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The Universe is Deterministic

Cynic

Graduate Poster
Cynic
Joined
Aug 26, 2009
Messages
1,329
westprog said:
I think it's the idea that probability represents only our lack of knowledge about a deterministic system. But, as you've pointed out, reality is not deterministic. The location of the electron is genuinely random.
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I've created this thread because I disagree with these last two statements completely (and didn't want to derail the thread they were posted in).

While it may be impossible to prove, given our current understanding of physics, whether or not the universe is deterministic or not, there are no compelling reasons to therefor conclude that it isn't. All things in our experience have causes -- all of them. So why then is the prevaling opinion that the universe nondeterministic?
 
Cynic said:
I've created this thread because I disagree with these last two statements completely (and didn't want to derail the thread they were posted in).

While it may be impossible to prove, given our current understanding of physics, whether or not the universe is deterministic or not, there are no compelling reasons to therefor conclude that it isn't. All things in our experience have causes -- all of them. So why then is the prevaling opinion that the universe nondeterministic?
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Because quantum events are stochastic.
 
Cynic said:
I've created this thread because I disagree with these last two statements completely (and didn't want to derail the thread they were posted in).

While it may be impossible to prove, given our current understanding of physics, whether or not the universe is deterministic or not, there are no compelling reasons to therefor conclude that it isn't. All things in our experience have causes -- all of them.
Click to expand...

I'm not sure that is true, but I'll accept it for now. A more serious problem with this argument is that our experience is pretty much limited to one scale of distance and time. I mean, I very rarely observe events smaller than I can see, or larger than can be fitted in my field of view. The same goes for time. I cannot detect an event shorter than maybe a millisecond (might be off by a few orders of magnitude in either direction), or something much longer than my lifetime.

So what you're saying is basically that events on one scale appear to be deterministic, and assuming that this therefore has to be true on all scales. I don't think that's a reasonable assumption.

So why then is the prevaling opinion that the universe nondeterministic?
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One problem with determinism is that it requires information to travel faster than light—that is: backwards in time. So I guess it's partly a question of what you think is most unlikely: time travel or non-determinism. Most people have picked the latter, for reasons which I guess have as much to do with personal taste as anything else.

There are probably more reasons as well, but this is what I could think of right now.
 
arthwollipot said:
That's a claim I haven't heard before - can you elaborate?
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I can try. Basically, my knowledge about the subject consists of "This experiment proves that local determinism is impossible. We'll go through the details of why in the advanced QM course next year. Have a nice vacation.", but I can try to wiki it up.

This page and this page sort of describe why no local hidden variable theory can work.

Otherwise, we can wait until the more advanced posters turn up. They'll either explain it in much better, or explain why I've totally misunderstood it.
 
Haven't we had experiments where information has been transported faster than light?
 
thaiboxerken said:
Haven't we had experiments where information has been transported faster than light?
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Not with information that you can actually use for anything. That is, you can send "collapse into a spin-up electron" or "collapse into a spin-down electron" to an electron, but you don't get to choose which. So anyone checking the spin will get no information, since as far as they know, it might have been their own checking which collapsed the wave function.
 
Dorfl said:
The double-slit experiment doesn't rule out there being hidden variables determining the distribution of the particles, does it?
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No, but subsequent experiments have ruled out such hidden variables.
 
westprog said:
No, but subsequent experiments have ruled out such hidden variables.
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Yes. I just thought the double-slit was a strange example in a discussion which is basically about the existence of hidden variables.
 
Dorfl said:
Doesn't non-locality require there to be something which travels faster than light?
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But given the restrictions on what that something is in QM it doesn't give you any meaningful time travel that I can see - I think any reasonable definition of time travel should involve transport of an observer or an ability to observe locations at times you 'shouldn't' be able to.
 
edd said:
But given the restrictions on what that something is in QM it doesn't give you any meaningful time travel that I can see - I think any reasonable definition of time travel should involve transport of an observer or an ability to observe locations at times you 'shouldn't' be able to.
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Oh. I used the definition of time travel as "a process by which something travels backwards in time". But whatever: we seem to agree on what actually happens, if not on the correct term to describe it.
 
Cynic said:
I've created this thread because I disagree with these last two statements completely (and didn't want to derail the thread they were posted in).

While it may be impossible to prove, given our current understanding of physics, whether or not the universe is deterministic or not, there are no compelling reasons to therefor conclude that it isn't. All things in our experience have causes -- all of them. So why then is the prevaling opinion that the universe nondeterministic?
Click to expand...

Depends on what you mean by deterministic, there isa difference between causal and philosophicaly determined.

QM seems probablistic, so it could be chaotic, totaly random or semi random.
 
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