And the launch window for the scheduled shakedown cruise would open in just ten minutes. Time enough. And then she could accept her operation order for her true mission. Close the file, please, Libby. Snip the last bit. And get John Metternes up here.

16: JAMES CLERK MAXWELL.

The lightship that was to take them to Mars came swimming out of the dark. It was called the James Clerk Maxwell. The sail was a shadow, and Bisesa caught glimpses of rigging, rectilinear flashes immensely long.

As the hour of the pickup neared Bisesa grew even tenser. You didnt have to know anything about the engineering to understand that a ship that sailed on sunlight must be gossamer-fragile. And their knotty little spider, a spinning lump of metal, was going to come plummeting in among this fantasy of sails and rigging. She continually expected alarms to sound, and to see a wispy mirror-sail fold around her like Christmas paper.

Myra grew anxious too, despite her own astronautics experience. But Alexei Carel was entirely unfazed. As the rendezvous approached he sat by his softscreens, monitoring obscure graphic displays, occasionally uttering a mild word that was transmitted to the approaching ships systems along a narrow-beam laser link. He seemed to trust absolutely the mixture of orbital mechanics and exotic celestial seamanship that was bringing the spider ever closer to the Maxwell.

In the last moments the Maxwells main hull came looming out of the dark. Bisesa imagined she was in a small boat, watching the approach of a liner across some vast ocean. The rough cylinder bristled with antenna dishes and booms, and around its upper rim Bisesa made out a ring of pulleys, mundane bits of technology that anchored kilometers of rigging.

A transparent tube a couple of meters across snaked out from the hull, probed at the spider uncertainly, and locked on with an audible rattle. There was a jolt as the mechanical linkage soaked up the last minor differences in momentum. Then the tube contracted like a concertina, drawing the two hulls together, until they docked with a firm clang.

Alexei sat back, a broad grin on his face. Thank Sol for universal docking protocols.

Well, thats that. He peeled the softscreen off the wall in front of him, crumpled it up and stuffed it in a pocket. Time to get packed up. Take everything you want; dump anything you dont need in here.

We arent taking the spider, Bisesa said slowly.

Of course not.

Bisesa felt oddly reluctant to leave the haven of the spider. Maybe Im just getting too old for all this change.

Myra squeezed her arm. She made this sort of affectionate gesture spasmodically; Bisesa accepted whatever her wounded daughter had to give her. Mum, if I can cope with it, you can. Come on, lets get ready.

When Alexei opened the hatch in the cabin wall, the outer hull of the Maxwell, exposed, smelled faintly of burning. Bisesa touched it curiously, a surface that had endured the vacuum of space for long months. It felt hot.

The Maxwells hatch dilated away.

They crossed into an interior that was clean, brightly lit, and smelled faintly of soap. The suitcase followed with a clatter. Little sucker pads shot out of it on fine threads, fixing themselves to the walls, so that the case hauled itself around like a clumsy, fat-bodied spider.

The hatches closed behind them, and Bisesa felt a gentle shudder as the greater mass of the Maxwell reacted to the casting-off of the spider. There was no window in the hatch. She would have liked to see the discarded spider fall away.

Alexei gave them one bit of warning. Just remember they pared off every gram to build this thing. The whole ship masses only around ten tonnesand that includes the sail. You could easily put your foot through the hull. He tapped an internal floor-to-ceiling partition panel. And this stuffs a kind of rice paper. Light but fragile. He poked a finger through it to show them, then he tore off a tiny strip and popped it in his mouth. Edible too. In case of dramas, eat the furniture.

Bisesa asked, Dramas? What dramas?

Myra said slowly, I suppose about the worst thing that could happen is to lose the sail, or to foul it up beyond usefulness. In which case youd be stranded, falling away on whatever trajectory you happened to be on. Rescue would be possible, but it would likely take months, if not years.

Bisesa pondered. How many accidents have there been?

Very few, Alexei said. And none fatal. He lectured them briefly about various levels of fail-safe in the design of the mission profile, so that if you did lose your sail youd still coast somewhere accessible. Its more likely your body will fail you before a ship like this does, he said to Bisesa, not entirely reassuringly.

