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Alternate timeline

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Multiple realities
(covers information from several alternate timelines)
Krenim weapon ship firing on Zahl colony

A Zahl colony fired upon by the Krenim weapon ship...

Zahl colony erased from history

...and the alternate timeline where the colony never existed.

For the alternate timeline created by Nero's incursion, please see alternate reality.

Alternate timelines were altered versions of a single timeline. There were several methods of temporal manipulation that could create an altered version of the timeline.

Alternate timeline display

A display featuring several alternate timelines created by the Krenim

As a rule, Starfleet officers were forbidden to cause changes in the timeline or to share their knowledge of future events by the Temporal Prime Directive. (VOY: "Shattered") The Department of Temporal Investigations was tasked to ensure that time travel events did not contaminate the timeline. (DS9: "Trials and Tribble-ations") By the 28th century, changing the timeline had become more universally illegal after the Temporal Accord was established. (ENT: "Cold Front") By the 29th century, Starfleet had taken it on as a mission to use time travel as a means of upholding the integrity of the timeline by fixing changes in the past. It was also Starfleet policy by then to integrate different versions of people into one, when several coexisting ones appeared due to paradoxes and time travel. (VOY: "Relativity")

While the prime timeline was usually restored by operatives from the 29th to the 31st centuries, in some cases, the influence of alternate timelines remained as a part of the chain of events in the prime timeline. Spock for instance would not have learned that he had to travel to the past to save himself from being killed by a Le-matya when he was seven years old, had he not accidentally traveled to an alternate timeline, where he had not yet saved himself. (TAS: "Yesteryear") Warnings, temporal incursions and information of alternate futures were also an integral part of the prime timeline. Such was the case, when Captain Jean-Luc Picard shared his experiences of the future shown to him by Q, to his crew in 2370, causing them to make different life choices that created a new and entirely different future. (TNG: "All Good Things...") USS Voyager was rescued and aided by its crew members from the future. In 2375, a transmission from Harry Kim from an alternate 2390 averted the crash landing of the Voyager. In 2378, technology and assistance from Admiral Kathryn Janeway from an alternate 2404 saved the ship from a longer disastrous journey through the Delta and Beta Quadrants. (VOY: "Timeless", "Endgame")

For a list of all the various time travel and alternate timeline episodes in Star Trek, see: time travel episodes and alternate timeline episodes.

Alternate realitiesEdit

Different versions of a timeline also sometimes coexist as parallel universes. Most active temporal anomalies allow interaction between two different alternate timelines for a moment, making them parallel realities in relation to one another.


The Narada appearing out of a black hole, creating an alternate reality

The writers of Star Trek, Alex Kurtzman and Roberto Orci, were asked about the implications of the new alternate reality that was introduced in the film in an interview. They explained the new reality runs parallel to the prime reality as a new quantum reality, as the concept was explained by Data in the episode TNG: "Parallels". [1]
  • In 2370, Q allowed Picard to shift his consciousness between three different timeframes, one in the past, one in the present and one in the future from Picard's point of view, in order for him to create an anti-time eruption. The eruption was linking these timelines together, and when it collapsed the timelines ceased to exist. (TNG: "All Good Things...")
Several statements in Star Trek suggest that all alternate timelines co-exist. It was stated in ENT: "Azati Prime" that the Sphere-Builders have technology that allows them to examine alternate timelines. In the episode, Daniels even had the technology to take Archer to the future of an alternate timeline. The time vortex was called a focal point of "all timelines" in TAS: "Yesteryear".
The term "alternate reality" was used as a synonym for "parallel universe" by the mirror universe version of T'Pol in ENT: "In a Mirror, Darkly"

Pockets, folds, and fragmentsEdit

USS Enterprise-E enters temporal vortex

An alternate Earth, assimilated by the Borg after their temporal incursion, seen from the wake of a temporal vortex

  • The race of the alien who took the shape of Cosimo existed in temporal inversion folds of the space-time matrix. The folds were parallel time streams visible as temporal anomalies intersecting the prime reality. Inside the folds, reality remained unaffected by changes in the timeline. It was possible to utilize a fold to exchange one's consciousness with an alternate timeline version of oneself. (VOY: "Non Sequitur")
  • Temporal causality loops create independent fragments of time, inside which the time of the universe repeats itself. From outside the loop, it appears as if the things inside had simply vanished from the space-time continuum. For people inside the loop the memories from previous loops begin to assert themselves as a sense of déjá vu and eventually as clearer memories. (TNG: "Cause and Effect")

Time continuumsEdit


The Devidian time continuum

Within the universe there were also several parallel time continuums occupying the same space but in a different time. (TNG: "Time's Arrow")

  • Elysia was a small parallel time continuum that periodically touched the prime universe in the Delta Triangle region. Elysia was described by Devna as a pocket in the garment of time. The collisions between the two alternate universes produced time warp vortexes in the time barrier between the universes, that allowed passage from one side to the other at high warp speed. (TAS: "The Time Trap")

List of alternate timelines Edit

Appendices Edit

Appearances Edit

Alternate timelines are depicted in the following episodes or films:

Related topics Edit

Apocrypha Edit

According to the Star Trek: Myriad Universes story "Places of Exile" by Christopher L. Bennett in the 2008 novel of the series, Infinity's Prism, the concept of quantum realities is synonymous with all types of alternate timelines. According to the 2008 novel Fearful Symmetry by Olivia Woods, the mirror universe is also a parallel quantum universe, further suggesting that even trans-dimensional realms are alternate timelines.

The Star Trek: Department of Temporal Investigations novel Watching the Clock, goes into detail about how and why some forms of time travel create parallel alternate realities and others lead to the overwriting of the same timeline. According to the novel, the only way one timeline could replace another is if they coexisted side by side from the moment of their divergence and were merged together again at a later point. Timelines diverge when they shift sufficiently out of phase to become non-interacting, but it is not impossible for them to interfere again at a later point in time. If they did become entangled as a single system, quantum information theory demands that only one of the two conflicting sets of information survive, as quantum history has to be self-consistent. After the merge, it would be as if one timeline suddenly transformed into another. The previous events would still have occurred, but they would no longer be remembered, as the information would have been destroyed. Two different timelines coming back into phase would violate entropy, so there needs to be some kind of force acting to merge them back together.

The game Star Trek: Armada features the USS Premonition (β) a starship came from an alternate future where the Borg controlled most of the Alpha Quadrant. Captain Thaddius Deming of the Premonition hoped to warn the Federation of a coming Borg invasion in time to prevent the Borg victory. With the help of Captain Jean-Luc Picard of the USS Enterprise-E, and after making two further temporal incursions, the Premonition's mission was a success and she returned back to the future.

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