparently exactly what they are doing. This could also be a reference to the common response to the question Megan asks in the first panel, "nothing", a response that is almost certainly false, and usually means the same thing that Cueball said, but is usually accepted, if not expected. [Megan and Cueball are chatting. She has hair.] Megan: What've you been up to? Cueball: Definitely not spending every day consumed with worry over stupid things I never talk to anyone about. Megan: Oh, yeah, me neither. Cueball: That's good. Megan: Yeah. [The final panel is silent.]

Dwarf Fortress

Dwarf Fortress

https://www.xkcd.com/1223

https://www.explainxkcd.com/wiki/index.php/1223:_Dwarf_Fortress

[Cueball sits at a desk with a computer, hands on the keyboard, talking to an unseen observer.] Cueball: If the corporate surveillance state monitors and controls every aspect of my life... Big Brother: We do. Cueball: And I play Dwarf Fortress all day... Big Brother: You do. Cueball: Then you're effectively Dwarf Fortress players watching your dwarves play Dwarf Fortress. Big Brother: ... Oh God. [Caption below the panel:] Big Brother realizes he's trapped in the most tedious possible Hell.

This comic is a reaction to the recent reveal of a U.S. electronic telecom surveillance program called PRISM , run by the NSA . There is a Guardian article about it. PRISM, leaked by a former NSA official, incited some controversy since it provides government access to private data (e-mails, videos, chats, file transfers, etc.). Dwarf Fortress is a freeware strategy game in which the player builds a civilization by giving orders to — as opposed to directly controlling — a group of dwarves. It is famous for having a very detailed simulation of its world and for allowing deep micro-management (as well as an incredibly steep learning curve). "Big Brother" means "a tyrannical government body that constantly monitors all its citizens." The term comes from the classic dystopian novel Nineteen Eighty-Four by George Orwell, wherein propaganda videos are narrated by an actor with the stage name of Big Brother and the dystopia's surveillance system is said to be monitored by Big Brother himself. Cueball has a discussion with Big Brother ("corporate surveillance state"), in which he mocks Big Brother's interest in the inconsequential activity of playing a video game ( Dwarf Fortress in particular) by drawing a parallel between Big Brother's omniscient surveillance of Cueball and Cueball's omniscient surveillance of the dwarves. Big Brother appears to be mortified when it realizes the accuracy of Cueball's comparison. Informally, a system exhibits Turing-completeness when it is theoretically capable of executing any algorithm. One of the simplest Turing-complete systems is the Turing machine , a device that manipulates symbols on a strip of tape according to a table of rules — it can be proven to have the same capabilities as any ordinary programming language. Other very simple systems include Rule 110 , lambda calculus , Conway's game of life , and Brainfuck . The reason we don't work with these is because they're a real pain in the ass. Would you rather build a network of spaceships that collide with each other to simulate the successor function, or just write i := i + 1 ? A common CS nerd challenge is to prove the Turing-completeness of a system that wasn't intended to be that way — games in particular. The usual way to do this is to construct a Turing machine simulator within the system. It has been done for Dwarf Fortress , (infinite) Minesweeper (pdf), Magic the Gathering , Little Big Planet , Minecraft ( another Minecraft example ) 1 , Pokémon Yellow (through the elaborate use of many in-game glitches) and 3D chess . These kinds of proofs often involve formulating ridiculously complex creations just to simulate a little machine writing symbols on a tape! 2 Finally, Randall makes a crack that users will try to nest their Turing-complete computers; after finishing his Turing-complete Dwarf Fortress computer, someone else will try to make the Dwarf Fortress computer run Minecraft (a highly inefficient process that would be a nightmare to coordinate, and would run incredibly slowly). 1 The youtuber legomasta99 even built a whole programmable PC in Minecraft as can be seen here . 2 Technically, a computer is not really Turing-complete. A Turing-complete system has to have unlimited space, and that's not possible for a memory-limited computer or any software running inside it. But even if we don't have access to Turing-completeness, we can build a theoretical machine and show how it can be extended indefinitely. In a few of the games, we prove Turing-completeness in infinite variants. [Cueball sits at a desk with a computer, hands on the keyboard, talking to an unseen observer.] Cueball: If the corporate surveillance state monitors and controls every aspect of my life... Big Brother: We do. Cueball: And I play Dwarf Fortress all day... Big Brother: You do. Cueball: Then you're effectively Dwarf Fortress players watching your dwarves play Dwarf Fortress. Big Brother: ... Oh God. [Caption below the panel:] Big Brother realizes he's trapped in the most tedious possible Hell.

Council of 300

Council of 300

https://www.xkcd.com/1224

https://www.explainxkcd.com/wiki/index.php/1224:_Council_of_300

[A secret society meets in a darkened chamber; a kitschy video involving two people and an RC helicopter is projected onto the background.] Master: ...then it is settled. We the 300 members of the Secret Council, decree that this video meets our standards, and shall "go viral". Master: send it to one of our agents to be leaked to the common folk. Steward: Some of them are noticing the number. Master: ...add a plus sign to throw them off. Steward: very well. Soon... [A communication sent to Cueball, one of the many unsuspecting plebeians of the world.] Email: Ooh! check out this great video I found! [Zoom in on the viewer count of a YouTube video.] 301+

YouTube (a video sharing site) used to have an odd quirk in its view counter. When a video hit 301 views, the view counter briefly stopped updating. This meant that YouTube was checking the views to make sure that no foul play was going on. The choice of the number 301 is due to a harmless off-by-one error; Numberphile produced a video that explains all this very well (and has comically its view counter frozen at 301). At times the number 301 would catch some YouTubers off guard — for very popular videos, it might appear that the video has more likes than views. However, this bug is no longer present (although very new videos having more likes and comments than views IS still present). Randall plays with the near coincidence of this number, and a conspiracy theory entity known as the Committee of 300 . In this case, the video's first 300 views come from each of the Committee's council members who determine if the video will go viral . The video is then released to the public by sending it to a regular person ( Cueball in this comic) making the total number of views 301. The title text elaborates on this by explaining that the council also hypnotizes somebody to make him think they uploaded and shared that particular video. According to the title text, the council does not seem to tolerate contradiction, because the member that suggests changing 301 to a random number to avoid suspicion is shot, silenced permanently, and removed from the council. [A secret society meets in a darkened chamber; a kitschy video involving two people and an RC helicopter is projected onto the background.] Master: ...then it is settled. We the 300 members of the Secret Council, decree that this video meets our standards, and shall "go viral". Master: send it to one of our agents to be leaked to the common folk. Steward: Some of them are noticing the number. Master: ...add a plus sign to throw them off. Steward: very well. Soon... [A communication sent to Cueball, one of the many unsuspecting plebeians of the world.] Email: Ooh! check out this great video I found! [Zoom in on the viewer count of a YouTube video.] 301+

Ice Sheets

Ice Sheets

https://www.xkcd.com/1225

https://www.explainxkcd.com/wiki/index.php/1225:_Ice_Sheets

[Caption above the four panels:] Thickness of the ice sheets at various locations 21,000 years ago compared with modern skylines. [In four panels the skylines of four major metropolises are superimposed against a blue ice sheet of the proper thickness for the aforementioned time period. The panels are much taller than the skyline reaching about 3500 meter up above ground level. Below the gray skylines there is a black slab indicating this ground level, above the ice the air is white. Also above the ice sheet the hight of the ice is noted in light gray text. Inside the ice sheet the name of the city is written in black. Some clear landmarks can be seen in each skyline.] [The first skyline shows among other a tall TV tower. The ice reaches more than halfway to the top of the panel.] 2100m Toronto [The second skyline shows several skyscrapers with specially one towering over the other. The ice reaches about a quarter of the way to the top. This is the lowest of the ice sheets only reaching about twice as high as the tallest building in the city.] 900m Chicago [The third skyline shows only a few skyscrapers with two of them clearly taller than the rest of the skyline. The ice reaches a bit more than a third towards the top.] 1250m Boston [The fourth skyline do not have many real skyscrapers but there are three buildings that are taller than the rest of the skyline. The ice reaches almost to the top, making it the tallest ice sheet. The name of the city clearly is written higher up in the ice than the other three. Even above the lowest ice sheet of the second panel.] 3300m Montreal

The comic shows the ice levels at major North American cities at the peak of the last ice age , 21,000 years ago. During this period, a vast amount of frozen water covered North America as well as other areas around the world. So much ice that it affected the global sea level (see Sea level rise ) to lower it by more than a hundred meters. Toronto and Montreal are both Canadian cities, while Boston and Chicago are in the United States . The skylines of each city are shown at the bottom of the ice sheet to scale. The tallest structure shown is the CN Tower in Toronto, the tallest free-standing structure in the Western Hemisphere , at a height of 553 m. The tallest ice sheet is 3.3 km tall, almost six times as tall as that tower. Although, over Toronto, the ice was "only" 2.1 km tall. The tallest ice sheet takes up 265 pixels. From that, each pixel is about 12.4 meters and the height of the panels is 3.7 km with less than 200 m of the ground shown in black below the cities making the white "air" above ground reaching up to 3.5 km, leaving only 200 m of air above the highest ice sheet. The title text references the " The Laurentide and Innuitian ice sheets during the Last Glacial Maximum (PDF) ," an actual series of scientific papers about the ice sheet (see figure 4). But it also refers to the animated Ice Age film series, specifically to Ice Age: the Meltdown , and Ice Age: Continental Drift which are the second and fourth Ice Age films. Ice sheets over Boston during the last ice age was also referenced in 1379: 4.5 Degrees . The image of Boston in this comic is reused at the top of the huge chart in 1732: Earth Temperature Timeline , and had already been reused earlier in the what if? post Google's Datacenters on Punch Cards . Randall lives in that area. Although this comic doesn't mention (modern) climate change, it does show the difference climate can have on our surroundings. And in the two later comics mentioned above, Randall makes it clear that we are now heading as far in the opposite hotter direction compared to the "normal" temperature during the rise of human civilization, as the ice age temperature was colder. [Caption above the four panels:] Thickness of the ice sheets at various locations 21,000 years ago compared with modern skylines. [In four panels the skylines of four major metropolises are superimposed against a blue ice sheet of the proper thickness for the aforementioned time period. The panels are much taller than the skyline reaching about 3500 meter up above ground level. Below the gray skylines there is a black slab indicating this ground level, above the ice the air is white. Also above the ice sheet the hight of the ice is noted in light gray text. Inside the ice sheet the name of the city is written in black. Some clear landmarks can be seen in each skyline.] [The first skyline shows among other a tall TV tower. The ice reaches more than halfway to the top of the panel.] 2100m Toronto [The second skyline shows several skyscrapers with specially one towering over the other. The ice reaches about a quarter of the way to the top. This is the lowest of the ice sheets only reaching about twice as high as the tallest building in the city.] 900m Chicago [The third skyline shows only a few skyscrapers with two of them clearly taller than the rest of the skyline. The ice reaches a bit more than a third towards the top.] 1250m Boston [The fourth skyline do not have many real skyscrapers but there are three buildings that are taller than the rest of the skyline. The ice reaches almost to the top, making it the tallest ice sheet. The name of the city clearly is written higher up in the ice than the other three. Even above the lowest ice sheet of the second panel.] 3300m Montreal

Balloon Internet

Balloon Internet

https://www.xkcd.com/1226

https://www.explainxkcd.com/wiki/index.php/1226:_Balloon_Internet

[Cueball sits on a hill reading a book.] [Cueball remains engrossed in the book. A balloon with a box at the end of the string begins to descend behind him.] [Cueball continues reading. The balloon is getting lower.] [The balloon's box is now right behind Cueball's ear.] Balloon box: Internet . Cueball: Augh! [Cueball throws the book in surprise.] [The balloon ascends rapidly, while the startled Cueball looks up.]

The comic references Google's Project Loon , a balloon powered Internet service which was officially announced June 14, 2013 (3 days before this comic was published) and was in proof-of-concept testing stages by that time. A test above New Zealand, involving about 30 balloons and about 50 users, was successfully conducted on June 16. The project, taglined "Internet for Everyone", was intended to eventually provide Internet access to people in rural areas and in disaster areas that have limited or no access to land-based Internet services. As of 2019 Loon LLC was an individual Google subsidiary instead of a mere project and was present in multiple places across the world for either Internet in rural areas, full coverage of a country or disaster relief. In March of 2021, Alphabet , Google's parent company, announced the closure of Loon, LLC. Randall is poking fun at the tagline "Internet for Everyone" — meant to mean anyone could have Internet access regardless of location — by instead literally bringing the Internet to Cueball , who retired in a deserted area, away from all technology, to read a standard paper book. In the comic, one of the balloons sneaks up on Cueball before speaking and startling Cueball, effectively becoming a nuisance, interrupting Cueball's reading of a book and leaving Cueball wondering what has happened. In Randall's world, the tagline could be restated as "Internet for Everyone — whether they want it or not". The title text describes Randall's own plan to provide rural internet. He will operate in a region where Verizon Wi-Fi infrastructure already exists, and take advantage of their 14-day return policy to effectively obtain internet access for free, which he will then sell under his own brand. [Cueball sits on a hill reading a book.] [Cueball remains engrossed in the book. A balloon with a box at the end of the string begins to descend behind him.] [Cueball continues reading. The balloon is getting lower.] [The balloon's box is now right behind Cueball's ear.] Balloon box: Internet . Cueball: Augh! [Cueball throws the book in surprise.] [The balloon ascends rapidly, while the startled Cueball looks up.]

The Pace of Modern Life

The Pace of Modern Life

https://www.xkcd.com/1227

https://www.explainxkcd.com/wiki/index.php/1227:_The_Pace_of_Modern_Life

The art of letter-writing is fast dying out. When a letter cost nine pence, it seemed but fair to try to make it worth nine pence ... Now, however, we think we are too busy for such old-fashioned correspondence. We fire off a multitude of rapid and short notes, instead of sitting down to have a good talk over a real sheet of paper. The Sunday Magazine 1871 It is, unfortunately, one of the chief characteristics of modern business to be always in a hurry. In olden times it was different. The Medical Record 1884 With the advent of cheap newspapers and superior means of locomotion... The dreamy quiet old days are over... For men now live think and work at express speed. They have their Mercury or Post laid on their breakfast table in the early morning, and if they are too hurried to snatch from it the news during that meal, they carry it off, to be sulkily read as they travel ... leaving them no time to talk with the friend who may share the compartment with them ... The hurry and bustle of modern life ... lacks the quiet and repose of the period when our forefathers, the day's work done, took their ease... William Smith, Morley: Ancient and Modern 1886 Conversation is said to be a lost art ... Good talk presupposes leisure, both for preparation and enjoyment. The age of leisure is dead, and the art of conversation is dying. Frank Leslie's popular Monthly , Volume 29 1890 Intellectual laziness and the hurry of the age have produced a craving for literary nips. The torpid brain ... has grown too weak for sustained thought. There never was an age in which so many people were able to write badly. Israel Zangwill, The Bachelors' Club 1891 The art of pure line engraving is dying out. We live at too fast a rate to allow for the preparation of such plates as our fathers appreciated. If a picture catches the public fancy, the public must have an etched or a photogravured copy of it within a month or two of its appearance, the days when engravers were wont to spend two or three years over a single plate are for ever gone. Journal of the Institute of Jamaica , Volume 1 1892 So much is exhibited to the eye that nothing is left to the imagination . It sometimes seems almost possible that the modern world might be choked by its own riches, and human faculty dwindle away amid the million inventions that have been introduced to render its exercise unnecessary. The articles in the Quarterlies extend to thirty or more pages, but thirty pages is now too much so we witness a further condensing process and, we have the Fortnightly and the Contemporary which reduce thirty pages to fifteen pages so that you may read a larger number of articles in a shorter time and in a shorter form. As if this last condensing process were not enough the condensed articles of these periodicals are further condensed by the daily papers, which will give you a summary of the summary of all that has been written about everything. Those who are dipping into so many subjects and gathering information in a summary and superficial form lose the habit of settling down to great works. Ephemeral literature is driving out the great classics of the present and the past ... hurried reading can never be good reading. G. J. Goschen, First Annual Address to the Students , Toynbee Hall. London 1894 The existence of mental and nervous degeneration among a growing class of people , especially in large cities, is an obvious phenomenon ... the mania for stimulants ... diseases of the mind are almost as numerous as the diseases of the body... This intellectual condition is characterized by a brain incapable of normal working ... in a large measure due to the hurry and excitement of modern life , with its facilities for rapid locomotion and almost instantaneous communication between remote points of the globe ... The Churchman , Volume 71 1895 If we teach the children how to play and encourage them in their sports ... instead of shutting them in badly ventilated schoolrooms , the next generation will be more joyous and will be healthier than the present one. Public Opinion: A Comprehensive Summary of the Press Throughout the World , Volume 18 1895 The cause of the ... increase in nervous disease is increased demand made by the conditions of modern life upon the brain . Everything is done in a hurry. We talk across a continent, telegraph across an ocean , take a trip to Chicago for an hour's talk... We take even our pleasures sadly and make a task of our play ... what wonder if the pressure is almost more than our nerves can bear. G. Shrady (from P.C. Knapp) "Are nervous diseases increasing?" Medical Record 1896 The managers of sensational newspapers ... do not try to educate their readers and make them better, but tend to create perverted tastes and develop vicious tendencies. The owners of these papers seem to have but one purpose, and that is to increase their circulation. Medical Brief , Volume 26 1898 To take sufficient time for our meals seems frequently impossible on account of the demands on our time made by our business... We act on the apparent belief that all of our business is so pressing that we must jump on the quickest car home, eat our dinner in the most hurried way, make the closest connection for a car returning ... Louis John Rettger. Studies in Advanced Physiology 1898 In these days of increasing rapid artificial locomotion, may I be permitted to say a word in favour of a very worthy and valuable old friend of mine, Mr. Long Walk? I am afraid that this good gentleman is in danger of getting neglected, if not forgotten. We live in days of water trips and land trips, excursions by sea, road and rail-bicycles and tricycles, tram cars and motor cars .... but in my humble opinion, good honest walking exercise for health beats all other kinds of locomotion into a cocked hat. T. Thatcher, "A plea for a long walk", The Publishers Circular 1902 The art of conversation is almost a lost one. People talk as they ride bicycles–at a rush–without pausing to consider their surroundings ... what has been generally understood as cultured society is rapidly deteriorating into baseness and voluntary ignorance. The profession of letters is so little understood , and so far from being seriously appreciated, that ... Newspapers are full, not of thoughtful honestly expressed public opinion on the affairs of the nation, but of vapid personalities interesting to none save gossips and busy bodies. Marie Corelli, Free opinions, freely expressed 1905 There is a great tendency among the children of today to rebel against restraint , not only that placed upon them by the will of the parent. But against any restraint or limitation of what they consider their rights ... this fact has filled well minded people with great apprehensions for the future. Rev. Henry Hussmann, The authority of parents 1906 Our modern family gathering, silent around the fire, each individual with his head buried in his favourite magazine , is the somewhat natural outcome of the banishment of colloquy from the school ... The Journal of Education , Volume 29 1907 Plays in theatres at the present time present spectacles and deal openly with situations which no person would have dared to mention in general society forty years ago ... The current representations of nude men and women in the daily journals and the illustrated magazines would have excluded such periodicals from all respectable families two decades ago... Those who have been divorced ... forty and fifty years ago lost at once and irrevocably their standing in society, while to-day they continue in all their social relationships, hardly changed... Editorial, The Watchman , Boston 1908 We write millions more letters than did our grandfathers, but the increase in volume has brought with it an automatic artificial machine-like ring ... an examination of a file of old letters reveals not only a remarkable grasp of details. But a fitness and courtliness too often totally lacking in the mechanical curt cut and dried letters of to-day. Forrest Crissey, Handbook of Modern Business Correspondence 1908 A hundred years ago it took so long and cost so much to send a letter that it seemed worth while to put some time and thought into writing it. Now the quickness and the cheapness of the post seem to justify the feeling that a brief letter to-day may be followed by another next week–a "line" now by another to-morrow. Percy Holmes Boynton, Principles of Composition 1915

The debate as to whether or not the pace of modern life is detrimental to society, culture, and the human experience in general has been going on for longer than we may realize. Presently, the debate has focused on technology such as smartphones, tablets, and other portable electronics; however, many of the same arguments were made against newspapers , magazines, telegraphs, telephones, and even written correspondence 100 years ago. People often tend to think of older times as better. The people complaining compare their present time to the time they lived in before, that is, a couple of decades ago, and this has been happening for over a century (at least). This comic makes a point that the older times people refer to, were also criticized in exactly the same fashion. Since the same criticism is applied to each generation by the generation before that one, every generation thinks that the one they were born in is the good one. This is presentism as explained by Randall in 24: Godel, Escher, Kurt Halsey . The comic begins and ends with very similar arguments, perhaps emphasizing how these debates cycle and repeat over time. The comic does not directly state whether these opinions and criticisms were justified or simple fallacies. There is a desire to consider our present existence as good and reasonable and that society has been improving over time. The difficulty lies in considering the possibility that each generation was perhaps correct in their criticism. On reading all of these quotes, one may find these quotes redundant and tiresome to read. Readers may find themselves skimming the text and skipping several quotes once they get the overall idea. This could be a self-referential point demonstrating that the writing style of older times was less convenient than the oft-criticized brief modern style. Some parts of all that long texts are in bold, others not. Here is the summary for only this bold text, picturing just our Modern World : The art of letter-writing is fast dying out. We fire off a multitude of rapid and short notes, instead of sitting down to have a good talk over a real sheet of paper. In olden times it was different. Men now live think and work at express speed. Sulkily read as they travel leaving them no time to talk with the friend who may share the compartment with them. The age of leisure is dead, and the art of conversation is dying. A craving for literary nips. There never was an age in which so many people were able to write badly. The art of pure line engraving is dying out. We live at too fast a rate nothing is left to the imagination and human faculty dwindle away amid the million inventions that have been introduced to render its exercise unnecessary. Thirty pages is now too much. Fifteen pages further condensed a summary of the summary. Those who are dipping into so many subjects and gathering information in a summary and superficial form lose the habit of settling down to great works. Hurried reading can never be good reading. Mental and nervous degeneration among a growing class of people, a brain incapable of normal working in a large measure due to the hurry and excitement of modern life, almost instantaneous communication between remote points of the globe. Teach the children how to play instead of shutting them in badly ventilated schoolrooms, increased demand made by the conditions of modern life upon the brain. We talk across a continent, telegraph across an ocean, we take even our pleasures sadly and make a task of our play. The managers of sensational newspapers create perverted tastes and develop vicious tendencies. To take sufficient time for our meals seems frequently impossible, may I be permitted to say a word in favour of a very worthy and valuable old friend of mine, Mr. Long walk? I am afraid that this good gentleman is in danger of getting neglected, if not forgotten. People talk as they ride bicycles–at a rush–without pausing to consider their surroundings the profession of letters is so little understood, tendency among the children of today to rebel against restraint. Our modern family gathering, silent, each individual with his head buried in his favourite magazine, deal openly with situations which no person would have dared to mention in general society forty years ago. A hundred years ago it took so long and cost so much to send a letter that it seemed worth while to put some time and thought into writing it. A brief letter to-day may be followed by another next week–a "line" now by another to-morrow. The style of the comic is very similar to that of 1311: 2014 , which was released half a year later. The title text shows that the meaning of the institute of marriage debate has likewise been going on for quite some time. The art of letter-writing is fast dying out. When a letter cost nine pence, it seemed but fair to try to make it worth nine pence ... Now, however, we think we are too busy for such old-fashioned correspondence. We fire off a multitude of rapid and short notes, instead of sitting down to have a good talk over a real sheet of paper. The Sunday Magazine 1871 It is, unfortunately, one of the chief characteristics of modern business to be always in a hurry. In olden times it was different. The Medical Record 1884 With the advent of cheap newspapers and superior means of locomotion... The dreamy quiet old days are over... For men now live think and work at express speed. They have their Mercury or Post laid on their breakfast table in the early morning, and if they are too hurried to snatch from it the news during that meal, they carry it off, to be sulkily read as they travel ... leaving them no time to talk with the friend who may share the compartment with them ... The hurry and bustle of modern life ... lacks the quiet and repose of the period when our forefathers, the day's work done, took their ease... William Smith, Morley: Ancient and Modern 1886 Conversation is said to be a lost art ... Good talk presupposes leisure, both for preparation and enjoyment. The age of leisure is dead, and the art of conversation is dying. Frank Leslie's popular Monthly , Volume 29 1890 Intellectual laziness and the hurry of the age have produced a craving for literary nips. The torpid brain ... has grown too weak for sustained thought. There never was an age in which so many people were able to write badly. Israel Zangwill, The Bachelors' Club 1891 The art of pure line engraving is dying out. We live at too fast a rate to allow for the preparation of such plates as our fathers appreciated. If a picture catches the public fancy, the public must have an etched or a photogravured copy of it within a month or two of its appearance, the days when engravers were wont to spend two or three years over a single plate are for ever gone. Journal of the Institute of Jamaica , Volume 1 1892 So much is exhibited to the eye that nothing is left to the imagination . It sometimes seems almost possible that the modern world might be choked by its own riches, and human faculty dwindle away amid the million inventions that have been introduced to render its exercise unnecessary. The articles in the Quarterlies extend to thirty or more pages, but thirty pages is now too much so we witness a further condensing process and, we have the Fortnightly and the Contemporary which reduce thirty pages to fifteen pages so that you may read a larger number of articles in a shorter time and in a shorter form. As if this last condensing process were not enough the condensed articles of these periodicals are further condensed by the daily papers, which will give you a summary of the summary of all that has been written about everything. Those who are dipping into so many subjects and gathering information in a summary and superficial form lose the habit of settling down to great works. Ephemeral literature is driving out the great classics of the present and the past ... hurried reading can never be good reading. G. J. Goschen, First Annual Address to the Students , Toynbee Hall. London 1894 The existence of mental and nervous degeneration among a growing class of people , especially in large cities, is an obvious phenomenon ... the mania for stimulants ... diseases of the mind are almost as numerous as the diseases of the body... This intellectual condition is characterized by a brain incapable of normal working ... in a large measure due to the hurry and excitement of modern life , with its facilities for rapid locomotion and almost instantaneous communication between remote points of the globe ... The Churchman , Volume 71 1895 If we teach the children how to play and encourage them in their sports ... instead of shutting them in badly ventilated schoolrooms , the next generation will be more joyous and will be healthier than the present one. Public Opinion: A Comprehensive Summary of the Press Throughout the World , Volume 18 1895 The cause of the ... increase in nervous disease is increased demand made by the conditions of modern life upon the brain . Everything is done in a hurry. We talk across a continent, telegraph across an ocean , take a trip to Chicago for an hour's talk... We take even our pleasures sadly and make a task of our play ... what wonder if the pressure is almost more than our nerves can bear. G. Shrady (from P.C. Knapp) "Are nervous diseases increasing?" Medical Record 1896 The managers of sensational newspapers ... do not try to educate their readers and make them better, but tend to create perverted tastes and develop vicious tendencies. The owners of these papers seem to have but one purpose, and that is to increase their circulation. Medical Brief , Volume 26 1898 To take sufficient time for our meals seems frequently impossible on account of the demands on our time made by our business... We act on the apparent belief that all of our business is so pressing that we must jump on the quickest car home, eat our dinner in the most hurried way, make the closest connection for a car returning ... Louis John Rettger. Studies in Advanced Physiology 1898 In these days of increasing rapid artificial locomotion, may I be permitted to say a word in favour of a very worthy and valuable old friend of mine, Mr. Long Walk? I am afraid that this good gentleman is in danger of getting neglected, if not forgotten. We live in days of water trips and land trips, excursions by sea, road and rail-bicycles and tricycles, tram cars and motor cars .... but in my humble opinion, good honest walking exercise for health beats all other kinds of locomotion into a cocked hat. T. Thatcher, "A plea for a long walk", The Publishers Circular 1902 The art of conversation is almost a lost one. People talk as they ride bicycles–at a rush–without pausing to consider their surroundings ... what has been generally understood as cultured society is rapidly deteriorating into baseness and voluntary ignorance. The profession of letters is so little understood , and so far from being seriously appreciated, that ... Newspapers are full, not of thoughtful honestly expressed public opinion on the affairs of the nation, but of vapid personalities interesting to none save gossips and busy bodies. Marie Corelli, Free opinions, freely expressed 1905 There is a great tendency among the children of today to rebel against restraint , not only that placed upon them by the will of the parent. But against any restraint or limitation of what they consider their rights ... this fact has filled well minded people with great apprehensions for the future. Rev. Henry Hussmann, The authority of parents 1906 Our modern family gathering, silent around the fire, each individual with his head buried in his favourite magazine , is the somewhat natural outcome of the banishment of colloquy from the school ... The Journal of Education , Volume 29 1907 Plays in theatres at the present time present spectacles and deal openly with situations which no person would have dared to mention in general society forty years ago ... The current representations of nude men and women in the daily journals and the illustrated magazines would have excluded such periodicals from all respectable families two decades ago... Those who have been divorced ... forty and fifty years ago lost at once and irrevocably their standing in society, while to-day they continue in all their social relationships, hardly changed... Editorial, The Watchman , Boston 1908 We write millions more letters than did our grandfathers, but the increase in volume has brought with it an automatic artificial machine-like ring ... an examination of a file of old letters reveals not only a remarkable grasp of details. But a fitness and courtliness too often totally lacking in the mechanical curt cut and dried letters of to-day. Forrest Crissey, Handbook of Modern Business Correspondence 1908 A hundred years ago it took so long and cost so much to send a letter that it seemed worth while to put some time and thought into writing it. Now the quickness and the cheapness of the post seem to justify the feeling that a brief letter to-day may be followed by another next week–a "line" now by another to-morrow. Percy Holmes Boynton, Principles of Composition 1915

Prometheus

Prometheus

https://www.xkcd.com/1228

https://www.explainxkcd.com/wiki/index.php/1228:_Prometheus

[Cueball addresses his Cueball-like friend, who just walked in-panel. Cueball points at Prometheus (who is also Cueball-like). Prometheus is holding his hand to his chin and holding a colorful flaming torch in the other hand.] Cueball: Prometheus has stolen fire from the Gods! Prometheus: Well, sort of. I mean, when you use a fire to make another fire, the first fire doesn't go away. So really, it's more like "sharing". [Caption below the frame:] Fire wants to be free.

This comic is most likely about copyright and patent, which are temporary government-granted monopolies for authors and inventors. It refers to the cultural hero Prometheus in Greek mythology who stole fire from the gods and gave it to humanity. In this case, Prometheus claims that it is more like sharing than stealing because the gods still have the original fire. By analogy, uploading music, movies, and software is more like sharing than stealing because the authors and inventors still have the original files. Fire-sharing is a pun for file-sharing . "Fire wants to be free" is a pun for the slogan " Information wants to be free ." This could also be a reference to the strict punishments of copyright laws as one could be fined a lot for failing to comply with the copy and Prometheus was also heavily punished by having an eagle rip out his liver every day and the liver regrowing every night. The title text refers both to Michael Bay , the director of the movies Transformers and Armageddon , who is known for using over the top special effects, and to the novel "Salvation War" by Stuart Slade, in which Humanity goes to war just as described. "Returning fire to the gods with interest" is also the plot of the Terry Pratchett novel The Last Hero ; Randall has previously made references to Terry Pratchett. [Cueball addresses his Cueball-like friend, who just walked in-panel. Cueball points at Prometheus (who is also Cueball-like). Prometheus is holding his hand to his chin and holding a colorful flaming torch in the other hand.] Cueball: Prometheus has stolen fire from the Gods! Prometheus: Well, sort of. I mean, when you use a fire to make another fire, the first fire doesn't go away. So really, it's more like "sharing". [Caption below the frame:] Fire wants to be free.

Screensaver

Screensaver

https://www.xkcd.com/1229

https://www.explainxkcd.com/wiki/index.php/1229:_Screensaver

I've been staring at the screen every night for twenty years, and it finally happened. [A star field.] [The same star field, but there's a larger white dot glowing in the middle.] [The same star field, but that larger white dot's looking bigger now. Oh. It's clearly a star.] [The screen is filled with white. It's coming straight for us.] [The screen is filled with static.] signal lost

This comic features the "Starfield" screensaver , a popular Windows screensaver of the 1990s, which presents a moving starfield, like what would be seen by an observer moving past stars at superluminal speeds (see a video example ). This illusion is generally created by drawing white dots on the computer screen, and then moving these dots outwards towards the edge of the screen before disappearing. Some of the "stars" appear to pass closer to the viewing point than others, resulting in movements of visually greater speeds, and more excitement; one can also fixate the center of the screen, hoping to see the appearance of a star as close as possible to it, which would later on pass very close to the viewpoint. This comic extends it to the situation where the observer actually collides with one of these stars, something that never happens with screensavers of this type. The "signal lost" error message appears because the source of the signal is no longer transmitting, since it was destroyed when colliding with said star. The "Duck Hunt gun" is a reference to the NES Zapper used with the Nintendo Entertainment System game Duck Hunt , originally published in 1984. The user would point the Zapper at the connected television screen while playing Duck Hunt, and the NES would recognize whether or not the zapper was pointed at an appropriate target or not. " Flying Toasters " is another old screensaver (in the After Dark package, made for computers but not for the NES). In the title text, Randall states that he is trying to use the NES Zapper to shoot down flying toasters. However, the Flying Toaster screensaver and the NES Zapper are two separate things that were never meant to be used together, so the flying toasters will never react to being "shot" at by the NES Zapper. I've been staring at the screen every night for twenty years, and it finally happened. [A star field.] [The same star field, but there's a larger white dot glowing in the middle.] [The same star field, but that larger white dot's looking bigger now. Oh. It's clearly a star.] [The screen is filled with white. It's coming straight for us.] [The screen is filled with static.] signal lost

Polar/Cartesian

Polar/Cartesian

https://www.xkcd.com/1230

https://www.explainxkcd.com/wiki/index.php/1230:_Polar/Cartesian

[Caption above the panel:] Certainty that this is a clockwise polar plot, not a Cartesian one, as a function of time: [There is a graph. The Y axis is marked out from 0% to 100%. The X axis is unmarked. A red line starts at 50% and traces out a roughly parabolic trend downwards along the X axis.]

