The Space Trilogy

by Arthur C. Clarke

  Five

  There were still those who believed that Man would have been happier had he stayed on his own planet; but it was rather too late, now, to do anything about that. In any case, had he remained on Earth, he would not have been Man. The restlessness that had driven him over the face of his own world, that had made him climb the skies and plumb the seas, would not be assuaged while the Moon and planets beckoned to him across the deeps of space.

  The colonization of the Moon had been a slow, painful, sometimes tragic and always fabulously expensive enterprise. Two centuries after the first landings, much of Earth's giant satellite was still unexplored. Every detail had, of course, been mapped from space, but more than half that craggy globe had never been examined at close quarters.

  Central City and the other bases that had been established with such labour were islands of life in an immense wilderness, oases in a silent desert of blazing light or inky darkness. There had been many who had asked whether the effort needed to survive here was worthwhile, since the colonization of Mars and Venus offered much greater opportunities. But for all the problems it presented him, Man could not do without the Moon. It had been his first bridgehead in space, and was still the key to the planets. The liners that plied from world to world obtained all their propellent mass here, filling their great tanks with the finely divided dust which the ionic rockets would spit out in electrified jets. By obtaining that dust from the Moon, and not having to lift it through the enormous gravity field of Earth, it had been possible to reduce the cost of space-travel more than ten-fold. Indeed, without the Moon as a refuelling base, economical space-flight could never have been achieved.

  It had also proved, as the astronomers and physicists had predicted, of immense scientific value. Freed at last from the imprisoning atmosphere of Earth, astronomy had made giant strides, and indeed there was scarcely a branch of science that had not benefited from the lunar laboratories. Whatever the limitations of Earth's statesmen, they had learned one lesson well. Scientific research was the lifeblood of civilization; it was the one investment that could be guaranteed to pay dividends for eternity…

  Slowly, with countless heartbreaking setbacks, man had discovered how to exist, then to live, and at last to flourish on the Moon. He had invented whole new techniques of vacuum engineering, of low-gravity architecture, of air and temperature control. He had defeated the twin demons of the lunar day and the lunar night, though always he must be on the watch against their depredations. The burning heat could expand his domes and crack his buildings; the fierce cold could tear apart any metal structure not designed to guard against contractions never encountered on Earth. But all these problems had, at last, been overcome.

  All novel and ambitious enterprises seem much more hazardous and difficult from afar. So it had proved with the Moon. Problems that had appeared insuperable before the Moon was reached had now passed into lunar folklore. Obstacles that had disheartened the first explorers had been almost forgotten. Over the lands where men had once struggled on foot, the mono-cabs now carried the tourists from Earth in luxurious comfort.

  In a few respects, conditions on the Moon had helped rather than hindered the invaders. There was, for example, the question of the lunar atmosphere. On Earth it would have counted as a good vacuum, and it had no appreciable effect on astronomical observations. It was quite sufficient, however, to act as a very efficient shield against meteors. Most meteors are blocked by Earth's atmosphere before they get to within a hundred kilometres of the surface; they have been checked, in other words, while travelling through air no denser than the Moon's. Indeed, the Moon's invisible meteor shield is even more effective than Earth's, since thanks to the low lunar gravity it extends much farther into space.

  Perhaps the most astonishing discovery of the first explorers was the existence of plant life. It had long been suspected, from the peculiar changes of light and shade in such craters as Aristarchus and Eratosthenes, that there was some form of vegetation on the Moon, but it was difficult to see how it could survive under such extreme conditions. Perhaps, it was surmised, a few primitive lichens or mosses might exist, and it would be interesting to see how they managed to do it.

  The guess was quite wrong. A little thought would have shown that any lunar plants would not be primitive, but would be highly specialized—extremely sophisticated, in fact, so that they could cope with their hostile environment. Primitive plants could no more exist on the Moon than could primitive Man.

  The commonest lunar plants were plump, often globular growths, not unlike cacti. Their horny skins prevented the loss of precious water, and were dotted here and there with transparent "windows" to let sunlight enter. This astonishing improvisation, surprising though it seemed to many, was not unique. It had been evolved independently by certain desert plants in Africa, faced with the same problem of trapping sunlight without losing water.

  The unique feature of the lunar plants, however, was their ingenious mechanism for collecting air. An elaborate system of flaps and valves, not unlike that by which some sea creatures pump water through their bodies, acted as kind of compressor. The plants were patient; they would wait for years along the great crevasses which occasionally gush forth feeble clouds of carbon or sulphur dioxides from the Moon's interior. Then the flaps would go frantically to work, and the strange plants would suck into their pores every molecule that drifted by, before the transient lunar mist dispersed into the hungry near-vacuum which was all the atmosphere remaining to the Moon.

  Such was the strange world which was now home to some thousands of human beings. For all its harshness, they loved it and would not return to Earth, where life was easy and therefore offered little scope for enterprise or initiative. Indeed, the lunar colony, bound though it was to Earth by economic ties, had more in common with the planets of the Federation. On Mars, Venus, Mercury and the satellites of Jupiter and Saturn, men were fighting a frontier war against Nature, very like that which had won the Moon. Mars was already completely conquered; it was the only world outside Earth where a man could walk in the open without the use of artificial aids. On Venus, victory was in sight, and a land surface three times as great as Earth's would be the prize. Elsewhere, only outposts existed: burning Mercury and the frozen outer worlds were a challenge for future centuries.

