- This article refers to the general concept of alternate realities, for the timeline of the 2009 movie Star Trek see alternate reality (Nero, 2233), for other specific timelines see listings below.
An alternate reality (which may also be referred to as an alternate quantum reality, alternate timeline or parallel timeline) is a divergent timeline, a distinct branch in any one universe. The terms "alternate universe" or "parallel universe" are sometimes also used to refer to alternate realities, however such usage is inaccurate; a universe is a distinct separate place, divided from other universes by higher dimensions (and may have its own alternate timelines), while an alternate reality is merely a different quantum facet of any one universe, with the same laws of physics, just different histories. (VOY - Myriad Universes novel: Places of Exile)
As understood by quantum theory, any event creates an infinite number of possible outcomes, all of which are played out in alternate quantum realities. Each alternate reality is ordinarily separate from the others, and distinguished by its unique quantum signature. Alternate realities, together with alternate universes (and their own alternate realities), form the multiverse. (TNG episode: "Parallels"; VOY - Myriad Universes novel: Places of Exile; TNG novel: I, Q)
Knowledge of other realitiesEdit
In theory there are an infinite number of realities, ever branching with one for every infinite outcome. As of the 2370s, Starfleet had records of 285,000 different quantum realities. (TNG episode: "Parallels"; ST reference: The Starfleet Survival Guide)
Other cultures have exhibited far greater knowledge and even control of the timelines. The Sphere Builders had technology which allowed them examine timelines. When they were manipulating the Xindi into trying to destroy Earth in the 2150s, they could see when the actions of the starship Enterprise were generating more timelines with unfavorable outcomes for themselves and acted to try and alter the flow of the events to something they preferred. (ENT episodes: "Azati Prime", "Zero Hour")
El-Aurians seemed had an innate ability to read timelines. In at least two different alternate timelines, both of which, for different reasons, had seen the Federation and the Klingon Empire go to war, Guinan provided counsel to Jean-Luc Picard as she was concerned that things were not as they should be. She could sense there was another more peaceful timeline and sought to have actions taken to change the timelines to avert the wars. (TNG episode: "Yesterday's Enterprise"; TNG - The Last Generation comic: "Do Not Close Your Eyes")
In the 22nd century the Krenim scientist Annorax created the Krenim temporal weapon ship, armed with a weapon which could wipe entire civilizations out of time, and in doing so create new divergent timelines. Over the next two centuries Annorax made alteration after alteration, carefully monitoring the timelines to try and restore the Krenim Imperium to greatness. (VOY episode: "Year of Hell")
In 2376, Iliana Ghemor, driven mad by years of captivity and believing she was Kira Nerys, devised a plan to travel to as many alternate realities as she could access and kill all other Kira Nerys; determined she would be the only one. (DS9 novel: Warpath)
By the 29th century Starfleet had an advanced knowledge of time travel and alternate realities and employed temporal agents to monitor them. One agent, Captain Braxton became aware of massive event that literally destroyed the galaxy; he could not determine what caused the event due to the temporal chaos surrounding it, but could see that only timeline in which the Federation no longer existed survived it. In trying to undo the catastrophe and save as many timelines as possible Braxton made alterations through time, including attempting to sabotage the Khitomer Accords. (TNG - The Last Generation comic: "The End of History")
22nd century alternate timelinesEdit
23rd century alternate timelinesEdit
In the 2250s and 2260s, Christopher Pike commanded the UESS Enterprise in a timeline in which United Earth became isolationist following Terra Prime's successful attack on the Coalition of Planets conference in 2155. (TOS - Myriad Universes novel: A Less Perfect Union)
In 2267, Doctor Leonard McCoy traveled through the Guardian of Forever to 1930, creating a timeline in which Edith Keeler did not die in a traffic accident. (TOS episode: "The City on the Edge of Forever" and TOS novel: Provenance of Shadows)
- See mirror universe article for other crossovers with the main mirror universe and alternate mirror universes.
