Marian Smoluchowski

Marian Smoluchowski was born in 1872 near Vienna and became one of the founders of the modern theory of stochastic processes. Working at the universities of Lwów and Kraków, he developed, independently of Einstein and by a more directly physical method, a quantitative theory of Brownian motion in 1906.

Smoluchowski's central conviction was that thermal fluctuations are real and observable, and he pursued their consequences across many phenomena. He worked out the kinetics of coagulation in colloids and formulated the Smoluchowski equation describing the evolution of probability under combined drift and diffusion.

In 1908 he explained critical opalescence — the milky scattering of light by a fluid near its critical point — as the optical signature of density fluctuations grown large enough to scatter light, a result Einstein refined in 1910. Together with his Brownian-motion work, this provided some of the most compelling evidence of the era for the molecular constitution of matter.

Smoluchowski's career was cut short when he died of dysentery in 1917 at the age of forty-five, at the height of his powers.