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The 2nd of Thermodynamics and Evolution

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1/3/2014 4:19:25 PM
Posted: 4 years ago
It is often claimed (most recently by Installgentoo) that evolution either violates the second law of thermodynamics because it supposedly reduces the amount of entropy, or alternatively that because of the second law of thermodynamics, evolution results in randomness. However, these claims are fundamentally flawed based on a lack of understanding of thermodynamics and how natural selection works.

To begin, only entropy as a whole can never decrease. What this means is that only in an isolated system can the entropy never decrease. However, the Earth is not an isolated system. For example, the sun shines on the Earth and heat radiates off. Because of this flow of energy, local systems can have their entropy decreased without having the entire system's as a whole decrease. Further, entropy is not the same as disorder, and order can sometimes increase as entropy increases.

Further, no physical law prevents evolution. The only processes necessary for evolution to occur are reproduction, heritable variation, and selection. All of these are seen to happen all the time, so, obviously, no physical laws are preventing them. In fact, connections between evolution and entropy have been studied in depth, and never to the detriment of evolution. Several scientists have proposed that evolution and the origin of life is driven by entropy. Some see the information content of organisms subject to diversification according to the second law, so organisms diversify to fill empty niches much as a gas expands to fill an empty container. Others propose that highly ordered complex systems emerge and evolve to dissipate energy (and increase overall entropy) more efficiently.

In that way, evolution does not result in complete randomness either. The genetic variation that occurs in a population because of mutation is random, but selection acts on that variation in a very non-random way; genetic variants that aid survival and reproduction are much more likely to become common than variants that don't. Natural selection is not random.

Here is a passage from an article from TalkOrigins that explains this point more scientifically:

"As with any other irreversible change, there will be an increase in over-all entropy. This means that the entropy increase of the water going over the wheel is greater than the entropy decrease of water pumped up to the higher elevation.

This will be confirmed mathematically in the following paragraphs. will stand for the Greek letter gamma, representing unit weight in pounds per cubic foot. An increase in the value of a parameter will be represented by .
Let: = unit weight of water, lbs./cubic foot
h = height of reservoir above downstream side, feet
h = potential energy of water in reservoir
h = additional height above reservoir (to which water is pumped)
h + h = height to which water is pumped, feet above downstream side
w = work of pumping water to higher elevation
q = heat loss due to pump friction and downstream agitation
f = fraction of water pumped to elevation h + h

From the flow equation, energy in = energy out: h = q + w

Where: h = the total energy expended by the water
in falling from height h.
q = the energy wasted as heat of splashing
w = work expended in pumping the water to a higher elevation

q = TS (from equation 1)
w = f(h + h)

The total energy available, h, is divided into pump work, f(h + h), and energy lost, TS: h = TS + f(h + h)

Rearranging: TS = h - f(h + h) (8)

When no pump work is done, then: TS' = h (9)

Combining equations (8) and (9), we get: S' - S = f(h + h)/T (10)

In the case where the water falls freely without turning the water wheel or operating the pump: let q'= heat of splashing
q'= TS'
where S' is the entropy increase on free fall

Equation (10) shows that S' is larger than S, and that the entropy increase due to pump friction and downstream agitation is "backed up" by the even larger entropy increase that takes place when water falls freely. Equation (10) also shows that the lower the value of S, the more efficient the pump, and the greater the value of f, the fraction of water pumped.

Creationists assume that a change characterized by a decrease in entropy can not occur under any circumstances. In fact, spontaneous entropy decreases can, and do, occur all the time, providing sufficient energy is available. The fact that the water wheel and pump are man-built contraptions has no bearing on the case: thermodynamics does not concern itself with the detailed description of a system; it deals only with the relationship between initial and final states of a given system (in this case, the water wheel and pump).

A favorite argument of creationists is that the probability of evolution occurring is about the same as the probability that a tornado blowing through a junkyard could form an airplane. They base this argument on their belief that changes in living things have a very low probability and could not occur without "intelligent design" which overcomes the laws of thermodynamics. This represents a fundamental contradiction in which (they say) evolution is inconsistent with thermodynamics because thermodynamics doesn't permit order to spontaneously arise from disorder, but creationism (in the guise of intelligent design) doesn't have to be consistent with the laws of thermodynamics."[1]

(Note that all "S"s are supposed to be preceded by deltas, meaning change in).

Overall, it is easy to see how evolution does not violate the second law of thermodynamics in the broadest sense, and any violation that may be found is based on a misconception of how thermodynamics works. Further, because evolution is orderly and very succinctly chooses superior alleles over inferior alleles, evolution is not random.


We are not dead. We have never lived. - Varg Vikernes, "Det som en gang var"
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1/3/2014 5:02:37 PM
Posted: 4 years ago
Good stuff.

Below is a link to some pictures of an almost perfect circle of ice that formed in a river recently

For some reason many people think that entropy means that everything is always becoming more disorderly at all times. As you point that is not true.

If that were true this disc of ice would never ever form.