Alexander Friedmann

It’s the birthday of Alexander Friedmann, who was born in 1888 in St Petersburg, Russia. Friedmann studied mathematics at St Petersburg State University and went on to teach the subject at the Saint Petersburg Mining Institute. After serving in World War I as an army pilot, Friedmann returned to academia. In 1922 he published his famous paper, On the Possibility of a World with Constant Negative Curvature of Space. In it, he described an expanding universe, consistent with Albert Einstein’s general theory of relativity, whose fate depended on the energy density and the curvature of space. Friedmann’s solution to Einstein’s equations was arrived at later, and independently, by Georges Lemaître and by Howard Robertson and Arthur Walker. In their collective honor, the solution of the Einstein field equations that describes a homogeneous and isotropic universe is known as the Friedmann-Lemaître-Robertson-Walker metric.

Date in History: 16 June 1888