Ringworld

by Larry Niven

  “Can they have lost their civilization?” Nessus mused. “It would be silly of them, considering.”

  “Perhaps they are dead,” Speaker said viciously. “That too would be silly. Not to contact us has been silly. Let us land and find out.”

  Nessus whistled in panic. “Land on a world which may have killed its indigenous species? Are you mad?”

  “How else can we learn?”

  “Of course,” Teela chimed in. “We didn’t come all this way just to fly in circles!”

  “I forbid it. Speaker, continue your attempts to contact the Ringworld.”

  “I have ended such attempts.”

  “Repeat them.”

  “I will not.”

  In stepped Louis Wu, volunteer diplomat. “Cool it, furry buddy. Nessus, he’s right. The Ringworlders don’t have anything to say to us. Otherwise we’d know it by now.”

  “But what can we do other than keep trying?”

  “Go on about our business. Give the Ringworlders time to make up their minds about us.”

  Reluctantly the puppeteer agreed.

  They drifted toward the Ringworld.

  Speaker had aimed the Liar to pass outside the Ringworld’s edge: a concession to Nessus. The puppeteer feared that hypothetical Ringworlders would take it as a threat if the ship’s course should intersect the ring itself. He also claimed that fusion drives of the Liar’s power had the look of weapons; and so the Liar moved on thrusters alone.

  To the eye there was no way of judging scale. Over the hours the ring shifted position. Too slowly. With cabin gravity to compensate for from zero to thirty gee of thrust, the inner ear could not sense motion. Time passed in a vacuum, and Louis, for the first time since leaving Earth, was ready to gnaw his fingernails.

  Finally the ring was edge-on to the Liar. Speaker used the thrusters, braking the ship into a circular orbit around the rim; and then he sent them drifting in toward the

  Now there was motion.

  The rim of the Ringworld grew from a dim line occluding a few stars, to a black wall. A wall a thousand miles high, featureless, though any features would have been blurred by speed. Half a thousand miles away, blocking ninety degrees of sky, the wall sped past at a hellish 770 miles per second. Its edges converged to vanishing points, to points at infinity at either end of the universe; and from each point at infinity, a narrow line of baby blue shot straight upward.

  To look into the vanishing point was to step into another universe, a universe of true straight lines, right angles, and other geometric abstractions. Louis stared hypnotized into the vanishing point. Which point was it, the source or the sink? Did the black wall emerge or vanish in that meeting place?

  ... from out of the point at infinity, something came at them.

  It was a ledge, growing like another abstraction along the base of the rim wall. First the ledge appeared; then, mounted on the ledge, a row of upright rings. Straight at the Liar they came, straight at the bridge of Louis’s nose. Louis shut his eyes and threw his arms up to protect his head. He heard a whimper of fear.

  Death should have come in that instant. When it didn’t, he opened his eyes. The rings were going by in a steady stream; and he realized that they were no more than fifty miles across.

  Nessus was curled in a ball. Teela, her palms pressed flat against the transparent hull, was staring avidly outward. Speaker was fearless and attentive at the control board. Perhaps he was better than Louis at judging distance.

  Or perhaps he was faking it. The whimper could have come from Speaker.

  Nessus uncurled. He looked out at the rings, which were smaller now, converging. “Speaker, you must match velocities with the Ringworld. Hold us in position by thrusting at one gravity. We must inspect this.”

  Centrifugal force is an illusion, a manifestation of the law of inertia. Reality is centripetal force, a force applied at right angles to the velocity vector of a mass. The mass resists, tends to move in its accustomed straight line.

  By reason of its velocity and the law of inertia, the Ringworld tended to fly apart. Its rigid structure would not allow that. The Ringworld applied its own centrifugal force to itself. The Liar, matching speed at 770 miles per second, had to match that centripetal force.

  Speaker matched it. The Liar hovered next to the rim wall, balanced on .992 gee of thrust, while her crew inspected the spaceport.

  The spaceport was a narrow ledge, so narrow as to be a dimensionless line until Speaker moved the ship inward. Then it was wide, wide enough to dwarf a pair of tremendous spacecraft. The craft were flat nosed cylinders, both of the same design: an unfamiliar design, yet clearly the design of a fusion-ramship. These ships were intended to fuel themselves, picking up interstellar hydrogen in scoops of electromagnetic force. One had been cannibalized for parts, so that it stood with its guts open to vacuum and its intimate structure exposed to alien eyes.

  Windows showed around the upper run of the intact ship, allowing those eyes to gauge that ship’s size. In the random starlight, the glitter of windows was precisely like crystal candy sprinkled on a cake. Thousands of windows. That ship was big.

  And it was dark. The entire spaceport was dark. Perhaps the beings who used it did not need light in the “visible” frequencies. But to Louis Wu, the spaceport looked abandoned.

  “I don’t understand the rings,” said Teela.

  “Electromagnetic cannon,” Louis answered absently. “For takeoffs.”

  “No,” said Nessus.

  “Oh?”

