# xkcd- The explanations **URL:** \ **Category:** Cafe Society\ **Created:** [April 30, 2009, 2:38am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804 "2009-04-30T02:38:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Bosstone](https://avatars.discourse-cdn.com/v4/letter/b/22d042/32.png) [@Bosstone](https://boards.straightdope.com/u/Bosstone)\ **Post date:** [April 30, 2009, 5:07am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/21 "2009-04-30T05:07:26Z")
As for the Computational Linguists one, suffice it to say that the strip is implying computational linguists are a bunch of bullshitters. Most soft sciences can be said to be bullshit, really. 😛 (I say that as a linguist.) ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [April 30, 2009, 5:15am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/22 "2009-04-30T05:15:15Z")
> [@Sir\_T-Cups](#): > > Also if anyone else wants to contribute to the list with stuff they don’t get…go right ahead. Would someone tell me if the math has any significance in [George Clinton](http://xkcd.com/19/) (“I once tried to start the urban legend that George Clinton has a B.A. in mathematics”). Even if you don’t know a funking thing about Parliament et al, any idea of what’s on the board may be a clue. ---
**Author:** ![Alan\_Smithee](https://avatars.discourse-cdn.com/v4/letter/a/2acd7d/32.png) [@Alan\_Smithee](https://boards.straightdope.com/u/Alan_Smithee)\ **Post date:** [April 30, 2009, 5:37am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/23 "2009-04-30T05:37:17Z")
> [@Bosstone](#): > > As for the Computational Linguists one, suffice it to say that the strip is implying computational linguists are a bunch of bullshitters. Most soft sciences can be said to be bullshit, really. 😛 (I say that as a linguist.) But Chomsky was a computational linguist, right? (That’s what the mouseover says.) And doesn’t Chomsky has a reputation even among linguists of being a bullshitter? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 30, 2009, 5:40am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/24 "2009-04-30T05:40:55Z")
Fourier Transform: The Fourier transform of a function is a different function that’s related to your original function in a particular way. Basically, it tells you how you can break your original function up into a sum of a whole bunch of sine waves. The Fourier transform of a single sine wave looks like just a spike, and the Fourier transform of a function that’s a sum of two sine waves looks like two spikes, with the position and size of the two spikes telling you the frequencies and amplitudes of the two sine waves, and so on. As a general rule of thumb, if you start with something nice and smooth, and take the Fourier transform of it, you get something really jagged and spiky. A cat is relatively smooth, so its Fourier transform would look something like the thing you see there. Right-Hand Rule: There’s a certain kind of product of two vectors called a cross product. If I have two vectors **A** and **B** , then there’s a vector **C** such that **C** = **A** × **B**. The direction of the vector **C** is such that it’s perpendicular to both **A** and **B**. But that still leaves you two different directions to choose from. Which one is it? For that, you need the Right-Hand Rule. There are many variations of it, but one version is “Point the fingers on your right hand in the direction of **A**. Now curl your fingers in the direction of **B**. The direction your thumb has to point in to make this possible is the direction of **C**.”. But you could use any object with a “handedness” for this rule, not just a hand. He’s suggesting a few others. What XKCD really means: As you probably guessed, there’s no connection between any of the panels, and the name XKCD is really just random. But for the third panel: Ackerman’s function is a function in mathematics which grows really incredibly insanely fast, such that nobody even knows how to calculate the number you get out of it if you feed in, say, 6. Graham’s number, meanwhile, is the largest number that’s ever been used in any mathematical proof, and is so mindbogglingly huge that it takes a couple of pages just to explain the special notation you need to express it. So using Graham’s number as an argument in the Ackerman function is basically just a recipe for making your head explode. I think that covers all of them, now. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [April 30, 2009, 10:42am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/25 "2009-04-30T10:42:54Z")
**Sir T-Cups** , if you don’t get these, or have difficulty understanding these on first viewing, I’m going to suggest that xkcd is not the comic for you. Much of what he pokes fun at is either science or math related, and unless you have a pretty good background in the stuff, it’s gonna go flying by without tickling your funny bone, even if someone eventually does explain it to you. 😉 ---
**Author:** ![bup](https://avatars.discourse-cdn.com/v4/letter/b/6bbea6/32.png) [@bup](https://boards.straightdope.com/u/bup)\ **Post date:** [April 30, 2009, 11:46am UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/26 "2009-04-30T11:46:02Z")
> [@](#): > > Blogofractal- This seems like another one that might be too complicated to explain, but I’ll put it here regardless Fractals are mathematical mappings, the graphs of which are interesting patterns, and no matter how small a piece of the graph you look at, the pattern remains interesting. They don’t have much mathematical interest, but about 15 years ago everyone thought they were cool to look at on computer screens. So blogofractal, playing off blogosphere, is his attempt to show a very dense pattern. Presumably, if you drilled into any one blog, it would expand to just as dense a mapping of other blogs. ---
