Originally published in the July 1999 issue of Humanist News and Views by the Humanist Association of Minnesota, this article was written by Bob Kern.

Last month's article by Richard Dean observed that Duane Gish again brought up the Second Law of Thermodynamics in his argument for Creationism. It's not clear how he used it this time, but in the past Creationists have claimed that evolution is a violation of this law of physics.

I studied thermodynamics when I was an undergraduate engineering student. When I first saw someone argue that evolution violates this law I thought to myself that they would really be embarrassed when they found out that they had totally misinterpreted the law. Silly me. About twenty-five years have gone by and they are still making this bad argument.

Unfortunately, relatively few people have studied thermodynamics and so most people don't understand what is wrong with the argument. I'd like to take a stab at explaining it to the humanist readership.

The Second Law says that in a closed system, entropy is always increasing. I will talk about "disorder" rather than the scientific quantity "entropy" since disorder is probably more meaningful to people and entropy does imply a certain kind of disorder.

The argument made by the creationist is that the Second Law says that the universe is becoming increasingly disordered, but evolution represents a steady increase in "orderedness," so evolution violates the law. Bearing in mind that the word "ordered" is a bit sloppy compared to the actual definition used by physicists, the very simple rebuttal is this: The Second Law only says the universe as a whole (or any part of it that doesn't have energy flowing in or out) has increasing disorder. It is extremely obvious to physicists that there can be increasing order in one place if it makes use of a greater decrease in order someplace else.

In the case of evolution, the sun is losing "order" at a staggering rate as it radiates energy out into space and onto the earth. The process of evolution makes use of a tiny amount of the "order" lost by the sun to produce increasingly complex life forms in a thin layer on the surface of our small planet. The Second Law does reliably tell us that without the sun or some suitable replacement source of energy, evolution could not take place, and I'm sure there would be little disagreement among scientists about that.

The absurdity of the Creationist position is even clearer if we consider the context in which the Second Law is ordinarily used. The First Law of Thermodynamics says that energy is conserved, meaning that no process can create or destroy energy. If we have a boulder at 500 degrees and an equal sized one at 0 degrees and put them together in a perfectly insulated chamber, they will both wind up with a temperature of 250 degrees. Heat being a form of energy, the energy one gains will equal the energy the other loses. However, when there was a big temperature difference, it would have been possible to use this energy to run a steam engine by having the cold boulder cool water and the hot boulder boil it. This engine could create useful work, but it could not run once the boulders have reached the same temperature. The second law of thermodynamics captures the idea that the ability to do useful work declines over time even though the total energy doesn't.