The ergodic hypothesis is a fundamental concept in statistical mechanics, first proposed by Boltzmann. Roughly put, it says that time and ensemble averages are the same. It is this hypothesis that gives raison d'etre for equilibrium statistical mechanics.

The hypothesis is difficult to prove. Most proofs are highly abstract and far removed from physics. Starting from the time average side seldom pursued, I have been able to formulate this problem simply and have found the physical basis for the hypothesis.

(Based on an article appearing in Phys Rev Lett 17 Dec 01)