Point of Divergence

In discussion of counterfactual history, a divergence point (DP), also referred to as a departure point or point of divergence (POD), is a historical event with two possible postulated outcomes. Typically these represent the actual course of historical events (Napoleon lost the Battle of Waterloo) and another, such as Napoleon won the Battle of Waterloo.

In alternate history fiction, the POD is used as the starting point for the extrapolation, as it is indeed in much of the science fiction genre.

In Philip K. Dick's The Man in the High Castle, an alternate history novel in which Germany and Japan win World War 2, the point of divergence is Franklin D. Roosevelt's fictional assassination by Giuseppe Zangara in 1933.

In Ward Moore's Bring the Jubilee, the point of divergence is the fictional victory of the Confederates at the Battle of Gettysburg in 1863. In Eric Flint's alternate history (a time travel variation) he postulates an Assiti Shard event which juxtaposes parts of our planet including the town of Grantville, West Virginia in both space and time—a twist on scientist's referring to a space-time continuum in relativistic (Einsteinian) physics. Similar implausible points of divergence are often referred to as being done by alien space bats.

One multiverse theory posits that PODs are occurring all the time, with an infinite variety of possible outcomes that each creates a universe, this having been used as a premise to the 1990s U.S. television series Sliders. Speculative fiction is full of universes based loosely on the concept of multiple universes, including many fantasy milieus.