The Clockwork Rocket

news that the spin of the Peerless had stopped the impact flashes. “The luxagens are swapped,” she said. “Any that would be positive in our own materials will be negative for that dust, and vice versa.”

“Can you say why?” Yalda pressed her.

“It’s come to us… around the cosmos,” Tamara struggled, tracing out a loop with one hand.

“And why does that matter?” Yalda persisted. “How does that swap the luxagens?”

“I don’t know,” Tamara confessed.

Yalda sketched out the general idea.

She said, “Suppose the orthogonal stars, the orthogonal worlds, are fragments that broke off the primal world backward. They’ve come full circle around the cosmos, and we’re moving alongside them with our arrows of increasing entropy in agreement. We know that those arrows agree, because otherwise the orthogonal stars would be invisible to us.

“But Nereo’s equation ties the field around a luxagen to a vector that points along its history—and there’s no reason for that arrow to have anything to do with entropy; it should simply stay the same along the luxagen’s entire history. That vector determines whether the luxagen is positive or negative: if we meet a luxagen with the vector pointing into our future, we call it positive; if the vector’s pointing into our past, we call it negative.”

“So who drew the arrows on the luxagens?” Fatima joked.

“Well, exactly,” Yalda conceded. “No one really knows what this vector means. Still, we ought to be able to tell when two luxagens have different signs. Close up, a negative luxagen will repel a positive one, and the whole pattern of potential energy seen by a positive luxagen around a negative one will be upside down: all the usual peaks will become valleys, all the usual valleys will become peaks.”

“Which would cause havoc if you mixed the two,” Prospera suggested.

“Not necessarily,” Yalda replied. “You can’t replace a positive luxagen with a negative one in exactly the same location in a solid, but the negative one wouldn’t want to be there anyway—it sees the potential energy curve upside down, so it would prefer to be at a peak rather than in a valley. And if it’s located at a peak, it won’t disrupt the original pattern, it will reinforce it.”

“So it’s not really clear why a speck of dust with its luxagens swapped should cause any more damage when it collides with ordinary rock than an ordinary speck of dust traveling at the same speed. But then… we don’t really know how plant-derived liberators work, nor do we understand why rocks don’t simply burst into flames all by themselves. So we’re a very long way from determining what will or won’t set any given solid on fire.”

Yalda paused to take in the students’ expressions, to see who was beginning to look burdened by the uncertainty they were facing, and who was exhilarated by the prospect of searching for something entirely new.

“I don’t have the answers,” she said. “All I can do is give you some tools that will help you probe these mysteries, then stand back and see what you discover.”

“Yalda, can I speak with you?”

Yalda looked up from her notes to see Lavinio on the ropes at the entrance to her office. “Of course.”

As he approached, the solemnity of his demeanor became apparent. “Don’t tell me it’s the wheat,” Yalda begged him.

“The wheat’s fine,” Lavinio assured her. “But there’s blight in some of the goldenrod.”

“Some of it?”

“Not every plant is showing signs of infection,” he said, “but there are infected plants in all four gardens.”

“How could that happen?” The gardens were worked by different staff, and even Lavinio refrained from visiting all of them. An infection in one should not have spread easily to the others.

“We can’t know for sure.”

“Can’t we make a guess, to try to stop it happening again?” If the protocols for disease limitation were flawed, they needed to be corrected urgently.

Lavinio said, “It was probably all the re-planting work, just before the spin-up. All that dust in the air was impossible to contain; it would have spread throughout the mountain.”

That did make sense—and if the hazard had not been avoidable, at least there was a chance it would never be repeated.

Yalda braced herself. “So, how do things stand?”

“We’ve taken three cuttings of goldenrod from each garden and started growing them in a dozen new locations,” Lavinio said. “The transfer was done with all possible care; two separate couriers who’d never been in any of the gardens took each cutting part of the way, and I’ve recruited new people to look after the plants. But realistically, we can’t expect them all to stay free of the blight.”

“No.”

“We can’t risk harvesting petals from the cuttings at all, until they’re established,” Lavinio continued. “And it might be unwise to take too many from the original plants either, right now; we don’t want to weaken them unduly before we know that at least some of the new ones have ended up in good condition.”

“I understand.” For the next few stints there would not be much holin produced; that was unavoidable.

But Lavinio had done everything possible to safeguard their future supplies. With a bit of luck, the shortage need not be severe or long-lasting.

Yalda said, “Let me know if anything changes.”

In the pharmacy, Sefora checked the stock of holin tablets. “We have enough for about seven stints at our current usage,” she said. “There are some petals still being processed, but that will only add a day or two to the supply.”

Since the launch, every woman on the Peerless had been taking a regular dose of holin that depended on her age, using tables Daria had drawn up that erred on the side of caution. Until now, the gardens had been providing more than enough goldenrod petals to keep the stores replenished; the real limit on building up a larger stockpile had been the shelf life of the drug.

“Can you draw up new dosage tables?” Yalda asked.

“On what basis?”

“We need to stretch out the stockpile—but there’s no point letting the holin sit and go bad.”

“So… stretch it out how long?” Sefora pressed her.

“It’s hard to say,” Yalda admitted. “It’s not clear when the gardens will be producing again.”

“How much are you willing to cut the dosages?”

“How much can I, without putting people at risk?”

“No one has those numbers,” Sefora replied. “Holin’s efficacy has never been properly studied, never quantified. All we’ve ever had are anecdotal reports: if you heard of a woman of a given age who wasn’t protected by the dose you heard she’d been taking, you assumed it would be wise to take more.”

On the Peerless, that uncertainty was meant to have been subsumed by a constant surplus of the drug—and with four bountiful gardens, that should have been possible.

“I suppose it’s too late to start testing it on arborines,” Yalda lamented.

“That would take years,” Sefora agreed.

“Not to mention some actual holin we could spare.”

Sefora said, “I’ll draw up dosage tables that will let the stockpile last ten stints. Any longer than that, and I wouldn’t trust the quality. Do you want me to make any exceptions?”

“Exceptions?”