Tau Zero

by Poul Anderson

  Three gravities was not the limit. With scoopfields fully extended, and in regions where matter occurred more densely than hereabouts, such as a nebula, she could have gone considerably higher. In this particular crossing, given the tenuousness of the local hydrogen, any possible gain in time was not enough — since the formula involves a hyperbolic function — to be worth reducing her safety margin. Other considerations, e.g., the optimization of mass intake versus the minimization of path length, had also entered into computing her flight pattern.

  Thus, tau was no static multiplying factor. It was dynamic. Its work on mass, space, and time could be observed as a fundamental thing, creating a forever new relationship between men and the universe through which they fared.

  In a shipboard hour that the calendar said was in April and the clock said was in morning, Reymont awoke. He didn’t stir, blink, yawn, and stretch like most men. He sat up, immediately alert.

  Chi-Yuen Ai-Ling had ended sleep earlier. His suddenness caught her kneeling in Asian fashion at the foot of the bed, regarding him with a seriousness altogether unlike her playful mood of the night before.

  “Is anything wrong?” he demanded.

  She had only shown startlement in a widening of eyes. After a moment, her smile came to slow life. “I knew a tame hawk once,” she remarked. “That is, it wasn’t tame in dog fashion, but it hunted with its man and deigned to sit on his wrist. You come awake the same way.”

  “Mph,” he said. “I meant that worried look of yours.”

  “Not worried, Charles. Thoughtful.”

  He admired the sight of her. Unclad, she could never be called boyish. The curves of breast and flank were subtler than ordinary, but they were integral with the rest of her — not stuccoed on, as with too many women — and when she moved, they flowed. So did the light along her skin, which had the hue of the hills around San Francisco Bay in their summer, and the light in her hair, which had the smell of every summer day that ever was on Earth.

  They were in his crew-level cabin half, screened off from his partner Foxe-Jameson. It made too drab a setting for her. Her own quarters were filled with beauty.

  “What about?” he inquired.

  “You. Us.”

  “It was a gorgeous night.” He reached out to stroke her beneath the chin. She made purring noises. “More?”

  Her gravity returned. “That’s what I was wondering.” He cocked his brows. “An understanding between us. We’ve had our flings. At least, you have had, in the past few months.” His face darkened. She went doggedly on: “To myself, it wasn’t that important; an occasional thing. I don’t want to continue with it, really. If nothing else, those hints and attempts, the whole courtship rite, over and over … they intefere with my work. I’m developing some ideas about planetary cores. They need concentration. A lasting liaison would help.”

  “I don’t want to make any contracts,” he said grimly.

  She caught his shoulders. “I realize that. I’m not asking for one. Nor offering it. I have simply come to like you better each time we have talked, or danced, or spent a night. You are a quiet man, mostly; strong; courteous, to me at any rate. I could live happily with you — nothing exclusive on either side, only an alliance, for the whole ship to see — as long as we both want to.”

  “Done!” he exclaimed, and kissed her.

  “That quickly?” she asked, astonished.

  “I’d given it some thought too. I’m also tired of chasing. You should be easy to live with.” He ran a hand down her side and thigh. “Very easy.”

  “How much of your heart is in that?” At once she laughed. “No, I apologize, such questions are excluded… Shall we move into my cabin? I know Maria Toomajian won’t mind trading places with you. She keeps her part closed off anyway.”

  “Fine,” he said. “Sweetheart, we still have almost an hour before breakfast call—”

  Leonora Christine was nearing the third year of her journey, or the tenth year as the stars counted time, when grief came upon her.

  Chapter 7

  An outside watcher, quiescent with respect to the stars, might have seen the thing before she did; for at her speed she must needs run half-blind. Even without better sensors than hers, he would have known of the disaster a few weeks ahead. But he would have had no way to cry his warning.

  And there was no watcher anyhow: only night, bestrewn with multitudinous remote suns, the frosty cataract of the Milky Way and the rare phantom glimmer of a nebula or a sister galaxy. Nine light-years from Sol, the ship was illimitably alone.

