As far as I know, if your dealing with unobservable phenomena (i.e. what happened "millions of years ago), it ain't science.
Atomic theory and the curvature of space time, ie quantum mechanics and general relativity, are also not science by this standard. I think you've got the wrong standard for science. In order to be science, an idea must make predictions of observations that, up until the present time, have not been made. These predictions must be such that, if they are not borne out by observation, the idea will be abandoned. The theory that the earth is very old carries certain consequences. Among these are the expected concentrations of various radioactive isotopes, the appearance and composition of rock layers, and the geological structure of various features on the surface of the earth. There are predictions that can be made from this model in all of these areas. Many of these predictions have been confirmed by observations. Does this constitute proof of the old earth theory? Absolutely not, but then again there is no scientific theory that is ever proven. All theories, as I mentioned above, generate predictions as to what will be observed. It is always possible that some observation will be made in the future that will render a theory false. This applies to ALL theories in science. Now, please enlighten me as to which observations would render a belief in God and the creation story as given in Genesis invalid. (Hint: There aren't any such observations)