Science IS built on observations. However, the syntheses of observations that scientists use to frame the explanations of data gathered from observations (e.g., evolution) are theories. Theories are unproven ideas. Because they are unproven and often unable to be observed, one must choose to have faith (complete trust or confidence in someone or something) in them. The big bang is not able to be observed. Therefore, it is a theory. Creation is not able to be observed. Therefore, it is a theory. It simply comes down to a matter of what direction one chooses to direct their faith in. Atheistic scientists have chosen a direction that I have chosen to reject. I chose to reject it because it provides no peace or directive for me to live my life, love, and raise a family. Why, honestly, would anyone choose a perspective on life that only offers a dead end with no prospect of meaning?
That being said, I think there is plenty of room for science within the context of God. There are multiple perspectives on the biblical account of Creation, but, simply put, if God explained everything about creation in the bible, it would require volumes. The point is that God is responsible. That is the theory that I choose to place my faith in.