lot of people like cross-genre fiction, but I personally
don't like it much. This type of fiction involves mixing magical elements
with technology. Magic, in this view, is seen as "ancient" as compared
with "modern" technology.
In a Fantasy world, however, magic is not "ancient."
That is looking at it from our primary world perspective where
we have ancient magic replaced by modern technology. In a Fantasy
world, magic has always been, and it will always be. The development
of technology and science in a Fantasy world will actually kill
the Fantasy world. I think this has to do with the fact that
most Fantasy worlds are set in a "pre-industrial" or
what someone has called a "pastoral" society--no trains,
toasters, or ATM machines. Fantasy worlds--at least Tolkienesque
Fantasy worlds--have horses, wagons, forests, and mountains.
And magic. . . .
Bringing actual toasters, computers, or rockets into
the Fantasy world would make the magic seem trivial. On the other
hand, if you had a spell or glamour that could cause bread to
toast, or a crystal that could communicate with another crystal,
or a stone that could provide heat in a frozen climate, you would
imitate modern technology without lugging it into a place where
it ought not to be.
Could Fantasy make use of the concept of a post-cataclysmic
earth, where the Fantasy story takes place on the same continuum,
though with a different time or climate? I don't think so. You
would really be talking about a science fiction story in that
case. Why? Because a Fantasy world is not just our mundane world
in a different time or our world to a different degree;
it's rather a different kind of world. For instance, in
Tolkien, Lewis, Jordan, and Hambly, magic is a different kind
of power, not simply a different degree of power, as is
true in science fiction. When a Fantasy world character finds
a glowing sphere, its light is produced by magic. When
a science fiction character finds a glowing sphere, its light
is produced by a more advanced technology. The sf character
the light is produced by a different kind of power--like
magic--and he'll be amazed by it and awed, but we, the readers,
know it's really a different degree of power, and we hope
he gains access to this power. The technology is what gives the
science fiction character his "edge."
Mixing Fantasy and science fiction gives place to an ontological free-for-all. It is like having the characters from the Flintstones show up on the set of Gone With The Wind. It might be interesting in a bizarre sort of way, but who would want to do it? Such cross-genre fiction is rarely done well.