by Larry Niven
Ali smiled. “Yes, Rachel. Just watch. Gabriel had to make the crater taller and thicker twice just to contain the force of the water and tides.”
“You made this? I thought you oversaw the planting.”
“I do oversee the planting. But first I designed Selene. Someone had to bring water in for the plants.”
“Duh,” Harry said.
“So you just . . . made . . . the Hammered Sea? All by yourself?” Rachel was eyeing the far side, looking between Gabriel and the huge sea in front of her.
Ali laughed again, louder, her head thrown back. “I wouldn’t underestimate Gabriel if I were you, Rachel.”
Gabriel tried to look stern. It had been hard to shape this sea. He was proud enough to babble some. “I had help, of course. Mostly from a really smart program named Astronaut.”
Ali glared at him. Her parents had died on Jupiter Station when the AI that ran it lost interest. Ali didn’t like AIs.
“Ali helped too.” He sighed. Time to teach. They only knew part of the story. “There wasn’t any Selene when we came here. There was an oversized gas giant planet, Harlequin, and almost a hundred moons. We picked a big moon for a foundation. It had no spin—no day or night with reference to Harlequin. We made that, hitting it over and over in the same place, from the same angle, making tilt and spin. Days and seasons. Building Selene. Then we—went—cold—for a long time, to let the whole system stabilize and cool.
“We woke up to a pockmarked ball covered in regolith. There was a little ice, a few small pockets of underground water, and the beginnings of an atmosphere, but humans need lots of easy-to-reach water, and thick atmosphere to shield us from space. So we brought in comets. Then we went cold again. Then we brought in more comets. The comets gave us the water you see here.”
“So the water is from space?” Rachel asked.
“Isn’t everything? This deep sea is the motor that drives Selene’s hydrology. We need this much water for the humidity to grow tropical plants rather than cactus. But we had to contain most of the water to limit the effect of the tides, which are worse here than on Earth, because of Harlequin.” He pointed at the gas giant, which hung just off center in the sky. “Gravity pulls the water toward Harlequin. If we didn’t contain it, Selene would be flooded with every high tide. We could have made hundreds of small seas instead of what we did make; the Hammered Sea and Erika’s Folly, but they would have been harder to manage. Oh, lots of craters have a little water in them, but over half our water is right here.” He paused, and said, “Besides, I wanted to make a real sea.” That made him feel giddy still: to build a sea because he wanted to! “Feel the damp wind on your face, Rachel?”
She nodded, holding her arms over the sea below them.
“It blows up the crater walls, carrying water vapor. It’s cooler than the air it meets on the far side. It would stay inside the crater and rain here, except we’ve built paths for it to funnel through. So we drive the rain to fall mostly outside the Hammered Sea, where it fills streams. We have pumps that take care of it when Selene doesn’t, a backup system that sends water through the crater walls to fill the streams. We used the out-pumps a lot, early on. But we haven’t had to use them for years—we test them every month, but I dunk we could turn them off if we wanted to.” Gabriel waited a bit for the children to find one of the huge pipes. They were hard to spot, colored like the crater for camouflage. Erika had insisted on that. He and Erika had argued for months over the costs and time involved, but now, with this view, he was glad Erika had won.
“That’s brute force engineering—the pipes. Real terraforming, with a whole planet and tectonics, would use temperature and humidity and wind. Selene doesn’t have the raw materials to do it right.” He turned around and pointed down slope behind them. “The gentle angle of the outside walls, here, what we just climbed, drains the water to the plains you see below, and there some of it subducts. We capture that water and pump it back into the sea. The remaining water moves through surface streams, some of which we channel into engineered viaducts, like the Aldrin viaduct. The water we use in Aldrin comes from here. Other viaducts carry water back here eventually. That’s the hard part—we may never get the water back into the Hammered Sea without the in-pumps.” He paused to let the children absorb the beauty of Selene’s hydrological engineering.
“Some of the viaducts are open. You made those deep enough that the water stays in,” Harry said. “I saw some on the way over here.”
