Ninety years ago, in 1922, Alexander Friedman (1888-1925) demonstrated for the
first time that the General Relativity theory admits non-static solutions and
thus the Universe may expand, contract, collapse, and even be born. His
fundamental equations describing possible scenarios for the evolution of the
world provide the basis for the current cosmological theories of the Big Bang
and the Accelerating Universe. Friedman's unexpected achievement initially
met with strong resistance and since then has been often misrepresented in the
literature. This paper clarifies some persistent confusion regarding Friedman's
cosmological theory in comparison with corresponding theories by
Albert Einstein, Willem de Sitter, Arthur Eddington, and Georges Lemaitre.
Friedman's little known topological and astronomical ideas of how to check
the General Relativity in practice are also described.