The vagueness of the dates Alvarez quoted baffled her. Why be so elusive? The astrophysicists who had come up with this prediction seemed so precise about everything else that they would surely have narrowed it down to a day.

The date was surely selected by the Firstborn, of course, as was everything about this event. They would pick a day that mattered to them, somehow. But what could matter about a day in April 2042? Surely nothing in the human domain: the Firstborn were creatures of the stars … Something astronomical, then.

“Aristotle,” she said softly.

“Yes, Bisesa?”

“April 2042. Can you tell me what’s going on in the sky in that month?”

“You mean an ephemeris?”

“A what?”

“A table of astronomical data that predicts the daily position of the planets, stars, and—”

“Yes. That’s it.”

The President’s image shrank down to a corner of the wall. The rest of it filled up with columns of figures, like map coordinates. But even the columns’ titles meant little to Bisesa; evidently astronomers spoke a language of their own.

“I’m sorry,” Aristotle said. “I’m not sure of your level of expertise.”

“Assume nonexistent. Can you show me this graphically?”

“Of course.” The tables were replaced by an image of the night sky. “The view from London on April 1, 2042, midnight,” Aristotle said.

At the vision of the impossibly clear, starry sky, a sharp memory prodded at Bisesa’s mind. She remembered sitting with her phone, under the crystalline sky of another world, as the little gadget had labored to map the sky and work out the date … But she’d had to leave everything behind on Mir, even her phone.

Aristotle scrolled through display options, showing her stick-figure constellation diagrams, lines of celestial longitude and latitude.

She dumped all that. “Just show me the sun,” she said.

A yellow disk began to track, impossibly, against a black, star-filled sky, and a date and time box flickered in the corner. She ran through the month, April 2042, from end to end, and watched the sun ride across the sky, over and over.

And then she thought of what she had seen on her strange journey back from Mir with Josh. “Please show me the Moon.”

A gray disk with a sketchy man-in-the-Moon mottling appeared.

“Now start from April 1 and run forward again.”

The Moon made its stately way across the sky. Its phase welled until it became full, and then it began to shrink down, through half full, and to a crescent that enclosed a disk of darkness.

That black disk tracked across the image of the sun.

“Stop.” The image froze. “I know when it’s going to happen,” she breathed.

“Bisesa?”

“The sunstorm … Aristotle. I know this is going to be hard for you to arrange. But I need to speak to the Astronomer Royal—the President mentioned her—Siobhan McGorran. It’s very, very important.”

She stared at sun and Moon, neatly overlapped on her softwall. The date of the simulated solar eclipse was April 20, 2042.

Part 3

19: Industry

Bud Tooke met Siobhan off the Komarov, just as before.

She had already told Bud she wanted to get straight to work, no matter the local time of day. He smiled as he rode with her to the main domes. “No sweat. We’re working a twenty-four-hour-a-day shift here anyhow—have been for six months, ever since the President’s directive came in.”

“It’s appreciated back home,” she said warmly.

“I know. But it’s not a problem. We’re all highly motivated up here.” He sniffed up a deep breath, expanding his chest. “A challenge is energizing. Good for you.”

Siobhan had felt on the edge of exhaustion for the last six months. She said dubiously, “I guess so.”

He eyed her, concern penetrating his military brusqueness. “So how was the trip?”

“Long. Thank God for Aristotle, and e-mail.”

This was Siobhan McGorran’s third trip to the Moon. Her first voyage had been wonderful, something she had dreamed of as a child. Even the second had been exciting. But the third was just a chore—and time consuming at that.

The trouble was, here they were, halfway through 2038, a whole year after June 9, already six months since Alvarez had made her epochal Christmas announcement—and now less than four years before sunstorm day. Siobhan knew intellectually, from her Gantt charts and dependency diagrams and critical paths, that the various subprojects of the mighty shield program were actually going quite well. But inside her head a calendar-clock ticked steadily down.

She tried to explain to Bud. “I’m a natural pessimist,” she said. “I expect things to go wrong, and am suspicious when they go well.” She forced a smile. “Some attitude for a leader.”

He angled his head so his frosting of crew-cut hair caught the corridor strip lights. “You’re doing fine. Anyhow, when it comes to motivation, leave that to me. I was once a pain-in-the-butt sergeant at training camps in the Midwest. I can get them down and dirty. Maybe between us we’ll turn out to be a good team.” And he put his arm around her shoulders and gave her a squeeze.

She could feel his strength, and detected a scent of aftershave. Bud did sometimes seem like a relic of the 1950s. But his indomitability, straightforwardness, and sheer good humor were very welcome. All of which was rationalizing, of course.

As he held her, she felt a deep and pleasant warmth spread out through her belly and rise to her face. She was sorry when the brief hug ended.

On her first visit, Artemis Dome had been a scene of lunar industrial experiments. Now, just a few months later, the scale of the operation had changed utterly. The dome had been sliced open and crude extensions built on it to provide a lot more acreage of processing facility, most of it in vacuum. It was an infernal scene, Siobhan thought, with grotesque spacesuited figures gliding through banks of pipes, ducts, and metallic vessels, and everything stained the ubiquitous charcoal gray of the Moon, like a caricature of the darkest days of England’s Industrial Revolution.

The product of this mighty effort was metal.

Aluminum was the main structural component of the mass driver launch system, while iron would be required for the electromagnetic systems that would be its working muscles. But the mass driver was going to be kilometers long. The lunar colonists were having to jump straight from a trialed process to industrial-scale production; the scale change was tremendous, the pressure immense.

Bud sketched some of the difficulties. “These are tried-and-tested processes on Earth,” he said. “But up here nothing behaves the same, not a heap of ball bearings or oil flowing in a pipe …”

“But you’re getting there.”

“Oh, yes.”

Meanwhile Selene Dome, once the Moon’s first farm, had been turned into a glass factory. It was simple: you pushed lunar regolith in one end, applied focused solar heat, and drew glass out the other end, shimmering hot, to be molded into prefabricated sections.

Bud said, “Every time a journalist gets through to me, I’m asked the same damn question: why are we making the infrastructure of the shield from lunar glass? And every time I have to give the same answer: because this is the Moon. And wonderful though it is, the Moon doesn’t give you a lot of choice.”

The Moon’s peculiar composition was dictated by its formation. The NASA geologists who had studied the first samples returned by the Apollo astronauts had been puzzled: this iron-deficient, volatile-free stuff seemed quite unlike the rocks of Earth’s crust. It was more like the material of Earth’s mantle, the thick layer between crust and core. It turned out that this was because the Moon was made of Earth’s mantle—or rather, of the great gout of it that had been splashed away by that primordial, Moon-making impact.