The City and the Stars/The Sands of Mars

by Arthur C. Clarke

  Hilvar was about to suggest that they should return to the ship and fly across to the nearest of the surrounding buildings when Alvin noticed a long, narrow crack in the marble floor of the amphitheater. They walked along it for a considerable distance, the crack widening all the time until presently it was too broad for a man’s legs to straddle.

  A moment later they stood beside its origin. The surface of the arena had been crushed and splintered into an enormous shallow depression, more than a mile long. No intelligence, no imagination was needed to picture its cause. Ages ago— though certainly long after this world had been deserted— an immense cylindrical shape had rested here, then lifted once more into space and left the planet to its memories.

  Who had they been? Where had they come from? Alvin could only stare and wonder. He would never know if he had missed these earlier visitors by a thousand or a million years.

  They walked in silence back to their own ship (how tiny that would have looked beside the monster which once had rested here!) and flew slowly across the arena until they came to the most impressive of the buildings flanking it. As they landed in front of the ornate entrance, Hilvar pointed out something that Alvin had noticed at the same moment.

  “These buildings don’t look safe. See all that fallen stone over there— it’s a miracle they’re still standing. If there were any storms on this planet, they would have been flattened ages ago. I don’t think it would be wise to go inside any of them.”

  “I’m not going to; I’ll send the robot— it can travel far faster than we can, and it won’t make any disturbance which might bring the roof crashing down on top of it.”

  Hilvar approved of this precaution, but he also insisted on one which Alvin had overlooked. Before the robot left on its reconnaissance, Alvin made it pass on a set of instructions to the almost equally intelligent brain of the ship, so that whatever happened to their pilot they could at least return safely to Earth.

  It took little time to convince both of them that this world had nothing to offer. Together they watched miles of empty, dust-carpeted corridors and passageways drift across the screen as the robot explored these empty labyrinths. All buildings designed by intelligent beings, whatever form their bodies may take, must comply with certain basic laws, and after a while even the most alien forms of architecture or design fail to evoke surprise, and the mind becomes hypnotized by sheer repetition, incapable of absorbing any more impressions. These buildings, it seemed, had been purely residential, and the beings who had lived in them had been approximately human in size. They might well have been men; it was true that there were a surprising number of rooms and enclosures that could be entered only by flying creatures, but that did not mean that the builders of this city were winged. They could have used the personal antigravity devices that had once been in common use but of which there was now no trace in Diaspar.

  “Alvin,” said Hilvar at last, “we could spend a million years exploring these buildings. It’s obvious that they’ve not merely been abandoned— they were carefully stripped of everything valuable that they possessed. We are wasting our time.”

  “Then what do you suggest?” asked Alvin.

  “We should look at two or three other areas of this planet and see if they are the same— as I expect they are. Then we should make an equally quick survey of the other planets, and only land if they seem fundamentally different or we notice something unusual. That’s all we can hope to do unless we are going to stay here for the rest of our lives.”

  It was true enough; they were trying to contact intelligence, not to carry out archaeological research. The former task could be achieved in a few days, if it could be achieved at all. The latter would take centuries of labor by armies of men and robots.

  They left the planet two hours later, and were thankful enough to go. Even when it had been bustling with life, Alvin decided, this world of endless buildings would have been very depressing. There were no signs of any parks, any open spaces where there could have been vegetation. It had been an utterly sterile world, and it was hard to imagine the psychology of the beings who had lived here. If the next planet was identical with this, Alvin decided, he would probably abandon the search there and then.

  It was not; indeed, a greater contrast would have been impossible to imagine.

  This planet was nearer the sun, and even from space it looked hot. It was partly covered with low clouds, indicating that water was plentiful, but there were no signs of any oceans. Nor was there any sign of intelligence; they circled the planet twice without glimpsing a single artifact of any kind. The entire globe, from poles down to the equator, was clothed with a blanket of virulent green.

  “I think we should be very careful here,” said Hilvar. “This world is alive— and I don’t like the color of that vegetation. It would be best to stay in the ship and not to open the air lock at all.”

  “Not even to send out the robot?”

  “No, not even that. You have forgotten what disease is, and though my people know how to deal with it, we are a long way from home and there may be dangers here which we cannot see. I think this is a world that has run amok. Once it may have been all one great garden or park, but when it was abandoned Nature took over again. It could never have been like this while the system was inhabited.”

  Alvin did not doubt that Hilvar was right. There was something evil, something hostile to all the order and regularity on which Lys and Diaspar were based, in the biological anarchy below. Here a ceaseless battle had raged for a billion years; it would be well to be wary of the survivors.

  They came cautiously down over a great level plain, so uniform that its flatness posed an immediate problem. The plain was bordered by higher ground, completely covered with trees whose height could only be guessed— they were so tightly packed, and so enmeshed with undergrowth, that their trunks were virtually buried. There were many winged creatures flying among their upper branches, though they moved so swiftly that it was impossible to tell whether they were birds or insects— or neither.

