The Sentinel

by Arthur C. Clarke

  “Then we have to play safe and assume intelligence. For the present, therefore, this expedition comes under all the clauses of the Prime directive.”

  There was a long silence while everyone on the radio circuit absorbed the implications of this. For the first time in the history of space flight, the rules that had been established through more than a century of argument might have to be applied. Man had—it was hoped—profited from his mistakes on Earth. Not only moral considerations, but also his own self-interest demanded that he should not repeat them among the planets. It could be disastrous to treat a superior intelligence as the American settlers had treated the Indians, or as almost everyone had treated the Africans . . .

  The first rule was: keep your distance. Make no attempt to approach, or even to communicate, until “they” have had plenty of time to study you. Exactly what was meant by “plenty of time,” no one had ever been able to decide. It was left to the discretion of the man on the spot.

  A responsibility of which he had never dreamed had descended upon Howard Falcon. In the few hours that remained to him on Jupiter, he might become the first ambassador of the human race.

  And that was an irony so delicious that he almost wished the surgeons had restored to him the power of laughter.

  7. Prime directive

  It was growing darker, but Falcon scarcely noticed as he strained his eyes toward that living cloud in the field of the telescope. The wind that was steadily sweeping Kon-Tiki around the funnel of the great whirlpool had now brought him within twelve miles of the creature. If he got much closer than six, he would take evasive action. Though he felt certain that the medusa’s electric weapons were short-ranged, he did not wish to put the matter to the test. That would be a problem for future explorers, and he wished them luck.

  Now it was quite dark in the capsule. That was strange, because sunset was still hours away. Automatically, he glanced at the horizontally scanning radar, as he had done every few minutes. Apart from the medusa he was studying, there was no other object within about sixty miles of him.

  Suddenly, with startling power, he heard the sound that had come booming out of the Jovian night—the throbbing beat that grew more and more rapid, then stopped in mid-crescendo. The whole capsule vibrated with it like a pea in a kettledrum.

  Falcon realized two things almost simultaneously during the sudden, aching silence. This time the sound was not coming from thousands of miles away, over a radio circuit. It was in the very atmosphere around him.

  The second thought was even more disturbing. He had quite forgotten—it was inexcusable, but there had been other apparently more important things on his mind—that most of the sky above him was completely blanked out by Kon-Tiki’s gasbag. Being lightly silvered to conserve its heat, the great balloon was an effective shield both to radar and to vision.

  He had known this, of course; it had been a minor defect of the design, tolerated because it did not appear important. It seemed very important to Howard Falcon now—as he saw that fence of gigantic tentacles, thicker than the trunks of any tree, descending all around the capsule.

  He heard Brenner yelling; “Remember the Prime directive! Don’t alarm it!” Before he could make an appropriate answer that overwhelming drumbeat started again and drowned all other sounds.

  The sign of a really skilled test pilot is how he reacts not to foreseeable emergencies, but to ones that nobody could have anticipated. Falcon did not hesitate for more than a second to analyze the situation. In a lightning-swift movement, he pulled the rip cord.

  That word was an archaic survival from the days of the first hydrogen balloons; on Kon-Tiki, the rip cord did not tear open the gasbag, but merely operated a set of louvers around the upper curve of the envelope. At once the hot gas started to rush out; Kon-Tiki, deprived of her lift, began to fall swiftly in this gravity field two and a half times as strong as Earth’s.

  Falcon had a momentary glimpse of great tentacles whipping upward and away. He had just time to note that they were studded with large bladders or sacs, presumably to give them buoyancy, and that they ended in multitudes of thin feelers like the roots of a plant. He half expected a bolt of lightning—but nothing happened.

  His precipitous rate of descent was slackening as the atmosphere thickened and the deflated envelope acted as a parachute. When Kon-Tiki had dropped about two miles, he felt that it was safe to close the louvers again. By the time he had restored buoyancy and was in equilibrium once more, he had lost another mile of altitude and was getting dangerously near his safety limit.

