The Space Trilogy

by Arthur C. Clarke

  Earth is the densest of all the planets, only Venus approaching it in this respect. But Venus has no satellite, and the Earth-Moon system forms a double world of a type found nowhere else among the planets. Its mode of formation is a mystery still, but it is known that when Earth was molten the Moon circled at only a fraction of its present distance, and raised gigantic tides in the plastic substance of its companion.

  As a result of these internal tides, the crust of the Earth is rich in heavy metals—far richer than that of any other of the planets: They hoard their wealth far down within their unreachable cores, protected by pressures and temperatures that guard them from man's depredations. So as human civilization spread outward from Earth, the drain on the mother world's dwindling resources steadily increased.

  The light elements existed on the other planets in unlimited amounts, but such essential metals as mercury, lead, uranium, platinum, thorium and tungsten were almost unobtainable. For many of them no substitutes existed; their large-scale synthesis was impractical, despite two centuries of effort—and modern technology could not survive without them.

  It was an unfortunate situation, and a very galling one for the independent republics on Mars, Venus and the larger satellites, which had now united to form the Federation. It kept them dependent upon Earth, and prevented their expansion toward the frontiers of the solar system. Though they had searched among the asteroids and moons, among the rubble left over when the worlds were formed, they had found little but worthless rock and ice. They must go cap in hand to the mother planet for almost every gram of a dozen metals that were more precious than gold.

  That in itself might not have been serious, had not Earth grown steadily more jealous of its offspring during the two hundred years since the dawn of space travel. It was, thought Sadler, an old, old story, perhaps its classic example being the case of England and the American colonies. It has been truly said that history never repeats itself, but historical situations recur. The men who governed Earth were far more intelligent than George the Third; nevertheless, they were beginning to show the same reactions as that unfortunate monarch.

  There were excuses on both sides; there always are. Earth was tired; it had spent itself, sending out its best blood to the stars. It saw power slipping from its hands, and knew that it had already lost the future. Why should it speed the process by giving to its rivals the tools they needed?

  The Federation, on the other hand, looked back with a kind of affectionate contempt upon the world from which it had sprung. It had lured to Mars, Venus and the satellites of the giant planets some of the finest intellects and the most adventurous spirits of the human race. Here was the new frontier, one that would expand forever toward the stars. It was the greatest physical challenge mankind had ever faced, it could be met only by supreme scientific skill and unyielding determination. These were virtues no longer essential on Earth; the fact that Earth was well aware of it did nothing to ease the situation.

  All this might lead to discord and interplanetary invective, but it could never lead to violence. Some other factor was needed to produce that, some final spark which would set off an explosion echoing round the solar system.

  That spark had now been struck. The world did not know it yet, and Sadler himself had been equally ignorant a short six months ago. Central Intelligence, the shadowy organization of which he was now a reluctant member, had been working night and day to neutralize the damage. A mathematical thesis entitled "A Quantitative Theory of the Formation of the Lunar Surface Features" did not look like the sort of thing that could start a war—but an equally theoretical paper by a certain Albert Einstein had once ended one.

  The paper had been written about two years ago by Professor Roland Phillips, a peaceable Oxford cosmologist with no interest in politics. He had submitted it to the Royal Astronomical Society, and it was now becoming a little difficult to give him a satisfactory explanation of the delay in publication. Unfortunately—and this was the fact that caused great distress to Central Intelligence—Professor Phillips had innocently sent copies to his colleagues on Mars and Venus. Desperate attempts had been made to intercept them, but in vain. By now, the Federation must know that the Moon was not as impoverished a world as had been believed for 200 years.

  There was no way of calling back knowledge that had leaked out, but there were other things about the Moon which it was now equally important that the Federation should not learn. Yet somehow it was learning them; somehow, information was leaking across space from Earth to Moon, and then out to the planets.