While Alexei disappeared to what he called the bridge to check over the ships systems, Myra and Bisesa explored and unpacked.

It didnt take long to figure out the layout of the Maxwell. The pressurized hull was a cylinder only a few meters tall. Divided up by sheets of that rice-paper partitioning, it was split into three main decks. At the base was what Alexei called the utilities deck. Peering through hatches, they saw heaps of stores, life support, EVA and repair gear, cargo. Alexeis bridge was the upper deck.

The middle deck contained living quarters. Aside from a dedicated galley and bathroom it was sliced up by movable partitions into rooms that could serve as rest quarters, bedrooms, workrooms for a crew of up to ten. The walls were thick with cupboards and space-saving fold-out bunks and chairs. Bisesa and Myra spent some time moving the partitions around. They settled on constructing three small bedrooms as far as possible from each other and from the lavatory; the paper-thin partitions werent particularly soundproof.

The accommodation was almost as pokey as aboard the spider. But the cramped corridors and low-ceilinged rooms had a unique mix of architectures designed for ground and space. The sail could offer an acceleration of no more than one percent of Earths gravitynot enough to stick you to the floor. So the design emulated space stations with hand- and footholds, Velcro pads, and a color coding with brown beneath and blue above, so that you could always know at a glance which way up you were.

But on the other hand that one percent of G was steady and unrelenting. Experimenting, Bisesa found that if she clambered up to the ceiling and let go, she would drift down to the floor in six or seven seconds, falling like a snowflake and settling softly. That little bit of gravity was surprisingly useful, for it induced dust to settle and any disturbed clutter to fall eventually out of the air; here she would not have to wrestle with rogue blankets, or track down stray droplets shimmering away from her coffee cup.

The bridge of the Maxwell was set out pretty informally with chairs and tables. Bisesa was reminded that this wasnt a military ship. When Bisesa and Myra came drifting up the short ladder from the lower deck Alexei was sitting in one of those chairs, patiently watching displays unfold across a softscreen.

The walls were utterly transparent.

Space was starless, empty save for three lamps, sun, Earth, and Moon, which hung in a tremendous triangle around the ship. Something in Bisesa quailed before this array of worlds. For some reason she thought of Mir and the man-apes she had seen there, australopithecines with the legs of humans and the shoulders of gorillas.

Myra saw her reaction and tugged her hand. Mum. Its just another fairground ride. Never mind feeling dizzy. Look up.

Bisesa lifted her head.

She saw a disk of not-quite-darkness, a little grayer than the deep velvet of the sky. Highlights, sun-dazzling bright, rippled across its face. It was the sail, a sheet of foil big enough to have wrapped up the whole of inner London. She could hear gentle, intermittent whirs that must be the tiny pulleys fixed around the roof, tugging at the rigging that ran up and out from the roof above her, rectilinear threads that caught the sunlight.

The hull that enclosed her was a tuna can hanging under a parachute. Welcome aboard the James Clerk Maxwell, Alexei said, grinning. All this from sunlight.

Yes. Alexei held up his hand in a shaft of sunlight that crossed the cabin. The pressure of all those tiny photons, pinging off a reflecting surface. On your face on a sunny day on Earth, that force amounts to only maybe one ten-thousandth of a gram. We have enough sail area, and a low enough mass, for an acceleration of a hundredth of a G. But its continuous, and free, and it just keeps on pushing and pushing...Which is how we can reach Mars in twenty days.

The sail itself was based on a mesh of nanotube string, the same super-strong stuff they made the space elevator ribbons from. The fabric was an ultra-thin film of boron, only a few hundred atomic diameters thick. It had to be sprayed on.

The sail fabric is so fine that if you handle it its more like smoke than anything substantial, Alexei said. But its robust enough to be able to stand a dip into the suns heat inside the orbit of Mercury.

Ribs of light washed across the face of the mirror; tiny pulleys whirred.

You get these oscillations all the time, Alexei said. Thats why we make the sails smart, as the sun shield was. The fabric is embedded with actuators and tiny rocket motors. Max, the ships AI, can keep himself positioned correctly. And he does most of the navigation; I just tell him where I want to go. Max is in charge, really. Thank Sol he doesnt brag about it too much.

