1381: Margin

2014-07-03T09:45:28Z

Carlrobert: /* Trivia */

{{comic
| number = 1381
| date = June 13, 2014
| title = Margin
| image = margin.png
| titletext = PROTIP: You can get around the Shannon-Hartley limit by setting your font size to 0.
}}

==Explanation==
This is a reference to {{w|Fermat's Last Theorem}}, of which {{w|Pierre de Fermat}} claimed he had a proof that was too large to fit in the margin of a copy of ''{{w|Arithmetica}}''. Despite its simple formulation, the problem remained unsolved for three centuries; it was cracked only with advanced techniques developed in the 20th century, leading many to believe that Fermat didn't actually possess {{w|Fermat's Last Theorem#Did Fermat possess a general proof?|a (correct) proof}} (see [[#trivia|trivia]]).

In the comic, the person writing in the margin attempts to pull a similar trick, without actually having any proof, by claiming that he has found a proof that information is infinitely compressible, but pretending not to be able to show it due to lack of space in the margin. In this particular case, however, this approach backfires, precisely because if information was actually infinitely compressible, the writer ''would'' be able to fit the proof in the margin (due to his own proof). The writer realizes that if he had a proof he should be able to fit it into the margin, and thus he realizes that he cannot pull this trick. Or perhaps the writer really thought he had a proof, but then realized that his statement was a counterexample, and was disappointed that his idea for a proof was wrong.

What it seems he did not realize, is that it would be impossible to read the proof if the writer actually was able to compress his proof to fit in the margin. This is because you would need to know the algorithm described in the proof before you could decompress the proof text so you can read it. So he could actually have used this trick instead, writing that he had compressed it into - say a dot "'''.'''" - and then people would have to find his proof to read it. And since they cannot find such a proof - they could not check his dot. Unfortunately this would also have backfired - because there is already a {{w|Pigeonhole principle#Uses and applications|proof that this is not possible}}!

The title text, yet another [http://www.explainxkcd.com/wiki/index.php/Category:Protip protip], makes a reference to the {{w|Shannon–Hartley theorem}}, which limits the maximum rate at which information can be transmitted. Setting the font size of text only changes its ''representation'' on the screen, and not the actual characters themselves. Trying to decrease the amount of space needed to store or transmit it like advised would be nonsensical.

==Transcript==
Written on the margin of a page:

:I have
:discovered
:a truly
:marvelous
:proof that
:information
:is infinitely
:compressible,
:but this
:margin is too
:small to...

:...oh

:never mind :(

==Trivia==
*Fermat's Last Theorem states that no three positive integers ''a'', ''b'', and ''c'' can satisfy the equation ''a''''n'' + ''b''''n'' = ''c''''n'' for any integer value of ''n'' greater than two.
**In the case with n=2 it is reduced to the {{w|Pythagorean theorem}} which has an infinite number of integer solutions for a, b and c, such as ''3''''2'' + ''4''''2'' = ''5''''2''.
*Fermat's Last Theorem was {{w|Wiles' proof of Fermat's Last Theorem|solved}} in 1995 by {{w|Andrew Wiles}} with some assistance by {{w|Richard Taylor (mathematician)|Richard Taylor}} who helped him close a gap in his original proof from 1993.
**The proof involved some of the most complicated mathematics used today, and it has been speculated that only a handful of people in the world would be able to understand it.
**For people interested in the subject, {{w|Simon Singh}} has written a [http://simonsingh.net/books/fermats-last-theorem/the-book/ popular science book] about it, called ''{{w|Fermat's Last Theorem (book)|Fermat's Last Theorem}}''.
***[https://www.youtube.com/watch?v=qiNcEguuFSA Fermat's Last Theorem - Numberphile]
***[https://www.youtube.com/watch?v=FXbsIbRVios Fermat's Last Theorem (extra footage) - Numberphile]
*There are US Patents in this very area, analyzed by [http://gailly.net/05533051.html Jean-loup Gailly].

{{comic discussion}}
[[Category:Protip]]
[[Category:Math]]

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1381: Margin