0816: "Applied Math"
Moderators: Moderators General, Prelates, Magistrates
 LucasBrown
 Posts: 299
 Joined: Thu Apr 15, 2010 2:57 am UTC
 Location: Poway, CA
0816: "Applied Math"
Alt text: "Dear Reader: Enclosed is a check for ninetyeight cents. Using your work, I have proven that this equals the amount you requested."
The principle of explosion returns.
 cjmcjmcjmcjm
 Posts: 1158
 Joined: Tue Jan 05, 2010 5:15 am UTC
 Location: Anywhere the internet is strong
Re: 0816: Applied Math
A logical proof that disproves logic? How interesting!
HI JOEE!
HI JOEE!
frezik wrote:Antiphotons move at the speed of dark
DemonDeluxe wrote:Paying to have laws written that allow you to do what you want, is a lot cheaper than paying off the judge every time you want to get away with something shady.

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
Only 1,317,408 errors?
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
Re: 0816: Applied Math
cjmcjmcjmcjm wrote:A logical proof that disproves logic? How interesting!
HI JOEE!
Today, mes amis, I've ordered the metaphysics special with a side of Gödel's incompleteness theorems. I expect our discussion will be as lively as ever.
"Si ad naturam vives, numquam eris pauper; si ad opiniones, numquam eris dives."
Live rightly and you shall never be poor; live for fame and you shall never have wealth.
~Epicurus, via Seneca
Live rightly and you shall never be poor; live for fame and you shall never have wealth.
~Epicurus, via Seneca

 Posts: 64
 Joined: Wed Aug 25, 2010 8:25 am UTC
 Contact:
Re: 0816: Applied Math
I'll bet she divided by zero somewhere in there... _

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
Randall hasn't updated the > button yet.
Edit: Now he has.
Edit: Now he has.
Last edited by black_hat_guy on Mon Nov 08, 2010 5:06 am UTC, edited 1 time in total.
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
Re: 0816: Applied Math
A flowchart? Seriously? Real mathematicians use 4pt serif font when writing on the blackboard. Because secretly, it's all done with tex. (Insert comment about knuth here.)
Re: 0816: Applied Math
Alright, I need an explanation. Did the book author promise to send someone money if they found errors in his/her book?
Re: 0816: Applied Math
HI JOEE x INFINITY
Also, the pricely sum of 2^8 x 10^{2} per error is nice.
edit: wow, I only just read http://en.wikipedia.org/wiki/Knuth_reward_check from the link below.. that man is awesome.
Also, the pricely sum of 2^8 x 10^{2} per error is nice.
edit: wow, I only just read http://en.wikipedia.org/wiki/Knuth_reward_check from the link below.. that man is awesome.
Last edited by glasnt on Mon Nov 08, 2010 5:26 am UTC, edited 2 times in total.
Hi joee! (origin story)
Re: 0816: Applied Math
black_hat_guy wrote:Randall hasn't updated the > button yet.
He has not changed it. And he will not. It points to xkcd.com/, not any specific number. So it is /always/ uptodate.
Re: 0816: Applied Math
mikebolt wrote:Alright, I need an explanation. Did the book author promise to send someone money if they found errors in his/her book?
Yup. Donald Knuth's http://en.wikipedia.org/wiki/Art_of_Computer_Programming
Re: 0816: Applied Math
mikebolt wrote:Alright, I need an explanation. Did the book author promise to send someone money if they found errors in his/her book?
This isn't restricted to mathematics; my classics professors will send in grammar errors and assorted typos that they catch in our references.
"Si ad naturam vives, numquam eris pauper; si ad opiniones, numquam eris dives."
Live rightly and you shall never be poor; live for fame and you shall never have wealth.
~Epicurus, via Seneca
Live rightly and you shall never be poor; live for fame and you shall never have wealth.
~Epicurus, via Seneca
Re: 0816: Applied Math
Of course, since we all know $0.98 is the same thing as $0.098, that check's not worth the paper it's printed on.
Oh no, I've said too much; I haven't said enough

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
bytbox wrote:black_hat_guy wrote:Randall hasn't updated the > button yet.
He has not changed it. And he will not. It points to xkcd.com/, not any specific number. So it is /always/ uptodate.
That's a good point. I've come to expect that xkcd.com has the latest comic on it.
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.

