Tau Zero Read online

  “No doubt,” she said. “But will they beam the results to us?”

  “I expect not, unless we inquire. And if we do, we’ll be very old, or dead, before the reply arrives.” Williams leaned toward her across the bench. “The thing is, why should we care? Whatever type of biology we find at Beta Three, we know it won’t resemble this. Are you keeping your hand in?”

  “Partly that,” she admitted. “I do think it will be of practical value. The broader a view I have of life in the universe, the better I should be able to study the particular case where we are going. And so we learn sooner, more certainly, whether we can build our homes there and call others to follow us from Earth.”

  He rubbed his chin. “Yeah, I guess you’re right. Hadn’t thought of that angle.”

  Awe dwelt beneath the prosaic words. For the expedition was not merely going for a look: not at such cost hi resources, labor, skill, dreams, and years. Nor could it hope for anything as easy to subdue as America had been.

  At a minimum, these people would spend another half decade in the Beta Virginis System, exploring its worlds in the ship’s auxiliary craft, adding what little they could to the little that the orbiting probe had garnered. And if the third planet really was habitable, they would never come home, not even the professional spacemen. They would live out their lives, and be like their children and grandchildren too, exploring its manifold mysteries and flashing their discoveries to the hungry minds on Earth. For indeed, any planet is a world, infinitely varied, infinitely secret. And this world appeared to be so terrestroid that the strangenesses it must hold would be yet the more vivid and enlightening.

  The folk of Leonora Christine were quite explicit in their ambition to establish that kind of scientific base. Their further, largest hope was that their descendants would find no reason ever to go back: that Beta Three might evolve from base to colony to New Earth to jumping-off place for the next starward leap. There was no other way by which men might possess the galaxy.

  As if shying away from vistas that could overwhelm her, Glassgold said, reddening a trifle: “Besides, I care about Eridanian life. It fascinates me. I want to know what … makes it tick. And as you point out, if we do stay we aren’t likely to get the answers told us while we are alive.”

  He fell silent, fiddled with a titration setup, until ship-drive and ventilator breath, sharp chemical odors, bright colors on the reagent and dye shelves, shoved forward into consciousness. At length he cleared his throat. “Uh, Emma.”

  “Yes?” She seemed to feel the same diffidence.

  “How about knocking off? Come on down to the club with me for a drink before dinner. My ration.”

  She retreated behind her instruments. “No, thank you,” she said confusedly. “I, I do have a great deal of work.”

  “You have time for it, too,” he pointed out, bolder. “Okay, if you don’t want a cocktail, what about a cup of coffee? Maybe a stroll through the gardens — Look, I don’t aim to make a pass. I’d just like to get better acquainted.”

  She swallowed before she smiled, but then she gave him warmth. “Very well, Norbert. I would like that myself.”

  A year after she started, Leonora Christine was close to her ultimate velocity. It would take her thirty-one years to cross interstellar space, and one year more to decelerate as she approached her target sun.

  But that is an incomplete statement. It takes no account of relativity. Precisely because there is an absolute limiting speed (at which light travels in vacuo; likewise neutrinos) there is an interdependence of space, time, matter, and energy. The tau factor enters the equations. If v is the (uniform) velocity of a spaceship, and c the velocity of light, then tau equals

  The closer that v comes to c, the closer tau comes to zero.

  Suppose an outside observer measures the mass of the spaceship. The result he gets is her rest mass — i.e., the mass that she has when she is not moving with respect to him — divided by tau. Thus, the faster she travels the more massive she is, as regards the universe at large. She gets the extra mass from the kinetic energy of motion; e=mc 2.

  Furthermore, if the “stationary” observer could compare the ship’s clocks with his own, he would notice a disagreement. The interlude between two events (such as the birth and death of a man) measured aboard the ship where they take place, is equal to the interlude which the observer measures … multiplied by tau. One might say that time moves proportionately slower on a starship.

  Lengths shrink; the observer sees the ship shortened in the direction of motion by the factor tau.

