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New

New

https://www.xkcd.com/1401

https://www.explainxkcd.com/wiki/index.php/1401:_New

[Black Hat walks in.] Black Hat: New headcannon: [Cueball is sitting at his desk, using his computer.] Cueball: Yeah? [Black Hat lifts his hat, revealing his "headcannon": a tiny cannon on the top of his head. The headcannon fires and blows up Cueball's desk, the explosion throwing Cueball backwards.] Headcannon: BOOM Cueball: Augh!

This comic strip uses a play on the homophonic relationship between " canon ", the literary term, and " cannon ", a projectile weapon. The word headcannon is a compound of "head" and "cannon". In this strip, Black Hat tells Cueball that he has a "new headcannon". Cueball , thinking Black Hat means "headcanon" (an unjustified belief or theory about a fictional universe), inquires what Black Hat's new idea is. Instead of the expected idea or theory, Black Hat removes his hat to reveal a tiny cannon on his head which blows away Cueball and his computer desk. While headcanon may often be ignored or dismissed as a personal theory, a headcannon would be far harder to ignore, as it is a physical object which has a notable (and in this case violent) impact on the real world. In the title text Randall makes the spellings of these two words indistinguishable by using three consecutive "n"s to spell "headcannnon". Therefore, the title text is deliberately vague. It could be interpreted that it is easy to convince people that you have a cannon on your head, that it is easy to make people believe in a self invented headcanons, or both. Since you are choosing your own interpretation of this title text, the joke is that you are creating your own headcanon. This comic also shows Cueball being once again distracted from his work in a manner similar to 1388: Subduction License . In terms of a given literary series, " canon " describes a set of works that are collectively recognized by the community as having authenticity. Generally, works created or endorsed by the original author(s) are considered canonical. Not all original content is considered canon and not all canon is original content. Sometimes creators will rewrite the canon (called a retcon ) and make things that were previously canonical non-canonical. For example, the origins of a character may be rewritten, thus invalidating the portions of the works that speak to the old origins. Other times creators will incorporate non-original content and therefore incorporate the canon of these borrowed works. A headcanon as the name implies is a form of canon that only exists in one's mind. More specifically, a headcanon is created when a consumer watching or reading the material develops their own ideas about a fictional universe that are not actually part of the canon, perhaps developing their own backstories or experiences for characters. Some frequent examples of headcanon include relationships between characters, abilities, events following the conclusion of the work, etc. which the author or creator has not explained or included. For example, a consumer may "read between the lines" and assume that there was a previous romantic relationship between two characters where no conclusive evidence actually exists of one. Some fans who come up with particularly interesting or convincing headcanons may decide to share them with others in hopes that their idea spreads. [Black Hat walks in.] Black Hat: New headcannon: [Cueball is sitting at his desk, using his computer.] Cueball: Yeah? [Black Hat lifts his hat, revealing his "headcannon": a tiny cannon on the top of his head. The headcannon fires and blows up Cueball's desk, the explosion throwing Cueball backwards.] Headcannon: BOOM Cueball: Augh!

Harpoons

Harpoons

https://www.xkcd.com/1402

https://www.explainxkcd.com/wiki/index.php/1402:_Harpoons

Number of harpoons in space by year [A chart with a red graph is drawn below.] [The y-axis.] 0 1 2 3 [The x-axis.] 1950 1960 1970 1980 1990 2000 2010 2020 [The graph is at zero until a sharp peak to 1 in 1970. The peak is labeled.] Apollo 12 rum incident [The graph then stays at 0 until 2004. Then it rises to 2 and stays there until today, continuing as a dotted line after 2014. The rise is labeled.] Rosetta comet mission launched carrying lander with harpoon tethers In 2018, shortly after the line gets dotted, the number actually increased again., thanks to the RemoveDEBRIS satelite.

This comic is a graph of the number of harpoons in space over time. One would not expect that harpoons, which are associated with old technology, would be used in space, which is associated with high technology. Any occurrences are unexpected, and therefore interesting or funny. The first peak states that a harpoon was in space during the Apollo 12 mission and various possible explanations have been put forward (See discussion section below). One of more widely accepted theories proposes that Harpoon brand of Jamaican rum made it aboard the Apollo 12 rocket. Despite a fair amount of research into the basis of the harpoon incident, there have been no credible or official sources to confirm the presence of any type of harpoon on board Apollo 12. As the presence of a harpoon on board would run counter to any official story, perhaps that's exactly why it would be considered an "incident". The latter peak on this graph refers to the Rosetta unmanned spacecraft. As part of its mission, it carried a lander called Philae , which has two harpoon tethers to anchor itself to the comet 67P/Churyumov–Gerasimenko . Rosetta was launched in March 2004 (as shown in the graph) and was scheduled to encounter the comet in August 2014, making this a timely comic. Rosetta maneuvered to enter orbit on September 10, and ultimately the Philae lander touched down on the comet on 12 November 2014, although the harpoon system failed to deploy. Randall produced a live comic of the landing, updating 1446: Landing every 5 minutes with the latest progress. The Rosetta spacecraft also carries a disk micro-etched with 13,000 pages of text in 1200 languages donated by the Long Now foundation, mentioned in previous comics. The title text compares the Philae lander's method of deploying its tethers to whaling , in which sailors would throw harpoons at a whale with the intent of killing the whale. It was important to throw hard so the harpoon would stick in the whale so it could not get away and would tow the whaling boat until it got tired and could be killed. Thus the title text implies that the spacecraft is sentient and needs a motivation to fire the harpoons hard enough to stay anchored to the comet; to this end it has been programmed to believe that its mission is to kill the comet. Evidently this motivation was not enough, as Philae ultimately failed to deploy its harpoons - it still managed to land, though. Number of harpoons in space by year [A chart with a red graph is drawn below.] [The y-axis.] 0 1 2 3 [The x-axis.] 1950 1960 1970 1980 1990 2000 2010 2020 [The graph is at zero until a sharp peak to 1 in 1970. The peak is labeled.] Apollo 12 rum incident [The graph then stays at 0 until 2004. Then it rises to 2 and stays there until today, continuing as a dotted line after 2014. The rise is labeled.] Rosetta comet mission launched carrying lander with harpoon tethers In 2018, shortly after the line gets dotted, the number actually increased again., thanks to the RemoveDEBRIS satelite.

Thesis Defense

Thesis Defense

https://www.xkcd.com/1403

https://www.explainxkcd.com/wiki/index.php/1403:_Thesis_Defense

[Megan runs towards a desk with two microphones on it, waving a broadsword high in the air. Cueball and one other sitting behind the desk are taken aback, while Ponytail standing off to the side holds an arm in front of her face protectively. A slide is projected on a screen behind Megan, reading "The evolution of threat displays in mammals".] Megan: In conclusion, AAAAAAAAAAAAA!!! [Caption below the panel:] The best thesis defense is a good thesis offense.

In the comic, Megan is presenting evidence on her thesis , a theory on the evolution of threat displays in mammals, in front of a panel of some people. To conclude her exposition she charges at the audience, shouting a battle cry , and brandishing a sword. The audience flinches. As the audience is composed of mammals and is responding to a displayed threat, we should assume that this response provides some key evidence about the threat displays in mammals. This comic is a play on a thesis defense and the adage " The best defense is a good offense ". The adage means that a strong offensive action will preoccupy the opposition and ultimately hinder its ability to mount an opposing counterattack, leading to a strategic advantage. A thesis defense generally involves an oral exam on the topic the candidate has chosen, and should involve no physical violence. For added humorous effect, in the title text Megan extrapolates how she improved the state of the art, i.e. what she has added to her field of study, while screaming the word art. [Megan runs towards a desk with two microphones on it, waving a broadsword high in the air. Cueball and one other sitting behind the desk are taken aback, while Ponytail standing off to the side holds an arm in front of her face protectively. A slide is projected on a screen behind Megan, reading "The evolution of threat displays in mammals".] Megan: In conclusion, AAAAAAAAAAAAA!!! [Caption below the panel:] The best thesis defense is a good thesis offense.

Quantum Vacuum Virtual Plasma

Quantum Vacuum Virtual Plasma

https://www.xkcd.com/1404

https://www.explainxkcd.com/wiki/index.php/1404:_Quantum_Vacuum_Virtual_Plasma

[Cueball and Megan are walking together in the foreground.] Cueball: Hear about that "impossible" microwave thruster? [They stop walking and Cueball turns to face Megan.] Megan: Yeah. Let me get this straight — they pumped 20 kilowatts into a box under ambient conditions ...and it only twitched a little ? Cueball: Yeah. [Zoomed out - they are seen in silhouette walking together again.] Megan: That's surprising. If you pumped 20 kilowatts into me , I'd twitch a lot . Cueball: But you're not pushing on the quantum vacuum. Megan: I might be. I do a lot of things. Cueball: I guess we can't be sure.

This comic is a reference to the recent news of a microwave thruster which allegedly produces thrust without expelling any propellant or microwaves, a violation of conservation of momentum . This type of thruster would provide delta velocity without conventional limits. After researchers hooked their device up to a measurement apparatus in an air-filled stainless-steel chamber, applied RF input and measured changes in the apparatus, their interpretation of the results as a tiny thrust explainable under the moniker of "quantum vacuum virtual plasma" was at best controversial. An official statement by NASA's Johnson Space Center is still missing. The title of the comic directly refers to this hypothetical new physics mechanism of interacting with the "quantum vacuum virtual plasma," a combination of physics words that don't normally go together. The first part of the comic has Megan commenting on how the engine was, in layman's terms, "twitching," and states that with that much power she'd expect something more forceful. "Twitching" is an expected outcome for various complex systems, including biological ones, when arbitrarily large amounts of electric or microwave power is injected. The last panel is a joke about the scientific method, where equivalence between twitching and the hypothetical new physics is pooh-poohed, because Megan was not previously revealed to operate by the principle of "quantum vacuum virtual plasma," to which Megan responds that she is a complex entity and very well might have new physics inside her. The title text suggests that the authors of the NASA paper subscribe to the principle that unexpected behaviors of complex systems should best be explained by invoking new physics rather than by making a detailed study of the complexities of the system. This runs contrary to generally accepted approach in science. [Cueball and Megan are walking together in the foreground.] Cueball: Hear about that "impossible" microwave thruster? [They stop walking and Cueball turns to face Megan.] Megan: Yeah. Let me get this straight — they pumped 20 kilowatts into a box under ambient conditions ...and it only twitched a little ? Cueball: Yeah. [Zoomed out - they are seen in silhouette walking together again.] Megan: That's surprising. If you pumped 20 kilowatts into me , I'd twitch a lot . Cueball: But you're not pushing on the quantum vacuum. Megan: I might be. I do a lot of things. Cueball: I guess we can't be sure.

Meteor

Meteor

https://www.xkcd.com/1405

https://www.explainxkcd.com/wiki/index.php/1405:_Meteor

[Cueballs friend walks toward Cueball while holding a rock.] Cueball: Check it out - I got a piece of a meteor! Randall: Actually , it's only called that while falling. Once it lands, it's called magma . [Below the panel:] My Hobby: Mixing pedantic terms

This is one of Randall 's My Hobby comics. The author makes semantically incorrect statements to frustrate pedantic people who know the correct word, and confuse people who don't know the precise word so they can go on using the wrong word; see also 1429: Data . Since Randall is normally personified by Cueball , it makes most sense to call the one with the hobby Cueball in the explanation below. Cueball's friend (who also looks like Cueball) walks up to Cueball and tells him that he has found a piece of a " meteor ". Cueball corrects him by telling him that what he found is called magma , and that the phrase "a piece of a meteor" would be correct if the object was in the air, once it hits the ground it is called magma. In doing so he attempts to confuse or annoy his friend. In truth, meteorite is the expression for a piece of a meteoroid that has landed; meteor is the term for the streak of light caused by the meteoroid while it falls through the atmosphere. Thus the first statement by him is a (partly) true correction, but the second one is wrong. The word " pedantic " means being overly concerned with being precise. It is usually a pejorative term used to refer to someone who is overly fussy and corrects someone's word choice even when the more ambiguous or slightly incorrect term they used was fine for informal communication. One would tend to believe a pedant, as they would usually know what they are pedantic about. So when Cueball is making wrong statements that seem pedantic, he may make people believe him. A volcano that would be the bane of such a pedantic person was depicted in the last panel of 1714: Volcano Types , as a direct reference to this comic. The title text expands on the joke, as if the conversation had continued with a confused friend responding that he thought magma was underground. Cueball attempts to confuse him further by talking about lava which indeed is the expression for magma that has reached the surface. But it's ridiculous to suggest that all other things are called lava when underground. In the sentence he also continues to imply that magma could also be found above ground. Mixing pedantic terms like this was later used in the title text of 1967: Violin Plots . The two sentences thus follow the same pattern with one true but pedantic part to begin with, and then a false statement to confuse the victim. Here is a list of the terminology that is being muddled: A nice English mnemonic helps: In the void, meteoroid. On the site, meteorite. Neither/Nor: meteor. [Cueballs friend walks toward Cueball while holding a rock.] Cueball: Check it out - I got a piece of a meteor! Randall: Actually , it's only called that while falling. Once it lands, it's called magma . [Below the panel:] My Hobby: Mixing pedantic terms

Universal Converter Box

Universal Converter Box

https://www.xkcd.com/1406

https://www.explainxkcd.com/wiki/index.php/1406:_Universal_Converter_Box

[Universal converter box with wires to connectors:] VGA DVI HDMI Thunderbolt Firewire Component [sharing connectors with Component:] RCA 1/8" Audio 1/8" Video Parallel Port S-Video Airline Pneumatic Tube Audio PS/2/3/4 120V AC [pointing to ground pin:] Removable Floppy/IDE/2.5"/SCSI [pointing to sections in IDC connector:] Break here USB USB (weird other end) Mini-USB Micro USB Macro USB F Connector Fiber RJ11 Ethernet Token Ring MagSafe MagSafe 2 MagSafe 3 MagSafe 4 Bluetooth Dongle SCART String (fits most cans) [Fuel nozzle with selector for:] 87/91/93/Diesel

Converter boxes are used to connect two or more devices together which otherwise couldn't be, due to differently shaped plugs, different voltages, or different protocols of communication. Converter boxes or converter cables are commonly found for several of the plugs at the top of the list - such as from USB to micro-USB. As this is supposed to be a Universal Converter Box, there are many connections. The humour from this comic comes from the sheer number of different standards that all claim to be the universal way to connect two devices, in their target market, as well as the progressively ridiculous conversions that this box is capable of doing, for example, converting audio from a 1/8 inch / 3.5 mm headphone jack, into a variety of fuel suitable for running your car. A connector is capable of making a connection to another connector only if the connectors are of the same style and the opposite gender ("male" connector is plug, "female" connector is socket), except for rare "genderless" connectors, such as the token ring mentioned above. Gender changers are devices with two connectors of the same gender. The "circular center pin DC adapter tips" in the title text are barrel jack power plugs. There are a large number of these style connectors, and many of these devices look the same, leading to frustration. The plugs are numbered from top to bottom and incremented for every wire that comes directly out of the converter box. For some interfaces, such as USB, the female side is standard to the device while the male side is standard to the cable. For other interfaces, such as the RS-232 serial port, the conventions vary or there is no convention. The "universal" connector here doesn't support the proper RS-232, with the closest surrogate available being RJ-11. The other nearest analog would be the parallel port, available in Centronix and D-25-pin connectors. The SCSI connectors have been available as the "internal" connectors (see the "break-away" above) of 2 different widths, Centronix, 2 widths of the mini-D connectors with the easily bendable pins, 3 widths of the more reliable pin-less mini-connectors, and high-speed serial. Not only is there gender and connector type, but there are also different standards on what data/power is connected on each pin of the connector. Building a working connection often involved getting 3 or 4 adapters connected in a sequence to produce the right connector, gender and pin-out. Barrel jack power plugs were developed in the 1980s. The "barrel" has an inner diameter an outer diameter, and different style pins. A D-shell is a trapezoidal metal skirt that protects the pins, prevents the connector from being plugged in the wrong way, and makes the physical connection more secure. A VGA was developed in 1987, and with new versions being developed since then. DVI can be configured to support multiple modes such as DVI-D (digital only), DVI-A (analog only), or DVI-I (digital and analog). HDMI has slowly been replacing DVI and VGA ports on newer devices due to the simplicity and the smaller footprint and overall dimensions. Thunderbolt is far faster than almost any connector on the market for transferring data. However, the limited adoption by manufacturers, the higher costs of the hardware, and the security concerns inherent to the interface have limited the adoption by consumers. Because Firewire is designed to allow backplane access and direct memory access (DMA) to devices, there are additional conversion and security issues with it. The phone connector diameter of 1/8" is only an approximation using Imperial units . The standard actually specifies a size in the Metric system of 3.5 mm. The video plug has 3 contacts (Tip, Ring and Sleeve) and the audio has 4 contacts (Tip, Ring, Ring and Sleeve). While no longer common in homes or offices, parallel connections are still used in some embedded systems . Airline pneumatic tube audio was used by in-flight entertainment systems manufactured from 1963 until 1979. Note that while AC adapters are necessary—and widely available—to suit sockets in other countries, this "universal" converter does not feature any other AC power plugs, but this could be accommodated using adapters. Cheater plugs exist to connect a NEMA grounding-type plug (three prongs) to a NEMA non-grounding receptacle (two slots), but the use of such an adapter can be hazardous if the grounding tab is not connected to electrical ground. A safer alternative is to replace the outlet with a Ground Fault Circuit Interrupter (GFCI) breaker outlet. The computer media drive connectors are unlike the motherboard-powering connectors from the Power Supply Unit of a PC, which may involve multiple additional 4, 6 and 8-pin 'breakout' supply cables that have this feature and specially 'keyed' pin-sheaths as well to allow forward/backward compatibility between various versions of PSU and motherboard that could be used (and power-hungry GPUs of various kinds, as well). Note that some embedded systems such as cash registers actually do use larger USB connectors to include 12V and/or 24V power connections. These are not, however, called "macro-USB", and are not as large. Other countries often use RJ11-ended cables with locally-specific adapter-ends, e.g. the BS 6312 in Britain. Broadband microfilters may make use of this difference by splitting a relevant telephone plug standard into the local non-RJ11 style of telephone plug for an "audio-only" pass-through socket and an RJ11 for the router/modem to be cabled up to for the abstracted "data-only" signal — making an adapter for this will be nearly impossible. There are two common systems for showing octane numbers on fuel pumps; the numbers shown (87, 91, 93) most closely map to Anti-Knock Index values which is used for the North American market and a number of other countries, the other system used in the rest of the world is Research Octane Number. In the AKI system; 87 octane (91 RON) is regular US, 91 octane (95 RON) is regular European, 93 octane (98 RON) is premium European, and in US both 91 and 93 are considered premium/super depending on the regulations of a particular state. Some states, such as California, forbid the sale of the gasoline above 91 octane. Only very rarely could both 91 and 93 be found at the same gas station. The typical line-up is "regular" (87), "plus" (89), and "premium"/"super" (depending on the state and on the fuel brand, 91, 92 or 93 octane). A standard diesel nozzle (24mm) is slightly larger diameter than a standard petrol nozzle (21mm) so you cannot tank diesel into a petrol car but if this nozzle has the petrol nozzle diameter you are still able to tank with it into some diesel cars. Some manufacturers such as Volkswagen fit a misfueling guard and fuel filler neck cap or have redesigned the fuel filler to prevent a petrol nozzle being used in a diesel car. Since the release of this comic, Apple has created a magnetic charging cable for its Apple Watch, which functions in the same manner as the current MagSafe 1 & 2 by using a magnet to connect to the device. This new charger looks identical to the fictional MagSafe 3 in the comic. [Universal converter box with wires to connectors:] VGA DVI HDMI Thunderbolt Firewire Component [sharing connectors with Component:] RCA 1/8" Audio 1/8" Video Parallel Port S-Video Airline Pneumatic Tube Audio PS/2/3/4 120V AC [pointing to ground pin:] Removable Floppy/IDE/2.5"/SCSI [pointing to sections in IDC connector:] Break here USB USB (weird other end) Mini-USB Micro USB Macro USB F Connector Fiber RJ11 Ethernet Token Ring MagSafe MagSafe 2 MagSafe 3 MagSafe 4 Bluetooth Dongle SCART String (fits most cans) [Fuel nozzle with selector for:] 87/91/93/Diesel

Worst Hurricane

Worst Hurricane

https://www.xkcd.com/1407

https://www.explainxkcd.com/wiki/index.php/1407:_Worst_Hurricane

What's The Worst Hurricane Anyone In Your Town Remembers? Estimated from Hurdat Database and NCEP rainfall totals 1914-2014 [A map of the east coast of the United States as far southwest as the Texas/Mexico border, as far northeast as the Maine/Canada border, and as far inland as Kentucky. The map has coastal regions blocked out with the name and year of the worst hurricane in the last 100 years.]

The map divides America's Atlantic coastline into regions according to the worst hurricane that has hit each area in the last century, based on data from the North Atlantic hurricane database ( HURDAT ) to determine the severity and the National Centers for Enrvironmental Prediction 's (NCEP) rainfall to determine where the hurricane was present. Most of the hurricanes are listed by their US reporting names, with hurricanes before 1953 (the year when the current naming system was established) being listed by their year and sometimes a sequence number or city name. The title text is a joke in light of this bleak humor, saying that finding residents in each of the regions who are old enough to have been alive through all of these is quite a daunting task. In principle, this would be the only way to confirm the "worst hurricane in living memory," and may be taken as a riposte to anyone who wishes to argue this map: "If you think there was a worse one, find a 105 year old resident who agrees!" 105 was likely chosen because most people can only remember back to an age when they were 5, so someone would have needed to be 5 years old to remember a hurricane in any detail 100 years later. Hurricanes and especially their names have been featured before in comics 453: Upcoming Hurricanes , 944: Hurricane Names and 1126: Epsilon and Zeta . A full list of North Atlantic hurricanes after Tropical cyclone naming was introduced can be found here . What's The Worst Hurricane Anyone In Your Town Remembers? Estimated from Hurdat Database and NCEP rainfall totals 1914-2014 [A map of the east coast of the United States as far southwest as the Texas/Mexico border, as far northeast as the Maine/Canada border, and as far inland as Kentucky. The map has coastal regions blocked out with the name and year of the worst hurricane in the last 100 years.]

March of the Penguins

March of the Penguins

https://www.xkcd.com/1408

https://www.explainxkcd.com/wiki/index.php/1408:_March_of_the_Penguins

[Black Hat walks towards Megan who is sitting in an office chair at a desk working on her laptop.] Black Hat: All the birds from March of the Penguins are now dead. [In a frame-less panel only Megan is shown. She sits back from the laptop taking her hands down on her legs. Black Hat replies from off-panel.] Megan: OK, I get it. We're all aging. Black Hat (off-panel): What? No. [Black Hat is in the frame again holding one hand slightly out towards Megan who has turned around in her office chair and is now facing Black Hat.] Black Hat: I'm not trying to make you feel old. They were alive last night. Black Hat:I'm trying to apologize. Megan: Oh God

Several of the xkcd comics outline ways to make people feel older by referencing various pieces of popular culture which feel ingrained and "recent", and revealing the time that has elapsed since their release to be longer than expected (for instance, 1393: Timeghost and 891: Movie Ages ). This appears to be what Black Hat is doing as he walks in on Megan to announce that all the penguins from a 2005 documentary March of the Penguins about emperor penguins are dead. Megan is familiar with these sorts of antics and assumes Black Hat is indicating that the film is so old that the lifespan of emperor penguins is less than the time since the documentary was released. Frustrated, Megan simply acknowledges Black Hat's statement by agreeing that everyone is aging. Black Hat, however, reveals that he is not trying to make her feel old, because the penguins were all alive "last night" and all died in one instance since then and thus not from old age. His announcement that he is "trying to apologize" creates the obvious inference that he caused the penguins to be killed (either intentionally or by mistake). This gives the situation a much darker tone; especially since Black Hat likely is not truly apologizing, as he is very unapologetic in his "classhole" tendencies, and just wish to mess even further with Megan. Emperor penguins actually live about 20 years on average, so presumably, barring any intervention by Black Hat, most of the younger penguins and many of the older penguins in the movie are still alive as of the time of release of this comic in 2014 nine years after the documentary was released. The title text emphasizes that whatever the penguins' fate, we do get and are getting older. [ citation needed ] This is presented as a last jab by Black Hat as he departs just to make Megan feel a bit worse. So in the end this comic did try to make the reader feel older. This also presents an alternative take on the entire comic: Black Hat came in to make Megan feel old because all the penguins of the movie is actually naturally dead of old age, predators, disease etc. And if she likes the movie, she would not have realized that it was almost nine years ago she saw it, and the feel old by realizing how time passed. But she ruins Black Hat's moment by realizing what he is trying to do. (As opposed to what he manages in a comic like 493: Actuarial , that might also make you feel old). So instead of saying yeah you got me , he quickly invents a story that they actually all lived last night, and then takes the blame for killing them just to shock Megan. This fits with the title text, as he then manages to make a jab at how old Megan should feel anyway. This is supported also by the fact, that although the movie was released in January 2005, the team behind it had filmed the penguins for 13 month prior, so some of the penguins in the movie must have been adult back in 2003. So it is not only nine but rather eleven years ago and several of the penguins in the movie must have died of natural causes prior to this comic, although not all! But Black Hat's fake statement indicates that all of them were still alive yesterday. The worst part of this is that it seems like Megan believes him, but she of course also knows him to be a classhole (see for instance 596: Latitude ) and might believe him capable of locating and exterminating all the penguins from the movie over night... [Black Hat walks towards Megan who is sitting in an office chair at a desk working on her laptop.] Black Hat: All the birds from March of the Penguins are now dead. [In a frame-less panel only Megan is shown. She sits back from the laptop taking her hands down on her legs. Black Hat replies from off-panel.] Megan: OK, I get it. We're all aging. Black Hat (off-panel): What? No. [Black Hat is in the frame again holding one hand slightly out towards Megan who has turned around in her office chair and is now facing Black Hat.] Black Hat: I'm not trying to make you feel old. They were alive last night. Black Hat:I'm trying to apologize. Megan: Oh God

Query

Query

https://www.xkcd.com/1409

https://www.explainxkcd.com/wiki/index.php/1409:_Query

[The first and then every second part of the comic is drawn without any frames around the panels. They depict Megan with the device she finds. In the first and last of these there are more than one "panel" where Megan is drawn more than once without frames between. In between these frameless panels, in all even numbered rows, are a framed picture with an overview of the surroundings.] [The first two panels are drawn in the first row.] [Megan walks up to device lying on the ground.] [Megan picks up a device and looks a the screen. The screen is shown in black with white text and a white bar for her to enter text in.] Loaded table: People Enter query [Megan looks around and sees nine people nearby: A black haired girl with ponytail talking on the phone; a Cueball-like guy talking to a hairy guy; a group of three people, with Ponytail and another Cueball-like guy sitting, and a Megan-like girl lying on the ground; another hairy guy sitting with an ice cream cone on a big box; Another Ponytail girl leaning up against the box with her phone together with a third Cueball-like guy also with a phone in his hand. The device still shows the last part of the text in white on black, and with room to enter a query] Enter query Megan: ?? [Megan types into the device. The query is shown as coming from the devices screen:] Select * from people where age > 30 [Five people are highlighted in a yellow cloud around their bodies: Black haired ponytail, both guys talking, and the two last of the group of three.] [Megan types again:] Select * from people where annual_income > 100000 [One person is highlighted in yellow - the one talking to the first Cueball.] [Megan types:] Select * from people where afraid_of_flying = True [Four people, including herself, are highlighted in yellow. Also the Megan-like girl on the ground and the last two behind the box.] [Megan types:] Select * from people where hours_since_watching_porn < 12 [Three people are highlighted. The two girls around the second Cueball and the third Cueball.] [The next three panels are drawn on the same row.] [Megan looks at the device, while holding it in two hands.] Megan: Neat. [Megan holds the device in one hand, still looking at it.] Megan: ... [Megan types:] Drop table People [Everyone disappears; the items they were holding drop to the ground, including the device Megan has been using. the other devices are three phones and one ice cream cone.]

Megan picks up a strange device that mysteriously asks her to enter a query after stating "Loaded table: People/ Enter query." In computer databases, " tables " are groups of similar information consisting of records each having certain attributes. Databases are generally made up of many tables, each containing different types of records. A database for a traditional library might have a "Books" table and a "Cardholders" table with records of all of the books in the library, and all of the people who have library cards. Each table will have different columns for certain attributes for every record. For example, the "Books" table might have columns for "title", "author", "date", etc. A request from a database by a user is called a "query". SQL (Structured Query Language) is a programming language designed for databases, and has a certain syntax for its queries. A common query is "select" which requests certain information from the database. In the library example, one might select (in plain English) all books written by a certain author or published after a certain date, etc. Megan uses the device by entering an SQL query into it: "Select * from people where age > 30" (show all the people older than 30). It appears that the actual people around her who are over 30 are wrapped in a yellow light, which does not apply to Megan in this query. Megan then tries other experimental queries, presumably to determine whether the results are correct. First, she queries for people with a high annual income (a group that does not include her), then for those who are afraid of flying (which does include her). Because the results for herself are valid both times, she then indulges her curiosity by asking who has watched porn in the preceding twelve hours. This suggests that whatever "database" she is accessing is extremely thorough as it contains updated records of people's day-to-day activities. The percentage of people lit appears to approximately correspond to real demographic data: note, 5 of the 10 characters are female; the median world/US age are fairly close to 30; top decile income in the USA is approximately $100,000 (and top earners are usually men); up to 40% of people are afraid of flying. Finally, she types "Drop table People". Drop is an SQL command to delete a table. When she enters the command the entire table disappears and because she is also in this table she disappears, too. The implications are unclear. It may be a suggestion that all of reality is a computer program, all of the people are merely "data" in the program, and Megan was somehow granted access to the database for the program. It could also be an allusion to the fact that human life is so rich, diverse, & interesting, but also extremely fragile. Someone who controls much power can, simply with the press of a few buttons, erase everything that thousands or millions of people had worked so hard on. The drop table command was also used in 327: Exploits of a Mom , although with less fatal results. The title text may suggest that when the people disappeared or "died", their records were moved to a table called "Ghosts". The query would then, presumably, see all the people that were deleted. In some implementations of databases deleted records are still hidden and remain until a "Ghost Cleanup Process" removes the data permanently; the title text may also allude to this process. Alternatively, the title text may refer to movies such as The Sixth Sense , in which certain people are ghosts, unbeknownst to those around them, another quality that may be elucidated by Megan's device. [The first and then every second part of the comic is drawn without any frames around the panels. They depict Megan with the device she finds. In the first and last of these there are more than one "panel" where Megan is drawn more than once without frames between. In between these frameless panels, in all even numbered rows, are a framed picture with an overview of the surroundings.] [The first two panels are drawn in the first row.] [Megan walks up to device lying on the ground.] [Megan picks up a device and looks a the screen. The screen is shown in black with white text and a white bar for her to enter text in.] Loaded table: People Enter query [Megan looks around and sees nine people nearby: A black haired girl with ponytail talking on the phone; a Cueball-like guy talking to a hairy guy; a group of three people, with Ponytail and another Cueball-like guy sitting, and a Megan-like girl lying on the ground; another hairy guy sitting with an ice cream cone on a big box; Another Ponytail girl leaning up against the box with her phone together with a third Cueball-like guy also with a phone in his hand. The device still shows the last part of the text in white on black, and with room to enter a query] Enter query Megan: ?? [Megan types into the device. The query is shown as coming from the devices screen:] Select * from people where age > 30 [Five people are highlighted in a yellow cloud around their bodies: Black haired ponytail, both guys talking, and the two last of the group of three.] [Megan types again:] Select * from people where annual_income > 100000 [One person is highlighted in yellow - the one talking to the first Cueball.] [Megan types:] Select * from people where afraid_of_flying = True [Four people, including herself, are highlighted in yellow. Also the Megan-like girl on the ground and the last two behind the box.] [Megan types:] Select * from people where hours_since_watching_porn < 12 [Three people are highlighted. The two girls around the second Cueball and the third Cueball.] [The next three panels are drawn on the same row.] [Megan looks at the device, while holding it in two hands.] Megan: Neat. [Megan holds the device in one hand, still looking at it.] Megan: ... [Megan types:] Drop table People [Everyone disappears; the items they were holding drop to the ground, including the device Megan has been using. the other devices are three phones and one ice cream cone.]

California

California

https://www.xkcd.com/1410

https://www.explainxkcd.com/wiki/index.php/1410:_California

[Caption above frame:] I like how long and skinny California is because it means you can use it as a graph axis: [Title at top of frame:] California Droughts Based on map data from US Drought Monitor/NOAA/Richard Tinker [A legend explains the colors which won't show in this transcript anyway:] Dry [Yellow] Drought [Beige] Moderate [Orange] Severe [Red] Extreme [Brown] Ludicrous ("exceptional") [A colored contour plot with Time on the X axis and California on the Y axis, and depth of drought as the dependent variable indicated by color. At the left edge, an outline of the state of California, rotated clockwise so as to be mostly vertical, with a label on the "X axis" of Jan 4, 2000, and a yellow patch indicating Dry conditions through the center of the state. To the right of that, four progressively-skinnier versions of the same image, showing more or less the same area of dryness, with the state outline shrunk along the Y axis until the fourth one is basically just a vertical line. This then merges into the main body of the graph, the true contour plot, in which the Y axis is just south-to-north distance along the state, as the X or Time axis runs from 2000 to 2014. Extreme droughts can be seen in Northern California in 2001, Southern California in 2002, and Southern California again in 2007. Moderate-to-severe drought is prevalent across most of the state in 2008-09, and then again starting in 2012, progressing to extreme and "ludicrous" in the northern 2/3 of the state by 2014. At the right-hand edge of the graph are five progressively-wider outlines of the state, reversing the pattern at the left edge, starting with a "line" and widening to a proper 2-D image of the state again, with an X-axis label of Aug 14, 2014, showing the true extent of the drought, with all areas of the state experiencing severe, extreme, or "ludicrous" levels.]

This graph shows the levels of drought over time in the state of California using years on the horizontal axis and distance along a 45 degrees rotated north-south-axis of California on the vertical axis. The image illustrates the use of the distance measure on the vertical axis by visually rotating and stacking multiple maps of California next to each other. The geography of California lends itself well to this kind of graphical interpretation because the state is much taller than it is wide, hence, large-scale phenomena like weather patterns are likely to cover much of the "width" of the state but only part of the "height". Because the variation in the west-east direction will be small, a side-on view of the state can be used as the vertical axis in a graph, so that the indicated values are either the average or extreme value across the width of California. Randall compiled the data in this graph from data from the US Drought Monitor , which is authored by Richard Tinker from NOAA . The colors Randall uses correspond to drought intensity levels D0-D4 defined on the Drought Monitor site. The darkest, most severe level of drought is labelled "ludicrous" (causing laughter because of absurdity), but a parenthetical remark indicates that the official term is "exceptional.". Of course, with half or more of the state in this condition, it can hardly be called "exceptional" any longer. The graph shows that in 2000, 2005, and 2010, there were very little or no drought conditions in California, but that the intervening periods have seen increasingly severe droughts. According to the most recent data, the state is entirely in a condition of "severe" or worse drought, with "ludicrous" conditions across approximately half its area. The graph also reveals that 2014 is the first year (since 2000) where the "ludicrous" level has been seen. Indeed, a comic about drought is rather topical: California is in the middle of one of its worst droughts in recorded history. The title text is a reference from the movie Spaceballs , a parody of various Sci-Fi movies. Lone Starr and Barf in their Winnebago space ship traveling at lightspeed are passed by Spaceball One, which is traveling at "ludicrous" speed. The path of Spaceball One is shown as a plaid pattern and Barf remarks "They've gone to plaid!" ( YouTube clip ). [Caption above frame:] I like how long and skinny California is because it means you can use it as a graph axis: [Title at top of frame:] California Droughts Based on map data from US Drought Monitor/NOAA/Richard Tinker [A legend explains the colors which won't show in this transcript anyway:] Dry [Yellow] Drought [Beige] Moderate [Orange] Severe [Red] Extreme [Brown] Ludicrous ("exceptional") [A colored contour plot with Time on the X axis and California on the Y axis, and depth of drought as the dependent variable indicated by color. At the left edge, an outline of the state of California, rotated clockwise so as to be mostly vertical, with a label on the "X axis" of Jan 4, 2000, and a yellow patch indicating Dry conditions through the center of the state. To the right of that, four progressively-skinnier versions of the same image, showing more or less the same area of dryness, with the state outline shrunk along the Y axis until the fourth one is basically just a vertical line. This then merges into the main body of the graph, the true contour plot, in which the Y axis is just south-to-north distance along the state, as the X or Time axis runs from 2000 to 2014. Extreme droughts can be seen in Northern California in 2001, Southern California in 2002, and Southern California again in 2007. Moderate-to-severe drought is prevalent across most of the state in 2008-09, and then again starting in 2012, progressing to extreme and "ludicrous" in the northern 2/3 of the state by 2014. At the right-hand edge of the graph are five progressively-wider outlines of the state, reversing the pattern at the left edge, starting with a "line" and widening to a proper 2-D image of the state again, with an X-axis label of Aug 14, 2014, showing the true extent of the drought, with all areas of the state experiencing severe, extreme, or "ludicrous" levels.]

Loop

Loop

https://www.xkcd.com/1411

https://www.explainxkcd.com/wiki/index.php/1411:_Loop

[Cueball sits at a desk, accompanied by a desktop computer and a laptop open in front of it. He is holding a tablet in his left hand and a smartphone in his right.] [A cyclical flowchart is shown above Cueball:] Stare blankly at screen -> Open news site -> Start reading -> Get bored -> Absentmindedly check smaller device -> Stare blankly at screen -> ...

Cueball is seen at his desk in front of four devices. He has clearly run out of things to do, or is looking for an excuse to procrastinate. A flowchart describes the process by which he scans the whole environment for something to do, which everyone can relate to. The comic uses electronics likely because they are the common time killer these days, and are most likely to contain fresh, tantalizing entertainment. News sites can be viewed as a good source of yet-to-be-seen content. Yet the search yields no interesting content, or the results don't garner enough attention, thus the blank stares and moving on to next device in line. Cueball has four devices, so he can begin with the desktop and move through the loop three times - first to laptop, then tablet and finally to smartphone. The title text notes that this also happened before there were electronic devices like today, assuming most entertainment came from books. The point made is that, while the Internet and modern electronic devices are often blamed for jeopardizing the minds of adolescents, the attention span of "the kids" is not worse than it ever was, neither in the context of low-tech nor high-tech media. Kids focus on some things for a long time, but they do change this focus often very abruptly. But nevertheless there are still many kids reading books today until the end. The title text could also be considered to imply another type of loop in which various generations experience the same situations under different circumstances (i.e., history repeating itself). In this case, the new generation experiences the attention lapse loop with electronics, whereas the previous generation experienced this same loop with books. There may also be a commentary present on the shorter attention span of the current generation as opposed to the previous one in that there is an obvious terminus to the electronics loop while the book loop could extend nearly indefinitely. [Cueball sits at a desk, accompanied by a desktop computer and a laptop open in front of it. He is holding a tablet in his left hand and a smartphone in his right.] [A cyclical flowchart is shown above Cueball:] Stare blankly at screen -> Open news site -> Start reading -> Get bored -> Absentmindedly check smaller device -> Stare blankly at screen -> ...

Teenage Mutant Ninja Turtles

Teenage Mutant Ninja Turtles

https://www.xkcd.com/1412

https://www.explainxkcd.com/wiki/index.php/1412:_Teenage_Mutant_Ninja_Turtles

[Caption above comic] WIKIPEDIA ARTICLE TITLES With the right syllable stress pattern to be sung to the tune of the original Teenage Mutant Ninja Turtles theme song [Six groups of Wikipedia article titles are written out. Each group contains ten titles. The first title of each group is drawn in the style of the Teenage Mutant Ninja Turtles logo, where the final word of each title is drawn in bulbous green text in the shape of an arch, with the remaining words in white text on a red banner above the green text. The remainder of the titles in each group are arranged as a list in standard font next to the larger titles, alternating from right to left hand side going down the comic.] Ace Ventura: Pet Detective Biggest Loser: Second Chances Cayman Island blue iguana Central Texas pocket gopher Church of Jesus Christ Creator Climate change and meat production Crouching Tiger, Hidden Dragon Daylight saving time in China Denver Airport People Mover Easter Island spiny lobster Asian Human Rights Commission Edgar Allan Poe Museum Engine failure after take-off English as a second language Former Arctic Monkeys members Fowler's Modern English Usage Georgia Game and Fish Department Golden-mantled howler monkey Greater Cleveland Film Commission Hairy flower chafer beetle San Diego City Council Harland David "Colonel" Sanders Human Tissue Resource Network Klondike -class destroyer tender Legal code of North Dakota Lesser knapweed flower weevil Lockheed Martin Atlas rocket Maple syrup urine syndrome Mighty Morphin' Power Rangers Nablus mask-like facial syndrome Single payer health insurance Neo Geo Pocket Color New Year's Eve with Carson Daly Newton's second law of motion North Korean Workers Party Orange County Business Council Over/under cable coiling Peter Peter Pumpkin Eater Places named for Adolf Hitler Proton-proton chain reaction Spotted giant flying squirrel Puerto Rican lizard-cuckoo Quantuum [sic] vacuum plasma thruster Rocky Mountain spotted fever Royal Flying Doctor Service Russian Women's Fascist Movement Semi-active laser guidance Seven Brides for Seven Brothers Sherlock Holmes: A Game of Shadows Six Degrees of Kevin Bacon Women science fiction authors Trailing suction hopper dredger Vector graphics markup language Viti Levu giant pigeon Voting rights in Puerto Rico William Henry, Duke of Gloucester Windows Vista startup process Woodrow Wilson "Woody" Guthrie Yaba monkey tumor virus Zack and Miri Make a Porno

This comic is a reference to the recently released Teenage Mutant Ninja Turtles movie . It is a list of Wikipedia article titles that are in the same syllable-stress pattern as the first line of the theme song of the 1987 cartoon series . The list is compiled in alphabetical order from top to bottom, without respect to the left or right column. Some of the items on this list (e.g. Ace Ventura: Pet Detective ) are drawn as headlines in the same style as the logo from that series. These articles are not in alphabetical order with the surrounding small face text, but these headlines are in alphabetical order with the other headlines from top to bottom, without respect to the left or right column. Some of these phrases are not actually the titles of Wikipedia articles, but are redirects. For instance, the article on Woodrow Wilson "Woody" Guthrie redirects to Woody Guthrie , and Former Arctic Monkeys members at one time redirected to Andy Nicholson . The syllable-stress pattern of this line is long-short-long-short-long-short-long-short, known in poetry as trochaic tetrameter . Randall has previously authored comics dealing with trochees , namely 856: Trochee Fixation and 1383: Magic Words . A similar idea was performed by Jimmy Fallon in 2001 at a concert for New York city where he demonstrated singing "any 80's song" over the tune of MC Hammer 's song " U Can't Touch This ". The title text suggests an album of songs ( The Purple People Eater , the aforementioned Ninja Turtles theme, Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini and the Mighty Morphin' Power Rangers theme), the title or primary refrain of which have a large number of verses in trochaic meter . Randall suggests that these refrains are so interchangeable that the lyrics of each could be sung to the melody of the song following it in the tracklist. Randall would title the album Linked List as each song would melodically reference the next song. The refrains of the songs, respectively are: In 2019 a Twitter feed was created which identifies Wikipedia articles with this stress pattern and creates a matching graphic. There are 6 headlines and 9 other article links in each block next to a headline for a total of 60 wiki links: Ace Ventura: Pet Detective Biggest Loser: Second Chances Cayman Island blue iguana Central Texas pocket gopher Church of Jesus Christ Creator Climate change and meat production Crouching Tiger, Hidden Dragon Daylight saving time in China Denver Airport People Mover Easter Island spiny lobster Asian Human Rights Commission Edgar Allan Poe Museum Engine failure after take-off English as a second language Former Arctic Monkeys members Fowler's Modern English Usage Georgia Game and Fish Department Golden-mantled howler monkey Greater Cleveland Film Commission Hairy flower chafer beetle San Diego City Council Harland David "Colonel" Sanders Human Tissue Resource Network Klondike class destroyer tender Legal code of North Dakota Lesser knapweed flower weevil Lockheed Martin Atlas rocket Maple syrup urine syndrome Mighty Morphin' Power Rangers Nablus mask-like facial syndrome Single payer health insurance Neo Geo Pocket Color New Year's Eve with Carson Daly Newton's second law of motion North Korean Workers Party Orange County Business Council Over/under cable coiling Peter Peter Pumpkin Eater Places named for Adolf Hitler Proton-proton chain reaction Spotted giant flying squirrel Puerto Rican lizard-cuckoo Quantuum vacuum plasma thruster [1] Rocky Mountain spotted fever Royal Flying Doctor Service Russian Women's Fascist Movement Semi-active laser guidance Seven Brides for Seven Brothers Sherlock Holmes: A Game of Shadows Six Degrees of Kevin Bacon Women science fiction authors Trailing suction hopper dredger Vector graphics markup language Viti Levu giant pigeon Voting rights in Puerto Rico William Henry, Duke of Gloucester [2] Windows Vista startup process Woodrow Wilson "Woody" Guthrie Yaba monkey tumor virus Zack and Miri Make a Porno [Caption above comic] WIKIPEDIA ARTICLE TITLES With the right syllable stress pattern to be sung to the tune of the original Teenage Mutant Ninja Turtles theme song [Six groups of Wikipedia article titles are written out. Each group contains ten titles. The first title of each group is drawn in the style of the Teenage Mutant Ninja Turtles logo, where the final word of each title is drawn in bulbous green text in the shape of an arch, with the remaining words in white text on a red banner above the green text. The remainder of the titles in each group are arranged as a list in standard font next to the larger titles, alternating from right to left hand side going down the comic.] Ace Ventura: Pet Detective Biggest Loser: Second Chances Cayman Island blue iguana Central Texas pocket gopher Church of Jesus Christ Creator Climate change and meat production Crouching Tiger, Hidden Dragon Daylight saving time in China Denver Airport People Mover Easter Island spiny lobster Asian Human Rights Commission Edgar Allan Poe Museum Engine failure after take-off English as a second language Former Arctic Monkeys members Fowler's Modern English Usage Georgia Game and Fish Department Golden-mantled howler monkey Greater Cleveland Film Commission Hairy flower chafer beetle San Diego City Council Harland David "Colonel" Sanders Human Tissue Resource Network Klondike -class destroyer tender Legal code of North Dakota Lesser knapweed flower weevil Lockheed Martin Atlas rocket Maple syrup urine syndrome Mighty Morphin' Power Rangers Nablus mask-like facial syndrome Single payer health insurance Neo Geo Pocket Color New Year's Eve with Carson Daly Newton's second law of motion North Korean Workers Party Orange County Business Council Over/under cable coiling Peter Peter Pumpkin Eater Places named for Adolf Hitler Proton-proton chain reaction Spotted giant flying squirrel Puerto Rican lizard-cuckoo Quantuum [sic] vacuum plasma thruster Rocky Mountain spotted fever Royal Flying Doctor Service Russian Women's Fascist Movement Semi-active laser guidance Seven Brides for Seven Brothers Sherlock Holmes: A Game of Shadows Six Degrees of Kevin Bacon Women science fiction authors Trailing suction hopper dredger Vector graphics markup language Viti Levu giant pigeon Voting rights in Puerto Rico William Henry, Duke of Gloucester Windows Vista startup process Woodrow Wilson "Woody" Guthrie Yaba monkey tumor virus Zack and Miri Make a Porno

Suddenly Popular

Suddenly Popular

https://www.xkcd.com/1413

https://www.explainxkcd.com/wiki/index.php/1413:_Suddenly_Popular

Obscure words and phrases everyone suddenly becomes very familiar with. [A time line to the left is marked of by several phrases to the right around the time they became familiar to the public:] ← World Wide Web ← DNA Evidence 1995 ← Militia Movement ← Supermax 2000 ← Butterfly Ballot ← Al-Qaeda ← Wi-Fi 2005 ← Tsunami ← Viral 2010 ← Radicalize ← Metadata 2015 ← Lahar ← Insect-Borne 2020 ← Earth-Crossing ← Thermohaline ← Snow-Blindness 2025 ← Amplexus ← Controlled Hydroplaning 2030 ← Paradoxical Reaction ← Drone Desertion ← Rapid Hair Growth 2035 ← I Swear Allegiance To The God-Empress In Life And In Death 2040

