- 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.
- any sudden forceful beginning or radical change
- (modifier) of or relating to the big-bang theory
- (sometimes capitals) the major modernization that took place on the London Stock Exchange on Oct 27 1986, after which the distinction between jobbers and brokers was abolished and operations became fully computerized
hypothetical explosive beginning of the universe, developed from the work of Monsignor Georges Henri Joseph Édouard Lemaître and George Gamow, the name first attested 1950 (said to have been used orally 1949) by British astronomer Fred Hoyle (1915-2001) in an attempt to explain the idea in laymen’s terms.
- The explosion of an extremely small, hot, and dense body of matter that, according to some cosmological theories, gave rise to the universe between 12 and 20 billion years ago. Compare big crunch steady state theory. See also open universe.
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.