July 12, 2015 by Zerub Roberts
I once asked Gerard t’Hooft similar question, and this was his response –
(My exact question – 2. You are inclined to believe that universe could be eternal in the past. If so, why would the quantum gravity regime turned into classical space time only 13.7 b years ago? )
Our best models of cosmology (Inflation etc) don’t say much about the pre-big bang era. There are models where you could have time before the creation of our universe, where entropy decreases with time, interestingly enough (the Caroll-chen model). This of course presupposes the multiverse and seems to offer a solution to the arrow of time. But it has it’s own bigger problems.
More viable models however put an absolute beginning to space-time. One of them being The Borde-Guth-Vilenkin theorem which shows that spacetime cannot be infinetly extended to the past. The simpler answer would be to say that given observational data, as of now (From PLANK, COBE and WMAP) – the three best sources of cosmological data – the evidence underdeterminative. It could go either way.
But the best theoretical models would suggest that time had an absolute beginning. Although one wouldn’t put high credence on it until there’s satisfactory empirical confirmation.