Today And Tomorrow

Sf can be set in the past, present or future, on or off Earth, whereas mainstream fiction has to be contemporary and on Earth. However, if an author sets a novel at the time of writing, then, on a regular writing schedule, adds sequels in which the original characters' children and grandchildren grow to adulthood, then, over perhaps three years of writing, that series has grown perhaps four decades into the future. This could be one point of transition from contemporary to futuristic fiction. The present is so transient.

An sf future can be "day after tomorrow," i.e., the world is as we know it but with just one change or innovation. CS Lewis' That Hideous Strength, published in 1945 and set vaguely after the war, presents one tangential technological innovation but many behind-the-scenes supernatural and extra-terrestrial interventions - this written by a man who did believe in regular divine, angelic and demonic interventions. Poul Anderson's Brain Wave begins in the 1950s USA - when a cosmic force increases animal and human intelligence and changes human motivations, a Wellsian premise.

Imagine a futuristic series that avoids cliches like FTL or humanoid aliens but traces ecological and human developments through a finite future period. Poul Anderson did write different kinds of future history series, changing from FTL with aliens to STL without aliens. His Technic History begins with a possible near future scenario. His Genesis summarizes past history, accelerates through the writer's present and reaches a remote post-human future that will not be counterfactualized for a very long time.