Perspective

Explanation:
Firefox is a popular browser, and in 2006, it was the second most commonly used browser. Its more fervent supporters sometimes wrote as if there was a moral imperative to use Firefox rather than Internet Explorer.
Cueball , presumably representing Randall , wakes up with a reasonable perspective on the relative unimportance of an internet browser within the world at large, but quickly loses that perspective as his enthusiasm for nerdy things like Firefox gets the better of him. The humor stems from the irony that Cueball is relieved to trade a richer perspective for a simpler, browser-oriented world view.
The title text references Richard Stallman , an American software freedom activist and computer programmer, and Cirque du Soleil , an entertainment company specializing in big-top circus performances. The two have no connection with one another, so this is one example of an odd combination of topics that would only (and commonly) be connected in dreams.
Alternately, the dream may be a reference to Stallman's forceful defense of software freedom, which could be seen as "over-the-top" or circus-like.
Another possible joke is that the comic, unlike most other xkcd comics, is drawn with perspective as well as being about a more metaphorical perspective.
Sometimes, when I first wake up, I am caught in the horrible grip of perspective. [Cueball sitting up in bed.] Cueball: It may be a jewel of open source, but Firefox is just a browser. It shows webpages. What the hell is wrong with us? Fortunately, this subsides quickly.


Right-Hand Rule

Explanation:
The right-hand rule is a mathematics and physics trick to learning how to find the cross product of two Cartesian vectors in three dimensions. First, extend the fingers of your right hand in the direction of the first vector (in the example diagram in the comic, this is to the left). Then, curl your fingers in the direction of the second vector (out of the page/screen, in the example). Now point your thumb perpendicular to the other fingers, and it will point in the direction of the cross product of those two vectors (upwards, in the example). Note that reversing the order of the two vectors also reverses the direction of the cross product.
The book rule is an actual alternative to the right hand rule that might be useful to some physics students doing exercises out of their textbooks. However, it would give incorrect results with books in languages that are read from right to left, such as most Jewish prayer books.
The gun rule also technically works, but it would be extremely impractical, expensive, and dangerous to use and fire a loaded gun every time you want to find the result vector. It would also be very awkward to hold the gun in line with the vectors.  It also assumes that the safety latch is consistently on the same side of all guns; if a gun was made with the safety latch on the other side, then it would give incorrect results.
The body rule is for males only, which limits the number of people who are able to use this rule. With the right arm oriented along one vector and the legs along the second, the result vector is found along the penis of the person, which is conveniently erected by watching porn.
The title text refers to Edwin Abbott Abbott , author of the book Flatland, a story about a two-dimensional world.
Orientability is a property that refers to a space with continuously varying surface normals , which are essentially just vectors that are perpendicular to the surface of the space. Nearly every space commonly encountered is orientable; this is likely why the porn is referred to as mind expanding and superior to Edwin Abbot Abbott's work.
[Picture of a right hand with fingers curved, thumb pointed away, with axes drawn to demonstrate the right-hand rule of physics.] Alternatives to the Right-Hand Rule in vector multiplication: [A slightly-open book with labeled axes drawn on.] Book Rule: Open the front cover along the first vector and the back cover along the second. The result vector is along the spine, out the top. [A handgun with axes.] Handgun Rule: Point the grip along the first vector and rotate it so that the second vector is on the safety latch side. Fire. The result vector is toward the bullet holes. [A person with right arm extended.] Body Rule (males only): Point your right arm along the first vector and your legs along the second, then watch some porn.


Bill Nye

Explanation:
Bill Nye is an educator well known in the United States for his science-focused television show targeted to elementary school children ( website ).
A mother, Blondie , is sitting at a table in a restaurant with her two children, asking them a science-related question about the ice cubes in their drinks. She is hoping to prompt Bill Nye, sitting at the next table, to join the conversation and perhaps inspire her kids.  Thinking he has not heard, the mother then coughs slightly and starts to repeat the question. His then immediate and abrupt dismissal of her is antithetical to his television persona, where he is consistently enthusiastic about science and keen to take any opportunity to teach the viewer.
The use of the word "tribulation" implies that being recognized and accosted in public is a cause of much suffering and misery to Mr. Nye.
The title text contains another joke. He eats a meal in public where he does not want to be recognized or harassed with questions; however, he wears a lab coat. Regardless of Bill Nye's otherwise iconic and recognizable appearance, wearing a lab coat in public will probably draw the gazes and curiosity of others, no matter who is wearing it.
Ice pops and cracks when dropped in a glass of water because of thermal contraction: the much warmer water causes the surface of the ice to shrink, resulting in audible internal fractures in the brittle structure.
[A restaurant. Blondie is with two small Cueballs at a table; Bill Nye with black hair in a white lab coat sits at the next table with his back turned towards them. Two other tables can be seen at the edge of the panel at either side. A caption is written above them:] The tribulations of Bill Nye: Blondie: Hey, kids, see how the ice cracks and pops in your water? I wonder what causes that... Blondie: *Ahem* I said, I wonder what— Bill Nye: Know what? Maybe I just wanna enjoy my goddamn meal.


Christmas GPS

Explanation:
In the comic, Cueball has gotten a GPS device and asks Megan what to do with it. She suggest that they take their current coordinates and modify the latitude and longitude with a simple function based on their birthdays, thereby pointing to an arbitrary, non-random location. For example, if Cueball was born on, let's say, April 1, 1986 and Megan on August 12, 1988 and they are somewhere in New York ( 40.768062,-73.98468 ), the coordinate they type could make ( 40.040186, -73.081288 ) (assuming US date format), or ( 40.860401, -73.880812 ) (assuming following ISO 8601 ). The good thing about keeping the number before the decimal point is that the distance is still realistic to get to by car. Megan suggests to make out in this place. This procedure is somewhat of a precursor to Geohashing .
The comic is a Christmas comic, since it came online on Christmas Day 2006.
The title text suggests that if the location you make for yourselves is over water (which the example above happens to be), you either need to find a boat or find some rule that you can change to preserve the promise of making out, and if you can't do either, then there is no way you'd get to make out.
Cueball: Check it out - I got a GPS receiver for Christmas! What should we do with it?
Megan: Let's take our latitude & longitude, put our birthdays after the decimal points, then go to that spot and make out.
[Cueball is in love.]
Merry Christmas from XKCD [ sic ] [Car driving off in to the distance.]


YouTube

Explanation:
This comic is pointing out the fact that many of the comments on YouTube videos are insipid and poorly informed, being pointless arguments over some minor topic or factually incorrect position ( conspiracy ). At the time of this comic, YouTube was fairly new, and the comic's observation about the inanity of YouTube comments was novel. Since then, this observation has become a widely accepted truism about the Internet. In this case, the Moon landing hoaxers are at the receiving end of Randall 's pen.
The reputation of YouTube comment threads as cesspools of abject stupidity and blatant trolling is revisited in 301: Limerick and 481: Listen to Yourself .
The username CrackMonkey74 appears again in 406: Venting and 574: Swine Flu .
The title text is the first reference to Sheeple , which appeared a few more times in xkcd comics.
[Caption above the panel:] The Internet has always had loud dumb people, but I've never seen anything quite as bad as the people who comment on YouTube videos. [Below shows a still of a 44-second video of Moon landing. An astronaut is seen at the center of the still with an Apollo lunar lander at the background.] [Below the video shows a list of comments, top to bottom:] Comments & Responses [The name of the commenters and the time when the comment was posted is shown above each comment in a gray background.] rocckir (48 minutes ago) this is so obviously faked its unbilevable, why r people so gullible??? morons (reply) (mark as spam) bigmike133 (35 minutes ago) ive seen the space shuttle ass hole it definetly landed on the moon do some research... (reply) (mark as spam) GunPistolMan (22 minutes ago) if it was real why is their gravity? americans r fucken sheep (reply) (mark as spam) crackmonkey74 (17 minutes ago) u dont think we went to the moon why not tell louis armstrong to his face (reply) (mark as spam) simpleplan2009 (5 minutes ago) it was a soundstage on mars (reply) (mark as spam)
In July 2009, a restored video showing Neil Armstrong's first moonwalk was uploaded to YouTube. User Michael Huang copied to that video's comments section all the sentences in this comic. Then, after some other users took some of his comments seriously, he later added another comment stating, "This entire comment chain is from the famous webcomic, xkcd." The comments are copied verbatim, including typos and grammar errors. The only mistake is in the first comment: Michael Huang included only one question mark when the comic has three of them.


Hallucinations

Explanation:
Cueball on the right is talking to his (Cueball-like) friend about dreaming but using words and phrases to make dreaming sound much more dramatic than we usually think that it is. However, the description is technically correct.
Randall is using the comic to make a point about how we think dreaming is so normal, but if we actually realize what's happening, dreaming is very strange:
The character on the left takes this as though the experience is normal. Which it indeed is, but that is why Randall has the caption above the guys: Sometimes it seems bizarre to me that we take dreaming in stride.
The title text is about lucid dreaming , where the dreamer is aware that they are dreaming. This is even more fascinating to Randall. He uses this type of dream in 269: TCMP .
[Two Cueball-like guys are talking. Above them is the following caption:] Sometimes it seems bizarre to me that we take dreaming in stride.
Friend: Are you coming to dinner? Cueball: Yeah, but first I'm gonna go comatose for a few hours, hallucinate vividly, and then maybe suffer amnesia about the whole experience. Friend: Okay, Cool.


