He glanced up to find the Earth, which rode a quarter of the way up the sky. It was a matter of regret for him that the Earth was so difficult to see from Shackleton, down at the pole. As seen from here at Clavius, Earth, tens of times brighter than the full Moon in its own skies, bathed the shadowed lunar lands with a silver-blue light. The home world’s phases, always the mirror image of the Moon’s, followed a stately monthly cycle, but unlike the Moon, Earth spun on its axis every day, bringing new landforms, oceans, and cloud formations into view. And of course, unlike the Moon’s slow journeying, the Earth never shifted from its position in the lunar sky.
After April 2042 the Earth would still be hanging up there, just as it always had. But he wondered how it would look then.
Eugene continued to watch the President’s broadcast. “She’s being vague about the date.”
“What do you mean?”
Eugene glanced at him. Today that lovely face was contorted by a stress Mikhail hadn’t seen before. “Why doesn’t she just say April 20? Everybody knows.”
Evidently not, Mikhail thought. Perhaps Alvarez had some psychological motivation in mind. Maybe overprecision would make the whole prospect too scary—it would start doomsday clocks ticking in people’s heads. “I don’t think it matters,” he said.
But to Eugene, author of the prediction, it evidently did.
Mikhail sat down. “Eugene, it must be very strange for you to hear the President herself speaking to the whole human race about something that you figured out.”
“Strange. Yes. Something like that,” Eugene said, his speech rapid and broken. He held his hands parallel before him. “You have the sun. And you have my model of the sun.” He locked his fingers together. “They are different entities, but they connect. My work contained predictions that were borne out. So my work is a valid map of reality. But it is only a map.”
“I think I understand,” Mikhail said. “There are categories of reality. Even though we can predict it to nine decimal places, we can’t imagine the sun’s peculiar behavior actually intervening in our cozy human world.”
“Something like that,” Eugene said uneasily. His big hands plucked at each other, a man’s hands but a child’s gesture. “Like the walls between model and reality are breaking down.”
“You know, you’re not the only person who feels this way, Eugene. You aren’t alone.”
“Of course I’m alone,” Eugene said. His expression closed up.
Mikhail longed to hold him, but knew he must not.
The President said, “We intend to build a shield in space. Made of the finest film, it will be a disk wider than the Earth itself. It will be so vast, in fact, that as it begins to take shape it will be visible from every home, every school, every workplace on Earth, for it will be a human-made structure as big in our sky as the sun or the Moon.
“I am told it may even be visible, to the naked eye, from Mars. We will indeed be stamping our mark on the solar system.” She smiled.
Siobhan thought back to the session with her “motley crew” in the Royal Society, where Aristotle had first come up with the notion.
The idea couldn’t have been simpler, in principle. On a sunny day, if the light was too strong, you put up a parasol. So, for protection from the storm, you would build a parasol in space, a mighty cover big enough to shield the whole Earth. And on that crucial day, humankind would shelter safely in the shadow of an artificial eclipse.
“Its center of gravity would be at L1,” Mikhail had said. “Between sun and Earth, co-orbiting.”
Toby asked, “And what is L1?”
L1 is the first Lagrange point of the Earth–sun system. An object circling between Earth and the sun, such as Venus, follows its orbit more rapidly than Earth. But Earth’s gravity field tugs at Venus, though much more feebly than the sun’s. Put a satellite much closer to the Earth—about four times the distance to the Moon—and Earth’s gravity is so strong that the satellite is dragged back just so by Earth, and made to orbit the sun at the same rate as the Earth.
This point of equilibrium is called L1, the first Lagrangian point, for the eighteenth-century French mathematician who discovered it. In fact there are five such Lagrangian points, three on the sun–Earth line, and the other two on the path of Earth’s own orbit, at sixty degrees from the Earth–sun radius.
“Ah,” Toby had said, nodding. “Earth and satellite co-rotate. As if both Earth and satellite were glued to a great rigid clock hand that sticks out from the sun.”