Harry would make a good engineer someday. “I like the open design. It encourages water evaporation, increases humidity.”
Ali picked up where Gabriel left off. “It’s the water cycle that determines where we live and plant, where we place our cities. The first engineering we do anywhere is for water. We picked Aldrin for a major base because it is far from here. That makes it safer. Imagine a quake big enough to break down a crater wall and let the water loose? All the water in the Hammered Sea? Remember, it’s kilometers deep.”
“So why did you build Clarke Base?” Ursula asked.
“So they can make what they need to keep the Hammered Sea working,” Harry said.
Ursula stuck her tongue out at Harry’s back.
Gabriel grinned. “Largely right, Harry. Think of it as a huge dam.” He noticed the puzzled looks on their faces. “Okay—a huge machine. It needs people to maintain it, to fix it if it breaks, and even more, to be sure it doesn’t break. We grow fruit and vegetables here on the plain, where there’s water. So Clarke Base is a food production plant and a maintenance shop. This is also where we make the planters and planes and some of the other machines you see and use.”
“Don’t you make almost everything on John Glenn?” Ursula asked.
“Well, when we started,” Ali said. “But even John Glenn is too small to make everything we need for Selene. It’s hard to move heavy things between the ship and here—and we don’t need to.”
“How do you make so many miles of pipe?” Harry asked.
Gabriel frowned and looked at Ali, who licked her lip and said, “We use nanocytes,” as if it were a dirty word. “Trillions of tiny machines. Just for raw materials,” she qualified. The children looked puzzled.
“Someday I’ll show you,” Gabriel said, turning toward Harry. “So, do you understand the basics of our hydrology?”
“It’s nice to see it. I understand it better than when you first told me.”
“The cycle will vary as we get more plant cover. That’s the beauty of a self-regulating system; we both watch for change and cause change. Terraforming is one long search for balance. We can tweak the system—generate wind if we need it over the lake, affect the surface temperature—there’s a soletta in geostationary orbit—”
Harry interrupted. “Soletta?”
“The soletta is a bank of mirrors that focuses light from Apollo onto Selene, increasing the insolation—the light level from Apollo. We can turn mirrors on or off to affect insolation and tweak the temperature and energy supply. It’s working so well it’s been virtually automatic longer than you’ve been alive.”
“Which isn’t very long,” Ali said dryly. “And it was a fight. Gabriel has had to rebuild the touchy thing twice so far. Once a single asteroid from a swarm got past our defenses and smashed the mirrors to shards. There wasn’t much atmosphere yet, so some of them made it to the surface. Wear shoes!”
Gabriel laughed. “You’d have to dig pretty far to find any remains of that glass.”
Ali went on, unfazed. “Oh, and the second time, it just disappeared. Just flat disappeared. We were all cold, one of our long down times. Astronaut woke me up to say there was nothing there. Astronaut didn’t see it happen: Selene was between John Glenn and the soletta when it disappeared. The soletta might be the single most fragile part of our whole system. But without it, we couldn’t regulate temperature, and Selene would get too cold to live on.”
“Did you help him rebuild it?” Ursula asked Ali.
“I was
cold. Erika did that.”
“I haven’t met Erika,” Rachel observed. “Where is she?”
“Cold,” Gabriel muttered.
Rachel turned her eyes on Gabriel, and he saw pain flash across them. “Like Mom?” she asked.
Ali’s answer was sharp. “We don’t know about your mom. Be patient.”
Rachel’s jaws clenched. She looked down into the crater as if she could see the bottom.
They brought out water bottles and lapsed into uncomfortable silence. Harlequin was almost straight above them now. “Can you see the water rising?” Gabriel asked.
“At the edges?” Rachel replied.
“The whole sea will be affected. A tide is a response to gravity—all of Selene feels the pull of Harlequin; the elasticity of water illustrates it.”
Water crept up the sides of the great bowl below them. Rocks were slowly dampened by wind spray, and then submerged in rising waves.
