The Einstein–de Sitter universe is a model of the universe proposed by

Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...

and Willem de Sitter in 1932. On first learning of

Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects previously ...

's discovery of a linear relation between the redshift of the galaxies and their distance, Einstein set the

cosmological constant In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), alternatively called Einstein's cosmological constant, is a coefficient that Albert Einstein initially added to his field equations of general rel ...

to zero in the

Friedmann equations The Friedmann equations, also known as the Friedmann–Lemaître (FL) equations, are a set of equations in physical cosmology that govern cosmic expansion in homogeneous and isotropic models of the universe within the context of general relativi ...

, 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 Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

model for a flat matter-only Friedmann–Lemaître–Robertson–Walker metric (FLRW) universe. Lars Bergström & Ariel Goobar: "''Cosmology and Particle Astrophysics''", 2nd ed.

Springer Springer or springers may refer to: Publishers * Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag. ** Springer Nature, a multinationa ...

(2004), p. 70+77. . 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 ''H''₀² = ''кρ''/3, where ''H''₀ is the

Hubble constant Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther a galaxy is from the Earth, the faste ...

, ''ρ'' is the average density of matter and ''к'' is the Einstein gravitational constant. The size of the Einstein–de Sitter universe evolves with time as

a\propto t^

, making its current age 2/3 times the Hubble time. 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 just at the limit of eventually contracting. 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. The Einstein–de Sitter universe was particularly popular in the 1980s, after the theory of cosmic inflation predicted that the curvature of the universe should be very close to zero. This case with zero

implies the Einstein–de Sitter model, and the theory of

cold dark matter In cosmology and physics, cold dark matter (CDM) is a hypothetical type of dark matter. According to the current standard model of cosmology, Lambda-CDM model, approximately 27% of the universe is dark matter and 68% is dark energy, with only a sm ...

was developed, initially with a cosmic matter budget around 95% cold dark matter and 5% baryons. However, in the 1990s various observations including galaxy clustering and measurements of the

led to increasingly serious problems for this model. Following the discovery of the accelerating universe in 1998, and observations of the

cosmic microwave background The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

and galaxy

redshift survey In astronomy, a redshift survey is a astronomical surveys, survey of a section of the sky to measure the redshift of astronomical objects: usually galaxies, but sometimes other objects such as galaxy clusters or quasars. Using Hubble's law, the ...

s in 2000–2003, it is now generally accepted that

dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...

makes up around 70 percent of the present energy density while

contributes around 25 percent, as in the modern

Lambda-CDM model The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components: # a cosmological constant, denoted by lambda (Λ), associated with dark energy; # the postulated cold dark mat ...

. The Einstein–de Sitter model remains a good approximation to our universe in the past at redshifts between around 300 and 2, i.e. well after the radiation-dominated era but before dark energy became important.

Notes and references

{{DEFAULTSORT:Einstein-de Sitter universe General relativity Albert Einstein

See also

Notes and references