Garuth thought for a moment. “But we can start them up okay?”
“We can,” Jassilane confirmed. “But once those black holes start whirling round inside the toroids, the angular momentum they’ll build up will be phenomenal. Without the retardation system to slow them down, they’ll take years to coast down to a
speed at which the drives can be deactivated. We’d be under main drive all the time, with no way of shutting down.” He made a helpless gesture. “We could end up anywhere.”
“But we’ve no choice,” Garuth pointed out. “It’s fly or fry. We’ll have to set course for home and orbit the Solar System under drive until we’ve dropped to a low enough return velocity. What other way is there?”
“I can see what Rog’s getting at,” the chief scientist interjected. “It’s not quite as simple as that. You see, at the velocities that we would acquire under years of sustained main drive, we’d experience an enormous relativistic time-dilation compared to reference frames moving with the speed of Iscaris or Sol. Since the Shapieron would be an accelerated system, much more time would pass back home than would pass on board the ship; we know where we’d end up all right . . . but we won’t be too sure of when.”
“And, in fact, it would be worse than just that,” Jassilane added. “The main drives work by generating a localized space- time distortion that the ship continuously ‘falls’ into. This also produces its own time-dilation effect. Hence you’d have the compound effect of both dilations added together. What that would mean with an unretarded main drive running for years, I couldn’t tell you-I don’t think anything like it has ever happened.”
“I haven’t done any precise calculations yet, naturally,” the chief scientist said. “But if my mental estimates are anything to go by, we could be talking about a compound dilation of the order of millions.”
“Millions?” Garuth looked stunned.
“Yes.” The chief scientist looked out at them soberly. “For every year that we spend slowing down from the velocity that we’ll need to escape the nova, we could find that a million years have passed by the time we get home.”
Silence persisted for a long time. At last Garuth spoke in a voice that was heavy and solemn. “Be that as it may, to survive we have no choice. My orders stand. Chief Engineer Jassilane, prepare for deep-space and bring the main drives up to standby readiness.”
Twenty hours later the Shapieron was under full power and hurtling toward interstellar space as the first outrushing front of the nova seared its hull and vaporized behind it the cinder that had once been Iscaris III.
chapter one
In a space of time less than a single heartbeat in the life of the universe, the incredible animal called Man had fallen from the trees, discovered fire, invented the wheel, learned to fly and gone out to explore the planets.
The history that followed Man’s emergence was a turmoil of activity, adventure and ceaseless discovery. Nothing like it had been seen through eons of sedate evolution and slowly unfolding events that had gone before.
Or so, for a long time, it had been thought.
But when at last Man came to Ganymede, largest of the moons of Jupiter, he stumbled upon a discovery that totally demolished one of the few beliefs that had survived centuries of his insatiable inquisitiveness: He was not, after all, unique. Twenty-five million years before him, another race had surpassed all that he had thus far achieved.
The fourth manned mission to Jupiter, early in the third decade of the twenty-first century, marked the beginning of intensive exploration of the outer planets and the establishment of the first permanent bases on the Jovian sateffites. Instruments in orbit above Ganymede had detected a large concentration of metal some distance below the surface of the moon’s ice crust. From a base specially sited for the purpose, shafts were sunk to investigate this anomaly.
The spacecraft that they found there, frozen in its changeless tomb of ice, was huge. From skeletal remains found inside the ship, the scientists of Earth reconstructed a picture of the race of eight-foot-tall giants that had built it and whose level of technology was estimated as having been a century or more ahead of Earth’s. They christened the giants the “Ganymeans,” to commemorate the place of the discovery.