Louise shook her head. “I can’t make sense of this. What’s causing the amplification?”
He shrugged, theatrically. “Beats me.” He glanced around the sky. “But look around. The Ring is contained in a shell of galactic material, Louise. The frequencies of the radio waves are below the plasma frequency of the interstellar medium. So the waves are trapped in this galaxy-walled box. We’re inside an immense resonant cavity, ten million light years across, with reflecting walls.”
Morrow looked beyond the skydome uncertainly. “Trapped? But what happens when — ”
Lieserl cut in, “Mark, I think I’ve figured it out. The cause of the radio-wave amplification.”
He glanced at her. “What?”
“It’s the inertial drag. We’re seeing super-radiant scattering from the gravitational field. A photon, falling into the Ring’s gravity well, is coupled to the Ring by the inertial drag, and is then thrown out with additional energy — ”
“Ah. Right.” Mark nodded, looking distant. “That would give an amplification of a few tenths of one percent each traverse… just about fitting my observations.”
Morrow frowned. “Did I understand that? It sounds as if the photons are doing gravitational slingshots around this Ring.”
Louise smiled at him, sensing his fear. “That’s right. The inertial drag is letting each photon extract a little energy from the Ring; the radiation is amplified, and the Ring is left spinning just a fraction slower…
“Lieserl. Tell us more about the spacetime metric.” She looked up, at the point of light at the heart of the Ring. “What do we see, there, at the center?”
Lieserl looked up, her face composed. “I think you know, Louise. It is a singularity, at the center of the Ring itself. The singularity is hoop-shaped, a circular flaw in space: a rip, caused by the rotation of the immense mass of the Ring. The singularity is about three hundred light-years across — obviously a lot smaller than the diameter of the material Ring…
“If the Ring were spinning more slowly, the Kerr metric would be quite well behaved. The singularity would be cloaked in two event horizons — one-way membranes into the center — and, beyond them, by an ergosphere: a region in which the inertial drag is so strong that nothing sublight can resist it. If we were in an ergosphere, we’d have no choice but to rotate with the Ring. In fact, if it weren’t rotating at all, the Kerr field would collapse into a simple, stationary black hole, with a point singularity, a single event horizon and no ergosphere.
“But the Ring is spinning… and too rapidly to permit the formation of an event horizon, or an ergosphere. And so…”
Louise prompted, “Yes, Lieserl?”
“And so, the singularity is naked.”
Michael Poole sat with his legs crossed comfortably on the shoulder of the nightfighter. His gaze was on Spinner’s face, steady, direct.
The Ring is a machine, whose sole purpose is to manufacture that naked singularity. Don’t you see? The Xeelee constructed this huge Ring and set it spinning — in order to tear a hole in the Universe.
Spinner-of-Rope enhanced the false-color of the central singularity in her faceplate imager. The flaw looked like a solid disc — a coin, perhaps — almost on edge toward her, but tipped slightly so that she could see its upper surface.
In that surface, white starlight swam. (White?)
She said to Poole, “The Xeelee built all of this — they modified history, disrupted spacetime, drew in galaxies to their destruction across hundreds of millions of light-years — just for this?”
Poole lifted his eyebrows. It is the greatest baryonic artifact, Spinner-of Rope. The greatest achievement of the Xeelee…
The singularity was like a jewel, surrounded by the undisciplined string scribble of the Ring itself.
“It’s very beautiful,” she conceded.
Poole smiled. Ah, but its beauty lies in what it does…
He turned his gaunt, tired face up to the singularity. Spinner-of-Rope, humans have imputed many purposes to this artifact. But the Ring is not a fortress, or a last redoubt, or a battleship, or a base from which the Xeelee can reclaim their baryonic Universe, he said sadly. Spinner, the Xeelee know they have lost this war in Heaven. Perhaps they have always known that, even from the dawn of their history.
“I don’t understand.”
Spinner, the singularity is an escape hatch.
Lieserl and Mark turned to each other, inhumanly quickly. They stared into each other’s eyes, as if exchanging data by some means invisible to humans, their blank expressions tike mirror images.
“What is it?” Louise asked. “What’s happened?”
Pixels, defects in the Virtual projection, crawled across Mark’s cheek. “We need Spinner-of-Rope,” he snapped. “We can’t wait for the repairs to the data links. We’re trying to find bypasses — working quickly — ”
Louise frowned. “Why?”
Mark turned to her, his face expressionless. “We’re in trouble, Louise. The cops are here.”
Spinner-of-Rope asked, “How do you destroy a loop of cosmic string ten million light-years across?”
It isn’t so difficult… if you have the resources of a universe, and a billion years, to play with, Spinner-of Rope. Poole, perched on the shoulder of the nightfighter, pointed at a hail of infalling galaxies swamping a nearby section of the Ring. If the Ring tangles — if cosmic string self-intersects — it cuts itself, he said. It intercommutes. And a new subloop is formed, budding off the old. And perhaps that subloop, too, will self-intersect, and split into still smaller loops… and so on.
Spinner nodded. “I think I understand. It would be an exponential process, once started. Pretty soon, the Ring would decay into the torus of debris we found will find a hundred thousand years from now…”
Yes. No doubt the motion of the Ring has been designed by the Xeelee so that it does not cut itself. But all one need do is start the process, by disrupting the Ring’s periodic behavior. And that is evidently what the photino birds are endeavoring to do, by hurling galaxies — like thrown rocks at the Ring.
Spinner sniffed. “Seems kind of a crude technique.”
Poole laughed. Baryonic chauvinism, Spinner-of-Rope? Besides, the birds have other mechanisms. I —
“…Spinner. Spinner-of-Rope. Can you hear me?”
Spinner sat bolt upright in her couch and clutched at her helmet. “Lieserl? Is that you?”
“Listen to me. We don’t have much time.”
“Oh, Lieserl, I was beginning to think I’d never — ”
“Spinner! Shut up, damn you, and listen.”
Spinner subsided. She’d never heard Lieserl use a tone like that before.
“Use the waldoes, Spinner. You have to get us out of here. Take us straight up, with the hyperdrive, over the plane of the Ring. Have you got that? Use the longest jump distance you can find. We’ll try to patch subroutines into the waldoes, but — ”
“Lieserl, you’re scaring the pants off me. Can’t you tell me what’s wrong?”
“No time, Spinner. Please. Just do it…”
The Universe darkened.