The brightest minds in our field have been trying to find a definition of science fiction for these past seventy years. The short answer is, science fiction stories are given as possible, not necessarily here and now, but somewhere, sometime.
Larry NivenAs for AIDS, it's a plague. We are human, we get plagues. They come along every so often, kill off two thirds of the population; in the next generation it's a quarter; after that it's a childhood disease.
Larry NivenThe Product of Freedom and Security is a constant (F X S = k). Giving up freedom for security is beginning to look naive.
Larry NivenThere were timelines branching and branching, a mega-universe of universes, millions more every minute. Billions? Trillions? The universe split every time someone made a decision. Split, so that every decision ever made could go both ways. Every choice made by every man, woman, and child was reversed in the universe next door.
Larry Niven