Theories in science, especially on the vague outskirts, lends itself to ideas that are a bit further than science could claim. This is the realm of fantasy.
Forms of propulsion in fiction can outstrip the confines of the purely scientific world. A lot of this stuff has a scientific basis but some – occasionally – goes a little further and taps into things from realms where science does not tread.
Magic is the basis of most fantasy, at least that of the epic sort. Tolkein, Eddings, and the like steep their tales in the stuff.
But what of the borderlands between the two?
Heinlein’s “Magic Inc” was a marvelous excursion into a magical world viewed scientifically. Sure there was magic but it followed rules and “scientific” theorems.
The magic in the Harry Potter stories attempted to stay “true” to the history of the arcane arts but fell far short of any sort of “science” of magic.
I think a lot of what we today call “parapsychology” – the sixth sense, e.s.p., and such – though still considered pseudoscience, is tantalizingly close to what we know of fringe science.
Sure, it’s fantasy, but it is almost science.