Re: COLLISION 2

[John Denker <jsd@MONMOUTH.COM>]

At 07:20 PM 11/28/99 -0800, Leigh Palmer wrote:
>  When Joule was twirling his oar he was
> increasing the entropy of the water.

Agreed.

> It is true that he was not heating the water.

Aaaarrgghhh.  I will grudgingly concede that it is possible to define "heat
transfer" in such a way that the oar did not "transfer heat" to the
water.  But I'm not sure that the participle "heating" can be defined so
narrowly that Dr. Joule was "not heating" the water.  In any case there is
no pedagogical or practical advantage to defining it that way.

It is an obviously losing strategy to talk about flow or transfer of things
that are not conserved.

A much better strategy is to talk about changes as opposed to
transfers.  Dr. Joule was definitely increasing the thermal energy content
of the water.  I know a lot of very fine physicists who would say that he
was heating the water.

>Change in entropy is not associated with an actual process;

Huh?  I would have said just the opposite.  Entropy doesn't just
change.  There has to be some actual process that changes it.

>it is associated with *any* hypothetical reversible process
> capable of taking an identical system from the same initial to the
> same final state as the system in question.

Huh?  I wouldn't have said that at all.  Entropy changes occur in
irreversible as well as reversible processes.  And entropy changes occur
under lots of conditions that are not closed cycles.  And not hypothetical,
either.