In 2270, Dr. Georges Mordreaux conducted time travel experiments that resulted in alternate timelines, including one in which his insane future self killed Kirk with a spiderweb gun. (TOS novel: The Entropy Effect)
24th century alternate timelinesEdit
In 2366, a timeline was created in which the removal of the USS Enterprise-C from 2344 resulted in war between the Federation and the Klingons. The Tasha Yar of this timeline joined the crew of the Enterprise-C, and later became the mother of Sela. (TNG episode: "Yesterday's Enterprise")
In 2369, Jean-Luc Picard, with the aid of Q, created a timeline in which he did not get into a fight with a group of Nausicaans in his youth and, consequently, never assumed command of the Enterprise-D. In that year, he was a lieutenant junior grade serving in the ship's stellar cartography department. (TNG episode: "Tapestry")
In 2370, Montgomery Scott traveled back to 2293 and rescued Kirk from his apparent death on the Enterprise-B, thus creating a timeline in which the Borg invasion of 2063 was successful. (ST novel: Engines of Destiny)
In 2371, members of the crew of Deep Space 9 accidentally created a timeline in which the social reforms that followed the Bell Riots never occurred. Consequently, neither United Earth nor the United Federation of Planets ever existed while the Romulan Star Empire was able to expand its territory to Alpha Centauri. (DS9 episodes: "Past Tense, Part I", "Past Tense, Part II")
Later that year, while Kirk lay dying on Veridian III, the Organians showed him a timeline in which he had resigned from Starfleet following his initial encounter with the Guardian of Forever. (TOS short story: "Reflections")
Later that year, the removal of Benjamin Sisko from normal space-time created an alternate timeline in which Jake Sisko spent the rest of his life trying to get his father back. In this timeline, the Federation-Klingon War intensified following Captain Sisko's disappearance, resulting in the Federation's withdrawal from Deep Space Nine and the existence of poor relations between the two former allies well into the 25th century. Furthermore, Jadzia Dax was still alive in 2422 and the Dominion War never took place. (DS9 episode: "The Visitor")
Later that year, a timeline was created in which the USS Defiant traveled back in time 200 years and crashed on a planet in the Gamma Quadrant, forcing the crew to colonize it. (DS9 episode: "Children of Time")
Later that year, Wesley Crusher created a timeline in which the Battle of the Border was fought between the Federation and the Cardassian Union in late 2370. (TNG short story: "Gods, Fate, and Fractals")
In one timeline, Captain Braxton believed that Voyager would be responsible for accidentally destroying Earth in the 29th century, and attempted to prevent this by destroying Voyager first. (VOY episode: "Future's End")
That year also saw the creation of a timeline in which the opening of a second wormhole in the Bajoran system destroyed Deep Space 9. (DS9 - Millennium novels: The Fall of Terok Nor, The War of the Prophets, Inferno)
In 2375, an attempt to use a quantum slipstream drive to return Voyager to the Alpha Quadrant created a timeline in which the ship crashed on an ice planet, killing everyone aboard and leaving Chakotay and Harry Kim as the only surviving crewmembers. (VOY episode: "Timeless")
In 2376, an alternate timeline was created in which the Borg successfully assimilated Ambassador Spock, leading to the destruction of Starfleet Command and the assimilation of Earth. (TNG video game: Armada)
In a timeline in which Khan Noonien Singh won the Eugenics Wars and Humans underwent genetic engineering en masse, Princeps Julian Bashir commanded the Khanate of Earth starship Defiance during the late 24th century. (DS9 - Myriad Universes novel: Seeds of Dissent)
The majority of Star Trek stories take place in "prime reality", a singular timeline which runs from the present day through to all the Star Trek series. The prime reality has generated numerous alternate timelines, though these normally are only explored for the duration of one story. One major exception is the "mirror universe", which has been developed in multiple stories across multiple series (so much so in fact that a number of alternate mirror universes have even been seen). The 2009 movie Star Trek saw a significant movement in the Star Trek universe, with the film establishing a new alternate reality, which rather than being "repaired" back to the prime universe has become the new leading edge of the franchise, with new movies to be set in the continuation of this timeline rather than the original prime timeline. Meanwhile stories from across the franchise continue to be told in both the prime and new timeline, and in the Myriad Universes series even in other alternate timelines.
In his annotations for Places of Exile, Christopher L. Bennett postulates a rationalization for why divergent timelines, even centuries after the point of divergence, manage to generate the same characters, settings and scenarios, even when the same settings recurring so similarly are so improbable: Bennett suggests that because a being in a different timeline is merely one outcome for the same matter that "the physical connection across different timelines means that there can be a sort of quantum resonance: the shared "inertia" of different quantum facets of the same being causes their lives -- and their genetics -- to develop along similar lines"