  “The cannon must have been intended for landing the ships. One can even surmise the method used. The ship must go into orbit alongside the rim wall. It will not attempt to match the ring’s velocity, but will position itself twenty-five miles from the base of the rim wall. As the ring rotates, the coils of the electromagnetic cannon will scoop up the ship and accelerate it to match the velocity of the ring. I compliment the ring engineers. The ship need never come close enough to the ring to be dangerous.”

  “You could also use the ring for takeoff.”

  “No. Observe the facility to our left.”

  “I’ll be tanjed,” said Louis Wu.

  The “facility” was little more than a trap door big enough to hold one of the ramships.

  It figured. 770 miles per second was ramscoop speed. The rings launching facility was merely a structure for tumbling the ship off into the void. The pilot would immediately accelerate away on ramscoop-fusion power.

  “The spaceport facility seems to be abandoned,” said Speaker.

  “Is there power in use?”

  “My instruments sense none. There are no anomalous hot spots, no large-scale electromagnetic activities. As for the sensors which operate the linear accelerator, they may use less power than we can sense.”

  “Your suggestion?”

  “The facilities may still be in operational condition. We can test this by proceeding to the mouth of the linear accelerator and entering.”

  Nessus curled himself into a ball.

  “Wouldn’t work,” said Louis. “There could be a key signal to start the thing, and we don’t know it. It might react only to a metal hull. If we tried to go through the cannon at the speed of the Ringworld, we’d hit one of the coils and blow everything to bits.”

  “I have flown ships under similar conditions during simulated war maneuvers.”

  “How long ago?”

  “Perhaps too long. Never mind. Your suggestion?”

  “The underside,” said Louis. The puppeteer uncurled at once.

  They hovered beneath the Ringworld floor, matching velocities, thrusting outward at 9.94 meters per second. “Spotlights,” said Nessus.

  The s
pots reached across half a thousand miles; but if their light touched the back of the ring, it did not return. The spots were for landings.

  “Do you still trust your engineers, Nessus?”

  “They should have anticipated this contingency.”

  “But I did. I can light the Ringworld, if I may use the fusion drives,” said the kzin.

  “Do so.”

  Speaker used all four: the pair facing forward, and the larger motors facing back. But on the forward pair, the pair intended for emergency braking and possibly for weapons, Speaker choked the nozzle wide open. Hydrogen flowed though the tube too fast, emerged half-burnt. Fusion-tube temperature dropped until the exhaust, usually hotter than the core of a nova, was as cool as the surface of a yellow dwarf star. Light thrust forward in twin spears to fall across the black underside of the Ringworld.

  First: the underside was not flat. It dipped and rose; there were bulges and indentations.

  “I thought it would be smooth,” said Teela.

  “Sculptured,” said Louis. “I’ll make you a bet. Wherever we see a bulge, there’s a sea on the sunlit side. Where we see a dent, there’s a mountain.”

  But the formations were tiny, unnoticeable until Speaker drew the ship close. The Lying Bastard drifted in from the Ringworld’s edge, half a thousand miles beneath her underbelly. Sculptured bulges and sculptured indentations, they drifted by, irregular, somehow pleasing ...

  For many centuries excursion boats had drifted in like manner across the surface of Earth’s Moon. The effect here was much the same: airless pits and peaks, sharp-edged blacks and whites, exposed on the Moon’s dark side by the powerful spotlights carried by all such boats.

  Yet there was a difference. At any height above the Moon, you could always see the lunar horizon, sharp and toothy against black space and gently curved.

  There were no teeth in the Ringworld’s horizon, and no curves. It was a straight line, a geometer’s line, unimaginably distant; barely visible as black-against-black. How could Speaker stand it? Louis wondered. Hour after hour, driving the Liar across and beneath the belly of this ... artifact.

  Louis shuddered. Gradually he was learning the size, the scale of the Ringworld. It was unpleasant, like all learning processes.

  He drew his eyes away from that terrible horizon, back to the illuminated area below/above them.

  Nessus said, “All the seas seem to be of the same order of magnitude.”

  “I’ve seen a few ponds,” Teela contradicted him. “And look, there’s a river. It has to be a river. But I haven’t seen any big oceans.”

  Seas there were in plenty, Louis saw—if he was right, and those flat bulges were seas. Though they were not all the same size, they seemed evenly distributed, so that no region was without water. And—“Flat. All the seas have flattened bottoms.”

  “Yes,” said Nessus.

  “That proves it. All the seas are shallow. The Ringworlders aren’t sea-dwellers. They use only the top of an ocean. Like us.”

  “But all the seas have squiggly shapes,” said Teela. “And the edges are always ragged. You know what that means?”

  “Bays. All the bays anyone can use.”

  “Though your Ringworlders are land-dwellers, they do not fear boats,” said Nessus. “Else they would not need the bays. Louis, these people will resemble humans in outlook. Kzinti hate water, and my species fears to drown.”

  You can learn a lot about a world, Louis thought, by looking at its underside. Someday he would write a monograph on the subject ...

  Teela said, “It must be nice to carve your world to order.”

  “Don’t you like your world, playmate?”

  “You know what I mean.”

  “Power?” Louis liked surprises; he was indifferent to power. He was not creative; he did not make things; he preferred to find them.

