Tau Zero

by Poul Anderson

  He fell silent, less like a man ending a lecture than a machine running down.

  “Have we no directional control whatsoever?” Reymont asked, still toneless.

  “Yes, yes, we do have that,” Boudreau said. “The accelerator pattern can be varied. We can damp down any of the four Venturis and boost up any others — get a sidewise as well as a forward vector. But don’t you see, no matter what path we take, we must continue accelerating or we die.”

  “Accelerating forever,” Telander said.

  “At least,” Lindgren whispered, “we can stay in me galaxy. Swing around and around its heart.” Her gaze went to the periscope, and they knew what she thought of: behind that curtain of strange blue stars, blackness, intergalactic void, an ultimate exile. “At least … we can grow old … with suns around us. Even if we can’t ever touch a planet again.”

  Telander’s features writhed. “How do I tell our people?” he croaked.

  “We have no hope,” Reymont said. It was hardly a question.

  “None,” Fedoroff replied.

  “Oh, we can live out our lives — reach a reasonable age, if not quite what antisenescence would normally permit,” said Pereira. “The biosystems and organocycle apparatus are intact. We could actually increase their productivity. Do not fear immediate hunger or thirst or suffocation. True, the closed ecology, the reclamations, are not 100 per cent efficient. They will suffer slow losses, slow degrading. A spaceship is not a world. Man is not quite the clever designer and large-scale builder that God is.” His smile was ghastly. “I do not advise that we have children. They would be trying to breathe things like acetone, while getting along without things like phosphorus and smothering in things like earwax and belly-button lint. But I imagine we can get fifty years out of our gadgets. Under the circumstances, that seems ample to me.”

  Lindgren said from nightmare, staring at a bulkhead as if she could see through: “When the last of us dies — We must put in an automatic cutoff. The ship must not keep on after our deaths. Let the radiation do what it will, let cosmic friction break her to bits and let the bits drift off yonder.”

  “Why?” asked Reymont.

  “Isn’t it obvious? If we throw ourselves into a circular path … consuming hydrogen, always traveling faster, running tau down and down as the thousands of years pass … we get more massive. We could end by devouring the galaxy.”

  “No, not that,” said Telander. He retreated into pedantry. “I have seen calculations. Somebody did worry once about a Bussard craft getting out of control. But as Mr. Pereira remarked, any human work is insignificant out here. Tau would have to become something like, shall we say, ten to the minus twentieth power before the ship’s mass was equal to that of a minor star. And the odds are always literally astronomical against her colliding with anything more important than a nebula. Besides, we know the universe is finite in time as well as space. It would stop expanding and collapse before our tau got that low. We are going to die. But the cosmos is safe from us.”

  “How long can we live?” Lindgren wondered. She cut Pereira off. “I don’t mean potentially. If you say half a century, I believe you. But I think in a year or two we will stop eating, or cut our throats, or agree to turn the accelerators off.”

  “Not if I can help it,” Reymont snapped.

  She gave him a dreary look. “Do you mean you would continue — not just barred from man, from living Earth, but from the whole of creation?”

  He regarded her steadily in return. His right hand rested on his gun butt. ‘‘Don’t you have that much guts?” he replied.

  “Fifty years inside this flying coffin!” she almost screamed. “How many will that be outside?”

  “Easy,” Fedoroff warned, and took her around the waist. She clung to him and snatched after air.

  Boudreau said, as carefully dry as Telander: “The time relationship appears to be somewhat academic to us, n’est-ce pas? It depends on what course we take. If we let ourselves continue straight outwards, naturally we will encounter a thinner medium. The rate of decrease of tau will grow proportionately smaller as we enter intergalactic space. Contrariwise, if we try for a cyclical path taking us through the densest hydrogen concentrations, we could get a very large inverse tau. We might see billions of years go by. That could be quite wonderful.” His smile was forced, a flash in the spade beard. “We have each other too. A goodly company. I am with Charles. There are better ways to live but also worse ones.”

