xkcd

by **ndookie** » Wed Aug 12, 2009 4:00 am UTC

http://xkcd.com/622

Alt-Text : After somewhere around 40 hours, there's no academic reason to go to the class. Only go for the hallucinations.

Q.E.D. Bitches !

by **Lleu** » Wed Aug 12, 2009 4:03 am UTC

I love it. Pure win. That is all.

by **J the Ninja** » Wed Aug 12, 2009 4:05 am UTC

Crap.....school is coming back soon. Good thing Fall term doesn't start for me until 9/22. I swear I won't start loading my backpack until a week or two before.

by **yahiek** » Wed Aug 12, 2009 4:05 am UTC

haiku(s?) about math;
xkcd can make me
hallucinate more

by **mrsaturn** » Wed Aug 12, 2009 4:06 am UTC

Holy crap, after reading this
ideas to optimize a prime number finder thing i was working on entered my brain.

by **dasada122** » Wed Aug 12, 2009 4:07 am UTC

Does the infinite prime thing have to do with flying, or is that just random?

by **glasnt** » Wed Aug 12, 2009 4:07 am UTC

This comic made me laugh
Lectures can be fun some times...
Also, hi joee!

by **Eternal Density** » Wed Aug 12, 2009 4:09 am UTC

Just yesterday I was in an online discussion about the effects of Lack Of Sleep. It's uncannily coincidental that it showed up in the very next xkcd! Get out of my posts, Randall!
Also, hi joee and glasnt!

by **ndookie** » Wed Aug 12, 2009 4:12 am UTC

Why doesn't the second panel have a border :S...

by **FCN** » Wed Aug 12, 2009 4:12 am UTC

Top prime's divisors? Huh?

by **glasnt** » Wed Aug 12, 2009 4:18 am UTC

FCN wrote:Top prime's divisors? Huh?

Haiku's are awesome.
But they don't have to make sense...
Refrigerator.

by **Eternal Density** » Wed Aug 12, 2009 4:19 am UTC

FCN wrote:Top prime's divisors? Huh?

My thought exactly.

by **Rabscuttle** » Wed Aug 12, 2009 4:20 am UTC

FCN wrote:Top prime's divisors? Huh?

yeah, that doesn't make sense proofwise. The divisors of a prime are itself and 1. The top prime's divisors' product plus one is just the top prime plus one.

multiply all primes.
add one to that. factors are...?
QED Bitches!

by **Raptor Jesus** » Wed Aug 12, 2009 4:21 am UTC

I had to manually enter this comic's number into my browser :evil:

Ah well its ok xkcd I forgive you

glasnt wrote:
FCN wrote:Top prime's divisors? Huh?

Haiku's are awesome.
But they don't have to make sense...
Refrigerator.

Or

This is a haiku
Just Japanese poetry
Buy a Honda

Poetry does have 3 syllables right? Haha :mrgreen:

by **Doodle77** » Wed Aug 12, 2009 4:22 am UTC

It's saying something like Given prime n, what are n+1's factors?

by **Crysm** » Wed Aug 12, 2009 4:23 am UTC

Rabscuttle wrote:
FCN wrote:Top prime's divisors? Huh?

yeah, that doesn't make sense proofwise. The divisors of a prime are itself and 1. The top prime's divisors' product plus one is just the top prime plus one.

multiply all primes.
add one to that. factors are...?
QED Bitches!

Yeah, I came here to see if anyone had figured that bit out. Well, it can all be pegged to sleep-deprived hallucinations I guess.

by **Crysm** » Wed Aug 12, 2009 4:24 am UTC

Crysm wrote:
Rabscuttle wrote:
FCN wrote:Top prime's divisors? Huh?

yeah, that doesn't make sense proofwise. The divisors of a prime are itself and 1. The top prime's divisors' product plus one is just the top prime plus one.

multiply all primes.
add one to that. factors are...?
QED Bitches!

Yeah, I came here to see if anyone had figured that bit out. Well, it can all be pegged to sleep-deprived hallucinations I guess.

EDIT:

Doodle77 wrote:It's saying something like Given prime n, what are n+1's factors?

That's not quite how I read it, but if that's the case, n+1 isn't a prime (it'll be divisible by 2... except for n=2) so it doesn't further the argument.

