Schild’s Ladder

one thing and not another.

Rainzi didn’t pursue the argument; he followed her in silence as she clambered into the display chamber. This was a small cavity in the Quietener’s outer structure, not much larger than her room at the station, equipped with a single chair. There was no question of Cass being allowed any closer to the action; even the processor on which the Mimosans were running, scrupulously designed to spill as little noise into the environment as possible, was banished to the rim of the Quietener. Lacking the same antinoise features herself, she had to agree to be snap-frozen to a few Kelvin, three minutes before each run. Apart from being immobilized, this had no unpleasant side effects, but it served as an uncomfortable reminder of the fact that the closed-cycle “breathing” of her Mimosan body was pure placebo. Still, she’d been willing to put up with it twenty times so far, merely for the sake of sparing herself the three-second time lag for data to make its way back to the station.

As she took her place in the cryogenic chair, the other Mimosans began to appear around her. Teasing her, congratulating her on her stamina. Livia joked, “We should have had a wager as to whether or not the incremental targets would turn out to be a waste of time. You could have relieved me of all my worldly goods by now.” Livia’s sole material possession was a replica of an ancient bronze coin, carved from leftover asteroid metal.

Cass shook her head. “What would I have put up? My left arm?” They’d been right to do things Livia’s way, and Cass had long ago ceased resenting it. Not only was it safer, it was better science, testing each novel structure one by one.

It turned out that Livia was alluding to a real wager: Bakim admitted that he’d made a bet with Darsono that Cass would not remain at Mimosa to the end. But he was unable to explain the stakes to her; her Mediator couldn’t find a suitable analogy, and nothing she suggested herself was even close. No precious object or information would change hands, nor was there any token act of servitude or humiliation in store for the loser. Cass was amused by the bet itself, but it bothered her that she could only grasp half of what was going on. When her friends asked her about the Mimosans, would all her stories end with apologies for her own incomprehension? She might as well have visited one of the great cities back on Earth and spent her time living in a storm-water drain, having shouted conversations through a narrow grill with the people at street level, full of misunderstandings about objects and events she couldn’t even glimpse.

Rainzi had clearly been delegated to put the Nuclear Question to her, because no one else broached the subject. Cass found it slightly galling that they wouldn’t even suffer a moment’s embarrassment when they took up their superior vantage point. They wouldn’t depart, they wouldn’t abandon her; they’d simply clone their minds into the nuclear substrate. With no expectation of recovering the clones, the originals would have no reason to pause, even for a picosecond, while their faster versions ran.

The target graph appeared on the wall in front of her. The four distinctive node patterns they’d tried in every other combination were all present now. Just as virtual particles stabilized the ordinary vacuum?—?creating a state of matter and geometry whose most likely successor was itself?—?Cass’s four patterns steered the novo-vacuum closer to the possibility of persistence. The balance was only approximate: according to the Sarumpaet rules, even an infinite network built from this motif would decay into ordinary vacuum in a matter of seconds. At the Planck scale, that was no small achievement; a tightrope walker who managed to circum-navigate the Earth a few billion times before toppling to the ground might be described as having similarly imperfect balance. In reality, any fragment of novo-vacuum they managed to create would be surrounded from the start by its older, vastly more stable relative, and would face the inevitable about a trillion times faster.

Ilene reeled off a list of measurements from the instrument probes that were monitoring their environment, out to a radius of more than a light-hour. There was nothing on its way that could wreck the experiment?—?or at least, nothing traveling slower than ninety-five percent of lightspeed. Zulkifli followed with a status report from the machinery deep inside the Quietener. Systems that had been preparing themselves for the last twelve hours were now minutes away from readiness.

The single graph on the wall was just a useful shorthand for the state they were hoping to create; the novo-vacuum itself was the sum of equal parts of forty-eight variations of the target graph, all generated by simple symmetry transformations of the original. All the individual variations favored one direction over another, but the sum combined every possible bias, canceling them all out and giving rise to a perfectly isotropic state. Since none of the graphs could be found in nature, this elegant description was useless as a recipe, but it wasn’t hard to show that the same state vector could also be described by a different sum: forty-eight regions of ordinary vacuum, each slightly curved, oriented in forty-eight different directions.

