Flux xs-3

by Stephen Baxter

  Farr frowned. Reluctantly he released the branch and pushed himself away. “You were? But I feel as if — as if I’m about to be pulled out of this tree…”

  “It’s called being frightened of falling.”

  “But that’s ridiculous. Isn’t it?” To Farr, “falling” meant losing your grip on the Magfield when Waving. It was always over in a few mansheights at the most — the tiny resistance of the Air and the currents induced in your skin soon slowed you down. Nothing to fear. And then you could just Wave your way around the Magfield to where you wanted to get to.

  Dura grinned. “It’s a feeling as if…” She hesitated. “…as if you could let go of this tree, right now, and not be able to stop yourself sliding down, across the Magfield and across the vortex lines, faster and faster, all the way to the Sea. And your belly clenches up at the prospect.”

  “That’s exactly it,” he said, wondering at how precise her description was. “What does it mean? Why should we feel like that?”

  She shrugged, plucking at a leaf. The heavy plate of flesh came free of its attaching branch with a sucking sound. “I don’t know. Logue used to say it’s something deep inside us. An instinct we carried with us, when humans were brought to this Star.”

  Farr thought about that. “Something to do with the Xeelee.”

  “Perhaps. Or something even older. In any event, it’s not something you need to worry about. Here.” She held out the leaf toward him.

  He took it from her cautiously. It was a bronze-gold plate, streaked radially with purple and blue, about as wide as a man’s hand. It was thick and pulpy — springy between his fingers — and, like the wood, was warm to the touch, although, away from its parent branch, it seemed to be cooling rapidly. He turned it over, prodding it with a fingertip; its underside was dry, almost black. He looked up at Dura. “Thanks,” he said. “What shall I do with it?”

  She laughed. “Try eating it.”

  After a cautious inspection of her face to make sure this wasn’t some kind of joke — Dura didn’t usually play tricks on him; she was a little too serious for that… but you never knew — Farr lifted the leaf to his lips and bit into it. The flesh of the leaf was thin, surprisingly insubstantial, and it seemed to melt against his tongue; but the taste it delivered was astonishingly sweet, like the meat of the youngest Air-piglet, and Farr found himself cramming his mouth.

  Within seconds he was swallowing the last of the leaf, savoring the lingering flavor on his tongue. It had been delicious but really quite light, and had done little but whet his hunger further. He looked around avidly. Here on the upper side of the treetop ceiling he could see the leaves turned downward toward the Quantum Sea, like a layer of broad, flattened child-faces. Farr reached down to pluck another leaf.

  Dura, laughing, restrained him. “Take it easy. Don’t strip the whole damn tree.”

  Around a full mouth Farr said, “It’s delicious.”

  She nodded. “I know. But it won’t fill your belly. Not unless you really do strip the tree… That’s why we have to hunt the Air-pigs, who eat the leaves — and the grass — for us.” She pursed her lips. Then, in a tone suddenly and, to Farr, shockingly similar to their lost father’s, she said, “Let’s have a little lesson. Why do you think the leaves are so tasty?”

  Farr thought about that. “Because they’re full of protons.”

  Dura nodded seriously. “Near enough. Actually they are laced with proton-rich isotopes — of krypton, strontium, zirconium, molybdenum… even a little heavy iron. Each nucleus of krypton, for instance, has a hundred and eighteen protons, while the tin nuclei of our bodies have just fifty each. And our bodies need protons for their fuel.” The heavy nuclei fissioned in human stomachs. Protons combined with neutrons from the Air to make more tin nuclei — tin was the most stable nucleus in the Air — and gave off energy in the process. “Now. Where does the proton-rich material come from?”

  “From the Crust.” He smiled. “Everyone knows that.”

  The Crust, no more substantial than Air, was a gossamer solid. Its outermost layer was composed of iron nuclei. Further in, steepening pressures drove neutrons into the nuclei of the solid, forming increasingly heavy isotopes… until the nuclei became so soft that their proton distributions began to overlap, and the neutrons dripped out to form the Air, a superfluid of neutrons.

