Time for the Stars is one of Robert A. Heinlein's most famous juvenile novels. The basic idea is derived from the "Twin paradox" thought experiment in special relativity.
Tom has always resented his twin brother Pat, but then they get involved in "Project Lebensraum" and are discovered to have a telepathic bond. When Pat is chosen to go on board a relativistic starship while he stays behind to send and receive messages to/from his twin he is instantly jealous. But then Pat is paralyzed in a skiing accident and Tom has to go out into space in his place.
Tom spends less than three years in space, having to watch from light-years away while his brother ages more than seventy years.
- All Planets Are Earthlike: Averted, the Lewis and Clark explores four systems and only finds two inhabitable planets. And as far as they can tell the other ships find even fewer.
- Bunny-Ears Lawyer: Some of the telepaths are not the most sociable people, as their abilities are what's needed.
- Character Development: Tom returns home to find his brother is an elderly patriarch who expects him to take over the family business. Tom puts his foot down and makes it clear that Pat is not going to dictate the course of his life any more (though Vicky might end up doing so).
- Deliberate Values Dissonance: Played for Laughs when Tim returns to Earth and starts going on about how in his day girls weren't allowed to walk around naked. Turns out he's referring to them not wearing anything on their heads. Hats have apparently gone out of fashion, and many females he sees have their heads shaved.
- Double Don't Know: Tom is unhappy because Pat arranged to sign the space travel contract last, making him the one who gets to go to space. Tom wonders to himself in his journal if Pat did this deliberately, and would he have done it.Was Pat trying to put one over on me right then? If so, I didnt catch him wording his thoughts. Contrariwise, would I have tried the same thing on him if I had thought of it? I dont know, I just dont know.
- Eternal English: Turns out the Conlang being used so people on the ship share a common language is actually a modification of English. It's become the universal language when they return to Earth, and the protagonist has no problem learning it.
- Extreme Doormat: Tim always complains that his brother Pat gets preferential treatment, including getting on the mission which he's convinced that Pat arranged somehow. It's pointed out to him that this is a self-fulfilling prophecy — he's so convinced that Pat will get to go on the mission he doesn't make his own desires known.
- Fish out of Temporal Water: After the second jump they start noticing slang that they don't recognizing through the telepathic communiques. When they get back to Earth they're so out of place that most of them want to go back into space.
- Fourth Date Marriage: More like a no-date marriage; the moment Tom meets Vicky face-to-face she announced they're getting married. She states that she's read his mind since she was a child and knows Tom better that he thinks. Tom isn't inclined to dispute the matter.
- Generation Ship: The Lewis and Clark is out in space for years at a maximum speed just under the speed of light, multiple crewmembers marry and have children in that time.
- Incest Is Relative: When Tom gets back to Earth he marries his great-great-niece and current primary telepartner Vicki.
- Lightspeed Leapfrog: After losing most of the crew to hostile natives on Elysia they are ordered to remain in the area for a month so an FTL ship can pick them up.
- The Mutiny: After the captain is killed along with a large number of crew, the new captain wants to continue with the mission. As the only effective telepath left, Rod finds himself the focus of efforts to force them to return to Earth (by refusing to send messages) and ends up confined to quarters on suspicion of inciting mutiny. He's not happy when he discovers that there's an actual mutiny brewing, inspired by his arrest.
- Noodle Incident: Reference is made to a "horrible" past event on Mars. No details are given, but the result is that none of the exploring ships are allowed to engage in a first-contact situation should any intelligent race be discovered.
- Population Control: The twins father has to pay extra tax because the birth of twin boys exceeded his family's non-taxable quota. And such population control measures are necessary too, what with the world straining under the pressure of feeding five billion people.
- Psychic Link: Twin Telepathy is by far the most common form, but other relationships are seen such as "Uncle Alf" and his great-niece "Sugarpie", both of whom Tom learns to form a link with. As the Earthside telepartners age and lose their connections the institute figures out how to form new connections, such as Pat's descendants.
- Rock Beats Laser: The amphibious natives of one planet massacre the landing party in a well-coordinated attack, using only knives, ropes, and the ability to squirt high-powered jets of water that can knock helicopters from the sky. The only thing they can't sink is the Lewis & Clark because the humans turn on the engines when they try.
- Starship Luxurious: The expedition spaceships have a much large crew than needed for both redundancy and social stability.
- Stay in the Kitchen: Played straight when the captain asks for volunteers for a dangerous rescue mission. The entire crew steps forward, so he orders all the women to stand aside next to the pantry (they're in the messhall) and then picks only the oldest male crewmen for the mission, led by himself. All but one get killed when the helicopter is shot down.
- Theme Naming: The twin's father wanted to name them after American Historical figures (a Heinlein staple), and his mother wanted to name them after Renaissance artists. They compromise, naming the children Patrick Henry Michelangelo, and Thomas Paine Leonardo Da Vinci.
- Synchronization: Tim links to his brother for moral support while he's having a surgical operation. This means that when Pat is anaesthetized his mind is still conscious, while Tim feels both his brother's fear and the pain of the surgeons cutting into him.
- Time Dilation: Relativistic. As they speed up the Earthside twin starts to sound like they're jabbering and the space-faring twin is drawling. When they get near the speed of light contact is impossible without a lot of drugs and hypnosis.