  He peered anxiously through the overhead windows, though he did not expect to see anything except the obscuring bulk of the balloon. But he had sideslipped during his descent, and part of the medusa was just visible a couple of miles above him. It was much closer than he expected—and it was still coming down, faster than he would have believed possible.

  Mission Control was calling anxiously. He shouted: “I’m O.K.—but it’s still coming after me. I can’t go any deeper.”

  That was not quite true. He could go a lot deeper—about one hundred and eighty miles. But it would be a one-way trip, and most of the journey would be of little interest to him.

  Then, to his great relief, he saw that the medusa was leveling off, not quite a mile above him. Perhaps it had decided to approach this strange intruder with caution; or perhaps it, too, found this deeper layer uncomfortably hot. The temperature was over fifty degrees centigrade, and Falcon wondered how much longer his life-support system could handle matters.

  Dr. Brenner was back on the circuit, still worrying about the Prime directive.

  “Remember—it may only be inquisitive!” he cried, without much conviction. “Try not to frighten it!”

  Falcon was getting rather tired of this advice and recalled a TV discussion he had once seen between a space lawyer and an astronaut. After the full implications of the Prime directive had been carefully spelled out, the incredulous spacer had exclaimed: “Then if there was no alternative, I must sit still and let myself be eaten?” The lawyer had not even cracked a smile when he answered: “That’s an excellent summing up.”

  It had seemed funny at the time; it was not at all amusing now.

  And then Falcon saw something that made him even more unhappy. The medusa was still hovering about a mile above him—but one of its tentacles was becoming incredibly elongated, and was stretching down toward Kon-Tiki, thinning out at the same time. As a boy he had once seen the funnel of a tornado descending from a storm cloud over the Kansas plains. The thing coming toward him now evoked vivid memories of that black, twisting snake in the sky.

  “I’m rapidly running out of options,” he reported to Mission Control. “I now have only a choice between frightening it—and giving it a bad stomach-ache. I don’t think it will find Kon-Tiki very digestible, if that’s what it has in mind.”

  He waited for comments from Brenner, but the biologist remained silent.

  “Very well. It’s twenty-seven minutes ahead of time, but I’m starting the ignition sequencer. I hope I’ll have enough reserve to correct my orbit later.”

  He could no longer see the medusa; once more it was directly overhead. But he knew that the descending tentacle must now be very close to the balloon. It would take almost five minutes to bring the reactor up to full thrust . . .

  The fuser was primed. The orbit computer had not rejected the situation as wholly impossible. The air scoops were open, ready to gulp in tons of the surrounding hydrohelium on demand. Even under optimum conditions, this would have been the moment of truth—for there had been no way of testing how a nuclear ramjet would really work in the strange atmosphere of Jupiter.

  Very gently something rocked Kon-Tiki. Falcon tried to ignore it.

  Ignition had been planned at six miles higher, in an atmosphere of less than a quarter of the density and thirty degrees cooler. Too bad.

  What was the shallowest dive he could get away with, for the air scoops to work? Wh
en the ram ignited, he’d be heading toward Jupiter with two and a half g’s to help him get there. Could he possibly pull out in time?

  A large, heavy hand patted the balloon. The whole vessel bobbed up and down, like one of the Yo-yo’s that had just become the craze on Earth.

  Of course, Brenner might be perfectly right. Perhaps it was just trying to be friendly. Maybe he should try to talk to it over the radio. Which should it be: “Pretty pussy”? “Down, Fido”? Or “Take me to your leader”?

  The tritium-deuterium ratio was correct. He was ready to light the candle, with a hundred-million-degree match.

  The thin tip of the tentacle came slithering around the edge of the balloon some sixty yards away. It was about the size of an elephant’s trunk, and by the delicate way it was moving appeared to be almost as sensitive. There were little palps at its end, like questing mouths. He was sure that Dr. Brenner would be fascinated.

