She grunted in reply to Louise.

It was Spinner’s tenth day in the nightfighter cage.

She loosened her restraints and looked around — and found herself staring into intergalactic emptiness. In the distance were patches of muddy light which could have been galaxies, or clusters of galaxies — so remote that even at the ’fighter’s immense speed of three million light-years a day, she could make out no discernible movement.

Spinner slumped back into her couch. “Lethe. Another day in the middle of this gray, lifeless desert,” she said sourly.

Louise — watching, Spinner knew, from her encampment on the Northern’s forest Deck — laughed, sounding sympathetic. “But today should be a little more interesting than most, Spinner-of-Rope. We’ve reached a milestone. Or rather, a mega-light-year-stone…”

“We have?”

“After ten days, we’ve come thirty million light-years from Sol. Spinner, we’ve reached the center of the Virgo Cluster — the supercluster of galaxies of which our Galaxy is a member. Way behind you is a little patch of light: that’s the Local Group — three million light-years across, the small cluster dominated by our Galaxy and the Andromeda galaxy. And to your left, at about eleven o’clock, you’ll see the center of the Virgo Cluster itself: that massive group of several thousand bright galaxies. They used to be bright, anyway…”

Spinner made out the central galaxy group. It was a gray, grainy cloud of light. “Fascinating.”

“Oh, come on, Spinner. Look, we’re making an epic journey here — we’re traveling so far we’re making progress through the large-scale structure of spacetime. You can’t fail to be — well, uplifted.”

“But I can’t see any of it, Louise,” Spinner said fretfully.

Louise was silent for a moment. Then she said, “All right, Spinner. I’ll show you where you are.”

A ball of brilliant white light, expanding rapidly to about a foot across, appeared a few yards in front of the ’fighter cage.

Spinner slouched in her couch and folded her arms. “Another educational Virtual display, Louise?”

“Bear with me, Spinner-of-Rope. Look at this. Here’s the Universe, expanding from the Big Bang — as it was after perhaps three hundred thousand years. The cosmos is a soup of radiation and matter — a mixture of the dark and light variants.

“The temperature is still too high for atoms to form. So the baryonic matter forms a plasma. But plasma is quite opaque to radiation, so the pressure of the radiation stops the matter from clumping together. There are no stars, no planets, no galaxies.”

Abruptly the Virtual Universe expanded to double its size, and turned clear; a flash of light flooded out over Spinner’s face, making her blink.

“Now the temperature has fallen below three thousand degrees,” Louise said. “Suddenly the electrons can combine with nuclei, to form atoms — and atoms don’t interact strongly with photons. So the Universe is transparent for the first time, Spinner. The radiation, free to fly unhindered across space, will never interact with matter again. And in fact we can still see the primordial radiation today — if we care to look, its wavelength greatly stretched by the expansion of the Universe — as the cosmic background microwave radiation.

“But the key point is, Spinner, that after this decoupling the radiation could no longer stop the matter from clumping together.”

The model Universe was now a cloud of swarming, jostling particles.

“It looks like a mist,” Spinner said.

“Right. Think of it as like a dew, Spinner. It’s spread out thin and uniform: on average there’s one hydrogen atom in a space the size of one of our transport pods. And at this point the expansion of the Universe is pushing the dew-drops still further apart. But now, the structures of matter the galaxies, the clusters and superclusters of galaxies are ready to coalesce; they’ll condense out like dewdrops on a spider web.”

Spinner smiled. “Some spider. But where’s the web?”

The ball of mist was filled, now, by a fine tracery of lines; the toy Universe looked like a cracked, glass sphere. “Here’s the web, Spinner,” Louise said. “You’re looking at cosmic strings. Strings are defects in spacetime — ”

“I know about string,” Spinner said. “The Xeelee used strings — and domain walls — in the construction of the nightfighter.”

“Right. But these strings formed naturally. They are remnants of the phase transitions of the early Universe, remnants left over after the decomposition of the GUT unified super-force which came out of the singularity… Cosmic strings are residual traces of the ultrahigh, symmetric vacuum of the GUT epoch, embedded in the ‘empty space’ of our Universe — like residual lines of liquid water in solid ice. And the strings are superconducting; as they move through the primordial magnetic fields, huge currents of a hundred billion billion amps or more — are induced in the strings…”

The strings writhed, like slow, interconnected snakes, across space. The particles of mist, representing the uniform matter distribution, began to drift toward the strings. They coalesced in narrow columns around the strings, and in thin sheets in the wake of the strings.

“It’s beautiful,” Spinner said.

“The strings are moving at close to lightspeed,” Louise said. “They leave behind them flat wakes — planes toward which matter is attracted, at several miles a second. Structure starts to form in the wakes, so we get a pattern of threads and sheets of baryonic matter surrounding voids…” Now the baryonic matter, coalescing around the string structure, imploded under its own gravity. Tiny Virtual galaxies — charming, gem-like — twinkled to life, threaded along the webbing of cosmic string.

“And there’s more,” Louise said. “Look at this.”

Now there was a loop of cosmic string, twisting in space and oscillating wildly.

“String loops can form, when strings cross each other,” Louise said. “But they’re unstable. When loops form they decay away rapidly… unless they are stabilized, as the Xeelee have made stable their nightfighter wings. Now: remember I told you that the strings are superconducting threads, carrying immense electrical currents? When the strings decay, all that electromagnetic energy has to go somewhere…”

Abruptly the loop shrank, precipitately, and once again light blasted into Spinner’s face.

Spinner lifted her hand to her faceplate. “I wish you’d stop doing that,” she said.

“Sorry. But watch, Spinner. See what’s happened?”

Spinner dropped her hand and blinked dazzled eyes.

The explosion of the loop of string had blown out a huge hole, in the middle of the mesh of galaxy threads.

Spinner nodded. “I get it. There’s a pulse of electromagnetic energy, which blows a bubble in the clouds of matter.”

“Not quite,” Louise said. “Spinner, remember that dark matter is transparent to photons — to electromagnetic radiation. So the loop’s electromagnetic pulse blows out just the baryonic matter; it leaves a hole, filled by dark matter but scoured clean of star stuff.

“Spinner, all this cosmic engineering induced by the strings — the primordial seeds — has left us with a fractal structure, fractal means the foam has the same general structure at all scales. It looks the same, no matter how far out or how close in you study. Our Galaxy is part of a small cluster — the Local Group — which, together with several other clusters, is part of a supercluster called the Virgo Cluster… which in turn — ”

“I get the idea,” Spinner said.

“The baryonic matter is clustered in filaments and sheets, around huge voids filled only with dark matter. It’s like a froth, Spinner — and it’s a very active froth, like an ocean’s surface, perhaps; the strings are whipping through space at near lightspeed, and so there are huge movements, currents in the foam.”