Drea snorted. “You’re very literal, aren’t you, Rustie?”

Alia walked forward to the nearest of the low structures on the floor. It was a box no more than waist-high. She found a disc of some translucent substance set in its wall. When she passed her hand before the disc a spot of light, a very faint blue, showed up on her palm. She asked, “Lasers?” Glancing around, she imagined a network of the beams criss-crossing the huge chamber.

And now she heard a scuttling, glimpsed a hunched form. It ran through the shadows, hurrying from the cover of one of the laser boxes to another. It had huge eyes, eyes like saucers.

Drea said dryly, “I take it that was a Listener. Another specialist drone type?”

Alia said, “I suppose so. But what do they listen to?”

Berra said, “To the echoes of time.”

The Transcendence did not see itself as an end for which the desolation of past lives had merely been a necessary means. It believed it must somehow redeem the past, if it were to be cleansed — if it were to be perfect.

But once the goal of Redemption had been formulated, the nascent Transcendence had had to face profound questions. How was the past to be redeemed? Throughout the Commonwealth, Colleges of Redemption were established to address this question. At the very least, it was soon realized, the Transcendence — and indeed the mankind from which it arose — must be aware of the past, so that the past could be taken into the awareness of the Transcendence, a part of its eternal whole.

In the first attempts, vast museums were established. Many of them were virtual, shared between worlds, with no single physical presence. And in these museums immense dioramas were shown, great events of the past brought before the eyes of the present, based on the best reconstructions of the historians and archaeologists.

But it was not enough.

For one thing the present was an imperfect window of the past. Human records were always incomplete, and often full of lies anyhow. Of course there were physical traces to be retrieved, and legions of new archaeologists descended on all the worlds of mankind, and especially Earth. Some elements of the past were recorded in the genetic legacy of mankind itself, still carried within human bodies, even though they had been scattered across the Galaxy, morphing and changing as they went. But various catastrophic events, natural or otherwise, had left huge blanks in all such records.

And no matter how complete the records might be, there was still the question of interpretation — of the meaning of the events, the motivations and intentions of the characters of the times, many so remote from the Transcendents as to be practically another species. A new generation of historians sprang up, arguing over differences of meaning great and small.

It was all very unsatisfactory. So, even as the first dioramas were established, efforts continued to deepen and widen the Redemption. And at last a new way to excavate the past was discovered.

On the Nord, only very small children thought the universe was infinite. Just because it looked that way didn’t make it so, any more than the apparent flatness of a planet meant it had to be an infinitely flat plane. The universe was finite: closed, folded over on itself. To Alia the finiteness of the universe was as obvious and intuitive as, to an Earthborn child, it was obvious that the sun was a star.

And it was useful. As the Transcendence had sought ways to recover its past, it had fallen on the closure of the universe. For time and space were not separate entities but merged into one unity, spacetime. And so in a finite universe the closure must be complete in time as well as in space. Just as one side of the universe was connected to the other, so the very far future was connected to the very remote past.

And that was how you could detect the past: by listening for its echoes.

The finite universe had a topology, a connectedness imposed at the Big Bang, the instant of the initial singularity. Sitting inside the universe, you couldn’t see that topology directly. But there were ways to sense its presence.

Alia had once had a toy, a virtual game. It was like a slab of sky inside a cubical box. Battling spacecraft,

black alien bad guys and heroic Exultant greenships, would slide through the sky, firing cherry-red beams at each other. But the game wasn’t confined to the walls of the box. If a ship hit a wall, it would disappear — but would reappear on the other side of the box, heading the same way. So, even though they were separated in space, the points on each wall mapped precisely onto the corresponding points on the opposite wall. It was as if the whole of the universe were tiled, filled with identical copies of the game, joined side to side. Once you got used to it you could use the strange folded-over property as part of your tactics; you could send your greenships to sneak around the universe’s “curve” and fall on the aliens from behind.

And you could play other games. You could imagine setting off an explosion somewhere in the box. A spherical shock wave would set off in all directions. It would stay a simple sphere until the front passed through the walls of the box, after which it would fold around and intersect itself, forming circular arcs all over the place. Alia could see that if you sat in the middle of the box and watched those shock-circles blossoming all over your sky, you could use the pattern to figure out the geometry of your box-cosmos. It was just as you could figure out the lattice structure of a crystal by studying the patterns in the way electrons were diffracted passing through it. The whole of spacetime was a lens, shaping the radiation that washed through it.

The Listeners’ purpose was to explore this tremendous diffraction. They mapped gravity waves, ripples in spacetime itself, deep and long, spreading at light speed from the universe’s most titanic events: the explosive deaths of stars and galaxy cores, the collisions of black holes and galaxies. Gravity ripples passed further than any other, and they offered, indirectly, the clearest possible map of the universe, its structure, and its contents. “Remarkable,” Reath breathed. “And so these ‘Listeners’ watch the laser light with those big eyes of theirs. These long light beams are sensitive to disturbance by the gravity waves which wash through the core of the planet.” Strangely, some gravity wave frequencies were in the rages of a few thousand cycles per second: converted to sound waves, they were audible to human ears. The Listeners actually heard the chirp of colliding neutron stars, the warble of one black hole absorbing another.

The gravity-wave echoes washed around the closed universe, from pole to pole — and from future to past. The information the Listeners sought from their gravity waves wasn’t just about the great physical events of the universe. It was about the history of mankind.

The Transcendence had conceived a great project. It would build a probe that it would send into the furthest future, and thereby hurl it into the deepest past. And there, hiding in the dark at the rim of Sol system, this monitor from the future would witness the unfolding of mankind’s deepest history — and it would send the whole complex story back around the curve of the universe to the great entity that had constructed it. The Listeners recorded these whispers, sent from the deepest past to the furthest future. Once retrieved, the news from history was analyzed and stored in Coalescent archives, and disseminated to form the basis of the Witnessing.

Thus the past was brought into the present of the Transcendence. And, buried somewhere in that immense lode of data mined from the past, was the wormlike thread of Michael Poole’s biography.