Schild’s Ladder

the start, but some extreme, systematic distortion here was interfering with their attempts to navigate.

The toolkit collated all the evidence and reached its own conclusion. “There’s curvature engineered into the graphs here. You can invade these vendeks where the current opens out, but in the process they reorient your time axis.”

It took Tchicaya a moment to digest this. Patterns in a quantum graph persisted by replicating themselves in future versions of the graph, but “the future” could only be defined by the orientation of the pattern itself. If you sliced the space-time foam one way to find a graph with vendek A in it, but needed to take a slice at a different angle to find vendek B, the two vendeks would see time as lying in different directions, and mere persistence, on their own terms, would put them in relative motion.

So “reorient your time axis” was toolkit-speak for “change your velocity.” The vendek current couldn’t sweep anything along the way a river did, with pressure and momentum, but it could twist the local definition of being “stationary” progressively further away from its original orientation. In a sense it was like ordinary gravity, but on the near side the symmetries of the vacuum imposed a rigid austerity on the possibilities for space-time curvature. Here, the curvature had been tailored on the spot, woven directly into the graphs by the choice of vendeks.

“These people engineer space-time the way we do polymer design,” he marveled. “Choose the right monomers, get their shape and reactivity right, and you can create whatever properties you desire.”

Mariama smiled. “Except that they’re more like microbes than monomers. Everything comes down to breeding and blending the right vendeks.”

“So what is this? A waste-disposal system?” If they wanted to toss the banner away, they could have done that from the surface with their towing bubble, but this accelerated sewer might send it further, faster.

The Colonists had paused at the entrance to the cave, but now they began to move along a shallow spiral, inching their way down toward the velocity gradient. They weren’t discarding the banner in the black river. They were going with it.

Tchicaya groaned. “I know what this is! We saw the rest of it, from the outside. It’s a transport system. We’re on the entry ramp to a highway.”

Mariama agreed. “Maybe this whole place is just a tiny outpost, and the artifact is such a big deal that they’re rushing it straight to the nearest expert.”

The conga line of Colonists was winding its way toward the axis of the cave, actively fighting the effect of the black vendeks in order not to get dashed against the wall where the current exited. The Sarumpaet was still obediently following the towing bubble; if they wanted to break away from the convoy, they’d have to do it in the next few seconds.

There was no way of knowing how long the journey would take. They’d seen this highway disappearing into the haze, into the depths Xof the far side. This outpost was where the danger would strike first, where the people needed to be told what was coming so they could fight it, or evacuate.

But if the banner was being taken to the Signalers themselves, that could be the expedition’s one opportunity to meet people with the knowledge and motivation needed to understand the warning at all.

Mariama said, “You don’t want to back out?” Perhaps she was afraid that if this turned out to be the wrong choice, he’d hold her responsible for urging him down here in the first place.

Tchicaya said, “No. We have to trust these people to take us to someone who’ll work hard to communicate with us. If that’s not what they’re planning, then we’re screwed?—?but if we hang back and miss the chance to meet the experts, we’re screwed anyway.” Ahead of them, the banner was blinking feebly; undamaged still, but it had never been designed to modulate all the forms of illumination that filled the cave.

The bubble arced smoothly down into the gray fog of the entry ramp. As they followed it, the fog around them actually seemed to grow thinner; once the Sarumpaet began to surrender to the highway’s demands, the probes had an easier task finding their way back to it?—?though the rest of the cave rapidly vanished from sight. Tchicaya felt a pang of frustration that he was insulated from any sense of the dynamics at play here. What would it feel like, for a native, to be whisked into motion like this? Would there be something akin to tidal effects, as different parts of your body were brought up to speed? It was a trivial thing to ponder, but he needed to cut through the barriers that separated him from the Colonists. He needed to imagine himself inside their skins, any way he could.

The convoy straightened out. They were in the center of the highway now, portrayed by the probes as a narrow tube of clarity surrounded by fog. The Colonists themselves had begun emitting some of the parasprites that had illuminated the tunnels and the cave; the bubble and its cargo blocked the view ahead, but Tchicaya could still catch glimpses of them, shy luminescent starfish waving their four legs lethargically. They were probably relaxing, free from the arduous demands of the Bright?—?or if those demands were trivial, perhaps this trip was so dull for them that they’d entered something close to suspended animation. The Sarumpaet was doing absolutely nothing to keep up with them; as far as it was concerned, everyone was motionless. The highway had them all free-falling effortlessly toward their destination.

Mariama asked the toolkit, “Can you tell how fast we’re moving?”

“I have no direct access to the Bright around us, and interpreting the acceleration process we’ve just been through is difficult.”

“Don’t be such a killjoy; take a wild guess. In the broadest, most naive, near-side terms.”

“We might be doing something comparable to relativistic speeds.”

Mariama looked around the scape, her eyes shining. “Do you remember what Rasmah said?” She was addressing Tchicaya now. “When she spoke to the Preservationists before the moratorium vote?”

“Of course.” Tchicaya had to make a conscious effort to summon up the memory, but he’d had a few other things on his mind.

“She was right,” Mariama declared. “Her whole vision of this place was exactly right. Not in the details; she couldn’t anticipate half the things we’ve seen here. But she understood precisely what the far side could mean for us.”

Tchicaya experienced a twinge of irritation, bordering on jealousy. What right did she have to share Rasmah’s vision? He was ashamed of himself immediately; she’d earned it, at least as much as he had.

“You’ve had a change of heart,” he observed mildly.

“I told you I’d never fight for an exotic wasteland,” she said, “but that’s not what this is. And I’ll fight for the Signalers because they deserve our help, but that’s not the end of it. Not anymore.”

She took Tchicaya’s hands. “Some astronomically rare event created sentient life on the other side of the border, but that’s all it was: bad luck, an accident of birth. We’ve found ways to live with all the hardships: the distance, the loneliness. That’s a great achievement, an amazing feat, but that’s no reason to sentence ourselves to repeat it for eternity.

“How can we go on living in that wasteland, when even space is alive here? This is where we belong, Tchicaya. I’ll fight for this place because it’s our home.”

In the eerie calm of the highway, Tchicaya felt himself losing his grip on reality. A whole universe was at stake, and here he was playing stowaway on a road train? Unknown multitudes would die, because he lacked the nerve to tap the driver on the shoulder and make his presence known. He could get his message across to anyone, if he put his mind to it. He’d managed to converse with twenty-third-century zealots with flesh for brains; how much harder could a glowing starfish be?

When the highway began to disgorge them after barely two hours, he almost wept with relief. His gamble might yet fail to pay off, but at least it hadn’t irrevocably sunk the whole endeavor.

As they spiraled out of the darkness, the Sarumpaet steeled itself for the worst contingencies the toolkit could imagine. The Bright had been a challenge, but there was no reason to believe that it was the most extreme environment the far side could contain.

Probes began returning. Parasprites flooded in. The convoy slipped out of the ramp into a vast, tranquil space. The toolkit analyzed the vendeks around them; the mixture was not honeycombstable, but it was like the Bright tamed, domesticated. The airconditioning in the colony had gone a short way in the same direction, but it was like the difference between a mesh cage in the open ocean, keeping the largest predators at bay, and an aquarium of hand-picked species that could coexist and thrive with a minimum of drama.

The six Colonists were not alone here; the scape showed hundreds of similar four-branched xennobes moving around them in a multitude of neat, loosely defined rows, as if the place was crisscrossed with invisible