Parallel universe

Overview
A parallel universe (or alternate universe) is a separate and self-contained universe existing as consequence of different choices and outcomes than those that led to our own state of reality.

There exists an infinite number of parallel universes (sometimes known as quantum universes, quantum realities or quantum states), one for every possible outcome of every possible event that occurs throughout time. For example, in one parallel universe Jean-Luc Picard was lost to the Borg; in another the Borg triumphed over the Federation. In another, Worf married Deanna Troi. (TNG: "Parallels")

The most frequent contacts between "our" universe and a parallel universe involved the so-called mirror universe, with the first reported crossover occurring in 2267. (TOS: "Mirror, Mirror")

Alternate timelines differ from parallel universes. An alternate timeline is created by time travel within the same universe, spawning a different set of historical events. Multiple timelines are a result of time travel, which can both alter and restore the timeline.

Parallel universes are considered the 5th dimension by The Guardians. (Star Trek: Pioneer)

Fan fiction
Many Star Trek fan-fiction venues are, by their nature, set in parallel/alternate universes. Following are some examples:
 * ARC undefined

Mirror universe
Parallel mirror universes:

There are also those series which are set in the primary universe but crossover into parallel universes:


 * Dark Reflection
 * A Mirror, Shattered
 * Reality's Threshold, Parts 1 and 2
 * Infinite Empires
 * Moebius, Parts 1 and 2
 * Immunity Against Doomsday
 * Immunity Against Doomsday

An anthological series of one-off stories, Parallel Lives is part of the Star Trek: Special Operations universe of fan-fiction. Each story deals with a parallel universe counterpart of Special Ops lead character Scott Freeman. Among those written so far, there have been a universe where the British Empire never ended and replaces the UFP, one where Freeman was born a girl and one based on the Mirror Universe.


 * Special Ops' fifth part, 'Reflections' sees the crew transported into an alternate universe where the Borg are running rampant.
 * Special Ops' fifth part, 'Reflections' sees the crew transported into an alternate universe where the Borg are running rampant.

Canon references

 * ENT:
 * "In a Mirror, Darkly"
 * "In a Mirror, Darkly, Part II"
 * TOS:
 * "Mirror, Mirror"
 * "The Tholian Web"
 * TNG:
 * "Parallels"
 * DS9:
 * "Crossover"
 * "Through the Looking Glass"
 * "Shattered Mirror"
 * "Resurrection"
 * "The Emperor's New Cloak"