America

Explanation:
On April 20, 1979, U.S. President Jimmy Carter was allegedly " attacked by a giant swimming rabbit " while solo-fishing on a boat in his hometown. The reality is a little more nuanced: According to Carter, the rabbit had actually been chased into the water by some hounds and swam near his boat. Carter splashed some water on it to compel the rabbit not to come any closer.
Nevertheless, the newspapers ate it up, reveling in the ridiculous notion that anyone would feel threatened by a rabbit (considered by some to be small, harmless herbivores [ citation needed ] ), with respected paper The Washington Post putting the story "President Attacked by Rabbit" on the front page. Since the White House refused to release the photograph, the paper created a cartoon parody of the rabbit, calling it PAWS, in reference to the blockbuster film JAWS , about a killer shark. Carter's opponents used it as fodder for their arguments that Carter's presidency was weak and ineffectual, and basically, the whole thing was blown way out of proportion by the American media, as so often happens with goofy events such as this.
This comic treats the Killer Rabbit attack as a dark day for the United States and uses the phrase "America Must Never Forget," which usually applies to days like the Pearl Harbor attack or 9/11 .  It essentially claims that, for the entire history of the United States (which starts with the signing of the Declaration of Independence ), it is the only event worth remembering.
The rabbit incident is also referenced in 1688: Map Age Guide and in 2086: History Department .
The title text is an assumption that the event has not been remembered in the way the comic jokes that it should have been, and as a result, younger readers will think he is kidding when he says Carter was attacked by a rabbit.
[A timeline with only three ticks with years noted. Each tick is labeled with a line going to the tick. The second tick is much closer to the last on the right and has its year written below the line. The other two have it above the line and vice versa with the labels. Below in the middle there is a caption.] 1776 Declaration of independence 1979 Jimmy Carter attacked by giant swimming rabbit. 2007 Present day
[Caption:] America must never forget.


Candy Button Paper

Explanation:
This comic refers to Candy Buttons , a type of candy sold by Necco in the U.S. since 1980. Because they were glued to paper, each candy button would have some paper stuck to it. As said in the comic, some kids would carefully check each candy button to make sure they would not accidentally eat paper, while some kids didn't care and ripped them off, eating large scraps of paper in the process.
Because of the resemblance of the strips of paper to the tape of a Turing Machine , a small minority of children (possibly only Randall or some of his friends) pretended to be a Turing Machine by creating rules and executing them upon the tape of candy exactly like a real Turing Machine would do.
The title text refers to the fact that, although it would be hypothetically possible to create a Turing Machine that can only delete symbols, the information density of the tape would be greatly reduced, and the original Turing Machine could read and write from the tape it operated on.
When it came to eating strips of candy buttons, there were two main strategies. Some kids carefully removed each bead, checking closely for paper residue before eating. [To the right, a small section of a strip of Candy Buttons paper is shown. Two red buttons have been removed from the top of the strip.] [To the left, a long strip is shown. It seems to be waving in the air.] Others tore the candy off haphazardly, swallowing large scraps of paper as they ate. Then there were the lonely few of us who moved back and forth on the strip, eating rows of beads here and there, pretending we were Turing machines. [A strip is shown from bird's eye view. Many rows of buttons have already been eaten.]


Reno Rhymes

Explanation:
This comic starts with a line from the song "Folsom Prison Blues" by Johnny Cash. Cash is noted as saying, "I sat with my pen in my hand, trying to think up the worst reason a person could have for killing another person, and that's what came to mind," which fits pretty well with the personality of Black Hat . Rather than react badly, Cueball starts a rhyming game, which they continue until Black Hat refers to the horrifying My Lai Massacre , which is apparently going too far for Cueball.
You know, I once shot a man in Reno, just to watch him die. Black Hat starts with the original line from the song.
Really? Well I once shot a man in Reno but I couldn't tell you why. Cueball then begins the rhyming game by saying that he can't tell the reason why he killed the man.
I once shot a man in Reno then I went home to cry. Black Hat continues by saying that he got emotional after killing the man... Unlikely, given that he's Black Hat , and it could be him trying to continue, or he could be being sarcastic.
I once shot a man in Reno then I watered his cacti. An unlikely action after you have just killed someone, unless you're elaborately trying to cover up your actions. More likely, Cueball is just trying to continue the rhyme.
I once shot a man in Reno 'cause they cancelled Firefly. Firefly was a TV series that aired on Fox during 2002. Its cancellation was a source of much annoyance to its fans, a fact frequently referenced in xkcd. In this case, Black Hat goes as far as to murder someone for this.
I once shot a man in Reno, him and all his succubi. Cueball says he shot a man and a bunch of female demons. Unlikely to happen in real life, and is just probably Cueball attempting to continue.
I once shot a man in Reno and a bunch more in My Lai. The My Lai Massacre was an atrocity committed by US soldiers in Vietnam during the Vietnam war. Here, Black Hat says he not only shot a man in Reno, he shot a bunch more in My Lai , meaning that he was actually part of the massacre. Cueball is obviously horrified by this, and he ends the rhyme with a "I think we're done," signifying his horror at Black Hat's words.
The title text continues the rhyme, but changes the roles: now the speaker is asking someone else if they shot a man in Reno. It may be a reference to The Princess Bride (Inigo says the "I don't mean to pry" part to Westley).
[Cueball and Black Hat stand facing one another. Black Hat is on the left.] Black Hat: You know, I once shot a man in Reno, just to watch him die. Cueball: Really? Well, I once shot a man in Reno, but I couldn't tell you why.
Black Hat: I once shot a man in Reno, then I went home to cry. Cueball: I once shot a man in Reno, then I watered his cacti.
Black Hat: I once shot a man in Reno 'cause they cancelled Firefly. Cueball: I once shot a man in Reno, him and all his succubi.
Black Hat: I once shot a man in Reno and a bunch more in My Lai. Cueball: I think we're done.


What xkcd Means

Explanation:
This comic purports to finally answer the question, " What does 'xkcd' mean? " However, instead of giving an answer as to what the letters actually mean (according to Randall, it's literally "just a word with no phonetic pronunciation"), he offers five quirky behaviors. This is reminiscent of TV commercials that ask, "What does [brand name] mean? It means [happy activity]!".
The first panel shows a driver, marked by a red line, making a right turn at a red light , a U-turn on the connecting road, and then another right turn, returning them to their original direction presumably faster than waiting for the light. Right turns at red lights and U-turns are legal in all 50 states, but some intersections do not allow them (and turning at a red light is illegal everywhere in Europe). Hence, this complicated maneuver is "questionably legal". However, under certain circumstances in the US state of Oregon, it appears that this is actually legal .
The second panel shows Cueball searching for his mobile phone by having his friend call it to locate the ringtone, only to hear a ring from inside of his dog's stomach, possibly a reference to Jurassic Park III .
In the third panel, Graham's number is a (very) large number (once celebrated as the largest number ever used in a proof, although it is no longer the record holder), and the Ackermann function is a (very) fast-growing function, thus the function's output must be insanely large. (In fact, A(g 64 , g 64 ) is actually smaller than g 65 .)
The fourth panel shows somebody walking in a pattern based on the position of black and white tiles on the floor. This is further referenced in 245: Floor Tiles .
The title text refers to stigmata , marks corresponding to Jesus' crucifixion wounds. Devout Catholics have claimed to have spontaneously developed stigmata.
[Caption above the panels:] What does xkcd mean?
[Two cars sitting at a red light at a multi-lane intersection; one of them makes a right turn, then shifts over to the left lane and makes a U-turn across the dividing line to go back the way it came. It then shifts back to the right lane and makes another right turn, continuing down the road past the traffic light. This is shown with a red arrow.] It means saving a few seconds at a long red light via elaborate and questionably legal maneuvers.
[In an inset circle in the panel, someone is on a cell phone. In the panel itself, a second person is looking at a dog.] It means having someone call your cell phone to figure out where it is. Dog's stomach: Ring
[The mathematical function "A(g 64 , g 64 )=" appears in the panel. Next to the equal sign stands a mathematician, clutching his head.] It means calling the Ackermann function with Graham's number as the arguments just to horrify mathematicians. Mathematician: Aughhh
[An approximately 8 by 8 square of floor tiles is shown; the first, fourth, and seventh across in the first, fourth, and seventh rows are black, and the rest are white. A guy and girl are shown next to it, walking on what is presumed to be the same pattern of floor tiles.] It means instinctively constructing rules for which floor tiles it's okay to step on and then walking funny ever after. [Line indicating the uppermost right black tile: Black tiles okay.] [Line indicating tile directly below it: White tiles directly between black tiles okay.] [Line indicating a white tile in the last column over: Not okay.]


Regular Expressions

Explanation:
The comic begins with Randall saying how every time he develops a new skill, he finds himself daydreaming about using it to save the day. Computer skills aren't usually superhero material, which lends itself to the humor of the comic.
In computing, a regular expression ("regex") provides a concise and flexible means to "match" (specify and recognize) strings of text, such as particular characters, words, or patterns of characters.
Manually trying to look for a specific pattern through 200 MB of text is equivalent to looking for a needle in a haystack. But this task can be made easy by using regexes, since a script can read through text and match specific string patterns much faster than humans can achieve.
Perl is a popular scripting language that has often been referenced favorably in the comic. Perl is also the most acknowledged language when it comes to the performance while evaluating regular expressions. [ citation needed ]
The "PERL!" in the fifth panel is reminiscent of old superhero serials, particularly Batman (TV series) , in which sound effects such as "BAM!" "POW!" "ZAP!" would be displayed on screen in similar spiky bubbles. This fits with the theme of the comic, with Cueball being a "superhero" who fights crime using computer skills.
The title text refers to how sensitive regexes can be to small mistakes or missing characters. In 1168: tar , another potential hero fails (and gets blown up by a nuclear bomb that is only able to be disarmed by typing in a valid tar command, but blows up if you don't do it on the first try) because the syntax of some commands and programming languages are just too difficult to remember by heart.
Whenever I learn a new skill I concoct elaborate fantasy scenarios where it lets me save the day.
Megan: Oh no! The killer must have followed her on vacation! [Megan points to computer.] Megan: But to find them we'd have to search through 200 MB of emails looking for something formatted like an address! Cueball: It's hopeless!
Off-panel voice: Everybody stand back.
Off-panel voice: I know regular expressions.
[A man swings in on a rope, toward the computer.]
tap tap The word PERL! appears in a bubble.
[The man swings away, and the other characters cheer.]
A similar T-shirt in the xkcd store based on this comic says "stand back...I'm going to try science."