This comic plays upon the difference between reading a polar coordinate plot and the more common cartesian coordinate plot . The graph purports to show the certainty in the viewers mind that it is a clockwise polar plot, as a function of time. If seen as a Cartesian plot, the y (vertical) axis represents 'certainty' while the x (horizontal) axis represents 'time'. Each point on the plot is represented by two coordinates, the x-value and the y-value. As time increases, we move to the right and see the initial certainty of 50% decreases gradually to zero. That is, after a certain amount of time, we are certain that it is NOT a Polar plot. In a Polar plot, each point on the plot is also located by two values, but in this case they are the radius (the distance from the origin) and the angle between the radius and an arbitrary starting line. Here, the radius represents 'certainty' and the angle to the vertical represents 'time'. In this view, we see that as time increases (as we move clockwise around the plot) the initial certainty (the same 50%) now increases to a final value of 100%. That is, after a certain amount of time, we are certain that it IS a Polar plot. The intended joke seems to be that the graph is an exercise in confirmation bias. Whichever type you initially hypothesize is correct, that view will be confirmed by investigation. This is because the two different views are both correct - the graph can equally be considered a Cartesian or Polar plot. This is somewhat counter-intuitive. Throughout the graph, the sum of the two probabilities is 100%, i.e. (polar-observer's certainty that the graph is polar) + (cartesian-observer's certainty that the graph is polar) = 100%. The shape of the graph appears to be (in clockwise polar form) r(t)=100/(1+cos(t)). If the reader is open-minded, they would never reach certainty (0% / 100% depending on how you read the graph) because there isn't enough information to clearly decide either way. The title text is a joke that if you are unsure how to label any two-axis (two-dimensional) graph, you can just say it represents the 'coordinates of the ants crawling across my screen as a function of time', and nobody could then argue with your data. "Hey, that's the path they walked!" [Caption above the panel:] Certainty that this is a clockwise polar plot, not a Cartesian one, as a function of time: [There is a graph. The Y axis is marked out from 0% to 100%. The X axis is unmarked. A red line starts at 50% and traces out a roughly parabolic trend downwards along the X axis.]

Habitable Zone

Habitable Zone

https://www.xkcd.com/1231

https://www.explainxkcd.com/wiki/index.php/1231:_Habitable_Zone

[Cueball stands in front of a huge telescope, looking through the eyepiece.] Cueball: I've discovered an Earth-sized planet in a star's habitable zone! It even has oceans! And visible weather! [Caption below the panel:] To mess with an astronomer, put a mirror in the path of their telescope.

While searching for extrasolar planets this gullible astronomer is very excited because he believes he has found a planet in a star's habitable zone , with oceans and visible weather. From these observations, he has determined that it is quite likely to have life on it, which would be a major groundbreaking discovery. The caption explains, however, that someone has used a mirror as a prank to fool the astronomer, so he is in fact looking at a reflection of the Earth. The title text goes on says that the astronomer would also be able to see the reflection of his telescope, which would convince him that there definitely is intelligent life on the other planet, looking straight back at him no less! There are quite a number of issues (listed below) with the practical implementation of this prank, though of course they don't matter much in terms of the joke itself [Cueball stands in front of a huge telescope, looking through the eyepiece.] Cueball: I've discovered an Earth-sized planet in a star's habitable zone! It even has oceans! And visible weather! [Caption below the panel:] To mess with an astronomer, put a mirror in the path of their telescope.

Realistic Criteria

Realistic Criteria

https://www.xkcd.com/1232

https://www.explainxkcd.com/wiki/index.php/1232:_Realistic_Criteria

[Cueball and White Hat stand talking. White Hat is making a forward gesture with his hand.] White Hat: We shouldn't be exploring other planets until we've solved all our problems here on Earth. Cueball: Sounds reasonable. So, what's the timeline on "Solving all problems"? Ten years? Fifteen?

Many people are opposed to space exploration. While the overall budget of NASA is not very large compared to the big spenders such as health, education, social services and the military, individual space missions seem very expensive to the general public (typically hundreds of millions of dollars) and the actual benefits derived from them can seem intangible. To put it simply, many people think that the money can be better spent on Earth, where there are real, serious problems that need to be addressed. The decision on how to best allocate our money is not a simple one. White Hat believes we should not explore space until "we have solved all our problems here on Earth". This is unreasonable. It is vague, broad and near-impossible to achieve, at least within the span of a human life. The basic problems that face us all - war, disease, hunger, climate change, natural disasters, general malaise - have been with us since the dawn of humanity at least, and will certainly be around for much longer than ten or fifteen years; in fact, it is unclear if some of these problems will ever be solved. As of 2021, eight years after this comic, it seems humanity has rather created more problems than it solved, so it is very unlikely indeed that the goal of ten years could be reasonably achieved. Cueball, however, is playing the naive engineer, thinking that everything is as easy and simple as the math problems he uses everyday. Alternatively, he could be replying sarcastically, knowing that there is no timeline for solving all of Earth's problems. This serves two purposes: First, it highlights the untenability of White Hat's statement by emphasizing their size, and second, it serves as a punchline, as anyone with a modicum of common sense knows nothing is that simple when humans are involved. In the title text, Randall leans towards fifteen years, as ten doesn't seem sufficient, given all the problems. This also may be said by Cueball, or White Hat replying to Cueball. [Cueball and White Hat stand talking. White Hat is making a forward gesture with his hand.] White Hat: We shouldn't be exploring other planets until we've solved all our problems here on Earth. Cueball: Sounds reasonable. So, what's the timeline on "Solving all problems"? Ten years? Fifteen?

Relativity

Relativity

https://www.xkcd.com/1233

https://www.explainxkcd.com/wiki/index.php/1233:_Relativity

[We see a head and shoulders view of Einstein. He looks pensive.] [Einstein's "line" is in a thought bubble.] Einstein: If I were traveling at the speed of light, my butt would look awesome . Einstein was famed for his Gedankedank .

Gedankedank is a humorous portmanteau of Gedankenexperiment (German for " thought experiment ") and badonkadonk (slang term for an attractive, round butt ). Albert Einstein often used thought experiments to explore scientific hypotheses too impractical or impossible to actually perform, in order to examine their consequences. Moving close to the speed of light, c , is nigh-impossible with existing technology; and according to Einstein's theory of special relativity accelerating a mass exactly to c is impossible. Einstein is well known not to have cared about his appearance (e.g. his uncombed hair , the tongue photo, etc.) so it is unlikely that he pondered how relativistic velocity would affect the appearance of his butt. Lorentz contraction is a consequence of special relativity, whereby objects contract in the direction of travel. The appearance of rotation while moving close to the speed of light is known as Terrell rotation . The title text then connects this rotation to the Shakira song " Hips Don't Lie ". [We see a head and shoulders view of Einstein. He looks pensive.] [Einstein's "line" is in a thought bubble.] Einstein: If I were traveling at the speed of light, my butt would look awesome . Einstein was famed for his Gedankedank .

Douglas Engelbart (1925-2013)

Douglas Engelbart (1925-2013)

https://www.xkcd.com/1234

https://www.explainxkcd.com/wiki/index.php/1234:_Douglas_Engelbart_(1925-2013)

San Francisco, December 9th, 1968: [We see a figure talking into a headset. It's a fair assumption that it's Douglas Engelbart.] Douglas: ...We generated video signals with a cathode ray tube... We have a pointing device we call a "mouse"... I can "copy" text... ... and we have powerful joint file editing... underneath the file here we can exchange "direct messages"... [Douglas continues to narrate. Some music is playing.] Douglas: ...Users can share files... ... files which can encode audio samples, using our "masking codecs"... The file you're hearing now is one of my own compositions... Music: I heard there was a secret chord [Douglas continues to narrate.] Douglas: ...And you can superimpose text on the picture of the cat, like so... This cat is saying "YOLO", which stands for "You Only Live Once"... ...Just a little acronym we thought up...

The comic describes and references the engineer Douglas Engelbart's computer demonstration The Mother of All Demos in honor of Engelbart, who died on July 2, 2013. The demo is renowned for the numerous technologies Douglas' team introduced, which the comic references before sliding into apocryphal claims. In the first panel he presents various inventions, including the Computer Mouse . The second panel contains the opening lyrics of Leonard Cohen's song Hallelujah . The "Secret Chord" is a reference to the "Chord Key Set" that he presented at this demo. This relatively obscure device, essentially a piano with five keys, was meant as an alternative to the well-known keyboard. The way he introduces the song is also a reference to musical demo tapes , in which an artist presents a new piece of original music, tying it back to the Mother of All Demos title. The third is a reference to contemporary internet memes, specifically cat pictures and YOLO . The title text is a reference to recent revelations about spying by the United States National Security Agency , which was making headlines when this comic was published. While it might have seemed like an advantage at the time, in a modern context this aspect of the internet appears disturbing. Several of the inventions presented by Douglas in 1968 were years ahead of their time, and many would prove to be very influential in the development of personal computing. Some of the technologies demonstrated found success in the following decades, while others did not. Although the following technologies were shown in the demo, Munro's text does not follow a transcript . Cathode ray tube The German physicist Ferdinand Braun invented the Cathode ray tube , or CRT, in 1897. The Russian scientist Boris Rosing was the first to use the CRT to receive a video signal. CRT was the most common technology used for television screens and computer monitors in the last century, but has since been succeeded by modern devices such as OLED , plasma display , or the ubiquitous LCD . In the demo, Douglas used CRT monitors to demonstrate video conferencing, as well as collaborative real-time editing. Computer mouse Douglas did refer to this device as a "mouse", but officially it was named the "X-Y Position Indicator for a Display System". He filed a patent for this device on June 21, 1967 and received the patent on November 17, 1970. The demo transcript records that Douglas stated: "I don’t know why we call it a mouse...it started that way and we never did change it." Text movement/cloning This is well known today as "cut, copy and paste". On some early text-based systems, the user moved the cursor to the beginning of the text to be copied, typed <CTRL>+K+B , and then moved the cursor to the end of the copied text and typed <CTRL>+K+E. At the demo, Douglas demonstrated that the same task could be accomplished with the mouse. Today, many people do not use keyboard commands for cut, copy and paste, and instead use the mouse exclusively. Joint file editing Text editors were in the nascent stage of their development in 1968. Douglas demonstrated the first text editor capable of "joint file editing". The first successful system to implement joint file editing came 15 years later, when CVS was made available in the middle of the 1980's. E-mail Although not referred to as e-mail, Douglas demonstrated the exchange of "direct messages", which fulfills a similar role to modern e-mail. Nowadays, though, the name will be more familiar as the term for Twitter's private messaging function. File sharing The demo also demonstrated the exchange of files between users, paving the way for modern file sharing, and the associated legal and ethical debate. Audio codec Douglas demonstrated a "masking codec" capable of coding and decoding an audio stream. This would eventually lead to the development of the wide variety of modern audio codecs, including the MP3 codec, which was produced by the Fraunhofer Society . From the bottom of the second panel the comic exaggerates the idea that Douglas introduced the future to a hilarious and ridiculous level. "Hallelujah" This song was first released by Leonard Cohen in 1984, sixteen years after Douglas's demo. Image macros A form of image with large text, typically block capitals in the font "Impact", superimposed over a photograph, typically for humorous effect. LOLcats The most famous of the image macros, featuring cats. YOLO As the fictional Douglas states, this is an acronym for "you only live once". The phrase has been around for at least a century, but was coined as an acronym around 2011, and became a popular catchphrase following its use in the rap song "The Motto" by rapper Drake. San Francisco, December 9th, 1968: [We see a figure talking into a headset. It's a fair assumption that it's Douglas Engelbart.] Douglas: ...We generated video signals with a cathode ray tube... We have a pointing device we call a "mouse"... I can "copy" text... ... and we have powerful joint file editing... underneath the file here we can exchange "direct messages"... [Douglas continues to narrate. Some music is playing.] Douglas: ...Users can share files... ... files which can encode audio samples, using our "masking codecs"... The file you're hearing now is one of my own compositions... Music: I heard there was a secret chord [Douglas continues to narrate.] Douglas: ...And you can superimpose text on the picture of the cat, like so... This cat is saying "YOLO", which stands for "You Only Live Once"... ...Just a little acronym we thought up...

Settled

Settled

https://www.xkcd.com/1235

https://www.explainxkcd.com/wiki/index.php/1235:_Settled

[A graph with percentage from 0 to 100 on the Y-axis with three ticks with labels, top, middle and bottom. The X-axis is a timeline with years with labeled ticks at every five years interval from 1980 but also including a final tick at the year of release, 2013, which is written in a smaller font. The graph shown a red line that starts before 1980 at just above 0% and stays there through the 80s, rises a little past 1990 and reached 1-2% at around 2000, but then it rises rapidly to 10% at 2005, 75% at 2010, and around 90% at 2013, where the rise begins to flatten out asymptotically towards 100 %. There is a caption for what the Y-axis represents over the flat part of the curve:] Percentage of the US population carrying cameras everywhere they go, every waking moment of their lives: Y-axis labels: 100% 50% 0% X-axis labels: 1980 1985 1990 1995 2000 2005 2010 2013 [Caption below the panel:] In the last few years, with very little fanfare, we've conclusively settled the questions of flying saucers, lake monsters, ghosts, and Bigfoot.

Displayed is a timeline chart showing the percentage of people in the United States who have a camera at every moment. Randall refers to the fact that today most people carry embedded camera devices using their cell phones or the even more modern smartphones . The chart shows that after the 1980s the percentage increases rapidly, almost reaching 100% by 2013. The text below the image states that "We have conclusively settled the questions of flying saucers , lake monsters [such as the Loch Ness Monster ], ghosts , and Bigfoot ", implying that because almost everyone carries a camera the evidence should have arisen by now to settle any question about such phenomena. Of course, such evidence has not arisen — but that doesn't stop many people from continuing to believe the myths. But at least now it is hard to claim that you saw something, but didn't have a camera to capture it with. If something moved by so fast that you did not have time to take a picture, then it could also be questioned if you have time to see that it was a ghost etc. The title text declares that, in the case of ghosts, only the questions regarding phenomena that can be captured with a camera have been settled - leaving, in other words, ghosts that can't be seen, heard, or felt are essentially indistinguishable from an absence of ghosts. The title text also makes a joke about the ghosts of Ghostbusters , a popular film that featured highly visible and noisy ghosts which left a slime. If such ghosts existed, recording them would be very easy. [A graph with percentage from 0 to 100 on the Y-axis with three ticks with labels, top, middle and bottom. The X-axis is a timeline with years with labeled ticks at every five years interval from 1980 but also including a final tick at the year of release, 2013, which is written in a smaller font. The graph shown a red line that starts before 1980 at just above 0% and stays there through the 80s, rises a little past 1990 and reached 1-2% at around 2000, but then it rises rapidly to 10% at 2005, 75% at 2010, and around 90% at 2013, where the rise begins to flatten out asymptotically towards 100 %. There is a caption for what the Y-axis represents over the flat part of the curve:] Percentage of the US population carrying cameras everywhere they go, every waking moment of their lives: Y-axis labels: 100% 50% 0% X-axis labels: 1980 1985 1990 1995 2000 2005 2010 2013 [Caption below the panel:] In the last few years, with very little fanfare, we've conclusively settled the questions of flying saucers, lake monsters, ghosts, and Bigfoot.

Seashell

Seashell

https://www.xkcd.com/1236

https://www.explainxkcd.com/wiki/index.php/1236:_Seashell

[At the top of the panel is an equation showing Bayes' Theorem for the probability that a person is near the ocean given that they just picked up a seashell.] P(I'm near the ocean|I picked up a seashell) = P(I picked up a seashell|I'm near the ocean)P(I'm near the ocean) ------------------------------------------------------------------------------------------------ P(I picked up a seashell) [The probability that I'm near the ocean given I picked up a seashell equals the probability I picked up a seashell given I'm near the ocean times the probability I'm near the ocean all divided by the probability I picked up a seashell.] [Cueball holds a seashell and stands to the left of the panel, to the right, a few birds are flying around and the sound of a wave crashing against the shore is depicted.] Crashhh Sploosh Statistically speaking, if you pick up a seashell and don't hold it to your ear, you can probably hear the ocean. Note that while this form of Bayes's theorem is often taught in statistics classes, at least one statistician tries to show in a philosophical way that unconditional probability does not exist, which would make the equation improper as stated.

This method of relating the probabilities of two events is known as Bayes' Theorem . If you put a seashell up to your ear, you might hear a sound similar to the ocean apparently inside the shell. But the idea that this sound is actually the sound of the sea is just a popular myth: hold only your hands close to your ears and you will hear the same sound, as it is the sound of your blood moving through your blood vessels that causes the sound. The comic, through an application of Bayes' Theorem, points out that most of the time when you pick up a seashell, you are in fact at the beach next to the real ocean, so hearing the ocean at that location is not all that impressive, but it's just real. The equation should, however, be read as follows: (The probability that I'm near the ocean, given that I picked up a seashell) is equal to (The probability that I picked up a seashell, given that I'm near the ocean) multiplied by (The probability that I'm near the ocean) divided by (The probability that I picked up a seashell). The title text points out that most instances where the author has picked up a seashell have been at the beach, and nearly all of the times where he has picked up a seashell and not put it to his ear have been there. This comic was released late. In the first version, the formula was incorrect, but it has since been corrected. [At the top of the panel is an equation showing Bayes' Theorem for the probability that a person is near the ocean given that they just picked up a seashell.] P(I'm near the ocean|I picked up a seashell) = P(I picked up a seashell|I'm near the ocean)P(I'm near the ocean) ------------------------------------------------------------------------------------------------ P(I picked up a seashell) [The probability that I'm near the ocean given I picked up a seashell equals the probability I picked up a seashell given I'm near the ocean times the probability I'm near the ocean all divided by the probability I picked up a seashell.] [Cueball holds a seashell and stands to the left of the panel, to the right, a few birds are flying around and the sound of a wave crashing against the shore is depicted.] Crashhh Sploosh Statistically speaking, if you pick up a seashell and don't hold it to your ear, you can probably hear the ocean. Note that while this form of Bayes's theorem is often taught in statistics classes, at least one statistician tries to show in a philosophical way that unconditional probability does not exist, which would make the equation improper as stated.

QR Code

QR Code

https://www.xkcd.com/1237

https://www.explainxkcd.com/wiki/index.php/1237:_QR_Code

[A smartphone. On the display, the following text:] "To continue installing, scan this code. 12 seconds remaining" [A particularly recursive QR code is displayed on the screen.] [Caption below the panel:] How to freak out a mobile app user.

QR codes (quick response codes) are a type of 2D barcode that can be scanned using any of several apps on a smartphone. This comic illustrates installation of a new application that requires the smartphone to scan a QR code on its own screen. There is no conceivable purpose for such a step, so it would be completely silly. Even with two mirrors or a front-facing camera and mirror, most smartphones would be unable to simultaneously display the camera feed for the QR scanner and the QR code itself. The only way to do it would be to take a picture of the QR code with a digital camera and then scan the screen of the camera. The "12 seconds remaining" part indicates that there is a time limit for this, and thus a quick response is necessary. If scanned, the QR code in the comic reads http://xkcd.com/1237/scan/ , a link to a nearly identical image, but the line above the QR code reads, "To continue reading," and the caption reads, "How to trap a webcomic reader in an infinite loop". The QR code is identical to the previous one. So, if scanned again, it would simply return the scanner to the same image in an "infinite loop". [A smartphone. On the display, the following text:] "To continue installing, scan this code. 12 seconds remaining" [A particularly recursive QR code is displayed on the screen.] [Caption below the panel:] How to freak out a mobile app user.

Enlightenment

Enlightenment

https://www.xkcd.com/1238

https://www.explainxkcd.com/wiki/index.php/1238:_Enlightenment

[The two Internet Bodhisattvas Ponytail and Cueball lecture Megan encircled by a wheel placed upon the ground.] Ponytail: To achieve internet enlightenment , you must free yourself from insecurity. Megan: But insecurity keeps me humble! [Ponytail continues talking.] Ponytail: No. Insecurity leads to conceit. Conceit leads to judgment. Ponytail: Judgment leads to being an asshole. [A laptop is placed on a stand in front of Megan.] Megan: I'm ready. How do I begin? Ponytail: Type this sentence. [White text on black background.] I heard you're idea's and their definately good. [The laptop has been smashed to the floor. Megan is no longer in the circle.] Ponytail: She wasnt ready. Cueball: Its a difficult road.

This comic is a reference to a scene one might imagine in Star Wars Episode I: The Phantom Menace in which Yoda expresses doubt in a young Anakin 's potential to join the Jedi order. Yoda delivers a speech similar to the one that Ponytail gives here, except that the end of the sequence he presents is " the dark side " instead of "being an asshole". Yoda is ultimately correct; Anakin's fears lead him to join the dark side so that he may keep his loved ones from dying; this is at the expense of the stability of the galaxy, however, and his actions are in vain, as his wife dies nonetheless. The circle on the ground is also taken from the Star Wars scene, and Cueball is presumably in the Mace Windu role. Here, Randall compares Anakin's decision to join the dark side to the propensity of many Internet commenters to correct others on their spelling and grammar, and to the extreme prevalence of criticism over commendation or confirmation. Randall's point is that correcting people, like joining the dark side, ultimately stems from insecurity. Ponytail and Cueball challenge Megan to type the sentence "I heard you're idea's and their definately good", which contains four common misspellings ( you 're instead of you r , idea ' s instead of ideas [see greengrocers' apostrophe ], the ir instead of the y're , and defin a tely instead of defin i tely ), a misapplied verb ("heard" instead of "read"), and a grammatical error ( a missing comma [1] before the word "and"). Regarding the content, this sentence is one that is highly unlikely to be ever read in an internet argument, as almost every time people still have things they claim to know better about. Megan thus can't bring herself to typing this sentence, having spent so much time judging others for their trivial errors, even when they're saying helpful things like the sentence in question. Instead, it is strongly implied that she smashes the computer and runs away — demonstrating the sort of anger that "Grammar Nazis" and internet wiseacres like her can feel about punctuation and spelling errors, and about content-related errors respectively. Cueball and Ponytail remark on this, both failing to use apostrophes . The title text refers to Terry Pratchett 's novel Equal Rites , in which the characters discover that the most powerful magic is not using magic — with the distinction that not using magic because you don't know how is not the same as choosing to refrain from using magic when you do know how. Randall is comparing this with use or misuse of the rules of Standard English: not even knowing the rules is not admirable, whereas knowing the rules but choosing to disregard them is. There is also a double meaning - not writing anything at all is in fact "saying nothing". [The two Internet Bodhisattvas Ponytail and Cueball lecture Megan encircled by a wheel placed upon the ground.] Ponytail: To achieve internet enlightenment , you must free yourself from insecurity. Megan: But insecurity keeps me humble! [Ponytail continues talking.] Ponytail: No. Insecurity leads to conceit. Conceit leads to judgment. Ponytail: Judgment leads to being an asshole. [A laptop is placed on a stand in front of Megan.] Megan: I'm ready. How do I begin? Ponytail: Type this sentence. [White text on black background.] I heard you're idea's and their definately good. [The laptop has been smashed to the floor. Megan is no longer in the circle.] Ponytail: She wasnt ready. Cueball: Its a difficult road.

Social Media

Social Media

https://www.xkcd.com/1239

https://www.explainxkcd.com/wiki/index.php/1239:_Social_Media

[Cueball heads a press conference.] Cueball: NASA has confirmed that the asteroid is heading directly for us. Cueball: ...Yes, a question? Reporter 1: What role has social media played in this asteroid's orbit? Cueball: * sigh * Reporter 2: Has Twitter changed the way we respond to asteroid threats? Cueball: Well, it's made the press conference questions stupider. Reporter 3: Fascinating! Reporter 4: What about Facebook?

This comic parodies how journalists tend to focus on social networking. Specifically in the case of revolutions, social media is given a lot of weight, even in countries with limited internet access. A direct parallel is made to the so-called Twitter Revolutions . On Twitter you can send text messages with a maximum of 280 characters (140 at the time of writing). This means that there could not be much content in a single post, but often many people follow the people doing these tweets . People who are not on social media tend to react like Cueball and come to the conclusion that Twitter makes press coverage more stupid, just because those messages lack much detail. Cueball is also surprised about the stupidity of trying to link social media to the orbit of the asteroid — social media has no impact on the orbit of any space objects. [ citation needed ] The title text continues the joke. The negativity on Twitter concerning an Earth-bound asteroid has nothing to do with the press conference that announced it but rather with the negativity of wiping out life on earth in general. Again, journalists give undue weight to social media. It's simply that "How has Twitter affected this" has become a standard question for journalists, posed in complete disregard of the actual event. [Cueball heads a press conference.] Cueball: NASA has confirmed that the asteroid is heading directly for us. Cueball: ...Yes, a question? Reporter 1: What role has social media played in this asteroid's orbit? Cueball: * sigh * Reporter 2: Has Twitter changed the way we respond to asteroid threats? Cueball: Well, it's made the press conference questions stupider. Reporter 3: Fascinating! Reporter 4: What about Facebook?

Quantum Mechanics

Quantum Mechanics

https://www.xkcd.com/1240

https://www.explainxkcd.com/wiki/index.php/1240:_Quantum_Mechanics

[Cueball and Ponytail stand facing each other, talking. Cueball has a small dog on a leash.] Cueball: But dogs can observe the world, which means that according to quantum mechanics they must have souls. [Caption below the frame:] Protip : You can safely ignore any sentence that includes the phrase "According to quantum mechanics". Anyone who is not shocked by quantum theory has not understood it.

This comic plays with the fact that quantum mechanics is a very complex subject that is frequently misapplied by laymen. Many of the phenomena studied in quantum mechanics are contrary to common sense and can only be expressed in complex mathematics. Yet, since the field is fundamental to our understanding of reality, it is commonly cited to support broad sweeping philosophical generalizations. The phrase “according to quantum mechanics” betrays the speaker's lack of knowledge about the subject. To a physicist, it is almost as vague as “according to physics”. Somebody who understands the subject would use a more precise term, such as “according to the uncertainty principle” or “according to a paper by such-and-such.” Cueball explains to Ponytail that dogs must have souls . This would be against the doctrine of certain religions, including some sects of Christianity, which teach that only humans have souls. The question of whether animals have souls comes up for many reasons in theological and philosophical discussions. One major one is the wish of many dog owners to meet their pets in Heaven . For this to come to pass, it would be necessary for dogs not only to have souls, but also immortal souls. This distinction comes up in Catholicism, for example, where the commonly taught doctrine, as in Aquinas, S.C.G. II, C. 82 , is that, while animals do have souls, their souls are mortal, and therefore die with their bodies. In this case, animals cannot enter Heaven, Hell , or Purgatory . Cueball, however, uses quantum mechanics as an argument, even though quantum mechanics is only applicable on the atomic scale and not on macroscopic objects like animals. It also only applies to matter and energy, and not to souls, which are held by most doctrines to be immaterial. His argument, however, is a reference to the concept of an ' observer ' in quantum physics, as well as theories about the collapse of wave functions . It should also be noted that science does not equate the ability to observe the world and possession of a soul, and that the latter is merely a theological concept, not used in science and not proven to exist in real world. The vast majority of people do not have a sufficient understanding of quantum mechanics to judge whether Cueball's statement is correct. Nevertheless, Randall's message is: you don't need to understand quantum mechanics to judge the statement. No matter what the sentence is, it is almost certainly incorrect, so “you can safely ignore” it. The title text refers to “science assertions” — that is, claims about scientific knowledge — that include the words “quantum mechanics”. If “quantum mechanics” is the most complicated term in the sentence, then the speaker probably does not know what they are talking about. If a scientist is correctly applying quantum mechanics, they will use more specific (and hence more complicated) language. [Cueball and Ponytail stand facing each other, talking. Cueball has a small dog on a leash.] Cueball: But dogs can observe the world, which means that according to quantum mechanics they must have souls. [Caption below the frame:] Protip : You can safely ignore any sentence that includes the phrase "According to quantum mechanics". Anyone who is not shocked by quantum theory has not understood it.

Annoying Ringtone Champion

Annoying Ringtone Champion

https://www.xkcd.com/1241

https://www.explainxkcd.com/wiki/index.php/1241:_Annoying_Ringtone_Champion

[At the top of the frame is an annoying humming tone shown. Cueball is cringing while raising his arms above his head. Black Hat pulls out his phone looking at it.] Ringtone: h MM M MM M M M M M MM MM M MMM Cueball: Augh! Black Hat: Oh, I've gotta take this. [Caption below the frame:] By unanimous decision, the winner of the Awful Ringtone Championship is "the sound a mosquito makes as it buzzes past your ear".

This comic satirizes the large variety of ringtones that may be used on their cell phones. While many are simply tunes that personalize a user's phone, some will use ringtones that resemble everyday sounds, such as doorbells, coughing, alarm noises, or in this case, the buzzing of a mosquito. Although rather innocuous, these ringtones can get very annoying to some people, which is what this comic is getting at. Here, Black Hat has set his ringtone to "The sound a mosquito makes as it buzzes past your ear", the winner of the "Awful Ringtone Championship". Cueball , hearing the sound, cries out and swats the air around his head, mistaking the ringtone for an actual mosquito buzzing past his ear. In addition to being an extremely unpleasant sound, it could also cause confusion to others, as shown in the comic, thus being unanimously decided as the most annoying ringtone. Black Hat 's response is likely a pun meaning both "Oh, I've got to take this [call]" (like someone who has been interrupted by a phone call) and need to leave and respond and "Oh, I've got to take this [competition]" since the ringtone is so annoying. The title text refers to four other annoying ringtones, apparently none of which were deemed as annoying as a mosquito buzzing: [At the top of the frame is an annoying humming tone shown. Cueball is cringing while raising his arms above his head. Black Hat pulls out his phone looking at it.] Ringtone: h MM M MM M M M M M MM MM M MMM Cueball: Augh! Black Hat: Oh, I've gotta take this. [Caption below the frame:] By unanimous decision, the winner of the Awful Ringtone Championship is "the sound a mosquito makes as it buzzes past your ear".

Scary Names

Scary Names

https://www.xkcd.com/1242

https://www.explainxkcd.com/wiki/index.php/1242:_Scary_Names

[A scatter-plot, with 12 labeled dots. Both axis are labeled but neither has an arrow at its end. The dots are scattered from left to right and top to bottom. Below all labels are given, first for the axis, and then for each dot in approximately normal reading order, left to right top to bottom, but in the order it would make sense to read them:] Y-axis: Scariness of name X-axis: Scariness of thing name refers to [Top left]: Chernobyl packet [Top halfway right]: Kessler syndrome [Top three quarters towards right]: Demon core [Top right]: Flesh-eating bacteria [A third down left]: Bomb calorimeter [Halfway down three quarters towards right]: Bird flu [Halfway down right]: Nuclear football [Dead center]: Mustard gas [Just below and right of center]: Superbug [Bottom halfway right]: Soil liquefaction [A third up three quarters towards right ]: Criticality incident [Very bottom two-thirds to the right]: Grey goo

This chart humorously explores how things are often named colloquially and without regard to accuracy in correlating actual scariness with apparent scariness. It is interesting to note how people react to the items near the bottom right of the chart "scary things with not-very-scary names" when compared to how they may react to items in the upper left "not-very-scary things with scary names". Some of the entries on the chart are especially interesting examples considering that portions of the names that are associated with significant historical or cultural events and themes. i.e. Chernobyl Packet, Demon Core. All items are described in the table below including the title text on Helvetica Scenario. On the chart, things toward the right are scary/dangerous/very bad, while things toward the top sound scary without necessarily being scary. Note that Randall uses similar diagrams in both 388: Fuck Grapefruit , 1501: Mysteries and 2466: In Your Classroom , which also contain different items. The first two also have an extra point, and the last two extra points mentioned in the title text. Only the first and the last comics points are also off the chart, whereas for the second the description of the point is too long to fit on the chart. Extra info outside the chart is also used in the title text of 1785: Wifi , but this is a line graph. [A scatter-plot, with 12 labeled dots. Both axis are labeled but neither has an arrow at its end. The dots are scattered from left to right and top to bottom. Below all labels are given, first for the axis, and then for each dot in approximately normal reading order, left to right top to bottom, but in the order it would make sense to read them:] Y-axis: Scariness of name X-axis: Scariness of thing name refers to [Top left]: Chernobyl packet [Top halfway right]: Kessler syndrome [Top three quarters towards right]: Demon core [Top right]: Flesh-eating bacteria [A third down left]: Bomb calorimeter [Halfway down three quarters towards right]: Bird flu [Halfway down right]: Nuclear football [Dead center]: Mustard gas [Just below and right of center]: Superbug [Bottom halfway right]: Soil liquefaction [A third up three quarters towards right ]: Criticality incident [Very bottom two-thirds to the right]: Grey goo

Snare

Snare

https://www.xkcd.com/1243

https://www.explainxkcd.com/wiki/index.php/1243:_Snare

[Cueball is talking to Black Hat. Black Hat is using a laptop.] Cueball: They said on the news that they found a giant ring lying in a field outside Chicago. Strung with some kind of superstrong mesh. Black Hat: Mhm? Cueball: Then they found a 260 mile long shaft connected to the ring, running from Chicago to St. Louis. In St. Louis they found a gigantic winch. Black Hat: Did they. Cueball: It sounds kind of like... Cueball: ...a butterfly net. Cueball: ...are you planning on catching the International Space Station? Black Hat: I'm planning to catch an international space station. Black Hat: Not sayin' which.

This comic paints another one of Black Hat 's evil activities as an unlikely supervillain. As Cueball states, there have been some strange discoveries in the news including a gigantic ring strung with superstrong mesh, a long pole, and a gigantic winch . As Cueball outlines these items, Black Hat responds casually to each detail, seeming preoccupied with his computer. Cueball realizes that the pole, ring and net combination sounds like a butterfly net , albeit one of immense size. Given Black Hat's history of nefarious activities and the specific length of the pole (260 miles or 420 km, the same as the height of the International Space Station's orbit above Earth), Cueball infers and then accuses Black Hat of wanting to catch the International Space Station (ISS) by winching the pole up so that the Space Station orbit leads it to fly into the net, therefore catching it. Black Hat does not deny the charge, but he dissimulates by saying it is not necessarily the ISS that he intends to catch, but just an international space station. While his statement implies that it could be targeted at some other international space station, it is transparently obvious which one he is targeting since there's only one international space station in existence. [ citation needed ] Any international space station that he can catch must be the ISS. (As for non-international space stations, the only one in orbit at the time of the comic’s publication was the Chinese Tiangong-1 , which has since deorbited.) The title text is a reference to how butterfly collections are usually presented. The insects are mounted in glass display cases, each skewered through the body with a pin, and labeled. The text is spoken by Black Hat, who again tries to imply that he is not to blame, as it may not be meant for his collection of satellites. Perhaps he is just catching a space station for a friend. The real buildings may belong to these structures: [Cueball is talking to Black Hat. Black Hat is using a laptop.] Cueball: They said on the news that they found a giant ring lying in a field outside Chicago. Strung with some kind of superstrong mesh. Black Hat: Mhm? Cueball: Then they found a 260 mile long shaft connected to the ring, running from Chicago to St. Louis. In St. Louis they found a gigantic winch. Black Hat: Did they. Cueball: It sounds kind of like... Cueball: ...a butterfly net. Cueball: ...are you planning on catching the International Space Station? Black Hat: I'm planning to catch an international space station. Black Hat: Not sayin' which.