Inside the Quietener, an asteroid’s-mass worth of helium had been cooled into a Bose-Einstein condensate, and manipulated into a state where it was equally likely to be found in any of forty-eight different places. These alternative locations were distributed across the surface of a sphere six kilometers wide. Ordinary matter?—?or any kind of matter interacting with the outside world?—?would have behaved as if each distinct position had already become the sole reality; if a swarm of dust particles wandering by had made themselves part of the system, or if the helium’s behavior en masse had merely hinted at the detailed motion of its own atoms, then that behavior could only have told half the story?—?the classical half?—?and all the quantum subtleties would have been lost in the fine print. But the condensate was isolated as scrupulously as any cycling Qusp, and it had been cooled to the point where the states of all its individual atoms were dictated completely by its macroscopic properties. With no hidden complications, inside or out, the result was a quantum-mechanical system the size of a mountain.

The geometry of the vacuum in the Quietener inherited the helium’s multiplicity: its state vector was a sum of the vectors for forty-eight different gravitational fields. Once the condensate’s components had all been nudged into place, the quantum geometry at the center of the sphere would be equivalent to the novo-vacuum, and a new kind of space-time would blossom into existence.

That was the idealized version: a predictable event in a known location. In reality, the outcome remained hostage to countless imperfections and potential intrusions. If the experimenters were lucky, sometime over a period measured in minutes, somewhere over a region measured in meters, a few thousand cubic Planck lengths of novo-vacuum would be created, and survive for an unprecedented six-trillionths of a second.

Yann turned to Cass. “Are you ready to freeze?” The first time he’d asked her this, she’d been almost as nervous as the moment before she’d been transmitted from Earth, but the question had rapidly become a formality. Of course she was ready. That was how things were done. Just a few minutes of numb immobility, watching the data appear on the screen in front of her, and the odds were good that it would be the last time. A five-hour trip back to the station, a day or two of analysis, a brief celebration, and she would depart. Her Earth body, frozen more deeply than this one had ever been, was waiting for her. She’d step across the light-years in a subjective instant, a new set of memories to sweep away the icy cobwebs of her old self.

She said, “No. I’m not ready.”

Yann looked alarmed, but only for a moment. Cass suspected that he’d just conferred privately with someone better able to guess what she had in mind. Though the Mimosans didn’t think any more rapidly than she did?—?running on Qusps themselves, they faced the same computing bottlenecks?—?they could communicate with each other about five times faster than her own form of speech allowed. That only annoyed her when they used it to talk about her behind her back.

She added dryly, “Tell Rainzi I’ve changed my mind.”

Yann smiled, clearly delighted, and then his icon was instantly replaced by Rainzi’s. Fair enough: with the countdown proceeding, the Mimosans had better things to do than fake inertia for its own sake.

Rainzi’s response was more cautious than Yann’s. “Are you certain you want to do this? After everything you told me?”

“I’m the quintessential singleton,” Cass replied. “I weigh up all my choices very carefully.”

There was no time to spell out in glacial words everything she was feeling, everything that had swayed her. Part of it was the same sense of ownership that had brought her all this distance in the first place: justifiably or not, she didn’t want the Mimosans to have a better view than she did of the thing they were about to create together. There was the same longing for immediacy, too: she would never see, or touch, any graph as it really was, but to remain locked in a body that could only perceive a fraction of the data, milliseconds after the fact, would leave her feeling almost as detached from the event, now, as if she’d stayed on Earth, waiting for the centuries-old news of an experiment conducted light-years away. Every viewpoint was a compromise, but she had to be as close as she could get.

Beyond the experiment itself, though, it was clear to her now that she couldn’t leave Mimosa without doing