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

Battle of Waterloo

The Battle of Waterloo was fought on Sunday 18 June 1815 near Waterloo in present-day Belgium, then part of the United Kingdom of the Netherlands...

) 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

Extrapolation

In mathematics, extrapolation is the process of constructing new data points. It is similar to the process of interpolation, which constructs new points between known points, but the results of extrapolations are often less meaningful, and are subject to greater uncertainty. It may also mean...

, as it is indeed in much of the science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 genre.

In Philip K. Dick

Philip K. Dick

Philip Kindred Dick was an American novelist, short story writer and essayist whose published work is almost entirely in the science fiction genre. Dick explored sociological, political and metaphysical themes in novels dominated by monopolistic corporations, authoritarian governments and altered...

's The Man in the High Castle

The Man in the High Castle

The Man in the High Castle is a science fiction alternate history novel by American writer Philip K. Dick. It won a Hugo Award in 1963 and has since been translated into many languages....

, the point of divergence is Franklin D. Roosevelt

Franklin D. Roosevelt

Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...

's fictional assassination in 1933

Giuseppe Zangara

Giuseppe Zangara was the assassin of Chicago mayor Anton Cermak, though United States President–elect Franklin Delano Roosevelt may have been his intended target. Roosevelt escaped injury, but five people were shot including Cermak.- Early life :Zangara was born in Ferruzzano, Calabria, Italy...

. In Ward Moore

Ward Moore

Ward Moore was the working name of American author Joseph Ward Moore. Moore grew up in New York City, and later moved to Chicago, and then to California....

's Bring the Jubilee

Bring the Jubilee

Bring the Jubilee by Ward Moore is a 1953 novel of alternate history. The point of divergence occurs when the Confederate States of America wins the Battle of Gettysburg and subsequently declares victory in the "War of Southron Independence" on July 4, 1864 after the surrender of the United States...

, the point of divergence is the fictional victory of the Confederates at the Battle of Gettysburg

Battle of Gettysburg

The Battle of Gettysburg , was fought July 1–3, 1863, in and around the town of Gettysburg, Pennsylvania. The battle with the largest number of casualties in the American Civil War, it is often described as the war's turning point. Union Maj. Gen. George Gordon Meade's Army of the Potomac...

 in 1863. In Eric Flint

Eric Flint

Eric Flint is an American author, editor, and e-publisher. The majority of his main works are alternate history science fiction, but he also writes humorous fantasy adventures.- Career :...

'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

Grantville, West Virginia

Grantville is a fictional West Virginia town that appears in Eric Flint's 1632 series. The American town - including land, people, resources and all - was transported back in time from the year 2000 to the middle of 17th century Europe in central Germany by irresponsible aliens...

 in both space and time—a twist on scientist's referring to a space-time continuum in relativisic (Einsteinian) physics. Similar implausible points of divergence are often referred to as being done by alien space bats

Alien space bats

Alien space bats is a neologism for plot devices used in alternate history to create a point of divergence that would otherwise be implausible.-Definition:...

.

One multiverse

Multiverse (science)

The multiverse is the hypothetical set of multiple possible universes that together comprise everything that exists and can exist: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them...

 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.

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 television series Sliders

Sliders

Sliders is an American science fiction television series. It was broadcast for five seasons, beginning in 1995 and ending in 2000. The series follows a group of travelers as they use a wormhole to "slide" between different parallel universes. The show was created by Robert K. Weiss and Tracy Tormé...

. Speculative fiction

Speculative fiction

Speculative fiction is an umbrella term encompassing the more fantastical fiction genres, specifically science fiction, fantasy, horror, supernatural fiction, superhero fiction, utopian and dystopian fiction, apocalyptic and post-apocalyptic fiction, and alternate history in literature as well as...

is full of universes based loosely on the concept of multiple universes, including many fantasy milieus.