  An automatic alarm roused Captain Telander. As he struggled upward from sleep, Lindgren’s voice followed on the intercom: “Kors i Herrens namn! ” The horror in it jerked him fully awake. Not stopping to acknowledge, he ran from his cabin. Nor would he have stopped to dress, had he been abed.

  As it happened, he was clad. Lulled by the sameness of time, he had been reading a novel projected from the library and had dozed off in his chair. Then the jaws of the universe snapped shut.

  He didn’t notice the gaiety that now covered passageway bulkheads, or the springiness underfoot or the scent of roses and thundershowers. Loud in his awareness beat the engine vibrations. The stairs made a metal clatter beneath his haste, which the well flung back.

  He emerged on the next level up and entered the bridge. Lindgren stood near the viewscope. It was not what counted; at this moment, it was almost a toy. What truth the ship could tell was in the instruments which glittered across the entire forward panel. But her eyes would not leave it.

  The captain brushed past her. The warning which had caused him to be summoned was still blazoned on a screen linked to the astronomical computer. He read. The breath hissed between his teeth. His gaze went across the surrounding meters and displays. A slot clicked and extruded a printout. He snatched it. The letters and figures represented a quantification: decimal-point detail, after more data had come in and more calculation had been done. The basic Mene, Mene stood unchanged on the panel.

  He stabbed the general alert button. Sirens wailed; echoes went ringing down the corridors. On the intercom he ordered all hands not on duty to report to commons with the passengers. After a moment, harshly, he added that channels would be open so that those people standing watch could also take part in the meeting.

  “What are we going to do?” Lindgren cried into a sudden stillness.

  “Very little, I fear.” Telander went to the viewscope. “Is anything visible in this?”

  “Barely. I think. Fourth quadrant.” She shut her eyes and turned from him.

  He took for granted that she meant the projection for dead ahead, and peered into that. At high magnification, space leaped at him. The scene was somewhat blurred and distorted. Optical circuits were not able to compensate perfectly for speeds like this. But he saw starpoints, diamond, amethyst, ruby, topaz, emerald, a Fafnir’s hoard. Near the center burned Beta Virginis. It should have looked very like the sun of home, but something of spectral shift got by to tinge it ice blue. And, yes, on the edge of perception … that wisp? That smoky cloudlet, to wipe out this ship and these fifty human lives?

  Noise broke in on his concentration, shouts, footfalls, the sounds of fear. He straightened. “I had better go aft,” he said, flat-voiced. “I should consult Boris Fedoroff before addressing the others.” Lindgren moved to join him. “No, keep the bridge.”

  “Why?” Her temper stretched thin. “Regulations?”

  He nodded. “Yes. You have not been relieved.” A smile of sorts touched his lean face. “Unless you believe in God, regulations are now me only comfort we have.”

  In this moment, the drapes and murals of the gymnasium-auditorium had no more significance than the basketball goals or the bright casual clothes of the people. They had not taken time to unfold chairs. Everyone stood. Every gaze locked onto Telander while he mounted the stage. Nobody stirred save to breathe. Sweat glistened on countenances and could be smelled. The ship muttered around them.


  Telander rested his fingers on the lectern. “Ladies and gentlemen,” he said into their silence, “I have bad news.” Quickly: “Let me say at once that our prospects of survival are far from hopeless, judging by present information. We are in trouble, though. The risk was not unforeseen, but by its nature is one that cannot be provided against, at any rate not in our early stage of Bussard drive technology—”

  “Get to the point. God damn it!” Norbert Williams shouted.

  “Quiet, you,” said Reymont. Unlike most of them, who stood with male and female hands clutched together, he held apart, near the stage. To a drab coverall he had pinned his badge of authority.

  “You can’t—” Someone must have nudged Williams, for he spluttered into silence.

  Telander’s frame grew visibly tenser. “Instruments have … have detected an obstacle. A small nebula. Extremely small, a clot of dust and gas, no more than a few billion kilometers across. It is traveling at an abnormal velocity. Maybe it’s a remnant of a larger thing cast out by a supernova, a remnant still held together by hydromagnetic forces. Or maybe it’s a protostar. I do not know.

