Question

what is big bounce theory?

Answer 1

big bounce theory is a concept which is a hypithetical cosmological model for the origin of the known universe

Answer 2

Expansion and contraction. The concept of the Big Bounce envisions the Big Bang as the beginning of a period of expansion that followed a period of contraction. In this view, one could talk of a Big Crunch followed by a Big Bang, or more simply, a Big Bounce.