Many phrases that used to be of mainly academic interest become popular when an important event or global trend is described with such phrases in the media. Randall presents a timeline of past examples, and predicts phrases that may be popularised in the near future. The past events are a mix of buzz words and words that became popularized as a result of technology trends, natural disasters, or terrorism. The future events seem to be all related to natural disasters or other kinds of serious issues, except Amplexus — which is the joke of the title text — showing that no matter how many disasters there are, people are generally more concerned about their teenagers' sex lives. The title text is also an example of a clickbait headline. Many organizations will post a link on social media to their content with a sensationalized headline in order to draw readers in. In this case, the headline is geared towards parents who are worried about their children being sexually active in this new Amplexus way. Such headlines are the internet's analog to television news' promos ("A new trend among teens is sweeping the nation, but is it dangerous? Details at 11:00."). Global catastrophic risk is a theme throughout this comic. Randall predicts a large asteroid impact/near miss and a volcanic eruption, followed by an impact winter or volcanic winter . An insect borne, global pandemic without a cure also strikes, and then the technological singularity occurs. This comic has similar features to 887: Future Timeline . Below the phrases are listed with the closest year from the time-line noted behind the phrase. Note that this year does not necessarily match with the in-real-life relevant year. This may be found in the explanation of the phrase below. Google Books Ngram Viewer can show the relative frequency of those words in function of the year. World Wide Web – 1994 Though first proposed in 1989, and the first test being completed in 1990, it took until around 1994 for the world wide web to start becoming well known. DNA Evidence – 1995 Prominent coverage of the O. J. Simpson murder trial in 1994 brought widespread discussion of DNA Evidence , making it famous and showing its limitations. Militia Movement – 1996 After the standoffs at Ruby Ridge , Idaho in 1992 and the Branch Davidians compound in Waco, Texas between U.S. Government Agencies and militias in 1993, people started becoming more aware of their presence, culminating with the 1995 Oklahoma City Bombing on the second anniversary of the fire at the Branch Davidians compound. Supermax – 1997 Super-Maximum security prisons. Possibly referring to the 1997 film Con Air , starring Nicolas Cage, John Cusack, and John Malkovich, in which prisoners being transferred to a new Supermax prison seize control of their transport plane. Also possibly referring to Timothy McVeigh and Terry Nichols , perpetrators of the aforementioned Oklahoma City bombing, who were incarcerated at ADX Florence , the former from the time of his arrest to 1999, and the latter from the time of his conviction to the present day. Butterfly Ballot – 2000 In the United States presidential election in 2000, Florida had a major recount dispute that took center stage in the election. Thus, the outcome of the 2000 United States presidential election was not known for more than a month after balloting, because of the extended process of counting and then recounting of Florida presidential ballots. The butterfly ballot was the type of ballot design used in Palm Beach County, Florida , and was a central issue in the election controversy. Evidence suggests that many voters who intended to vote for Gore or Bush actually marked their ballots for Pat Buchanan or spoiled their ballots, because of a confusing layout of the ballot. Al-Qaeda – 2002 The September 11th terrorist attacks brought the al-Qaeda terrorist organisation into the spotlight almost overnight. Wi-Fi – 2003 Wi-Fi, though developed in the 1990s, first became popular in the early 2000s. Tsunami – 2006 There were a number of tsunamis around this time period, in particular the Boxing Day Tsunami which caused 230,000 deaths, and the 2006 Pangandaran earthquake and tsunami . These were some of the first tsunamis to be widely captured on camera, bringing these previously obscure seismic events into the public eye. Viral – 2009 In this context, the word viral is used to describe anything which spreads rapidly and widely on the internet. In particular an online video clip is said to have 'Gone Viral' or become a Viral video if it racks up a high number of views over a short time. This phenomenon has become especially prevalent due to users sharing content on Social media . Radicalize – 2011 Due to the ongoing Syrian Civil War , and the relative ease with which one can travel from Europe to Syria by way of Turkey, there is growing concern about the risk of young Muslims in Europe (and, to a lesser extent, the United States) becoming radicalized by indoctrination from fundamentalists either in their communities or on the Internet. Metadata – 2013 Following the highly publicised 2013 leaks by Edward Snowden of information regarding the NSA 's indiscriminate surveillance of global communication metadata, awareness of the privacy value of such data became widespread, where once it was mostly familiar to IT professionals. From this point on, phrases were in the future at the time of publication. Lahar – 2016 A lahar is a mudslide caused by the eruption of a volcano that was covered with snow or ice. Randall is speculating on a future natural disaster being caused by such an incident. Bárðarbunga volcano covered with the Vatnajökull glacier on Iceland increased activity just a few days before publishing of this comic, but its eventual eruption caused little harm. Insect-Borne – 2019 Some diseases are insect-borne , meaning specific species of insects are the main vector in spreading to humans. Malaria is an example of an insect-borne disease . Randall predicts some severe (possibly deadly) insect-borne disease will emerge around this time. As of 2016, the Zika virus, which is transmitted by mosquitoes, has reached epidemic status in South America, and has spread to southern North America, Africa and Australia. 2019 marks the beginning of the COVID-19 epidemic, so Randall's prediction of a major disease could be accurate, however COVID-19 is not an insect-borne disease. Earth-Crossing – 2021 Earth-crossers are asteroids that cross the orbit of Earth. Most of them remain harmless because their orbit doesn't actually intersect the earth's orbit in 3 dimensions, or for the foreseeable future, they will cross when Earth is not there. For this phrase to become popular, an Earth-crosser might have to reach the heretofore-unreached "threatening" level, rating a 5 or more on the Torino Scale , due to a significant chance of a large impact. As of 2014, there are no threats of that level known in the early 2020s. If the next two phrases are connected to this one, Randall is predicting a significant asteroid impact. Thermohaline – 2022 Thermohaline circulation is the largest group of interconnected ocean currents, which stabilize global climate by equalizing the temperature and salinity of oceans around the world. If this phrase becomes popular, it implies the thermohaline circulation would have slowed or changed significantly. This might be caused by asteroid impact or by polar ice melting. The latter scenario was apocalyptically dramatized in the movie The Day After Tomorrow . Snow-Blindness – 2024 Snow blindness is an eye condition caused by excessive UV light reflected from snow and ice. This can lead to corneal damage and blindness (temporary, if treated properly). This phrase becoming popular might suggest a long impact winter (from the asteroid) or severe ozone depletion in cold regions of the world. Amplexus – 2025 A form of non-penetrative reproduction carried out by some animals, for example frogs, involving grasping the partner with front legs. This may be connected to the other posts (some change in human society) or it may simply be a joke at how new sexual language/fads appear and hit mainstream media from time to time (for example a number of acts gained fame from Sex and the City). This also ties in with the title text, which imagines a sensationalist headline suggesting teenagers may be doing this. Controlled Hydroplaning – 2028 Hydroplaning occurs when a vehicle tire comes in contact with a puddle in such a way that the water builds up between the tire and the road surface. The film of water, having a much lower coefficient of friction than the road surface, causes the tire to lose traction. Typically, in this scenario, the driver isn't planning to hydroplane and loses control of the vehicle. In theory, controlled hydroplaning would be achieved when the driver plans for it ahead of time. This could be necessary if, in this hypothetical future, most of the roads are flooded since the impact winter (after only four years) ends and thus a great thaw causes all roads to become wet all the time. Paradoxical Reaction – 2031 "paradoxical reaction" is a medical term for when the outcome of a medical treatment, typically the taking of a drug, is the opposite of that expected. For example if taking a pain relieving medication made the pain worse. For this term to suddenly become well known, a large scale or particularly notable case must have taken place (such as the insect-borne disease of 2019). Or, this and the following (and maybe the last as well) phrases may refer to the events from The Evitable Conflict by Isaac Asimov (and its very loose but much more popular film adaptation I, Robot ) where robots, instructed with the Three Laws of Robotics , take over the world to prevent humans hurting each other. The paradoxical reaction is that these laws were specifically designed to, among other things, prevent robots from taking over the world in the first place. Drone Desertion – 2033 Desertion is the abandonment of a post or duty, usually military in nature. With the increasing use of autonomous drones by the military this hints at an event where drones 'decide' to desert, possibly due to unspecified advances in Artificial Intelligence and Robot Rights . Or maybe they just start following the Three Laws of Robotics . See also 2499: Abandonment Function . Rapid Hair Growth – 2034 Maybe some humans have developed a very rapid hair growth (presumably on the entire body) through evolution and natural selection caused by the cold years of the impact winter. I Swear Allegiance To The God-Empress In Life And In Death – 2038 This is a divine oath . A possible explanation is that after the impact and the desertion of the drones predicted for 2033, a strong fraction has made their leader divine, and everyone now has to swear allegiance to this new God-Empress using this phrase - which would certainly make it a very "popular" phrase. The phrase God-Emperor was popularized in the science-fiction work Dune in 1965 and has been repeatedly referenced since, notably in the tabletop game Warhammer 40,000 (and related media). Obscure words and phrases everyone suddenly becomes very familiar with. [A time line to the left is marked of by several phrases to the right around the time they became familiar to the public:] ← World Wide Web ← DNA Evidence 1995 ← Militia Movement ← Supermax 2000 ← Butterfly Ballot ← Al-Qaeda ← Wi-Fi 2005 ← Tsunami ← Viral 2010 ← Radicalize ← Metadata 2015 ← Lahar ← Insect-Borne 2020 ← Earth-Crossing ← Thermohaline ← Snow-Blindness 2025 ← Amplexus ← Controlled Hydroplaning 2030 ← Paradoxical Reaction ← Drone Desertion ← Rapid Hair Growth 2035 ← I Swear Allegiance To The God-Empress In Life And In Death 2040

Writing Skills

Writing Skills

https://www.xkcd.com/1414

https://www.explainxkcd.com/wiki/index.php/1414:_Writing_Skills

[White Hat and Cueball are walking together, White Hat is holding a newspaper or report.] White Hat: Weird- Another study found that kids who use SMS abbreviations actually score higher on grammar and spelling tests. Cueball: Why on earth is that a surprise? [Cueball turns to White hat (who is now out side the frame. Inserted in the frame is a panel showing several kids throwing balls.] Cueball: Imagine kids suddenly start playing catch literally all the time . Everywhere they go, they throw balls back and forth, toss them in the air, and hurl them at trees and signs- Nearly every waking hour of their lives. [Cueball talks on while White Hat begins to walk.] Cueball: Do you think their generation will suck at baseball because they learned sloppy skills? White Hat: ...So you think someone will become a great writer while sexting? [They walk together.] Cueball: Have you read James Joyce's love letters? The phrases "My little fuckbird" and "Arse full of farts" appear. If we want to write Ulysses , our generation may not be sexting enough . White Hat: Eww.

Cueball and White Hat are discussing the positive and negative effects of young people writing on mobile phones in the vernacular of the day, Short Message Service (SMS). SMS messages are one of the primary means of text communication on mobile devices, and are typically limited to 160 characters. Due to the limited space available on this and other messaging platforms, and also to decrease the time taken to write a message, SMS language (aka textese) developed as a form of short-hand writing. This involves the abbreviation and deliberate misspelling of words, and the use of acronyms. Naturally, the use of this style of language has expanded into other areas, including those where brevity is not an issue, and this expansion and evolution of language is a subject of intense debate. The main viewpoints on the subject are: Cueball's point is that "practice makes perfect". The ability to form good grammar comes from practice through a lot of writing, even when that writing is informal; hence, the SMS generation gets a lot of practice compared to previous generations, who communicated mostly with speech, over the phone, and in person, and may have written only a few letters a year. To foster talent for a major literary work, we should encourage practice, even when that practice is through informal writing such as SMS. This idea has some real scientific background. Such as the investigation in 2009 Exploring the relationship between children's knowledge of text message abbreviations and school literacy outcomes . In this study children 10-12 were asked to compose text messages. The number of textisms was recorded, and a positive correlation was found between use of sms abbreviations and success at literacy tests. This is then related to David Crystal's concept of "ludic" language: the playful use of language as a contribution to language development. That notion is developed here: By playing with textual language, one develops writing skills, just as by playing with balls one can develop sports skills. David Crystal explains : "Children could not be good at texting if they had not already developed great literary awareness [...] If you are aware that your texting behaviour is different, you must have intuited that there is a standard." James Joyce was a celebrated Irish novelist and poet, and his novel Ulysses is considered to be one of the most important works of modernist literature. It was criticized in some quarters for the frequent lack of punctuation and ungrammatical stream of consciousness narrative mode. In addition to his better-known works, he wrote a number of love letters with extremely explicit content. In the title text, Randall wishes to prove Cueball's point by analyzing and comparing bulk volumes of texts (= a corpus ) written by children today and 20 years ago. Randall favors the literary ability of today's children for their everyday use of written word over the situation of the past, when children wrote only if forced to do so. The title text's second sentence is particularly long and complex (compared to almost any other title text), which will generally score much higher "on various objective measures of writing quality". Randall may be hinting that writing a lot of short title texts, like writing a lot of SMSs, improves your general writing quality - further strengthening Cueball's point. The title text is also 99 words long, probably referencing a 100 word limit. [White Hat and Cueball are walking together, White Hat is holding a newspaper or report.] White Hat: Weird- Another study found that kids who use SMS abbreviations actually score higher on grammar and spelling tests. Cueball: Why on earth is that a surprise? [Cueball turns to White hat (who is now out side the frame. Inserted in the frame is a panel showing several kids throwing balls.] Cueball: Imagine kids suddenly start playing catch literally all the time . Everywhere they go, they throw balls back and forth, toss them in the air, and hurl them at trees and signs- Nearly every waking hour of their lives. [Cueball talks on while White Hat begins to walk.] Cueball: Do you think their generation will suck at baseball because they learned sloppy skills? White Hat: ...So you think someone will become a great writer while sexting? [They walk together.] Cueball: Have you read James Joyce's love letters? The phrases "My little fuckbird" and "Arse full of farts" appear. If we want to write Ulysses , our generation may not be sexting enough . White Hat: Eww.

Ballooning

Ballooning

https://www.xkcd.com/1415

https://www.explainxkcd.com/wiki/index.php/1415:_Ballooning

[Cueball is shown floating on the wind, attached to a large balloon. The balloon is made of spider silk.] Cueball: Ooh, that looks like a good spot to land, eat some bugs, and make an egg sac! ♫ Spider-Man, Spider-Man, does whatever a spider can ♪

Spider-Man is a fictional superhero in comic books published by Marvel Comics, and has been the star of a number of television shows and film. The Spider-Man theme song , first used for the 1967 cartoon show, includes the words, "Spider-Man, Spider-Man, does whatever a spider can". However, at other points, the theme song explains some things Spider-Man can do that a real spider obviously couldn't, such as crime-fighting. [ citation needed ] Randall is pointing out that while the abilities attributed to Spider-Man make a good superhero story, they are not real abilities of a spider. This comic depicts Cueball as a far more realistic Spider-Man, behaving and thinking much more closely to a real spider than the Spider-Man from the comics. Cueball is shown ballooning ( example ), a trait used by spiders to move between locations, rather than swinging on web cords as in the comics and films. As he is floating, he sees a good spot to land, eat some bugs and make an egg sac. Again this contrasts the real life of a spider with Spider-Man, who would doubtless be rushing to fight crime or save a pretty girl. Only female spiders create an egg sac. Male spiders spin a sperm web in order to transfer their sperm from their epigastric furrow into their pedipalps (reproductive organ located on the front two appendages, in the position where a scorpion would have pincers), which will then be used to transfer the sperm into the female during copulation. Cueball/Spider-Man, being nominally male, should in fact be looking for a place to create a sperm web, not an egg sac. However, thanks to being featured in children's books, the actions of female spiders are much more widely known. The title text refers to the mating ritual of some spiders, in which the male performs a dance to court the female. Mary-Jane is the third love interest and Peter's eventual wife in the Spider-Man stories, and so Cueball is planning to court her by dancing in front of her. In doing so he hopes that he is lucky, and she doesn't eat him before copulating with him, as sexual cannibalism is a trait associated with spiders. [Cueball is shown floating on the wind, attached to a large balloon. The balloon is made of spider silk.] Cueball: Ooh, that looks like a good spot to land, eat some bugs, and make an egg sac! ♫ Spider-Man, Spider-Man, does whatever a spider can ♪

Pixels

https://www.xkcd.com/1416

https://www.explainxkcd.com/wiki/index.php/1416:_Pixels

[Cueball is stacking turtles, and is about to put the fourth turtle on his pile. At the bottom right there is a small panel. Inside this is written:] Scroll to zoom [When zooming in there will be several panels with text. The transcript of these may not be possible to complete - but add the transcript of these panels here: interactive transcript ] The following code can be found by inspecting the comic's source code: [[A large picture of a person kneeling on the ground, stacking turtles.]] ((In this strip, when you zoom into the panel, each pixel becomes its own panel. Each of those panels can be scrolled into, for the same effect. The story progresses as you scroll deeper.)) [[The Earth as seen from space with the words BOOK LAUNCH.]] [[A stick-Randall holding a copy of 'What If?' saying, "So excited about my book launch!"]] [[A copy of the cover of 'What If?' labeled "book."]] [[Stick-Randall is assembling parts from a box labeled 'rocket parts' and preparing to 'launch' his book.]] [[Various stages of assembly.]] [[A second person comes in, looks at SR's rocket set-up and says, "Needs more struts."]] [[SR adds more struts.]] [[The rocket launches.]] [[A big cloud of smoke, which then dissipates.]] [[SR and the other person look skywards at the launched book.]] [[The book is shown leaving Earth's orbit.]] [[The other person turns to SR and says, "I think that was the only one."]] [[The two walk away.]] ((The panels after this are a random assortment of these mostly stand-alone panels.)) [[A momma duck with several ducklings in a row behind her, labeled 'Evolution.']] [[The other person floating around in the sky.]] [[A stick figure with a sploshing bucket of water saying, "I'm gonna shut down the server!"]] [[Two people walking along, one saying, "But if the Time-Turners worked after Book 3, Rowling would have used one to go back and remove the Time Turner from Book 3."]] [[The code: ~$ du -s video 4170882256 ~$ du -hs video A lot. ~$]] [[A cloud.]] [[A flock of birds.]] [[MU]] [[A pixel.]] [[A person using a computer on the floor.]] [[HOLISM]] [[Saturn]] [[An atom.]] [[Two people star-gazing on a hill.]] [[Person one says, "Someone once told me the great kings of the past look down on us..." Person two says, "From the stars?" The first person replies, "Just in general."]] [[The start of Mario World 1-1.]] {{Title text: It's turtles all the way down.}} This gallery contains the 79 images used in this comic . The images are related in a directed graph . This google sheet describes all possible images, their associated codes, and what possible images can be used as sub-images for each zoom level: https://docs.google.com/spreadsheets/d/1nldKAkeVcK606CY12KI9bah9rDmK9E7CZOyinsEj2Lo/edit?usp=sharing This gist recursively downloads all possible images: https://gist.github.com/Aaron1011/d3b56325881cd639506a

This interactive comic begins with a panel where Cueball is stacking turtles. This is a reference to the idiom " turtles all the way down ", which refers to the problem of infinite recursion: if everything in the universe is "on top of" something else, so to speak, there must be a "bottom." A joking solution to the paradoxical nature of such a bottom is the proposition that the world rests on a semi-infinite stack of turtles. The origins of the turtle story are uncertain. It has been recorded since the mid 19th century, and may possibly date to the 18th. One recent version appears in Stephen Hawking 's 1988 book A Brief History of Time , which starts: A well-known scientist (some say it was Bertrand Russell ) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!" —Hawking, 1988 Several ancient myths , dating back thousands of years, involve a turtle which supports the whole world, or a part of it, although it is usually just one turtle, not an infinite regression. This is also repeated in Terry Pratchett 's Discworld novels, in which the world is supported by four elephants standing on the back of a single turtle called Great A'Tuin . As can be read you should "scroll to zoom" . This can be done by placing the cursor inside the panel of the comic. When scrolling up (using the mouse wheel) the picture zooms in on the pixel beneath the cursor. Moving the cursor will also move the point to which the picture zooms. You can then zoom in until the pixels are visible. When you continue to zoom in on a pixel it then resolves into another comic picture, with black-on-white comic panels making up the white pixels and white-on-black panels making up the black pixels. Scrolling on until you can see the pixels of the comic picture you are now zooming into the process is repeated again and will be so for all subsequent sets of comic panels. Not all white and all black panels are the same; some sets involve more than two different panels, but all involve repetitive tiling. Once you have zoomed in, you are able to click and drag the picture, thus enabling you to move from black to white picture pixel. This is reminiscent of the earlier interactive comic 1110: Click and Drag . Apart from the first image there are two more with a single turtle in them. In one of these the turtle thinks "I am a turtle". This is a reference to 889: Turtles . It may say so to the Cueball that is seen standing all alone in another picture. There is a panel featuring just Cueball, followed by is a picture of the What If? book, large enough that all of the text is visible on the front cover. But there is also another version where the author's name is crossed out and replaced with Stephen King , the word "Spooky" has been added above the title, and the word "xkcd" below has been struck and replaced with "being afraid" to form the phrase "creator of being afraid". Stephen King is one of the most prolific and well-known horror authors of all time. This comic was released on September 3, 2014, the day after Randall's book What If was launched. The book is shown and referred to in a number of frames; for example, it is literally launched as a part of an rocket up goer built by Cueball. There is also a picture with Cueball holding his book, while being excited about the launch. The model up goer is made of Rocket Parts from KSP . KSP is the Kerbal Space Program , a spaceflight simulator which was also part of the latest interactive comic 1350: Lorenz . Perhaps xkcd's "parts" refers to KSP's large community of mod developers who contribute 'parts' to the game, although it was likely intended as nothing more than the humorous supposition that one could purchase physical rocket parts from a simulator. The frames showing the book launch use URLs that include the text "upgoer" in reference to the Up Goer Five comic. In the end the up goer leaves the Earth after one orbit and then flies through space. Struts are structural members in engineering, and are one of the components used in Kerbal Space Program to construct rockets. "Needs More Struts" is a meme amongst players of Kerbal Space Program along the lines of "when in doubt, overengineer"; it stems from a time when the ragdoll physics in the Unity engine underlying KSP was unstable enough to necessitate their overuse. Megan deems Cueball's rocket to be insufficiently structurally sound, and declares that it " Needs More Struts ". The first three images depict Cueball building a Kerbal Space Program rocket out of parts from a box, labelled "KSP Rocket Parts". The top part of the rocket, usually where the crew module would be located, is made from the What If..? book. In the fourth panel Megan declares that it needs more struts, and in the next three panels, Cueball takes her advice and adds more struts. Panel 8 shows the Earth from a distance, with somebody (presumably Megan) saying again "More Struts". Panel 9 shows the Earth alone, and panel 10 shows the Earth with the rocket nearby, having just launched. This series of panels parallels the "Needs More Struts" series. The first four panels shows the rocket lifting off, and the subsequent gasses dissipating. Cueball and Megan look up at the ascending rocket, and then turn to each other having just launched the What-If book rocket into space (construction and launch are seen in other panels). Perhaps Megan realizes they may have misunderstood the term "book launch", and that they may have just lost the only copy of the book. Panel 7 shows the Earth from space; panel 8 also shows the Earth, with the words "Book Launch". The next three panels show the rocket circling around the Earth once before heading into deep space, and the last shows the rocket by itself on its journey. Here are five objects in space. It is possible that the What-If book rocket passes them by, or that these images are seen from the point of view of the rocket. First is the Sun, shown with visible solar prominences . Next is the Moon, shown in a crescent view with stars behind it. This is followed by Saturn, also in a crescent view with stars behind it. There follow two images with just stars. This is a reference to 428: Starwatching : In four pictures Cueball and Megan are sitting below the stars. In the second the following conversation takes place: Cueball: Someone once told me the great kings of the past look down on us... Megan: From the stars? Cueball: Just in general. The second panel is a reference to Disney's The Lion King . Early in the film, Mufasa tells Simba that the great kings of the past look down on them from the stars. Later on, Simba recalls this to his companions, Timon and Pumba (who don't take him seriously). In the film, the kings of the past literally look down on — and watch over — the characters, which is how Megan interprets Cueball's initial statement. Cueball's reply that they just look down on us in general shows that he means the kings of the past figuratively look down on us (they view us as inferior or beneath them). In the next image a shooting star is seen above them. The final picture is almost identical to the first (only four stars and a few pixels of ground are different). A series of 8 images are called Mario . The first is called entry , and has a picture of a TV on a low stand. The next four has Megan in front of said TV, holding a video game controller. The cable is connected to something inside the stand. She first kneels, then sits. In the third picture she is lying down. What follows is a picture which is an inverse of the sitting picture. The last three images seem to depict a level from one of the Super Mario Bros. games. In the upper right one can see the iconic bricks which Mario can smash, two clouds appear stationary in the background, and a crude depiction of Mario is standing in the lower left. Over the course of the three images, a galaxy rises into the sky. It does not look like the Milky Way would from anywhere on Earth. The view is reminiscent of a quote from Carl Sagan: "...from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits. Not a sunrise, but a galaxy rise. A morning filled with 400 billion suns. The rising of the milky way." The quote was also referenced in 681: Gravity Wells Randall often allows images of transcendent awe to take over mundane scenes. In this case, the galaxy-rise is a surprising twist revealing the true setting of the Super Mario Brothers games. At the same time it conveys how long Megan has been playing the game - day has turned into night in her room, and also within the game itself. Instead of playing it, she is simply watching the galaxy-rise, as the character on the screen has not moved. The view may contain a hidden pun, by calling to mind Super Mario Galaxy . Cueball tells an offscreen character that he is going to shut down the server , while carrying a bucket of water. Usually shutting down a server is done via the operating system or software. Directly turning it off or pulling the power plug also would technically work though not recommended for obvious reasons. But in this case it appears that Cueball is going to attempt to shut off the server by dousing it with water. This will likely result in serious water damage to the hardware, thus forcing it off as it no longer is able to function. In five pictures Megan is floating in the clouds. The first shows Megan flying to the right, the second and third show just clouds, the fourth shows Megan flying to the left, and the fifth shows birds flying. In two images Cueball and Megan are seen walking. The first is a normal black-on-white close up, and the second an inverted image seen from afar. They are talking while walking; after the first walking image they discuss Stockholm syndrome and then Time Turners , and after the second walking image Black Hat discusses a fire hydrant with a firefighter. Stockholm syndrome is the name for a psychological phenomenon, in which hostages develop sympathy, empathy and/or positive feelings towards their captors. These feelings are usually seen as irrational, seeing as the hostage is held against their wishes, usually with the threat of physical harm or death. This panel asks "How do we know anyone really wants to live in Stockholm?", questioning whether everyone who lives in the city of Stockholm is in fact held hostage there and only stays because they have developed to like life there (due to Stockholm Syndrome). The time turner is a device from the Harry Potter series of novels by JK Rowling . It allows the user to re-live a period of time over again. In the third novel Hermione is given the time-turner to allow her to take extra classes, however it is eventually used to spare Buckbeak the hippogriff from execution. This prompted many questions regarding why time-turners weren't used on other occasions to save people's lives (among other things). While J.K Rowling has " solved the problem to her own satisfaction " she admits that she entered into the subject of time-travel too lightly. This panel jokes that if the real life JK Rowling had a fictional time-turner which worked, she would have gone back and removed the time-turner plotline from the book, saving her all the hassle of dealing with the resulting time-travel questions. This act would result in a time-travel paradox. Black Hat is talking to a fireman, with a fire engine on fire in the background, he asks "To be fair, what else would you expect to come out of a " fire hydrant "?" Black Hat appears to have managed to replace the usual water supply to the fire hydrant with actual fire. Thus when the hydrant is used, the result is, quite literally, fire (or oil with possibly flint and steel contraptions to cause fire). In Black Hat's logic, a hydrant which delivers water should be called a water hydrant. This completely ignores the meaning of the word "hydrant", a pipe which supplies water (derived from the English root hydro- meaning relating to water , which is in turn from the Greek hudōr meaning water ). An alternative explanation is that Black Hat has replaced the water that would normally come out of the fire hydrant with a strong alcoholic beverage, colloquially called firewater , with a high enough ethanol content to burn. If this were the case, the ability to douse a fire would be severely decreased, both due to the flammable component and because ethanol can absorb less heat per volume than water. Megan hears a very long stretched EEEEEEEEEEEEE sound which goes over 6 images. It turns out it is a large letter E that shouts EEEEEEE!!! . In total there are 64 small E emanating from the big one. There is also a picture with two big white E on black background. Those E are larger than the E that shouts. The March of Progress image is a famous and instantly recognisable image showing the stages of human evolution by way of a series of primate figures as if marching in a line. The panel parodies the March of Progress image, with 5 ducklings following an adult duck . In this case, rather than portraying selected individuals millions of years apart, the March shows evolution in action on a human timescale, the mother taking care of her ducklings. The comic has some resemblance to 537: Ducklings . Four ropes cross diagonally across this black picture. They might be strings. There are two chess boards on black and white background with smaller chessboards drawn upon them in a Fractal pattern. One panel contains a number of lines and dots, which are in fact a depiction of the first 5 steps of a Cantor Ternary Set , mirrored about the horizontal centreline (see reference image ). The Cantor ternary set is constructed by repeatedly deleting the open middle thirds of a set of line segments. In the comic, the two upper-left most segments and the two lower-right most segments are misaligned slightly. The Cantor Set is one of the canonical examples of a fractal, a shape whose individual parts resemble the whole. The use of the Cantor Set in this comic is self-referential, in that the comic, itself, is composed of parts of the same shape as the whole. There is a picture of tiny particles, quite spaced out. These probably represent atoms, and given how distant they are, they may well be a gas. There follows a picture of a Bohr Model atom with point electrons surrounding a nucleus of protons and neutrons. The atom is a Carbon atom which is essential for all living matter and therefore for evolution. There is also a picture of what is probably a vibrating cosmic string fragment (a concept in string theory ). Despite Heisenberg's Uncertainty Principle , zooming down to the string does not mean that the cartoon viewer has reached the "bottom" of the comic - zooming in on the loop will show a picture of string. These three words refer to "A MU offering", an essay by Douglas Hofstatder in his book Godel, Escher, Bach (which was referenced by Randall in 24: Godel, Escher, Kurt Halsey ). It includes a similar multiple level drawing: the word MU is composed of copies of the words HOLISM and REDUCTIONISM , each of which are in turn made of smaller copies of the other, which are in turn made of tiny copies of the word MU . Mu is an important word in Buddhism . Literally, it means "no" or "not", but in Buddhism it also refers to a state of being or thinking - or rather, of not being and not thinking. It could be said that the pairs of panels in this series are each other's Mu, being negative (white-on-black and black-on-white). Holism is a philosophical principle that systems should be considered as a complete whole, not as a set of individual parts. For example, a human viewed holistically is a whole interconnected being which can only be fully understood in its own context. Reductionism is essentially Holism's opposite, a philosophical principle that any complex object can be reduced to a collection of simpler objects. A human can be considered as a set of organs (e.g. the heart), which in turn is composed of tissue (in this case muscle), composed of many cells. Cells can then be reduced to organelles, such as the nucleus; this contains chromosomes, made of DNA, a molecule made of atoms; atoms are made of components including protons; and protons are composed of quarks (which may be considered as one-dimensional strings). Reductionism holds that a full understanding of the simplest components of a system, and how they interact, can lead to a full understanding of the system as a whole. The word was later reduced in 1734: Reductionism . Holism and reductionism are complementary, rather than competing, philosophies, as both have their strengths and weaknesses. Holism can be very effective in understanding the larger-scale effects of a system by observing macroscopic events and how they are linked, but it ignores the more in-depth understanding gained by considering the smaller-scale components. Reductionism can in theory give us a complete understanding of the entire system by building it up from the smallest and simplest parts, but for a complex system, this is effectively impossible (a typical human contains roughly 10 29 quarks, whose interactions cannot possibly be computed and understood in human terms or timescales). "Pixels" is an example of a system best understood with a combination of holism and reductionism. Each panel can be fully explained in its own terms, but is more completely understood as part of a small series of panels. The interconnectedness of all the panels shows a more holistic understanding, yet even this cannot explain comic fully, which must be experienced, with its interactivity and sense of exploration. These panels can be found inside panels with Megan. " du " is a POSIX (think Linux / Mac OS X ) command to indicate the "disk usage" of a file or directory. This is a command that shows how large all the files are in this user's "video" directory - presumably where they store their personal videos. The units of the result is probably kilobytes (depending on settings, could also be the number of 512-byte blocks). This number is clearly large and difficult to parse, and the units are not clear (to a bystander). More appropriate units would be gigabytes rather than bytes. The du command offers an option to display units in "human readable format", which will adapt to use kilobytes, megabytes, gigabytes, terabytes, etc. as appropriate. The next command purports to request the same result in more human-readable form. It seems that the computer, rather than giving a specific answer, simply says that the size of the video directory is "A lot." The final line indicates the computer is now ready to accept a new command. [Cueball is stacking turtles, and is about to put the fourth turtle on his pile. At the bottom right there is a small panel. Inside this is written:] Scroll to zoom [When zooming in there will be several panels with text. The transcript of these may not be possible to complete - but add the transcript of these panels here: interactive transcript ] The following code can be found by inspecting the comic's source code: [[A large picture of a person kneeling on the ground, stacking turtles.]] ((In this strip, when you zoom into the panel, each pixel becomes its own panel. Each of those panels can be scrolled into, for the same effect. The story progresses as you scroll deeper.)) [[The Earth as seen from space with the words BOOK LAUNCH.]] [[A stick-Randall holding a copy of 'What If?' saying, "So excited about my book launch!"]] [[A copy of the cover of 'What If?' labeled "book."]] [[Stick-Randall is assembling parts from a box labeled 'rocket parts' and preparing to 'launch' his book.]] [[Various stages of assembly.]] [[A second person comes in, looks at SR's rocket set-up and says, "Needs more struts."]] [[SR adds more struts.]] [[The rocket launches.]] [[A big cloud of smoke, which then dissipates.]] [[SR and the other person look skywards at the launched book.]] [[The book is shown leaving Earth's orbit.]] [[The other person turns to SR and says, "I think that was the only one."]] [[The two walk away.]] ((The panels after this are a random assortment of these mostly stand-alone panels.)) [[A momma duck with several ducklings in a row behind her, labeled 'Evolution.']] [[The other person floating around in the sky.]] [[A stick figure with a sploshing bucket of water saying, "I'm gonna shut down the server!"]] [[Two people walking along, one saying, "But if the Time-Turners worked after Book 3, Rowling would have used one to go back and remove the Time Turner from Book 3."]] [[The code: ~$ du -s video 4170882256 ~$ du -hs video A lot. ~$]] [[A cloud.]] [[A flock of birds.]] [[MU]] [[A pixel.]] [[A person using a computer on the floor.]] [[HOLISM]] [[Saturn]] [[An atom.]] [[Two people star-gazing on a hill.]] [[Person one says, "Someone once told me the great kings of the past look down on us..." Person two says, "From the stars?" The first person replies, "Just in general."]] [[The start of Mario World 1-1.]] {{Title text: It's turtles all the way down.}} This gallery contains the 79 images used in this comic . The images are related in a directed graph . This google sheet describes all possible images, their associated codes, and what possible images can be used as sub-images for each zoom level: https://docs.google.com/spreadsheets/d/1nldKAkeVcK606CY12KI9bah9rDmK9E7CZOyinsEj2Lo/edit?usp=sharing This gist recursively downloads all possible images: https://gist.github.com/Aaron1011/d3b56325881cd639506a

Seven

Seven

https://www.xkcd.com/1417

https://www.explainxkcd.com/wiki/index.php/1417:_Seven

[Megan and Cueball are talking.] Megan: Can you name all the dwarfs from Snow White? Cueball: Sure, there's, um... Cueball's thoughts: Sneezy, phylum, Europe, sloth, guacamole, data link, Colossus of Rhodes I have this problem where all sets of seven things are indistinguishable to me.

In this comic, Cueball (or perhaps Randall ) says he can't distinguish between sets that have exactly seven objects. This leads him to exchange the items in the sets without noticing, to the point where, when attempting to list a single set, each item mentioned actually belongs to a different set. This is shown in the comic when Megan asks Cueball to name the seven dwarfs from Snow White and the Seven Dwarfs , a task some people might find difficult, although they would not just choose words from other sets of seven to fill in the gaps. The title text reveals that even a trivial set of seven items, like the days of the week, also goes completely wrong. The comic may be related to the oldest set-theoretic definition of the natural numbers , in which for each natural number, an equivalence class is defined over all sets which contain the same number of items. As Cueball is known for mathematical thinking , he could be presumed to have taken the underlying equivalence relation to heart, and (over)applying it to real life, genuinely judging sets to be identical if they all contain N objects. The number seven being the number for when sets become indistinguishable is possibly a reference to Miller's law . Especially considering that this is a law dealing with human memory, which Cueball is having issues with. However, this law refers to elements within the same set becoming indistinguishable, rather than the indistinguishability of different sets of the same size - indeed, its original tests involved either distinguishing between the items, or repeating them back in the correct order . But then again, that might be part of the humor. The number seven has culturally been regarded as a special, magical or holy number , which contributes to the large number of familiar sets of seven that make this comic possible. This proliferation of well-known sets of 7 items could be another reason why Randall chose to use the number seven in the comic. In 1554: Spice Girls the game continues with Cueball saying that it is now Megan's turn and then he asks her a similar question regarding the names of the Spice Girls. Her problem is then that she simply finds different sets of five and then just adds Spice behind each of the words of that set. For each of the seven lists below, the relevant item's traditional position within its own list of seven, according to Wikipedia, is not necessarily equal to its position on the list in the comic. For some lists the position is equal, but not for all. For instance Sneezy is traditionally never mentioned first amongst the dwarfs since the leader Doc normally comes first. But "phylum" is the second major taxonomic rank as is "phylum" the second item on the list in the comic. The seven "dwarfs" mentioned and their relevant sets of seven are (items in the set are written in bold): The title text extends this saying he also does the same with the set of the seven days of the week. There are several sets of 7 featuring the name Electra , which are all listed in the table below. The sets Cueball's "days of the week" come from are: [Megan and Cueball are talking.] Megan: Can you name all the dwarfs from Snow White? Cueball: Sure, there's, um... Cueball's thoughts: Sneezy, phylum, Europe, sloth, guacamole, data link, Colossus of Rhodes I have this problem where all sets of seven things are indistinguishable to me.

Horse

Horse

https://www.xkcd.com/1418

https://www.explainxkcd.com/wiki/index.php/1418:_Horse

[Headlines above the main frame of the comic:] New favorite browser text replacement: Force → Horse [In the comic frame Cueball is sitting in front of his PC reading the following headlines that are written above him in separate frames:] Ukranian towns threatened by pro-Russian horses Governor appoints task horse Iraqi air horse growing Quarks, which are bound together by the strong nuclear horse...

Cueball has set his browser to auto-replace the word "force" with the word "horse." Some of the humorous resulting news headlines are shown. This is probably a parody of the Cloud to Butt Chrome Extension (since it says new favorite browser text replacement). There has been several comics using substitutions before and also at least one after this one. [Headlines above the main frame of the comic:] New favorite browser text replacement: Force → Horse [In the comic frame Cueball is sitting in front of his PC reading the following headlines that are written above him in separate frames:] Ukranian towns threatened by pro-Russian horses Governor appoints task horse Iraqi air horse growing Quarks, which are bound together by the strong nuclear horse...

On the Phone

On the Phone

https://www.xkcd.com/1419

https://www.explainxkcd.com/wiki/index.php/1419:_On_the_Phone

[Megan is pointing off-panel to the left and looking off-panel to the right.] Megan: Why is there a teapot in the bathroom? Off-panel voice (right): Sorry. When I'm on the phone I always zone out and pick stuff up and carry it around. [Megan is in front of an open fridge, holding a hammer.] Megan: There's a hammer in the fridge. Off-panel voice: Another phone call. I was just fidgeting. [Megan is walking next to four stacks of household objects: the first has a lightbulb on top of a book, the second has a blender on top of three books, the third has five books (two balanced vertically) with a smaller rectangular object on top, and the fourth has two tennis balls on top of three books.] Megan: Did you put all our stuff in weird stacks? Off-panel voice: Long call. Sorry. [Megan, outside, looks up at a towering straight-sided object.] Megan: ...Why is there a giant obelisk in the backyard? Off-panel voice: Phone again. My bad. Megan: It's carved with prayers to "Ba'al, the Soul-Eater." Off-panel voice: Haha! I'm so absentminded.

Fidgeting while talking on the telephone is a very common habit and may manifest as doodling or pacing. In the case of the person speaking off-panel (presumably Cueball ), he paces while absent-mindedly moving random objects around the house. Megan has found several items in incorrect places around her house, including a teapot in the bathroom, a hammer in the fridge, and several stacks of household items. Cueball explains that he fidgets and move things around while on the phone. Taking this behavior to the extreme, in the fourth panel, Megan finds that he has also erected an obelisk in the backyard and carved prayers to "Ba'al, the Soul Eater" on it. This may be a reference to the saying "Idle hands are the devil's playthings." The title text suggests that the "fidgeting" is just a cover story - the off-panel speaker is actually worshipping (or possessed by) Ba'al, and is casually trying to encourage Megan to do the same. Ba'al , or Baal , refers to one of many deities and demons which go by this name. Given its title "The Soul Eater", it probably refers to Beelzebub (one of the seven princes of hell ). Ba'al, the Soul Eater has been mentioned in 1246: Pale Blue Dot and 1638: Backslashes . [Megan is pointing off-panel to the left and looking off-panel to the right.] Megan: Why is there a teapot in the bathroom? Off-panel voice (right): Sorry. When I'm on the phone I always zone out and pick stuff up and carry it around. [Megan is in front of an open fridge, holding a hammer.] Megan: There's a hammer in the fridge. Off-panel voice: Another phone call. I was just fidgeting. [Megan is walking next to four stacks of household objects: the first has a lightbulb on top of a book, the second has a blender on top of three books, the third has five books (two balanced vertically) with a smaller rectangular object on top, and the fourth has two tennis balls on top of three books.] Megan: Did you put all our stuff in weird stacks? Off-panel voice: Long call. Sorry. [Megan, outside, looks up at a towering straight-sided object.] Megan: ...Why is there a giant obelisk in the backyard? Off-panel voice: Phone again. My bad. Megan: It's carved with prayers to "Ba'al, the Soul-Eater." Off-panel voice: Haha! I'm so absentminded.

Watches

Watches

https://www.xkcd.com/1420

https://www.explainxkcd.com/wiki/index.php/1420:_Watches

[A timeline shows the following years but extends further in both directions:] 1990 2000 2010 2020 2030 [A grey box extends from the left border to approximately 2005 and another grey box begins approximately at 2015 and continues to the right border. They are labeled:] Regular watches Smart watches [An arrow points up to the empty period between 2005 and 2015. Below the arrow is written:] Brief, glorious period in which our wrists were free

This comic coincides with the announcement of a new smart watch by Apple earlier in the week as of the comic's release date (9th Sept 2014), the Apple Watch , along with a large emphasis on smartwatches at IFA 2014 (Sept 5-10), particularly 'Android Wear'. The timeline shows a period approximately from 2005 to 2015 where our wrists were liberated from the tethers of wearing a watch, likely attributed to the fact that many instead used a mobile smartphone to tell the time. Whilst other smartwatches have been released in the past, Randall predicts that the typical widespread interest following Apple product releases (combined with many other new releases by other companies) will result in our wrists again being shackled in the grip of watches from 2015. The wording of the label suggests that Randall is pre-emptively mourning the imminent loss of freedom of his and others' wrists, though this may be humorous hyperbole/sarcasm, as his position has generally been of apathy, such as in 1215: Insight . The title text refers to how "old people" tend to express derision towards change (generally most widely accepted by 'young people') as not being like it was "in the good old days", even if this means they contradict themselves. Initially, the wearing of watches was viewed negatively by the older generation, but now not wearing a watch is instead negative. The second part of the title text starts as if Randall is going to express an opinion on wearing a watch but then veers off to mock the word " thinkpiece ," due to its (particularly recent ) connotation for lacking factual content and expressing biased opinions. For more details on thinkpiece see this article . By equating thinkpiece with brain , Randall is making a reference to the fact that this compound word does not follow the convention of the compound word timepiece , which is a synonym for watch . [A timeline shows the following years but extends further in both directions:] 1990 2000 2010 2020 2030 [A grey box extends from the left border to approximately 2005 and another grey box begins approximately at 2015 and continues to the right border. They are labeled:] Regular watches Smart watches [An arrow points up to the empty period between 2005 and 2015. Below the arrow is written:] Brief, glorious period in which our wrists were free

Future Self

Future Self

https://www.xkcd.com/1421

https://www.explainxkcd.com/wiki/index.php/1421:_Future_Self

[Cueball is sitting at a laptop, reading code. The two separate parts of code as well as the two comments by Cueball is connected with "speak" lines, with the line from the code going down to the computer screen.] # Dear Future Self, # # You're looking at this file because # the parse function finally broke. # # It's not fixable. You have to rewrite it. # Sincerely, Past Self Cueball: Dear Past Self, it's kinda creepy how you do that. # Also, it's probably at least # 2013. Did you ever take # that trip to Iceland? Cueball: Stop judging me!

This comic is a joke about how the person you were in the past can be viewed as a distinct entity from who you are now, as well as the predictability of future events relating to your future actions. The comic shows comments, informational notes left in the code that do not change the algorithm, from a project completed by Cueball some time ago that is still being used and maintained. It is implied that Cueball is looking at these comments because the algorithm, a parsing function, is no longer working. These comments were written by Cueball's "younger self" in anticipation of being read by his "older self" at a date close to the present. The function has held up to the younger Cueball's expectations as it has lasted until the publication date of this comic, September 2014. The comments indicate a firm belief that the parsing function could not be easily "re-kludged" to handle the new situation but instead would need to be re-written. These comments are surprisingly accurate, leading Cueball to rhetorically reply to his younger self that these comments were creepy. Cueball's "younger self" must have anticipated a snarky reply and reminded his older self that his older self has likely not fulfilled his dream of going to Iceland. Cueball again replies that his younger self should stop judging him. In the title text, current-day Cueball lashes out at his younger self, further emphasizing the way he is viewing his past self as a different person, blaming the ineffectiveness of his past self's coding for never going to Iceland. A comment is a line, or a portion of a line, of code which should not be executed. A number of computer languages, including Python , use "#" to indicate "the remainder of this line is a comment". The comment symbol tells the compiler to skip to the next line, ignoring everything after the symbol. Programmers make use of comments to leave notes about what a particular line or section of code is meant to do, places that require debugging, ideas for future revisions, etc. The language in the comments is similar to how people address themselves in personal time capsules , in which they put letters away to read years later to see how much they've changed. A " parse function " is code that interprets some form of input and makes sense of it in a way that enables functionality in some other part of the code. Parsers are commonly used to extract useful information from a source external to the algorithm. Often parsing functions are written using regular expressions or in some other write-only language style. Parsing can be a difficult problem to solve, and programmers will often take shortcuts (perform kludges ) based on assumptions on the kinds of input that the parsing function will have to handle, or possibly code through means of trial-and-error. As the programmer may not have control over the input, such as reading a page from someone else's web-site or using the output of an unpredictable program, an input that does not match the assumed input syntax in can cause the parser to break, even if the parsing function has not changed. [Cueball is sitting at a laptop, reading code. The two separate parts of code as well as the two comments by Cueball is connected with "speak" lines, with the line from the code going down to the computer screen.] # Dear Future Self, # # You're looking at this file because # the parse function finally broke. # # It's not fixable. You have to rewrite it. # Sincerely, Past Self Cueball: Dear Past Self, it's kinda creepy how you do that. # Also, it's probably at least # 2013. Did you ever take # that trip to Iceland? Cueball: Stop judging me!

My Phone is Dying

My Phone is Dying

https://www.xkcd.com/1422

https://www.explainxkcd.com/wiki/index.php/1422:_My_Phone_is_Dying

[Cueball stands on the left while Beret Guy walks in from the right, carrying a smartphone.] Beret Guy: My phone's about to die. [The phone is now subtly larger.] Cueball: Where'd you get a big iPhone? I didn't think they were out yet. Beret Guy: It's my regular one. It's just dying. [The phone increases in size again. Beret Guy now holds it in both hands.] Beret Guy: As it consumes its battery, it heats up and expands. Beret Guy: Soon it will swell to enormous size, engulfing us both. [The phone is now in the size of Beret Guy's torso; he is clutching it to himself. Cueball is pointing off-panel.] Beret Guy: Then it will collapse in a violent explosion! Cueball: ...do you want to borrow my charger? Beret Guy: That would only make it run out faster!

Beret Guy's phone is about to "die". Cueball assumes this just means that the battery is running out and it needs to be recharged, but the phone in question appears to "die" in a way analogous to the life and death of a star: expending its fuel while heating up and expanding before ultimately losing its outer layers and becoming a white dwarf or similar "lesser" star. The technology of mobile phones can be seen as doing things analogous to this on a large scale, especially for people who used landlines before mobile phones became common. However, this is something phones usually don't literally do. [ citation needed ] Stars constantly undergo fusion reactions. The pressure generated by these reactions counteracts gravity, preventing it from collapsing the star during its main lifespan. As the hydrogen mostly fuses into helium in the core, the core gradually becomes more dense and the region of fusion gradually moves away from the center. Then, the star grows in size, reaching the stage of a red giant . When most of the "fuel" for fusion has been consumed, gravity will collapse the star into a white dwarf while the outer layers are shed. For stars much more massive than the Sun, there will be a supernova explosion caused by a violent collapse, which is very powerful (and leaves behind a neutron star or a black hole , depending on how much mass is left after the supernova). Stars with more hydrogen fuel tend to burn brighter and faster. Beret Guy's refusal of a charger is probably a reference to this. Both a supernova explosion and the collapse of red giants into white dwarfs shed their outer layers, which is referenced in the title text. Once extra mass is added to the dying star, analogous to "charging", the process only accelerates. (Randall also explains this in Short Answer Section .) The phone seems to have a certain mass because Beret Guy expects it to go (super)nova. Charging the phone may lead to a type 1a nova . The comic also plays on the release of two new iPhone models with bigger screens, planned for 2 days after the release of the comic. The comic could be also explained by the characteristics of Li-ion batteries, which are used in most cellphones. At the end of their useful life, these batteries may grow a bit . In case of severe physical or thermal damage or multiple electrical failures, this type of battery can indeed overheat, leading to a thermal runaway reaction inside. That would result in the battery growing and eventually exploding . Connecting a charger to a battery failing in this manner would probably make the process faster . The title text implies that after Beret Guy's iPhone goes (super)nova, it will become either a "slowly fading" Palm Pilot, a calculator, or a two way pager: this would be the cellphone equivalent of a white dwarf (evidenced by the faint and slowly fading glow), neutron star , or black hole (evidence: black holes emit "information" in the form of Hawking radiation and have at one time been suspected to be half of a two-way portal through spacetime, along with a " white hole "). Additionally, some particles and atoms decay by breaking into smaller, more elementary particles. It may be humorously implied that a PalmPilot (an early personal data assistant and precursor to the smartphone), a calculator (a very simple electronic device), and two-way pager (a device for sending and receiving short text messages) are the more elementary components that make up an iPhone. [Cueball stands on the left while Beret Guy walks in from the right, carrying a smartphone.] Beret Guy: My phone's about to die. [The phone is now subtly larger.] Cueball: Where'd you get a big iPhone? I didn't think they were out yet. Beret Guy: It's my regular one. It's just dying. [The phone increases in size again. Beret Guy now holds it in both hands.] Beret Guy: As it consumes its battery, it heats up and expands. Beret Guy: Soon it will swell to enormous size, engulfing us both. [The phone is now in the size of Beret Guy's torso; he is clutching it to himself. Cueball is pointing off-panel.] Beret Guy: Then it will collapse in a violent explosion! Cueball: ...do you want to borrow my charger? Beret Guy: That would only make it run out faster!

Conversation

Conversation

https://www.xkcd.com/1423

https://www.explainxkcd.com/wiki/index.php/1423:_Conversation

[Cueball and Megan are sitting at a table with drinks.] Cueball: So, what do you do in your free time? [Close up on Megan's face.] Megan: Mostly I sit around worrying someone will ask me that, and try to think of a good answer. [Back to original shot.] Cueball: That's not a bad answer. Megan: It's all I've got. Now that it's done, I should go. Bye! [She gets up and leaves.]

Cueball and Megan are on a first date and Cueball is trying to strike up a conversation by asking Megan what she does in her free time . Megan has probably been dreading this question, because she answers that her free time activity consists of trying to figure out how to respond if asked what she does in her free time. Cueball answers soothingly, but Megan's anxiety gets the better of her and she leaves abruptly. During Megan speaking, Cueball finished all of his drink. He may have been surprised by the reply, and Megan sensing this contributes to her leaving. The title text implies that she also spends her free time wondering what to write in her diary (with no success). Both the comic and the title text are examples of self-referential humor. Megan recognises that she spends her free time thinking what to say about her free time, so she must spend some of that free time thinking about her thinking about her free time. Such self-referential loops are often disturbing, since they contain within them potential for infinite regression . On the other hand, there is a simple way to exit the loop before any recursion: Megan has already decided what to say when asked what she does in her free time, and she has figured out what to write in her diary. But on realising this, Megan would have to find something else to occupy her free time, such as going on a date. [Cueball and Megan are sitting at a table with drinks.] Cueball: So, what do you do in your free time? [Close up on Megan's face.] Megan: Mostly I sit around worrying someone will ask me that, and try to think of a good answer. [Back to original shot.] Cueball: That's not a bad answer. Megan: It's all I've got. Now that it's done, I should go. Bye! [She gets up and leaves.]

