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On number theory and so-called "useless" knowledge

Prokhor Zakharov

Graduate Poster
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May 11, 2016
Messages
1,110
Edited by Agatha: 
Removed material 'calling out' another poster


Accordingly, here I would like to discuss the value of the branch of mathematics called number theory, which concerns the properties of and relations between integers, and in particular the final achievement of a fully general proof of Fermat's last theorem, the deceptively simple claim that there are no three positive integers that satisfy the equation an + bn = cn for any integer value of n above two.

A good deal of what we now call number theory goes back to antiquity; the proof that the square root of two is irrational is something a lot of students still go through today and a likely apocryphal legend has it that a member of the Pythagorean sect was drowned out of hatred by other members for having achieving this. It really began to come into its own in the 19th century though, and started to be recognized as a distinct branch of mathematics. In fact, the prolific 19th century mathematician Carl Friedrich Gauss once said: "Mathematics is the queen of the sciences and number theory is the queen of mathematics."

However, conspicuously absent during all of this time was much in the way of any applications of number theory. The number theorist Leonard Dickson, whose time came after that of Gauss, but died only a decade after the advent of the digital computer, said: "Thank God that number theory is unsullied by any application." But due to the increasing entrenchment of the digital computer in life in industrial countries, applications of number theory have blown up rapidly in more recent decades for all sorts of calculations. The use of number theory is especially marked in cryptography, and without modern cryptographic methods there wouldn't be many things considered to be of practical value, among them, the entirety of e-commerce. In this way, even accepting the very, very dubious claim that knowledge is of no value for its own sake, all these centuries of work seemed to have paid off after all.

One might still consider all this effort a waste and contend that individuals with more "practical" orientations would have come up with these things anyway. There is a very serious issue with that contention though: it's ahistorical. If there is any example of an elite go-getter with both their feet firmly on the ground, focused only on knowledge of "real" value, who ever came up with such advances as the past centuries have seen in number theory, I'd definitely like to see it. I certainly can't think of any myself, and you would think that people with such a superior, focused worldview would be better thinkers overall.

Now I'd like to turn my attention to Fermat's last theorem. This was stated in a margin of a copy of an ancient mathematical text by the mathematician Pierre de Fermat. He claimed to have a "marvelous proof" of the same that wouldn't fit in the margin (and is widely considered to have been mistaken), but never wrote it down. Fermat's last theorem was finally proven in a truly general form by Andrew Wiles in 1994, after over 350 years of effort by many others as well. This event is considered a great milestone in mathematical history, but I am not aware of any practical applications of Fermat's last theorem as such, except to other claims in pure mathematics. I am under the impression that, along the way, there were developments in what are called elliptic curves that have applications to cryptography presently, that were vital for the proof. But that doesn't mean that Fermat's last theorem per se has any practical applications. What is the value of such a thing to someone with a "pragmatic" outlook, in scare quotes? Was this 350+ years full of wasted time? If it were some sort of multigenerational business venture to yield practical, profitable outcomes, I can tell you everyone involved would have taken a bath on it, thus far at least. Maybe Fermat's last theorem will have practical applications one day, maybe not. The question of course is whether the value of the theorem is solely contingent on whether these applications ever arise.

To draw things to a close, I want to say that even if such things as Fermat's last theorem are "useless" per se, which I of course do not believe, it seems as though it is often the case that the only way to find the practical applications you might want is by not looking for them at all and that people who fancy themselves "pragmatic" when they deride "useless" knowledge are actually just a different word: myopic.
 
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Geeking out a bit, but basically when I hear stuff like what I'm picking apart in the OP, I can't help but think of SMAC faction leader CEO Nwabudike Morgan and how much he, on balance, irritates me in that game (although this is not an entirely great analogy because some of the things he says are very insightful and what theprestige says, to me anyhow, is really pretty much crapola), more specifically this:

"You ivory tower intellectuals must not lose touch with the world of industrial growth and hard currency. It is all very well and good to pursue these high-minded scientific theories, but research grants are expensive and you must justify your existence by providing not only knowledge, but concrete and profitable applications as well."

