 How does rejuvenation work?
But with the Procyon shuttle arriving yesterday, there was no telling what might turn up. They found it drifting half a light-year out and captured it. For eighty years now, they’d been sending out the little ships that vanished at greater than the speed of light, equipped with every conceivable device to make them return automatically after taking pictures of wherever they arrived. So far, none had ever returned or been located. This was the first hope they’d found that the century-long trips between stars in the ponderous shuttles might be ended and he should have been filled with excitement at Jordan’s hasty preliminary report. Scientists there had puzzled over it, reset it and sent it back. Only his youngest son would have sent an elaborate tercentenary greeting verse—one that would arrive ninety years too late! He barely mentioned being married on the way or his dozen children, but filled most of the frame with glowing description and a plea for his father to join him there! He had no desire to spend ninety years cooped up with a bunch of callow young emigrants, even in one of the improved Exodus shuttles. And even if Exodus ever got the super-light drive working, there was no reason he should give up his work. The discovery that men could live practically forever had put an end to most family ties; sentiment wore thin in half a century—which wasn’t much time now, though it had once seemed long enough. It was enough like an old model Earth conveyance to pass casual inspection, but it floated wheellessly above the ground. Faint blur lines indicated it had been moving when the picture was taken. Earth was becoming a backwater world; no real progress had been made in two centuries; the young men were sent out as soon as their first fifty years of education were finished, and the older men were too conservative for really new thinking. “We’re still ahead in medicine and we’ll get the other discoveries eventually, without interrupting the work of making the Earth fit for our longevity. That missile reached Sirius in less than ten days. It took two accidents to get the thing back to us—and with a half-light-year miss that delayed it about twenty years before the Procyon shuttle heard its signal. Pre-setting a course may take centuries, if we can ever master it. We know it’s fast enough to reach Procyon in two weeks. We can’t put human pilots into a ship with our drive until we’ve tested it more thoroughly, Bill, even if they could correct for errors on arrival.
 it re-trains the brain to develop younger cells
 it re-trains the brain to develop younger cells  it injects a serum in the body that reverses time  exercises are done to re-energize muscles  drugs convince the body to feel younger