Is the mean free path the mean of a distribution?

Abstract

We bring attention to the fact that Maxwell's mean free path for a dilute hard-sphere gas in thermal equilibrium, $(\sqrt{2}\sigma n{)}^{-1}$, which is ordinarily obtained by multiplying the average speed by the average time between collisions, is also the statistical mean of the distribution of free path lengths in such a gas.

19 pages, 5 figures; added discussion of results for hard-sphere gas; improvements to text to increase clarity; published version