Re: heat is a form of energy

[William Beaty <billb@ESKIMO.COM>]

On Wed, 8 Sep 1999, Jim Green wrote:

> Bill Beaty says --
>
>
> > When GR took the reins from Newtonian Mechanics early this century,
> > Newton's Laws became a special case of a more general model.  In other
> > words, they became "wrong".  At least it became wrong to apply them
> > universally as had been done before this change.  Yet Newton's Laws
> > remained just as useful in everyday application.
>
> Bill, I see your point here, but I also think that I see a fatal flaw in
> this analogy --


> Newtonian Mechanics is to me more like a special case of GR --- and the
> laboratory frame a special case of that -- I hope that this is thought is
> accepted here,  Newtonian Mechanics is very accurate for most of us most of
> the time -- and should  be taught as such -- an appropriate part of intro
> physics.

Yep, I certainly agree.


> BUT caloric ideas -- of a substantive heat or energy flowing -- has always
> been dead wrong

If it's dead wrong, you need to convince me.  In my view it is "wrong"
like Newton's laws are "wrong":  it works over a limited conceptual range,
but as soon as things like entropy-machines or chemical reactions or phase
change are a factor, we have to abandon "heat" and look to a more complete
theory.

> -- not a special case of anything.  We as teachers should
> not perpetuate these ideas.  I don't see some sort of over-reaching
> thermal-physics which reduces to "heat flow" or "energy flow" in some kind
> of special case.

The special case I'm imagining is when a hot object touches a cold object,
and then under a simplified mental model we say that "heat flows".  But
dump some sugar into water and the temperature drops.  This violates the
"heat flow" model, just as relativistic velocities produce phenomena which
are not predicted by Newton's laws.


>  No matter how it is couched, it is and has always been wrong.

Stating this does not make it so.  I need to see some reasoning and
examples.  Yes, I know many examples which violate the limits of the "heat
flow" paradigm.  However, I also know many examples which prove Newton's
Laws to be faulty and oversimplified, yet this doesn't make me stop using
Newton's laws.


> I don't think that any of us would hold that it would be useful to teach in
> an intro class that projectile motion is linear until the projectile runs
> out of "impetus" and then falls vertically downward as it was taught
> centuries ago -- this is not a special case of any mechanics -- it is just
> plain wrong.  This surely should not be taught in a physics class except as
> an example of cartoon physics

Agreed.  And yet...  if I was forced to teach a 2-yr old kid how
projectile motion occurred, I might intentionally use the "impetus"
fallacy, since there's no way they could understand anything more
advanced.  As the kid got older, they would see that projectile motion
doesn't at all resemble the "impetus" description, and they would start
hankering for something better.  (Although from the examples I've seen in
sci.physics debates, some would descend into extreme closemindedness, and
react emotionally if anyone dared to question Impetus.)


> -- nor should a substantive heat or energy --
> nor that "heat" is somehow a form of "energy".

The usefulness of the "heat-stuff" concept is not destroyed by the limited
realm over which it applies.  Same as with Newton's laws.  If you insist
that "heat" is not useful, then you simply are wrong, since a significant
contingent here on phys-L finds it to be extremely userful.  It might not
be useful to *you*, but perhaps that's because you refuse to include it in
your toolbox.


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