I recently rewatched the Matt Smith episodes of Doctor Who. Starship UK was a ship created because of solar flares from the sun threatening life. I would like to know where the ship went after the Doctor and Amy’s encounter. Did SS UK go to New Earth? Does anyone have a fact or theory that stays with the continuity of the storyline? This is something I’ve been questioning since I was 8 years old when the season first came out. I am looking for any theories that are as close to fact as possible, no personal opinion, please use canon.
The existence of Starship UK is consistent with storylines from much earlier serials, The Ark in Space and The Sontaran Experiment, from the 12th season of the original series, which aired in 1975. These stories established that Earth became uninhabitable in the late 29th century due to solar flares, the same era mentioned in "The Beast Below." Earth's scientists believed that these conditions would last for 5,000 years, so humanity took to the stars. It seems that the vessels operated according to their own philosophies; Starship UK was a generation ship, while the Nerva space station in The Ark in Space had a crew in suspended animation. They had intended to sleep for 5,000 years, but the facility was sabotaged and they hibernated for 10,000 years instead. Earth was still uninhabited, but was now habitable and they resettled it. So that would have been about the year 12,900. The Nerva crew's orders described them as the sole survivors of humanity, which is incompatible with the fact that entire nations worth of humans fled on starships.
SS UK's exact plans are never stated, but we do know certain things about the later "history" of humanity on Earth. First, SS UK could not have been going to New Earth; New Earth was not established until much later, 5 billion AD or so, after the destruction of Earth in that time period (in "The End of the World"). Second, Earth was again heavily populated with humans in the year 200,000 ("The Long Game"). There could be stories that depict Earth at points between 12,900 and 200,000, but I don't know them offhand. (In fact, the show's continuity is far from perfect; the episode "Planet of the Ood" takes place in 4126 and states that Earth is heavily populated, resulting in the Second Great and Bountiful Human Empire ruling three galaxies.) Given that Earth is generally depicted as the center of human civilization in much more distant future time periods, the most likely answer is that SS UK intended to return to Earth when it was habitable again, rather than to seek out a new planetary home for its residents. But that's not explicitly stated.