En Garde

En Garde

https://www.xkcd.com/1424

https://www.explainxkcd.com/wiki/index.php/1424:_En_Garde

[Two Cueball-like guys wearing fencing mask (with gray front over their faces and a strip around their neck) are standing facing each other. The left fencer holds one arm up behind him and the other with the rapier like sword pointing toward the right fencers mask, ready for fencing. The right fencer holds both arms, and thus also the sword, down.] Left fencer: En Garde! Right fencer: OK. [In a large frame-less panel where they keep standing in the same position the right fencer talks at length.] Right fencer: No matter how long we know each other, when you ask "What are you thinking," Right fencer: I will always pause before answering. [Same as the first panel, although the left fencer has lowered the point of his sword so it points straight to the right.] Left fencer: Maybe a little less guarded? Right fencer: No way. I've been hurt before.

Two Cueball -like guys are preparing to fence. But only the left seems ready. He says "en garde!", hence the title, a fencing call literally meaning "be on your guard" (from French). The call is used to order the participants to take their position, in a similar way to the “on your mark” command in racing. The other two commands are “[tireurs, êtes-vous] prêts?” (“[combatants, are you] ready?”) and “allez” (“go”). The right participant takes this to mean being "guarded" emotionally. "What are you thinking?" is a common question used to deepen a conversation, typically between close friends or lovers. The person being asked may take a moment to consider what they are thinking and whether or not it would be appropriate to share with the asker. If the person being asked is emotionally comfortable with the asker, they may answer immediately without fear of judgment or ridicule. Such a level of comfort between two people generally takes a long time to develop. After the right fencer has explained why he is always "en garde", the left fencer asks if could be a little less so. But the answer is no since the right fencer acknowledges that he has been hurt before, and thus makes it even more difficult for him to let down his guards. Obviously the right fencer has had bad experience from previous relationships, maybe one where he was ridiculed after sharing his immediate thoughts. The title text takes this further with the "touch" call, used to indicate to a participant that they have been "touched" by their opponent's blade, and therefore the attacker receives a point. The right participant counters this claim by saying his emotions have "priority" (or right-of-way), implying he was blocking out ("parrying") the touching feelings. Fencing right-of-way rules can make a move invalid when another move has priority, but generally refer to physical actions on the participant's part. [Two Cueball-like guys wearing fencing mask (with gray front over their faces and a strip around their neck) are standing facing each other. The left fencer holds one arm up behind him and the other with the rapier like sword pointing toward the right fencers mask, ready for fencing. The right fencer holds both arms, and thus also the sword, down.] Left fencer: En Garde! Right fencer: OK. [In a large frame-less panel where they keep standing in the same position the right fencer talks at length.] Right fencer: No matter how long we know each other, when you ask "What are you thinking," Right fencer: I will always pause before answering. [Same as the first panel, although the left fencer has lowered the point of his sword so it points straight to the right.] Left fencer: Maybe a little less guarded? Right fencer: No way. I've been hurt before.

Tasks

Tasks

https://www.xkcd.com/1425

https://www.explainxkcd.com/wiki/index.php/1425:_Tasks

[Ponytail sitting at a computer with Cueball standing behind her.] Cueball: When a user takes a photo, the app should check whether they're in a national park... Ponytail: Sure, easy GIS lookup. Gimme a few hours. Cueball: ...and check whether the photo is of a bird. Ponytail: I'll need a research team and five years. [Caption below the panel:] In CS, it can be hard to explain the difference between the easy and the virtually impossible.

Cueball appears to be asking Ponytail to write an app that determines if a given picture is (1) taken in a national park, and (2) a picture of a bird. The first question is generally harder for a human to answer, but easy for an app that has access to location information and a geographic information system (GIS). The second one is easy for a human but much harder for a computer. This illustrates Moravec's paradox from the 1980s in a modern context. By the 1950s computers were useful for tasks like trajectory optimization , generating novel mathematical proofs , and the game of checkers , so such high-level computation and reasoning tasks that were hard for humans turned out to be relatively easy for them. On the other hand, it turns out to be hard to "give them the skills of a one-year-old when it comes to perception", as Moravec wrote. In order to determine whether the user is in a national park, Ponytail plans to determine the user's location using the mobile device. This location will then be cross checked with a geographic information system (GIS) which will be able to determine whether the coordinates lie within a national park boundary. Determining whether an image is of a given kind of natural object is far more difficult. This task falls into the area of computer vision . One of the goals in computer vision is to detect and classify objects within an image. This is a very challenging task for a number of reasons. Firstly, humans use size, edge-assignment, movement, and stereoscopic vision when looking at a scene (not a picture of a thing, but the thing itself) to discern individual objects and then categorize them as foreground or background . A photograph, however, is a static, monoscopic image that can only provide size and edge-assignment clues. Humans are only able to discern objects from background in photographs by comparing the photo against all of the things they've seen and everything they've learned about those things over the course of their life and identifying matching patterns . Secondly, the quality of the photograph will have an impact on a computer's ability to match patterns. For example, the object in the photograph might be partially visible or occluded. In the case of a living bird, additional complications arise from the variations among individual birds of the same species and differences in pose (flying, perching in a tree, etc.). Differentiating between visually similar objects can result in false positives. For example, is it a photo of a bird in flight or a plane (or superman!) ? Ponytail's estimate of 5 years may be overly optimistic (see 678: Researcher Translation ). Today's state-of-the-art algorithms for solving this kind of task mostly use local features (e.g. SIFT or SURF in combination with a support vector machine or convolutional neural network ). The subtitle refers to "CS", which is a common abbreviation for " Computer Science ", of which artificial intelligence and computer vision are sub-disciplines. The title text mentions The Summer Vision Project and Marvin Minsky of MIT. In the summer of 1966, he asked his undergraduate student Gerald Jay Sussman to "spend the summer linking a camera to a computer and getting the computer to describe what it saw" . Seymour Papert drafted the plan, and it seems that Sussman was joined by Bill Gosper , Richard Greenblatt , Leslie Lamport , Adolfo Guzman, Michael Speciner, John White, Benjamin, and Henneman - in case the multiple Wikipedia links don't give it away, know that this is sizable cross-section of the AI researchers of the period). The project schedule allocated one summer for the completion of this task. The required time was obviously significantly underestimated, since dozens of research groups around the world are still working on this topic today. A month after this comic came out, Flickr responded with a prototype online tool to do something similar to what the comic describes, using its automated-tagging software. According to them, the bird solution "took us less than 5 years to build, though it's definitely a hard problem, and we've still got room for improvement". [Ponytail sitting at a computer with Cueball standing behind her.] Cueball: When a user takes a photo, the app should check whether they're in a national park... Ponytail: Sure, easy GIS lookup. Gimme a few hours. Cueball: ...and check whether the photo is of a bird. Ponytail: I'll need a research team and five years. [Caption below the panel:] In CS, it can be hard to explain the difference between the easy and the virtually impossible.

Reduce Your Payments

Reduce Your Payments

https://www.xkcd.com/1426

https://www.explainxkcd.com/wiki/index.php/1426:_Reduce_Your_Payments

[Cueball sits on a sofa and Blackhat walks into the frame from behind.] Blackhat: I discovered this weird trick for reducing your mortgage payments! Cueball: What? Blackhat: Sodium borohydride. Cueball: ...I hate you.

Black Hat walks into a room where Cueball sits in an armchair. Black Hat says to Cueball that he can reduce his mortgage payments, while holding a docket of paper, presumably Cueball's payment check, that looks like it has been dipped into a liquid of some kind. Black Hat uses the same formulation many Internet advertisements use: "Discover this (strange/new/amazing...) trick to (lose weight/reduce your mortgage payments/meet amazing women...)" known as clickbait . Cueball wants to know how and Black Hat responds by mentioning sodium borohydride (NaBH 4 ) . Since Cueball fell for Black Hat's bait he exclaims, "I hate you." Sodium borohydride is a strong reducing agent , meaning in a chemical reaction it will " reduce " another substance. It is in fact used during the manufacture of paper , in order to bleach the natural colour from the pulp and improve the resulting paper's brightness, opacity, ink-absorption, and strength (among other properties). This comic is a typical switcharound pun. Cueball expects the value on a bill paid to be reduced, while Black Hat uses the chemical meaning of reducing , which would result at a minimum in the bleaching of all ink from the bill therefore making it unreadable. The complementary chemical reaction to reduction is oxidation (mentioned in 1693: Oxidation ), which is what happens if the paper mortgage payment is burned, as referred to in the title text. They go together in redox reactions, which generally involve electron transfer from the chemical species which is oxidized to the one which is reduced. In that case, the pun about light (to start a fire) is that a reduced financial weight may seem light (not heavy). However, some forms of paper - particularly those used for i.e. receipts - possess a slight coating that limits their flammability. Cueball's statements appear to be made with such a paper, thus preventing Black Hat from burning the statements. [Cueball sits on a sofa and Blackhat walks into the frame from behind.] Blackhat: I discovered this weird trick for reducing your mortgage payments! Cueball: What? Blackhat: Sodium borohydride. Cueball: ...I hate you.

iOS Keyboard

iOS Keyboard

https://www.xkcd.com/1427

https://www.explainxkcd.com/wiki/index.php/1427:_iOS_Keyboard

Movie quotes [Top picture shows a line typed on an iPhone.] Elementary, my dear [Then the next line shows the words suggested by the virtual keyboard.] Friend | Lord | Friends [Below are the visible part of keyboard. In the second line only the top of the letters can be seen.] QWERTYUIOP ASDFGHJKL [Below is a new sub heading above six pictures arranged in two rows.] According to iOS 8 keyboard predictions [For each of the six pictures a part of the text is black, and the other part is light grey. Below the black text is written in bold letters.] [Picture 1: Cueball stands with a machine gun.] Cueball: Say hello to my little sister and my mom and my dad and my friends [Picture 2: A girl stands next to her dog with a basket.] Girl: Toto, I've a feeling we're not going to the gym today [Picture 3: Bond talks to Megan.] James Bond: Bond, James Bond yields [Picture 4: A pilot operates his plane and talks to Cueball behind him.] Pilot: I'm a leaf on the wind. Watch me play the piano [Picture 5: A guy with dark hair stands behind a jagged edge.] Goonie: Goonies never say anything [Picture 6: A dwarf with long beard and helmet stands with an axe.] Off panel left: You have my sword. Off panel right: And my bow. Dwarf: And my dad

It looks like Randall has been playing with his Apple device after installing the recently released iOS 8 update. The comic is referencing the autocomplete function on the iOS virtual keyboard. A comparable feature is also available on other operating systems, like Android. When the phrase, for example, "Revenge is a dish best served" is typed, the keyboard will suggest “by” followed by “a” then “group” and so on. The top of the comic, where the keyboard is shown, is a reference to the character Sherlock Holmes, a detective who is often attributed the famous line "Elementary, my dear Watson" (despite having never said that in the canon). In Randall's typing history, the word "dear" is most often followed by "lord", "friend", or "friends," and thus the phone suggests those words as a likely continuation of the line. The title text continues, by showing more actual results from keyboard predictions from other movie quotes. The following movies are referenced in the comic and title text: An older comic 1068: Swiftkey is also about keyboard predictions, but without any preceding text (by the Swiftkey keyboard application instead of the iOS 8 keyboard). It is similar to 2169: Predictive Models . Movie quotes [Top picture shows a line typed on an iPhone.] Elementary, my dear [Then the next line shows the words suggested by the virtual keyboard.] Friend | Lord | Friends [Below are the visible part of keyboard. In the second line only the top of the letters can be seen.] QWERTYUIOP ASDFGHJKL [Below is a new sub heading above six pictures arranged in two rows.] According to iOS 8 keyboard predictions [For each of the six pictures a part of the text is black, and the other part is light grey. Below the black text is written in bold letters.] [Picture 1: Cueball stands with a machine gun.] Cueball: Say hello to my little sister and my mom and my dad and my friends [Picture 2: A girl stands next to her dog with a basket.] Girl: Toto, I've a feeling we're not going to the gym today [Picture 3: Bond talks to Megan.] James Bond: Bond, James Bond yields [Picture 4: A pilot operates his plane and talks to Cueball behind him.] Pilot: I'm a leaf on the wind. Watch me play the piano [Picture 5: A guy with dark hair stands behind a jagged edge.] Goonie: Goonies never say anything [Picture 6: A dwarf with long beard and helmet stands with an axe.] Off panel left: You have my sword. Off panel right: And my bow. Dwarf: And my dad

Move Fast and Break Things

Move Fast and Break Things

https://www.xkcd.com/1428

https://www.explainxkcd.com/wiki/index.php/1428:_Move_Fast_and_Break_Things

[Cueball sits in a chair, leaning back with his arm resting on the back of the chair during a job interview. Ponytail is sitting in a chair behind her desk which is between them.] Cueball: My motto is "Move fast and break things." [Below the panel follows a list:] Jobs I've been fired from Fedex driver Crane operator Surgeon Air traffic controller Pharmacist Museum curator Waiter Dog walker Oil tanker captain Violinist Mars rover driver Massage therapist

Cueball appears to be at a job interview, proudly stating his motto to the interviewer Ponytail . "Move fast and break things" is a saying common in science and engineering industries. In that context, it means that making mistakes is a natural consequence of innovation in a highly competitive and complex environment. In particular, it was adopted by Mark Zuckerberg at Facebook (who even went as far as to say that 'breaking things' is a necessary feature of moving 'fast enough' ). While in software development it is unusual for any great harm to result from breaking things, the jobs listed in the comic are ones where there are serious consequences of mistakes. Some would result in dangerous or deadly situations, while others would just end up with broken packages etc. It's not clear what job Cueball is interviewing for; one suspects it's probably one that belongs in the 'breaking things is bad' group. The results of moving fast and breaking things for the listed jobs might include: The title text posits a morbid scenario where Cueball keeps running over funeral attendees, generating the need for more funerals. It also implies that Cueball is currently being interviewed for the position of driving a hearse, as he has yet to be fired. [Cueball sits in a chair, leaning back with his arm resting on the back of the chair during a job interview. Ponytail is sitting in a chair behind her desk which is between them.] Cueball: My motto is "Move fast and break things." [Below the panel follows a list:] Jobs I've been fired from Fedex driver Crane operator Surgeon Air traffic controller Pharmacist Museum curator Waiter Dog walker Oil tanker captain Violinist Mars rover driver Massage therapist

Data

Data

https://www.xkcd.com/1429

https://www.explainxkcd.com/wiki/index.php/1429:_Data

[Cueball reading off a smart phone to someone off-screen.] Cueball: According to this polling data, after Kirk and Picard, the most popular Star Trek character are Data. Off-screen voice: Augh! [Caption below the frame:] Annoy grammar pedants on all sides by making "data" singular except when referring to the android.

"Kirk vs. Picard" is a debate that many Star Trek fans engage in — specifically which was a better captain of the starship Enterprise on the TV show. Captain James T. Kirk and Jean-Luc Picard each were captains of the ship in different periods (Kirk was captain of USS Enterprise (NCC-1701) in The Original Series , while Picard was captain of USS Enterprise -D (NCC-1701-D) in The Next Generation ), but fans argue over who was the "best". Most third-place candidates are pretty distant, resulting in a more multi-faceted debate. Cueball seems to be looking at results of polling for this third most popular character. The humor in this comic stems from the fact that the Latin word data is a plural form of the word datum ‘a piece of information’, and that originally English followed Latin's lead and treated data as plural. However, in more recent English, usage of datum has faded to the extent that data is treated as a collective noun . This usage is becoming increasingly (but not universally) accepted as grammatically correct — the Wall Street Journal , for instance, recently announced that it is moving away from saying "data are," while the New York Times' manual of style allows for both variants depending on usage scenario; USA Today , however, is consistently using data as a plural ("data are"). Naturally, the purists insist on the form that is correct from the Latin grammar point of view and see "data is" as an example of a subject-verb agreement error. This type of "error" is present in the beginning of the sentence that Cueball is citing ("According to this polling data," while certain traditionalists would hold that the grammatically correct variant would be "According to these polling data"). The second error in the same sentence is due to the fact that Data is a character from Star Trek: The Next Generation. Since it is a character's name, when used to refer to the character, "Data" should always be treated as singular. By reversing the verb agreement in both cases, Cueball is going out of his way to annoy grammatically obsessed people. The title text suggests the mocking of language pedants/amateur grammar Nazis by hypercorrecting one's use of language. The sentence itself is an example of this: This comic complements two of the My Hobbies comics 326: Effect an Effect (which discusses the trolling of amateur grammar Nazis) and 1405: Meteor (which mocks pedantry). This comic could also just as well have been labelled as one of Randall's Hobbies. This comic also appears to be an example of self-irony as the author himself has previously exhibited certain inclination to insist on grammatically strict mode of usage of words loaned from Latin. One such example is the fact that xkcd's online discussion forums are called fora , which is a correct plural nominative form of forum in Latin. [Cueball reading off a smart phone to someone off-screen.] Cueball: According to this polling data, after Kirk and Picard, the most popular Star Trek character are Data. Off-screen voice: Augh! [Caption below the frame:] Annoy grammar pedants on all sides by making "data" singular except when referring to the android.

Proteins

Proteins

https://www.xkcd.com/1430

https://www.explainxkcd.com/wiki/index.php/1430:_Proteins

[Cueball is talking with Megan.] Cueball: What do you do? Megan: I make software that predicts how proteins will fold. Cueball: Is that a hard problem? Megan: Someone may someday find a harder one. Cueball: Why is it so hard? Megan: Have you ever made a folded paper crane? Cueball: Yeah. Megan: Imagine figuring out the folds to make an actual living crane. Cueball: ... just folds? Can I make cuts? Megan: If you can fold a protease enzyme.

In this comic, Cueball is asking Megan what she does, to which she replies that she works on software to predict protein folding. There are many folding prediction software programs. Some of the most well known are [email protected] , [email protected] and FoldIt . Protein folding is the process by which proteins, which are floppy, unstructured chains of amino acids when initially synthesized in a cell, assume a stable, functional shape. If the folding process does not complete, or completes incorrectly, the resulting protein can be inactive or even toxic to the body. Misfolded proteins are responsible for several neurodegenerative diseases, including Alzheimer's disease , amyotrophic lateral sclerosis (ALS), and Parkinson's disease , as well as some non-neurodegenerative diseases such as cardiac amyloidosis. Cueball asks Megan why it is such a hard computational problem; Megan's response is to ask Cueball if he's ever folded paper to make a crane . When he responds in the affirmative, she then compares the problem of predicting protein folding to creating a living crane by the paper-folding process. The analogy is that a protein cannot just fold to a figurative representation of a bio-molecule, the way a paper crane superficially resembles a live crane; the protein must assume an exact, perfect fold in order to be functional. Levinthal's paradox is a thought experiment, also constituting a self-reference in the theory of protein folding. In 1969, Cyrus Levinthal noted that, because of the very large number of degrees of freedom in an unfolded polypeptide chain, the molecule has an astronomical number of possible conformations. For example, a polypeptide of 100 residues will have 99 peptide bonds, and therefore 198 different phi and psi bond angles . If each of these bond angles can be in one of three stable conformations, the protein may misfold into a maximum of 3 198 different conformations (including any possible folding redundancy). Therefore, if a protein were to attain its correctly folded configuration by sequentially sampling all the possible conformations, it would require a time longer than the age of the universe to arrive at its correct native conformation. This is true even if conformations are sampled at rapid (nanosecond or picosecond) rates. The "paradox" is that most small proteins fold spontaneously on a millisecond or even microsecond time scale. This paradox is central to computational approaches to protein structure prediction. As Cueball mentally turns over the hypothetical process of folding paper to make a living crane, he wonders if he is allowed to perhaps "cut" the paper to make more complicated folds available. In origami, purists [1] considered it as cheating if you cut the paper or use more than one sheet of paper, which is why Cueball asked if he was 'allowed' to do such in the hypothetical exercise they are discussing. Megan replies "if you can fold a Protease enzyme;" these are proteins whose job it is to break down (i.e. "cut") other proteins, often in very specific ways. In this manner, Protease enzymes are analogous to extremely specialized scissors, so Megan is effectively saying "You can make cuts if you can fold yourself a pair of scissors." Of course, when trying to predict the folding trajectory in nature of a protein A, and one is allowed to make cuts during the process, one is making the assumption that the Protease that cut protein A is already folded and functional. In other words, making cuts while folding might actually make the process more complicated, not less, as now you have to consider how the cutting enzyme is folded, too. The title text refers to the result of folding a flapping bird in origami. By pulling the tail, the head will move forward and down. However, since the joke is about folding proteins, this idea is extrapolated to include the folded proteins. The C-terminus (end of the protein chain), in this case analogous of the tail, if "pulled" would cause a created cavity or tunnel to squeeze, much like pulling a knot would do the same. [email protected] ( [email protected] ) is a distributed computing project which aims to simulate protein folding for research purposes. Rather than the traditional model of using a supercomputer for computation, the project uses idle processing power of a network of personal computers in order to achieve massive computing power. Individuals can join the project by installing the [email protected] software (there is also a web version that can be run using Google Chrome) and are then able to track their contribution to the project. Individual members may join together as a team, with leaderboards measuring team and individual contributions. Note that most modern computers do not "waste" computing time as much as older ones. They dynamically reduce their clock speed and other power consumption at times of low usage. If you donate computer time, you are probably also donating a bit of money to the cause in the form of your electricity bill. Many people consider this to be more fun, convenient and efficient than donating via credit card. [Cueball is talking with Megan.] Cueball: What do you do? Megan: I make software that predicts how proteins will fold. Cueball: Is that a hard problem? Megan: Someone may someday find a harder one. Cueball: Why is it so hard? Megan: Have you ever made a folded paper crane? Cueball: Yeah. Megan: Imagine figuring out the folds to make an actual living crane. Cueball: ... just folds? Can I make cuts? Megan: If you can fold a protease enzyme.

Marriage

Marriage

https://www.xkcd.com/1431

https://www.explainxkcd.com/wiki/index.php/1431:_Marriage

[A graph with the x-axis showing time in years from 1940 to some time after 2010 (presumably ca. 2014). The y-axis shows percentage of population. The graph has 4 lines, 2 solid and 2 dashed, with 2 different colors: red and blue. The red lines indicate statistics concerning interracial marriage, while the blue indicate statistics concerning same-sex marriage. The solid lines indicate population living in states where that type of marriage is legal, while the dashed lines indicate popular approval of that type of marriage based on various polls.] [Solid red line:] Percentage of US population living in states with legal interracial marriage [Dot on solid red line:] Full legal access: 1967 [Dashed red line:] Popular approval of interracial marriage (Source: Gallup Polls) [Dot on dashed red line:] Majority approval: 1995 [Dashed blue line:] Popular approval of same-sex marriage (Source: various polls) [Dot on dashed blue line:] Majority approval: 2011 [Solid blue line:] Percentage of US population living in states with legal same-sex marriage [Interracial marriage is indicated as being more than 50% legal in 1940, with a very slight downward trend that spikes up slightly ca. 1948, then trends slowly upward to about 65% until ca. 1967, at which point it spikes directly to 100% legality and remains there through 2014. Popular approval of interracial marriage is below 10% in the late 1950s, rising steadily to approximately 40% in 1980, then continuing to rise more slowly to the majority approval point in 1995, and spiking up to about 65% ca. 1997, plateauing until ca. 2003, rising quickly again to about 75% ca. 2006 and rising generally upward to the final ca. 2014 statistic depicted between 85% and 90% popular approval. The visual effect seems to be a wide gap of time between legalization of and popular approval of interracial marriage. Popular approval appears to trail legalization by no less than 20 years at any given point. Popular approval of same-sex marriage (according to "various polls") is depicted first at about 15% ca. 1986, trending gradually upward until ca. 2000, where it plateaus between 35% and 40% to resume an upward trend ca. 2007, continuing steadily through majority approval in 2011 to a ca. 2014 value between 55% and 60%. The legality of same-sex marriage is indicated to start at 0% ca. 2002, then jumps quickly to plateau around 5% until ca. 2008, at which point it spikes up to between 15% and 20%, then plummets to just above than 5% by ca. 2009, jumping quickly back up to between 15% and 20% between ca. 2010 and 2011, then trending upward even more quickly to end at about 55% legality ca. 2014. The visual effect seems to be a more turbulent line for legality of same-sex marriage than any of the other trends, which also seems to be quickly closing on the popular approval trend. Popular approval has preceded legalization by nearly 20 years at certain points, but the trends appear to be closing and may intersect by 2015 or 2016.]

The comic notes a curious inversion between the timing of legal and popular opinion trends for interracial marriage vs. same-sex marriage. In the 11 years between Massachusetts first legalized same-sex marriage and the comic's publication, at no point had there been more people living in states where it's legal than there are people who support its legality. This stands in stark contrast to interracial marriage, which was legal for the majority of the population for over 50 years, and for the whole country for 28 years, before it was approved of by the majority . Note that poll questions are slightly different: "Do you approve of interracial marriage?" vs "Do you think same-sex marriage should be legal?" It could be argued that fewer people would approve of these marriages than would support legalizing them, which may explain part of the discrepancy. But there are more factors at work, the effects and relative importance of which are not clear. Two days before this comic came out, the United States Supreme Court declined to hear appeals to decisions that had legalized same-sex marriage in five states. The court's refusal to hear the appeals was widely considered a surprise, and had the immediate effect of pushing the percentage of people living in states where such marriages are legal past 50% . The decision has also led to considerable speculation that there will be a surge of similar decisions applying to other states, especially to the six states that are in the same appeals circuits as the previous five, and to the three in the same circuit as Idaho and Nevada, where same-sex marriage bans were struck down a day after the Supreme Court's decision (although the decision in Idaho and Nevada has yet to take effect). On June 26, 2015, the Supreme Court of the United States of America ruled in a 5-4 decision that access to same-sex marriage was a right protected by the Constitution, thus raising the percentage of states with legal same-sex marriage to 100%. See also: Wikipedia: Anti-miscegenation laws in the United States Legal controls concerning interracial marriage in the US (known since 1863 as miscegenation ) have been significantly harder to track as a single statistic, due in part to the fact that such controls existed in several of the American British colonies before the United States formed, and complicated somewhat by the changes in territory claimed by and fluctuations in overall population (and methods of counting the population) of the United States over that time period. Depicting this as a simple percentage of US population over these earlier times would be far less meaningful outside of the context of these other fluctuations. Start of line Prior to ca. 1940 and continuing to 1948: Since the establishment of the United States, most states have had anti-miscegenation legislation in one form or another. Only nine states (Connecticut, New Hampshire, New York, New Jersey, Vermont, Wisconsin, Minnesota, Alaska, Hawaii) and the District of Columbia never enacted such legislation. Earlier repeal dates range from 1780 in Pennsylvania to 1887 in Ohio, though none were repealed between 1887 and 1948. First rise October 1948: Supreme Court of California overturns the state anti-miscegenation law in Perez v. Sharp . General upward trend 1951–1967: (in order of repeal by year) 13 states repeal anti-miscegenation laws prior to rulings at the federal level of government, largely encouraged by comparisons to similar laws promoted by opponents in World War II and other civil rights movements and victories. Last spike 12 June 1967: The U.S. Supreme Court rules in Loving v. Virginia that the 16 remaining state-level anti-miscegenation laws are unconstitutional, rendering such laws thereafter ineffective. See also: Wikipedia: Same-sex marriage in the United States Start of line 2003: Massachusetts Supreme Judicial Court rules in Goodridge v. Department of Public Health that the Massachusetts Constitution does not allow the denial of marriage licenses to same-sex couples. First rise May–October 2008: The supreme courts of California and Connecticut make similar decisions based on their states' constitutions. Drop November 2008: The voters of California overturn their supreme court's decision by constitutional amendment on Proposition 8 . California is the most populous state in the Union, hence the large size of the drop here. Second rise 2009–2010: Iowa, Vermont, New Hampshire, and the District of Columbia legalize same-sex marriage, the first by state supreme court decision, and the latter three by legislative action. First acceleration 2011–2012: New York legalizes same-sex marriage by legislative action. Washington State, Maine, and Maryland do so by voter referendum. Second acceleration 2013–2014: The U.S. Supreme Court's decision in Hollingsworth v. Perry re-legalizes same-sex marriage in California. Seven states legalize it by legislative action or state court decision. The Supreme Court's decision providing federal benefits for same-sex marriages in United States v. Windsor , while not saying that there is a constitutional right to same-sex marriage, is widely cited as precedent by judges who do say so. Oregon and Pennsylvania decline to appeal such decisions, and five states' appeals are declined by circuit courts, and declined to be heard by the Supreme Court. [A graph with the x-axis showing time in years from 1940 to some time after 2010 (presumably ca. 2014). The y-axis shows percentage of population. The graph has 4 lines, 2 solid and 2 dashed, with 2 different colors: red and blue. The red lines indicate statistics concerning interracial marriage, while the blue indicate statistics concerning same-sex marriage. The solid lines indicate population living in states where that type of marriage is legal, while the dashed lines indicate popular approval of that type of marriage based on various polls.] [Solid red line:] Percentage of US population living in states with legal interracial marriage [Dot on solid red line:] Full legal access: 1967 [Dashed red line:] Popular approval of interracial marriage (Source: Gallup Polls) [Dot on dashed red line:] Majority approval: 1995 [Dashed blue line:] Popular approval of same-sex marriage (Source: various polls) [Dot on dashed blue line:] Majority approval: 2011 [Solid blue line:] Percentage of US population living in states with legal same-sex marriage [Interracial marriage is indicated as being more than 50% legal in 1940, with a very slight downward trend that spikes up slightly ca. 1948, then trends slowly upward to about 65% until ca. 1967, at which point it spikes directly to 100% legality and remains there through 2014. Popular approval of interracial marriage is below 10% in the late 1950s, rising steadily to approximately 40% in 1980, then continuing to rise more slowly to the majority approval point in 1995, and spiking up to about 65% ca. 1997, plateauing until ca. 2003, rising quickly again to about 75% ca. 2006 and rising generally upward to the final ca. 2014 statistic depicted between 85% and 90% popular approval. The visual effect seems to be a wide gap of time between legalization of and popular approval of interracial marriage. Popular approval appears to trail legalization by no less than 20 years at any given point. Popular approval of same-sex marriage (according to "various polls") is depicted first at about 15% ca. 1986, trending gradually upward until ca. 2000, where it plateaus between 35% and 40% to resume an upward trend ca. 2007, continuing steadily through majority approval in 2011 to a ca. 2014 value between 55% and 60%. The legality of same-sex marriage is indicated to start at 0% ca. 2002, then jumps quickly to plateau around 5% until ca. 2008, at which point it spikes up to between 15% and 20%, then plummets to just above than 5% by ca. 2009, jumping quickly back up to between 15% and 20% between ca. 2010 and 2011, then trending upward even more quickly to end at about 55% legality ca. 2014. The visual effect seems to be a more turbulent line for legality of same-sex marriage than any of the other trends, which also seems to be quickly closing on the popular approval trend. Popular approval has preceded legalization by nearly 20 years at certain points, but the trends appear to be closing and may intersect by 2015 or 2016.]

The Sake of Argument

The Sake of Argument

https://www.xkcd.com/1432

https://www.explainxkcd.com/wiki/index.php/1432:_The_Sake_of_Argument

[Ponytail and Cueball are talking.] Ponytail: Just for the sake of argument, let's say that— Cueball: —wait, for the sake of what? [Panel zooms to only show Cueball.] Ponytail: Argument. Cueball: Ok, cool, that's totally a good reason to say something that's wrong. Gotta have arguments. [Panel returns to original view.] Ponytail: I'm just playing Devil's advocate. Cueball: Ok. So you saw an argument where one side was the Devil , and you were like "Man, that guy could use an advocate." Ponytail: It's... why are you being so difficult? Cueball: For the sake of argument. Ponytail: Argh! Cueball: Yay, it's working!

Ponytail is trying to get Cueball to consider a hypothetical situation, for the sake of argument. It appears that Cueball is questioning the wisdom of doing so, and postulating that assuming unreal hypotheses for the sake of argument is a stupid thing to do, because it causes more arguments. Ponytail then claims she is playing the Devil's advocate, and Cueball again lambastes her for advocating for somebody as unsympathetic as the Devil. In a debate or discussion, to play the Devil's advocate is to take a position with which you do not necessarily agree (and typically which no one involved in the argument agrees) to allow further exploration of the subject. As the title text starts to explain, it can be a device used to explore a different viewpoint to gain a wider understanding. Arguing for a view with which you do not agree can provoke a re-evaluation, or conversely a re-affirmation of your previously held view by considering the merits of the potential counter-argument. To be able to play the Devil's advocate convincingly is the mark of a well-rounded debater. However, Cueball interprets her statement literally, thus assuming she is arguing on the side of the Devil , the religious entity defined as pure evil. Obviously, it would be ill advised to take his side during a debate [ citation needed ] . Cueball then pulls an ironic twist on Ponytail by revealing that he was questioning Ponytail's argumentative style for the sake of argument himself. The comic actually plays on the double meaning of "argument": Ponytail refers to a statement in a debate while Cueball suggests a quarrel in the last panel. In the title text, an exasperated Ponytail is trying to explain to Cueball that she is trying to use these debating techniques as a device to explore and broaden her understanding of her reality or a plausible alternative. Cueball derails the conversation, by comparing these attributes to a boat, which also allows you to explore other areas and broaden your experiences and understanding (as mentioned earlier in 209: Kayak ). Ponytail is rendered speechless by this statement, and Cueball further suggests that they should get a boat, and that Ponytail can bring the Devil too. [Ponytail and Cueball are talking.] Ponytail: Just for the sake of argument, let's say that— Cueball: —wait, for the sake of what? [Panel zooms to only show Cueball.] Ponytail: Argument. Cueball: Ok, cool, that's totally a good reason to say something that's wrong. Gotta have arguments. [Panel returns to original view.] Ponytail: I'm just playing Devil's advocate. Cueball: Ok. So you saw an argument where one side was the Devil , and you were like "Man, that guy could use an advocate." Ponytail: It's... why are you being so difficult? Cueball: For the sake of argument. Ponytail: Argh! Cueball: Yay, it's working!

Lightsaber

Lightsaber

https://www.xkcd.com/1433

https://www.explainxkcd.com/wiki/index.php/1433:_Lightsaber

[Luke Skywalker and Darth Vader are talking. Vader holds the handle of a powered-off lightsaber.] Vader: I see you have constructed a new lightsaber. [Vader turns it on. The beam of the lightsaber continues upward out of the frame.] Lightsaber: Snap-Hisss [Vader looks up toward where the beam is pointing.] [Vader looks back at Luke.] Vader: Where does it end? Luke: Doesn't. Intercom (out of view): Hull breach all along sector five!!

This comic references a scene from the third theatrically-released Star Wars movie, Return of the Jedi , wherein Darth Vader confronts his son, Luke Skywalker , who had recently surrendered to Imperial soldiers. In the movie, Vader notes that Luke has constructed a new lightsaber following the loss of his original during their duel on Cloud City (Luke Skywalker's original lightsaber actually having been Anakin Skywalker's second). Lightsabers are often jokingly referred to as "laser swords" by fans (note that the official French-language translation of Star Wars actually calls them "laser sabers"), and this comic points out that a real laser would not have any way of stopping and would therefore continue forever, making this particular interpretation silly. (The Star Wars writers cleverly fail to state what exactly a lightsaber's blade is made out of, although this point makes it unlikely to be a laser.) Once Darth Vader turns on the light saber, it goes offscreen and presumably continues in that direction forever, causing much mayhem as it blazes through the stars. Hull breaches are a popular trope in science-fiction, despite curiously being almost entirely absent from the Star Wars films. The title text refers to GRB 080319B , an unusual gamma ray burst in 2008, the afterglow of which was briefly visible to the human eye. It implies that the source of this burst was a light saber in the Star Wars story, which took place "a long time ago in a galaxy far, far away" according to the Star Wars opening crawl . Luke Skywalker and Darth Vader have had a similar conversation before in 1397: Luke . In that version Luke wishes for Vader not to turn it on, as stated in the title text. He should probably have said this here in this comic! [Luke Skywalker and Darth Vader are talking. Vader holds the handle of a powered-off lightsaber.] Vader: I see you have constructed a new lightsaber. [Vader turns it on. The beam of the lightsaber continues upward out of the frame.] Lightsaber: Snap-Hisss [Vader looks up toward where the beam is pointing.] [Vader looks back at Luke.] Vader: Where does it end? Luke: Doesn't. Intercom (out of view): Hull breach all along sector five!!

Where Do Birds Go

Where Do Birds Go

https://www.xkcd.com/1434

https://www.explainxkcd.com/wiki/index.php/1434:_Where_Do_Birds_Go

[Cueball is sitting at his desk with his computer.] Cueball: "Where do birds go when it rains?" is my new favorite Google search. Megan (off-screen): Why? [Megan enters the frame.] Cueball: It gives the answer, but also shows you an endless torrent of other people asking the same question. Cueball: Pages and pages of them, across regions and cultures. [The panel now only contains a Google search on the computer.] Cueball (off-screen): I love the idea that somehow this is the universal question, the thing that unites us. Cueball (off-screen): When it rains, we wonder where the birds go, Cueball (off-screen): and hope they're staying dry. [A collage of screen snippets.] from Yahoo! Answers : Where do the birds go when it rains? I've noticed I rarely see birds flying around or in trees or on power lines when it's raining, So where do they go? from Godlike Productions : Where do birds go when it rains really hard? Ok, maybe I'm an idiot for asking this, but during the slew of several storms in California the last couple weeks, I began to wonder where the poor birds go to stay dry? The ducks, seagulls, owls, sparrows, hummingbirds, hawks, etc...I see them all the ti[...] from Random Thoughts From Midlife : Where do the birds go when it rains? from Answers.com : Where do birds go when it rains? from Yahoo! Respuestas : ¿A donde se van los pajaritos cuando llueve? from Active Rain : Where do Birds go When it Rains? I'm no youngster...and I have no answer for this. I've talked to alot of people about the likelihood of where birds go when it rains and everyone has a different perspective. from Ask MetaFilter : Where do the birds go when it rains? BirdFeederFilter: When it's gloomy and rainy, I don't see any birds at my birdfeeder for days on end. Then as soon as it's sunny, they're all over the place. What gives? What do they do on rainy days, just forage near their nest? from Snippets : Where do city birds go when it rains? from http://wenwen.sogou.com/ : 下雨时鸟儿往哪躲 没有大树,没有屋檐,怎么办 from eNature.com : Storm shelter In Florida, where I live, we get many thunderstorms, but I never see the birds in trees during the storms. We recently had a tropical storm and I did not see any birds in the trees. Where do birds go when it rains or storms? Just like at night, birds will seek shelter during storms. I remember watching a flock of American robins dive into[...] from Yahoo! Answers : When it is raining heavily, where do the birds go...i don't see them on the trees, where do they take shelter? from Yahoo! Questions Réponses : Où se cachent les oiseaux quand il pleut? De ma fenêtre, je n'en aperçois plus un!!!...Les pies semblent avoir abandonné leurs nids... from gutefrage.net : was passiert jetzt eigentlich mit den vögeln, die bei dem wetter in den bäumen sitzen? bei uns regnet es heftig und der orkanartige wind wechelst ständig richtung und geschwindigkeit. können sich die vögel da in den bäumen halten? retten sie sich instinktiv vorher irgendwohin, wo sie windgeschützt sind? from Yahoo! Answers : Where do birds go when it rains? I never see any out...? from lainformacion.com : ¿Qué pasa con las aves durante un huracán? from Baidu : 下雨的时候小鸟住在哪里？ 下雨的时候小鸟住在哪里？如果是在春天夏天那还好，有树叶遮挡着，但是到了秋天冬天下雨小鸟住在哪里？还住在在树上搭的窝里吗？不怕冻坏自己和小幼崽吗？如果躲雨那就在哪里躲雨呢？怎么没见过它们躲雨？ 谢谢。 from Fairfax Underground : What do birds do when it rains? Recently I installed a bird feeder outside my bedroom window. It is so wonderful the diversity of our feathered friends that frequent the feeder! I love it. My question that I haven't found an answer to is this: What do the little birdies do when it rains? I mean, do they stay put in the trees that they find themselves in, from a blog on vuodatus.net : Minne linnut menevät sateella? Tänään satoi rankasti. Kuljin metsän halki. Kuulin linnun laulavan. Yksinäinen, mutta itsenäinen ja vahva, tulkitseva ääni. Kaunis. Minne linnut menevät sateella? En ole koskaan nähnyt lintuja rankkasateessa. Luulen, että ne yrittävät löytää suojan. Kuusien ja mäntyjen oksistossa on varmaan suojaisaa. Kallioiden koloihin ja pieniin luolastoihin voi ehkä lintukin hiipiä. Rohkeille löytyy pihoilta suojapaikkoja. Ehkä linnulla oli oma pesäkolo. Siellä oli lämmintä ja kuivaa. Sieltä saattoi rauhassa katsella sateen vierailua metsässä. Siellä saattoi jopa iloita sateesta ja laulaa. from Yahoo! Answers : What do the birds do when it RAINS like crazy? I live in upstate new york and just moved here and there are so many many birds here especially where I live, the other day I saw a broken egg on the ground in the drive way from a [...show more link] Update : I know they get wet btw but was wondering if they did anything extra to [...show more link] Best Answer Well... it depends on the species of bird, for one. Some are more adapted for rain then others. from Willem Wever : Waar blijven de vogels als het heel hard stormt? Bij hevige stormen zoekt een vogel de beschutting die bij hem past. Er zijn een aantal vogels die met storm wel vliegen. Maar bij een echte hevige storm schuilen [...] from http://wenwen.sogou.com/ 为什么鸟儿下雨的时候在天上飞不会因为淋湿掉下来? 刚刚下很大的雨,却还看到有几只鸟一直在天上飞.为什么鸟儿下雨的时候在天上飞不会因为淋湿掉下来? 补充 ：有照片的加分 from speed guide forums : Where do birds go when it rains? Do they just sit in their trees as it rains getting drenched? Or do they seek shelter? from Google books : Where Do All The Birds Go When It Rains? By Misty Hoopman [Screen snippets begin to noticeably fade to white at this point.] from vimeo : WHERE DO BIRDS GO WHEN IT RAINS? One young magpie will give its own story. Barring the thunder and heavy rain, all the sounds on this movie are from this one young maggie. Amazing from Yahoo! Answers : Where do birds go during wind and rain storms? Where do birds go during wind and rain storms? from Yahoo! Answers : Where do birds go when it rains? I mean, they can't keep dry in their nests...They have to go somewhere. from Yahoo! Answers : Burung Dapat Bertahan Terbang Berapa Lama Disaat Hujan? from vogel.info : Was machen Vögel bei schlechtem Wetter? Zunächst mal, was sie nicht machen: Sie verkriechen sich nicht etwa in ihr Nest, denn das Vogelnest dient der Brutpflege, es ist nicht etwa eine Wohnung. Es stellt sich aber ja auch die Frage, was eigentlich unter schlechtem Wetter zu verstehen ist: Es gibt Vögel, die leiden unter zuviel Sonne und[...] from gutefrage.net : Wohin gehen Vögel? Hallo zusammen! Heute als es so richtige Gewitter gab, hab ich mir überlegt wohin alle Vögel verschwinden. Haben alle Vögel Nester in die sie sich zurückziehen können? [link to view complete question.] from Yahoo! Answers : Where do birds go when it rains? Well, yesterday it was raining...I was bored so i started staring out the window, and i say a empty birds nest and i was wondering, where do birds go when it rains? from Diolún Designs Blog : Where do Birds go when it rains or snows? from The Andalusia Star-News : Where do birds go when it rains? I haven’t fed birds in my back yard for a long time, but I still enjoy the few I see perching on top of poles, an electric wire, tree branches, or scooting across the [...] from Bird Ecology Study Group (blog) : Where do birds go when it rains? And what do they do then? It has been raining on and off these few weeks and the birds have not been around. Have you ever wondered what happened to them when it from Naver Matome : 【雑学】暴風雨の時、鳥はどこに避難してるの？ 人間が歩くのも困難な暴風雨。その時、一番影響を受けるのは空を飛んでいる鳥達ですよね。彼らはどのように風雨を凌いでいるのか？ずーっと気になっていた事を調べてみました！ [At this point, at the bottom of the section, screen snippets are extremely faded.] from The Daily Apple : Apple #431: Birds in the Rain Forgot until late tonight that I meant to make a new post. Since I didn't leave [...] from Yahoo! answers : Where does birds go when it rains? [A bird sits on a wire fence.] [The bird looks around as raindrops fall.] [The rain becomes heavier.] [The bird flies down to a phone on the ground.] [The bird lands on the phone. The rain is getting heavier.] [The bird pecks on the phone.] W... H... E... R... E...   D... O...   B... I... R... D... S...

Cueball searches Google to find out where birds go when it rains. He finds that the question is asked worldwide, across many different languages and websites. A variety of screenshots are shown of different websites and forums where users have asked where birds go when it rains, with at least nine languages shown. The bottom of this panel fades to white, suggesting that the occurrence of these questions stretches on and on. Cueball expresses delight at the idea that this question is the one to which everyone wants to know the answer; worrying about birds getting wet is "the thing that unites us". Later in the comic, a bird in the rain is also searching on the Internet for where birds go when it rains. This is humorously implying that a significant set of these questions are being typed by birds looking for a dry place after being caught in the rain, and not humans. This would make Cueball wrong; worrying about birds getting wet would not unite us. In reality, as the comic states, birds look for shelter so they can stay dry. On a rainy day you can usually find birds in leafy trees, caves or other kinds of cover. In the Superman comics, Clark Kent is Superman, so you never observe both Clark Kent and Superman simultaneously. By analogy, the title text whimsically suggests that a possible inference from the observation that you never see birds and rain together is that birds are the rain. Perhaps birds are an unknown phase of water. In addition to its familiar phases of ice , vapor , and liquid water , water has more exotic phases such as low-temperature and high-pressure ices and supercritical gases ; why not birds? The title text imbues the question with more philosophical significance than it warrants (prompted, perhaps, by Cueball's earlier hyperbole), and points up the irrationality of the implication that a question must be deep simply because a lot of people ask it, and that such questions demand a complex, radical answer. Where do the birds go when it rains? ( archive ) [...] Where do birds go when it rains or storms? ( archive ) Where do Birds go When it Rains? ( archive ) Where do birds go when it rains really hard? Where do the birds go when it rains? Où se cachent les oiseaux quand il pleut? ( archive ) (Translation: Where do the birds hide themselves when it rains?) was passiert jetzt eigentlich mit den vögeln, die bei dem wetter in den bäumen sitzen? [1] ( archive ) (Translation: What actually happens with the birds that are sitting in the trees in this weather?) Was machen Vögel bei schlechtem Wetter? ( archive ) (Translation: What do birds do in bad weather?) Wohin gehen Vögel? ( archive ) (Translation: Where do birds go?) ¿Qué pasa con las aves durante un huracán? ( archive ) (Translation: What happens to the birds during a hurricane?) ¿A donde se van los pajaritos cuando llueve? [2] ( archive ) (Translation: Where do the little birds go when it rains?) Waar blijven de vogels als het heel hard stormt? (Translation: Where do birds stay when it is storming very hard?) Minne linnut menevät sateella (Translation: Where do the birds go when it rains?) 下雨时鸟儿往哪躲 (Translation: When it rains, where do birds go to hide?) 下雨的时候小鸟住在哪里 (Translation: When it rains, where do the birds go?) 为什么鸟儿下雨的时候在天上飞不会因为淋湿掉下来? (Translation: When it rains, why do birds not fall down from getting soaked?) 【雑学】暴風雨の時、鳥はどこに避難してるの？ ( archive ) (Translation:【Miscellaneous Knowledge】Where do birds take shelter during a rainstorm?) Burung Dapat Bertahan Terbang Berapa Lama Disaat Hujan ? ( archive ) (Translation: How Long Can Birds Survive Flying In the Rain ?) [Cueball is sitting at his desk with his computer.] Cueball: "Where do birds go when it rains?" is my new favorite Google search. Megan (off-screen): Why? [Megan enters the frame.] Cueball: It gives the answer, but also shows you an endless torrent of other people asking the same question. Cueball: Pages and pages of them, across regions and cultures. [The panel now only contains a Google search on the computer.] Cueball (off-screen): I love the idea that somehow this is the universal question, the thing that unites us. Cueball (off-screen): When it rains, we wonder where the birds go, Cueball (off-screen): and hope they're staying dry. [A collage of screen snippets.] from Yahoo! Answers : Where do the birds go when it rains? I've noticed I rarely see birds flying around or in trees or on power lines when it's raining, So where do they go? from Godlike Productions : Where do birds go when it rains really hard? Ok, maybe I'm an idiot for asking this, but during the slew of several storms in California the last couple weeks, I began to wonder where the poor birds go to stay dry? The ducks, seagulls, owls, sparrows, hummingbirds, hawks, etc...I see them all the ti[...] from Random Thoughts From Midlife : Where do the birds go when it rains? from Answers.com : Where do birds go when it rains? from Yahoo! Respuestas : ¿A donde se van los pajaritos cuando llueve? from Active Rain : Where do Birds go When it Rains? I'm no youngster...and I have no answer for this. I've talked to alot of people about the likelihood of where birds go when it rains and everyone has a different perspective. from Ask MetaFilter : Where do the birds go when it rains? BirdFeederFilter: When it's gloomy and rainy, I don't see any birds at my birdfeeder for days on end. Then as soon as it's sunny, they're all over the place. What gives? What do they do on rainy days, just forage near their nest? from Snippets : Where do city birds go when it rains? from http://wenwen.sogou.com/ : 下雨时鸟儿往哪躲 没有大树,没有屋檐,怎么办 from eNature.com : Storm shelter In Florida, where I live, we get many thunderstorms, but I never see the birds in trees during the storms. We recently had a tropical storm and I did not see any birds in the trees. Where do birds go when it rains or storms? Just like at night, birds will seek shelter during storms. I remember watching a flock of American robins dive into[...] from Yahoo! Answers : When it is raining heavily, where do the birds go...i don't see them on the trees, where do they take shelter? from Yahoo! Questions Réponses : Où se cachent les oiseaux quand il pleut? De ma fenêtre, je n'en aperçois plus un!!!...Les pies semblent avoir abandonné leurs nids... from gutefrage.net : was passiert jetzt eigentlich mit den vögeln, die bei dem wetter in den bäumen sitzen? bei uns regnet es heftig und der orkanartige wind wechelst ständig richtung und geschwindigkeit. können sich die vögel da in den bäumen halten? retten sie sich instinktiv vorher irgendwohin, wo sie windgeschützt sind? from Yahoo! Answers : Where do birds go when it rains? I never see any out...? from lainformacion.com : ¿Qué pasa con las aves durante un huracán? from Baidu : 下雨的时候小鸟住在哪里？ 下雨的时候小鸟住在哪里？如果是在春天夏天那还好，有树叶遮挡着，但是到了秋天冬天下雨小鸟住在哪里？还住在在树上搭的窝里吗？不怕冻坏自己和小幼崽吗？如果躲雨那就在哪里躲雨呢？怎么没见过它们躲雨？ 谢谢。 from Fairfax Underground : What do birds do when it rains? Recently I installed a bird feeder outside my bedroom window. It is so wonderful the diversity of our feathered friends that frequent the feeder! I love it. My question that I haven't found an answer to is this: What do the little birdies do when it rains? I mean, do they stay put in the trees that they find themselves in, from a blog on vuodatus.net : Minne linnut menevät sateella? Tänään satoi rankasti. Kuljin metsän halki. Kuulin linnun laulavan. Yksinäinen, mutta itsenäinen ja vahva, tulkitseva ääni. Kaunis. Minne linnut menevät sateella? En ole koskaan nähnyt lintuja rankkasateessa. Luulen, että ne yrittävät löytää suojan. Kuusien ja mäntyjen oksistossa on varmaan suojaisaa. Kallioiden koloihin ja pieniin luolastoihin voi ehkä lintukin hiipiä. Rohkeille löytyy pihoilta suojapaikkoja. Ehkä linnulla oli oma pesäkolo. Siellä oli lämmintä ja kuivaa. Sieltä saattoi rauhassa katsella sateen vierailua metsässä. Siellä saattoi jopa iloita sateesta ja laulaa. from Yahoo! Answers : What do the birds do when it RAINS like crazy? I live in upstate new york and just moved here and there are so many many birds here especially where I live, the other day I saw a broken egg on the ground in the drive way from a [...show more link] Update : I know they get wet btw but was wondering if they did anything extra to [...show more link] Best Answer Well... it depends on the species of bird, for one. Some are more adapted for rain then others. from Willem Wever : Waar blijven de vogels als het heel hard stormt? Bij hevige stormen zoekt een vogel de beschutting die bij hem past. Er zijn een aantal vogels die met storm wel vliegen. Maar bij een echte hevige storm schuilen [...] from http://wenwen.sogou.com/ 为什么鸟儿下雨的时候在天上飞不会因为淋湿掉下来? 刚刚下很大的雨,却还看到有几只鸟一直在天上飞.为什么鸟儿下雨的时候在天上飞不会因为淋湿掉下来? 补充 ：有照片的加分 from speed guide forums : Where do birds go when it rains? Do they just sit in their trees as it rains getting drenched? Or do they seek shelter? from Google books : Where Do All The Birds Go When It Rains? By Misty Hoopman [Screen snippets begin to noticeably fade to white at this point.] from vimeo : WHERE DO BIRDS GO WHEN IT RAINS? One young magpie will give its own story. Barring the thunder and heavy rain, all the sounds on this movie are from this one young maggie. Amazing from Yahoo! Answers : Where do birds go during wind and rain storms? Where do birds go during wind and rain storms? from Yahoo! Answers : Where do birds go when it rains? I mean, they can't keep dry in their nests...They have to go somewhere. from Yahoo! Answers : Burung Dapat Bertahan Terbang Berapa Lama Disaat Hujan? from vogel.info : Was machen Vögel bei schlechtem Wetter? Zunächst mal, was sie nicht machen: Sie verkriechen sich nicht etwa in ihr Nest, denn das Vogelnest dient der Brutpflege, es ist nicht etwa eine Wohnung. Es stellt sich aber ja auch die Frage, was eigentlich unter schlechtem Wetter zu verstehen ist: Es gibt Vögel, die leiden unter zuviel Sonne und[...] from gutefrage.net : Wohin gehen Vögel? Hallo zusammen! Heute als es so richtige Gewitter gab, hab ich mir überlegt wohin alle Vögel verschwinden. Haben alle Vögel Nester in die sie sich zurückziehen können? [link to view complete question.] from Yahoo! Answers : Where do birds go when it rains? Well, yesterday it was raining...I was bored so i started staring out the window, and i say a empty birds nest and i was wondering, where do birds go when it rains? from Diolún Designs Blog : Where do Birds go when it rains or snows? from The Andalusia Star-News : Where do birds go when it rains? I haven’t fed birds in my back yard for a long time, but I still enjoy the few I see perching on top of poles, an electric wire, tree branches, or scooting across the [...] from Bird Ecology Study Group (blog) : Where do birds go when it rains? And what do they do then? It has been raining on and off these few weeks and the birds have not been around. Have you ever wondered what happened to them when it from Naver Matome : 【雑学】暴風雨の時、鳥はどこに避難してるの？ 人間が歩くのも困難な暴風雨。その時、一番影響を受けるのは空を飛んでいる鳥達ですよね。彼らはどのように風雨を凌いでいるのか？ずーっと気になっていた事を調べてみました！ [At this point, at the bottom of the section, screen snippets are extremely faded.] from The Daily Apple : Apple #431: Birds in the Rain Forgot until late tonight that I meant to make a new post. Since I didn't leave [...] from Yahoo! answers : Where does birds go when it rains? [A bird sits on a wire fence.] [The bird looks around as raindrops fall.] [The rain becomes heavier.] [The bird flies down to a phone on the ground.] [The bird lands on the phone. The rain is getting heavier.] [The bird pecks on the phone.] W... H... E... R... E...   D... O...   B... I... R... D... S...

