"Hard" science fiction probes alternative possible futures...

"Hard" science fiction probes alternative possible futures by means of reasoned extrapolations in much the same way that good historical fiction reconstructs the probable past. Even far-out fantasy can present a significant test of human values exposed to a new environment. Deriving its most cogent ideas from the tension between permanence and change, science fiction combines the diversions of novelty with its pertinent kind of realism.