Origin of life, thermodynamics 2

Paul Brown (pdb@novell.uidaho.edu)
Sat, 29 Mar 1997 10:29:51 PST8PDT

This is the second of what I hope will be a series stating why I think
thermodynamics presents a problem for the origin of life. Again, I
would appreciate comments. My training was not specialized in
thermodynamics, so comments and criticisms will help to clarify
thoughts on this subject.

An open system.
A standard argument toward those that use the 2nd law as an argument
against evolution is that the earth is an open system. True, and
there must be an open system for life to exist. The growth of a
living system is dependent upon the flow of mass and energy through
the system. But for the origin of life, simply making an appeal to an
open system is not enough. Let's consider a certain type of open
system where this can be seen.

Energy can be thought of in a couple
of different ways. One property might be considered the energy level
(in our case measured as T, which is a measure of the kinetic motion
of molecules), while the other might be considered the energy flow
(heat, measured in joules or calories). Temperature as an energy
level can be illustrated by imagining a thimble full of water at 98
oC vs a pot of water at 98 oC. The energy level as
measured by molecular motion of a microsite would be the same in both
cases - they have the same temperature. Additionally, there would be
no heat transfer between the pot and the thimble since they have the
same energy level. However, the total amount of energy as measured
by heat flow to a body at lower temperature would be vastly
different, and could be readily verified in non-scientific terms if
one versus the other happened to spill on you.

When heat is transferred to a system from the surroundings, the energy is
manifested in an increase in molecular motion; the temperature will
rise. This kind of open system can be illustrated by placing our
pot of water on a stove with the burner on. The problem of simply
making an appeal to our open system is clear. We can add all the
energy we want until the water boils and turns to steam, but we will
only succeed in increasing the entropy of the system, not decreasing
it as the order of life requires. This is a different way of
stating the 3rd law, which is, as the temperature increases, entropy
increases. The 3rd law, in effect, tells us that as far as entropy
is concerned, an open system where a transfer of thermal energy is
involved, may not help the problem, but can actually exacerbate it.
This demonstrates that we need to consider additional factors beside
that of an open system.

Regards, Paul
Paul D. Brown
Dept of PSES, Ag Sci 242
University of Idaho
Moscow, ID 83844
Phone: 1 (208) 885-7427 or 885-7505
e-mail: pdb@uidaho.edu