The Cylinder of Van Troff

Many, many years later, a stellar expedition returned to its home planet with a ship to the Zeta worlds. The crew landed on the Moon, brought the settlement to Luna I, and keep them imprisoned. It turns out that over the years a social catastrophe has occurred on Earth, and human society split into two branches. One—the dead-end one—remained on Earth, while the other flew to the Moon, hoping to preserve human civilization and wait until Earthlings destroy themselves—then return. But the astronauts decided to sort everything out on their own.