July 18, 1905 - Albert Einstein publishes his second study of Brownian motion

Between March and September 1905, the German scientific journal "Annales der Physik" mailbox received four studies that would forever change the laws of physics and, ultimately, the conception of the reality of light, matter, time, and space.

The author was a 26-year-old Albert Einstein who, at the time, was working at the patent office in Berne (Switzerland). His career as a physicist had stalled after the rejection of his doctoral thesis, and his scientific passion had been relegated to his spare time and long idle hours in the office. However, this year was a miraculous one for Einstein with these four significant studies.

Movimiento Browniano de Einstein
Einstein's Brownian Motion

The second study was published on 18 July under the title "On the motion required by the kinetic molecular theory of the heat of small particles suspended in a stationary liquid".

Einstein found in a physical phenomenon (Brownian motion) the empirical evidence for what many scientists thought at the time, that matter is composed of atoms. In attempting to explain this curious phenomenon, Einstein not only mathematically confirmed the existence of atoms and molecules but also inaugurated a new field in the study of Physics, Statistical Physics.

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