Entropy

[Kenelm Philip]

	A lot has been said about entropy during this discussion that began
with the 'purpose' of butterfly wings. Most recently we had the following:

> the Sun will probably be blowing higher entropy particles off

Entropy has _nothing_ to do with the speed of individual particles. In fact,
a collimated beam of fast particles has essentially zero entropy, regardless
of its speed. Entropy is defined as K (natural log (omega)), where K is
Boltzmann's constant, and omega is the number of configurations. A colli-
mated beam of particles has a single velocity (speed and direction) for
each particle, and thus one configuration. Log (1) = 0. In common parlance,
entropy is a measure of the degree of randomness, and decreases as order
is increased. Also, a _single_ particle has no entropy (unless it can have
internal states). Entropy is also tied in with information theory--since
entropy is associated with our degree of ignorance of the precise state
of s system. It is a rather subtle concept--and I don't claim to under-
stand it more than superficially myself.

	I am reminded of a famous classroom experiment done some years ago.
The teacher asked a class of university students if they understood the
concept of an electrical circuit--and all of themn said they did. Each
studend was then handed three items: a battery, a flashlight bulb, and
a length of copper wire--and instructed to arrange these items so as to
light the bulb. Most of the students ran the wire from one terminal of
the battery to the other, and then touched the base of the bulb to the
(rapidly heating) wire. The bulb, naturally, did not light.

	The moral of this tale is that we learn to use scientific (or
other specialized) terms in conversation--but may not have the least idea
as to what these terms actually _mean_. The resulting conversation may
have a few problems...

	I am not attacking any individual here--we all do this whenever we
venture outside of our own field of competence. I do it--everyone does it.
Nothing is easier than constructing apparently coherent sentences when you
haven't the faintest idea what you're talking about--that's how language
works. But one should be cautious about drawing any _conclusions_ from
such sentences...

							Ken Philip
fnkwp at uaf.edu