Alternate history

Television
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Several TV series also exploit the concept of alternate history. The science fiction television show Sliders presented alternate histories under the science-inspired guise of quantum-navigating the multiverse. The vast majority of alternate Americas in most episodes are nasty dystopias, although sometimes this is not evident at first.

In Lost, the characters time travel to 1977 past and attempt to create an alternate history. However, while the only intended ramifications were for Flight 815 to land in Los Angeles, instead, it is revealed that their actions were the cause of the crash, ultimately.

Other non-alternate history television shows have explored the concept. Star Trek has used the theme several times. Examples include: TOS—"The City on the Edge of Forever" (alternate World War II outcome); Animated Series—"Yesteryear"; NG—"Yesterday's Enterprise". Also, the universe of "Mirror, Mirror", while in the original episode was just implied to be a parallel universe, was in later episodes shown to have an alternate history.

The British TV series Doctor Who had a few episodes that involved an alternate Earth where Pete Tyler, father of Rose Tyler, was alive, successful, and rich, unlike the Pete Tyler on the original Earth, who died when Rose was a baby and had been unsuccessful in business. The Tenth Doctor, Rose, and Mickey Smith visited the alternate Earth by accident in "Rise of the Cybermen" and "The Age of Steel". The second season finale "Army of Ghosts" and "Doomsday" also involved travel to the same alternate Earth, and the series four episode "Turn Left" showed an alternate history where the Tenth Doctor has been killed. During the Third Doctor's tenure he visited an alternative Earth with a fascist-style British Government (and fascist counterparts of His friends/companions Liz Shaw, Brigadier Lethbridge-Stewart and Sergeant Benton) in Inferno.

In the seventies SF children's series The Tomorrow People, "A Stitch in Time" (1974) depicted an attempted historical change by time travellers from an alternate-universe Roman Empire that developed steam engines in the first century CE, never fell as a result, had a fifteen hundred year technological head-start over our own world and by its 'twentieth century', controlled a galactic empire.

In the Twilight Zone episode "The Parallel", an astronaut is transported to an alternate Earth where history plays out differently, but no-one believes him when he discovers this.