  When there's a leak in the house, thought Sadler, you send for the plumber. But how do you deal with a leak which you can't see—and which may be anywhere on the surface of a world as large as Africa?

  He still knew very little about the scope, size and methods of Central Intelligence—and still resented, futile though that was, the way in which his private life had been disrupted. By training, he was precisely what he pretended to be—an accountant. Six months ago, for reasons which had not been explained and which he probably never would discover, he had been interviewed and offered an unspecified job. His acceptance was quite voluntary; it was merely made clear to him that he had better not refuse. Since then he had spent most of his time under hypnosis, being pumped full of the most various kinds of information and living a monastic life in an obscure corner of Canada. (At least, he thought it was Canada, but it might equally well have been Greenland or Siberia.) Now he was here on the Moon, a minor pawn in a game of interplanetary chess. He would be very glad when the whole frustrating experience was over. It seemed quite incredible to him that anyone would ever voluntarily become a secret agent. Only very immature and unbalanced individuals could get any satisfaction from such frankly uncivilized behaviour.

  There were a few compensations. In the ordinary way, he would never have had a chance of going to the Moon, and the experience he was gathering now might be a real asset in later years. Sadler always tried to take the long view, particularly when he was depressed by the current situation. And the situation, both on the personal and interplanetary levels, was depressing enough.

  The safety of Earth was quite a responsibility, but it was really too big for one man to worry about. Whatever reason said, the vast imponderables of planetary politics were less of a burden than the little cares of everyday life. To a cosmic observer, it might have seemed very quaint that Sadler's greatest worry concerned one solitary human being. Would Jeannette ever forgive him, he wondered, for being away on their wedding anniversary? At least she would expect him to call her, and that was the one thing he dared not do. As far as his wife and his friends were concerned, he was still on Earth. There was no way of calling from the Moon without revealing his location, for the two-and-a-half-second time-lag would betray him at once.

  Central Intelligence could fix many things, but it could hardly speed up radio waves. It could deliver his anniversary present on time, as it had promised—but it couldn't tell Jeannette when he would be home again.

  And it couldn't change the fact that, to conceal his whereabouts, he had had to lie to his wife in the sacred name of Security.

  Three

  When Conrad Wheeler had finished comparing the tapes, he got up from his chair and walked three times round the room. From the way he moved, an old hand could have told that Wheeler was a relative newcomer to the Moon. He had been with the Observatory staff for just six months, and still overcompensated for the fractional gravity in which he now lived. There was a jerkiness about his movements that contrasted with the smooth, almost slow-motion gait of his colleagues. Some of this abruptness was due to his own temperament, his lack of discipline, and quickness at jumping to conclusions. It was that temperament he was now trying to guard against.

  He had made mistakes before—but this time, surely, there could be no doubt. The facts were undisputed, the calculation trivial—the answer awe-inspiring. Far out in the depths of space, a star had exploded with unimaginable violence. Wh
eeler looked at the figures he had jotted down, checked them for the tenth time, and reached for the phone.

  Sid Jamieson was not pleased at the interruption. "Is it really important?" he queried. "I'm in the darkroom, doing some stuff for Old Mole. I'll have to wait until these plates are washing, anyway."

  "How long will that take?"

  "Oh, maybe five minutes. Then I've got some more to do."

  "I think this is important. It'll only take a moment. I'm up in Instrumentation 5."

  Jamieson was still wiping developer from his hands when he arrived. After more than three hundred years, certain aspects of photography were quite unchanged. Wheeler, who thought that everything could be done by electronics, regarded many of his older friend's activities as survivals from the age of alchemy.

  "Well?" said Jamieson, as usual wasting no words.

  Wheeler pointed to the punched tape lying on the desk.

  "I was doing the routine check of the magnitude integrator. It's found something."

  "It's always doing that," snorted Jamieson. "Every time anyone sneezes in the Observatory, it thinks it's discovered a new planet."