  Now measurements made on shipboard are every bit as valid as those made elsewhere. To a crewman, looking forth at the universe, the stars are compressed and have gained in mass; the distances between them have shriveled; they shine, they evolve at a strangely reduced rate.

  Yet the picture is more complicated even than this. You must bear in mind that the ship has, in fact, been accelerated and will be decelerated in relation to the total background of the cosmos. This takes the whole problem out of special and into general relativity. The star-and-ship situation is not really symmetrical. The twin paradox does not arise. When velocities match once more and reunion takes place, the star will have passed through a longer time than the ship did.

  If you ran tau down to one one-hundredth and went into free fall, you would cross a light-century in a single year of your own experience. (Though, of course, you could never regain the century that had passed at home, during which your friends grew old and died.) This would inevitably involve a hundredfold increase of mass. A Bussard engine, drawing on the hydrogen of space, could supply that. Indeed, it would be foolish to stop the engine and coast when you could go right on decreasing your tau.

  Therefore, to reach other suns in a reasonable portion of your life expectancy: Accelerate continuously, right up to the interstellar midpoint, at which point you activate the decelerator system in the Bussard module and start slowing down again. You are limited by the speed of light, which you can never quite reach. But you are not limited in how close you can approach that speed. And thus you have no limit on your inverse tau factor.

  Throughout her year at one gravity, the differences between Leonora Christine and the slow-moving stars had accumulated imperceptibly. Now the curve entered upon the steep part of its climb. Now, more and more, her folk measured the distance to their goal as shrinking, not simply because they traveled, but because, for them, the geometry of space was changing. More and more, they perceived natural processes in the outside universe as speeding up.

  It was not yet spectacular. Indeed, the minimum tau in her flight plan, at midpoint, was to be somewhat above 0.015. But an instant came when a minute aboard her corresponded to sixty-one seconds in the rest of the galaxy. A while later, it corresponded to sixty-two. Then sixty-three … sixty-four … the ship time between such counts grew gradually but steadily less … sixty-five … sixty-six … sixty-seven…

  The first Christmas — Chanukah, New Year’s, solstice festival season — that the crew spent together had come early in their voyage and was a feverish carnival. The second was quieter. People were settling down to their work and their fellows. Nevertheless, improvised ornaments glittered on all decks. The hobby rooms resounded, the scissors and needles clicked, the galley grew fragrant with spice, as everybody tried to make small gifts for everybody else. The hydroponics division found it could spare enough green vines and branches for an imitation tree in the gymnasium. From the enormous microtape library came films of snow and sleighs, recordings of carols. The thespian contingent rehearsed a pageant. Chef Carducci planned banquets. Commons and cabins rollicked with parties. By tacit agreement, no one mentioned that each second which passed laid Earth three hundred thousand kilometers farther behind.

  Reymont made his way through a bustling recreation level. Some groups were stringing up the most newly made decorations. Nothing could be wasted, but aluminum-foil chains, blown-glass globes, wreaths twisted from bolts of clot
h, were reclaimable. Others played games, chattered, offered drinks around, flirted, got boisterous. Through the chatter and laughter and shuffling, hum and crackle and rustle, music floated out of a loudspeaker:

  Adeste, fideles,

  Laeti, triumphantes,

  Venite, venite, in Bethlehem.

  Iwamoto Tetsuo, Hussein Sadek, Yeshu ben-Zvi, Mohandas Chidambaran, Phra Takh, or Kato M’Botu seemed to belong with it as much as Olga Sobieski or Johann Freiwald.

  The machinist bellowed at Reymont: “Guten Tag, mein lieber Schutzmann! Come share my bottle!” He waved it in the air. His free arm was around Margarita Jimenes. Suspended above them was a slip of paper on which had been printed MISTLETOE.

  Reymont halted. He got along well with Freiwald. “Thank you, no,” he said. “Have you seen Boris Fedoroff? I expected him to come here when he got off work.”

