The boundary between science fiction and social reality is an optical illusion.
Donna Haraway, A Cyborg Manifesto (1991) 
This is no fantasy... no careless product of wild imagination. No, my good friends.
The opening lines of Richard Donner's Superman (1978) 
In a 1950 film serial entitled Atom Man vs Superman  television executive and evil genius Lex Luthor sends Superman into a ghostly limbo he calls "The Empty Doom." Trapped in this phantom void, Superman's infinite powers are rendered useless, for although he can still see and hear the "real" world his ability to interact with it has all but disappeared. Over the following decades this paraspace —to use Samuel Delany's term for a fictional space, accessed via technology, that is neither within nor entirely separate from the 'real' world—would reappear in the Superman mythos in various forms, beginning in 1961. Eventually dubbed "The Phantom Zone," its back story was reworked substantially, until by the mid 60s it had become a parallel dimension discovered by Superman's father, Jor El. Once used to incarcerate Krypton's most unsavory characters, The Phantom Zone had outlasted its doomed home world and eventually burst at the seams, sending legions of super-evil denizens raining down onto Earth. Beginning its life as an empty doom, The Phantom Zone was soon filled with terrors prolific enough to make even The Man of Steel fear its existence.