She looked from one to the other, in the green gloom. “We’ve all come into this project from different directions. I’m interested in the technical challenge. And some of you, with Superet sympathies, have rather more ambitious goals to achieve. But we four, above all others, have the responsibility of making this project work. The forest is a symbol for us all. If these trees survive our ten centuries, then surely our human cargo will too.”

Serena Milpitas tilted back her head; Mark followed her example, and found himself peering up at the remote stars through a gap in the canopy. Suddenly he had a shift of perspective — a discontinuity of the imagination which abruptly revealed to him the true nature of this toy jungle, with empty, lightless space above it and a complex warren of humans below.

Garry Uvarov said, “But if the Superet projections are correct, who knows what stars will be shining down on these trees in a thousand years?”

Mark reached out and touched a tree bole; he found something comforting about its warm, moist solidity. He heard a shrieking chorus, high above him; in the branches above his head he saw a troupe of birds of paradise — at least a dozen of them — dancing together, their ecstatic golden plumage shimmering against the transPlutonian darkness beyond the skydome.

A thousand years…

Dark matter could age a star.

The photino knot at the heart of the Sun lowered the temperature, and thereby suppressed the rate of fusion reaction. Naively, Lieserl supposed, one might think that this would extend the life of the Sun, not diminish it, by slowing the rate at which hydrogen was exhausted.

But it didn’t work out like that. Taking heat energy out from the core made the Sun more unstable. The delicate balance between gravitational collapse and radiative explosion was upset. The Sun would reach turnoff earlier — that is, it would leave the Main Sequence, the family of stable stars, sooner than otherwise.

According to the Standard Model, photinos should reduce the life of the Sun only by a billion years.

Only?

A billion years was a long time — the Universe itself was only around twenty billion years out of its Big Bang egg — but the Sun would still be left with many billions of years of stable, Main Sequence existence…

According to the Standard Model. But she already knew the Model was wrong, didn’t she?

Lieserl.

“Hmm?”

We have the answer. We think.

“Tell me.”

The Standard Model predicts the photino cloud should be contained within the fusing core, within ten percent of the total Solar diameter. Right? But, according to the best fits we’ve made to your data —

“Go on, Kevan.”

There are actually significant photino densities out to thirty percent of the diameter. Three times as much as the Model; nearly a third of the —

“Lethe.” She looked down. The heart of the Sun still glowed peacefully in interleaved shades of pink and blue. “That must mean the fusion core is swamped with photinos.”

Even through the crude wormhole telemetry link she could hear the distress in his voice. The temperature at the center is way, way down, Lieserl. In fact —

“In fact,” she said quietly, “it’s possible the fusion processes have already been extinguished altogether. Isn’t it, Kevan? Perhaps the core of the Sun has already gone out, like a smothered flame.”

Yes. Lieserl, the most disturbing thing for me is that no one here can come up with a mechanism for such a photino cloud to form naturally…

“What’s the lifecycle prediction? How long has the Sun left to live?”

No hesitation this time. Zero.

At first the blunt word made no sense. “What?”

Zero, on the scales we’re talking about — timescales measured in billions of years. In practice, we’re looking at perhaps one to ten million years left. Lieserl, that’s nothing in cosmic terms.

“I know. But it ties in with the predictions out of Superet, doesn’t it? The data they collected through Michael Poole’s wormhole daisy-chain.”

Yes.

“Kevan, you shouldn’t feel too distressed. Five million years is fifty times the length of human history so far — ”

Maybe. Kevan’s voice took on a harder edge, as if he personally resented the aging of the Sun. But I have kids. I hope to have descendants still alive in five million years. Damn it, I hope to be sentient still myself. Why not? It’s only five megayears; we’re out of the Dark Ages now, Lieserl.

She peered deep into the heart of the Sun, subvocally trying to press more of her functions into play. She had senses to pick up the ghostly shades of neutrino and photino fluxes, and if she just — tried — hard enough, she ought to be able to make out the dark matter cloud itself.

“I’ll have to go deeper,” she murmured.

What?

“I said I’m going deeper. I want to find out what’s down there. In the core.”

Lieserl —

“Come on, Kevan. Spare me any warnings about caution. You can’t tell me that Superet has invested so much in me so far, only to have me turn back just inside the damn photosphere.”

You’ve already achieved an astonishing amount.

“And I can achieve a lot more. I’m going in, Kevan. Just as I’ve been designed to. I want to see just what has put out our Sun.” Or, she thought uneasily, who.

Scholes hesitated. The truth is, you’re only an experiment, Lieserl. Damn it, we didn’t even know what conditions you would encounter in there.

“So I’ll take my time. You can redesign me en route. I’ve all the time in the world.

“I’ll follow the bouncing photons. Maybe it will take me a million years to drift into the center. But I’m going to get there.”

Lieserl, Superet wants you to go on. But — you must listen to this — it is prepared to risk you not returning. Your trip could be one way, Lieserl. Do you understand? Lieserl?

She shut out the whispering, remote voice, and stared into the oceanic depths of the Sun.

His legs locked around a branch of the kapok tree, Arrow Maker raised his bow toward the skydome. The taut bowstring dug into the tough flesh of his three middle fingers, and the bow itself had a feeling of heaviness, of power. The arrow balanced in his grasp, light, perfect.

Maker’s bare, hairless skin was slick from the exertion of climbing. He was close to the top of the canopy here, and the clicks, rustles, trills and coughs of the approaching evening sounded from everywhere within the great layer of life around him. Somewhere a group of howler monkeys were calling out their territorial claims, their eerie, almost choral wails rising and falling.

He released the bow string.

The arrow hissed into the air, and the guide line it towed unraveled past Arrow Maker’s face with the faintest of breezes.

He heard a clatter in the branches, a few yards away from him, as the arrow returned. But the line didn’t fall back; Maker had succeeded in hooking it over an upper branch of the kapok.

He slung his bow across his shoulder, retrieved his quiver, and clambered across the branches, his bare feet easily finding purchase on moss-laden bark. He found the arrow in a mound of moss at the junction of a banyan’s trunk with a branch. Working quickly and efficiently, Arrow Maker unraveled a rope from his waist and attached it to the line; the rope — spun by his daughter from liana fiber — was as thick as his finger, and, working by touch. Maker found the rope heavy and difficult to knot.

When the rope was firmly attached Arrow Maker began to haul at the guide line. The rope slithered up through layers of leaves. Soon Maker had pulled the rope over the branch above. He tugged at the rope; there was some give, as the unseen kapok branch flexed, but the hold was more than strong enough to support his weight.