  Here and there a forest giant had managed to climb a few scores of feet above its battling neighbors, who had formed a brief alliance to tear it down and destroy the advantage it had won. Despite the fact that this was a silent war, fought too slowly for the eye to see, the impression of merciless, implacable conflict was overwhelming.

  The plain, by comparison, appeared placid and uneventful. It was flat, to within a few inches, right out to the horizon, and seemed to be covered with a thin, wiry grass. Though they descended to within fifty feet of it, there was no sign of any animal life, which Hilvar found somewhat surprising. Perhaps, he decided, it had been scared underground by their approach.

  They hovered just above the plain while Alvin tried to convince Hilvar that it would be safe to open the air lock, and Hilvar patiently explained such conceptions as bacteria, fungi, viruses, and microbes— ideas which Alvin found hard to visualize, and harder still to apply to himself. The argument had been in progress for some minutes before they noticed a peculiar fact. The vision screen, which a moment ago had been showing the forest ahead of them, had now become blank.

  “Did you turn that off?” said Hilvar, his mind, as usual, just one jump ahead of Alvin’s.

  “No,” replied Alvin, a cold shiver running down his spine as he thought of the only other explanation. “Did you turn it off?” he asked the robot.

  “No,” came the reply, echoing his own.

  With a sigh of relief, Alvin dismissed the idea that the robot might have started to act on its own volition— that he might have a mechanical mutiny on his hands.

  “Then why is the screen blank?” he asked.

  “The image receptors have been covered.”

  “I don’t understand,” said Alvin, forgetting for a moment that the robot would only act on definite orders or questions. He recovered himself quickly and asked: “What’s covered the receptors?”

  “I do not know.”

  The literal-mi
ndedness of robots could sometimes be as exasperating as the discursiveness of humans. Before Alvin could continue the interrogation, Hilvar interrupted.

  “Tell it to lift the ship— slowly,” he said, and there was a note of urgency in his voice.

  Alvin repeated the command. There was no sense of motion; there never was. Then, slowly, the image re-formed on the vision screen, though for a moment it was blurred and distorted. But it showed enough to end the argument about landing.

  The level plain was level no longer. A great bulge had formed immediately below them— a bulge which was ripped open at the top where the ship had torn free. Huge pseudo-pods were waving sluggishly across the gap, as if trying to recapture the prey that had just escaped from their clutches. As he stared in horrified fascination, Alvin caught a glimpse of a pulsing scarlet orifice, fringed with whiplike tentacles which were beating in unison, driving anything that came into their reach down into that gaping maw.

  Foiled of its intended victim, the creature sank slowly into the ground— and it was then that Alvin realized that the plain below was merely the thin scum on the surface of a stagnant sea.

  “What was that—thing?” he gasped.

  “I’d have to go down and study it before I could tell you that,” Hilvar replied matter-of-factly. “It may have been some form of primitive animal— perhaps even a relative of our friend in Shalmirane. Certainly it was not intelligent, or it would have known better than to try to eat a spaceship.”

  Alvin felt shaken, though he knew that they had been in no possible danger. He wondered what else lived down there beneath that innocent sward, which seemed to positively invite him to come out and run upon its springy surface.

  “I could spend a lot of time here,” said Hilvar, obviously fascinated by what he had just seen. “Evolution must have produced some very interesting results under these conditions. Not only evolution, but devolution as well, as higher forms of life regressed when the planet was deserted. By now equilibrium must have been reached and— you’re not leaving already?” His voice sounded quite plaintive as the landscape receded below them.

  “I am,” said Alvin. “I’ve seen a world with no life, and a world with too much, and I don’t know which I dislike more.”

  Five thousand feet above the plain, the planet gave them one final surprise. They encountered a flotilla of huge, flabby balloons drifting down the wind. From each semitransparent envelope, clusters of tendrils dangled to form what was virtually an inverted forest. Some plants, it seemed, in the effort to escape from the ferocious conflict on the surface, had learned to conquer the air. By a miracle of adaptation, they had managed to prepare hydrogen and store it in bladders, so that they could lift themselves into the comparative peace of the lower atmosphere.

  Yet it was not certain that even here they had found security. Their downward-hanging stems and leaves were infested with an entire fauna of spidery animals, which must spend their lives floating far above the surface of the globe, continuing the universal battle for existence on their lonely aerial islands. Presumably they must from time to time have some contact with the ground; Alvin saw one of the great balloons suddenly collapse and fall out of the sky, its broken envelope acting as a crude parachute. He wondered if this was an accident, or part of the life cycle of these strange entities.

  Hilvar slept while they waited for the next planet to approach. For some reason which the robot could not explain to them, the ship traveled slowly— at least by comparison with its Universe-spanning haste— now that it was within a Solar System. It took almost two hours to reach the world that Alvin had chosen for his third stop, and he was a little surprised that any mere interplanetary journey should last so long.

  He woke Hilvar as they dropped down into the atmosphere.

  “What do you make of that?” he asked, pointing to the vision screen.

