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'Alexander Alexandrovich Friedman' or Friedmann () (June 16 1888, Saint Petersburg, Imperial Russia – September 16 1925, Leningrad, USSR) was a Russian and Soviet cosmologist and mathematician.
Alexander Friedmann lived much of his life in Leningrad. He fought in World War I (on behalf of Imperial Russia) as a bomber and later lived through the Russian Revolution of 1917.
He discovered the expanding-universe solution to general relativity field equations in 1922, which was corroborated by Edwin Hubble's observations in 1929.(Ferguson, 1991: 67). Friedmann's 1924 papers, including "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" (On the possibility of a world with constant negative curvature of space) published by the German physics journal ''Zeitschrift für Physik'' (Vol. 21, pp. 326-332), demonstrated that he had command of all three Friedmann models describing positive, zero and negative curvature respectively, a decade before Robertson and Walker published their analysis.
This dynamical cosmological model of general relativity would come to form the standard for the Big Bang and steady state theories. Friedman's work supports both theories equally, so it was not until the detection of the cosmic microwave background radiation that the steady state theory was abandoned in favor of the current favorite Big Bang paradigm.
The classic solution of the Einstein field equations that describes a homogeneous and isotropic universe is called the "Friedmann-Lemaître-Robertson-Walker metric", or "FLRW", after Friedmann, and Robertson, Walker and Georges Lemaître who worked on the problem in 1920's and 30's independently of Friedmann.
In addition to general relativity, Friedmann's interests included hydrodynamics and meteorology. In June 1925 he was given the job of the director of Main Geophysical Observatory in Leningrad. In July 1925 he participated in a balloon flight, reaching the elevation of 7400 m.
Friedmann died on September 16, 1925, at the age of 37, from typhoid fever that he contracted during a vacation in Crimea.
Another famous physicist, George Gamow, was a student of Friedmann.

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References

★ Ferguson, Kitty (1991). ''Stephen Hawking: Quest For A Theory of Everything''. Franklin Watts. ISBN 0-553-29895-X.

★ Friedman, A: Über die Krümmung des Raumes, Z. Phys. 10 (1922), 377-386. (English translation in: Gen. Rel. Grav. 31 (1999), 1991-2000.)

★ Friedmann, A: Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes, Z. Phys. 21, (1924), 326-332. (English translation in: Gen. Rel. Grav. 31 (1999), 2001-2008.)

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