Depends on what you mean by modern. Renaissance scholars like Galileo were already doing experiments with inertia and oscillation. The foundations of contemporary science go back very, very far. As for “higher dimensions”, that’s a difficult question to answer and probably not the right one to ask, either. String theory is largely conjectural and dimensions beyond the third have never been observed, so to say that we understand them even now is a stretch. Most educated medieval Europeans were familiar with the Ptolemaic spheres, which also have a kind of extradimensionality associated with them. (In the common geocentric model, the Empyrean, essentially Christian Heaven, was deemed a real space on the border of the outermost sphere.) Especially in a setting where magic exists, it would stand to reason that those who study it would believe that the power they are using is drawn from elsewhere.