Mere looked at a diamond sphere, and inside it, the suspended fragment of the polypond mind. Warmth and an array of delicate silver fingers had allowed a feeble life to emerge. The fragment was thinking. This was what it seemed to be thinking. Again, Mere stared at the display cube nestled in her hand, exhausted eyes working their way through the intricate web of three-dimensional symbols.

“This is my friend’s mind?”

“It is a very simple representation, yes.” A hint of pride surfaced as the machine remarked, “The amount of information is impressive. Despite time and the mind’s damage, it has retained this much.”

“A three-dimensional image?”

“And more, madam.”

She hesitated. “There’s a time component?”

“Yes.”

“Show me.”

Every thread of the web slowly shifted position, and after a little while, all began to contract or to melt away. The display shriveled into a smaller, denser shape that eventually became nothing but a dark smudge.

“This is the past?”

“It seems so,” the machine offered.

Mere nodded, her tiny face pale and drawn. Then an instinct tickled her, and smiling, she said, “There’s more, isn’t there?”

“Several curiosities, yes.”

The AI ran the image forward in time. The smudge enlarged and grew thinner, becoming a lacework of tiny details rendered in three dimensions. Turning the cube in her hands, she studied its final shape. “I see a resemblance,” she muttered. “Is this a map of the Inkwell?”

“Perhaps.”

“Are these strands the rivers of ice?”

“No.”

“Okay,” she said. “The curiosities. Show me.”

A tiny portion of the display was enlarged a thousandfold, revealing an equally intricate set of features. The central strand was composed of a multitude of tiny flecks and round forms and new strands as straight as taut hairs. Again, time ran backward. The various features shifted and sometimes vanished, and the round shapes passed out of view or shrank down to tiny points that moved together, swirling in unison much the same as the polypond buds swam inside their birthing space.

“Watch carefully,” the AI advised.

Time ran forward, ending with something very close to the present.

“Did you notice?”

“I doubt it.”

Like an endlessly patient teacher, the AI said, “Watch again.”

Three times, the process was repeated. And then Mere said, “Enough,” as she touched the display with the nail of one finger. “There are always differences, is that right? The positions of these features … they seem to shift a little bit …”

“Minuscule differences, but genuine. I have unfolded this thought more than twelve thousand times, and each replay is unique.”

Mere opened her mouth, then closed it again.

“This is a partial memory,” the machine offered. “Perhaps your friend is struggling to recall everything with precision.”

“No,” Mere said. Then she set the cube aside, drifting out of the tiny lab, trying to coax her weary mind into using its own deep and perishable memories.

A navigational AI whispered, “You asked to be informed, madam.”

“More buds moving?”

An image filled the nearest touch screen. Several light-months deeper inside the Satin Sack, a multitude of watery bodies were beginning to accelerate, engines flinging much of their bodies into the dusty gloom, giving them momentum while stealing away most of their lazy mass.

“I want to see the ship now, please.”

Still far behind her, the ancient vessel was visible only in the infrared, the blaze of its engines and the wild discharging of its shields producing a sloppy dot that would brighten over the next months and years. While Mere watched, a tiny flash of light swept across the leading face. The laser array had struck some burly hazard. Another few seconds told her that the blow was successful. If anything substantial had reached the hull, she would have seen the blast. In her present mood, she probably would have felt it, too.

“I assume these little ones are also aiming for the Great Ship.”

“Presumably, yes,” said the navigator AI.

“And when?”

“As with the rest—” the voice began.

She named the year. This was a slow stately chase, and everything about it seemed inevitable. Irresistible.

Mere returned to the other AI. “You mentioned more than one curiosity. What else is there?”

“I have to warn you. I’m not trained in the details and every side-shoot concept that involves these high mathematics.”

“Okay.”

“But more than four dimensions are folded into the memory. They are invisible, but they seem to have a genuine value.”

She nodded, watching the polyponds rise to meet the ship.

“When I said that this is a partial memory,” the AI continued, “and perhaps your friend is struggling to recall—”

“I said, ‘No.’”

“Would you explain why, madam?”

Every AI listened now. A glance at the main touch pad told her that she was the focus of considerable interest.

Recovering the display cube, she offered, “I don’t think this is a genuine memory, and it isn’t a map, either.” Then she shook her head, adding, “This is a lesson, I’m guessing. Search our library. Learn what you can about mathematical treatments of time … treatments that erase the concept of an authentic past … and then apply what you learn there to what we have with us here …”

A moment passed.

“This is a very complicated subject,” the AI complained.

“Then you aren’t thinking about it properly,” she chided gently. Then she pushed the cube aside, ordered the cabin lights down, and forced herself to crawl inside her sacklike bed and rise into a dreamless deep sleep.

BUT THERE WAS such a creature as the Past: a remote and simple and pure entity, and everything of consequence had leaped from its beautiful self. What every Tilan understood instinctively, and what Mere had learned in her long early life, was that the future was infinite and unknowable. Every instant of time had no choice but to explode into long lines of potential. Existence was a multitude of rivers born from an ever-increasing assortment of springs. Mere was born in one moment and one place, and now she lived on a million worlds and between the worlds and in places she could never imagine.

This Mere had a past that she knew well and cherished.

This Mere only appeared solitary, but she was part of a rich thread of interlinked moments leading directly from that slightly younger, slightly less informed woman who had told her AI, “Then you aren’t thinking about it properly.”

Eleven months had passed, and Mere was cold again. She had dismantled and dispersed the Osmium, power minimal and her own body chilled to the brink of death. Surrounding her was an ebony shell of motionless dust, smothering and dense and surprisingly warm within. When she studied the cloud earlier, in visual light and from a great distance, she saw nothing. Her best eyes had stared at the same points for hours, absorbing only the occasional glimmer of radio noise and the wandering photons that had pierced the banks of dust and molecular hydrogen. But the infrared was richer, revealing a network of starlike dots and tidy smears arranged with precision. And more telling, her surviving neutrino detector—a minimal sensor on its finest day—was loudly proclaiming, “Something bright, I see! I see!”

Similar clouds were scattered throughout the neighborhood. Each was a neat sphere held together by electrostatic charges and youth. Each was smaller than a solar system and blackened with buckyballs and other carbon grits, natural and otherwise. But only one of the clouds lay close enough to be reached. A series of little bums could push Mere into a collision course, and against the sober advice of her resident AIs, she had accepted that grand chance.

Months later, her disassembled ship plunged into the cloud. After several hours of pushing through thickening dusts, she spotted her potential targets. They were tiny objects. Remote. Yet the gap was barely 50 million kilometers now, which was no distance at all. On her present course, Mere would pass by the first of the mysteries in less than nine minutes. The entire collection of bodies would fall behind in another half hour. They were warm objects, pieces of them fiercely hot, each wearing elaborate radiators that pumped the excess heat into cold sinks and the surrounding cloud, and they were intriguing enough that even the most cautious AIs had stopped their public worrying.