Schild’s Ladder

escalators. Compared to the crush of the outpost, though, conditions were far from crowded. Layer walls undulated gently in the distance, dotted with parasprite lamps, but there was none of the density of structure they’d seen in the tunnels. High above Tchicaya?—?'above” according to the random orientation in which the Sarumpaet had emerged?—?other dark highways were visible.

“I believe we’re in a railway station,” he said. “The question is, where?”

Mariama declared confidently, “This is the big smoke. All space and comfort.”

“Where we came from wasn’t exactly a ghost town.”

“No, just a small village with no entertainment, and no contraception.”

Tchicaya scowled, but then he realized that she was being neither serious nor entirely flippant. Tossing a few anthropomorphic parodies at the least important of the ten thousand unanswered questions they faced might at least stop them wasting energy trying to fill in the same blanks with earnest hypotheses that were just as likely to be wrong.

As the Colonists crossed the atrium, alien cargo and its wouldbe puppeteers in tow, Mariama mimed cracking a whip. “Take me to your linguists,” she said. “And don’t spare the vendeks.”

If they were in a city, they had no way of judging its size from within, no way of knowing if they were moving from building to building through something like open air, or merely navigating through the rooms of a single, vast, hermetically sealed structure.

They passed through narrow apertures and wide corridors; they wove through denser crowds; they encountered structures as baffling and varied as the machinery?—?or artwork, or gardens?—?of the outpost in the Bright. The probes gathered information, and the toolkit puzzled over it, but even when it made sense it was just another tiny piece of a vast mosaic. Grabbing hints of how the vendek populations were interacting inside some gadget?—?or pet?—?that they passed was all grist for the mill, but it was not going to make the whole city and its people snap into focus in an instant.

Still, Tchicaya clung stubbornly to the notion that it was better to observe whatever he could, and provisionally entertain some wildly imperfect guesses, than to close his eyes and surrender to the verdict that he might as well have been a flea aspiring to understand the culture of a great metropolis. The scale in that analogy was right, but nothing else was. Both he and his hosts possessed general intelligence, and however mutually foreign their needs and drives, there was nothing?—?including each other’s lives, customs, and languages?—?that could remain incomprehensible to them, given time, patience, and motivation.

Time, they did not have, but he’d leave it to the Planck worms to declare when the supply was exhausted.

Mariama drank in the sights like a happily dazed tourist. She treated their purpose at least as seriously as he did, and she’d confronted every problem they’d faced with ferocious energy and clarity, but something in her temperament refused to admit that the corollary of that dedication could ever be despair at the thought of failure. They’d accepted a burden that was constantly on the verge of crushing them both, but he’d rarely seen her so much as tremble beneath the load.

The procession came to a halt in a huge chamber, containing a structure resembling a cluster of grapes the size of a whale. The surface of this object was like nothing the probes had seen before, and the interior proved even more surprising, killing them off completely. Other, slightly more familiar techology was arrayed around this bizarre leviathan.

The Colonists broke rank; three of them fussed around the towing bubble, while the others went to one wall of the chamber and returned with some kind of small device, or creature. Whatever they were fetching didn’t need to be towed; it followed its summoners back under its own power.

When the Colonists burst the banner’s bubble and lured their apparatus closer to it, Tchicaya moved the Sarumpaet away. He didn’t want the ship caught up inadvertently in whatever they were about to do.

Sprayed by vendeks, the apparatus began to shine. It emitted sprites, not the related vendeks the Colonists seemed to favor.

Mariama said, “They’re illuminating the banner with the right kind of lighting. The signal is encoded in its transparency to sprites; they understood that much.”

“I think you’re right.” There was always a chance that they were misreading the action, but Tchicaya felt hopeful.

He surveyed the scene, trying to guess what would happen next. The banner was positioned between the sprite source and the giant bunch of grapes. Meaning what? This was their expert linguist? Another species of xennobe entirely, or some caste of the Colonists who sat motionless in this chamber like a bloated termite queen? He dismissed the notion immediately. They’d seen no other “castes.” A few teeming xennobes in a crowded “hive,” and he was starting to invent ridiculous insectile non sequiturs.

The Colonists moved back from the illuminated banner, and did nothing more. They floated at the edge of the chamber, branches twitching lazily in the gentle currents.

The toolkit said, “I’ve found a way to get probes into the unmapped structure now. This is very strange.”

Mariama said, “We’ll be the judge of strange. Just tell us what they’ve found.”

“Take a cluster of protons and neutrons, and compress it by a factor of a hundred million. That’s what this is.”

Tchicaya blinked, disbelieving, “We’re looking at a nugget of squashed near-side matter?”

“Yes. It’s wrapped in some complicated vendek-based layers that are helping to stabilize it, but basically it’s a pile of ordinary nucleons with most of the empty space squeezed out of them.”

Mariama turned to him. “It could be a kind of meteorite. With all the matter that’s passed through the border, some microscopic speck might have encountered conditions that preserved it.”

Tchicaya didn’t welcome the conclusion this suggested. “So this room could be nothing but a museum display? I can’t believe they’d go to the trouble of building the signaling layer, only to take the reply?—?proof of intelligent life behind the border?—?and stuff it in a cabinet for people to gawk at.”

“Or study. People will come to study it.”

“When?”

Mariama said, “If you want to draw crowds, maybe it’s time we changed the loop.”

Tchicaya sent instructions to the banner. It stopped counting out primes, and switched to a simple, ascending sequence of integers.

The Colonists responded with a flurry of activity: moving around the chamber, summoning new equipment. Tchicaya watched them, his hopes rising again. They had to realize that the banner was as good as alive, and ready to talk. Surely they’d reply now.

He was wrong. They aimed no shuttered sprite lamp back toward the banner, they flashed no answering sequence.

He switched to the Fibonacci series. This stirred the Colonists' branches a little, as if they welcomed the stimulation, but whatever the purpose of the equipment they’d gathered after the first change of message, it continued to be all they required.

They were happy to watch, but they had no intention of replying. They were politely, respectfully observing the alien emissary, but too cautious to engage with it and speed up the process of understanding its message.

“What do we have to do to get through to them?”

Mariama said, “We could push ahead with the mathematics leading to the GDL.”

“Just like that? As a monologue?”

“What choice do we have?”

The toolkit had developed a Graph Description Language, a precise set of semantic conventions for talking about vendeks, Planck worms, and what would happen when they met. Given some moderately sophisticated mathematical concepts?—?which could be built up from elementary ideas based on integer exemplars?—?quantum graphs were far easier to talk about than anything as abstract and contingent as social structures.

If the Colonists weren’t going to degin to reply, though, there’d be no way of knowing if the dictionary of concepts was coming at them too quickly, or even whether the basic syntax was being understood. They manipulated vendeks with skills that no QGT theoretician would dare aspire to, but that didn’t mean they