An alternate timeline was a reality that diverged from the "true" timeline due to the actions of time travellers or other temporal phenomena. They were different from parallel universes in that they did not separate cleanly at the point of creation resulting in the new timeline destroying the old one. (PROSE: Imperial Moon) The phenomenon was also described as an "interstitial spillage of time." (AUDIO: Project: Lazarus)
They may have diverged from points in history when there was temporal fluctuation. The power required to adjust the timeflow and overcome temporal inertia on such a scale couldn't fit on a single planet, but beings with enough power were capable of doing so, such as Sutekh, the Guardians of Time, Rassilon, and the Chronovores. Even the Doctor or the Master could have the know-how or inclination to create them. Because the universe only had a finite amount of mass and energy to exist as one universe, the creation of an alternate timeline adversely affected the real timeline, causing chaos throughout the universe; releasing enough energy could destroy the timeline and set history back on its correct course. (PROSE: Blood Heat)
From a metaphysical viewpoint, alternate timelines were always being extinguished as fewer and fewer choices became open. This was particularly affected by time travellers who changed the future whenever they arrived in a new time. This was the cosmic pain of the universe and in this manner Gabriel and Tanith were personifications of the timelines that never existed. (PROSE: Falls the Shadow)
Terminology
The phrase "alternate/alternative timeline/universe" was sometimes used interchangably with "parallel universe"; however, alternate timelines usually changed after a single moment in time, whereas parallel universes usually had more than one difference from the "normal" universe.
Have a question about how Alternate timeline relates to the rest of the DWU? See a problem here that's also happening on other pages of the wiki? Join us at our forum to have a good, ol' natter with the rest of our community. But if you want to talk about the editing of just this article, please click here and start talkin'.
By site policy, all video must come from the official YouTube channel of the copyright holder — typically the BBC or its licensees. It's likely that no such video exists. Or maybe Alternate timeline is a subject which was never caught on video.Only admin may add videos to this site.