Cyclic model
（重定向自Oscillating universe）
![Full-sky image derived from nine years' WMAP data](/Images/godic/202501/31/Ilc_9yr_moll40964217.png")
A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a big bang and ending with a big crunch; in the interim, the universe would expand for a period of time before the gravitational attraction of matter causes it to collapse back in and undergo a bounce.