**Author:** ![Strinka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/strinka/32/512_2.png) [@Strinka](https://boards.straightdope.com/u/Strinka)\ **Post date:** [April 30, 2009, 12:14pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/27 "2009-04-30T12:14:28Z")
> [@Sir\_T-Cups](#): > > [What xkcd means](http://xkcd.com/207/)- This is mostly the third panel. The [Ackermann function](http://en.wikipedia.org/wiki/Ackermann_function) is a function that grows very, very quickly. According to that Wikipedia page, A(4,1) = 65533. [Graham’s number](http://en.wikipedia.org/wiki/Graham%27s_number) is immensely huge. It’s larger than the largest number you can imagine. If you were to write one digit on every atom in the universe, you couldn’t write that number, and you couldn’t even write how many digits are in that number. Now, imagine combining the two. Yeah, neither can I. ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [April 30, 2009, 12:38pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/28 "2009-04-30T12:38:59Z")
I’ll point out, since you seem to be having trouble with a lot of them (hey - I write grants, I don’t get most of them), to make sure you’re checking the mouseover text to see if there’s any insight to be gleaned there. ---
**Author:** ![Madd\_Maxx](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@Madd\_Maxx](https://boards.straightdope.com/u/Madd_Maxx)\ **Post date:** [April 30, 2009, 4:21pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/29 "2009-04-30T16:21:27Z")
Hell, half the reason I’m in college is so I can some day “get” most of the xkcd comics. ---
**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\ **Post date:** [April 30, 2009, 4:35pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/30 "2009-04-30T16:35:56Z")
> [@Rhythmdvl](#): > > Would someone tell me if the math has any significance in [George Clinton](http://xkcd.com/19/) (“I once tried to start the urban legend that George Clinton has a B.A. in mathematics”). Even if you don’t know a funking thing about Parliament et al, any idea of what’s on the board may be a clue. I’m not sure I really get that joke (who is George Clinton, there seem to be several with wikis!) but the equations on the boards are the general definitiion of the [Laplace Transform](http://en.wikipedia.org/wiki/Laplace_transform) which, while I’ve used them in one course so far, I cannot explain to anyone’s satisfaction! ---
**Author:** ![Bosstone](https://avatars.discourse-cdn.com/v4/letter/b/22d042/32.png) [@Bosstone](https://boards.straightdope.com/u/Bosstone)\ **Post date:** [April 30, 2009, 4:43pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/31 "2009-04-30T16:43:54Z")
> [@mnemosyne](#): > > I’m not sure I really get that joke (who is George Clinton, there seem to be several with wikis!) Parliament Funkadelic, the [P-Funk!](http://www.youtube.com/watch?v=Qw-ie2ZzvFQ) (Clinton’s the long-haired dude in the white hat.) ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [April 30, 2009, 4:55pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/32 "2009-04-30T16:55:44Z")
> [@Alan\_Smithee](#): > > A little more detail on Schroedinger: You know how in quantum mechanics light (and everything else, in fact, but most noticeably light) sometimes seems like a wave and sometimes a particle, right? And how we can know where an electron is or how it is moving but not both (Heisenberg’s Uncertainty Principle)? QM is full of this sort of thing and according to the most common understanding, any attempt to get at the “real” answer is doomed because the real answer is that light is _both_ a wave and a particle, and the electron really _doesn’t have_ an exact location and an exact speed at the same time - these things only resolve when someone observes them, and the particle is over here or over there, but the rest of the time there literally _is no answer_ to how things really are. Things at a quantum level exist in a state of probability, not this or that but 50% this and 50% that. > > With me so far? > > Einstein objected that this isn’t possible, that it might seem to make sense when you’re looking at equations, but that the real world couldn’t work that way. Schroedinger countered that the real world works _exactly_ that way, and to show that he meant it he developed a thought experiment. What if one of these statistical probabilities had real-life consequences. Say you built a trigger that would release poison gas if the particle is here but not there. And then you locked a cat inside a box with the device and a piece of radioactive material that has a 50% chance of producing a particle here, such that the poison is released. Einstein (and most people) would say that the particle is either in the right place to set off the trigger or it isn’t, and so the cat is either alive or dead, one or the other. But Schroedinger said No! The particle hasn’t been observed yet (because the box is still locked) so the particle, the trigger, the poison, and the cat _all_ exist in a state of quantum indeterminacy: 50% here and 50% there, 50% dead and 50% alive. Only when you open the box and look at the cat, can you say that the particle did or didn’t get produced. Until then it is just a probability _with no actual answer one way or the other._ In other words, Schroedinger called Einstein’s bluff: even when you’re dealing with a real-life situation with a real live (or not) cat, the universe _does_ work that way and you can’t prove otherwise! And sure enough, Einstein and others tried and tried to prove that there is some way of showing that the cat either _is_ or _is not_ alive before you look in the box, but not only could they not prove Schroedinger was wrong, but any other way of looking at things meant that even stranger things had to be true (which also couldn’t be proved or disproved). Eventually most quantum physicists gave up and admitted that Schroedinger was right: that saying that the cat is both alive and dead at the same time makes _at least_ as much sense as anything else they could say, and it fits with the equations. Every now and then I read about scientists still trying to come up with an experiment that would prove whether or not the universe really works like this or not (the high IQ version of proving the light stays on when you close the fridge door), but so far they haven’t gotten anywhere as far as I know. Actually, if I remember correctly, Schroedinger was with Einstein. He came up with the cat experiment to show how absurd the probabilistic way of looking at quantum mechanics was. Of course, his thought experiment ended up being the standard way to show how wrong he was. Oh well. ---
