An Etymological Dictionary of Astronomy and Astrophysics

An early epoch in the history of the → Universe when the radiation → density parameter was Ω_r≈ 1, while other density parameters had negligible contributions. A radiation-dominated Universe is characterized by R/R₀ ∝ t^1/2, where R is the → cosmic scale factor and t is time. According to the → Big Bang model, the radiation-dominated phase was followed by the → matter-dominated phase.

See also: → radiation; → dominate; → Universe.