What is the repeating universe theory?
See explanation for a few thoughts...
I think the term "repeating universe theory" could have several different interpretations.
Let us look at an couple of possibilities.
Suppose the nature of the universe is such that it will stop expanding and eventually experience a "big crunch".
Suppose further that such a "big crunch" will be automatically followed by another "big bang" with the same amount of matter/energy, etc. We could call that a "repeating universe theory", but perhaps there's something more...
If such a cycle is inevitable then there are some theories that we might attach to it:
(1) The theory that the following "big bang" will of necessity be identical to that which started this cycle, and will result in exactly the same sequence of events. Such a theory is almost certainly false.
(2) The theory that there are a large but finite number of possible initial configurations for a "big bang" in such a recurring cycle, so if an infinite number of "big bang" - "big crunch" cycles occur then at least one configuration will repeat. OK so far, but does the initial configuration determine all following events? - probably not.
(3) Like (2), but since the length of a "big bang" - "big crunch" cycle is finite, then if spacetime is quantised, there are a finite number of possible states through which the universe goes during a cycle. So there is a ridiculously huge but finite number of possible cycles. So in an infinite number of cycles, at least one possible sequence will repeat.
The repeating universe theory is the concept of alternating periods of expansion like the big bang and contractions like the big crush
The previous theory was the steady state theory. Before Edwin Hubble discovered the doppler red shift of the universe scientists believed that the present universe was eternal in an unchanging state.
Hubble based on empirical evidence proposed that the universe was expanding from a small central beginning. Although the idea of an expanding evidence was resisted on philosophical grounds the empirical evidence became overwhelming. This resulted in the theory of the Big Bang.
The belief in material realism still demanded that matter and energy be eternal. To continue the belief in matter and energy being eternal the idea of a repeating universe was developed. This idea was that the universe would recycle. The big bang would be followed by a big crush. The universe would be drawn back into a super dense ball resulting in another big bang.
The most current empirical evidence disproves the alternating repeating universe. Studies of the rate of expansion of the universe in 1997 from studying distant pulsars show that the rate of expansion of the universe is increasing. The repeating universe theory predicted that the rate of expansion must be decreasing. If the empirical evidence is correct, matter and energy can not be eternal.
The repeating universe theory proposed that the present universe would recycle. The empirical evidence is that the universe had a beginning and will have an ending. The universe will not repeat it will end.