OrnotBitwise
Watermelon
I disagree. Science Fiction doesn't need to be set in the future, nor does it need to involve on a more advanced technology than that available to the author. What distinguishes Science Fiction from other genres of fiction -- and Fantasy, specifically -- is that S.F. is primarily concerned with the effects of science and technology on society, OR technology or science is used to illustrate a particular theme or point. The second permutation covers such things as Slaughter House Five, which I would never want to kick out of the club.Sci-fi is not only such. It must be set in a time with a higher tech level. In this case it was there. The world specifically didn't have "magic" just a different way of reacting to a mind.
In all cases of sci-fi there is some speculation. Such as "Earth" by David Brin where they create a "Grazer" (a Gravity beam) using a black hole created by humans using techniques that are not in reality today's science. He speculates.
In science fiction, technology becomes a character, as it were. And, like any character, it has to be consistent and believable.
The Darkover novels aren't science fiction simply because she never cared whether the effects to which her characters were subjected were plausible by the standards of science at the time. I say that knowing full well she would not be offended: she literally didn't care because her interest was entirely in the characters. The characters' emotional reactions were realistic, in her mind, so the world they were reacting to was largely immaterial.
That, right there, is the distinction between fantasy and science fiction.