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  An object forty kilometres across, with a rotation period of only four minutes—where did that fit into the astronomical scheme of things? Dr. Stenton was a somewhat imaginative man, a little too prone to jump to conclusions. He now jumped to one which gave him a very uncomfortable few minutes indeed.

  The only specimen of the celestial zoo that fitted this description was a collapsed star. Perhaps Rama was a dead sun—a madly spinning sphere of neutronium, every cubic centimetre weighing billions of tons.

  At this point, there flashed briefly through Dr. Stenton's horrified mind the memory of that timeless classic, H. G. Wells's “The Star.” He had first read it as a very small boy, and it had helped to spark his interest in astronomy. Across more than two centuries of time, it had lost none of its magic and terror. He would never forget the images of hurricanes and tidal waves, of cities sliding into the sea, as that other visitor from the stars smashed into Jupiter and then fell sunwards past the Earth. True, the star that old Wells described was not cold, but incandescent, and wrought much of its destruction by heat. That scarcely mattered; even if Rama was a cold body, reflecting only the light of the sun, it could kill by gravity as easily as by fire.

  Any stellar mass intruding into the solar system would completely distort the orbits of the planets. The Earth had only to move a few million kilometres sunwards—or starwards—for the delicate balance of climate to be destroyed. The Antarctic icecap could melt and flood all low-lying land; or the oceans could freeze and the whole world be locked in an eternal winter. Just a nudge in either direction would be enough…

  Then Dr. Stenton relaxed and breathed a sigh of relief. This was all nonsense; he should be ashamed of himself.

  Rama could not possibly be made of condensed matter. No star-sized mass could penetrate so deeply into the solar system without producing disturbances which would have betrayed it long ago. The orbits of all the planets would have been affected; that, after all, was how Neptune, Pluto and Persephone had been discovered. No, it was utterly impossible for an object as massive as a dead sun to sneak up unobserved.

  In a way, it was a pity. An encounter with a dark star would have been quite exciting.

  While it lasted…

  CHAPTER 3

  RAMA AND SITA

  THE EXTRAORDINARY MEETING of the Space Advisory Council was brief and stormy. Even in the twenty-second century, no way had yet been discovered of keeping elderly and conservative scientists from occupying crucial administrative positions. Indeed, it was doubted if the problem ever would be solved.

  To make matters worse, the current Chairman of the SAC was Professor Emeritus Olaf Davidson, the distinguished astrophysicist. Professor Davidson was not very much interested in objects smaller than galaxies, and never bothered to conceal his prejudices. And though he had to admit that ninety per cent of his science was now based upon observations from space-borne instruments, he was not at all happy about it. No less than three times during his distinguished career, satellites specially launched to prove one of his pet theories had done precisely the opposite.

  The question before the Council was straightforward enough. There was no doubt that Rama was an unusual object—but was it an important one? In a few months it would be gone for ever, so there was little time in which to act. Opportunities missed now would never recur.

  At rather a horrifying cost, a space probe soon to be launched from Mars to beyond Neptune could be modified and sent on a high-speed trajectory to meet Rama. There was no hope of a rendezvous; it would be the fastest fly-by on record, for the two bodies would pass each other at two hundred thousand kilometres an hour. Rama would be observed intensively for only a few minutes—and in real close-up for less than a second. But with the right instrumentation, that would be long enough to settle many questions.

  Although Professor Davidson took a very jaundiced view of the Neptune probe, it had already been approved and he saw no point in sending more good money after bad. He spoke eloquently on the follies of asteroid-chasing, and the urgent need for a new high-resolution interferometer on the Moon to prove the newly-revived Big Bang theory of creation, once and for all.

  That was a grave tactical error, because the three most ardent supporters of the Modified Steady State Theory were also members of the Council. They secretly agreed with Professor Davidson that asteroid-chasing was a waste of money; nevertheless…

  He lost by one vote.

  Three months later the space-probe, rechristened Sita, was launched from Phobos, the inner moon of Mars. The flight time was seven weeks, and the instrument was switched to full power only five minutes before interception. Simultaneously, a cluster of camera pods was released, to sail past Rama so that it could be photographed from all sides.

  The first images, from ten thousand kilometres away, brought to a halt the activities of all mankind. On a billion television screens, there appeared a tiny, featureless cylinder, growing rapidly second by second. By the time it had doubled its size, no one could pretend any longer that Rama was a natural object.

  Its body was a cylinder so geometrically perfect that it might have been turned on a lathe—one with centres fifty kilometres apart. The two ends were quite flat, apart from some small structures at the centre of one face, and were twenty kilometres across; from a distance, when there was no sense of scale, Rama looked almost comically like an ordinary domestic boiler.

  Rama grew until it filled the screen. Its surface was a dull, drab grey, as colourless as the Moon, and completely devoid of markings except at one point. Halfway along the cylinder there was a kilometre-wide stain or smear, as if something had once hit and splattered, ages ago.

  There was no sign that the impact had done the slightest damage to Rama's spinning walls; but this mark had produced the slight fluctuation in brightness that had led to Stenton's discovery.