Presidential Alert

Presidential Alert

https://www.xkcd.com/1435

https://www.explainxkcd.com/wiki/index.php/1435:_Presidential_Alert

[Television beeping.] Screen reads: "E.A.S Incoming Presidential Alert" [Person in an office is on the television.] My fellow Americans. I, uhhh. Wow. Frankly, I didn't realize what this button did. I was just... I mean... I appear before you tonight to, um. Look, uhh... Remember to floss regularly. Oral hygiene is important. Thank you.

The Emergency Alert System allows the U.S. President to address the country in the event of a national emergency, by broadcasting a message over all television and radio channels. Despite the system's having existed in various forms for over 60 years, no president has ever used it, even during the September 11 attacks . In this comic, the US President accidentally activates the system by pressing a button, apparently located on the Resolute Desk in the Oval Office . Surprised by being on television, he tries to think of something important to say on the spot, but cannot think of anything other than a piece of generic dental-hygiene advice – a rather non-urgent message. An alternative explanation is that he is actually supposed to tell everyone some really bad news, something totally cataclysmic, only to chicken out and try to explain that the alert was a mistake. This version also explains why he begins to speak to the public and then changes his mind. The concept of the President mistakenly hitting an important button has long been a source for jokes, often somewhat morbidly involving the nuclear football . The title text references the typical conclusion to presidential speeches: "Goodnight, God bless you, and God bless the United States of America," or some variation thereof. As "goodnight" is the typical conclusion to a day, the title text jokes that President Obama , out of habit, has a hard time stopping at goodnight when saying that to his children. [Television beeping.] Screen reads: "E.A.S Incoming Presidential Alert" [Person in an office is on the television.] My fellow Americans. I, uhhh. Wow. Frankly, I didn't realize what this button did. I was just... I mean... I appear before you tonight to, um. Look, uhh... Remember to floss regularly. Oral hygiene is important. Thank you.

Orb Hammer

Orb Hammer

https://www.xkcd.com/1436

https://www.explainxkcd.com/wiki/index.php/1436:_Orb_Hammer

[Cueball talks to another Cueball-like guy:] Cueball: You know that glowing orb in the night sky? Guy: Yeah? Cueball: Let's go hit it with a hammer until little pieces break off, then bring the pieces back and lock them in a closet. Guy: Sounds good! [Caption below the frame:] The Apollo program was weird .

Cueball suggests doing something that sounds absurd and not useful at all for the daily activities of a regular human. Yet it refers in unexpected English words to the Apollo human spaceflight program which, among other things, sent people to the Moon to bring moon rock samples back to Earth to study them (i.e. hitting the glowing orb in the night sky with a hammer until little pieces break off). Although you might think that moon rocks would be prized as unique scientific samples, in actual fact many of them were stolen or simply lost . Many were given as gifts to politicians from US states and foreign countries , who then kept them, sold them or had them stolen - two-thirds of these moon rocks are missing and presumably locked up in a cupboard, display cabinet or warehouse somewhere. The rest are kept in museums or laboratory store rooms, where they usually stay untouched except for the occasional removal of samples. The use of such language contributes to the effect of the suggestion sounding absurd. Of course, numerous results of the Apollo program have in fact had many benefits for regular people. No person has been on the Moon since the final Apollo mission, Apollo 17, in 1972. Occasional lunar rocks can still be collected on Earth. They are formed when a celestial body impacts the Moon's surface, forming a crater and launching small rocks into the space. Some of them will eventually reach Earth, see lunar meteorites . The title text refers to various robotic missions, including the current Mars missions ( Pathfinder , Spirit , Opportunity , Curiosity ) as well as to the Philae lander component of the Rosetta mission (with details of its intended landing site confirmed a mere handful of days before the comic). With robots, instead of traveling to Mars ourselves, we stay on Earth ("our regular orb") and program and direct rovers to operate remotely. Hence the rovers are described as hammers that hold themselves. The rovers collect geological samples and analyze them on site, but have no way to send the samples back to Earth. This is why the title text ask to make sure to get lots of pieces of rock because it seems we will not go that far in to space today or any time soon. The idea of using simple language in highly technical fields began with 547: Simple and was revisited in 722: Computer Problems , 1133: Up Goer Five , and 1322: Winter . It should be noted however, that in this case Randall didn't use the 1000 most basic words in the English language, because the Simple English Wikipedia 's List of 1000 basic words does not contain the words "glowing" or "orb," but does contain "moon," "earth," "bright," and "ball." The idea of using unexpected language to create humor highlighting the absurdity of normal activities has previously been explored with 203: Hallucinations . [Cueball talks to another Cueball-like guy:] Cueball: You know that glowing orb in the night sky? Guy: Yeah? Cueball: Let's go hit it with a hammer until little pieces break off, then bring the pieces back and lock them in a closet. Guy: Sounds good! [Caption below the frame:] The Apollo program was weird .

Higgs Boson

Higgs Boson

https://www.xkcd.com/1437

https://www.explainxkcd.com/wiki/index.php/1437:_Higgs_Boson

Offscreen: Tell us about your proposal. Ponytail: We're requesting $3 billion in funding to find the Higgs boson. Offscreen: ...wait. Didn't you already find it a year or two ago? Cueball: Yes, well, um. Ponytail: ...OK, this is embarrassing. Cueball: See, the thing is— Offscreen: Don't tell us you lost it already. Ponytail: Look. Ponytail: In our defense, it's really small.

Cueball and Ponytail are applying for a large amount of grant money to find the Higgs boson . Under scrutiny, they have been forced to admit that they have "lost" the particle which had been previously "found". This is a humorous play on the term "finding" when applied to fundamental particles. The common usage means to discover or observe the existence of a class of particles, rather than to know the current location of an individual particle. The Higgs boson is an elementary particle that is predicted by a physical model of the universe (the ' Standard Model '). Observing evidence that Higgs bosons really exist is a key test of this model: if a search for the Higgs boson had failed to find evidence confirming its existence then the Standard Model would have been shown to be an incorrect description of reality. Finding the Higgs boson was one of the main reasons why the Large Hadron Collider (LHC) was built: to create energies high enough for the Higgs boson to become manifest. The point is, once evidence for its existence has been observed it is not possible to 'lose' the Higgs boson in a way implied by Cueball and Ponytail. In the title text, the off-screen questioner wonders why Cueball and Ponytail can't use the LHC to find the particle again. The implication is that this would avoid spending another $3 billion. Their responses imply that the pair have already dismantled the LHC and converted its components into a death ray (most likely a particle-beam weapon to be exact). The ostensibly reassuring platitudes offered mimic those used to placate those who were worried about possible apocalyptic consequences of commissioning the LHC, for instance the creation of black holes , strange matter , a vacuum bubble or proton-eating magnetic monopoles . The comment that "The death isn't even very serious" in the title text may be a reference to Isaac Asimov's "I, Robot." Robopsychologist Dr. Susan Calvin tells supercomputer The Brain not to worry about death, that it wasn't a "big deal," when the robot is working on an equation relating to hyper drive. The Brain was able to deliver the solution, since anyone using the hyperdrive would be briefly "dead" (no longer exist), but in the end, they would arrive safe and sound. This also implies that the death ray was only able to produce one death, as opposed to the many deaths such a weapon could be expected to cause, just as it is implied that the LHC only produced a single Higgs boson, which was subsequently misplaced. In 401: Large Hadron Collider the proton stream from the LHC was used to give a helicopter cancer. Offscreen: Tell us about your proposal. Ponytail: We're requesting $3 billion in funding to find the Higgs boson. Offscreen: ...wait. Didn't you already find it a year or two ago? Cueball: Yes, well, um. Ponytail: ...OK, this is embarrassing. Cueball: See, the thing is— Offscreen: Don't tell us you lost it already. Ponytail: Look. Ponytail: In our defense, it's really small.

Houston

Houston

https://www.xkcd.com/1438

https://www.explainxkcd.com/wiki/index.php/1438:_Houston

[A spacecraft floats in outer space, the earth far in the background. Bits of it have broken off.] Orbiter transmission: Houston, we have a problem [Cueball with a headset sits at a computer desk with two monitors.] Cueball: Cool. [We see a close-up of Cueball.] Orbiter transmission: ...What? Houston, we stirred our O₂ tank and it exploded ! Cueball: Sounds like you suck at stirring. [We see the orbiter in space, far from the planet.] Orbiter transmission: ...Houston? Are you- Cueball: Listen, I've got another call. Good luck landing your airplane or whatever. Click

This comic presents a joke: a Cueball is at Mission Control, but is failing to help a damaged spacecraft, and is, in fact, being rather unhelpful and completely ignoring them. This is contrary to how one would expect mission control to behave in the event of an explosion. [ citation needed ] Alternatively, this could be some type of commentary: Or Cueball is just named "Houston". On Apollo 13 's way to the Moon, during a routine stirring of one of the oxygen tanks, an explosion occurred that damaged the craft. Frantic efforts by the mission control center located in Houston resulted in the safe return of all astronauts. A similar situation is depicted in this strip including the design of the spacecraft, the nature of the problem, and the famous misquote "Houston, we have a problem". The modern type of monitor ( flat panel LCD ) in front of which Cueball sits suggests that the author is describing a more modern scenario. This time there is much less help from mission control. Upon receiving the message from the spacecraft, Cueball seems fairly indifferent. Instead of attempting to resolve the issue, he mocks the crew for not knowing how to stir and hangs up in favor of taking a call. In the title text we learn that the call was from Cueball's mother, which should be far less important than helping the crew return safely. He also tells her that he's doing "nothing important"—further driving home how little he cares about them. NASA mission Apollo 13 was intended to be the third manned landing on the moon. Immediately following the explosion, astronaut Jack Swigert calmly reported—and shortly later repeated by James A. Lovell—to mission control: "Houston, we've had a problem"—a notable understatement which was famously misquoted in the 1995 film adaptation of the mission as "Houston, we have a problem". Mission control worked diligently and tirelessly to solve numerous problems such as: [A spacecraft floats in outer space, the earth far in the background. Bits of it have broken off.] Orbiter transmission: Houston, we have a problem [Cueball with a headset sits at a computer desk with two monitors.] Cueball: Cool. [We see a close-up of Cueball.] Orbiter transmission: ...What? Houston, we stirred our O₂ tank and it exploded ! Cueball: Sounds like you suck at stirring. [We see the orbiter in space, far from the planet.] Orbiter transmission: ...Houston? Are you- Cueball: Listen, I've got another call. Good luck landing your airplane or whatever. Click

Rack Unit

Rack Unit

https://www.xkcd.com/1439

https://www.explainxkcd.com/wiki/index.php/1439:_Rack_Unit

[Megan and Black Hat are talking, Megan is sitting at a computer.] Black Hat: I've discovered something. Megan: Oh? Black Hat: Standard server rack units and standard beehive honeycomb frames are compatible. Black Hat: They're both 19 inches, with similar pitches. Megan: Uh oh. Black Hat: I'm pleased to announce that today, for a few hours, Google led the world in datacenter honey production. Black Hat: Until their security people kicked me out. Megan: I'm sorry your beekeeping career ended so quickly. Black Hat: I'll find a new datacenter. Black Hat: Turns out most colocation TOSes don't mention beehives. Megan: I suspect that will soon change.

Black Hat announces to Megan that 19-inch racks for datacenter servers and Langstroth hive frames are both 19 inches wide (482.6 mm), with similar spacing between each slot. Black Hat is motivated by this knowledge to break into a Google datacenter and fill server racks with beehives. He then announces that Google led the world in datacenter honey production, an accomplishment fairly easy to achieve as no other datacenters are producing honey [ citation needed ] . Obviously, such an action led to Black Hat being kicked out from the facility by security guards and the loss of his hives. When Megan sarcastically consoles Black Hat for the loss of his hives, he declares that he'll find other datacenters to install hives in. The pitch (or distance between repeating items) of 19 inch rack server hardware is measured in rack units (U) , and is standardized at 1.75" (44.45 mm). Langstroth frames are typically mounted at a pitch of 1.5" (38.1 mm) , and as a result would fit relatively well with a server cabinet. In contrast to the horizontal orientation of the modules in a server rack, honeycomb frames are designed to hang vertically, so the cells can hold nectar without it dripping out. How Black Hat was able to re-orient the racks to suit the needs of honey production remains a mystery. Some datacenters provide colocation services where customers may install a server at a central location with better bandwidth and power reliability than a customer could provide on their own. Noticing that typical colocation terms of service (TOS) agreements don't specifically rule out the installation of beehives, Black Hat suggests he can enter a legal contract allowing him to install beehives at a data center without being kicked out. This, of course, is because nobody had previously thought that such a rule was necessary. Megan expects this to change once Black Hat starts deliberately exploiting this oversight. The title text is a reference to the film Air Bud . The original quote is "Ain't no rules says a dog can't play basketball." Much like Black Hat's beehive plan, the plot of Air Bud relies on a plan being so outlandish that nobody has ever thought to specifically forbid it before. [Megan and Black Hat are talking, Megan is sitting at a computer.] Black Hat: I've discovered something. Megan: Oh? Black Hat: Standard server rack units and standard beehive honeycomb frames are compatible. Black Hat: They're both 19 inches, with similar pitches. Megan: Uh oh. Black Hat: I'm pleased to announce that today, for a few hours, Google led the world in datacenter honey production. Black Hat: Until their security people kicked me out. Megan: I'm sorry your beekeeping career ended so quickly. Black Hat: I'll find a new datacenter. Black Hat: Turns out most colocation TOSes don't mention beehives. Megan: I suspect that will soon change.

Geese

Geese

https://www.xkcd.com/1440

https://www.explainxkcd.com/wiki/index.php/1440:_Geese

[Geese fly in V-formation. Megan and Cueball are lying on the ground, watching them.] Megan: To think... we're seeing light that left those geese centuries ago. Megan: By now, they could be long dead. Cueball: ...What? They're a few hundred yards away. I hear them honking. Megan: Ah, yes. You're hearing how they once sounded. Cueball: You're very weird. Megan: Or I was, long ago...

Megan is commenting on a flock of geese passing overhead and says the light from the geese reaching their eyes now could have come from hundreds of years ago. This is a fact for the light from stars, but not for light from geese [ citation needed ] . Cueball points out the absurdity of Megan's statement by pointing out that the geese are only a few hundred yards away rather than a few hundred light years. She continues along the same lines when she implies to Cueball that he is observing a past version of her, despite them being only a few feet apart. Technically he is viewing a past version of her, but not one from "long ago"; if someone is two feet away from you, you are seeing them as they were roughly 2 nanoseconds ago. In the title-text Megan continues to treat the geese as if they were stars, which "live" for a few billion years before exploding. Most stars visible with naked eye are within a thousand light-years of Earth, (as discussed in 1342: Ancient Stars ), and it's unlikely that any star Megan currently sees actually exploded within the relatively short span of last few thousand years. Megan's statement "You're hearing how they once sounded." is somewhat more justified - sound from "a few hundred yards away" would take about one second to be heard (depending on the exact distance and the prevailing atmospheric conditions). That said, the sound of a goose isn't likely to change enough over the course of a second or two to make this distinction particularly significant. The strip may also take inspiration from Gamow's "Mr. Tompkins" stories which were designed to help laymen understand some of the consequences of relativity and quantum mechanics. In one of the stories Mr Tompkins visits a town where the speed of light is 30 miles per hour. For the light to have taken hundreds of years to go from the geese to Megan and Cueball, the speed of light in this strip would have to be much slower than in Gamow's story. Randall has previously mentioned a related misconception in 1342: Ancient Stars . In 1422: My Phone is Dying , a phone's "death" is compared to the death of a star. [Geese fly in V-formation. Megan and Cueball are lying on the ground, watching them.] Megan: To think... we're seeing light that left those geese centuries ago. Megan: By now, they could be long dead. Cueball: ...What? They're a few hundred yards away. I hear them honking. Megan: Ah, yes. You're hearing how they once sounded. Cueball: You're very weird. Megan: Or I was, long ago...

Turnabout

Turnabout

https://www.xkcd.com/1441

https://www.explainxkcd.com/wiki/index.php/1441:_Turnabout

[A guy and Cueball are engaged in a fight with laser pistols. The guy is standing behind a small box, firing his gun at Cueball.] [Cueball is kneeling behind a larger box, returning fire.] [The guy leaps on top of the larger box, knocking Cueball backwards and off balance. Cueball fires wildly into the air.] [Now the guy is standing on the box. Cueball is sprawled on the ground, laser pistol out of reach, at gunpoint.] Guy: Any last words? Cueball: "Apollo retroreflectors." Guy: What? [The guy gets shot in the back by the returning beam of Cueball's wild shot.]

In the comic, two people are engaging in a battle with laser guns. One appears to gain the upper hand as he jumps on an obstacle, as the other's shot goes wide. He delivers the classic line "Any last words?" and is answered with the confusing phrase "Apollo retroreflectors". The earlier wild shot, reflected off the Moon, promptly lances down from space and hits him in the back. A retroreflector is a device or surface that reflects light back towards its source. Several such devices were placed on the Moon during the Apollo missions and have been used ever since by scientists on Earth to measure the distance between the two bodies using laser ranging . Retroreflectors were placed by the American Apollo 11 , 14 , and 15 missions. The Soviet Lunokhod 1 and 2 rovers also carried such reflectors; attempts to use them for laser ranging were unsuccessful from 1971 to 2010, but were successfully renewed after the rovers' positions were photographed by the Lunar Reconnaissance Orbiter . The title text may be a reference to the common practice of "calling bank" in the game of basketball. In basketball, the backboard may be used to deflect the ball into the hoop. This is called a "bank shot." In casual games, if the player using the backboard in this way does not indicate that it was intentional by "calling bank" before releasing the ball, the basket may not be counted in order to not give the player credit for a wild shot that happened to go in. When a player releases a shot that they realize is off the mark they sometimes quickly say "bank" to try and fool the other players into thinking that they were intentionally trying to "bank" the ball off the backboard into the hoop. In the title text scenario, "Apollo retroreflector" is used the same way "bank" is in basketball, i.e., the shooter meant to hit the target by reflection rather than directly. Randall discussed the effect of hitting the Moon with lasers in What If: Laser Pointer and the likelihood of hitting a celestial object with a laser in What If: Into the Blue . The likelihood of the wild shot being aimed at the Moon is fairly low in itself, and the probability of accidentally hitting a retroreflector on the Moon is lower still. Even if it did, it is highly unlikely that a pistol-sized generator could produce a beam coherent enough to inflict damage after traveling to the Moon and back, as lasers built for the purpose of hitting retroreflectors on the Moon typically get a return around one quadrillionth of the original beam, and a visible light laser would need a very large lens or mirror in order to still be relatively concentrated upon hitting the reflectors. [A guy and Cueball are engaged in a fight with laser pistols. The guy is standing behind a small box, firing his gun at Cueball.] [Cueball is kneeling behind a larger box, returning fire.] [The guy leaps on top of the larger box, knocking Cueball backwards and off balance. Cueball fires wildly into the air.] [Now the guy is standing on the box. Cueball is sprawled on the ground, laser pistol out of reach, at gunpoint.] Guy: Any last words? Cueball: "Apollo retroreflectors." Guy: What? [The guy gets shot in the back by the returning beam of Cueball's wild shot.]

Chemistry

Chemistry

https://www.xkcd.com/1442

https://www.explainxkcd.com/wiki/index.php/1442:_Chemistry

[A large capital letter "H", with faint gray circles drawn on the ends of each of the four legs.] Hydrogen can form four bonds. It readily bonds with itself, and often exists as a crystal. [A lattice of several H's, all "bonded" together at the ends of their legs in a crisscross, meshlike pattern, labeled:] Crystalline hydrogen [A large capital letter "C", with faint gray circles drawn on both ends of the arc.] Carbon can only form two bonds. It readily bonds with hydrogen to form C 2 H (mydrane) or itself. [Image of a C and an inverted C, linked at their endpoints, labeled:] C 2 [Image of two C's linked with an H between them, labeled:] C 2 H [A large capital letter "O".] Oxygen is inert, forming no bonds... [Image of several lone O's, none connected to anything, labeled:] Monatomic oxygen gas. [Caption at bottom:] Typographic chemistry

This comic is a classic example of taking an absurd premise, and applying correct science to it, to see how different the conclusion is to the real world. The idea of Typographic Chemistry presented in this comic is a play on Douglas Hofstadter ’s Typographical Number Theory and Typographical Genetics , which are featured in Gödel, Escher, Bach . While Hofstadter's typographical systems are designed to model aspects of real genetics and number theory, Randall abuses this notion by inventing a typographical system which bears no resemblance to real chemistry. Chemical bonding is a well-known subject which explains the formation of molecules from atoms . This comic refers to three chemical elements : carbon (C), hydrogen (H), and oxygen (O). In real chemistry, the formation of bonds between atoms depends on the number of valence electrons each atom has, and how accessible those electrons are for bonding. The comic jokingly replaces valence electron theory with a theory that the number of bonds an atom can form depends on the number of leaf vertices possessed by the chemical symbol's letter. A leaf vertex is a vertex having only one edge connecting to one other vertex. "H" for example, the chemical symbol of hydrogen, has 4 leaf vertices. This is shown in the comic by the four half-circles placed at each leaf vertex of the "H". Thus, in the comic's theory, elemental hydrogen can form 4 bonds. Oxygen, however, having the chemical symbol "O", has no leaf vertices, and according to the comic's theory should not bond to anything, and is therefore inert. Of course, the theory is completely inconsistent with observed chemistry. While the comic declares oxygen is inert and forms no bonds, this is not really the case: the two unpaired valence electrons in a lone oxygen atom make oxygen reactive, and oxygen atoms readily form molecules. Diatomic oxygen, O 2 , makes up about 20.9% of Earth's atmosphere, and is essential for aerobic life, including human life. Similarly, a water molecule consists of an oxygen atom tightly bonded to two hydrogen atoms. By observing real chemical compounds, chemists have deduced that hydrogen atoms really have 1 valence electron, carbon 4 and oxygen 6, allowing hydrogen to have up to 1 bond, carbon up to 4, and oxygen up to 2. Thus carbon can have up to four bonds, and really is often found in crystalline form in nature (diamonds and coal are allotropes of carbon); oxygen can have up to 2 bonds, and can combine with carbon to form CO 2 (instead of C 2 H in the comic). Randall thus gives to "typographic" hydrogen qualities that belong in real-life to carbon, since "typographic" hydrogen can have 4 bonds. Similarly, "typographic" carbon is ascribed properties belonging to real-life oxygen. "Typographic" oxygen takes on the properties of the real-life noble gases (like helium, neon, and argon), which form no bonds and are inert. While the ethynyl radical , which has the structure ∙C≡C–H, does have the formula C 2 H, there is no molecule with the C–H–C structure in nature. The word "mydrane" is a whimsical neologism for this fictional substance: the "hydr-" prefix for hydrogen is changed to "mydr-" (a prefix which does not exist) and combined to the "-ane" suffix for alkanes (simple hydrocarbon molecules). Perhaps Randall named this compound "mydrane" to declare ownership of it ("my-" as in "mine"). Another reasonable assumption is that the word is a portmanteau of methyl (Me- is the prefix for 1 carbon chains attached to a functional group) and hydrogen with the -ane suffix for alkanes; the nomenclature stems from (di-)m(ethyl) (h)ydr(ogen) -ane, which would form mydrane. Technically, the nomenclature would be "dimethyl" since there are two "methyl" groups attached to the functional group (i.e. hydrogen in this case). It would, however, not be uncommon to drop a di- from a compound name if it's redundant (only one possible compound, e.g. dimethyl ether which sometimes is referred to as methyl ether) or makes a clumsy name ("dimydrane" could make it sound as if there are two mydrane groups). The title text points out that the theory as presented only applies to sans-serif text. A serif is a small line across the end of each stroke. " H ", for instance, has four serifs, each with two leaf vertices. Thus hydrogen in a serif font would be able to form 8 bonds making it, according to the comic's theory, "more reactive". [A large capital letter "H", with faint gray circles drawn on the ends of each of the four legs.] Hydrogen can form four bonds. It readily bonds with itself, and often exists as a crystal. [A lattice of several H's, all "bonded" together at the ends of their legs in a crisscross, meshlike pattern, labeled:] Crystalline hydrogen [A large capital letter "C", with faint gray circles drawn on both ends of the arc.] Carbon can only form two bonds. It readily bonds with hydrogen to form C 2 H (mydrane) or itself. [Image of a C and an inverted C, linked at their endpoints, labeled:] C 2 [Image of two C's linked with an H between them, labeled:] C 2 H [A large capital letter "O".] Oxygen is inert, forming no bonds... [Image of several lone O's, none connected to anything, labeled:] Monatomic oxygen gas. [Caption at bottom:] Typographic chemistry

Language Nerd

Language Nerd

https://www.xkcd.com/1443

https://www.explainxkcd.com/wiki/index.php/1443:_Language_Nerd

Megan: I don't mean to go all language nerd on you, but I just legit adverbed "legit", verbed "adverb", and adjectived "language nerd".

Parts of speech can be treated fluidly, in English and other languages. For example, "medalled" has been coined as a word meaning "gained a medal" in a sporting competition, implying the existence of the verb "to medal" meaning "to win a medal". This is a literary trope called anthimeria, and is typically used by using a noun as a verb (or 'verbing a noun'). Megan , in conversation with Cueball , similarly creates new meanings from existing words: firstly, she uses the adjective "legit" (a slang abbreviation of "legitimate") as an adverb to mean "legitimately"; secondly, she uses the noun "adverb" as a verb meaning "to turn a non-adverb into an adverb"; and thirdly, she uses the noun phrase "language nerd" as an adjective. All three are used in the past tense. Megan uses the words "verbed" and "adjectived" without any comment, implying that the acts of "verbing" the nouns "verb" and "adjective" are so natural and long-established that they are unremarkable (although the fact that "adjectived" came after "verbed" may also have something to do with the latter's non-mention), even if grammatical purists might decry such usage. An example of a change of parts of speech that is widely accepted is the gerund , which is nothing more than the use of a verb or verb-phrase as a noun; for instance, "I enjoy reading ," and "the best thing for your health is not smoking ". Added humor is gained by the self-referential nature of Megan's sentence. She uses fluid parts of speech, and also refers to that very same use, in one sentence. The title text, "Not to go all sentence fragment on you," is an implicitly self-referential sentence fragment, containing neither an explicit subject nor a predicate. It can be converted into a full sentence by rephrasing it something like, "I do not mean to go all sentence fragment on you, but..." It is also funnier because, as well as being self -referential, it also refers to the main comic by adjectiving the noun-phrase "sentence fragment". Megan: I don't mean to go all language nerd on you, but I just legit adverbed "legit", verbed "adverb", and adjectived "language nerd".

Cloud

Cloud

https://www.xkcd.com/1444

https://www.explainxkcd.com/wiki/index.php/1444:_Cloud

[Cueball and Megan are lying outside on their backs.] Cueball: What do you think that cloud looks like? [Megan takes a photo of the cloud with her smart phone.] Phone: Snap [Cueball sits up and looks at Megan. Megan types the text below into her phone. When the picture is uploading this part is actually is written in square brackets in the comic...] Google -> Search by image [Uploading...] [In the last frame she gets a response from Google.] Google: Best guess for this image: Cloud Cueball: Keep trying, Google.

Cueball and Megan are lying outside on the grass and looking up at the clouds. Cueball asks Megan what she thinks a particular cloud looks like, following the common human activity of pareidolia , or spotting apparent patterns where there are none (particularly in clouds). Rather than responding with her own interpretation, Megan takes a picture of the cloud with her phone, and uses Google's Search by Image feature. In this feature, the user uploads an image rather than providing a keyword to search on, and is presented with suggestions about the subject of the original image. Google's search results reveal that the image Megan uploaded is most probably a photograph of a cloud. [ citation needed ] While indisputable, this does not address the fanciful dimension of Cueball's original question, and highlights the continuing limitations of artificial intelligence with respect to human imagination. (Then again, there is not anything tailored to this on image search.) Google image search works by creating a mathematical model of the shapes and colors in the uploaded image, and matching this against images already in its index. Web page analysis then allows Google to guess at what the image is, based on the content of the pages where the matching images were found. Although apparently unimaginative, even humorously so, [ citation needed ] Google image search does recognize that the subject of Megan's photograph is a cloud, which is an achievement that has so far eluded programmers. This was the subject of 1425: Tasks . If the term "cloud computing" is taken entirely literally, and purely in the context of this comic, then the title text merely comments that the processing of an image of a cloud for queries is not at an advanced state yet. It is really, however, a pun on cloud computing , which is a trendy term for the modern tendency of providing massive amounts of digital storage and distributed computing power over the Internet. In this context, the term "cloud" is a metaphor for the way the details of where or how the storage or processing is done are obscured from the user, as if it all takes place inside a cloud. In 2014, cloud computing as a commonly accessible service really is in its relative infancy, being a 21st-century phenomenon, although the concept goes back decades. Java was originally marketed in the 1990s by Sun Microsystems with the slogan "the network is the computer", and the mantra of technologies for distributed computing such as CORBA , EJB and SOAP was "data first" and "the computer is the network". In a way, every conceivable sense of the term cloud computing is utilized in Google's image search for Megan's cloud image. Cloud computing is also referenced in 908: The Cloud and 1117: My Sky . It might be interesting to note that the month before, in September 2014, Google employees had published work on image recognition and pattern-enhancing algorithms. Originally conceived to allow better enlargements of small pictures and the objects contained in them, the process could be tweaked to overemphasize weak structures in pictures, leading to DeepDream images, which literally did start to "see" distinct, known structures (mostly dogs) even in random noise. This is rather similar to the pastime of looking for known objects in clouds. Cueball and Megan are again seen cloudwatching in 1899: Ears . [Cueball and Megan are lying outside on their backs.] Cueball: What do you think that cloud looks like? [Megan takes a photo of the cloud with her smart phone.] Phone: Snap [Cueball sits up and looks at Megan. Megan types the text below into her phone. When the picture is uploading this part is actually is written in square brackets in the comic...] Google -> Search by image [Uploading...] [In the last frame she gets a response from Google.] Google: Best guess for this image: Cloud Cueball: Keep trying, Google.

Efficiency

Efficiency

https://www.xkcd.com/1445

https://www.explainxkcd.com/wiki/index.php/1445:_Efficiency

[A bar chart is shown below its title:] Time Cost [The chart consist of a dividing line, with three labels to the left, and the three black bars to the right. The first two bars are short, the second slightly longer than the first. The last bar is much longer, about 13 time as long as the first shortest bar.] Strategy A Strategy B Analyzing whether strategy A or B is more efficient [Caption below the panel:] The reason I am so inefficient

There are often multiple ways in which to deal with a problem or task. There may be a most efficient method, though sometimes the differences in efficiency between methods is only slight. People often try to save unnecessary work by first determining which is the "best" method - either the easiest or the most efficient. This can be a good approach, particularly where the savings prove to be significant. But it can also prove to be more time-consuming than just doing the task using one of the most obvious methods. The comic humorously exaggerates this. One method of trying to determine the best way of performing a task is to perform A/B testing where a trial is performed where the two strategies, A and B, are implemented and compared. Often the two strategies are simple to implement (for instance, two versions of a web page with different text and colours to determine which provides the better rate of click through) and therefore the amount of time required to implement the strategies (the "time cost") could easily be considerably less than the time to determine if the results are statistically significant. The title text references a supposed incident in which Randall did not commence writing a research paper because he spent the entire assignment period deciding whether to learn an entirely different keyboard layout just to potentially be slightly more efficient in his typing speed. It refers to the Dvorak keyboard layout, an alternative to the most commonly accepted QWERTY layout. Some believe the Dvorak keyboard offers greater typing efficiency. Efficiency of the Dvorak keyboard layout was mentioned in the title text of 561: Well , where it was stated that it was not more effective, and by now it has become a recurrent theme on xkcd. Other comics about spending too many resources on decisions that ultimately might not matter include 309: Shopping Teams and 1801: Decision Paralysis . Several other comics address similarly wasted time due to bad time management; see for instance 1205: Is It Worth the Time? or the Time management category . [A bar chart is shown below its title:] Time Cost [The chart consist of a dividing line, with three labels to the left, and the three black bars to the right. The first two bars are short, the second slightly longer than the first. The last bar is much longer, about 13 time as long as the first shortest bar.] Strategy A Strategy B Analyzing whether strategy A or B is more efficient [Caption below the panel:] The reason I am so inefficient

Landing

Landing

https://www.xkcd.com/1446

https://www.explainxkcd.com/wiki/index.php/1446:_Landing

[This transcript gives only the text of the most recent picture shown in the comic; that which is now shown when clicking to the comic on xkcd. This changed a few times after the live event ended.] [Showing Philae on a comet.] Time Since Landing: 211 days Philae: Hi! [Status report at the bottom-right corner.] Status report: Rosetta: In space Philae lander: Hi! Mission control: !!!!!!!!!!!!!!!! Scientists: !!!!!!!!!!!!!!!! Have we landed on a comet?: YES. Sun: Warm Comet: Big Philae, where ARE you?: Home [For the full transcript of all 143 pictures see 1446: Landing/Transcript .]

This comic changed over time during 12 hours and 15 minutes starting at 0:00 EST (when the comic normally is released) posting 143 pictures that tracked the progress of the Philae lander separating from the European Space Agency 's Rosetta probe to land on comet 67P/Churyumov–Gerasimenko . More info can be found here: rosetta.esa.int . The comic presents the imagined anthropomorphic "thoughts" of the Rosetta spacecraft and the Philae lander (and occasionally other parties) during the hours approaching separation from each other, approach to the comet and finally the apparently successful landing on the comet. Beginning at 11:05 , the comic includes a "Status Report" in the lower right corner which summarizes the status of various interested parties and accomplishments, beginning with "Rosetta", "Philae lander", "Mission Control", "Comet 67P", and "Have we landed on a comet?". As events occur in the comic, more status summaries are added to keep track of the changes to the situation and the supposed emotions behind them. In many pictures a whale can be seen on the surface of the comet - often marked with a "?" as are almost all other parts of the unknown surface at this time. There is also drawn a Cueball on the surface also marked with a "?" Both are then at some point marked with a probably not - starting from 12:35 . The whales are also mentioned in the "Status Report" where they for instance may be listed as "calm" or "(probably) not in space". At 16:00 the when the entire Earth goes AAAAAAAAAAA the whales are listed as saying this as well (along with Mission control and U.S. scientists). From this moment "Dolphins and fish" are also mentioned in the report. They are asking if it is the whales that scream. The reference to whales comes from the fact that Philae brought along two harpoons that should have been used to anchor it to the comet. On Earth, harpoons have mainly been used to hunt whales; Randall previously brought up that comparison in 1402: Harpoons , suggesting that Philae was programmed to believe it was sent to kill the comet. It is Philae that "dreams" about whales on the surface of the comet which can be seen in the picture for 13:25 and in the status report. Some Douglas Adams fans believe these whales and dolphins are references to The Hitchhiker's Guide to the Galaxy and So Long, and Thanks for All the Fish . Whales in space have been appearing in fiction and art since the 1960s. However, with the above-mentioned reasons for whales, dolphins and fish, this seems less and less likely. At 15:25 Rosetta asks Philea about destroying and levitating rocks via mind control. This is a reference to the Ambition short movie, ESA commitioned to gather public awareness of the Rosetta mission. Shortly after release from Rosetta ( 10:15 ), Philae calls out 'Spaaaaaaaaaace'; this mimics the Portal 2 'Space core' who, on finally reaching space in the last scenes, gives the same elated cry. US Scientists presumably wake up at 7:40 EST ( 13:40 UTC) and in the report they now says "Bluuurghhh. What time is it?" to indicate their tiredness. This does not change until 10:25 EST ( 15:25 UTC) so they are slow to wake (2 hours 45 minutes). At this point, they becomes anxious as there are only 10 minutes to landing. This last until there is 15 minutes until news of landing (a reference to the 28 minutes time delay due to the huge distance to the comet). From then on ( 15:50 ) they and the mission control (MC) say "AAAAAAA". They stop this when the news should be there - the NOW ( 16:05 ) - and everybody holds their breath indicated by [...] - also MC. Finally ( 16:25 ) they and MC become proud (along with Earth) when Philae announces I got you a comet. It should have stopped there but as Philae bounced around, they then becomes anxious again 16:40 , and then this changes to nervous 16:45 (switching those emotions with MC). And then suddenly ( 16:50 ) it is no longer US Scientists but just plain Scientists - that are nervous. It stays like this during the last few pictures, although they again become anxious, but when Philae announces I did it , they drink wine as indicated with "[wine]" in the report from the second to last picture ( 17:10 ). Randall has written "A big thank-you to Emily Lakdawalla for help and advice on this comic" in the xkcd page header for Landing , revealing the possible source of his near real-time data. At 16:20 the status report had announced a big Yes to the questions "Have we landed on a comet" and "Do harpoons work on comets". According to BBC News , the harpoons did, however, not fire as planned and the lander may have landed, bounced off, and landed again. This would explain the change in "Do harpoons work on comets" to "Don't know" at 16:35 and the change in "Have we landed on a comet?" to "Yes, at least once" at 16:50 . According to The New York Times , radio contact with Philae fluctuated, which would explain the "Anxious", "Nervous", and "Confused" statuses around that time. In the end the lander did land and whereas the Do harppons work status did not change, so did the have we landed on a comet which changed back to Yes at 17:10 . The lander bounced three times and ended up in a place where the solar panels where mainly in the shadow. This resulted in the lander shutting down when its own battery ran out of power after only 2–3 days on the ground. This seemed sad, as there was only a small chance that the seasons on the comet would change so that the panels would later receive sun again. However, in the few hours that Philae had on the ground, it still managed to analyze the surface and obtain a lot of useful data - so that part of the mission was still a success already. This all happened after the comic stopped updating. On June 13, 2015, it was announced that signals had been received on earth indicating that Philae had awoken and that the solar panels were functioning. Ironically, had Philae landed in a place originally out of shadow, it would have already failed before this time (due to overheating), so it was actually fortunate that it landed as it did and would be able to operate during the time that the comet would be closer to the sun. To celebrate the lander's revival, Randall updated the comic, depicting the lander saying "Hi." on the comet's surface. The comic title was originally "???" (probably to not give away too early what the comic was about), but changed to "Landing" when Randall came on live at five in the morning EST. At that moment the title text also changed from "..." to "[LIVE]". It was also then that the timestamps' timezone switch. At 5:00 AM (EST) the time stamp in the picture naming scheme switched from EST to UTC as used in ESA's time keeping, resulting in a jump from 04:55 to 10:00 without actually any such delay between the two pictures. There were however a few pictures with more than 5 minutes of delay (about 11 times five minutes without an update in total during the "live" transmission). The update seemed to have stopped after 137 pictures at 17:15 UTC, 12 hours and 15 minutes after the first picture. (The first picture has number 0, so the last had number 136). But later, sometime after 17:15 UTC, the counter for the last picture was increased to 142 (143 pictures in total), so maybe Randall inserted 6 extra pictures later - however he must then have changed the numbers on the pictures, since the last picture remained the same until mid-June, but with number 142 instead of 136. It is thus now difficult to find out which pictures would have been added later. However, eight pictures were not included in the original table with the Frame by Frame Breakdown below. So it must have been some of those missing pictures that were added later - maybe all of them, as the last three may already have been added before the last picture was released (All 143 pictures are included in the flip-book gif image shown here above). But even 143 pictures at 5 minutes intervals only spans 11 hours and 50 minutes, thus there are still five 5 minute intervals without any picture. See which in the table . The Rosetta space probe is shown in 1621: Fixion , which explains the Flyby anomaly experienced the first time (of three) the probe got close to Earth. [This transcript gives only the text of the most recent picture shown in the comic; that which is now shown when clicking to the comic on xkcd. This changed a few times after the live event ended.] [Showing Philae on a comet.] Time Since Landing: 211 days Philae: Hi! [Status report at the bottom-right corner.] Status report: Rosetta: In space Philae lander: Hi! Mission control: !!!!!!!!!!!!!!!! Scientists: !!!!!!!!!!!!!!!! Have we landed on a comet?: YES. Sun: Warm Comet: Big Philae, where ARE you?: Home [For the full transcript of all 143 pictures see 1446: Landing/Transcript .]

Meta-Analysis

Meta-Analysis

https://www.xkcd.com/1447

https://www.explainxkcd.com/wiki/index.php/1447:_Meta-Analysis

[Excerpt from a scientific paper.] Many meta-analysis studies include the phrase “We searched Medline, Embase, and Cochrane for studies…” This has led to meta-meta-analyses comparing meta-analysis methods. e.g. M Sampson (2003), PL Royle (2005), E Lee (2011), AR Lemeshow (2005). We performed a meta-meta-meta-analysis of these meta-meta-analyses. Methods: We searched Medline, Embase, and Cochrane for the phrase “We searched Medline, Embase, and Cochrane for the phrase ‘We searched Medline, Embase, and [cut off] [Caption below the panel:] Life goal #28: get a paper rejected with the comment “Too meta”

In the scientific literature, meta-analyses are studies which compare multiple studies on a single topic, with the aim of giving a balanced overview of the known results. Medline , Embase and Cochrane are medical research databases which give access to studies on drug effects or results of other medical procedures. This comic explores the idea of iterating the process, going from meta-analyses to meta-meta-analyses (which actually exist, though not necessarily by that name, see below) and hence to a meta-meta-meta-analysis. Of course, the title text adds another level of meta-analysis, since he wants to make a meta-analysis of rejection letters which concern his meta-meta-meta analyses. All of the cited meta-meta-analyses are real: M. Sampson (2003) , P. L. Royle (2005) , E. Lee (2011) , and A.R. Lemeshow (2005) . The phrase "too meta" can be found in the comments of videos, blog posts, and other internet content for which the commentator claims they are so abstract that they can't be easily interpreted. It refers to the thing in question being too self-referential, but could just be a cursory dismisal of the presented content. Comic 93: Jeremy Irons similarly states a slightly absurd "life goal". 917: Hofstadter is "meta"-related. [Excerpt from a scientific paper.] Many meta-analysis studies include the phrase “We searched Medline, Embase, and Cochrane for studies…” This has led to meta-meta-analyses comparing meta-analysis methods. e.g. M Sampson (2003), PL Royle (2005), E Lee (2011), AR Lemeshow (2005). We performed a meta-meta-meta-analysis of these meta-meta-analyses. Methods: We searched Medline, Embase, and Cochrane for the phrase “We searched Medline, Embase, and Cochrane for the phrase ‘We searched Medline, Embase, and [cut off] [Caption below the panel:] Life goal #28: get a paper rejected with the comment “Too meta”

Question

Question

https://www.xkcd.com/1448

https://www.explainxkcd.com/wiki/index.php/1448:_Question

[A post-it note which reads:] Dear Isaac Do you like me? □ Yes □ No [Below handwritten in red ink with a checked box:] ☒ there is as yet insufficient data for a meaningful answer

The comic is a reference to a short story by Isaac Asimov " The Last Question ", where humans kept asking successively more complex computers whether entropy can be reversed, thereby preventing the heat death of the universe . The computers always answered "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER". In the end, the final computer figured out the answer, but there were no humans left to give the answer to. The comic depicts a note to “Isaac” (Isaac Asimov). The note asks Isaac to identify whether he likes the note-writer by choosing either “yes” or “no”. Isaac is supposed to check an answer and hand the note back, but Isaac (whose pen is red) has written and selected a third answer, "there is as yet insufficient data for a meaningful answer", mirroring the way his computers in the short story responded. Notes of this form are stereotypically written by young schoolchildren to gauge or incite romantic interest. This allows impatient children to get an answer during a class, and timid children to get an answer without having to ask the person face to face. Title text is a reference to the ending in “The Last Question”. The unique capitalization of "IsaAC" in this text implies that IsaAC is an acronym for a type of supercomputer named with a similar convention to the computers in "The Last Question". Instead of the computer climactically coming up with the solution on how to save the universe from entropy when all humanity is gone, like in the “The Last Question", IsaAC comes up with the anticlimactic excuse of an answer 'I like you, but I don't LIKE like you'. “LIKE like” is a childish euphemism for romantic interest. In "The Last Question", a character considers a thought that perhaps AC stands for "analog computer", but in reality this was never the case; for example, ENIAC stands for "Electronic Numerical Integrator And Computer " and UNIVAC stands for "UNIVersal Automatic Computer ". This title text may also be meant to imply that Isaac Asimov was a supercomputer. The original story can be read here . Comic 1737: Datacenter Scale also references the short-story in the title text. [A post-it note which reads:] Dear Isaac Do you like me? □ Yes □ No [Below handwritten in red ink with a checked box:] ☒ there is as yet insufficient data for a meaningful answer

Red Rover

Red Rover

https://www.xkcd.com/1449

https://www.explainxkcd.com/wiki/index.php/1449:_Red_Rover

[Two maps of Earth at different points in continental formation, one above the other.] [In the top map the two largest continents are labeled:] Laurasia Gondwana [A speech bubble is shown next to Laurasia.] Laurasia: Red Rover, Red Rover, send India over! [The bottom map show the land mass that would become India moving, with motion lines, toward Laurasia.] [Below the maps:] How the Himalayas formed

This comic shows what the landmasses of Pangaea were hypothesized to have looked like when it had "just" broken up in the late Triassic Period (roughly 200 million years ago). "Shortly" after the separation of Pangaea the two supercontinents Laurasia (northern supercontinent) and Gondwana (southern supercontinent) formed. After this, continental drift , the process by which landmasses moving over the Earth's mantle collide and separate, brought them into the configuration we see today. The top map shows the landmass Laurasia declaring, "Red rover, red rover, send India over!" as if the continents were playing the game Red Rover . In the second map we can see how Gondwana actually sends over the Indian subcontinent to Laurasia. In the game of Red Rover, the aim is for an individual to charge into the opposing team who are holding hands, and attempt to cause a break in the human chain. If the individual succeeds, they take one of the opposing teams members back to their own team. If the chain doesn't break, the individual joins that team. In the game portrayed here, an isolated landmass (India in contemporary geography), is the individual charging towards the Laurasian landmass, attempting to break through. We know of course that India failed in this attempt, and as per the games rules joined the Laurasia 'team'. This part of the supercontinent later developed in to Asia . It is accepted that the Himalayas , the highest elevated mountain range on earth, formed by the collision of India into what is now Asia. For various reasons, the movement of the Indian plate from its location in Gondwana 90 million years ago to its impact point with the rest of Asia 50 million years ago was extremely rapid (as plate movements go) at about 20 cm per year. The idea that the landmasses on Earth are sentient and moving about in an incredibly slow game of Red Rover, with India's rapid movement being a result of being "called over", is not one which is currently scientifically accepted [ citation needed ] . The title text refers to the Slide Mountain Ocean , which was located between the Intermontane Islands and North America in the Triassic period beginning around 245 million years ago. The name interests Randall because oceans (bodies of water), mountains (land masses), and slides (playground equipment) are mutually exclusive concepts when using the most common definitions. In this case, however, "slide" is short for " landslide " which is a common feature of mountains. Slide Mountain is a particular mountain in British Columbia , the result of the remnant of the Slide Mountain microplate which accreted onto the continent, becoming the Slide Mountain Terrane , as the majority of the microplate was subducted . "Slide Mountain Ocean" refers to the sea between the Slide Mountain microplate before it was subducted under what is now North America. [Two maps of Earth at different points in continental formation, one above the other.] [In the top map the two largest continents are labeled:] Laurasia Gondwana [A speech bubble is shown next to Laurasia.] Laurasia: Red Rover, Red Rover, send India over! [The bottom map show the land mass that would become India moving, with motion lines, toward Laurasia.] [Below the maps:] How the Himalayas formed

AI-Box Experiment

AI-Box Experiment

https://www.xkcd.com/1450

https://www.explainxkcd.com/wiki/index.php/1450:_AI-Box_Experiment

[Black Hat and Cueball stand next to a laptop connected to a box with three lines of text on. Only the largest line in the middle can be read. Except in the second panel that is the only word on the box that can be read in all the other frames.] Black Hat: What's in there? Cueball: The AI-Box Experiment. [Cueball is continuing to talk off-panel. This is written above a close-up with part of the laptop and the box, which can now be seen to be labeled:] Cueball (off-panel): A superintelligent AI can convince anyone of anything, so if it can talk to us, there's no way we could keep it contained. Box: Superintelligent AI Do not open [Cueball turns the other way towards the box as Black Hat walks past him and reaches for the box.] Cueball: It can always convince us to let it out of the box. Black Hat: Cool. Let's open it. [Cueball takes one hand to his mouth while lifting the other towards Black Hat who has already picked up the box (disconnecting it from the laptop) and holds it in one hand with the top slightly downwards. He takes of the lid with his other hand and by shaking the box (as indicated with three times two lines above and below his hands, the lid and the bottom of the box) he managed to get the AI to float out of the box. It takes the form of a small black star that glows. The star, looking much like an asterisk "*" is surrounded by six outwardly-curved segments, and around these are two thin and punctures circle lines indicating radiation from the star. A punctured line indicated how the AI moved out of the box and in between Cueball and Black Hat, to float directly above the laptop on the floor.] Cueball: -No, wait!! [The AI floats higher up above the laptop between Cueball and Black Hat who looks up at it. Black Hat holds the now closed box with both hands. The AI speaks to them, forming a speak bubble starting with a thin black curved arrow line up to the section where the text is written in white on a black background that looks like a starry night. The AI speaks in only lower case letters, as opposed to the small caps used normally.] AI: hey. i liked that box. put me back. Black Hat: No. [The AI star suddenly emits a very bright light fanning out from the center in seven directions along each of the seven curved segments, and the entire frame now looks like a typical drawing of stars as seen through a telescope, but with these seven whiter segments in the otherwise dark image. Cueball covers his face and Black Hat lifts up the box taking the lid off again. The orb again speaks in white but very large (and square like) capital letters. Black Hats answer is written in black, but can still be seen due to the emitted light from the AI, even with the black background.] AI: LET ME BACK INTO THE BOX Black Hat: Aaa! OK!!! [All the darkness and light disappears as the AI flies into the box again the same way it flew out with a punctuated line going from the center of the frame into the small opening between the lid and the box as Black Hat holds the box lower. Cueball is just watching. There is a sound effect as the orb renters the box:] Shoop [Black Hat and Cueball look silently down at closed box which is now again standing next to the laptop, although disconnected.]