  So Earth considered. But the Federation could not wait, and Professor Phillips, in complete innocence, had brought its impatience to the breaking point. It was not the first time that a scientific paper had changed the course of history, and it would not be the last.

  Sadler had never seen the pages of mathematics that had caused all the trouble, but he knew the conclusions to which they led. He had been taught many things in the six months that had been abstracted from his life. Some he had learned in a small, bare classroom with six other men whose names he had never been told, but much knowledge had come to him in sleep or in the dreamy trance-state of hypnosis. One day, perhaps, it would be withdrawn from him by the same techniques.

  The face of the Moon, Sadler had been told, consists of two distinct kinds of terrain—the dark areas of the so-called Seas, and the bright regions which are usually higher in elevation and much more mountainous. It is the bright areas which are pitted with the countless lunar craters, and appear to have been torn and blasted by eons of volcanic fury. The Seas, by contrast, are flat and relatively smooth. They contain occasional craters and many pits and crevasses, but they are incomparably more irregular than the rugged highlands.

  They were formed, it seems, much later than the mountains and crater chains of the Moon's fiery youth. Somehow, long after the older formations had congealed, the crust melted again in a few areas to form the dark, smooth plains that are the Seas. They contain the wrecks of many older craters and mountains that have been melted down like wax, and their coasts are fringed with half-destroyed cliffs and ringed plains that barely escaped total obliteration.

  The problem which had long engaged scientists, and which Profess
or Phillips had solved, was this: Why did the internal heat of the Moon break out only in the selected areas of the Seas, leaving the ancient highlands untouched?

  A planet's internal heat is produced by radioactivity. It seemed to Professor Phillips, therefore, that under the great Seas must be rich deposits of uranium and its associated elements. The ebb and flow of tides in the Moon's molten interior had somehow produced these local concentrations, and the heat they had generated through millennia of radioactivity had melted the surface features far above them to form the Seas.

  For two centuries, men had gone over the face of the Moon with every conceivable measuring instrument. They had set its interior trembling with artificial earthquakes; they had probed it with magnetic and electric fields. Thanks to these observations, Professor Phillips had been able to put his theory on a sound mathematical basis.

  Vast lodes of uranium existed far below the Seas. Uranium itself was no longer of the vital importance that it had been in the twentieth and twenty-first centuries, for the old fission piles had long since given way to the hydrogen reactor. But where there was uranium, the heavy metals would be found as well.

  Professor Phillips had been quite sure that his theory had no practical applications. All these great deposits, he had carefully pointed out, were at such depths that any form of mining would be totally out of the question. They were at least a hundred kilometres down—and the pressure in the rock at that depth was so great that the toughest metal would flow like a liquid, so that no shaft or bore-hole could stay open even for an instant.

  It seemed a great pity. These tantalizing treasures, Professor Phillips had concluded, must remain forever beyond the reach of the men who needed them so badly.

  A scientist, thought Sadler, should really have known better than that. One day Professor Phillips was going to have a big surprise.

  Six

  Sadler lay in his bunk and tried to focus his mind on the past week. It was very hard to believe that he had arrived from Earth only eight of its days ago, but the calendar clock on the wall confirmed the notes he had made in his diary. And if he doubted both these witnesses, he had merely to go up to the surface and enter one of the observation domes. There he could look up at the unmoving Earth, now just past full and beginning to wane. When he had arrived on the Moon, it had been at its first quarter.

  It was midnight over the Mare Imbrium. Dawn and sunset were both equally remote, but the lunar landscape was ablaze with light. Challenging the Earth itself was Nova Draconis, already brighter than any star in history. Even Sadler, who found most astronomical events too remote and impersonal to touch his emotions, would occasionally make the trip "upstairs" to look at this new invader of the modern skies. Was he looking at the funeral pyre of worlds older and wiser than the Earth? It was strange that such an awe-inspiring event should take place at a moment of human crisis. It could only be coincidence, of course. Nova Draconis was a close star, yet the signal of its death had been travelling for twenty centuries. One had to be not only superstitious but also very geocentric to imagine that this event had been planned as a warning for Earth. For what of all the other planets of other suns in whose skies the nova blazed with equal or even greater brilliance?

  Sadler called home his wandering thoughts, and concentrated on his proper business. What had he left undone? He had visited every section of the Observatory, and met everyone of importance, with the single exception of the director. Professor Maclaurin was due back from Earth in a day or so, and his absence had, if anything, simplified Sadler's task. When the Boss returned, so everybody had warned him, life would not be quite so free and easy, and everything would have to be done through the Proper Channels. Sadler was used to that, but did not enjoy it any the better.

  There was a discreet purr from the speaker in the wall over the bed. Sadler reached out one foot and kicked a switch with the toe of his sandal. He could do this the first time now, but faint scars on the wall were a still-visible memento of his apprenticeship.

