I recall as a teenager talking about the universe with a friend at school and out attempts to understand infinity. I suggested the universe might end and we might be able to travel to its end (this was before theories of bubble universes and warped space) and my friend asked me what was on the other side when we hit the end. Nothing, I replied. And there was the dilemma for us because we had no conception of what nothing meant. If you touch a barrier, even an atom thick, there has to be a reverse side to it, that’s the way our minds work that is how we understand our three dimensions. We can understand the idea of a place where there is nothing within a space where there is something (such as a vacuum in a flask) but we cannot understand nothing because there is nothing to understand.
Imagine then how we feel when we are told that space and time are one and the same thing. So that time began when the universe began. How do we conceive of the moment before the universe and time began? How did that moment ever cross-over to the moment of creation (or singularity)? Our minds are simply not geared up to understand.
And knowing this does it mean anything for the things we do understand? Because there may be things in the universe that are there, but which we will never understand all. What would happen if we attained a Grand unified theory that worked, but which we could never fully understand? Into the gap between what is and what we cannot understand, we put god. God fills our ignorance.