How does science keep from becoming fiction?

The only way a scientific "fact" can become fiction is if it is proven wrong. Unfortunately most of science is either proven beyond a reasonable doubt to be correct or it is unprovable and just the only explanation they can come up with. If it is unprovable "big bang" they label it a theory, which to a lot of scientists is just as factual as something that has been proven. In a sense science is really nothing but another type of religion based on seen facts. No faith.