((Like I said, Star Wars is one of the precursors of modern sci-fi. And by your logic, Einsteinian Roulette is even more firmly in the category of fantasy than Star Wars, because it calls its magic magic and never really tries to explain it.))
((Actually, that is something that occurred to me. It's got magic (space magic
and STEPHEN HAWKING'S shamanic rituals), evil spirits, prophetic hallucinations, it's even got its own version of cessation of progress. Though I do believe the name of space magic is something that came from the players and piecewise just rolled with it. I don't think anybody in the actual setting who isn't a PC calls it that. And it's not that it doesn't try to explain it, it merely makes it very difficult to find out anything about it. So, without knowing the underlying knowledge of the matter, it's hard to gauge how fantastic ER actually is.))
(("Folklore and mythology" are more the ancestors of fantasy than "inspiration"; there isn't a strong divide. On the other hand, there is as strong divide between, say, Westerns or samurai movies and science fiction.))
((Doesn't fantasy also draw from samurai movies and westerns (well, at least certain subgenres of it)? There's stuff like urban fantasy, which takes stuff from the same contemporary narratives as science fiction, and low fantasy, which has elements of various realistic period pieces, and more. Even if we discount folklore and mythology (between which and fantasy there is indeed a strong divide, if only because of folklore and mythology being a mutable, variable invention of the people (the latter created to facilitate understanding of life, no less), while fantasy is a mostly immutable invention of what is usually a single person), fantasy has a whole lot of inspirations. Probably as many or more than science fiction, I would say.
And like piecewise said, you can't draw an absolute line between science fiction and fantasy. It's more of a gradient, really, in the middle of which science fiction is fantasy in a different dress and vice versa.))