EDIT2: WTF, how did that doublepost?

by **'; DROP DATABASE;--** » Wed Aug 12, 2009 4:25 am UTC

Yeah be careful with that. Last time I tried it, I mistook my chair for a toilet. O.o Fortunately I did not have to actually go at the time, nor did I remove my pants, even though I thought I was going... that was 72 hours though.

I was a bit confused by the "prime divisors" thing too... never really studied primes so I figured I was just wrong. >_>

by **lingomaniac88** » Wed Aug 12, 2009 4:26 am UTC

I was thinking the same thing about "Top prime's divisors" not making sense, and I tried revising it myself. It turns out that my revision was almost same as Rabscuttle's; my first line was, "Product of all primes." But I think "Multiply all primes" sounds a lot better.

by **FCN** » Wed Aug 12, 2009 4:26 am UTC

Rabscuttle wrote:multiply all primes.
add one to that. factors are...?
QED Bitches!

Or:
Product of the primes,
Plus one, has the divisors...?
QED, bitches!

by **Yiddishnun101** » Wed Aug 12, 2009 4:28 am UTC

It takes more than 40 hours for hallucinations to set in...

by **revolutionx897** » Wed Aug 12, 2009 4:29 am UTC

One proof that there's an infinite number of primes is to:
1- Assume a finite number of primes
2- Take the product of all primes (p₁, p₂,...,p_n with p₁ as the 1st prime and p_n as the last) and add 1
3- This number cannot be divisible by any of the primes in the list, so it must either be prime or divisible by a prime larger than p_n, and therefore the original assumption of a finite number of primes is invalid

This seems to be the proof Randall is using, but I'm not exactly sure what the divisors part is meant to be. Bad wording?

by **Soulshift** » Wed Aug 12, 2009 4:33 am UTC

The flying professor's declaration of "Q.E.D., Bitches!" caused me some serious cheese burnage

by **InsanePyros** » Wed Aug 12, 2009 4:34 am UTC

apparently at the 20 hour mark you keep on reading infinities instead of primes despite the fact that they sound nothing alike, the haiku doesn't work, and the proof makes even less sense. It's probably just because I love the fact that there are an infinite number of infinities. Or more accurately, an aleph-0 number of infinities.

by **joee** » Wed Aug 12, 2009 4:37 am UTC

Hi glasnt and eternal ~~destiny~~density (do I know you, btw?)

*exhausted* after getting back from sydney. should just go home and die

<3 comic though, apart from the crappy prime number proof

by **Kwiz** » Wed Aug 12, 2009 4:37 am UTC

revolutionx897 wrote:Bad wording?

Nope. Just hallucinatory wording.

by **dumbledore** » Wed Aug 12, 2009 4:38 am UTC

revolutionx897 wrote:One proof that there's an infinite number of primes is to:
1- Assume a finite number of primes
2- Take the product of all primes (p₁, p₂,...,p_n with p₁ as the 1st prime and p_n as the last) and add 1
3- This number cannot be divisible by any of the primes in the list, so it must either be prime or divisible by a prime larger than p_n, and therefore the original assumption of a finite number of primes is invalid

This seems to be the proof Randall is using, but I'm not exactly sure what the divisors part is meant to be. Bad wording?

i was having trouble seeing #3 until i thought of modular arithmetic... then it becomes obvious. guess i have too much sleep deprivation myself >_<

by **Simon17** » Wed Aug 12, 2009 4:39 am UTC

The proof was shitty and the haiku wasn't even clever.
And although "you hallucinate when you're tired" has potential to make a decent comic, this one didn't do anything remotely creative or original.
Also my uncle died from sleep deprivation. Not funny not cool such a shitty comic.

by **Raptor Jesus** » Wed Aug 12, 2009 4:41 am UTC

Simon17 wrote:...Also my uncle died from sleep deprivation. Not funny not cool such a shitty comic.

You are not Sje46 (I think that was the number)

And btw what ever happened to him?

by **Iluvatar** » Wed Aug 12, 2009 4:43 am UTC

Attempted revision:

Take primes one through N
Product (plus 1)'s factors are?
QED, Bitches

(I'm fairly certain Randall just thought up that last line and built a comic around it.)

by **PaleCommander** » Wed Aug 12, 2009 4:44 am UTC

If you (like me) are bugged by the given proof, consider the following:

What prime could divide
One more than all primes' product?
Q.E.D., bitches!

by **Simon17** » Wed Aug 12, 2009 4:48 am UTC

Raptor Jesus wrote:Your not Sje46 (I think that was the number)

HAY RAPTOR JESUS ~~YOUR~~ I'M RETARTED

Look, don't be a douche. Spelling mistakes can be annoying, but then there is also such a thing as foreigners and people with dyslexia who can be great people but not master English.

