big bang theory

noun

Astronomy.

1. 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.

big-bang theory

noun

1. a cosmological theory postulating that approximately 12 billion years ago all the matter of the universe, packed into a small superdense mass, was hurled in all directions by a cataclysmic explosion. As the fragments slowed down, the galaxies and stars evolved but the universe is still expanding Compare steady-state theory

Big Bang theory

1. In astronomy, a theory according to which the universe began billions of years ago in a single event, similar to an explosion. There is evidence for the Big Bang theory in the observed red shift of distant galaxies, which indicates that they are moving away from the Earth, in the existence of cosmic microwave background, and from other data. The Big Bang theory of the origin of the universe is accepted by most astronomers today.

Scientists have recently found that the expansion of the universe is actually speeding up. This effect is attributed to the presence of dark energy.

Word History and Origins

Origin of big-bang theory¹

First recorded in 1950–55