Starfarers
by Poul Anderson
Earth sends out a spaceship to investigate starfaring in far distance space of which traces have been found. The ship Envoy, manned by a crew of six men and four women, travels at speed close to the speed of light. At the end of the journey the crew meets a Centaur-like species on a planet they call Tahir that has left spacefaring behind. Sentient life is also detected in connection with at a nearby black hole, a reading confirmed by the Tahirans. Their interest aroused, the Earthlings can send a combined crew to investigate.
Communications with this "Holont" is established and much knowledge acquired. Differences aboard the ship, however, lead to the death of three men (Brent, Russek and Cleland), and female pilot Kilbirnie crashes into the black hole. The six Earthlings left drop the Tahirans off at their homeworld and head towards Earth.
In between the story jumps regularly back to the development of human society over the gaps of many thousand years and to that of the Kith, the closed group doing the starfaring, who are often shunned by the rest of Earth. The Kith have their own settlements on different planets, where some retire to from time to time.
Earth has changed over the long period of time taken up by the voyage of the Envoy, and no one is much interested in spacefaring anymore. On Harbor, a colony of Earth, the Envoy crew finds remainders of the Kith society, which still are connected to spacefaring. But the last ship to plot trade-routes in space, the Fleetwing, disappears from tracking. The cause is a Zero-Zero-failure ripping off the rear part of the ship. The Envoy sets out on a rescue mission as soon as possible but twenty years of outside time have passed by the time they reach the Fleetwing. They save the remaining crew, thus building a foundation of experienced spacefarers to start spacefaring anew with the knowledge acquired from the Holont.