And by the way, I wanted to point out that Kindred is not science fiction. You'll note there's no science in it. It's a kind of grim fantasy.
Fantasy is totally wide open; all you really have to do is follow the rules you've set. But if you're writing about science, you have to first learn what you're writing about.
But my problem with fantasy, and horror, and related genres, is that sometimes the problems are illogical.