Alexander Fridmann

Aleksandr Aleksándrovich Fridman (Russian: Александр Александрович Фридман, and can also be found written as Alexander Friedman or Friedmann) (Saint Petersburg, June 16, 1888 - Leningrad, September 16, 1925) was a Russian mathematician and meteorologist, specializing in relativistic cosmology.

Semblance

In 1922 Friedman discovered one of the first cosmological solutions to the equations of general relativity, the one corresponding to an expanding universe. In 1922 and 1924 Friedman published two articles in the German physics journal Zeitschrift für Physik, the first one «Über die Krümmung des Raumes» (On the curvature of space), in No. 10, 1922, p. 377 ff., and the second «Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes» (On the possibility of a world with constant negative curvature of space), ibid. 21, 1924, p. 326-332 [1], in which he studied three universe models as cosmological solutions to Einstein's equations, corresponding to universes with positive, zero, and negative curvature, respectively, a decade before Robertson and Walker published their memoirs. he. (See Friedman-Lemaître-Robertson-Walker Metric.) The first type model states that the Universe expands first and then collapses, space is curved on itself, just like the surface of a sphere. It is therefore finite in extent. In the second model, the Universe expands forever, space is curved to the contrary, that is, like the surface of a saddle, in this case, space is infinite. In the third model, the Universe has the critical rate of expansion, space is not curved and, therefore, it is also infinite.

The expansion of the universe was corroborated and discovered by observation by Georges Lemaître in 1927, seconded by Edwin Hubble in 1929, based on his measurements of the distance of different galaxies.

Eponymy

• Moon crater Fridman bears this name in his honor.