Friedmann

Friedmann is a surname of German origin. It has been borne by several notable individuals, including the Russian-born physicist and cosmologist Alexander Friedmann, whose work helped establish the expanding-universe model.

Alexander Friedmann (1888–1925) studied solutions to Einstein's field equations that assume a homogeneous and isotropic universe. In 1922 and 1924 he derived equations describing how the scale factor of the universe evolves over time, implying that the universe can expand or contract. His work preceded observational evidence of expansion.

Friedmann equations: The two key equations relate the expansion rate to the energy content of the universe, its spatial curvature, and the cosmological constant. They form the basis of Friedmann cosmology and are solved in conjunction with a specified matter-energy model to predict the history of cosmic expansion.

The standard cosmological model uses the Friedmann-Lemaitre-Robertson-Walker metric, which assumes homogeneity and isotropy. The metric is named after Friedmann, Georges Lemaitre, Howard Robertson, and Arthur Walker, reflecting contributions to its development.

In broader usage, Friedmann as a surname appears in various fields, including literature and education, but it remains most widely associated with cosmology due to Alexander Friedmann's pioneering work.