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Computer proof ‘blows up’ centuries-old fluid equations

quantamagazine.org

21–30 of 223 posts

Re: Computer proof ‘blows up’ centuries-old fluid equations

#21
"That’s because it’s impossible for a computer to calculate infinite values. It can get very close to seeing a singularity, but it can’t actually reach it"

Why not?

Is it impossible to calculate infinite values in general? I suspect not, My understanding is that a lot of calculus is in fact on how to calculate infinite values.

And a computer is a universal machine, this means that while it can not calculate everything, it can calculate anything that is calculable.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#22
post #3

Earlier quoted context omitted.

Huh? Mathemathical proof is not a social construct. This makes no sense.

The proof is not a social construct. The truth is. The proof is a mechanism to reach that consensus, by convincing other mathematicians of a specific truth. That is all it is. There is a naive idea that a proof is a purely mechanical series of steps that provides access to truth. Last I checked, this isn't so for the vast majority of proofs in math. Such a proof would be way too tedious to construct or check by mathe…

> The proof is not a social construct.

> The truth is.

Yeah, that is how it feels like nowadays, however the truth is bound in a narrow set of assumptions. These assumptions are bound in reality even in mathematics (One apple is one apple, you add another one, you have two). And while there is an epistemologic level to reality, you would dismiss reality entirely by calling it a social construct.

The details of how a truth is communicated is in a sense a social contruct, because communication as a whole is, however nobody would call it like that. It is maybe a small reminder that meddling with language for no apparent reason is a warning sign, but this is going a bit off-topic.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#23

> Hou and Luo’s work was suggestive, but not a true proof. That’s because it’s impossible for a computer to calculate infinite values. It can get very close to seeing a singularity, but it can’t actually reach it — meaning that the solution might be very accurate, but it’s still an approximation. I feel certain that if you run a process that approaches infinity using ordinary floating-point numbers, you will actually…

It does not have to use floating point numbers, while floating point numbers are hardware accelerated and thus very fast, there are infinite precision number libraries.

But more likely, the program would have to be built where it understands the symbolic forms involved, more like a proof solver than simple cfd math.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#24
post #21

"That’s because it’s impossible for a computer to calculate infinite values. It can get very close to seeing a singularity, but it can’t actually reach it" Why not? Is it impossible to calculate infinite values in general? I suspect not, My understanding is that a lot of calculus is in fact on how to calculate infinite values. And a computer is a universal machine, this means that while it can not calculate everythin…

Almost all functions aren't computable, as they aren't discrete.

A "computer" is just a function from {0,1}^N -> {0,1}^M

Re: Computer proof ‘blows up’ centuries-old fluid equations

#25

Earlier quoted context omitted.

> and that nothing was true until a social consensus had been reached between mathematicians. So how do calculators and computers work then?

1+1=2 is a social construct. It’s simple, repeatable and therefore programable - but still a social construct.

Well if "1+1=2" is a social construct then "there are planets, stars, and, in general, objects" is also a social construct. No kind of society can make 1+1=3, and also there is mathematical proof that 1+1=2 (built of course on some sort of axioms that somebody might also consider social constructs).

Re: Computer proof ‘blows up’ centuries-old fluid equations

#26
post #6

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

There are such reachable truths, but every mathematical system has a non empty set of axioms - or assumptions- which are 'given'.

These axioms are not given in course of socialization and generally are observations of nature rather than human.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#27

> Hou and Luo’s work was suggestive, but not a true proof. That’s because it’s impossible for a computer to calculate infinite values. It can get very close to seeing a singularity, but it can’t actually reach it — meaning that the solution might be very accurate, but it’s still an approximation. I feel certain that if you run a process that approaches infinity using ordinary floating-point numbers, you will actually…

So are they trying to find particles in the fluid with a flow of 0?

Re: Computer proof ‘blows up’ centuries-old fluid equations

#28
post #21

"That’s because it’s impossible for a computer to calculate infinite values. It can get very close to seeing a singularity, but it can’t actually reach it" Why not? Is it impossible to calculate infinite values in general? I suspect not, My understanding is that a lot of calculus is in fact on how to calculate infinite values. And a computer is a universal machine, this means that while it can not calculate everythin…

Almost all functions aren't computable, as they aren't discrete. A "computer" is just a function from {0,1}^N -> {0,1}^M

Symbolic engines are way above and beyond number crunching in many respects.

Re: Computer proof ‘blows up’ centuries-old fluid equations

#29

Earlier quoted context omitted.

Double precision floats have a maximum value of 1.7976931348623158 E + 308

That is not correct; they have a maximum value of positive infinity. See what you get when you square 1.7e+307.

A computer is always just a function from {0,1}^N -> {0,1}^M

The "Inf" interpretation, of, eg., 11111111111111111 isnt infinity.

And, in general, almost every function isnt representable on the discrete domain above.

floats are a hacky interpretation of discrete bit patterns

Re: Computer proof ‘blows up’ centuries-old fluid equations

#30

I remember my math professor at university telling me that truth in mathematics was a social construct, and that nothing was true until a social consensus had been reached between mathematicians. This struck me at the time as a very powerful statement, yet unexpected, since very much not what most people expect from mathematics. After all, it's supposed to be a field where there is such a thing as a (most of the time…

"Yes profesor, truth in any academic field is result of agreement between the people working on that field. Just wondering... its everything Ok at home?"
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