Off at the horizon, DIGGER could see silhouetted against the rising sun the thin glistening line of the space elevator, a diamond tower rising from Colchis’s equator up into orbit, where DIGGER’S colleagues worked.
Some of those orbiting robots, DIGGER knew, were positioning parasols of sodium-coated mylar to angle sunlight onto Colchis’s massive polar caps. Others were carefully shepherding the paths of asteroids that had been brought into low orbits, their torquing force helping to stabilize Colchis’s polar wobble and axial tilt, just as Luna’s presence does for Earth.
Although one level of DIGGER’S consciousness was always dedicated to these and other terraforming problems, another made sure to find time each day to let thoughts wander from the work at hand. At this moment, it contemplated the message from Vulpecula, received by the UCFS observatory all those years ago. Those humans who had been proponents of SETI had always laughed at the fears of the public. There was no harm in answering any message we might receive, they said. If the message came from a star five hundred light-years distant, it would take five hundred years for our reply to reach them, and another five hundred minimum for any response, electromagnetic or material, to reach us.
With the forty-seven-light-year baseline between Sol and Eta Cephei along which to measure signal parallax, it was a trifling computation to determine the distance from Colchis to that fourth moon of the sixth planet of a star in Vulpecula from which those strange tripods—some spindly, some squat-sent their hail: 1,422 light-years. Far enough that their star, an F-class subgiant, was invisible without powerful telescopic aids.
What had compelled DIGGER to respond to the message once he had arrived at Colchis, he could not say. It had seemed monumentally important that he do so; now, no matter how many diagnostics he ran, he could find no instruction set to explain his actions. But respond he had, with the same signature the Senders in Vulpecula had used, binary bitmaps of the prime numbers 1, 3, 5, 7, 11, and 13 forward and backward, backward and forward.
It would be thirty-five thousand years before the last surviving humans decelerated into orbit around Colchis. A long, long time, thought DIGGER. But there was much to do yet, enough to fill every second of those millennia. DIGGER shunted his attention back to the tasks at hand, but one stray thought continued to echo through his RAM matrix. Who, he wondered, would arrive here first? The Argonauts? Or the aliens?