marcus said:
BTW I don't think of locations in space as having physical existence .
Neither do I think of them as little discrete specks of existence. Instead, I would take the condensed matter, soliton, perspective of Laughlin, Volvik, etc, which also would be the systems science approach taken more generally in other fields of science.
In a handwaving description of this downward causality approach, the universe would be a "weight" of constraint bearing down on every location, shaping up its existence. So there is nothing "there" at a locale before the act of "observation" - we could say decoherence even. But something is created "there" as the limit, the event horizon, of this downward constraint.
So the macro-system creates its micro-state locations. Causality then acts both ways because the accumulation of these locations then constructs the macrosystem. Enough top-down stablised locations can add up to a "constant temperature" ambience, the stable macrostate which is bearing down to create those locations.
This is the kind of strange loop causality Douglas Hofstadter (Escher, Godel, Bach) was getting at. And which has been applied in mind science by neural networkers such as Stephen Grossberg (Adaptive Resonance Theory nets). And it is being suggested by condensed matter and phase transition guys now.
So the Planck scale in this view would be seen as the limit of resolution for an observing universe - a weight of decohering constraint that cannot resolve its locales into anything smaller, thus creating a countable grain of microstates.
marcus said:
Say the prior classical continuum (vaguely like ours, but contracting) has evolved a huge number of black holes of all sizes, stellarsize, supermassive etc etc. These BHs represent a huge amount of entropy. An observer before the bounce is witness to all that entropy.
Does anyone suggest that these black holes blow all their entropy out the other side - so as white holes, they are spawning other universes? All that created entropy could be exported to balance the books?
I don't like the black holes/spawning universe approach much, but that might be the "out" here.
marcus said:
Mr Before infers there is a vast complex termite-ridden structure of BHs falling into BHs. Like a fractal, every BH has other BHs falling into it and each of them has still others falling in. When bounce density is reached (estimated around 40 % of Planck) gravity repels and all that structure is invalid.
Another alternative out. But if black holes have a reasonable physical size, then they would all be on top of each other at quite a large scale?
marcus said:
There were amenities available to facilitate earlier proofs (like a single observer throughout, with a single coarse-graining---like conventional geometry and conservation laws) which one may not be able to invoke.
I think there is a problem here in the idea of the second law being defined from the point of view of a single observer. I know it is a traditional way to talk (Maxwell's demon, etc) but in the systems science approach, the observer would be the global scale of the system. It is not an external observer who becomes ignorant of the microstates to create a macrostate (like a single temperature or pressure reading) but the system itself which forms a macrostate (an ambience, a stable equillibrium).
So as a thought experiment, mr before and mr after would be misleading. My view is that the system is the "mr" and I would be alarmed that mr universe dissolves to a QM foam, disappears as a system, then somehow pops out again in reversed form the other side.
I have my eye on the macrostate and want to track it back. You perhaps have your eye on the microstates which do not appear to suffer as much trauma - because there seems to be room for them inside the foaminess.
I would say the safety of those microstates is an illusion because they are in fact being created - soliton-like, via downward constraint - by the macrostate. So in my view, the microstates also get dissolved.
The only way to cope with this is the idea of vagueness. Instead of anything actually disappearing (either the macro or micro), the two just get squished to a single common scale and thus become a symmetry, indistinguishable. They are both "in there", but you cannot tell them apart.
So yes, in this view, perhaps they could then grow away (symmetry break) to the other side. But then there are wider reasons, from the systems science and vagueness ontology perspective I am raising, why that would not be the case.
For one thing, expansion seems "wired in" to my preferred story. That would take a bit of explaining. But anyway, this approach I suggest would give us a somewhat different framing of the second law.
Traditionally, the second law is talked about as an asymmetric arrow pointing from order to disorder (and even among classical thermodynamicists, it is realized that the idea of order/disorder is very unsatisfactory - loose speak).
In my story, the arrow of time, the arrow of system development, points from vagueness to crispness. So dissipation is always the dissipation of a potential into crisper (more crisply developed) states of organisation.
A large cold expanding void, is just such a crisp outcome. Entropic in that everything has been broken down to the same lowest level microstate within the one perfectly expressed macrostate (I love the Davies/Lineweaver tale of blackbox photons - the final fractal residue of a radiation created purely out of ever-expanding event horizons).
It is disorderly in terms of classical work/heat calculations. But supremely crisply organised from a systems perspective. A broader notion of entropy.
This idea of a vague-crisp approach to entropy modelling is not standard of course. But I have been working on it with a few other second law, dissipative structure, thinkers. It may come to something one day.