First mover argument

 "everything that begins to exist has a cause". Therefore, the universe has a cause because science has shown that the universe is expanding, which means it started expanding from somewhere - it has a beginning. Therefore, God exists, He must have created the universe. God is, by definition, eternal and uncaused and personal.

However, science does not show that the universe begins to exist. It shows that it began to expand. Which means it could have existed eternally, but only at some point began to expand. Then again, this doesn't work. Things don't just "begin to happen" there has to be a cause. The universe cannot be in an eternal steady state and then suddenly become unstable and start moving. It has to be either eternally steady, or eternally moving (either by newton's laws of motion, which don't apply to the beginning of the universe, or by logic, which, hopefully, does).

If the universe is eternally steady - God exists too, because an eternally steady universe won't suddenly expand unless something triggers it externally.

If the universe is eternally moving - Well, we need to find the mechanism for a big crunch. Absent that mechanism, then the eternally moving universe fails because we know our universe is expanding and if it can't contract, that it'll eventually be over and it isn't eternal.

But what if there is a different explanation? There is the proposal of this bubbling quantum field thing, before the universe began to exist. What if the bubbling quantum field is the eternally moving source of our universe and many others? Our own universe need not be eternal, as long as the field is. Imagine a field, always bubbling, each bubble a universe and its anti-matter twin (thereby conserving energy and matter). An eternally moving source of non-eternal, finite universes. There. Problem solved. It's a beautiful solution too, because you can't expect to detect such a quantum field that lies outside our universe, nor can we expect to detect our anti-matter twin, or any of the other bubbles.

Wait, wait, wait. No. Because if the quantum field wants to exist, its laws must exist. Where do those laws come from? 

Oh, don't worry about that. The laws are part of its nature, just as your God's attributes (loving, omnipotent etc etc) would be if He existed. 

Oh, ok. But would it then be reasonable to expect to find in our universe, similar quantum fields at work on a smaller scale? Matter and antimatter spontaneously popping in and out? 

I don't know. I know antimatter and matter do regular appear in nuclear reactions, and always in opposite pairs.

And what is the difference between the postulation of this and postulating God?

Probably only that we are more used to being the masters rather than the students of inquiry; we much prefer to discover new heights and new mysteries than to find the next elaborate easter egg on a hunt prepared by a parent, and much more eager to discover mechanisms than artificers. Because as long as what we discover isn't a person, we get to be trailblazers, frontliners and pioneers. As long as we don't find God at the end, we won't be little children in a school's discovery garden. We will have done it, we will have discovered and conquered by determination, cunning and innovation. It's fine if nature got there first as long as we're the first minds to get there. 

In a word, it's pride. It's no longer fun if we don't get to show off to ourselves.