Six Words

Six Words

https://www.xkcd.com/1244

https://www.explainxkcd.com/wiki/index.php/1244:_Six_Words

[Caption above the frame:] The six words you never say at NASA: [A diagram shows a possible trajectory path for a space probe starting at Earth and involving two slingshots around two other planets, and finally the Sun. There is a title above and a label beneath the diagram. The diagram is being presented by Cueball in front of three other Cueball-like guys. Behind Cueball Ponytail appears to be taken by surprise by his six words, and holds her hand to her mouth.] Title: Proposal: Label: Oberth Kuiper Maneuver Cueball: And besides— Cueball: It works in Kerbal Space Program.

The six words are: "It works in Kerbal Space Program ". The Kuiper Belt is a region of the outer Solar System beyond the orbit of Neptune consisting of numerous small icy bodies, including the dwarf planets Pluto and Eris . An Oberth maneuver is a spaceflight maneuver, specifically an engine burn performed during the flyby of a celestial body. The point of this is to optimize usable energy, because rocket burns are more effective to perform at high speeds than at low speeds. The more massive the body and the lower the altitude, the higher the flyby speed will be, and the greater the performance gain due to the Oberth effect. The theoretical way to use rocket fuel most efficiently is therefore to execute the burn during a flyby of the most massive celestial body available, as close as possible. Cueball is proposing to implement an "Oberth Kuiper Maneuver", and the proposal diagram shows the spacecraft using gravity assists to travel first towards (presumably) Venus for a first boost, then towards Jupiter for another swing by, aiming it back towards the Sun , the most massive Solar System body, to perform an Oberth maneuver at the point of closest approach, as indicated by a small dot along the spacecraft trajectory. It is possible that the diagram might only be a simplified outline of a more complex flight plan. For example, the trajectory from Earth to Venus would require two separate burns in deep space. The first burn would occur immediately after escaping Earth's sphere of influence. The second burn would occur about halfway to Venus. Alternatively, Cueball may have gotten it wrong, or Randall may simply not have concerned himself with such things for the purpose of a webcomic sketch. An Oberth maneuver in the close vicinity of the Sun, while theoretically possible and extraordinarily effective at the speeds the spacecraft would reach, would however be very difficult to carry out in real life, because the neighborhood of the Sun is an extremely hostile environment [ citation needed ] and the spacecraft could be incinerated during a too-close flyby. Cueball's argument for why the maneuver will work in real life is that it works in Kerbal Space Program (KSP), a sandbox spaceflight simulator game. While KSP does simulate a lot of the physics of space flight, it is (necessarily) simplistic in its modeling of orbital dynamics. For example, KSP does not do any N-body simulations , so if one were flying a rocket from Earth to the moon, in the game the rocket would only be affected by Earth's gravity until it reaches a certain point where it will only be affected by the moon's gravity, unlike in real life where the rocket would feel the effects of both celestial bodies at all times. Therefore, orbits modeled using KSP would poorly reflect the actual orbital behavior of a probe traveling through the solar system on a multi-year mission involving multiple fly-by maneuvers. Another reason why using KSP would not inspire confidence is that many players playing the game use a 'trial-and-error' method, field testing designs and inevitably either crashing them or running out of fuel stranding the craft in deep space. Inside a game this is not a major issue as one can simply reload an earlier save with no repurcussions, but in real life this would result in expensive costs constructing new spacecraft and even loss of human life, which NASA would likely frown on. The humor in referencing KSP in the comic lies in using a simple game program to simulate complex space missions which in reality take a great number of experts to plan and implement. Fly-by maneuvers, used to minimize the fuel needed to reach a destination, need to be very carefully timed - often to within seconds - so the use of Kerbal Space Program to simulate them isn't a good enough argument for NASA to agree to implement the proposal, and implies simplistic thinking on the part of the proposer; therefore one should not say it at NASA. The title text refers to Orbiter , which is another spaceflight simulator program. The title text suggests that the argument doesn't work for NASA, not because it's not scientifically sound, but because NASA relies on the Orbiter simulator rather than the Kerbal simulator (although the proposed maneuver would appear to work in both). [Caption above the frame:] The six words you never say at NASA: [A diagram shows a possible trajectory path for a space probe starting at Earth and involving two slingshots around two other planets, and finally the Sun. There is a title above and a label beneath the diagram. The diagram is being presented by Cueball in front of three other Cueball-like guys. Behind Cueball Ponytail appears to be taken by surprise by his six words, and holds her hand to her mouth.] Title: Proposal: Label: Oberth Kuiper Maneuver Cueball: And besides— Cueball: It works in Kerbal Space Program.

10-Day Forecast

10-Day Forecast

https://www.xkcd.com/1245

https://www.explainxkcd.com/wiki/index.php/1245:_10-Day_Forecast

[Cueball sits behind a computer desk when Megan calls to him.] Megan (off-panel): Is it going to rain this weekend? I have a thing. Cueball: Lemme check. *type type* Cueball: ...Uhh. What? [A caption is written above ten small panels in two rows. In each panel is an indication of the weather. Below each panel a label tells which day it is referring too.] Your 10-day forecast: [A yellow sun.] Today [Two gray clouds in front of the sun.] Tomorrow [Thunderstorms, with three gray clouds and a single lightning bolt.] Friday [Extreme thunderstorms with many large gray clouds and seven lightning bolts] Saturday [A swarm of insects, with one large black one close by and seven others close enough to discern details. The rest of the swarm is grayed out and just shown as small dots behind these other eight insects.] Sunday [Images of distorted people with very long legs. One Megan, one Cueball and someone in the background.] Monday [A humanoid figure with two large horns or a winged helmet silhouetted against a bleak red background. The ground beneath the figure is black.] Tuesday [Grey static] Tuesday [Black screen] Tuesday [Black screen] Tuesday [Megan has entered the panel and stands behind Cueball looking at his laptop over his shoulder. She points to the screen. Cueball holds his hand to his chest.] Megan: ...Oh! You typed a minus sign in the ZIP code. The negative ZIP codes are all like that. Cueball: Let's never move there.

The 10-day forecast is a prediction of the weather extending 10 days into the future (with the accuracy decreasing exponentially). However, when Cueball checks the forecast for his local area, it apparently predicts progressively extreme lightning storms, a plague of insects which appear to be locusts, what appears to be The Rapture , and the appearance of a demon-like creature. Upon the arrival of the creature (or perhaps The Antichrist , Woden , or Mothra ) appearing, the forecast falls into static and nothingness with the day stuck on Tuesday, meaning that the world has ended. When asked about this, Megan casually explains that Cueball put a minus (-) sign in front of his ZIP code. A ZIP code is a numeric postal code used in the United States, but many more countries use similar systems. As ZIP codes are tied to a geographic location, it is also often used to specify a local region for the purposes of weather reports. Many computer systems that let the user write in a number only work with certain numbers (such as positive numbers). Numbers the system is not designed to work with, such as negative numbers, may lead to errors or unpredictable behavior (or, more often, the system will just refuse to proceed until you input a valid number). When this happens with the number of a video game level, it can result in data of another type being loaded, creating a level with a corrupted or physically-impossible landscape; this is sometimes known as a " Minus World ". Megan states that you get this result for any negative zip code. This may be an error deliberately put in by the programmers creating the system, to freak out any people who make a mistake. Cueball, on the other hand reacts as if this negative zip code actually represents an actual geographical location, or a real-life Minus World, and that the weather forecaster is indeed showing an accurate forecast for the (corrupted) area. Since Megan stated that the forecast is always like that for these zip code Cueball expresses that he would never move there. In the title text, Megan agrees with Cueball's desire not to move to that ZIP code area, the punchline being that her reason isn't to avoid the apocalypse, but to retain access to Amazon Prime, which shows that her priorities are amusingly bizarre. The service Amazon Prime is provided by Amazon , where the user pays a flat annual fee and in exchange they get access a number of "enhanced" Amazon services, including free two-day shipping, free access to a library of streaming videos, and the ability to borrow books. Later, a Five-Day Forecast was also made into a comic. [Cueball sits behind a computer desk when Megan calls to him.] Megan (off-panel): Is it going to rain this weekend? I have a thing. Cueball: Lemme check. *type type* Cueball: ...Uhh. What? [A caption is written above ten small panels in two rows. In each panel is an indication of the weather. Below each panel a label tells which day it is referring too.] Your 10-day forecast: [A yellow sun.] Today [Two gray clouds in front of the sun.] Tomorrow [Thunderstorms, with three gray clouds and a single lightning bolt.] Friday [Extreme thunderstorms with many large gray clouds and seven lightning bolts] Saturday [A swarm of insects, with one large black one close by and seven others close enough to discern details. The rest of the swarm is grayed out and just shown as small dots behind these other eight insects.] Sunday [Images of distorted people with very long legs. One Megan, one Cueball and someone in the background.] Monday [A humanoid figure with two large horns or a winged helmet silhouetted against a bleak red background. The ground beneath the figure is black.] Tuesday [Grey static] Tuesday [Black screen] Tuesday [Black screen] Tuesday [Megan has entered the panel and stands behind Cueball looking at his laptop over his shoulder. She points to the screen. Cueball holds his hand to his chest.] Megan: ...Oh! You typed a minus sign in the ZIP code. The negative ZIP codes are all like that. Cueball: Let's never move there.

Pale Blue Dot

Pale Blue Dot

https://www.xkcd.com/1246

https://www.explainxkcd.com/wiki/index.php/1246:_Pale_Blue_Dot

[Cueball stands in front of a large gray picture of the Pale Blue Dot . (There is no evidence that there is any blue in this comic). He holds up a stick with one hand towards it. He is interrupted by several hecklers from off-panel.] Cueball: Consider this Pale Blue Dot. That's here. That's home. That's us. Everyone you love, every human being who ever was, every saint and sinner in the history of our species lived out their lives on this mote of dust suspended in a sunbeam. All our- Heckler 1 (off panel): I think that's a stuck pixel. We're the speck on the left. Cueball: ...Ok, this Pale Blue Dot is everything you- Heckler 2 (off panel): No, you were right before. That one is earth. Cueball: Look, it doesn't matter! Heckler 3 (off panel): I knew it! Heckler 4 (off panel): I think this is just a lens cap picture.

The Pale Blue Dot is a picture of the Earth taken in the year 1990 by the Voyager 1 space probe at a distance about 6 billion kilometers (3.7 billion miles). It was part of the Family Portrait , a series of images of the entire Solar System from beyond it. The picture was taken at the request of Carl Sagan , a well known space scientist at that time. In 1994 Sagan wrote the book " Pale Blue Dot: A Vision of the Human Future in Space " inspired by this picture. In the book, Sagan waxed eloquent about the picture in a widely quoted passage. The complete passage can be found in Wikiquote , and you can hear Carl Sagan himself reciting it in this YouTube video . Cueball quotes from a condensed version of this passage until he is interrupted by several Hecklers who begins an argument over which speck in the picture is actually the Earth. Then, when Cueball cries out in exasperation that it doesn't matter, one heckler takes it the wrong way and points out that he just said that the picture doesn't matter. This pokes fun at the fact that the Pale Blue Dot picture has very little to no visual attractiveness, apart from the intellectual interest relying on the viewer's knowledge that the central speck is actually our home planet, Earth, seen from a very great distance. The first two sentences of the title text are also a quotation from Sagan's paean to the Pale Blue Dot picture, but then the text veers humorously into non-scientific mysticism that starkly contrasts with the attitude and intent of the original work. The title text evokes Cosmicism , a philosophy developed and exemplified by the fictional Cthulhu Mythos . This Mythos is expounded in fantasy/horror works of H.P. Lovecraft and, later, August Derleth, and features a cosmology in which humanity is depicted as inconsequential within a greater existence that is unknowable and frightening. Cosmicism asserts that humanity is doomed to death and destruction through the workings of vastly more powerful supernatural forces way beyond our understanding. There are many instances in the fiction of H.P. Lovecraft of factions that embrace the destruction of humanity and actively work towards bringing about that end through the invocation of the unknowable and powerful forces that supporters of Cosmicism believe surround everything. The text also references Ba'al , originally a Semitic deity that has been since associated with demonic or otherwise evil forces. The name Ba'al, and other variants of the same, has been included in many other fictional works often as a villain or antagonist. For example, the fictional System Lord Ba'al from the television show Stargate . The title text supplants all of the supernatural forces associated with Cosmicism in the works of other authors with Ba'al. Cueball, who continues his discourse in the title text, may be acting as a Cosmicist and is calling on a Congress, to which he is speaking, to fund the space exploration program as a means to join with Ba'al, the Eater of Souls. The fact that a Ba'al cultist would be speaking in front of a government body in such a manner is absurd [ citation needed ] and thus hilarious. Ba'al, the Eater of Souls (sometimes as Ba'al the soul eater) has been mentioned later in 1419: On the Phone and 1638: Backslashes . [Cueball stands in front of a large gray picture of the Pale Blue Dot . (There is no evidence that there is any blue in this comic). He holds up a stick with one hand towards it. He is interrupted by several hecklers from off-panel.] Cueball: Consider this Pale Blue Dot. That's here. That's home. That's us. Everyone you love, every human being who ever was, every saint and sinner in the history of our species lived out their lives on this mote of dust suspended in a sunbeam. All our- Heckler 1 (off panel): I think that's a stuck pixel. We're the speck on the left. Cueball: ...Ok, this Pale Blue Dot is everything you- Heckler 2 (off panel): No, you were right before. That one is earth. Cueball: Look, it doesn't matter! Heckler 3 (off panel): I knew it! Heckler 4 (off panel): I think this is just a lens cap picture.

The Mother of All Suspicious Files

The Mother of All Suspicious Files

https://www.xkcd.com/1247

https://www.explainxkcd.com/wiki/index.php/1247:_The_Mother_of_All_Suspicious_Files

[Browser download warning box containing the following text.] WARNING! This type of file can harm your computer! Are you sure you want to download: http://65.222.202.53/~TILDE/PUB/CIA-BIN/ETC/INIT.DLL?FILE=__AUTOEXEC.BAT.MY%20OSX%20DOCUMENTS-INSTALL.EXE.RAR.INI.TAR.DOÇX.PHPHPHP.XHTML.TML.XTL.TXXT.0DAY.HACK.ERS_(1995)_BLURAY_CAM-XVID.EXE.TAR.[SCR].LISP.MSI.LNK.ZDA.GNN.WRBT.OBJ.O.H.SWF.DPKG.APP.ZIP.TAR.TAR.CO.GZ.A.OUT.EXE [Cancel and Save buttons (Save button disabled)]

The save dialog box shows a download from the address http://65.222.202.53 , an IP address that hosted JavaScript malware during a recent attack on the Tor anonymity network , with a very long file title. Many of the extensions used inside there indicate executable code; multiple file extensions are sometimes used to disguise a trojan program as a document. You can also see common download syntax for a pirated movie, Hackers , likely included to appear malicious to anyone skimming but is actually a movie about hackers, making it a benign reference rather than malicious. It is described as " _BLURAY_CAM ", which contradicts itself (" _BLURAY " would imply it was ripped from a copy on Blu-ray Disc , while " _CAM " would mean it was copied by pointing a camera at the screen in the cinema). " _BLURAY_CAM " would probably indicate a search-keyword-stuffed fake copy; fake pirated media often contain viruses (although this is more likely to be a problem with newer media, before the first real pirated copy appears). The URL contains the path " ~tilde/pub/cia-bin/etc ". The first part is a public folder of a user named "tilde" (which is also the name for the ~ symbol ), " cgi-bin " is a common folder on a web server for server-side executables ( Randall changes the name to " cia -bin "), and " etc " is a standard folder for configuration files – normally never accessible through a web server. The program "init.dll" isn't executable at all, it's a Windows Dynamic Link Library which can't be run standalone, and is rarely referenced in URLs (even though such syntax is still being employed, even on reputable websites (Google search) or here at eBay , indicating the webserver is a Microsoft ASP server). The question mark indicates the start of a parameter list, and in this case we have only one named " FILE ". The "Save" button is greyed out, suggesting that it is disabled; you can click only the "Cancel" button. For security reasons, some browsers (like Firefox) disable the "Save" button for a few seconds before enabling it. This prevents users from accidentally accepting a download while entering input, like a malicious CAPTCHA. The complete content sent to the server, starting with " /~tilde... " and ending with " ...out.exe ", is exactly 256 characters long. On HTML 3 specifications you have a limitation of 1024 characters, whereas later HTML specifications don't have this limit; it just depends on the web server's capabilities. But posting parameters directly at the URL is still a worse choice. The content of the parameter is shown here: The title text suggests changing from http to https , as if encrypting a suspicious file before downloading it is somehow better than downloading it unencrypted. http (Hypertext Transfer Protocol) and https (Hypertext Transfer Protocol – Secure) are the two common protocols for getting web pages and web downloads. http is the simple download, whereas https adds an SSL encryption layer so the item being downloaded cannot be viewed unencrypted by anyone except the end recipient. Changing http to https is a common suggestion to improve security when browsing the web from an insecure network (such as a public WiFi hotspot) to avoid surveillance or hijacking to a malicious website; Google automatically switches to https for all mail accounts and is starting to do so with searches. The end recipient will still get whatever nasties were in the original, however — encrypting it doesn't change the content at all. The IP address referenced in the comic, 65.222.202.53 , was, at the time this article was authored, being used by the shellcode of a JavaScript zero-day exploit for the Tor Browser Bundle being run by the FBI to phone home over the clearnet [1] and deanonymize visitors to websites on Freedom Hosting that are serving child pornography. [2] As the last extension in the file is .exe, a Windows computer would run the file like an application. Usually, it is not safe to run unknown .exe files. [Browser download warning box containing the following text.] WARNING! This type of file can harm your computer! Are you sure you want to download: http://65.222.202.53/~TILDE/PUB/CIA-BIN/ETC/INIT.DLL?FILE=__AUTOEXEC.BAT.MY%20OSX%20DOCUMENTS-INSTALL.EXE.RAR.INI.TAR.DOÇX.PHPHPHP.XHTML.TML.XTL.TXXT.0DAY.HACK.ERS_(1995)_BLURAY_CAM-XVID.EXE.TAR.[SCR].LISP.MSI.LNK.ZDA.GNN.WRBT.OBJ.O.H.SWF.DPKG.APP.ZIP.TAR.TAR.CO.GZ.A.OUT.EXE [Cancel and Save buttons (Save button disabled)]

Sphere

Sphere

https://www.xkcd.com/1248

https://www.explainxkcd.com/wiki/index.php/1248:_Sphere

Cueball: How are you? Megan: Trapped on the surface of a sphere. [A beat.] Cueball: That astronomy class has made you suck at small talk. Megan: The universe is too big for small talk.

Megan has taken or visited an astronomy class and has become more conscious and aware about the colossal size of the universe, and our own minuscule place in it. She ponders that she can only observe and learn about the rest of the universe; she cannot explore it directly as she is trapped, probably by the constraints of our gravity well, time and human technology. The sphere she mentions here is the Earth , whose surface is roughly spherical in shape. The figure of the Earth is an irregular shape which can be better approximated as an oblate spheroid , or more specifically as a geoid . Her disinclination to make " small talk " with Cueball is a reference to how astronomers and people of other 'big-science' specializations can be so focused on their topic that they become disconnected from the simple details of everyday life. This has also been touched upon in 663: Sagan-Man and 786: Exoplanets . The concept of "small talk", which is usually used as a colloquial term meaning insignificant chatter with others, is taken quite literally by Megan to be small in size. The word itself is juxtaposed with the size of the universe shortly after, which also ties into her previous sentence of being trapped on a "sphere". It seems that astronomy, which deals with ideas of a vastly large scale, has expanded Megan's views to the point where she feels insignificant herself, as well as other matters that concern her. Her gaze outwards also reinforces this suggestion, especially during her conversation with Cueball. She does not engage in eye-to-eye contact, instead replying without looking directly at him. This implies that she is disregarding the current conversation as insignificant as well, which furthers the assumption of Megan's expanded scope of viewpoint. The title text is a continuation of this theme. The name "Society of Astronomers Trapped on the Surface of a Sphere" or, "SATSS", follows a common naming practice for scientific communities, Society, or Association, or Union of <Scientists> of <Country, Nationality, or What Ever>. Cueball: How are you? Megan: Trapped on the surface of a sphere. [A beat.] Cueball: That astronomy class has made you suck at small talk. Megan: The universe is too big for small talk.

Meteor Showers

Meteor Showers

https://www.xkcd.com/1249

https://www.explainxkcd.com/wiki/index.php/1249:_Meteor_Showers

[A list of 16 meteor showers, with a caption above, labels on the three columns and then every other row in gray, beginning with a gray row beneath the line below the column labels.] The xkcd guide to meteor showers Name Peak Notes Quadrantids January 4 th Bring pets inside during peak activity Tricuspids January 21 st Not viewable in region 2 countries Centaurids February 6 th Too faint to see without going outside Beta Aquariids February 10 th Inverted shower converges toward Aquarius instead of radiating away Chelyabids February 15 th Only one meteor per shower, but it's big. Lyrids April 22 nd Meteors sometimes scream Daytime Zeta Perseids June 9 th Likely a NASA hoax June Boötids June 27 th 50/50 mix of meteors and shooting stars Southern Delta Aquariids July 19 th Meteors very bright, but stationary Dromaeosaurids July 22 nd Fast, highly intelligent, can open doors Perseids August 12 th Instead of falling from sky, meteors erupt from ground Tau Pyramids August 15 th Visible even when eyes are closed Draconids October 8 th Very slow, but follow you if you run Orionids October 21 st Entire shower happens at once Leonids November 17 th In 1966, unusually active Leonid shower killed God Geminids December 13 th Can be deflected with tennis rackets

This comic spoofs the way that astronomical events are often reported in the mass media — events are often tagged with undeserved superlatives or described as being more dramatic than they actually are. In some cases, outright misinformation is spread. This phenomenon occurs in part by the result of over-eager scientists, but mostly because of journalists with no deeper knowledge on the subject they write about. Meteor showers typically occur regularly each year. It always happens at the same days because the Earth is crossing the dust path of a particular comet . Sometimes meteor showers are in fact likely to be relatively spectacular when the peak of the shower occurs while your part of the world is in darkness and there is little moonlight. However, even in these cases it must be understood that there is nothing unusual about the meteor shower itself. The shower consists of small particles about one millimeter in diameter. Only their high speed lets them produce enough light to be visible from Earth's surface. The names of the showers refer to the constellation from which they appear to radiate. Most of the meteor showers listed in the comic are real, but some are made up (and indicated as such below). While keeping pets inside may be reasonable on days when fireworks are let off in the beginning of a new year, no regular meteor shower poses much danger to pets. Apparently a play on the tricuspid valve in mammalian hearts, or possibly on bicuspid teeth. The mention of "Region 2" is a reference to region locking , a digital rights management (DRM) scheme intended to restrict media to certain areas. [ citation needed ] DRM of course does not apply to natural events. However, meteor showers are also geographically restricted, and the visible area might roughly coincide with a DRM region (Though Region 2 covers a large and scattered area, not being strictly geographical). Since indoor lights and window glass make them harder to see, it would take a very bright meteor (like the Chelyabids two entries below) to be visible without going outside. This fictional shower would collect shooting stars into the origin to prepare for the real Eta Aquariids meteor shower associated with Halley's comet and diverging from Eta Aquarii in Aquarius; the real shower peaks around May 6th. Due to perspective, meteor showers appear to radiate outwards from a certain point in the sky. Meteor showers may be seen to converge on a point on the opposite side of the sky, but with the earth in the way there would only be a few visible going past the edge, seen as nearly parallel streaks overhead, so the convergence point would hardly be notable. A reference to the February 15, 2013, Chelyabinsk meteor whose explosion shattered windows within a large radius. A meteor large enough to reach the lower atmosphere could produce sound audible to observers on the ground, but this is very unusual. This shower is mostly observed via its effects on radio and TV signals, and therefore a good target for conspiracy theorists responding to June's Invisible Meteors - NASA Science . The "50/50 mix of meteors and shooting stars" is a joke, as "meteor" and "shooting star" are synonymous. This is saying that they are indistinguishable from stars, or that the stars themselves are actually meteors. Dromaeosaurids are a family of dinosaurs containing the genus Velociraptor , well-known from the movie Jurassic Park in which they are presented as a deadly menace, fast and especially intelligent to the point of understanding how to open a door; this representation of Velociraptors is a recurrent topic in xkcd . Erupting from the ground is the funny inverse of falling from the sky, what meteors always do. Probably a reference to Pyramidal cells , a type of neuron. The "tau" reference has two possibilities. The "visible even when eyes are closed" could refer to the Tau particle, a heavy sibling of the electron. When they traveled outside of Earth's magnetosphere on their way to the Moon, Apollo astronauts saw flashes of light about every three minutes even with their eyes closed; these were caused by high energy particles (cosmic rays) penetrating their eyes and brain. The other possibility is that it refers to Tau protein , a normal structural protein within brain neurons. In Alzheimer's Disease, abnormal Tau proteins can aggregate within pyramidal cells to form insoluble skeins. The number of these " neurofibrillary tangles " roughly correlate with the severity of cognitive impairment. This may have something to do with the fact that "draconids" etymologically means "of the dragon", which could make for a fearsome meteor shower. And if you run it will track you down, albeit slowly. This may also be a reference to Boo , a character in the Mario series of video games that is slow but follows you if you turn your back on them. In the game Terraria, meteors (or rather, "meteor heads") follow this exact behavior. Rather than taking place over the course of a week, all the meteors in the shower happen at the same time. This would involve about 3000 meteors appearing simultaneously, which would be quite an impressive sight. There was a very active Leonid shower (a "meteor storm") in 1966, and a precursor to it in 1965. The article Is God Dead? was published in Time Magazine on April 8 of 1966. Perhaps this suggests that the meteors killed God earlier in the year when they and He were further out in the solar system? Meteors usually don't reach the surface of the Earth, being destroyed in the atmosphere. If they do approach the surface, deflecting them with tennis racquets would probably not be the most effective strategy [ citation needed ] , unless Randall is implying that the Geminid swarm is composed of tennis balls. The title text refers to the folk wisdom that lightning strikes the tallest thing around, but this has never been applied to meteors, where it is basically the size (area) that determines the likelihood of an impact with a given object. Randall expressed frustration over how "maddeningly inexact" the lightning statement is, and elaborated on the problem mathematically, in the what if? Today's topic: Lightning . [A list of 16 meteor showers, with a caption above, labels on the three columns and then every other row in gray, beginning with a gray row beneath the line below the column labels.] The xkcd guide to meteor showers Name Peak Notes Quadrantids January 4 th Bring pets inside during peak activity Tricuspids January 21 st Not viewable in region 2 countries Centaurids February 6 th Too faint to see without going outside Beta Aquariids February 10 th Inverted shower converges toward Aquarius instead of radiating away Chelyabids February 15 th Only one meteor per shower, but it's big. Lyrids April 22 nd Meteors sometimes scream Daytime Zeta Perseids June 9 th Likely a NASA hoax June Boötids June 27 th 50/50 mix of meteors and shooting stars Southern Delta Aquariids July 19 th Meteors very bright, but stationary Dromaeosaurids July 22 nd Fast, highly intelligent, can open doors Perseids August 12 th Instead of falling from sky, meteors erupt from ground Tau Pyramids August 15 th Visible even when eyes are closed Draconids October 8 th Very slow, but follow you if you run Orionids October 21 st Entire shower happens at once Leonids November 17 th In 1966, unusually active Leonid shower killed God Geminids December 13 th Can be deflected with tennis rackets

Old Accounts

Old Accounts

https://www.xkcd.com/1250

https://www.explainxkcd.com/wiki/index.php/1250:_Old_Accounts

[Caption above the frame:] The internet is filled with derelict accounts aggregating news about friends long forgotten. [Cueball sits at a desk, typing on a laptop.] Cueball: *Click* Computer (friend): Uhh, is everything OK? Cueball: *Click* Computer (another friend): Dude, what the hell? Cueball: *Click* [Caption below the frame:] When you find yourself drifting away from a community, remember to clean up after yourself by slowly unfriending everyone, one by one, in the reverse order that you added them.

Cueball is very dramatically following the described process of removing himself from a social network by first unfriending each contact in reverse order that he friended them. Such actions are not necessary on any well-designed website. Actively unfriending people individually could be perceived as rude, antisocial, or in need of help. On the other hand, if a user simply abandons his or her account without cleaning it up, then even years later, it will still be sitting there, gathering friends' statuses, opinions and comments. The reverse order to unfriend people refers to practice of correct resource management in computer programming. Computer programs typically require access to many resources at a time, and some of those resources may only be available insofar as the program has access to other more basic resources. For example, if you wanted to watch a movie from a rental service, you would first acquire a keep case with a disk inside of it, and then you would remove the DVD from the case in order to play it on a TV. Once you had watched the movie, you would put the DVD back inside the case. Then you would return the case to the store. The process for "releasing" these two resources (the DVD and the keep case) follows the reverse order of how they were obtained: the case was retrieved from the store before the disk was removed, but the disk must be put back before you return the case. A computer program must release resources in a valid order, though it is often difficult for programmers to ensure this, due to the many paths of execution a program can follow. If resources are released in the wrong order, then a newer resource may reference an older resource that has already been destroyed, and when attempting to use the remaining resource, a variety of bad things could happen if the program attempted to access the already lost resource. While resources do not always need to be released in exactly the reverse order of how they were obtained, doing so ensures that, as each resource is released, none of the resources that existed when it was acquired (and thus which it could be dependent upon) will have been released yet. In the case of unfriending users on a social networking site, it is imagined that Cueball or any other user could have made newer friends through older friends, and as such, that the newer friend should not exist without the older friend and must therefore be released first. The title text appears to be referencing related issue affecting databases used on websites such as social networking sites. When an account is deactivated, the database entries for users that were friends with the account may maintain a link to it. This would result in the database storing useless data, so a well-designed database might try to mitigate this. A well-written program accessing the database would be able to recognize that this data should be ignored. Since no user account would be directly dependent on the existence of another account, the accounts can safely be deleted without worrying about resource management as described earlier. Ultimately, the inefficiency of a database containing useless data about deleted accounts is negligible, and in fact it may not even be worthwhile to take the time to update all the entries compared to how little time it would save when performing lookups. "Database linkage accumulation slowdown" really is a thing that Randall just made up. This may be a satire of popular fears of made-up technological problems, often held by those who are not technologically savvy. [Caption above the frame:] The internet is filled with derelict accounts aggregating news about friends long forgotten. [Cueball sits at a desk, typing on a laptop.] Cueball: *Click* Computer (friend): Uhh, is everything OK? Cueball: *Click* Computer (another friend): Dude, what the hell? Cueball: *Click* [Caption below the frame:] When you find yourself drifting away from a community, remember to clean up after yourself by slowly unfriending everyone, one by one, in the reverse order that you added them.

Anti-Glass

Anti-Glass

https://www.xkcd.com/1251

https://www.explainxkcd.com/wiki/index.php/1251:_Anti-Glass

[Two police officers stand outside an apartment door. The male officer is bald (and half cut of by the left frame of this thin panel), and the other is Ponytail, both are wearing peaked caps with white emblem. Ponytail is holding a pair of glasses down in one hand. The glasses have a small white box with a smaller tip in the front attached to one of the frames. A person (turns out to be Black Hat) answers through the door which has a peephole.] Ponytail: Police. Open up. Ponytail: Did you make this glasses attachment? Black Hat (off-panel through door): Oh, yeah. [Black Hat is sitting in an office chair at his laptop with his back to the door. The door is not visible but the officers voices come through it off-panel from the left.] Ponytail (off-panel): What's it do? Black Hat: It detects when someone near you is wearing Google Glass and shines a laser pointer at their eyepiece. Ponytail (off-panel): Why?? Black Hat: The best defense is an indiscriminate offense. [Cut back a frame-less panel with a wider view of the two officers outside the apartment so the male officer is not cut off.] Male officer: It seems you've mailed these devices to people across Silicon Valley, including the children of every Google executive. Black Hat (off-panel through door): Yeah. It's a viral marketing campaign for an upcoming movie. [Same scene but with frame around the panel.] Male officer: What movie? Black Hat: Haven't decided yet. Anything good coming out this fall? Male officer: Sir, open the door. Black Hat: First stare at the peephole for a sec.

Black Hat makes an attachment for eyeglasses which shines a laser light at people using Google Glass . The quote "The best defense is an indiscriminate offense" plays off the adage " The best defense is a good offense ". Black Hat's goal seems to be to interfere with the Google Glass user potentially recording the person with the laser, and possibly blinding Google Glass users, undermining the project. By mailing one to the children of every Google executive, who are likely to be Google Glass users, he's clearly aiming to disrupt the entire Google Glass project. "Silicon Valley" is a term for where many technologically up-to-date people live who are more likely to work in the computer industry and use Google Glass. The "viral marketing campaign" excuse seems to play off how battery-powered LED placards were mistaken for terrorism in the 2007 Boston bomb scare . He pretends that his terrorism is actually a viral marketing campaign, but seems to have not thought this excuse through. He then tries to get them to look into a laser light. The title text shows the irony between Black Hat's needlessly complicated technical solution, and his apparent hate of Google Glass, a relatively new technology. In addition, he remarks that he wouldn't do something as old-fashioned as shining a laser in peoples' eyes, as this does not live up to his technical expertise. However, he could shine a laser through the peephole, which would have the same effect on the police officers. It seems generally that Randall is no fan of Google Glass, which was also shown later in 1304: Glass Trolling . It was the second time they are mentioned in xkcd after 1215: Insight , but this was the first direct mocking of people wearing these glasses. Google Glass has become a recurring theme in xkcd. [Two police officers stand outside an apartment door. The male officer is bald (and half cut of by the left frame of this thin panel), and the other is Ponytail, both are wearing peaked caps with white emblem. Ponytail is holding a pair of glasses down in one hand. The glasses have a small white box with a smaller tip in the front attached to one of the frames. A person (turns out to be Black Hat) answers through the door which has a peephole.] Ponytail: Police. Open up. Ponytail: Did you make this glasses attachment? Black Hat (off-panel through door): Oh, yeah. [Black Hat is sitting in an office chair at his laptop with his back to the door. The door is not visible but the officers voices come through it off-panel from the left.] Ponytail (off-panel): What's it do? Black Hat: It detects when someone near you is wearing Google Glass and shines a laser pointer at their eyepiece. Ponytail (off-panel): Why?? Black Hat: The best defense is an indiscriminate offense. [Cut back a frame-less panel with a wider view of the two officers outside the apartment so the male officer is not cut off.] Male officer: It seems you've mailed these devices to people across Silicon Valley, including the children of every Google executive. Black Hat (off-panel through door): Yeah. It's a viral marketing campaign for an upcoming movie. [Same scene but with frame around the panel.] Male officer: What movie? Black Hat: Haven't decided yet. Anything good coming out this fall? Male officer: Sir, open the door. Black Hat: First stare at the peephole for a sec.

