A modification of the Big Bang theory, in which an expanding universe eventually reverses and collapses back to a Big Crunch before starting to expand again, forming one cycle of an endless series. In such a model, each cycle has a finite duration but the universe itself can last for an infinite time. It is not known whether our Universe is of this type, or whether it will expand for ever. See also Closed Universe; Open Universe.
Subjects: Astronomy and Astrophysics.