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However, Friedmann abandoned the idea in his first paper "On the curvature of space". Starting with Einstein's 10 equations of relativity, Friedmann applies the symmetry of an isotropic universe and a simple model for mass-energy density to derive a relationship between that density and the curvature of spacetime.
Removing the cosmological constant term from the Friedmann equations on the grounds that it was both unsatisfactory and unnecessary, Einstein arrived at a model of a universe that expands and then contracts, a model that was later denoted the Friedmann–Einstein model of the universe. [3] [4] In the model, Einstein derived simple expressions ...
The Friedmann–Lemaître–Robertson–Walker metric (FLRW; / ˈ f r iː d m ə n l ə ˈ m ɛ t r ə ... / ) is a metric that describes a homogeneous , isotropic , expanding (or otherwise, contracting) universe that is path-connected , but not necessarily simply connected .
Unaware of Friedmann's work, in 1927 Belgian astronomer Georges Lemaître independently formulated an evolving Universe. [4] In June 1925 Friedmann was given the job of the director of the Main Geophysical Observatory in Leningrad. In July 1925 he participated in a record-setting balloon flight, reaching the elevation of 7,400 m (24,300 ft). [5]
Λ is positive and has a magnitude greater than gravity. Universe has initial high-density state ("primeval atom"). Followed by a two-stage expansion. Λ is used to destabilize the universe. (Lemaître is considered the father of the Big Bang model.) Oscillating universe (Friedmann-Einstein) Favored by Friedmann 1920s Expanding and contracting ...
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The concept of an expanding universe was scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The Einstein–de Sitter universe is a model of the universe proposed by Albert Einstein and Willem de Sitter in 1932. [1] On first learning of Edwin Hubble's discovery of a linear relation between the redshift of the galaxies and their distance, [2] Einstein set the cosmological constant to zero in the Friedmann equations, resulting in a model of the expanding universe known as the Friedmann ...
He was the earliest to employ Alexander Friedmann's and Georges Lemaître's non-static solutions of Einstein's gravitational equations describing a universe of uniform matter density and constant spatial curvature. Gamow's crucial advance would provide a physical reification of Lemaître's idea of a unique primordial quantum.