Siobhan said, “I thought L1 is a point of unstable equilibrium.” At Toby’s baffled look she said, “Like a football sitting at the summit of a mountain, rather than in a valley. The ball’s stationary, but liable to fall off in any direction.”
“Yes,” Mikhail said. “But we have placed satellites at such positions before. You can actually orbit the Lagrangian point, use a small amount of fuel to station-keep. It’s well within the envelope of experience: astronautically, not a problem.”
Toby had held his hand up to the ceiling light, experimentally shadowing his face. “Forgive a stupid question,” he said. “But how big would this shield have to be?”
Mikhail sighed. “For simplicity, assume the sun’s rays are parallel as they reach Earth. Then you can see you need a screen as large as the object you’re trying to shield.”
Toby said, “So the shield has to be a disk with at least the diameter of the Earth. Which is—”
“About thirteen thousand kilometers.”
Toby’s jaw had dropped. But he pressed on doggedly. “So we’re talking about a shield thirteen thousand kilometers across. To be built in space. Where the largest structure we’ve put up so far is—”
“I suppose the International Space Station,” Mikhail said. “Much less than a kilometer.”
Toby said, “No wonder I didn’t find this before. When I ran my own search for solutions, I screened out the obviously implausible. And this is obviously implausible.” He glanced at Siobhan. “Isn’t it?”
Of course it was. But the three of them had hammered at their softscreens to figure out more.
Toby said, “There have been studies of this sort of thing before. Hermann Oberth seems to have been the first to come up with the idea.”
“You’d use ultrathin materials, of course,” Mikhail said.
Siobhan said, “Everyday plastic wrap comes in at ten micrometers thick.”
“And you can get aluminum foil the same thickness,” Mikhail said. “But surely we can do better.”
Toby said, “So with an area density of less than a gram per square meter, say, and even adding an element for structural components, your weight could be as little as a few million tonnes.” He looked up. “Did I really just say as little as?”
Siobhan said, “We don’t have the heavy-lift capacity to get that amount of material off the Earth, even given years.”
“But we don’t need to lift it off Earth,” Mikhail said. “Why don’t we build it on the Moon?”
Toby stared at him. “Now that really is crazy.”
“Why so? On the Moon we already manufacture glass, process metals. And we have our low gravity, remember: it’s twenty-two times easier to launch a payload into space from the Moon as from Earth. And we’re already building a mass driver! There’s no reason the Sling project couldn’t be accelerated. Its launch capacity will be huge.”
They factored an estimate of the Sling’s launch capacity into their back-of-the-envelope calculations. It was immediately clear that if they could launch the bulk of the shield’s mass from the Moon, the energy savings would indeed be prodigious.
And there was still no obvious showstopper. Siobhan had felt frightened to breathe, as if she might break the spell, and they had worked on.
But now, sitting in her flat with her mother and daughter, listening to Alvarez announce this preposterous idea to the whole world, different emotions surged in her. Suddenly restless, she walked to the window.
It was
nearly Christmas, 2037. Outside, kids were playing soccer. They were wearing T-shirts. While Santa Claus still bundled up on the Christmas cards, snow and frost were nostalgic dreams of Siobhan’s childhood; in England it was more than ten years since the temperature had dipped below freezing anywhere south of a line from the Severn to the Trent. She remembered her last Christmas with her father before his death, when he had railed about having to cut his lawn on Boxing Day. The world had changed hugely in her own lifetime, shaped by forces far beyond human control. How could she be so arrogant as to suppose she could manage an even greater change, in just a few years?
“I’m afraid,” she blurted.
Perdita glanced at her, troubled.
“Of the storm?” Maria asked.
“Yes, of course. But I had to work hard to get the politicians to accept the idea of the shield.”
“And now—”
“Now Alvarez is calling my bluff, in front of the whole world. Suddenly I’ve got to deliver on my promises. And that’s what frightens me. That I might fail.”