Increased Risk

Increased Risk

https://www.xkcd.com/1252

https://www.explainxkcd.com/wiki/index.php/1252:_Increased_Risk

[Cueball, Ponytail, and Beret Guy are standing around. Cueball and Ponytail have beach towels. Ponytail is looking at her cell phone. Beret Guy has his hands up to his face, looking distressed.] Ponytail: We should go to the north beach. Someone said the south beach has a 20% higher risk of shark attacks. Cueball: Yeah, but statistically, taking three beach trips instead of two increases our odds of getting shot by a swimming dog carrying a handgun in its mouth by 50%! Beret Guy: Oh no! This is our third trip! [Caption below the panel:] Reminder: A 50% increase in a tiny risk is still tiny .

The panel satirises the common misunderstanding of the concept of percentage. Quoting a percentage change without mentioning the base probability that this ratio acts on is meaningless (outside of arithmetic for arithmetic's sake). Most everyday communication, however, succumbs to such incompleteness. In the aftermath of this ambiguity, people tend to conflate relative and absolute changes. If the probability of a shark attack at the North beach is 5 per million, then the probability of shark attack at the South beach is still not more than 6 per million. The difference between these values is not enough to normally justify choosing one beach over the other, even though a "20% greater" chance sounds significant when stated out of this larger context. Cueball parodies the concern by noting that by going to a beach three times instead of two, their chances of attack by dogs with handguns in their mouths (a ludicrous and unrealistic scenario as dogs cannot buy guns [ citation needed ] and are not likely to pick one up off the ground) increases by 50%. If the chance of the dog attack is one per billion on each visit to the beach, then the chance of attack increases over multiple visits; regardless it's still one in a billion for any specific visit. This does not change the overall improbability of there ever being a dog swimming with a gun in its mouth. Beret Guy misunderstands Cueball's probability, exhibiting the gambler's fallacy by believing that since they haven't been attacked in their first two trips, the chance of attack by dogs with handguns is higher on this outing. This is a common misunderstanding of statistics. While the overall probability of an attack in three trips would be higher than in a single trip, it doesn't change the fact that in each individual trip, the probability is still the same; whether or not they managed to avoid being attacked in their first two trips, the results of these trips do not factor into the probability equation of the third trip. This also can be illustrated by coin flips: if one flips a "fair" coin ten times in a row, no matter what the result of each previous flip is (even if it were nine heads in a row), the odds of getting heads on the tenth coin flip theoretically remains 50%. In other words, past experience does not impact subsequent flips. In practice, if the odds on each flip were 50%, then the odds of nine heads in a row would be 0.2%, so after it might be worth considering the possibility that the coin has been bent or weighted to alter the odds, or even a counterfeit with "heads" on both sides. The caption clarifies Cueball's point, but without sarcasm. Then again, the title text objects to this point (that a tiny risk increased by 50% is still tiny). If this 50% increment is done repeatedly, the risk can get arbitrarily high, while the statement says that it is still tiny. This can be compared to the Sorites paradox (the "paradox of the heap"), which involves a "heap" of sand from which grains of sand are removed individually. If one assumes that, after removing a single grain, a heap of sand is still considered a heap of sand, and that there are a limited number of grains of sand in the heap, then one is forced to accept the conclusion that it can still be considered a heap of sand even if there is only a single grain of sand (or even none at all). Being shot by a swimming dog with a handgun in its mouth is also specifically referenced in what if? 146, Stop Jupiter . [Cueball, Ponytail, and Beret Guy are standing around. Cueball and Ponytail have beach towels. Ponytail is looking at her cell phone. Beret Guy has his hands up to his face, looking distressed.] Ponytail: We should go to the north beach. Someone said the south beach has a 20% higher risk of shark attacks. Cueball: Yeah, but statistically, taking three beach trips instead of two increases our odds of getting shot by a swimming dog carrying a handgun in its mouth by 50%! Beret Guy: Oh no! This is our third trip! [Caption below the panel:] Reminder: A 50% increase in a tiny risk is still tiny .

Exoplanet Names

Exoplanet Names

https://www.xkcd.com/1253

https://www.explainxkcd.com/wiki/index.php/1253:_Exoplanet_Names

[Text above the first frame of the comic:] August 2013: The International Astronomical Union decides to start naming exoplanets, and—for the first time ever—asks for suggestions from the general public. They immediately regret this decision. [Ponytail is facepalming while Megan and Cueball are looking at a computer screen on a desk. Hairbun points to the screen.] Cueball‏‎: Can't you filter out the worst ones? Hairbun: This is after the filter! [Below is a table showing the list of planet names as seen on the computer screen with gray background around the edges of the table.] [The table is in two separate columns, but there is only headings over the left, so the right column is a direct continuation of the left. In the table it is mentioned when the right column begins. There is a small arrow pointing from the word "Planet" down to the second column of the table. The headings in the comic are not inside the table as they are here below. The text at the bottom of the left list seems to continue on below, at least the last entry is cut below the middle, although it is still easy to read. Similarly the text at the top right list, seems to continue from above, the top entry missing the very top of the text. This is as if the list is much longer and here is just shown part of the list. To further indicate this the first entry in the right list begins at "c" instead of at "b" which is else the case for all other instances.] Star Planet Suggested Name Gliese 667 b Space Planet c PILF d A Star e e'); DROP TABLE PLANETS;-- f Blogosphere g Blogodrome h Earth Tau Ceti b Sid Meier's Tau Ceti B c Giant Dog Planet d Tiny Dog Planet e Phil Plainet f Unicode Snowman Gliese 832 b Asshole Jupiter Gliese 581 b Waist-deep Cats c Planet #14 d Ballderaan e Eternia Prime f Taupe Mars g Jelly-Filled Planet Epsilon Eridani b Skydot c Laser Noises Gliese 176 b Pandora c Pantera Kepler-61 b GoldenPalace.com [Below is the right column.] Upsilon Andromidae c Stampy d Moonchild e Ham Sphere HD 20794 b Cosmic Sands c Legoland d Planet with Arms HD 85512 b Lax Morality HD 40307 b Good Planet c Problemland d Slickle e Spare Parts f New Jersey VI g How Do I Join the IAU Gliese 163 b Neil Tyson's Mustache c [email protected] d Hair-Covered Planet Pi Mensae b Moon Holder HD 189733 b Permadeath Kepler-22 b Blue Ivy Kepler-3284 b Blainsley Kepler-3255 b Unicorn Thresher Kepler-2418 b Spherical Discworld Kepler-1686 b Emergency Backup Earth Kepler-3010 b Feeeoooooooop Kepler-442 b Liz

On the 14th August 2013, the International Astronomical Union (IAU) issued a document about public naming of astronomical objects. It stated, "IAU fully supports the involvement of the general public, whether directly or through an independent organized vote, in the naming of planetary satellites, newly discovered planets, and their host stars." The text above the image states the fact above and then notes that the IAU immediately regret this decision. As we can see from Cueball's question, from Ponytail's facepalm, and the fact that even Megan is speechless, the suggestions are appalling. It becomes even worse when Hairbun tells them that an automatic filter has already been applied to the results, one designed to remove inappropriate entries that don't meet certain criteria. This implies that the list would have been even worse if presented in its unfiltered form (as seen below in the table). The naming document also contained, amongst other things, guidelines that suggested names should meet. These include stipulations such as "16 characters or less", "preferably one word", being "pronounceable (in as many languages as possible)", "not too similar to an existing name of an astronomical object", avoiding commercial names, and being "respectful of intellectual property". If we go down the list, we can see that many of Randall's suggestions do indeed violate the guidelines. Which is part of the joke as it reflects the tendency of internet submissions to ignore such softly suggested guidelines. The randomness and inappropriateness of the suggested names reflects the commonly expected response from anonymous submitters on the internet. Many forums and contests that call for online response and do not apply strict control over the responses receive similar collections of random, inappropriate and obscure submissions that are often only tangentially related to the original subject. For example, Greenpeace held a naming contest for one of the whales recently tagged in their research and preservation campaign and even after selecting the finalists the online voting resulted in naming the whale "Mr. Splashypants". PepsiCo had even less restrictive controls in their marketing campaign that asked the internet to name a new flavour of Mountain Dew. They had to shut down the contest in order to avoid naming the new beverage "Hitler did nothing wrong" which was the current leader at the time and only marginally the most inappropriate of the top ten voted suggestions. Even more recently is the case of Boaty McBoatface , in which the internet decided to dub a British research vessel "Boaty McBoatface". The boat was given the name RRS Sir David Attenborough in the end, with its Autonomous Underwater Vehicle being called "Boaty McBoatface." The document also states that naming suggestions may be sent to the email that Randall included in the title text. This comic was updated in 1555: Exoplanet Names 2 . [Text above the first frame of the comic:] August 2013: The International Astronomical Union decides to start naming exoplanets, and—for the first time ever—asks for suggestions from the general public. They immediately regret this decision. [Ponytail is facepalming while Megan and Cueball are looking at a computer screen on a desk. Hairbun points to the screen.] Cueball‏‎: Can't you filter out the worst ones? Hairbun: This is after the filter! [Below is a table showing the list of planet names as seen on the computer screen with gray background around the edges of the table.] [The table is in two separate columns, but there is only headings over the left, so the right column is a direct continuation of the left. In the table it is mentioned when the right column begins. There is a small arrow pointing from the word "Planet" down to the second column of the table. The headings in the comic are not inside the table as they are here below. The text at the bottom of the left list seems to continue on below, at least the last entry is cut below the middle, although it is still easy to read. Similarly the text at the top right list, seems to continue from above, the top entry missing the very top of the text. This is as if the list is much longer and here is just shown part of the list. To further indicate this the first entry in the right list begins at "c" instead of at "b" which is else the case for all other instances.] Star Planet Suggested Name Gliese 667 b Space Planet c PILF d A Star e e'); DROP TABLE PLANETS;-- f Blogosphere g Blogodrome h Earth Tau Ceti b Sid Meier's Tau Ceti B c Giant Dog Planet d Tiny Dog Planet e Phil Plainet f Unicode Snowman Gliese 832 b Asshole Jupiter Gliese 581 b Waist-deep Cats c Planet #14 d Ballderaan e Eternia Prime f Taupe Mars g Jelly-Filled Planet Epsilon Eridani b Skydot c Laser Noises Gliese 176 b Pandora c Pantera Kepler-61 b GoldenPalace.com [Below is the right column.] Upsilon Andromidae c Stampy d Moonchild e Ham Sphere HD 20794 b Cosmic Sands c Legoland d Planet with Arms HD 85512 b Lax Morality HD 40307 b Good Planet c Problemland d Slickle e Spare Parts f New Jersey VI g How Do I Join the IAU Gliese 163 b Neil Tyson's Mustache c [email protected] d Hair-Covered Planet Pi Mensae b Moon Holder HD 189733 b Permadeath Kepler-22 b Blue Ivy Kepler-3284 b Blainsley Kepler-3255 b Unicorn Thresher Kepler-2418 b Spherical Discworld Kepler-1686 b Emergency Backup Earth Kepler-3010 b Feeeoooooooop Kepler-442 b Liz

Preferred Chat System

Preferred Chat System

https://www.xkcd.com/1254

https://www.explainxkcd.com/wiki/index.php/1254:_Preferred_Chat_System

[Cueball stands, talking on his cell phone.] Cueball: Sorry for the voicemail, but I'm confused about how to reach you. Cueball: When I text you, you reply once on GChat, then go quiet, yet answer IRC right away. I emailed you, and you replied on Skype and mentioned that the email "woke you up". Cueball: You're very responsive - I just have no sense of how you use technology. [An owl flies into the panel.] Cueball: ?!? [The owl perches on Cueballs's head. It has delivered a note to Cueball.] Note: did you try to call me? use my google voice number next time.

As more options become available for communication, it becomes more difficult to determine the social etiquette of communicating with others. It is customary (or at least rarely incorrect) to return a communication from someone using the same medium as the initial contact. For example, a voicemail is generally returned with a phone call (perhaps resulting in another voicemail), and an email with an email, etc. However, sometimes people respond through a different channel, such as texting a response to a voicemail or emailing a reply to a text. This can create confusion that Randall is pointing out, because the recipient may be unsure whether to go back to their original communication method, or if the response was a signal that the recipient prefers the new method. Similarly, it becomes important for people to know what type of communication is preferred by a recipient, or most likely to reach the recipient quickly and generate the most useful response. Randall portrays the difficulty Cueball is facing when communicating with a seemingly irrational recipient. Today's multitude of social networks and communication systems amplifies the problem. After several misses, Cueball is leaving a voicemail for his intended recipient to clarify the best way to reach them. He initially tried texting the recipient, to which they made one reply on the instant-messaging service Google Talk (commonly called GChat). This is unusual because instant messaging services are usually used to engage in longer conversations than one message. Cueball further is confused because the recipient, although silent on Google Talk, continues responding on IRC . Cueball then attempted to communicate by email, but the response came on Skype , another instant messaging service that features voice and video chat along with text. The recipient mentions that the email " woke [them] up ", implying that they have e-mail configured to make an audible alert, possibly by being forwarded to a cell phone. Cueball clarifies that he appreciates that the recipient is very quick to respond, but his confusion stems from his inability to determine the proper medium to use. As he finishes his voicemail, an owl flies towards him carrying a written message. This appears to be a reference to owl post , which is a form of communication in the Harry Potter lore which itself is presumably based on the real-world usage of carrier pigeons . The owl post message indicates that the voicemail was received, and suggests using Google Voice next time, which is yet another form of voice and text communication, one that bypasses the standard telecom companies and gives the user a range of controls such as which device is called depending on who is calling or what time of day it is, or to simply ignore the call altogether. Randall seems to have an interest in bird-related communications; RFC 1149 - IP over Avian Carriers has been mentioned in previous comics. The title text mentions a pager , a low-tech, low-cost wireless telecommunications device that beeps or vibrates when it receives a message. Simpler pagers can display numbers, usually the caller's phone number plus a couple of additional digits, while more sophisticated ones can receives text messages. The usual intent of a pager is for the recipient to call the number back or, today, to tell you that your table is ready. Pager use peaked in the 1980s and 1990s, but declined thereafter as cellular phones became ubiquitous. There can be absolutely no need for this hyper-connected individual to use a pager, and having your own cellphone forward messages to your pager makes almost no sense. The question in the beginning of the owl-message further suggests, that the reciever did not actually recieve the voicemail, but just had Cueball's phone number displayed on his pager. A possible suggestion is that they are intentionally using such an abundance of communications options to, perversely, make it harder to have a conversation with them. So far, it seems to be working. If this is true, the person Cueball is trying to contact may very well be Black Hat. Another suggestion is that Cueball is attempting to contact Beret Guy, as Beret Guy is known for doing odd things such as this. This comic is closely related to a later comic, 1789: Phone Numbers . [Cueball stands, talking on his cell phone.] Cueball: Sorry for the voicemail, but I'm confused about how to reach you. Cueball: When I text you, you reply once on GChat, then go quiet, yet answer IRC right away. I emailed you, and you replied on Skype and mentioned that the email "woke you up". Cueball: You're very responsive - I just have no sense of how you use technology. [An owl flies into the panel.] Cueball: ?!? [The owl perches on Cueballs's head. It has delivered a note to Cueball.] Note: did you try to call me? use my google voice number next time.

Columbus

Columbus

https://www.xkcd.com/1255

https://www.explainxkcd.com/wiki/index.php/1255:_Columbus

[White Hat talks to two children sitting in front of him on the floor to the right. A boy with hair like Hairy with his arms round his knees and behind him Science Girl with two hair buns, sitting cross leged on her knees. Megan interrupts him from off-panel right.] White Hat: Everyone said the world was flat, but Columbus knew it was round. Megan (off-panel): *Sigh* no, no, no. [Megan walks in holding a hand palm up. White Hat partly lifts his arm closest to her. The children between them turn their heads towards her. The boy leans back on one hand.] Megan: So he took his ships and sailed west— Megan: —in a line tangent to the surface. The sea fell away, and he landed in Valinor. [White Hat has taken his arm down, Megan holds her arms out to each side. The children still looks at her, now also Science Girl leans back on one arm.] Megan: A Silmaril on his brow, he wanders the heavens as the morning star, still believing he reached India. White Hat: Stop making stuff up. Megan: You first.

The comic starts with White Hat telling the two children shown on the first panel that Christopher Columbus knew the world was round, but that others believed it to be flat. However, this is a false narrative known as the Myth of the Flat Earth . Educated people in Columbus's time knew the world was round, and knew the approximate radius of the Earth. Columbus claimed that the distance to sail west from Canary Islands to Japan to be about 3,700 km, drastically lower than others believed, but he was wrong about this . If another continent and the " West Indies " had not been fortuitously in the right place, Columbus and his crew probably would have died at sea. As White Hat begins his explanation, Megan objects, though not explaining why. White Hat continues, so Megan interrupts, saying that Columbus went in a straight line as the world curved away, ending up in Valinor and the Undying Lands . Megan's story is an allusion to The Silmarillion , by J. R. R. Tolkien , set in the same world as The Lord of the Rings and The Hobbit . The claim that Columbus sailed on a tangent to the surface alludes to how the elves' ships leave the curved sea surface and sail in a straight line to reach Valinor on the same route that they sailed when the world was still flat. The mentions of a silmaril and the morning star are a reference to Eärendil the Mariner , the only mortal sailor to reach the Undying Lands, with one of the Silmarils (though Eärendil's journey occurred at the end of the First Age and the world was only changed into a sphere near the end of the Second Age). Megan humorously conflates these myths, suggesting that they are all equally false. Columbus in fact wasn't the first to claim the world was round; the ancient Greeks had discovered it long before. It was, however, disputed by some Christian scholars in late antiquity due to disagreements over its congruence with biblical canon. In Megan's telling, Columbus ends up as the morning star, which is actually the planet Venus (the same fate as Eärendil's in Tolkien's mythology). The joke is that when White Hat tells her to stop making up the story, Megan pointedly replies "You first", indicating that she originally complained about White Hat's retelling of the Columbus story because his account didn't really happen, and so he was also "making things up". Megan's fantasy tale was then delivered to make a point. The title text refers to the transfer of smallpox to the Americas by Europeans, which caused the deaths of untold millions of Native Americans. The introduction of smallpox to the Undying Lands would indeed make their name ironic. However, the Undying Lands are named after immortal Valar , Maiar , and Elves living there, not because they confer immortality. A more proper name would be the Lands of the Undying, and Valar, Maiar, and Elves are not susceptible to diseases in Tolkien's mythos in any case. Similar discussions between White Hat and Megan can be found in 1605: DNA and 1731: Wrong , in the latter Megan even finishes with a similar *sigh* as she started with here. [White Hat talks to two children sitting in front of him on the floor to the right. A boy with hair like Hairy with his arms round his knees and behind him Science Girl with two hair buns, sitting cross leged on her knees. Megan interrupts him from off-panel right.] White Hat: Everyone said the world was flat, but Columbus knew it was round. Megan (off-panel): *Sigh* no, no, no. [Megan walks in holding a hand palm up. White Hat partly lifts his arm closest to her. The children between them turn their heads towards her. The boy leans back on one hand.] Megan: So he took his ships and sailed west— Megan: —in a line tangent to the surface. The sea fell away, and he landed in Valinor. [White Hat has taken his arm down, Megan holds her arms out to each side. The children still looks at her, now also Science Girl leans back on one arm.] Megan: A Silmaril on his brow, he wanders the heavens as the morning star, still believing he reached India. White Hat: Stop making stuff up. Megan: You first.

Questions

Questions

https://www.xkcd.com/1256

https://www.explainxkcd.com/wiki/index.php/1256:_Questions

[This strip is a rectangular word cloud, titled 'Questions found in Google autocomplete'. Embedded in the cloud are 5 single panels, with illustrated questions. These are described at the end. Questions are given in roughly columnar order. None of the questions have question marks.] Questions found in Google Autocomplete Why do whales jump Why are witches green Why are there mirrors above beds Why do I say uh Why is sea salt better Why are there trees in the middle of fields Why is there not a Pokemon MMO Why is there laughing in TV shows Why are there doors on the freeway Why are there so many svchost.exe running Why aren't there any countries in antarctica Why are there scary sounds in Minecraft Why is there kicking in my stomach Why are there two slashes after HTTP Why are there celebrities Why do snakes exist Why do oysters have pearls Why are ducks called ducks Why do they call it the clap Why are Kyle and Cartman friends Why is there an arraow on Aang's head Why are text messages blue Why are there mustaches on clothes Why are there mustaches on cars Why are there mustaches everywhere Why are there so many birds in Ohio Why is there so much rain in Ohio Why is Ohio weather so weird Why are there male and female bikes Why are there bridesmaids Why do dying people reach up Why aren't there varicose arteries Why are old Klingons different Why is programming so hard Why is there a 0 ohm resistor Why do Americans hate soccer Why do rhymes sound good Why do trees die Why is there no sound on CNN Why aren't Pokemon real Why aren't bullets sharp Why do dreams seem so real Why aren't there dinosaur ghosts Why do iguanas die Why do testicles move Why are there psychics Why are hats so expensive Why is there caffeine in my shampoo Why do your boobs hurt Why aren't economists rich Why do Americans call it soccer Why are my ears ringing Why are there so many Avengers Why are the Avengers fighting the X men Why is Wolverine not in the Avengers Why are there ants in my laptop Why is Earth tilted Why is space black Why is outer space so cold Why are there pyramids on the moon Why is NASA shutting down Why is there Hell if God forgives Why are there tiny spiders in my house Why do spiders come inside Why are there huge spiders in my house Why are there lots of spiders in my house Why are there spiders in my room Why are there so many spiders in my room Why do spider bites itch Why is dying so scary Why is there no GPS in laptops Why do knees click Why aren't there E grades Why is isolation bad Why do boys like me Why don't boys like me Why is there always a Java update Why are there red dots on my thighs Why is lying good Why is GPS free Why are trees tall Why are there slaves in the Bible Why do twins have different fingerprints Why are Americans afraid of dragons Why is there lava Why are there swarms of gnats Why is there phlegm Why are there so many crows in Rochester, MN Why is psychic weak to bug Why do children get cancer Why is Poseidon angry with Odysseus Why is there ice in space Why are there female Mr Mimes Why is there an owl in my backyard Why is there an owl outside my window Why is there an owl on the dollar bill Why do owls attack people Why are AK47s so expensive Why are there helicopters circling my house Why are there gods Why are there two Spocks Why is Mt Vesuvius there Why do they say T minus Why are there obelisks Why are wrestlers always wet Why are oceans becoming more acidic Why is Arwen dying Why aren't my quail laying eggs Why aren't my quail eggs hatching Why aren't there any foreign military bases in America Why is life so boring Why are my boobs itchy Why are cigarettes legal Why are there ducks in my pool Why is Jesus white Why is there liquid in my ear Why do Q tips feel good Why do good people die Why are ultrasounds important Why are ultrasound machines expensive Why is stealing wrong Why is YKK on all zippers Why is HTTPS crossed out in red Why is there a line through HTTPS Why is there a red line through HTTPS on Facebook Why is HTTPS important Why are there weeks Why do I feel dizzy Why are dogs afraid of fireworks Why is there no king in England [We see Cueball from the torso up, with arms outstretched.] Cueball: Why aren't my arms growing [Megan stands with a grey ghost on either side of her.] Megan: Why are there ghosts [Beret Guy stands, looking at a squirrel.] Beret Guy: Why are there squirrels [Cueball stands.] Cueball: Why is sex so important. [We see Ponytail from the torso up.] Ponytail: Why aren't there guns in Harry Potter

Google , a rather popular [ citation needed ] internet search engine, has a feature known as autocomplete that guesses at search queries before they are fully typed out. These guesses are generally made based on popular searches by other people. From time to time, a particularly strange or hilarious one may be found, as is evidenced in this comic. The largest pictured questions are: "Why are there slaves in the bible" and "Why are there ants in my laptop". All of the questions in the comic are "why" questions, so many of them are predicated on false assumptions, such as "Why are there pyramids on the moon". Originally, all these questions and many more (33,171 in total) could be found at http://xkcd.com/why.txt . ( Archived Version ) Regarding the title text: in the Peter Jackson films of The Lord of the Rings trilogy , Arwen becomes sickly for unspecified reasons as the plot advances, apparently giving Aragorn a more personal reason to fight. The only explanation given is by Elrond, who says "As Sauron's power grows, her [Arwen's] strength wanes." This subplot is entirely absent from the original novels . The tables below have been created so as to split the comic into almost entirely arbitrary blocks, which have then been identified with similarly arbitrary numbers. As a general rule, section numbers work top to bottom, then right to left. http://www.reddit.com/r/xkcd/comments/1l3na7/questions/cbvigrd , answers to all the questions. [This strip is a rectangular word cloud, titled 'Questions found in Google autocomplete'. Embedded in the cloud are 5 single panels, with illustrated questions. These are described at the end. Questions are given in roughly columnar order. None of the questions have question marks.] Questions found in Google Autocomplete Why do whales jump Why are witches green Why are there mirrors above beds Why do I say uh Why is sea salt better Why are there trees in the middle of fields Why is there not a Pokemon MMO Why is there laughing in TV shows Why are there doors on the freeway Why are there so many svchost.exe running Why aren't there any countries in antarctica Why are there scary sounds in Minecraft Why is there kicking in my stomach Why are there two slashes after HTTP Why are there celebrities Why do snakes exist Why do oysters have pearls Why are ducks called ducks Why do they call it the clap Why are Kyle and Cartman friends Why is there an arraow on Aang's head Why are text messages blue Why are there mustaches on clothes Why are there mustaches on cars Why are there mustaches everywhere Why are there so many birds in Ohio Why is there so much rain in Ohio Why is Ohio weather so weird Why are there male and female bikes Why are there bridesmaids Why do dying people reach up Why aren't there varicose arteries Why are old Klingons different Why is programming so hard Why is there a 0 ohm resistor Why do Americans hate soccer Why do rhymes sound good Why do trees die Why is there no sound on CNN Why aren't Pokemon real Why aren't bullets sharp Why do dreams seem so real Why aren't there dinosaur ghosts Why do iguanas die Why do testicles move Why are there psychics Why are hats so expensive Why is there caffeine in my shampoo Why do your boobs hurt Why aren't economists rich Why do Americans call it soccer Why are my ears ringing Why are there so many Avengers Why are the Avengers fighting the X men Why is Wolverine not in the Avengers Why are there ants in my laptop Why is Earth tilted Why is space black Why is outer space so cold Why are there pyramids on the moon Why is NASA shutting down Why is there Hell if God forgives Why are there tiny spiders in my house Why do spiders come inside Why are there huge spiders in my house Why are there lots of spiders in my house Why are there spiders in my room Why are there so many spiders in my room Why do spider bites itch Why is dying so scary Why is there no GPS in laptops Why do knees click Why aren't there E grades Why is isolation bad Why do boys like me Why don't boys like me Why is there always a Java update Why are there red dots on my thighs Why is lying good Why is GPS free Why are trees tall Why are there slaves in the Bible Why do twins have different fingerprints Why are Americans afraid of dragons Why is there lava Why are there swarms of gnats Why is there phlegm Why are there so many crows in Rochester, MN Why is psychic weak to bug Why do children get cancer Why is Poseidon angry with Odysseus Why is there ice in space Why are there female Mr Mimes Why is there an owl in my backyard Why is there an owl outside my window Why is there an owl on the dollar bill Why do owls attack people Why are AK47s so expensive Why are there helicopters circling my house Why are there gods Why are there two Spocks Why is Mt Vesuvius there Why do they say T minus Why are there obelisks Why are wrestlers always wet Why are oceans becoming more acidic Why is Arwen dying Why aren't my quail laying eggs Why aren't my quail eggs hatching Why aren't there any foreign military bases in America Why is life so boring Why are my boobs itchy Why are cigarettes legal Why are there ducks in my pool Why is Jesus white Why is there liquid in my ear Why do Q tips feel good Why do good people die Why are ultrasounds important Why are ultrasound machines expensive Why is stealing wrong Why is YKK on all zippers Why is HTTPS crossed out in red Why is there a line through HTTPS Why is there a red line through HTTPS on Facebook Why is HTTPS important Why are there weeks Why do I feel dizzy Why are dogs afraid of fireworks Why is there no king in England [We see Cueball from the torso up, with arms outstretched.] Cueball: Why aren't my arms growing [Megan stands with a grey ghost on either side of her.] Megan: Why are there ghosts [Beret Guy stands, looking at a squirrel.] Beret Guy: Why are there squirrels [Cueball stands.] Cueball: Why is sex so important. [We see Ponytail from the torso up.] Ponytail: Why aren't there guns in Harry Potter

Monster

Monster

https://www.xkcd.com/1257

https://www.explainxkcd.com/wiki/index.php/1257:_Monster

[Four people are standing around a table-top crisis planning model. Cueball and Ponytail are wearing police-style hats; Megan holds a clipboard and Blondie has her hands on the table.] Megan: It's as long as a football field. Runs as fast as a cheetah. Cueball: Weighs as much as a blue whale. Blondie: Can we negotiate with it? Ponytail: No. It has the intelligence of a two-year-old child. [Caption below the panel:] By the time the Frequently-Made Comparisons Monster was finally defeated, it had eaten enough people to fill a stadium and devastated an area the size of Rhode Island.

In this comic, officials and police are evidently trying to describe the extraordinary qualities of a huge monster by comparing it with everyday objects instead of numbers, which seems to be a recurring theme on xkcd (see 526: Converting to Metric , 1047: Approximations ) and also in the Blag article Dictionary of Numbers where Randall says that he doesn't "like large numbers without context." This comic pokes fun at how common it is in the media to compare things of extraordinary qualities to a certain narrow set of well-known objects. The comic features people discussing a fictional monster which - apparently - can be only described by these overused comparisons. The three used by Megan , Cueball and Ponytail are: The caption below the panel names the monster the Frequently-Made Comparisons Monster , joking that the monster was created by comparing it to things, and continues the joke by comparing the number of killed people to those that could fill a (sports) stadium (of the order tens of thousands), and the area of devastation to the smallest state in the US Rhode Island (1,214 sq mi/3,140 km 2 ) (a state Randall also used for comparison in the What if? Everybody Jump . In another What if? he uses a football stadium filled with ants as a comparison: Lethal Neutrinos .) The title text takes the joke one step further by comparing the nuclear bomb used to destroy the monster to the bomb dropped on Hiroshima at the end of the Second World War, i.e. they dropped a relatively small nuclear bomb on it (nuclear weapons have advanced significantly since WWII). Here is an example from Wikipedia of such a comparison with the strength of a meteor strike. [Four people are standing around a table-top crisis planning model. Cueball and Ponytail are wearing police-style hats; Megan holds a clipboard and Blondie has her hands on the table.] Megan: It's as long as a football field. Runs as fast as a cheetah. Cueball: Weighs as much as a blue whale. Blondie: Can we negotiate with it? Ponytail: No. It has the intelligence of a two-year-old child. [Caption below the panel:] By the time the Frequently-Made Comparisons Monster was finally defeated, it had eaten enough people to fill a stadium and devastated an area the size of Rhode Island.

First

First

https://www.xkcd.com/1258

https://www.explainxkcd.com/wiki/index.php/1258:_First

[Cueball sits at his desk, using a computer.] [Cueball is still sitting at the desk, but with hands off the keyboard in his lap.] [Cueball is in the same position as before, talking with off-panel.] Cueball: After a couple of unbearable decades, the "first post" thing seems to be dying a quiet death. Off-screen: Shh. You'll jinx it.

Firstposting , or thread sniping , is the habit of posting short messages to obnoxiously point out that you have found and seen the content first. This practice was far more common in the years leading up to this comic, when high-traffic and poorly-moderated social media sites tended to display comments in increasing chronological order by default; as such, the oldest comments would be most prominently displayed at the top, while the newest comments would be buried at the bottom. In the first two panels, Cueball stares at his screen, implying that a long time passes before he finally points this out. He has probably submitted a post and is awaiting for comments that are not coming. Cueball might actually have mixed feelings about the practice slowly dying out. However, someone offscreen is worried he will jinx it, encouraging more people to do so. In reality, Cueball's observation has held true, due to changes in best practices for web design. Social media sites in particular often sort comments by user rating; as such, the most appreciated comments are given the most prominence, and trollish comments like the cliche "F1rst p0st!!" are buried. Meanwhile, low-traffic forums with smaller communities still display comments from oldest to newest; in these environments, firstposters are reported and dealt with by human moderators in a timely fashion. In short, the internet as a whole does not reward or reinforce firstposting the way it once did pre-2013. However, the small children who think that posting "FIRST!!!" makes them somehow relevant or funny still remain. Only growing up and realising how unnecessary and obnoxious posting "first" is will stop them. See also 269: TCMP and 1019: First Post . The title text sarcastically states that no new annoying internet behaviors have emerged since the "first post" trend began which would continue to annoy users: a fact which is clearly wrong to anyone who spends a length of time on the internet. See for instance 493: Actuarial . [Cueball sits at his desk, using a computer.] [Cueball is still sitting at the desk, but with hands off the keyboard in his lap.] [Cueball is in the same position as before, talking with off-panel.] Cueball: After a couple of unbearable decades, the "first post" thing seems to be dying a quiet death. Off-screen: Shh. You'll jinx it.

