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Re: definitions of heat +- fish



At 10:12 AM 2/1/01 +0800, julie wrote:
do we then say "heat energy" or "thermal energy" ? Or it really doesn't
matter?

1) As far as I can tell, most of the disputes about the word "heat" are
analogous to a dispute about whether clams are a type of fish. According
to my dictionary, fish (definition 1) is restricted to vertebrates, while
fish (definition 2) includes all aquatic animals, including shellfish.

Such disputes have only minor importance. In practice, it rarely matters
exactly what definition is being used, and in cases where it does matter,
it is usually obvious from context what meaning the author intended.

In the few cases where the details actually matter, it would be nice to
have a simple, common word that indisputably means "vertebrate fish not
shellfish". It would facilitate communication. AFAIK no such word exists,
yet life goes on.

2) You can use the expression "thermal energy" if you like. Anyone who
wants to understand you will understand you.

3) You can use the word "heat" as a synonym for "thermal energy" if you
like. Again, anyone who wants to understand you will understand
you. "Heat energy" strikes me as a bit redundant, but harmless.

4) When reading what another author has written, you must be prepared for
the possibility that the author has used the word "heat" in some
more-specialized sense; see below for more on this.

5) The dispute over words is particularly unimportant in physics, because
in the rare cases where the details actually matter, physicists communicate
the details using equations, not English words.

6) There are two goals: understanding the physics, and communicating the
physics.

By way of analogy: If you tie a rope in a particular way, how well it holds
depends on the physical conformation; it does not depend on whether you
call it a knot or a bend or a hitch or whatever. On the other hand,
communication is facilitated if such things have standard names.

So it is with physics: If you build a particular piece of thermodynamic
apparatus, it will behave the same no matter what you say about its heat or
its thermal energy. On the other hand, communication would be facilitated
if the relevant physical quantities had standard names.

Since we do not have an agreed-upon single meaning for "fish" or "heat",
the careful author will (a) pick one of the meanings and stick to it, and
(b) explain which one has been picked. The well-meaning reader will try to
read the word the way the author intended.

7) The disputes about "heat" seem particularly odd, since for about 150
years (~1798 to ~1955) there was only one technical definition of heat,
namely thermal energy. Since then competing definitions have popped
up. The old definition shows no sign of dying out; it is still widely
used, by experts and non-experts alike.

8) Sheep can be called by specialized terms such as rams and ewes and
lambs; that isn't a problem. Water can be called by specialized terms
such as rain and snow and frost and dew; that isn't a problem.

In contrast, the word "heat", for which the technical definition was
already a specialization of the vernacular definition, has been encrusted
with new technical meanings which are hyper-specializations of the
long-standing original technical definition. To advocate this
hyper-specialization, rather than coining a new word, seems ill-advised.

9) Prominent among the hyper-specialized concepts to which the name "heat"
is sometimes attached is the notion of "energy transferred from one body to
another due to a difference in temperature". We all agree that such
transfers can and do take place. However, it seems bizarre to focus
attention on such transfers, rather than on the concept of "thermal energy"
which is much more fundamental.

It is like focusing heavy attention on the specialized concept of "rain",
to the near-exclusion of the concept of "water" which is much more
fundamental. How did the rain originate? What happens to it when it hits
the ground and isn't rain anymore?

In particular: Suppose I use a cold spoon to vigorously stir a pot of
tepid molasses. The molasses gets hot. The molasses has acquired thermal
energy that was not transferred in from a higher-temperature body. Yet
this thermal energy is indistinguishable from that which would have been
transferred in from a higher-temperature body. Thermal energy is the
important concept. Temperature-driven transfer is a hyper-special case.

To be explicit: I am making two quite separate arguments:
a) Temperature-driven transfer is not a good thing to focus on, no
matter what name you give it.
b) If you have a new concept of whatever sort that needs a name, please
don't name it "heat". That word is already taken. Throughout the history
of thermodynamics, up to the present day, "heat" has been used to denote
"thermal energy". Using the word in new ways is an impediment to
communication. It's not the end of the world, but it certainly causes
confusion. I hope the new usages die out (but I recognize that they have
not yet done so).

10) Saying "heat" is not a noun is ludicrous.