How to you have time without space-time? The big bang is actually not the exact start of the universe. It’s pretty close, but not quite. It is the expansion of the universe. Before that it’s in a very dense high energy state, but it does exist. It explains how it went from this state to the current state, but not how it came into existence at all.
I don’t think it’s believed to have sat in this dense high energy state for infinite time before the big bang, so it must have come into existence, not just existed forever. If that’s the case that means space-time came into existence. You can’t have time without space-time, so there is no time before it exists. At some point space-time exists, and as such there is no before, since there is not time.
It seems odd to consider. How do things happen without space-time? We can’t really think about this concept, because we’re space-time beings. It doesn’t even make sense to consider. However, having an intelligence start things doesn’t help. It only then begs the question where they came from. Surely the universe just starting is more likely than an intelligence appearing for some reason, then it deciding to start the universe. That’s a vastly more complex set of circumstances.
I linked it somewhere, but it wasn’t this chain.
https://scienceandnonduality.com/article/quantum-prediction-something-is-created-from-nothing/
It’s a bigger leap to consider that space-time came into existence for no reason than that an intelligence that exists outside of that created it? Where did they come from? They must have come from either nothing (which seems more crazy than a random thing like space-time that is not organized), or something created them, which only pushes the question to what created that thing.
It doesn’t simplify it. It only makes it more complicated. The universe just starting at some point is incredibly simple, though fairly crazy to consider since we’re space-time beings that did not evolve to consider a lack of space-time. We can’t imagine four dimensions easily, let alone zero dimensions. (tangent: zero took a long time to develop, because the concept of nothing is so hard to even hold in our minds.)
The universe just appearing/starting is the simplest answer. The other two answers I can think of is that it always existed (in which case, how can it exist for infinite time; that’s as hard to consider as it just starting at zero) or something created it, which then just begs the question: who created them, ad infinitum. Occam’s razor applies and says the most likely (though not necessarily correct) answer is the simplest.
We can’t prove any of this obviously. It’s, I think, literally impossible to prove, and certainly we’re incapable of testing it with existing capabilities. Its a philosophical discussion, not a scientific one.