  There were solid grounds for Jamieson's scepticism. The integrator was a tricky instrument, easily misled, and many astronomers thought it more trouble than it was worth. But it happened to be one of the director's pet projects, so there was no hope of doing anything about it until there was a change of administration. Maclaurin had invented it himself, back in the days when he had had time to do some practical astronomy. An automatic watchdog of the skies, it would wait patiently for years until a new star—a "nova"—blazed in the heavens. Then it would ring a bell and start calling for attention.

  "Look," said Wheeler, "there's the record. Don't just take my word for it."

  Jamieson ran the tape through the converter, copied down the figures and did a quick calculation. Wheeler smiled in satisfaction and relief as his friend's jaw dropped.

  "Thirteen magnitudes in twenty-four hours! Wow!"

  "I made it thirteen point four, but that's good enough. For my money, it's a supernova. And a close one."

  The two young astronomers looked at each other in thoughtful silence. Then Jamieson remarked:

  "This is too good to be true. Don't start telling everybody about it until we're quite sure. Let's get its spectrum first, and treat it as an ordinary nova until then."

  There was a dreamy look in Wheeler's eyes.

  "When was the last supernova in our galaxy?"

  "That was Tycho's star—no it wasn't—there was one a bit later, round about 1600."

  "Anyway, it's been a long time. This ought to get me on good terms with the director again."

  "Perhaps," said Jamieson dryly. "It would just about take a supernova to do that. I'll go and get the spectrograph ready while you put out the report. We mustn't be greedy; the other observatories will want to get into the act." He looked at the integrator, which had returned to its patient searching of the sky. "I guess you've paid for yourself," he added, "even if you never find anything again except spaceship navigation lights."

  Sadler heard the news without particular excitement in the Common Room an hour later. He was too preoccupied with his own problems and the mountain of work which faced him to take much notice of the Observatory's routine program, even when he fully understood it. Secretary Wagnall, however, quickly made it clear that this was very far from being a routine matter.

  "Here's something to put on your balance sheet," he said cheerfully. "It's the biggest astronomical discovery for years. Come up to the roof."

  Sadler dropped the trenchant editorial in Time Interplanetary which he had been reading with growing annoyance. The magazine fell with that dreamlike slowness he had not yet grown accustomed to, and he followed Wagnall to the elevator.

  They rose past the residential level, past Administration, past Power and Transport, and emerged into one of the small observation domes. The plastic bubble was scarcely ten meters across, and the awnings that shielded it during the lunar day had been rolled back. Wagnall switched off the internal lights, and they stood looking up at the stars and the waxing Earth. Sadler had been here several times before; he knew no better cure for mental fatigue.

  A quarter of a kilometre away the great framework of the largest telescope ever built by man was pointing steadily toward a spot in the southern sky. Sadler knew that it was looking at no stars that his eyes could see—at no stars, indeed, that belonged to this universe. It would be probing the limits of space, a billion light-years from home.

  Then, unexpectedly, it began to swing toward the north. Wagnall chuckled quietly.

  "A lot of people will be tearing their hair now," he said. "We've interrupted the program to turn the big guns on Nova Draconis. Let's see if we can find it."

  He searched for a little while, consulting a sketch in his hand. Sadler, also staring into the north, could see nothing in the least unusual. All the stars there looked just the same to him. But presently, following Wagnall's instructions, and using the Great Bear and Polaris as guides, he found the faint star low down in the northern sky. It was not at all impressive, even if you realized that a couple of days before only the largest telescopes could have found it, and that it had climbed in brilliance a hundred thousand times in a few hours.

  Perhaps Wagnall sensed his disappointment.

  "It may not look very spectacular now," he said defensively, "but it's still on the rise. With any luck, we may really see something in a day or two."

  Day lunar or day terrestrial? Sadler wondered. It was rather confusing, like so many things here. All the clocks ran on a twenty-four hour system and kept Greenwich Mean Time. One minor advantage of this was that one had only to glance at the Earth to get a reasonably accurate time check. But it meant that the progress of light and dark on the lunar surface had no connection at all with what the clocks might say. The sun could be anywhere above or below the horizon when the docks said it was noon.

