Time travel is the having the ability to or the act of traveling forward or backward in time. The study of this phenomenon is one of the focuses of temporal mechanics. Irreparable alterations in the space-time continuum can cause, among other things, alternate timelines and realities.
The United Federation of Planets had some form of time travel ability since at least 2268. It is possible that at least some of the regulations regarding time travel trace their origins back to this date. However, capability at this point was most likely inaccurate, making any attempt at time travel experimental and dangerous.
In addition to the Federation, the Borg Collective, Bajorans, and Klingon Empire were known to have some form of time travel capabilities. (Star Trek: First Contact; DS9: "Wrongs Darker Than Death or Night"; VOY: "Endgame")
As of 2378, at least forty different instances of some form of time travel had been noted in Federation records. Technologically speaking, the Federation's capabilities concerning time travel, for the most part, remained unclear.
Crewman Daniels, an alleged time traveler from the 31st century, showed Jonathan Archer a group of time-traveling anthropologists from 2769 observing the building of the pyramids of Giza. (ENT: "Cold Front")
In 2267, after an encounter with a black star, the Enterprise was hurled three hundred years into the past. Eventually, the Enterprise's science officer Spock devised a method for returning the Enterprise back to its original period. (TOS: "Tomorrow is Yesterday")
Though other instances of time travel had been noted, this appears to be the first instance of controlled time travel by the Federation. Later that year, officers Kirk, Spock, and McCoy traveled to Earth's early 20th century and back via the Guardian of Forever. (TOS: "The City on the Edge of Forever")
In 2286, Admiral James T. Kirk and his senior staff took a stolen Klingon Bird-of-Prey back in time to the year 1986 to retrieve a pair of then (2286)-extinct humpback whales to save Earth from destruction by an alien probe. (Star Trek IV: The Voyage Home)
In 2371, Captains Jean-Luc Picard and James T. Kirk used the Nexus as a means of controlled time travel, going to just before the destruction of the Veridian star, which Picard intended to save. (Picard arrived at the Nexus from just after the destruction of said star, whereas Kirk arrived from some 78 years before). (Star Trek Generations)
Twice, Q took Picard back in time; once when Picard lay dying in a Starbase Medical facility during a replacement of a defective artificial heart that he received as a result of a a Nausicaan knife being stabbed through his heart immediately after Picard had graduated from Starfleet Academy on Starbase Earhart (TNG: "Tapestry") and another time to the beginning of life on Earth and also back and forth in Picard's lifetime. (TNG: "All Good Things...")
During a transporter accident above Earth in the USS Defiant caused by chroniton particles, Benjamin Sisko, Julian Bashir, and Jadzia Dax were sent back in time to mid 21st century, just before the Bell Riots. This causes the Federation and Starfleet to vanish in the present, after the time travelers' interference leads to the death of Gabriel Bell. Only the Defiant was left protected by the chroniton particles. Sisko took on the identity of Gabriel Bell to ensure that he was remembered for saving hostages during the events, and ultimately allowing the Federation to come into being centuries later. (DS9: "Past Tense, Part I")
Akorem Laan, a poet and seer from Bajor's past (which history had recorded had mysteriously disappeared) was sent to the future by the Prophets, believing he was the Emissary of the Prophets. Ultimately, Sisko convinced the Prophets to send Laan back into his own period. Laan later went on to finish one of his prophetic poems, which Kira remembered as unfinished, after Laan had disappeared. Sisko points out that the ending of the poem had appeared in databases, along with new history of his life after his return to Bajor. Kira wonders why she could remember the previous timeline, if said previous timeline had been wiped out. Sisko commented that time works in mysterious ways whenever the Prophets are involved. (DS9: "Accession")
In 2373, the USS Defiant, commanded by Captain Sisko, traveled back in time to 2268 via the Bajoran Orb of Time, in an attempt by Arne Darvin to kill James T. Kirk and change the timeline. The crew of the Defiant stopped Darvin without any notable damage. (DS9: "Trials and Tribble-ations")
Around Stardate 50814.2 (of an unknown year), the Defiant became stuck behind a barrier on a planet in the Gamma Quadrant, where they met the inhabitants who told them they were the descendants of the crew of that crashed on the planet two hundred years in the past. With foreknowledge of the crash, the crew surmised that if they escaped that fate, the timeline would collapse and everything on the planet cease to exist. The descendant of Jadzia Dax, Yedrin, surmised that it would be possible to save their colony, due to an energy discharge that had hit Major Kira, which had created a subspace doubling effect, and for an instant created corresponding quantum duplicates of every molecule in her body. By amplifying the doubling effect through modifications to the Defiant, they could make a quantum duplicate of the entire ship, and this second ship would then be the one that would crash on the planet preserving the original timeline. However, the other Defiant would be able to escape as well.
