Akademik

(cosmology) the theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature

: a theory in astronomy: the universe originated billions of years ago in an explosion from a single point of nearly infinite energy density — compare steady state theory herein

a theory that deduces a cataclysmic birth of the universe (big bang) from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics. Also called big-bang model. Cf. steady state theory.

[1950-55]

big bang theory,

a theory which maintains that the universe originated in a cosmic explosion of hydrogen, which became condensed into galaxies.