Re: h**t

[Leigh Palmer <palmer@SFU.CA>]

At 3:51 PM -0700 8/4/99, John Denker wrote:

> Uhhh, what am I missing?  Heat may be spelled with four letters, but it is
> not an expletive or an obscenity.
>
> I spent six years doing thermodynamics for a living in an Ivy League
> physics laboratory.  The folks there used "heat" as a noun, as a verb, and
> as several other parts of speech.  We spoke of heat, heating, specific
> heat, latent heat, heat engines, heat exchangers, heat leaks, heat sinks,
> heat switches, the heat equation, and more besides.  I don't recall anybody
> spending even a single millisecond being confused about what the word meant
> in any of these contexts.
>
> I'm sure that it is *possible* to misunderstand this concept.  The set of
> all possible bad ideas is much larger than the set of good ideas.  But the
> light shines, and the darkness will never overpower it.
>
> I would be surprised and disappointed if the folks on this list couldn't
> rapidly come to a consensus on this.

I hope that you won't be too disappointed (or intolerant) of those
among us who advocate the use of a more restricted meaning when the
term is used by itself in scientific context. We feel that heat is
analogous to work. It is a measure of a process in energy units that
is represented by a term in the first law of thermodynamics. It has
no reality or substance. One cannot calculate the amount of heat in a
system, unlike the change of internal energy of (not "in") a system
which is associated with a change in the thermodynamic state of the
system, which can be calculated.

Some among us think that the misconception that energy is real (which
in an earlier form was called the "caloric theory") is reinforced by
some of the the common uses of the term "heat". By this I mean "heat"
*per se*, distinct from the many compound forms you have mentioned
above in which the word appears. Zemansky uses the term "heat flow"
where Jim and I would use "heat", but he does it correctly. Reif uses
"heat absorbed" and "heat given off", a better usage in my opinion,
since they are analogous to "work done on" and "work done by". Callen
also uses "heat flow" as Zemansky does, but he also uses "heat" in
the way I do, and "heat flux". In all cases I saw he uses the term
only at a system boundary, and to refer to a process by which the
energy of one system changes and the energy of the second system
changes, and heat preserves the law of conservation of energy for the
isolated supersystem consisting of the coupled systems. One does not
imagine energy flowing like water; one only reckons changes in system
energies. There is no need to hypothesize that anything flows just
because the results are consistent with a flow model, and it can't be
shown that flow is not occuring. A similar statement can be made
regarding the angels that impel planets in their appointed rounds.

Leigh