Bern Switzerland, May 11, 1905

Einstein's Seventh paper, On the Movement of Small

Particles Suspended in Stationary Liquids Required by the
Molecular-Kinetic Theory of Heat, Annalen der Physik 17: pg. 549-560.

For the first time, Einstein discussed Brownian motion, the irregular movement of microscopic particles suspended in a liquid, which was named after the eighteenth-century Scottish botanist who first observed it.

As Einstein explained ia letter to his friend Conrad Habicht on May 25, he proved in this paper that particles about 1/1000 millimeter in diameter suspended in liquids and too small to see move randomly because of thermal dynamics.

By inventing Boltzmann's formula, Einstein described its mathematics, deriving the probability of a macroscopic state for the distribution of gas molecules. This paper led to experiments validating the kinetic-molecular theory of heat. To date, this is Einstein's most-cited paper.