  The images from the other cameras added nothing new. However, the trajectories their pods traced through Rama's minute gravitational field gave one other vital piece of information: the mass of the cylinder.

  It was far too light to be a solid body. To nobody's great surprise, it was clear that Rama must be hollow.

  The long-hoped-for, long-feared encounter had come at last. Mankind was about to receive its first visitor from the stars.

  CHAPTER 4

  RENDEZVOUS

  COMMANDER NORTON REMEMBERED those first TV transmissions, which he had replayed so many times, during the final minutes of the rendezvous. But there was one thing no electronic image could possibly convey—and that was Rama's overwhelming size.

  He had never received such an impression when landing on a natural body like the Moon or Mars. Those were worlds, and one expected them to be big. Yet he had also landed on Jupiter VIII, which was slightly larger than Rama—and that had seemed quite a small object.

  It was very easy to resolve the paradox. His judgement was wholly altered by the fact that this was an artifact, millions of times heavier than anything that Man had ever put into space. The mass of Rama was at least ten million million tons; to any spaceman, that was not only an awe-inspiring, but a terrifying thought. No wonder that he sometimes felt a sense of insignificance, and even depression, as that cylinder of sculptured, ageless metal filled more and more of the sky.

  There was also a sense of danger here that was wholly novel to his experience. In every earlier landing he had known what to expect; there was always the possibility of accident, but never of surprise. With Rama, surprise was the only certainty.

  Now Endeavour was hovering less than a thousand metres above the North Pole of the cylinder, at the very centre of the slowly turning disc. This end has been chosen because it was the one in sunlight; as Rama rotated, the shadows of the short enigmatic structures near the axis swept steadily across the metal plain. The northern face of Rama was a gigantic sundial, measuring out the swift passage of its four-minute day.

  Landing a five-thousand-ton spaceship at the centre of a spinning disc was the least of Com
mander Norton's worries. It was no different from docking at the axis of a large space station; Endeavour's lateral jets had already given her a matching spin, and he could trust Lieutenant Joe Calvert to put her down as gently as a snowflake, with or without the aid of the nay computer.

  'In three minutes,' said Joe, without taking his eyes from the display, 'we'll know if it's made of antimatter.'

  Norton grinned, as he recalled some of the more hair-raising theories about Rama's origin. If that unlikely speculation was true, in a few seconds there would be the biggest bang since the solar system was formed. The total annihilation of ten thousand tons would, briefly, provide the planets with a second sun.

  Yet the mission profile had allowed even for this remote contingency; Endeavour had squirted Rama with one of her jets from a safe thousand kilometres away. Nothing whatsoever had happened when the expanding cloud of vapour arrived on target—and a matter-antimatter reaction involving even a few milligrams would have produced an awesome firework display.

  Norton, like all space commanders, was a cautious man. He had looked long and hard at the northern face of Rama, choosing the point of touch-down. After much thought, he had decided to avoid the obvious spot—the exact centre, on the axis itself. A clearly marked circular disc, a hundred metres in diameter, was centred on the Pole, and Norton had a strong suspicion that this must be the outer seal of an enormous airlock. The creatures who had built this hollow world must have had some way of taking their ships inside. This was the logical place for the main entrance, and Norton thought it might be unwise to block the front door with his own vessel.

  But this decision generated other problems. If Endeavour touched down even a few metres from the axis, Rama's rapid spin would start her sliding away from the pole. At first, the centrifugal force would be very weak, but it would be continuous and inexorable. Commander Norton did not relish the thought of his ship slithering across the polar plain, gaining speed minute by minute until it was slung off into space at a thousand kilometres an hour when it reached the edge of the disc.

  It was possible that Rama's minute gravitational field—about one thousandth of Earth's—might prevent this from happening. It would hold Endeavour against the plain with a force of several tons, and if the surface was sufficiently rough the ship might stay near the Pole. But Commander Norton had no intention of balancing an unknown frictional force against a quite certain centrifugal one.

  Fortunately, Rama's designers had provided an answer. Equally spaced around the polar axis were three low, pillbox-shaped structures, about ten metres in diameter. If Endeavour touched down between any two of these, the centrifugal drift would fetch her up against them and she would be held firmly in place, like a ship glued against a quayside by the incoming waves.

  'Contact in fifteen seconds,' said Calvert.

  As he tensed himself above the duplicate controls, which he hoped he would not have to touch, Commander Norton became acutely aware of all that had come to focus on this instant of time. This, surely, was the most momentous landing since the first touchdown on the Moon, a century and a half ago.

  The grey pill-boxes drifted slowly upwards outside the control port. There was the last hiss of a reaction jet, and a barely perceptible jar.

  In the weeks that had passed, Commander Norton had often wondered what he would say at this moment. But now that it was upon him, History chose his words, and he spoke almost automatically, barely aware of the echo from the past:

  'Rama Base. Endeavour has landed.'

