Schild’s Ladder

"That’s it," Tchicaya marveled. "We’ve done it." A lattice of diagonals ran along the path, marking the way, carrying the arrow forward. No compass, no stars to steer by, but they’d found a way to copy the arrow faithfully from start to finish.

"It’s beautiful, isn’t it?" his father said. "This is called Schild’s ladder. All throughout geometry, all throughout physics, the same idea shows up in a thousand different guises. How do you carry something from here to there, and keep it the same? You move it step by step, keeping it parallel in the only way that makes sense. You climb Schild’s ladder."

Tchicaya didn’t ask if the prescription could be extended beyond physics; as an answer to his fears, it was only a metaphor. But it was a metaphor filled with hope. Even as he changed, he could watch himself closely, and judge whether he was skewing the arrow of his self.

"There’s one more thing you should see," his father said. He drew a second path on the globe, joining the same two points but following a different route. "Try it again."

"It will be the same," Tchicaya predicted confidently. "If you climb Schild’s ladder twice, it will copy the arrow the best way, both times." It was like being asked to add up a dozen numbers twice, grouping them in different ways. The answer had to be the same in the end.

"So try it again," his father insisted.

Tchicaya complied.

"I’ve made a mistake," he said. He erased the second ladder, and repeated the construction. Again, the second copy of the arrow at the end of the path failed to match the first.

"I don’t understand," Tchicaya complained. "What am I doing wrong?"

"Nothing," his father assured him. "This is what you should expect. There’s always a way to carry the arrow forward, but it depends on the path you take."

Tchicaya didn’t reply. He’d thought he’d been shown the way to safety, to persistence. Now it was dissolving into contradictions before his eyes.

His father said, "You’ll never stop changing, but that doesn’t mean you have to drift in the wind. Every day, you can take the person you’ve been, and the new things you’ve witnessed, and make your own, honest choice as to who you should become.

"Whatever happens, you can always be true to yourself. But don’t expect to end up with the same inner compass as anyone else. Not unless they started beside you, and climbed beside you every step of the way."

Tchicaya made the globe vanish. He said, "It’s late. I’d better go to sleep now."

"All right." His father stood as if to leave, but then he reached down and squeezed Tchicaya’s shoulder. "There’s nothing to be afraid of. You’ll never be a stranger, if you stay here with your family and friends. As long as we climb side by side, we’ll all change together."

"Tchicaya? Can you hear me?"

It was Mariama.

"Loud and clear," he said. "Are you all right?"

"That depends what you mean by me. My Qusp is fine. Parts of my Mediator got fried; I only have a short-range IR link left. My body’s not a pretty sight, but it’s recovering."

The signal was coming to him via the Left Hand; she’d freed the shuttle and gone there in person. The long-range transceivers in both the module and the shuttle must have suffered irreparable radiation damage, which said something about the likely state of her body.

"What about the others?"

"Wael and Alejandro received similar exposure. They helped me get the shuttle unglued, but they weren’t interested in sticking around, with no mod cons and such poor company. Birago’s body seemed to be in better shape than mine, but the builders halted his Qusp, so he’s as good as departed. When I left, the other rebels were all in a bad way; some of their bodies had reverted to undifferentiated goo, and even in the ones that were still intact and breathing, I’d be surprised if their minds have survived the repair process."

She was probably right; the bodies would make liberal use of apoptosis to kill off radiation-damaged cells, and there was no reason for them to treat neural tissue any differently.

Mariama said, "I went to the Right Hand first, but it had already scribed the Planck worms. It wasn’t pursuing the border down, but I gave it a nudge in the opposite direction, too fast for it to reverse. If we find some use for it, I could go and drag it back, but I’m hoping the Left Hand will be enough."

"It will have to be." Nothing they did to the Right Hand would render it trustworthy.

"Branco told me about the toolkit Yann gave you, while he was cutting us loose, but I didn’t have time to get a copy myself. The simplest thing might be if you send it to me now, before I go chasing the border."

"What?" Tchicaya stared at the red-shifted stars above the horizon, checking the view for any sign that he’d departed from reality and was hallucinating this entire encounter. "Why would that be simplest? You’re coming to get me, aren’t you?"

"That would be an awful waste of fuel. You don’t need to be here, physically."