Re: entropy

[palmer@sfu.ca (Leigh Palmer)]

I can only assume that this was not meant to be posted to the
whole group, but since it is out there I feel I should answer it
in the group. If you don't already have me in your "delete before
reading" file you may want to put me there now. I try not to
flame more than about 25% of the time, but the following may be
quite incendiary. You have been warned.

> Dear Leigh:
>    You seem to advocate the teaching of physics without using the
> everyday English language, since its terms are vague and ill defined.
> How would you teach it? Just by gestures? WE MUST NECESSARILY USE IT.
> But we must undergo the process of REFINING it, in order to arrive at
> the correct physical concepts. I don't see any alternative!

Nonsense! I advocate the skillful use of standard English in all
teaching. I believe that is the only way we can hope to save the
language, by exemplifying its proper use in our teaching. There
is more than physics at stake here! Whenever I have an opportunity
to convey a concept to my students using (my) everyday language I
try to do so. Rather than "refining" the language as you advocate,
I use the language as it is, or rather as it was when last it was
capable of precision of expression.

Don't you see, on rereading the paragraph above, that you have
abandoned the use of everyday language when you "refine" it? You
acknowledge implicitly the error in identification of entropy with
disorder (in its everyday sense) by requiring that the word
"disorder" be redefined before use. Not only do I think that is an
unreasonable and unnecessary thing to do, I think that in practice
it is not done in as many as one one-hundredth of the cases in
which teachers ejaculate that particular homily. In everyday
language, get real!

>    Example: In mathematics, an ORDERED SET is defined as a set
> X={a,b,c,...} and a relation "<" such that for any two distict elements
> a,b of X, one and only one of the two relations a<b or b<a is correct.
>    From here it follows, for example: THEOREM: Any deck of cards
> given to you is ordered. PROOF: define a<b if card a is higher
> in the deck than card b.
>    You see, there do not exist "disordered" decks of cards! This
> contradicts the usual use of the word "disordered"!

I believe I made that point already, but I think I did it using
ordinary language, and with physics rather than mathematics. I
said that the order of the cards in a deck contributes absolutely
nothing to its entropy. If you believe that the ordinary meaning
of order when applied to a deck of cards is in need of refinement
then you had better avoid playing poker with nonmathematicians.

You seem capable of finding disagreement in what I'm saying even
when I agree with you. Must I learn to write in upper case to
communicate my ideas, or would it, perhaps, be worthwhile for you
to read what I write in more nearly ordinary language?

>    Comment about entropy NOT depending on information: Assume you have
> one liter of oxygen gas, at standard atmospheric pressure, 0 deg.C,
> in a container in steady state of equilibrium.

I'm not sure it is worth reading farther here. You have just made
a fundamental physical error. Each of the terms "steady state" and
"equilibrium" has a precise meaning, and those meanings are very
different. My guess is that you mean "thermodynamic equilibrium".

> Its entropy is certainly
> defined. Do you KNOW the state of the gas? Of course, NOT - the
> microscopic state, I mean, the position and velocity of each of its
> molecules. So that information has something to do with this whole
> circle of concepts. To have a CLEAR IDEA one must, of course,study
> statistical (Boltzmann-) mechanics.

I'm sorry, Emilio, but after reading that I find myself unable to
restate your point; I don't get it. In the words of Wolfgang Pauli,
"It's not even wrong."

> Best regards              Emilio