You can't "prove" scientifically that God exists because that would require him to be physical, visible. He is outside of his creation, although he can and has entered into it.
When you start with absolutely no premeditated thoughts about what God is like, but simply take a look at the universe from a scientific standpoint, the big blank "thing" that brought the whole universe into existence fits the basic definitions of God in the dictionaries and encyclopedias.
If big bang theory could take into account the complexity of intelligence in the way that the universe shows complexity to exist, big bang might be able to be considered to be God. There are too many holes in BB theory to match what exists in ways other than the "simple" theoretical math that suggests BB might exist.