  "Yes," he said. "Who's that?"

  "Transport Section here. I'm closing the list for tomorrow. There are still a couple of seats left—you want to come along?"

  "If there's room," Sadler replied. "I don't want any more-deserving causes to suffer."

  "O.K.—you're down," said the voice briskly, and clicked off,

  Sadler felt only the mildest twinge of conscience. After a week's solid work, he could do with a few hours in Central City. He was not yet due to meet his first contact, and so far all his reports had gone out through the normal mail service, in a form that would have meant nothing to anyone happening to read them. But it was high time he got to know his way around the city, and indeed it would look odd if he took no holidays at all.

  His main reason for the trip, however, was purely personal. There was a letter he wanted to post, and he knew that the Observatory mail was being censored by his colleagues in Central Intelligence. By now they must be indifferent to such matters, but he would still prefer to keep his private life to himself.

  Central City was twenty kilometres from the spaceport, and Sadler had seen nothing of the lunar metropolis on his arrival. As the monocab—much fuller this time than it had been on the outward journey—pulled once more into the Sinus Medii, Sadler no longer felt a complete stranger. He knew, at least by sight, everyone in the car. Almost half the Observatory staff were here; the other half would take their day off next week. Even Nova Draconis was not allowed to interfere with this routine, which was based on common sense and sound psychology.

  The cluster of great domes began to hump themselves over the horizon. A beacon light burned on the summit of each, but otherwise they were darkened and gave no sign of life. Some, Sadler knew, could be made transparent when desired. All were opaque now, conserving their heat against the lunar night.

  The monocab entered a long tunnel at the base of one of the domes. Sadler had a glimpse of great doors closing behind them —then another set, and yet another. They're taking no chances, he thought to himself, and heartily approved of such caution. Then there was the unmistakable sound of air surging around them, a final door opened ahead, and the vehicle rolled to a halt beside a platform that might have been in any station back on Earth. It gave Sadler quite a shock to look through the window and see people walking around outside without spacesuits…

  "Going anywhere in particular?" asked Wagnall as they waited for the crush at the door to subside.

  Sadler shook his head.

  "No—I just want to wander round and have a look at the place. I want to see where you people manage to spend all your money."

  Wagnall obviously couldn't decide whether he was joking or not, and to Sadler's relief did not offer his services as a guide. This was one of the occasions when he would be quite happy to be left on his own.

  He walked out of the station and found himself at the top of a large ramp, sloping down into the compact little city. The main level was twenty meters below him. He had not realized that the whole dome was countersunk this far into the lunar plain, thus reducing the amount of roof structure necessary. By the side of the ramp a wide conveyor belt was carrying freight and luggage into the station at a leisurely rate. The nearest buildings were obviously industrial, and though well kept had the slightly seedy appearance which inevitably overtakes anything in the neighbourhood of stations or docks.

  It was not until Sadler was halfway down the ramp that he realized there was a blue sky overhead, that the sun was shining just behind him, and that there were high cirrus clouds floating far above.

  The illusion was so perfect that he had taken it completely for granted, and had forgotten for a moment that this was midnight on the Moon. He stared for a long time into the dizzy depths of that synthetic sky, and could see no flaw in its perfection. Now he understood why the lunar cities insisted upon their expensive domes, when they could just as well have burrowed underground like the Observatory.

  There was no risk of getting lost in Centr
al City. With one exception each of the seven interconnected domes was laid out in the same pattern of radiating avenues and concentric ring-roads. The exception was Dome Five, the main industrial and production centre, which was virtually one vast factory and which Sadler decided to leave alone.

  He wandered at random for some time, going where his stray impulses took him. He wanted to get the "feel" of the place, for he realized it was completely impossible to know the city properly in the short time at his disposal. There was one thing about Central City that struck him at once—it had a personality, a character of its own. No one can say why this is true of some cities and not of others, and Sadler felt a little surprised that it should be of such an artificial environment as this. Then he remembered that all cities, whether on Earth or on the Moon, were equally artificial…

  The roads were narrow, the only vehicles small, three-wheeled Open cars that cruised along at less than thirty kilometres an hour and appeared to be used exclusively for freight rather than passengers. It was some time before Sadler discovered the automatic subway that linked the outer six domes in a great ring, passing under the centre of each. It was really a glorified conveyor belt, and moved in a counter-clockwise direction only. If you were unlucky, you might have to go right round the city to get to the adjacent dome, but as the circular tour took only about five minutes, this was no great hardship.

  The shopping centre, and main repository of lunar chic, was in Dome One. Here also lived the senior executives and technicians—the most senior of all in houses of their own. Most of the residential buildings had roof gardens, where plants imported from Earth ascended to improbable heights in this low gravity. Sadler kept his eyes open for any lunar vegetation, but saw no signs of it. He did not know that there was a strict rule against bringing the indigenous plants into the domes. An oxygen-rich atmosphere, it had been found, over-stimulated them so that they ran riot and promptly died, producing a stench which had to be experienced to be believed when their sulphur-loaded organisms began to decay.