Science Fiction explores the probable consequences of some improbable or impossible transformation of the basic conditions of human (or intelligent non-human) existence. This transformation need not be a technological invention, but may be some mutation of known biological or physical reality: artificial or extraterrestrial life-forms and travel through time are favourite subjects. Science Fiction stories may involve Utopian political speculation, or satire, but most rely on the marvellous appeal of fantasy. The term Science Fiction was first given general currency by Hugo Gernsback, editor of the popular Amazing Stories magazine from 1926. Once uniformly dismissed as pulp trash, SF gained greater respect from the 1950s, as writers like Isaac Asimov, Ray Bradbury, Arthur C. Clarke, and John Wyndham expanded its range; themes of alien invasion and brain-washing became especially popular at the height of the Cold War.