  Lindgren hid against Fedoroff’s breast. He held her, patted her with a clumsy hand. After a while (an hour or so in the history of the stars) she raised her face again.

  “I’m sorry,” she gulped. “You’re right. We do have each other.” Her glance went among them, ending at Reymont.

  “How shall I tell them?” the captain beseeched.

  “I suggest you do not,” Reymont answered. “Have the first officer break the news.”

  “What?” Lindgren said.

  “You are simpбtico, ” he answered. “I remember.”

  She moved from Fedoroff’s loosened grasp, a step toward Reymont.

  Abruptly the constable tautened. He stood for a second as if blind, before he whirled from her and confronted the navigator.

  “Hoy!” he exclaimed. “I’ve gotten an idea. Do you know—”

  “If you think I should—” Lindgren had begun to say.

  “Not now,” Reymont told her. “Auguste, come over to the desk. We have a bit of figuring to do … fast!”

  Chapter 10

  The silence went on and on. Ingrid Lindgren stared from the stage, where she stood with Lars Telander, down at her people. They looked back at her. And not a one in that chamber could find words.

  Hers had been well chosen. The truth was less savage in her throat than in any man’s. But when she came to her planned midpoint—” We have lost Earth, lost Beta Three, lost the mankind we belonged to. We have left to us courage, love, and and, yes, hope” — she could not continue. She stood with lip caught between teeth, fingers twisted together, and the slow tears flowed from her eyes.

  Telander stirred. “Ah … if you will,” he tried. “Kindly pay attention. A means does exist…” The ship jeered at him in her tone of distant lightnings.

  Glassgold broke. She did not weep loudly, but her struggle to stop made the sound more dreadful. M’Botu, beside her, attempted consolation. He, though, had clamped such stoicism on himself that he might as well have been a robot. Iwamoto withdrew several paces from them both, from them all; one could see how he pulled his soul into some nirvana with a lock on its door. Williams shook his fist at the overhead and cursed. Another voice, female, started to keen. A woman considered the man with whom she had been keeping company, said, “You, for my whole life?” and stalked from him. He tried to follow her and bumped into a crewman who snarled and offered to fight if he didn’t apologize. A seething went through the entire human mass.

  “Listen to me,” Telander said. “Please listen.”

  Reymont shook loose the arm which Chi-Yuen Ai-Ling held, where they stood in the first row, and jumped onto the stage. “You’ll never bring them around that way,” he declared sotto voce. “You’re used to disciplined professionals. Let me handle these civilians.” He turned on them. “Quiet, there! “Echoes bounced around his roar. “Shut your hatches. Act like adults for once. We haven’t the personnel to change your diapers for you.”

  Williams yelped with resentment. M’Botu bared teeth. Reymont drew his stunner. “Hold your places!” He dropped his vocal volume, but everyone heard him. “The first of you to move gets knocked out. Afterward we’ll court-martial him. I’m the constable of this expedition, and I intend to maintain order and effective cooperation.” He leered. “If you feel I exceed my authority, you’re welcome to file a complaint with the appropriate bureau in Stockholm. For now, you’ll listen!”

  His tongue-lashing activated their adrenals. With heightened vigor came self-possession. They glowered but waited al
ertly.

  “Good.” Reymont turned mild and holstered his weapon. “We’ll say no more about this. I realize you’ve had a shock which none of you were prepared psychologically to meet. Nevertheless, we’ve got a problem. And it has a solution, if we can work together. I repeat: if.”

  Lindgren had swallowed her weeping. “I think I was supposed to—” she said. He shook his head at her and went on:

  “We can’t repair the decelerators because we can’t turn off the accelerators. The reason is, as you’ve been told, at high speeds we must have the force fields of one system or the other to shield us from interstellar gas. So it looks as if we’re bottled in this hull. Well, I don’t like the prospect either, though I believe we could endure it. Medieval monks accepted worse.

  “Discussing it in the bridge, however, we got a thought. A possibility of escape, if we have the nerve and determination. Navigation Officer Boudreau ran a preliminary check for me. Afterward we called in Professor Nilsson for an expert opinion.”