Bisesa said, I can see how you can be pushed away from the sun. But how can you sail inward from Mars in toward Earth, say? I guess its sort of like tacking into the wind.

Its not a good analogy, Alexei said evenly. You have to remember that all objects in the solar system are essentially in orbit around the sun. And that determines how the sail functions... Orbital mechanics could be counter to common sense. If I speed up, I raise my orbit. But if I fix my sail so that the sunlight pressure opposes my motion, my orbital velocity falls, and I will spiral in toward the sun... Bisesa studied the diagrams he produced on the softscreens, but when he started scrolling equations she gave up.

This is all intuitively obvious to you, isnt it? The principles of celestial mechanics.

He waved a hand at the worlds around them. You can see why. Up here you can see those laws working out. Ive often wondered how Earthbound scientists were able to make any sense out of all the clutter down there. The first lunar astronauts, a hundred years ago, the first to come out this way, came back changed, for better or worse. A lot of us Spacers are deists, or theists, or pantheistssomewhere on that spectrum.

Believing that God is to be found in physical laws, Myra said.

Or God is those laws.

I suppose it makes sense, Bisesa said. Religions and gods dont have to go together. Buddhists dont necessarily believe in a supreme being; you can have religion independent of any god.

Myra nodded. And we can believe in the Firstborn without having any religion at all.

Alexei said mildly, Oh, the Firstborn arent gods. As they will learn one day.

Bisesa said, But you arent a theist. Are you, Alexei? You like to quote the Bible, but Ive heard you prayThank Sol?

He looked sheepish. You got me. He lifted his face to the sunlight. Some of us have a sneaking regard for the Big Guy. The engine that keeps us all alive, the one object you can see however far you roam across the system.

Myra nodded. I heard of this. A cult of Sol Invictus. One of the last great pagan godsfrom the Roman empire, just before they proclaimed Christianity their official cult. Didnt it sprout on Earth again, just before the sunstorm?

Alexei nodded. There was a lot of propitiation of angry gods to be done in those days. But Sol Invictus was the one that took hold with the early Spacers, especially those who had worked on the shield. And he spread.

Bisesa remembered another sun god who had interfered in her own life: Marduk, forgotten god of Babylon. She said, You Spacers really arent like the rest of us, are you, Alexei?

Of course not. How could we be?

And is that why youre taking me to Mars? Because of a different perspective?

More than that. Because the guys down there have found something. Something the Earth governments would never even have dreamed of looking for. Although the governments are looking for you, Bisesa.

Bisesa frowned. How do you know?

Alexei looked uncomfortable. My father is working with the World Space Council. Hes a cosmologist...

So there it was, Bisesa thought, this new generational gap set out as starkly as it could be. A Spacer son spying on his Earthbound father.

But even though they were in deep space he would say no more about where Bisesa was being taken, and what was expected of her.

Myra pulled her lip. Its odd. Sol Invictushes such a contrast to the cool thinking of the theists.

Yeah. But dont you think that until we get these Firstborn assholes beaten, we need an Iron Age god? And Alexei grinned, showing his teeth, a shockingly primate expression bathed in the light of sun and Moon.

Bisesa, worn out by stress and strangeness, retreated to her newly constructed cabin. She rearranged her few possessions and strapped herself to the narrow bunk.

The partitioned-off room was small, but that didnt bother her. She had been in the army. As accommodations went, this was a lot better than the UN camp in Afghanistan where she had been stationed before falling into Mir.

It struck her that this living deck seemed cramped, though, even given the basic geometry of the tuna-can hull. She thought back to her inspection of the utility deck earlier; she had a good memory for spaces and volumes. Sleepy, she murmured aloud, So why is this deck so much smaller than the utility level?

A soft voice spoke. Because these walls are full of water, Bisesa. Is that you, Thales? No, Bisesa. Alexei calls me Max. The voice was male, softly Scottish. Max, for James Clerk Maxwell. Youre the ship.

Strictly speaking the sail, which is the smartest and most sentient component. I am a Legal Person (Non-Human), Max said calmly. I have a full set of cognitive capacities.

