The sublight colony starship Leonora Christine, powered by a Bussard Ramjet, is damaged while passing through a small nebula. The decelerator mechanism is disabled and cannot be repaired unless a region of empty space is reached. The crew elects to continue accelerating in order to find a refuge. Due to the effects time dilation as the ship claws ever closer to the speed of light, ship time and outside time become increasingly disconnected. As the months and years pass on board, eons pass outside.
Tau Zero is an acknowledged science fiction classic. Some parts have not aged too well, in particular the 1960s social mores and optimistic view of the human races’ collective rationality. Some of the content also feels a bit like padding, most likely because it started out as a short story. However it remains a well executed hard science fiction story which manages to bring home the insignificance of individuals, and even of humanity itself, when confronted with the almost unimaginable vastness of time and space.