 Of the following, which is the best plausible explanation for the behavior of the Earthen ships?
[Transcriber's Note: This etext was produced from Planet Stories Fall 1949. In the last hours the star ahead had grown brighter by many magnitudes, and had changed its color from a dazzling blue through white to the normal yellow, of a GO sun. That was the Doppler effect as the star's radial velocity changed relative to the Quest III , as for forty hours the ship had decelerated. They had seen many such stars come near out of the galaxy's glittering backdrop, and had seen them dwindle, turn red and go out as the Quest III drove on its way once more, lashed by despair toward the speed of light, leaving behind the mockery of yet another solitary and lifeless luminary unaccompanied by worlds where men might dwell. They had grown sated with the sight of wonders—of multiple systems of giant stars, of nebulae that sprawled in empty flame across light years. It was a subdued excitement; men and women, they came and stood quietly gazing into the big vision screens that showed the oncoming star, and there were wide-eyed children who had been born in the ship and had never seen a planet. The great chamber, a full cross-section of the vessel, had been at first a fuel hold. At the voyage's beginning eighty per cent of the fifteen-hundred-foot cylinder had been engines and fuel; but as the immense stores were spent and the holds became radioactively safe, the crew had spread out from its original cramped quarters. Now the interstellar ship was little more than a hollow shell. Eyes lifted from the vision screens to interrogate Knof Llud; he met them with an impassive countenance, and announced quietly, "We've sighted Earth." A feverish buzz arose; the captain gestured for silence and went on, "It is still only a featureless disk to the telescope. People pressed round the screens, peering into them as if with the naked eye they could pick out the atom of reflected light that was Earth, home. Earth's still there." He said, with a touch of tolerant amusement, "What did you think might have happened to Earth? It won't be the same world we left, the world we knew and fitted in...." There's a new course to be set now—for Earth." Gwar Den was finding that the actual observed positions of the planets thus far located agreed quite closely with his extrapolations from long unused charts of the Solar System. He had already set up on the calculator a course that would carry them to Earth.
 900 years passed on Earth. The populations were different enough that the Quest III Earthens scared the current Earthen population.
 Since the Quest III trip promised to locate more planets, the current Earthens didn't trust them when they learned of their success because of how unlikely it was.  Since the Quest III trip promised to locate more planets, the current Earthens didn't trust them when they learned of their failure.  Since the Quest III trip promised to locate more natural resources, the current Earthens didn't trust them when they learned of their failure.  900 years passed on Earth. The populations were different enough that the Quest III Earthens scared the current Earthen population.