Ringworld

by Larry Niven

  It was not the first time men had met their superiors. Thus far men had been lucky ...

  Abruptly Louis stood up and walked toward the dome wall. It didn’t work. The ring and the star receded before him until he touched a smooth surface. But he saw something he hadn’t noticed before.

  The ring was checkered. There were regular rectangular shadows along its blue back.

  “Can you give us a better picture?”

  “We can expand it,” said the contralto voice. The G2 star jerked forward, then shot blazing off to the right, so that Louis was looking down on the lighted inner surface of the ring. Blurred as it was, Louis could only guess that the brighter, whiter areas might be cloud, that regions of faintly deeper blue might be land where lighter blue was sea.

  But the shadowed areas were quite visible. The ring seemed to be laid out in rectangles: a long strip of glowing baby blue followed by a shorter strip of deep, navy blue, followed by another long strip of light blue. Dots and dashes.

  “Something’s causing those shadows,” he said. “Something in orbit?”

  “Yes, just that. Twenty rectangular shapes orbit in a Kemplerer rosette much nearer the primary. We do not know their purpose.”

  “You wouldn’t. It’s been too long since you had a sun. These orbiting rectangles must be there to separate night from day. Otherwise it would always be high noon on the ring.”

  “You will understand now why we called for your help. Your alien insights were bound to be of value.”

  “Uh huh. How big is the ring? Have you studied it much? Have you sent probes?”

  “We have studied the ring as best we could without slowing our velocity and without otherwise attracting notice to ourselves. We have sent no probes, of course. Since they would have to be remotely controlled by hyperwave, such probes might be traced back to us.”

  “You can’t track a hyperwave signal. It’s theoretically impossible.”

  “Perhaps those who built the ring have evolved different theories.”

  “Mmm.”

  “But we have studied the ring with other instruments.” As Chiron spoke, the scene on the dome wall changed to blacks and whites and grays. Outlines shifted and wavered. “We have taken photographs and holographs in all electromagnetic frequencies. If you are interested—“

  “They don’t show much detail.”

  “No. The light is too much bent by gravitational fields and solar wind and intervening dust and gasses. Our telescopes cannot find further detail.”

  “So you haven’t really learned much.”

  “I would say that we have learned a good deal. One puzzling point. The ring apparently stops on the close order of 40 percent of neutrinos.”

  Teela merely looked bewildered; but Speaker made a startled sound, and Louis whistled very low.

  That eliminated everything.

  Normal matter, even the terrifically compressed matter in the heart of a star, would stop almost no neutrinos. Any neutrino stood a fifty-fifty chance of getting through several light years’ thickness of lead.

  An object in a Slaver stasis field reflected all neutrinos. So did a General Products hull.

  But nothing known would stop 40 percent of neutrinos, and let the rest through.

  “Something new, then.” said Louis. “Chiron, how big is this ring? How massive is it?”

  “The ring masses two times ten to the thirtieth power in grams, measures .95 times ten to the eighth power miles in radius, and something less than ten to the sixth power miles across.”

  Louis was not comfortable thinking in abstract powers of ten. He tried to translate the numbers into pictures.

  He had been right to think of inch-wide Christmas ribbon, balanced on edge and strung in a loop. The ring was more than ninety million miles in radius—about six hundred million miles long, he estimated—but less than a million miles across, edge to edge. It massed a little more than the planet Jupiter ...

  “Somehow that doesn’t seem massive enough,” he said. “Something that big should weigh as much as a good sized sun.”

  The kzin agreed. “One has the ludicrous picture of millions of beings trying to live on a construct no thicker than bookfilm.”

  “Your intuition is wrong,” said the puppeteer with silver curls. “Consider the dimensions. If the ring were a ribbon of hullmetal, for example, it would be approximately fifty feet thick.”

  Fifty feet? That was hard to believe.

  But Teela’s eyes had been turned to the ceiling, and her lips had been moving silently but rapidly. “He’s right,” she said. “The math works out. But what’s it for? Why would anyone build such a thing?”

  “Room.”

  “Room?”

  “Room to live,” Louis amplified. “That’s what it’s all about. Six hundred trillion square miles of surface area is three million times the surface area of the Earth. It’d be like having three million worlds all mapped flat and joined edge to edge. Three million worlds within aircar distance. That’d solve any population problem.

  “And what a problem they must have had! You don’t go into a project like that one just for kicks.”

  “A point,” said the kzin. “Chiron, have you searched neighboring stars for other, similar rings?”

  “Yes, we—“

  “And found none. As I thought. If the race that built the ring had known of faster-than-light travel, they would have settled other stars. They would not have needed the ring. Therefore there is only one ring.”

  “Yes.”

  “I am reassured. We are superior to the ringmakers in at least one respect.” The kzin stood suddenly. “Are we to explore the habitable surface of the ring?”

  “A physical landing might prove to be overambitious.”

  “Nonsense. We must inspect the vehicle you have prepared for us. Is its landing gear sufficiently versatile? When may we depart?”