Kayak

Explanation:
This comic deals with two linked themes, which both come under the umbrella of existentialism , a branch of philosophy.
Beret Guy invites Cueball to join him in a two-seat kayak trip. However, Cueball is confused by his intention.
Beret Guy initially words his invitation to Cueball as "come explore the future." However, this confuses Cueball, as he believes that Beret Guy's kayak can travel through time in a science fiction sense. In reality, Beret Guy is being more literal: after all, as the title-text emphasizes, "there's future everywhere;" everything is "traveling through time" simply by existing, as time is just another dimension. Beret Guy's comments show that he perceives all of life as an adventure, and just as exciting as time travel; his eagerness to "explore" it shows that he takes delight in the unpredictability of life. In this way, the comic criticizes people who become depressed with the lack of control they have over their future: Beret Guy suggests that, rather than continuously worrying, we should enjoy the thrill of the unknown.
Cueball asks Beret Guy why he wishes for a kayak trip, as there is no intrinsic purpose or logic behind this action. However, Beret Guy claims that, in fact, nothing has any intrinsic purpose in the long run, and thus there is no reason not to go on a kayak trip. In this case, if a kayak trip is likely to make you happy, it is the right thing to do. In this way, the comic could be seen as criticizing those who do not take advantage of life's opportunities.
Beret Guy's comments reference existentialism, which is a branch of philosophy that states that there is no intrinsic purpose or meaning to anything in life, as nothing will influence our eventual fate - death. It also states that there is no way of predicting what will happen to us, and that the future is always unknown. The solution is therefore to find one's own purpose in life, and make the most of life's opportunities while they are still available.
The title text may be a reference to the Calvin and Hobbes collection book "There's treasure everywhere!"
Making the most of life, and rationalizing the familiar, has also been explored in these comics:
[Beret Guy, in a kayak holding a paddle, is talking to Cueball, standing on a pier.] Beret Guy: Come explore the future with me! Cueball: Huh? What's that you're in? [Close up on Beret Guy and his kayak. The tip of the pier can be seen.] Beret Guy: A two seat kayak! Cueball: I see, but why do you have it? [Close up on Cueball. The tip of the kayak and the tip of the paddle can be seen. Beret Guy and the waterline cannot be seen.] Beret Guy: We'll find out! The future is a big place! Cueball: So the kayak travels through time? [Slightly zoomed-out version of the third panel. The tip of the paddle has disappeared but the waterline is visible again.] Beret Guy: Sure! Just like everything else! It also goes over water. Come on!


90's Flowchart

Explanation:
Here you can see an apparent flowchart. However, it has non-standard notation.  The oval normally represents either the start or stop of a process.  Here, both the yes and no end up in stop , which would normally imply that nothing below can be reached.
Unless we are in the 90s, this doesn't matter, as there is nothing after the stop. But in the 90s, two processing paths follow, and both are from the lyrics of two-hit rap songs from the 90s:
In both instances, the sense of the lyric is that you should interrupt what you are doing, and switch to the new action.  Interpreted in terms of flowchart terminology, we could consider that the 'stop' just pauses the main thread, and secondary threads are launched to perform the 'Hammertime' and the 'Collaborate' and 'Listen' activities.
The title text compares freestyle rapping with Markov chains . Markov chains are mathematical constructs in which the state at the next time step is dependent only upon the current state and probability, and not the state at previous times. This is somewhat similar to freestyle rapping, in which what is said next must bear some relationship to what was just said, but the "freestyle" part means that almost anything can be brought in (hence the probabilistic part); furthermore, freestyle rapping allows the rapper to say something next that bears a relationship to what was just said, but not to what was said before that.
There have been several flowchart comics, all of which are listed here .
Both Ice Ice Baby and U Can't Touch This were released in the year 1990, and so their status as "90s" music is disputable. The 1st decade didn't start until year 1 ( year 0 does not exist in the Georgian calendar system), so the 2nd decade didn't start until year 11, and the 3rd decade didn't start until year 21, etc. Whether those songs count as being released in the 90s would be discussed over 2000 comics later .
90's Flowchart Start: The 90's? No: Stop Yes: Stop Hammertime or Collaborate, Listen


Hamster Ball Heist

Explanation:
Wayne Coyne , the lead singer of the band The Flaming Lips , is indeed known to crowd-surf in a giant hamster ball .
Hamster balls are a recurring subject on xkcd, starting with 152: Hamster Ball , which in direct relation to this comic showed that Cueball's biggest and only wish is such a ball.
When Cueball's friend tells him about Wayne's hamster ball surfing, Cueball says "Let's go," suggesting that they should go and kidnap that hamster ball and Wayne.
The rest of the comic outlines an elaborate mission to acquire a human-sized hamster ball by infiltrating a music concert and stealing the hamster ball while it is in use, thus also kidnapping the rock star, who would be structurally powerless to fight back while trapped within a spherical object. At least four Cueball-like guys help with the mission at the concert, one keeping the crowd back as the other three push the hamster ball into the waiting truck where a fifth friend acts as the driver when they escape with their heist.  This has not been attempted, nor should be attempted in real life. [ citation needed ]
The title text is one of Randall 's many open promises, claiming to supply anyone who does this in real life with a free T-shirt, and one for Wayne, too.
It is later revealed in 577: The Race: Part 1 , that Cueball paid a large settlement for this heist.
[Cueball's Cueball-like friend tells him something.] Friend: You know that giant hamster ball you've always wanted? I just found out that Wayne Coyne from the Flaming Lips crowd-surfs in one. Cueball: Let's go.
[Wayne Coyne, with curly hair and full beard, is crowd-surfing inside a giant hamster ball shown rolling from right to left with three lines behind it. He keeps his balance be leaning/walking forward and holding his arms out. The crowd shown begins to the right with a Cueball-like guy who the ball has just passed, and after him and below the ball there are 8 more people from the crowd all holding their hands up. The first four (a Hairy and three more Cueball-like guys) have already pushed it on, the next three (a person with black hair and two more Cueball-like guys) are touching the ball, and finally Megan is standing with her arms up waiting for the ball to arrive. Behind her are three of Cueball's Cueball-like friends, then Cueball, and finally to the far left partly outside the panel frame is yet another Cueball-like guy from the crowd. Above Cueball and to the edge of the hamster ball is a frame with a caption:] Some weeks later... Cueball: Ready? Friends: Ready
[Cueball to the left and one of his friends to the right shove the crowd out of the way, causing the hamster ball with Wayne Coyne inside to fall to the ground, Wayne falling backwards with arms up. Cueball pushed three Cueball-like guys and a Megan into each other to the left, and one of his friends push four Cueball-like guys to the left, towards a fifth person only partly shown at the edge of the panel. (Cueball's other two friends are not shown; they could be in front and behind the ball doing the same, but not shown).] Cueball: Now! Wayne Coyne: Hey! Friend: Shove
[Cueball and two of his friends start pushing the hamster ball with Wayne Coyne to the right, Coyne again stands up as before but to the right. He looks over his shoulder at the three who pushed him. To the left of the crowd, four Cueball-like guys (the third pointing at the scene and Megan) watch, and to the right, the third friend pushes a Cueball-like guy out of the way.] Cueball: Okay, push! Wayne Coyne: What's going on?!
[Cueball and his two friends roll the hamster ball with Wayne Coyne up the ramp into the back of a truck, Wayne pushing the other way with both hands, while the third friend still holding the crowd back holding up his arms. Two Cueball-like guys from the crowd are shown also holding their arms up. At the front of the truck, a fourth Cueball-like friend stands by the door ready to drive.] Wayne Coyne: Help!
[The truck drives off with the fourth friend in the front of the truck, leaving the crowd in a large cloud of dust. Four Cueball-like guys are shown in the first row of the crowd, which now is shown to consist of many people, shown behind with lots of small heads (Cueball-like) fading off in the distance.]


Brain

Explanation:
The Swiss Family Robinson is a novel by the Swiss pastor and writer Johann David Wyss . In the novel, a shipwrecked family builds a tree house as good as a normal house complete with library and mechanical contraptions.
Growing up, many children grow a fascination with tree houses. Tree houses are a child's own special place to do stuff away from their parents, have some autonomy, perhaps form a club. The obsession with tree houses usually fades once a child reaches their teenage years, but of course some of us never grow up. Being an adult geek/scientist who still enjoys childish things, Randall wants to build a sophisticated tree house rather than a simple one, taking the theme from the above-mentioned novel.
The title text makes reference to the regular xkcd joke about how terrifying Velociraptors from the movie Jurassic Park are. But they never can reach a tree house, just because it's too high, as you can see here 87: Velociraptors .
"Raptors" might refer to the informal bird group, hawks and owls and such, a joke relying on the previous infatuation with velociraptors.
My Brain [Picture of Brain. Line points at a highlighted area.] Section that is devoted, no matter where I go in life, to planning the ultimate tree house*. *Oh man, it would be like Swiss Family Robinson, but with multiple trees connected by... hey come up to my room and see the blueprints!


Ghostbusters Marathon

Explanation:
Ghostbusters is a 1984 supernatural comedy film that spawned a sequel, a reboot, and two animated television series (the latter of which lasted less than a season, didn't feature the same cast of titular Ghostbusters, and therefore is probably being pointedly ignored). The box, a "Muon Containment Trap," is a device used in the film to capture ghosts. It is connected to a footswitch by a cable. The man trying to leave is about to be pulled into the box and held there indefinitely (against his will, of course).
The title text refers to Julius Caesar's crossing of the Rubicon , a river (or very large stream) that marked the border between Roman Italy and an area of land Caesar was the appointed governor of. At the end of his term, the Roman Senate ordered him to disband his army and return to Italy. Instead, he brought his forces past the border, an act of treason and rebellion against the Republic, instigating the Roman Civil War. The phrase "crossing the Rubicon" now means making a move with gigantic consequences that cannot be undone. In the film Ghostbusters , the protagonists use "proton packs" that fire "streams" of energy. The inventor of the device warns that these streams should not be crossed against each other, as doing so "would be bad." Just how bad? "Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light." Important safety tip.
Final quote taken from the 1984 movie Ghostbusters .
[Cueball and a friend are in a room. Cueball is standing up. There is litter around them.] Cueball: Okay, that's all the Ghostbusters marathon I can handle. Later! Friend: You can't leave! We just started the animated series!
Cueball: I've had my fill. I'm going home. Friend: I can't let you do that.
[Cueball walks along a cord and past a box. The friend clicks a switch.] Click
[Cueball is bathed in some kind of aura emitted by the box.]