Maria and Perdita walked over to her. Maria hugged her, and Perdita rested her head on her mother’s shoulder. “You won’t fail, Mum,” Perdita said. “Anyhow you have us, remember.”
Siobhan touched her daughter’s head.
On the softwall, the President continued to speak.
“I offer you hope, but not false hope,” Alvarez said. “Even the shield alone cannot save us. But it will turn an event that would be nonsurvivable for any of us into a disaster survivable for some. That’s why we must build it—and that’s why we must build on the chance it gives us.
“It goes without saying that this will be by far the most challenging space project ever undertaken, even dwarfing our colonization of the Moon and our first footsteps on Mars. Such a mighty project cannot be managed by one nation alone—not even America.
“So we have asked all the nations and federations of the world to come together, to pool their resources and energies, and to cooperate in this most vital of space projects. I am delighted to say that we have had a virtually unanimous response.”
“ ‘Virtually unanimous’ my arse,” Miriam Grec grumbled. Here in her Euro-needle office she sipped her whiskey and settled a little deeper into the sofa. “How can you call it ‘unanimous’ when the Chinese have refused to take part?”
Nicolaus replied, “The Chinese play a long game, Miriam. We’ve always known that. No doubt they see this problem with the sun as just another geopolitical opportunity.”
“Maybe. But God alone knows what they are up to with all those taikonauts and Long March boosters . . .”
“Surely they will come around, in the end.”
She studied him. Even as he spoke, Nicolaus Korombel had one eye on the softscreen bearing Alvarez’s image, the other on monitors that showed in a variety of ways the world’s response to Alvarez’s unfolding message. Miriam had never met anybody with Nicolaus’s ability to parallel-process. It was just one of the reasons she valued him so much.
Although it was an odd thing, she thought, that his very hard-nosed, almost cynically robust thinking, which made him so valuable to her, also made him very opaque. She really knew very little about what he thought and believed, deep inside. Sometimes a faint worry about that gnawed at the edge of her awareness. She must get him to open up, she thought, get to know him better. But there was never any time. And in the meantime he was just too useful.
“So how’s the reaction?”
“Markets down seventeen percent,” Nicolaus said. “As a snap reaction goes, that’s not as bad as we feared. Space and high-tech stocks are booming, needless to say.”
Miriam marveled at such a response. She supposed the impulse to get rich was natural enough—indeed, the global economy wouldn’t work without it. But she did wonder what those eager investors imagined they might achieve if their financial feeding frenzy hindered the ability of the aerospace companies and others to actually get the job done.
Still, it could be worse, she told herself. At least the President’s speech was being made. Even getting the project this far had been a close-run thing.
In the world’s grandest councils, there had been a lot of heated discussion about the wisdom of the solution Miriam had pushed. The shield project would absorb the economic energies of the participating countries for years—and for what? Even the energy the shield was bound to leak through would still add up to a devastating disaster.
And were you really going to bust your balls to save the whole world? Including the Chinese who were refusing to take part, and the Africans who, recovering from the disasters of the twentieth century, were becoming newly resurgent? Couldn’t you just save America, Europe? The military chiefs had even started to develop scenarios for what might follow the sunstorm, when Eurasia and America, if they were the only industrial powers left standing, began to move out from their fortresses to “aid” the remnants of a shattered world. It really would be a new world order, Miriam was earnestly advised, a restructuring of geopolitical power that might last a thousand years . . .
It had taken some deep conversations with Siobhan McGorran before Miriam had been able to wrap her own limited politician’s imagination around the magnitude of the problem. The sunstorm wasn’t another June 9; it wasn’t Krakatoa or Pompeii; it wasn’t a plague or a flood. And you just couldn’t see this as an opportunity to seek petty advantage. The extinction of humankind, indeed of all life on Earth, was possible. This really was a case of all or nothing—a message Miriam had, at last, managed to batter into the heads of the rest of the world’s decision makers.
President Alvarez spoke on, calmly.
