[ Science is not and has never been ' fixed ' at any one point at any one time ever. For obvious reasons. ]
Astrophysicist Dave Goldberg:
Members of the general public (along with people with an ideological axe to grind) hear the word "theory" and equate it with "idea" or "supposition." We know better. Scientific theories are entire systems of testable ideas which are potentially refutable either by the evidence at hand or an experiment that somebody could perform. The best theories (in which I include special relativity, quantum mechanics, and evolution) have withstood a hundred years or more of challenges, either from people who want to prove themselves smarter than Einstein, or from people who don't like metaphysical challenges to their world view. Finally, theories are malleable, but not infinitely so. Theories can be found to be incomplete or wrong in some particular detail without the entire edifice being torn down. Evolution has, itself, adapted a lot over the years, but not so much that it wouldn't still be recognize it. The problem with the phrase "just a theory," is that it implies a real scientific theory is a small thing, and it isn't.
[ And America needs to stop elevating being gleefully ignorant as a fucking virtue. It's not. It's wrecking our country. Yeah, I said it. ]