  “All right,” said Dura. “So how do the isotopes get all the way from the Crust to these leaves?”

  “That’s easy,” Farr said, reaching to pluck another succulent leaf. “The tree pulls them down, inside its trunk.”

  “Using veins filled with Air. Right.”

  Farr frowned, feeling his cheeks bulge around the leaf. “But why? What’s in it for the tree?”

  Dura’s mouth opened and closed, and then she smiled, her eyes half-closed. “That’s a good question,” she said. “One I wouldn’t have thought of at your age… The isotopes make the leaves more opaque to the neutrinos shining out of the Quantum Sea.”

  Farr nodded, chewing.

  A flood of neutrinos, intangible and invisible, shone continually from the Sea — or perhaps from the mysterious Core deep beneath the Sea itself — and sleeted through the vortex lines, through the bodies of Farr and the other humans as if they were ghosts, and through the Crust to space. The trees turned slightly neutrino-opaque leaves to that unseen light, absorbing its energy and turning it into more leaves, branches, trunk. Farr pictured trees all over the interior of the Crust, straining toward the Sealight with their leaves of krypton, strontium and molybdenum.

  Dura watched him eat for a moment; then, hesitantly, she reached out to ruffle his hair-tubes. “I’ll tell you a secret,” she said.

  “What?”

  “I’m glad you’re here.”

  Briefly he considered pushing her hand away, of saying something funny, or cruel, to break up the embarrassing moment. But something made him hold back. He studied her face. It was a strong face, he supposed, square and symmetrical, with small, piercing eyes and shining yellow nostrils. Not beautiful, but with something of the strength of their father; and now with the first lines of age it was acquiring a bit more depth.

  But there was uncertainty in that face. Loneliness. Indecision, a need for comfort.

  Farr thought about it. He felt safe with Dura. Not as safe as when Logue was alive… But, he thought ruefully, as safe as he would ever feel again. Dura wasn’t really all that strong, but she did her best.

  And this moment, as the others moved away from them, being together and talking quietly and tasting the leaves, seemed to be important to her. So he said, gruffly: “Yes. Me too.”

  She smiled at him, then bent to pluck a leaf for herself.

  * * *

  Adda slid silently through the treetops, following the circumference of a rough circle twenty mansheights wide. Then he moved a little further up into the suspended forest, working parallel to the lines of the trunks. The trees grew along the Magfield flux lines, and he kept his spear pointing along the Magfield as he worked his way along the smooth bark.

  Save for the low, tinkling rustle of the leaves, the subdued talk of his companions, he found only silence.

  He pulled himself back along the length of the tree trunk to the inverted canopy of leaves. None of the Human Beings — except, maybe, Logue’s boy Farr, who was looking a little lost — had even noticed he’d been absent. Adda relaxed a little, munching on the thin, deceptively tasty meat of a leaf. But he kept his good eye wide open.

  The Human Beings were bunched together around one trunk, nibbling leaves desultorily and clinging, one-handed, to branchlets. They were huddled together for warmth. Here, where the Air was attenuated by height, it was cold and hard to breathe: so hard, in fact, that Adda felt his reflexes — his very thinking — slowing down, turning sluggish. And it wasn’t as if he had a lot of margin in that area, he reflected. It was as if the very Air which drove his bones was turning to a thin, sour soup.

  The boy Farr was cr
ouched against a section of bark a mansheight or so from everyone else. He looked as if he were suffering a bit: visibly shivering, his chest rising and falling rapidly in the attenuated Air, his hands pushing leaves into his downturned mouth with an urgency that looked more like a craving for comfort than for food.

  Adda, with a single flip of his legs, Waved briskly over to the boy; he leaned toward Farr and winked with his good eye. “How are you doing?”

  The boy looked up at him, lethargic despite the shivering, and his voice, when he spoke, was deepened by the cold. “I can’t seem to get warm.”

  Adda sniffed. “That’s the way it is, up here. The Air’s too thin for us, see. And if you go higher, toward the Crust, it gets thinner still. But there’s no need to be cold.”

  Farr frowned. “What do you mean?”

