Scientific hypotheses are rated according to their credibility; as more and more data support a scientific hypothesis, the greater our confidence in it.If that hypothesis fits into a common pattern, successfully interlocking with established theories, then it gets another big plus.
Indeed, nothing in science is ever "proven" beyond all possible doubt; there is no way of knowing, with 100% certainty, that one's proof is foolproof.One can always dream up possible scenarios that will contradict even the best scientific models.Facts successfully explained do carry weight and cannot be ignored; facts that don't fit are not necessarily fatal to the central ideas behind a hypothesis.Good scientific judgment is the art of weighing all these variables and properly evaluating the big picture.Since careful inspection shows no signs of such a flood, the earth can't be older than a few weeks! We do need to know something about the system under study. No one familiar with tides would assume that the rate of water going out is constant over weeks of time!
Just as obvious, at least to the experts, our sun could not have been continuously shrinking over millions of years as described by some creationists. This magic bullet mentality, the tendency to rely on a single, isolated argument to win all the chips, has gotten creationists into more trouble than possibly anything else.Unfortunately, Mother Nature does not give little, gold ribbons to certify the accuracy of our proofs!Great care is taken to survey all the relevant literature and to arrive at a balanced judgment of the known facts.Scientists are trained to overcome a one-shot, "cowboy" mentality.Consequently, the complaint that evolution is merely a (scientific) theory is a little like saying that an athlete is merely a gold-medal winner!