Bee Orchid

Bee Orchid

https://www.xkcd.com/1259

https://www.explainxkcd.com/wiki/index.php/1259:_Bee_Orchid

[Beret Guy and Megan are walking through a wood.] Megan: There are these orchids whose flowers look like female bees. When males try to mate with them, they transfer pollen. [Megan kneels next to a flower.] Megan: This orchid - Ophrys Apifera - makes flowers, but no bees land on them because the bee it mimics went extinct long ago. [Megan stands.] Megan: Without its partner, the orchid has resorted to self-pollinating, a last-ditch genetic strategy that only delays the inevitable. Nothing of the bee remains, but we know it existed from the shape of this flower. [They walk on past the flower.] Megan: It's an idea of what the female bee looked like to the male bee... Megan: ...as interpreted by a plant. Beret Guy: Wow, so... [We see a full-colour painting of an orchid flower. It has purple-pink petals on a mottled grey background, along with the bee-like parts. It's quite a realistic painting.] ...the only memory of the bee is a painting by a dying flower. [The flower is alone in a panel.] [Beret Guy walks back on screen.] [Beret Guy kneels down next to it.] Beret Guy: I'll remember your bee, orchid. I'll remember you. [Beret Guy walks off-panel again.]

Megan is explaining the evolutionary phenomenon of mimicry of female insects which fools male insects into trying to mate with the flower ( pseudocopulation ). This causes the pollen of the flower to stick to the male bee, who may make the same mistake with another flower, allowing for pollination. This particular orchid mimicked the solitary bee Eucera , which now only pollinates it in the Mediterranean (the bee isn't really extinct yet). This may eventually lead to the extinction of the orchid due to lack of reproduction. In most areas where it grows, the orchid is using a method of self-pollination , which can be detrimental to the genetic vitality of the species as it is a form of in-breeding. Photographs of Ophrys apifera : Female Eucera (Synhaolonia) guarding nests (left) and male Eucera (right): In a similar way, some plants depend on animal species now extinct, but as the dependency was not about pollination but about spreading seeds across the land, those plant species can still last millions of years after the animal species extinction. For instance, it’s the case of the avocado . The comic plays on the subject of levels of indirectness of memory or knowledge representation. The female bee is extinct, remembered only by the male bee's perception of her; the male bee is also extinct, but its memory of the female is preserved in the orchid's shape; the orchid, due to self-pollination, is nearing extinction, but the memory of the female bee is now preserved by Beret Guy's memory of the orchid, remembering the male bee's memory of her. The title text culminates this theme by invoking the idea that some day human beings will, likewise, be extinct, and aliens will be able to learn about us through the distorted and faded representations of ourselves that we leave behind - Axe commercials which, like the orchid, present an idealized form to deceptively attract mates. We are left to speculate whether these aliens will be able to construct, somehow, through three levels of indirectness (the human representation, the orchid's representation and the male bee's perception) any memory of the female Eucera, and, if so, how distorted a view of the bee it will be. [Beret Guy and Megan are walking through a wood.] Megan: There are these orchids whose flowers look like female bees. When males try to mate with them, they transfer pollen. [Megan kneels next to a flower.] Megan: This orchid - Ophrys Apifera - makes flowers, but no bees land on them because the bee it mimics went extinct long ago. [Megan stands.] Megan: Without its partner, the orchid has resorted to self-pollinating, a last-ditch genetic strategy that only delays the inevitable. Nothing of the bee remains, but we know it existed from the shape of this flower. [They walk on past the flower.] Megan: It's an idea of what the female bee looked like to the male bee... Megan: ...as interpreted by a plant. Beret Guy: Wow, so... [We see a full-colour painting of an orchid flower. It has purple-pink petals on a mottled grey background, along with the bee-like parts. It's quite a realistic painting.] ...the only memory of the bee is a painting by a dying flower. [The flower is alone in a panel.] [Beret Guy walks back on screen.] [Beret Guy kneels down next to it.] Beret Guy: I'll remember your bee, orchid. I'll remember you. [Beret Guy walks off-panel again.]

LD50

LD50

https://www.xkcd.com/1260

https://www.explainxkcd.com/wiki/index.php/1260:_LD50

[A figure in a white coat lies on the floor, crushed beneath a giant pile of binders & paper. Megan and Cueball in white coats stand next to him, looking on. Megan is holding a clipboard.] [Caption below the panel:] The LD 50 of toxicity data is 2 kilograms per kilogram.

LD 50 is a term used in toxicology that identifies the median lethal dose of a toxin, or how much is required to kill 50% of a given population. LD 50 s are usually measured in g/kg, as the amount of toxin to kill something is usually linearly related with its mass. The lower the LD 50 , the more lethal the toxin. An LD 50 can be determined for almost any substance: for example, the LD 50 for sugar (in rats) is 29.7 g/kg. However, Botulinum toxin (commercially known as Botox in the beauty industry), the most acutely toxic substance known, has a LD 50 of roughly 1 ng/kg, or 0.000000001 g/kg, a vanishingly small amount. The comic is making the joke that the LD 50 of papers on toxicology is 2 kg/kg, so it takes 2 kilograms of papers on toxicology to kill a person for each kilogram they weigh. The worldwide average weight of an adult is 62 kg (137 lb), so the lethal dose would be 124 kg (273 lb) of toxicology papers. Death is apparently caused by compression or smothering. The title text says it will take less paper to kill a person if the paper is shoved down their throat instead of dropped on them, either by suffocation or by bursting the subject's stomach. A third method of delivering a toxin is by subcutaneous injections which are highly effective in administering vaccines and medications, but that number is omitted since they couldn't figure out how to do it. If they could, the amount of paper required to trigger a fatal blood vessel blockage would probably be fairly small. [A figure in a white coat lies on the floor, crushed beneath a giant pile of binders & paper. Megan and Cueball in white coats stand next to him, looking on. Megan is holding a clipboard.] [Caption below the panel:] The LD 50 of toxicity data is 2 kilograms per kilogram.

Shake That

Shake That

https://www.xkcd.com/1261

https://www.explainxkcd.com/wiki/index.php/1261:_Shake_That

[Megan stands in a disco, surrounded by dancing figures. She looks confused.] PA system: Shake what your mama gave you Megan: ??? [Megan walks out of the club door.] [We see a mug on a table, labelled "World's Greatest Daughter".] [Megan shakes the mug.]

Visiting a club, Megan is exhorted by a phrase used in several songs, to "shake what your mama gave you", a crude euphemism typically used to encourage shaking one's body parts, referring to any of the sexually appealing anatomical parts of the dancer. Taking this exhortation extremely literally, Megan proceeds to locate a mug presumably given to her by her "mama" labeled "World's greatest daughter" and shakes it. The phrase "shake what your mama gave ya" was in use as early as 1992, when it was the title of a song by Poison Clan , a southern hip-hop group that was influential from 1990–1995. Another version by Stik-E & Da Hoodz was released in 1995 by Phat Wax records. The line gained a wider audience when it was sampled by Fatboy Slim in the similarly titled "Ya Mama" on his 2000 album Halfway Between the Gutter and the Stars . More recently the line was featured in the Lil Jon single "Stick That Thang Out". In fitting with the general thematic composition of such a song, a large part of which revolves around either goading a woman to, or describing one who is dancing seductively in a nightclub - this line asks a girl to dance, thereby swaying her hips & buttocks, or breasts, the most common male 'fetishes' — making them more conspicuous in the usually dim ambiance because of the phase lag with the rest of the body, which may be attributed to non-rigidity of the elastic structures — for purposes of her male audience's gratification (whether it be solicited or voyeuristic). The title text refers to another lyrical cliche, "work it", which typically refers to "working" one's body; again, generally seductively. The action may be considered work either from the point of mechanical work, or as a reference to a professional dancer. This naturally leads Megan to further confusion (as indicated by the title text) when taken literally, as she responds "it's already working!" It is not entirely clear if she is again referring to the mug, or simply another generic object not displayed in the comic. 1291: Shoot for the Moon may be a continuation of this, due to Megan misunderstanding common saying or references. [Megan stands in a disco, surrounded by dancing figures. She looks confused.] PA system: Shake what your mama gave you Megan: ??? [Megan walks out of the club door.] [We see a mug on a table, labelled "World's Greatest Daughter".] [Megan shakes the mug.]

Unquote

Unquote

https://www.xkcd.com/1262

https://www.explainxkcd.com/wiki/index.php/1262:_Unquote

[Two figures with spiky hair and backpacks are conversing. One is riding in a hover-car, or similar.] Future Hair: Bye! Friend: May the Force be with you! Future Hair: Huh? Friend: It's just something my grandma used to say. No idea what it means. [Caption below the panel:] I wonder on what date Star Wars will be quoted for the last time.

In this comic, Randall poses the future possibility that at some time in the future, even a popular film as Star Wars will become forgotten by society. " May the Force be with you " is one of the many famous phrases from the Star Wars movies. Star Wars has become popular enough to remain part of today's popular culture almost forty years since its initial release, and the source and meaning of the quote is commonly recognized. This comic suggests that eventually even the enormously popular Star Wars will fade into obscurity — by which time, ironically, Star Wars-like hovercraft will have been invented. It is not uncommon for once-popular sayings to lose popularity and come into disuse; particularly when the sayings are sourced from a pop-culture reference such as a book or film. In fact, there are entire books dedicated to such topics. Each generation generally develops its own pop culture-references which frequently become unrecognizable to the next generation. Only a handful of pop-culture quotes tend to survive for decades. For example, the phrase "Sit on it", coined by the creators of " Happy Days " as a TV-friendly but derogatory-sounding comeback for the character Fonzie. The phrase was very popular during the show's 1970s-80s heyday, but today is far less recognizable to those born after that era, and is not commonly referenced today. The title text suggests that the characters will write off the phrase as a saying from the "Old Country" (the foreign country or place where one's ancestors emigrated from). This is a play on the fact that ubiquitous film and TV quotes have not been around long enough for society to generally forget their origins, and the most common source for unfamiliar sayings in today's world are sayings from other countries where one's ancestors originated. The use of the expression in this comic implies that the speaker has no idea about the origins of the phrase. To him it might be a translation of a foreign expression, or from a long left-behind homeland. A similar topic was addressed in 493: Actuarial , with Black Hat predicting when the last of the original Star Wars cast would die, and in 1093: Forget , predicting when the release of The Return of the Jedi would be forgotten. Also, 794: Inside Joke is about how much pop culture of centuries past has been forgotten. The sentiment in this comic is similar to a quote from psychiatrist and author Irvin D Yalom: [Two figures with spiky hair and backpacks are conversing. One is riding in a hover-car, or similar.] Future Hair: Bye! Friend: May the Force be with you! Future Hair: Huh? Friend: It's just something my grandma used to say. No idea what it means. [Caption below the panel:] I wonder on what date Star Wars will be quoted for the last time.

Reassuring

Reassuring

https://www.xkcd.com/1263

https://www.explainxkcd.com/wiki/index.php/1263:_Reassuring

[Megan is sitting at a computer, and Cueball is standing behind her.] Megan: Looks like computers will beat humans at Go pretty soon. Cueball: Wow. Cueball: That's the last of the big ones. Megan: Yeah. [Megan looks back over her shoulder at him.] Cueball: Well, at least humans are still better at, uh, Cueball: coming up with reassuring parables about things humans are better at? Megan: Hmm. [Megan types on her computer.] type type [She leans back over her chair again and addresses Cueball.] Megan: I made a Python script that generates thousands of reassuring parables per second. Cueball: Dammit. Computer: Computers will never understand a sonnet computers will never enjoy a salad comp—

Go is an abstract strategy board game considered computationally difficult, compared to chess. Because of the size and number of possible combinations, computers don't have an easy way to exhaustively search for the best move. Still, they are getting better and better playing it . Megan suggests that computers may soon reach the level of being able to beat the best human players, an artificial intelligence milestone that has already been accomplished with other games. At the time of this comic, Go was one of the last games where a computer can still be beaten by top humans (see 1002: Game AIs ). However, in May 2017, Google's AI AlphaGo defeated the world's top human Go player . This was referenced three months later in 1875: Computers vs Humans . As a common human response, Cueball attempts to offer the consolation or defensive statement that humans remain better than computers at something else (see also 894: Progeny ). In this case, the first thing he thinks of is that humans are better at making such consoling statements. However, Megan disproves Cueball's statement by creating a script in the Python programming language to create an abundant supply of such statements. An irony here is that each of the statements the computer generates defends humans, not computers. Another such statement is made in the title text, that humans are better at quietly amusing themselves, oblivious to our "pending obsolescence" - which may refer alternatively to our inevitable deaths, or to the comic's own topic of our being replaced and surpassed by computers. The title text then again suggests, however, that the human statement is not true, referring to an Inspiron model of Dell computer which "quietly amuses itself" by showing a geometric screensaver as it presumably one day will be obsolete and replaced by a newer computer. The original purpose of screensaver programs was to prevent images or characters from being burned into the phosphor layer of the older CRT displays. In more modern displays, including newer CRTs (cca mid-90s or newer), this could be achieved by simply turning it off after some period of time but originally there was no way to turn the display off programmatically. Thus the screensaver itself is already obsolete. Gwern Branwen has used GPT-3 to generate reassuring parables . [Megan is sitting at a computer, and Cueball is standing behind her.] Megan: Looks like computers will beat humans at Go pretty soon. Cueball: Wow. Cueball: That's the last of the big ones. Megan: Yeah. [Megan looks back over her shoulder at him.] Cueball: Well, at least humans are still better at, uh, Cueball: coming up with reassuring parables about things humans are better at? Megan: Hmm. [Megan types on her computer.] type type [She leans back over her chair again and addresses Cueball.] Megan: I made a Python script that generates thousands of reassuring parables per second. Cueball: Dammit. Computer: Computers will never understand a sonnet computers will never enjoy a salad comp—

Slideshow

Slideshow

https://www.xkcd.com/1264

https://www.explainxkcd.com/wiki/index.php/1264:_Slideshow

Dear website operators, [This strip is in the form of an animated gif. The panels transition with a Ken Burns-like fade-and-pan.] Cueball: I will never ... Cueball: ...want to browse a series of images... Cueball: ...like this.

It is very common for websites to feature a gallery of images – a website for a school, for example, might feature pictures of the students and teachers. Some websites display images in the form of a slideshow like this comic, with slow zoom and pan effects and fades between the images. This effect has been dubbed the Ken Burns effect after documentary filmmaker Ken Burns who popularized the effect. In many cases, the slideshow is a fixed element, and can't be controlled by the user. This prevents the user from navigating through the images at their own pace or viewing any one image for an extended period, and can be distracting. Randall expresses frustration at this. The title text suggests points will be awarded to whoever can add that annoying effect to the text editors of the developers of Flickr , a photo-hosting website, so they can be subjected to the same thing to which they are subjecting Randall. This may be a response to recent changes to Flickr's website that includes such slideshows as one option; that said, Flickr has always allowed users to browse galleries in a normal grid layout and with user-controlled photo-by-photo full-window layout. Dear website operators, [This strip is in the form of an animated gif. The panels transition with a Ken Burns-like fade-and-pan.] Cueball: I will never ... Cueball: ...want to browse a series of images... Cueball: ...like this.

Juicer

Juicer

https://www.xkcd.com/1265

https://www.explainxkcd.com/wiki/index.php/1265:_Juicer

[We see a shelf. On it, from left to right, are: a bag of fruit gushers; a juicer; a bottle of bright red liquid; a bottle of bright blue liquid; and another bottle of bright red liquid.] "Oh yeah, juicers are great! I use mine all the time."

Juicers are typically used to crush fruits and/or vegetables, thereby extracting the liquid juice and creating a tasty, refreshing and easy to consume drink. However, in this case, instead of actual fruits or vegetables, someone is making juice from Fruit Gushers , a chewy fruit-flavored candy, thereby extracting a nearly nutritionless artificial "juice" out of a candy casing which was formulated specifically for human consumption. This may or may not be a parody of recent "Fruit Gushers" television commercials, in which Fruit Gushers are shown to squirt out nearly limitless amounts of "juice". The title text asserts that the rind is where all the vitamins in the fruit reside. This is a common belief of actual fruits, although it is an untrue urban legend for many fruits; even fruits like apples do not contain most of the fiber in the skin itself, but rather directly below; although when you peel an apple you remove more than just the skin, losing also some high fiber content anyway. It is absolutely absurd as in this case, though, as the "rind" of a Fruit Gusher consists mainly of sugar. This text mocks the usual sentiment that the less desirable part of a food is the part that is "better" for you. It is also a parody of the notion that buying a juicer, or other things like exercise equipment, will automatically make people healthier. Here it is shown that what you do with the juicer is the relevant factor. It is a little hidden joke that there is way more red than blue, pointing out how Gushers (unfairly, because blue is the best flavor) always have more red than blue. The comic can also be interpreted as parodying the idea of fruit juices being healthy. Though this is widely believed, recent studies demonstrate otherwise. [We see a shelf. On it, from left to right, are: a bag of fruit gushers; a juicer; a bottle of bright red liquid; a bottle of bright blue liquid; and another bottle of bright red liquid.] "Oh yeah, juicers are great! I use mine all the time."

Halting Problem

Halting Problem

https://www.xkcd.com/1266

https://www.explainxkcd.com/wiki/index.php/1266:_Halting_Problem

[A short computer program.] [Caption below the panel]: The big picture solution to the halting problem.

In 1936 Alan Turing proved that it's not possible for an algorithm to decide whether an arbitrary program will eventually halt, or run forever. This was later called the Halting problem by Martin Davis . The official definition of the problem is to write a program (actually, a Turing Machine ) that accepts as parameters a program and its parameters. That program needs to decide, in finite time, whether that program will ever halt running these parameters. The halting problem is a cornerstone problem in computer science. It is used mainly as a way to prove a given task is impossible, by showing that solving that task will allow one to solve the halting problem. Randall , however, is providing a simpler solution. He implements his own code for the question "Does it halt?" which always returns "true", and directs us to think about the bigger picture. From a physical perspective, according to our current understanding of physics, this is right. Given enough time, any program will halt. This is due to factors external to the actual program. Sooner or later, electricity will give out, or the memory containing the program will get corrupted by cosmic rays, or corrosion will eat away the silicon in the CPU, or the second law of thermodynamics will lead to the Heat death of the universe . Nothing lasts forever, and this includes a running program. From a mathematical point of view, this is not true: a Turing machine will never have a hardware failure because it's not a physical machine. It's a theoretical construct, and it's defined mathematically, independent of any physical hardware. Similarly, ⅓ + ⅓ + ⅓ = 1 no matter what any physical hardware you are computing it on claims. Another interpretation of Randall 's code is that, assuming the language uses an eager evaluation strategy, the Program in the parentheses is actually being run whenever his function is called. In this case, the function would wait until the program finishes and exits before returning "True". Therefore, Randall 's function is mathematically accurate. It does not solve the problem though, as it simply shifts the question to whether the function itself will ever halt. If his language uses lazy evaluation, the input program is completely ignored, and it reduces to the incorrect mathematical interpretation. From a practical point of view, there are of course times that a programmer would want to return "false", since some programs can be mathematically shown to run forever. The title text further relates to this issue by claiming to have found a case where something need not die, but Randall does not know how to actually show it to anyone, because just the fact everyone will die sooner than it doesn't prove it will not die. The wording of the title text might also be a reference to Fermat's Last Theorem . It should be noted that Randall's solution, barring its unsoundness, solves more than the halting problem in the form it is usually stated. The halting problem requires two parameters (a program and its parameters), while Randall's function only accepts one (the program). The question of whether a program halts for every input can be shown to be even harder to solve than the halting problem, meaning that even if a Turing machine had an additional instruction allowing it to check whether a program halts with given parameters, it still could not always confirm that a given program that halts for all parameters does so. The code in this comic is written in pseudocode , to demonstrate the "algorithm" rather than an implementation in some existing programming language. The syntax resembles a mix of C and Python . The proof that the halting problem is unsolveable is to write a new function that uses Randall's program: DEFINE META_DOESITHALT(): IF ( DOESITHALT(META_DOESITHALT) ) WHILE ( TRUE ) DO_NOTHING; ELSE HALT; If Randall's function says that META_DOESITHALT halts by returning "TRUE" - then that makes META_DOESITHALT loop forever. But if it decides that it must halt by returning "FALSE" - then META_DOESITHALT halts. This proves that DOESITHALT can't possibly work - no matter what it actually does. This is the software equivalent of "Everything I say is a lie". [A short computer program.] [Caption below the panel]: The big picture solution to the halting problem.

Mess

Mess

https://www.xkcd.com/1267

https://www.explainxkcd.com/wiki/index.php/1267:_Mess

[Cueball and his Cueball-like friend walk into the friend's bedroom. The friend walks ahead while Cueball stand behind at the door. There's a made bed, a picture on the wall with a river and a sun at the horizon, some curtains around the window, a rug, and one unidentifiable item lying on the floor.] Friend: Sorry it's such a disaster in here. Cueball thinking: Whoa— what's wrong with me? [Caption below the panel:] My room never looks as nice as the rooms other people apologize for. The painting in Cueball's friend's room strongly resembles the painting in 1159: Countdown .

There is a common psychological phenomenon which causes people to mentally magnify their own flaws, while failing to notice the flaws of others, so common it apparently doesn't have a specific scientific categorization. Many self-conscious people apologize for "the mess" in their home whenever they have guests over, no matter how clean it may actually be. If the house is neater than the guest's own home, the guest is likely to say to themself: "If she thinks this is messy, what would she think of my place?!" This phenomenon is shown in the comic when Cueball's friend apologizes for the mess, despite the only thing appearing out of order is what seems to be a crumpled article of clothing on the floor. This "mess" only amplifies Cueball's fears about his own lifestyle, as he is surely wondering what his friend might think of his messy lifestyle based on their much higher standards. In the title text, Cueball's anxiety in further amplified when the host left out a glass of water from the night before and apologies for it. Cueball is nervous because when this seemingly small oversight, when applied to his friend's very high standards, might seem like a huge problem, and in his mind, making his home akin to something he thinks is no better than a garbage pit. In 1565: Back Seat the exact opposite reaction to having to show other people a real messy place is used for the joke. [Cueball and his Cueball-like friend walk into the friend's bedroom. The friend walks ahead while Cueball stand behind at the door. There's a made bed, a picture on the wall with a river and a sun at the horizon, some curtains around the window, a rug, and one unidentifiable item lying on the floor.] Friend: Sorry it's such a disaster in here. Cueball thinking: Whoa— what's wrong with me? [Caption below the panel:] My room never looks as nice as the rooms other people apologize for. The painting in Cueball's friend's room strongly resembles the painting in 1159: Countdown .

Alternate Universe

Alternate Universe

https://www.xkcd.com/1268

https://www.explainxkcd.com/wiki/index.php/1268:_Alternate_Universe

[Captions above the panel:] Imagine you were transported to an alternate universe just like your own, except people occasionally ate spiders. You can't convince anyone this is weird. [Megan is holding a very large spider, with another similar spider before her on the ground, and Cueball is standing behind her, leaning away with his hands out to each side shocked, as shown with three small lines going out from his head.] Megan: Mmm... Cueball: No! What are you doing!? [Caption below the panel:] This is how I feel about lobster.

Randall is trying to make the point that eating lobsters is as weird as eating spiders . Crustaceans and arachnids are both arthropods , members of the same phylum, so his comparison isn't too far off. Then again, humans are in the same phylum ( chordates ) as sea squirts , so any perceived similarities are not exactly rooted in a close biological relationship. In addition, lobsters were once considered the "cockroaches of the sea", and a captain trying to feed his crew with lobster would often be seen as cruel; although there is some justification for that mindset as lobsters were served by being crushed into mush, shell and all, and boiled into a bland gruel. On the other hand, cooked tarantula spiders are considered a delicacy in Cambodia . One common objection to eating spiders, crickets, roaches, and ants is that they are sometimes eaten whole, with guts, feces, and chitin devoured indiscriminately. However, many people eat only the actual muscles of the lobster, the same as one would any vertebrate. In the title text, Randall suggests a fantastical reason for why he is so repulsed by eating lobster; he was actually born on a world almost completely identical to Earth, and was unknowingly relocated to our Earth when he was a teenager. The sentiment expressed here is that the act of eating lobster feels outright alien to him. This might be a reference to the Mandela Effect , which is a suggestion by various peoples - some jokingly, some seriously - that groups of people occasionally get transported into alternate realities as an explanation for why so many people were certain that Nelson Mandela died in the 1980s despite him actually dying in 2013. (Contrary to popular belief, the Mandela Effect is not rationalising those false memories but rather why so many people have the same false memory.) To feel that strongly about shellfish-based cuisine, he would have to have not been exposed to it until his adolescent years; this seems unlikely, as the real Randall Munroe was born about 60 miles inland from the United States' northern east coast, where said cuisine is particularly prevalent. In reality, he is probably merely grossed out by the idea of eating lobster, and is probably exaggerating his feelings for comic effect. The title text also references changing clocks to and from Daylight Saving Time (DST), a practice which Randall has previously shown disdain for, mocking its irrational premise in several comics . Again, he is likely comically exaggerating his feelings, unless he literally doesn't recall a time before his teenage years when his parents ever changed the clocks in accordance with DST. The term " Earth Prime " is typically used in fictional multiverse settings, as a way to conveniently distinguish the Earth in which the narrative is rooted from any other Earths featured in the story. The idea of a alternative universe where Brussels sprouts taste good was the subject in 2241: Brussels Sprouts Mandela Effect . [Captions above the panel:] Imagine you were transported to an alternate universe just like your own, except people occasionally ate spiders. You can't convince anyone this is weird. [Megan is holding a very large spider, with another similar spider before her on the ground, and Cueball is standing behind her, leaning away with his hands out to each side shocked, as shown with three small lines going out from his head.] Megan: Mmm... Cueball: No! What are you doing!? [Caption below the panel:] This is how I feel about lobster.

Privacy Opinions

Privacy Opinions

https://www.xkcd.com/1269

https://www.explainxkcd.com/wiki/index.php/1269:_Privacy_Opinions

Opinions on Internet Privacy The Philosopher: Megan: "Privacy" is an impractical way to think about data in a digital world so unlike the one in which our soci-- Ponytail: So bored. The Crypto Nut: Cueball: My data is safe behind six layers of symmetric and public-key algorithms. Friend: What data is it? Cueball: Mostly me emailing with people about cryptography. The Conspiracist: [Cueball talks to Megan.] Cueball: These leaks are just the tip of the iceberg. There's a warehouse in Utah where the NSA has the entire iceberg. I don't know how they got it there. The Nihilist: Megan: Joke's on them, gathering all this data on me as if anything I do means anything. The Exhibitionist: [Cueball is watching a surveillance console, Officer Ponytail stands behind him.] Console: Mmmm, I sure hope the NSA isn't watching me bite into these juicy strawberries!! Oops, I dripped some on my shirt! Better take it off. Google, are you there? Google, this lotion feels soooo good. Cueball: Um. The Sage: [Beret Guy and Cueball sitting at a table. Beret Guy is holding a burrito.] Beret Guy: I don't know or care what data anyone has about me. Data is imaginary. This burrito is real.

This comic is about opinions on internet privacy in general. Six positions are offered as options. Four of the positions are tagged negatively by Randall by their subtitles alone: the Crypto Nut, the Conspiracist, the Nihilist, and the Exhibitionist, all of which have negative meanings in contemporary English. That the viewer is encouraged to identify negatively with these four positions is further encouraged by the content of the panels, as those characters are depicted either as having such boring lives that they have no need for privacy (the Crypto Nut, the Nihilist), or as being crazy (the Conspiracist, the Exhibitionist). A fifth position, the Philosopher, is tagged somewhat ambivalently by Randall: Megan, or possibly a look-alike, is depicted as boring her interlocutor, yet in the title text, Randall admits that he is usually the Philosopher. Also, “Philosopher” in vernacular English is neutrally valenced, potentially having the ability to expound either wisdom ("sophia") or sophistry . It is also a synonym for Sage, the sixth position. As Randall condones his own movement from Philosopher to Sage, he thus indicates that the Philosopher is to be viewed negatively, even if it is a tempting position to hold. The title of the sixth position, the “Sage”, is positively valenced in contemporary English, and the author in the title text states that once he obtains a “burrito” — i.e., a “real” thing, he switches from the Philosopher to the Sage. The internal evidence presented thus far therefore is entirely consistent; Randall encourages the reader to identify with the Sage. However, the choice of Beret Guy to represent the Sage undercuts this somewhat as Beret Guy is frequently seen as bizarrely disconnected from reality in a way that is maladaptive (e.g. 1030: Keyed ) and overly obsessed with food to the point of creating trouble and potential self-harm (e.g. 452: Mission ). By presenting five negatively tagged positions followed by a positively tagged sixth and final one, the author follows a rhetorical commonplace of listing and refuting a number of positions one by one, concluding with the favored and best one, which is not refuted and should be accepted both on its own merits and by virtue of being the last one standing. The comic therefore implies that no other (significant) positions exist. Having completed the rhetorical analysis of the comic, we are now in a position to understand the meaning of “Internet Privacy”. Panels #3 and 5 directly reference the American NSA. Panel #5's “exhibitionist” also references Google, but the characters in the panel appear to be NSA agents (one wears an official cap and they are viewing the exhibitionist on an official, government-looking monitor). Likewise, the focus of the “Nihilist” is that the joke is on the people who gather the data, rather than those who are subsequently able to make use of it (such as Facebook's users rather than “Facebook” itself; i.e., Facebook's employees and, by extension, its advertisers). The content of the actual data is only mentioned in panels #2, 4, and 5, and in each panel, it is suggested that it is meaningless or trivial. The Sage underscores the notion that any data known about him does not bother him, and therefore must be meaningless or trivial. The reader is thus encouraged to believe that it does not actually matter whether others discover personal data about him/her. The comic is therefore what social theorists call reductive , because it reduces the range of possibilities of “Opinions on Internet Privacy” to an artificially and simplistically narrow subset; in this case, individuals concerned with government or corporate agencies using data that they have gathered on individuals, and the futility of worrying about such things. The comic does not admit the possibility of other “opinions on internet privacy” – namely, that individuals might have legitimate concerns with governmental or corporate uses of their data, let alone other individuals' access to data that is assembled and distributed by corporations such as Facebook. The comic likewise does not consider the possibility of individuals having more interesting lives than the characters depicted, and therefore very real concerns about their privacy due to the activities that they engage in that are potentially more career limiting (should they be discovered) than obsessing about cryptography or eating a burrito. The comic is “functionally” reductive, as opposed to “intentionally” reductive, because the reduction is the function or effect of the comic for readers who read it straightforwardly. There is not enough internal evidence in the comic to maintain that the author intentionally excluded other viable opinions on internet privacy; it could be that they are just not on his radar. For example, we do not have enough information in the comic to claim that Randall is against civil rights; it could be simply that he doesn't often think about them. Likewise, it would exceed the evidence of the comic to claim that the author believes that schoolteachers who use the internet to facilitate legal but frowned-upon sexual behaviors should lose their jobs if they are found out due to internet privacy breaches; it could be that Randall simply hasn't bothered to worry about these matters if they don't affect him personally. This adjudication – whether the comic is “intentionally” reductive or not – may only be made on the basis of external evidence; that is, data known about Randall from sources beyond this comic. An alternative interpretation of the title text is that it is not Randall speaking his own opinion, but instead represents Beret Guy's (i.e. the “Sage's”) perspective. Randall may indeed have some concern with internet privacy, which would be consistent with the views on open-source security expressed in 463: Voting Machines , for example. In other cases, such as 1490: Atoms and 1419: On the Phone , the title text has been used as additional, farcical statements made by characters in the strip, rather than as Randall expressing his own views. Under this interpretation, Beret Guy would be prone to philosophizing about security, but then be easily distracted by a burrito; this is consistent with Beret Guy's general behavior. Additional observations about the comic follow. Since a large percentage of people and companies present in the internet don't have the ability or intention to do strong cryptography, the crypto nut's communication is limited to talking with other crypto nuts - which indicates cryptography as a topic. A real crypto nut will encrypt not just the important stuff because otherwise the attacker (in this context, assumed to be a government agency, network operator or corporation) will know which mails contain stuff that was secret enough to warrant encrypting, thus giving them information about whom he's doing secret business with. The (data) warehouse mentioned is the Utah Data Center which seems to be of impressive size. The punchline is created by taking the iceberg and warehouse analogies literally. This type is predominantly associated with twitter, but other social networks as well. This archetype is humorously combined with a sexual exhibitionist, who gets a sexual rise from the knowledge that others are spying on him/her. The awkwardness of the spying officials is magnified by the fact that they appear to be of opposite sexes, increasing the discomfort of the seated male. The monologue alludes to a scene in The Matrix in which Cypher arranges with the evil machines to become a traitor. The Sage is apparently immediately satisfied when he has food and prosperity. He does not need privacy or other democratic rights as long as he does not individually suffer from their absence. The release of the comic on this date could be to coincide with the premiere of South Park 's 17th season on the same date, which starts with an episode ( Let Go, Let Gov ) in which Cartman discovers that the NSA has been spying on him. The title text is to suggest that he enjoys burritos so much that being handed one even while philosophizing (his natural state) would stop him in his tracks to eat the burrito, thus becoming a pseudo-sage concerned only with the burrito at the exclusion of the topic of internet security. The burrito is later mentioned as a way to stay connected to the real word (compared to the world of art) in 1496: Art Project . Opinions on Internet Privacy The Philosopher: Megan: "Privacy" is an impractical way to think about data in a digital world so unlike the one in which our soci-- Ponytail: So bored. The Crypto Nut: Cueball: My data is safe behind six layers of symmetric and public-key algorithms. Friend: What data is it? Cueball: Mostly me emailing with people about cryptography. The Conspiracist: [Cueball talks to Megan.] Cueball: These leaks are just the tip of the iceberg. There's a warehouse in Utah where the NSA has the entire iceberg. I don't know how they got it there. The Nihilist: Megan: Joke's on them, gathering all this data on me as if anything I do means anything. The Exhibitionist: [Cueball is watching a surveillance console, Officer Ponytail stands behind him.] Console: Mmmm, I sure hope the NSA isn't watching me bite into these juicy strawberries!! Oops, I dripped some on my shirt! Better take it off. Google, are you there? Google, this lotion feels soooo good. Cueball: Um. The Sage: [Beret Guy and Cueball sitting at a table. Beret Guy is holding a burrito.] Beret Guy: I don't know or care what data anyone has about me. Data is imaginary. This burrito is real.

Functional

Functional

https://www.xkcd.com/1270

https://www.explainxkcd.com/wiki/index.php/1270:_Functional

[White Hat stands behind Cueball, who is sitting at a computer.] White Hat: Why do you like functional programming so much? What does it actually get you? Cueball: Tail recursion is its own reward.