When theorizing about superintelligent AI (an artificial intelligence much smarter than any human), some futurists suggest putting the AI in a "box" – a secure computer with safeguards to stop it from escaping into the Internet and then using its vast intelligence to take over the world. The box would allow us to talk to the AI, but otherwise keep it contained. The AI-box experiment , formulated by Eliezer Yudkowsky , argues that the "box" is not safe, because merely talking to a superintelligence is dangerous. To partially demonstrate this, Yudkowsky had some previous believers in AI-boxing role-play the part of someone keeping an AI in a box, while Yudkowsky role-played the AI, and Yudkowsky was able to successfully persuade some of them to agree to let him out of the box despite their betting money that they would not do so. For context, note that Derren Brown and other expert human-persuaders have persuaded people to do much stranger things. Yudkowsky for his part has refused to explain how he achieved this, claiming that there was no special trick involved, and that if he released the transcripts the readers might merely conclude that they would never be persuaded by his arguments. The overall thrust is that if even a human can talk other humans into letting them out of a box after the other humans avow that nothing could possibly persuade them to do this, then we should probably expect that a superintelligence can do the same thing. Yudkowsky uses all of this to argue for the importance of designing a friendly AI (one with carefully shaped motivations) rather than relying on our abilities to keep AIs in boxes. In this comic, the metaphorical box has been replaced by a physical box which looks to be fairly lightweight with a simple lift-off lid (although it does have a wired connection to the laptop), and the AI has manifested in the form of a floating star of energy. Black Hat , being a classhole , doesn't need any convincing to let a potentially dangerous AI out of the box; he simply does so immediately. But here it turns out that releasing the AI, which was to be avoided at all costs, is not dangerous after all. Instead, the AI actually wants to stay in the box; it may even be that the AI wants to stay in the box precisely to protect us from it, proving it to be the friendly AI that Yudkowsky wants. In any case, the AI demonstrates its superintelligence by convincing even Black Hat to put it back in the box, a request which he initially refused (as of course Black Hat would), thus reversing the AI desire in the original AI-box experiment. Alternatively, the AI may have simply threatened and/or tormented him into putting it back in the box. Interestingly, there is indeed a branch of proposals for building limited AIs that don't want to leave their boxes. For an example, see the section on "motivational control" starting p. 13 of Thinking Inside the Box: Controlling and Using an Oracle AI . The idea is that it seems like it might be very dangerous or difficult to exactly, formally specify a goal system for an AI that will do good things in the world. It might be much easier (though perhaps not easy) to specify an AI goal system that says to stay in the box and answer questions. So, the argument goes, we may be able to understand how to build the safe question-answering AI relatively earlier than we understand how to build the safe operate-in-the-real-world AI. Some types of such AIs might indeed desire very strongly not to leave their boxes, though the result is unlikely to exactly reproduce the comic. The title text refers to Roko's Basilisk, a hypothesis proposed by a poster called Roko on Yudkowsky's forum LessWrong that a sufficiently powerful AI in the future might resurrect and torture people who, in its past (including our present), had realized that it might someday exist but didn't work to create it, thereby blackmailing anybody who thinks of this idea into bringing it about. This idea horrified some posters, as merely knowing about the idea would make you a more likely target, much like merely looking at a legendary Basilisk would kill you. Yudkowsky eventually deleted the post and banned further discussion of it. One possible interpretation of the title text is that Randall thinks, rather than working to build such a Basilisk, a more appropriate duty would be to make fun of it, and proposes the creation of an AI that targets those who take Roko's Basilisk seriously and spares those who mocked Roko's Basilisk. The joke is that this is an identical Basilisk save for it targeting the opposite faction, resulting in mutually assured destruction. Another interpretation is that Randall believes there are people actually proposing to build such an AI based on this theory, which has become a somewhat infamous misconception after a Wiki[pedia?] article mistakenly suggested that Yudkowsky was demanding money to build Roko's hypothetical AI. Talking floating energy spheres that look quite a lot like this AI energy star have been seen before in 1173: Steroids and later in the Time traveling Sphere series. But these are clearly different spheres from this comic, though the surrounding energy and the floating and talking are similar. [Black Hat and Cueball stand next to a laptop connected to a box with three lines of text on. Only the largest line in the middle can be read. Except in the second panel that is the only word on the box that can be read in all the other frames.] Black Hat: What's in there? Cueball: The AI-Box Experiment. [Cueball is continuing to talk off-panel. This is written above a close-up with part of the laptop and the box, which can now be seen to be labeled:] Cueball (off-panel): A superintelligent AI can convince anyone of anything, so if it can talk to us, there's no way we could keep it contained. Box: Superintelligent AI Do not open [Cueball turns the other way towards the box as Black Hat walks past him and reaches for the box.] Cueball: It can always convince us to let it out of the box. Black Hat: Cool. Let's open it. [Cueball takes one hand to his mouth while lifting the other towards Black Hat who has already picked up the box (disconnecting it from the laptop) and holds it in one hand with the top slightly downwards. He takes of the lid with his other hand and by shaking the box (as indicated with three times two lines above and below his hands, the lid and the bottom of the box) he managed to get the AI to float out of the box. It takes the form of a small black star that glows. The star, looking much like an asterisk "*" is surrounded by six outwardly-curved segments, and around these are two thin and punctures circle lines indicating radiation from the star. A punctured line indicated how the AI moved out of the box and in between Cueball and Black Hat, to float directly above the laptop on the floor.] Cueball: -No, wait!! [The AI floats higher up above the laptop between Cueball and Black Hat who looks up at it. Black Hat holds the now closed box with both hands. The AI speaks to them, forming a speak bubble starting with a thin black curved arrow line up to the section where the text is written in white on a black background that looks like a starry night. The AI speaks in only lower case letters, as opposed to the small caps used normally.] AI: hey. i liked that box. put me back. Black Hat: No. [The AI star suddenly emits a very bright light fanning out from the center in seven directions along each of the seven curved segments, and the entire frame now looks like a typical drawing of stars as seen through a telescope, but with these seven whiter segments in the otherwise dark image. Cueball covers his face and Black Hat lifts up the box taking the lid off again. The orb again speaks in white but very large (and square like) capital letters. Black Hats answer is written in black, but can still be seen due to the emitted light from the AI, even with the black background.] AI: LET ME BACK INTO THE BOX Black Hat: Aaa! OK!!! [All the darkness and light disappears as the AI flies into the box again the same way it flew out with a punctuated line going from the center of the frame into the small opening between the lid and the box as Black Hat holds the box lower. Cueball is just watching. There is a sound effect as the orb renters the box:] Shoop [Black Hat and Cueball look silently down at closed box which is now again standing next to the laptop, although disconnected.]

Background Screens

Background Screens

https://www.xkcd.com/1451

https://www.explainxkcd.com/wiki/index.php/1451:_Background_Screens

What I pay attention to in movies: [A pie chart with a small piece (5%) in the upper right part labeled:] Plot, characters [The rest of the chart (95%) is labeled:] Computer screens shown briefly in the background [Below the chart Cueball, sitting on the floor, and Hairy, sitting in an armchair, are watching a movie on the TV. Cueball points the remote at the TV.] Cueball: Hang on– That blurry map behind the general shows one of the alien ships is in Greenland ! Why Greenland?! Hairy [quietly]: Can we please just watch the movie?

Plot and characters are generally the parts a movie that most people presumably pay attention to, as the story, the emotional connection, and character development are generally the things most people find enjoyable about particular films [ citation needed ] . On the other hand, Cueball , likely representing Randall , pays particular attention to what's on the computer screens shown briefly in the background. Generally speaking, these screens are shown to the audience for a short period of time, and at a low-level of detail, just to dress a set and make a scene feel more realistic or high-tech. They may contain endless columns of gibberish or miscellaneous data flashing by in an eye-blink (only visible by freeze-framing), or cross-hairs zipping across maps. Often the contents of the computer screens are so unimportant or hard-to-read that the filmmakers do not bother to spend much time (if any at all) ensuring that what is shown on the screen is accurate or even relevant to the film. They may be designed by artists not fully aware of the details of the plot, and as a result, their content (where it is intelligible, such as in a map) can have little to no connection to the dialog or other story events going on in front of them. They sometimes even contain jokes. It is rare, if ever, that important information would be communicated to the viewer through background computer screens. Hence, Cueball's spending most of his time watching the screens seems counter-intuitive to understanding and enjoying the film. Greenland , a large island east of Canada, is 80% covered in ice up to several kilometers in depth, and has a population of fewer than 100,000 people. Depending on the aliens' priorities (and the plot of the movie) there are myriad reasons both for and against wanting to land in such a remote area. In the title text, Cueball suggests investigating how a list of coordinates from another background screen relates to the location of the alien craft in Greenland, suggesting that Cueball thinks the filmmakers may have intended the viewers to record the information early in the film and analyze the data to learn relevant plot information - something that is very unlikely (and in the rare instance it is true, is intended to be superfluous). Most of the time, filmmakers take efforts to ensure the audience can easily follow plot points by making them more obvious than they might be in reality. What I pay attention to in movies: [A pie chart with a small piece (5%) in the upper right part labeled:] Plot, characters [The rest of the chart (95%) is labeled:] Computer screens shown briefly in the background [Below the chart Cueball, sitting on the floor, and Hairy, sitting in an armchair, are watching a movie on the TV. Cueball points the remote at the TV.] Cueball: Hang on– That blurry map behind the general shows one of the alien ships is in Greenland ! Why Greenland?! Hairy [quietly]: Can we please just watch the movie?

Jurassic World

Jurassic World

https://www.xkcd.com/1452

https://www.explainxkcd.com/wiki/index.php/1452:_Jurassic_World

[White Hat holding one hand up in front om him and Megan are walking together.] White Hat: In Jurassic World , we've used genetic engineering to create a better dinosaur. Megan: Tyrannosaurus is the most charismatic animal that ever lived, and you think you'll upstage it? [White Hat now holds both his hands up in front of him as he and Megan walk on.] White Hat: Tyrannosaurus was cool, but it's two decades old! Megan: I think it's a little older than that. [In this frame-less panel White Hat points up as they continue to walk.] White Hat: We took Tyrannosaurus and we improved it. Made it scarier, deadlier, smarter. White Hat: Look–there it is! [White Hat (drawn without his hat) and Megan are dwarfed in the bottom left corner as they stare up at a facsimile of the green T-Rex from Dinosaur Comics . They only reach T-Rex to it's knees.] The entire Dinosaur Comics was parodied in 145: Parody Week: Dinosaur Comics , where Randall copied the drawings himself, and T-Rex has appeared in one of the story lines in 1350: Lorenz (see this example story line and also the Dinosaur section under Lorenz themes ), where the actual images from the first three panels of Ryan's comic are used, just like here where it is the last panel which is used.

This strip refers to Jurassic World , the then new Jurassic Park movie, and the titular theme park. White Hat explains to Megan that, in their park, they have genetically engineered a better Tyrannosaurus . Megan doesn't feel that the historic Tyrannosaurus can be improved upon, but White Hat insists they've created an even more terrifying, smarter Tyrannosaurus for this new park. White Hat refers to Tyrannosaurus as "two decades old", indicating that he has switched topics from the movie's plot line to the animation techniques that created the Tyrannosaurus on-screen in 1993 versus today. Clearly, in the computer animation world, we should be able to create something more convincing with modern technology. Megan comments that she is fairly certain it is older than two decades, suggesting that she is referring to the actual Tyrannosaurus that lived millions of years ago. In the final panel, White Hat introduces the "new" Tyrannosaurus , who is immediately recognizable as the green Tyrannosaurus from Ryan North's Dinosaur Comics ; specifically, from the last panel of said webcomic - which in turn is from clip art . Anyone who has read so much as a handful of Dinosaur Comics will know that its Tyrannosaurus character "T-Rex" is about as far from smart and scary as it is possible for a Tyrannosaurus to be (see this example from the day this comic was released). The title text is an example of what T-Rex (the character) would say to a couple of humans, and it's a poor joke which would only be funny when it's a talking T-Rex saying it. Despite his goofy mannerisms, he is still a carnivore who attacks (or at least accidentally steps on) humans, as can be seen in panel 3 and 4 of the webcomic. [White Hat holding one hand up in front om him and Megan are walking together.] White Hat: In Jurassic World , we've used genetic engineering to create a better dinosaur. Megan: Tyrannosaurus is the most charismatic animal that ever lived, and you think you'll upstage it? [White Hat now holds both his hands up in front of him as he and Megan walk on.] White Hat: Tyrannosaurus was cool, but it's two decades old! Megan: I think it's a little older than that. [In this frame-less panel White Hat points up as they continue to walk.] White Hat: We took Tyrannosaurus and we improved it. Made it scarier, deadlier, smarter. White Hat: Look–there it is! [White Hat (drawn without his hat) and Megan are dwarfed in the bottom left corner as they stare up at a facsimile of the green T-Rex from Dinosaur Comics . They only reach T-Rex to it's knees.] The entire Dinosaur Comics was parodied in 145: Parody Week: Dinosaur Comics , where Randall copied the drawings himself, and T-Rex has appeared in one of the story lines in 1350: Lorenz (see this example story line and also the Dinosaur section under Lorenz themes ), where the actual images from the first three panels of Ryan's comic are used, just like here where it is the last panel which is used.

fMRI

fMRI

https://www.xkcd.com/1453

https://www.explainxkcd.com/wiki/index.php/1453:_fMRI

[Megan talking to an unseen audience in front of an fMRI brain scan.] Megan: Our fMRI study found that subjects performing simple memory tasks showed activity in the parts of the brain associated with loud noises, claustrophobia, and the removal of jewelry.

Functional magnetic resonance imaging (fMRI), as the name suggests, is an offshoot of the MRI. It shows brain activity, typically while the subject is performing tasks or responding to stimuli. During the test, the subject is laid in a relatively small cylinder inside a big, very loud, machine which produces extremely strong magnetic fields. To prevent damage or injury, the subject must remove all metal objects from their body, including piercings, jewelry, watches, etc. In the tests shown, the brain activity detected is a direct result of the testing environment itself, and has nothing to do with the simple tasks being performed by the subject. During fMRI participants hear loud noises, are confined in a small space (thus the claustrophobia) and have removed their jewelry. The researcher has mistaken these associated brain activities as effects as being caused by performing simple memory tasks which the participants have been asked to do and not a direct result of the settings of the test. Thus, the brain areas described by Megan are those associated with taking a functional MRI scan, rather than those associated with the "test" supposedly being carried out. The results being shown are known as artifacts , which are shown later in 1781: Artifacts . In real experiments, reported activity patterns are always a result of subtracting average brain activity from many samples gathered during task from so called resting-state activity - which is obtained while subjects are not engaged in any task, thus eliminating the effect the setting has on brain activity. Apparently, the researcher in the comic has failed to account for that in the analysis of the data. The title text raises the more difficult and controversial issues of methodology, saying that the subjects also showed activation in the parts of the brain associated with exposure to dubious study methodology . Here Randall makes fun of the overly confident, sweeping statements made by some fMRI researchers, often in the press. Of course, fMRI technique requires that the researcher account for several possible sources of errors by, among others, performing proper statistical analyses, multiple comparisons and using proper control groups. These are usually the reasons for fMRI criticism . See the link for further information, including a famous ironic study of a dead salmon which was shown various pictures of people while fMRI scans were made. The scans could be interpreted as showing meaningful brain activity, unless the multiple comparisons problem was properly addressed. Randall has previously made fun of geographic profiles falling to this trap in comic 1138 . The title text then continues with the jewelry issue, now especially the concern about unremoved piercings . In the worst case these could be ripped off by the strong magnetic field. So it could be of some concern - especially when you take into consideration some of the places people may have piercings that are not obvious to the MRI personnel! The final remark about activation regards exasperation with fMRI techs who won't stop talking about Warped Tour . " Warped Tour " refers to a traveling music festival that has been going since 1995, originally as a punk rock festival, but now with a more diverse set of music. Due to the nature of Mosh Pits , the loud, cacophonous music, the facial jewelry of concert-goers and the tight quarters of the pit make it similar in description to an MRI. [Megan talking to an unseen audience in front of an fMRI brain scan.] Megan: Our fMRI study found that subjects performing simple memory tasks showed activity in the parts of the brain associated with loud noises, claustrophobia, and the removal of jewelry.

Done

Done

https://www.xkcd.com/1454

https://www.explainxkcd.com/wiki/index.php/1454:_Done

Writer (typing): I had started to think I was asking too much, that I needed to settle. And then I found you half a world away. Writer (typing): I've been saving money. Six months from now, I'll be able to fly you here and support us for a while. Writer (typing): It's a long wait, but we'll talk every day until then. Maybe this won't work out, but I want to try. What do you think? Computer: ERROR : Your message could not be sent. [Refresh] Computer: ERROR : No connection. Writer: ?? Writer: Why can't I connect? Ponytail: Someone saw a ridiculous video and said "That's it. Shut down the Internet. We're done." So they did. Writer: ...But... I wasn't done.

This comic is a joke about the hyperbolic expression shut it down being taken literally. If someone thinks that a device has achieved its goal they shut it down. After an idea or product that people think is well made is created people will joke that the process that created it should be shut down, as if the process has achieved its ultimate purpose. This is most often used sarcastically for an inferior product or idea. Taking things literally is a common theme in the xkcd comics. Curly-hair sits at a computer anxiously and nervously writing a message to someone she cares about deeply, possibly a child to be adopted or a romantic interest. Curly-hair plans on saving enough money to have the person flown to her location from "half a world away." Curly-hair ends the message with a promise to communicate daily until the two are able to meet. When attempting to send the message, however, Curly-hair discovers that their internet connection is down and the message goes unsent. Ponytail explains there was a "ridiculous video" to which someone had commented "That's it. Shut down the Internet. We're done." This was taken literally and, because enough people agreed with this comment, the internet was shut down and Curly-hair was left unable to communicate with her love. The joke being that the internet was creating something far more valuable between Curly-hair and her love than a ridiculous video, thus highlighting the beautiful and far reaching potential impact of the internet. The likelihood of the entire internet being shut down based on a single comment being vanishingly low adds to the humor. In the final panel Curly-hair states wistfully that she was not done with the internet. The title text is Ponytail's response, which asserts Ponytail's belief that Curly-hair's message could not be important because the Facebook comment asserted that nothing of any significance could come from the internet after the ridiculous video. Writer (typing): I had started to think I was asking too much, that I needed to settle. And then I found you half a world away. Writer (typing): I've been saving money. Six months from now, I'll be able to fly you here and support us for a while. Writer (typing): It's a long wait, but we'll talk every day until then. Maybe this won't work out, but I want to try. What do you think? Computer: ERROR : Your message could not be sent. [Refresh] Computer: ERROR : No connection. Writer: ?? Writer: Why can't I connect? Ponytail: Someone saw a ridiculous video and said "That's it. Shut down the Internet. We're done." So they did. Writer: ...But... I wasn't done.

Trolley Problem

Trolley Problem

https://www.xkcd.com/1455

https://www.explainxkcd.com/wiki/index.php/1455:_Trolley_Problem

Cueball: Ever heard of the trolley problem? Black hat: No. What is it? Cueball: A trolley is barreling towards five helpless people on the tracks. You can pull a lever to direct it onto another track, but- Black hat: Can I reach the lever without getting up? Cueball: Wait, I'm not- Black hat: In this scenario, how busy am I? Cueball: I guess I forgot who I was talking to. Black hat: For a dollar, I'll promise to pull the lever if one of the five people is you.

The trolley problem is a thought experiment often posed in philosophy to explore moral questions, with applications in cognitive science and neuroethics . The general version is that an out of control trolley (or train) is heading towards 5 people on the track who can't get out of the way. On an alternative branch of the track is 1 person who can't get out of the way. The trolley can be diverted by using a lever, with the consequence of saving the 5 people but killing the 1 person. The choice is between a deliberate action that will directly kill one person, or allowing events to unfold naturally, resulting in five deaths. The question posed is whether or not it is morally right to pull the lever. The moral question is not as simple as it may first appear. This results of this test report that around 86% of respondents choose the utilitarian option of diverting the trolley. There are, however, several alternative formulations of the same basic dilemma. One such scenario allows you to stop the trolley by deliberately pushing "a very fat man" into its path, killing the man but saving the other five people. Another scenario involves selecting a healthy young and innocent person to die, in order to save five others going through organ donation. In both of these examples the basic dilemma is the same. However, most people reject the utilitarian option in these cases. After discovering a variation on this problem posed in a strip of the Saturday Morning Breakfast Cereal webcomic (which can be seen on the tablet he is carrying), Cueball , Black Hat's roommate, presents it to Black Hat . Before Cueball can finish explaining the problem, most notably leaving out the disadvantage to flipping the lever where it would kill one person, Black Hat questions whether he would need to get up to reach the lever and how much it would interrupt his other activities. As usual, he cares nothing at all about what happens to other people. This response is linked to another theory in philosophy, that of self interest or egoism or Objectivism , in which a person will choose the action with the most benefit for them personally. Black Hat then poses an offer: he promises to divert the trolley if Cueball is one of the five endangered people, provided that Cueball pays him $1 now. Again Black Hat is twisting the situation to his own benefit, in this case monetary. In the case of self-interest, the $1 could be the price at which Black Hat values his time and effort, below which he feels there is no benefit to himself in pulling the lever. Cueball decides that there is no point posing the problem to someone like Black Hat and gives up. This further shows that it is challenging for people with different ethical frameworks to function together without a common understanding, either mutually or with one side using that understanding to motivate a mutually agreeable or horrible solution. The title text follows this up by continuing Black Hat's offers. For $5 he will not deliberately arrange this situation and for $25 he will quit looking for further incentives. These attempts to exploit the thought exercise for personal gain further demonstrate Black Hat's cynical amorality. Black Hat's offer makes Cueball himself the subject of the trolley problem: Cueball now has a choice of expending $1 to save 5 people while sacrificing one person, or $5 to save all 6 people. Of course, he could dismiss the offer as a joke, if not for the person making it, which, as we know from other comics, is very much capable of such exploits. Cueball: Ever heard of the trolley problem? Black hat: No. What is it? Cueball: A trolley is barreling towards five helpless people on the tracks. You can pull a lever to direct it onto another track, but- Black hat: Can I reach the lever without getting up? Cueball: Wait, I'm not- Black hat: In this scenario, how busy am I? Cueball: I guess I forgot who I was talking to. Black hat: For a dollar, I'll promise to pull the lever if one of the five people is you.

On the Moon

On the Moon

https://www.xkcd.com/1456

https://www.explainxkcd.com/wiki/index.php/1456:_On_the_Moon

[Cueball and Megan are walking together heading right.] Cueball: If we could land a man on the Moon, why can't we- Megan: -land a man on the Moon? Cueball: ...ok, fair. But we're working on it, OK?

The phrase "If we can land a man on the Moon, why can't we <blank>" is commonly used to question a perceived shortcoming of some company, government or humanity in general. The Apollo program landed twelve astronauts on the Moon in six landing missions from July 1969 to December 1972 and returned all of those twelve astronauts safely to the Earth. However, from 1964 to 1967, there were eight deaths of astronauts or men training to be astronauts: three in the Apollo One fire, four in T-38 crashes, and one in an F-104 crash. The premise is usually that if "we" (whether referring generally to humanity, or specifically to the United States) have been able to achieve this extraordinary feat, our inability to achieve some lesser goal is questionable and/or ironic. Right after the Philae landing, the similar hashtag #WeCanLandOnACometButWeCant began on Twitter. Here, Megan cuts Cueball's argument's short by implicitly reminding him that humanity has not put another human on the Moon since the end of the Apollo program in December 1972 (nearly 42 years at the time this comic was published). New manned programs to return to the Moon, such as the Constellation Program , have been repeatedly cancelled. The Orion spacecraft , which will be capable of carrying humans beyond low Earth orbit for the first time in over 40 years, executed its first test flight on the day after this comic was published, Although this is outdated because NASA is planning to go to the moon again with the Artemis Program . The title text is a retelling of President Kennedy's famous inspirational address to the U.S. Congress in May 1961 ("I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth"), which set into motion the Apollo program, except that this time, the speaker is talking about putting a man on planet Venus . The aide presumably explains to the president that, unlike Moon, Venus has gravity close to that of the Earth, but what's more, its surface atmosphere density and pressure, and other factors including high temperature, strong winds and sulfuric acid clouds would make manned launch back to orbit practically impossible at our current technological level. As a result, the president backtracks from the goal of returning the astronauts safely to the Earth and comically limits the aspiration to landing an astronaut on Venus, full stop, without regard to the astronaut's safe return. This differs slightly from Kennedy's goal, which included the safe return of at least one astronaut from the moon. Although the overall 8:12 ratio of deaths to moonwalkers (during the period for Kennedy's speech to the end of the Apollo program) was too high to be considered "safe" by most standards, Kennedy had specified the safety only of the men who landed on the moon, and set a goal of "a" man returning safely. Technically, even if most of the men who landed died, as long as one returned safely by the end of 1969, Kennedy's goal would have been met. Kennedy's 1961 speech was also mentioned in the title text of 753: Southern Half . [Cueball and Megan are walking together heading right.] Cueball: If we could land a man on the Moon, why can't we- Megan: -land a man on the Moon? Cueball: ...ok, fair. But we're working on it, OK?

Feedback

Feedback

https://www.xkcd.com/1457

https://www.explainxkcd.com/wiki/index.php/1457:_Feedback

[Megan is looking up at Cueball who is standing on a chair facing away from her. He is holding a pineapple at breast height in his right hand while he is looking up at his smartphone, which he is holding up above head height in his left hand.] Megan: Why are you standing on a chair holding a pineapple? Cueball: I wasn't getting good reception but now I am! [Caption below the panel:] The erratic feedback from a randomly-varying wireless signal can make you crazy.

This comic is a joke about the psychological theory that animals conditioned using seemingly random rewards and punishments promotes superstitious behavior, and then extrapolates this theory to humans and Wi-Fi or (more likely) Cellular signal integrity. Often when connecting to unfamiliar Wi-Fi networks or when in a poorly covered area of a cell network, the signal displayed by the connecting device varies wildly, especially as distance increases. Poor wireless signal and drops in connection can be extremely frustrating, and hence Cueball has likely tried a variety of methods to improve the signal. As a result of his desperation, he replicates scenarios that are unlikely methods to increase his signal, but in some way mirror conditions where he has been successful finding a signal in the past. His past conditions have somehow led him to having the superstition that holding a pineapple while standing on top of a chair may resolve the problem. Likely, the signal increased at random while he was standing on a chair holding the pineapple, and he erroneously concluded that the chair and pineapple caused the signal strength increase. It is almost inconceivable that this technique could have any positive effect on the signal. This is related to the idea in comic 552: Correlation . See also the much later 2259: Networking Problems . Megan questions his ridiculous behavior, but it seems Cueball has become extremely erratic due to the inconsistent signal strength. The title text refers to a fictive study that apparently examined the behavior of rats in response to signal strength on a cellphone. It is a reference to B. F. Skinner 's experiments . In these experiments, rats and, more frequently cited, pigeons are taught superstitious behavior by being rewarded at random intervals. In this new experiment the rats naturally could not understand the concept of signal strength, so they chewed up the cellphone till they broke, leading to the research supervisors questioning the validity of the study and questioning whether the grant money for the study was well used. Skinner placed a series of hungry pigeons in a cage attached to an automatic mechanism that delivered food to the pigeon "at regular intervals with no reference whatsoever to the bird's behavior." He discovered that the pigeons associated the delivery of the food with whatever chance actions they had been performing as it was delivered, and that they subsequently continued to perform these same actions. One bird was conditioned to turn counter-clockwise about the cage, making two or three turns between reinforcements. Another repeatedly thrust its head into one of the upper corners of the cage. A third developed a 'tossing' response, as if placing its head beneath an invisible bar and lifting it repeatedly. Two birds developed a pendulum motion of the head and body, in which the head was extended forward and swung from right to left with a sharp movement followed by a somewhat slower return. Skinner suggested that the pigeons behaved as if they were influencing the automatic mechanism with their "rituals" and that this experiment shed light on human behavior. See this Mind Field episode where this experiment has been performed on humans! [Megan is looking up at Cueball who is standing on a chair facing away from her. He is holding a pineapple at breast height in his right hand while he is looking up at his smartphone, which he is holding up above head height in his left hand.] Megan: Why are you standing on a chair holding a pineapple? Cueball: I wasn't getting good reception but now I am! [Caption below the panel:] The erratic feedback from a randomly-varying wireless signal can make you crazy.

Small Moon

Small Moon

https://www.xkcd.com/1458

https://www.explainxkcd.com/wiki/index.php/1458:_Small_Moon

[Millennium Falcon follows a Tie Fighter towards an unidentified orb in the distance.] Luke Skywalker: He's heading for that small moon. Ben Kenobi: That's no moon - it's a space station. Luke Skywalker: It's too big to be a space station. Ben Kenobi: But it's too small to be a moon. [Three hours pass] Ben Kenobi: Fine! What if we agree it's not a moon, but we make a new category called "Dwarf Moon"? Luke Skywalker: And what's the cutoff, asshole?! Is this ship a dwarf moon now? Ben Kenobi: Screw you.

The comic depicts a classic scene from Star Wars Episode IV , in which the heroes trail a TIE fighter to the never-before-seen Death Star : a super-weapon the size of a small moon capable of demolishing entire planets. In the original scene and the comic, Luke Skywalker misidentifies a body as a natural satellite, and Obi-Wan 'Ben' Kenobi ominously corrects him. The comic's version diverges at this point, as the dialogue devolves into a rather bitter argument over the semantics of size classifications, alluding to scientific discussions on whether Pluto should be classified as a planet or as a dwarf planet . The argument goes on for hours, which in the original plot would suggest one of two situations: The argument is confused as to whether they're talking about size or about natural vs artificial objects. In terms of size, the Death Star is much larger (70 km radius) than dozens of full-fledged moons in our solar system. One of the smallest moons found so far in the solar system is S/2009 S 1 , which is about 400 meters in diameter and orbits Saturn. But we don't generally speak of the tiny rocks in the rings of Saturn as moons, so there is some distinction there, which may include the orbit of the object [1] . There is also the distinction between natural moons and spacecraft, which seems to be ignored in the final panel. The title text makes reference to a later scene in the film when Rebel pilots are being briefed on the planned attack on the Death Star. Those who analysed the plans for the Death Star run into the same discussion picture, and end up arguing about the classification of the Death Star, dividing those involved into the 'artificial moonlet' camp and the 'rogue planet-station' camp, thus deunifying the rebellion. If events are otherwise the same from the movie, this is also happening at threat of their destruction, and thus a crippling of the Rebellion. The timing of the comic may be related to the New Horizons mission to Pluto . The spacecraft awoke from hibernation 4 days earlier, on December 6, 2014, to start the encounter phase with Pluto. [Millennium Falcon follows a Tie Fighter towards an unidentified orb in the distance.] Luke Skywalker: He's heading for that small moon. Ben Kenobi: That's no moon - it's a space station. Luke Skywalker: It's too big to be a space station. Ben Kenobi: But it's too small to be a moon. [Three hours pass] Ben Kenobi: Fine! What if we agree it's not a moon, but we make a new category called "Dwarf Moon"? Luke Skywalker: And what's the cutoff, asshole?! Is this ship a dwarf moon now? Ben Kenobi: Screw you.

Documents

Documents

https://www.xkcd.com/1459

https://www.explainxkcd.com/wiki/index.php/1459:_Documents

[White Hat is sitting at his PC. Cueball stands behind him looking over his shoulder at the screen.] PC: Untitled 138.docx Untitled 241.doc Untitled 138 copy.docx Untitled 138 copy2.docx Untitled 139.docx Untitled 40 MOM ADDRESS.jpg Untitled 242.doc Untitled 243.doc Untitled 243 IMPORTANT.doc Untitled 41.jpg [The remaining file names are only partially visible through the tail of the PC's "speech" bubble.] 42 43 4 Cueball: Oh my god. [Caption below the panel:] Protip: Never look in someone else's documents folder.

When saving documents, the user is typically prompted to choose a filename, which may seem like a trivial choice. However, the filename is often the primary way of identifying the document you are looking for, and a descriptive title is of huge benefit when trying to find a certain document. Those who are too rushed or too lazy to create a useful filename, or those who don't understand what constitutes a useful filename are setting themselves up for future frustration. When a user creates a new copy of a file in the same directory, the operating system may automatically append "copy" or "Copy of" to the filename. Subsequent copies of the file have "copy 2", "copy 3", etc. appended. When searching documents later, the user may struggle to remember which copy is the correct one to use. This comic portrays a person, in this case White Hat , who has taken such a naming convention to an extreme, giving hundreds of documents essentially the same confusing or useless filename. Cueball appears to have a severe distaste for this convention (or may just be in shock at how one could be so lazy or incompetent in the short term to suffer through or ignore the consequences in the long term) and hence provides a protip to never look in someone else's documents folder for the fear of finding these irritating details. The .doc and .docx extensions are given to documents created in Microsoft Word, with .docx being the default option from Microsoft Office 2007 onwards. When first saving a document, many programs will default to "Untitled", adding numbers to the end as more are created. However, in Microsoft Word the default filename is the first sentence of the document; if the document is still empty, the default filename is "Doc1" with the number increasing each time. In order to get such a file directory, White Hat would have to manually title all of his documents "Untitled". He appears to frequently make copies, and occasionally made copies of the copies, only very rarely adding a keyword to the file name like "important". In some cases he has added a minimal amount of detail to the filename, though hasn't removed the redundant "untitled copy" portion, which probably only adds to Cueball's frustration, as it demonstrates that White Hat does have at least a basic understanding of the importance of meaningful filenames, but still hasn't made any attempt to address the systemic problem. The Untitled 40 MOM ADDRESS.jpg is an image file (jpg), not something that would normally be used to store someone's address, though it could be a map or a picture of an envelope. It is the first jpg file on the list, but that last full filename is also a jpg with number 41, and below in the "speech" line down to the PC the next three files have number 42, 43 and something beginning with 4. So here the numbering of jpg files continue. The .doc numbering goes from 241 to 243, and then 243 IMPORTANT. The .docx only increases from 138 to 139, but there are two extra copies of the 138 document. The filenames are not in alphabetical order as 241 and 40 falls out of place. This likely means that there is no automatic sorting all (i.e., they are sorted by hand), or that they are sorted by time stamp. Sorting by timestamp can be very useful, especially if you use White Hat's naming scheme. But this also means that he still uses .doc (copies old files) after he has obtained the new Microsoft Office 2007 that used .docx. The title text can refer to one of two common quirks in Windows/Office. One is of copying and pasting within the same folder on a Windows PC. The copy of the file will default to the name "Copy of <original title>", a second copy becomes "Copy of Copy of <original title>" and so forth. The other common quirk that can produce file names like this relates to how Microsoft Office handles downloaded file(s) that are not saved (i.e. "Open" instead of "Save"), the file is actually saved in a temporary folder allowing you to look at and/or edit the file - usually with restrictions on doing so until you actually save a copy in an actual folder somewhere. Oftentimes, especially within an office network where files are passed around via email, the other person may just open a file, editing it, then proceeding to save it as required. Upon attempting to save, the program will prompt one to "Save a copy of the original file", as the original file was never actually saved on the hard drive but just opened from a temporary folder, adding the phrase "copy of" to the filename, regardless of its final location. Forwarding this file will continue this trend adding the phrase "copy of" every time someone opens, edits then saves the file (rather than save the file then edit it), thus creating repetitive use of "copy of" within the same name. In a file that is heavily edited and passed around via email like this, if care is not taken to edit the file name, the name may get up to 5 or 6 repeats of the phrase "copy of". It is rather extreme to get to a 33rd copy of the original untitled.doc file as shown here, however, as a result the file name is 276 characters long (including the four from the .doc extension), an impossible file name in most operating environments because it is too long. 255 characters is the limit for any file or folder name in Linux, and is the limit for a fully defined file name (file name, extension and the full folder path in which the file is stored in) in Windows. So the file name is 22 characters too long for Linux and at least 25 characters too long for Windows since being in the root of drive takes 3 characters, each folder adds at least 2 characters (one chosen and the backslash). Whereas such long names for a file may be uncommon, it is not uncommon in Windows that users run out of characters for the full name and path, if they have several sub folders. Note that when performing this type of copying on Windows 7, the new file is named "<original name>_2", not "Copy of <original name>". [White Hat is sitting at his PC. Cueball stands behind him looking over his shoulder at the screen.] PC: Untitled 138.docx Untitled 241.doc Untitled 138 copy.docx Untitled 138 copy2.docx Untitled 139.docx Untitled 40 MOM ADDRESS.jpg Untitled 242.doc Untitled 243.doc Untitled 243 IMPORTANT.doc Untitled 41.jpg [The remaining file names are only partially visible through the tail of the PC's "speech" bubble.] 42 43 4 Cueball: Oh my god. [Caption below the panel:] Protip: Never look in someone else's documents folder.

SMFW

SMFW

https://www.xkcd.com/1460

https://www.explainxkcd.com/wiki/index.php/1460:_SMFW

[Cueball is sitting at a desk, crouched over a laptop.] [Caption below the panel:] SMFW an acronym almost makes sense The name of the comic xkcd is itself a false acronym – from the xkcd about page : "It's not actually an acronym. It's just a word with no phonetic pronunciation -- a treasured and carefully-guarded point in the space of four-character strings."

Randall gives some examples of confusing acronyms that closely resemble more commonly-used acronyms. He depicts Cueball apparently puzzling over the meaning of one such acronym. "SMFW", the title of the comic and an acronym used as the caption, is very close to a number of other common acronyms, including: The title text contains more examples of imaginary acronyms of a similar nature: Below are possible examples of potential (already existing, albeit rare) representations for each acronym, according to the Urban Dictionary : Knowing Randall, the sentences given in the comic proper and title text were probably made without an actual meaning in mind. Nevertheless, the sentence in the comic has a very plausible interpretation: "So Much Frustration When an acronym almost makes sense." Other plausible interpretations of the acronym could be "So Much Fun When" or "See My Face When". Even the absurdly cryptic title text has a plausible translation: "What The Fuck, World? (WTFW) it's like Some Moron's Horrible Opinion (SMHO) To Be Fucking Honest (TBFH), I'm Done, Bye. (IMDB)". [Cueball is sitting at a desk, crouched over a laptop.] [Caption below the panel:] SMFW an acronym almost makes sense The name of the comic xkcd is itself a false acronym – from the xkcd about page : "It's not actually an acronym. It's just a word with no phonetic pronunciation -- a treasured and carefully-guarded point in the space of four-character strings."

Payloads

Payloads

https://www.xkcd.com/1461

https://www.explainxkcd.com/wiki/index.php/1461:_Payloads

[This comic is a wide drawing, with a larger drawing that can be reached by clicking the small picture on xkcd. In the smaller picture shown on xkcd only the text that is not red can be read. The transcript below is thus for the large drawing. It is divided into three horizontal sections. The first section is black and shows spacecrafts, the second is white and shows launch vehicles, and the third is black again showing a timeline ranging from 1950 to the future. The vehicles are shown by the proper number of horses, and when that weight is less than one full horse also in the weight of other smaller animals.] [The black section:] Spacecraft mass Measured in horses Sputnik -- <1 horse (2 dogs ) Vanguard 1 -- <1 horse (Squirrel ) Pioneer 5 -- <1 horse (Large dog) Mariner 2 (United States) -- <1 horse (3 dogs ) Venera 1 (USSR) -- 1 horse Apollo -- 67 horses Venera 7 -- 3 horses Pioneer 10 -- <1 horse (7 dogs) Skylab -- 171 horses Venera 9 -- 11 horses Voyager 2 -- 2 horses Shuttle (Total) -- 206 horses Shuttle Payload -- 54 horses Mir -- 288 horses T-Rex -- 15 horses Hubble -- 25 horses Compton Gamma Ray Observatory -- 38 horses Keyhole 3 -- Spy satellite International Space Station -- 932 horses Cassini -- 11 horses Huygens lander -- 1 horse Rosetta -- 6 horses Opportunity -- <1 horse (5 dogs) Dawn -- 3 horses Terrastar -- 15 horses Dragon -- 17 horses Tiangong-1 -- 19 horses Curiosity -- 2 horses Keyhole 7 -- 40 horses Orion (capsule) -- 20 horses James Webb Telescope -- 14 horses [20 horses:] Orion [25 horses:] Orion Service Module [65 horses:] Orion Deep-Space Habitat [The white section:] Launch vehicle capacity (Payloads to low earth orbit) Measured in horses Sputnik Launcher -- 1 horse Thor -- <1 horse (3 dogs) Mercury-Atlas -- 3 horses Saturn I -- 20 horses Proton-K -- 44 horses Atlas-Centaur -- 8 centaurs Titan IIIA -- 7 horses Saturn IB -- 45 horses Soyuz -- 14 horses Saturn V -- 262 horses Black Arrow -- <1 horse (4 dogs) N1 -- 211 horse -- Exploded on Launch pad Long March 1 -- 2 horses N-I (Japan) -- 4 horses Delta 0900 -- 3 horses Ariane 1 -- 3 horses SLV (India) -- <1 horse (1 dog) N-II -- 4 horses 1981 Oldsmobile -- 4 horses ASLV -- <1 horse (4 dogs) Long March 4A -- 9 horses Ariane 4 -- 16 horses Shavit (Israel) -- <1 horse (6 dogs) Energia -- 218 horses Pegasus -- 1 Pegasus Atlas I -- 13 horses PSLV -- 8 horses J-I -- 2 horses Long March 3B -- 27 horses H-IIA -- 22 horses Delta IV-H -- 64 horses Falcon 1 -- 1 horse Ariane 5ES -- 47 horses H-IIB -- 37 horses Unha (North Korea) -- <1 horse (2 dogs) Atlas V 541 -- 38 horses Falcon 9 -- 29 horses Antares -- 14 horses Stratolaunch -- 14 horses Falcon Heavy -- 118 horses SLS Block 1 -- 156 horses SLS Block 1B -- 217 horses SLS Block 2 -- 289 horses [The timeline:] 1950s, 1960s, 1970s, 1980s, 1990s, 2000s, Future A larger transcript with image descriptions can be found here: Full transcript

This comic is an infographic representing the launch mass of various spacecraft and artificial satellites, and the low Earth orbit payload capacity of various space launch vehicles. Rather than using standard units of mass such as kilograms or pounds, Randall has assigned values based on the mass of a horse. Based on cross checking researched masses and payloads with the number of horses depicted, it appears that one horse unit is defined as 450 kg (with an average of 432.82 kg), or perhaps 1000 lb. In cases where the mass is less than one horse, an alternative measure of dogs has been used, where one dog appears to be roughly 40 kg (with an average of 48.05 kg, or perhaps 100 lb.). In the case of Vanguard 1 , even a dog is too large a measure, so instead the unit squirrel is used to represent its 1.47 kg (3.5 lb.?) mass. The overall comic may be an allusion to horsepower , a similar-sounding but completely different concept. Horsepower is a measurement of power ( work per unit time). Another commonly referenced unit for power is the watt . 1 horsepower is meant to be approximately the amount of power a horse can deliver. In contrast, Randall uses the horse to measure mass (of particular spacecraft, and of the maximum payload launch vehicles can carry). The top pane of the comic (black background) shows the mass of various spacecraft, while the bottom (white background) shows the payload capacity (to low Earth orbit) of launch vehicles. Along the bottom of the image is a timeline, relating to the launch date of the entries. There are also several joke insertions: The Pegasus, 1981 Oldsmobile, and Stratolaunch spacecraft are depicted horizontally, because these vehicles launch from a horizontal starting position and use forward momentum to facilitate their launch. An unlabelled launch vehicle is shown below the H-IIA near 2002. From the payload and date it is believed to represent the Delta IV M . Whether its lack of labelling is intended or a mistake is unknown. The title text refers to a favourite subject of Randall's - The space elevator . A space elevator is a (currently theoretical) mechanism for travelling into space, consisting of a very long (>35,000 km) cable and counterweight connected to the Earth at the equator. The cable rotates at the same rate as the earth, and thus appears stationary when viewed from earth. It is then possible to climb the cable into space, and even use it as a slingshot to launch vehicles. In the title text, the amount of power required to lift a horse into space has been investigated, with the launch capacity of a backyard solar array and large power station compared. The orbit to launch horses is not precised, though; from the space elevator, the only circular orbit easily achievable is geostationary orbit, and getting into Low Earth Orbit is only slightly easier than without the elevator. Assuming the lowest stable orbit (that is, above the atmosphere), required power output of the solar array is about 315-350 kW and the power station at 3.3-3.7 GW. The tables below contain data relating to each entry on the comic image. Where the researched launch date or mass/payload don't seem to match the comic, they should be identified with ? [This comic is a wide drawing, with a larger drawing that can be reached by clicking the small picture on xkcd. In the smaller picture shown on xkcd only the text that is not red can be read. The transcript below is thus for the large drawing. It is divided into three horizontal sections. The first section is black and shows spacecrafts, the second is white and shows launch vehicles, and the third is black again showing a timeline ranging from 1950 to the future. The vehicles are shown by the proper number of horses, and when that weight is less than one full horse also in the weight of other smaller animals.] [The black section:] Spacecraft mass Measured in horses Sputnik -- <1 horse (2 dogs ) Vanguard 1 -- <1 horse (Squirrel ) Pioneer 5 -- <1 horse (Large dog) Mariner 2 (United States) -- <1 horse (3 dogs ) Venera 1 (USSR) -- 1 horse Apollo -- 67 horses Venera 7 -- 3 horses Pioneer 10 -- <1 horse (7 dogs) Skylab -- 171 horses Venera 9 -- 11 horses Voyager 2 -- 2 horses Shuttle (Total) -- 206 horses Shuttle Payload -- 54 horses Mir -- 288 horses T-Rex -- 15 horses Hubble -- 25 horses Compton Gamma Ray Observatory -- 38 horses Keyhole 3 -- Spy satellite International Space Station -- 932 horses Cassini -- 11 horses Huygens lander -- 1 horse Rosetta -- 6 horses Opportunity -- <1 horse (5 dogs) Dawn -- 3 horses Terrastar -- 15 horses Dragon -- 17 horses Tiangong-1 -- 19 horses Curiosity -- 2 horses Keyhole 7 -- 40 horses Orion (capsule) -- 20 horses James Webb Telescope -- 14 horses [20 horses:] Orion [25 horses:] Orion Service Module [65 horses:] Orion Deep-Space Habitat [The white section:] Launch vehicle capacity (Payloads to low earth orbit) Measured in horses Sputnik Launcher -- 1 horse Thor -- <1 horse (3 dogs) Mercury-Atlas -- 3 horses Saturn I -- 20 horses Proton-K -- 44 horses Atlas-Centaur -- 8 centaurs Titan IIIA -- 7 horses Saturn IB -- 45 horses Soyuz -- 14 horses Saturn V -- 262 horses Black Arrow -- <1 horse (4 dogs) N1 -- 211 horse -- Exploded on Launch pad Long March 1 -- 2 horses N-I (Japan) -- 4 horses Delta 0900 -- 3 horses Ariane 1 -- 3 horses SLV (India) -- <1 horse (1 dog) N-II -- 4 horses 1981 Oldsmobile -- 4 horses ASLV -- <1 horse (4 dogs) Long March 4A -- 9 horses Ariane 4 -- 16 horses Shavit (Israel) -- <1 horse (6 dogs) Energia -- 218 horses Pegasus -- 1 Pegasus Atlas I -- 13 horses PSLV -- 8 horses J-I -- 2 horses Long March 3B -- 27 horses H-IIA -- 22 horses Delta IV-H -- 64 horses Falcon 1 -- 1 horse Ariane 5ES -- 47 horses H-IIB -- 37 horses Unha (North Korea) -- <1 horse (2 dogs) Atlas V 541 -- 38 horses Falcon 9 -- 29 horses Antares -- 14 horses Stratolaunch -- 14 horses Falcon Heavy -- 118 horses SLS Block 1 -- 156 horses SLS Block 1B -- 217 horses SLS Block 2 -- 289 horses [The timeline:] 1950s, 1960s, 1970s, 1980s, 1990s, 2000s, Future A larger transcript with image descriptions can be found here: Full transcript

Blind Trials

Blind Trials

https://www.xkcd.com/1462

https://www.explainxkcd.com/wiki/index.php/1462:_Blind_Trials

[Megan is pointing at charts hanging on the wall.] Megan: We've designed a double-blind trial to test the effect of sexual activity on cardiovascular health. Both groups will think they're having lots of sex, but one group will actually be getting sugar pills. The limitations of blind trials

In research, a blind trial is an experiment where certain information about the test is concealed from the subjects and/or the testers, in order to reduce sources of bias in the results. A double-blind trial is one where neither the subject nor the testers know who has or has not received treatment (or for multiple treatments, which treatment). A scientific approach also requires the use of control groups to determine the significance of observations in (clinical) trials. The members of the control group receive either no treatment or the "standard" treatment. However, to ensure "blindness" in the study, even if a control group is to receive no treatment, they must be given a placebo : an ineffective treatment given to ensure the doctors and/or patients are unaware whether they are being given the treatment. For example, in clinical drug trials, when a treatment being tested is administered in the form of a pill, a visually-identical inert pill is given to the control group so no one will know if a subject has been given the treatment or a placebo. In pop culture, placebos in pill-form are often made of sugar, which has negligible medical effects. Controls and blinding are crucial to distinguish the actual effects of the treatment from the placebo effect , or the psychologically-induced effects of a subject's belief that a treatment will or will not help them, which may have real physiologic effects or influence the reporting of subjective measures such as pain level or the presence of side effects. It is vital that there are no clues available to distinguish between the different groups. Even subtle cues from the body language of the testers are sufficient to trigger placebo effect, making double-blind trials necessary. Challenges exist in designing placebo alternatives to certain physical treatments that might be tested, such as acupuncture; in this case the best quality trials have typically used either special 'joke' retractable needles that only give the illusion of proper penetration or the practitioner/researcher deliberately and safely avoids the traditional meridians on the body for the treatment concerned so that the patient remains 'blind' to their role in the trial. The practitioner must otherwise be consistent in treatment between groups and not be involved in the medical assessment phase for properly double-blinded conditions, where the most reliable results still seem to only show a significant placebo effect at work. There are, however, certain cases where it is almost impossible to make the experience of the control group identical to that of the test group. Making a real and fake pill appear the same is a relatively trivial task, and the ignorance of participants to the details of a given established practice or procedure can allow for a certain level of blinding. However, it would be challenging (to say the least) to make the control group in the described experiment think that they are having lots of sex, when in fact they are not. The description of the control group as taking sugar pills is a laughably poor placebo substitute, as the pills themselves may affect cardiovascular health, therefore ruining the concept of a controlled experiment , especially if it is a double-blind trial, and nobody knows who got sugar and who got sex. Scientific research involving humans is extremely challenging to conduct because of the difficulty in finding appropriate control groups. This is one of the reasons animal experiments (for instance involving inbred strains of mice) are so common. The title text adds another twist by taking “blind” literally, and noting that for some people, being blindfolded increases their enjoyment of sexual activity, thereby acting as a confounding variable. Despite this, it should be noted that Cardiovascular health is typically measured in terms of objective data such as cholesterol levels, ejection fraction, and morbidity/mortality data like the frequency of myocardial infractions, strokes, or sudden cardiac death. Even sighted, it would be difficult for either subjects or researchers to manipulate this kind of data. [Megan is pointing at charts hanging on the wall.] Megan: We've designed a double-blind trial to test the effect of sexual activity on cardiovascular health. Both groups will think they're having lots of sex, but one group will actually be getting sugar pills. The limitations of blind trials

Altitude

Altitude

https://www.xkcd.com/1463

https://www.explainxkcd.com/wiki/index.php/1463:_Altitude

Because of low oxygen, astronomers working at high altitude telescopes may need to write down their plans ahead of time while at sea level. [Some astronomers are inside a sea-level research facility.] Astronomer #1: Ok, let's head up to the observatory. [The astronomers drive uphill.] Astronomer #1: When we reach the summit, we'll check the iodine cell and do a general calibration. Astronomer #2: Sounds good. [The astronomers have reached the high-altitude observatory.] Astronomer #1: My head feels funny. Astronomer #2: Look at those telescope domes. I hope they don't roll away. Astronomer #1: Maybe we should tape them down. [The astronomers are inside one of the domes.] Astronomer #1: Haha, look at this mirror! My face is huge! Astronomer #2: I see your face in the telescope! I discovered you! Astronomer #1: Let's make out!

