LizR wrote:
On 13 November 2014 00:15, Bruce Kellett <[email protected]
<mailto:[email protected]>> wrote:
LizR wrote:
On 11 November 2014 14:48, Bruce Kellett
<[email protected] <mailto:[email protected]>
<mailto:bhkellett@optusnet.__com.au
<mailto:[email protected]>>> wrote:
The AoT exists regardless of such processes.
I don't see how. The expansion made a state with no AOT turn
into one that had one, by cooling the plasma to the
point where
a phase transition could occur.
No, we have gone as far as we can on this -- and you are wrong.
I would appreciate a short, simple explanation of why.
First, the expansion does not increase any entropy limit.
Why not? Informally, from a quantum viewpoint it makes more states
available, in a manner similar to Max Tegmartk's calculation of how far
away one's duplicate is in a level 1 multiverse. The analogy used by
Paul Davies is that if you have a gas at equilibrium inside a container
and expand the container, the gas will stop being at equilibrium in the
new configuration. It has more states available, and hence its entropy
ceiling has been raised. This seems to me a valid argument. Where has
Davies (and Tegmark) gone wrnog?
The problem would seem to be with Davies' analogy. If you expand a
container containing gas at equilibrium, the temperature will drop and
the entropy will rise, but this is because you have extracted heat from
the system. Moving the walls outwards means that molecules that bounce
off the walls will recoil with lower velocity -- transferring energy
from the gas to the outside world. This does not happen in the expanding
universe. The gas cools, but energy is not conserved in the expansion --
it does not go anywhere. There is no reservoir at a lower temperature to
act as a sink, and there is no change in entropy. With no change in
entropy, the gas does not cease to be at equilibrium if it were
initially so, and there is no change in the number of available states.
This is a peculiarity of GR since energy is not globally conserved in an
expanding universe.
Second, we get the thermodynamic AoT without expansion.
In standard BB cosmology, the expansion cools the initial very hot
state. But it is not necessary to start with a hot BB to get an AoT.
We could image some different mechanism of cosmogenesis whereby the
initial state was a relatively thin cool gruel of hydrogen and a few
other bits. Something like in the current model when the universe is
a few million years old. Imagine it started in that state, but with
no further expansion. We would still get gravitational collapse
around local inhomogeneities, galaxies and stars would form. Planets
and occasionally life would arise. All within a thermodynamic AoT.
In other words, we could get to exactly where we are no without any
expansion at all. So expansion cannot be a necessary prerequisite
for an AoT.
You're invoking graviation to create the AOT. I am explicitly trying to
explain the AOT without invoking gravitation - obviously the universe
has to be smooth, this is what else can occur on top of that.
Gravity is one of the laws of physics. The AoT occurs within physics, so
why not use gravity to explain what happens? The problems arise -- as I
have tried to point out -- when you ignore gravity. Cosmogenesis is,
after all, the quintessential GR/gravitational problem.
Also, the
presence of hydrogen in the above is unexplained, but you need something
like atoms for the 2nd law to operate. It doesn't operate inside a q-g
plasma at equilibrium at several trillion degrees, for example. Hence
you need to create those little bundles of negative entropy, so to
speak, before you have something on which the statistics of the 2nd law
can operate.
You have to beware of making contingent facts into apparent logical
necessities.
I will resist making any similarly patronising and irrelevant comments.
The comment is apposite. It is neither patronizing nor irrelevant.
Bruce
--
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.
