Picture- Cosmic Background Radiation

Oscillating universe theory

This is a basic theory to start off. This theory states that the universe goes into a periodic cycle. It has the big bang, and ends with the big crunch or any other theory in which the universe gets obliterated. If this theory is correct then this universe is fourth of fifth along in the line of universes.

Richard Tolman thought of this theory.

Sorry this is short, it was quite a basic theory so not much detail went into it.