Re: [Phys-l] heat +- impulse

[John Denker <jsd@av8n.com>]

On 11/05/2007 01:03 PM, LaMontagne, Bob wrote:

> I am in general agreement with this approach. 

:-)

> However, I'm still not
> sure what your intent for "heat" is. Would you still attach the concept
> of "vector" with it - as you do for TdS?

My intent for "heat" is to entirely disestablish it from the
technical vocabulary.

At present, different folks mean different things by "heat".  
It's not hard to find three different, mutually-contradictory 
definitions of "heat" even within a single textbook.

There is one school of thought that says 
     -P dV _is_ the work and
      T dS _is_ the heat
in this context.  Just the other day I saw somebody write
      dE = heat + work
with this meaning.  So if we adhere to this school of thought, 
then yes, absolutely, heat is a vector.

This leaves us with N-1 other schools of thought where "heat" 
means something else.  I don't feel obliged to stick my head
into that shooting gallery.

At this point you may be wondering how it is possible to tolerate
N incompatible definitions of something as important as "heat".
My answer is that toleration is possible because "heat" is *not*
very important.

In my experience, instead of trying to quantify "heat", it has
always been easier to quantify other things instead, usually
energy and entropy.  I am reminded of the history of phlogiston.
People had a devil of a time figuring out whether it meant
"oxygen" or whether it meant "energy".  Eventually they just
gave up, and the one idea (phlogiston) was replaced by two
ideas (oxygen and energy).  I think heat, as a technical term,
has outlived its usefulness.  One idea (heat) needs to be
replaced by two ideas (energy and entropy).  AFAICT for all
practical purposes, this has already happened;  people just
need to realize that it has happened.