Cosmic string wasn’t actually one-dimensional; it was a Planck length across, a fine tube containing charged particles: quarks, electrons and their antiparticles, gathered into super-heavy clusters. As a result, string acted as a superconducting wire.
The string knot was cutting through this galaxy’s magnetic field. As it did so immense electrical currents — of a hundred billion billion amps or more — were induced in the string. These currents generated strong magnetic fields around the string.
The string’s induced field was stronger than a neutron star’s, and dominated space for tens of light-years around the knot.
Mark said, “The string has a maximum current capacity. If it’s overloaded, the string starts to shed energy. It glows with gamma radiation. And the lost energy crystallizes into matter: ions and electrons, whispering into existence all along the length of the string.” Spinner saw representations of particles — out of scale, of course — popping into existence around the string image. “So the string is glowing as brightly as a star.”
“Yes,” Louise put in. “But the distribution of the radiation is odd, Mark. Look at this. The radiation is beamed forward of the loop’s motion — parallel to that forward spike of gravitational radiation.”
“Like a searchlight,” Morrow said.
Or a spear…
She heard Morrow saying, “Mark, what is driving the string? What is impelling it through space, and into this galaxy?”
“Gravitational radiation,” Mark said simply.
Louise said, “Morrow, gravity waves are emitted whenever large masses are moved through space. Because the loop is asymmetrical it’s pushing out its gravitational radiation in particular directions — in spikes, ahead of and behind it. It is pushing out momentum… It is a gravitational rocket, using its radiation to drive through space.”
Mark said, “Of course the gravitational radiation is carrying away energy — the string is shrinking, slowly. In the end it will collapse to nothing.”
“But not fast enough to save this galaxy,” Uvarov growled.
“No,” Louise said. “Before it has time to decay away, the string is going to reach the core — and devastate the galaxy.”
Close your eyes.
Spinner-of-Rope shivered. Once again the voice had come from her left — from somewhere outside her suit. She stared at the Virtual image in her faceplate, not daring to look around.
Close your eyes. Think about your vision again — of the string loop, cutting through the stars. It frightened you, didn’t it? What did that image mean, Spinner-of-Rope? What was it telling you?
Suddenly she saw it.
“Mark,” she said. “This is not just a gravitational rocket.”
“What?”
“Think about it. The string knot must be a missile.”
The galaxy images dimmed, leaving Mark and Lieserl suspended in a crimson-tinged darkness. Then, against that background, new forms began to appear: speckles of light, indistinct, making up the ghostly outline of a torus, its face tipped open toward her.
“Of course this is a false color representation,” Mark said. “The images have been reconstructed from gravity wave and gamma ray emissions…”
The torus as a whole reminded her, distantly, of Saturn’s rings; it was a circle which spanned the galaxy-walled cavity.
At first she thought the component speckles were mere points of light: they were like stars, she thought, or diamonds scattered against the velvet backdrop of the faded galaxy light. But as she looked more closely she could see that some of the nearer objects were not simple points, but showed structure of some kind.
So these weren’t stars, she thought, and nor was this some attenuated galaxy: there were only (she estimated quickly) a few thousand of the shining forms, as opposed to the billions of stars in a galaxy… And besides, this cavity spanning torus was immense: she could see how the blood-dark corpses of galaxies sailed through its sparse structure.
She knew that the Galaxy of humans had been a disc of stars a hundred thousand light-years in diameter. This torus must be at least a hundred times as broad — more than ten million light-years across.
She turned to Mark; he studied her face, a certain kindness showing in his eyes now. “I know how you’re feeling. It’s magnificent, isn’t it?”
“It can’t be the Ring,” she said slowly. “Can it? As far as we know, Jim Bolder reported a solid object — a single, continuous artifact.”
“Look more closely, Lieserl. Cheat a little; enhance your vision. What do you see?”
She turned her head and issued brisk subvocals. A section of the torus exploded toward her; the fragments, rushing apart, gave her a brief, disorienting impression of sudden velocity.
Her view steadied. Now, it was as if she was within the torus itself, and the sparkling component objects were all around her.
The fragments weren’t simple discs — or ellipses, or any of the shapes into which a star or galaxy might be distorted by the presence of others. She could see darkness within the heart of these objects.
The fragments were knots.
“Mark — ”
“You’re looking at loops of cosmic string,” he said calmly. “This immense torus is made up of string knots, Lieserl ten thousand of them, each a thousand light years across.”
She was aware of her hand convulsing closed around his. “I don’t understand. This is — fantastic. But it isn’t the Ring Bolder described.”
He looked distant, wistful. “But it must be. We know we’ve come to the right place, Lieserl. This is undoubtedly the site of the Great Attractor: the loops, together, have sufficient mass to cause the local streaming of galaxies.
“And we know this assemblage must be artificial. Primeval string loops could have formed during the formation of the Universe, after the singularity. But there should have been no more than a million of them — in the entire Universe, Lieserl — spaced tens of millions of light-years apart. It simply isn’t possible for a collection of ten thousand of the damn things to have gathered spontaneously within a cavity a mere ten million light-years across…”
“But,” Lieserl said patiently, “but Bolder said the Ring was solid. If he was right — ”
“If he was right then the Ring has been destroyed, Lieserl. These loops are rubble. We’re looking at the wreckage of the Ring. The photino birds have won.” He turned to her, his face a sculpture, expressionless, obviously artificial. “We’re too late, Lieserl.”
She felt bewildered. “But if that’s true — where are we to go?”
Mark had no answer.
Louise said, “What are you talking about, Spinner?”
“Can’t you see it?” She closed her eyes and watched, once again, as the string loop punched through the fragile superstructure of the galaxy. “Mark — Louise this string loop was aimed, quite precisely. It’s a weapon. It is blasting through this galaxy with its gravitational rockets, destroying all in its path with focused beams of electromagnetic and gravitational energy…”
Louise snapped, “Mark?”
Mark hesitated. “We can’t prove she’s right, Louise. But the chances of the loop hitting such a precise trajectory at random are tiny…”
“It seems crazy,” Morrow said. “Who would dare use a thousand-light-year loop of cosmic string as a weapon of war?”
Uvarov grunted. “Isn’t that obvious? The very entities we have come all this way to seek, from whom we hope to obtain shelter — the Xeelee, Morrow; the baryonic lords.”
“But why?” Mark asked. “Why destroy a galaxy like this?”
“In defense,” Uvarov snapped.
“What?”
“Isn’t that clear too? The Xeelee were masters of the manipulation of spacetime. Their weaponry consisted of these immense structures of spacetime flaws. And the flaws have been used against the weapons of their enemies — like this galaxy.”