She showed Spinner some data on the signal. “Here’s a graphic of the main sequence, Spinner-of-Rope.” A bar-chart, in gaudy yellow and blue, marched across Spinner’s faceplate. “We’re getting pretty excited about this. For one thing it’s periodic — the same pattern recurs every two hours or so. So we’re pretty sure it has to be artificial. And look at this,” Louise said. A sequence of thirty bars, buried among the rest, was now highlighted with electric blue. “Can you see that?”
Spinner looked at the ascending sequence of bars, trying hard to share Louise’s excitement. “What am I looking for, Louise?”
She heard Louise growl with impatience. “Spinner, the amplitude of these pulses is increasing, in proportion with the first thirty prime numbers.”
The electric-blue bars were split into discrete blocks, now, to help Spinner see the pattern. She counted the blocks: one, two, three, five, seven…
She sensed an invisible smile. Just like a child’s puzzle, isn’t it?
“Oh, shut up,” she said easily.
“What was that?”
“Nothing… I’m sorry, Louise. Yes, I see it now.”
“Look what’s exciting about finding this sequence of primes is that it means the signal is almost certainly human.”
“How do you know that, just from this pattern?”
“We don’t know for sure, of course,” Louise said impatiently. “But it’s a damn good clue, Spinner-of Rope. We’ve reason to believe the prime numbers are of unique significance to humans.
“The primes are fundamental structures of arithmetic — at least, of the discrete arithmetic which seems to come naturally to humans. We are compact, discrete creatures: I’m here, you are out there somewhere. One, two. Counting like this seems to be natural to us, and so we tend to think it’s a fundamental facet of the Universe. But it’s possible to imagine other types of mathematics.
“What of creatures like the Qax, who were diffuse creatures, with no precise boundaries between individuals? What of the Squeem, with their group minds? Why should simple counting be natural to them? Perhaps their earliest forms of mathematics were continuous — or perhaps the study of infinities came naturally to them, as naturally as arithmetic to humans. With us, Cantor’s hierarchy of infinities was quite a late development. And — ”
Spinner barely listened. Humans? Here, at the edge of time and space? “Louise, have you decoded any of the rest of it?”
“Well, we can figure some of it out,” Louise said defensively. “We think, anyway. But remember, Spinner, we may be dealing with humans from a culture far removed in time from our own — by millions of years, perhaps. The people of such a distant future could be almost as remote from us as an alien species. Not even Lieserl has been able to help us work this out…
“But you’ve made some progress. Right?”
Louise hesitated. “Yes. We think it’s a distress call.”
“Oh, great. Well, we’re certainly in a position to help out god-humans from five million years after our birth.”
“Who knows?” Louise said drily. “Maybe we are. Anyway, that’s what we’re going to find out.”
…There was motion at Spinner’s left. She turned.
Suddenly, the forest-dream man was visible. He was sitting there, quite casually — outside the cage — on the construction-material shoulder of the nightfighter. He wore no environment suit, nothing but a plain gray coverall. His hands were folded in his lap. Light — from some unseen source — caught the lines around his mouth, the marks of tiredness in his eyes.
At last he had emerged. Gently, he nodded to her.
She smiled.
“…Spinner?”
“I’m here, Louise.” She tried to focus her attention on her tasks; she reached for the hyperdrive waldo. “Are you ready?”
“Yes.”
The nightfighter flickered through hyperspace. Traveling at more than a hundred thousand light-years per hour, the Northern edged around the torus of fragmented string loops, like a fly around the rim of a desert.
The journey took ten hours. As it neared its end Spinner-of Rope took a brief nap; when she woke, she had her suit’s systems freshen her skin, and she emptied her bladder.
She checked a display on her faceplate. Twenty jumps to go. Twenty more seconds, and -
Something vibrant-blue exploded out of space at her, ballooning into her face.
She cried out and buried her faceplate in her arms.
It’s all right, Poole said softly.
“I’m sorry, Spinner-of-Rope,” Louise Armonk said. “I should have warned you…”
Spinner lowered her arms, cautiously.
There was string, everywhere.
A tangle of cosmic string, rendered electric blue by the faceplate’s false coloring, lay directly ahead of the ship. Cusps, moving at lightspeed, glittered along the twisted lengths. She leaned forward and looked up and down, to left and right; the threads of string criss-crossed the sky as far as she could see, a textured wall across space. Looking deeper into the immense structure. Spinner saw how the individual threads blurred together, merging into a soft mist at infinity.
The string loop was a barrier across the sky, dividing the Universe in two. It was quite beautiful, she thought — but deadly. It was a cosmic web, with threads long enough to span the distances between stars: a web, ready to trap her and her ship.
And, she knew, this was just one thousand-light-year fragment, among thousands in the torus…
“Lethe,” she said. “We’re almost inside this damn thing.”
“Not quite,” Louise said. Her voice, nevertheless, was tight, betraying her own nervousness. “Remember your distance scales, Spinner. The string loops in this toroidal system are around a thousand light-years across. We’re as far from the edge of that loop as the Sun was from the nearest star.”
“Except,” Mark Wu cut in, “that the loop has no easily definable edge. It’s a tangle. Cosmic string is damn hard to detect; the display you’re looking at, Spinner, is all Virtual reconstruction; it’s just our best guess at what lies out there.”
“Then are we at risk by being here?” Spinner asked.
Of course, Michael Poole said.
“No,” Louise said.
“Yes,” Mark said. “Come on, Louise. Spinner, we’re working to minimize the risks. But the danger is there. Spinner, you need to be ready to react — to get us out of here, quickly. We have escape routines laid into the waldoes, for both hyperdrive and discontinuity drive.”
“I’ll be ready,” she said calmly. “But why are we here? Is the human signal coming from somewhere in there — inside the string?”
“No,” Louise said. “Thankfully, Spinner, the signal is coming from the system of a neutron star — just a few light hours away from here. We’ve laid in — ”
” — a discontinuity-drive sequence into the waldoes,” Spinner said drily. “I know.” She reached for her controls. “Tell me when you’re ready, Louise.”
Poole looked tired, his brown eyes deep in a mesh of wrinkles. You know, I worked with Louise Armonk, he said. He smiled. And here we are, together again. Small world, isn’t it? She was a good engineer. I guess she still is.
“I know you decided to close your wormhole time bridge,” Spinner said. “Tell me what happened to you.”