  Below them was a bleak landscape of blacks and grays, showing no sign of vegetation or any other direct evidence of life. But there was indirect evidence; the low hills and shallow valleys were dotted with perfectly formed hemispheres, some of them arranged in complex, symmetrical patterns.

  They had learned caution on the last planet, and after carefully considering all the possibilities remained poised high in the atmosphere while they sent the robot down to investigate. Through its eyes, they saw one of the hemispheres approach until the robot was floating only a few feet away from the completely smooth, featureless surface.

  There was no sign of any entrance, nor any hint of the purpose which the structure served. It was quite large— over a hundred feet high; some of the other hemispheres were larger still. If it was a building, there appeared to be no way in or out.

  After some hesitation, Alvin ordered the robot to move forward and touch the dome. To his utter astonishment, it refused to obey him. This indeed was mutiny— or so at first sight it seemed.

  “Why won’t you do what I tell you?” asked Alvin, when he had recovered from his astonishment.

  “It is forbidden,” came the reply.

  “Forbidden by whom?”

  “I do not know.”

  “Then how— no, cancel that. Was the order built into you?”

  “No.”

  That seemed to eliminate one possibility. The builders of these domes might well have been the race who made the robot, and might have included this taboo in the machine’s original instructions.

  “When did you receive the order?” asked Alvin.

  “I received it when I landed.”

  Alvin turned to Hilvar, the light of a new hope burning in his eyes.

  “There’s intelligence here! Can you sense it?”

  “No,” Hilvar replied. “This place seems as dead to me as the first world we visited.”

  “I’m going outside to join the robot. Whatever spoke to it may speak to me.”

  Hilvar did not argue the point, though he looked none too happy. They brought the ship to earth a hundred feet away from the dome, not far from the waiting robot, and opened the air lock.

  Alvin knew that the lock could not be opened unless the ship’s brain had already satisfied itself that the atmosphere was breathable. For a moment he thought it had made a mistake— the air was so thin and gave such little sustenance to his lungs. Then, by inhaling deeply, he found that he could grasp enough oxygen to survive, though he felt that a few minutes here would be all that he could endure.

  Panting hard, they walked up to the robot and to the curving wall of the enigmatic dome. They took one more step— then stopped in unison as if hit by the same sudden blow. In their minds, like the tolling of a mighty gong, had boomed a single message:

  DANGER. COME NO CLOSER.

  That was all. It was a message not in words, but in pure thought. Alvin was certain that any creature, whatever its level of intelligence, would receive the same warning, in the same utterly unmistakable fashion— deep within its mind.

  It was a warning, not a threat. Somehow they knew that it was not directed against them; it was for their own protection. Here, it seemed to say, is something intrinsically dangerous, and we, its makers, are anxious that no one shall be hurt through blundering ignorantly into it.

  Alvin and Hilvar stepped back several paces, and looked at each other, each waiting for the other to say what was in his mind. Hilvar was the first to sum up the position.

  “I was right, Alvin,” he said. “There is no intelligence here. That warning is automatic— triggered by our presence when we get too close.”

  Alvin nodded in agreement.

  “I wonder what they were trying to protect,” he said. “There could be buildings— anything— under these domes.”

  “There’s no way we can find out, if all the domes warn us off. It’s interesting— the difference between the three planets we’ve visited. They took everything away from the first— they abandoned the second without bothering about it— but they went to a lot of trouble here. Perhaps they expected to come back some day, and wanted eve
rything to be ready for them when they returned.”

  “But they never did— and that was a long time ago.”

  “They may have changed their minds.”

  It was curious Alvin thought, how both he and Hilvar had unconsciously started using the word “they.” Whoever or whatever “they” had been, their presence had been strong on that first planet— and was even stronger here. This was a world that had been carefully wrapped up, and put away until it might be needed again.

  “Let’s go back to the ship,” panted Alvin. “I can’t breathe properly here.”

  As soon as the air lock had closed behind them, and they were at ease once more, they discussed their next move. To make a thorough investigation, they should sample a large number of domes, in the hope that they might find one that had no warning and which could be entered. If that failed— but Alvin would not face that possibility until he had to.

  He faced it less than an hour later, and in a far more dramatic form than he would have dreamed. They had sent the robot down to half a dozen domes, always with the same result, when they came across a scene that was badly out of place on this tidy, neatly packaged world.

  Below them was a broad valley, sparsely sprinkled with the tantalizing, impenetrable domes. At its center was the unmistakable scar of a great explosion— an explosion that had thrown debris for miles in all directions and burned a shallow crater in the ground.

  And beside the crater was the wreckage of a spaceship.

  CHAPTER

  21

  They landed close to the scene of this ancient tragedy, and walked slowly, conserving their breath, toward the immense, broken hull towering above them. Only a short section— either the prow or the stern— of the ship remained; presumably the rest had been destroyed in the explosion. As they approached the wreck, a thought slowly dawned in Alvin’s mind, becoming stronger and stronger until it attained the status of certainty.

  “Hilvar,” he said, finding it hard to talk and walk at the same time, “I believe this is the ship that landed on the first planet we visited.”