LizR wrote:
On 11 November 2014 12:34, Bruce Kellett <[email protected]
<mailto:[email protected]>> wrote:
LizR wrote:
On 11 November 2014 10:32, Bruce Kellett
<[email protected] <mailto:[email protected]>
<mailto:bhkellett@optusnet.__com.au
<mailto:[email protected]>>> wrote:
LizR wrote:
OK, so are you saying that the formation of bound states
like
nucleons has no bearing on the existence of an AOT?
It certainly doesn't play a role in the origin of the AoT.
Formation
of bound states is just a routine physical process that follows
conventional dynamical laws, including the second law of
thermodynamics. Since the second law governs these
processes, they
are subject to an AoT.
You appear to be assuming the AOT in order to explain something
that emerged from a state in which there was no distinct AOT.
The quark soup starts in a high energy, essentially
time-reversible state (any nucleons that happen to form sill
rapidly fall apart again) - how can the 2nd law apply at that point?
I think we have covered this. The quark-gluon plasma is a thermal
state of only those degrees of freedom -- other degrees of freedom,
particularly gravitational, are not thermalized, so it is not a
state of maximum entropy. It is, in fact, a low entropy state
compared with what might be expected -- we could have a soup of
black holes for instance, which would have the same energy density
but vastly higher entropy. Why do we not have such a state? That is
the past hypothesis -- things started in an unusually low entropy state.
Yes, I have already agreed with this. The flatness of space-time does
indeed need explaining (perhaps by inflation?). I'm talking about the
(perhaps residual) entropy gradient arising from mainly
non-gravitational processes, like the fact that atoms can only exist to
the "future" side of a certain point in an expanding universe. The AOT
we experience may be many order of magnitude away from the one
theoretically attainable by gravitational processes, however I'm
assuming the universe got flat somehow, and asking how, given that, the
AOT of everyday life might have arisen. Maybe it only arises from
flatness, but if so we need a mechanism. My suggestion is that flatness
plus cosmological expansion plus our tie-symmetric laws of physics are
enough to give the observed AOT.
It is not really a question of the flatness of space-time. That arises
from the setting of the parameter k in the Friedmann equations, which is
not a dynamical feature. I think you really mean 'smoothness' -- why is
space-time smooth and not 'lumpy' as it would be in a soup of black
holes. Inflation is supposed to solve this problem, but the solution has
been made opaque by recent developments in inflationary theory --
particularly the reheating problem.
If the universe were not expanding, and hence cooling the initial
plasma, then the gravitational degrees of freedom would gradually
become excited, and eventually fully thermalized. The entropy would
rise throughout this process, even though no expansion is
hypothesized. The second law applies because the state has a much
lower entropy than other states which are equally likely. The second
law is there in the statistics of the degrees of freedom -- it does
not have to 'emerge' from anywhere.
In other words, the gravitational entropy would rise. I agree. And I
agree that the second law applies to states in low entropy, as flat
space-time clearly is. The flatness of space-time needs to be explained,
but that isn't the whole story. I'm discussing whether the expansion
turning the q-g plasma into bound states could contribute to the AOT
that we experience, given that we're made from those bound states and
live off energy generated from them inside stars.
These are straightforward physical process that obey the second law. The
AoT exists regardless of such processes.
Given that the laws of physics are (almost) time-symmetric, there needs
to be some mechanism by which an AOT emerges, and an obvious starting
point is the observed boundary conditions on space-time.
Which is what I am pointing to -- the past hypothesis, or the fact that
the entropy was low at the BB. Currently this fact is unexplained. Wrong
explanations do not advance understanding.
Bruce
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