Earth in science fiction

An overwhelming majority of fiction is set on or features the Earth. However, authors of speculative fiction novels and writers and directors of science fiction film deal with Earth quite differently from authors of conventional fiction. Unbound from the same ties that bind authors of traditional fiction to the Earth, they can either completely ignore the Earth or use it as but one of many settings in a more complicated universe, exploring a number of common themes through examining outsiders perceptions of and interactions with Earth.

The overarching plot in both the original and re-imagined Battlestar Galactica is the quest to find Earth, which is thought to be the location of the lost thirteenth colony of Kobol. Colonial history dictates that Kobol is the homeworld of all humanity, and that the Thirteen Tribes of Kobol fled that world thousands of years earlier, with twelve tribes founding the Twelve Colonies and the thirteenth heading to Earth. Both shows are similar in that the location of Earth is initially unknown, but clues to its location are gradually discovered by the refugee fleet from the Twelve Colonies. In both series, the exodus of the Thirteen Tribes took place so far in the past that most modern Colonials have come to assume that the stories of Earth are simply religious myths.

In the original series, several clues indicate that the existence of Earth is real. On the prison planet of Proteus, Starbuck encounters drawings of star systems on the wall of a cell once occupied by a mysterious prisoner. The star charts turn out to be that of the Solar System. Additionally, when the Galactica later reaches a planet called Terra, it is inhabited by humans who use Earth units of measurement (hours, minutes, etc.) rather than Colonial units of measurement, suggesting that it was settled by members of the lost Thirteenth Tribe thousands of years earlier on their way to Earth.

In Galactica 1980, a continuation of the original series, the fleet did eventually discover Earth as it was in 1980.

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