Histories: alternate, future, and secret

Science fiction can set stories in the conventional past, like any garden-variety historical novel. Or SF can move characters -- see my previous post about the Time Travel Trope -- in and out of the conventional past. But SF can do so much more. The genre also offers:

Alternate history: What if history had gone a different way, like the South winning the Civil War? (Or, more intriguingly: What slight change -- like a Confederate battle plan not lost before the Battle of Antietam -- would lead to the South winning?) Thereafter, how might events unfold? Example: Harry Turtledove’s How Few Remain.

Future history: A story set against a future so richly imagined that it feels like history. Examples: Isaac Asimov’s Foundation series or -- from the guy who arguably invented the concept -- Robert Heinlein’s Future History stories.

Secret history: A story that unfolds within history as we know it -- while making us understand that history in a new way. Example: Michael Flynn’s Eifelheim, in which aliens were stranded in medieval Germany. More mainstream: Dan Brown’s The Da Vinci Code.

Combinations: Why not mix ’em up?

Playing with history, past and future, is a lot of fun. It must be -- we SF authors do it often. And mea culpa. Fleet of Worlds and, more so, Juggler of Worlds, both of which I co-wrote with Larry Niven are -- while standalone -- also secret future histories within Larry's Known Space.