  This seemed about as good a time as any. He gave a swift scan of the entire control board, started the final four-second ignition count, broke the safety seal, and pressed the JETTISON switch.

  There was a sharp explosion and an instant loss of weight. Kon-Tiki was falling freely, nose down. Overhead, the discarded balloon was racing upward, dragging the inquisitive tentacle with it. Falcon had no time to see if the gasbag actually hit the medusa, because at that moment the ramjet fired and he had other matters to think about.

  A roaring column of hot hydrohelium was pouring out of the reactor nozzles, swiftly building up thrust—but toward Jupiter, not away from it. He could not pull out yet, for vector control was too sluggish. Unless he could gain complete control and achieve horizontal flight within the next five seconds, the vehicle would dive too deeply into the atmosphere and would be destroyed.

  With agonizing slowness—those five seconds seemed like fifty—he managed to flatten out, then pull the nose upward. He glanced back only once and caught a final glimpse of the medusa, many miles away. Kon-Tiki’s discarded gasbag had apparently escaped from its grasp, for he could see no sign of it.

  Now he was master once more—no longer drifting helplessly on the winds of Jupiter, but riding his own column of atomic fire back to the stars. He was confident that the ramjet would steadily give him velocity and altitude until he had reached near-orbital speed at the fringes of the atmosphere. Then, with a brief burst of pure rocket power, he would regain the freedom of space.

  Halfway to orbit, he looked south and saw the tremendous enigma of the Great Red Spot—that floating island twice the size of Earth—coming up over the horizon. He stared into its mysterious beauty until the computer warned him that conversion to rocket thrust was only sixty seconds ahead. He tore his gaze reluctantly away.

  “Some other time,” he murmured.

  “What’s that?” said Mission Control. “What did you say?”

  “It doesn’t matter,” he replied.

  8. Between two worlds

  “You’re a hero now, Howard,” said Webster, “not just a celebrity. You’ve given them something to think about—injected some excitement into their lives. Not one in a million will actually travel to the Outer Giants, but the whole human race will go in imagination. And that’s what counts.”

  “I’m glad to have made your job a little easier.”

  Webster was too old a friend to take offense at the note of irony. Yet it surprised him. And this was not the first change in Howard that he had noticed since the return from Jupiter.

  The Administrator pointed to the famous sign on his desk, borrowed from an impresario of an earlier age: ASTONISH ME!

  “I’m not ashamed of my job. New knowledge, new resources—they’re all very well. But men also need novelty and excitement. Space travel has become routine; you’ve made it a great adventure once more. It will be a long, long time before we get Jupiter pigeonholed. And maybe longer still before we understand those medusae. I still think that one knew where your blind spot was. Anyway, have you decided on your next move? Saturn, Uranus, Neptune—you name it.”

  “I don’t know. I’ve thought about Saturn, but I’m not really needed there. It’s only one gravity, not two and a half like Jupiter. So men can handle it.”

  Men, thought Webster. He said “men.” He’s never done that before. And when did I last hear him use the word “we”? He’s changing, slipping away from us . . .

  “Well,” he said aloud, rising from his chair to conceal his slight uneasiness, “let’s get the conference started. The cameras are all set up and everyone’s waiting. You’ll meet a lot of old friends.”

  He stressed the last word, but Howard showed no response. The leather mask of his face was becoming more and more difficult to read. Instead, he rolled back from the Administrator’s desk, unlocked his undercarriage so that it no longer formed a chair, and rose on his hydraulics to his full seven feet of height. It had been good psychology on the part of the surgeons to give him that extra twelve inches, to compensate somewhat for all that he had lost when the Queen had crashed.

  Falcon waited until Webster had opened the door, then pivoted neatly on his balloon tires and headed for it at a smooth and silent twenty miles an hour. The display of speed and precision was not flaunted arrogantly; rather, it had become quite unconscious.

  Howard Falcon, who had once been a man and could still pass for one over a voice circuit, felt a calm sense of achievement—and, for the first time in years, something like peace of mind. Since his return from Jupiter, the nightmares had ceased. He had found his role at last.

