 What motivates Pop Young to live on the far side of the moon?
The shack and the job he filled were located in the medieval notion of the physical appearance of hell. Once in two weeks Earth-time a rocketship came around the horizon from Lunar City with stores for the colony deep underground. The Crack, of course, was that gaping rocky fault which stretches nine hundred miles, jaggedly, over the side of the Moon that Earth never sees. There is nothing like it on Earth, of course. When it was first found, scientists descended into it to examine the exposed rock-strata and learn the history of the Moon before its craters were made. Pop lived in it all alone, and in his spare time he worked industriously at recovering some missing portions of his life that Sattell had managed to take away from him. There were air-tight bulkheads for safety, and a hydroponic garden to keep the air fresh, and all sorts of things to make life possible for men under if not on the Moon. In the Moon's slight gravity, a man is really adjusted to existence when he has a well-developed case of agoraphobia. With such an aid, a man can get into a tiny, coffinlike cubbyhole, and feel solidity above and below and around him, and happily tell himself that it feels delicious. He'd shipped out, whimpering, to the Moon to get far away from Pop, and Pop was just about a mile overhead and there was no way to get around him. It doesn't take too long for the low gravity to tear a man's nerves to shreds. And those kinks— The first men to leave the colony had to be knocked cold and shipped out unconscious. Even now there were some who had to be carried, but there were some tougher ones who were able to walk to the rocketship if Pop put a tarpaulin over their heads so they didn't have to see the sky. In any case Pop was essential, either for carrying or guidance.
 He is close to Sattell's location, which enhances his memories of his wife and children
 He is being compensated for a wrongful death suit that occurred back on Earth  He is close to Sattell's location, which enhances his memories of his wife and children  If he left his post, there would be no one to monitor the mines in the Big Crack  If he returned to Earth, he would be arrested for the murder of his family