 Posts: 98
 Joined: Fri Feb 19, 2010 5:48 am UTC
 Eternal Density
 Posts: 5581
 Joined: Thu Oct 02, 2008 12:37 am UTC
 Contact:
Re: 0816: Applied Math
Inb4 .02 cents!
Play the game of Time! castle.chirpingmustard.com Hotdog Vending Supplier But what is this?
In the Marvel vs. DC filmmaking war, we're all winners.
In the Marvel vs. DC filmmaking war, we're all winners.

 Posts: 199
 Joined: Sat May 24, 2008 4:17 am UTC
Re: 0816: Applied Math
Turing Machine wrote:http://plato.stanford.edu/entries/dialetheism/
seriously not terribly highlevel logic here, guy
The point is that it could be derived from an arbitrary P with the bare minimum of assumptions used in most useful problems, thus proving any P impossible.
Of course, hasn't it been proven that such a proof is impossible?
Finally, keep in mind that the Incompleteness Theorem, as the name suggests, showed only that a system cannot be both complete and consistent, that is to say, it can't precisely address every question that could possibly be posed to it (which would have to include "will this system answer 'no' to this question?") without running into an inconsistency.

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
Apparent inconsistency of logic arises from assuming logic is complete. Logic is not complete since it's consistent.
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.

 Posts: 20
 Joined: Thu Apr 01, 2010 8:18 pm UTC
 Location: Orbiting this neato star called "Sol"
Re: 0816: Applied Math
Man, I walked in to say that Knuth proved that the reader requested an amount of money equal to 98 cents by the reason of that other comic where assuming contradictory premises led to any true conclusion the thinker liked.
Um...oh dear, how to contribute now...? I've got it! Poorlyexecuted computer science joke!
So, I notice that the conclusion here is P and notP. Now, we have a pretty good guess that P != NP, but does notP = NP?
Um...oh dear, how to contribute now...? I've got it! Poorlyexecuted computer science joke!
So, I notice that the conclusion here is P and notP. Now, we have a pretty good guess that P != NP, but does notP = NP?
while (!spoon) {
fork();
}
fork();
}
 Arancaytar
 Posts: 1642
 Joined: Thu Mar 15, 2007 12:54 am UTC
 Location: 52.44°N, 13.55°E
 Contact:
Re: 0816: Applied Math
This just made me realize that there should be a Knuth Facts website to accompany the Schneier one.
The man's a legend.
The man's a legend.
"You cannot dualwield the sharks. One is enough." Our DM.

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
memcginn wrote:Man, I walked in to say that Knuth proved that the reader requested an amount of money equal to 98 cents by the reason of that other comic where assuming contradictory premises led to any true conclusion the thinker liked.
Um...oh dear, how to contribute now...? I've got it! Poorlyexecuted computer science joke!
So, I notice that the conclusion here is P and notP. Now, we have a pretty good guess that P != NP, but does notP = NP?
If P!=NP, then that must mean P=NP!
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
Re: 0816: Applied Math
I expect she'll be killed at a zebra crossing.