Highlighting

Highlighting

https://www.xkcd.com/1271

https://www.explainxkcd.com/wiki/index.php/1271:_Highlighting

[A paragraph of text is shown. The highlight starts away from the leftmost edge of the highlight, and is a different distance to that between the rightmost edge of the highlight and the highlight end. Red X.] [A paragraph is shown. The highlight's starting point, end point, and number of lines included is such that there is an internal square in the middle, illustrated in green. Green tick.] [A paragraph is shown. Not only does it have an internal square, but the distance between the leftmost edge and the highlight start point is the same as the distance between the rightmost edge and the highlight end point. Green tick.] [A paragraph is shown. The entire paragraph is highlighted, making one big rectangle. Green tick.] [A paragraph is shown. The whole paragraph is selected, but the highlight starts away from the leftmost margin. This is shown with a red box, an arrow, and "?!?!". Red X.] [A paragraph is shown. Over the top is overlaid "[Clicking to highlight text is disabled]". Many, many red Xes.] I absentmindedly select random blocks of text as I read, and feel subconsciously satisfied when the highlighted area makes a symmetrical shape.

A number of people find it easier to read long texts by marking their place as they move through the reading. When done on paper, this may be done with a ruler, pencil, or finger. On-screen, however, one of the most effective methods is by highlighting the text being read. People accustomed to this form of reading often do it absentmindedly. Some people simply highlight parts of an article they're consulting without regards to which line they're currently reading, just to occupy their hands. Highlighting, however, has the potential to create shapes on screen. Randall is referring to the fact that the shapes created may occasionally be symmetrical, which creates satisfaction. Different highlighting patterns may be caused by the user's browser, the site provided, or by simply dragging one's cursor across the screen with the mouse button held down, and releasing at different patterns.. The top example shows tight-fitting highlight syntax, which only covers the text of the paragraph. This is the most common result of highlighting an entire paragraph, but as paragraphs are rarely symmetrical, this example is marked by an X. The second example starts the highlighting a few words in and continues to the end of the paragraph, while the third example begins another half-word in and continues down a line and a word before ending. Both of these patterns would be caused by manually highlighting the text with the mouse button, rather than rapidly-clicking until a segment is highlighted. The second example forms a square where the three lines of highlighted text overlap, while the third has rotational symmetry of the selected region; both are marked with checks. The fourth example highlights the entire paragraph, as well as the whitespace caused by the indentation of the paragraph and at the end of the paragraph when the last line does not continue to the opposite margin. This example has both rotational and divisible symmetry, and is marked with a check. The fifth example highlights the whitespace after the end of the paragraph, but not the whitespace of the indentation, leaving an odd block at the start of it. This ruins the paragraph's symmetry, and so this example is marked with an X. The bottom example refers to the practice of websites adding a script to disable highlighting, often to discourage readers from copying their content. This creates a great dissatisfaction in readers accustomed to highlight as they read, shown by the many overlapping "X"s. Ironically since the comic is an image, the text in the comic can also not be highlighted. The title text refers to the practice of websites of adding a script that searches upon clicking any word in the text; most notably done by Yahoo! news in years prior. The search may be of the site, the web, or of an advertisement provider. The script sometimes creates a popup, which, Randall says, causes him to "panic", and consequently never want to return to the site again. It is in fact quite annoying to the occasional highlighter, causing him to lose his place and interrupting his train of thought. [A paragraph of text is shown. The highlight starts away from the leftmost edge of the highlight, and is a different distance to that between the rightmost edge of the highlight and the highlight end. Red X.] [A paragraph is shown. The highlight's starting point, end point, and number of lines included is such that there is an internal square in the middle, illustrated in green. Green tick.] [A paragraph is shown. Not only does it have an internal square, but the distance between the leftmost edge and the highlight start point is the same as the distance between the rightmost edge and the highlight end point. Green tick.] [A paragraph is shown. The entire paragraph is highlighted, making one big rectangle. Green tick.] [A paragraph is shown. The whole paragraph is selected, but the highlight starts away from the leftmost margin. This is shown with a red box, an arrow, and "?!?!". Red X.] [A paragraph is shown. Over the top is overlaid "[Clicking to highlight text is disabled]". Many, many red Xes.] I absentmindedly select random blocks of text as I read, and feel subconsciously satisfied when the highlighted area makes a symmetrical shape.

Shadowfacts

Shadowfacts

https://www.xkcd.com/1272

https://www.explainxkcd.com/wiki/index.php/1272:_Shadowfacts

[Gandalf sits on a horse, addressing three hobbits.] Gandalf: This is Shadowfacts, lord of all horses, and he– Shadowfacts: The outer part of a shadow is called the penumbra! Gandalf: Shut up.

This comic is a parody of J.R.R. Tolkien 's The Lord of the Rings . The name of the horse, Shadowfacts, is a pun on Shadowfax , the horse Gandalf rides in the books. As the name "Shadowfacts" suggests, this horse interjects into conversations various facts about shadows. There is a possible deeper level to the pun, referring to the cat facts meme . The three parts of a shadow are the umbra , penumbra and antumbra . In the title text, Gandalf continues to speak, and is interrupted again by the horse with another fact about shadows. "Look to my coming on the fifth day. At dawn, look to the east." is what Gandalf said before the battle of Helm's Deep when he went to get reinforcements. The horse notes that if the sun is in the east, the shadows will be to the west of the objects that cast them. A similar talking horse appears in 936: Password Strength . [Gandalf sits on a horse, addressing three hobbits.] Gandalf: This is Shadowfacts, lord of all horses, and he– Shadowfacts: The outer part of a shadow is called the penumbra! Gandalf: Shut up.

Tall Infographics

Tall Infographics

https://www.xkcd.com/1273

https://www.explainxkcd.com/wiki/index.php/1273:_Tall_Infographics

BY THE YEAR 2018 2019 2020 ALL INFO Rmation [Graph representing all information.] [X axis of graph: 6 YEARS from now ( 72 months)] WILL BE [in two segments of a pie chart] Megan: COMMUNICATED Hairy: Yes! in THIS CLEAR and CONCISE [in a Venn diagram] F O R M A T [on the x axis of a bar graph of where these letters fall in the alphabet (the bar labeled T is shaded with a different color)] [Arrow pointing to the bar labeled "T": T ]

This comic is a satirical infographic , which is usually used to simplify and help visualize information that would be dreadfully boring otherwise. Randall takes this "simplification" to the extreme by making an unhelpful infographic, complete with unnecessary data and ironic and blatant misuse of common graphs and charts. At this point, he is not even simplifying his sentence "By the year 2019, all information will be communicated in this clear and concise format." He makes a sarcastic claim, pointing out how needlessly complicated some infographics make things they are supposed to condense. In the chart: It is also likely that this comic is a send up of the recent trend towards presenting information in tall graphics that are easily viewed on smartphone screens. A tall graphic with the same pixel width as an iPhone, for example, can be viewed without zooming and using only vertical scrolling. Another discussion venue for the topic and this comic is Gizmodo: Tall Infographics Suck . The prediction communicated in the comic did not actually happen by the year 2019. Alternatively, it did happen but was reversed so quickly nobody noticed it happened. The title text mentions the often-hyped term " big data ." "Big data" normally refers to the challenges of working with and visualizing a quantity of data which is hard to process using traditional tools and methods. Randall, now speaking unsarcastically, tells us that just because the font size is huge doesn't mean you have handled the big data well. BY THE YEAR 2018 2019 2020 ALL INFO Rmation [Graph representing all information.] [X axis of graph: 6 YEARS from now ( 72 months)] WILL BE [in two segments of a pie chart] Megan: COMMUNICATED Hairy: Yes! in THIS CLEAR and CONCISE [in a Venn diagram] F O R M A T [on the x axis of a bar graph of where these letters fall in the alphabet (the bar labeled T is shaded with a different color)] [Arrow pointing to the bar labeled "T": T ]

Open Letter

Open Letter

https://www.xkcd.com/1274

https://www.explainxkcd.com/wiki/index.php/1274:_Open_Letter

[The picture shows a letter.] October 7 th 2013 To: The Freemasons, the Illuminati, Scientology, FEMA, the New World Order, the Federal Reserve, Citigroup, Halliburton, Google, the Vatican, Bilderburg, Walmart, the Rothschilds, the Knights Templar, HAARP, the UN, Skull & Bones, Bohemian Grove, the Koch Brothers, George Soros, the Trilateral Commision, the Knights of Malta, the CFR, Exxon Mobil, the Zionists, the Vril Society, the Lizard People, and everyone else who secretly controls the US government Can you please get your shit together? This is embarrassing. Sincerely, A Concerned Citizen

This comic is a reference to the US government shutdown in 2013 that had been ongoing for a week and was still current as of the time of this comic. Under some circumstances, the United States Federal Government can temporarily shut down pending budget legislation being passed by the United States Congress. These shutdowns are typically due to political disagreements between the President, the House of Representatives, and the Senate. Due to the shutdown, numerous government services and facilities are shut down, often resulting in many logistical issues for the public. Over the years, various conspiracy theories have been proposed claiming that the United States Government is not controlled by publicly-elected officials, but rather by one or more organizations that secretly control the actions of the government (sometimes termed a "shadow government" ). In this strip, Randall writes a letter to the shadow government, telling them that the situation (having the country's government shut down) is embarrassing and asking them to fix the problem. This comic also implicitly argues against the plausibility of the aforementioned conspiracy theories if one assumes that a shadow-controlled government would be more likely to operate with a singular purpose and therefore be less susceptible to paralyzing political disagreements. Randall previously alluded to this in the title text to comic 1081 : "Really, the comforting side in most conspiracy theory arguments is the one claiming that anyone who's in power has any plan at all." This is one of several comics in which Randall expresses dismay at how many intelligent people can fall for absurd conspiracy theories; see comics 258 and 690 , among others. The title text addresses the leadership of the shadow government in more colloquial terms, asking if they are suffering from personal problems that are impeding their ability to keep things under control. This is patronizing, and thus hilarious. The message, as titled, is in the form of an " Open Letter ", being a directed and 'personal' message to a person or group of people which is nonetheless intended by the sender to be publicly aired (unlike a standard commentary or editorial, which is intended for public consumption, but addresses the concerned 'target' almost as an aside). In some cases this may be to ensure the correspondence is not kept confidential by the recipients and/or that the public as a whole are also indirectly addressed ('Cc'ed) in the correspondence, without having to compose a companion piece for that purpose. In this case, however, it may additionally be because the intended recipient(s) are not so easily identified for direct communication, and a public airing would ensure 'delivery' even without compromising the integrity of the message. Open Letters are often aired (or pre-copied, verbatim, from actual correspondence) in one or area or other of the public media, and while web-comics aren't necessarily the most publicised of forums, the xkcd readership almost certainly leads to covering both the 'named' recipients and the intended public view. [The picture shows a letter.] October 7 th 2013 To: The Freemasons, the Illuminati, Scientology, FEMA, the New World Order, the Federal Reserve, Citigroup, Halliburton, Google, the Vatican, Bilderburg, Walmart, the Rothschilds, the Knights Templar, HAARP, the UN, Skull & Bones, Bohemian Grove, the Koch Brothers, George Soros, the Trilateral Commision, the Knights of Malta, the CFR, Exxon Mobil, the Zionists, the Vril Society, the Lizard People, and everyone else who secretly controls the US government Can you please get your shit together? This is embarrassing. Sincerely, A Concerned Citizen

int(pi)

int(pi)

https://www.xkcd.com/1275

https://www.explainxkcd.com/wiki/index.php/1275:_int(pi)

[Inside a frame a formula is shown:] volume(r) = (4/int(pi))*pi*r^int(pi) [Caption below the frame:] Programming Tip: The number "3" is cursed. Avoid it.

This comic purports to provide a tip to programmers, that the number " 3 " is cursed and shouldn't be used. There is no explanation given as to why the number 3 is cursed, and it could well have been chosen arbitrarily. The title text hints that the consequence for using the cursed number is non-functioning code, a pain for any programmer. The absurdity of the number 3 somehow being cursed is part of the humor. To assist the programmer, the comic gives an example of how to avoid the use of the number 3, by using a slightly convoluted method of using int(pi) , which means the integer part of pi , without the fractional part . Pi, an irrational number , has a value starting 3.14159... , making int(pi) equal to 3. This is demonstrated in a formula to calculate the volume of a sphere , normally (4/3)*pi*(r^3), but converted for avoidance of the number 3 to (4/int(pi))*pi*(r^int(pi)). For a number of reasons it is a good programming practice to use variables and constants where a value is used in multiple places, however this is not typically used in the case of natural numbers. There are unusual situations where this type of programming is a valid method, however typically for more specific circumstances, and not a certain number being seen as cursed. In the title text, Randall takes the joke a step further, suggesting the usage of floor and ceiling functions : ceiling(pi) would be pi rounded up to the next integer, which is 4 ; and floor(pi) is pi rounded down to the next integer, which is 3. (Note that int(n) and floor(n) have the same value when n is greater than or equal to zero. For values less than zero, int(n) is equal to ceiling(n) .) The joke here plays on the fact that basic rules of programming are confusing and novice programmers are often told to simply not do certain things without any explanation (see 292: goto ). This includes, in particular, a general proscription against " magic numbers " in the code. Replacing all significant magic numbers with named constants makes programs easier to read, understand and maintain. Randall takes this to an extreme by suggesting that certain numbers could be inherently problematic, but the general idea is perfectly believable. Mmm... Floor pie. is a reference to The Simpsons. See also Cargo cult programming . [Inside a frame a formula is shown:] volume(r) = (4/int(pi))*pi*r^int(pi) [Caption below the frame:] Programming Tip: The number "3" is cursed. Avoid it.

Angular Size

Angular Size

https://www.xkcd.com/1276

https://www.explainxkcd.com/wiki/index.php/1276:_Angular_Size

The size of the part of Earth's surface directly under various space objects [Several images are shown, of space objects of differing size and at different distances from Earth, illustrating the differing sizes of their "shadows" as mapped onto Earth's surface viewed from the center of the Earth.] [The first image merely sets the stage: Earth is a full circle, with two figures — Cueball and Megan — standing on it; a small space object casts a "shadow" on Megan, while a slightly larger object, though proportionally farther away, casts just about the same size shadow next to Cueball.] [The second image is a map showing London, with the Thames running through it, and a ring highway running around it labeled "London's M25 Orbital Freeway". A grey circle is overlaid, just about the diameter of the M25; it is labeled "The Sun and The Moon (about the same size)".] [The third image has a small grey rectangle in one corner labeled "Soccer field" for comparison. The image is dominated by four large, grey circles, considerably larger than the soccer field, labeled "Saturn", "Mars", "Jupiter", and "Venus", with Mars slightly larger than Saturn, Jupiter approximately twice the diameter of Saturn, and Venus approximately three times the diameter of Saturn. Smaller circles are labeled "Mercury", "Uranus", and "Neptune", with Mercury still somewhat larger than the soccer field, Uranus about its size, and Neptune slightly smaller.] [The fourth image has the soccer field blown up to take up much of the view; its center circle, goal areas, and corner kick areas are visible. Labeled grey circles of various circles are again overlain: Callisto and Ganymede are about as large as one half of the field; Io, Titan, and Europa are somewhat smaller than half the field; and Ceres, Triton, and Pluto are much smaller (all three together would probably fit into the soccer field's center circle).] [In the fifth image, there is a different grey rectangle, this one labeled "Ping Pong table", with a few balls and paddles visible. An irregular ovoid labeled "Phobos" is about the size of the table, as is a circle labeled "R. Doradus". An irregular circular shape labeled "Deimos" is about the size of half the table; a circle labeled "Betelgeuse" is a little smaller, and a circle labeled "Eris" is a little smaller, though still comfortably filling most of half of the table.] [In the sixth image, a light grey image of laptop computer keyboard and screen is shown, viewed from directly above. An irregular shape labeled "4942 Munroe" is slightly larger than the laptop, while circles labeled "Alpha Centauri A", "Sirius", and "Alpha Centauri B" form a descending series somewhat smaller than it. Circles labeled "Proxima Centauri" and "Barnard's Star" are considerably smaller than the laptop: Proxima Centauri would fit on the trackpad, while Barnard's Star covers perhaps four keys on the keyboard.] [In the seventh image we see a greatly zoomed-in shape which is identified as the "Tilde on laptop keyboard". A circle labeled "HD 189733 b (permadeath)" is almost as large as the tilde is wide; a circle labeled "Tau Ceti C (giant dog planet)" is somewhat smaller. Circles labeled "Gleise 581 g (jelly-filled planet)", "Gleise 667 C c (PILF)", and "HD 20794 c (moonchild)" are all 1/2 to 1/3 as wide as the tilde is wide. A smaller circle labeled "Event horizon of the black hole at the center of our galaxy" fits comfortably within the tilde's stroke width. A very small dot off in one corner (much smaller than the tilde or anything else in the image) is labeled "KOI-1686.01 (emergency backup earth)".] [Finally, in the eighth image, the size comparison is to the grey outlines of four bacilliform bacteria labeled "E. coli". The outlines of two interstellar probes are shown, with circular main housings and protruding instruments and antennae. They are labeled "Voyager 1" and "Voyager 2".] The exact dimensions of a professional soccer field are not precisely defined. In international matches they must be between 64 and 75m wide and between 100 and 110m long. Therefore soccer fields aren't well suited as a precise unit of measurement. However, they are commonly used to give people a rough understanding of an areas size. According to the angular diameter of the referenced celestial objects, Randall did his calculations using dimensions of 105m × 68m. A similar model of representing the angular diameter of celestial objects as portions of the Earth's surface seen from its center was described in Isaac Asimov's May 1961 essay "Heaven on Earth".

This comic is a comparison of the angular diameters (or apparent diameter) of various celestial objects at the surface of the earth relative to a vertex at the center of the Earth as diagrammed in the opening panel. The objects' scales are compared to actual objects on earth. Each size given is for the object at its closest approach to earth. London's M25 motorway is around 60 km (35 miles) across, a soccer field is about 100 meters long (109 yards), a ping pong table is 274 centimeters long (9 feet), a laptop is about 35 centimeters across (13.75 inches), the tilde symbol on a keyboard is about 5 millimeters long (197 mils), and a cell of E. coli is about 2 microns long (78.75 millionths of an inch). A simple formula can be used to find the size on earth of a celestial object when the size of or distance to the object is known. This is done by taking the radius of the earth, multiplying by the diameter of the object, and dividing by the distance to the object from the center of the earth. The space objects referenced in the panels are: The title text states that astronomy would be much easier if the celestial sphere were mapped to the earth - like a giant globe . Due to the distance of the stars you would just need magnifying glass to see the areas representing distant stars instead of an expensive powerful telescope to see huge distances. Approximate values for the mappings to the Earth sphere (based on mean Earth radius at 6,371.0 km or 3,958.8 mi.): The size of the part of Earth's surface directly under various space objects [Several images are shown, of space objects of differing size and at different distances from Earth, illustrating the differing sizes of their "shadows" as mapped onto Earth's surface viewed from the center of the Earth.] [The first image merely sets the stage: Earth is a full circle, with two figures — Cueball and Megan — standing on it; a small space object casts a "shadow" on Megan, while a slightly larger object, though proportionally farther away, casts just about the same size shadow next to Cueball.] [The second image is a map showing London, with the Thames running through it, and a ring highway running around it labeled "London's M25 Orbital Freeway". A grey circle is overlaid, just about the diameter of the M25; it is labeled "The Sun and The Moon (about the same size)".] [The third image has a small grey rectangle in one corner labeled "Soccer field" for comparison. The image is dominated by four large, grey circles, considerably larger than the soccer field, labeled "Saturn", "Mars", "Jupiter", and "Venus", with Mars slightly larger than Saturn, Jupiter approximately twice the diameter of Saturn, and Venus approximately three times the diameter of Saturn. Smaller circles are labeled "Mercury", "Uranus", and "Neptune", with Mercury still somewhat larger than the soccer field, Uranus about its size, and Neptune slightly smaller.] [The fourth image has the soccer field blown up to take up much of the view; its center circle, goal areas, and corner kick areas are visible. Labeled grey circles of various circles are again overlain: Callisto and Ganymede are about as large as one half of the field; Io, Titan, and Europa are somewhat smaller than half the field; and Ceres, Triton, and Pluto are much smaller (all three together would probably fit into the soccer field's center circle).] [In the fifth image, there is a different grey rectangle, this one labeled "Ping Pong table", with a few balls and paddles visible. An irregular ovoid labeled "Phobos" is about the size of the table, as is a circle labeled "R. Doradus". An irregular circular shape labeled "Deimos" is about the size of half the table; a circle labeled "Betelgeuse" is a little smaller, and a circle labeled "Eris" is a little smaller, though still comfortably filling most of half of the table.] [In the sixth image, a light grey image of laptop computer keyboard and screen is shown, viewed from directly above. An irregular shape labeled "4942 Munroe" is slightly larger than the laptop, while circles labeled "Alpha Centauri A", "Sirius", and "Alpha Centauri B" form a descending series somewhat smaller than it. Circles labeled "Proxima Centauri" and "Barnard's Star" are considerably smaller than the laptop: Proxima Centauri would fit on the trackpad, while Barnard's Star covers perhaps four keys on the keyboard.] [In the seventh image we see a greatly zoomed-in shape which is identified as the "Tilde on laptop keyboard". A circle labeled "HD 189733 b (permadeath)" is almost as large as the tilde is wide; a circle labeled "Tau Ceti C (giant dog planet)" is somewhat smaller. Circles labeled "Gleise 581 g (jelly-filled planet)", "Gleise 667 C c (PILF)", and "HD 20794 c (moonchild)" are all 1/2 to 1/3 as wide as the tilde is wide. A smaller circle labeled "Event horizon of the black hole at the center of our galaxy" fits comfortably within the tilde's stroke width. A very small dot off in one corner (much smaller than the tilde or anything else in the image) is labeled "KOI-1686.01 (emergency backup earth)".] [Finally, in the eighth image, the size comparison is to the grey outlines of four bacilliform bacteria labeled "E. coli". The outlines of two interstellar probes are shown, with circular main housings and protruding instruments and antennae. They are labeled "Voyager 1" and "Voyager 2".] The exact dimensions of a professional soccer field are not precisely defined. In international matches they must be between 64 and 75m wide and between 100 and 110m long. Therefore soccer fields aren't well suited as a precise unit of measurement. However, they are commonly used to give people a rough understanding of an areas size. According to the angular diameter of the referenced celestial objects, Randall did his calculations using dimensions of 105m × 68m. A similar model of representing the angular diameter of celestial objects as portions of the Earth's surface seen from its center was described in Isaac Asimov's May 1961 essay "Heaven on Earth".

Ayn Random

Ayn Random

https://www.xkcd.com/1277

https://www.explainxkcd.com/wiki/index.php/1277:_Ayn_Random

[Cueball sitting at a laptop, White Hat behind him.] Cueball: This Ayn Random number generator you wrote claims to be fair, but the output is biased toward certain numbers. White Hat: WELL, MAYBE THOSE NUMBERS ARE JUST INTRINSICALLY BETTER!

The comic is an attack on the problems with the philosophy of "Objectivism". White Hat explains to Cueball a program he wrote, the "Ayn Random Number Generator", which is a pun on Ayn Rand , the name of a writer who created a philosophical system known as Objectivism . The joke is an attack on her philosophy, which claims to be a completely fair mechanism for distributing resources, but inherently favors those who start out with more resources, or already in a position to acquire the resources. It also has a strong overarching theme that people that believe in objectivism are inherently better than other people, and thus deserve what extra resources can be acquired - as with the Ayn Random Number Generator, which claims to be completely fair and balanced, but actually favors some numbers - which White Hat explains by saying that they deserve to come up more because they're inherently better. Now, objectivists, of course, would challenge the above portrayal, but the joke is, in the end, an attack on Ayn Rand's philosophies. A more nuanced description is that objectivists believe that the primary aim of life is to maximise personal happiness. In their view, if some humans are born more capable of satisfying their desires than other people, they deserve to reap greater rewards from life than others, no matter the cost to those others. As an aside, "biased" random number generators exist. They're called weighted random number generators, and they have many practical applications when the programmer isn't lying about the number generator's function and output. The title text identifies a group of people whose names match the regular expression /(\b[plurandy]+\b ?){2}/i . A step-by-step explanation of the expression: Overall, it matches two words separated by a space, composed entirely of the letters in [plurandy], which is what all the names listed have in common. This could suggest that those letters are, to quote White Hat, intrinsically better. As an aside, if the entirety of the title text is matched against the regular expression, it matches "and Duran" instead of "Duran Duran". Since the primary virtue in Objectivist ethics is rationality (or, at least, "rationality" as defined by Rand: her critics argue that the conclusions she reached do not actually derive inevitably from her premises and that additional, unstated assumptions are necessary to make the system work), the implication may be that the random number generator favors rational numbers (numbers that can be written as a fraction, i.e. a quotient p/q). On the other hand, given computers cannot store data of unlimited length, it is impossible for any real world computer random number generator to produce an irrational number in any of the usual integer or floating point representations—so probably not. (Although a computer could encode irrationals or generate them randomly if it uses another representation, one of the standard algebraic number representations, for instance.) Alternately, an Objectivist might argue that if the intent of the comic is to attack or mock Objectivism, then the comic inadvertently satirizes itself via the "rationality" interpretation. [Cueball sitting at a laptop, White Hat behind him.] Cueball: This Ayn Random number generator you wrote claims to be fair, but the output is biased toward certain numbers. White Hat: WELL, MAYBE THOSE NUMBERS ARE JUST INTRINSICALLY BETTER!

Giraffes

Giraffes

https://www.xkcd.com/1278

https://www.explainxkcd.com/wiki/index.php/1278:_Giraffes

My Hobby: [Silhouette of a giraffe with a sauropod's tail.] Convincing genetic engineers that giraffes would look better if they had sauropod tails

Genetic engineering is the scientific approach towards altering and modifying the genome of organisms. In the process, DNA material is extracted from a source organism and then inserted into the genome of a host organism. It is thus possible to create hybrids between species that would not crossbreed naturally. The technique is also applied in order to expedite the sometimes lengthy process of selective breeding . The comic suggests the creation of genetically modified giraffes . Following the recurring theme in the comics that dinosaurs and dinosaur-like traits make life more interesting, Randall expresses his desire to see genetic engineers insert DNA from extinct sauropods into the giraffe's genome, resulting in giraffes with very large and thick tails. Randall has previously shown great interest in dinosaurs and their integration into the modern age. It is possible that Randall wishes to combine the two due to the fact that they'd look very "cool" together as they are both seemingly weird animals. Giraffes are distinctive for their extremely long neck and sauropods have extremely long tails; the drawing would indicate that the giraffe's neck and sauropod's tail are of equal height/length, thus creating a bizarrely satisfying sense of symmetry. The idea of extracting and reproducing DNA material of dinosaurs appears most prominently in the 1993 motion picture Jurassic Park . The concept is regarded by scientists as rather implausible because DNA disintegrates soon after the death of the organism (read: around 500 years ) and would not be preserved in fossils. Furthermore, the science of genetic engineering is not yet able to accomplish major alterations in complex genomes. While mice and other small vertebrates have successfully been modified for research purposes, the daily use of genetic engineering is limited to plants and monads . That besides, the less closely related the starting species are to each other, the more difficult it would be to successfully combine them. So while the field of genetic engineering is always advancing, combining the body of a modern-day mammal with the tail of a dinosaur will remain a pipe dream for a long time yet. (Also, there are no known cases of preserved non-avian dinosaur DNA being discovered, and current chemistry knowledge indicates that no DNA can survive over 1 million years.) In general, genetic engineering is a highly controversial topic with regards to the responsibility of science. While some praise the scientific progress and welcome the possibilities it brings, others fear that genetic science might enable man to alter the ways of nature and to presume the role of an almighty creator. The creation of hybrid animals (so called Chimeras ) is often regarded as the ultimate hubris and the climax of moral decay. Some countries have therefore installed strong legal restrictions for the modification of genetic material extracted from humans and animals. The title text refers to Kickstarter , a funding platform for creative projects. Any person who wants to start a creative project, but lacks the resources to do so, can create a Kickstarter campaign where donors can contribute donations. Usually, the owner of the Kickstarter promises exclusive benefits to donors of certain tiers. For example, the title text could well be finished to say If you fund my Kickstarter with a donation of $20 or more, I will give you exclusive access to my weekly blog on the development stages of the giraffosaurus. If you donate $100 or more, you can receive a life-sized cardboard cut-out of the giraffosaurus. Donations of $10,000 or more will earn your name in a raffle for ownership of the first three giraffosauruses. This may also be a reference to 1055: Kickstarter . While dinosaurs are a recurring trope since the beginning of xkcd, giraffes have been featured in some what-if articles as a measurement of height. Interestingly enough, there seems to have been a species of sauropod dinosaur that bore a certain likeness to the modern giraffe and has therefore been christened Giraffatitan . My Hobby: [Silhouette of a giraffe with a sauropod's tail.] Convincing genetic engineers that giraffes would look better if they had sauropod tails

Reverse Identity Theft

Reverse Identity Theft

https://www.xkcd.com/1279

https://www.explainxkcd.com/wiki/index.php/1279:_Reverse_Identity_Theft

If your email address is [First initial]+[Last name]@gmail.com you gradually get to know lots of older people who have the same name pattern Cueball: Yes, I know it would make sense if that were your email address, but it's not. Person on the phone: But how did you get my number? Cueball: Your phone bill.

Identity theft is the criminal method of assuming the identity of an unsuspecting person, usually to get credit in their name. While this is done deliberately, the comic introduces the idea of reverse identity theft: An older person with little knowledge of computers involuntarily uses another person's email address because they supposed it to be their own. Since most email addresses follow a generic pattern, they simply adapt the pattern to conform with their own name, unaware that someone with the same initial and last name already owns the address. Most internet users face at some point the message that their desired email address is "already taken". Because email addresses must be unique and only a limited set of characters is allowed, people with common names usually add numbers to their name. The comic suggests that elder people might easily forget that they had to take, for instance, [email protected] when they signed up. Instead, the person would tell everyone that their address was [email protected] , since that follows the generic pattern and is the most intuitive assumption for them. They are in complete ignorance that the address belongs, in fact, to whomever claimed it first. In this case, the address belongs to Randall himself. (In case you're wondering, yes, [email protected] is Randall's email according to the xkcd blag .) The comic has Cueball call an older person, who apparently gave Cueball's email address to the phone company, which now emails Cueball the bills - this could have been avoided if said company confirmed an email address first. The person is not able to understand why this is not their email address (as it corresponds with their name) and is also very confused how Cueball got their phone number. The latter reveals a major problem of reverse identity theft: Using another person's email address for your own business matters exposes your own identity. The owner of the address could easily take advantage of the situation, leading to a scenario of regular identity theft. Fortunately, Cueball seems to be more honest; Black Hat probably would not have given any warning. Due to the sheer mass of people online, nearly all simple nicknames are already taken; and the number of possible combinations is further diminished by services (e.g., Gmail ) which ignore the dot sign altogether and does not allow the use of hyphens or underscores. This policy is designed to prevent fraud, but it forces users to add numbers or other unique identifiers to their names. Apart from the scenario addressed in the comic, another subsequent problem is the use of wrong email addresses by third parties. Someone sending sensitive personal information to the wrong recipient can just as easily expose a person's identity as the person himself. In the end, there is no practical solution to the problems arising from the uniqueness of usernames and email addresses. Instead, it is simply the consequence of naming itself: While a name was originally intended to distinguish its bearer from a limited number of people (e.g. the rest of the village), the Internet makes it necessary to distinguish ourselves from the entire rest of the world (or at least everybody online). Note that Gmail ignores everything behind a plus sign. Like ignoring dots, this is used as a way to create email aliases . The plus sign in the formula used in the comic should therefore considered to be only an indicator for concatenation, not a literal character in the address. If your email address is [First initial]+[Last name]@gmail.com you gradually get to know lots of older people who have the same name pattern Cueball: Yes, I know it would make sense if that were your email address, but it's not. Person on the phone: But how did you get my number? Cueball: Your phone bill.

Mystery News

Mystery News

https://www.xkcd.com/1280

https://www.explainxkcd.com/wiki/index.php/1280:_Mystery_News

[Cueball sitting at a laptop.] Laptop: It's day five of the trade summit, and still no... Cueball: Dammit click click click I get most of my news from autoplaying videos in browser tabs I can't find. Title text : If you find and stop the video, but you've--against all odds--gotten curious about the trade summit, just leave the tab opened. It will mysteriously start playing again 30 minutes later!

With the introduction of tabbed browsing, many users, even on widescreens, will have so many tabs open that it is hard to find any given one. At 44 tabs on Google Chrome on a 1080p screen, the user can no longer see any text on the tabs. Long before this point (~20 tabs), the text is so short as to be unusable. Randall refers to this tendency to open many tabs without closing them in this comic. Many modern tabbed browsers can remember what tabs were open upon closure if this setting is on, and will reload the same tabs on startup. This will start any auto-playing videos, such as YouTube videos (although some browsers, like Firefox, have since fixed this by forcing videos to pause), which appear on any of the open pages. This situation can also occur during browsing when an auto-playing video does not begin playing until after a user has moved on to a new tab, when a page with a video refreshes in the background, or when a site with such a video automatically opens in a tab that does not become the active tab when it opens. This generally leads the user to clicking through all of the open tabs to try to find where the sound is coming from. This can be even more difficult if the video is not obvious and not centered on the screen of whatever tab it is playing in. Years after the release of this comic, Google Chrome began to indicate to the user which tabs are playing audio, thus alleviating this problem. The title text refers to websites that refresh in the background , causing videos (and ads) to start playing again even if you stopped them previously. Many news sites, such as CNN, will do this if you stay on the same page for 30 minutes . [Cueball sitting at a laptop.] Laptop: It's day five of the trade summit, and still no... Cueball: Dammit click click click I get most of my news from autoplaying videos in browser tabs I can't find. Title text : If you find and stop the video, but you've--against all odds--gotten curious about the trade summit, just leave the tab opened. It will mysteriously start playing again 30 minutes later!

Minifigs

Minifigs

https://www.xkcd.com/1281

https://www.explainxkcd.com/wiki/index.php/1281:_Minifigs

[Graph: x-axis 1980, 1990, 2010, 2020; y-axis 1, 2, 3, 4, 5, 6, 7, 8 billions.] [Plot-line 1: Number of people in the world.] [Plot-line 2: Number of Lego People in the world.] [Label above the x-axis at 2013 reads "Today".] [Shortly before 2020, both plot lines cross.] [Caption below the graph:] By 2019, humans will be outnumbered.