The Problem with Wikipedia

Explanation:
This comic illustrates the "problems" of information explosion coupled with a dense web of hypertext links . Through most of human history, written media has been both slow and linear. Hypertext allows a new type of information consumption, through small chunks of information linked together in a web of related concepts, and by being digital, each new chunk can be retrieved quickly and effortlessly. Wikipedia applies this principle very strongly, and because it covers so many topics, it is common for a reader to skim an article about a topic they need or want to know about, and end up following a series of links out of curiosity. Since each new page also has several links, the overall navigation pattern resembles a tree that branches out, "exploding" in size with each new level of link-clicking, thus resulting in many wasted hours (over three in this case) of reading stuff unrelated to the original goal, and lots of open browser tabs holding a wide variety of articles, which are seemingly unrelated, but have common "ancestors." (The problem, for Randall , of wasting time on Wikipedia was later referenced in the title text of 1501: Mysteries , and the more general problem of getting trapped following a never-ending chain of interesting links was covered in 609: Tab Explosion .) The large diversity in end links may also be a reference to the Wikipedia game .
One can also see this effect occur in other MediaWiki -powered wikis such as this very website, where one comic can lead to another of similar relation or category. In the table below, a possible route for each entry has been found.
Finding routes between the start and end points of the two pages above and the six below makes good challenges in the Wikipedia game .
The title text refers to two of the articles that were supposedly reached at the bottom. William Howard Taft was the 27th President of the U.S., in office from 1909 to 1913, who was notorious for being so overweight that when a White House chief usher invented a story about him getting stuck in the White House bathtub , people took it seriously. A wet T-shirt contest is an exhibitionistic competition typically featuring young women contestants at a nightclub, bar, or resort. Clearly the combination of these two would be rather bizarre.
There is an online game that involves trying to get from one Wikipedia page to another in the shortest possible route: http://thewikigame.com/ .
Table of paths
Due to the ever changing nature of Wikipedia, the Tacoma Narrows Bridge entry on Wikipedia no longer links to Structural collapse , requiring an intermediate step via Tacoma Narrows Bridge (1940) , and since Structural collapse now redirects to Structural integrity and failure , most pages on Wikipedia that linked to Structural collapse have been changed to rename this link.
The table below lists one valid route for each destination article, though it is not necessarily the most efficient route. And that these routes may become invalid as articles are edited. They all have been updated on March 21, 2015. All links then could be found directly on the page. This was not the case in the original version of the paths, where some links were in hidden parts of the page.
[Heading above the chart:] The PROBLEM with WIKIPEDIA:
[Text in a frame below the heading:] Tacoma Narrows Bridge
[Lines lead down both left and right to two new frames with the following entries:] Suspension bridge Structural collapse
[Two more lines lead down from the left frame and one from the right frame, and all lines end on a wiggling line from left to right. Below this wiggled line in square brackets it reads:] Three hours of fascinated clicking
[Further below there is a similar wiggling line, from where six lines lead to new frames below:] William Howard Taft 24-hour analog dial Lesbianism in erotica [This frame is followed by a second:] Batman; Fatal hilarity Taylor Hanson [This frame is followed by a chain of two others:] Cotton; T-Shirt; Wet T-shirt contest


Letting Go

Explanation:
In fiction, a character who has had a romantic relationship end will be shown taking some act to remove a sign of their partner's presence in their life, e.g. removing/selling a wedding or engagement ring, removing the partner's toiletries from the bathroom, or deleting the partner's phone number from a cell phone. This is used to symbolize that the character has accepted the end of the relationship and is ready to move on, no longer pining for their loss or seeking to restore the relationship.
The first three panels imply that Cueball was presumably in a now-terminated relationship with Megan . The final panel shows him using the Unix command 'userdel' to delete her user account from his computer. The joke here is that he considers this to be a significant part of accepting that she is no longer a part of his life, where most people would consider it a routine administrative task.
The title text refers to Cueball's thankfulness that he never gave Megan the password to the administrator ('root') account on the computer. It is unclear why this is; he might be worried that she would have used the access to perform malicious actions after the breakup, or simply glad to be spared the need to change the root password. Alternately, it could be a metaphor for marriage and/or a closer emotional relationship, and he is glad that he did not allow her an even greater hold on his heart before the breakup (which would, of course, have entailed commensurately more pain when she did leave him). Not sharing the root password is indicative of a lack of trust in their relationship, which could be a factor in the initial breakdown.
This was only the second time the name Megan was used in xkcd, the first time being in 159: Boombox .
[Cueball is holding a picture of himself and Megan in a heart; it has been ripped down the middle, separating the two people.]
[Cueball sits at computer, looking at the picture.]
[The panel has been inverted. Cueball still sits at the computer with the picture in front of him and his head drooped.]
[Cueball types on the computer.] Text from computer: [email protected] :~# userdel megan


Romantic Drama Equation

Explanation:
In a group of n people, such as the cast of a TV romantic drama like Queer as Folk , the number of possible different pairs of people is n(n-1)/2. A romantic drama will often consider, over time, many possible romantic pairs of its cast members, even seeming to test the limit of how many pairs are possible. Through an austerely binaristic lens, this comic explores the implication of sex and sexual orientation in characterizing the possible pairs.
If everyone in the group is male or female, then each pair could be classified as gay or straight. The formulas in the comic give how many of the possible pairs are gay and how many are straight, as a function of the total number of people and how many are male (or, equivalently, how many are female.) For example, of the 9 principal cast of Firefly, 5 are men and 4 are women. With n=9 and x=5, we have 16 possible gay pairs and 20 possible straight pairs.
A graph shows how the relative number of males and females affects the number of gay pairs and straight pairs. When the group is all male (or all female), all of the possible pairs are gay, but as the minority sex's number is increased, more of the pairs are straight. When the group is half male and half female, the number of straight pairs is maximized, and straight pairs slightly outnumber gay pairs. The curves are labeled "gay cast" and "straight cast", perhaps alluding that a "gay cast" would consider only gay pairs, and a "straight cast" would consider only straight pairs.
There is a note that the graph describes large casts. Because all the quantities involved are discrete, for a small [n] there are only a few points to plot on the graph, and the smooth, continuous curves seen in the comic are less recognizable.
The title-text mentions that Randall made a graph of his prospective dating pool over time and was depressed by the results. As he gets older, his dating pool gets smaller: fewer people his age are single. But as Randall later shows in 314: Dating Pools , age is not the problem--he is!
The formulas may be derived as follows:
Each straight pair needs to include one of the x males and one of the (n-x) females, so there are x(n-x) possible ways of combining one of each.  E.g., if there are n=5 people, of whom x=2 are male, then there will be 3 possible pairings involving the first male, and 3 possible pairings involving the second, yielding 2(5-2)=6 possible pairs.
Wolfram|Alpha: x*(n-x)
Each gay pair needs to include either two males or two females.  To choose two males, we can start with any of the x males and choose any of the (x-1) remaining males.  However, that counts each possible pair twice.  E.g., Adam&Steve got counted when we chose Adam first and Steve second, and again when we chose Steve first and Adam second.  To avoid double-counting the pairs, we therefore need to divide the product by 2.  So there are x(x-1)/2 possible pairs of two males.  Similarly, there are (n-x)(n-x-1)/2 possible pairings of two females. Summing these, we get the total number of possible gay pairs as [x^2 - x  +  n^2 - nx - n - xn + x^2 + x]/2.  That simplifies to [n^2 - n   +   2 x^2 - 2 xn]/2.  The left two terms can be combined together as n(n-1) and the right two terms can be combined together as -2x(n-x) or 2x(x-n) [which is negative, because x-n<0].  Since the sum of these terms was divided by 2, we get that the total number of possible gay pairs is n(n-1)/2 - x(n-x), or n(n-1)/2 + x(x-n), which is what the cartoon says.
Wolfram|Alpha: n*(n-1)/2+x*(x-n)
TV Romantic Drama Equation (Derived during a series of 'Queer as Folk' episodes) [A table shows equations for possible romantic pairings in a TV show. The equation under "gay" is n(n-1) 2+x(x-n); the equation under "straight" is x(n-x).] x: Number of male (or female) cast members. n: total number of cast members.
[A graph plots pairings (for large casts) against cast makeup. Each of the above equations forms a curve. "Gay cast" starts high for an all male cast, dips down at 50/50 cast makeup, and then rises again for all female. "Straight cast" starts at zero for an all male cast, peaks at 50/50 cast makeup, and then drops to zero again for an all female cast. The two curves intersect at two points close to the middle.]


e to the pi Minus pi

Explanation:
e is a mathematical constant roughly equal to 2.71828182846. π is another, roughly equal to 3.14159265359.
The first panel discusses e π − π, which is around 19.999099979 — very close to 20. Black Hat explains how he tricked a programming team into believing that e π − π really equals 20 — instead of just being weirdly close — thus that any noticeable deviation from 20 results from errors in the code. This made them waste a lot of time trying to find a nonexistent bug until they realized that Black Hat was lying (clearly they had not known him for very long, and clearly they weren't very knowledgeable in mathematics).
Floating point numbers are how computers store non-integer real numbers as decimals — or rather, in most cases, approximate them: infinite amounts of data would be required to represent most numbers in decimal form (exceptions are integers and terminating decimals ). The "floating-point handlers" would be the code performing the e π − π calculation.
ACM is the Association for Computing Machinery , which at the time of writing sponsored the International Collegiate Programming Contest . It is likely that it was this competition, in which Black Hat wasted his teams time, for which he got kicked out.
Some random facts about the math here:
The title text pokes fun at another coincidence: ∜(9² + 19²/22) ≈ 3.1415926525, equating close to π (deviating only in the 9th decimal place). The humor comes from the fact that π is transcendental . Transcendental numbers are numbers that cannot be expressed through basic arithmetic with integers; one cannot end up with the exact value for any transcendental number (including π) by adding, subtracting, multiplying, dividing, exponentiating, and/or taking the nth root of any rational number, meaning the title text cannot possibly be true.
A much later comic, 1047: Approximations , puts forth quite a few more mathematical coincidences.
Cueball: Hey, check it out: e π − π is 19.999099979. That's weird. Black Hat: Yeah. That's how I got kicked out of the ACM in college. Cueball: ...what? Black Hat: During a competition, I told the programmers on our team that e π − π was a standard test of floating-point handlers -- it would come out to 20 unless they had rounding errors. Cueball: That's awful. Black Hat: Yeah, they dug through half their algorithms looking for the bug before they figured it out.