 Posts: 111
 Joined: Tue Jul 20, 2010 8:34 pm UTC
Re: 0816: Applied Math
StClair wrote:I expect she'll be killed at a zebra crossing.
Yes. And Donald Knuth will disappear in a puff of logic.
Billy was a chemist.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
He isn't any more.
What he thought was H_{2}O
was H_{2}SO_{4}.
Re: 0816: Applied Math
I notice she would have gotten nearly twice as much money by pointing out that she proved all of the Millennium Prize Problems. In any case, I'm sure they'd consider that more important than any of them, and the should at least give her one milliondollar prize.
Shouldn't she use a proof checker? I wouldn't trust a human with something like that. Or just one proof checker for that matter.
Shouldn't she use a proof checker? I wouldn't trust a human with something like that. Or just one proof checker for that matter.
Re: 0816: Applied Math
Women start from the conclusion and work backwards.
 sugarhyped
 Posts: 548
 Joined: Wed Feb 27, 2008 5:16 am UTC
 Location: california
Re: 0816: Applied Math
black_hat_guy wrote:StClair wrote:I expect she'll be killed at a zebra crossing.
Yes. And Donald Knuth will disappear in a puff of logic.
that makes little sense if you're american and dont know that zebra crossing is crosswalk.
Thats what I have taken away from this topic...
I wanted a signature. I don't know what to put here yet.
 RebeccaRGB
 Posts: 336
 Joined: Sat Mar 06, 2010 7:36 am UTC
 Location: Lesbians Love Bluetooth
 Contact:
Re: 0816: Applied Math
The title text burnt my cheese.
Stephen Hawking: Great. The entire universe was destroyed.
Fry: Destroyed? Then where are we now?
Al Gore: I don't know. But I can darn well tell you where we're not—the universe!
Fry: Destroyed? Then where are we now?
Al Gore: I don't know. But I can darn well tell you where we're not—the universe!
Re: 0816: Applied Math
Godel's theorem comes in two parts: one implies that predicate logic is incomplete. It's actually the second part that's weirder, it says that any sufficiently powerful axiom system CANNOT prove itself to be CONSISTENT! Yes I'm serious. It's really weird. But let's say even if a system COULD prove itself consistent: this wouldn't actually mean anything, because it might still be an inconsistent system, since inconsistent systems CAN prove themselves to be consistent, it's just that they can also prove themselves to be inconsistent, and all sorts of other contradictions. There IS no proof, and cannot be, that second order predicate logic will never prove 1 = 0 and A = not A, although (hopefully?) it is true. Weird. http://everything2.com/title/Godel%2527 ... e+syllable you might want to check out the wikipdedia page also. And here's a talk I just found going into what it would actually mean if the current foundations of mathematics were to be found inconsistent! (Which actually happened once before when it was attempted to build up mathematics from naive set theory which lead to russel's paradox. http://en.wikipedia.org/wiki/Russel%27s_paradox)
Re: 0816: Applied Math
SocialSceneRepairman wrote:Of course, hasn't it been proven that such a proof is impossible?
So tell me, what would you actually use to make such a proof?
Re: 0816: Applied Math
To be a small sticker on notation:
where it says [imath]P \Lambda \bar{P}[/imath], what you probably meant, the adjoint (conjugate transpose for finitedimensional spaces), is usually written [imath]P^*[/imath] rather than [imath]\bar{P}[/imath] to distinguish it from only doing complex conjugate (without doing transpose) of all the elements in the matrix. So [imath]P \Lambda P^*[/imath] is how you usually see it. Unless this was the hidden joke and Randall was trying to troll mathematicians or something.
Also I don't really see what the comic has to do with applied math at all. Consistency of logic systems is about as far from applied math as you can get (restricting yourself to the realm of math). Unless this is part of the joke too? I don't know.
where it says [imath]P \Lambda \bar{P}[/imath], what you probably meant, the adjoint (conjugate transpose for finitedimensional spaces), is usually written [imath]P^*[/imath] rather than [imath]\bar{P}[/imath] to distinguish it from only doing complex conjugate (without doing transpose) of all the elements in the matrix. So [imath]P \Lambda P^*[/imath] is how you usually see it. Unless this was the hidden joke and Randall was trying to troll mathematicians or something.
Also I don't really see what the comic has to do with applied math at all. Consistency of logic systems is about as far from applied math as you can get (restricting yourself to the realm of math). Unless this is part of the joke too? I don't know.
 RebeccaRGB
 Posts: 336
 Joined: Sat Mar 06, 2010 7:36 am UTC
 Location: Lesbians Love Bluetooth
 Contact:
Re: 0816: Applied Math
mafaraxas wrote:Also I don't really see what the comic has to do with applied math at all.
The application is getting the $3,372,564.48.
Stephen Hawking: Great. The entire universe was destroyed.
Fry: Destroyed? Then where are we now?