  Chiron whistled, a startled burst of discord. “You must be mad. Consider the power of those who built this ring! They make my own civilization seem savages!”

  “Or cowards.”

  “Very well. You may go to inspect your craft when the one you call Nessus returns. For the time previous to that event, there are more data regarding the ring.”

  “You try my patience,” said Speaker. But he sat down.

  You liar, thought Louis. You take it well, and I’m proud of you. His own stomach was queasy as he returned to his couch. A baby blue ribbon stretched across the stars; and man had met superior beings—again.

  The Kzinti had been first.

  When men first used fusion drives to cross the gaps between the stars, the Kzinti were already using the gravity polarizer to power their interstellar warships. It made their ships faster and more maneuverable than human ships.

  Man’s resistance to the Kzinti fleet would have been nominal, had it not been for the Kzinti Lesson: A reaction drive is a weapon devastating in direct proportion to it’s efficiency as a drive.

  Their first foray into human space had been a terrific shock to the Kzinti. Human society had been peaceful for centuries, for so long that they had virtually forgotten war. But human interstellar ships used fusion-powered photon drives, launched by a combination of photon sail and asteroid-based laser cannon.

  So the Kzinti telepath continued to report that the human worlds had no weapons at all ... while giant laser cannon chopped at the Kzinti ships, and smaller mobile cannon darted in and out on the light pressure of their own beams ...

  Slowed by unexpected human resistance and by the barrier of lightspeed, the war had run for decades instead of years. But the Kzinti would have won eventually.

  Except that an Outsider ship ha
d stumbled across the small human colony on We Made It. They had sold the mayor the secret of the Outsider hyperdrive shunt, on credit. We Made It had not known of the Kzinti war; but they learned of it fast enough when they had built a few faster-than-light ships.

  Against hyperdrive the Kzinti hadn’t a prayer.

  Later, the puppeteers had come to set up trading posts in human space ...

  Man had been very lucky. Three times he had met races technologically superior to him. The Kzinti would have crushed him without the Outsider hyperdrive. The Outsiders, again, were clearly his superiors; but they wanted nothing that man could give them, except supply bases and information, and these they could buy. In any case the Outsiders, fragile beings of Helium II metabolism, were too vulnerable to heat and gravity to make good warriors. And the puppeteers, powerful beyond dreams, were too cowardly.

  Who had built the Ringworld? And ... were they warriors?

  Months later, Louis was to see Speaker’s lie as his personal turning point. He might have backed out then—on Teela’s behalf, of course. The Ringworld was terrifying enough as an abstraction in numbers. To think of approaching it in a spacecraft, of landing on it ...

  But Louis had seen the kzin in terror of the puppeteers’ flying worlds. Speakers lie was a magnificent act of courage. Could Louis show himself a coward now?

  He sat down and turned to face the glowing projection; and as his eyes brushed Teela he silently cursed her for an idiot. Her face was alive with wonder and delight. She was as eager as the kzin pretended to be. Was she too stupid to be afraid?

  There was an atmosphere on the ring’s inner side. Spectroanalysis showed the air to be as thick as Earth’s, and of approximately the same composition: definitely breathable to man and kzin and puppeteer. What kept it from blowing away was a thing to be guessed at. They would have to go and look.

  In the system of the G2 sun there was nothing at all but the ring itself. No planets, no asteroids, no comets.

  “They cleaned it out,” said Louis. “They didn’t want anything to hit the ring.”

  “Naturally,” said the puppeteer with silver curls. “If something did strike the ring, it would strike at a minimum of 770 miles per second, the speed of rotation of the ring itself. No matter how strong the material of the ring, there would always be the danger of an object missing the outer surface and crossing the sun to strike the unprotected, inhabited inner surface.”

  The sun itself was a yellow dwarf somewhat cooler than Sol and a touch smaller. “We will need heat suits on the ring,” said the kzin—rubbing it in, Louis thought.

  “No,” said Chiron. “The temperature of the inner surface is quite tolerable, to all of our species.”

  “How would you know that?”

  “The frequency of the infrared radiation emitted by the outer surface—“

  “You see me exposed as a fool.”

  “Not at all. We have been studying the ring since its discovery, while you have had a few eights of minutes. The infrared frequency indicates an average temperature of 290 degrees absolute, which of course applies to the inner as well as the outer surface of the ring. For you this will be some ten degrees warmer than optimum, Speaker-To-Animals. For Louis and Teela it is optimum.

  “Do not let our attention to details mislead or frighten you,” Chiron added. “We would not permit a landing unless the ring engineers themselves insisted. We merely wish you to be ready for any eventuality.”

  “You don’t have any detail of surface formations?”

  “Unfortunately, no. The resolving power of our instruments is insufficient.”

  “We can do some guessing,” said Teela. “The thirty hour day-night cycle, for instance. Their original world must have turned that fast. Do you suppose that’s their original system?”

  “We assume that it is, since they apparently did not have hyperdrive,” said Chiron. “But presumably they could have moved their world to another system, using our own technique.”