Nintendo Surgeon

Explanation:
The Nintendo Entertainment System , released in North America in 1985, helped revitalize the video-game industry after the video-game crash of 1983, with such games as the Super Mario Bros. series, The Legend of Zelda , the Mega Man series, Castlevania , and Metroid helping it stand alone as what is still considered by many people today, the greatest video-game console of all time.
However, it was notorious for glitching games upon start-up, due in no small part to the unusual shape of the game console, which required one to open the door, push the game cartridge inside, push down to lock it in place, and push the power button. The console was deliberately designed this way so that it wouldn't look like a regular video-game console (and wouldn't be associated with the still-fresh stigma of the video-game crash only two years previous), but it caused no end of pain for people wanting to play the games. It would work fine for about two years, but after that "cartridge tilt" would become a problem as either the game's or the console's electric contacts could become misaligned.
A ubiquitous fix for this problem among gamers was to take the cartridge out, blow into it, and put it back inside, all to clean out any dust inside the cartridge that would make "cartridge tilt" worse and occur more frequently. This was not a recommended solution by Nintendo of America, and didn't always work, but it worked frequently enough to enter gamer culture, and even today, people who had the NES as children remember having to do that.
The NES was 22 years old as of the date this comic was written. Someone who was 10 years old when they got their Nintendo for Christmas could very well be old enough in 2007 to have attained their doctorate degree, and so this comic hearkens back to the aforementioned cartridge fix by suggesting that a heart surgeon might try that on a real-life heart patient. And like the introduction states, that is a scary thought.
The title text is one of many xkcd references to the terrifying Velociraptor predator from the dinosaur movie Jurassic Park .
Scary Thought #137: The NES came out over two decades ago. Those kids are all grown-ups now. [Two surgeons are in an operating room, leaning over a patient.] First Surgeon: He's going into cardiac arrest. Stand by for defibrillation. Second Surgeon: Wait. First let's try taking out the heart, blowing into the ventricles, and putting it back in.


Blanket Fort

Explanation:
In an apparent continuation of comic 150: Grownups , Megan is showing off a blanket fort to her friend Ponytail . Ponytail answers that Megan's childishness stems from a fear of growing up.
Megan responds that she's fine with growing up. She sees her behavior as a mature realization that some of the things she enjoyed as a child are still enjoyable. When pressed for evidence that she has in any way become an "adult," it is revealed that her boyfriend is inside the blanket fort. He has not spoken because he fears to be found by them when "not exactly dressed," thus implying that "adult" activities had been going on in the fort.
The title text provides another example of this: They built a fort in the woods, another type of fort that a kid would love to have, but then used it to hide a body. This implies that they killed someone, which is not usually something associated with children. [ citation needed ] A hooker is also more formally known as a prostitute , which is also not usually something associated with children. [ citation needed ]
[Megan and Ponytail are talking with each other. There is a fort made of cushions and blankets on the left.] Megan: Like my fort? It uses every blanket and cushion in the apartment.
Ponytail: Okay, no offense, but this is like that ball pit you made -- Cute, but don't you worry you're clinging to childhood games because you're afraid of change?
Megan: No. I'm happy to grow up. But I won't pretend fun things aren't still fun out of fear of looking silly. Ponytail: But you're 24 and building blanket forts. How have you changed? What's adult about that?
Megan: Well, there's my boyfriend curled up in the back. Ponytail: ...Ah. Boyfriend [from inside the fort]: Excuse my shyness. I'm not exactly dressed.


Philosophy

Explanation:
In all of philosophy , perhaps the most important questions consider the meaning of life and can be expressed as "Why are we here?" or "What does it all mean?" Many philosophers and theologians have attempted to answer the question over the course of human history, and every religion claims to have some sort of answer.
Megan has been considering that the question is essentially meaningless. However, if that is true, she can't understand why it continues to be in her thoughts. This might feel frustrating for Megan. Two of her friends (both Cueball -like) notice that she is seemingly stuck in this existential question and have a short-term solution for her. One friend reaches for a Super Soaker 50, a powerful toy squirt gun, to shoot at Megan while she is having an existential crisis . (Megan uses this soaker later against Cueball in 517: Marshmallow Gun and 2334: Slide Trombone , and in comic 625: Collections , she has another one of her crises.)
The title text refers to the operant conditioning technique (a form of behavioral modification) commonly used with house cats. If they start scratching the furniture, many people spray them with a squirt bottle (since they hate water) to discourage that behavior (though it seldom works).  It may also allude to the idea of hitting a break key where a program is stuck in a logical loop.
Megan has since this comic had existential crises both in 1111: Premiere and in 1822: Existential Bug Reports .
[Megan sits on a chair for two panels without moving.]
[In the third panel, Megan has still not moved but makes the following comment to no one in particular.] Megan: If the question of what it all means doesn't mean anything, why do I keep coming back to it?
[Two Cueball-like friends of Megan are talking to each other. One of them is standing behind the office chair in which the other friend is sitting, behind a desk with a computer. The standing friend starts to walk toward Megan. The sitting friend pulls a large yellow and green super soaker from a drawer.] Standing friend: She's getting existential again. Sitting friend: It's okay, I have a super soaker.


Random Number

[A computer program.]

Explanation:
The comic specifies a function (in a C similar syntax), which judging by its name should be designed to return a random number. Most functions of this form are random number generators , meaning that on subsequent calls they return different random numbers. But the programmer has instead implemented a function that just returns the same random number each time, which, while it could indeed have been truly randomly chosen by rolling a die as the comment documented, is essentially worthless were it ever to be called more than once (with the expectation of different, i.e., random, results).  In other words, the results over time would not be random at all, but completely predictable and deterministic.
The IEEE is the organization responsible for maintaining a number of computer standards. An RFC, or Request for Comments , is a formal document put out to computing experts by IETF in the hopes of becoming a future standard. However, RFC 1149 was an April Fools' joke , defining how carrier pigeons can be used to transmit Internet packets. "RFC 1149.5," meanwhile, simply does not exist.
[A computer program.]


Small Talk

Explanation:
Cueball is approached by his friend who offers one of the standard greetings of, "What's Up? How've you been?" In standard "small talk," an appropriate answer would be only one or two words (e.g. "Fine" or "Pretty good"). These are generally positive responses, with negative ones only offered in extreme circumstances. In this situation, Cueball forgets that this type of answer is what his friend is expecting. Instead, he contemplates thoroughly on his condition, wanting to provide accurate, detailed information to his friend. His response sheds light on the many layers of meaning a simple question such as "What's up?" can have. His friend, thrown off by the delayed response, snaps his fingers to regain Cueball's attention and reminds him that they are having a conversation, which is best facilitated by the standard short responses.
The title text shows that Cueball was more interested in accuracy than the ease of the conversation, simply out of respect for his friend.
This was one of the earliest examples of problems with social interactions for Cueball (or Randall ). Since this comic it has been a recurring theme on xkcd. It is especially similar to the much later 1961: Interaction .
[Two Cueballs standing next to each other]: [Header box on top of the panel:] Sometimes I forget how to do small talk.
Friend: Hey! Cueball: Hey, man! Friend: What's up? How've you been? Cueball: Well...
[Three overlapping identical frames of the two Cueballs standing next to each other indicate the passage of time.]
[The Cueball on the left snaps his fingers at the Cueball on the right.] Friend: Uh, you ok? Cueball: Yeah! It's just an interesting question. I'm trying to decide what best sums up my-- Friend: Hey. Conversation. Cueball: Oh, right. I'm fine. You? Snap


Valentine's Day

Explanation:
As mentioned in the comic, love is already pretty complicated, even more so on Valentine's Day . Valentine's Day makes it more complicated by introducing all kinds of questions. Is our relationship such that it should be acknowledged on Valentine's Day? If so, how? If by a card, what kind of card would be best? If by something more than a card, what? Candy? Flowers? A Date? What does the Valentine I received really mean? Friendship? Love? A covert request for sex? (see 63: Valentine - Heart ). As an example of the kinds of dilemmas that can arise, see also 1016: Valentine Dilemma .
The phrase "Because love isn't quite complicated enough as it is" is an obvious use of sarcasm , as love is really complicated, according to Randall ( see above ).
Referenced in the title text, Joey Comeau is the author of the webcomic A Softer World . It is a queer comic whose work also discusses love in various forms, so between them, Randall Munroe and he are a good team to consider working on "subverting the hetero-normative paradigm." Heteronormativity is the body of lifestyle norms holding that people fall into two distinct genders with natural and complementary roles in life. Whether or not anything that cartoons can do would fix the Valentine's Day problem is another issue. Among other things, ditching the hetero-normative paradigm presumably complicates things in terms of potential love relationships, which now include more possibilities than male-female, as is shown in 216: Romantic Drama Equation . All of these might face the Valentine's Day issues in various ways.
Valentine's Day [There is a large, shaded, red heart.] Because love isn't quite complicated enough as it is.