  “N-no. I would expect it too, as lively as things are tonight. He’s become a lot happier lately for some reason, hasn’t he? What do you want of him?”

  “Business matter.”

  “Business, forever business,” Freiwald said. “I swear your personal amusement is fretting. Me, I’ve got a better one.” He hugged Jimenes to him. She snuggled. “Have you called his cabin?”

  “Naturally. No response. Still, maybe—” Reymont turned. “I’ll try there. Later I’ll come back for that schnapps,” he added, already leaving.

  He took the stairs down past crew level to the officers’ deck. The music followed. “—Iesu, tibi sit gloria.” The passageway was deserted. He pushed Fedoroff’s chime button.

  The engineer opened the door. He was clad in lounging pajamas. Behind him, a bottle of French wine, two glasses, and some Danish-style sandwiches waited on the dresser top. Surprise jarred him. He took a backward step. “Chto — you?”

  “Could I speak with you?”

  “Um-m-m.” Fedoroff’s glance flickered. “I expect a guest.”

  Reymont grinned. “That’s obvious. Don’t worry, I won’t linger. But this is rather urgent.”

  Fedoroff bridled. “It cannot wait until I am on duty?”

  “The thing is, it had better be discussed confidentially,” Reymont said. “Captain Telander agrees.” He slipped around Fedoroff, into the cabin. “An item was overlooked in the plans,” he went on, speaking fast. “Our schedule has us changing over to high-acceleration mode on the seventh of January. You know better than I how that takes two or three days of preliminary work by your gang and considerable upsetting of everybody else’s routine. Well, somehow the flight planners forgot that the sixth is important in West European tradition. Twelfth Night, the Eve of the Three Holy Kings, call it what you will, it climaxes the merrymaking part of the holidays. Last year celebrations were so riotous that nobody thought about it. But I learn that this year a final feast and dance, with the old rituals, is being talked of, as something that would be pleasant if only it were possible. Think what such a reminder of our origins can do to help morale. The skipper and I wish you’d check the feasibility of postponing high acceleration a few days.”

  “Yes, yes, I will look into it.” Fedoroff urged Reymont toward the open door. “Tomorrow, please—”

  He was too late. Ingrid Lindgren came around its edge. She was in uniform, having hurried up from the bridge when her watch ended.

  “Gud!” broke from her. She stopped dead.

  “Why, why, Lindgren,” Fedoroff said frantically, “what brings you here?”

  Reymont had sucked in a single breath. Every expression went out of his face. He stood moveless, except that his fists clenched till nails dug into palms and skin stretched white across knuckles.

  A new carol began.

  Lindgren looked back and forth, between the men. Her own features were drained of blood. Abruptly, though, she straightened and said: “No, Boris. We’ll not lie.”

  “It wouldn’t help any more,” Reymont agreed without tone.

  Fedoroff whirled on him. “All right!” he cried. “All right! We have been together a few times. She’s not your wife.”

  “I never claimed she was,” Reymont answered, his eyes on her. “I did intend to ask her to be, when we arrived.”

  “Carl,” she whispered. “I love you.”

  “No doubt one partner gets boring,” Reymont said like winter. “You felt the need of refreshment. Your privilege, of course. I did think you were above slinking behind my back.”

  “Let her alone!” Fedoroff grabbed blindly for him.

  The constable flowed aside. His hand chopped edge-on. The engineer gasped in anguish, collapsed to a seat on the bed, and caught his injured wrist in the other hand.

  “It’s not broken,” Reymont told him. “However, if you don’t stay where you are till I leave, I’ll disable you.” He paused. Judiciously: “That’s not a challenge to your manhood. I know single combat the way you know nucleonics. Let’s stay civilized. She’s yours anyway, I suppose.”

  “Carl.” Lindgren took a step and another toward him, reaching. Tears whipped down her cheeks. He sketched a bow. “I will remove my things from your cabin as soon as I have found a vacant berth.”