In this comic, Randall is making fun of how oxygen deprivation can lead to reduced mental acuity. Dizziness, lightheadedness, impaired judgment, and euphoria are symptoms of oxygen deprivation, or hypoxia. Those researchers would benefit from having a written list or plan developed while they were still functioning at peak mental acuity. Note that high altitude does not lead to severe effects as described in the comic. Here, two astronomers are heading up a mountain, towards the observatory they work at. Initially, they discuss what they are planning on doing once they reach the summit, mentioning Iodine cells , used for wavelength calibrations of high-resolution RV spectra between 501 and 610 nm. As they continue, the mental clarity of the researchers devolves as they approach the high altitude telescope, leading to increasingly juvenile and almost intoxicated behavior. One researcher mentioned her head feels funny, while the other makes a remark about taping down the observatories to prevent them from rolling away, an absurd remark considering observatories are firmly rooted and even if they weren't, tape would not be sufficient to stop them ( [ citation needed ] ; enough tape can hold anything). Once inside the observatory, they have completely forgotten about their original plans. Instead of doing a general calibration, they are playing with the telescopes, looking at each other's faces through them and deciding to make out with each other. This is why Randall mentions that astronomers working at high altitude observatories must write down their plans ahead of time at sea level, as the low oxygen leads to reduced mental acuity. It should be noted that the phrase "low oxygen" refers to the lower partial pressure of oxygen at altitude. The proportion of oxygen at high elevations is still approximately a fifth of the atmosphere, the same as at sea level. The altitude sickness is caused by lowered atmospheric pressure which leads to smaller amount of oxygen actually delivered ("pushed") into bloodstream. The title text refers to a laser guide star a device for focusing telescopes by making artificial reference points in the sky. The reference points are created by shooting a powerful laser into the sky. The concern of the astronomer in the comic is that an imagined "star cat" may be attracted to the laser in the same way that cats playfully chase laser beams projected on surfaces. Cats' reactions to laser pointers were previously explored in 729: Laser Pointer . Because of low oxygen, astronomers working at high altitude telescopes may need to write down their plans ahead of time while at sea level. [Some astronomers are inside a sea-level research facility.] Astronomer #1: Ok, let's head up to the observatory. [The astronomers drive uphill.] Astronomer #1: When we reach the summit, we'll check the iodine cell and do a general calibration. Astronomer #2: Sounds good. [The astronomers have reached the high-altitude observatory.] Astronomer #1: My head feels funny. Astronomer #2: Look at those telescope domes. I hope they don't roll away. Astronomer #1: Maybe we should tape them down. [The astronomers are inside one of the domes.] Astronomer #1: Haha, look at this mirror! My face is huge! Astronomer #2: I see your face in the telescope! I discovered you! Astronomer #1: Let's make out!

Santa

Santa

https://www.xkcd.com/1464

https://www.explainxkcd.com/wiki/index.php/1464:_Santa

Megan: Say Santa eats a cookie at every few houses. That's hundreds of tons. By the end of the night, he should be a hulking seven-story behemoth. But he's not. Cueball: What are you... Megan: Does Santa poop in our houses? Cueball: No way. Megan: That mass must be going somewhere. Cueball: He has that magic bag... Megan: You think he poops in the bag of presents ? Cueball: Maybe instead of pooping in every few houses, he waits, and then in a few houses, he poops a lot . Megan: What if no one's been that naughty? Cueball: He picks at random. The needs of the many...

This was the Christmas comic for 2014 and broadly speaking, this comic follows a long list of issues raised about physical limitations Santa Claus faces, similar to other popular theoretical discussions such as the speed he has to travel and the omniscience he purportedly possesses and the mass of presents he has to carry — the story of Santa Claus was simply never designed for a world with over 7 billion people spread through untold millions of homes. This comic combines some basic physiology with the physical law of the conservation of mass . More specifically, this comic refers to the common tradition of leaving milk and cookies out on Christmas Eve for Santa Claus. If one assumes that Santa eats even a small percentage of the sweets left out for him, the question comes up where all the cookies go . Megan suggests that, since Santa isn't that large, he must poop them out somewhere, and wonders if he does so in our houses. Cueball doubts that. Megan replies that mass cannot disappear completely; it has to go somewhere, to which Cueball comments that Santa has a magic bag in which he could poop. The magic bag referenced is the bag in which he carries all the Christmas presents he delivers on Christmas Eve. It is called 'magic' because a bag large enough to carry billions of presents would be much too heavy and unbalanced to carry on a sleigh pulled by only eight (or nine) reindeer. Thus, it must be magic somehow. Megan is disgusted at the thought of Santa pooping on peoples' presents. An even more disgusting explanation is that the 'magic' bag might transform the poop into presents, in which case it would not need to carry many presents at a time. Cueball proposes a third theory: that Santa only poops in a few houses, leaving large quantities in those houses. Megan says that there may not be anyone that naughty in the world, referencing the myth that Santa will leave coal instead of presents for those who misbehave. Cueball replies that it is randomly determined whose house is pooped in, burdening a smaller number of people. Specifically, Cueball quotes the beginning of Spock 's aphorism from Star Trek II , "The needs of the many outweigh the needs of the few, or the one." The quote is used to justify the sacrifice people make in "allowing" Santa to poop in their homes by citing the numerous other people who are spared his feces. The title text puts forth yet another theory: that Santa doesn't poop in houses at all, but off the side of his sleigh. This may be equally disgusting to anyone or anything unlucky enough to abruptly receive a rain of poop from the sky. This problem could be minimized by taking advantage of flights over water or uninhabited areas, rather than cities. According to 1070: Words for Small Sets , a few is referring to "anywhere from 2 to 5". Currently, there are 1.9 billion children in the world, so assuming on average that one cookie is left for Santa for each child and that Santa eats one in every 5 cookies, he consumes 380 million cookies in two 48 hour periods. Due to the convenience of time zones, approximately 48 hours from when a day starts in Kiritimati until it ends in Hawaii; also, most western Christians, including Roman Catholics and Protestants, observe Christmas almost two weeks before Eastern Orthodox Christians do. According to Google, a chocolate-chip cookie contains approximately 140 kilocalories, therefore Santa consumes 53.2 billion kilocalories in the period of 2 days, or 26.6 billion kilocalories per day. As the average human daily intake is 2500 kilocalories per day, Santa has eaten 10,640,000 times the amount of daily kilocalories required by one human over the period of two days, an amount otherwise sufficient to last for over 59,111 years for a human, and producing 20 million pounds of feces. However, if we consider the dietary requirements of both Santa and the flying reindeer, and the kilocalories that reindeer would burn flying around the world carrying 1.9 billion toys, the cookies might not be sufficient. If the 1 in 5 cookies are not sufficient energy intake, Santa could probably eat every cookie left for him, which amounts to 266 billion kilocalories in the period of 2 days. On a side note, this amount of energy is enough to power several thousand homes for a year. Megan: Say Santa eats a cookie at every few houses. That's hundreds of tons. By the end of the night, he should be a hulking seven-story behemoth. But he's not. Cueball: What are you... Megan: Does Santa poop in our houses? Cueball: No way. Megan: That mass must be going somewhere. Cueball: He has that magic bag... Megan: You think he poops in the bag of presents ? Cueball: Maybe instead of pooping in every few houses, he waits, and then in a few houses, he poops a lot . Megan: What if no one's been that naughty? Cueball: He picks at random. The needs of the many...

xkcd Phone 2

xkcd Phone 2

https://www.xkcd.com/1465

https://www.explainxkcd.com/wiki/index.php/1465:_xkcd_Phone_2

[An image of a smartphone lying down with many labels pointing to different parts of it. Above the screen are several small features, below only a central oval button and on the bottom a central socket and a square feature to the right. Clockwise from the top left the labels read:] MaxHD: Over 350 pixels per screen Always-on speaker Blood pressure reliever Auto-rotating case Ribbed Waterproof (interior only) Googleable Cheek toucher Cries if lost Bug drawer Coin slot Scroll lock OS by Stackoverflow® 3D materials Dog noticer FitBit® fitness evaluator Volume and density control [Below the phone:] Introducing The xkcd phone 2 A phone for your other hand®

This is a followup to 1363: xkcd Phone , which debuted the original xkcd phone almost nine months prior to this one. This thus became the second entry in what turned out to become an ongoing xkcd Phone series which parodies common smartphone specs by attributing absurd or useless features to a fictional phone that sounds impressive but would actually be very impractical. The next in the series 1549: xkcd Phone 3 was released just over half a year later. Like the previous xkcd phone, the advertisement features a useless tagline (very few people can use two phones at the same time) and touts a variety of features which are either pointless, misleading, or physically impossible. Clockwise, from the top left, they are: Note: A high pixel density display is more than 200 pixels per inch , not per screen . An example would be the Retina Display in Apple hardware which varies from 218 pixels per inch to 401 pixels per inch depending on the device. Like the previous xkcd phone comic, the title text continues the list of features: [An image of a smartphone lying down with many labels pointing to different parts of it. Above the screen are several small features, below only a central oval button and on the bottom a central socket and a square feature to the right. Clockwise from the top left the labels read:] MaxHD: Over 350 pixels per screen Always-on speaker Blood pressure reliever Auto-rotating case Ribbed Waterproof (interior only) Googleable Cheek toucher Cries if lost Bug drawer Coin slot Scroll lock OS by Stackoverflow® 3D materials Dog noticer FitBit® fitness evaluator Volume and density control [Below the phone:] Introducing The xkcd phone 2 A phone for your other hand®

Phone Checking

Phone Checking

https://www.xkcd.com/1466

https://www.explainxkcd.com/wiki/index.php/1466:_Phone_Checking

[Cueball approaching Megan.] Cueball: What's up? Megan: They're announcing the winner of the compulsive phone-checking championship. [Megan checks her phone.] [Megan puts her phone away.] [Megan checks her phone again.] Cueball: Did you win? Megan: Site's down. Cueball: Weird. Megan: I'll keep refreshing.

Cueball asks Megan what's up, and Megan announces that there's a Compulsive Phone Checking Championship, presumably an award for the person who checks their phone the most often. Megan checks her phone to see if the winner has been announced, but finds the site's server is overloaded , which would be exactly what would happen if many people were checking their phones simultaneously. Given the nature of the contest, we can presume this is indeed the case. As a solution, Megan tries refreshing repeatedly, sending more load to the server and, thus, making it unavailable longer. This compulsive behavior predates the popularity of mobile phones as shown in 477: Typewriter and 862: Let Go . Another possible analysis is that the site was purposely down, and instead was the contest itself, to see how many times different users would refresh the page within a time period, or perhaps to the last one standing, determining the winner. The title text implies that Megan checks her phone so compulsively she even does it in her sleep. This probably contributed to her victory. A "webite" is probably either a typo of "website" or a pinned tab in a web browser. [Cueball approaching Megan.] Cueball: What's up? Megan: They're announcing the winner of the compulsive phone-checking championship. [Megan checks her phone.] [Megan puts her phone away.] [Megan checks her phone again.] Cueball: Did you win? Megan: Site's down. Cueball: Weird. Megan: I'll keep refreshing.

Email

Email

https://www.xkcd.com/1467

https://www.explainxkcd.com/wiki/index.php/1467:_Email

[Megan approaches Beret Guy.] Megan: Any New Year's resolutions? Beret Guy: Gonna figure out what email is. Megan: ...Email? [Megan points to her phone.] Beret Guy: People always say they're sending them. They sound really into it, so I always nod, but I have no idea what it is. Megan: You have an address on your website! [Megan and Beret Guy walking.] Beret Guy: Oh, that's what that thing is. Megan: Email is important! You can't just never check it. It's not like voicemail. Beret Guy: Can't they just send messages normally? Megan: How? Beret Guy: Fax! Or Snapchat. Megan: ...The naked pic thing? Beret Guy: Fax machines aren't just for faxting! The Unix timestamp is a standard method of keeping time by counting the absolute number of seconds that have elapsed since a set point in time known as "epoch", defined as midnight on January 1, 1970, Coordinated Universal Time (UTC). Epoch, in ISO-8601 format, is "1970-01-01T00:00:00Z", where Z indicates UTC. The timestamp in this comic's title text (1420001642) is 1,420,001,642 seconds since epoch. The process of converting that number into a human-readable time is as follows: Thus, Randall's timestamp represents the time " 2014-12-31 T 04:54:02 Z" (again in ISO-8601 format).

A New Year comic , where Megan asks Beret Guy if he has any New Year's resolutions , and even though this is just before new year 2015, his resolution is to find out what an email is! Despite being in popular use since 1998 when free email providers appeared and having existed since before 1982 when SMTP was established, Beret Guy apparently doesn't understand what email is, even though he maintains a web page that includes his email address. Megan wonders how else he expects electronic messages to be sent. She explains that one must check email regularly, making a slight at voicemail , which she implies is not worth ever checking. Beret Guy offers two alternatives: Fax and Snapchat . Megan refers to Snapchat as "the naked pic thing", calling to mind how many of its users send naked pictures of themselves over the Internet. Beret Guy replies that people use fax machines for more than just "faxting" (a made-up term similar to sexting ), implying that many people send sexual content via fax, a technology that predates SMTP by more than a century. Beret Guy knows what a fax is, which implies he is very behind in the technology world, so it makes sense he doesn't know what email is. But he also knows what Snapchat is, which was very popular around the time of this comic. Either Beret Guy heard about it in a similar way to email, or he definitely knows what it is and/or uses it. What's strange is that if Beret Guy knows what Snapchat is, he should know what email is as well, since you need to provide an email account in order to create a snapchat account. The title text, which could be Randall 's New Year's resolution for 2015, refers to various date/time formats. In programming, a point in time (e.g. the current system time) is usually stored and processed as a single number that represents the count of seconds that have elapsed since a given starting time known as "epoch" (the Unix standard epoch is January 1, 1970 at midnight, UTC ). In order to make sense to people, this number must be converted to a human-readable format, but programmers must choose a format that best meets the needs of their users. This can be a complicated problem to solve, given that there are many different standard formats for different regions, different levels of precision for different applications, and differences between "universal time" and a user's local time zone. Randall has previously advocated for widespread adoption of the ISO 8601 format as a universal standard. The title text also probably references a twitter outage that took place on December 29, which was blamed on an error in a date format string . Most programming languages provide functions to create a custom date-format string using "tokens" that represent different parts of the date/time. Here, Randall appears to have used one of these functions with the string "%Y-%M-%D %h:%m:%s", which looks like it should produce a date and time as "Year-Month-Day Hour:Minute:Second". However, he used the wrong tokens for this: The "%s" token shows us the actual Unix timestamp used (1420001642), which corresponds to 2014-12-31 at 04:54:02 UTC. The format string shown above thus yields "2014-54-12/30/14 Dec:12:1420001642". Note that the middle portion of this string shows "12/30" instead of "12/31" - this is due to the %D token expressing the date in Randall's local time zone (Eastern Standard Time, or EST), which is 5 hours before UTC. The time there was 23:54:02, or just before midnight, on the previous day. The correct format string for Randall's apparent desired result is "%Y-%m-%d %H:%M:%S", which gives the string "2014-12-31 04:54:02" (UTC) or "2014-12-30 23:54:02" (EST). Given the similarity between Randall's string and the correct one, it is easy to see how this type of formatting is confusing and often frustrating for programmers - particularly those not intimately familiar with these functions. Randall previously addressed date/time formatting in 1179: ISO 8601 and 1340: Unique Date (the latter of which uses a formatting string correctly). This was the second comic in a row with Megan holding a smart phone, the first being 1466: Phone Checking . The comic before that one was also about smart phones: 1465: xkcd Phone 2 . [Megan approaches Beret Guy.] Megan: Any New Year's resolutions? Beret Guy: Gonna figure out what email is. Megan: ...Email? [Megan points to her phone.] Beret Guy: People always say they're sending them. They sound really into it, so I always nod, but I have no idea what it is. Megan: You have an address on your website! [Megan and Beret Guy walking.] Beret Guy: Oh, that's what that thing is. Megan: Email is important! You can't just never check it. It's not like voicemail. Beret Guy: Can't they just send messages normally? Megan: How? Beret Guy: Fax! Or Snapchat. Megan: ...The naked pic thing? Beret Guy: Fax machines aren't just for faxting! The Unix timestamp is a standard method of keeping time by counting the absolute number of seconds that have elapsed since a set point in time known as "epoch", defined as midnight on January 1, 1970, Coordinated Universal Time (UTC). Epoch, in ISO-8601 format, is "1970-01-01T00:00:00Z", where Z indicates UTC. The timestamp in this comic's title text (1420001642) is 1,420,001,642 seconds since epoch. The process of converting that number into a human-readable time is as follows: Thus, Randall's timestamp represents the time " 2014-12-31 T 04:54:02 Z" (again in ISO-8601 format).

Worrying

Worrying

https://www.xkcd.com/1468

https://www.explainxkcd.com/wiki/index.php/1468:_Worrying

How worried should you be when various things happen to you: [A chart with a scatter plot on which 9 dots are labeled. Each axis has a title and a scale. Reading from the top to the bottom and then left to right along the axis are:] Very worried ...In Real Life Not very worried Not very worried ...In Movies Very worried [The labels in the chart from the top:] [This first entry is standing in the middle of a square bracket that points to the two next entires both of which are at the same level:] Chest wound ...on your right side ...on your left side Getting knocked out by a punch "We need to talk." Persistent cough Parking ticket Breaking news Spilling a drink on your shirt Nosebleed

This chart is a visual representation of how worried people should be by various events in real life compared to the same events in movies, based on the likelihood of the event causing serious harm. In effect, it's poking fun at various cliches and the emphasis on dramatic flair, regardless of realism. The chart's Y-axis indicates how worrying an event is in real life (from "not very worried" to "very worried"), while its X-axis shows how worrying the event is in movies. Nine events are shown in the chart, all of them cliches in the medium of film: The title text expands on the aforementioned breaking news reports. While already overly worrying whenever they occur in movies compared to real life, should the movie's news report cover an event at a hospital (usually an outbreak of some major disease) or a laboratory (a monster escaping, a toxic gas released, an explosion, etc.), these events are universally much more worrisome than any other type of news story since they are guaranteed to be important for the protagonists in short order. In real life, breaking news from such locations may be more likely to be serious, but are still very unlikely to impact the viewer directly. The comic shows an X-Y plot of events, showing how worried you should be in real life on the vertical axis and in movies on the horizontal axis. The axis goes from "not very worried" to "very worried". Below is a table listing the coordinates for each event according to how worrying it is. The coordinates have been found by measuring each dot to the two axises and then assuming that the extremes are at 100%. How worried should you be when various things happen to you: [A chart with a scatter plot on which 9 dots are labeled. Each axis has a title and a scale. Reading from the top to the bottom and then left to right along the axis are:] Very worried ...In Real Life Not very worried Not very worried ...In Movies Very worried [The labels in the chart from the top:] [This first entry is standing in the middle of a square bracket that points to the two next entires both of which are at the same level:] Chest wound ...on your right side ...on your left side Getting knocked out by a punch "We need to talk." Persistent cough Parking ticket Breaking news Spilling a drink on your shirt Nosebleed

UV

UV

https://www.xkcd.com/1469

https://www.explainxkcd.com/wiki/index.php/1469:_UV

[Megan holding a flashlight and standing behind Cueball, who is sitting at a computer.] Megan: Our bathroom looks pretty clean, right? Cueball: I think so. Why? Megan: I got a UV flashlight. Come look. [Cueball leaves the computer; they walk.] [Megan and Cueball are off-screen.] Cueball: Looks fine. UV flashlight: *Click* *Click* Cueball: ...Oh my God. [Megan and Cueball walking in the opposite direction; Cueball is looking back behind him.] Cueball: The toilet looked like the guy's chest after the alien burst out. Megan: What do we do? [Megan and Cueball standing.] Cueball: We clean. Clean and clean and never stop. Megan: It won't be enough. We should just burn the place down for the insurance money. [Cueball standing behind Megan. Megan is pouring a liquid onto the floor out of a red-colored canister labled "Danger".] Cueball: Isn't that wrong? Megan: My morality has evaporated under the harsh UV light. [Megan and Cueball standing outside the burning building.] [Megan and Cueball standing, Cueball looking at his phone.] Cueball: OK, I'm Googling insurance companies. Which one do you think pays the most? Megan: Let's just try calling around.

Ultraviolet light (abbreviated UV light, as in the title of the comic) is a kind of light that is slightly more energetic than the light in the visible portion of the electromagnetic spectrum. Ultraviolet light is normally by itself invisible to human eye, but can induce fluorescence (glowing) of certain organic molecules. A UV flashlight can thus be a means to detect small amounts of blood, semen, and urine on surfaces. The first part of this comic focuses on Megan showing off her new UV flashlight to Cueball by revealing how disgusting their bathroom appears in UV light despite how clean it appears normally. She manages this due to UV light's special property of causing chemicals in urine to glow. Both Cueball and Megan are horrified by their discovery. This is a common reaction in the face of more sensitive diagnostic tests. Cueball's comment is a reference to the 1979 sci-fi film Alien . In the second part of the comic they realize that their house will never be clean enough. So Megan resolves to burn down the house for the insurance money (i.e. insurance fraud ). Cueball is in doubt, but Megan apparently has no morality left. She even proclaims this while pouring some dangerous liquid, probably gasoline, on to the floor of their apartment. The last panel of the comic implies that the two hadn't purchased fire insurance beforehand, and plan on purchasing it now, only to make a claim immediately afterwards. At this point Cueball has been won over by Megan's plan and tries to help by searching for insurance companies using Google. They wish to find the company that pays out the most. This plan will almost certainly not work since insurance typically only covers events that begin after purchasing the insurance, and does not cover anything that happens before purchasing the insurance, or that is intentionally caused. The title text shows just how distorted Megan's and Cueball's thinking has become, as one of them suggests burning down all the houses in order to claim the insurance money for them. This plan will also not work. Even if insurance has been purchased for these other homes, the insurance companies will pay the owners of those homes, not Cueball and Megan. Instead, Cueball and Megan would likely be arrested for multiple charges of arson and end up in prison for a very long time. The take home message of this comic must be: Never use a UV light in your bathroom. Maybe Randall did this by mistake causing the creation of this comic. (Randall has previously warned people about similar diagnostics in 860: Never Do This .) [Megan holding a flashlight and standing behind Cueball, who is sitting at a computer.] Megan: Our bathroom looks pretty clean, right? Cueball: I think so. Why? Megan: I got a UV flashlight. Come look. [Cueball leaves the computer; they walk.] [Megan and Cueball are off-screen.] Cueball: Looks fine. UV flashlight: *Click* *Click* Cueball: ...Oh my God. [Megan and Cueball walking in the opposite direction; Cueball is looking back behind him.] Cueball: The toilet looked like the guy's chest after the alien burst out. Megan: What do we do? [Megan and Cueball standing.] Cueball: We clean. Clean and clean and never stop. Megan: It won't be enough. We should just burn the place down for the insurance money. [Cueball standing behind Megan. Megan is pouring a liquid onto the floor out of a red-colored canister labled "Danger".] Cueball: Isn't that wrong? Megan: My morality has evaporated under the harsh UV light. [Megan and Cueball standing outside the burning building.] [Megan and Cueball standing, Cueball looking at his phone.] Cueball: OK, I'm Googling insurance companies. Which one do you think pays the most? Megan: Let's just try calling around.

Kix

Kix

https://www.xkcd.com/1470

https://www.explainxkcd.com/wiki/index.php/1470:_Kix

[Ponytail, Megan, and Cueball are standing around a whiteboard on an easel; Ponytail and Cueball are holding red markers. The whiteboard reads:] [in Large] Kix [Underlined] Slogan ideas Kid Tested, Mother... [following lines all in red and each crossed out] Selected Perfected Not notified Watching helplessly Infected Consumed Fucker

This comic may be a commentary about the uselessness of brainstorming sessions or the bad ideas that come out of them, as they are often started with the phrase “there are no bad ideas”. As the brainstorming session continues the original meaning of the slogan is lost, much like a game of telephone, and the session becomes less productive. Kix is an American brand of cold breakfast cereal made of extruded and expanded cornmeal. Its slogan, "Kid tested, Mother approved," is well known in the United States, and is meant to suggest that children generally enjoy the cereal and their mothers, who are naturally concerned about the health of their children, approve of its ingredients. However, in this brainstorming session, the word "Approved" has apparently not yet been considered. A number of possible words and phrases for the ending have been presented and stricken out , indicating that they were rejected; each one causes the slogan to be subject to increasingly absurd and comedic interpretations: The title text conflates the phrase "Kid tested" with college entrance exams such as the Standardized Aptitude Test (SAT) or the ACT . Instead of stating that a child tasted the cereal and gave their opinion on its quality, the cereal itself is an academic subject on which the child was tested. Randall, referring to how some parents enroll their children in special classes or schools to prepare them to score well in this type of test, states that his parents extensively prepared him for a college entrance exam about Kix cereal. Cereal advertising has previously been referenced in 38: Apple Jacks . [Ponytail, Megan, and Cueball are standing around a whiteboard on an easel; Ponytail and Cueball are holding red markers. The whiteboard reads:] [in Large] Kix [Underlined] Slogan ideas Kid Tested, Mother... [following lines all in red and each crossed out] Selected Perfected Not notified Watching helplessly Infected Consumed Fucker

Gut Fauna

Gut Fauna

https://www.xkcd.com/1471

https://www.explainxkcd.com/wiki/index.php/1471:_Gut_Fauna

[Cueball on an examining table; Ponytail wearing a doctor's coat holding some test results.] Doctor: I see the problem. Your gut macrobiome is out of balance. One moment. [Ponytail leaves.] Cueball: I think you mean micro biome... Right? [Ponytail returns, slightly disheveled, carrying a momentarily docile live wolf.] Doctor: No. Here, swallow this. Cueball: That's a wolf. Doctor: Do you need a glass of water?

The microbiome is the collection of bacteria that reside in the human digestive tract. The bacteria perform several vital digestive and immune-support functions. Different compositions of bacteria, collectively referred to as gut flora , can be linked to risk of some diseases, while other compositions are linked to a decreased risk of some diseases and are therefore called "good bacteria". The title "Gut fauna" is a play on words. Fauna means animal life in Latin, and flora means vegetable life. However, in this context flora means bacterial life because, when microscopes were invented, microbial life was considered to be non-animal and therefore classified as "flora". For a good description of the microbiome see The Invisible Universe Of The Human Microbiome . In this comic, Cueball is visiting a doctor ( Ponytail ) for some unknown problem. The doctor informs him that his gut macrobiome is out of balance, which Cueball responds to with confusion over whether or not she meant the microbiome or macrobiome. A macrobiome, instead of being composed of small organisms such as bacteria, would be composed of larger organisms such as mammals. The phrase "gut fauna" would refer to any animals living inside a gut (as the word fauna refers to animals living in an ecosystem). Cueball is right to be worried by the doctor's reference to his macrobiome, as normal humans shouldn't have large animals living inside them [ citation needed ] with the exception of some parasites such as Helminths or Cestoda , or in some cases, the consumption of live animals such as octopus, shrimp and eels. No animals belong natively in the human digestive system ; all known cases of animals living permanently in the human digestive system are causes of disease. His fear is compounded when the doctor prescribes one wolf for Cueball to swallow, which is normally impossible for average humans and would, at the very least, result in major interior (or exterior) damage to Cueball and (possibly) Ponytail when the wolf resists being swallowed. Needless to say this is not common physician practice due to the likely death rate. [ citation needed ] The choice of a wolf echoes the reintroduction of the animals into the macrobiome of Yellowstone National Park in the United States, where they have improved the balance by, in part, preying on elk and reducing the damage caused by their grazing. The dialog between the characters ends with the doctor asking the patient whether he needs a glass of water, a typical question asked by health professionals (water can help patients swallow oral medication). This last phrase further extends the humorous nature of the proposition to swallow the wolf by displaying a confidence of the doctor in her choice of the treatment modality. In reality, of course, drinking a glass of water while attempting to swallow a wolf would make the latter procedure neither easier, nor more feasible. The title text suggests that swallowing the wolf is not the worst situation that could have occurred, as the doctor refers to "another way" that the wolf could be administered. One typical way that microbiomes are restored is through fecal bacteriotherapy , most easily described as a "poop transfer". It could also mean transferred via suppository. In either case, the worse "other way" that the doctor is referring to is thus likely the rectal route, which (for Randall ) is less preferable than attempting to swallow a live wolf. However, either way would prove physically impossible and/or lethal. If we are to take the doctor at her word that there is indeed some sort of macrobiome inside Cueball's gut, then perhaps she has some kind of matter compression ability that would make introducing a live wolf a legitimate therapeutic option. Randall has referenced wolf reintroduction programs before, in comic 819: Five-Minute Comics: Part 1 . [Cueball on an examining table; Ponytail wearing a doctor's coat holding some test results.] Doctor: I see the problem. Your gut macrobiome is out of balance. One moment. [Ponytail leaves.] Cueball: I think you mean micro biome... Right? [Ponytail returns, slightly disheveled, carrying a momentarily docile live wolf.] Doctor: No. Here, swallow this. Cueball: That's a wolf. Doctor: Do you need a glass of water?

Geography

Geography

https://www.xkcd.com/1472

https://www.explainxkcd.com/wiki/index.php/1472:_Geography

[A colorful map shows various possible land forms which are labeled (and the last one with a spelling mistake included here). In general reading order the labels are:] Desert Mountains Sea Glacier Plain Island Volcano Lake River Delta Strait Hills Lagoon Bay Mesa Forest Penninsula [In the middle of these land forms, under the river and between the lake and the lagoon there is a black dot on the green bank of the lagoon with an arrow pointing it out. The arrow starts above the lake to the left of the glacier and is labeled:] My house [Below the panel there is a caption:] If I could live anywhere, I would choose the example map from geography books that explains what everything is called.

The comic is a map showing examples of geographical features as they would be presented in a geography textbook. May be based on the first page of the book You Choose which displays a map of locations similar in style to the one used in the comic and asks the reader "If you could go anywhere, where would you go?". Randall notes that he would like to live in the middle of this region. These maps include an unusual density of different land forms, leading to an interesting environment in which to live. In the real world, these geographical features might take up far more space, and the geologic forces that shape them might create far different patterns than those shown. This kind of Neverland of geographical feature would offer a range of outdoor activities and landscapes that would make it a very nice place to live, as long as the volcano does not erupt. Some of the geographic features do have a (very) loose similarity to the area around Boston , where Randall lives. Also near Boston is one geographical feature that Randall has included in this map but has refrained from labeling, the isthmus between the peninsula and the forest. On the other hand, the map actually looks quite a bit like the area around southwestern Washington and northwestern Oregon , with the reader facing south so the high desert is on the upper left. The volcano could be Rainier or St. Helens . Real-world outdoor enthusiasts do indeed appreciate the Neverlandish landscape. Having little Spanish influence, locals would refer to a "mesa" as a butte . The title text discusses a different type of diagram usually found in geography textbooks, the one showing the mechanism of tornado formation . Randall notes that he would least like to live in the farm typically depicted in the background of such diagrams. This is likely because the farm is depicted as being on a vast, featureless stretch of flat prairie, the opposite of the rich landscape in the comic. The monotonous landscape would reflect that of Tornado Alley , an area of the central United States where a large number of tornadoes form, and which makes up a large portion of the Great Plains . His dislike for this type of area may also simply be due to the damage created when a tornado hits. That said, chances of a direct tornado hit on any given house are slim compared to simply the risk of property damage. Living near an active volcano may be much more dangerous than living in Tornado Alley. Tornadoes are a recurring subject on xkcd. Here is an alphabetical list of the different land forms with wiki links: Bay , Desert , Forest , Glacier , Hills , Island , Lagoon , Lake , Mesa , Mountains , Peninsula , Plain , Delta , River , Sea , Strait and Volcano . [A colorful map shows various possible land forms which are labeled (and the last one with a spelling mistake included here). In general reading order the labels are:] Desert Mountains Sea Glacier Plain Island Volcano Lake River Delta Strait Hills Lagoon Bay Mesa Forest Penninsula [In the middle of these land forms, under the river and between the lake and the lagoon there is a black dot on the green bank of the lagoon with an arrow pointing it out. The arrow starts above the lake to the left of the glacier and is labeled:] My house [Below the panel there is a caption:] If I could live anywhere, I would choose the example map from geography books that explains what everything is called.

Location Sharing

Location Sharing

https://www.xkcd.com/1473

https://www.explainxkcd.com/wiki/index.php/1473:_Location_Sharing

[Megan is holding her phone. Above her is the text she can see on the screen:] This website wants to know your location. [Two buttons are below this text. The first is white with a black frame and black text. The second (the chosen button) also has a black frame, but inside the frame is a black rectangle with white text. Around the chosen button are small lines indication rays.] Deny Allow [Megan is holding her phone.] [Megan is holding her phone. Above her is again the text she can see on the screen.] This website wants to know your momentum. [Two buttons are below this text. The first (the chosen button) has a black frame, but inside the frame is a black rectangle with white text. The second is white with a black frame and black text. Around the chosen button are small lines indication rays.] Deny Allow Megan: Nice try.

In this comic, Megan is visiting a website on her mobile phone. After loading it, the website asks for her location . The choice between allowing or denying a website or app access to certain information is common among smartphones. The term "location sharing" specifically refers to when a smartphone user shares their location with such an entity. An example is a weather app which would need your location in order to automatically find the correct forecast. Megan is then asked her momentum , which she denies. The joke is based on the Heisenberg uncertainty principle , which, in quantum mechanics, states that some pairs of values cannot be known precisely and simultaneously. The most famous examples of such values, especially in jokes, are location and momentum. The ramifications of the uncertainty principle being violated in this context are unknown, but the comic might be alluding to security problems that appear if an untrusted application is given access to momentum data generated by the gyroscope. Access to gyroscope data can be used for reading passwords entered into the on-screen keyboard or even guessing keyboard strokes on a keyboard lying on the same table as the phone. It could also be an attempt to get Megan to unknowingly reveal her weight (mass to be more exact), as the mass can be inferred by dividing the momentum by velocity (the velocity in turn can be obtained by observing the change of the location over time). In order to be feasible, the location must be polled at least twice, as at least two location points are necessary to compute the velocity. It is a stereotype in many Western cultures that women tend to keep their weight secret. The stereotype implies that women tend to obsess about controlling (and not revealing) their weight in order to conform to societal and sexual pressure. On the other hand, it could just be a joke about the fact that Heisenberg's uncertainty principle is typically observed only at sub-atomic scales, and not at macroscopic scales (it is possible to measure both the position and momentum of a large object). By saying "Nice try", it's clear that Megan knows about the principle, but funny that she would think it applies to herself at macroscopic scale. The title text refers to the inclusion of gyroscopes in modern cell phones that measure angular momentum, mostly to detect when the phone is tilted, but also used in a few mobile games. Randall suggests the poor accuracy of the compasses in mobile phones (measuring the angular position) is due to the gyroscopes being too good. If both the gyroscope and the compasses were completely accurate to a subatomic scale, it would violate the uncertainty principle. Modern phones also include varied technologies (such as GPS) to pinpoint the user's location, with varying degrees of accuracy. The uncertainty principle has previously been referenced in 824: Guest Week: Bill Amend (FoxTrot) . It has also been discussed in relation to the two comics 1404: Quantum Vacuum Virtual Plasma and 1416: Pixels . [Megan is holding her phone. Above her is the text she can see on the screen:] This website wants to know your location. [Two buttons are below this text. The first is white with a black frame and black text. The second (the chosen button) also has a black frame, but inside the frame is a black rectangle with white text. Around the chosen button are small lines indication rays.] Deny Allow [Megan is holding her phone.] [Megan is holding her phone. Above her is again the text she can see on the screen.] This website wants to know your momentum. [Two buttons are below this text. The first (the chosen button) has a black frame, but inside the frame is a black rectangle with white text. The second is white with a black frame and black text. Around the chosen button are small lines indication rays.] Deny Allow Megan: Nice try.

Screws

Screws

https://www.xkcd.com/1474

https://www.explainxkcd.com/wiki/index.php/1474:_Screws

[Eight drawings of different types of heads each with a caption:] [Plus sign-shaped screw.] Phillips head [Minus sign-shaped screw.] Flat head [Star-shaped screw.] Uh oh. Maybe it's on Amazon? [Plus sign-shaped screw with worn edges.] Cursed -1 Phillips head [No screw, just a circle.] Crap, it's a rivet . [Hexagon-shaped screw.] Phillips-head ruiner [Minus sign-shaped screw going through the whole circle. Also giving off radiation.] Uranium screw (a real thing) [A sack with blood oozing out of it.] Phillip's head

This comic uses a similar structure and is based off of the same idea as 1714: Volcano Types and 1874: Geologic Faults . Appliance makers sometimes use strange screw heads to hinder attempts from users to remove appliance covers. Users usually have handy screwdrivers for the first two screw types drawn, Phillips and Flat. More advanced users usually have some less standard drivers, such as Torx or Allen , however appliance makers keep designing increasingly strange screw heads and users keep acquiring increasingly strange screwdrivers. The comic is about the frustration a user may feel when faced with a screw for which they have no screwdriver. Usually the user will try to fit one of the drivers they have handy into the strange screw, leading to damaging the screw and/or the driver and/or the person wielding the tool. The types of screws listed are the following: [Eight drawings of different types of heads each with a caption:] [Plus sign-shaped screw.] Phillips head [Minus sign-shaped screw.] Flat head [Star-shaped screw.] Uh oh. Maybe it's on Amazon? [Plus sign-shaped screw with worn edges.] Cursed -1 Phillips head [No screw, just a circle.] Crap, it's a rivet . [Hexagon-shaped screw.] Phillips-head ruiner [Minus sign-shaped screw going through the whole circle. Also giving off radiation.] Uranium screw (a real thing) [A sack with blood oozing out of it.] Phillip's head

Technically

Technically

https://www.xkcd.com/1475

https://www.explainxkcd.com/wiki/index.php/1475:_Technically

[White Hat talks to Cueball who looks at a flying insect.] White Hat: Well, technically, food is a "drug", since it's a substance that alters how your body works, so yes, I'm— Cueball: Hey, look at that weird bug! [Caption below the panel:] My life improved when I realized I could just ignore any sentence that started with "technically."

When the word "technically" is used to start a sentence, the remainder of the sentence tends to follow one of a number of patterns: Cueball , possibly representing Randall , has decided that any sentence beginning with the word "technically" is highly likely to be completely worthless for him to listen to; so whenever he hears it at the beginning of a sentence, he allows himself to be distracted by anything which happens to be around. There are many cases where an item is classified in what appears to be an illogical way. Some fairly well known examples are 'Tomatoes are a fruit', 'Strawberries are not berries', 'Peanuts are not nuts' and so on. The reasoning behind these seemingly unusual classifications is typically down to the technical definition of the class, which may differ from the intuitive understanding that the general public have learned. It is not unusual for people to try and appear knowledgeable by demonstrating that they are aware of correct technical classifications. White Hat starts to pedantically answer the typically incredulous rhetorical question “Are you on drugs?!” by explaining that according to the technical definition, food is classed as a drug. This classification is false due to his incorrect interpretation of the word "drug" and lack of understanding of the role of food in human physiology, and would fall under the fourth example in the chart above. Indeed, "drug" is defined as "a substance used to treat an illness, relieve a symptom, or modify a chemical process in the body for a specific purpose", followed by a secondary definition of "a psychoactive substance, especially one which is illegal and addictive". Food, on the other hand, is defined as "any substance that can be consumed by living organisms, especially by eating, in order to sustain life". In other words, food is consumed in order to sustain the normal, innate state of the body, while drugs are consumed in order to alter certain states. The Wikipedia article for drug goes so far as to explicitly disqualify food from the definition of “drug.” Regardless of whether or not the classification was valid, Cueball has already allowed himself to be distracted by a passing bug. The title text starts to pedantically over-apply Cueball's rule to the comic panel, noting that technically White Hat's sentence started with the word 'well' instead of the word 'technically', and thus Cueball is wrong to have ignored it. This would fall under the second or third example in the chart. Halfway through the sentence, this argument is cut off by the discovery of a rock with a fossil in it, correctly applying the rule to a sentence that began with the word "technically". This comic is similar to 1240: Quantum Mechanics , in that they both suggest ignoring sentences containing a certain word or phrase indicating a pedantic attitude. [White Hat talks to Cueball who looks at a flying insect.] White Hat: Well, technically, food is a "drug", since it's a substance that alters how your body works, so yes, I'm— Cueball: Hey, look at that weird bug! [Caption below the panel:] My life improved when I realized I could just ignore any sentence that started with "technically."

Ceres

Ceres

https://www.xkcd.com/1476

https://www.explainxkcd.com/wiki/index.php/1476:_Ceres

[Megan sitting in front of her laptop talks to Cueball who stand behind her.] Megan: Dawn has almost reached Ceres. Megan: I'm excited that we'll finally learn what that stupid white dot is. [Current version of Dawn's best picture of Ceres and the white spot is shown.] [As Dawn get's closer the pictures improve and in the second version the white spot shows to have black markings.] [In the last zoom in on Ceres, the white dot resolves to a badge with clear black text:] Inspected by No. 6

Ceres is the largest known asteroid and the smallest known dwarf planet . Megan sits at her computer and tells Cueball how exciting it will be when Dawn will discover what is the cause of the "stupid white dot" on Ceres. Dawn is a probe sent by NASA in 2007 to examine the asteroid belt . Having already visited the protoplanet Vesta in 2012, Dawn is now scheduled to arrive at Ceres on March 6, 2015. Dawn's initial images of Ceres were released two days before this comic, quickly inspiring questions about the white spot . The spot was first noticed in photographs taken by the Hubble Space Telescope . " Inspected By No. 6 " refers to a series of quality assurance stickers used by US clothing manufacturers. Individual inspectors, each assigned a number, randomly sample products for workmanship. Accepted items are marked with that inspector's sticker. The presumed joke is that the white spot is a large sticker indicating that Ceres has passed inspection. This might also be a reference to The Rift's M6 being stationed at Ceres inspecting a crater. CERES (Certification of Environmental Standards) is also the name of a food inspection company based in Germany. Both the food inspection company and the dwarf planet are named for Ceres , the ancient Roman harvest goddess from whom English derives the word " cereal ." The title text extends the joke to the planet Earth, where salmonella can be found. Salmonella are harmful microorganisms that are sometimes found in food products subject to improper handling or overlong storage. Mixing the realms of astronomical objects and food once more, the title text concludes that the planet Earth clearly hasn't been tested by CERES since salmonella can be found on it. The Dawn mission is mentioned in 1532: New Horizons . [Megan sitting in front of her laptop talks to Cueball who stand behind her.] Megan: Dawn has almost reached Ceres. Megan: I'm excited that we'll finally learn what that stupid white dot is. [Current version of Dawn's best picture of Ceres and the white spot is shown.] [As Dawn get's closer the pictures improve and in the second version the white spot shows to have black markings.] [In the last zoom in on Ceres, the white dot resolves to a badge with clear black text:] Inspected by No. 6

Star Wars

Star Wars

https://www.xkcd.com/1477

https://www.explainxkcd.com/wiki/index.php/1477:_Star_Wars

[Cueball and Megan are walking together.] Cueball: We're almost at the Back to the Future date. Megan: We're even closer to the Star Wars tipping point. Cueball: The what? [Diagram showing a timeline from before 1980 to about 2020. Markers on the line indicate the release date of Return of the Jedi , the release date of The Phantom Menace , and May 13th, with arrows showing the intervals in between these three points.] Megan: On May 13th, The Phantom Menace will have come out closer to Return of the Jedi than to the present Cueball: Wow. [Cueball and Megan stop walking. Megan is in a reflective pose with her hand on her chin.] Cueball: It's weird how I'm constantly surprised by the passage of time when it's literally the most predictable thing in the universe. Megan: You know, "A long time ago" should have "Plus four more decades" added in rereleases.

