What is the theory behind the concept of the infinite big bang and its implications for the origin and expansion of the universe?

The theory of the infinite big bang suggests that the universe has no definite beginning or end, and that it has been expanding and contracting infinitely. This theory challenges the traditional idea of a single, finite big bang that started the universe. It implies that the universe has always existed in some form and will continue to exist indefinitely, with cycles of expansion and contraction. This concept raises questions about the origin and nature of the universe, as well as the possibility of multiple universes existing simultaneously.