Time for the Stars is a science fiction novel by Robert A. Heinlein published by Scribner's in 1956 as one of the Heinlein juveniles. The basic plot line is derived from a 1911 thought experiment in special relativity, commonly called the twin paradox, proposed by French physicist Paul Langevin.
It is found that some twins and triplets can communicate with each other telepathically. The process seems to be instantaneous and unweakened by distance, making it the only practical means of communication for ships traveling many light years away from Earth. Before announcing the discovery, the foundation first recruits as many of these people as it can.
Testing shows that teenagers Tom and Pat Bartlett have this talent. Both are eager to sign up. Pat, the dominant twin, manipulates things so that he gets selected as the crewmember, leaving a fuming Tom to stay behind. However, Pat does not really want to leave and his subconscious engineers a convenient accident so that Tom has to take his place at the last minute.
On board, Tom is pleased to find his uncle Steve, a military man, has arranged to get assigned to the same ship. The trip is fraught with problems as trivial as an annoying roommate and as serious as mutiny.
The ship visits several star systems. Due to the nature of relativistic travel (see Twin paradox), the twin who remained behind ages faster and eventually the affinity between them is weakened to the point that they are no longer able to communicate easily. However, some of the spacefaring twins, including the protagonist, are able to connect with the descendants of the Earthbound twins. Tom works with his niece, then his grandniece and finally his great-grandniece.
The last planet scouted proves to be particularly deadly. Unexpectedly intelligent and hostile natives capture and kill a large portion of the remaining crew, including the captain and Tom's uncle. The reserve captain takes charge, but is unable to restore the morale of the devastated survivors. When he insists on continuing the mission rather than returning to Earth, the crew begins to consider mutiny.
Shortly after he notifies Earth of the dire situation, they are surprised by the appearance of a more advanced spaceship. The scientists on Earth have discovered faster-than-light travel, in part due to research into the nature of telepathy, and are collecting the remaining crews of the Long Range Foundation starships. The explorers return to an Earth they no longer recognize, and in most cases, no longer fit in. Tom, however, returns to marry his last telepathic partner, his own great-grandniece.