Alexei should have introduced us.

That would have been pleasant.

The water in the walls?

It was there to protect frail human cargo from the hard radiations of space; even a few centimeters of water was a surprisingly effective shield.

Max. Why the name?

It is appropriate...

The Scottish physicist James Clerk Maxwell had in the nineteenth century demonstrated that light exerted a pressure, the fundamental principle on which mankinds new fleet of lightships had been built. His work had laid the foundations for Einsteins conceptual breakthroughs.

Bisesa smiled. I suppose Maxwell would have been astonished to see how his basic insight has been translated into technology, two centuries later.

Actually Ive made something of a study of Maxwell. I have rather a lot of spare time. I think he could have conceived of a solar sail. The physics was all his, after all.

Bisesa propped an arm behind her head. When I read about Athena, the shield AI, I always wondered how it felt to be her. An intelligence embedded in such an alien body. Max, how does it feel to be you?

I often wonder how it feels to be you, he replied in his soft brogue. I am capable of curiosity. And awe.

It surprised Bisesa that he should say that. Awe? At what?

Awe at finding myself in a universe of such beauty yet governed by a few simple laws. Why should it be so? And yet, why not?

Are you a theist, Max?

Many of the leading theist thinkers are AIs.

Electronic prophets, she thought, wondering. I think James Clerk would have been proud of you, Maxwell Junior.

Thank you.

Light, please.

The light dimmed to a faint crimson glow. She fell into a deep sleep, the gentle gravity just enough to reassure her inner ear that she wasnt falling any more.

It was some hours later that Max woke her, for, he said apologetically, they were approaching the Moon.

On the bridge Alexei said, Its fortuitous of course that our path to Mars should take us near the Moon. But I was able to work a gravitational slingshot into our trajectory design...

Bisesa stopped listening to him, and just looked.

The swelling face of the Moon, nearly full, was not the familiar Man-in-the-Moon that had hovered over the Manchester streets of her childhood. She had come so far now that the Man had turned; the great right eye of Mare Imbrium was swiveled toward her, and a slice of Farside was clearly revealed, a segment of crater-pocked hide invisible to mankind until the advent of spaceflight.

But it was not the geology of the Moon that interested her but the traces of humanity. Eagerly she and Myra picked out the big Nearside bases, Armstrong and Tooke, clearly visible as blisters of silver and green against the tan lunar dust. Bisesa thought she saw a road, a line of silver, cutting across the crater called Clavius within which Tooke Base nestled, and from which it had taken its first name. Then she realized it must be a mass driver, an electromagnetic launching track kilometers long.

The modern Moon was visibly a place of industry. Vast stretches of the lava-dust plains of the maria looked as if they had been combed; the lunar seas were being strip-mined, their dust plundered for oxygen, water, and minerals. At the poles immense solar-cell farms splashed, and new observatories gleamed like bits of coal, made of jet-black glass microwaved direct from the lunar dirt. Strung right around the equator was a shining chrome thread: the alephtron, mightiest particle accelerator in the system.

Something about all this industry disturbed Bisesa. So much had changed on the Moon after four billion years of chthonic calm, in just a single century since Armstrongs first small step. The economic development of the Moon had always been the dream of Bud Tooke himself. But now she wondered how the Firstborn, who may themselves have been older than the Moon, might view this disquieting clatter.

Myra pointed. Mum, look over there, at Imbrium. Bisesa looked that way. She saw a disk that must have been kilometers across. It glinted with reflected sunlight, and shuddering waves spread across it.

Thats the solar-sail factory, Alexei murmured. They lay down the webbing and spray on the boron filmthey spin it up from the start, to hold it rigid against the Moons gravity...

That glinting disk seemed to spin, and ripple, and then, without warning, it peeled neatly away from the mare surface as if being budded, and drifted up toward space, oscillating as it rose.

Its beautiful, Bisesa said.

Alexei shrugged. Pretty, yes. To be honest most of us dont find the Moon very interesting. They arent true Spacers down there. Not when you can commute to Earth in a day or two. We call it Earths attic...

Max murmured, Closest approach coming up.