Supersymmetry predicted that every baryonic particle should have a supersymmetric twin: a sparticle. The electron was paired with a selectron, the photon with the photino — and so on.

The particular unified-theory variant called Spin (10) had, with time, become the standard. Lieserl rolled that around her tongue, a few times. Spin (10). A suitably absurd name for the secret of the Universe.

The divergence, of theory from observation, was immense — and increased toward the center of the Sun.

“Kevan, it’s way too hot out here.”

We see it, Lieserl, he said wryly. For now we’re just logging the data. Just as well you didn’t pack your winter coat.

She looked within herself, at some of her subsidiary senses. “And I’m already picking up some stray photino flux.”

Already? This far out from the center? Scholes sounded disturbed. Are you sure?

As a star like the Sun swept along its path about the center of the galaxy through a huge, intangible sea of dark matter — photinos fell into its pinprick gravity well, and clustered around its heart.

The photinos actually orbited the center of the Sun, swarming through its core around the geometric center like tiny, circling carrion-eaters, subatomic planets with orbital “years” lasting mere minutes. The photinos passed through fusing hydrogen as if it were a light mist…

Almost.

The chances of a photino interacting with particles of the plasma were remote but not zero. Once every orbit, a photino would scatter off a baryonic particle, perhaps a proton. The photino took some energy away from the proton. The gain in energy boosted the orbital speed of the photino, making it circle a little further out from the heart of the Sun.

Working this way, passing through the fusing hydrogen with its coagulated mass of trapped photons, the photinos were extremely efficient at transporting heat out from the center of the Sun.

According to the Standard Model, the temperature at the center should have been suppressed by a tenth, and the fusion heat energy smoothed out into the surrounding, cooler regions, making the central regions nearly isothermal — at a uniform temperature. The core would be a little cooler than it should otherwise have been, and the surrounding material a little warmer.

…Just a little. According to the Standard Model.

Now, Lieserl studied the temperature contours around her and realized how far the reality diverged from the ancient, venerated theoretical image. The isothermal region stretched well beyond the fusion core — far, far beyond the predictions of the Standard Model with its modest little knot of circling photinos.

“Kevan, there is much more heat being sucked out of the core than the Standard Model predicted. You do realize that there’s no way the Model can be made to fit these observations.”

No. There was a silence, and Lieserl imagined Scholes sighing into his microphone. I guess this means goodbye to an old friend.

She allowed the contour forms of the Standard Model to lapse from her sensorium, leaving exposed the gradient curves of the physical properties of the medium around her. Without the spurious detail provided by the overlay of Standard Model contours, the gradient curves seemed too smooth, deceptively featureless; she felt a remnant of her earlier deprived-sensorium tranquility return to her. There was no sense of motion, and no real sense of scale; it was like being inside overlaid clouds glowing pink and blue from some hidden neon source.

“Kevan. Am I still falling?”

You’ve reached your nominal depth now.

“Nominal. I hate that word.”

Sorry. You’re still falling, but a lot more slowly; we want to be sure we can handle the energy gradients.

But she’d barely breached the surface of the plasma sea; eighty percent of the Sun’s radius — a full two light-seconds — still lay beneath her.

And you’re picking up some lateral drift, also. There are currents of some kind in there, Lieserl.

It was as if her Virtual senses were dark-adapting; now she could see more structure in the waxy temperature-map around her: pockets of higher temperature, slow, drifting currents. “Right. I think I see it. Convection cells?”

Maybe. Or some new phenomenon. Lieserl, you’re picking up data they’ve never seen before, out here. This stuff is only minutes old; it’s a little early to form hypotheses yet, even for the bright guys in Thoth.

I wish you could see the Interface — out here, at the other end of your heat sink. Deep Solar plasma is just spewing out of it, pumping from every face; it’s as if a small nova has gone off, right at the heart of the System. Lieserl, you may not believe this, but you’re actually illuminating the photosphere. Why, I’ll bet if we looked hard enough we’d find you were casting shadows from prominences.

She smiled.

I can hear you smiling, Lieserl. I’m smart like that. You enjoy being the hero, don’t you?

“Maybe just a little.” She let her smile broaden. I’m casting shadows onto the Sun. Not a bad monument.

The uppermost level of the Northern’s habitable section was a square mile of rain forest.

The four air-scooters rose through a cylindrical Lock. Mark found himself rising up, like some ancient god, into the midst of jungle.

The air was thick, stifling, laden with rich scents and the cries and hoots of birds and animals. He was surrounded by the branchless boles of trees, pillars of hardwood — some extravagantly buttressed — that reached up to a thick canopy of leaves; the boles disappeared into the gloom, rank on rank of them, as if he were inside some nature-born temple of Islam. The floor of the forest, starved of light by the canopy, was surprisingly bare and looked firm underfoot: it was a carpet of leaves, pierced by Lock entrances which offered incongruous glimpses of the cool, huge spaces beneath this sub-world. Fungi proliferated across the floor, spreading filaments through the leaf litter and erecting fruiting bodies in the shape of umbrellas and globes, platforms and spikes hung about by lace skirts.

On a whim, Mark rose through a hundred feet alongside the rotting carcass of a dead tree. The bark was thick with ferns and mosses which had formed a rich compost in the bark’s crevices. Huge, gaudy orchids and bromeliads had colonized the bark, drawing their sustenance from leaf mold and collecting moisture from the air with their dangling roots.

He drew alongside a wild banana. Its broad, drooping leaf was marked by a line of holes on either side of the midrib. Mark lifted the leaf, and found suspended from the underside a series of white, fur-coated balls perhaps two inches across: nomadic bats, sheltering from the rainfall of this artificial forest.

There was a motion behind him; he turned.

Uvarov had followed him, and was now watching appraisingly. “Each day,” Uvarov intoned, his face long in the gloom, “an artificial sun will ride its chariot across the glass sky of this jungle-world. And machines will pipe rainfall into artificial clouds. We’re living in a high-technology realization of our most ancient visions of the Universe. What does the fact that we’ve built this ship in such a way tell us about ourselves, I wonder?”

Mark didn’t answer. He pushed himself away from the tree, and they descended to join the others, just above the forest floor.

Louise slapped the bole of a tree. She grinned. “One of the few real objects in the whole damn ship,” she said. She looked around. “This is Deck Zero. I wanted our tour today to end here. I’m proud of this forest. It’s practical — it’s going to be the lungs of the ship, a key part of our ecology — and it has higher purposes too; with this aboard we’ll never be able to forget who we are, and where we came from.”