Alexander Alexandrovich Friedman (June 16 1888 – September 16 1925) was a Russian cosmologist and mathematician. He discovered the expanding-universe solution to general relativity field equations in 1922, which were proved by Edwin Hubble's observations in 1929 Friedmann's 1924 papers, including "Uber die Moglichkeit einer Welt mit konstanter negativer Krummung des Raumes" (About the possibility of a world with constant negative curvature) published by the Brussels Academy of Sciences on the 7th of January 1924, 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.

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