was a deeper mystery. Rising like an island out of the strange sea that guarded them, the Mountains of Inaccessibility remained a challenge for the next generation of explorers. Despite their name, it was now easy enough to reach them—but with millions of square kilometers of less difficult territory still unexamined, they would have to wait their turn.
Selene was swinging into their shadows; before anyone had realized what was happening, the low-hanging Earth had been eclipsed. Its brilliant light still played upon the peaks far overhead, but down here all was utter darkness.
“I'll turn off the cabin lights,” said the stewardess, “so you can get a better view.”
As the dim red background illumination vanished, each traveler felt he was alone in the lunar night. Even the reflected radiance of Earth on those high peaks was disappearing as the cruiser raced farther into shadow. Within minutes, only the stars were left—cold, steady points of light in a blackness so complete that the mind rebelled against it.
It was hard to recognize the familiar constellations among this multitude of stars. The eye became entangled in patterns never seen from Earth, and lost itself in a glittering maze of clusters and nebulae. In all that resplendent panorama, there was only one unmistakable landmark—the dazzling beacon of Venus, far outshining all other heavenly bodies, heralding the approach of dawn.
It was several minutes before the travelers realized that not all the wonder lay in the sky. Behind the speeding cruiser stretched a long, phosphorescent wake, as if a magic finger had traced a line of light across the Moon's dark and dusty face. Selene was drawing a comet tail behind her, as surely as any ship plowing its way through the tropical oceans of Earth.
Yet there were no microorganisms here, lighting this dead sea with their tiny lamps. Only countless grains of dust, sparking one against the other as the static discharges caused by Selene's swift passage neutralized themselves. Even when one knew the explanation, it was still beautiful to watch—to look back into the night and to see this luminous, electric ribbon continually renewed, continually dying away, as if the Milky Way itself were reflected in the lunar surface.
The shining wake was lost in the glare as Pat switched on the seaichlight. Ominously close at hand, a great wall of rock was sliding past. At this point the face of the mountain rose almost sheer from the surrounding sea of dust; it towered overhead to unknown heights, for only where the racing oval of light fell upon it did it appear to flash suddenly into real existence.
Here were mountains against which the Himalayas, the Rockies, the Alps were newborn babies. On Earth, the forces of erosion began to tear at all mountains as soon as they were formed, so that after a few million years they were mere ghosts of their former selves. But the Moon knew neither wind nor rain; there was nothing here to wear away the rocks except the immeasurably slow flaking of the dust as their surface layers contracted in the chill of night. These mountains were as old as the world that had given them birth.
Pat was quite proud of his showmanship, and had planned the next act very carefully. It looked dangerous, but was perfectly safe, for Selene had been over this course a hundred times and the electronic memory of her guidance system knew the way better than any human pilot. Suddenly, he switched off the searchlight—and now the passengers could tell that while they had been dazzled by the glare on one side, the mountains had been stealthily closing in upon them from the other.
In almost total darkness, Selene was racing up a narrow canyon—and not even on a straight course, for from time to time she zigged and zagged to avoid invisible obstacles. Some of them, indeed, were not merely invisible, but nonexistent; Pat had programmed this course, at slow speed and in the safety of daylight, for maximum impact on the nerves. The “Ah's” and “Oh's” from the darkened cabin behind him proved that he had done a good job.
Far above, a narrow ribbon of stars was all that could be seen of the outside world; it swung in crazy arcs from right to left and back again with each abrupt change of Selene's course. The Night Ride, as Pat privately called it, lasted for about five minutes, but seemed very much longer. When he once again switched on the floods, so that the cruiser was moving in the center of a great pool of light, there was a sigh of mingled relief and disappointment from the passengers. This was an experience none of them would forget in a huny.
Now that vision had been restored, they could see that they were traveling up a steep-walled valley or gorge, the sides of which were slowly drawing apart. Presently the canyon had widened into a roughly oval amphitheater about three kilometers across-the heart of an extinct volcano, breached aeons ago, in the days when even the Moon was young.
The crater was extremely small, by lunar standards, but it was unique. The ubiquitous dust had flooded into it, working its way up the valley age after age, so that now the tourists from Earth could ride in cushioned comfort into what had once been a cauldron filled with the fires of Hell. Those fires had died long before the dawn of terrestrial life, and would never wake again. But there were other forces that had not died, and were merely biding their time.
When Selene began a slow circuit of the steeply walled amphitheater, more than one of her passengers remembered a cruise in some mountain lake at home. Here was the same sheltered stillness, the same sense of unknown depths beneath the boat. Earth had many crater lakes, but the Moon only one—though it had far more craters.
Taking his time, Pat made two complete circuits of the lake, while the floodlights played upon its enclosing walls. This was the best way to see it; during the daytime, when the sun blasted it with heat and light, it lost much of its magic. But now it belonged to the kingdom of fantasy, as if it had come from the haunted brain of Edgar Allan Poe. Ever and again one seemed to glimpse strange shapes moving at the edge of vision, beyond the narrow range of the lights. It was pure imagination, of course; nothing moved in all this land except the shadows of the Sun and Earth. There could be no ghosts upon a world that had never known life.
It was time to turn back, to sail down the canyon into the open sea. Pat aimed the blunt prow of Selene toward the narrow rift in the mountains, and the high walls enfolded them again. On the outward journey he left the lights on, so that the passengers could see where they were going; besides, that trick of the Night Ride would not work so well a second time.
Far ahead, beyond the reach of Selene's own illumination, a light was growing, spreading softly across the rocks and crags. Even in her last quarter, Earth still had the power of a dozen full moons, and now that they were emerging from the shadow of the mountains, she was once more the mistress of the skies. Every one of the twenty-two men and women aboard Selene looked up at that blue-green crescent, admiring its beauty, wondering at its brilliance. How strange that the familiar fields and lakes and forests of Earth shone with such celestial glory when one looked at them from afar! Perhaps there was a lesson here; perhaps no man could appreciate his own world until he had seen it from space.
And upon Earth, there must be many eyes turned toward the waxing Moon—more than ever before, now that the Moon meant so much to mankind. It was possible, but unlikely, that even now some of those eyes were peering through powerful telescopes at the faint spark of Selene's floodlights as it crept through the lunar night. But it would mean nothing to them when that spark flickered and died.
For a million years the bubble had been growing, like a vast abscess, below the root of the mountains. Throughout the entire history of Man, gas from the Moon's not yet wholly dead interior had been forcing itself along lines of weakness, accumulating in cavities hundreds of meters below the surface. On nearby Earth, the ice ages had marched past, one by one, while the buried caverns grew and merged and at last coalesced. Now the abscess was about to burst.
Captain Harris had left the controls on autopilot and was talking to the front row of passengers when the first tremor shook the boat. For a fraction of a second he wondered if a fan blade had hit some submerged obstacle; then, quite literally, the bottom fell out of his world.
It fell slowly, as all things must upon the Moon. Ahead of Selene, in a circle many acres in extent, the smooth plain puckered like a navel. The Sea was alive and moving, stirred by the forces that had waked it from its age-long sleep. The center of the disturbance deepened into a funnel, as if a giant whirlpool were forming in the dust. Every stage of that nightmare transformation was pitilessly illuminated by the earthlight, until the crater was so deep that its far wall was completely lost in shadow, and it seemed as if Selene were racing into a curving crescent of utter blackness—an arc of annihilation.
The truth was almost as bad. By the time that Pat had reached the controls, the boat was sliding and skittering far down that impossible slope. Its own momentum and the accelerating flow of the dust beneath it were
