On 7 November 2014 14:59, Bruce Kellett <[email protected]> wrote:
> I agree that the past hypothesis, while it explains the thermodynamic AoT, > itself stands in need of explanation. This is the great unsolved problem of > cosmology -- at least according to many cosmologists. The initial big bang > might be assumed to be in thermodynaic equilibrium, but that is essentially > the same assumption as the assumption of low entropy. It's the opposite assumption. A quark-gluon plasma at a few trillion degrees should rapidly tend towards thermodynamic equilibrium, given the chance. Deriving the AOT from the expansion should let the AOT emerge from almost any initial conditions, because it basically says that the universe has no need to start in a low entropy state. It can start in a state near maximum entropy, then chase behind the entropy ceiling, which is continually raised by the expansion. Another way to look at this is that expansion makes more states available for the system to explore. The universe starts with a limited number of available states and wanders amongst them, probably reaching a state of high entropy in the process. In the meantime, the expansion brings more available states into existence - phase space expands, so to speak, as well as real space. The universe continues to explore its options, doing a drunkard's walk through the available states for billions of years, always tending towards higher entropy, while the number of states available to explore continues to increase. > The question remains as to why it was in equilibrium. Generic creation > events might actuallybe expected to produce extremely lumpy universe down > to the smallest scaels. I.e., state with very high entropy. > > I don't think anyone is in a position to answer that question, but certainly inflation (eternal or otherwise) naturally produces a very smooth background. But somewhat lumpy backgrounds should work. This is a question of the timescales involved, I imagine - the relaxation time of a volume of matter against the expansion time. I'm not in a position to answer that. Maybe someone else can (Brent?) However the bottom line is that deriving the AOT from the cosmic expansion doesn't require any particular special starting state. It appears that the universe did in fact have a special (smooth) starting state, however, which is why it's a natural assumption that this must be connected to the AOT. But there's no particular reason for this to be a necessary condition that I can see - one can get an expansion derived AOT from many initial conditions, simply because expansion raises the entropy ceiling constantly. So the smooth start is an interesting piece of data that may relate to inflation or whatever, but not necessarily to the AOT. No doubt it affects the way the AOT plays out - similarly all over the universe, presumably, rather than some regions being ahead or behind others. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