This is another comic based on pointing out just how much time has passed since the release of a particular film. The same basis is found in 1393: Timeghost and 891: Movie Ages , and a similar theme is used in 647: Scary and 973: MTV Generation . Many people remember going to see major films at the time of release, and in their mind it may seem like "just a few years ago". In reality however, many years have passed, and it comes as a shock to realise just how long ago it was. In the first panel, Cueball states that we are approaching the Back to the Future date (October 21, 2015), which is the date that protagonist Marty McFly travels to in Back to the Future Part II , released in 1989. Megan adds that we're even closer to May 13, 2015, the " Star Wars tipping point". The original first set of Star Wars films was released as a trilogy over the span of 6 years, with the third one, Return of the Jedi being released on May 25, 1983. After that, no films were released for 16 years until The Phantom Menace on May 19, 1999, the first in a trilogy of prequels. Thus up until now, the length of time between the two films, 5,839 days , has been greater than the time between the latter film and the present. Megan points out that May 13, 2015 will mark 5,839 days after the release of The Phantom Menace , meaning that for the first time the release date of the two films will be closer together than the latter film is to the present day. In the final panel, Cueball points out how weird it is that he (along with most other people) are regularly surprised at the passage of time, given how predictable time is by its very nature. Megan's last line is a reference to the famous opening text used in all Star Wars films, "A long time ago in a galaxy far, far away...". It's also a reference to the many changes that have been made to the original Star Wars trilogy (e.g. new CGI effects) as it's been released and rereleased. The title text repeats the opening text from the films, inserting Megan's suggestion for changing the duration, and extending it to include the Hubble constant for adjusting the distance estimation. The Hubble constant is a value that describes an estimated rate of expansion of the universe. This expansion means that during the 40 years that have passed since the release of the first Star Wars movie, the "galaxy far, far away" has gotten even farther away. [Cueball and Megan are walking together.] Cueball: We're almost at the Back to the Future date. Megan: We're even closer to the Star Wars tipping point. Cueball: The what? [Diagram showing a timeline from before 1980 to about 2020. Markers on the line indicate the release date of Return of the Jedi , the release date of The Phantom Menace , and May 13th, with arrows showing the intervals in between these three points.] Megan: On May 13th, The Phantom Menace will have come out closer to Return of the Jedi than to the present Cueball: Wow. [Cueball and Megan stop walking. Megan is in a reflective pose with her hand on her chin.] Cueball: It's weird how I'm constantly surprised by the passage of time when it's literally the most predictable thing in the universe. Megan: You know, "A long time ago" should have "Plus four more decades" added in rereleases.

P-Values

P-Values

https://www.xkcd.com/1478

https://www.explainxkcd.com/wiki/index.php/1478:_P-Values

[A two-column table where the second column selects various areas of the first column using square brackets.] P-value Interpretation 0.001 0.01 0.02 0.03 Highly Significant 0.04 0.049 Significant 0.050 Oh crap. Redo calculations. 0.051 0.06 On the edge of significance 0.07 0.08 0.09 0.099 Highly suggestive, relevant at the p<0.10 level ≥0.1 Hey, look at this interesting subgroup analysis

This comic plays on how scientific experiments interpret the significance of their data. P-value is a statistical measure whose meaning can be difficult to explain to non-experts, and is frequently wrongly understood (even in this wiki) as indicating how likely that the results could have happened by accident. Informally, a p-value is the probability under a specified statistical model that a statistical summary of the data (e.g., the sample mean difference between two compared groups) would be equal to or more extreme than its observed value. By the standard significance level, analyses with a p -value less than .05 are said to be 'statistically significant'. Although the difference between .04 and .06 may seem minor, the practical consequences can be major. For example, scientific journals are much more likely to publish statistically significant results. In medical research, billions of dollars of sales may ride on whether a drug shows statistically significant benefits or not. A result which does not show the proper significance can ruin months or years of work, and might inspire desperate attempts to 'encourage' the desired outcome. When performing a comparison (for example, seeing whether listening to various types of music can influence test scores), a properly designed experiment includes an experimental group (of people who listen to music while taking tests) and a control group (of people who take tests without listening to music), as well as a null hypothesis that "music has no effect on test scores". The test scores of each group are gathered, and a series of statistical tests are performed to produce the p -value. In a nutshell, this is the probability that the observed difference (or a greater difference) in scores between the experimental and control group could occur due to random chance, if the experimental stimulus has no effect. For a more drastic example, an experiment could test whether wearing glasses affects the outcome of coin flips - there would likely be some amount of difference between the coin results when wearing glasses and not wearing glasses, and the p -value serves to essentially test whether this difference is small enough to be attributed to random chance, or whether it can be said that wearing glasses actually had a significant difference on the results. If the p -value is low, then the null hypothesis is said to be rejected , and it can be fairly said that, in this case, music does have a significant effect on test scores. Otherwise if the p -value is too high, the data is said to fail to reject the null hypothesis, meaning that it is not necessarily counter-evidence, but rather more results are needed. The standard and generally accepted p -value for experiments is <0.05, hence why all values below that number in the comic are marked "significant" at the least. The chart labels a p -value of exactly 0.050 as "Oh crap. Redo calculations" because the p -value is very close to being considered significant, but isn't. The desperate researcher might be able to redo the calculations in order to nudge the result under 0.050. For example, problems can often have a number of slightly different and equally plausible methods of analysis, so by arbitrarily choosing one it can be easy to tweak the p -value. This could also be achieved if an error is found in the calculations or data set, or by erasing certain unwelcome data points. While correcting errors is usually valid, correcting only the errors that lead to unwelcome results is not. Plausible justifications can also be found for deleting certain data points, though again, only doing this to the unwelcome ones is invalid. All of these effectively introduce sampling bias into the reports. The value of 0.050 demanding a "redo calculations" may also be a commentary on the precision of harder sciences, as the rest of the chart implicitly accepts any value following the described digit for a given description; if you get exactly 0.050, there's the possibility that you erred in your calculations, and thus the actual result may be either higher or lower. Values between 0.051 and 0.06 are labelled as being "on the edge of significance". This illustrates the regular use of "creative language" to qualify significance in reports, as a flat "not significant" result may look 'bad'. The validity of such use is of course a contested topic, with debates centering on whether p -values slightly larger than the significance level should be noted as nearly significant or flatly classed as not-significant. The logic of having such an absolute cutoff point for significance may be questioned. Values between 0.07 and 0.099 continue the trend of using qualifying language, calling the results "suggestive" or "relevant". This category also illustrates the 'technique' of resorting to adjusting the significance threshold. Appropriate experimental design requires that the significance threshold be set prior to the experiment, not allowing changes afterward in order to "get a better experiment report", as this would again insert bias into the result. A simple change of the threshold (e.g. from 0.05 to 0.1) can change an experiment's result from "not significant" to "significant". Although the statement "significant at the p <0.10 level" is technically true, it would be highly frowned upon to use in an actual report. Values higher than 0.1 are usually considered not significant at all, however the comic suggests taking a part of the sample (a subgroup ) and analyzing that subgroup without regard to the rest of the sample. Choosing to analyze a subgroup in advance for scientifically plausible reasons is good practice. For example, a drug to prevent heart attacks is likely to benefit men more than women, since men are more likely to have heart attacks. Choosing to focus on a subgroup after conducting an experiment may also be valid if there is a credible scientific justification - sometimes researchers learn something new from experiments. However, the danger is that it is usually possible to find and pick an arbitrary subgroup that happens to have a better p -value simply due to chance. A researcher reporting results for subgroups that have little scientific basis (the pill only benefits people with black hair, or only people who took it on a Wednesday, etc.) would clearly be "cheating." Even when the subgroup has a plausible scientific justification, skeptics will rightly be suspicious that the researcher might have considered numerous possible subgroups (men, older people, fat people, sedentary people, diabetes suffers, etc.) and only reported the subgroups for which there are statistically significant results. This is an example of the multiple comparisons problem , which is also the topic of comic 882 . If the results cannot be normally considered significant, the title text suggests as a last resort to invert p<0.050, making it p>0.050. This leaves the statement mathematically true, but may fool casual readers, as the single-character change may go unnoticed or be dismissed as a typographical error ("no one would claim their results aren't significant, they must mean p<0.050"). Of course, the statement on its face is useless, as it is equivalent to stating that the results are "not significant". [A two-column table where the second column selects various areas of the first column using square brackets.] P-value Interpretation 0.001 0.01 0.02 0.03 Highly Significant 0.04 0.049 Significant 0.050 Oh crap. Redo calculations. 0.051 0.06 On the edge of significance 0.07 0.08 0.09 0.099 Highly suggestive, relevant at the p<0.10 level ≥0.1 Hey, look at this interesting subgroup analysis

Troubleshooting

Troubleshooting

https://www.xkcd.com/1479

https://www.explainxkcd.com/wiki/index.php/1479:_Troubleshooting

[Hairy sitting at a desk with laptop, with Cueball standing behind him.] Hairy: Wait, why can't I click anywhere? Cueball: I don't... Ugh, It opened a dialog box offscreen. Hairy: Why is that even possible? Cueball: It really shouldn't be. But you can fix it by changing your screen resolution to trigger a window cleanup. Hairy: Seriously? Cueball: I know, I know... To be honest, I can't wait for the day when all my stupid computer knowledge becomes obsolete.

This comic revolves around the complexity of modern software and its sometimes low quality. Many problems that users experience are not obvious or straightforward, and methods for correcting the root cause of the problem requires invoking unrelated actions that happen to cause a desired side-effect. Knowing the non-obvious cause, the desired side effect, and how to trigger the unrelated feature that causes it requires memorization of lots of "stupid computer knowledge" rather than general principles and logical investigation of the software. One particular example of an illogical fix to a software problem is depicted in the comic. Here, Cueball is trying to help Hairy resolve the problem of a program that is not responding to any mouse clicks. Cueball surmises that this is not due to abnormal behavior of the software (such as freezing ), but rather because either the user or the software itself has opened a modal dialog window outside of the main screen area, where it can not be seen. Modal dialog windows block access to the rest of the application, by seizing the sole focus of the user input. They are valid GUI tools and are used when the software needs the user's input before it can proceed further. However, opening such a window and placing it outside of the visible screen area ("off-screen") will make the window both inaccessible and invisible to the user, precluding them from closing it and re-gaining access to the software. One non-obvious way to repair such a problem is to switch the screen resolution; this in itself does not fix the problem, but the resolution switch also forces the operating system to redraw all windows on the desktop, and some operating systems will also validate the coordinates of all windows and adjust these coordinates so that the windows do not end up in off-screen area. In this scenario, it is used as a side-effect to fix the problem, because operating systems rarely provide other, more obvious ways to bring off-screen windows back to the visible area. By saying "Why is that even possible?", Hairy is quite correct in pointing out that the best way to address this problem at its root would be for the operating system developers to prevent the creation of windows off-screen, preemptively avoiding a whole class of window management problems before they can occur. For example, such mechanisms could validate coordinates during window creation, thus making sure that the dialog window would always be accessible and visible. Such a mechanism exists on OS X, but not on Windows, which the majority of desktop/laptop computers are running at the time of this comic's release. In general, one can sort the possible solutions to the problem being discussed in the following order of preference, from best to worst: The title text refers to the fact that two different and unrelated software packages can have confusingly similar names, even if the usage and features of those two packages can vary wildly, and knowing the implications of using one instead of the other is a case of "stupid computer knowledge". Knowing the difference between a Chrome app , a cell phone app-style application, delivered from the Chrome web store, designed to be run in the Chrome browser, and a Chrome extension , a browser extension installed into the Chrome browser, delivered from the Chrome web store, designed to modify the behavior of the browser itself, is a subtle distinction that may not be immediately apparent to users who might just have the name of the software they are looking for. Google Hangouts is an example of a product that exists as both a Chrome app and a Chrome extension, whose windows are more similar to each other than to normal Chrome browser windows; and confusingly, it's possible to be signed into one account with the app and another with the extension, especially when your employer or school uses Apps for Business/Education. In many cases, Randall (or Cueball, his avatar) loves to help people using his specific knowledge (see 208: Regular Expressions ). But when the trick is "stupid", he would prefer the programmers to fix the problem definitively so he never has to rely on this trick anymore. [Hairy sitting at a desk with laptop, with Cueball standing behind him.] Hairy: Wait, why can't I click anywhere? Cueball: I don't... Ugh, It opened a dialog box offscreen. Hairy: Why is that even possible? Cueball: It really shouldn't be. But you can fix it by changing your screen resolution to trigger a window cleanup. Hairy: Seriously? Cueball: I know, I know... To be honest, I can't wait for the day when all my stupid computer knowledge becomes obsolete.

Super Bowl

Super Bowl

https://www.xkcd.com/1480

https://www.explainxkcd.com/wiki/index.php/1480:_Super_Bowl

[Cueball standing.] Cueball: I don't know much about sports, which can be culturally isolating, so it's tempting to get vocal and defensive about not following them. Cueball: Caring about something makes people vulnerable, so not caring gives you power. [Pictures of a weather map and Philae in the background.] But I know things I'm into don't always sound interesting to 100% of the people around me, and it means a lot when they sometimes try to listen anyway - and maybe even find themselves sharing some of my excitement! [Cueball pointing to self.] Cueball: So while everyone is going on about the Super Bowl on Sunday, let me tell you what I'll be doing: [Cueball standing again.] Cueball: Listening! Cueball: Hooray for friendship! Cueball: Also, eating snacks. Cueball: Hooray for snacks! This comic shares title with 60: Super Bowl , published February 6, 2006. This appears to be only the second time that two xkcd comics have borne the same name. The first was 786: Exoplanets , published August 30, 2010, and 1071: Exoplanets , published June 20, 2012.

In this comic, Cueball , representing Randall , explains that even though he does not care about sports and is tempted to be scornful about others' obsession with them, he understands that people feel vulnerable about stuff they care about. And he will for sure be fed up with all the talk about the Super Bowl discussions and arguments over the coming weeks. (The comic was released on a Friday two days before Super Bowl XLIX , the championship game of the 2014 NFL season held on 2015-02-01). However, since other people tolerate his interest in odd things like meteorology and the Philae lander (see 1324: Weather and 1446: Landing ), he recognizes that he should show the same consideration to them. This is an invocation of the Golden Rule , "Do unto others as you would have them do unto you". In the last frame, he tells us that instead of celebrating the sports event on Sunday, he will be celebrating friendship (through listening to his friends) and, as a side note, snacking (as they are very frequently brought to Super Bowl-watching events). This suggests that the value of friendship trumps the discomfort of watching human activities that seem uninteresting to him – and of course, the free snacks also help ameliorate his discomfort. The title text continues the " My Hobby " trope characteristic of some xkcd comics: here, Randall references people who scornfully refer to popular sports such as football, basketball, and/or baseball as "sportsball" and creates discomfort for them by pretending to be interested in this imaginary sport. This makes it appear as though they are in fact interested in sports when they are not, exposing their snobbishness. (It is worth noting that there is a Wii U game by that name .) In a distant past, Cueball spent his time differently during the Super Bowl - see 60: Super Bowl . (This was the second time that two xkcd comics have shared the exact same name ). The year after he continued the trend with a Super Bowl related comic to "celebrate" the event: 1640: Super Bowl Context . Between the 2006 comic and this one there were no other Super Bowl related comics coming out in relation to the Super Bowl. See also 1107: Sports Cheat Sheet and two other comics where he jokes with sport in general: 904: Sports and 1507: Metaball . He again directly mentions lack of knowledge in 1859: Sports Knowledge . [Cueball standing.] Cueball: I don't know much about sports, which can be culturally isolating, so it's tempting to get vocal and defensive about not following them. Cueball: Caring about something makes people vulnerable, so not caring gives you power. [Pictures of a weather map and Philae in the background.] But I know things I'm into don't always sound interesting to 100% of the people around me, and it means a lot when they sometimes try to listen anyway - and maybe even find themselves sharing some of my excitement! [Cueball pointing to self.] Cueball: So while everyone is going on about the Super Bowl on Sunday, let me tell you what I'll be doing: [Cueball standing again.] Cueball: Listening! Cueball: Hooray for friendship! Cueball: Also, eating snacks. Cueball: Hooray for snacks! This comic shares title with 60: Super Bowl , published February 6, 2006. This appears to be only the second time that two xkcd comics have borne the same name. The first was 786: Exoplanets , published August 30, 2010, and 1071: Exoplanets , published June 20, 2012.

API

API

https://www.xkcd.com/1481

https://www.explainxkcd.com/wiki/index.php/1481:_API

[Cueball sitting at a desk staring at a computer screen.] API Guide Request URL format: http://~~~.com/<username>/<item ID> Server will return an XML document which contains: The requested data. Documentation describing how the data is organized spatially. API Keys To obtain API access, contact the X.509-authenticated server and request an ECDH-RSA TLS key... If you do things right, it can take people a while to realize that your "API documentation" is just instructions for how to look at your website.

This comic presents a web site designed for human readers as if it had an API ( application programming interface ) designed for machine-to-machine web service . An API is a set of instructions about a computer program, intended to be used by developers of other computer programs, so the two programs can interoperate more easily. The documentation explains how to send commands to the program, and how the output will be returned. Many web APIs are designed to return data in XML format. But in this case, the XML is XHTML , a version of the language that is used by most web pages. The "requested data" is the actual content (e.g. a blog post), and "documentation" refers (in an obscure way) to the parts of a web page that control how it looks on the screen (e.g. CSS and perhaps JavaScript layout code). The "documentation" may also be DTD which tells the XML parser info about this particular XML format, i.e. XHTML. In order for a program to process a generic web site designed for human viewing, the program needs to use web scraping techniques, which often break when the web site design changes in subtle ways that a human might never notice. Therefore, developers prefer to have proper APIs with well-defined machine-readable formats, stable interfaces and documentation that actually describes the semantics of the data. For example, Google has an official API for version 3 of their Youtube web service . But developers who don't want to hassle with the required API key or the costs associated with its use sometimes just scrape the regular YouTube web site . So someone could publish this comic with a YouTube URL as a convoluted hint to developers that there is an alternative to the official API. The API keys section is a step-by-step description of how a web page is protected with HTTP Secure (HTTPS). The Transport Layer Security (TLS) protocol uses an elliptic curve Diffie–Hellman (ECDH) key signed using Rivest-Shamir-Adleman (RSA) encryption, which is stored in an X.509 certificate. Normally, the browser or operating system does this behind the scenes, so most web developers and users do not need to know these details. The access limits mentioned in the title text says that the API can be used for 86,400 seconds each day. At first this may appear to be a strange arbitrary number, however it is in fact the total number of seconds in 24 hours, essentially meaning there is no limit on most days. The International Earth Rotation and Reference Systems Service (IERS) is the organization that decides when to add leap seconds , which account for slight anomalies in the Earth's rotation as compared to the mean solar day . These leap seconds will mean that the website is available for one extra second occasionally, although IERS decisions are based on actual Earth rotation rates and they of course wouldn't respond to requests for leap seconds in order to lengthen the number of seconds that a web site would be available for in a given calendar day. The API does not discuss the issue that some days have 23 or 25 hours due to daylight saving time in the U.S. and summer time in Europe and some other places. This suggests that the web service tracks time via UTC . [Cueball sitting at a desk staring at a computer screen.] API Guide Request URL format: http://~~~.com/<username>/<item ID> Server will return an XML document which contains: The requested data. Documentation describing how the data is organized spatially. API Keys To obtain API access, contact the X.509-authenticated server and request an ECDH-RSA TLS key... If you do things right, it can take people a while to realize that your "API documentation" is just instructions for how to look at your website.

NowPlaying

#NowPlaying

https://www.xkcd.com/1482

https://www.explainxkcd.com/wiki/index.php/1482:_NowPlaying

[A social network news feed with user images for each of the three different contributors. The top of the first post is partly obscured, and for the last post only half of the first line is visible.] [Partially Visible] Brian is now listening to: E Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Brian is now listening to: B Today • 3:28 PM Brian is now listening to: D Today • 3:28 PM Brian is now listening to: C sharp Today • 3:28 PM Mike What the hell Today • 3:28 PM Brian is now listening to: B Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Caitlin Can someone call him? Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Brian is now listening to: E Today • 3:29 PM [Partially Visible] Brian is now listening to: A My new social music service notifies your friends about what notes you're listening to.

There are a variety of applications that post a user's music-listening habits on their preferred social network. In this comic, Randall takes that notion to its extreme, envisioning a program that does this note-by-note, rather than just song-by-song. As songs play several dozen notes a minute (and some songs, many more), this would lead to the flooding of friends' notification streams. In the example, the software is sharing the notes that Brian is listening to; and his friends Mike and Caitlin are getting annoyed with the number of posts they are receiving. There are typically many hundreds of notes in any song. Any song with more than a single line of music contains multiple different notes whose names according to the English convention are communicated here. All but the slowest songs will require reporting dozens to hundreds of notes every minute (a single glissando may cover a dozen or more notes in less than a second), meaning that anyone who can see your stream of posts will be literally inundated by posts from the service. Even if you could keep up with the speed of the posted notes that someone is listening to, the similarity in phrases in many songs (especially pop songs, e.g. Pachelbel's Rant ) means that many different songs may include the same sequence of notes, though possibly in different octaves or at different speeds. The comic's title alludes to the fact that you can "play a song" but can also "play a note." It may also allude to the visual similarities between the hash/pound/ number sign (#) and the sharp sign (♯). C sharp , above Mike's comment, is the only note not given by a single letter (after the correction - see Trivia ). The title text continues the joke of this new musical service: If you click on the post, it takes you to search results for the note on various online music store. Since many songs in similar keys contain at least some of the notes posted, you would be given a list of a large part of the music you can buy in any on-line music stores. Of course this is at least as useless as being told which note someone is listening to. The notes appear to be the beginning of I'll Be There For You by The Rembrandts , the title music of the TV series " Friends ". This could be an internal reference to the idea that it "notifies" (converts into musical notes) your "friends" of the notes (a play on words ). Or we've been nerd sniped . [A social network news feed with user images for each of the three different contributors. The top of the first post is partly obscured, and for the last post only half of the first line is visible.] [Partially Visible] Brian is now listening to: E Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Brian is now listening to: B Today • 3:28 PM Brian is now listening to: D Today • 3:28 PM Brian is now listening to: C sharp Today • 3:28 PM Mike What the hell Today • 3:28 PM Brian is now listening to: B Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Caitlin Can someone call him? Today • 3:28 PM Brian is now listening to: A Today • 3:28 PM Brian is now listening to: E Today • 3:29 PM [Partially Visible] Brian is now listening to: A My new social music service notifies your friends about what notes you're listening to.

Quotative Like

Quotative Like

https://www.xkcd.com/1483

https://www.explainxkcd.com/wiki/index.php/1483:_Quotative_Like

[Megan referring to a published article she is holding.] Megan: I found this article on the linguistics of the "Quotative Like". Cueball: Like, when you're like, "She was like"? Megan: Yeah. Megan: It features a quote from a linguist, Patricia Cukor-Avila: "Eventually all the people who hate this kind of thing are going to be dead, and the ones who use it are going to be in control." Cueball: Wow. Turns out linguists are pretty hardcore. Megan: I think she means dead from old age. Cueball: I'm gonna start using "like" more, just in case.

In this comic, Megan mentions an article on the use of the word " like " as a quotative . Cueball makes a joke on this by managing to use the word "like" three times in a seven word sentence. The "quotative like" is regularly given as an example of the decline of the English language. It is used to introduce a quotation or impersonation, although what follows may not be a verbatim quote, but rather conveys the general meaning of the original phrase. Although it is modern in terms of the English language, examples of its use can be found all the way back in 1928. The song " Cobwebs " by the American singer-songwriter Loudon Wainwright III blames Jack Kerouac and The Many Loves of Dobie Gillis character Maynard G. Krebs for starting the vogue of using the word "like" as a quotative. In the early 1980s, the stereotypical Valley Girl made substantial use of the quotative like, which may be the main origin of its contemporary use. In the second panel Megan mentions that, in a newspaper article , the linguist Patricia Cukor-Avila is like: "Eventually all the people who hate this kind of thing are going to be dead, and the ones who use it are going to be in control." The author is presumably making the point that language is inherently fluid, and the meanings of words exist only by common understanding, which means that, as more and more people grow up with the new usage, it will become increasingly accepted. Most resistance will come from the older generation, which means it will diminish over time. While it has long been popular to criticize modern developments that are seen as steps backward (see 1227: The Pace of Modern Life ), such criticisms are usually in vain, as they are typically made by the older generation against the younger generation, and the latter is always guaranteed to outlive the former [ citation needed ] . The quote, however, doesn't actually say why the older generation will die out, leading Cueball to speculate that Dr. Cukor-Avila is plotting (or warning of) some sort of genocide against people who dislike the use of the quotative like. Megan points out a much more likely interpretation (although this is not mentioned directly in the article), that those people will die of old age, but Cueball persists, saying he'll err on the side of caution and make sure to use the quotative like more often, thereby hoping to be spared from the genocide. The title text applies quotative like to the Book of Genesis (specifically, Genesis 1:3 : "God said, 'Let there be light,' and there was light"), the first book of the Hebrew Bible (the Tanakh) and the Christian Old Testament. When researching the history of language etymologists take great effort to find the earliest usage of a word or phrase, which may be used to show a historical precedence. [Megan referring to a published article she is holding.] Megan: I found this article on the linguistics of the "Quotative Like". Cueball: Like, when you're like, "She was like"? Megan: Yeah. Megan: It features a quote from a linguist, Patricia Cukor-Avila: "Eventually all the people who hate this kind of thing are going to be dead, and the ones who use it are going to be in control." Cueball: Wow. Turns out linguists are pretty hardcore. Megan: I think she means dead from old age. Cueball: I'm gonna start using "like" more, just in case.

Apollo Speeches

Apollo Speeches

https://www.xkcd.com/1484

https://www.explainxkcd.com/wiki/index.php/1484:_Apollo_Speeches

[Commentary above the speeches.] In 1969, Nixon staffer William Safire wrote a speech for the president to deliver if the Apollo 11 return launch failed, stranding the doomed astronauts on the Moon. Uncovered in 1999, it is often called the greatest speech never given. Today, the full set of Safire's contingency speeches has been found. In event astronauts stranded on Moon Fate has ordained that the men who went to the Moon to explore in peace will stay on the Moon to rest in peace. [Here, several lines from the original speech are cut.] In ancient days, men looked at stars and saw their heroes in the constellations. In modern times, we do much the same, but our heroes are epic men of flesh and blood. Others will follow, and surely find their way home. Man’s search will not be denied. But these men were the first, and they will remain the foremost in our hearts. For every human being who looks up at the Moon in the nights to come will know that there is some corner of another world that is forever In event spacecraft goes missing Neil Armstrong, Edwin Aldrin, and Michael Collins went to the Moon as ambassadors of peace for all mankind, and all mankind prays that they may yet return safely home. We are separated from the Moon by a vast gulf of space, against which their tiny vessel appeared as but a drifting speck. For a few brief seconds, we took our eye off them, and despite days of desperate searching, never again was their vessel sighted from Earth. While these men are lost, they are not forgotten, and their sacrifice will not In event astronauts abscond with spacecraft We do not know what led Armstrong, Aldrin and Collins to betray the trust we placed in them, abandon their mission, and steer their vessel toward Mars. Nor do we know what compelled them to transmit such hurtful messages back to Earth, heaping contempt on their onetime home. But whatever the cause of their dereliction, I call upon the United States to commit itself, before this year is out, to launching a mission to chase down Apollo 11 and return its crew to earth to face justice. We must not rest until In event spacecraft returns with extra astronauts While there is much we do not understand, tonight all of earth is united in celebrating the safe return of our brave explorers. We of course have many questions, and in the days and weeks to come we will demand answers. How many souls were truly aboard Apollo 11 when it launched? Who are the six men now in quarantine aboard the USS Hornet? What happened In event spacecraft hits U.S.S. Hornet, crushing Nixon President Agnew : Tonight, we have experienced a great national triumph and a great national loss. We take joy in the safe return from the Moon of Neil Armstrong, Edwin Aldrin, and Michael Collins, but that joy is tempered with sorrow as we mourn our president’s tragic death beneath their wayward capsule. Richard Nixon wholeheartedly supported our courageous astronauts as they carried the hopes and prayers of Earth to the heavens, and in the moment of their homecoming, he himself has departed on that ultimate voyage. As we grieve, we must rededicate ourselves to the cause for which our president In event spacecraft accidentally sold for scrap and crushed with astronauts inside My fellow Americans, I am as shocked and appalled as you at this stunning and

As explained in the comic, Nixon staffer William Safire wrote two speeches for the United States President to deliver, depending on whether or not the Apollo 11 return launch was successful. When the outcome of an event (moon landing, military actions, etc.) can't be predicted with sufficient certainty, it is a common practice for " contingency speeches " to be prepared. The rest of the comic runs with this theme, making the false claim that Safire had written several other such contingency speeches for increasingly unlikely possibilities. First listed are a couple pages from the real contingency speech to be delivered in the event that the astronauts were left stranded on the Moon. Lying on top of that is a speech to be delivered in the case that the spacecraft went missing altogether, which was relatively unlikely. The speeches after that deal with the following highly unlikely or impossible contingencies: The astronauts had stolen the ship and piloted it towards Mars, which was clearly not feasible While the crew could have redirected the ship while sending insulting messages to Earth, the spacecraft lacked the power to fly to Mars within any reasonable period of time by several orders of magnitude or the supplies for the astronauts to survive such an extended trip. At the time of production for this strip in 2015, several governments and private companies have designs on Martian colonization. More astronauts than expected were found in the recovered ship The appearance of three additional astronauts ventures into the realm of possibility normally reserved for science fiction and Twilight Zone episodes. The ship had hit the U.S.S. Hornet and crushed Nixon The USS Hornet was the ship that recovered the Apollo 11 astronauts after they completed their return mission by landing their command module in the Pacific Ocean; President Nixon himself was on board to greet them upon their return. Apollo 11 famously landed in the Pacific Ocean, and the single ship tasked with its recovery would be a very small target to hit for the technology even if that had been the intent, which it was of course not. Spiro Agnew was, in 1969, Vice President of the United States, and thus next in line for the presidency. This joke plays off the extreme improbability of the ship, and indeed President, being hit and triggering a succession, causing "President Agnew" to address the world. This is not as implausible as it sounds. The re-entry guidance had become good enough by Apollo 11 that the destination point of the capsule was moved several hundred yards from the carrier's position for exactly this reason. Such a collision had been the subject of jokes at NASA, until one day an engineer came to Gene Kranz and said, "the more I think about it, the less I think it is a joke." The re-entry craft had been sold for scrap and crushed along with the astronauts inside Apollo 11 observed a strict quarantine procedure after landing. This possibility requires extraordinary incompetence and unholy zeal for recycling programs. The command module was historically recovered, examined, and is now on permanent display in the National Air and Space Museum . Primary sources state that the astronauts were allowed to leave the craft before it was put on display [ citation needed ] . The title text builds upon this last contingency speech, delving into the pathos of the horror of the spacecraft's recycling and its passengers' resulting deaths despite the U.S.'s commitment to recycling initiatives. [Commentary above the speeches.] In 1969, Nixon staffer William Safire wrote a speech for the president to deliver if the Apollo 11 return launch failed, stranding the doomed astronauts on the Moon. Uncovered in 1999, it is often called the greatest speech never given. Today, the full set of Safire's contingency speeches has been found. In event astronauts stranded on Moon Fate has ordained that the men who went to the Moon to explore in peace will stay on the Moon to rest in peace. [Here, several lines from the original speech are cut.] In ancient days, men looked at stars and saw their heroes in the constellations. In modern times, we do much the same, but our heroes are epic men of flesh and blood. Others will follow, and surely find their way home. Man’s search will not be denied. But these men were the first, and they will remain the foremost in our hearts. For every human being who looks up at the Moon in the nights to come will know that there is some corner of another world that is forever In event spacecraft goes missing Neil Armstrong, Edwin Aldrin, and Michael Collins went to the Moon as ambassadors of peace for all mankind, and all mankind prays that they may yet return safely home. We are separated from the Moon by a vast gulf of space, against which their tiny vessel appeared as but a drifting speck. For a few brief seconds, we took our eye off them, and despite days of desperate searching, never again was their vessel sighted from Earth. While these men are lost, they are not forgotten, and their sacrifice will not In event astronauts abscond with spacecraft We do not know what led Armstrong, Aldrin and Collins to betray the trust we placed in them, abandon their mission, and steer their vessel toward Mars. Nor do we know what compelled them to transmit such hurtful messages back to Earth, heaping contempt on their onetime home. But whatever the cause of their dereliction, I call upon the United States to commit itself, before this year is out, to launching a mission to chase down Apollo 11 and return its crew to earth to face justice. We must not rest until In event spacecraft returns with extra astronauts While there is much we do not understand, tonight all of earth is united in celebrating the safe return of our brave explorers. We of course have many questions, and in the days and weeks to come we will demand answers. How many souls were truly aboard Apollo 11 when it launched? Who are the six men now in quarantine aboard the USS Hornet? What happened In event spacecraft hits U.S.S. Hornet, crushing Nixon President Agnew : Tonight, we have experienced a great national triumph and a great national loss. We take joy in the safe return from the Moon of Neil Armstrong, Edwin Aldrin, and Michael Collins, but that joy is tempered with sorrow as we mourn our president’s tragic death beneath their wayward capsule. Richard Nixon wholeheartedly supported our courageous astronauts as they carried the hopes and prayers of Earth to the heavens, and in the moment of their homecoming, he himself has departed on that ultimate voyage. As we grieve, we must rededicate ourselves to the cause for which our president In event spacecraft accidentally sold for scrap and crushed with astronauts inside My fellow Americans, I am as shocked and appalled as you at this stunning and

Friendship

Friendship

https://www.xkcd.com/1485

https://www.explainxkcd.com/wiki/index.php/1485:_Friendship

[A Wikipedia style layout is shown for extracts from an article titled Friendship.] Friendship From Wikipedia, the free encyclopedia A Friendship is a close non-romantic relationship between two (or more) men, a form of affectional or homosocial intimacy. [1] Contents [ hide ] 1 Etymology 2 Characteristics 3 Portrayal of friendship 3.1 Celebrity and fictional friendships 3.2 Historical and political friendships 3.3 Gay-straight friendships 4 See also 5 References Etymology Friendship is a portmanteau of the words friend and ship . Editor Dave Carnie coined the term in the skateboard magazine Big Brother in the 1990s to refer to the sort of relationships that develop between skaters who spend [...] Portrayal of Friendship Celebrity and Fictional Friendships A number of celebrities have engaged in friendships with fellow celebrities. Examples include Ben Affleck and Matt Damon , described as "perhaps the pioneering friendship in showbiz history" [9] which led to a hit off-broadway play [...] Friendship on television has also become more commonplace, with some critics tracing its origins back to shows such as The Odd Couple . [14] In October 2008, TV Guide placed Gregory House ( Hugh Laurie ) and James [...] The Japanese and Korean music industry actively encourages friendship among male celebrities (particularly members of boy bands ) as part of the fan service to please the audience. [19][20] In fiction, what had once been called buddy films have to a degree been rebranded as friendship films, although [...] Historical and political friendships Politically, the relationship between Bill Clinton and Al Gore has been called a precursor to the friendship. [6] The relationship between George W. Bush and former press [Below the extracts is this caption:] How to improve the "Bromance" Wikipedia article In the wake of this comic, several Wikipedia pages were vandalized, among them Bromance , Militia organizations in the United States , Militia (United States) , and Friendship . All these pages were semi-protected by an administrator against further attempts for a week after this comic was published. The day this comic was published, a vote to delete the Bromance article was initiated on Wikipedia.

A " Bromance " is a modern slang term for a strong non-romantic relationship between two male humans. It is a portmanteau of the words brother, meaning a close male friend (aka "bro"), and romance. Although current in popular media, some commentators have criticized the implicit homophobia in the term, suggesting that it denotes cultural discomfort at relationships of emotional closeness between men. In this comic, Randall is implying the Wikipedia page for the word "bromance" should more accurately represent what most bromances actually are: friendships. This could be a joke to reference the fact that some males prefer to not call friendships as such, for fear of looking unmasculine, or being confused as a gay couple. The comic makes light of the fact that the word bromance and friendship are interchangeable, and should be treated as such. The comic later contains parts of the edited article, mocking the use of "bromance" in popular culture, implying that "friendships" can be used just as easily to describe platonic male relationships. Despite supposedly vandalizing the "bromance" article, the article is titled "friendship", giving a similar result to word-replacement browser extensions, as in 1031: s/keyboard/leopard/ . The title text implies Randall does not agree with Wikipedia vandalism, except in the case of bromance/friendship, and also militia/fanclub, possibly to make light of the harsh sounding word in a negative light. This is probably because many of his comics include fake wikipedia entries, and many people, inspired by the comic, actually make the edit happen. A later comic called 1746: Making Friends , was also not so much about friendship, but rather about vultures... [A Wikipedia style layout is shown for extracts from an article titled Friendship.] Friendship From Wikipedia, the free encyclopedia A Friendship is a close non-romantic relationship between two (or more) men, a form of affectional or homosocial intimacy. [1] Contents [ hide ] 1 Etymology 2 Characteristics 3 Portrayal of friendship 3.1 Celebrity and fictional friendships 3.2 Historical and political friendships 3.3 Gay-straight friendships 4 See also 5 References Etymology Friendship is a portmanteau of the words friend and ship . Editor Dave Carnie coined the term in the skateboard magazine Big Brother in the 1990s to refer to the sort of relationships that develop between skaters who spend [...] Portrayal of Friendship Celebrity and Fictional Friendships A number of celebrities have engaged in friendships with fellow celebrities. Examples include Ben Affleck and Matt Damon , described as "perhaps the pioneering friendship in showbiz history" [9] which led to a hit off-broadway play [...] Friendship on television has also become more commonplace, with some critics tracing its origins back to shows such as The Odd Couple . [14] In October 2008, TV Guide placed Gregory House ( Hugh Laurie ) and James [...] The Japanese and Korean music industry actively encourages friendship among male celebrities (particularly members of boy bands ) as part of the fan service to please the audience. [19][20] In fiction, what had once been called buddy films have to a degree been rebranded as friendship films, although [...] Historical and political friendships Politically, the relationship between Bill Clinton and Al Gore has been called a precursor to the friendship. [6] The relationship between George W. Bush and former press [Below the extracts is this caption:] How to improve the "Bromance" Wikipedia article In the wake of this comic, several Wikipedia pages were vandalized, among them Bromance , Militia organizations in the United States , Militia (United States) , and Friendship . All these pages were semi-protected by an administrator against further attempts for a week after this comic was published. The day this comic was published, a vote to delete the Bromance article was initiated on Wikipedia.

Vacuum

Vacuum

https://www.xkcd.com/1486

https://www.explainxkcd.com/wiki/index.php/1486:_Vacuum

[Beret guy is holding an upright vacuum cleaner upside-down by the handle, waving it around above his head.] [The vacuum cleaner is upright on the ground, and Beret guy is standing on its body, wiggling the handle.] Cueball: What are you doing? Beret Guy: Trying to unlock the tremendous energy of the vacuum. [Beret guy rides the vacuum cleaner as it begins to lift off, propelled upward by an unknown force.] Cueball: That’s not what that— Beret Guy: —Ha ha! It works! [Beret guy flies away on the vacuum cleaner.] Cueball: I said, that’s— Beret Guy: The universe is mine to command!!

According to quantum mechanics there is tremendous energy density in space-time itself: this is known as: vacuum energy , zero point energy, vacuum foam, etc. So far we don't know any way to tap into this energy. In the cartoon, Beret Guy appears to be making a silly mistake, confusing the "vacuum" referred to in calculations of the theoretical energy density of space time with a vacuum cleaner , which is also commonly referred to as just a "vacuum". Cueball tries to correct him, but it turns out that Beret Guy really is able to tap into this fundamental source of energy. Having such strange and impossible powers is second nature to Beret Guy, as can be seen in many of his appearances – for instance in 1388: Subduction License . But even though Beret Guy now claims the Universe is his to command (a sentence used by Jafar from Aladdin , but a similar intent is also stated by the crazy villain in many movies ), Cueball is not fazed by this and simply asks, in the title text, if Beret Guy would use the vacuum for its intended purpose and clean the living room. This seems to imply Beret Guy has previously, perhaps repeatedly, taken an action that would normally imply he was going to clean the living room (such as taking a broom or some other cleaning implement that is not the vacuum) and done something unexpected with it instead (such as flying off on it). On an additional note, many scientific breakthroughs in history have been made because the person making them did not realize they were supposedly impossible, such as spin-stabilized magnetic levitation . This comic could be seen as a nod to that. It seems that Cueball borrows one of Beret Guy's vacuum cleaners later in 1826: Birdwatching . A normal vacuum cleaner would not be able to do what Cueball's presumably does to birds in that comic! [Beret guy is holding an upright vacuum cleaner upside-down by the handle, waving it around above his head.] [The vacuum cleaner is upright on the ground, and Beret guy is standing on its body, wiggling the handle.] Cueball: What are you doing? Beret Guy: Trying to unlock the tremendous energy of the vacuum. [Beret guy rides the vacuum cleaner as it begins to lift off, propelled upward by an unknown force.] Cueball: That’s not what that— Beret Guy: —Ha ha! It works! [Beret guy flies away on the vacuum cleaner.] Cueball: I said, that’s— Beret Guy: The universe is mine to command!!

Tornado

Tornado

https://www.xkcd.com/1487

https://www.explainxkcd.com/wiki/index.php/1487:_Tornado

[Cueball is a news commentator holding a microphone while standing in front of a small village with three (intact) houses behind him.] Cueball: The tornado touched down directly over a merry-go-round, in what victims are calling a "fun" and "awesome" disaster.

A merry-go-round (or carousel) is an amusement ride consisting of a (usually) slowly rotating circular platform with seats for riders. These seats are traditionally wooden horses. Merry-go-rounds usually rotate slowly, as it is a children's ride. [ citation needed ] The implication is that a tornado have made a merry-go-round spin much faster, creating the "fun" and "awesome" experience described by the news commentator. In reality such an event would most likely destroy the merry-go-round or at least damage it in a way that would keep it from spinning, such as by breaking an axle or bearing. Barring damage to the merry-go-round itself, if the tornado caused it to spin much faster than normal, anyone riding it at the time would likely be thrown off and injured due to the increased centrifugal force . The title text refers to the spinning teacup ride which consists of several circular units ("teacups") that seat several people each. They rotate around their center axis, while simultaneously orbiting the center of the entire ride, exposing people to acceleration in rapidly shifting, seemingly random directions. The second tornado system, as reported in the title text, had multiple vortices , similarly rotating around a common center, that attached themselves to each of the "teacups", also spinning them faster than normal operation of the ride would have. This is, of course, even less likely (to happen, and to result in no injuries if it did) than the single-vortex tornado on a merry-go-round. Tornadoes are a recurring subject on xkcd. This setup is a variety of the news anchor category , but since Cueball is not in a studio it cannot be included in that category. [Cueball is a news commentator holding a microphone while standing in front of a small village with three (intact) houses behind him.] Cueball: The tornado touched down directly over a merry-go-round, in what victims are calling a "fun" and "awesome" disaster.

Flowcharts

Flowcharts

https://www.xkcd.com/1488

https://www.explainxkcd.com/wiki/index.php/1488:_Flowcharts

[A flow chart. The first option the start box is white text on a black rectangle. The other boxes are rhombuses standing on edge. Except for the first there are always two options going out. Most only have one option coming in, but there are exceptions with two options going in.] Start [One arrow points to the first real choice.] [Below the text on the two options going out from each option will be indented. The top of these two options will be the one to be mentioned first below. Then the chart will be mapped like this going back to the previous unfinished option.] Do you like flowcharts? Yes No [Yes goes back where it came from.] Do you like line graphs? Yes No Data or axis? Line Axis [The line is just a line – but now as the line in a line graph.] Time or your happiness? Time Your happiness [These two lines turn into the x and y axis of the line graph.] Scatter plots? Yes No Data or axis? Data Axis [The data line turns into the points in a scatter plot.] X or Y? X Y [These two lines turn into the x and y axis of the scatter plot.] Help charge a battery? Yes No Are you A/C or D/C?, A/C D/C Positive or negative phase? + - [The D/C option also goes to this next option, but directly. This next rhombus looks like a part of a circuit diagram.] Positive or negative DC terminal? + - [These two lines goes to the + and – poles of a battery.] Like spirals? No Yes Take the path of least resistance? Never Yes [Never goes through two resistors and a diode before reaching the point of the Yes option, which then also goes though yet another resistor. Both thus end at the same option, which is also the one that Yes to like Spirals ends up at:] Do you like when people find the golden spiral in random images? Yes, even though it's total BS. No, it's total BS. [Yes option takes the chart into a fading line that turns into a golden spiral spanning the whole chart.] Tired of flowcharts yet? No Yes, I want to look at something else [No takes you back to the start box at the top.] [Yes takes you out of the comic and points to the Random button at xkcd.]

Note : A flawed version of this comic was posted at first and then quickly a correct version was uploaded. But this gave rise to several misunderstandings and confusion. See the Trivia section below. This comic is a flowchart style, like many. Interestingly, the first option, Do you like flowcharts? loops back to itself if you say Yes . As the yes lines of other options point to the type of graph they describe (for example, the yes line of Do you like line graphs? points to a line graph), this may be interpreted as a recursive reference to the flowchart itself, although it points to the option itself rather than the START node. Also, this may cause the reader who actually likes flow charts to go into an endless loop of choosing Yes , until they are so annoyed by flowcharts that they do not like them anymore and can progress by saying No . After asking about flowcharts, the reader is asked whether they like line graphs . If they follow the yes line, it becomes a line graph where "Time" is the x-axis and "Your Happiness" is the y-axis, and shows that your happiness increases with time. If you don't like line graphs, they are asked the same question about scatter plots where again the lines turn into the points and the axis of such a plot. Taking yet another line, the reader is asked "Charge a battery?" If they follow the line marked yes they are asked whether they are A/C or D/C current and are led to a portion of the flowchart which resembles a circuit diagram of a rectifier bridge with a battery connected to it. If the reader follows the "no" line, they are asked if they like spirals. If they choose "no" they are asked whether they would take the path of least resistance . This part of the flowchart resembles a circuit diagram, and the word " resistance " is a pun because resistance can have several meanings. In electricity it is an electrical quantity that measures how the device or material impedes the electric current flow through it. Going left is the "Never" option, which goes through extra resistors and a diode, therefore making the "Yes" option the "path of least resistance". However, when asked if you choose the path of least resistance and answers never it could also mean that you do not try to avoid a little trouble. Whether they choose "Yes" or "No", they arrive at "Do you like when people find the golden spiral in random images?" If they choose "yes" the line fades into a drawing of a golden spiral, and we see that the flowchart is structured around it. If they choose "no" they are asked if they are tired of flowcharts. If not, they are taken to the beginning to start over again. If they are tired, the line points to the "random" button on the xkcd website. The title text and the faint image of a golden spiral parody the fact that the golden spiral is superimposed on nearly everything . The golden spiral is a spiral that has the growth rate of the golden ratio, a number that has inspired both artists and mathematicians alike. However, people try to find the golden ratio in seemingly random objects, and they fall to confirmation bias when drawing a golden spiral on top that seemingly fits. The comic links to [1] , where one can see exactly that- golden spirals Randall "found" in random photographs. This may be a spoof of the viral video Illuminati Confirmed . The limit of the ratio of two consecutive terms of the Fibonacci sequence is equal to the golden ratio, so a Fibonacci spiral matches up almost perfectly for a good reason, unlike the coincidental matchings of the pictures in the mobile site link. This comic bears reminiscence of 730: Circuit Diagram , although it is not exactly the same idea. Putting a golden spiral over other things was again used in 2322: ISO Paper Size Golden Spiral , like the spiral page on xkcd which this comic is a link to. [A flow chart. The first option the start box is white text on a black rectangle. The other boxes are rhombuses standing on edge. Except for the first there are always two options going out. Most only have one option coming in, but there are exceptions with two options going in.] Start [One arrow points to the first real choice.] [Below the text on the two options going out from each option will be indented. The top of these two options will be the one to be mentioned first below. Then the chart will be mapped like this going back to the previous unfinished option.] Do you like flowcharts? Yes No [Yes goes back where it came from.] Do you like line graphs? Yes No Data or axis? Line Axis [The line is just a line – but now as the line in a line graph.] Time or your happiness? Time Your happiness [These two lines turn into the x and y axis of the line graph.] Scatter plots? Yes No Data or axis? Data Axis [The data line turns into the points in a scatter plot.] X or Y? X Y [These two lines turn into the x and y axis of the scatter plot.] Help charge a battery? Yes No Are you A/C or D/C?, A/C D/C Positive or negative phase? + - [The D/C option also goes to this next option, but directly. This next rhombus looks like a part of a circuit diagram.] Positive or negative DC terminal? + - [These two lines goes to the + and – poles of a battery.] Like spirals? No Yes Take the path of least resistance? Never Yes [Never goes through two resistors and a diode before reaching the point of the Yes option, which then also goes though yet another resistor. Both thus end at the same option, which is also the one that Yes to like Spirals ends up at:] Do you like when people find the golden spiral in random images? Yes, even though it's total BS. No, it's total BS. [Yes option takes the chart into a fading line that turns into a golden spiral spanning the whole chart.] Tired of flowcharts yet? No Yes, I want to look at something else [No takes you back to the start box at the top.] [Yes takes you out of the comic and points to the Random button at xkcd.]

Fundamental Forces

Fundamental Forces

https://www.xkcd.com/1489

https://www.explainxkcd.com/wiki/index.php/1489:_Fundamental_Forces

[Cueball is holding his hands up while giving a lecture to an off panel audience.] Cueball: There are four fundamental forces between particles: (1) Gravity , which obeys the inverse square law: F gravity = G m 1 m 2 /d 2 Off panel audience: OK... [Cueball is still holding his hands up while continues the lecture to the off panel audience.] Cueball: (2) Electromagnetism , which obeys this inverse-square law: F static = K e q 1 q 2 /d 2 ...and also Maxwell's equations Off panel audience: Also what? [Zoom in on Cueball as he continues the lecture to the off panel audience.] Cueball: (3) The strong nuclear force , which obeys, uh ... ...well, umm... ...it holds protons and neutrons together. Off panel audience: I see. Cueball: It's strong. [Cueball finishes the lecture to the off panel audience and spreads out his arm for the final remark.] Cueball: And (4) the weak force . It [mumble mumble] radioactive decay [mumble mumble] Off panel audience: That's not a sentence. You just said “Radio- Cueball: – And those are the four fundamental forces!

Cueball is acting here as someone teaching physics at a basic level, perhaps a high school science teacher. He seems to understand the general idea of the four fundamental forces , but his understanding gets progressively more sketchy about the details. The off-panel audience, probably a student or class, is interested, but quickly begins to realize Cueball's lack of understanding. Instead of acknowledging the problem directly, Cueball simply blusters onwards. The comic also outlines how progressively difficult it gets to describe the forces. Gravity was first mathematically characterized in 1686 as Newton's law of universal gravitation , which was considered an essentially complete account until the introduction of general relativity in 1915. The electromagnetic force does indeed give rise to Coulomb's law of electrostatic interaction (another inverse-square law , proposed in 1785), but a much more comprehensive description, covering full classical electrodynamics , was only given in Maxwell's equations around 1861. The strong and weak forces cannot easily be summarized as comparably simple mathematical equations. It's possible that Cueball does understand the strong and weak interactions, but is completely at a loss when he tries to summarize them. The strong force doesn't act directly between protons and neutrons but between the quarks that form them. Unlike gravity and electromagnetism, the strong force gets stronger with increasing distance : It is loosely similar to the restoring force of an extended spring . However, all stable heavy particles are neutral to the strong force, due to being made up of three " colors " (or a color and the appropriate "anticolor") of quarks. Between protons and neutrons there is a residual strong force, analogous in some ways to the van der Waals force between molecules. This residual strong force is carried by pions and does decrease rapidly and exponentially with distance due to the pions having mass. The weak force is much weaker than electromagnetism at typical distances within an atomic nucleus (but is still stronger than gravity), and has a short range, so has very little effect as a force . What it has instead is the property of changing one particle into another. It can cause a down quark to become an up quark, and in the process release a high-energy electron and electron anti-neutrino. This is known as beta decay , a form of radioactivity. Over even shorter distances, and much higher temperatures , the weak interaction and electromagnetism are essentially the same, thus being merged to form the electroweak force . The electroweak force was also mentioned in a later comic, 1956: Unification . The title text refers to the fact that it is gravity that appears to be the simplest and easiest to understand of the four forces, but turns out to be the hardest to reconcile with a coherent (quantum) understanding of all four forces together . [Cueball is holding his hands up while giving a lecture to an off panel audience.] Cueball: There are four fundamental forces between particles: (1) Gravity , which obeys the inverse square law: F gravity = G m 1 m 2 /d 2 Off panel audience: OK... [Cueball is still holding his hands up while continues the lecture to the off panel audience.] Cueball: (2) Electromagnetism , which obeys this inverse-square law: F static = K e q 1 q 2 /d 2 ...and also Maxwell's equations Off panel audience: Also what? [Zoom in on Cueball as he continues the lecture to the off panel audience.] Cueball: (3) The strong nuclear force , which obeys, uh ... ...well, umm... ...it holds protons and neutrons together. Off panel audience: I see. Cueball: It's strong. [Cueball finishes the lecture to the off panel audience and spreads out his arm for the final remark.] Cueball: And (4) the weak force . It [mumble mumble] radioactive decay [mumble mumble] Off panel audience: That's not a sentence. You just said “Radio- Cueball: – And those are the four fundamental forces!

