How valid is the Block Universe theory?

[PeterDonis]

there has to be some medium

The only sure test you have is evidence.

 

[PAllen]

This implicitly assumes deteterminism, as I posted before. But it also, as I said, seems inconsistent since "simultaneous in one frame means in the past (or future) in another" comes from relativity, and non-relativistic QM is not consistent with relativity. You would have to do the analysis using QFT, which doesn't have "state reduction" in the form it's used in the argument.


And the refutation I gave in the Insights article linked to earlier in the thread would apply to it, even leaving aside the other issue I raised.

Look, I’m not supporting this argument. You just said no one used block universe with nondeterministic evolution, and i am supplying what I remember about people doing just that. In any case, determinism and block universe are independent, even in different categories. One is a statement about the mathematical structure of a theory, the other is a belief about “unobservable reality”.

Here is whole book about the notion I refer to:

https://www.google.com/books/edition/Beyond_the_Dynamical_Universe/9u9IDwAAQBAJ?hl=en&gbpv=0

 

[PeterDonis]

I’m not supporting this argument.

I understand.

You just said no one used block universe with nondeterministic evolution, and i am supplying what I remember about people doing just that.

I understand that too, but I think we're to the point where I would need some references. Otherwise all I have is what you're posting, and what you're posting doesn't convince me that this idea even makes sense. It's not one I've seen in the literature, so unfortunately I have no references of my own. So we're probably at a stopping point unless some references turn up.

determinism and block universe are independent, even in different categories. One is a statement about the mathematical structure of a theory, the other is a belief about “unobservable reality”.

I don't think determinism, at least in physics, is just a statement about the mathematical structure of a theory. I think it's also a physical claim about how the physical laws actually work.

That said, I agree that determinism in itself does not require adopting a block universe interpretation.

 

[PAllen]

I added a reference to my last post. I could also add more, in the context of the retrocaual interpretation in quantum mechanics, but the reference i added is more in line with my memory of this notion.

 

[PeterDonis]

I added a reference to my last post

Thanks, I'll take a look.

Edit: I see this is the book of which @RUTA is one of the authors, which IIRC has been discussed in other PF threads. I think those other threads probably already capture the key points of the view it's advocating.

 

[Dale]

So in 1905 Einstein didn't come up with a new theory called special relativity? Just a new interpretation of the already-existing Lorentz aether theory?

I wouldn’t say it was even a new interpretation so much as a new derivation. His main contribution was taking Lorentz aether theory, with its ad hoc length contraction and ad hoc local time, and showing that it could be derived based on two sound theoretical principles. In the derivation he also showed that the aether was superfluous, but the derivation is the reason why he is correctly recognized as the inventor of relativity.

 

[bhobba]

It's an interpretation, so not testable as far as we know. It's far and away the most popular interpretation, and fits well with the maths, but others are possible.

I never knew it was that popular, but it certainly is an interpretation, just not to my taste.

My interpretation is that it's just the consequences of the symmetry definition of an inertial frame, the POR (which is very intuitive), and a fixing of a constant that naturally occurs in the theory, which, from many experiments and theoretical considerations, is the speed of light.

I gave it my upvote for pointing out that it is an interpretation.

Thanks
Bill

 

[ohwilleke]

Whether the block universe is truly real is ultimately a metaphysical question.
However, mathematically it is precisely what general relativity delivers:
the Choquet-Bruhat theorem guarantees that well-posed initial data uniquely determine a maximal globally hyperbolic development (a complete four-dimensional spacetime).
In my framework, I adopt this not as a philosophical commitment but as a mathematical constraint, building the theory upon the full block-universe solution of Einstein's field equations.
ORCID: 0009-0002-9098-1203

To this extent, the block universe could arguably be disproven because in quantum gravity, which is not deterministic, neither the future nor the past is determined definitively by a specific slice of perfect data about the present (indeed, even perfect data about the present is theoretically impossible and not just impossible as a practical matter) in quantum mechanics.

Proof that gravity is quantum rather than classical would present a strong challenge to the block universe model, although even the existence of stochastic Standard Model physics for non-gravitational physics already presents a challenge to the block universe which you need something like superdeterminism to overcome.

And, while proving that gravity is quantum in nature rather than classical is a very challenging engineering and instrumentation problem, it isn't, in principle, impossible to distinguish the two possibility with experiments that future, well-funded scientist from Earth could conduct.

The very things that make quantum v. classical gravity hard to distinguish experimentally, also mean that a block universe would still be a good approximation of reality (especially after the very early universe after the Big Bang has settled out a bit), even if it wasn't precisely true.

 

[PAllen]

To this extent, the block universe could arguably be disproven because in quantum gravity, which is not deterministic, neither the future nor the past is determined definitively by a specific slice of perfect data about the present (indeed, even perfect data about the present is theoretically impossible and not just impossible as a practical matter) in quantum mechanics.

Again, you could, in principle, disprove determinism. But, as I have argues above, determinism and block universe are actually completely orthogonal concept. You can construct a valid philosophical position with any combination of them.

 

[DarkloidNeos]

Where? Can you give a specific reference?

Well it was an AI overview so I don't know how accurate it is.

 

[PeterDonis]

Well it was an AI overview so I don't know how accurate it is.

Generally we don't recommend using AI as a source. The last six words of your post quoted above are a good quick summary of why.

 

[DarkloidNeos]

Generally we don't recommend using AI as a source. The last six words of your post quoted above are a good quick summary of why.

That is a valid view that I've come to learn.