(June 29, 2017 at 2:33 pm)Alex K Wrote:(June 28, 2017 at 5:56 pm)ManofYesterday Wrote: What are your arguments and evidence for thinking it's quite plausible.
If you turn back time you get to a very dense and very hot state, and before that, either something like inflation or something alternative. When you turn the clock further you can run into singularities, but these do likely not exist in quantum theory and are just a sign that the classical theory becomes invalid. Quantum theory is expected to smooth these things out by virtue of the uncertainty principle etc, and if one then turns time back some more, what can happen other than going away from this extreme dense state again, i.e. entropy rises. The laws of nature are almost exactly the same backwards and forwards, so I'd expect that something similar can happen going back than when going forward.
"If you turn back time you get to a very dense and very hot state"
Turn back to what? Do you mean extrapolating backward to the point of the big bang?
"and before that"
Scientists don't know what happened before that. Scientific laws break down at this point. Some scientists say it doesn't even make sense to ask what happened prior to the big bang.
"When you turn the clock further you can run into singularities"
Further? The big bang itself is a singularity.
Moreover, the quantum vacuum itself would need a beginning, according to contemporary science.
In any case, the entropy problem isn't a problem unless you believe the universe is past-eternal and most cosmologists don't think the universe is past-eternal.
