Science fiction is a genre of futuristic storytelling commonly based on alternatives to what is currently considered scientifically possible, as in reviving long dead Charles Darwin, or based on extrapolations from present-day scientific knowledge, as in human teleportation. The stories are often set in the future and often in non-Terrestrial locales, but science fiction tales may be set in the past as well, particularly through the use of story lines involving alternate history and time travel.
Although controversial, many people like to separate Fantasy writing (which may include "magic", unbelievable things which one never could expect to be realized by technology in the future) from writing about things which might be possible technologically someday. Defining this genre is so frought that some people in recent years have sought to rebrand it as speculative fiction and make no distinction between science fiction and fantasy. There does not seem to be any widespread agreement on whether these topics can or should be separate or together. With sub-genres such a time travel or alternate universes, people have an especially difficult time agreeing on classification; hence the catch-all term speculative fiction seems to be gaining in popularity.
Science fiction stories can manifest in short stories, novels, novellas, motion pictures, animated films, television shows, radio programs, comic books, graphic novels, theatrical plays, and poetry.
Science fiction is generally considered to have been introduced in the nineteenth century by authors such as Jules Verne, Edgar Allan Poe, and H. G. Wells, although elements of what would come to be called science fiction can be found in earlier literature as well. The genre became more widely popular in the second half of the twentieth century. Once a fringe genre, today science fiction is not only mainstream, but has spawned a number of sub-genres, including speculative fiction and space opera [1]. What constitutes true science fiction and what crosses over into other categories, including fantasy and horror, are subjects of heated discussion among aficionados.
Science fiction experienced a strong increase in popularity from the late 1930's throughout the 1950's. The time period is referred to as the Golden Age and its origin is credited to the beginning of John W. Campbell's tenure as editor of the science fiction magazine Astounding in 1938. Campbell demanded greater focus on scientific realism and more in depth characterization. Most science fiction authors of the time credited Campbell as their greatest influence, including Isaac Asimov and Robert A. Heinlein.