Just a follow up to Richard's comment:
>Anyway, it will serve as a timely example of how a decrease in entropy does
>*not* require a "code-driven energy-conversion system". There is obviously
>no such system in the Sun.
This is quite true. But we certainly don't have to consider anything as
esoteric as the solar interior for such a counterexample. Such examples
occur at the *simplest* level of all thermodynamic processes. One of the
most trivial thermodynamic processes imaginable is the flow of heat from
a region at higher temperature to a region at a lower temperature. In
such a process the higher temperature region has its entropy *decrease*
with time as the entropy of the lower temperature region increases by an
amount which is greater than the decrease that occurs in the high
temperature region. There is *no* need for any "code-driven energy-
conversion system" for such an entropy decrease to take place in the
region of high temperature. This process does *not* "overcome" the 2nd
law. In fact, it is one of the simplest imaginable manifestations of
that law operating as normally and simply as possible. The simple fact
is that the 2nd law does not require, nor even address the issue of, the
existence of such an "energy conversion system". To append such a
requirement to the second law *is* inventing one's own idiosyncratic
(and incorrect) formulation of thermodynamics. Also, it is a simple
demonstrable fact that many instances of local entropy decrease are *not*
accomplished via such an "energy conversion system"; many other instances
of local entropy decrease *are* accomplished with such a system that
itself spontaneously forms in situ; and some instances *do* require a
previously constructed such system. Sometimes such a "energy conversion
system" is used for the production of a local *increase* in entropy.
Whether or not such a system is needed for a given process or not is a
function of the particular process at hand. It is *not* a concern of the
2nd law.
Whether or not a given system will spontaneously form varying degrees of
complexity with or without an externally previously built special
apparatus is simply *not relevant* to the 2nd law. No matter what
apparatus is or is not needed to enable a given process, the 2nd law is
obeyed as usual, and isn't violated nor "overcome". The formation of
complexity is *not* necessarily thermodynamically "uphill". Sometimes
it is "downhill" (such as in the spontaneous formation of Prigogine's
"dissipative structures" in far-from-equilibrium systems whose
disequilibrium is maintained via externally imposed gradients across the
system of one or more intensive thermodynamic potentials). All
naturally occuring processes are, by the very operation of the 2nd law,
thermodynamically "downhill". But to see that it really is "downhill"
one has to consider all the relevant interactions associated with the
process, because *any* such process will involve some entropy-increasing
aspects and other entropy-decreasing aspects. The net generation of
thermodynamic entropy in a physical process (being related to the
relevant microscopic degrees of freedom in the process) is quite
unrelated to whether or not various patterns of complexity or order do or
do not form at the macroscopic level. I do not know how to make this any
more plain.
Although I hesitate to do so, I will risk using a gravitational analogy
(initially used earlier by DNAunion to illustrate his idea of the 2nd
law being "overcome"). Consider any solid object that I drop out of my
hand to the floor, or consider any object significantly more dense than
1 kg/L being dropped into a swimming pool. Because of the interaction
of the mass of the body, the mass of the surrounding air or water, and
the gravitational field of the earth, as the object falls, the fluid (air
or water) surrounding it is displaced out of the way to make room for the
body, since the fluid and the object it is immersed in do not occupy the
same space at the same time. As there is a net displacement of the
object downward, there is a net associated motion *upward* of the
displaced fluid. If we focussed our attention on the displaced fluid we
would see its gravitational potential energy *increase*. If we focussed
our attention on the the body we would see its potential energy decrease.
The sum of the potential energies of the surrounding fluid and the object
decreases. Gravity is *not* overcome by this process of rising fluid.
If, OTOH, the body was released at the bottom of the swimming pool, and
it had a density less than that of the water, or if a helium balloon was
released from my hand in air, then the object would rise and the
displaced surrounding fluid would fall. In this case gravity is *not*
overcome *either*. It's just that in this latter case, the increase in
the gravitational potential energy of the object (balloon in the air or
block of wood in the pool) is less than the decrease in the
gravitational potential energy of the surrounding fluid medium. In
*both* cases the total gravitational potential energy of the object and
the displaced fluid decreases as the object either sinks or rises--as the
case may be.
So it is with the 2nd law. *Any* thermodynamic process will involve
some subsystems whose entropy decreases, and others, whose entropy
increases. When we include the sum of the entropy changes of all the
parts which are interacting as part of the process, we find that the
net total entropy change is positive with time. In *no* such case is the
2nd law ever "overcome" or violated.
>I think that, if we strip away the misleading talk of "code-driven
>energy-conversion systems" and processes "overcoming" the Second Law, what
>the objectors are really asking is this: what is the process by which
>energy (e.g. from the Sun) drives a decrease in entropy in pre-biotic
>structures?
I certainly don't pretend to know in detail how biogenesis came about.
But if it was via some fully natural abiogenetic process, it will be
found that the 2nd law was *not* overcome nor violated in that process.
If the entropy of some pre-biotic structures happened to have decreased,
then the entropy of some other relevant subsystems of the process
increased by a greater amount. This is not conceptually any different
than any other naturally occurring process regarding issues of the 2nd
law.
It *is* an open question, I believe, as to whether or not a fully
naturalistic scenario for the development of life exists or not. But the
issue will be decided on other grounds than on appeals to the 2nd law.
I personally, can't imagine how life could have gotten started via a
fully naturalistic scenario. But this might just be a lack of
imagination on my part. I'm undecided about such a question of
abiogenesis. But I am confident that if it abiogenesis occurred in a
fully natural manner, there is nothing of the 2nd law for it to have
"overcome". Not every process that is found to be effectively impossible
(because the probability of its occurance is much too low to ever have
happened anywhere in the causally connected region of our universe) is
necessarily related in any way to an *overcoming* of the 2nd law. It
can be probabilistically impossible for other reasons (e.g. reasons
pertaining to missing detailed dynamical pathways, low tunneling
probabilities, etc.). Since no one yet has a convincing detailed
account of abiogenesis, the jury is still out on whether it could have
happened in a fully naturalistic manner. It is *quite* premature to
be making impossibility verdicts based on bogus 2nd law arguments.
>I think the short answer to the question is "through chemical reactions
>(and possibly other physical processes) which require heat." Without heat, the
>chemical reactions could not take place. Of course, this doesn't just apply
>to prebiotic structures. There are all sorts of inorganic structures whose
>entropy decrease is driven (directly or indirectly) by heat. Commonly cited
>examples are snowflakes, crystals and tornados. But they can also simply be
>molecules undergoing chemical reactions to form lower-entropy compounds.
True.
>If these can experience decreases in entropy without a "code-driven
>energy-conversion system", then obviously pre-biotic structures
>can do so too.
I disagree here. The above is a non sequiter. It is not obvious *at
all* what is needed for the appropriate structures to form. But it is
true that *if* it should be the case that some foreignly implanted
"code-driven energy-conversion system" is necessary to form the necessary
structures, then that necessity is not imposed by the 2nd law, and any
appeal to it to argue for such a structure is invalid.
>I hope David will correct me if I've got anything wrong here. Sorry, David,
>but I hope you won't consider it a waste of time to educate me. ;-)
Here are my comments. I really did not intend to take up nearly as much
time as I ended up spending on this post. I hope that time was not
wasted (w.r.t. list members *other* than Richard who seems to value
my occasional tomes).
David Bowman
David_Bowman@georgetowncollege.edu
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