"But once the Qax begin their assault—"

"It will be too late." Berg took Michael’s arm; the fear still masked her face, he saw, but some of her determination, her cunning, seemed restored. "Listen to me. The best chance of hitting them is going to be now… in the first few minutes after the Spline emerge from the portal."

Poole nodded. "Right. Causality stress."

"The Spline are living creatures," Berg said. "Maybe that’s a weakness we can play on; the Qax, and their ships, are surely going to take a while to ramp up to full effectiveness. If we can hit them fast maybe there’s a chance."

Berg was right, of course. There was a kind of inevitability to all of this, Poole thought. It’s going to be up to us. He closed his eyes, longing for the silence — the lack of decisions — of the Oort Cloud.

Harry laughed, his voice brittle and too bright. "Hit them fast? Sure. With what, exactly?"

Poole whispered, "With the singularity cannon."

Berg looked at Michael sharply, possibilities lancing through her mind. "But — even if we get the Friends to agree — the cannon wasn’t designed as a weapon."

Michael sighed, looking tired. "So we adapt."

Harry said. "As long as the damn things can be pointed and fired. Tell me how the things are supposed to work. You fire black holes into Jupiter…"

"Yes," Michael said. "A pair of singularities is launched in each cannon shot. Essentially the device is a true cannon; once the singularities are launched their paths are ballistic. Orbiting each other, a few yards apart, the singularities enter Jupiter’s gravity well. The trajectories are designed to merge at a specified point in the body of the planet."

Berg frowned. "Ultimately the hole, or holes, will consume Jupiter…"

"Yes. The Project’s design is to render Jupiter into a single, large black hole of a specified mass—"

"But that could take centuries. I know the holes’ growth would be exponential, but still you’re starting from a miniscule base; the holes can only grow as fast as their area allows them."

"That’s true." He smiled, almost wistfully. "But the time scale of the Project is longer than centuries; far longer."

Berg tried to drag ideas from her mind, ignoring the lowering sky above her.

How could they use this planetbuster cannon to disable a Spline? If they simply shot off black holes, the tiny singularities would pass through the flesh of the warship. No doubt tidal and other effects would hurt the Spline as the holes passed through, and maybe they’d strike it lucky and disable some key component… but probably not; the Spline was a mile wide and the wounds inflicted by the traversing holes would surely be not much worse than isolated laser shots.

A multiple strike, a barrage? "What if we launched two singularities to come to rest at the center of mass of the Spline? Could we do that?"

"Of course." Michael frowned; she could almost see trajectory curves rolling through his head. "We’d simply need to launch the singularities with a low velocity — below the earth-craft’s escape velocity, essentially."

"Yes." Berg pictured it. Like stones hurled into the air, the singularities would come to rest, hover in the body of the Spline itself… But only for a moment, before falling back. What good would that do? It would take days for the holes to consume the Spline’s mass — hours, probably, to absorb enough material to inflict any significant damage — not the few seconds they would be present in the volume of the Spline.

Anyway, they wouldn’t have hours to spare.

Then what?

"Why send the singularities into Jupiter on such complex trajectories? Why have them merge before they reach the center?"

Michael shook his head. "You haven’t grasped the subtleties of the design," he said seriously.

"Evidently not," Harry said dryly.

"Do you understand what happens when two singularities converge, combine?" He mimed, with his two fists, the singularities approaching each other, whirling around each other, finally merging. "The event horizons merge into a single horizon of greater net area… entropy, proportional to the area, increases. The singularities themselves, the flaws in space at the heart of the holes, fall in on each other; blue-shifted radiation increases the effective mass until the final merger occurs on Planck time scales — the immense gravitational fields generated effectively deflate time. And the joint event horizon quivers like a soap bubble, generating radiation through quadrupolar effects."

Berg nodded slowly. "And what form does this — radiation — take?"

He looked surprised by the question. "Gravitational, of course. Gravity waves."

She took a deep breath, felt her blood surge through her veins a little faster. Gravity waves.

Michael explained further.

These weren’t the dinky little ripples in spacetime, propagating at lightspeed, which had been studied by human astronomers for centuries… When two massive singularities merged, the gravity waves were monstrous. Nonlinear distortions of spacetime itself.

"And the radiation is directed," Michael said. "It pulses along the axis of the hole pair. By choosing precisely the placement and orientation of the holes at merger inside the carcass of the planet, you can direct gravity-wave pulses as you choose. You can sculpt the implosion of Jupiter by working its substance on a massive scale; it was the Friends’ intention, I believe, even to remove some of the mass of the planet before the final collapse. The precise size, angular momentum, and charge of the final black hole are evidently important parameters for the success of—"

But Berg was no longer listening. Then the earth-ship wasn’t just — just — a singularity cannon platform. It was a gravity-wave gun.

A human-built starbreaker.

They could fight back.

Michael looked up and gasped. The color of the sky had changed, and cast gray shades across his face.

Berg looked up. A vast moon of flesh slid complacently toward the zenith, its gunmetal-gray surface pocked with eye sockets and weapon emplacements. Bloody scars a hundred yards wide disfigured the skin-hull. Berg searched for the Interface portal and made out another of the great elephant-ships emerging from the wormhole passage to the future. Its limb brushed the sky-blue wire framework of the portal, and a layer of flesh boiled away as exotic matter raised tides in living tissue.

Spline…

It had begun.

Jasoft Parz, suspended in entoptic fluid, clung to the rubbery material of the Spline’s cornea and peered out at the past.

Parz’s ship was climbing out of Jupiter’s gravity well now, on its way to its hyperspace jump-off point to the inner planets. The wormhole Interface portal was receding; the portal looked like a bluish scar against the swollen cheek of Jupiter. Parz could see that a second Spline ship, the companion of his own, already loomed over the scrap of Earth green that was the rebels’ craft.

Parz sighed. "The rebel ship is elegant."

The Qax said, "It is a scrap of mud hurled into space by hyperactive apes."

"No. Look at it again, Qax. A camouflaging layer of earth built over a shell of Xeelee construction material… They must have stolen a Xeelee flower, constructed this thing in some deep hollowed-out cavern." He laughed. "And all under your watchful gaze."

"Under my predecessor’s gaze," the Qax said slowly. "According to the ship’s sensors the thing is constructed around a layer of singularities. A thousand of them, the total amounting to an asteroid-scale mass…"

Parz whistled. "That doesn’t sound possible. How—"