A Cyclic Universe

Theoretical cyclic cosmologies exist in which cosmic expansion is followed by contraction and a transition into another expansion phase. Some models describe repeated “bang–crunch” epochs or a bounce, but this is not a confirmed description of our universe; current observations indicate accelerated expansion. Cyclic models do not mean that time itself alternately speeds up and slows down: the universe’s scale factor and dynamics change, not a universal clock rate in that simple sense.