Lisp

Explanation:
Lisp is a computer programming language with simple, highly regular syntax. The language's most notable feature is that programs take the same form as the language's primary data structure (the linked list). This blurs the line between code and data and permits programs to inspect and even alter their own source code, thereby opening up deep opportunities for metaprogramming . Lisp is also a functional programming language (though not purely functional, as some more recent languages are ), meaning that programs are expressed in terms that are simple elaborations or extensions of the lambda calculus , a formal mathematical model of computation. This gives programs written in functional languages such as Lisp a distinctively abstract, mathematical form that is commonly considered difficult to fully grok (see 1270: Functional ).
The phrase A suffusion of blue is a reference to Douglas Adams ' book The Long Dark Tea-Time of the Soul . In it, an I Ching calculator calculates that everything above the value of 4 is a suffusion of yellow .
In the comic, Cueball marvels at the fundamental and complete nature of the language of creation that he sees in his dream. In the Lisp programming language, "car" is a primitive (i.e. basic) function that produces the first item in a list. The line "My God, It's full of ' car 's" is a pun, most likely referring to the movie 2010: The Year We Make Contact , the sequel to 2001: A Space Odyssey . In the book 2001: A Space Odyssey , when astronaut David Bowman accidentally activates a star gate, he exclaims as he enters it "The thing's hollow — it goes on forever — and — oh my God - it's full of stars!", although he does not say anything in the first movie during the final sequence. This likely also includes a transitive reference a chapter in The Little Schemer , a popular introductory Lisp book, called *Oh My Gawd*: It's Full of Stars , also itself a reference to 2001.
In the second panel, Cueball remarks that, "At once, just like they said, I felt a great enlightenment." This is a reference to a pattern of observations among programmers and computer scientists that while Lisp often seems alien or arcane — even deliberately so, even to experienced hackers, even with repeated exposure over time — truly understanding Lisp in a deep, non-superficial way, results in a profound epiphany, a sudden and abiding illumination wherein one's preconceived notions about computation and programming are fundamentally transfigured, oftentimes over the course of a very short span such as during a single all-day hacking binge. Lispers commonly describe the experience as being akin to learning programming for the first time again ; Daniel P. Friedman (author of much ground-breaking research and many popular introductory texts on Lisp and programming language design) described it as "[learning] to think recursively ," and contended that " thinking about [functional] computing is one of the most exciting things the human mind can do ."
Cueball's remarks about patterns, metapatterns, and the disappearance of syntax are reactions to the elegant simplicity of the Lisp programming language, in which it is relatively easy to build immensely sophisticated programs using simple recursive elaborations of structure. This is fundamentally unlike the much more typical and common imperative programming languages , in which programs are written as chains of instructions for the machine to follow.
Cueball then, in the third, borderless panel, muses that this has to have been the language the gods used to create the universe, which is a pretty bold statement that Cueball seems to make because he views Lisp as something flawless and perfect, as these are qualities that often subjectively apply to things that people, like Cueball, claim to have been made or used by gods or other holy beings.
A cloudy, bearded man, presumably representing God, states that this is untrue, and after a surprised inquiry from Cueball replies that the universe was actually hacked together with the programming language Perl . Perl employs an idiosyncratic syntax that borrows liberally from a number of other languages. Although a versatile language often employed for assembling projects quickly (the much-loved Programming Perl introduces it as "[the] language for getting your job done "), Perl has a reputation for being ugly and inelegant, partly as a result of its pidgin-like fusion of many inconsistent language elements and code styles. It was famously described as a " Swiss-Army chainsaw," because it is very powerful but also unwieldy and unattractive. By way of contrast to Daniel Friedman above, Larry Wall , the creator of Perl, criticized the highly cerebral Lisp attitude toward programming with the words
The joke is that the Creator, like many software developers, was a bit rushed and chose to quickly throw together a working prototype rather than do the job right from the beginning; concurrently, that Cueball, thinking he has discovered an amazing and beautiful secret in the hidden world of Lisp, learns that in fact the real world is filled with ugly hacks and quick-and-dirty imperative code.
A (possible) hidden joke might be an oblique reference to Greenspun's tenth rule when God replies with "I mean, ostensibly, yes." Greenspun's tenth rule says that any sufficiently complex program written in another high level programming language will necessarily contain an imperfect, undocumented, slow, and bug-ridden implementation of about half of Common Lisp . Greenspun's tenth rule was meant to express the belief that Common Lisp, a large, full-featured Lisp dialect, is so flexible and robust that any attempt to render any really sophisticated program in most other languages requires the programmer to expend extraordinary effort unwittingly reinventing, in needlessly convoluted fashion, features and systems that would be elegant and trivial in Common Lisp. This explains why such a program might look or feel "Lispy" to an unfamiliar observer, and why the universe (if viewed as such a program) might look to mathematicians and scientists as though it probably has a beautifully simple mathematical basis, even if in reality it was just hacked together with a bunch of ersatz, special-case rules.
The title text continues the analogy by suggesting that the theory of quantum mechanics was written in regular expressions ("regexes"), a complex language for pattern matching used heavily in Perl. Regular expressions are often criticized as being a write-only language , that is, a language so complicated in syntax that any significant program written in them cannot be understood by anybody (often not even the original author). Documentation is essential to assist in the understanding of complex regular expressions. The title text claims that at some point, the documentation for quantum mechanics was lost, which explains why quantum mechanics is so bizarre and counterintuitive.
[Floating in space.] Speaker: Last night I drifted off while reading a Lisp book. Cueball: Huh? Speaker: Suddenly, I was bathed in a suffusion of blue.
[Floating in space before a vast concept tree.] Speaker: At once, just like they said, I felt a great enlightenment. I saw the naked structure of Lisp code unfold before me. Cueball: My God Cueball: It's full of 'car's Speaker: The patterns and metapatterns danced. Syntax faded, and I swam in the purity of quantified conception. Of ideas manifest.
[Close-up of floating in space before part of a concept tree.] Truly, this was the language from which the gods wrought the Universe.
[Floating in space with God appearing through a line of clouds.] God: No, it's not. Cueball: It's not? God: I mean, ostensibly, yes. Honestly, we hacked most of it together with Perl.


Open Source

Explanation:
Richard Stallman , or rms after his handle, is an old-school hacker known for establishing the Free Software Foundation (FSF) and initiating the GNU Project in the early 1980s, which produced major portions of what would later be the GNU/Linux [1] operating system. In this capacity, he's also known for being one of the most ardent and outspoken proponents of open source software , often referred to by Stallman as free software . In fact, his advocacy is so emphatic and polemical that he has garnered active dislike from traditionalists who believe that software source code should be retained as a trade secret by its developer(s). Stallman has expressed that he did not even wish to be in a comic using the phrase Open Source (see the trivia section).
While this dislike may not rise to the level of hiring ninja assassins to remove him from the world though that is historically inaccurate, it is strong. The joke of the comic, as it also turns out, is that the two Cueballs dressed up as ninjas were just out to have a fun time teasing Stallman, and they seemed to know that Stallman's paranoia about Microsoft makes him sleep with no fewer than two katana swords near his bed. This type of sword was one of the traditionally made Japanese swords that were used by the samurai of feudal Japan mainly as a sidearm. A ninja or more accurately a Shinobi no mono was basically special forces in feudal Japan. They specialized in espionage, sabatoge, etc. they were a rough combination of MI6, CIA, and Navy SEAL in feudal japan. Although they did not specialize in assassinations, that is something that they could do. Although samurai could also be shinobi/ninjas if they chose to do that job, samurai is a social class while shinobi no mono/ninjas were a job, not a social class. So this makes sense in this comic with Stallman, the samurai, and the ninjas, the lackeys of the oppressing Microsoft (at least in his mind). It also turns out that they specifically choose targets for their raids who have reason to be paranoid of larger companies that might send someone after them, and thus sleep with weapons near their beds. Stallman has received a Katana due to this comic (see the trivia section).
GPL refers to the 'GNU General Public License', which is a copyright license written by the FSF that covers much GNU software and plenty of other free software besides. It stipulates that software so copyrighted must always be provided along with full source code, and that everyone in possession of such software is free to use, study, modify, and redistribute it for any purpose whatsoever (including sale or resale), provided they give due credit to any other contributing developers and provide access to the complete source code and retain all copyright notices.
Legally, this gives all users of such software exactly the same rights under copyright as the developer(s) and prevents any developers from ever taking away those rights from users, which is the defining feature of ' free-as-in-libre ' software. It also has the effect of making all software derived from GPL software thereby also GPL, even if 'derived' merely means 'borrowed a few lines of code from'. Some (e.g. Microsoft's Steve Ballmer ) have therefore argued that this makes GPL software behave as a kind of 'license virus' , which spreads GPL-guaranteed freedoms to any software used in close conjunction with GPL'd software during development, such that businesses should actively avoid adopting free and open source software , so as not to jeopardize software developers' legal standing with regard to proprietary IP copyrights .
During the attack, Richard Stallman begins to speak like he quotes an old play. For instance, the wording "For a GNU dawn!" is pronounced "For a g'new dawn!", following the pronunciation of GNU , so it is a version of New Dawn , a sentence used often in fiction. He even gets annoyed when it turns out that the ninjas just run away. He had clearly waited a long time to, even looking forward to, defending himself with his katanas.
Because the two "ninjas" had so much fun pranking Stallman, they plan to do more of these raids, even mentioning two other possible future targets on their way out of the window:
Eric S. Raymond is a famous hacker who wrote The Cathedral and the Bazaar and has been something of an unofficial spokesperson for open source as a software development methodology . The plan to prank Eric Raymond could be a bad one, since he is an experienced martial artist, swordsman, and firearm enthusiast. However, this seems to be the attraction of these two "ninjas," as can be seen by what they seem to know about their other possible target:
Linus Torvalds is the creator of the Linux kernel , a free/open source operating system kernel inspired by the Unix kernel, which proved to be the final component that, combined with then pre-existing GNU system functions and userland components, produced the first fully free operating system, Linux . The plan to prank Torvalds would at first sound more boring as the mild-mannered Finn , while known to be strongly, abrasively opinionated, is otherwise mostly harmless. However, one of the ninjas seems to know otherwise, since it is rumored that Linus sleeps with nunchucks in the same way that Stallman sleeps with two katana swords. The nunchaku is a traditional Okinawan martial arts weapon consisting of two sticks connected at one end by a short chain or rope.
A third possible target of this prank is mentioned in the title text. Ralph Nader is a famous consumer rights advocate, most famous for his controversial 2000 presidential run , and the 1965 book Unsafe at Any Speed . Nader is an environmentalist and a member of the Green Party, and he supports clean energy, thus naturally being opposed to "Big Oil" companies.
[The first panel has the second panel inside it. It also has a slightly light gray background color. Just above the inlaid second panel is Richard Stallman lying in his bed sleeping, the bottom part at the foot of the bed hidden behind the second panel below. Below his bed under his head lies a katana sword in its sheath, and another one hangs in its sheath behind the end of the bed. Two ninjas with swords and black cloths around their heads jump through the skylight, smashing it so glass scatters around them. Each of them is hanging one-handed from the same rope coming down from the skylight. The rope ends just above the inlaid frame below. The two ninjas shout at Richard Stallman, from four speech bubbles that have pointy ends to indicate how the two alternately speak. (These bubbles are white, not gray.)] Richard Stallman: Zzzz Top Ninja: Richard Stallman! Your viral open source licenses have grown too powerful. Bottom Ninja: The GPL must be stopped. Top Ninja:  At the source. Bottom Ninja: You.
[In the second inlaid panel (with normal white background), Richard Stallman wakes up immediately, and while sitting up in bed, he pulls out both his katana swords from their sheaths, leaving the sheaths under and behind the bed. One hand is up in the air with the sword from behind the bed, and the other is still pointing down with the swords from below the bed. Lines indicate the fast movement of the swords. His three speech bubbles are like those of the ninjas, the last two even breaking the panel entering into the large first panel.] Katana swords: Shing! Shing! Richard Stallman: Hah! Microsoft lackeys! So it has come to this! Richard Stallman: A night of blood I've long awaited. But be this my death or yours, free software will carry on! For a GNU dawn! For freedom! Richard Stallman: ...Hey, where are you going?
[An outside scene at night with black sky. Richard Stallman's gray house can be seen with the broken white skylight on the roof. The ninjas are jumping out of a window at ground height while taking off their ninja cloth around their heads, holding them in their hand, thus revealing that they both look like Cueball. The first one is already on the grassy ground beneath the window, his sword pointing down and to the left; the other just jumps from the window pane, his sword pointing up and to the right. Again, they have speech bubbles like before. It is not possible to tell which of the two ninjas from before is first out the window.] Ninja in window: Man, you're right, that never gets old. Ninja on the grass: Let's do Eric S. Raymond next. Ninja in window: Or Linus Torvalds. I hear he sleeps with nunchucks.