It had to be Alvarez up there on the world’s screens, of course. It had been Miriam who had so far led the political effort behind the shield project. It was she who had firmed up a solid industrial and financial base for the project, she who had gathered together the political will in her own fractious Eurasian Union and beyond to make this unlikely project happen—and she who had used up a good deal of her own political credit in the process. But by common consent, in situations like this it had to be the President of the United States who had to give the world the bad news, and the good, as it had been for generations.
“Alvarez is doing a good job,” Miriam said. “We’re lucky we got somebody like her in the hot seat at the right time.”
Nicolaus snorted. “She’s the best actor in the White House since Reagan, that’s all.”
“Oh, she’s more than that. But she might raise false hopes. Whatever we do,” she said grimly, “people are going to die.”
“But far fewer than might otherwise,” Nicolaus said. “And whatever we do, don’t expect medals. Remember, this is engineering, not magic; no matter how well this works, people are sure to die, in great numbers. And in hindsight people will blame us. We will be called the worst mass murderers in history. That is certainly the Polish way!” He grinned with an odd sort of cheerful gloominess.
“You’re too cynical sometimes, Nicolaus.” But her mood was mellow, softened by the whiskey. She sipped it sparingly, letting Alvarez’s warm voice wash over her.
“The shield will be immense in size. But most of it will be made of a vanishingly thin film, and so its mass will be kept to the minimum. The bulk of its substance will be launched from the Moon, where the lower gravity allows space launches many times easier than from the Earth. The “smart” components that will be required to control the shield will be manufactured on Earth, where the most sophisticated manufacturing processes are available.
“All our resources must be dedicated to this project, and other dreams put on hold, for now. That is why I have decided to recall the Aurora 2, the second of our Mars spacecraft, already bound for the red planet. It will serve as our work shed, if you will.”
Born on ripples of electromagnetism, the President’s words washed past the Moon and, some minutes later, reached Mars.
To Helena Umfraville, the voice in her he
lmet speakers was tinny. But it was her choice to hear Alvarez like this. To watch the flyby of Aurora 2 she had decided to go EVA, to be immersed in Martian nature. Even a president’s speech couldn’t compete with that.
So she had clambered into her EVA suit. It was an “isolation suit” that you left docked to a hatch of your rover or your hab, and then crawled in through the back, so that you never came into contact with its outer surface—and Mars, with its putative native ecology, was never touched by the oily, watery, bug-ridden mass that was you. And now she stood beside her rover, with her feet planted squarely in crimson dirt, as close to Mars as she was allowed to get.
Around her a rock-strewn plain stretched away, unmarked by humanity save for her own tire tracks. The ground was pinkish brown, and the sky was a yellowy butterscotch color that gathered to orange around the shrunken disk of the sun, almost like an Earth sunrise. The rocks on the ground, scattered at random by some long-gone impact, had been in place so long that they had been polished smooth by windborne dust. This was an old, silent world, like a museum of rocks and dust. But there was weather here, sometimes surprisingly violent when that thin air stirred itself.
And on the horizon she could make out an outcrop of layered rock. It was sedimentary, just like a sandstone bed on Earth—and just like terrestrial sandstone it had been laid down in water. You could search the dry Moon from pole to pole and not find one formation like that unspectacular outcropping. This was Mars: the thought still thrilled her.
But Helena was stranded here.
Of course the Aurora 1 astronauts had known basically what the President was going to say long before she had opened her mouth. Mission control at Houston had broken the news of Aurora 2’s wave-off gently and carefully, well in advance.
Aurora 2 was actually the Mars expedition’s third ship. The first, labeled Aurora Zero, had delivered an unmanned factory to the surface of Mars, which had patiently labored to turn Martian dirt and air into methane and oxygen, the fuel that would send home the human crews that followed. Then Aurora 1 had made the mighty journey, powered by thermal nuclear rockets and carrying six crew. Footprints and flags had come at last to Mars.