  He saw something ahead of them. A deeper bulge ... and a projecting fin, black in the light of the throttled drives, hundreds of thousands of square miles in area.

  It the others were seas, this was an ocean, the king of all oceans. It went by them endlessly; and its underbelly was not flat. It looked like a topographical map of the Pacific Ocean: valleys and ridges, shallows and depths and peaks tall enough to be islands.

  “They wanted to keep their sea life,” Teela guessed. “They needed one deep ocean. The fin must be to keep the depths cool. A radiator.”

  An ocean not deep enough, but easily broad enough, to swallow the Earth.

  “Enough of this,” the kzin said suddenly. “Now we must see the inner surface.”

  “First then are measurements to take. Is the ring truly circular? A minor deviation would spill the air into space.”

  “We know that there is air, Nessus. The distribution of water on the inner surface will tell us how the ring deviates from circularity.”

  Nessus surrendered. “Very well. As soon as we reach the further rim.”

  There were meteor wormholes. Not many, but they were there. Louis thought with amusement that the Ringworlders had been remiss in cleaning out their solar system. But no, these must have come from outside, from between the stars. One conical crater floated by in the fusion light and Louis saw a glint of light at the bottom. something shiny, reflecting.

  It must be a glimpse of the ring floor. The ring floor, a substance dense enough to stop 40 percent of neutrinos, and presumably very rigid. Above/inward from the ring floor, soil and seas and cities, and above these, air. Below/outward from the ring floor, a spongy material, like foam plastic perhaps, to take the brunt of a meteoroid impact. Most meteoroids would vaporize within the thick foamed material; but a few would get through, to leave conical holes with shiny bottoms ...

  Far down the length of the Ringworld, almost beyond its infinitely gentle curve, Louis’s eyes found a dimple. That must have been a big one, he thought. Big enough to show by starlight, that far away.

  He did not call attention to the meteoroid dimple. His eyes and mind were not yet used to the proportions of the Ringworld.

  Chapter 9 -

  Shadow Squares

  Blazing, the G2 sun dawned beyond the straight black rim of the ring. It was uncomfortably bright until Speaker touched a polarizer; and then Louis could look at the disc, and he found an edge of shadow cutting its arc. Shadow square.

  “We must be careful,” Nessus warned. “If we were to match velocities with the ring and hover above the inner surface, we would surely be attacked.”

  Speaker’s answer came in a slurred rumble. The kzin must be tiring after so many hours behind the horseshoe of controls. “By what weapon would we be attacked? We have shown that the Ringworld engineers do not have so much as a working radio station.”

  “We cannot guess at the nature of their communications. Telepathy, perhaps, or resonant vibrations in the ring floor, or electrical impulses in metal wires. Similarly, we know nothing of their weaponry. Hovering over their surface, we would be a serious threat. They would use what weapons they have.”

  Louis nodded his agreement. He was not naturally cautious, and the Ringworld held him by the curiosity bump; but the puppeteer was right.

  Hovering over the surface, the Liar would be a potential meteor. A big one. Moving at merely orbital speed, such a mass was a hellish danger; for one touch of atmosphere would send it shrieking down at several hundred miles per second. Moving at faster than orbital speed, holding a curved path with the drives, the ship would be a lesser but a surer threat; for if the drive were to fail, “centrifugal force” would hurl the ship outward/down at populated lands. The Ringworlders would not take meteors lightly. Not when a single puncture in the ring floor would drain all the world’s breathing-air and spew it at the stars.

  S
peaker turned from the control board. It put him eye to eye with the puppeteer’s flat heads. “Your orders, then.”

  “First you must slow the ship to orbital speed.”

  “Then?”

  “Accelerate toward the sun. We can inspect the ring’s habitable surface to some extent as it diminishes below us. Our major target shall be the shadow squares.”

  “Such caution is unnecessary and humiliating. We have no slightest interest in the shadow squares.”

  Tanj! Louis thought. Tired and hungry as he was, would he now be called on to play peacemaker for the aliens? It had been too long since any of them had eaten or slept. If Louis was tired, the kzin must be exhausted, spoiling for a fight.

  The puppeteer was saying, “We have a definite interest in the shadow squares. Their area intercepts more sunlight than does the Ringworld itself. They would make ideal thermoelectric generators for the Ringworld’s power supply.”

  The kzin snarled something venomous in the Hero’s Tongue. His reply in Interworld seemed ludicrously mild. “You are unreasonable. We surely have no interest in the source of the Ringworld’s power. Let us land, find a native, and ask him about his power sources.”

  “I refuse to consider landing.”

  “Do you question my skill at the controls?”

  “Do you question my decisions as leader?”

  “Since you broach the subject—“

  “I still carry the tasp, Speaker. My word governs the disposal of the Long Shot and the second quantum hyperdrive, and I am still Hindmost aboard this ship. You will bear in mind—“

  “Stop,” said Louis. They looked at him.

  “Your arguments are premature,” said Louis. “Why not turn our telescopes on the shadow squares? That way you’ll both have more facts to shout at each other. It’s more fun that way.”