The man who grew the universe.

This article focuses on the foundational contributions of Russian mathematician and cosmologist Alexander Friedmann to modern evolutionary cosmology, marking the centenary of his seminal papers from 1922 and 1924. Friedmann demonstrated that Einstein's general relativity allows for dynamic, evolving universes—both expanding and contracting—introducing models that include closed, open, and oscillating universes governed by the cosmological constant (λ). His work established the theoretical framework for the Big Bang theory, linking cosmic expansion, mass density, geometry, and the age of the universe, concepts later supported by Edwin Hubble's observations and the discovery of dark energy. Friedmann's models remain central to contemporary cosmology, providing a basis for understanding the universe's origin, structure, and accelerated expansion.