Re: Second law stuff

David Bowman (dbowman@tiger.gtc.georgetown.ky.us)
Wed, 04 Feb 1998 0:01:13 EST

Concerning Wesley's comments:

>. . . . Nor is it certain that
>the "local" environment of just the bodies of a population of organisms
>will ever display an entropy decrease. I can't guarantee that there is
>no counterexample, which is the only reason that I don't say that even
>that is contraindicated.

A counterexample usually happens every night in most ecosystems.
Essentially most of the exposed plants, bacteria, fungi, and cold-blooded
animals (indeed every organism that is not warm blooded and which has a
negligible growth rate) tend to have their body temperatures drop when the
environmental temperature drops as the earth's surface cools at night. The
entropy of each of these organisms drops with their body temperature. It
should also be noted that the entropy of the (nonliving) air, water, rocks,
and soil also drops as their temperature drops as well. The reason such an
entropy decrease happens is that the temperature of that part of the
earth's surface is hotter than the temperature of deep space, and thermal
energy in the stuff at the earth's near surface environment continues to
be lost as the stuff radiates IR radiant energy out into space. As this
happens in the absence of any incoming radiant sunlight to replace the
lost energy, the entropy and the thermal energy in the stuff, therefore,
decreases. It should be noted that this entropy decrease process is an
example of the the second law in action since the outgoing IR radiant
energy possesses more entropy than the amount of the entropy decrease of the
stuff that emitted the radiation.

Actually, every time heat flows from a warmer system to another cooler
system the entropy of the warmer system *decreases*. This happens because
this entropy decrease is overcompensated by the greater entropy increase of
the cooler system which is being heated. This localized entropy decrease
process in the warmer system does *not* require any special 'energy
conversion mechanisms', 'control codes', etc. to operate. Only the existence
a cooler body with which to be in thermal contact with is necessary.

> . . .
>Just to be completely clear, I don't see any reason to suppose that
>evolutionary change represents a decrease in entropy of any sort at
>all.

Certainly this is true for thermodynamic entropy (which is the only sort
of entropy to which the 2nd law applies).

> A monotonically increasing entropy in the universe is completely
>compatible with evolutionary mechanisms.

Hear, Hear.

David Bowman
dbowman@gtc.georgetown.ky.us