"At the moment my closest approach is sixty miles; it will increase to about a hundred as Japetus rotates beneath me, then drop back to zero. I'll pass directly over the thing in thirty days—but that's too long to wait, and then it will be in darkness, anyway.

  "Even now, it's only in sight for a few minutes before it falls below the horizon again. It's damn frustrating—I can't make any serious observations.

  "So I'd like your approval of this plan. The space pods have ample delta vee for a touchdown and a return to the ship. I want to go extravehicular and make a close survey of the object. If it appears safe, I'll land beside it—or even on top of it.

  "The ship will still be above my horizon while I'm going down, so I won't be out of touch for more than ninety minutes.

  "I'm convinced that this is the only thing to do. I've come a billion miles—I don't want to be stopped by the last sixty."

  For weeks, as it stared forever sunward with its strange senses, the Star Gate had watched the approaching ship. Its makers had prepared it for many things, and this was one of them. It recognized what was climbing up toward it from the warm heart of the Solar System.

  If it had been alive, it would have felt excitement, but such an emotion was wholly beyond its powers. Even if the ship had passed it by, it would not have known the slightest trace of disappointment. It had waited three million years; it was prepared to wait for eternity.

  It observed, and noted, and took no action, as the visitor checked its speed with jets of incandescent gas. Presently it felt the gentle touch of radiations, trying to probe its secrets. And still it did nothing.

  Now the ship was in orbit, circling low above the surface of this strangely piebald moon. It began to speak, with blasts of radio waves, counting out the prime numbers from 1 to 11, over and over again. Soon these gave way to more complex signals, at many frequencies—ultraviolet, infrared, X rays. The Star Gate made no reply; it had nothing to say.

  There was a long pause, then, before it observed that something was falling down toward it from the orbiting ship. It searched its memories, and the logic circuits made their decisions, according to the orders given them long ago.

  Beneath the cold light of Saturn, the Star Gate awakened its slumbering powers.

  Chapter 39

  Into the Eye

  Discovery looked just as he had last seen her from space, floating in lunar orbit with the Moon taking up half the sky. Perhaps there was one slight change; be could not be sure, but some of the paint of her external lettering, announcing the purpose of various hatches, connections, umbilical plugs, and other attachments, had faded during its long exposure to the unshielded Sun.

  That Sun was now an object that no man would have recognized. It was far too bright to be a star, but one could look directly at its tiny disk without discomfort. It gave no heat at all; when Bowman held his ungloved hands in its rays, as they streamed through the space pod's window, he could feel nothing upon his skin. He might have been trying to warm himself by the light of the Moon; not even the alien landscape fifty miles below reminded him more vividly of his remoteness from Earth.

  Now he was leaving, perhaps for the last time, the metal world that had been his home for so many months. Even if he never returned, the ship would continue to perform its duty, broadcasting instrument readings back to Earth until there was some final, catastrophic failure in its circuits.

  And if he did return? Well, he could keep alive, and perhaps even sane, for a few more months. But that was all, for the hibernation systems were useless with no computer to monitor them. He could not possibly survive until Discovery II made its rendezvous with Japetus, four or five years hence.

  He put these thoughts behind him, as the golden crescent of Saturn rose in the sky ahead. In all history, he was the only man to have seen this sight. To all other eyes, Saturn had always shown its whole illuminated disk turned full toward the Sun. Now it was a delicate bow, with the rings forming a thin line across it—like an arrow about to be loosed, into the face of the Sun itself.

  Also in the line of the rings was the bright star of Titan, and the fainter sparks of the other moons. Before this century was half gone, men would have visited them all; but whatever secrets they might hold, he would never know.

  The sharp-edged boundary of the blind white eye was sweeping toward him; there was only a hundred miles to go, and he would be over his target in less than ten minutes. He wished that there was some way of telling if his words were reaching Earth, now an hour and a half away at the speed of light. It would be the ultimate irony if, through some breakdown in the relay system, he disappeared into silence, and no one ever knew what had happened to him.

  Discovery was still a brilliant star in the black sky far above. He was pulling ahead as he gained speed during his descent, but soon the pod's braking jets would slow him down and the ship would sail on out of sight—leaving him alone on this shining plain with the dark mystery at its center.

  A block of ebony was climbing above the horizon, eclipsing the stars ahead. He rolled the pod around its gyros, and used full thrust to break his orbital speed. In a long, flat arc, he descended toward the surface of Japetus.

  On a world of higher gravity, the maneuver would have been far too extravagant of fuel. But here the space pod weighed only a score of pounds; he had several minutes of hovering time before he would cut dangerously into his reserve and be stranded without any hope of return to the still orbiting Discovery. Not, perhaps, that it made much difference. . . .

  His altitude was still about five miles, and he was heading straight toward the huge, dark mass that soared in such geometrical perfection above the featureless plain. It was as blank as the flat white surface beneath; until now, he had not appreciated how enormous it really was. There were very few single buildings on Earth as large as this; his carefully measured photographs indicated a height of almost two thousand feet. And as far as could be judged, its proportions were precisely the same as TMA-1's—that curious ratio 1 to 4 to 9.

