On 7 November 2014 21:07, Bruce Kellett <[email protected]> wrote:
> LizR wrote: > >> SO the AoT comes from the statistics of increasing entropy and is >> quite disjoint from the expansion of the universe. >> >> Bruce, I haven't got time to reply at length but one thing stands out. >> You have said a few times that the AOT derives from the 2nd law / >> increasing entropy. That is however just the definition of the >> (thermodynamic) AOT. They're equivalent - you need something else from >> which to /derive/ the 2nd law. That is, you have to answer the question - >> why was the universe in a low entropy state in the past? >> > > No, I don't have an explanation for the low entropy of the early universe. Well that's the great thing about my explanation, by raising the entropy ceiling with time you don't have to worry about there being a low entropy initial state. In fact the evidence is that there wasn't one, that the BB fireball was more or less isotropic / homogeneous, which implies it was more or less at thermodynamic equilibrium. The definition of entropy as most likely state causes some problems here, because gravitationally a smooth state is *a priori* unlikely (without some antecedent cause) while for mass-energy it's very likely, given a smooth space-time background. > One could play with anthropic explanations (if the entropy had been > maximal then there could not have bee an entropy gradient and we couldn't > exist.) This argument has some legs, but I must admit to generally not > being convinced by anthropic arguments. Such arguments can explain > anything, so they really explain nothing. > They should be treated with caution, certainly. > > There are arguments for generation of low entropy starting states from a > pre-existing deSitter universe (Sean Carroll favours such arguments, I > think). But my problem with this is that the real problem arises during > reheating after inflation -- the original birth of the universe from > nothing, or tunnelling from some pre-existing universe, or whatever becomes > irrelevant by the time you get to reheating. > I think you have reached the limits of my bear's little brain. Could you explain some more what the problem is? I am probably missing something important which will make the "expansion causing bound states" idea fall apart, I realise that. It is fairly simplistic and assumes all sorts of things. > > Re-heating is a great mystery in normal inflationary theory, and I do not > actually feel called on to explain absolutely everything. It is more > straightforward to find the flaws in other arguments. Of course. I was just curious. -- 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.