Swingset

Explanation:
In the opening panel of this comic, Blondie , possibly as Miss Lenhart , sees Cueball sitting on a swing set. She tells him that during his swing, he becomes weightless. Cueball then imagines that at the peak of his swing he is able to become permanently weightless, floating above the ground without any support.
When on a swing or other pendulum ride , there is a moment between swinging forwards/backwards and swinging back down again when the forces of gravity, friction, air resistance, etc., bring the velocity of the swing to zero. At this moment, there is no acceleration toward the pivot of the swing (since the centripetal acceleration is proportional to the square of the speed). So the swinger experiences no centripetal force. Of course, gravity still acts on the person, but if the swing is horizontal at that point, then there is no reaction force, so for one moment, the swinger is in free-fall and experiences weightlessness . However, that weightlessness can only be maintained for a fraction of a second, so if Cueball tried this in real life, he would come crashing to the ground.
In the title text, Cueball asks for a pocket fan, believing he could fly around the yard using this small device perhaps as a propeller.
[Woman talking to Cueball on swing-set.] Woman: You know, at the peak of a big swing, you become weightless. [Thought bubble from Cueball.] [Cueball swings higher and higher. At the peak of a big swing, he shoves himself off the swing. Cueball remains hovering in the air.] Cueball: Hey guys. Come check this out.


Color Codes

Explanation:
Resistors are electronic components carrying color-coded bands indicating their value (measured in ohms ) and tolerance (e.g. 5%). Cueball has been hunched over his work for so long that, when asked for his phone number (by his Cueball-like friend), he absentmindedly reads out his phone's area code as a sequence of colors found on the aforementioned resistors (each colour corresponding to one of the ten decimal digits, in this case 718 – see Resistor color-coding ). He realizes his mistake after these first three digits and begins again using numbers to state the entire phone number. His friend points out that such a mistake means it's a good time to take a break, and Cueball concurs.
It's not uncommon for readers to try calling phone numbers they see inside a book or a comic strip, just to discover what it actually goes to. Randall foresees this, and in the title text he simply tells you what the phone number is.
TMBG is They Might Be Giants , an alternative rock band responsible for toe-tapping chart-topping "Birdhouse In Your Soul." At one point, they recorded individual songs on an answering machine and advertised the phone number so people could call and listen to the song on the machine. Hence, Dial-A-Song . However, the number was changed to (844)-387-6962 in 2015. TMBG has also created a website with the same function: https://dialasong.com .
Resistor color codes were mentioned again in 1604: Snakes .
[Cueball sits hunched over his desk, which is littered with objects. His Cueball-like friend holding his cell phone talks to him.] Friend: Hey, what's your cell number? Cueball: (Violet Brown Gray)— Uh, I mean, (718)-387-6962. Friend: Okay, you are putting down those resistors and going outside for a while. Cueball: That's probably a good idea.


Resonance

Explanation:
Resonance is the tendency for an object to oscillate when energy is transferred to it at a specific set of frequencies known as harmonics of the natural frequency of the object. A simple example of this is pushing a child on a swing: by pushing the child at the right moment, more and more energy is transferred to the system and the amplitude of the oscillation grows, making the child swing higher.
In this comic, the friend is jiggling his leg up and down at a harmonic of the natural frequency of Cueball 's desk. This causes Cueball's desk to vibrate more and more until objects on it start to bounce around. Rather than have the friend stop, Cueball wants him to slightly increase the frequency of the jiggling in order to spill the drink on Steve's desk (not pictured). In xkcd, no one likes Steve, as demonstrated in comics 1532 and 1672 as well as this one. However, it is hard to have a person control a subconscious movement exactly, let alone increase or decrease by exact figures.
In the title text, his friend confesses the obvious fact that he couldn't control the frequency very well. (Alternatively, Randall may have made this observation himself through experimentation.)
[Cueball is sitting at a desk, which is vibrating.] clatter clatter [He leans back and turns to face someone sitting at another desk behind him.] Cueball: Excuse me--you're jiggling your leg up and down. It's traveling through the floor and making my desk resonate. Friend: Oh, I didn't even realize! I'll stop. [Cueball passes a sheet of paper to the friend.] Cueball: Actually, can you just shift the frequency up by 15%? I think you can get resonance with Steve's desk instead. Friend: Uh huh... Cueball: Here are the calculations. Let's coordinate and try to spill his drink.


Graffiti

Explanation:
The humor in this comic comes from the irony of a deep philosophical musing on the nature of individuals sharing a private space in a public place, unknown to one another and separated by time. The graffiti text is juxtaposed with more common bathroom stall scrawlings - insults, slurs, and "[Name] was here."
This comic makes use of the existential idea of "finding meaning where you look for it," a recurring theme in xkcd. The caption implies that a bathroom stall isn't a place where Randall would like to find meaning in life, so he shouldn't look for it there.
The title text parodies one of the archetypical pieces of graffiti: "For a good time, call [phone number]," which indicates that the person reachable at that number is available for prostitution, casual sex, and/or phone sex. However, 'good' has been replaced with 'intriguing,' implying that instead of sex, the writer is offering witty and insightful conversation.
There may be a reference to this comic in 1810: Chat Systems with the chat system called Wall (bathroom) .
[Cueball sits on a toilet in a bathroom. The stall sidewall next to him is covered in graffiti: "you suck," "Mike sucks cock," "CUNT," "fuck," "BITCHAS," "dane was here" struck through and "dane is a fag" written under it, a crude pictogram of a penis, and various other unreadable scribbles.] [One block of graffiti is salient:] This graffiti is fleeting human contact both of us lost, but for a moment we're lost together. I wonder who you are.
I think I look for meaning in the wrong places sometimes.


Hamiltonian

Explanation:
Cueball , presumably in class, decides that the subject of optimizing routing algorithms is not important in the larger context of life and love. However, he later realizes while in bed with Megan that there is a flaw in the proof presented, and suddenly wants to focus on the mathematics again, in a humorous reversal of his position about what is meaningful.
In graph theory, a Hamiltonian path is a path that connects all the vertices (nodes) and passes through each one exactly once. (Think connect the dots with rules!) A Hamiltonian cycle is a Hamiltonian path such that the final vertex is adjacent to the initial one (intuitively, it "begins and ends with the same vertex," but recall that paths are required to only pass through each vertex once). The presenter is using graph theory to optimize a routing algorithm by solving a Hamiltonian path problem . Cueball's realization is that the proof he had followed in part actually requires a Hamiltonian cycle, not just a path, so the presenter's proof of the existence of a Hamiltonian path is insufficient to solve the problem.
The title text plays on a dual interpretation of bidirectional: just as any graph cycle can be traversed in two directions, a change in perspective can be traversed in two directions (from mathematics to love, and then from love to mathematics).
Lecturer: And therefore, based on the existence of a Hamiltonian path, we can prove that the routing algorithm gives the optimal result in all cases. Cueball: Oh my God.
[Close-up of Cueball.] Offscreen: What? What is it? Cueball: A sudden rush of perspective. What am I doing here? Life is so much bigger than this!
[Cueball running out of room.] Cueball: I have to go.
[Cueball enters darkened room, where Megan waits by window.] [Cueball and Megan embrace...]
[...and get into bed.]
[A heart appears over the supine bodies.] Megan: Ohh... grip
Cueball (out of frame): Wait a moment. Megan (out of frame): What is it?
[Silence.]
Cueball (out of frame): His proof only holds if there's a Hamiltonian cycle as well as a path! Megan (out of frame): ...excuse me? Cueball (out of frame): Paper, I need some paper. Hey, do you mind if I jot down some notes on your chest?


Cat Proximity

Explanation:
This comic refers to the use of " baby talk " when speaking to pets, especially cats . A person's voice becomes falsetto and cooing , vocabulary becomes simplified, and phrases are repeated, such as "Here, kitty, kitty, kitty."
The chart shows that a person's apparent intelligence decreases, and that the inanity (i.e. uselessness or emptiness) of their statements increases, the closer they get to a cat.
Most people act like this when they're playing with cats or trying to call them over to them.
Thankfully, being close to a cat doesn't actually cause any decrease of intelligence in normal circumstances; the graph technically refers to demonstrated intelligence rather than actual IQ levels. [ citation needed ]
The title text continues Cueball's obvious statement (and thus inane/useless point made) from below the graph.
In 1535: Words for Pets , Randall again mentions how people often talk strangely to their pets.
[A graph with the x-axis labeled, and the scale indicated from left to right:] Far Human proximity to cat Near [Two curves are  drawn and labeled, first the one starting on top, which then veers downwards and crosses the other as that curve veers upwards.] Intelligence Inanity of statements
[Below the graph, Cueball is seen standing at three distances from a cat that is drawn to the far right. The two first Cueballs are just standing, one below far, the other in the middle, and the last is standing close to the cat (below near) with his hands up, and he is speaking.] Cueball: You're a kitty!