  The astronomer harrumphed and looked important. Jane Sadler seemed less impressed than others.

  “We have a chance of success,” Reymont informed them.

  A sound like a wind passed through the assembly. “Don’t make us wait!” cried a young man’s voice.

  “I’m glad to see some spirit,” Reymont said. “It’ll have to be kept on a tight rein, though, or we’re finished. To make this as short as I can — afterward Captain Telander and the specialists will go into detail — here’s the idea.”

  His delivery might have been used to describe a new method of bookkeeping. “If we can find a region where gas is practically nonexistent, we can safely shut down the fields, and our engineers can go outside and repair the decelerator system. Astronomical data are not as precise as we’d like. However, apparently throughout the galaxy and even in nearby intergalactic space, the medium is too dense. Much thinner out there than here, of course; still, so thick, in terms of atoms struck per second, as to kill us without our protection.

  “Now galaxies generally occur in clusters. Our galaxy, the Magellanic Clouds, M31 in Andromeda, and thirteen others, large and small, make up one such group. The volume it occupies is about six million light-years across. Beyond them is an enormously greater distance to the next galactic family. By coincidence, it’s in Virgo too: forty million light-years from here.

  “‘In that stretch, we hope, the gas is thin enough for us not to need shielding.”

  Babble tried to break out afresh. Reymont lifted both hands. He actually laughed. “Wait, wait!” he called. “Don’t bother. I know what you want to say. Forty million light-years is impossible. We haven’t the tau for it. A ratio of fifty, or a hundred, or a thousand, does us no good. Agreed. But.”

  The last word stopped them. He filled his lungs. “But remember,” he said, “we have no limit on our inverse tau. We can accelerate at a lot more than three gee, too, if we widen our scoopfields and choose a path through sections of this galaxy where matter is dense. The exact parameters we’ve been using were determined by our course to Beta Virginis. The ship isn’t restricted to them. Navigator Bou-dreau and Professor Nilsson estimate we can travel at an average of ten gee, quite likely more. Engineer Fedoroff is reasonably sure the accelerator system can stand that, after certain modifications he knows he can make.

  “So. The gentlemen made rough calculations. Their results indicate we can swing halfway around the galaxy, spiraling inward till we plunge straight through its middle and out again on this side. We’d be slow about any course change anyway. We can’t turn on a tea-цre coin at our speed! And this’ll enable us to acquire the necessary tau. Don’t forget, that’ll decrease constantly. Our transit to Beta Vee would have been a lot quicker if we hadn’t meant to stop there: if, instead of braking at mid-passage, we’d simply kept cramming on velocity.

  “Navigator Boudreau estimates — estimates, mind you; we’ll have to gather data as we go; but a good, informed guess — considering the speed we already have, he thinks we can finish with this galaxy and head out beyond it in a year or two.”

  “How long cosmic time?” sounded from the gathering.

  “Who cares?” Reymont retorted. “You know the dimensions. The galactic disk is about a hundred thousand light-years across. At present we’re thirty thousand from the center. One or two hundred millennia altogether? Who can tell? It’ll depend on what path we take, which in turn will depend on what long-range observation can show us.”

  He stabbed a finger at them. “I know. You wonder, what if we hit a cloud such as got us into this miserable situation? I have two answers for that. First, we have to take some risks. But second, as our tau gets less and less, we’ll be able to use regions which are denser and denser. We’ll have too much mass to be affected as we were this time. Do you see? The more we have, the more we can get, and the faster we can get it in ship’s time. We may conceivably leave the galaxy with an inverse tau on the order of a hundred million. In that case, by our clocks we’ll be outside this entire galactic family in days!”

  “How do we get back?” Glassgold said — but vigilant and interested.

  “We don’t,” Reymont admitted. “We keep on to the Virgo cluster. There we reverse the process, decelerate, enter one of the member galaxies, bring our tau up to something sensible, and start looking for a planet where we can live.