  He now knew why he had dreamed about that superchimp aboard the doomed Queen Elizabeth. Neither man nor beast, it was between two worlds; and so was he.

  He alone could travel unprotected on the lunar surface. The life-support system inside the metal cylinder that had replaced his fragile body functioned equally well in space or under water. Gravity fields ten times that of Earth were an inconvenience, but nothing more. And no gravity was best of all . . .

  The human race was becoming more remote, the ties of kinship more tenuous. Perhaps these air-breathing, radiation-sensitive bundles of unstable carbon compounds had no right beyond the atmosphere; they should stick to their natural homes—Earth, Moon, Mars.

  Some day the real masters of space would be machines, not men—and he was neither. Already conscious of his destiny, he took a somber pride in his unique loneliness—the first immortal midway between two orders of creation.

  He would, after all, be an ambassador; between the old and the new—between the creatures of carbon and the creatures of metal who must one day supersede them.

  Both would have need of him in the troubled centuries that lay ahead.

  THE SONGS OF

  DISTANT EARTH

  This is a little complicated, so we had better start at the beginning . . .

  And that, incredibly, is in February 1957, half a year before Sputnik I heralded the dawn of the Space Age. I would have sworn it was a decade later, but the evidence in my notebooks is indisputable.

  For some reason, at the beginning of that momentous year a phrase lodged in my mind and wouldn’t go away; it echoed round and round my skull as persistently as the theme from the last movement of Sibelius’ 2nd Symphony. It was obviously the title of a story, which I eventually had to write: you’ll find it in The Other Side of the Sky.

  Call that Mark I. What follows here is Mark II. The exorcism was incomplete, for in 1979, a mere twenty-two years later, the title started bugging me again.

  And that was not the only thing bugging me. I had just seen two spectacular and highly successful space movies—Star Wars, Close Encounters of the Third Kind—and Star Trek was still doing reruns all over the planet. They were well done and I greatly enjoyed them, but they all had one thing in common. They were not, in the strictest sense, science fiction, but fantasy.

  Now, I like fantasy every bit as much as science-fiction—its literary standards are usually higher, too—but I recognize the distinction between the g
enres. Critics have been trying for decades to define both categories, without much success. Here is my working definition: Fantasy is something that couldn’t happen in the real world (though often you wish it would); Science Fiction is something that really could happen (though often you’d be sorry if it did).

  Today, we are 99.99 percent certain that it will always be impossible to travel faster than light, which means that journeys to even the nearest star systems will take decades. This is no problem to the fantasy writer, who can happily cling to the 0.01 percent chance that there may be a loophole that Einstein didn’t notice—and go racing round the galaxy, saving civilization once a week in prime time.

  In September 1979, during one of my brief visits to England, I decided to accept the Universe as it really is. (As Dr. Johnson once said: “You’d better . . . ”) Was it possible, I asked myself, to write a completely realistic story using an interstellar—as opposed to a “merely” interplanetary—background?

  I also decided to kill two birds with one typewriter. Ever since 2001, Stanley Kubrick had been saying wistfully, “What sort of movie should we have made?”, or words to that effect. So I decided to write Mk II in the form of a movie outline.

  This would have two advantages. The first, and most important, was the saving of time and energy. An outline compresses, in a few pages, all the basic elements of a complete novel—locale, characters, plot. Though the act of creation may take months, the actual typing can be done in a couple of hours; you can have all the fun and none of the drudgery. (Of course, you sacrifice emotion, atmosphere, “fine writing.” But they can be added later, and perhaps on a firmer foundation.)

  The second advantage was that it would keep Stanley quiet, at least for a while. In the event, he returned the outline with an unenthusiastic “Interesting . . . ”—which was exactly what I’d expected. (If he’d said, “O.K.—when can we get started?”, I would have been in a real dilemma. I owe Stanley so much that I would have felt morally obliged to cooperate—even if it killed me. Which it probably would . . . )