Dear Organlearners,
Stuart Harrow <bvc2206@dcrb.dla.mil> writes:
> You might be interested in "Thermodynamics of Culture: The Relationship
> Between Classical Entropy and Chaos," by Jerome Heath. I found this
> posted at http://www2.hawaii.edu/~heathj/Dynamics.htm
I had a look at this article. I applaud the intention of the author to
break out of the conventional applications of thermodynamics so as to
enter the realm of human culture.
However, I must speak up when you want to understand Ilya Prigogine and
his work on self-organising dissipative systems. The paper by Jerome Heath
is on entropy in the sense of classical thermodynamics. The founding stone
of classical thermodynamics is systems which undergo reversible process.
In a reversible process the system transforms from an intitial equilibrium
state A to a final equilbrium state B through uncountably many states of
which each one is very close (infinitesimal close) to equilibrium. Being
infinitesimally close to equilibrium means that during any change of the
process it is possible to reverse the process in the opposite direction
with only a very small change.
The only changes in entropy allowed in classical thermodynamics is the
reversible exchange of entropy between the system and its surroundings. If
the system gains (or losses) an amount X in entropy, then the surroundings
looses (or gains) the same amount X. Working with reversible changes makes
it possible to take two snapshots of the system, one at the beginning and
one at the end. These two snapshots then have all the information how the
system would evlove through any reversible path from A to B. But they
cannot tell anything about any irreversible path followed between A and B!
But this classical thermodynamics is far from Prigogine's contributions.
He concerned himself with systems moving away from equilibrium, following
paths which cannot be reversed because of the entropy created (produced)
along such a path. He eventually came to the conclusion that classical
thermodynamics is merely the limiting case for the general theory of
irrversible thermodynamics. The key to Prigogine's thinking is not
"entropy", but "entropy creation". I prefer to use the term "entropy
production" rather than "entropy creation". The term "entropy production"
is used by many other irreversible thermodynamists, for example De Groot
and Mazur.
Prigogine seldom use the term "entropy creation", but rather use the term
"entropy dissipation". But whenever he uses the term "entropy
dissipation", he thinks of it as "entropy creation". Take it from me and
shove it back to me if I am wrong.
Now, please fasten your seat belts because here comes something tricky to
understand. Before him, almost all physicists, chemists and engineers
thought of "entropy creation" as "entropy dissipation". Whenever a system
changed irreversibly, it dissipated ordered forms of energy into the heat
(the prime disordered form of energy). Since the operational definition of
entropy makes use of heat, they thought that entropy was dissipated along
with the heat! This was the general mindset of all scientists when he
began his great, fundamental work. If he thus still uses the word "entropy
dissipation" because of the historical context in which he had to work,
who are we to castigate him.
Now what did Prigogine accomplish? Firstly, he discovered how entropy is
created when a system change irreversibly. Secondly, he discovered that
dissipation (dispersion, chaos) is not the only thing which happens during
an irreversible change, but also that constructions with energy (the
opposite of dissipation of energy) are also possible. Thirdly he
discovered that almost all irreversible constructions in a system happen
in a way which we could describe as self-organisation. Fourthly, he
discovered that irreversible processes has the effect of bridging
(connecting) seemingly unrelated phenomena. This bridging effect is a main
theme in his book "From Being to Becoming". (He also discovered a number
of other fundamental things, but this is not directly related to this
contribution.)
In the web-paper to which Stuart refers, no mention is even made of
"entropy production" or "entropy creation" or even "entropy dissiaption"
a-la Prigogine. Thus this web-paper will help be of little help to
understand Prigogine's way of thinking.
How can I put it clear to you? Let me again use the following metaphor.
When you think of the "entropy" of a system, think about a snapshot
(picture) which depicts the organisation of a system at a particular
instant of time. When you think of the "entropy production", think about a
movie (cinema picture) which depicts how the organisation of the system
changes over a long time interval. A snapshot is about a being, but a
movie is about the becoming of being. There is no becoming of the being in
the web-paper refered to - it is as simple as that. Prigogine discovered
that we cannot image life with a thermodynamical picture, we need a
thermodynamical movie. Thus a neat way of saying what classical
thermodynamics is all about, is to call it "thermostatics". Consequently
irreversible thermodynamics is "proper thermodynamics". Keep up with
proper thermodynamics if you want understand Prigogine.
Best wishes
--At de Lange Gold Fields Computer Centre for Education University of Pretoria Pretoria, South Africa email: amdelange@gold.up.ac.za
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