When the colony ship almost traversed into a black hole, each of the ship's floors was affected by time dilation. Located approximate to the middle of the ship, time travelled faster on floor 507 than on the floors above, but slower than on the floors below. (TV: World Enough and Time) The floor appeared to be perfectly habitable. The time dilation with the other floors was still years in difference; the Cybermen down below had enough time reach their maximum upgrade over the two weeks the Doctor and his companions were there. (TV: The Doctor Falls)
Many years before Bill Potts arrived on floor 1056, there was an expedition from 1056 to 507. The Mondasians who went on the expedition never returned. (TV: World Enough and Time) It was revealed this group had actually been subdued by the residents of floor 507, being shot down by night and strung up on crucifixes by day. The floor eventually came under siege from the Cybermen, who had manage to fully evolve themselves and had committed entirely to Operation Exodus, planning to conquer all of the colony ship. However, Nardole used a computer to hack into the fuel lines of the solar farm, detonating them to destroy the first wave of Cybermen, buying the residents enough time to evacuate to floor 502, another solar farm. The Doctor and Bill stayed behind to confront the next group, the Doctor eventually igniting the entire floor, destroying the majority of the Cybermen. The resulting explosion left the floor an uninhabitable wasteland, now littered with the remains of various models of Cybermen. (TV: The Doctor Falls)
Behind the scenes Edit
This number has made it into RTD-era scripts, including TV: Boom Town, Army of Ghosts, The Shakespeare Code, 42, Voyage of the Damned and The Poison Sky. Death of the Doctor, a script penned by Davies for The Sarah Jane Adventures, has the Eleventh Doctor claim he has 507 regenerations.