What I think you’re saying, correct me if I’m wrong, is that there’s a few big unknowns as to how QM applies to gravity or on cosmological scales, and because of this the answer to my chain of reasoning is “we just don’t know”?
We do know—QM predicts the wrong vacuum energy density by several orders of magnitude. We’ve measured this value empirically. Read the Baez link; he explains everything pretty clearly.
my sentence can be reworded with my intended meaning if you swap it to “emerges from”, which is specifically allowed by that post.
The critical unanswered question is how “underlying quantum effects” generate the (observed) geometry of space-time. If there were a solution to that question, I’d take no issue with you saying it emerges from those quantum effects—but we don’t know if it’s actually the other way around, that is, if it’s actually relativistic effects on the microscale that generate quantum phenomena. Or if this is just the wrong question entirely, and that both are caused by a third thing.
That’s how you fell into the emergence/magic trap.
EY has to spend a lot of time in the QM sequence insisting that QM is natural and fundamental to get over people’s preconceptions of it as unnatural. However, that leads to people taking it as the unique baseline physical theory, which it is not.
Okay, I think I see where you’re coming from better now. I have read that link, and at least feel like I conceptually understand some of the problems with applying quantum physics to the large scale. However, I’m still very curious as to exactly how the incompatibility in theories applies to this specific argument, and curious as to whether looking at a purely quantum universe (making the assumption that there is some way to derive relativistic experimental results from QM that we’ve missed, rather than that QM needs major changes) would give the results I’m describing, or whether I’m misunderstanding something about amplitude or thermodynamics in a heat death.
Hm, how to explain clearly.. It seems like what’s being said is QM is at odds with observation (vacuum energy density) and at odds with our other best theory, relativity, (event horizon, thanks for chiming in shminux), so QM is wrong or incomplete in some way. I accept this as a likely conclusion, though I do not understand either theory deeply enough to be able to follow the arguments for inconsistency in full.
However, dismissing a thought experiment about a widely used theory with some possible implications (if I’ve not missed anything and have understood various things better than I’d guess I have, that chain of reasoning could show a certain interpretation (MW) is incompatible with finite space+infinite time, while a different interpretation (collapse) would not be), due to the underlying theory (QM) being wrong/incomplete for other reasons seems.. limiting. Even if the line of reasoning only holds meaning with the assumption that the universe is fundamentally quantum, local, and macro effects are all explainable in principle by the laws which govern the smallest parts, I’m interested in whether or not it holds.
I’m primarily trying to refine my mental model of how decoherence works with these thoughts, and an answer focused on whether in a quantum universe would, from our current understanding of quantum physics, do as I suppose (that is, in finite space+infinite time, it could never even slightly decohere due to probability 1 arriving at an identical configuration eventually), or have I made some error in my reasoning which can be explained and would allow me to improve my model of decoherence?
We do know—QM predicts the wrong vacuum energy density by several orders of magnitude. We’ve measured this value empirically. Read the Baez link; he explains everything pretty clearly.
The critical unanswered question is how “underlying quantum effects” generate the (observed) geometry of space-time. If there were a solution to that question, I’d take no issue with you saying it emerges from those quantum effects—but we don’t know if it’s actually the other way around, that is, if it’s actually relativistic effects on the microscale that generate quantum phenomena. Or if this is just the wrong question entirely, and that both are caused by a third thing.
That’s how you fell into the emergence/magic trap.
EY has to spend a lot of time in the QM sequence insisting that QM is natural and fundamental to get over people’s preconceptions of it as unnatural. However, that leads to people taking it as the unique baseline physical theory, which it is not.
Okay, I think I see where you’re coming from better now. I have read that link, and at least feel like I conceptually understand some of the problems with applying quantum physics to the large scale. However, I’m still very curious as to exactly how the incompatibility in theories applies to this specific argument, and curious as to whether looking at a purely quantum universe (making the assumption that there is some way to derive relativistic experimental results from QM that we’ve missed, rather than that QM needs major changes) would give the results I’m describing, or whether I’m misunderstanding something about amplitude or thermodynamics in a heat death.
Hm, how to explain clearly.. It seems like what’s being said is QM is at odds with observation (vacuum energy density) and at odds with our other best theory, relativity, (event horizon, thanks for chiming in shminux), so QM is wrong or incomplete in some way. I accept this as a likely conclusion, though I do not understand either theory deeply enough to be able to follow the arguments for inconsistency in full.
However, dismissing a thought experiment about a widely used theory with some possible implications (if I’ve not missed anything and have understood various things better than I’d guess I have, that chain of reasoning could show a certain interpretation (MW) is incompatible with finite space+infinite time, while a different interpretation (collapse) would not be), due to the underlying theory (QM) being wrong/incomplete for other reasons seems.. limiting. Even if the line of reasoning only holds meaning with the assumption that the universe is fundamentally quantum, local, and macro effects are all explainable in principle by the laws which govern the smallest parts, I’m interested in whether or not it holds.
I’m primarily trying to refine my mental model of how decoherence works with these thoughts, and an answer focused on whether in a quantum universe would, from our current understanding of quantum physics, do as I suppose (that is, in finite space+infinite time, it could never even slightly decohere due to probability 1 arriving at an identical configuration eventually), or have I made some error in my reasoning which can be explained and would allow me to improve my model of decoherence?