Re: Second law + evolution


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Posted by Scott Ellis (65.193.194.199) on June 11, 2002 at 11:29:15:

In Reply to: Second law + evolution posted by Davis Landstrom on June 11, 2002 at 06:39:24:

Davis,
Of course you are right, that in the largest sense, Life and evolution do not contradict the 2nd Law. In the closed system of the Universe, entropy continues to increase despite the local decreases represented by living things. The universal increase more than offsets the local decreases, so the 2nd Law holds. So I retract my original statement to the contrary. (FYI: neither Stephan Wolfram nor I are creationists by any stretch!)

BUT... (you knew that was coming!)
I stand my statement that insofar as the sun is a perpetual motion machine, then so is Life, which is intimately coupled with the sun's energy/entropy flow. And I think it is important to realize that the whole process is started and constantly driven by the action of gravity.

For those that would argue that the sun is not a PMM, since it only burns for about 10 billion years, of course you are technically right. To my mind, though, what constitutes a PMM has more to do with practical human purposes than exact definitions. Something that produces energy for 10 billion years is a PMM as far as human beings are concerned...

Finally, Davis, I want to ask you a question. Acknowledging that Life does not violate the 2nd Law in the broadest sense, isn't it still peculiar that Life results in such persistent local decreases in entropy? Are there other examples of natural systems that cause perpetually self-sustaining local decreases like this?

Order can and does arise spontaneously during certain natural transfers of energy. For example, ice crystals forming on a window pane:

http://www.student.oulu.fi/~ktikkane/eJARJ.htm

But as far as I know, none of these naturally occurring local decreases are self-sustaining in the same way that Life is.

You mentioned the example of a refrigerator, but to my mind, a refrigerator is anything but a natural occurrence. As a product of the human mind, refrigerators seem like natural extensions of our own low entropy, like all the other order that we create and maintain on this planet.

Best,
Scott


: As an evolutionary biologist by profession, I feel that I must clear up one thing Scott.
: The process of evolution is not a violation of the second law of thermodynamics at all.
: The second law of thermodynamics deals with the model concept of a closed system at time (lets say) 1, possesing a quantity of energy in isolation made to do work, the entropy of that system will increase to the point where the initial quantity of energy will be unable to perform the same work at time (lets say) 8.
: This is because of an increase in 'dissorder' in the system, but more specifically because that system is irreversable, despight the fact that it is closed and isolated, it is still coupled with time and the universe, hence the closed system (at time 8) could never restore (regenerate) its self to the same entropic state that it was at time 1.
: The initial and final states of the system are different entropically, hence the Second law of thermodynamics joke: 'You can never break even'
: HOWEVER, if we were to take this system and energetically couple it to another system (make it open), then we could use the output of the coupled energy source to create a local reduction in entropy by performing work on the system, the entropy in the system that was orrigionally colsed will decrease and will remain decreased (depending on the amount of work being done on that system by the coupled source system) HOWEVER this entropy reduction comes at a cost, there HAS to be a pay off of entropy somewhere along the line, that pay off is either to the systems evironment (depending on the degree of 'openness') or it occures in what ever process is driving the coupled source system.

: I shall give two examples to illustrate the above:

: 1.The evolution of life - some evolutionary lineages since the precambrian have indeed increased in complexity. If we take a life form to be a system, we immediately see that it is by no means isolated, i both contraversial and orthadox)
: If he is claiming that evolution is a violation of the second law of thermodynamics then I strongly urge you to take his claims with scepticism as it sounds to me like he is basing his argument on this flawed basis.
: One more thing, in my profession I frequently hear the claim that evolution violates the second law of thermodynamics, however not from evolutionists, but from creationists and we all know about their pseudoscience!




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