See first quotes from Kingsley Amis
science fiction n. | 1960 | New Maps of Hell 14 Science fiction is that class of prose narrative treating of a situation that could not arise in the world we know, but which is hypothesized on the basis of some innovation in science or technology, or pseudo-science or pseudo-technology, whether human or extra-terrestrial in origin.
space opera n. | 1960 | New Maps of Hell ii. 44 In space-opera, Mars takes the place of Arizona with a few physical alterations, the hero totes a blaster instead of a six-gun.