However, Yedrin had falsified information in his plan, with the intent of making sure that the original (un-duplicated) single Defiant would crash on the planet, thus ensuring that the colony would continue to exist. The Defiant crew ultimately made the decision to sacrifice the ship by flying into the temporal anomaly, in order to save the eight thousand colony members. However, the ship's flight plan was changed by Odo so that it would clear the barrier. This erased the settlement and all of its' inhabitants from the planet. (DS9: "Children of Time")
Kira used the Orb of Time to learn about her mother's life on Terok Nor. Before she began her orb experience, she was warned not to interfere with the timeline by Sisko. Kira nearly assassinated her own mother and Dukat, but changed her mind at the last moment. The orb then returned her to the present. (DS9: "Wrongs Darker Than Death or Night")
Upon returning to Golana through the time portal three hundred years into the past, an adult Molly helped the younger Molly return to the present. Shortly after saving the younger Molly, the older Molly ceased to exist, vanishing from existence as the timeline corrected itself. (DS9: "Time's Orphan")
Also in 2373, an encounter with the 29th century timeship Aeon threw Voyager back to an alternate 1996. History was corrected when Captain Janeway destroyed the timeship before it could travel to the future and accidentally cause a temporal explosion. Voyager was returned to the correct time by an alternate version of the Aeon from the correct timeline. (VOY: "Future's End", "Future's End, Part II")
An alternate future version of Janeway (from 2404) traveled back to 2378 through the use of a chrono deflector to bring Voyager home from the Delta Quadrant sixteen years earlier than it had arrived in that alternate future. This future Janeway was killed in the attempt but succeeded in returning Voyager home and even delivered a crippling if not fatal blow to the Borg. (VOY: "Endgame")
In 2387, Nero and Spock were sent back in time through a Red matter black hole which had prevented a supernova from destroying the galaxy (but not before it had destroyed Romulus in the process). Nero was sent back to the past to 2233, where he destroyed the USS Kelvin, then went into hiding for twenty-five years awaiting Spock's arrival. Spock arrived in Nero's new timeline in 2258. Nero destroyed Vulcan, while Spock watched from Delta Vega. The crew of the USS Enterprise with the help of James T. Kirk, stopped Nero from destroying Earth. (Star Trek)
Temporal Cold WarEdit
The events of the Temporal Cold War further complicated the understanding of Federation time travel capabilities.
As of the 28th century, a time traveling faction represented by a mysterious individual, could only communicate and exchange information and technologies through time, appearing as non-corporeal entities. By the 29th century, this technology was perfected to allow physical travel.
According to a Temporal Enforcement Agent from the 31st century named Daniels, all time travelers were bound by the observance of strict procedures set forth in the Temporal Accords. Daniels stated that the Temporal Accords were enacted after time travel was developed by all time travel-capable species to prevent catastrophic tampering with the timeline.
In 2153, the Sphere-Builders, a group previously thought to possess the ability only to examine alternate timelines, sent Xindi-Reptilians back to 21st century Detroit to develop a bio-weapon to destroy the Human race. (ENT: "Carpenter Street")
Ultimately the war ended when the Na'kuhl returned from an alternate 1944 (created by their very actions) and caused the Cold War to go hot with time-travelers changing time as they liked. Daniels brought Enterprise and Archer back to 1944 to stop Vosk, leader of the Nak'uhl, from returning to the future. With the help of Silik, a member of another faction of the Temporal Cold War, Archer shut off Vosk's compound's shields, allowing Enterprise to destroy it and thus destroying the temporal conduit and killing Vosk just as he was about to travel back to the future. Daniels pulled Archer to a place where they watched the time stream as all of the events that occurred when the Temporal Cold War went hot were undone and time reset itself to normal. Archer refused to have anything to do anymore with Daniels' "damn Temporal Cold War" and Daniels agreed, claiming it was finally coming to an end thanks to Archer's actions. (ENT: "Storm Front", "Storm Front, Part II")
- Black hole created by red matter
- Chrono deflector
- Light-speed breakaway factor (Slingshot effect)
- Orb of Time
- Q powers
- Temporal causality loop
- Temporal conduit
- Temporal transporter
- Temporal vortex
- Time portal
- Department of Temporal Investigations
- Janeway Factor
- Temporal anomaly
- Temporal Integrity Commission
- Temporal Prime Directive
In the novel Ishmael, Captain Spock embarked incognito aboard a Klingon ore transport, refitted with time travel capacity. The ore transport managed to go back to 1867 Earth after an acceleration close to a white dwarf near Starbase 12. The USS Enterprise was modified to follow the ship to 1867, becoming the first instance that a Federation ship utilized intentional and controlled time travel.
In the video game Star Trek: The Next Generation - Future's Past for the Super Nintendo, the computer mentions several temporal near-catastrophes in the 23rd century: the New York incident, the above-mentioned "Ishmael incident," and the "Eyeglass Loop Paradox" referring to what Kirk did in Voyage Home with his glasses.
The Department of Temporal Investigations novels Watching the Clock and Forgotten History go into detail about the principles of time travel, as well as the hows and whys of the various time travel incidents in Star Trek's history. The most significant of these demonstrates how Starfleet became aware that history could change- previously they had assumed that changing history just created an alternate timeline that those who changed history happened to get 'stuck' in-; when the DTI created Timeship One with the intention of deliberately travelling three days into the future, a future version of the ship appeared in their time thirty-two hours before it was due to launch, the crew all dead or dying from an accident that had occurred when they overshot. With this discovery postponing the planned launch, the future Timeship One and its crew disappeared once the time of the original launch had passed, confirming that history could be changed.