  "I'm only three miles away now, holding altitude at four thousand feet. Still not a sign of activity—nothing on any of the instruments. The faces seem absolutely smooth and polished. Surely you'd expect some meteorite damage after all this time!

  "And there's no debris on the—I suppose one could call it the roof. No sign of any opening, either. I'd been hoping there might be some way in. . . .

  "Now I'm right above it, hovering five hundred feet up. I don't want to waste any time, since Discovery will soon be out of range. I'm going to land. It's certainly solid enough—and if it isn't I'll blast off at once.

  "Just a minute—that's odd—"

  Bowman's voice died into the silence of utter bewilderment. He was not alarmed; he literally could not describe what he was seeing.

  He had been hanging above a large, flat rectangle, eight hundred feet long and two hundred wide, made of something that looked as solid as rock. But now it seemed to be receding from him; it was exactly like one of those optical illusions, when a three-dimensional object can, by an effort of will, appear to turn inside out—its near and far sides suddenly interchanging.

  That was happening to this huge, apparently solid structure. Impossibly, incredibly, it was no longer a monolith rearing high above a flat plain. What had seemed to be its roof had dropped away to infinite depths; for one dizzy moment, he seemed to be looking down into a vertical shaft—a rectangular duct which defied the laws of perspective, for its size did not decrease with distance. . . .

  The Eye of Japetus had blinked, as if to remove an irritating speck of dust. David Bowman had time for just one broken sentence which the waiting men in Mission Control, nine hundred million miles away and eighty minutes in the future, were never to forget:

  "The thing's hollow—it goes on forever—and—oh my God!—it's full of stars!"

  Chapter 40

  Exit

  The Star Gate opened. The Star Gate closed.

  In a moment of time too s
hort to be measured, Space turned and twisted upon itself.

  Then Japetus was alone once more, as it had been for three million years—alone, except for a deserted but not yet derelict ship, sending back to its makers messages which they could neither believe nor understand.

  PART SIX

  THROUGH THE STARGATE

  Chapter 41

  Grand Central

  There was no sense of motion, but he was falling toward those impossible stars, shining there in the dark heart of a moon. No—that was not where they really were, he felt certain. He wished, now that it was far too late, that he had paid more attention to those theories of hyperspace, of transdimensional ducts. To David Bowman, they were theories no longer.

  Perhaps that monolith on Japetus was hollow; perhaps the "roof" was only an illusion, or some kind of diaphragm that had opened to let him through. (But into what?) As far as he could trust his senses, he appeared to be dropping vertically down a huge rectangular shaft, several thousand feet deep. He was moving faster and faster—but the far end never changed its size, and remained always at the same distance from him.

  Only the stars moved, at first so slowly that it was some time before he realized that they were escaping out of the frame that held them. But in a little while it was obvious that the star field was expanding, as if it was rushing toward him at an inconceivable speed. The expansion was nonlinear; the stars at the center hardly seemed to move, while those toward the edge accelerated more and more swiftly, until they became streaks of light just before they vanished from view.

  There were always others to replace them, flowing into the center of the field from an apparently inexhaustible source. Bowman wondered what would happen if a star came straight toward him; would it continue to expand until he plunged directly into the face of a sun? But not one came near enough to show a disk; eventually they all veered aside, and streaked over the edge of their rectangular frame.

  And still the far end of the shaft came no closer. It was almost as if the walls were moving with him, carrying him to his unknown destination. Or perhaps he was really motionless, and space was moving past him. . . .

  Not only space, he suddenly realized, was involved in whatever was happening to him now. The clock on the pod's small instrument panel was also behaving strangely.

  Normally, the numbers in the tenths-of-a-second window flickered past so quickly that it was almost impossible to read them; now they were appearing and disappearing at discrete intervals, and he could count them off one by one without difficulty. The seconds themselves were passing with incredible slowness, as if time itself were coming to a stop. At last, the tenth-of-a-second counter froze between 5 and 6.

  Yet he could still think, and even observe, as the ebon walls flowed past at a speed that might have been anything between zero and a million times the velocity of light. Somehow, he was not in the least surprised, nor was he alarmed. On the contrary, he felt a sense of calm expectation, such as he had once known when the space medics had tested him with hallucinogenic drugs. The world around him was strange and wonderful, but there was nothing to fear. He had traveled these millions of miles in search of mystery; and now, it seemed, the mystery was coming to him.

  The rectangle ahead was growing lighter. The luminous star streaks were paling against a milky sky, whose brilliance increased moment by moment. It seemed as if the space pod was heading toward a bank of cloud, uniformly illuminated by the rays of an invisible sun.

  He was emerging from the tunnel. The far end, which until now had remained at that same indeterminate distance, neither approaching nor receding, had suddenly started to obey the normal laws of perspective. It was coming closer, and steadily widening before him. At the same time, he felt that he was moving upward, and for a fleeting instant he wondered if he had fallen right through Japetus and was now ascending from the other side. But even before the space pod soared out into the open he knew that this place had nothing to do with Japetus, or with any world within the experience of man.

