Regarding DNAunion's comments about his "Teeter-totter Analogy":
It seems that you use the terms "overcome", "downhill", & "uphill" in a
way that has led to some unnecessary confusion. Apparently, you want to
use the terms to refer to particular *parts* of composite processes and
*parts* of composite interacting systems where you imagine excising the
said parts from of the interacting system at hand and imagine such parts
as a separate independent system which is no longer in interaction with
the rest of the interacting process. And then you imagine the behavior
of said parts to continue to be the same as it was when the part
with its partial contribution to the composite process was acting in full
interaction with the rest of the previous integrated system. If this
continued behavior when the part and partial process is isolated becomes
non-spontaneous and thermodynamically unfavorable under the new
disconnected conditions, you dub it as "uphill" and say that the full
process of the integrated system is "overcoming" the 2nd law as this
subsystem's partial process is driven "uphill". Unfortunately, the
spontaneous behavior of such an excised and isolated piece of the
interacting system has little, if anything, to do with its behavior as
part of the integrated system. *Of course* changing the system will
change the observed behavior. But I would not want to call the operation
of the integrated interacting system as "overcoming" the 2nd law, nor
especially, would I want to label the operation of the full process as
"uphill". The behavior of the isolated subsystem doesn't tell us
anything about the behavior of the integrated interacting system, and is
irrelevant to it. Each system with its own particular internal
connections to its parts and to its surroundings and their conditions has
its *own* kind of spontaneous "downhill" behavior.
The way I was using the terms was in reference to the *actual interacting
system* at hand since it is the behavior of *that* system that is
relevant, by definition or by tautology (i.e. the behavior of the
interacting system is what is relevant to the interacting system). When
we focus on the fully integrated system at hand we see that any process
that happens in nature is thermodynamically favorable and is "downhill",
and its operation is just another example of the 2nd law working
normally. It *doesn't matter* if the interacting system is a complicated
biological system or a cup of tea cooling off in a cooler room (as far as
any potential appeal to the 2nd law is concerned).
If you take the hot tea out of the cooler room and isolate it in a sealed
super-insulated dewar it behaves differently than when it is in strong
thermal contact with the air of the cold room. When it is in contact
with the cold air of the room the tea's entropy and temperature quickly
falls as it cools down to the ambient temperature, and some of this
cooling is via evaporation of water from the tea/air interface at the
tea's top surface. This changes the concentration of the tea as well as
further decreasing the entropy of the remaining tea. When the tea is
isolated in the dewar from the room's cold air, its entropy, mass,
temperature, internal energy, concentration, etc. remain fixed. I would
say that the cooling tea in the cooler room is an example of a
thermodynamically "downhill" process even though the tea's entropy
decreases. I would not say that the tea's "tendency to disorder" is
"overcome" by the process. The tea doesn't even *have* any specifically
defined tendency at all until the rest of the system with which it
interacts is properly specified. Its tendency is not the same in a
dewar as in a cold room, and neither of these is its tendency when it is
in a room that is much hotter than the tea, with air that is
supersaturated with humidity. In the latter case the tea's entropy and
temperature and water concentration *increases*.
Similarly, with biological systems. If you take parts of them out of
the system, they behave differently in a different environment than when
they are left in the integrated system. The way they behave in the
integrated system is "downhill" as the 2nd law constrains the system's
overall behavior. The *different* way they behave when isolated from
the other biological structures is also "downhill" since the different
environmental conditions redefine just what it means to *be* "downhill"
in the different context. In neither case is the 2nd law "overcome".
Back to the teeter-totter analogy. What it *means* to be "downhill" in
a problem that is driven by gravitational forces, is to move in such a
manner as to decrease the total gravitational potential energy of the
system *no matter* how many teeter-totters have frozen confections on
them that are interactively automatically dumped from one basket to
another. Whatever the system does *is* "downhill". Certainly, if
various subparts of the system are isolated from the interacting system
then their behavior under the influence of the Earth's gravity is
expected to change according to the circumstances they find themselves
in. But however they end up behaving, in any of those various
circumstances, it is in a way that reduces the total gravitational
potential energy of the subsystem at hand and is thus "downhill"
behavior. In one case a particular end of a teeter-board may go up, and
under some changed circumstances it may go down. But whatever it does,
the system of which it is a part will decrease its total gravitational
potential energy, and the system's operation will be "downhill" in its
gravitational potential energy.
Back to thermodynamics. *Whichever* way a thermodynamic system
spontaneously behaves, it is found to be thermodynamically "downhill"
in that its behavior increases the net total entropy of all the
relevant interacting parts of the system (where the surroundings are
to also count as part of the system if they are in interaction with
the rest of the system in any significant way). Just because a
composite process involves parts of the system decreasing in entropy and
other parts coupled to them increasing in entropy is no indication of the
second law being overcome, since any given part per se doesn't even
*have* a prior "tendency" apart from a particular specification of how it
is to be in interaction with other parts of the system & surroundings.
It is certainly true that biological processes *are* multiple orders of
magnitude more complicated that a process as cooling tea, but as far
as the relevance of the 2nd law is concerned, *it doesn't matter*. In
either case, when a process happens, *that's* it tendency, in that
particular circumstance. When it doesn't happen in some other
circumstance, then *that's* it tendency in the modified circumstance.
David Bowman
David_Bowman@georgetowncollege.edu
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