ultra@cmcl2.UUCP (11/20/84)
From SOR Pamphlet #2: > Some may wonder about the implications of the second law of ther- > modynamics. Are there not instances of disorder being transformed > into order? For example, a seed growing into a tree or a pile of > bricks being built into a house represent examples of an increase in > order and complexity. What is happening here? > In every instance when order increases, several prerequisites > must be met. First, the system must be open to available energy. > Evolution meets this requirement, since it is open to energy from the > sun. That, however, is a necessary but not sufficient condition. The > transformation to a higher energy state must be accompanied by an en- > ergy converting mechanism using a preset plan. Bricks only become a > house as an intelligent human discriminantly orders them according to > the blueprints. The seed grows into a tree as it follows the plan > stored in its genetic code, the DNA. Evolution, however, depends upon > chance chemical reactions and random mutations, and has no plan forc- > ing its direction upwards towards greater complexity. Leaving aside the problem of defining `preset plan' in a rigorous way, please explain why, by your reasoning, the formation of snowflakes doesn't violate the second law of thermodynamics. Isaac Dimitrovsky
rob@osiris.UUCP (Robert St. Amant) (05/16/85)
Someone used the Second Law of Thermodynamics as an argument for creationism. In a philosophy course I attended here at Hopkins, the idea was presented that the Second Law isn't a law, but an observation. Entropy may follow a jagged sort of curve, increasing sometimes, decreasing other times (on a _very_ large time scale.) Any comments from those in the know? I don't know that much about physics. Rob St. Amant
ethan@utastro.UUCP (Ethan Vishniac) (05/20/85)
> Someone used the Second Law of Thermodynamics as an argument for creationism. > In a philosophy course I attended here at Hopkins, the idea was presented > that the Second Law isn't a law, but an observation. Entropy may follow a > jagged sort of curve, increasing sometimes, decreasing other times (on a > _very_ large time scale.) > > Any comments from those in the know? I don't know that much about physics. > > Rob St. Amant You've got it right. The second law is a statement about probable states. If a system has enough time to reach equilibrium then the chances are overwhelming that it will be in certain states, and not in others. The statement that entropy shouldn't decrease is a probabilistic one, not an absolute statement. Given enough time a system in equilibrium will sample *all* accessible states. Some large number of them will appear indistinguishable on a macroscopic scale. This means that the odds will favor a system occupying this macroscopic state at any one time. It is not a guarantee. A good example is the distribution of air in a room. There are many many microscopic states which correspond to an even distribution of air. There are very few that correspond to "all the air in the upper left corner of the room". Therefore, if we check the air in a room we expect to find it evenly distributed. "Don't argue with a fool. Ethan Vishniac Borrow his money." {charm,ut-sally,ut-ngp,noao}!utastro!ethan Department of Astronomy University of Texas