Our universe can be described mathematically by a simple model developed in 1922 at Petrograd (St. Petersburg) by Alexander Friedmann (1888-1925). Without the benefit of observational evidence, Friedmann predicted that the whole universe would expand and evolve with time. This astonishing prediction was confirmed seven years later by Edwin Hubble. Its originator, unfortunately didn't live to savor this triumph. This vivid biography of an outstanding scientist sets his life and work against a wide backdrop of the history of cosmological studies and its major players, such as Einstein and others. The book is a window on Friedmann's school and university years, military service, and teaching and research during a seminal period of Soviet history. The authors include unique archival material, such as Friedmann's letters from the Russian Front, as well as contemporary records and reminiscences of colleagues. There is a detailed treatment of his work in theoretical cosmology (1922-1924), set in the context of the organization of Soviet science at the time.