  For answer Adda grinned. He raised his spear of hardened wood and aligned it parallel to the tree trunk, along the direction of the Magfield flux lines. He hefted it for a few seconds, feeling its springy tension. Then he said, “Watch and remember.”

  The boy, eyeing the quivering spear with wide eyes, scrambled back out of the way.

  Adda braced himself against the Magfield. With a single movement — he remained lithe in spite of everything, Adda congratulated himself — Adda thrust the spearpoint deep into the bulk of the tree. The first stab took the spearpoint through the bark and perhaps a hand’s length into the wood. By working the haft of the spear, twisting it in his hands, Adda was able to drive the spear further into the flesh of the branch, to perhaps half an arm’s length.

  That done, feeling his chest drag at the thin Air, Adda turned to make sure Farr was still watching. “Now,” he rasped. “Now comes the magic.”

  He twisted in the Air and placed his feet against the branch, close to the line of his half-buried spear. Then he bent and wrapped both hands around the protruding shaft of the spear, squatted so that his legs were bent and his back was straight, and heaved upward, using the spear as a lever to prize open the wood of the branch.

  …Actually it was a long time since he’d done this, he realized a few heartbeats after starting. His palms grew slick with superfluid sweat, a steady ache spread along his back, and for some reason the vision of his good eye was starting to tremble and blur. And, though the spear bowed upward a bit as he strained, the branch did little more than groan coldly.

  He let go of the spear and wiped his palms against his thighs, feeling the breath rattle in his chest. He carefully avoided eye contact with the boy.

  Then he bent to the spear again.

  This time, at last, the branch gave way; a plate of it the size of his chest yielded and lifted up like a lid. Adda felt his aching legs spring straight, and he tumbled away from the branch. Quickly recovering his dignity, he twisted in the Air, ignoring the protests from his back and legs, and Waved back to Farr and the opened branch. He looked down at his handiwork appraisingly and nodded. “Not as difficult as it looks,” he growled at the boy. “Used to do that one-handed… But trees have got tougher since I was your age. Maybe something to do with this damn spin weather.”

  But Farr wasn’t listening; he crept forward to the wound in the branch and stared into it with fascination. Close to the rim of the ripped bark the wood was a pale yellow, the material looking much like that of the spear Adda had used. But further in, deeper than a hand’s length, the wood was glowing green and emitting a warmth which — even from half a mansheight away — Adda could feel as a comforting, tangible presence against his chest. The glow of the wood sparkled against Farr’s face and evoked verdant shadows within his round eyes.

  Dura, Logue’s ungainly daughter, joined them now; she shot a brief smile of thanks to Adda as she crouched beside her brother and raised her palms to the warmth of the wood. The green fire scattered highlights from her limbs and face which made her look, Adda thought charitably, half-attractive for once. As long as she didn’t move about too much and reveal her total lack of grace, anyway.

  Dura said to Farr, “Another lesson. What’s making the wood burn?”

  He smiled at her, eyecups full of wood-glow. “Heavy stuff from the Crust?”

  “Yes.” She leaned toward Farr so that the heads of brother and sister were side by side over the glowing wood, their faces shining like two leaves. Dura went on, “Proton-rich nuclei on their way to the leaves. The tree branch is like a casing, you see, enclosing a tube where the pressure is lower than the Air. But when the casing is breached the heavy nuclei inside fission, decaying rapidly. What you’re seeing is nuclei burning into the Air…”

  Adda saw how Farr’s smooth young face creased with concentration as he absorbed this new bit of useless knowledge.

  Useless?

  Well, maybe, he thought; but these precious, abstract facts, polished by retelling and handed down from the earliest days of the Human Beings — from the time of their expulsion from Parz City, ten generations ago — were treasures. Part of what made them human.

  So Adda nodded approvingly at Dura and her attempts to educate her brother. The Human Beings had been thrust into this upflux wilderness against their will. But they were not savages, or animals; they had remained civilized people. Why, some of them could even read; a handful of books scraped painfully onto scrolls of pigskin with styli of wood were among the Human Beings’ principal treasures…

  He leaned toward Dura and said quietly, “You’ll have to go on, you know. Deeper into the forest, toward the Crust.”

