The following is a slightly edited 1994 Usenet posting from NASA/JPL
physicist Timothy J. Thompson.
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Hopefully, this will provide a more complete view of what the word
"entropy" really means, and how it is mis-used by creation
"scientists". You have to keep in mind that the concept of "entropy"
is used in many disciplines, not just physics, but it has a different
meaning for each discipline. You can't just use the definition, for
instance, from information theory, as if it were also a valid concept
in thermodynamics.
Here it is ...
Look in any textbook on thermodynamics, and you will find a definition
for entropy. Here it is:
S = k ln(N(E))
where S is entropy, k is Boltzmann's constant, and N(E) is the total number
of states accessible to the system, in the energy interval between E and E+de,
"de" being the infamous "infinitesimal interval" of energy, well approximated
in practice by some number very small relative to the system in question.
Now consider the famous second law of thermodynamics. Here is a statement
of that law, from "Fundamentals of Statistical and Thermal Physics" by
F. Reif, a very standard book on the subject. See section 3.11, page 122.
Emphasis on the word "isolated" is not mine, it is Reif's.
QUOTE
Second law: An equilibrium macrostate of a system can be characterized by a
quantity S (called "entropy"), which has the properties that
a. In any process in which a thermally ISOLATED system goes from one
macrostate to another, the entropy tends to increase, i.e.,
ds >= 0
b. If the system is not isolated and undergoes a quasi-static infinitesimal
process in which it abdorbs heat dQ, then
ds = dQ/T
where T is a quantity characteristic of the macrostate of the system (T is
called the "absolute temperature" of the system).
ENDQUOTE
Now look again at the definition. I don't see either the words, or the
concepts, of "disorder" or "order" mentioned anywhere. I do see a reference
to the total number of accessible states. Now consider the surface of the
earth. It is an open system, at or near equilibrium with its environment.
Since it is not an isolated system, it is not bound by part "a" above, but
it clearly is bound by part "b".
However, now consider the process of evolution, the change from a basically
lifeless and simple system to a very complex system. The complex system is far
richer in states accessible, as a function of energy, than the simple system.
It would seem that the process of evolution does, in fact, considerably
increase the entropy of the system, rather than to decrease it, as creation
scientists would like to believe.
In short, the creation science definition of entropy is thermodynamically
bogus. The creation science claim that evolution violates the second law of
thermodynamics is equally bogus. I see no flaw in my line of reasoning here,
but you are welcome to point out any that you find.
But why do creation scientists persist with their inappropriate
definition for entropy? The book "Decision Theory" by D.J. White (the only
book I have on this field), a definition of entropy is given for the field
of information and communication theory. I can't put an upper case sigma, the
mathematical symbol for a summation here, so I will use 'SUM(X)' to mean a
big sigma, with an 'X' under it.
E = -SUM(X) {p(X)log2(p(X))}
where E is entropy, X is any valid propositional form, p is the probability
the the proposition X is true, and log2 is a base 2 logarithm. You can see for
youself that if p(X) is near 1 (almost certainly true), or near 0 (almost
certainly false), in either case, the entropy as defined will tend toward a
minimum. This entropy will tend toward a maximum where P(X) tends toward 1/2,
or where uncertainty is at a maximum. In information theory we see entropy as
a measure of uncertainty. This is not disorder, but it could be construed as
such by the unwary. I think you will find this definition of entropy in the
popular literature, but construed as a measure of disorder. Creation scientists
have lifted this popularized version of entropy, and dropped it into a
thermodynamic setting, where it is quite inappropriate. In my mind, this lends
great credence to the notion that creation science is far from proper science.
Timothy J. Thompson, Timothy.J.Thompson@jpl.nasa.gov
http://www.geocities.com/CapeCanaveral/8851/
NASA/JPL Terrestrial Science Research element
Advanced Spaceborne Thermal Emission and Reflection Radiometer.
Atmospheric Corrections Team - Scientific Programmer.