Alexandr Friedmann. Portrait of the Russian cosmo- logist and mathematician, Alexandr Alexandrovich Friedmann (1888-1925). Friedmann studied at St Petersburg, Russia, where he became a lecturer. From 1920 he was at the Academy of Sciences, also in St Petersburg, where he worked on Einstein's general theory of relativity. His various solutions to the equations of this theory showed that not only is the universe the same everywhere at a given time, but its size and density vary as a function of time. In 1917 he proposed that the universe was expanding, 12 years before Hubble found evidence for it. The expansion was later explained in the Big Bang theory.