From: btd@iastate.edu (Benjamin T Dehner)
Subject: Re: Thermodynamics FAQ
Organization: Iowa State University, Ames IA
Date: Fri, 24 Jul 1992 16:56:34 GMT

In <henley.920723165933@wilbur.eng.auburn.edu> henley@eng.auburn.edu (James Paul Henley) writes:

	A very long article about thermodynamics, most of which comes from a
somewhat outdated engineering text.  While it is essentially correct, there
is one thread running through it that is wrong, and I would like to pick up
the pieces of it below.  Points of ellipses (...) indicates where I have
deleted a great deal of the quoted text/explanation in the article.

...

>The first law is generally stated in terms of a closed system, also called
>a control mass.  So an auxiliary law is the conservation of mass:

>               THE LAW OF THE CONSERVATION OF MASS

>    "The mass of a control mass never changes."  [1, p.120]

	I can see we have a problem here already.  More on this in a bit.

...

>**An isolated system is one in which there is no mass or energy transfer
>  across system boundaries.  (see How do the Laws...Apply to Various Systems)

	Keep this one in mind as well.

...

>This definition does not include energy that exists apart from matter.  For
>example, radiation in space.  Pure energy, apart from matter, is not
>measureable.  This is somewhat like the uncertainty principle.  In order to
>measure energy, you must first allow it to interact with matter, and then you
>measure the effect on the matter.  But once you have done that, it is no
>longer pure energy, so you can't be certain that what you are measuring is
>accurate for pure energy.  For example, the speed of light.  We must depend
>on the interaction of light with matter to measure the speed, but in so doing,
>we are no longer measuring light *apart from* matter, but rather measuring the
>effect of light *on* matter.  By this definition of the universe, pure energy
>exists in another dimension - outside of the space-time continuum that we call
>the universe.  It is only when energy interacts with matter that it enters the
>universe.  This gives us a clue about the nature of entropy - anytime energy
>interacts with matter, some of that energy is transferred to the matter, and
>some of that energy becomes disordered.

Okay, here we go.  You are trying to equate change in energy with a
physical change in mass through mechanical/chemical processes.  This is 
incorrect.  While a change in energy can be related to a change in mass via 
the Einstein relation (E=m*c**2) you do not need a physical transport of 
mass to change the energy of a system.  Example: photons striking a photo-
voltaic cell producing useable energy.  By your analysis, the photovoltaic
cells are a closed system (no mass being added) but they are producing
energy, and thus violate the laws of thermodynamics.  

...

>Closed system, or Control Mass, which means that the mass of the system is
>constant, and mass is not allowed to cross the system boundaries.

By this reasoning, when I go home and close all the doors and windows in my
apartment, it it then a closed system, since there is no mass being added
to the appartment through the power cables connected outside.  Or through the
heat exchanger coils on the outside wall.

...

>Take the earth - we know that gas molecules can occasionally escape into space,
>meteors occasionally shower down into the atmosphere, and space missions leave
>the earth.  So in the strictest sense, the earth is an open system.  But if
>we study the rate of overall energy transfer, and compare that with the rate
>of transfer due to matter entering and leaving, then for all practical
>purposes the earth is currently a closed system, because the effect on the
>overall energy balance is negligible.  If we take the upper reaches of the
>atmosphere as the system boundary, then we can also say that the system
>has a fixed boundary.  In effect, we are really saying that a balloon is a
>model of the earth - for the purpose of thermodynamic analyses.

	This is just plain wrong; see above.  You are saying that since there
is no direct mass exchange on a large scale, ie, hail of meteors or atmosphere
boiling off, the earth is a closed system.  This is WRONG.  The energy flux
from the sun still counts as an energy input from outside, so the earth is not
a closed system; see the above example with the photocells.

	It seems that most of this FAQ is based on a careful misinter-
pretation of outdated texts.  (I could make allusions to creationism here,
but I'm too nice a person :).  While most of it is essentially correct, there
is a careful thread of illogical through here, hidden behind the truthful 
parts and carefully disguised by sophistry.  Without careful reading, one
could almost accept the arguements and definitions given here.  
	It is rather unfortunate that I am familiar with the opinions of 
the author of the article, because it then becomes too easy to assign 
motives behind the errors I found.  The base conclusion that is aimed at 
in the article is 'the earth is a closed system (therefore evolution violates 
thermodynamics)'.  On the other hand, I sincerely hope that this is a case 
of either misunderstanind or bad science, and not a deliberate attempt to
deceive.  I simply must wonder which came first; the conclusion or the bad
science.
	
-----------------------------------------------------------------------------
Benjamin T. Dehner          Department of Physics and Astronomy 
btd@iastate.edu             Iowa State University 
                            Ames, IA 50011

"And if I seem to inconclusive, it's just that it's all so elsusive" 
-- Kansas