Schild’s Ladder

"Just thinking about home." Birago nodded vaguely in the direction of the blue shift, but Tchicaya knew which star he meant. It had been chosen by the people on Viro before they were scattered, and Tchicaya had had it pointed out to him by the evacuees he’d encountered on half a dozen worlds. The spore packages had already been launched from Gupta, and the evacuees — who’d spread out to many different intermediate destinations, to avoid overtaxing the hospitality of the locals — would follow within a couple of centuries. "We’re not losing this one," he said. "Not until the sun burns out."

Tchicaya had heard the slogan many times before. Whether it was a matter of being the oldest community of evacuees, or some other factor in the original culture, people from Viro always appeared more focused on their new home than on the loss of the old. Birago himself had no clear memories of Viro — he’d left as an infant, and moved from world to world a dozen times — but if his family had wrapped him in any vision of permanence, any sense of belonging, it was anchored to their future, not their past.

Tchicaya said, "There’s good reason to be hopeful now." That wasn’t giving anything away: the Preservationists would know, at the very least, that his side had had a series of breakthroughs. Their understanding was snowballing; a concrete plan for some form of stable compromise could only be a matter of time now.

Birago laughed. "Hope is for when you have nothing else. When I was a child, no one around me would ever look up at the border and say, It’s too big. We’re too late. It’s unstoppable. We had no plans, we had no remedies; the only strength we had came from refusing to give up. Which was all very laudable…but you can’t go on like that forever. There has to come a time when hope turns into something more tangible."

"Honey or ashes."

"Ah, know-it-all travelers." Birago smiled, but there was an edge to his voice. Picking up a few idiomatic phrases in passing didn’t mean you understood anything.

"We’ll both have certainty soon," Tchicaya insisted. "I can’t believe it will be much longer now."

"We? What counts as certainty for you?"

"Safeguarding the far side."

Birago was amused. "And you think that could ever be part of certainty for us?"

Tchicaya felt a chill of disappointment, but he persisted. "I don’t see why not. Once we understand this thoroughly, we’ll know what is and isn’t safe. No one runs around extinguishing stars out of fear that they might go supernova."

Birago gestured with his right hand, "There are tens of billions of stars to learn from" — then with his left, toward the border — "but there’s only one Mimosa."

"That doesn’t mean it will remain a mystery forever."

"No. But no one’s patience lasts forever. And I know where the benefit of the doubt belongs."

Tchicaya arrived late in the Blue Room, missing the start of Suljan’s experiment. Many more people had chosen to avoid the crush and watch from their cabins, so the place was far less crowded than before, to the point where there was space for furniture.

As Tchicaya joined Rasmah, Yann, and Umrao at a table not far from the console, Rasmah was saying, "I’m not optimistic about seeing anything new, such a short distance in. If the outermost mixture of vendeks is converting our vacuum at the fastest possible rate, there could be light-years of them behind the border."

"Light-years?" Yann regarded her with amusement, as if she’d made some kind of category error: a liter of energy, a kilogram of space. The normal geometrical meaning of a quantum graph was intimately bound up with the presence of particles, and they were yet to unravel any simple notion of distance for the far side.

"You know what I mean," Rasmah retorted. "Ten-to-the-fiftieth nodes' worth."

Umrao said, "The hardest thing for me to wrap my mind around is the complete lack of Lorentz invariance. If you picture the graph’s history as a foam — the edges all extending into surfaces, the nodes all extending into lines — you’d actually see different vendek populations if you re-sliced that foam in a different way."

Tchicaya grimaced. "Doesn’t that imply that there’s a preferred reference frame? Couldn’t you assign yourself an absolute velocity, just by seeing what kind of vendeks you were made from?"

Umrao gestured with his hands in a fashion that Tchicaya’s Mediator translated as negation. "Without any external cues to guide you, you’d always slice your own world foam the same way, and see yourself as being made from the same vendeks. Other people moving past you might see your constituents change, depending on their velocity relative to you, but you’d see them change in the same way. And both of you would be entitled to claim that you were the best judge of your own composition."