Matter-Dominated Era
Encyclopedia
The matter-dominated era was the epoch in the evolution of the Universe that began after the radiation-dominated era
ended, when the Universe was about 70,000 years old. Although it was often said that we still live in the matter-dominated era, it is more correct to say that when the Universe was about 5 billion years old, this era ended and was replaced by the dark-energy-dominated era. This change of the perspective occurred when the cosmological constant
or dark energy
was first observed in the late 1990s.
In the matter-dominated era, the energy density of matter exceeds the energy density of radiation in the universe (and it should exceed the vacuum energy density i.e. dark energy, too).
For a matter dominated universe the evolution of the scale factor in the Friedmann-Lemaitre-Robertson-Walker metric is easily obtained solving the Friedmann equations
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Radiation-Dominated Era
The radiation-dominated era refers to one of the three phases of the known universe, the other two being the matter-dominated era and the dark-energy-dominated era. During this era, the dynamics of the universe were set by radiation, which refers generally to the constituents of the universe which...
ended, when the Universe was about 70,000 years old. Although it was often said that we still live in the matter-dominated era, it is more correct to say that when the Universe was about 5 billion years old, this era ended and was replaced by the dark-energy-dominated era. This change of the perspective occurred when the cosmological constant
Cosmological constant
In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...
or dark energy
Dark energy
In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted theory to explain recent observations that the universe appears to be expanding...
was first observed in the late 1990s.
In the matter-dominated era, the energy density of matter exceeds the energy density of radiation in the universe (and it should exceed the vacuum energy density i.e. dark energy, too).
For a matter dominated universe the evolution of the scale factor in the Friedmann-Lemaitre-Robertson-Walker metric is easily obtained solving the Friedmann equations
Friedmann equations
The Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity...
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