Sometime in the future, the human race realizes how much the population is outgrowing the planet and decides to train people to go explore the galaxy to look for other inhabitable planets. The trainees are chosen for their intelligence at a very young age, then spend their entire childhood learning a skill such as medicine, engineering, physics, etc. When they reach adulthood, the best six of them are sent off to other star systems to spend the rest of their lives searching for a place that may be hospitable to humans.