Lego minifigures (often abbreviated as minifigs ) are tiny plastic people designed by the Danish toy manufacturer Lego as part of their construction toy sets. Since 1978, over four billion minifigures have been sold, so they still have a long way to go before they surpass the human population (which is around 7.8 billion). The figures resemble simplified humans, often with a yellow skin colour and featuring interchangeable body parts, such as legs, torsos, heads, hair, and hats. The graph depicted in the comic extrapolates the total number of minifigures and compares it to the growth of the world population , which reached 7 billion in March 2012. By the extrapolations of the comic, Lego minifigures will outnumber the human population by 2019. The extrapolation of statistical data has appeared in various xkcd comics, e.g. in 605: Extrapolating , 1007: Sustainable , and 1204: Detail . However, unlike the other extrapolated scenarios, the prognosis of this comic seems quite likely. Since Lego is designed to resemble nature and civilization on a miniaturized scale, some sets also contain Lego cars as vehicles for the minifigures. With over 381 million Lego tires produced for these miniature cars, Lego is already the world's largest manufacturer of tires . This fact is addressed in the title text. Lego (as of mid-October 2013) calculates they have made 7 billion+ figures. Earlier in 2013, they believed they would surpass the human count in 2014, but revised their numbers on the day this comic was released to what this chart says. [Graph: x-axis 1980, 1990, 2010, 2020; y-axis 1, 2, 3, 4, 5, 6, 7, 8 billions.] [Plot-line 1: Number of people in the world.] [Plot-line 2: Number of Lego People in the world.] [Label above the x-axis at 2013 reads "Today".] [Shortly before 2020, both plot lines cross.] [Caption below the graph:] By 2019, humans will be outnumbered.

Monty Hall

Monty Hall

https://www.xkcd.com/1282

https://www.explainxkcd.com/wiki/index.php/1282:_Monty_Hall

[A figure - Monty Hall - stands on stage, holding a microphone. There are three doors; two labelled "A" and "C", which are closed, and one that is being held open by Monty. There's a ramp to the right, down which a goat is being led by Beret Guy.] Beret Guy: ...and my yard has so much grass, and I'll teach you tricks, and... Goat: ♥

This comic is a reference to the US game show Let's Make a Deal , and more specifically the Monty Hall problem , a probability puzzle based on the show and named after its original host, Monty Hall . The premise of the show was that Hall would offer "deals" to contestants pulled from the audience in which they could win cash and prizes. Some deals involved games/tasks the contestant had to perform, while others simply involved the contestant making choices between a series of doors or boxes. In such games of choice, there were often several prizes and typically at least one "zonk", the show's name for an undesirable "gag" prize, which on the original Monty Hall version of the show were frequently animals such as goats. In the classic version of the Monty Hall Problem , a contestant is offered a choice of three doors. Behind two of the doors are goats, and behind one of them is a car. First, the contestant chooses a door, which remains closed. The host then opens one of the two remaining doors and reveals a goat. The contestant is then offered a final choice of whether to switch their choice to the remaining closed door, or keep the door they originally chose. The problem involves an analysis of the probability of the contestant choosing the car given certain circumstances. The problem assumes that a contestant would want to win a car, and would be disappointed to win a goat, which most contestants would have no ability to house, and no use for. The comic shows that Beret Guy , upon the host revealing that door B has a goat behind it, chooses to take the goat to keep as a pet, which makes them both very happy. This is much like, and may be an allusion to, the Simpsons episode Bart Gets an Elephant , in which Bart opts for the gag prize of an African Elephant rather than the $10,000 award. According to an interview with Monty Hall, several contestants actually decided to keep the animals; although rare, it was allowed since the animals were offered as prizes (and they were a lot more expensive than the consolation cash prize). The title text references the car and the other goat, untouched behind the remaining doors. For an in-depth analysis of the Monty Hall Problem, see its article at Wikipedia The apparent "paradox" of the Monty Hall Problem is that many people's initial reaction once the host opens a door to reveal a goat, is that there are two remaining doors, one with a car and one with a goat; and therefore there is an equal probability the car is behind each door. Many people therefore believe that switching makes no difference to the odds of winning a car. However, assuming that the host has knowledge of which doors contain goats, and that their choice of which door to open is always an unchosen door containing a goat, it is actually twice as likely that the contestant will win the car if they switch than if they keep their original choice. This is because the contestant initially had a one-in-three chance of choosing the car and a two-in-three chance of choosing a goat. Switching always wins the car in those two-thirds of cases where the contestant initially chose a goat. The probability of winning by switching is therefore the same as the probability that the contestant initially chose a goat. The switch essentially gives the contestant both remaining doors instead of just the one door originally chosen. Because the host always has at least one goat available, the fact that the host reveals a goat does not provide the contestant any new information about their initially chosen door. The initial door still has a two-in-three chance of being a goat, and switching still has a two-in-three chance of winning. Opening a goat-door simply shifts all of the probability of the remaining two doors being a car to the remaining unchosen door. Simple explanation : Imagine there are 100 doors instead of just 2, and after you pick a door, the host opens all but one, revealing all goats. Do you switch to the remaining door or keep your initial pick? Just as there is a 2/3 chance of picking the car when switching in the 3-door scenario, there is now a 99/100 chance of picking the car when switching in the 100 door scenario. In this scenario, it becomes obvious that it is not a 50/50 chance when two doors remain. Important Side Note : There has been great debate about the precise wording of the problem, and what assumptions or rules might apply. These variants can greatly change the probabilities. One variant has the host open one of the two remaining doors at random, which could result in the car being revealed, and the game ending. In that scenario, if a goat has been revealed, the probability that the first pick is correct is now 1/2 and switching is not advantageous. In 1/3 of all possible games, the first pick is correct. The host cannot pick the car. In 1/3 of all possible games, the first pick is wrong but the host does not reveal the car. In 1/3 of all possible games, the first pick is wrong and host will reveal the car. We now know those cases are impossible. With only 2/3rds of all possible games remaining, the chance that switching will win the car is now (1/3)/(2/3) = 1/2. Likewise, not switching also has a 1/2 chance of winning. Note that this variant requires that the host picks a door at random. Another variant has the host only offering to switch if the first choice is correct. In this case, switching always loses. [A figure - Monty Hall - stands on stage, holding a microphone. There are three doors; two labelled "A" and "C", which are closed, and one that is being held open by Monty. There's a ramp to the right, down which a goat is being led by Beret Guy.] Beret Guy: ...and my yard has so much grass, and I'll teach you tricks, and... Goat: ♥

Headlines

Headlines

https://www.xkcd.com/1283

https://www.explainxkcd.com/wiki/index.php/1283:_Headlines

[Caption above the frame:] 20th Century Headlines Rewritten to get more clicks [The years are always written at the center. The text has a line pointing to the relevant year. The first text is written to the left of the year. Then the texts below is alternately written to the right and to the left, finishing at the right in 1990.] 1905 - How a shocking new theory, discovered by a dad, proves scientists are wrong about everything! 1912 - 6 Titanic survivors who should have died 1920 - 17 things that will be outlawed now that women can vote 1928 - This one weird mold kills all germs 1929 - Most embarrassing reactions to the stock market crash [GIFs] 1945 - These 9 Nazi atrocities will make you lose faith in humanity 1948 - 5 insane plans for feeding West Berlin you won't believe are real 1955 - Avoid Polio with this one weird trick 1957 - 12 nip slips potentially visible to Sputnik 1968 - This year's assassinations ranked from most to least tragic 1969 - This is the most important photo of an astronaut you'll see all day 1986 - This video of a terminally ill child watching the Challenger launch will break your heart 1989 - You won't believe what these people did to the Berlin wall! [Video] Jan 1, 1990 - 500 signs you're a 90s kid

This comic satirizes the sensationalist language used in Internet headlines. Many websites generate ad revenue for getting visitors ("getting more clicks"), so some unscrupulous editors seek to manipulate their readers using tantalizing yet formulaic and crass headlines, designed to attract readers rather than summarize the article's contents. You might recognize this technique from those ridiculous text advertisements — "local mom discovers 1 weird tip to reduce belly fat." The practice is nothing new: tabloid journalism has been doing this for many years (e.g. National Enquirer ). The numbers shown at the headline are also often wrong and not covered by the article. Signs of a dishonest headline include giving undue weight to trivial topics, or appealing to readers' emotions or needs (fear, outrage, pity, lust, laziness) instead of offering serious information. In severe cases, it may be a bait-and-switch , claiming to offer something it isn't. By failing to give a useful summary of the story, whilst attempting to force the reader to click on every story on the off-chance that it's interesting, they amount to an intentionally deceptive form of spam. Randall parodies the formula in this comic with such trivializing headlines for important historical events: Albert Einstein published his Annus Mirabilis papers , which changed views on space, time, mass, and energy, and laid the groundwork for much of modern physics. They included his papers on special relativity and on mass–energy equivalence ("E = mc 2 "). He had an infant son in 1905 (born May 1904). The use of the term "dad" helps readers tune in emotionally. "Proving scientists wrong about everything" is obviously an inflation of Einstein's achievements, though not completely incorrect as Einstein's discoveries did undermine current theories about fundamentals of the universe such as space, time and motion. Einstein was awarded the Nobel Prize in 1921 for his work on the photoelectric effect ; his work on relativity was still not accepted by many physicists at that time. Sinking of the RMS Titanic . "should have died" seems to be referring to six passengers whose survival was downright miraculous, though the wording is (deliberately) ambiguous to imply the six passengers deserved to have died. Possibly referred to here is the survival of J. Bruce Ismay , chairman and managing director of the White Star Line (the company responsible for the Titanic), who was condemned as a coward for leaving the sinking liner. The Nineteenth Amendment to the United States Constitution was passed, guaranteeing voting rights for women in all US states. The prediction of new prohibitions is a reference to alcohol prohibition under the authority granted to the federal government by the Eighteenth Amendment to the United States Constitution . While the Eighteenth Amendment was ratified before women's suffrage was guaranteed by the Nineteeth, alcohol prohibition was widely seen as an issue driven by women's opinions (hence the suggestion that more things would be prohibited now that women had the vote). Penicillin was discovered by Alexander Fleming. This is a reference to the Wall Street Crash of 1929 , the most devastating stock market crash in history and the beginning of the Great Depression. The "embarassing reactions" may be a reference to the suicides of people suddenly impoverished by the depression. [GIFS] indicates that the post will contain animated GIF images, which are a crude form of short video. Presumably, these GIFs will feature the aforementioned suicides, which would be considered tasteless at best. The GIF89a specification which supports animation was released in 1990, so animated GIFs (or computers for that matter) didn't exist in 1929. 1945 is the year that World War II ended. It's also the year that many war crimes committed by Nazi Germany were discovered or declassified. These events would be cause enough for anyone to re-evaluate their belief in the inherent goodness of the human race. However, the specific phrase "lose faith in humanity" is one often employed on the web by rather over-dramatic people in response to something someone did to exasperate them; and because that particular wording is closely associated with exaggerative tendencies, its usage in relation to Nazi war crimes only downplays their seriousness. 1948 is when the Soviet Union established the Berlin Blockade , preventing food and other critical supplies from reaching occupied Berlin. In response, Western forces organized the Berlin Airlift (previously referenced in 1037: Umwelt , where it became Berlin Chairlift instead). The polio vaccine was developed. "One weird trick" is a common phrase used in Internet ads: see this article for more information. It may also refer to the fact that polio viruses were used as the first vaccines. The Soviet Union launched Sputnik 1 , the world's first artificial satellite. A nip slip is when a woman unintentionally exposes all or part of one or both of her nipples; in the context of the internet, it generally refers to a photograph capturing such a moment. Saying that 12 were visible from space implies that they were really big 'nip slips', or at least that only those 12 were big enough to be visible to telescopes. Martin Luther King Jr. and Robert F. Kennedy ( John F. Kennedy's younger brother) were both assassinated in 1968 (five years after JFK). Assassinations are rare and considered to be always tragic, so "ranking" them trivializes the political and emotional depth of the events. Apollo 11 performed the first manned lunar landing. During this historic trip newspapers printed as many pictures of astronauts as they could. Space Shuttle Challenger broke apart 73 seconds into its flight. See Space Shuttle Challenger disaster for details. This was the first shuttle mission that included a teacher on board as part of the crew ( Christa McAuliffe , Teacher in Space Project ), so there were many children -- a New York Times poll put the number at 48% of 9-13 year olds in the US -- watching this particular launch live as teachers around the country had TV sets in their classrooms showing the ill-fated launch in real time. The launch was not shown on most mainstream TV stations; only CNN broadcast it live. Since this many children did see it, there would also have been several terminal ill children watching, and likely also some press out at one such place. So they could get this picture. And again toy with our emotions. Fall of the Berlin Wall . [video] indicates a link to a video. A 90s kid is someone born in the late 80s or early 90s (and spent most their childhood in the 1990s). Headlines like this one from BuzzFeed toy with their readers' sense of nostalgia. The parody headline is funny because it starts precisely on the first day of the 1990s, meaning that the only "90s kids" that it would apply to would be newborns. This is a reference to a common joke about the 90s not having a concrete identity in some ways like the 70s or 80s did in terms of popular culture, and yet those born in that decade always seem to have long lists of things that make you a "90s kid". Einstein published his theory of General relativity , which is a vast generalization of the theory of Special relativity from 1905 and provides a model for gravity. In 1916 Einstein had two sons who lived in Zurich while he lived in Berlin. [NSFW] is "Not Safe for Work" - a tag to identify explicit images. Here it is used to trick readers hoping to find pornography. [PICS] tells the potential viewer that there are images embedded. This topic is re-used in 1307: Buzzfeed Christmas . [Caption above the frame:] 20th Century Headlines Rewritten to get more clicks [The years are always written at the center. The text has a line pointing to the relevant year. The first text is written to the left of the year. Then the texts below is alternately written to the right and to the left, finishing at the right in 1990.] 1905 - How a shocking new theory, discovered by a dad, proves scientists are wrong about everything! 1912 - 6 Titanic survivors who should have died 1920 - 17 things that will be outlawed now that women can vote 1928 - This one weird mold kills all germs 1929 - Most embarrassing reactions to the stock market crash [GIFs] 1945 - These 9 Nazi atrocities will make you lose faith in humanity 1948 - 5 insane plans for feeding West Berlin you won't believe are real 1955 - Avoid Polio with this one weird trick 1957 - 12 nip slips potentially visible to Sputnik 1968 - This year's assassinations ranked from most to least tragic 1969 - This is the most important photo of an astronaut you'll see all day 1986 - This video of a terminally ill child watching the Challenger launch will break your heart 1989 - You won't believe what these people did to the Berlin wall! [Video] Jan 1, 1990 - 500 signs you're a 90s kid

Improved Keyboard

Improved Keyboard

https://www.xkcd.com/1284

https://www.explainxkcd.com/wiki/index.php/1284:_Improved_Keyboard

[Cueball walks on screen, holding a phone, and starts talking to Black Hat.] Cueball: Did you get my texts? Black Hat: You should install this keyboard I found. Cueball: What? Why? Is it better than SwiftKey? Black Hat: In some ways. [Black Hat begins to walk off-panel.] Cueball: Ok, installing... Cueball: It's not working. The key area is blank—I can't type anything. [Black Hat has left. Cueball stares at his phone.] [Beat frame. Cueball lets his hands fall to their side.] Cueball: ...Hey.

Modern smartphones and tablets have touchscreen LCD displays which completely cover the device's surface; for this reason they rely on software keyboards to input text such as text messages. The simplest software keyboards simply display a standard QWERTY keyboard and allow the user to tap on the letters they wish to enter, but this is slow. More sophisticated software keyboards such as SwiftKey facilitate faster text entry through gestures supported by language models. Because this space is still under development, new software keyboards promising better text entry continue to appear. Black Hat is annoyed about Cueball 's text messages, so he sends Cueball a "better" keyboard that actually doesn't work — with the desired result that Cueball is not able to text him at all. His statement that the app is better than SwiftKey "in some ways" is literally true — it's better for him , not for Cueball. The Android keyboard app SwiftKey has been mentioned before , and Black Hat has done something similar in 156: Commented . According to the title text, Randall does often try out new keyboard apps, only to be reminded each time that he ends up wasting more time learning the new gestures than he saves in typing more quickly. Alternatively, the increased effort and thought put into typing makes him realize that nothing he would type is really worth it to him anymore. Similar problems arise later in 1586: Keyboard Problems and 1678: Recent Searches‎ . [Cueball walks on screen, holding a phone, and starts talking to Black Hat.] Cueball: Did you get my texts? Black Hat: You should install this keyboard I found. Cueball: What? Why? Is it better than SwiftKey? Black Hat: In some ways. [Black Hat begins to walk off-panel.] Cueball: Ok, installing... Cueball: It's not working. The key area is blank—I can't type anything. [Black Hat has left. Cueball stares at his phone.] [Beat frame. Cueball lets his hands fall to their side.] Cueball: ...Hey.

Third Way

Third Way

https://www.xkcd.com/1285

https://www.explainxkcd.com/wiki/index.php/1285:_Third_Way

[To the left a group with three Cueballs, a Ponytail and Megan at the front which face another group with two Cueballs, a Ponytail and a black haired ponytail at the front. Each group has a placard. A Cueball in the left group has a cutlass and a Cueball in the right group has a spear as they are angrily facing off against each other. Off to the far right side stands a lone Cueball also with a placard.] Left placard: Two spaces after a period Middle placard: One space after a period Right placard: Line break after every sentence

This comic refers to the debate occurring in the United States about the correct number of space characters after a period at the end of a sentence . While typewriter typists in the United States were traditionally taught to use two spaces between sentences, this is becoming less common and many sources now recommend having only one space, although this topic is still controversial . Cueball is advocating a line break after every sentence, the eponymous "third way". This obviates the problem, as a period will always appear at the end of a line and the spacing after it becomes moot. A line break after every sentence is sometimes called " semantic linefeeds ". This is particularly useful when plain text files based on a markup language (such as HTML , TeX , or Wiki markup ) are edited by multiple people using a version control system where it helps to facilitate comparison of changes and avoid merge conflicts. In most markup languages, a single line feed in the source is rendered as a simple space, while two linefeeds generate a paragraph break. This approach allows the source to be easily manipulated and versioned, while the rendered output still keeps the regular flow and justification abilities of running text. (Incidentally, HTML and languages derived from it such as BBCode and Wiki markup will generally render multiple consecutive whitespace characters as a single space, so pretty much every page on the Internet uses single spacing whether the author wants to or not.) The title text uses single spaces between the back-and-forth quotations; but within each quotation, the quoted speaker's preferred spacing is used; when the single-spacing advocate claims to be using double spacing, this is indeed a lie. However, realistically, it is implausible that one can hear whitespace. [ citation needed ] Randall's mocking characterization in the title text of overzealous advocates using the phrase "WAKE UP, SHEEPLE" has appeared in previous comics: 496: Secretary: Part 3 and 1013: Wake Up Sheeple . Note that this is not the first time Randall has proposed a controversial third way , and this debate is later referenced in 1989: IMHO . Sentence spacing was previously mentioned in the title text of 1070: Words for Small Sets . [To the left a group with three Cueballs, a Ponytail and Megan at the front which face another group with two Cueballs, a Ponytail and a black haired ponytail at the front. Each group has a placard. A Cueball in the left group has a cutlass and a Cueball in the right group has a spear as they are angrily facing off against each other. Off to the far right side stands a lone Cueball also with a placard.] Left placard: Two spaces after a period Middle placard: One space after a period Right placard: Line break after every sentence

Encryptic

Encryptic

https://www.xkcd.com/1286

https://www.explainxkcd.com/wiki/index.php/1286:_Encryptic

[Caption above the panel:] Hackers recently leaked 153 million Adobe user emails, encrypted passwords, and password hints. Adobe encrypted the passwords improperly, misusing block-mode 3DES. The result is something wonderful: [Caption below the panel:] The greatest crossword puzzle in the history of the world

Web sites and other computers that authenticate users via passwords need to be able to know if the user typed in the right password. But storing the password itself on the computer has been known to be unnecessarily risky since the publication of Password Security: A Case History in 1978. In that paper, Robert Morris and Ken Thompson demonstrated the practice of using a slow, cryptographically-secure one-way hash function , so that even if the password file is stolen, it will be very hard to figure out what the passwords are, so long as the passwords themselves are suitably complex. They also pioneered the use of a "salt" which makes each password hash completely different even if two users use the same password. See A tour of password questions and answers for background on salts and suitably slow hash functions. Adobe, however, ignored these well-known principles, and instead stored over a hundred million passwords in a reversibly encrypted way, using a terrible choice of encryption methods which exposes a great deal of information about the passwords, and does not involve a salt. This password database was recently obtained by someone and released on the Internet. In particular, Adobe used Triple DES , an older encryption algorithm which can still be relatively secure when properly used, but they used it improperly. It works on 64-bit (8 character) blocks. Assuming that the passwords are stored in plain ASCII, this means that a sequence of 8 characters in a password which starts on a character position which is a multiple of eight is always encrypted to the same result. Therefore, two passwords starting with "12345678" would start with the same block after being encrypted. Furthermore, this means that you can actually get a very good idea of the length of the password since anything with only one block is a password with length between 1 and 8 characters, and having two blocks implies it has between 9 and 16 characters, etc. Adobe also stored hints users created for their passwords. That means that an attacker knows not only if the same 8 characters are used for multiple passwords but also has some hints for guessing them. That means that common password portions should be easy to recover and that any user may be "compromised" by someone else using a part of the same password and providing a good hint. As an example, a password having three hints "Big Apple", "Twin Towers" and "If you can make it there" is probably "New York" or a simple variation on that. The weakness here is that no decryption and therefore no hard cracking has to take place, you just group the passwords by their encrypted blocks and try to solve them like a crossword puzzle. These weaknesses have already been used to presumably identify a password used by Edward Snowden , as discussed at 7 Habits of Highly Effective Hackers: Can someone be targeted using the Adobe breach? . The examples are not taken from the actual leaked file, since that uses a different format , and the examples are evidently cleverly crafted to make a nice crossword-like puzzle, which can be solved as shown in the Passwords section below. As mentioned on http://filosottile.github.io/analyzing-the-adobe-leaked-passwords/ the data in the comic isn't real and contains a hidden message. If the "user password" hashes are Base64 encoded, they read: More readable: E.g., with the initial unique hash blocks: python2 -c "print '4e18acc1ab27a2d6a0a2876eb1ea1fca'.decode('hex_codec').encode('base64')" The last letter "r" is not fully encoded in the data shown, but any letter from "g" to "v" produces the same binary data. The title text makes a reference to a previous comic: Black Hat's trouble with what to do with stolen passwords . It also states that users of pirated Photoshop are the winners here. This is because in order to make Photoshop pirate-able, it was modified (cracked) by removing the requirement for registration so their passwords were not sent to Adobe and therefore are not present in the leaked file. Soon after this comic was published, the most common 1000 passwords were actually compiled into a set of 10 interactive online crosswords , inspired by the comic. The title itself is a reference to cryptic crosswords . Note that characters in the passwords could be upper or lower case, and they may involve common substitutions like "0" (number zero) for "O" (letter O); therefore, the clues cannot guarantee that the answer shown here is precisely correct. Nevertheless, we have plenty of information for a brute force attack. [Caption above the panel:] Hackers recently leaked 153 million Adobe user emails, encrypted passwords, and password hints. Adobe encrypted the passwords improperly, misusing block-mode 3DES. The result is something wonderful: [Caption below the panel:] The greatest crossword puzzle in the history of the world

Puzzle

Puzzle

https://www.xkcd.com/1287

https://www.explainxkcd.com/wiki/index.php/1287:_Puzzle

[A game board with 8×8 white squares and black borders, like a go board or an all white chessboard, there are white chess pieces in starting position on the bottom after e3, d4, Nf3, Nc3, Bd2 and five black Go pieces on the vertices in the center of the board at d4 d5 c6 g4 g6.] [Caption below the frame:] White to continue insisting this is a chessboard

The game of go (also called Weiqi, Baduk or Igo) is usually played on the 19×19 intersections of a grid, but sometimes a faster, simpler version is played on the 9×9 intersections of a grid; which thus has 8×8 squares, as a chessboard, though they are not colored in an alternating pattern – introduced to chess in the 13th century . In the comic, white has chess pieces and plays against black, which uses go stones. In chess, particularly in puzzles, the phrasing "White to move" indicates that it's the White player's turn; "White to play and win" indicates that it's White's turn and if White plays correctly, the next series of moves will result in an advantageous position or possibly outright win for White. The caption "White to continue insisting this is a chessboard" is a play on this traditional phrasing. The same kind of phrasing is also used in Go puzzles . In Go puzzles the objectives are often of a local or tactical character, such as "White to capture four black stones" or "White to live in the corner". Two versions of the board were posted by Randall: both had white after e3, d4, Nf3, Nc3, but the first with an extra bishop at e4 ( [email protected] ), the second after Bd2. It is unclear who has gone first. In Go it is traditional for black to go first, while in Chess it has been traditional for white to go first for about a century. Indeed, both players have made five moves, although the caption/"punchline" implies it is the start of white's sixth turn; though if black did go first, none of his/her pieces are in the 3-3 handicap positions marked on a 9×9 Go board. The title text refers to the (at the time) upcoming 2013 World Chess Championship between Carlsen and Anand. Magnus Carlsen is (at publishing of this comic) a 23 year old Norwegian chess grandmaster. Viswanathan Anand is (at publishing time) a 44 year old Indian grandmaster. Both have been (and as of 2019 are) among the world top chess players. The game transcript in the title text refers to the ending of the famous Opera Game between Paul Morphy and the Duke of Brunswick and Count Isouard. That game ends with 16. Qb8+ Nxb8 17. Rd8#. In the title text, Black continues to make moves as if he has not been checkmated, over White's protests. After White uses his rook to capture Black's king to emphasize the checkmate, Black defiantly writes "0-1" (the notation symbolizing a Black victory) on his scoresheet. When informed that his move cannot be to declare victory, he flips the board. "0-1" may also represent a position on a go board (first down on the top left corner) in certain coordinates systems . The game transcript is written in standard algebraic notation . The destination square is represented by a lowercase letter (a-h, on the x-axis) and a number (1-8, on the y-axis), with the bottom-left square being a1 and the top-right square being h8. The uppercase letters refer to the piece that is moving to that square (e.g., Q = Queen, K = King, N = Knight, R = Rook), so Qa1 would mean moving the Queen to the bottom-left square. The absence of an uppercase letter refers to a pawn's move (e.g., "f6" means moving a pawn to f6). If the move captures a piece, an "x" is inserted between the piece and the destination (e.g., Nxb8). Checks are indicated by +, and checkmate by #. [A game board with 8×8 white squares and black borders, like a go board or an all white chessboard, there are white chess pieces in starting position on the bottom after e3, d4, Nf3, Nc3, Bd2 and five black Go pieces on the vertices in the center of the board at d4 d5 c6 g4 g6.] [Caption below the frame:] White to continue insisting this is a chessboard

Substitutions

Substitutions

https://www.xkcd.com/1288

https://www.explainxkcd.com/wiki/index.php/1288:_Substitutions

[Caption above the panel:] Substitutions that make reading the news more fun: [A table of words/sentences on the left that changes into those on the left. Between each set of words, there is a gray arrow pointing from the right.] Witnesses ➜ These dudes I know Allegedly ➜ Kinda probably New study ➜ Tumblr post Rebuild ➜ Avenge Space ➜ Spaaace Google Glass ➜ Virtual Boy Smartphone ➜ Pokédex Electric ➜ Atomic Senator ➜ Elf-lord Car ➜ Cat Election ➜ Eating contest Congressional leaders ➜ River spirits Homeland security ➜ Homestar Runner Could not be reached for comment ➜ Is guilty and everyone knows it

This is the first comic in the Substitution series where Randall has suggested substitutions that will make reading the news more fun. But there have been several comics using substitutions both before and after these ones. The series as of 2016: Randall is playing off of the fact that many readers of modern news articles quickly become bored with the legal and political jargon. He suggests that substituting certain words for others can make reading the article more interesting, albeit less accurate. Although since Randall doesn't think very highly of the news, he's probably suggesting this chart wouldn't make them less accurate at all. (See for instance 558: 1000 Times and 932: CIA .) For example, a sentence that reads Witnesses reported that the suspect allegedly escaped unharmed. would be changed to These dudes I know reported that the suspect kinda probably escaped unharmed. This substitution does not change the meaning much, and the original sentence does not lose much of its accuracy. However, for substitutions later in the comic, a sentence may be changed as follows: A new study finds that senators and other congressional leaders are increasingly likely to view election results on their smartphone. into A Tumblr post finds that elf-lords and other river spirits are increasingly likely to view eating contest results on their Pokédex. Which is less meaningful, but more interesting. The final substitution returns from the realm of the ridiculous to replacing "could not be reached for comment" with "is guilty and everyone knows it." If a journalist writes a story about an accused suspect but is unable to contact them or receives no response from them, they will write that the person "could not be reached for comment." Randall's whimsical assumption that silence implies guilt is so common that juries are instructed that they should not infer guilt if the defendant fails to testify, particularly in nations that have a right against self-incrimination. Chrome and Firefox extensions are available for applying the substitutions on webpages. 'Spaaace' could be a reference to the Space Core from Portal 2 , or to the way The Muppet Show presented Pigs in Spaaace . The Virtual Boy is a table-top video game console made by Nintendo released in 1995 and discontinued about the same year. It achieved true-3D graphics through the use of a large visor containing a pair of LED screens, though it considered having done so incredibly poorly, while also lacking any form of ergonomic comfort and sporting several critical design flaws. As a result, it is commonly mocked as one of Nintendo's biggest failures (sometimes by Nintendo itself). The Pokédex is a device in the Pokémon world that records the data of captured Pokémon. Homestar Runner is the title character of a Flash-animated web cartoon series, known for being an idiot. It seems generally that Randall is no fan of Google Glass, which was also shown earlier in 1251: Anti-Glass and later in 1304: Glass Trolling . Thus explaining why Google Glass has such a ridiculous substitution as Virtual Boy . Google Glass has become a recurring theme in xkcd. In the title text Elon Musk is mentioned. He is (amongst other things) the CEO of Tesla Motors , which produces electric cars. In the title text the sentence "Electric cars" was replaced by "atomic cats" according to the chart of the comic. News reports about new studies ( Tumblr posts) are further lampooned in 1295: New Study , a comic posted two weeks later. [Caption above the panel:] Substitutions that make reading the news more fun: [A table of words/sentences on the left that changes into those on the left. Between each set of words, there is a gray arrow pointing from the right.] Witnesses ➜ These dudes I know Allegedly ➜ Kinda probably New study ➜ Tumblr post Rebuild ➜ Avenge Space ➜ Spaaace Google Glass ➜ Virtual Boy Smartphone ➜ Pokédex Electric ➜ Atomic Senator ➜ Elf-lord Car ➜ Cat Election ➜ Eating contest Congressional leaders ➜ River spirits Homeland security ➜ Homestar Runner Could not be reached for comment ➜ Is guilty and everyone knows it

Simple Answers

Simple Answers

https://www.xkcd.com/1289

https://www.explainxkcd.com/wiki/index.php/1289:_Simple_Answers

[Caption above the chart:] The simple answers to the questions that get asked about every new technology: Will [ ] make us all geniuses? No Will [ ] make us all morons? No Will [ ] destroy whole industries? Yes Will [ ] make us more empathetic? No Will [ ] make us less caring? No Will teens use [ ] for sex? Yes Were they going to have sex anyway? Yes Will [ ] destroy music? No Will [ ] destroy art? No But can't we go back to a time when- No Will [ ] bring about world peace? No Will [ ] cause widespread alienation by creating a world of empty experiences? We were already alienated

This is Randall 's commentary on some of the baseless skepticism and equally baseless optimism directed at new technologies. Related: 1215: Insight and 1227: The Pace of Modern Life . While it's always healthy to evaluate the advantages and disadvantages of cutting-edge tech before blindly diving in and adopting it, it's not healthy to base that evaluation on unrealistically high standards and expectations. [ citation needed ] New developments will have pros and cons, and it's hard to tell whether they make the world a better place or not. Randall has set up a Q&A for this kind of questioning. Most of the them are straightforward, but we'll provide some commentary on selected questions. Will [ ] destroy whole industries? Yes. A widely adopted technology usually causes another to gradually phase out, and industries will rise and fall as technologies do. This is a bit of a loaded question because "destroy industries" sounds negative, and only covers half the effect — instead of merely destroying them, we're also replacing them with something (hopefully) better. Will teens use [ ] for sex? Yes. Were they going to have sex anyway? Yes. Sex is pretty important to almost everyone, so it'll find its way into most generic technologies. Hormone-crazed tech-savvy teenagers are a particularly strong intersection of the two. Parents fearing teen sex might be worried about how their kids would use the technology, but the second question puts such concerns into their proper context quite concisely. Will [ ] destroy music/art? No. Every new technology for reproducing musical and artistic works (such as player pianos and video cassette recorders ) has been accompanied by warnings that it will destroy the industry that supplies it content. The reality is a special case of the "destroy industries" question - old business models will fall but new ones will arise in their place, and art and music as a whole will survive. But can't we go back to a time when— No. Elderly people express their disapproval of today's technological luxuries, nostalgically longing for a time before Foo or Bar came around. That's just how the stereotype goes, but there is a large helping of truth to it. Usually, their sentiments are not a fair judgement, but an emotional attachment to the olden days and a resistance to change . Will [ ] bring about world peace?- No. People have been trying to bring about world peace for centuries; sadly, other people are in no such hurry and insist on more conflict to solve their own problems. The final answer is a depressing and strangely beautiful comment on human nature: Will [ ] cause widespread alienation by creating a world of empty experiences? We were already alienated. Skeptics may be concerned that a new technology will make people's pleasures and interactions more artificial and shallow; Randall comments that this is already something well known in our society. From the Title Text, Will [ ] allow us to better understand each other and thus make war undesirable? describes the usual theory that a technology might use to bring about world peace. Unfortunately, not only does the answer seem to be "no" to World Peace either way, but there's no indication that increased global communication actually facilitates understanding and empathy between distant communities. In fact, many cynics say the Internet has in fact caused the opposite effect, causing people to fracture into like-minded cliques rather than intermingle. [Caption above the chart:] The simple answers to the questions that get asked about every new technology: Will [ ] make us all geniuses? No Will [ ] make us all morons? No Will [ ] destroy whole industries? Yes Will [ ] make us more empathetic? No Will [ ] make us less caring? No Will teens use [ ] for sex? Yes Were they going to have sex anyway? Yes Will [ ] destroy music? No Will [ ] destroy art? No But can't we go back to a time when- No Will [ ] bring about world peace? No Will [ ] cause widespread alienation by creating a world of empty experiences? We were already alienated

Syllable Planning

Syllable Planning

https://www.xkcd.com/1290

https://www.explainxkcd.com/wiki/index.php/1290:_Syllable_Planning

Cueball: Man, that is ridicu -fucking—... ...Hang on, I inserted "fucking" too late and now there's just one awkward syllable left. Can I back up? [Cueball is standing next to Megan.]