Al Gore: I don't know. But I can darn well tell you where we're not—the universe!
Fry: Destroyed? Then where are we now?
Al Gore: I don't know. But I can darn well tell you where we're not—the universe!
Re: 0816: Applied Math
mafaraxas wrote:To be a small sticker on notation:
where it says [imath]P \Lambda \bar{P}[/imath], what you probably meant, the adjoint (conjugate transpose for finitedimensional spaces), is usually written [imath]P^*[/imath] rather than [imath]\bar{P}[/imath] to distinguish it from only doing complex conjugate (without doing transpose) of all the elements in the matrix. So [imath]P \Lambda P^*[/imath] is how you usually see it. Unless this was the hidden joke and Randall was trying to troll mathematicians or something.
Also I don't really see what the comic has to do with applied math at all. Consistency of logic systems is about as far from applied math as you can get (restricting yourself to the realm of math). Unless this is part of the joke too? I don't know.
P is a proposition, not a matrix. The girl has proved "P and not P."
Re: 0816: Applied Math
I was under the impression that The Art of Computer Programming was in italics because the writer was referring to the very foundations of computer programming, and thus, based on the gravity of this revelation, was using italics for emphasis!
I see now that it's a book. Also, I know what the deal is with the cheque. Much funnier now.
I see now that it's a book. Also, I know what the deal is with the cheque. Much funnier now.
 Yakk
 Poster with most posts but no title.
 Posts: 11128
 Joined: Sat Jan 27, 2007 7:27 pm UTC
 Location: E pur si muove
Re: 0816: "Applied Math"
I had a burning cheese problem with this one.
One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision  BR
Last edited by JHVH on Fri Oct 23, 4004 BCE 6:17 pm, edited 6 times in total.
Last edited by JHVH on Fri Oct 23, 4004 BCE 6:17 pm, edited 6 times in total.
 NumberFourtyThree
 Posts: 30
 Joined: Sun Feb 21, 2010 7:00 am UTC
 Location: Too many to list here, due to a cloning accident.
Re: 0816: Applied Math
SocialSceneRepairman wrote:Of course, hasn't it been proven that such a proof is impossible?
You forget the subject. If logic itself is inconsistent, then an apparently solid proof that something can't be proven might be also provably false, as you could prove contradictory and false things. By the very nature of the question to prove that such a proof is impossible would be irrelevant as the production of such a proof would show that the proof of its inability to be proved was invalid.
A more troubling objection is that all proofs rely on basic logic, so such a proof of logic's invalidity would thus prove itself to be invalid and unable to be relied on to prove anything, including logic being invalid.
The world is imperfect because it has to be. If everything were perfectly fair and without problems we would all live the exact same pointless life, with no possible meaning to it.
Re: 0816: "Applied Math"
SocialSceneRepairman wrote:Of course, hasn't it been proven that such a proof is impossible?
Of course. But it's also been proven that such a proof is possible.
Re: 0816: Applied Math
Turing Machine wrote:http://plato.stanford.edu/entries/dialetheism/
seriously not terribly highlevel logic here, guy
I was reading that link, and I got down to
(5) (5) is false, or neither true nor false, or the fourth thing.
And that's still supposed to be paradoxical, but I don't see how. Why can't 'the fourth thing' be a true thing? In which case, (5) is the fourth thing, and true. Which is not paradoxical.
Surely it would only be paradoxical if it was
(5) (5) is false, AND neither true nor false, or the fourth thing
or any other arrangement that says it can't be the fourth thing and true. Hahaha, what about
(5) (5) is false, or neither true nor false, or a paradox
Re: 0816: Applied Math
SocialSceneRepairman wrote:Of course, hasn't it been proven that such a proof is impossible?
Assume such a proof exists. Then P and not P. Contradiction. Therefore, no such proof exists.
Re: 0816: "Applied Math"
Assume such a proof exists. Then P and not P. Contradiction. Therefore, no such proof exists.
If you assume such a proof exists, that is, that logic is invalid, then you can't use logic to make the rest of your proof, can you?
Re: 0816: Applied Math
Ezbez wrote:SocialSceneRepairman wrote:Of course, hasn't it been proven that such a proof is impossible?
Assume such a proof exists. Then P and not P. Contradiction. Therefore, no such proof exists.
It happens that "P is provable; therefore, P is true" is not valid mathematical reasoning. In fact, adding this as an axiom to our systems of logic would make them inconsistent.
There is a significant chance that an artificial intelligence created within the next few decades will not value humanity and therefore will treat us as we treat animals. It would be awesome if xkcd mentioned this.

Find me on freenode as uorygl.

Find me on freenode as uorygl.
Return to “Individual XKCD Comic Threads”
Who is online
Users browsing this forum: mscha and 60 guests