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 human species really could have faced global thermonuclear war. During seventy years of Cold War we grew used to it.
Larry Niven