Ring

“Louise, there is no way this monster could have formed naturally. Our best theories say that any natural string loops should be a mere thousand light-years across.” She looked up, and the blue false color of the string images caught her profile, picking out the lines around her eyes. “Somehow — ” she laughed briefly ” — somehow the Xeelee found a way to drag cosmic string across space — or else to manufacture it on a truly heroic scale — and then to knit it up into this immense artifact.”

Louise stared up at the Ring, tracing the tangle of string around the sky, letting Lieserl’s statistics pour through her head. And I might have died without seeing this. Thank you. Oh, thank you…

“The cosmology here is… spectacular,” Lieserl said, smiling. “We have, essentially, an extremely massive torus, rotating very rapidly. And it’s devastating the structure of spacetime. The sheer mass of the Ring has generated a gravity well so deep that matter — galaxies — is being drawn in, toward this point, across hundreds of millions of light years. Even our original Galaxy, the Galaxy of mankind, was drawn by the Ring’s mass. So we know that the Ring was indeed the ‘Great Attractor’ identified by human astronomers.

“And the rotation has significant effects. Louise, we’re on the fringe of a Kerr metric — the classic relativistic solution to the gravitational field of a rotating mass. In fact, this is what’s called a maximal Kerr metric: because the torus is spi

“As Mark said, the Ring’s rotation is exerting a large torque on the ship. This is inertial drag: the twisting of spacetime around the rotating Ring.”

Morrow frowned. “Inertial drag?”

Lieserl said, “Morrow, naive ideas of gravity predicted that the spin of an object wouldn’t affect its gravitational field. No matter how fast a star rotated, you’d be attracted simply toward its center, just as if it wasn’t rotating at all.

“But relativity tells us that isn’t true. There are nonlinear terms in the equations which couple the rotating mass to the external field. In other words, a spi

“What else?” Louise asked. “Mark?”

He nodded. “The first point is, we’re drowning in radio wavelength photons — ”

That was unexpected. “What are you talking about?”

“I mean it,” he said seriously, turning to face her. “That’s the single most significant difference in our gross physical environment, compared to the era we came from: we’re now immersed in a dense mush of radio waves.” He looked absent for a moment. “And the intensity of it is increasing. There’s an amplification going on, slow, but significant on the timescales of this war; the doubling time is around a thousand years. Louise, none of this shows up in the future era. By then, the radio photons will be gone.”

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 spi

“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 spi

“But the Ring is spi

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 Spi

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 spi