An umbrella title for the novelette Universe and its sequel novella Common Sense, published originally in 1941 in two different issues of Astounding Science Fiction. First published under this title in 1963.

Heinlein gives us one of the earliest uses in science fiction of the "generation ship" idea, a huge spaceship transporting an entire community of humans to a destination so distant that generations will pass during its journey. And as Heinlein demonstrates, the origins of the community can become forgotten, misinterpreted, and otherwise distorted with the long passage.