In a sense, yes. The following image shows it rather neatly IMO (it's everywhere on the 'net so I suppose I'm allowed to post it here as well):
By now we understand that, whatever theory we come up with, it most likely has a range of validity. So we're always searching for theories with
different applicability ranges. Of course, if such an applicability range overlaps with that of an earlier theory, which has proven itself to work very well, we would like to see some (mathematical) limit such that the new theory reduces to the old one on the overlap range. Preferably, you don't get
exactly the same, but something
very slightly different -- some effect that can only be seen in a very accurate measurement, for example -- that allows you to test the new theory.
There is always an interplay between theory and experiment. On one hand experimentalists come up with new results which theorists try to explain by "modifying equations" in a way that makes some kind of sense (e.g. we can of course just
define an equation that gives the right answer, but that's not what we usually mean by "doing physics"). On the other hand theorists come up with new principles as to how nature works, and experimentalists test this by supporting or contradicting the theoretical predictions.