Gabriel had seen this hundreds of times. He watched the children. He wanted them awed. Rachel and Harry stood side by side, both rapt and fully attentive. Ursula was on Rachel’s far side, farther back, still sitting, craning her neck to see into the crater without being near the edge.
Gabriel leaned back, looking up at the gas giant overhead. The ring, of course, was edge on to him, bisecting the planet. A huge storm tracked slowly across the surface, the fractal edges of its motion lulling him into a near trance state. Ali’s voice was backdrop; talk about tidal pulls and bulges. He heard her explain that most moons were tidally locked, that Selene’s core had been once, and Selene would be again. Finally, he heard Rachel point out that the water level was falling. He took a deep breath and stood up, strapping on his wings.
They all stood at the edge, backs to the sea, and looked down over the long slope of the outside crater rim between silver threads of waterfall. White and red rock filled with pillows of pumice crunched under their feet. Below them was rocky ledge after rocky ledge; then, starting nearly a third of the way down, a gentle slope turning greener as it flowed into checkered fields.
One by one they ran and leaped up, snapping wings open in time to start the long flight down to Clarke Base. The children rose high in the thermals, almost immediately, circling and swooping and chasing each other. Gabriel finessed his glide, letting his mind go completely into the flight, focusing on small muscles and tiny changes in air and wind. Calculations and vectors flowed in his head, and he followed them as best he could, changing the tilt of his legs or arms to follow the places his mind said he could take the flight, working to gain the most lift and speed from minute motions. He laughed to hear Rachel taunting Ursula, driving her to reach higher, higher.
Gabriel and Ali lagged behind, evaluating the children’s flight.
The teens stopped halfway down the long slope. They hadn’t even bothered to tell Gabriel or Ali. Gabriel used his radio to talk to Ali. “Let’s lurk a bit behind them, and see if they get concerned.”
Ali landed just ahead of him, graceful and quick as she swept her wings closed. They settled above the children, out of sight, and Gabriel released a camera-bot with instructions to hover above and behind the kids.
Ali looked worried, a small frown furrowing her brow. He guessed at her worry. “Rachel asked about her mom after the flare. What’s this about Rachel’s mother? Why did you tell her you can’t find out what happened from here?”
“I checked the records.” Ali’s mouth was a tight line, and her eyes hugged the horizon.
“And?”
“She doesn’t want to come back.”
“We can’t tell Rachel that,” he said.
“You should,” Ali said quietly.
“When she’s older.”
“Why not now? The girl deserves some honesty—this is important to her.”
“This isn’t a good time to upset her,” Gabriel said.
“Better the sting of truth than a long painful uncertainty. Besides, we shouldn’t try to control her world. She has to hear hard things to grow. You can’t terraform people.”
Gabriel bit his tongue. “I’d like to talk to her mother first. Is she awake?”
“She’s cold.”
Gabriel changed the subject. “Have you checked on Andrew?”
“No new damage today.”
“We should never have given Andrew that second chance. It was a bad lesson for the others.”
He was surprised to feel Ali lean into him, laughing, her serious demeanor broken. His mood didn’t match hers, but he stripped wing gear from one arm anyway and laid it over her shoulders, asking, “What’s gotten into you?”
“You’re trying to control them. They’re people, not stones or air.”
“Picture . . . Andrew moving a little moon when he gets a temper tantrum.”
“Another sea in the wrong place? Andrew’s Hissy Fit?” She tugged his braid. “They’ll never get access to LPTs anyway. What about Andrew, though? Isn’t he just a teenager pushing boundaries?”
Gabriel had shown Ali Andrew’s destructive streak, what he’d done after they left. “He’s refusing to learn discipline. We can’t afford to let him run free—there’s no time to babysit him.”
“I mean, look, he’s just a kid. We were right to give him a chance; we’re right to limit him now. I meant it when I said I’d support you.” Ali’s black braid across his knees contrasted with the grays and reds of the slope as it fell away behind her. “But you still need to give them time to think for themselves. They have to be able to live after we’re gone.” Ali’s voice was angry again. “Why are we even doing this?”
