On 10.03.2011 01:29 1Z said the following:



On Mar 9, 7:22 pm, Evgenii Rudnyi<use...@rudnyi.ru>  wrote:
When you compare heat and molecular motion, first it would be good
to define what molecular motion is.

At the beginning, the molecules and atoms were considered as hard
spheres. At this state, there was the problem as follows. We bring
a glass of hot water in the room and leave it there. Eventually
the temperature of the water will be equal to the ambient
temperature. According to the heat theory, the temperature in the
glass will be hot again spontaneously and it is in complete
agreement with our experience.

OK.

With molecular motion, if we consider them as hard spheres there is
a nonzero chance that the water in the glass will be hot again.

I don't see the difference. Both seem to predict the same thing

The difference is that from the viewpoint of the heat theory the probability that the water in the glass spontaneously will be hot again is zero. In classical mechanics however according to the Poincaré recurrence such a probability is one. This, in my view, makes the difference.

Moreover, there is a theorem (Poincar recurrence) that states that
if we wait long enough then the temperature of the glass must be
hot again. No doubt, the chances are very small and time to wait is
very long, in a way this is negligible. Yet some people are happy
with such statistical explanation, some not. Hence, it is a bit too
simple to say that molecular motion has eliminated heat at this
level.

I still don't see the difference

Then we could say that molecules and atoms are not hard spheres
but quantum objects. This however brings even more problems, as we
do not have macroscopic objects then. Let me quote Laughlin to this
end

"By the most important effect of phase organisation is to cause
objects to exist. This point is subtle and easily overlooked, since
we are accustomed to thinking about solidification in terms of
packing of Newtonian spheres. Atoms are not Newtonian spheres,
however, but ethereal quantum-mechanical entities lacking that most
central of all properties of an object an identifiable position.
This is why attempts to describe free atoms in Newtonian terms
always result in nonsense statements such as their being neither
here nor there but simultaneously everywhere. It is aggregation
into large objects that makes a Newtonian description of the atoms
meaningful, not the reverse. One might compare this phenomenon with
a yet-to-be-filmed Stephen Spilberg movie in which a huge number of
little ghosts lock arms and, in doing so, become corporeal."

So I personally not that sure that molecular motion has more
meaning *ontologically* than heat

Ermm... so you are saying that the classical explanation of heat
reduces it to the motions of molecules with individually well-defined
positions and velocities --whereas Qm reuires that those things can
only be defined in a kind of reverse- reductionism scenario where the
parts acquire their properties from the whole? Is that right? I am
not sure that really breaks anything in thermodynamics, because
quantum entities still can have well-defined kinetic energies without
having well defined positions or velocities.

I have employed in my life quantum mechanics (more exactly quantum chemistry, I am a chemist) mostly pragmatically as what chemists do, that is, to earn some more money. Along this way there is nothing wrong with quantum mechanics.

Yet, if you look at discussions in this group: quantum mechanics and observer, quantum mechanics and consciousness, etc., things do not look that simple. The quote from Laughlin, in my view, offers some other look at this, but frankly speaking I do not know. It is not quite clear what molecular motion at the level of quantum mechanics is.

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