Comment by johncolanduoni | Hacker News Reader

Comment by johncolanduoni | Hacker News Reader

Parent Full thread

I've done enough mathematical proofs that I don't think I need to "google it", but I read the Wikipedia page anyway. It failed to explain how a mathematical proof could have anything to do with "proving" General Relativity in absence of empirical evidence. He certainly proved that (as I said before) it agreed with existing (experimentally backed) theories using mathematics, but if you have a method which allows you to deduce the truth of physical laws from purely mathematical proofs (no links to experiments at all!) you'll revolutionize epistemology. As it stands most scientists are using the crutch of experimental evidence at some level (either directly or by reasoning within theories that are at least for now validated by experiment).

> Whether or not it was empirically validated is irrelevant. It was true mathematically

If you mean it was a self-consistent theory, note that there are infinite physically incorrect theories which are "true mathematically". It is true mathematically in the same way number theory is "true mathematically", but you don't see anyone assume that we can describe gravity with prime number theory. If you mean it was mathematically proved consistent with previous physical theories backed by evidence, we're back to the experimental link, and also there are infinite physically incorrect theories which would agree with Newtonian mechanics and special relativity. If you mean he proved it satisfied some properties we expect from physical theories because they've been consistently upheld (e.g. energy conservation), there's an infinite number of wrong ones there too.

Mathematical convenience has been an excellent guide in physics, particularly fundamental physics (electromagnetic waves, antiparticles, and the Higgs Boson were all the results of positing things for mathematical convenience), but it is not a substitute for verifying novel experimental predictions. Nobody taken seriously in the physics (or mathematics for that matter!) community thinks it is, not even the often decried string theorists.

Interesting points. I still disagree, or perhaps I'm not doing a good job explaining.

My point is this: Something is true whether one accepts it or not. E.g. the earth was proven to be round before anyone actually went around it.

Another example is climate change deniers. To them there's no proof of; 1) Climate change; 2) That it's man made.

Another example is people who believe the earth is 10,000 years old (I'm not joking millions of ppl believe this). They will deny any evidence you put in front of them.

That's the beauty of maths. If you can prove it mathematically, it's true. Whether or not you believe it is irrelevant.

Epistemical simplicity is one of the things I love about math, but it's hard to extend it wholesale to physics. GR will almost certainly be proved wrong some day, at least in some regime (Einstein was ironically one of the first to feel it needed something more, as an alternative to the inelegant cosmological constant). If GR had been mathematically proven, this would be terrible, as it would prove our mathematics are inconsistent!

As for the existence objective reality, that's another thing that seems hard to prove conclusively. I'd suggest looking at some of the basic epistemology surrounding modern science (e.g. Popper[1]) for some thoughts on this.

As an interesting aside, while it's true that mathematical proofs (idealizing here and assuming incorrect proofs are never accepted by the mathematical community, because they on occasion are) are absolute statements of truth, they may not be stating precisely the truth you expect. Thanks to Godel[2], we know that it is not possible for any consistent mathematical theory rich enough to talk about addition and multiplication of natural numbers to prove it's own consistency. As a result, we may have a proof that 2+2 != 5, but that actually doesn't exclude the possibility that there is a proof of 2+2 = 5. In fact, his result shows we will never be able to prove such a thing does not exist (since it would imply the consistency of our mathematical system). So our absolute truths from proofs of X are actually of the form ZFC implies X, where ZFC is the background theory which is generally taken to underly modern mathematical works unless otherwise specified. So things are not so clear cut even here.

[1]: http://plato.stanford.edu/entries/popper/ [2]: https://en.m.wikipedia.org/wiki/G%C3%B6del%27s_incompletenes...

You've totally lost sight of the issue at hand. Now you're talking about things utterly unrelated to this discussion.

It seems you're more interested in dicing up and attacking what I said, instead of what I mean.

I'll re-articulate it for you once more: We don't have a way to mathematically prove a drug for depression or to explain psychological phenomena. The studies in the article are talking about those which rely on empirical observation.

Go home.

What? You've been talking about (a) whether GR needs empirical observation, (b) whether things are true whether people admit them or not (i.e. Objective reality) and (c) mathematical proofs being evidence of absolute truths. Those were my three paragraphs.

How many problems have you worked through in GR? Have you gone through the proofs that GR recreates Newtonian gravity in the low-energy limit? If not, don't go around talking about how Einstein proved GR was a true description of reality with naught but mathematical proof when he didn't think he did that.

Physics has the same requirements for empiric evidence as the life sciences, it's just that we work within regimes where we can apply fundamental, empirically validated mathematical theories directly. If you don't believe me, go ask another physicist.

Reply on news.ycombinator.com