Year Four

Nine-tenths of a light-year distant, the sun of Tahir stood lord among the stars. But it was another point of light that vision sought, nearly as bright as Sirius in the skies of Earth. Enhancing every other stellar image, the screen mildened this one, for it would have burned a hole in the retina of a naked eye.

"One millionth Solar luminosity," Dayan said like a prayer to a pitiless god, "shining from a body ten kilometers in diameter. Therefore nineteen thousand times the intensity; and that's just in the visible spectrum."

Her companions could well-nigh hear the thoughts prowling through her. The core of an exploded giant sun, a mass almost half again Sol's, jammed down by its own gravity till it's that small, that dense, no longer atoms but sheer neutrons, except that at the center the density may go so high that neutrons themselves fuse into something else, hyperons, about which we know little and I lust to know more. An atmosphere a few centimeters deep — incandescent gaseous iron? What storms go rampant through it, what quakes rack the ultimate hardness beneath, and why, why, why? A spin of hundreds per second, a magnetic field that seizes the interstellar matter and whips it outward till it nears the speed of light, kindles a radio beacon with it that detectors can find across the breadth of the galaxy. O might and mystery! Out of the whirlwind, God speaks to Job.

Cleland's voice trembled. "How close dare we come?"

"The ship will decide," Dayan answered, her tone flat, her mind still at the star. "Not very, I think. It's blazing X-rays, spitting plasma and neutrinos — lethal."

"Besides," Brent put in dryly, "we're at about two hundred AU now. Another jump in that direction, and we'd certainly fry."

"But we're no so far frae the planet we ken, are we?" Kilbirnie cried. "We'll tak' our station 'round it, no?" And explore it, said the glance she exchanged with Cleland.

Of the three Tahirians, Colin and Fernando stared as raptly at the object of the quest — and beyond it, into the cold cataract of the Milky Way? Leo stood aside, ens mane held stiff. The powers on Tahir, whoever they were and whatever their power meant, had required that a person whom they would pick come along to observe.

The spaceboat was not intended for humans. There was no way Envoy could have carried it or any of its kind on her expedition. Not only the hull docks but the entire control system would have had to be rebuilt, which would have caused dangerous instabilities elsewhere in the robotic complex that she was. Improvised facilities — for security, sanitation, nourishment, sleep — enabled humans to go as passengers in the boat. Lately Yu and the Tahirian physicist Esther had jerry-rigged circuits that allowed a skillful human to act as pilot — temporarily, under free-space conditions with plenty of safety margin.

"Hoo-ah!"

Ruszek tickled the board before him. The craft leaped. Nonetheless, weight inside held steady. The moon loomed enormous in sight, a sweep of smooth-fused stone studded with structures, curving sharply to a near horizon. Ruszek cut the drive. Zero gravity felt like an abrupt fall off a cliff. The three aboard had learned to take it as a bird does. The boat swung low around the globe on a hyperbolic hairpin and lined out for the great blue crescent of Tahir.

"That will do," said Yu from aft. "Let us return."

"Jarvany," grumbled Ruszek. "I hoped for more of this." His tone was genial, though, and a smile bent his mustache toward his brows.

Harnessed beside Yu, Esther asked, "(Did you record the data you need?)" En quivered and fluted; sweet odors wafted from the skin.

Yu nodded. "(I believe so.)"

"What's the result?" called Ruszek, whose back was to them.

"Excellent," Yu replied. "I think once I have analyzed these readings, with Esther's help, I will know how the field drive operates."

"You don't? I mean, uh, you told me before, you're sure it's a push against the vacuum."

Yu sighed. "An interaction with the virtual particles of the vacuum," she corrected. "Energy and momentum are conserved, but, loosely speaking, the reaction is against the mass of the entire universe, and approximately uniform. What I referred to was understanding the exact, not the general, principle."

"Uniform? Don't they adjust the field inside a hull? Weight's the same during any boost."

"In quantum increments, obviously." Yu paused. "Compared to this drive, jets are as wasteful as ... as burning petroleum, chemical feedstock, for fuel once was on Earth."

"What I like is the handling qualities. How soon can you and your computer design a motor for us, Wenji?"

"Not at all, I fear, until we're home. Besides, we couldn't possibly do so radical a retrofit on Envoy, or even her boats." Yu's voice lilted. "However, I think, with Hanny's help when she gets back, we can devise a unit that will compensate for linear acceleration and keep the vector in the wheels constant."

