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(Astronomy) 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
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|Noun||1.||big-bang theory - (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|
scientific theory - a theory that explains scientific observations; "scientific theories must be falsifiable"