  “Yes, yes, yes!” he rapped into the renewed surf of their speech. “Millions of years in the future. Millions of light-years hence. The human race most qwlikely extinct … in this corner of the universe. Well, can’t we start over, in another place and time? Or would you rather sit in a metal shell feeling sorry for yourselves, till you grow senile and die childless? Unless you can’t stand the gaff and blow out your brains. I’m for going on as long as strength lasts. I think enough of this group to believe you will agree. Will anyone who feels differently be so good as to get out of our way?”

  He stalked from the stage. “Ah … Navigation Officer Boudreau, Chief Engineer Fedoroff, Professor Nilsson,” Telander said. “Will you come here? Ladies and gentlemen, the meeting is open for general discussions—”

  Chi-Yuen hugged Reymont. “You were marvelous,” she sobbed.

  His mouth tightened. He looked from her, from Lindgren, across the assemblage, to the enclosing bulkheads. “Thanks,” he replied curtly. “Wasn’t much.”

  “Oh, but it was. You gave us back hope. I am honored to live with you.”

  He didn’t seen to hear. “Anybody could have presented a shiny new idea,” he said. “They’ll grasp at anything, right now. I only expedited matters. When they accept the program, that’s when the real trouble begins.”

  Chapter 11

  Force fields shifted about. They were not static tubes and walls. What formed them was the incessant interplay of electromagnetic pulses, whose production, propagation, and heterodyning must be under control at every nanosecond, from the quantum level to the cosmic. As exterior conditions — matter density, radiation, impinging field strengths, gravitational space-curvature — changed, instant by instant, their reaction on the ship’s immaterial web was registered; data were fed into the computers; handling a thousand simultaneous Fourier series as the smallest of their tasks, these machines sent back their answers; the generating and controlling devices, swimming aft of the hull in a vortex of their own output, made their supple adjustments. Into this homeostasis, this tightrope walk across the chance of a response that was improper or merely tardy — which would mean distortion and collapse of the fields, novalike destruction of the ship — entered a human command. It became part of the data. A starboard intake widened, a port intake throttled back: carefully, carefully. Leonora Christine swung around onto her new course.

  The stars saw the ponderous movement of a steadily larger and more flattened mass, taking months and years before the deviation from its original track was significant. Not that the object whereon they shone was slow. It was a planet-sized shell of incandescence, whe
re atoms were seized by its outermost force-fringes and excited into thermal, fluorescent, synchrotron radiation. And it came barely behind the wave front which announced its march. But the ship’s luminosity was soon lost across light-years. Her passage crawled through abysses which seemingly had no end.

  In her own time, the story was another. She moved in a universe increasingly foreign — more rapidly aging, more massive, more compressed. Thus the rate at which she could gulp down hydrogen, burn part of it to energy and hurl the rest off in a million-kilometer jet flame … that rate kept waxing for her. Each minute, as counted by her clocks, took a larger fraction off her tau than the last minute had done.

  Inboard, nothing changed. Air and metal still carried the pulse of acceleration, whose net internal drag still stood at an even one gravity. The interior power plant continued to give light, electricity, equable temperatures. The biosystems and organocycles reclaimed oxygen and water, processed waste, manufactured food, supported life. Entropy increased. People grew older at the ancient rate of sixty seconds per minute, sixty minutes per hour.

  Yet those hours were always less related to the hours and years which passed outside. Loneliness closed on the ship like fingers.

  Jane Sadler executed a balestra. Johann Freiwald sought to parry. Her foil rang against his in a beat. Immediately, she thrust. “Touchй!” he acknowledged. Laughing behind his mask: “That would have skewered my left lung in a real duel. You have passed your examination.”

  “None too soon,” she panted. “I’d … have … been out of air … ’nother minute. Knees like rubber.”

  “No more this evening,” Freiwald decided.

  They took off their head protection. Sweat gleamed on her face and plastered hair to brow; her breath was noisy; but her eyes sparkled. “Some workout!” She flopped onto a chair. Freiwald joined her. This late in the ship’s evening, they had the gymnasium to themselves. It felt huge and hollow, making them sit close together.