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Do physicists really believe in true randomness?

askamathematician.com

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Re: Do physicists really believe in true randomness?

#31

Post by tedsanders »

livingparadox wrote: post #9

Can someone explain this a bit better? As far as I can tell, the argument is basically "these particle effects should be predictable. I can't predict them, therefore they're impossible to predict". That sounds like nonsense to me... And I don't understand the cos equation. The argument seems to assume that the experiment is perfectly controlled, and given that we're still figuring out quantum effects, this seems to b…

No, no. This is what makes Bell's Theorem so amazing. It conclusively proves that local hidden variables is impossible (given some simple assumptions).

I know you asked for a better explanation, but it's rather long so I won't give one. But the general idea is that you can show that no system of hidden variables can simultaneously satisfy all the experimental results we see.

Re: Do physicists really believe in true randomness?

#32

Post by ngoldbaum »

cwzwarich wrote: post #21
ngoldbaum wrote: post #10

Earlier quoted context omitted.

But Bell's inequality says that these hidden variable theories are incompatible with the results of experiments. Real experiments. Like these: http://en.wikipedia.org/wiki/Bell_test_experiments It may be the case that there really is a hidden variable, but it would need to communicate it's value nonlocally, which I'd argue is stranger than the universe just being somewhat random.

The Copenhagen interpretation is arguably the most popular interpretation of quantum mechanics and is nonlocal.

True, but there are no hidden variables in the copenhagen interpretation.

Re: Do physicists really believe in true randomness?

#33

Post by colechristensen »

avalaunch wrote: post #22
pvnick wrote: post #19

I love the idea of true randomness because it seems, to my uninformed mind, to allow us the possibility of free will. Without true randomness, while we may enjoy the illusion of free will, our decisions are ultimately left to deterministic hidden variables. That makes me sad. But given true randomness, we may in fact have some mechanism whereby we are truly autonomous. How that might work is way beyond me and probabl…

I'm not sure random will is equivalent to free will. Is a choice still a choice if it's made randomly? Couldn't you say that the photon in the experiment has free will then? What's the difference?

True randomness eliminates determinism. With determinism free will is ruled out. That doesn't mean everything that shows true randomness has free will.

Re: Do physicists really believe in true randomness?

#34

Post by pdonis »

platz wrote: post #11

I thought some scientists hadn't really closed the book on bell's inequality, and though most agree with it there were some gotchas that leave room for doubt as to correctness https://news.ycombinator.com/item?id=5507848

I thought some scientists hadn't really closed the book on bell's inequality

That isn't what the post you linked to, or the links it gives, says. Bell's inequality is violated. The book is closed on that. (Technically, there are a few holdouts who won't be convinced unless we do the experiments with 100% accurate detectors, but they've been done with detectors that are better than 90% accurate and the inequality is violated.)

Re: Do physicists really believe in true randomness?

#35

Post by dimatura »

pvnick wrote: post #19

I love the idea of true randomness because it seems, to my uninformed mind, to allow us the possibility of free will. Without true randomness, while we may enjoy the illusion of free will, our decisions are ultimately left to deterministic hidden variables. That makes me sad. But given true randomness, we may in fact have some mechanism whereby we are truly autonomous. How that might work is way beyond me and probabl…

Suppose you program a simple robot (say, like a Neato) to try to move around while vacuuming and avoiding obstacles. It follows a purely deterministic program. Now suppose you have another robot controlled purely with a quantum-level source of randomness (say, it turns to the left each time a particle decays). Would the second robot really be more free? I think not. Intuitively, what we call "free will" seems proportional to the ability of an entity to interact with its environment in a complex way.

Re: Do physicists really believe in true randomness?

#36

Post by bkoa »

pvnick wrote: post #19

I love the idea of true randomness because it seems, to my uninformed mind, to allow us the possibility of free will. Without true randomness, while we may enjoy the illusion of free will, our decisions are ultimately left to deterministic hidden variables. That makes me sad. But given true randomness, we may in fact have some mechanism whereby we are truly autonomous. How that might work is way beyond me and probabl…

Just because CS people have a tendency to vastly overestimate their qualifications in other fields doesn't mean uniformed speculation about an incredibly well-discussed topic in philosophy is appropriate for HackerNews.

Re: Do physicists really believe in true randomness?

#37

Post by encoderer »

Russell91 wrote: post #20

This article completely misses the point. You can never disprove hidden variable theories in a stochastic system, because hidden variable theories make the exact same predictions as 'true random' theories - the difference is only philosophical. What you can disprove are local hidden variable theories, which were somewhat popular (and favored by Einstein, for example) prior to Bell's thought experiment being empirical…

"So in fact you do need instantaneous nonlocal interaction to explain the real world." Do you just mean quantum entanglement, or some other "spooky action"? (love that quote btw -- like many)

Re: Do physicists really believe in true randomness?

#39

Post by Xcelerate »

colechristensen wrote: post #33
avalaunch wrote: post #22

Earlier quoted context omitted.

I'm not sure random will is equivalent to free will. Is a choice still a choice if it's made randomly? Couldn't you say that the photon in the experiment has free will then? What's the difference?

True randomness eliminates determinism. With determinism free will is ruled out. That doesn't mean everything that shows true randomness has free will.

> With determinism free will is ruled out.

This is a popular statement but I've never thought that to be the case. Imagine you're creating a movie. You can pick the actors, the characters, the plot, etc. When you play the movie, the playback is completely deterministic. But that doesn't mean free will didn't design the film.

I could see something similar applying to reality. Your actions may be predetermined, but that doesn't specify exactly how they were determined.

Re: Do physicists really believe in true randomness?

#40

Post by jandrewrogers »

The difficulty with mathematical randomness (versus unpredictability) in physics is that you would not expect the Laws of Thermodynamics to exist in a universe governed by the former. Some literature on algorithmic information theory touches on this.

Consequently, if local determinism is not plausible (Bell) and randomness is not plausible (Kolmogorov et al), that leaves non-local determinism as the most sensible assumption. It does lend some credence to the idea that we perceive a low dimensionality projection of a higher dimensionality space.

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