The two genres I'm most exposed to, at least when it comes to reading, are science fiction and fantasy. I like it when there's some romance in there as well, but it's not a constant, and I definitely prefer it as a sub-genre... no "romance novels" for me, thanks. What I've been wondering about, though, is that dividing line between the genres of fantasy and science fiction, and when it's okay to cross them.
My understanding has always been that science fiction is about objects that can do amazing things, and fantasy is about people that can do amazing things. Sometimes that's cut and dried, sometimes it isn't.
Example 1: Lois McMaster Bujold's Vor series. Unquestionably science fiction. There are spaceships, wormholes, interplanetary travel, aliens. (In some ways it's a milieu story because the backdrops of Beta Colony and Barrayar are so important, but it boils down to a character story in the end.) Miles Vorkosigan is an absolutely unique guy, but there's nothing so obviously out of the ordinary that it would make it a fantasy tale.
Example 2: Jacqueline Carey's Kushiel series. Unquestionably fantasy. It takes place in an alternate history. Some characters' "gifts from the gods" could perhaps be undiagnosed medical/mental conditions, perhaps, but there are also men who control the seas, people who can see the future, curses and whatnot. (The two trilogies here are both character stories, and IMO the first is much stronger, but they're both very good.)
But what about...
Example 3: Sharon Shinn's Samaria books? In the beginning, the first book, Archangel, seems to be plainly fantasy. There are angels flying around, for crying out loud, actual men and women with wings who sing to the god, Jovah, for rain or medicine or whatnot. But then Shinn starts dropping clues about how this is taking place on what seems to be another planet, and maybe Jovah isn't a god after all, but a spaceship in orbit, and angels are only genetic freaks whose job it is to keep the ecosystem in balance. The uncovering of this apparent conspiracy actually becomes the plot of the next two books, and in a companion book, Angelica, the main character actually visits the ship, even though she doesn't know what she's seeing. And yet all of the books have a fantasy novel feel about them. If you look on amazon, the first book is tagged as fantasy or romantic fantasy, but by the time you get to the third, it's also tagged as science fiction.
It doesn't get much clearer when you get to TV. Okay, obviously the Stargate series are science fiction; even though they might play off of mythology, there is always a technical reason to it. The object that can do amazing things is (among other objects) the Stargate itself. In Star Trek we are usually focused on the amazing things that the ships can do; even though some of the characters can do amazing things, like read minds and shape-shift, this is always explained in terms of biology and science.
Example 4: But what about The X-Files? It's sci-fi, is the obvious conclusion. There are aliens, for Pete's sake, and it took place in the present day, modern world. But many of the Monster of the Week tales dealt with people that could do amazing things, like start fires with their minds or actually 'talk' someone into killing themselves. Sometimes we are given a medical reason for these abilities. Sometimes it's only hinted at, or offered up as a possibility, and the audience, along with Mulder, look at Scully with a "yeah, right" kind of expression.
Example 5: Star Wars. It's movie, not TV, but whatever. This is another hard one. There are ships, and amazing technology, and aliens. But there's also people, Jedis, who have amazing abilities, can move things with their minds and sense things that other people cannot. That borders on fantasy, doesn't it? (Of course, Episode I killed that with their talk of midichlorians, but I prefer not to think about Episode I unless I must.) We generally think of Star Wars as science fiction, but it incorporates fantasy elements... prophecies, for example.
Anyone else out there interested in this subject? Think of any other examples of sci-fi/fantasy hybrids?