  “And should have,” the kzin rumbled, “rather than destroy their own system in the course of building their ring. I think we will find their own system somewhere nearby, as denuded of worlds as this one. They would have used terraforming techniques to settle all of the worlds of their own system, before adapting this more desperate expedient.”

  Teela said, “Desperate?”

  “Then, when they had finished building their ring around the sun, they would have been forced to move all their worlds into this system to transfer their populations.”

  “Maybe not,” said Louis. “They might have used big STL ships to settle their ring if it was close enough to their own system.”

  “Why desperate?”

  They looked at her.

  “I would have thought they built the ring for—for—“ Teela floundered. “Because they wanted to.”

  “For kicks? For scenery? Finagles fist! Teela, think of the resources they’d have had to divert. Remember, they must have had a hell of a population problem. By the time they needed the ring for living room, they probably couldn’t afford to build it. They built it anyway, because they needed it.”

  “Mmm,” said Teela, looking puzzled.

  “Nessus returns,” said Chiron. Without another word the puppeteer turned and trotted away into the park.

  Chapter 7 -

  Stepping Discs

  “That was rude,” said Teela.

  “Chiron doesn’t want to meet Nessus. Didn’t I tell you? They think Nessus is—crazy.”

  “They’re all crazy.”

  “Well, they don’t think so, but that doesn’t make you wrong. Still want to go?”

  Teela’s answer was the same uncomprehending look she’d given him when he tried to explain whiplash of the heart. “You still want to go,” Louis confirmed sadly.

  “Sure. Who wouldn’t? What are the puppeteers afraid of?”

  “I understand that,” said Speaker-To-Animals. “The puppeteers are cowards. But I fail to see why they insist on knowing more than they do. Louis, they have already passed the ringed sun, traveling at nearly lightspeed. Those who built the ring assuredly did not have faster-than-light travel. Thus they can be no danger to the puppeteers, now or ever. I fail to understand our role in this matter.”

  “It figures.”

  “Must I take that as an insult?”

  “No, of course not. It’s just that we keep running up against population problems. Why should you understand?”

  “Quite so. Explain, if you please.”

  Louis had been scanning the tame jungle for a glimpse of Nessus. “Nessus could probably tell this better. Too bad. Okay, imagine a trillion puppeteers on this world. Can you do it?”

  “I can smell them individually. The very concept makes me itch.”

  “Now imagine them on the Ringworld. Better, yes?”

  “Uurr. Yes. With more than eight-to-the-seventh-power times as much room ... But still I fail to understand. Do you suppose the puppeteers plan conquest? But how would they transfer themselves to the ring afterward? They do not trust spacecraft.”

  “I don’t know. They don’t make war, either. That’s not the point. The point is, is the Ringworld safe to live on?”

  “Urrr.”

  “You see? Maybe they’re thinking of building their own Ringworlds. Maybe they expect to find an empty one, out there in the Clouds of Magellan. Not an unreasonable hope, by the way. But it doesn’t matter. They have to know if it’s safe before they do anything.”

  “Here comes Nessus.” Teela stood up and moved to the invisible wall. “He looks drunk. Do puppeteers get drunk?”

  Nessus wasn’t trotting. He came tippy-toe, circling a four-foot chrome-yellow feather with e
xaggerated wariness, moving one foot at a time, while his flat heads darted this way and that. He had almost reached the lecture dome when something like a large black butterfly settled on his rump. Nessus screamed like a woman, leapt forward as if clearing a high fence. He landed rolling. When he stopped rolling he remained curled into a ball, with his back arched and his legs folded and his heads and necks tucked between his forelegs.

  Louis was running. “Depressive cycle,” he shouted over his shoulder. By luck and memory he found the entrance in the invisible dome. He darted out into the park.

  All the flowers smelled like puppeteer. (If all the life of the puppeteer world had the same chemical basis, how could Nessus take nourishment from warm carrot juice?) Louis followed a right-angle zigzag of manicured dusty orange hedge and came upon the puppeteer.

  He knelt beside him. “It’s Louis,” he said. “You’re safe.” He reached gently into the tangled mop over the puppeteers skull and scratched gently. The puppeteer jerked at the touch, then settled down.

  This was a bad one. No need to make the puppeteer face the world just yet. Louis asked, “Was that thing dangerous? The one that landed on you.”

  “That? No.” The contralto voice was muffled, but beautifully pure, and without inflection. “It was only a flower-sniffer.”

  “How did it go with those-who-lead?”

  Nessus winced. “I won.”

  “Fine. What did you win?”

  “My right to breed, and a set of mates.”

  “Is that what has you so scared?” It wasn’t unlikely, Louis thought Nessus could be the counterpart to a male black widow spider, doomed by love. Then again, he might be a nervous virgin ... of either sex, or of any sex ...

  The puppeteer said, “I might have failed, Louis. I faced them down. I bluffed them.”

  “Go on.” Louis was aware that Teela and Speaker-To-Animals had joined them. He continued scratching gently in Nessus’s mane. Nessus had not moved.