Many factors come into play to make anyone believe in the existence of God. Of course the way we grew up, the people we knew, the experiences we had, everything that surrounds and has surrounded us is very important. However, if we are not completely stupid, and even if we grew up surrounded by a religious belief, we always reach a point when we ask ourselves:
"Do I really believe all this intangible theory that somewhere, or indeed everywhere, an higher being exists? One that has created us? One that knows us? And do I really have a soul? Does my spirit live after my body dies?" ... and lots of other similar questions.
Some reply to themselves:
"No", some reply to themselves
"Yes". The ones that pick the "Yes" to themselves will never prove anything to the ones that pick the "No". It's even futile to attempt that, because if the existence of God could be proven - scientifically - then God would himself be no different than the Universe. And the Universe isn't God.
It's a bit like the discussion in the other thread about Evolution vs. Creation. Some people think that there's opposition between these two concepts, when - really - there isn't, unless you read the Genesis as a factual account on how the universe was created (I know some people do, but I don't).
The point is: science can indeed discover one day how the universe is like it is now, they can even say that the universe will go eternally from big bang to big crunch and to big bang again .... however, and even if they prove beyond all doubt this theory ... people that believe in the existence of God will still have no trouble in keeping their belief. Because they will say (as I do)
"that's all fine with me, but I believe that is no different (other than in size) from everything else we can see and experiment. That is no different from day and night, from seeds and plants, from eggs and animals. That just explains what we see and how it has become to be the way we see it."
So, there's no point in trying to establish - based in our scientific knowledge - the existence or non-existence of God. The belief that God exists is not and cannot be based in what we see, taste, smell, hear or touch. And, respectively, what we can see, taste, smell, hear or touch doesn't prove that God doesn't exist. That's why I think scientific knowledge is completely irrelevant both as a foundation to faith and/or to put it in doubt and make it dissapear.
Sorry for the long post