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Re: Entropy, Objectivity, and Timescales

I do hope someone is getting some value out of all this. It takes a
lot of time! The thinking is probably good for me, but I haven't
got all that much extra time. My reply to Dan's last:

Of course I'm quite familiar with Feynman's parable of the blocks,
and I have used it often in my teaching. But I don't interpret it
as rigidly as you seem to.

I take the lesson very seriously. It reinforced my point of view
when I first read it, and I read it to all my introductory classes
verbatim, holding the book in front of me as I do. I'm sure it looks
very like I'm delivering a lesson in church; that's fine, beacause I
think it is a vital lesson that students should learn early. Too
often have I heard the expression "pure energy" from the lips of
students just out of high school. There is a misconception out there
that needs to be savaged in my view. Once past such misconceptions
understanding that entropy is a function of state is a piece of cake.

I am reminded of the following passages
from another atheist reductionist realist, Steven Weinberg (which
I quote not because I consider Weinberg an authority, but just
because he says it better than I can):

"When we say that a thing is real we are simply expressing a sort
of respect. We mean that the thing must be taken seriously because
it can affect us in ways that are not entirely in our control....
As a physicist I perceive scientific explanations and laws as
things that are what they are and cannot be made up as I go along...
and I therefore accord the laws of nature (to which our present laws
are an approximation) the honor of being real." (Dreams of a Final
Theory, page 46.)

That's the royal "we" Weinberg is using, to which I will reply (in
the immortal words of Tonto) "Whaddaya mean `we', white man?"

Weinberg here quite clearly justifies his use of the word "real".
He knows that it is not quite appropriate (and be assured he knows
just why it is not appropriate) but he's going to use it anyway in
this popular exposition. Had I been asked if that is a good idea I
would have said "no", of course. A better way for the logical
positivist to put this is that there is an orderly process by which
the universe unfolds. Its evolution is governed by a set of rules.
We can't say why the universe does this, and the rules themselves
need not be written down anywhere, but the orderly unfolding of
the universe is manifest in all processes. [Here "orderly" means in
the sense of "law and order" or "natural order".] I see Weinberg
being apologetic in this passage and you take it literally. Which
of us is the fundamentalist?

In another passage Weinberg explains that a scientific explanation
is more than just a logical deduction:

"Talk of more fundamental truths makes philosophers nervous....
But scientists would be in a bad way if they had to limit themselves
to notions that had been satisfactorily formulated by philosophers.
No working physicist doubts that Newton's laws are more fundamental
than Kepler's or that Einstein's theory of photons is more fundamental
than Planck's theory of heat radiation." (Page 27.)

No quibble there from me.

And I would add, that Boltzmann's statistical explanation of entropy
is more fundamental than the original formula of Clausius.
(Weinberg discusses the relation of thermodynamics to statistical
mechanics a few pages later, concluding "even though thermodynamics
has been explained in terms of particles and forces, it continues
to deal with emergent concepts like temperature and entropy that
lose all meaning on the level of individual particles".)

It is difficult for me to see the coupling of these two items as
being logical. I cannot see the truth in the first statement, and
doesn't Weinberg echo something I said earlier here?

Personally I find it incredibly useful to think of both energy and
entropy as physical substances, fluids that flow from one object
to another. I know this model is fundamentally wrong. I don't care.
I still think it's useful, at least for my weak mind which needs such
crutches. I know the limitations of these models and when necessary
I can use more sophisticated ideas.

I feel those are unnecessary constructs. They are not crutches at
all, but rather obstacles to conceptual mastery.

But at a more fundamental level, there's a huge difference between
energy and entropy. Energy seems to be at the root of the laws
of microscopic physics, the fundamental principles governing the
four forces. (We write these laws in terms of Lagrangians, basically
a fancy way of talking about energy.) Entropy, on the other hand,
completely disappears at the microscopic level. In this sense it's a
subjective quantity, useful only to macroscopic observers. Perhaps
someday we'll discover that energy is also subjective in a similar
way, but this hasn't happened yet.

I'm not sure exactly which of these comments (if any) Leigh would
agree with and which he would disagree with. But philosophical
attitudes toward physics are pretty slippery: there seems to be
a wide gray area between agreement and disagreement. So I'm not
trying to argue with Leigh here, I'm just trying to say (and quote)
some things that sound good to me.

Boltzmann killed himself in 1906. I don't think his understanding of
the microscopic themodynamics was strongly influenced by QM. Erwin
Schrodinger wrote a nice little book on statistical mechanics. He
discussed quantum statistics, too, but he didn't seem to find it
necessary to introduce the Schrodinger equation, and h only appears
to give a size to the phase space cell. Otherwise his discussion is
entirely classical. It seems to me that deep introspection using the
formalism of QM need not be the only path to enlightenment; indeed I
believe it is the path to obscurantism.

Let me end this with a favorite quote of my own from Bill Burke, a
brilliant theoretical physicist cut down in his prime by a tragic
automobile accident. From "Spacetime, Geometry, Cosmology":

The goal of abstraction is to find common structure in
different concrete situations, and then to discuss this
structure independently of the specific situations. Done
properly, this increases one's knowledge by pooling
information from diverse situations. But be careful.
Excessive abstraction is a very common error. Keep the
references to concrete instances in mind, but do not
give the abstract structures an existence of their own.
Treating ideas as things (reification), done to excess
in politics and religion, has no doubt murdered more
people than any other cognitive error.

-Bill Burke

Leigh