  “No, Carl, Carl.” She clutched his tunic. “I never imagined — Listen, Boris needed me. Yes, I admit it, I enjoyed being with him, but it was never deeper than friendship … help … while you—”

  “Why didn’t you tell me what you were doing? Wasn’t I entitled to know?”

  “You were, you were, but I was afraid — a few remarks you’d let drop — you are jealous — and it’s so unnecessary, because you’re the only one who counts.”

  “I’ve been poor my whole life,” he said, “and I do have a poor man’s primitive morality, as well as some regard for privacy. On Earth there might be ways to make matters — not right again, really, but tolerable. I could fight my rival, or go away on a long trip, or you and I could both move elsewhere. None of that is possible here.”

  “Can’t you understand?” she implored.

  “Can’t you?” He had closed his fists anew. “No,” he said, “you honestly — I’ll assume honestly — don’t believe you did me any harm. The years will be hard enough to get through without keeping up that kind of relationship.”

  He disengaged her from him. “Stop blubbering!” he barked.

  She shuddered and grew rigid. Fedoroff growled. He started to rise. She waved him back.

  “That’s better.” Reymont went to the door. There he stood and faced them. “We’ll have no scenes, no intrigues, no grudges,” he stated. “When fifty people are locked into one hull, everybody conducts himself right or everybody dies. Mister Engineer Fedoroff, Captain Telander and I would like your report on the subject I came to discuss as soon as can be managed. You might get the opinion of Miss First Officer Lindgren, bearing in mind that secrecy is desirable till we’re ready to make an announcement one way or another.” For an instant, the pain and fury struck out of him. “Our duty is to the ship, hell damn you!” Control clamped down. He clicked his heels. “My apologies. Good evening.”

  He left.

  Fedoroff got up behind Lindgren and laid his arms around her. “I am very sorry,” he said in his awkwardness. “If I had guessed this might happen, I would never—”

  “Not your fault, Boris.” She didn’t move.

  “If you would share quarters with me, I would be glad.”

  “No, thank you,” she answered dully. “I’m out of that game for the time being.” She released herself. “I’d better go. Good night.” He stood alone with his sandwiches and wine.

  O holy child of Bethlehem,

  Descend to us, we pray.

  The proper adjustments being made, Leonora Christine raised her acceleration a few days after Epiphany.

  It would make no particular difference to the cosmic duration of her passage. In either case, she ran at the heels of light. But by decreasing tau faster, and reaching lower values of it at midpoint, the higher thrust appreciably shortened the shipboard time.
r />   Extending her scoopfields more widely, intensifying the thermonuclear fireball that trailed her trailing Bussard engine, the ship shifted over to three gravities. This would have added almost thirty meters per second per second to a low velocity. To her present speed, it added tiny increments which grew constantly tinier. That was in outside measurement. Inboard, she drove ahead at three gee; and that measurement was equally real.

  Her human payload could not have taken it and lived long. The stress on heart, lungs, and especially on body fluid balance would have been too great. Drugs might have helped. Fortunately, there was a better way.

  The forces that pushed her nearer and nearer to ultimate c were not merely enormous. Of necessity, they were precise. They were, indeed, so precise that their interaction with the outside universe — matter and its own force fields — could be held to a nearly constant resultant in spite of changes in those exterior conditions. Likewise, the driving energies could safely be coupled to similar, much weaker fields when the latter were established within the hull.

  This linkage could then operate on the asymmetries of atoms and molecules to produce an acceleration uniform with that of the inside generator itself. In practice, though, the effect was left incomplete. One gravity was uncompensated.

  Hence weight inboard remained at a Steady Earth-surface value, no matter how high the rate at which the ship gained speed.

  Such cushioning was only achievable at relativistic velocities. At an ordinary pace, their tau large, atoms were insufficiently massive, too skittish to get a good grip on. As they approached c, they grew heavier — not to themselves, but to everything outside their vessel — until the interplay of fields between cargo and cosmos could establish a stable configuration.