I have a rather different gameplay style and different choice of factions and of course this tends to result in Morgan Industries becoming a subordinate or nonexistent faction.
 
The square root of 2??

What is irrational about that? Aren't you talking about the square root of -1?
The square root of two us not the ratio of two integers ave hence is irrational.

Not a good example of useless math, however.
 
Also, for square root of -1, I think you meant to say, "imaginary".
 
Also, for square root of -1, I think you meant to say, "imaginary".

The square root of -1 is also known as "i" and although imaginary is used quite a bit in mathematics as I recall from my studies of the subject many years ago in Australia. Yes English is my native tongue GodMark.
 
The square root of 2 is 1.4142....... so why is that irrational? Just because the number is not a whole number?



The term 'irrational' is used to describe a number which can't be expressed as the ratio of two integers.
 
What is the usefulness of Shakespeare? Or Picasso? Some aspects of mathematics can be treasured for their beauty.
 
The square root of 2 is 1.4142....... so why is that irrational? Just because the number is not a whole number?

As Jack by the Hedge said, a number is irrational if it cannot be expressed as the ratio of two integers.

The number 0.333... is rational, since it is equal to 1/3. The square root of two cannot be expressed as a rational number. In fact, any number whose digital expansion is infinite and does not "stabilize" in a sequence of repeating digits is irrational.

For a quick proof that sqrt(2) is irrational, let us take as given the following facts.

(1) Any ratio a/b of integers is equal to a ratio c/d where c and d have no common factors.
(2) If a^2 is even, then so is a.

Now, suppose that sqrt(2) is rational, i.e., that there are integers a and b such that
2 = (a/b)^2
Without loss of generality, using (1), assume that a and b have no common factors.

It follows that 2 b^2 = a^2 and hence that a^2 is even. Thus, a is even, i.e., a = 2*c for some c. Hence 2 b^2 = (2*c)^2 and hence b^2 = 2 c^2. Therefore, b^2 is even and thus b is even.

Here we have a contradiction, since a and b had no common factors and yet both are even (i.e., 2 is a common factor). Thus our assumption that we could write sqrt(2) as a ratio of two integers is false.

It is a brilliant little proof, perhaps my favorite.
 
Edited by Agatha: 
Removed material 'calling out' another poster
Long OP, did read
I'm just not sure who you're addressing with this rant? That's not to say I disagree with you. I just don't think it will sway any of the tiny minority of morons who would argue otherwise.
 
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I'm just not sure who you're addressing with this rant? That's not to say I disagree with you. I just don't think it will sway any of the tiny minority of morons who would argue otherwise.

It seems that discussing this aspect is verboten, but I will say that when PZ did say who he was calling out specifically it turned out that he was straw-manning that poster anyway. So there's that.
 
It seems that discussing this aspect is verboten, but I will say that when PZ did say who he was calling out specifically it turned out that he was straw-manning that poster anyway. So there's that.

He is welcome to come here and contest that putative "strawmanning", certainly. That being said, I don't see any reason to think that he really doesn't have a problem with rationality for its own sake; he said he does, explicitly.
 
I also want to point out here that lazily making accusations of some fallacy or another but never detailing how the offending reasoning is an example of such fallacy is the hallmark of a pseudointellectual.
 
It's worth pointing out that He Who Shall Not Be Named (but still is in one of my posts in this thread) is generally eager to try to point out the perceived absurdity and stupidity of everything I say, but not here.

One wonders why this might be the case.
 
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I'm just not sure who you're addressing with this rant? That's not to say I disagree with you. I just don't think it will sway any of the tiny minority of morons who would argue otherwise.

I agree that those who would argue otherwise are morons, but, sadly, not that they are any sort of tiny minority.
 

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