Chess Enlightenment

Explanation:
In this comic, Cueball finds his game of chess against Megan to be too difficult, and he attempts to tap his subconscious to find his next move. This is a common technique used in more physical competitions like baseball or golf, where overthinking can interfere with one's motion and thus "clearing one's mind" and relying on the subconscious is useful to overcome such mental barriers. However, chess is more a game of planning and strategy than natural movement, and the rules of chess are not ingrained into Cueball's subconscious, and so his subconscious ends up feeding him invalid moves and beginner questions concerning movement rules.
Chess is a board game in which two players take turns to move a variety of different pieces representing units on a battlefield to try to capture the other player's king. Chess has a lively tournament scene and takes much practice to attain a competent level of skill in the game. Different units can move and capture in different ways; pawns can only move forward by one square unless it's their first move, in which case they can move up two squares, but they can only capture by moving diagonally unless they perform an en passant , in which they move around an opposing pawn that had moved forward two squares on the previous turn. Other pieces have different rules.
Obi-Wan Kenobi is a character from the movie series Star Wars who played the mentor figure to the protagonist, Luke Skywalker . One of his pieces of advice to his mentee was to relax and listen to his subconscious in strenuous times. However, Obi-Wan gave this advice because Luke was connected to The Force, a mystical energy in the Star Wars universe that connects to the entire universe; not being a part of the Star Wars universe, Cueball is unable to tap into it. The Force does have similarities to real-life concepts used in various Eastern philosophies, but they are not typically used to play chess, for the same reasons given above.
The title text refers to a scene in the chess movie Searching for Bobby Fischer , in which Sir Ben Kingsley's character dramatically sweeps the pieces off the board and instructs his student to see the pieces in his mind, which the child proceeds to do. Randall considers this impractical, presumably for similar reasons as the Obi-Wan example.
[Cueball and Megan are playing chess; Cueball is leaning forward over the chessboard.] Cueball (thinking): Why is chess so hard? Maybe the answers lie within me. Maybe I just need to let go, relax, and let my instincts and subconscious speak.
[Cueball leans back and places his hands to his head.] Meditate
Cueball's subconscious: Knight to G-4
[Beat panel.]
Cueball: That's not even a legal move. Cueball's subconscious: Okay, hold on. How do the pawns capture, again? Cueball: Man, Obi-Wan was full of crap.


A New CAPTCHA Approach

Explanation:
A CAPTCHA is a verification system to stop automatic submissions to web forms by asking the user to do something a computer program could not do, such as type a distorted word into a box.
But here, the author has a new CAPTCHA, in which it references a sad event in the children's movie, The Land Before Time . It asks the subject if it felt sad. If the subject is human, then they most likely will have felt sad, so the answer will be "yes." If it's a computer program, however, it is supposed to answer "no," because computer programs cannot feel. This CAPTCHA would be extremely easy to break, however, because a computer could easily find the "yes" button and press it. However, the "trap" is that a computer program doesn't "know" that it's supposed to answer "yes," as it lacks human emotion and empathy. It is similar to the way that humans are very good at being shown simple drawings of an object or an action and being able to tell immediately what it is, while computers can't. The "no lying" instruction is ostensibly meant to patch that hole, but unfortunately, it turns out that spambots are not generally programmed with the Three Laws of Robotics.
Another reason why a CAPTCHA like this won't be very practical is that some humans haven't necessarily seen the movie in the question and would be unable to know if they did feel sad or not.
The title text references the Futurama episode " Jurassic Bark ". It claims that this episode is so sad that even spambots cry after seeing it.
To complete your web registration, please prove that you're human: When Littlefoot's mother died in the original 'Land Before Time', did you feel sad? [radio button.] Yes [radio button.] No (Bots: no lying)


Escape Artist

Explanation:
Harry Houdini (born Erik Weisz/Ehrich Weiss) was a famous escape artist, whose more famous routines included escaping straitjackets and switching places with an assistant while locked inside a box.
The word "escape" also has a meaning in computer science . To "escape" something in programming means to replace a character or character sequence that would usually have a special meaning with another character sequence that doesn't have this special meaning. One common way of escaping is to have a special escape character that removes the special meaning from whatever character follows it. For instance, many programming languages enclose text strings in quotation marks (e.g. "this is a string" ). If you tried to directly put a quotation mark inside the string, the compiler would interpret it as the end of the string. To avoid this, the quotation mark is escaped with a backslash: "He said, \"Goodbye!\", and went away."
The problem Cueball is having is related to the fact that the Bash shell interprets spaces as a special syntactic marker, when he actually just wants the spaces to be literal space characters. In this case, escaping the spaces with \ would force Bash to interpret his script in this way.
(There is one other way the escape character is sometimes used, but we'll ignore it for the sake of explaining the comic.)
The person talking to Cueball is having a separate conversation about Houdini as Cueball thinks aloud about his script issue, which results in diverging conversations. This eventually leads Cueball to suggest that Houdini might have "escaped" (freed himself from) handcuffs by "escaping" (removing the special meaning from) them with backslashes.
Sometimes, escape characters need to be "nested" - the backslash character itself can be escaped as \\ to produce a literal backslash, so if, for example, one needs to produce a literal quotation mark to output to a script file, and that script file also needs to have the quotation mark escaped, one would need to type it out as \\\", which would be output as \". If I needed to actually output that \\\", one would need to type it as \\\\\\\". The number of backslashes needed grows, and can be very hard to keep track of (see 1638: Backslashes ). This behavior is a type of n-level nested quotation mentioned in the title text. This could, in practice, be very easy with syntax highlighting showing where the parser sees the string as ending, making it trivial to escape out the characters that should be escaped, e.g.: "And then he said \"Hi\"." In this example, the nested quotes could be escaped until the editor shows the uniform color of strings.
An iron maiden is supposedly a medieval torture device, currently believed to have been invented for tourism purposes much later than the time period when it was said to have been used.
Harry Houdini's escapes include an escape from a purported "iron maiden," although it only vaguely resembles the "medieval" torture device.
[Cueball sits before a computer on a desk while another man stands behind him.] Man: I was fascinated by locks as a kid. I loved how they turned information and patterns into physical strength. Cueball: Why does my script keep dying?
[Closeup on Cueball sitting at the computer.] Man: And a lock invites you to try and open it. It's the hacker instinct. Only your ignorance stands in the way. Cueball: Wait it's passing bad strings.
[Returns to the two shot of both men.] Man: I admired Harry Houdini, how he could open any lock and free himself from any restraint. Cueball: Ah - Bash is parsing the spaces.
Man: Sure some of it was fakery and showmanship. But I still wonder how he so consistently escaped handcuffs. Cueball: Backslashes? Man: Huh? Cueball: Never mind.


Kite

Explanation:
This comic presents, through a surreal scenario, one of Randall's recurring themes: that it is better to take a chance and make an interesting choice .
Cueball flies a kite, then fixes it to a tree and climbs its string. In real life, of course, the string would not be able to support the weight of a human. [ citation needed ] Up in the sky, Megan appears hanging on a blimp, looking at him throughout the encounter. Cueball wonders about her and considers talking to her, but he does not act. After she has gone, Cueball is alone again; nothing has changed.
The title text explains the meaning of this metaphor. It is easy to regret an awkward conversation you had. In contrast, you don't regret the conversations you didn't have the nerve to start, because their cost is invisible--yet, they may have been missed opportunities, possibly a much higher cost than a simple awkward conversation.
Later in the 1614: Kites title text, it turns out that other people ( Beret Guy ) can also fly with a kite.
[Cueball readies a kite.] [Cueball starts to fly the kite.] [Cueball continues to fly the kite.] [Cueball ties the kite string to a tree.] [Cueball grabs the string.] [Cueball starts to climb the string.] [A scene showing Cueball holding onto the string at a high altitude, against a colour backdrop of the ground, clouds, water, and the sky.] [Black and white again. Megan comes into view holding onto a small blimp.] Cueball (thinking): Hey, there's someone else up here. I wonder what her story is. [Megan floats to the other side of the panel.] Cueball (thinking): Maybe I should say hi. [Cueball is alone holding onto the string.]
There is a fan made animated version of this comic .


Collecting Double-Takes

Explanation:
There's a fairly well-founded meme that singles looking for other singles ( mostly that being men for women, and vice-versa, but not exclusively) can make connections with others in the fresh produce sections of a supermarket. From a single lady's point of view, men who are buying such goods are more likely to be unattached, due to the traditionally skewed gender politics of who shops for what in a couple, and at the same time, the man is exhibiting good habits in not merely stocking up on ready-meals or subsisting on takeaways while living the bachelor life.
By standing in a produce aisle with a tube of K-Y Jelly (which is most commonly used as a sexual lubricant) in his hand and considering what produce to buy (between bananas, apples, oranges, zucchinis, and doubtless many more off-screen), Cueball is allowing other people to believe that he either has plans to have sex with any connection he might manage to take home with him, or also he plans to use the chosen produce item to pleasure himself, probably sexually.
Cueball is probably not actually planning on doing either [ citation needed ] , but he loves to see the look on people's faces; hence, he's collecting double-takes.
In the title text, he says he likes to play a game of "freak out the cashier using two items." Wire coat hangers have been used to perform do-it-yourself abortions , many times with disastrous effects, such as internal hemorrhaging and the death of the woman.
[Cueball is standing in the middle of the produce aisle in a supermarket, holding a tube of K-Y Jelly in one hand, the other on his chin. The signs read "Bananas" "Apples" "Oranges" and "Zucchini" from left to right.] MY HOBBY: Standing in the supermarket's produce section holding a tube of K-Y Jelly, looking contemplative.