be millions of light years from Earth. However, they find the vacuum of intergalactic space insufficient for safety; they must instead travel to a region between superclusters of galaxies to make repairs. They do, but the extremely thinly spread matter is then too dispersed to use for deceleration. They must wait, flying free but essentially without the ability to change course, until they randomly encounter enough galactic matter to decelerate enough to search for habitable planets. To make the waiting time shorter, they continue accelerating through the galaxy clusters they encounter, more and more closely approaching the speed of light with tau, or proper time, decreasing closer and closer to zero. Throughout the story, Charles Reymont, the ship's Constable, fights to keep hope alive in the confined community and at the same time maintain order and discipline, sometimes at great emotional cost to himself. He explains his system to his partner Chi-Yuen Ai-Ling: The storyline is similar to that of the long poem and later opera Aniara, in which the ship was unable to stop and doomed to travel endlessly, but Tau Zero has a more upbeat ending. By the time the ship is repaired, tau has decreased to less than a billionth and the crew experience "billion-year cycles which pass as moments". But by the time that they are ready to attempt to find a future home, they realize that the universe is approaching a Big Crunch. (The Big Crunch was a leading theory of the fate of the universe at the time this book was written.) The universe collapses (a process the starship survives because there is still enough uncondensed hydrogen for maneuvering outside the growing singularity) and then explodes in a new Big Bang. The voyagers then decelerate and finally disembark at a planet with a habitat suitably similar to Earth, on which the vegetation has a vivid bluish-green color. Prominent characters Ingrid Lindgren, Ship's First Officer – Swedish; she and Reymont had a relationship until he learned of her liaisons with Boris Federoff; she becomes the "face" of authority and the link between crew and passengers. Charles Reymont, Ship's Constable – Interplanetarian (i.e. no Earth-country citizenship, by choice), veteran of two previous interstellar flights; determined to maintain order and ensure survival in the face of disaster and hopelessness, he becomes the ship's de facto leader (although he defers to the ship's hierarchy). Boris Fedoroff, Ship's Chief