What are the theories about the universe before the big bang.?
There are several speculations on this. Ultimately they are *all* speculations because at this point we have no evidence to prefer one hypothesis over another. The first is that it simply makes no sense to talk about ‘before the Big Bang’. This is because time itself is part of the structure of the universe and the universe began at the Big Bang. It is sort of like asking what is north of the north pole. The coordinate just doesn’t go there. Scientists call this a ‘singularity’. The good thing about this view is that general relativity (on which it is based) is well verified. The bad thing is that it doesn’t take into account quantum effects. Another view is that there was a ‘Big Bounce’. In other words, there was a previous universe that was contracting and that Bounced to give ours. This has recently obtained more credibility from calculations done in quantum loop gravity (which is a proposed unification of general relativity and quantum mechanics). The problem is that quantum loop g
