A PRIMER ON ENTROPY (THE SECOND LAW OF THERMODYNAMICS)

A PRIMER ON ENTROPY (THE SECOND LAW OF THERMODYNAMICS)

© 2009, by John Tors. All Rights Reserved.

The significance of the Second Law of Thermodynamics (the Law of Entropy) for the question of the origin of life is profound, yet it is not well understood by the general public as it is a field of specialized study in engineering and physics; it is not something well taught in high schools.

First, to present this law in simple terms, it simply enunciates the fact that all natural processes tend towards maximizing disorder (“entropy”), i.e. things tend to get “messed up”.  Organized things tend to fall apart, which should be intuitively obvious to everyone.  A house, left alone long enough, will eventually decay into a pile of bricks and rubble, whereas a pile of bricks and rubble, left alone, will never spontaneously self-organize into a house, no matter how much time is given.

In more technical terms, according to the Second Law of Thermodynamics (i.e. the Law of Entropy), all natural reactions are governed by the following relationship:

ΔG = ΔH – T*(ΔS)

where:

Δ    = change (“delta”)
ΔG = change in Gibbs free energy
ΔH = change in enthalpy
ΔS = change in entropy
T   = temperature in Kelvins

Chemical reactions tend towards lower enthalpy and higher entropy.  Thus if ΔH is negative and ΔS is positive, the reaction will readily proceed spontaneously. If ΔH is positive and ΔS is negative, the reaction will not proceed spontaneously.

If ΔH is negative and ΔS is also negative, the reaction may proceed, if the enthalpy effect outweighs the entropy effect.  What this means is that reactions with a decrease in entropy do happen, but these only yield simple order, of the sort known as symmetrical redundancy (e.g. crystals, with simple, repeating patterns).  Reactions to yield products of specified complexity (e.g. a house, a cell) do not occur spontaneously.  This is not just conjecture; it is a law of science.

The significance of this for ideas of organic evolution should be obvious.  The theory of evolution begins with simple chemicals spontaneously self-assembling into extremely complex organic molecules.  This essential step, though, is impossible, according to the Second Law of Thermodynamics.

What do evolutionists do in the face of this problem?  They claim that the Second Law applies only to closed systems and so is not relevant here.  Some people even suggest that the system with which we are concerned is the entire universe, and so we can have this local decrease of entropy, as long as entropy is increasing at a faster rate elsewhere.  Others suggest that the energy input to the earth from the sun overrides the effects of the Second Law.

Both of these claims betray a fundamental lack of understanding of the Second Law of Thermodynamics.  First, if it were true that we can experience local decreases in entropy as long as entropy is increasing at a faster rate elsewhere in the universe, we should indeed see houses and cars spontaneously self-assembling.  Surely the increased entropy from exploding stars elsewhere in the universe should be more than enough to allow for a few houses and cars to build themselves!

Of course, it is intuitively obvious that this is absurd. But why does this not happen?  People who make such claims don’t even seem to understand what is meant by a system.  A system is the reactants and products of the process in question.  Consider the combustion of wood, for example.  In this process, the increased entropy of the resultant gases and ashes is directly linked with the energy released by the burning of the wood.  Or when sodium and chlorine react to form NaCl, the slight decrease in entropy is driven by the exothermic nature of the reaction itself.  In neither case is there any link to putative increases or decreases in entropy or enthalpy at some disconnected location elsewhere in the universe.

So, while it is true that the overall entropy of the universe continues to increase, the Second Law doesn’t hold merely for the universe as a whole, but for every individual system, open or closed, and each reaction is driven by the enthalpy/entropy effects of that reaction and not by something happening elsewhere.

What, then, is meant by an open or closed system, and how is this significant?  A closed system, for which the Second Law is enunciated, is simply one that has no energy passing either way past the boundary of the system (i.e. energy taken from the system, or introduced to the system by external sources, as opposed to the reactants and products themselves).  If a system is open, as most systems on earth are, we have to account for the energy that passes past the boundary.  However, this is not difficult as it is a well understood phenomenon in thermodynamics.  If free energy is introduced into a system, the rate of entropy increase will speed up.  If it is removed from a system, the rate of entropy increase will slow down, but it will not reverse (except, of course, in those reactions, such as the freezing of water, that yield simple, redundant order due to favourable enthalpy conditions).

The upshot of this is that the suggestion that the input of free energy from the sun to the earth can overcome the Second Law to allow for the spontaneous formation of complex organic molecules is nonsense.  Inputting free energy into a system simply speeds up the rate of entropy increase.  All other things being equal, shining the sun on a house causes it to decay into a pile of bricks and rubble sooner; it does not cause a pile of bricks and rubble to assemble spontaneously into a house.

Can energy be used to overcome the Second Law?  Yes, indeed, but only if it is directed energy, not free energy.  In other words, what is needed is some sort of mechanism to convert the energy into useful work, and some sort of plan to direct that useful work.  The sun’s energy can actually be used to turn a pile of bricks and rubble into a house, through the following procedure: the chloroplasts of plants convert the sun’s energy into stored chemical energy (carbohydrates).  These carbohydrates are consumed by a person and burned by his body to provide him with energy which he uses to pick up the bricks and rubble and arrange them according to the plans in his mind to make a house.  Two energy conversion mechanisms are used, the chloroplast and the human body.  Of course, neither of these nor any other, putative, energy conversion mechanism is available before the existence of plants and people to account for the spontaneous formation of the organic molecules needed to begin the process of organic evolution.  Furthermore, in addition to the energy conversion mechanisms, two plans are needed, the fixed one coded into the chloroplast, and the flexible one in the human brain.

Or consider what happens when gasoline is ignited.  Of course, this is a highly exothermic reaction, i.e. it releases a large amount of free energy in a very brief period of time.  If gasoline is ignited in the cylinders of an internal combustion engine, it is used to move a car, which can then do useful work.  But without the energy conversion mechanism (i.e. the internal combustion engine), igniting gasoline will not lead to useful work but will simply result in an explosion which will cause some rather major entropy increases around it.  (If it is done inside a house, that house will become a pile of brick and rubble almost instantly, much more quickly than it would if left to its own devices.)

In sum, it should now be obvious that the Second Law of Thermodynamics does indeed pose an insurmountable obstacle to the spontaneous formation of the highly complex organic molecules which would be necessary even to begin a process of evolution.  It should also now be obvious that the attempts by evolutionists to explain away the problem by appealing to the fact that the earth is an open system and by appealing to the sun’s energy are complete failures.  Such attempts may be understandable when made by biologists, who don’t necessarily know any more about thermodynamics than the average accountant or pastry chef, but they are inexcusable when made by physicists or engineers.

Comments: 1

  1. Tom S. says:

    Thank you for the concise summary of entropy as it relates to evolutionary theories!

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