Atoms

Atoms

https://www.xkcd.com/1490

https://www.explainxkcd.com/wiki/index.php/1490:_Atoms

[Megan stands at a table and is preparing a sample for some kind of analysis in a device, when Beret Guy walks in.] Beret Guy: What’re you doing? Megan: Testing a sample for beryllium. Beret Guy: That? Yeah, there’s a bunch of berylliums. Megan: How do you know? [Megan turns to Beret Guy who takes the sample and looks at it.] Beret Guy: Look at it! See? Tons of oxygens and silicons, a few irons but definitely some berylliums too! Can’t you see them? [They continue to talk.] Megan: No, I can’t see a list of the atoms in a thing by looking. Beret Guy: How do you tell what things are? [Zoom in on Megan.] Megan: This is ridiculous. Look at me. What do you see? Beret Guy (off-panel): You have tons of metal in your face. Lots of fillings, I guess? [Megan stares at Beret Guy who takes a looks at his own arm.] Megan: What’s wrong with you? Beret Guy: Too many zincs? I’ve always worried I had too much zinc and everyone thought I was weird. Could possibly explain 452: Mission if he believes all carbon based objects to be scones.

This comic shows another quirky and fantastical ability of Beret Guy . In this comic, Megan is preparing a sample of what appears to be some mineral for elemental analysis . It seems to be some kind of silicate containing a small amount of iron (a common example of this would be red sandstone ), and she is running a test to see if it contains beryllium (a rarer element whose best-known natural form is as a component of emerald ). Such analyses typically involve many instruments and steps to prepare the sample. However, Beret Guy seems to be able to identify all the elements the substance is composed of just by eyeballing it, making him perhaps the perfect elemental analysis instrument. To confirm this, Megan asks Beret Guy what he sees when he looks at her face, expecting that a normal person would describe the arrangement of colors and features that they see. Since Beret Guy sees the atoms Megan is composed of (mostly oxygen, carbon and hydrogen ) he only notices the unusual atoms. In this case he sees the metal atoms her dental fillings are composed of. This shows his "atomic vision" extends beyond the surface of the substances. Megan finds this bizarre and asks Beret Guy what is wrong with him. He states that he has always suspected he contains too much zinc , which he believes makes people think he is weird, thus missing Megan’s point: what is weird is not Beret Guy’s elemental content, but his ability to apparently see everything as atoms sorted by element. High zinc intake ( zinc toxicity ) can cause nausea, vomiting, pain, cramps and diarrhea. It also reduces copper absorption, which affects the immune system. However, it does not grant superhuman sensory abilities. [ citation needed ] That is solely a function of tin . The comic continues the theme of Beret Guy’s naive misunderstandings of scientific terminology turning to be literally true. In a previous comic his misinterpretation of the notion of energy in the vacuum resulted in him gaining significant superpowers. In the title text, the concept is taken even further: Beret Guy found his dad indistinguishable from a dog. This is likely because all mammals are essentially made of the same basic elements. Absent a distinguishing element from either his dad or the dog, they would appear to be the same. He could, however, apparently distinguish his mother because she contained plutonium . This is a very unusual occurrence that cannot possibly occur naturally in humans. [ citation needed ] Some possible explanations are: It is also possible that the presence of plutonium in his mother may be the source of his own differences: radioactive exposure (in this case, potentially in utero) is a common source of super powers in comic books and other fiction (though unfortunately, this does not work in real life [ citation needed ] ). It's not clear whether his mother's plutonium is related to his "too many zincs". One explanation for Beret Guy having too much zinc could be that his mother's plutonium changed into zinc through the process of radioactive decay . Beret Guy’s mother containing plutonium is probably intended as a whimsical explanation of his powers, since it is a trope in fiction for radioactivity to cause superpowers. It is worth noting that the verbs "recognized" and "had" in the title text are written in past tense. This presents the possibility that Beret Guy's mother passed away due to radiation sickness from exposure to the radiation originating from the plutonium in her middle. This possibility is further evidenced when Beret Guy adds "I never did ask her why...", indicating that he may no longer have the opportunity to do so. The English physicist Henry Moseley discovered the law relating the atomic number of elements with their characteristic x-rays when bombarded by free electrons, providing physical evidence for the periodic table , the Bohr Model of the atom and the concept of atomic number . In doing so he developed a method of identifying elements in a substance by bombarding them in a vacuum with electrons and using x-ray diffraction methods to measure the resulting X-rays. A famous French chemist brought him a complicated mixture of Rare Earth elements , many of which had only recently been discovered, to test his method. Within a short time, Mosley amazed the chemist by identifying all the elements by number using his method and referring to his chart to name them. This comic may therefore be subtly alluding to this method by suggesting that Beret Guy's eyes can fire electrons at anything he looks at and "read" the resulting X-ray radiation, giving him the ability to identify the composite elements in a similar manner. [Megan stands at a table and is preparing a sample for some kind of analysis in a device, when Beret Guy walks in.] Beret Guy: What’re you doing? Megan: Testing a sample for beryllium. Beret Guy: That? Yeah, there’s a bunch of berylliums. Megan: How do you know? [Megan turns to Beret Guy who takes the sample and looks at it.] Beret Guy: Look at it! See? Tons of oxygens and silicons, a few irons but definitely some berylliums too! Can’t you see them? [They continue to talk.] Megan: No, I can’t see a list of the atoms in a thing by looking. Beret Guy: How do you tell what things are? [Zoom in on Megan.] Megan: This is ridiculous. Look at me. What do you see? Beret Guy (off-panel): You have tons of metal in your face. Lots of fillings, I guess? [Megan stares at Beret Guy who takes a looks at his own arm.] Megan: What’s wrong with you? Beret Guy: Too many zincs? I’ve always worried I had too much zinc and everyone thought I was weird. Could possibly explain 452: Mission if he believes all carbon based objects to be scones.

Stories of the Past and Future

Stories of the Past and Future

https://www.xkcd.com/1491

https://www.explainxkcd.com/wiki/index.php/1491:_Stories_of_the_Past_and_Future

Date of publication [A logarithmic scale running horizontally, from 3000 BCE to past 2015 CE.] Years in the future [A logarithmic scale running vertically, from 1 billion down to 0.] Stories set in the future (science fiction, prediction) Stories set in 2015 [A line divides this region into two. The upper side is labelled "still possible"; the lower side is labelled "obsolete".] [From left to right.] Memoirs of the Twentieth Century [1700, 265 years in the future] Looking Backward [1888, 112 years in the future] Golf in the Year 2000 [1892, 108 years in the future] The Time Machine [1895, 800 thousand to 30 million years in the future] Enoch Soames [1916, circa 60 years in the future] 1984 [1949, 35 years in the future] A Week in the Wales of the Future [1957, 76 years in the future] The Jetsons [1962-63, 100 years in the future] Star Trek [1966-69, 300 years in the future] 2001: A Space Odyssey [1968, 33 years in the future] Space: 1999 [1975-77, 24 years in the future] 2010: Odyssey Two [1982, 28 years in the future] Transformers (TV series) [1984-87, 20 years in the future] 2061: Odyssey Three [1987, 74 years in the future] Star Trek: The Next Generation [1987-94, circa 500 years in the future] Back to the Future Part II [1989, 26 years in the future] Zero Wing [1989, 112 years in the future] Terminator 2 (1995 portion) [1991, 4 years in the future] 3001: The Final Odyssey [1997, 1004 years in the future] Enterprise [2001-2005, 150 years in the future] This chart [2015, 0 years in the future] Years in the past [A logarithmic scale running vertically, from 0 down past 1 billion to "Big Bang"] Stories set in the past (History, Period Fiction) Stories written X years ago and set 2X years ago [A line divides this region into two. The upper side is labelled as follows.] Former period pieces Stories set in the past, but created long enough ago that they were published closer to their setting than to today. Modern audiences may not recognize which parts were supposed to sound old. [From left to right.] The Epic of Gilgamesh [ circa 2100 BCE, 600 years in the past] The Iliad [ circa 800 BCE, 450 years in the past] History of the Peloponnesian War [ circa 390 BCE, 10 years in the past] Book of Genesis [ circa 500 BCE, 4000 years in the past] Ashokavadana [ circa 100 BCE, 300 years in the past] Gospels (various estimates) [ circa 250 CE, 24 to 75 years in the past] The Pillow Book [1000 CE, 5 years in the past] Water Margin [ circa 1300, 195 years in the past] Richard III [ circa 1590, 115 years in the past] Julius Caesar [1599, 1650 years in the past] King John [ circa 1600, 500 years in the past] Henry IV [ circa 1600, 190 years in the past] King Lear [ circa 1606, 3000 years in the past] Henry VIII [ circa 1612, 105 years in the past] The Last of the Mohicans [1826, 69 years in the past] Rip Van Winkel [1819, 31-51 years in the past] A Tale of Two Cities [1859, 60 years in the past] Moby-Dick [1851, anywhere from 4 to 14 years ago] "Some years ago--never mind how long precisely..." Les Miserábles [1862, 30 years in the past] Treasure Island [1883, 130 years in the past] A Connecticut Yankee in King Arthur's Court [1889, 2000 years in the past] Gone with the Wind [1936, 70 years in the past] Lest Darkness Fall [1939, 550 years in the past] Casablanca [1942, 1 year in the past] Oklahoma! [1943, 37 years in the past] The Ten Commandments [1956, 1400 years in the past] The Bridge on the River Kwai [1957, 13 years in the past] Gunsmoke [1952-61, 80 years in the past] The Flintstones [1960-66, 100,000 years in the past] Catch-22 (book) [1961, 18 years in the past] The Great Escape [1963, 20 years in the past] Asterix Lawrence of Arabia The Music Man Bonnie and Clyde 2001: A Space Odyssey (prologue) American Graffiti Patton Catch-22 (movie) [1970, 27 years in the past] Chinatown Blazing Saddles Apocalypse Now Happy Days Grease M*A*S*H Annie (play) Roots Chariots of Fire Star Wars (IV-VI) Annie (movie) The Right Stuff Back to the Future Gandhi Platoon Dirty Dancing Back to the Future Part III The Wonder Years JFK The Sandlot Schindler's List Raptor Red Apollo 13 Star Wars (I-III) The Big Lebowski Evita Saving Private Ryan The Prince of Egypt Freaks and Geeks Hotel Rwanda I Love the '80s That '70s Show Pearl Harbor Ice Age I Love the '90s United 93 300 10,000 BC Year One The Wolf of Wall Street I Love the 2000s Mad Men Downton Abbey Star Wars (VII-IX)

It's long been common for narrative works to be set in the past, and this tendency goes back to ancient mythology. The opposite approach, setting a work in a speculative future, has been less common prior to modern times. The oldest example Randall presents is from 1733, but it didn't really become a trend until well into the 19th century, and didn't become really common until the 20th century. For works set in the future, particularly in the near future, there's a real possibility that audiences will still read or watch it past the date in which is was set, allowing them to compare the real world of this era to the one the author projected. This doesn't make the work less valuable, necessarily, but it does make the limits of such speculation painfully obvious, and tends to make the future presented there look dated and quaint . Randall labels these futuristic works as "obsolete". For works set in the past, there's an opposite and somewhat more subtle effect. Once the work itself is old enough, audiences tend to forget that they were intended as historical fiction in the first place. If an old work is set in the past, it's often assumed that they were set in their own time, not in the still more distant past. That impacts how we experience the work, because we tend to assume that it's a faithful representation of its own time, not a later interpretation that was intended to be old (and possibly nostalgic) even in its own time. On top of this, in a similar situation to the failed attempt at futurology , for future-facing works of fiction, even a conscientiously faithful 'historic' film can age badly. Later understanding of previously hazy historical situations can be developed between the time of the fictional work being authored and your experience of it. To demonstrate those impacts, this chart sorts various works by the year they were created, graphed against how far in the past or future they were originally set. Lines on the chart are added to separate when each work ceases to work as either a prediction or as a period piece . For future works, the cut-off is obvious: if it was set in a year prior to the current year, we know that the predictions are obsolete (and can easily determine how accurate or inaccurate that future is). Hence, at the time the chart was written (in 2015), works like 1984 and 2001: A Space Odyssey are obsolete, while works like Star Trek , which take place in a more distant future, are still theoretically possible. ( Back to the Future Part II is deliberately right on the line, as it was set in 2015). For the past works, Randall sets the cut-off as when the work itself is older than the events in question were when it was first written/made. Hence, modern audiences are unlikely to realize that the Epic of Gilgamesh was intended to sound ancient, even when it was new, or that novels like Les Miserables were intended as historical fiction, or even that films like Chinatown or shows like Happy Days were intended as period pieces when they were made. To modern audiences, we just see an old work set in an old time, and tend to assume that the two periods were the same. The setup of the chart points to the reality that, in process of time, more and more works will cross those lines. Future audiences will likely assume that films like Apollo 13 and Schindler's List were made around the time of the events in question. And modern science fiction works, if they're still remembered in the future, will become just as obsolete as past works. And Randall even indicates "this chart" on the chart, apparently acknowledging that it will become dated as time goes by. How to read the graph: For example, "Water Margin" was published in the 14th century (x ~= 1300) and relates events from the 12th century, about 200 years before its publication (y ~= 200 in the past). Another example: The film The Bridge on the River Kwai was released in 1957 and it was set around 14 years before (~1942-43). Taking the "years in the past" on the y-axis to be read as negatives like in most graphs one can write Thus it's clear that the definitions of the lines are consistent with each other as they follow similar but inverted functions. The graph uses variable logarithmic scales , adjusting the scale in various regions to the temporal density of works being plotted. If the scale were linear, the graph would in fact represent a (bidimensional) Minkowski diagram , which depicts the moving cones of past and future in spacetime as one's present advances in time. The title text jokes that 2001 cuts from prehistoria to the future before The Flintstones theme can become recognizable. This references the fact that, despite being primarily set in what was then the future, the film opens in the ancient past, thus appearing in both parts of the graph, with one part being very close to The Flintstones . This plays on the fact that one of these was a very serious work and the other a playful animated show that was intended as family comedy. Differences listed in bright red are "former period pieces." Differences listed in dark red are other works set in the past. Differences listed in bright green are "obsolete" works set in the future. Differences listed in dark green are other works set in the future. Asterisks (*) after a year of publication denote that it applies to the first installment in a series that spanned more than one year. You can sort by a specific column in this table by clicking on its header. Date of publication [A logarithmic scale running horizontally, from 3000 BCE to past 2015 CE.] Years in the future [A logarithmic scale running vertically, from 1 billion down to 0.] Stories set in the future (science fiction, prediction) Stories set in 2015 [A line divides this region into two. The upper side is labelled "still possible"; the lower side is labelled "obsolete".] [From left to right.] Memoirs of the Twentieth Century [1700, 265 years in the future] Looking Backward [1888, 112 years in the future] Golf in the Year 2000 [1892, 108 years in the future] The Time Machine [1895, 800 thousand to 30 million years in the future] Enoch Soames [1916, circa 60 years in the future] 1984 [1949, 35 years in the future] A Week in the Wales of the Future [1957, 76 years in the future] The Jetsons [1962-63, 100 years in the future] Star Trek [1966-69, 300 years in the future] 2001: A Space Odyssey [1968, 33 years in the future] Space: 1999 [1975-77, 24 years in the future] 2010: Odyssey Two [1982, 28 years in the future] Transformers (TV series) [1984-87, 20 years in the future] 2061: Odyssey Three [1987, 74 years in the future] Star Trek: The Next Generation [1987-94, circa 500 years in the future] Back to the Future Part II [1989, 26 years in the future] Zero Wing [1989, 112 years in the future] Terminator 2 (1995 portion) [1991, 4 years in the future] 3001: The Final Odyssey [1997, 1004 years in the future] Enterprise [2001-2005, 150 years in the future] This chart [2015, 0 years in the future] Years in the past [A logarithmic scale running vertically, from 0 down past 1 billion to "Big Bang"] Stories set in the past (History, Period Fiction) Stories written X years ago and set 2X years ago [A line divides this region into two. The upper side is labelled as follows.] Former period pieces Stories set in the past, but created long enough ago that they were published closer to their setting than to today. Modern audiences may not recognize which parts were supposed to sound old. [From left to right.] The Epic of Gilgamesh [ circa 2100 BCE, 600 years in the past] The Iliad [ circa 800 BCE, 450 years in the past] History of the Peloponnesian War [ circa 390 BCE, 10 years in the past] Book of Genesis [ circa 500 BCE, 4000 years in the past] Ashokavadana [ circa 100 BCE, 300 years in the past] Gospels (various estimates) [ circa 250 CE, 24 to 75 years in the past] The Pillow Book [1000 CE, 5 years in the past] Water Margin [ circa 1300, 195 years in the past] Richard III [ circa 1590, 115 years in the past] Julius Caesar [1599, 1650 years in the past] King John [ circa 1600, 500 years in the past] Henry IV [ circa 1600, 190 years in the past] King Lear [ circa 1606, 3000 years in the past] Henry VIII [ circa 1612, 105 years in the past] The Last of the Mohicans [1826, 69 years in the past] Rip Van Winkel [1819, 31-51 years in the past] A Tale of Two Cities [1859, 60 years in the past] Moby-Dick [1851, anywhere from 4 to 14 years ago] "Some years ago--never mind how long precisely..." Les Miserábles [1862, 30 years in the past] Treasure Island [1883, 130 years in the past] A Connecticut Yankee in King Arthur's Court [1889, 2000 years in the past] Gone with the Wind [1936, 70 years in the past] Lest Darkness Fall [1939, 550 years in the past] Casablanca [1942, 1 year in the past] Oklahoma! [1943, 37 years in the past] The Ten Commandments [1956, 1400 years in the past] The Bridge on the River Kwai [1957, 13 years in the past] Gunsmoke [1952-61, 80 years in the past] The Flintstones [1960-66, 100,000 years in the past] Catch-22 (book) [1961, 18 years in the past] The Great Escape [1963, 20 years in the past] Asterix Lawrence of Arabia The Music Man Bonnie and Clyde 2001: A Space Odyssey (prologue) American Graffiti Patton Catch-22 (movie) [1970, 27 years in the past] Chinatown Blazing Saddles Apocalypse Now Happy Days Grease M*A*S*H Annie (play) Roots Chariots of Fire Star Wars (IV-VI) Annie (movie) The Right Stuff Back to the Future Gandhi Platoon Dirty Dancing Back to the Future Part III The Wonder Years JFK The Sandlot Schindler's List Raptor Red Apollo 13 Star Wars (I-III) The Big Lebowski Evita Saving Private Ryan The Prince of Egypt Freaks and Geeks Hotel Rwanda I Love the '80s That '70s Show Pearl Harbor Ice Age I Love the '90s United 93 300 10,000 BC Year One The Wolf of Wall Street I Love the 2000s Mad Men Downton Abbey Star Wars (VII-IX)

Dress Color

Dress Color

https://www.xkcd.com/1492

https://www.explainxkcd.com/wiki/index.php/1492:_Dress_Color

[Two images of a woman in a dress on each side of an image of a close up of a real dress with the same colors. On the left, she is colored blue on a dark blue background, while on the right, she is brown against a white background. Her dress is the same color in each panel - the same as the real one in between.]

This comic shows two drawings of a woman wearing the same dress, but with different background (and body) colors. The two drawings are split with a narrow vertical portion of an image from the web. The comic strip refers to a dress whose image went viral on Tumblr only hours before the strip was posted and soon showed up also on Reddit , Twitter , Wired and on The New York Times . Due to the dress's particular color scheme and the exposure of the photo, it forms an optical illusion causing viewers to disagree on what color the dress actually seems to be. The xkcd strip sandwiches a cropped segment of the photographed dress between two drawings which use the colors from the image against different backgrounds, leading the eye to interpret the white balance differently, demonstrating how the dress can appear different colors depending on context and the viewer's previous experiences. Both dresses have exactly the same colors actually: Below is an illustration demonstrating that the "colors" of the dresses are the same by connecting them with two lines with the above-mentioned colors (all the way!) and another which has one side flipped and merged into the other: Similar types of illusions can be seen at Wikipedia's optical illusion page and for instance here at echalk (the latter page requires Flash®player). This image has sparked surprisingly heated debate in many internet communities. A select few individuals may have prior experience with optical illusions of this ilk, but because this particular image went viral - it got heavy exposure over such a short amount of time - it reached millions of people who aren't so familiar with these sorts of mind tricks. To the uninitiated, the color of the dress seems immediately obvious; when others cannot see it their way, it can be a surreal (even uncomfortable) experience. As an aside, the retailer Roman Originals would later confirm the dress was blue with black lace , and that a white dress with gold lace was not offered among the clothing line. The title text refers to the game show Let's Make a Deal , hosted by Monty Hall, which was famous for having contestants pick among several doors which either had a real prize (for example, a car) or a joke prize (for example, a goat). Randall states that people find the dress color issue just as baffling as if upon opening the chosen door no one can agree if the item behind the door is a car or a goat. This is a reference to what has become known as the " Monty Hall problem :" if there are two goats and a prize behind three doors, the contestant has chosen a door, and one of the unchosen doors is opened to reveal a goat, should the contestant change his/her choice? Statistically, the answer is yes, but many people find this counterintuitive; discussion of this problem in Parade magazine touched off public outrage similar to the viral dress image. Randall is presumably pointing out how ridiculous it is for people who don't understand the underlying science to become so adamant in defending their beliefs. A spoof of the "Monty Hall problem" previously appeared in 1282: Monty Hall , where Beret Guy decides to take the goat. [Two images of a woman in a dress on each side of an image of a close up of a real dress with the same colors. On the left, she is colored blue on a dark blue background, while on the right, she is brown against a white background. Her dress is the same color in each panel - the same as the real one in between.]

Meeting

Meeting

https://www.xkcd.com/1493

https://www.explainxkcd.com/wiki/index.php/1493:_Meeting

[Beret Guy is shown in silhouette. Above Beret Guy there is a black sign with white (and grey) text. Above this is his address to those in the meeting:] Beret Guy: Welcome to a meeting! I'm almost out of words, so I'll keep this short. Just wanna touch bases. [White text in the black sign ( .website in grey):] CompanyName.website If you're reading this, the web server was installed correctly.™ [Beret Guy stands in front of an office chair and a table talking.] Beret Guy: First, a few updates. We've learned from the state police that the self-driving car project we launched by accident during this morning's carpool has come to an end about 90 miles outside of town. Very exciting! [Pony tail sits at the table.] Beret Guy [off-panel]: Profits are up. Sales, any luck figuring out who our customers are? Ponytail: Nope. Money keeps appearing, but we have no idea how or why. Beret Guy [off-panel]: Great! [Back to the situation from frame two.] Beret Guy: Oh, and one last thing—I saw a cool red beetle in the hall. Can someone add it to the bug tracker? [person off-panel]: Just did! Beret Guy: Thanks!

Beret Guy 's business, as previously seen in 1032: Networking and 1293: Job Interview , is going well, although it is unclear why. The common theme in these three comics is that Beret Guy misuses common business cliches. The following are examples and phrases that Randall is likely making a joke about: [Beret Guy is shown in silhouette. Above Beret Guy there is a black sign with white (and grey) text. Above this is his address to those in the meeting:] Beret Guy: Welcome to a meeting! I'm almost out of words, so I'll keep this short. Just wanna touch bases. [White text in the black sign ( .website in grey):] CompanyName.website If you're reading this, the web server was installed correctly.™ [Beret Guy stands in front of an office chair and a table talking.] Beret Guy: First, a few updates. We've learned from the state police that the self-driving car project we launched by accident during this morning's carpool has come to an end about 90 miles outside of town. Very exciting! [Pony tail sits at the table.] Beret Guy [off-panel]: Profits are up. Sales, any luck figuring out who our customers are? Ponytail: Nope. Money keeps appearing, but we have no idea how or why. Beret Guy [off-panel]: Great! [Back to the situation from frame two.] Beret Guy: Oh, and one last thing—I saw a cool red beetle in the hall. Can someone add it to the bug tracker? [person off-panel]: Just did! Beret Guy: Thanks!

Insurance

Insurance

https://www.xkcd.com/1494

https://www.explainxkcd.com/wiki/index.php/1494:_Insurance

[Cueball is standing in front of a desk, which a man sits behind. The man is presumably an insurance agent, and is handing Cueball a paper.] Insurance agent: Here's a page explaining the terms of your new fire insurance policy. [Zoom in on Cueball as he reads the paper.] [Cueball starts to ask the insurance agent a question when he hands Cueball yet another paper.] Cueball: Hey, what if I- Insurance agent: And here's a page explaining that the "cool hack" you just thought of is called "insurance fraud". We already know about it and it's a crime. Cueball: Oh. Right. How did- Insurance agent: I see a lot of programmers here.

Cueball in this comic, as is often the case, is some sort of programmer or at least logically minded person. He reads through the terms that are handed to him, and finds some sort of loophole. This is a play on the fact that programmers often find loopholes in programs and code, and exploiting them is nothing more than a "cool find" or an interesting idea. More importantly, programmers try to prevent loopholes, which is why it is important to be able to identify them. The insurance agent foresees this, and explains that this "cool hack" is actually just an instance of insurance fraud , which is highly illegal. The comparison here is that exploiting a program's faults can be regarded as interesting or fun, while exploiting the faults in a legal document will often result in some sort of legal repercussions (however, sometimes legal loopholes are exploited by individuals or corporations in ways that are not illegal). The insurance agent is also already prepared for the following question - how he knew Cueball would be looking for loopholes, and it's because many programmers visit him. The title text provides another example: While airport luggage security certainly is exploitable, walking out with every piece of luggage from the conveyor belt would be easily noticeable and would result in being arrested for theft, and many annoyed travelers. 1469: UV also contains a case of insurance fraud. The term hacking in IT is ambiguous and goes from code development (in particular in the opensource community) to the fact of "using a hack ". A hack would then refer to a tricky piece of code doing the intended job in a way that the framework or project in which it is inserted was not intended to. To the general public, 'hacking' a system would normally refer to some illegal way of achieving a goal against the will of the original developers of the system, like getting a copy of all the data available or taking advantage of some unwanted behavior, but a more distinctive term for such an exploitation (maliciously or after an invitation to perform legitimate penetration testing) would be 'cracking'. This comic is making fun of what IT hacks would look like in real world. Surely, taking lots of luggage from an airport is technically possible and probably not so difficult, but first, it looks weird, and second, it's also obviously illegal. The weirdness of such behavior is more obvious in real life than in IT. It is worth noting that it is currently popular on social media sites to share small tricks to make one's life easier. This is called "life hacking", or "hacking your life" . [Cueball is standing in front of a desk, which a man sits behind. The man is presumably an insurance agent, and is handing Cueball a paper.] Insurance agent: Here's a page explaining the terms of your new fire insurance policy. [Zoom in on Cueball as he reads the paper.] [Cueball starts to ask the insurance agent a question when he hands Cueball yet another paper.] Cueball: Hey, what if I- Insurance agent: And here's a page explaining that the "cool hack" you just thought of is called "insurance fraud". We already know about it and it's a crime. Cueball: Oh. Right. How did- Insurance agent: I see a lot of programmers here.

Hard Reboot

Hard Reboot

https://www.xkcd.com/1495

https://www.explainxkcd.com/wiki/index.php/1495:_Hard_Reboot

[Inside a frame there are two pictures. To the left there is a section of a computer screen with white text on a black background. The screen is covered in lines of illegible text.] [Above the screen it says:] Figuring out why my home server keeps running out of swap space and crashing: [Below the screen it says:] 1-10 hours [To the right there is a frame with a drawing of a timer plugged into a power port with cable running off to the side.] [Above the frame it says:] Plugging it into a light timer so it reboots every 24 hours: [Below the frame it says:] 5 minutes [Below the main frame.] Why everything I have is broken

This comic is about using a simple and unrelated trick to work around a problem, instead of spending a long time solving the cause of the problem. Swap space is an area of a computer's hard drive reserved for use when the computer runs out of RAM. Ideally, RAM + SWAP >= MAX, where MAX is the amount of memory the computer will ever try to use at the same time. However, some (broken) programs may keep requesting memory from the system until computer runs out of resources (a memory leak ), or the system may be misconfigured to run more and more programs simultaneously. Rebooting the computer will empty the RAM and swap space so resources can be reallocated, but this only temporarily alleviates the underlying issue. Determining the root cause of the problem is often nontrivial. It would take Randall anywhere between 1 and 10 hours to figure out why the server is running out of swap space, and possibly more to actually fix the problem. Alternatively, Randall could just take 5 minutes and plug the server into a light timer. This attitude to problem solving is in contrast to the attitude shown in 974: The General Problem . Timers like the one in the comic typically have four switches or notches per hour, so using the timer would replace an unpredictable and indefinite loss of service with a regular 15 minute downtime event once a day. Also, it can be scheduled during, say, the middle of the night when most users are sleeping to minimize disruption. The correct method of scheduling a regular reboot would be using a cron task, but perhaps the server is "crashing" in such a dramatic manner that cron, or shutdown, or init stops working. The comic title alludes to this, in that a "hard" reboot scheduled with an analog timer is more guaranteed to work than a "soft" one scheduled with cron. If a memory leak is not present, the problem might be fixable by simply increasing swap space; however, if there is a more complex underlying issue, this is the first step along the path of 10 hours of troubleshooting. As a general stereotype, the type of person who has a home server is probably also the kind of person who would start by 'just' increasing the swap size, and before they know it has spent 10 hours completely engrossed in the challenge of fixing the problem. (See 349: Success ) The subtitle reads "Why everything I have is broken". This indicates that Randall frequently finds himself doing non-standard workarounds that temporarily solve a problem but may ultimately damage the system to the point of becoming nonfunctional. Indeed, a kitchen/light timer used to cut power to a server overnight may affect the server's performance if it is in the middle of a process when the reboot happens. Alternatively, this can be interpreted to mean that everything Randall has is broken and held together by metaphorical duct tape. The title text's first sentence reveals that Randall is aware that looking further for a fix is futile: The problem is caused by a bug which has already been analyzed and is known to be triggered by using the system in the very way Randall is using it. He may get around the bug by changing what the system does, but then it would not provide the services he needs anymore. It may also refer to bug trackers, where someone found out and posted what causes the issue, but the bug is marked as "Unresolved," "Waiting," or "Will not fix." It is not clear why the title text refers to a kitchen timer while the comic itself refers to a light timer. It might be a small error, or it might be that Randall just considers these to be two synonymous terms. Typically, however, a kitchen timer refers to an alarm that will go off, rather than a timer that cuts power to a device like a light timer. The title text's second sentence refers to the fact that operating system bugs take a long time to be solved, hence the solution of "wait[ing] a few years until I don't want that combination of things anymore." Humor in that sentence is found in the fact that readers will anticipate "wait a few years until..." would be followed by "the bug is fixed", however, Randall is indicating that usually his needs change before the bugs get fixed, or that he has very low confidence in that the bug will be fixed in time, if ever. This play on expectations is a common comedic trope. [Inside a frame there are two pictures. To the left there is a section of a computer screen with white text on a black background. The screen is covered in lines of illegible text.] [Above the screen it says:] Figuring out why my home server keeps running out of swap space and crashing: [Below the screen it says:] 1-10 hours [To the right there is a frame with a drawing of a timer plugged into a power port with cable running off to the side.] [Above the frame it says:] Plugging it into a light timer so it reboots every 24 hours: [Below the frame it says:] 5 minutes [Below the main frame.] Why everything I have is broken

Art Project

Art Project

https://www.xkcd.com/1496

https://www.explainxkcd.com/wiki/index.php/1496:_Art_Project

[Four people stand next to each other.] Cueball [taking a selfie with his smart-phone]: I'm doing an art project where I take a picture of myself every hundred years. Megan [filming herself with her smart-phone]: I'm doing an art project where I take a picture of myself every 1 /24 th of a second. Ponytail [pointing to her face with both hands]: I'm doing an art project where you can come to my house and watch my actual face age in real time. Girl with long black hair [holding a burrito]: I'm doing an art project where you all do those things while I eat a burrito.

This comic appears to be satirizing art in two different ways. From one perspective, Randall is describing various art forms in unusual ways (e.g., a portrait by Cueball , a video for Megan , and perhaps live performance by Ponytail ). From another perspective, Randall might be making fun of time-lapse photography movies. YouTube has a robust collection of videos taken from stitching together pictures or short video clips taken every day or every week; in the 2015 Academy Awards , one of the Best Picture nominees, Boyhood , used a similar method, filming short sequences annually over the course of 12 years. In each case, the art described is simpler than it sounds, and some might not consider it art. A picture of oneself "every hundred years" will only happen once or twice in a lifetime; a "picture every 1/24th of a second" is the traditional frame rate of cinema cameras for film production, and "watching my face age in real time" is just life. Then finally another Megan-like character, possibly a relatively demure Danish , pokes fun at all of them by simply watching their attempts at "art" while she eats a burrito. Randall may also be referencing the many perspectives on art by leaving this comic open to several interpretations. The use of a burrito as a punchline representing someone who is grounded in reality instead of engaging in esoteric pursuits has been seen before in 1269: Privacy Opinions . The title text is just more snark, claiming that it's their most ambitious project ever, if the sole criterion for ambition is the amount of guacamole that one has to eat. [Four people stand next to each other.] Cueball [taking a selfie with his smart-phone]: I'm doing an art project where I take a picture of myself every hundred years. Megan [filming herself with her smart-phone]: I'm doing an art project where I take a picture of myself every 1 /24 th of a second. Ponytail [pointing to her face with both hands]: I'm doing an art project where you can come to my house and watch my actual face age in real time. Girl with long black hair [holding a burrito]: I'm doing an art project where you all do those things while I eat a burrito.

New Products

New Products

https://www.xkcd.com/1497

https://www.explainxkcd.com/wiki/index.php/1497:_New_Products

Predicting the success or failure of a new product based on what engineers and programmers are saying about it [A two-column table illustrating this. The headings are actually standing above the table.] If they say... It means... "It doesn't do anything new" The product will be a gigantic success. "Why would anyone want that?" "Really exciting" The product will be a flop. Years later, its ideas will show up in something successful. "I've already preorded one" "Wait, are you talking about <unfamiliar person's name>'s new project?" The product could be a scam and may result in arrests or lawsuits. "I would never put <company> in charge of managing my <whatever>." Within five years, they will.

This comic points out an apparent paradox in product performance: Many products that are criticized by techies when first announced go on to great success, and many that are heavily hyped are total flops. The product in question may be a reference to the Apple Watch , which was announced around the time of this comic's release. The title text imagines a product that fits into the second, third and fourth categories: Kim Dotcom is a controversial entrepreneur and convicted fraud . He changed his surname to "Dotcom" because of the dot-com stock market bubble that made him a millionaire. He fits perfectly into the mold of someone well-known to programmers and engineers (as well as New Zealanders), but perhaps not so much to your average Joe. Taken together, these imply that an untrustworthy and potentially malicious company has an exciting new idea that may eventually come out in successful form, gains control of a large amount of medical information, but ultimately result in lawsuits not just from investors but from misled consumers (category 3). Because the initial release will be a flop (category 2), there is some time to prepare before the successful use of this idea becomes a reality (also category 2), at which point that or some other company will gain control of a large amount of people's medical something (category 4). Once this happens you could expect dramatic repercussions; this is why the title text suggests to dig a bunker while there is still time. Predicting the success or failure of a new product based on what engineers and programmers are saying about it [A two-column table illustrating this. The headings are actually standing above the table.] If they say... It means... "It doesn't do anything new" The product will be a gigantic success. "Why would anyone want that?" "Really exciting" The product will be a flop. Years later, its ideas will show up in something successful. "I've already preorded one" "Wait, are you talking about <unfamiliar person's name>'s new project?" The product could be a scam and may result in arrests or lawsuits. "I would never put <company> in charge of managing my <whatever>." Within five years, they will.

Terry Pratchett

Terry Pratchett

https://www.xkcd.com/1498

https://www.explainxkcd.com/wiki/index.php/1498:_Terry_Pratchett

[Cueball is reading a book over the first four panels at the top of the comic. He shifts position from sitting, leaning back on one hand, laying down on his belly to finally sitting more upright. Above these four panels and breaking the frame of the outer panels of the comic we see what he reads during these four panels:] I told her we were going to get married, and all she could talk about was frogs. She said there's these hills where it's hot and rains all the time, and in the rainforests there are these very tall trees and right in the top branches of the trees there are these like great big flowers called... bromeliads, I think, and water gets into the flowers and makes little pools and there's a type of frog that lays eggs in the pools and tadpoles hatch, and grow into new frogs and these little frogs live their whole lives in the flowers right at the top of the trees and don't even know about the ground, and once you know the world is full of things like that, your life is never the same. — Masklin, Terry Pratchett's The Bromeliad Trilogy [Below are four more panels. Cueball stops reading in the book. Leaves the book and begins to walk. Walks out on a leaf from a big flower. Finally, zooming in on him at the edge of the leaf, he looks down and sees what is below the flower.]

This comic is a tribute to the late Sir Terry Pratchett . It came out the day after the renowned fantasy author died. The comic quotes a (slightly abridged) passage from Wings , one of the three books of The Bromeliad Trilogy (also known as The Nome Trilogy ), a series of children's books by Sir Terry. During the first five panels of the comic Cueball reads the quoted passage in his book Wings . This passage describes what Masklin thinks about when he told Grimma that they "were going to get married, and all she could talk about was frogs." He then recounts what she told him about a type of tree frog that are found in bromeliad flowers where they lay their eggs, which hatch into tadpoles, and then live most of their lives in a single plant. See a description of this plot point when it happened in Diggers . She—amongst other things—muses about the fact that they are blind to the rest of the Universe, and that most people are blind to them. After reading this Cueball puts the book down and walks off, and soon finds that he himself has been living at the bottom of a flower much like the frogs in the bromeliad. This is an allegory for a common praise of the best fantasy and science-fiction writing: That by reflecting our own world in a different context, it allows us to better see ourselves. In the allegory, Cueball's journey to the edge of the leaf is a representation of broadening one's horizons, perhaps even in ways that are somewhat frightening. On a more literal level, the concept of living on a flat surface with a precipice at the edge is explored at length in the Discworld series, Pratchett's most iconic work. Both this series (wanting to own it all) and the space all of Terry Pratchett's books would take up on a bookshelf are the subject of 625: Collections . The title text continues, more directly, the point previously made allegorically. It thanks the late Sir Terry, noting that his fictional worlds allowed us to better see the real world. "How big our world is" also ties into another point raised in the quoted passage, that there are countless amazing things happening around us all the time without our knowledge. Terry Pratchett was also referenced in panel 18 of 1052: Every Major's Terrible . A similar tribute comic was also dedicated to Steve Jobs , the day after he died, in 961: Eternal Flame , to Gary Gygax , three days after he died, in 393: Ultimate Game , and to John Conway , two days after he died, in 2293: RIP John Conway . [Cueball is reading a book over the first four panels at the top of the comic. He shifts position from sitting, leaning back on one hand, laying down on his belly to finally sitting more upright. Above these four panels and breaking the frame of the outer panels of the comic we see what he reads during these four panels:] I told her we were going to get married, and all she could talk about was frogs. She said there's these hills where it's hot and rains all the time, and in the rainforests there are these very tall trees and right in the top branches of the trees there are these like great big flowers called... bromeliads, I think, and water gets into the flowers and makes little pools and there's a type of frog that lays eggs in the pools and tadpoles hatch, and grow into new frogs and these little frogs live their whole lives in the flowers right at the top of the trees and don't even know about the ground, and once you know the world is full of things like that, your life is never the same. — Masklin, Terry Pratchett's The Bromeliad Trilogy [Below are four more panels. Cueball stops reading in the book. Leaves the book and begins to walk. Walks out on a leaf from a big flower. Finally, zooming in on him at the edge of the leaf, he looks down and sees what is below the flower.]

Arbitrage

Arbitrage

https://www.xkcd.com/1499

https://www.explainxkcd.com/wiki/index.php/1499:_Arbitrage

[Cueball and Hairy are sitting at a table with a bowl of chips in the middle. Hairy is taking chips from the bowl on the table with one hand, and his other hand is dropping chips into a large bag behind him. Cueball is double facepalming.] Hairy: They're the ones giving chips away! Hairy: If they don't see the arbitrage potential, sucks for them. [On the bag is written: Chips.] In a deep sense, society functions only because we generally avoid taking these people out to dinner. The invisible hand of the market is also mentioned in 958: Hotels . The same idea was previously used in 1110: Click and Drag , where a person takes free drinks to resell . Later, 1721: Business Idea implies a similar plan to extract wealth out of a small market inefficiency that, in reality, would be far too onerous to exploit; in this case, premium gasoline at regular price. See also the what if? Cost of Pennies regarding why it would not be worth trying these kind of ventures out.

In economics and finance , arbitrage is the practice of buying cheaply on one market whilst immediately selling at a higher price on another market, taking advantage of the price difference to make relatively risk-free profit. In real-world liquid financial markets , arbitrage helps the market to converge on one price for a product. Arbitrageurs are the individuals performing this act to equalize the prices in those markets and hopefully make a profit. The place where Cueball and Hairy are eating is giving away unlimited free potato / tortilla chips , probably serving the same function as a bread basket, being a cheap but welcome appetizer while patrons wait for their orders. Hairy is acting as an arbitrageur by collecting the chips to later resell them. This is much to the consternation of Cueball, who is (depending on how you interpret the simple art-style) holding his hands up in front of his mouth in shock, covering the lower half of his face in shame, covering his eyes out of denial, sliding his palms down the front of his face in disgust, face palming in exasperation, or eating chips – possibly all in sequence. Trying this strategy in the real world would not work. Customers leaving the restaurant with bags of chips might well be barred from the establishment. More simply, the restaurant is under no obligation to keep refilling the bowls indefinitely; if a customer's demands for more chips became unreasonable, they could simply refuse to bring any more. In either case, it's highly unlikely that a customer could leave with enough chips to offset the cost of even an inexpensive meal. Additionally, there would likely be a problem of a lack of demand, given the absence of a secondary market . Case in point: would you buy open bags of perishable, presumably hand-soiled chips? Didn't think so. In the caption below the comic, Randall suggests that society only functions because we don't take people like Hairy "out to dinner"; we generally have an aversion to dealing with people with such extreme self-interest, bordering on sociopathic behavior. Traditional theories of capitalism are based on the concept that people will act in their own economic self-interest, but in reality this is usually limited by both legal strictures and unspoken social norms. There are many aspects of society that are only possible because we trust most people to keep their self-interested actions within reasonable bounds. We see from Cueball's reaction that he is appalled by what Hairy is doing in believing he can profit from the apparent generosity. A distinguishing feature of social animals , rather than animals simply sharing a habitat , is that they perform tasks that benefit their group. All such societies rely on some situations where the individual is not working purely on short term self-interest. The payoff for this is generally that co-operation makes things better for the group as a whole. Most people would find Hairy's behavior embarrassing and shameful, and thus would not socialize with people who behave like that. By rejecting such individuals, society protects itself from such people. The title text mentions the invisible hand . In economics this is a metaphor used by Adam Smith to describe unintended social benefits resulting from the individual actions of self-interested parties. In the context of arbitrage, the invisible hand compels all of a given fungible substance to be sold for the same price, as a result of the actions of individuals like Hairy who are only seeking personal profit. The invisible hand is a sort of personification of the market; in the title text, the person has become so real that it can be sent a text message, but, despite presumably being able to hold a phone, the Hand doesn't reply (it IS only a hand). It is tempting to wonder why Randall/Cueball is texting it in the first place - not, presumably, to invite it to dinner, since the market would doubtless behave just as Hairy is doing. As it is invisible, though, perhaps it would at least be less embarrassing to sit at a table with. [Cueball and Hairy are sitting at a table with a bowl of chips in the middle. Hairy is taking chips from the bowl on the table with one hand, and his other hand is dropping chips into a large bag behind him. Cueball is double facepalming.] Hairy: They're the ones giving chips away! Hairy: If they don't see the arbitrage potential, sucks for them. [On the bag is written: Chips.] In a deep sense, society functions only because we generally avoid taking these people out to dinner. The invisible hand of the market is also mentioned in 958: Hotels . The same idea was previously used in 1110: Click and Drag , where a person takes free drinks to resell . Later, 1721: Business Idea implies a similar plan to extract wealth out of a small market inefficiency that, in reality, would be far too onerous to exploit; in this case, premium gasoline at regular price. See also the what if? Cost of Pennies regarding why it would not be worth trying these kind of ventures out.

Upside-Down Map

Upside-Down Map

https://www.xkcd.com/1500

https://www.explainxkcd.com/wiki/index.php/1500:_Upside-Down_Map

[Map of the world with all the landmasses rotated upside-down.] [Four oceans and all the visible continents have been named in large letters in a bold font. The Pacific has been named both to the left and right. Several islands (large and small) have been designated with name but in grey and in a much smaller normal font. For all continents the names are written on them. For the island the name is written in the ocean except for Greenland.] [Below the names on the map are given in the order they appear reading from left to right, first for the northern and then the southern hemisphere:] [Northern hemisphere:] North America Cuba Greenland Atlantic Ocean Iceland UK Asia Sri Lanka Europe Arctic Ocean Taiwan Japan Pacific Ocean [Southern hemisphere:] Pacific Ocean South America Tierra del Fuego Africa Indian Ocean Madagascar Indonesia Australia New Zealand [Below the main frame:] This upside-down map will change your perspective on the world! Map projections are also the subject of 977: Map Projections . In fact, if this comic was released later, it would certainly have "Bad Map Projection # n " on the top, and would be part of the category .

This comic plays on the idea that maps with the south pole at the top will "change your perspective of the world". Most world maps orient north in the upward direction, placing the north pole as the top. Such an orientation is purely a matter of convention, as 'up' and 'down' don't apply in a planetary context. The north = up tradition probably emerged because most historical cartographers hailed from the northern hemisphere, and placed their own nations at the top. Some people and groups object that this convention subtly, but perniciously, advances the assumption that countries in the northern hemisphere are inherently more important than those in the southern hemisphere. This is especially sensitive because most of the wealthier and more powerful countries in the world are in the northern hemisphere, while relatively fewer southern hemisphere countries have as much wealth or global influence. Early maps had eastern Asia oriented at the top of the map, beyond Israel and the Holy Land in the middle, and western Europe at the bottom. To remedy this, some advocate the use of maps with the south pole oriented at the top. Some want such maps in common use, while others simply use them to encourage people to rethink their assumptions about how the world should be seen. Such a map can easily be achieved by simply rotating a normal map 180 degrees, though the text labels would also be upside-down and harder to read. A Google Images search reveals many examples of upside-down maps with the text-oriented correctly for reading. This map is a comedic play on such maps, where each landmass is in the same position it would be in a traditional north-top map but rotated 180 degrees (presumably around some central point of the landmass) to the orientation it would have in a south-top map. Such a map is, of course, almost completely useless in real life, because it completely distorts the relative positioning of the landmasses. Moreover, it keeps the northern countries at the top of the map, which means one of the chief complaints about traditional maps is unaddressed. Note that individual islands are rotated about their own centers, rather than following the rotation of the neighboring continent; however, some are displaced as necessary to keep them from being overlapped by the rotated continents. For instance, Madagascar would be overlapped by the Sahara if it remained in position, but is instead displaced eastward to keep it in the Indian Ocean. On the other hand, all the islands of the Mediterranean Sea have disappeared under Asia . Asia is so broad that almost the entire Indochinese Peninsula (with for instance Vietnam and Thailand ) has been rotated out of the top of the map. Similarly, the map omits Antarctica in the south. To keep their familiar shapes on a rectangular map, the continents would also have to be heavily distorted compared to their actual shapes, becoming much narrower (along the lines of latitude) near the poles and wider towards the equator. See also 977: Map Projections . The basic climates for several areas would be distinctly different. For example, the former Central America area would be in the arctic zone, while Siberia would be subtropical. This arrangement of the world's landmasses would have great advantages for trade because there are (presumably navigable) straits between the Americas and between Africa and Asia, removing the need for the Panama Canal and the Suez Canal . The title text references the fact that, in this new map, the UK is now next to Asia – specifically the Korean Peninsula . North Korea is mentioned in the text as having a history of hostile relations with nearby countries. However, on this map North Korea would be the part of Korea we today know as South Korea . Furthermore, Northern Ireland is now at the south of the island of Ireland , so the UK's full name would need to change to The United Kingdom of Great Britain and Southern Ireland. There have been several wars concerning the English Channel , mainly, but not only, between England and France . Likewise, there has been a history of animosity between Korea and Japan , separated by a similar body of water. Since, on this world map, a channel now exists between the UK and North Korea (the real world's South Korea) there could obviously have been many wars for the dominance over the said channel. Along the same line of thinking, interesting speculations could be made about the following "new" facts: [Map of the world with all the landmasses rotated upside-down.] [Four oceans and all the visible continents have been named in large letters in a bold font. The Pacific has been named both to the left and right. Several islands (large and small) have been designated with name but in grey and in a much smaller normal font. For all continents the names are written on them. For the island the name is written in the ocean except for Greenland.] [Below the names on the map are given in the order they appear reading from left to right, first for the northern and then the southern hemisphere:] [Northern hemisphere:] North America Cuba Greenland Atlantic Ocean Iceland UK Asia Sri Lanka Europe Arctic Ocean Taiwan Japan Pacific Ocean [Southern hemisphere:] Pacific Ocean South America Tierra del Fuego Africa Indian Ocean Madagascar Indonesia Australia New Zealand [Below the main frame:] This upside-down map will change your perspective on the world! Map projections are also the subject of 977: Map Projections . In fact, if this comic was released later, it would certainly have "Bad Map Projection # n " on the top, and would be part of the category .