  Sadler glanced away from the north, back to the Observatory. He had always assumed—without bothering to think about it—that any observatory would consist of a cluster of giant domes, and had forgotten that here on the weatherless Moon there would be no purpose in enclosing the instruments. The thousand centimetre reflector and its smaller companion stood naked and unprotected in the vacuum of space. Only their fragile masters remained underground in the warmth and air of this buried city.

  The horizon was almost flat in all directions. Though the Observatory was at the centre of the great walled-plain of Plato, the mountain ring was hidden by the curve of the Moon. It was a bleak and desolate prospect, without even a few hills to give it interest. Only a dusty plain, studded here and there with blow-holes and craterlets—and the enigmatic works of man, straining at the stars and trying to wrest away their secrets.

  As they left, Sadler glanced once more toward Draco, but already he had forgotten which of the faint circumpolar stars was the one he had come to see. "Exactly why," he said to Wag-nail, as tactfully as he could—for he did not want to hurt the secretary's feelings—"is this star so important?"

  Wagnall looked incredulous, then pained, then understanding.

  "Well," he began, "I guess stars are like people. The well-behaved ones never attract much attention. They teach us something, of course, but we can learn a lot more from the ones that go off the rails."

  "And do stars do that sort of thing fairly often?"

  "Every year about a hundred blow up in our galaxy alone, but those are only ordinary novae. At their peak, they may be above a hundred thousand times as bright as the sun. A supernova is a very much rarer, and a very much more exciting affair. We still don't know what causes it, but when a star goes super it may become several billion times brighter than the sun. In fact, it can outshine all the other stars in the galaxy added together."

  Sadler considered this for a while. It was certainly a thought calculated to inspire a moment's silent reflection.

  "The
important thing is," Wagnall continued eagerly, "that nothing like this has happened since telescopes were invented. The last supernova in our universe was six hundred years ago. There have been plenty in other galaxies, but they're too far away to be studied properly. This one, as it were, is right on our doorstep. That fact will be pretty obvious in a couple of days. In a few hours it will be outshining everything in the sky, except the sun and Earth."

  "And what do you expect to learn from it?"

  "A supernova explosion is the most titanic event known to occur in nature. We'll be able to study the behaviour of matter under conditions that make the middle of an atom bomb look like a dead calm. But if you're one of those people who always want a practical use for everything, surely it's of considerable interest to find what makes a star explode? One day, after all, our sun may decide to do likewise."

  "And in that case," retorted Sadler, "I'd really prefer not to know about it in advance. I wonder if that nova took any planets with it?"

  "There's absolutely no way of telling. But it must happen fairly often, because at least one star in ten's got planets."

  It was a heart-freezing thought. At any moment, as likely as not, somewhere in the universe a whole solar system, with strangely peopled worlds and civilizations, was being tossed carelessly into a cosmic furnace. Life was a fragile and delicate phenomenon, poised on the razor's edge between cold and heat.

  But Man was not content with the hazards that Nature could provide. He was busily building his own funeral pyre.

  The same thought had occurred to Dr. Molton, but unlike Sadler he could set against it a more cheerful one. Nova Draconis was more than two thousand light-years away; the flash of the detonation had been travelling since the birth of Christ. In that time, it must have swept through millions of solar systems, have alerted the inhabitants of a thousand worlds. Even at this moment, scattered over the surface of a sphere four thousand light-years in diameter, there must surely be other astronomers, with instruments not unlike his own, who would be trapping the radiations of this dying sun as they ebbed out toward the frontiers of the universe. And it was stranger still to think that infinitely more distant observers, so far away that to them the whole galaxy was no more than a faint smudge of light, would notice some hundred million years from now that our island universe had momentarily doubled its brilliance…