Philip Kitcher

Thermodynamics, which began as the study of the movement of heat, is now the branch of physics that studies energy transfers in any context. From the study of thermodynamics comes the concept of entropy, the tendency of order to fall into chaos. The second law of thermodynamics states that any "system" by itself tends to become disordered, that is, less complex. Evolution, however, seems to cause things to become more complex. Hence it appears that evolution violates the second law of thermodynamics.

In this selection, Philip Kitcher explains the apparent contradiction between thermodynamics and evolution, and shows why this appearance of contradiction is mistaken. The second law of thermodynamics is an ideal statement about "closed" systems, and life on earth is not a closed system. Sunlight provides abundant available energy for reversing entropy in...