Firstly, it can only 'happen' spontaneously, as prior to the big bang, there is no dimension of spacetime. Prior to this, everything exists that exists now - without space and time (see quantum theory).

Now why that occurs (and it might not occur, it might just simply be that we're experiencing it from an internal perspective of existing within space and time - as from high dimensional topology objects in space time are different ie from a fifth dimensional perspective time is occurred not occuring) is the question.

However that 'big bang occured' only applies to a perspective within space-time as a dimension (i.e. we are simply see it as occurring, because we're a part of the process of something that has already occurred for a brief time.

Or if it was an event that causes big bang (and the term causal is reliant on time and space events), such as how dimensions function within a reality, how realities exist etc.

However, none of this requires god, or a creator or event really an event to trigger big bang. We call it big bang, as its a convenient method of explaining a very complex series of theoretical models, which are evidenced by astrophysical research, quantum and relative physics.

What really happens with big bang is that subatomic particles go from being in a null state, to the state we are experiencing them in (which is a state of entropic change that will result in an end state) - but we are also part of that entropic change.

From a 5th or higher state, that 'change' has occurred (much in the same way that we see 2D and 3D models as being constants, the same applies to 4D from a higher dimension).

But none of this requires a god. Prior to big bang everything existed, after big bang everything still existed, and we're a part of that process (briefly).

We're kind of like a Salmon in a stream trying to understand what land is.

I think we're all a big mistake. We are like the consequence of the infinite monkeys with infinite typewriters. Atoms that have come together and just so happened to have become a human race on a planet. An almost infinitely unlikely thing to have happened, but not quite infinitely unlikely/impossible.

Like Jamie says, because we can't explain that or reconcile the fact that something so coincidental could've happened, we've come up with some bloke that did it. Because Science is too complicated it must've been some bloke. And because to not be able to reconcile that there is no reason for us to exist at all, we've had to appease our fears by assuming we are part of some bloke's plan.

Well good for you if you're able to believe in some bloke who has a plan for you, but you'll be born and you'll die either way.

I'm not even saying I believe a god exists, I don't know. It's just that the instant belief given to various 'scientific' theories that come and go make me smile. As for God springing into existence, if God is omnipotent, God can do whatever God likes -
spring in and out of existence, change the past, present and future, appear in the guise of an ice cream van ...

Edited by hedgehog50 (03 Jul 2017 11.19am)

I just assumed that because I didn't understand any of the words longer than 4 letters that it was dead clever and sciencey. I don't know what to believe any more to be honest. Maybe I ought to go to church after all.