"Do you mean, when the ship's under boost, we won't have to cram like swine onto those manhater-designed gimbal decks?" Ruszek waved clasped hands above his shining pate. "Huzzah!" he bellowed.

Esther looked at ens friend. "(Does he rejoice?)" en asked; or so Yu thought en asked.

"(It is no large matter,)" the engineer replied. "(What I think we have really done, at last, is break some dams of misunderstanding. Now you and I can add a proper language of physics to Cambiante, and have it ready for Hanny Dayan when she returns. Before then, you should be able to explain some things to us. Hints of a strange, tremendous truth — )"

Her gaze went ahead, to the planet, where spring was gusting over Terralina.

Envoy rode as at anchor, circling a world of steel.

Cleland and Kilbirnie stood before the spaceview on a screen. Already their shipmates were busy. Robots would flit out to place instruments in orbit; Tahirian probes with Tahirian field drives would plunge toward the pulsar, wildly accelerated, bearing other instruments; preparations filled every waking hour and haunted many dreams. These two alone had little to contribute. Their yearnings reached elsewhere.

In the light from the heavens, the globe was barely bright enough for the unaided eye to search. Its plains were like vast, murky mirrors, mottled with ice fields. Gashes broke them here and there. Mountain ranges and isolated peaks thrust raw-edged. The limb arched slightly blurred against the stars.

"Mass about half Earth's, diameter about seventy percent — given the mean density, more or less the same surface gravity." Cleland was repeating what they had both heard a dozen times, as humans will when the matter is important. "Thin atmosphere, mostly neon, some hydrogen and helium retained at this temperature. Other volatiles frozen out, including water. Paradox, paradox. What's the answer?"

"What do you mean, Tim?" Kilbirnie asked. It was chiefly to encourage him — she had a fairly good idea — but she hoped for thoughts he might have had since the last general discussion. God is in the details, she reflected. And so is the devil, and the truth somewhere in between.

When he was into an enthusiasm he spoke fluently. "Look, we know this has to be the remnant of a bigger planet. The supernova vaporized the crust and mantle, left just the core and maybe not all of that. The loss of star mass caused it to spiral out into this crazy orbit it's got now. Meanwhile, taking off the upper layers released pressures — expansion, eruption, all hell run loose. It hasn't stabilized yet, I suspect. What's going on? Theoretically, it should be a smooth ball, but nonlinear processes don't pay much attention to theory, and so we've got rifts, grabens, highlands. How? Where did it get the atmosphere and ice — outgassing, cometary impacts, infall from the supernova cloud, or what? Oh, Jean, a million questions!"

She gripped his hand. "We'll go after the answers," she said, "yonder."

No doubt Dayan, the acting captain, would object, and still more would Envoy's robotic judgment. Kilbirnie's thought coursed about in search of arguments, demands, ways to override opposition: anything short of mutiny. She had not come this far, leaving her true captain behind her, to sit idle in a metal shell.

Summer heat lay on the settlement like a weight. Forest stood windless, listless beneath a leaden overcast. Thunder muttered afar.

Windows were not opaquable, but Nansen had drawn blinds over his and the air conditioning worked hard. In the dusk of the living room, a crystal sphere, a Tahirian viewer, shone cool white. Within it appeared the image of a being. Nansen leaned close. The form was bipedal, slanted forward, counterbalanced by a long, thick tail. From beneath a scaly garment reached clawlike hands and a hairless, lobate, greenish head. The effect was not repulsive, simply foreign.

"(I show you this,)" wrote the parleur of the Tahirian he called Peter, while attitudes and odors gave overtones he was beginning to interpret, "(because somehow, in your company, command flows through you. Later we will talk, and then you can decide what your others shall learn.)"

"(Everything,)" Nansen replied. I can't explain about tact, discretion, timing, especially when four of us are off beyond reach. (Jean, what are you doing as I sit here, how do you fare?)

He sensed grimness. "(Yes, you are free with information, whatever the hazard. Most of us would have kept knowledge of the black hole from you, for fear of what reckless things you may do. Too late.)"

Inevitable that that incident become known, I suppose. No mention of punishment Emil and the rest go about as freely as ever. A consensus society? What are the sanctions?

Maybe none were needed, only the slightest social pressures, until we came. The powers that be don't know how to handle us.

