"I thought of that. He's twenty-six, I'm seventeen, and yet we used to be twins. But the Fitzgerald Contraction does funny things." "That's for sure," Kandin said. "Well, time for me to start relaxing." He clapped Alan on the back, disentangled his long legs from the bench, and was gone. _The Fitzgerald Contraction does funny things_, Alan repeated to himself, as he methodically chewed his way through the rest of his meal and got on line to bring the dishes to the yawning hopper that would carry them down to the molecular cleansers. _Real funny things._ He tried to picture what Steve looked like now, nine years older. He couldn't. _As velocity approaches that of light, time approaches zero._ That was the key to the universe. _Time approaches zero._ The crew of a spaceship travelling from Earth to Alpha Centauri at a speed close to that of light would hardly notice the passage of time on the journey. It was, of course, impossible ever actually to reach the speed of light. But the great starships could come close. And the closer they came, the greater the contraction of time aboard ship. It was all a matter of relativity. Time is relative to the observer. Thus travel between the stars was possible. Without the Fitzgerald Contraction, the crew of a spaceship would age five years en route to Alpha C, eight to Sirius, ten to Procyon. More than two centuries would elapse in passage to a far-off star like Bellatrix. Thanks to the contraction effect, Alpha C was three weeks away, Sirius a month and a half. Even Bellatrix was just a few years' journey distant. Of course, when the crew returned to Earth they found things completely changed; years had passed on Earth, and life had moved on. Now the _Valhalla_ was back on Earth again for a short stay. On Earth, starmen congregated at the Enclaves, the cities-within-cities that grew up at each spaceport. There, starmen mingled in a society of their own, without attempting to enter the confusing world outside. Sometimes a Spacer broke away. His ship left him behind, and he became an Earther. Steve Donnell had done that. _The Fitzgerald Contraction does funny things._ Alan thought of the brother he had last seen just a few weeks ago, young, smiling, his own identical twin--and wondered what the nine extra years had done to him. _Chapter Two_ Alan dumped his breakfast dishes into the hopper and walked briskly out of the mess hall. His destination was the Central Control Room, that long and broad chamber that was the nerve-center of the ship's activities just as the Common Recreation Room was the center of off-duty socializing for the Crew. He found the big board where the assignments for the day were chalked, and searched down the long lists for his own name. "You're working with me today, Alan," a quiet voice said.