Schild’s Ladder

He searched for any hint of a flickering shadow from the banner on the surface below, but between the shimmering of the sprites and the erratic geometry of all the objects involved, that was too much to expect. Perhaps it was fortunate that the nearsiders would not arrive with anything like the drama of an artificial eclipse; even if these xennobes did belong to the same species as the Signalers, different cultures could still have varying degrees of sophistication, and an overblown spectacle might have terrified a group for whom the search for life beyond the border was a barely comprehensible endeavor, something that only an obscure, deranged minority would even contemplate.

On the other hand, since the banner had no significant effect on the ground, it was possible that no one would even notice it. It wasn’t clear that any of the Bright’s inhabitants focused the sprites to form an image; the rabbit had been close enough to the banner it attacked to sense its presence through a drop in overall irradiation, like a chill on the skin. It made evolutionary sense to expect all mobile xennobes to possess a detailed knowledge of their surroundings, but a sufficiently unnatural object might still be as invisible to them as a burst of neutrinos to a human.

The banner came to a halt at a predetermined altitude: some twenty times the Colonists' typical body size. Tchicaya gazed down at the crowd, wondering how he was going to distinguish panic from indifference. The Colonists weren’t as shapeless as the airflowers; their network of vendek tubes bifurcated twice to give four distinct clusters of branches, and their geometry at any moment tended to reflect this. They looked like medical scans of the circulatory system of some headless quadruped, dog-paddling ineffectually in extremely rough seas. But if that intrusive probe image was unlikely to reflect the way they saw each other, by sprites alone they resembled tortured, mutilated ghosts, trying to break through into the world of the living.

Mariama said, "I think it’s been noticed."

"Where?"

She pointed; a group of six Colonists had left the surface. As Tchicaya watched, they ascended rapidly, but as they grew nearer to the banner they slowed considerably. This cautious interest was not proof of anything, but it was an encouraging sign.

The Colonists surrounded the device, then began spraying it with a delicate mist of vendeks. "That’s cooperative sensing!" Mariama exclaimed. "One of them illuminates the object, the other looks at the transmitted pattern."

"I think you’re right." The group was arranged in pairs on either side of the banner, and the members of each pair took turns emitting the vendeks. The probes hadn’t encountered this species of vendek before; perhaps nothing inside the colony warranted the same kind of scrutiny as this alien object.

The Colonists retreated and formed a loose huddle away from the banner. "What now?" Tchicaya wondered. "How do you react to a mutated version of your own stratospheric beacon suddenly appearing on your doorstep?"

Mariama said, "I just hope they realize they don’t need to launch a new signaling layer in order to reply."

"Maybe we should try to make a more obvious proxy," he suggested. "Something that resembles one of their bodies."

"How would we decide which features to include, and which to leave out? We don’t even know the difference between their communications signals and their waste products. We’d probably come up with the equivalent of a glove puppet of a monkey that smelled exactly like human excrement."

She had a point; even the six Colonists high above the din — and/or stench — of the colony were now bathed in a confusing fog of vendeks, and it was beyond the Sarumpaet's resources to untangle their functions and meaning.

Tchicaya felt a sudden stab of pessimism. He believed he’d finally reached the people he’d come to find — but he had days, at most, not only to describe the Planck worms to them, but to reach a level of communication and trust that would enable them to work together to deal with the threat. However many subtleties, abstractions, and courtesies he omitted along the way, even conveying the core of the message was beginning to seem hopelessly ambitious.

He said, "Maybe we should change the signal right now, instead of waiting for them to reply? Just to make it clear that the banner’s not passive?"

Before Mariama could respond, the Colonists began regrouping around the banner. In unison, they released a stream of vendeks, denser than before; in the probe image, it looked as if the six veined bodies were blowing soap films. The individual sheets met at the edges and merged, forming a bubble, enclosing the banner.

The Colonists retreated again, then sprayed a new mixture at the bubble. It began to drift after them, down toward the surface.

Mariama said, "They’ve grabbed it! They’re towing it!"