  “The fact is, we are going to strike it. In about twenty-four hours, ship’s time. What will happen then, I don’t know either. With luck, we can ride out the impact and not suffer serious damage. Otherwise … if the fields become too overloaded to protect us … well, we knew this journey would have its hazards.”

  He heard indrawn breaths, like his own on the bridge, and saw eyes grow white-rimmed, lips flutter, fingers trace signs in the air. He persisted: “We cannot do much to prepare. A little battening down, yes; but in general, the ship is already as taut as can be. When the moment approaches, we will be in shock harness and space armor. So — The meeting is now open for discussion.” Williams’ hand rocketed past the shoulder of tall M’Botu. “Yes?” The chemist’s ruddiness showed indignation rather than fear. “Mister Captain! The robot probe observed no dangers on this route. At least, it beamed back no hint of them. Right? Who’s responsible for our blundering into this muck?”

  Voices lifted toward a babble. “Quiet!” Charles Reymont called. Though he didn’t speak loud, he pushed the sound from his lungs in such a way that it struck. Several resentful glances were cast at him, but the talkers came to order.

  “I thought I had explained,” Telander said. “The cloud is minute by cosmic standards, nonluminous, undetectable at any large distance. It has a high velocity, scores of KPS. Thus, supposing the probe had taken our identical path, the nebulina would have been well offside at the time — more than fifty years ago, remember. Furthermore … we can be certain the probe did not go exactly as we are going. Besides the relative motion of Sol and Beta Virginis, consider the distance between. Thirty-two light-years is more than our poor minds can picture. The slightest variation in the curves taken from star to star means a difference of many astronomical units in the middle.”

  “This thing couldn’t have been predicted,” Reymont added. “The chances were big against our running into it. Still, somebody has to draw the long odds now and then.”

  Telander stiffened. “I did not recognize you. Constable,” he said.

  Reymont flushed. “Captain, I was trying to expedite matters, so some snotbrains won’t keep you here explaining the obvious till we smash.”

  “No insults to shipmates. Constable. And kindly wait to be recognized before you speak.”

  “I beg the captain’s pardon.” Reymont folded his arms and blanked his features.

  Telander said with care: “Please do not be afraid to ask questions, however elementary they seem. You are all educated in the theory of interstellar astronautics. But I, whose profession this is, know how strange the paradoxes are, how hard to keep straight in one’s mind. Best if everyone understands exactly what we are meeting… Dr. Glassgold?”

  The molecular biologist lowered her hand and said timidly: “Can’t we — I mean — nebular objects like mat, they would count as hard vacuums on Earth. Wouldn’t they? And we, we are just under the speed of light, gaining more every second. And so more mass. Our inverse tau is about fifteen at the moment, I believe. That means our mass is enormous. So how can a bit of dust and gas stop us?”

  “A good point,” Telander replied. “If we are lucky, we will pass without too great hindrance. Not entirely. Remember, that dust and gas is moving equally fast with respect to us, with a corresponding increase of its mass.

  “The force fields have to do work on it, directing the hydrogen into the ramjet system and diverting all matter from the hull. This action has its reaction on us. Moreover, it will take place extremely rapidly. What the fields can do in, say, an hour, they may not be able to do in a minute. We must hope that they can, and that the material components of the ship can endure the resultant stresses.

  “I have spoken with Chief Engineer Fedoroff at his post. He thinks probably we will not suffer grave damage. He admits his opinion is a mere extrapolation. In a pioneering era, one learns chiefly by experience. Mr. Iwamoto?”

  “S-s-sst! I presume we have no possibility of avoidance? One day ship’s time is about two weeks cosmic time, no? We have not a chance to go around this nebu — nebulina?” “No, I fear not. In our own frame of reference, we are accelerating at approximately three gravities. In terms of the outside universe, however, that acceleration is not constant, but steadily decreasing. Therefore we cannot change course fast. Even a full vector normal to our velocity would not get us far enough aside before the encounter. Anyhow, we haven’t the time to make the preparations for such a drastic alteration of flight pattern. Ah, Second Engineer M’Botu?”