  There was no atmosphere, for he could see all details unblurred, clear down to an incredibly remote and flat horizon. He must be above a world of enormous size—perhaps one much larger than Earth. Yet despite its extent, all the surface that Bowman could see was tessellated into obviously artificia1 patterns that must have been miles on a side. It was like the jigsaw puzzle of a giant that played with planets; and at the centers of many of those squares and triangles and polygons were gaping black shafts—twins of the chasm from which he had just emerged.

  Yet the sky above was stranger—and, in its way, more disturbing—than even the improbable land beneath. For there were no stars; neither was there the blackness of space. There was only a softly glowing milkiness, that gave the impression of infinite distance. Bowman remembered a description he had once heard of the dreaded Antarctic "whiteout"—"like being inside a ping-pong ball." Those words could be applied perfectly to this weird place, but the explanation must be utterly different. This sky could be no meteorological effect of mist and snow; there was a perfect vacuum here.

  Then, as Bowman's eyes grew accustomed to the nacreous glow that filled the heavens, he became aware of another detail. The sky was not, as he had thought at first glance, completely empty. Dotted overhead, quite motionless and forming apparently random patterns, were myriads of tiny black specks.

  They were difficult to see, for they were mere points of darkness, but once detected they were quite unmistakable. They reminded Bowman of something—something so familiar, yet so insane, that he refused to accept the parallel, until logic forced it upon him.

  Those black holes in the white sky were stars; he might have been looking at a photographic negative of the Milky Way.

  Where in God's name am I? Bowman asked himself; and even as he posed the question, he felt certain that he could never know the answer. It seemed that space had been turned inside out: this was not a place for man. Though the capsule was comfortably warm, he felt suddenly cold, and was afflicted by an almost uncontrollable trembling. He wanted to close his eyes, and shut out the pearly nothingness that surrounded him; but that was the act of a coward, and he would not yield to it.

  The pierced and faceted planet slowly rolled beneath him, without any real change of scenery. He guessed that he was about ten miles above the surface, and should be able to see any signs of life with ease. But this whole world was deserted; intelligence had come here, worked its will upon it, and gone its way again.

  Then he noticed, humped above the flat plain perhaps twenty miles away, a roughly cylindrical pile of debris that could only be the carcass of a gigantic ship. It was too distant for him to see any details, and it passed out of sight within a few seconds, but he could make out broken ribs and dully gleaming sheets of metal that had been partly peeled off like the skin of an orange. He wondered how many thousands of years the wreck had lain here on this deserted checkerboard—and what manner of creatures had sailed it between the stars.

  Then he forgot the derelict, for something was coming up over the horizon.

  At first it looked like a flat disk, but that was because it was heading almost directly toward him. As it approached and passed beneath, he saw that it was spindle-shaped, and several hundred feet long. Though there were faintly visible bands here and there along its length, it was hard to focus upon them; the object appeared to be vibrating, or perhaps spinning, at a very rapid rate.

  It tapered to a point at either end, and there was no sign of propulsion. Only one thing about it was familiar to human eyes, and that was its color. If it was indeed a solid artifact, and not an optical phantom, then its makers perhaps shared some of the emotions of men. But they certainly did not share their limitations, for the spindle appeared to be made of gold.

  Bowman moved his head to the rear-view system to watch the thing drop behind. It had ignored him completely, and now he saw that it was falling out of the sky down toward one of those thousands of great slots. A few seconds later it disappeared
in a final flash of gold as it dived into the planet. He was alone again, beneath that sinister sky, and the sense of isolation and remoteness was more overwhelming than ever.

  Then he saw that he also was sinking down toward the mottled surface of the giant world, and that another of the rectangular chasms yawned immediately below. The empty sky closed above him, the clock crawled to rest, and once again his pod was falling between infinite ebon walls, toward another distant patch of stars. But now he was sure that he was not returning to the Solar System, and in a flash of insight that might have been wholly spurious, he knew what this thing must surely be.

  It was some kind of cosmic switching device, routing the traffic of the stars through unimaginable dimensions of space and time. He was passing through a Grand Central Station of the galaxy.

  Chapter 42

  The Alien Sky

  Far ahead, the walls of the slot were becoming dimly visible once more, in the faint light diffusing downward from some still hidden source. And then the darkness was abruptly whipped away, as the tiny space pod hurtled upward into a sky ablaze with stars.

  He was back in space as he knew it, but a single glance told him that he was light-centuries from Earth. He did not even attempt to find any of the familiar constellations that since the beginning of history had been the friends of man; perhaps none of the stars that now blazed around him had ever been seen by the unaided human eye.

  Most of them were concentrated in a glowing belt, broken here and there with dark bands of obscuring cosmic dust, which completely circled the sky. It was like the Milky Way, but scores of times brighter; Bowman wondered if this was indeed his own galaxy, seen from a point much closer to its brilliant, crowded center.