“Ask the damned High Council. Remember, I argued to use nano to build the assembler in space.” Ali hated nano. She should remember that none of the choices were good.
CHAPTER 6
STAR SYSTEMS
RACHEL WATCHED OUT the window as they flew into Aldrin early the next morning. They landed just outside the city, Apollo’s sunrise brightening the cloth tents just enough to make out color and shadow. She squeezed Ursula’s hand briefly and they darted down the path toward home together. It seemed to take a long time to get there. Ursula peeled off for her home, and Rachel ducked into her doorway, smelling warm rice and eggs as she buried herself in her father’s chest, filling his arms. She hadn’t been gone long, not really, but she felt taller, more his size.
He pushed her back from him, frowning. “You’d better go on up to the grove.”
“What? Why?”
“I think you’ll need to see for yourself.”
Gabriel stood by her final project. She ran up to him, then stopped, drew her breath in sharply. A broad swath of trees had been mowed down, driven over. Broken trunks littered the ground, dried and twisted, the life gone from them. It must have happened right after they left.
Almost half of Rachel’s project and a snippet of Ursula’s plot destroyed. Clearly someone had driven a work tractor through the grove. Tire tracks ran straight through, and in one place it looked like a blade had been let down and actually dug below ground. Pods and dirt and snapped seedlings mixed in a pile.
She knelt in the carnage, sweeping her hands back and forth through the dry dirt, picking out dead twigs and breathing in little gulps.
“Andrew,” she said, narrowing her eyes, fighting at the anger rising in her.
“Yes.”
“Why didn’t you tell me?”
“You didn’t need the distraction. We’ve taken care of the problem.”
The distinct snap of wings sounded over her head. Nick landed at the edge of the plot and quickly folded his gear away. He walked up to them with the harness still attached. His brow was creased and he looked down, watching the ground.
“I’m sorry. Gabriel said to leave it for you to see. But we kept the rest of your trees alive. We did okay, didn’t we?”
He looked so earnest she smiled a little. “Yes, Nick. Th . . . Thank you.”
Nick nodded.
“What . . . why? Why would he do this
?” Rachel asked, turning back to Gabriel.
Gabriel looked off at the horizon. “I suspect he was angry with me.”
“Where is he?”
“He’s safe. And Selene is safe from him for the moment. He’s been stripped of his data rights.”
“Data rights?”
“We’re keeping him busy. His pad is locked out of the system, except for warnings. All he gets is one-way data.”
To lose net access? How would Andrew learn anything new? She shuddered. “You really cut him off?”
“It’s not your problem, or your fault. Still, you will have to clean up.” Gabriel turned toward Nick. “Show me what you’ve done on the meadow grass,” he suggested, walking away with Nick in tow.
Rachel glared at Gabriel’s receding back. Her fists balled at her side. Andrew wasn’t there, and she might as well be angry at a rock as at Gabriel. She paced around her plot, kicking at clods of disturbed dirt.
She gathered a pile of dead sticks, then sat at the edge of the ruin and simply stared at it for a long time, turning dry twigs in her hands. They were rough and sharp against her fingers, their torn edges scratching her palms.
Gabriel had no right to hide this until she got here. It wasn’t carelessness: he’d taken pains to be in the grove when she saw it. Another lesson? Another test?
She didn’t understand Council. But why had Andrew done this? To her? Why was she always his target?
Rachel spent the next two days replanting and tending. After carefully looking at how the remaining plants had grown, Rachel worked out some changes to her original placement. Seeing improvements raised her spirits some. She carefully set up a communications net from her plot to her wrist pad. Now she’d have real-time flows; she’d know about any new damage.
The next morning Rachel’s dad walked up to her plot with her. He’d never looked closely at her work before, contenting himself with her stories. She squeezed his hand and pointed to a wide border of young plants. “See—that’s where the worst damage was. I lined the path with heliconias. I wanted the bright reds.”
