The Einstein–de Sitter universe is a model of the universe proposed by Albert Einstein and Willem de Sitter in 1932. On first learning of Edwin Hubble's discovery of a linear relation between the redshift of the galaxies and their distance, Einstein set the cosmological constant to zero in the Friedmann equations, resulting in a model of the expanding universe known as The Friedmann-Einstein universe. In 1932, Einstein and de Sitter proposed an even simpler cosmic model by assuming a vanishing spatial curvature as well as a vanishing cosmological constant. In modern parlance, the Einstein–de Sitter universe can be described as a cosmological model for a flat matter-only Friedmann–Lemaître–Robertson–Walker metric (FLRW) universe.
In the model, Einstein and de Sitter derived a simple relation between the average density of matter in the universe and its expansion according to H02= кρ/3 where H0 is the Hubble constant, ρ is the average density of matter and к is the Einstein constant. The Einstein–de Sitter universe became a standard model of the universe for many years because of its simplicity and because of a lack of empirical evidence for either spatial curvature or a cosmological constant. It also represented an important theoretical case of a universe of critical matter density poised between contraction or expansion at an ever-increasing rate. However, Einstein’s later reviews of cosmology make it clear that he saw the model as only one of several possibilities for the expanding universe.