Strictly speaking, every science fiction tale presents its own version of future and therefore there are as many science fiction universes as there are science fiction stories. Many SF tales follow dictates of a particular subgenre like Cyberpunk or Space Opera of which, see the separate entry.
... numbers, or more generally members of any field whose characteristic is not 2. (In a field of characteristic 2, the element 2a is zero and it is impossible to divide by ...