Cueball wants to say ri-fucking-diculous , but he inserts the fucking too late in the word. Now, he has to say ridicu-fucking-lous , which sounds ridiculous. This is an example of tmesis , the breaking up of a word to include another within it, and more specifically of expletive infixation . Normally, for rhythmic reasons the included word is inserted before the stressed syllable ( ri dic ulous becoming ri-fucking- dic ulous ) which is what Cueball messed up. However, in some cases it is also possible to break the word after a prefix instead, so for some words there are two ways to do it e.g. unbe-fucking- lie vable (before the stressed syllable) or un-fucking-be lie vable ; this is because unbelievable is a combination of un and believable to negate believable which is an actual English word [ citation needed ] and therefore it still sounds good. The title text introduces a further example, with speaker inserting the fucking too late into the word absolutely —which would have resulted in absolute-fucking-ly —but leaving the word unfinished when they realize their mistake. The more usual tmesis here would be abso-fucking-lutely . Cueball: Man, that is ridicu -fucking—... ...Hang on, I inserted "fucking" too late and now there's just one awkward syllable left. Can I back up? [Cueball is standing next to Megan.]

Shoot for the Moon

Shoot for the Moon

https://www.xkcd.com/1291

https://www.explainxkcd.com/wiki/index.php/1291:_Shoot_for_the_Moon

[Megan stands at a lectern.] Megan: Students, shoot for the moon. If you miss, [A surprisingly lunar-like object is starting to edge into the frame.] Megan: SHOOT AGAIN . Megan: Keep shooting and never stop. [The moon is now almost entirely in-frame.] Megan: Someday, one of us will destroy that stupid skycircle. And— Megan: ...What? What are you all— [The moon is now in frame, lurking ominously in the background.] Megan: ...it's right behind me, isn't it? Megan: Shit . Megan: Everyone act casual.

The comic and the title text both parody the motivational quote attributed to Leslie Brown , which originally says, "Shoot for the Moon. Even if you miss, you'll land among the stars." In the original form, the phrase "Shoot for the moon" is figurative, meant to inspire people to pursue ambitious goals, reasoning that even if they fail to achieve them, they may still accomplish other great things while trying. The comic and title text, on the other hand, is literally referring to the moon, and using the word "shoot" not in the sense of "aspire" but to mean "fire a weapon at." The comic further explores the humorous motivations for "shooting the moon"; Megan wants to destroy and kill the moon in order to humble it, feeling taunted by its orbiting merrily over her head, and so she inspires her students to physically attempt to destroy the moon whenever possible, only to become sheepish when she realizes the moon is right behind her, as if it were a person who could become offended by what she is saying. This is, of course, a common comedy trope . The title text invokes another literal interpretation of the phrase - if a space vehicle aims at the Moon and misses, it will end up in a new orbit, possibly (depending on its velocity) escaping from the Earth-Moon system and following a separate but nearby orbit around the Sun. A solar orbit is very hard, very fuel-intensive, and very lengthy to return from, despite physically meaning you will remain very close to Earth, even close enough to see it with some optical magnification. Thus, as a hypothetical space explorer's life support gradually ran out because his craft could not make it back to Earth in time, he would be taunted by Earth remaining close to him. Getting stranded on the Moon was the subject of the title text of 1510: Napoleon and of 1484: Apollo Speeches . [Megan stands at a lectern.] Megan: Students, shoot for the moon. If you miss, [A surprisingly lunar-like object is starting to edge into the frame.] Megan: SHOOT AGAIN . Megan: Keep shooting and never stop. [The moon is now almost entirely in-frame.] Megan: Someday, one of us will destroy that stupid skycircle. And— Megan: ...What? What are you all— [The moon is now in frame, lurking ominously in the background.] Megan: ...it's right behind me, isn't it? Megan: Shit . Megan: Everyone act casual.

Pi vs. Tau

Pi vs. Tau

https://www.xkcd.com/1292

https://www.explainxkcd.com/wiki/index.php/1292:_Pi_vs._Tau

[On the left is a "forbidden"-style slashed circle with the π symbol, captioned "Pi". On the right is a "forbidden"-style slashed circle with 2π, captioned "Tau". Between these is 1.5π, captioned "Pau".] [Caption below the panel:] A compromise solution to the Pi/Tau dispute Possibly, Randall used Wolfram|Alpha to calculate the result (he uses it a lot, for example What-if 70: The Constant Groundskeeper or What-if 62: Falling With Helium ). However, when the comic was published, there was a bug in Wolfram|Alpha so that, when getting 200 octal digits from "pau", it just calculates the decimal value rounded to 15 significant digits (this is 4.71238898038469) and expands that as octal digits as far as needed. This gives a periodically repeating number. In the first 200 digits of the octal expansion, the sequences 666 and 6666 do occur, twice and once, respectively. There are 4 occurrences, however, in the first three hundred and ten (310 in base 8 equals 200 in base 10) digits: Expansion that long indeed does contain 666 (the number of the beast ) four times (with one instance as 6666). It also contains 0000, 222, 444, and 7777, but they only appear once in a run. In the first 500 digits of the actual octal expansion of pau, we also find that 6666 occurs once, and 666 occurs two other times: (Note that this contains 500 digits after the decimal point.) No other run of 3 or more repeated digits (e.g. 111) occurs as many times, although 1111 occurs once, 111 occurs once elsewhere, and 333 and 777 also occur once each. 9 other strings of 3 digits occur 4 times, namely 164, 362, 521, 644, 432, 730, 43, 216, and 450, and only 573 occurs more often, as it occurs 6 times. Therefore, if 6666 is counted as two occurrences of 666, it is actually the joint second most common string of three numbers in the first 500 digits. Coincidentally , e+2 is also very similar to 1.5 pi, although only to a few digits.

This is yet another of Randall 's compromise comics . A few mathematicians argue as to whether to use pi , which is the ratio between a circle's circumference and its diameter, or tau , which is the ratio between a circle's circumference and its radius. Some consider pi to be the wrong convention and are in favor of using tau as the circle constant; see the Tau Manifesto , which was inspired by the article " Pi is wrong! " by mathematician Robert Palais and publicized by Vi Hart . Others consider proponents of tau to be foolish and remain loyal to pi (see the Pi Manifesto ). Of course, regardless of which convention is used, the change is merely in notation — the underlying mathematics remains unaltered. Still, the choice of pi vs. tau can affect the clarity of equations, analogies between different equations, and how easy various subjects are to teach. Most people know π (pi) by the approximation 3.14, but do not know τ (tau) which, by definition, is twice as large as pi. Randall is suggesting using "pau", which is a portmanteau of "pi" and "tau", as a number situated, appropriately enough, halfway between pi and tau, i.e. 1.5 pi or 0.75 tau. But of course his number would be inconvenient, as this value does not naturally turn up when working with circles or other mathematical constructs, so there are no commonly used formulas that would use pau. The title text claims that pau can be approximated by e+2, as both values are roughly 4.71 — a similarity that holds little since it requires another irrational constant, e (although knowing the value of pau is somewhat more helpful in remembering e to 2 digits). It also attributes the nickname "Devil's Ratio" to pau, due to the sequence 666 supposedly appearing four times in the first 200 digits of pau when expressed in the octal base. However, this is not the case, and was likely due to an error in the computer system used by WolframAlpha; for more details see below. The Tau/pi controversy was later mentioned in 2520: Symbols . [On the left is a "forbidden"-style slashed circle with the π symbol, captioned "Pi". On the right is a "forbidden"-style slashed circle with 2π, captioned "Tau". Between these is 1.5π, captioned "Pau".] [Caption below the panel:] A compromise solution to the Pi/Tau dispute Possibly, Randall used Wolfram|Alpha to calculate the result (he uses it a lot, for example What-if 70: The Constant Groundskeeper or What-if 62: Falling With Helium ). However, when the comic was published, there was a bug in Wolfram|Alpha so that, when getting 200 octal digits from "pau", it just calculates the decimal value rounded to 15 significant digits (this is 4.71238898038469) and expands that as octal digits as far as needed. This gives a periodically repeating number. In the first 200 digits of the octal expansion, the sequences 666 and 6666 do occur, twice and once, respectively. There are 4 occurrences, however, in the first three hundred and ten (310 in base 8 equals 200 in base 10) digits: Expansion that long indeed does contain 666 (the number of the beast ) four times (with one instance as 6666). It also contains 0000, 222, 444, and 7777, but they only appear once in a run. In the first 500 digits of the actual octal expansion of pau, we also find that 6666 occurs once, and 666 occurs two other times: (Note that this contains 500 digits after the decimal point.) No other run of 3 or more repeated digits (e.g. 111) occurs as many times, although 1111 occurs once, 111 occurs once elsewhere, and 333 and 777 also occur once each. 9 other strings of 3 digits occur 4 times, namely 164, 362, 521, 644, 432, 730, 43, 216, and 450, and only 573 occurs more often, as it occurs 6 times. Therefore, if 6666 is counted as two occurrences of 666, it is actually the joint second most common string of three numbers in the first 500 digits. Coincidentally , e+2 is also very similar to 1.5 pi, although only to a few digits.

Job Interview

Job Interview

https://www.xkcd.com/1293

https://www.explainxkcd.com/wiki/index.php/1293:_Job_Interview

[Beret Guy walks in, followed by a...'prospective hire'.] Beret Guy: Welcome to our company! We're headquartered here, in this real building I found! [Both people sit down at a table. The 'hire' has a tray with food and a beverage. Beret Guy has a bowl. In the adjacent wall, there is a power outlet with a paper label taped to it marked "Soup". A small roll of wire sits next to Beret Guy's chair.] 'Hire': What do you.. do ? Beret Guy: We make stuff for phones! Like apps and stickers. [Beret Guy grabs the roll of wire.] Beret Guy: We want to hire you to write on our computers. We can offer you a bunch of paychecks! There are ghosts here. [Beret Guy unrolls the wire and plugs it into the wall.] 'Hire': ...Are you sure this is a company? Beret Guy: I hope so! [Soup streams out of the plugged-in wire into Beret Guy's bowl.]

Following on from his attempts at networking , Beret Guy , the oddball of the xkcd cast, conducts an interview for a programmer position at his mysteriously successful company. Much like most of Beret Guy's interactions with people, Beret Guy is cheerful and upbeat, yet indicates that he has at best a scrambled understanding of how people in this situation normally act. Because of this, the job interview becomes increasingly bizarre, starting with Beret Guy's assertion that the company headquarters is a "real building [he] found", implying that the building's reality might be in question. In addition, "finding" the building may imply that he does not own or rent it, but simply found it empty and moved in. He says his company makes phone accessories, but then adds, "like apps and stickers," two wildly different products in terms of both production and profitability. He is strangely vague about both the position ("someone to write on our computers") and the salary ("a bunch of paychecks"). Then he mentions ghosts, which is either a powerful disincentive from joining the company, yet another sign that Beret Guy is mentally unsound, or both. The strip finishes with Beret Guy plugging a cord into an electrical outlet clumsily labeled "Soup," which then, implausibly, actually starts dispensing soup. Most electrical outlets do not function like this. [ citation needed ] However, this is a typical behaviour of Beret Guy - see a similar example in: 1395: Power Cord . The title text makes reference to the biblical story of Job (pronounced with a long O to rhyme with globe), who was put through many horrendous ordeals to test his faith in God. This suggests that the interviewee will be taking on not a "job experience" but rather a "Job experience" (i.e. the job will be a horrendous ordeal). Alternatively, it's a Homestarrunner reference . Other job interviews were portrayed in 125: Marketing Interview , 1088: Five Years , 1094: Interview , 1545: Strengths and Weaknesses , and 2597: Salary Negotiation . [Beret Guy walks in, followed by a...'prospective hire'.] Beret Guy: Welcome to our company! We're headquartered here, in this real building I found! [Both people sit down at a table. The 'hire' has a tray with food and a beverage. Beret Guy has a bowl. In the adjacent wall, there is a power outlet with a paper label taped to it marked "Soup". A small roll of wire sits next to Beret Guy's chair.] 'Hire': What do you.. do ? Beret Guy: We make stuff for phones! Like apps and stickers. [Beret Guy grabs the roll of wire.] Beret Guy: We want to hire you to write on our computers. We can offer you a bunch of paychecks! There are ghosts here. [Beret Guy unrolls the wire and plugs it into the wall.] 'Hire': ...Are you sure this is a company? Beret Guy: I hope so! [Soup streams out of the plugged-in wire into Beret Guy's bowl.]

Telescope Names

Telescope Names

https://www.xkcd.com/1294

https://www.explainxkcd.com/wiki/index.php/1294:_Telescope_Names

[A list of telescope names is given, with a series of checkboxes at right.] The Very Large Telescope ☑ The Extremely Large Telescope ☑ The Overwhelmingly Large Telescope ☑ (Canceled) The Oppressively Colossal Telescope ☐ The Mind-numbingly Vast Telescope ☐ The Despair Telescope ☐ The Cataclysmic Telescope ☐ The Telescope of Devastation ☐ The Nightmare Scope ☐ The Infinite Telescope ☐ The Final Telescope ☐

The Very Large Telescope is an existing telescope, while the (European) Extremely Large Telescope was in an advanced planning stage at the time of the comic's release. The Overwhelmingly Large Telescope was another proposed telescope that, as the comic mentions, was cancelled. The comic pokes fun at the generic nature of the names of the telescopes by proposing more generic but increasingly ridiculous names for future telescopes. The title text talks about the Thirty Meter Telescope , which is about to begin construction on Mauna Kea (a dormant volcano) in Hawaii, and seems to compare it to the Eye of Sauron . It is expected to be the most advanced and powerful optical telescope on Earth when completed. [A list of telescope names is given, with a series of checkboxes at right.] The Very Large Telescope ☑ The Extremely Large Telescope ☑ The Overwhelmingly Large Telescope ☑ (Canceled) The Oppressively Colossal Telescope ☐ The Mind-numbingly Vast Telescope ☐ The Despair Telescope ☐ The Cataclysmic Telescope ☐ The Telescope of Devastation ☐ The Nightmare Scope ☐ The Infinite Telescope ☐ The Final Telescope ☐

New Study

New Study

https://www.xkcd.com/1295

https://www.explainxkcd.com/wiki/index.php/1295:_New_Study

[Hairy as a news anchor with a perfect black news-anchor-hair-helmet is sitting behind his desk with hands folded in front om him.] Hairy: ...And in science news, according to a new study, 85% of news organizations repeat "new study" press releases without checking whether they're real.

Hairy as a news anchor is reporting on a new study. This is another of Randall's jabs at modern news networks. The joke is twofold: 1. news organizations often repeat press releases on scientific studies without fact checking; 2. the study being reported by the news organization in the comic is presumably itself invented and would not stand up to fact checking. Some examples of how true this can be: The title text implies there is an actual study being performed to determine what percentage of news organizations repeat "new study" press releases without checking whether they're real, and that the fake study being reported on by the (unknowing) reporter in the comic is part of the experiment being performed to find that true percentage. When this study concludes, the reporters will not know whether to report on its findings, either because they've already reported on a similar (but fake) story, or because they no longer trust stories of that nature. Related jokes: Side note: People making the substitutions in 1288: Substitutions , a comic posted two weeks before this one, will read this comic as one about Tumblr posts. [Hairy as a news anchor with a perfect black news-anchor-hair-helmet is sitting behind his desk with hands folded in front om him.] Hairy: ...And in science news, according to a new study, 85% of news organizations repeat "new study" press releases without checking whether they're real.

Git Commit

Git Commit

https://www.xkcd.com/1296

https://www.explainxkcd.com/wiki/index.php/1296:_Git_Commit

[Caption below the panel:] As a project drags on, my Git commit messages get less and less informative.

This comic refers to the Git source code revision control software, which saves earlier versions of files and folders for later access into a special repository. This comes in handy when you want to try out whether an idea works (branching). Further, you can collaborate with others by use of remote repositories. Perhaps most importantly, it allows members of the development team to find key changes in the history, later. Git has been discussed in 1597: Git as well. A commit is a saved version in a Git repository; a commit comes with a message that is supposed to describe what the commit contains, similar to the edit summaries used on MediaWiki sites such as explain xkcd and on this explanation . Randall , however, finds himself losing interest in the commit messages the more code he writes and winds up just using placeholder text or jokes to himself. Presumably, this is because his separate commits are part of a large effort that can't be effectively summarized, and where there's no particular urgent need to differentiate the commits. Seeing as in this context 12 hours of coding can be considered "dragging on," it's safe to assume that the kinds of commits Randall is talking about are not for some major in-production project, nor for something that a lot of other people are working on. In both of those cases, one would be much more likely to use descriptive commit messages, since you want to flag things that are important, either from a technical standpoint (e.g. "fix the thing that's making the site not work") or for the benefit of others who want to know which commits they should be paying attention to. The phrase "Merge branch 'asdfasjkfdlas/alkdjf' into sdkjfls-final" mimics the phrasing used by Git. A branch is a specific sequence of commits which can be made in parallel to other branches of development, and later merged. Here, we see that Randall has also gotten lazy with his branch names: "branch 'asdfasjkfdlas/alkdjf'" might be the series of two commits starting with "here have code". "sdkjfls-final" could be the branch indicated by the vertical string of circles on the left, into which the other more branch is merged in commit "adkfjslkdfjsdklfj". Most git tools show the commit history with the most recent commits first, so showing the oldest first like this would require something like the --reverse option. The comments go from being pretty detailed as to his thoughts and reasons for the code ("enabled config file parsing"), to relatively uninformative summaries ("misc bugfixes"), to completely uninformative words ("more code"), and then finally he doesn't even bother trying to come up with words, instead just hitting a key ("aaaaaaaa") or semi-random keys ("adkfjslkdfjsdklfj"), then goes back to typing words but words that have a bit of a craziness to them rather than having anything to do with describing the code ("my hands are typing words"). The "adkfjslkdfjsdklfj" line and similar garbage in the title text comes from having your hands on the " home row " on a standard QWERTY keyboard, then hitting "random" keys without moving your fingers from their standard home row positions. The keys you hit "randomly" will be combinations of A, S, D, and F on the left hand, and J, K, L, and ; on the right hand (although the ; key seems to have been avoided, possibly because without the presence of surrounding quotes a ; character will end the comment). It is common to see stuff like that when a person is required to type something — i.e. a mandatory field — but they have no interest in typing anything meaningful or no idea what to write, so they just hit the easiest keys to hit and call it done. [Caption below the panel:] As a project drags on, my Git commit messages get less and less informative.

Oort Cloud

Oort Cloud

https://www.xkcd.com/1297

https://www.explainxkcd.com/wiki/index.php/1297:_Oort_Cloud

[Three asteroids float in space.] ISON: Have you noticed that bright dot in the distance? Asteroid: Yeah. What's the deal with it? ISON: Dunno. I'm gonna go check it out. [Pause while ISON checks it out off screen.] ISON (broken up, with multiple tails): Wow. Do NOT go over there.

The Oort cloud is a hypothesized sphere containing many small Solar System bodies , reaching out to roughly 50,000 AU (astronomical units) or nearly one light-year from the sun. Gravitational forces from passing stars or collisions with other objects sometimes perturb one of these bodies enough to let it fall into the inner solar system. When it gets closer to the Sun, which is just a bright dot at that far distance, it warms up and some of its mass is lost as gas and dust, making it more visible as an object commonly referred to as a comet. This is what has happened to a comet called C/2013 UQ4 , AKA Comet Catalina. And although this is not what will happen to Catalina, comets that get close enough to the sun may break up entirely. There seems to be no definitive astronomical definition of the word "comet", and definitions can be challenging and problematic [1] , but in general terms a comet is a celestial object consisting of a nucleus containing a huge amount of ices and dust which, when near the sun, has an atmosphere (called coma ) and perhaps a 'tail' of ionized gas and dust particles pointing away from the sun. The comet pictured here upon its return strangely resembles the unusual asteroid P/2013 P5 . That object sported six comet-like tails, but it's not a comet. Rather, the six comet-like tails were suspected to be caused by rapid spinning of that object. Randal has drawn the hapless Oort Cloud object with its tails generally left of frame, i.e. away from the sun. Comet tails point away from the sun regardless of their direction of movement, as they are blown out by the solar wind which moves much faster than the comet. As neither of the other two objects have tails, this lends the picture a comical cartoon-like quality, as when Yosemite Sam is blasted by his own gun and it leaves his moustache tails statically pointing away from the direction of the blast. Comet ISON presumably came from the Oort cloud and reached its closest approach to the sun ( perihelion ) on the day before this comic was published. The comet passed very close to the sun, at a distance of 1,860,000 kilometers or 1,150,000 miles from the centre of the sun. It was thus within one sun-diameter of the surface of the sun itself (diameter of sun = 1,391,000 km). At that distance the temperature, at approx. 2,700 degrees Celsius, vaporizes rock as well as ice and can break the comet apart entirely. The broken-up object here is presumed to be ISON, and is labeled as such in the transcript, even though Randall hasn't unambiguously identified it. Note that it's not realistic that ISON still would have a tail so far away from the sun. On December 2, 2013 NASA released a statement that ISON did not survive its close perihelion with the sun. The Comet ISON Observing Campaign posted a delightful biographical sketch (In Memoriam Comet C/2012 S1 (ISON) Born 4.5 Billion BC, Fragmented Nov 28, 2013, age 4.5-billion yrs old) which touches on its early years, retreat to the Oort Cloud, career as a Sungrazer, "dynamic and unpredictable life, alternating between periods of quiet reflection and violent outburst", delicate inner working, and its tragic demise. The closest approach of ISON to the earth was predicted for December 27, 2013 at a distance at approx. 60 million kilometers or 37 million miles, 170 hundred times more than the moon. The Hubble Space Telescope looked for it on December 18 but saw nothing. This video shows an animation of the encounter at the sun: ISON 28.11.2013 . Some more information about comets will help put the comic in perspective: [Three asteroids float in space.] ISON: Have you noticed that bright dot in the distance? Asteroid: Yeah. What's the deal with it? ISON: Dunno. I'm gonna go check it out. [Pause while ISON checks it out off screen.] ISON (broken up, with multiple tails): Wow. Do NOT go over there.

Exoplanet Neighborhood

Exoplanet Neighborhood

https://www.xkcd.com/1298

https://www.explainxkcd.com/wiki/index.php/1298:_Exoplanet_Neighborhood

OUR NEIGHBORHOOD A portrait of all habitable-zone planets within 60 light-years of Earth (constructed from statistical data on typical planet sizes and orbits) [The image shows many planets in different colors and a legend shows planets at different sizes.] Planets around sun-like stars Planets around other stars [A marker on both sides:] Earth-sized planets [Center of the image.] Earth

The diagram is a graphical representation of the statistically predicted distribution of nearby exoplanets (planets not in our solar system), based on the assumption that the exoplanets that are currently known have a distribution of orbits, sizes, and star types that is similar to the actual distribution. Astronomers are particularly interested in exoplanets within 60 light years of Earth which lie in a habitable zone ; that is, a planet whose orbit is within a certain range of distance from a star such that water could exist in a liquid state. Since almost all life on Earth (which is the only place we've actually found life thus far) depends on liquid water in some way, these planets are considered the most likely to support life. The diagram categorizes exoplanets in two ways. The disc color indicates the characteristics of the central star, with a reddish tone indicating hypothetical planets that orbit stars similar in characteristics to our sun, while grey indicates those that orbit stars unlike our sun. The disc sizes indicates the hypothetical size of the exoplanets, with planets similar to Earth's size depicted in a slightly darker shade of either color. Because the discs represent a distribution, their positioning within the diagram is irrelevant; the spacing around the title and the Earth is an artistic choice. It appears that the diagram is intended to cause the viewer to conclude that there are a significant number of Earth-sized planets orbiting Sun-type stars which could be habitable, and even more possibly-habitable planets around other types of stars or in other sizes. The title text, "It's a beautiful day in the neighborhood!" is an allusion to the former PBS television show Mister Rogers' Neighborhood in which the same line presents itself in the opening song, "Won't You Be My Neighbor?" . The title of the comic was changed from what is currently the title text to "Exoplanet Neighborhood". Randall has commented on the results of exoplanet research before, in 786: Exoplanets and 1071: Exoplanets . OUR NEIGHBORHOOD A portrait of all habitable-zone planets within 60 light-years of Earth (constructed from statistical data on typical planet sizes and orbits) [The image shows many planets in different colors and a legend shows planets at different sizes.] Planets around sun-like stars Planets around other stars [A marker on both sides:] Earth-sized planets [Center of the image.] Earth

I Don't Own a TV

I Don't Own a TV

https://www.xkcd.com/1299

https://www.explainxkcd.com/wiki/index.php/1299:_I_Don%27t_Own_a_TV

[A graph is shown with an x- and y-axis.] How people feel when they say "I don't own a TV" by year [The x-axis is labled: 1950, 2000, today.] [The y-axis is labled neutral at zero, smug at top, and embarrassed to the bottom.] [A plot, similar to a negative sine curve between approximately 1960 and 2000, is shown in red, starting at 1950, moving into negative values, reaching the zero level again at the beginning of the 1980s, reaching its maximum shortly after 2000, and decreasing again until today. An arrow shows the current direction.]

This comic is yet another graph , describing how people who don't own a television feel throughout several time periods. While televisions have existed since 1928, regular scheduled broadcasts of television programs did not begin until the late 1940s. So before the 1950s, it was common not to own a television and therefore most people's feelings about it would be fairly neutral. This changed as televisions became cheaper and more people started owning them, meaning that if someone didn't own a television, it was generally because they couldn't afford one. This might lead to someone feeling embarrassment when admitting they don't have a television. Gradually, television ownership increased until eventually, nearly every household had at least one television, and those that did not were more and more likely to do so by choice rather than due to poverty. The graph therefore peaks at around the year 2000, when many people would be proud to say that they did not own a television. Randall suggests that these people would feel smug because they are resisting a popular trend (owning a television) which the rest of the public take part in. The graph tails downwards at the end, suggesting that Randall believes that people are becoming less smug. This could be because of the abundance of video content and other forms of entertainment on the internet and mobile devices. So, according to Randall, people are returning to not owning a television simply because it's not necessary and these people therefore feel neutral towards their lack of a television. Another point of view is that, with the advent of the Internet for news and weather along with video-on-demand services such as Netflix, televisions have become obsolete for some households and thus not owning one can be seen as moving with the times, or those that don't own one see those that still have one as old-fashioned, hence the smug. However in recent times television has become imbued with new technologies such as Internet access (known as smart TVs) and thus owning a television is seen as trendy again, thus the level of smugness drops. The initial upturn from embarrassment to smugness may also be a commentary on the quality of television programs over that period. In the 1950s and 1960s, television was a major source of news and information. Those without televisions might feel that they were missing out of the important stories of the day. Also, the limited number of stations and lack of recording devices meant that discussions of the previous night's television programming was far more inclusive, with more people watching the same programs at the same time. Until the advent of PVRs, the prior night's television programming was a popular "water cooler" topic (i.e. something discussed socially at the office the next day). This means that that those who had missed out on those programs might feel socially "out of the loop". By contrast, since 2000, many programs were criticized as poor quality or "mindless", e.g. daytime talk shows and reality shows. So, someone might feel more smug for not watching so-called "mindless television". Similarly, as television viewership increased from the 1950s through the 2000s, it is possible that other activities such as reading has decreased; especially given that the younger generation today don't remember a time without television. So, someone who did not own a television set might feel more smug because they take part in more "beneficial" activities like reading, exercise, and studying. The title text suggests that whether people feel embarrassed or smug doesn't depend directly on what percentage of the population owns TVs (TV ownership rate) or even on how quickly this percentage is growing (derivative of TV ownership rate with respect to time); instead it depends on how the change in this percentage is speeding up or slowing down (second derivative of TV ownership rate with respect to time). Specifically, as the rate at which people adopt TV ownership accelerates (positive second derivative of TV ownership rate with respect to time), people who don't own one feel embarrassed (negative smugness); and as the market is saturated and the rate at which people adopt TV ownership slows down (negative second derivative of TV ownership rate with respect to time), people who don't own one feel smug (positive smugness). If people feel twice as embarrassed/smug when this rate of acceleration/deceleration doubles, then we have Randall's formulation: "smugness is proportional to the negative second derivative of TV ownership rate with respect to time". As evidence for this, the adoption of TV ownership should theoretically follow a sigmoid curve , which is the graph of something that starts small, grows in a spurt, and then approaches a maximum capacity (in this case 100%). The negative second derivative of a sigmoid curve looks very much like Randall's graph. [A graph is shown with an x- and y-axis.] How people feel when they say "I don't own a TV" by year [The x-axis is labled: 1950, 2000, today.] [The y-axis is labled neutral at zero, smug at top, and embarrassed to the bottom.] [A plot, similar to a negative sine curve between approximately 1960 and 2000, is shown in red, starting at 1950, moving into negative values, reaching the zero level again at the beginning of the 1980s, reaching its maximum shortly after 2000, and decreasing again until today. An arrow shows the current direction.]

Galilean Moons

Galilean Moons

https://www.xkcd.com/1300

https://www.explainxkcd.com/wiki/index.php/1300:_Galilean_Moons

[Megan, who is being orbited by four small floating balls, approaches Cueball.] Megan: Check it out! Cueball: What? Megan: I've got Galilean moons! [Io is at the point in its orbit closest to Cueball.] Io: Hi! [Io, which completes a full orbit in each panel, is again near Cueball, as is Europa this time.] Io: Hi! Europa: What's your name? [Io alone again.] Io: Hi! [Europa returns to its position near Cueball with Io, and Ganymede joins them.] Io: Hi! Europa: What's your— Ganymede: MOOOOOON! [Io alone again.] Io: Hi! [Europa and Io again.] Io: Hi! Europa: What's your name? Callisto: [on the other side of Megan] Ugh . [Io alone again.] Io: Hi! Callisto: So annoying . [Europa, Ganymede, and Io again.] Io: Hi! Europa: What's y— Ganymede: MOOOOOON. [Io alone again. Callisto nudges toward Cueball.] Io: Hi! Callisto: ... almost ... ... almoooost ... [Io and Europa again. Callisto enters an orbit around Cueball.] Io: Hi! Europa: What's your name? Callisto: Yessss!

Megan has somehow acquired a set of Galilean moons similar to the four primary moons of Jupiter . The positions of the moons in the successive panels are reminiscent of the observations made by Galileo Galilei in 1610, which proved for the first time that objects in the heavens could orbit something other than the Earth (today these observations can be reproduced on successive nights by anyone looking at Jupiter with binoculars). As each of Megan's moons passes close to Cueball, it says something different. Io , the innermost and second-smallest, always says "Hi!" Europa , the second-innermost and smallest, always uses the phrase "What's your name?" Ganymede , the third moon from Jupiter but the largest in size, interrupts Europa by shouting "MOOOOOON!" Callisto, the farthest from Megan, expresses its annoyance at the antics of the other three moons. ("MOOOOOOON!" might be a reference to an old joke: Q: Knock Knock. A: Who's there? Q: Interrupting Cow. A: Interrupting Co-- Q: MOOOOOOO!) Because the inner moons orbit Jupiter faster (due to Kepler's Third Law ), they pass by Cueball more often: Io ten times, Europa five times, and Ganymede twice over the course of the comic. In fact, the outermost crater-scarred moon Callisto appears to have passed its closest approach to Cueball just before the first panel (perhaps before Megan and her retinue had walked up to Cueball) and does not approach Cueball again until the tenth panel. At that point, due to some apparent exertion on Callisto's part, it leaves Megan's orbit and begins to orbit Cueball instead. This process could be seen as analogous to the capture of moons from one planet to another, which can happen in less stable systems than our solar system if two planets were to pass close to each other, but is mostly just whimsical. The humour derives from attributing human characteristics to the moon Callisto in attempting to escape from the other three moons. The title text refers to the unusual orbital resonance among the three inner Galilean moons: Io has an orbital period of about 1.78 Earth days, Europa 3.55 days, and Ganymede 7.15 days, putting them into a 1:2:4 resonance. Callisto, with an orbital period of 16.69 days, is not part of the resonant system. This is illustrated in the animated picture at right, where you may notice that all conjunctions between Io and Europa take place at the "12 o'clock" position and all conjunctions between Europa and Ganymede take place at "6 o'clock" position. You may also notice at the animated picture that, unlike in the fifth and ninth panels of the comic, the three moons are never on the same side of Jupiter at the same time. It is thought that this resonance came about as the moons migrated outward due to tidal acceleration ; because the inner moons migrated more quickly, first Io caught up with the 2:1 resonance with Europa and then the two of them evolved outward in lockstep until Europa caught up with the 2:1 resonance with Ganymede. If the Jupiter system were to continue its current evolutionary path for long enough (several billion years), Ganymede would eventually catch up to the 2:1 resonance with Callisto and Callisto would also be trapped in the resonance, becoming the fourth member of a 1:2:4:8 system. The title text expresses Callisto's relief at escaping such a fate, describing the relationship among the other three moons as "their weird ...thing." Callisto also escapes a common practice among certain groups of humans in which the members greet each other with meaningless phrases, usually an inside joke, whenever they meet, which could also be described as "their weird ...thing." The word "orbit" could finish Callisto's sentence, as it can also mean a sphere of influence or interest. Later, in 2264: Satellite , Science Girl was orbited in a similar way by an abandoned satellite. [Megan, who is being orbited by four small floating balls, approaches Cueball.] Megan: Check it out! Cueball: What? Megan: I've got Galilean moons! [Io is at the point in its orbit closest to Cueball.] Io: Hi! [Io, which completes a full orbit in each panel, is again near Cueball, as is Europa this time.] Io: Hi! Europa: What's your name? [Io alone again.] Io: Hi! [Europa returns to its position near Cueball with Io, and Ganymede joins them.] Io: Hi! Europa: What's your— Ganymede: MOOOOOON! [Io alone again.] Io: Hi! [Europa and Io again.] Io: Hi! Europa: What's your name? Callisto: [on the other side of Megan] Ugh . [Io alone again.] Io: Hi! Callisto: So annoying . [Europa, Ganymede, and Io again.] Io: Hi! Europa: What's y— Ganymede: MOOOOOON. [Io alone again. Callisto nudges toward Cueball.] Io: Hi! Callisto: ... almost ... ... almoooost ... [Io and Europa again. Callisto enters an orbit around Cueball.] Io: Hi! Europa: What's your name? Callisto: Yessss!