Time is a function of change — if there were no change there would be and could be no time. Time in fact is only a way of measuring change by comparing it to a standard clock (a standard clock is something which changes in an extremely regular way). Since time is the result of a comparison of change to a standard clock, time can only exist if (1) a standard clock exists, (2) a change to be compared to the clock exists, and (3) a being capable of doing the comparison exists. This is a matter of logical necessity from the definition of time.
It follows that time only comes into existence once all three conditions are met. The most limiting condition is the 3rd, the existence of a being capable of doing the comparison, and I say this because 1 and 2 are known to come into existence billions of years before 3 comes into existence.
When Stephen Hawking and other cosmologists talk about time coming into existence with the big bang, they pretend that there is a scientist like them, a being capable of doing the comparison which creates time, right back there at the beginning of our universe looking on. That of course is a conceit. Since time is a comparison, it can only exist in a mind. Unless one is a theist (Hawking and most other cosmologists are not), one has to admit that time cannot exist until the evolution of organisms with minds capable of doing the right sort of comparison.
The scientific conceit is that we are right there at the big bang, looking on. If there is change occurring and a standard clock by which to measure it, why then “time” exists because the 3rd necessity — us — is looking on from our objective perch billions of years in the future. But if the 3rd element can be billions of years in the future why can’t the 1st element — the standard clock — also be billions of years in the future? In this case element 2 is all that really needs to be present before we can in our conceit declare the existence of time.
And the implication is this: the big bang is when that 2nd element — change — had its beginning.
That can’t be, and most cosmologists will agree with me on this. Change is an interaction and it cannot start cold from nothing. If the singularity is truly unchanging then it never changes. No big bang ensues, and our universe never gets started. Something must have been going on inside or outside the singularity for a big bang to result, and that mean the big bang cannot be the beginning of change.
To think otherwise is to abandon methodological naturalism. But it is also to do nothing other than declare that the impossible and inconceivable happened: that something unchanging suddenly changed for no possible explanation.
It is the same impossibility that theists assert of God: that unchanging deity suddenly and inexplicably changed and so created our world of change. Both God and an unchanging singularity represent the abandonment of explanation. Both beg the question: how can the unchanging ever lead to anything different, since it must change to do so?
Embracing that impossibility we find both theism and bad science.