# What information do we have about time before the big bang?

I've heard for awhile now that a lot of physicists think that time was created in the big bang as a dimension (just like space). When I try to look this up online though i just get on old lecture from Stephen Hawking about why that may or may not be true. I was wondering if anyone had any sources to back up the claim that there was no time before the Big Bang or at least something that suggests its probability.

There is some ongoing work about pre Big Bang physics. It's very tentative and hypothetical. Some of what I've seen involves M-Branes, a string theory type approach, such as two of those colliding and forming something which was what we see as the Big Bang. There's also a model where it's sort of a Big Bounce from a collapsing universe, maybe there there would be time unitl the Planck epoch (Planck epoch is around sizes less than $10^{-35}$ cms, where space and time may not have emerged yet). There are other hypotheticals of some model pre Big Bang that led to a Big Bang type effect. Whether time makes any sense then depends on those models.