  “Might it help if we decelerated? We must keep one or another mode operative at all times, forward or backward thrust, to be sure. But I should think that deceleration now would soften the collision.”

  “The computer has not made any recommendations about that. Probably the information is insufficient. At best, the percentage difference in speed would be slight. I fear … I think we have no choice except to — ah—”

  “Bull through,” Reymont said in English. Telander cast him a look of annoyance. Reymont didn’t seem to mind.

  As discussion progressed, though, his glance darted from speaker to speaker and the lines between mouth and nostrils deepened in his face. When at last Telander pronounced, “Dismissed,” the constable did not return to Chi-Yuen. He pushed almost brutally through the uncertain milling of the rest and plucked the captain’s sleeve.

  “I think we had better hold a private talk, sir,” he declared. The choppiness he had been losing was back in his accent.

  Telander said with a chill, “Now is hardly the time to deny anyone access to facts. Constable.”

  “Oh, call it politeness, that we go work by ourselves instead of bothering people,” Reymont answered impatiently.

  Telander sighed. “Come with me to the bridge, then. I’m too busy for special conferences.”

  A couple of others seemed to feel differently, but Reymont drove them off with a glare and a bark. Telander must perforce smile a bit as he went out the door. “You do have your uses,” he admitted.

  “A parliamentary hatchet man?” Reymont said. “I fear there’ll be more call on me than that.”

  “Conceivably on Beta Three. A specialist in rescue and disaster control might be welcome when we get there.”

  “You’re the one who’s concealing facts. Captain. You’re pretty badly shaken by what we’re driving into. I suspect our chances are not quite as good as you pretended. Right?”

  Telander looked around and did not reply until they were alone in the stairwell. He lowered his voice. “I simply don’t know. Nor does Fedoroff. No Bussard ship has been tested under conditions like those ahead of us. Obviously! We’ll either get by in reasonable shape or we’ll die. In the latter case, I don’t imagine it’ll be from radiation sickness. If any of that material penetrates the screens and hits us, it should wipe us out, a quick clean death. I saw no reason to ma
ke worse what hours remain for our people, by dwelling on that possibility.”

  Reymont scowled. “You overlook a third chance. We may survive, but in bad shape.”

  “How the devil could we?”

  “Hard to say. Perhaps we’ll take such a buffeting that personnel are killed. Key personnel, whom we can ill afford to lose … not that fifty is any great number.” Reymont brooded. Footsteps thudded in the mumble of energies. “They reacted well, on the whole,” he said. “They were picked for courage and coolness, along with health and intelligence. In a few instances, the picking may not have been entirely successful. Suppose we do find ourselves, let’s say, disabled. What next? How long will morale last, or sanity itself? I want to be ready to maintain discipline.”

  “In that connection,” Telander responded, cold once more, “please remember that you act under my orders and subject to the articles of the expedition.”

  “Damnation!” Reymont exploded. “What do you take me for? A would-be Mao? I’m requesting your authorization to deputize certain trustworthy men and prepare them quietly for emergencies. I’ll issue them weapons, stunner type only. If nothing goes wrong — or if something does but everybody behaves himself — what have we lost?”

  “Mutual trust,” the captain said.

  They had come to the bridge. Reymont entered with his companion, arguing further. Telander made a hacking gesture to shut him up and strode toward the control console. “Anything new?” he asked.

  “Yes. The instruments have begun to draw a density map,” Lindgren answered. She had flinched on seeing Reymont and spoke mechanically, not looking at him. “It is recommended—” She pointed to the screens and the latest printout.

  Telander studied them. “Hm. We can pass through a slightly less thick region of the nebula, it seems, if we generate a lateral vector by activating the Number Three and Four decelerators in conjunction with the entire accelerator system… A procedure with hazards of its own. This calls for discussion.” He flipped the intercom controls and spoke briefly to Fedoroff and Boudreau. “In the plotting room. On the double!”