Ehrenfest and Ehrenfest-Afanassjewa on the Ergodic Hypothesis

Ehrenfest and Ehrenfest-Afanassjewa’s seminal article on statistical mechanics highlighted a crucial assumption at the heart of Boltzmann’s statistical mechanics: the ergodic hypothesis. The importance of this article for transmitting the problems related with the ergodic hypothesis has been widely recognized, but Ehrenfest and Ehrenfest-Afanassjewa have been strongly criticized for not having provided a fair account of Boltzmann’s statistical mechanics. In this chapter, I outline Ehrenfest and Ehrenfest-Afanassjewa’s treatment of the ergodic hypothesis and I evaluate the role of this discussion for the development of the ergodic theory in the 20th century. I will conclude that the major contribution of Ehrenfest and Ehrenfest-Afanassjewa comes precisely from what has been regarded by some historians of science as historical inaccuracies of the article.