  As recently as a month ago, he would never have believed it possible. The ship had been on a routine mission, checking and emplacing asteroid warning beacons, when the order had come. Endeavour was the only spacecraft in the solar system which could possibly make a rendezvous with the intruder before it whipped round the sun and hurled itself back towards the stars. Even so, it had been necessary to rob three other ships of the Solar Survey, which were now drifting helplessly until tankers could refuel them. Norton feared that it would be a long time before the skippers of Calypso, Beagle and Challenger would speak to him again.

  Even with all this extra propellant, it had been a long hard chase; Rama was already inside the orbit of Venus when Endeavour caught up with her. No other ship could ever do so; this privilege was unique, and not a moment of the weeks ahead was to be wasted. A thousand scientists on Earth would have cheerfully mortgaged their souls for this opportunity; now they could only watch over the TV circuits, biting their lips and thinking how much better they could do the job. They were probably right, but there was no alternative. The inexorable laws of celestial mechanics had decreed that Endeavour was the first, and the last, of all Man's ships that would ever make contact with Rama.

  The advice he was continually receiving from Earth did little to alleviate Norton's responsibility. If split-second decisions had to be made, no one could help him; the radio time-lag to Mission Control was already ten minutes, and increasing. He often envied the great navigators of the past, before the days of electronic communications, who could interpret their sealed orders without continual monitoring from headquarters. When they made mistakes, no one ever knew.

  Yet at the same time, he was glad that some decisions could be delegated to Earth. Now that Endeavour's orbit had coalesced with Rama's they were heading sunwards like a single body; in forty days they would reach perihelion, and pass within twenty million kilometres of the sun. That was far too close for comfort; long before then, Endeavour would have to use her remaining fuel to nudge herself into a safer orbit. They would have perhaps three weeks of exploring time, before they parted from Rama forever.

  After that, the problem would be Earth's. Endeavour would be virtually helpless, speeding on an orbit which could make her the first ship to reach the stars—in approximately fifty thousand years. There was no need to worry, Mission Control had promised. Somehow, regardless of cost, Endeavour would be refuelled, even if it proved necessary to send tankers after her, and abandon them in space once they had transferred every gram of propellant. Rama was a prize worth any risk, short of a suicide mission.

  And, of course, it might even come to that. Commander Norton had no illusions on this score. For the first time in a hundred years an element of total uncertainty had entered human affairs. Uncertainty was one thing that neither scientists nor politicians could tolerate. If that was the price of resolving it, Endeavour and her crew would be expendable.

  CHAPTER 5

  FIRST EVA

  RAMA WAS SILENT as a tomb—which, perhaps, it was. No radio signals, on any frequency; no vibrations that the seismographs could pick up, apart from the micro-tremors undoubtedly caused by the sun's increasing heat; no electrical currents; no radioactivity. It was almost ominously quiet; one might have expected that even an asteroid would be noisier.

  What did we expect? Norton asked himself. A committee of welcome? He was not sure whether to be disappointed or relieved. The initiative, at any rate, appeared to be his.

  His orders were to wait for twenty-four hours, then to go out and explore. Nobody slept much that first day; even the crew members not on duty spent their time monitoring the ineffectually probing instruments, or simply looking out of the observation ports at the starkly geometrical landscape. Is this world alive? they asked themselves, over and over again. Is it dead? Or is it merely sleeping?

  On the first EVA, Norton took only one companion—Lieutenant Commander Karl Mercer, his tough and resourceful life-support officer. He had no intention of getting out of sight of the ship, and if there was any trouble, it was unlikely that a larger party would be safe. As a precaution, however, he had two more crew members, already suited up, standing by in the air lock.

  The few grams of weight that Rama's combined gravitational and centrifugal fields gave them were neither help nor hindrance; they had to rely entirely on their jets. As soon as possible, Norton told himself, he would string a cat's-cradle of guide ropes between the ship and the pillboxes, so that they cou
ld move around without wasting propellants.

  The nearest pillbox was only ten metres from the airlock, and Norton's first concern was to check that the contact had caused no damage to the ship. Endeavour's hull was resting against the curving wall with a thrust of several tons, but the pressure was evenly distributed. Reassured, he began to drift around the circular structure, trying to determine its purpose.

  Norton had travelled only a few metres when he came across an interruption in the smooth, apparently metallic wall. At first, he thought it was some peculiar decoration, for it seemed to serve no useful function. Six radial grooves, or slots, were deeply recessed in the metal, and lying in them were six crossed bars like the spokes of a rimless wheel, with a small hub at the centre. But there was no way in which the wheel could be turned, as it was embedded in the wall.

  Then he noticed, with growing excitement, that there were deeper recesses at the ends of the spokes, nicely shaped to accept a clutching hand (claw? tentacle?). If one stood so, bracing against the wall, and pulled on the spoke so…

  Smooth as silk, the wheel slid out of the wall. To his utter astonishment—for he had been virtually certain that any moving parts would have become vacuum-welded ages ago—Norton found himself holding a spoked wheel. He might have been the captain of some old windjammer standing at the helm of his ship.