As if en had read the thought, Peter said, "(Yours is the second starfaring race we have encountered. Now that communication is acceptably clear, I will tell you of the first.)"

Nansen steadied his mind.

"(Their nearest outpost was about three hundred light-years from Tahir, their home world twice as far,)" Peter said. "(As with you, the trails of their ships inspired our scientists and called our explorers — although for us the development took much longer than yours did. Already those trails were dwindling away. By the time we arrived, the beings had ended their ventures and withdrawn to their parent planet.)"

Nansen felt a chill in his flesh. "(Did you find out why?)"

"(We believe we did. Communication with such alien mentalities was slow and difficult. Your resemblance to us, however tenuous, is greater by orders of magnitude. They are communal creatures, descendants — we theorize — of animals that dwelt together in burrows, in large numbers, with just a few breeders of the young-bearing sex.)"

That experience might account for the Tahirians' eventual grasp of the roles of men and women, Nansen reflected. He also noted that Peter had not used the symbol for "female." Doubtless the analogy was not exact.

"(Their whole culture, identity itself, resides in the kin group,)" Peter went on. "(It is remarkable that they finally achieved a global civilization. We think electronic data processing and communications made it possible.

"(Over time, starship crews and even colonies proved insufficient to maintain it. Numbers were too few for mental health, contact with other nests too weak and sporadic for social ties. Madness(?) ensued, cultures twisted, destructive, evil(?). Some went extinct, through internecine conflicts that destroyed their basis of existence. One lashed out across interstellar space, and a continent was laid in radioactive ruin. Finally the sane core of the race succeeded in quelling the mad and recalling the survivors. Slowly they settled down into the peace that still prevailed when our last expedition visited them.)"

Peter blanked the view, as though the sight was too painful, and stood motionless. Nansen sank back in his chair, shaken. Thunder rolled closer.

"Tragico," the man muttered, for Cambiante had not yet found an utterance for that concept and perhaps Tahirians had never had it. He turned to his parleur. "(They were unfit for starfaring.)"

Peter's mane bristled more than was needful to convey ens feelings. "(In a sense, every race is. We have seen several other, more distant signs of it fading. A new one has sprung up in the past three thousand years, but we expect it will likewise prove mortal.)"

"(Why?)"

"(Probably always the cost becomes too great for the gain. The nature of the highest, least bearable cost may well vary from race to race, but in the end, either necessity or wisdom will call a halt, and starfaring will have been no more than an episode in the history of a planet's life.)"

Nansen's grip tightened on his parleur. "(Ours will not.)"

"(It should, on moral(?) grounds alone. What we have learned of your past, the cruelty(?) and slaughter, fills us with horror. Best for you as well as for the cosmos that you retire and study how to live with yourselves.)"

Nansen bit his lip but responded with the calm that this mode of discourse usually enforced. "(Are you afraid of us? We would never threaten you. How could we, across the gap between? Why should we?)"

"(You are already a threat. By your very existence.)"

"(I do not understand.)"

"(You have made some among us eager to travel anew, regardless of the infinite danger. The sane wish you would go away.)"

Nansen hesitated before asking outright, "(You cannot simply kill us, can you?)"

Peter flinched. A rank smell, like acid on iron, blew from en. "(That you can imagine that exemplifies the horror.)"

"(Have you and those who think like you absolutely never even considered it?)"

Peter seemed to draw on some inner source of composure. "(It would be counterproductive, an act almost as destabilizing as your presence.)"

So Tahirian society isn't as perfectly balanced as it seemed, Nansen thought.

"(Only go away,)" Peter said. "(We ask it of you, who have not treated you ill.)"

The plea touched Nansen and eased him a little. "(We plan to leave in another three (Tahirian) years, you know.)"

"(Will you? And what of those who may come afterward? What of your whole ruthless(?), willful race?)"

"(We few cannot speak for all.)" All who are to live after us.

"(Yes, that is part of what makes you terrible.)"

Resolution rose. Peter's torso drew erect. The middle eyes speared Nansen's. "(It is well, it is like providence(?), that wherever starfaring has begun, in a cosmically short time it has died,)" en said. "(The causes are surely many; but through them, does reality preserve itself?

"(I cannot now say more. You would not believe me. I am not versed in the subject. First, under proper tutelage, you must learn how to read the mathematical proof. You shall. Then your voyage here will have been not for harm but for good. You will bring a message back to your people and make them, too, call their ships home forever.)"