- fjafjan

by **Raptor Jesus** » Wed Aug 12, 2009 4:50 am UTC

Simon17 wrote:
Raptor Jesus wrote:
Simon17 wrote:...Also my uncle died from sleep deprivation. Not funny not cool such a shitty comic.

You are not Sje46 (I think that was the number)

HAY RAPTOR JESUS YOUR RETARTED

The hell? If you are gunna troll at least be original (Or entertaining)

To keep this on topic

Buy A Honda
They are not that cool or fun
Q.E.D. bitches!

Poetic license

by **Simon17** » Wed Aug 12, 2009 4:57 am UTC

Raptor Jesus wrote:The hell? If your gunna troll at least be original (Or entertaining)

http://www.wikihow.com/Use-You're-and-Your
AHHHH!!!!

by **Raptor Jesus** » Wed Aug 12, 2009 4:58 am UTC

Simon17 wrote:
Raptor Jesus wrote:The hell? If your gunna troll at least be original (Or entertaining)

http://www.wikihow.com/Use-You're-and-Your
AHHHH!!!!

See that had class haha I welcome that kind of troll but blatant (if that is a word?) yelling for a mistake?

Edit: But please grammar Nazi's eventually get annoying. I write "your" like that because its faster then typing "you're" but ah well

P.S.I fixed my mistakes if that makes you any happier because I'm sure your life depends on everything being perfect

Buh Duh Duh Duh Dah
Bah Duh Duh Dum Doh Hah Hah
Q.E.D. bitches!

by **Simon17** » Wed Aug 12, 2009 5:09 am UTC

Raptor Jesus wrote:Edit: But please grammar Nazi's eventually get annoying.

Yes, blatant is a word, but that's not how it's used.
There's a difference between being a "Nazi" and getting frustrated because I have to read multiple spelling and grammar errors in every post you make.
Also,
http://www.wikihow.com/Use-Apostrophes
...
I'm thinking that I just got trolled.

No grammar for you!

by **ysth** » Wed Aug 12, 2009 5:15 am UTC

Pretty sleep-deprived myself, I read "number of pirates" at first.

by **dougallj** » Wed Aug 12, 2009 5:23 am UTC

Primes being finite,
Take product of all, add one.
A prime! Q.E.D.

Lawsuits would be filed for using "bitches" as a form of address for students.

Furthermore, I want more haiku proofs.

by **Storm** » Wed Aug 12, 2009 5:32 am UTC

Awesome comic! I enjoy ending any argument with Q.E.D. but now I think I'm going to end them with haiku's and Q.E.D., Bitches.
*inspired*

Also.. I think the Prof used Python in the middle of the lecture.

by **Tarquin** » Wed Aug 12, 2009 5:35 am UTC

I find this particular proof a bit terse and unhelpful (again, ignoring the obviously incorrect "divisors of a prime part"--specifically, it requires a supporting lemma that escapes me at the moment.

So, we want to prove the following, in effect, for the proof as stated to be valid:

Given consecutive primes p1....pn starting at 2, the product x of p1 to pn plus one cannot be divisible by some combination of factors a1p1, a2p2.....anpn, where a1....an are integers.

A previous poster mentioned that this is doable via modular arithmetic, which I'm sure is accurate, but without thinking about it more in that vein this claim is not self evident. In particular, it's obvious that for sufficiently high values of ai, it's possible to have a1p1.......anpn greater than x, so what we're really trying to prove here is that THERE DOES NOT EXIST A COMBINATION OF INTEGERS a1.....an such that a1p1 *.... * anpn = (p1 * p2 *...... * pn) + 1, which strikes me as not immediately self-evident Can someone explain how best to go about this proof and why it might be considered obvious?

******
Edit: Wikipedia makes the argument clearer by the simple claim that clearly (x + 1) / pi must have a remainder of 1 since pi > 1 for all pi. Certainly the proof is simple in this context, although as stated in the comic its terseness is perhaps unwarranted....although maybe so, given its elegance and expressibility in haiku. Also, remembering that I actually took an Algebra class in college, I recall that p1^a1.....pn^an would have been a much more canonical way of expressing a composite as a product of primes. silly me.

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