  Dura started. She pulled away from the trunk-wound, the light of the burning nuclei shining from the long muscles of her neck. The other Human Beings, a few mansheights away, were still clustered about the treetops; most of them, having crammed their bellies full, were gathering armfuls of the succulent leaves. She said, “I know. But most of them want to go back to the camp already, with their leaves.”

  Adda sniffed. “Then they’re damn fools, and it’s a shame the spin weather didn’t take them instead of a few with more sense. Leaves taste good but they don’t fill a belly.”

  “No. I know.” She sighed and rubbed the bridge of her nose, ran a finger around the rim of one eyecup absently. “And we have to replace the Air-pigs we lost in the spin storm.”

  “Which means going on,” Adda said.

  She said with a weary irritation, “You don’t need to tell me, Adda.”

  “You’ll have to lead them. They won’t go by themselves; folk aren’t like that. They’re like Air-pigs: all wanting to follow the leader but none wanting to lead.”

  “They won’t follow me. I’m not my father.”

  Adda shrugged. “They won’t follow anyone else.” He studied her square face, seeing the doubts and submerged strength in its thin lines. “I don’t think you really have a choice.”

  “No,” she sighed, straightening up. “I know.” She went to talk to the tribesfolk.

  When she returned to the nuclear fire, only Philas, the widow of Esk, came with her. The two women Waved side by side. Dura’s face was averted, apparently riven with embarrassment; Philas’s expression was empty.

  Adda wasn’t really surprised at the reaction of the rest. Even when it was against their own damn interest, they’d snub Logue’s daughter.

  He was interested to see Philas with Dura, though. Everyone had known about Dura’s relationship with Esk; it was hardly the sort of thing that could be kept quiet in a community reduced to fifty people, counting the kids.

  It had been against the rules. Sort of. But it was tolerated, and hardly unique — as long as Dura obeyed a few unspoken conventions. Such as restricting her reaction to Esk’s death, keeping herself away from the widowed Philas.

  Just another bit of stupidity, Adda thought. The Human Beings had once numbered hundreds — even in the days of Adda’s grandfather there had been over a hundred adults — and maybe then conventions about adultery might have made sense. But not now.

  He shook his head. Adda had despaired of Human Beings long before Farr was born.r />
  “They want to go back,” said Dura, her voice flat. “But I’ll go on. Philas will come.”

  The woman Philas, her face drab and empty, her hair lying limply against her angular skull, looked to Adda as if she had nothing left to lose anyway. Well, he thought, if it helped the two women work out their own relationship, then fine.

  Some hunting expedition it was going to be, though.

  He lifted his spear.

  Dura frowned. “No,” she said. “I can’t ask you to…”

  Adda growled a soft warning to shut her up.

  Farr straightened up from the burning pit. “I’ll come too,” he said brightly, his face turned up to Dura.

  Dura placed her hands on his shoulders. “Now, that’s ridiculous,” she said in a parent’s tones. “You know you’re too young to…”

  Farr responded with bleated protests, but Adda cut across him impatiently. “Let the boy come,” he rasped to Dura. “You think he’d be safer with those leaf-gatherers? Or back at the place where the Net used to be?”

  Dura’s anxious face swiveled from Adda to her brother and back again. At length she sighed, smoothing back her hair. “All right. Let’s go.”

  They gathered their simple equipment. Dura knotted a length of rope around her waist and tucked a short stabbing-knife and cleaning brush into the rope, behind her back; she tied a small bag of food to the rope.

  Then, without another word to the others, the four of them — Adda, Dura, Farr and the widow Philas — began the slow, careful climb toward the darkness of the Crust.

  3

  They moved in silence.

  At first Dura found the motion easy. The tree slid beneath her, almost featureless, slowly widening as she climbed up its length. The tree trunk grew along the direction of the Magfield, and so moving along it meant moving in the easiest direction, parallel to the Magfield, with the superfluid Air offering hardly any resistance. It was barely necessary to Wave; Dura found it was enough to push at the smooth, warm bark with her hands.