**Author:** ![dotchan](https://avatars.discourse-cdn.com/v4/letter/d/9d8465/32.png) [@dotchan](https://boards.straightdope.com/u/dotchan)\ **Post date:** [April 30, 2009, 5:23pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/33 "2009-04-30T17:23:13Z")
The Kepler strip may also be referring to the ungodly levels of patience (and spare time) the man needed to peruse the observed data of Mars’ orbit in order to come up with his laws of Planetary Motion. ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [April 30, 2009, 5:24pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/34 "2009-04-30T17:24:39Z")
> [@AudreyK](#): > > Sudo is a Unix command used to allow the user emulate the user settings of someone else. Not quite. Sudo is, literally, “do [this] as if I was the superuser”, i.e. perform this command as if I was the system administrator and had every possible right. Sudo requires the administrator’s login and password before it runs by default, so it’s not like it’s a hacking, magical command. It is, however, very useful when trying to get a user-side app to do what it’s fucking told to. ---
**Author:** ![Sir\_T-Cups](https://avatars.discourse-cdn.com/v4/letter/s/ed655f/32.png) [@Sir\_T-Cups](https://boards.straightdope.com/u/Sir_T-Cups)\ **Post date:** [April 30, 2009, 5:51pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/35 "2009-04-30T17:51:09Z")
> [@DSYoungEsq](#): > > **Sir T-Cups** , if you don’t get these, or have difficulty understanding these on first viewing, I’m going to suggest that xkcd is not the comic for you. Much of what he pokes fun at is either science or math related, and unless you have a pretty good background in the stuff, it’s gonna go flying by without tickling your funny bone, even if someone eventually does explain it to you. 😉 I understood after the first viewing or so of the comic that a lot of it I wouldn’t totally understand. What annoys me more than anything are the things that are so damn familiar, but I just can’t place where or how. Schrodingers cat aside, all of the explanations and such I am getting quite quickly and on the first time, not to mention too that there are comics that I _didn’t_ have to ask the explination. ---
**Author:** ![Stormcrow](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@Stormcrow](https://boards.straightdope.com/u/Stormcrow)\ **Post date:** [April 30, 2009, 5:58pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/36 "2009-04-30T17:58:56Z")
I think the joke for the Schrodinger’s Cat strip is actually in the mouseover text more so than in the strip itself. ---
**Author:** ![SCSimmons](https://avatars.discourse-cdn.com/v4/letter/s/e495f1/32.png) [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)\ **Post date:** [April 30, 2009, 6:28pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/37 "2009-04-30T18:28:20Z")
> [@tr0psn4j](#): > > In programming if you want to write a comment in your script you write it next to a // and it shows up in green. In some programming languages. And to finish the explanation–comments are ignored completely by the compiler when it makes the executable program from your raw code. In other words, they effectively do not exist. So the character is geekily implying that the things the other character is saying are being completely ignored … ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 30, 2009, 7:16pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/38 "2009-04-30T19:16:42Z")
> [@](#): > > Not quite. Sudo is, literally, “do [this] as if I was the superuser”, i.e. perform this command as if I was the system administrator and had every possible right. Sudo requires the administrator’s login and password before it runs by default, so it’s not like it’s a hacking, magical command. It is, however, very useful when trying to get a user-side app to do what it’s fucking told to. Actually, **AudreyK** is correct: The command stands for “switch user do”, and can be used to run a program as any user. It’s just that the user you most often want to emulate is the superuser, to do things like installing programs into privileged spaces. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [April 30, 2009, 7:25pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/39 "2009-04-30T19:25:43Z")
xkcd also shows up from time to time in “[Comics I Don’t Understand](http://comicsidontunderstand.com/wordpress/).” ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [April 30, 2009, 7:33pm UTC](https://boards.straightdope.com/t/xkcd-the-explanations/494804/40 "2009-04-30T19:33:23Z")
> [@Chronos](#): > > Actually, **AudreyK** is correct: The command stands for “switch user do”, and can be used to run a program as any user. It’s just that the user you most often want to emulate is the superuser, to do things like installing programs into privileged spaces. Huh. I deny any responsibility then - my Unix teacher taught us it meant “super user do”. You can’t reasonably expect a student to do his own research, can you ? CAN YOU ? You effing truth Nazi…😃 [Previous page](https://boards.straightdope.com/t/xkcd-the-explanations/494804.md?page=1) [Next page](https://boards.straightdope.com/t/xkcd-the-explanations/494804.md?page=3)