From: jamsaeff@w250zrz.zrz.tu-berlin.de (J. Naghizadeh)
Subject: Physics 1A questions, Existence of matter
Organization: ZRZ/TU-Berlin
Date: Sun, 4 Oct 1992 22:13:45 GMT

Recently there has been a discussion of some physics questions in SCI.
I have been meaning to write on this issue, but my computer in San Francisco
was disconnected from the net for some time, and I have been receiving
SCI articles from other sites. I am now posting from my account in Berlin,
although I am still in San Francisco.

The basic question was on the nature of temperature. The notion of
temperature existed before the formulation of the laws of thermodynamics.
Therefore there is a zeroth law of thermodynamics which states that
temperature is a measurable and reproducible property and if a body A
is in thermal equilibrium with A body B and B is thermal equilibrium with
C then A and C are also in thermal equilibrium or have the same temperature.
The gas law can be formulated in terms of this empirical temperature scale.

The thermodynamic definition of temeprature first appears in the second law
which relates the convertibility of heat into mechanical work to a quantity
called thermodynamic temperatrue. This thermodynamic temperature is then
related to the temperature appearing in the gas law. This is arrived at by 
designing an engine which uses expansion and compression of gas for 
conversion of heat into work. Thus it is shown that thermodynamic
temperature is essentially the same scale as Centigrade except for
a change in origin. It is later shown that temperature is related
to the mean kinetic energy of a molecule in gas. (or mean square velocity).
The change in the cale from Farenheit to Centigrade etc. changes only the
proportionality constants and is the same as changing the measure of
length from centimeter to inch.

Other questions: Does the existence of temperature prove the existence of
matter, etc.. The answer to this question is quite simple: Physics
does not concern itself with the existence or non-existence of matter.
Physics seeks to find relationships between measurable quantities and in so
doing assumes the existence of matter.  The discussion of existence or non-
existence of matter belongs to philosophy.

Freezing of warm or cold water, which is faster?
This question is very badly formulated, I think the person who
formulated this meant that the thermal conductivity of warm water is
higher than the thermal conductivity of cold water. Otherwise the
question does not make sense.

Temperature field as opposed to uniform temperature:
This was raised in one of the replies to the original question. It is
however a very technical and delicate problem. Strictly speaking,
temperature is defined in equilibrium situations where the temperature
of the entire system must be uniform. Thermodynamics deals with these
equilibrium systems. A system in nonuniform temperature is not in equilibrium.
It is sometime assumed that local equilibrium exists (or locally, a 
maxwell distribution of velocities exists). This is probably true
near equilibriun where linear transport laws (Fourier law,..etc) are
valid. The study of nonuniform systems lies outside thermodynamics.

I just wanted to put my two cents in this discussion, however, I think
it is appropriate to discuss these in other newsgroups as sci.physics, etc.

--jamshid
Newsgroups: soc.culture.iranian