“Aha!” Galileo said. “Archimedes.”

“Yes, that’s right. He even showed him a laser—”

“—the mirror that could burn things at a distance!”

“Yes, that’s right. But it didn’t work. The analepsis, I mean. It was too anachronistic; there was no way to build the culture around the knowledge. Ganymede found out that the manifold is not so easily changed—to the despair of some of us, and the great relief of others, as you might imagine.”

“I should think so! What if he had changed you all right out of existence? You might have disappeared on the spot!”

“Well, maybe so. But how would that be any different from the way it is now? People disappear all the time.”

“Hmm,” Galileo said.

“Anyway, judging by a kind of tautology, since we existed, we didn’t think it could happen. And the manifold of manifolds doesn’t really work like that. I am not competent to speak to the physics involved, but I think I catch a glimpse of it in the analogy of the river mouth, with braiding channels, each one of which is a kind of reality, or a potentiality.”

“That’s the one Aurora told me about.”

“It’s a common image. You have your three or four or ten billion currents running concurrently, and tides running back upstream, and the riverbeds themselves all shifting in the force of the various flows. Some water goes upstream, some downstream, the banks get eroded, there’s cross-chop on the surface, and so on. Some streambeds go dry and get oxbowed, while new ones are carved.”

“Like at the mouth of the Po.”

“I’m sure. So, Ganymede thought he could kick a riverbank so hard that the subsequent erosion would carve an entirely new river downstream, if you see what I mean. But it isn’t like that. There’s a bigger topography somehow. And a single kick …”

He took another drink of wine, wiped his mouth. “In any case, it didn’t work. Archimedes—he got killed. And all that was lost. Even that device, that teletrasporta, to use your word for it.”

“Please do. It’s better than entangler—I mean, everything is already entangled, so that’s not what the device is doing.”

Cartophilus actually smiled at this. “You may be right. Whatever you call it, there’s one of them on the bottom of the Aegean, near An-tikytherae. It’s likely to last a long time, too. It was disguised to look like an Olympic calendar, but that won’t be enough to explain it if it’s ever found.”

“How did Ganymede get back to Jupiter?”

“He returned at the last moment before his ship sank, determined to try again. He’s a stubborn man, and the nature of analepsis makes it possible to try over and over. He decided he needed more time to prepare, to help on the scene. He read intensively in the historical record, and visited various resonant times, and decided you were his best chance to make a significant change in the disaster centuries that follow you. But he wanted to visit Copernicus too, and Kepler.”

“So you came back as Gypsies.”

“Exactly. With a different teletrasporta, probably the last one. I doubt they will send back any more.”

“That’s what Hera said, but why not?”

“Well, results have been uncertain, or bad. And there are philosophical objections to that kind of tampering. We are all entangled always, as you said, but introjections are a kind of assault on another part of time, according to some people. It’s been controversial from the start. Also, the energy requirements to actually move a device in the antichronos dimension are prohibitive.” He shook his head. “You wouldn’t believe it.”

“I might. I had quite a tutorial last time I was up there.”

“Well, you know how Jupiter is a gas giant, and Saturn is another, also Uranus and Neptune and Hades. Five gas giants.”

“Yes?”

“Well, before the analepses that sent back the devices, there were seven gas giants. Cronus and Nyx were farther out—so far out that their gravitational effect on the other planets was not crucial to the inner orbits. People argued against destroying them, but the interventionists did it anyway. They needed the power. Ganymede was part of that too. Black holes were created that sucked gas in, and the collapse energy was used to push everything in a small field antichronologically After a device was back here, it was possible to shift consciousness back and forth with hardly any energy expended. Its more a case of just stepping into the complementary field.”

“And how many teletrasportas were sent back?”

“Something like six or seven.”

“And so you came back with this one, to be a Gypsy.”

“Yes.” Cartophilus heaved a big drunken sigh. “I thought I could do some good. I was an idiot.”

“Don’t you ever want to go back?” Galileo asked. “Couldn’t you go back?”

“I don’t know. Even Ganymede has gone back for good, have you noticed? He’s done what he wanted to do here. Or decided the situation at home is so important he needs to be there. Everyone else was already gone. It’s hard to stay here.” He stopped speaking for a while, took another slug. “I don’t know,” he muttered finally. “Cartophilus can always leave if he wants to.”

“Cartophilus? You speak of someone else?”

The ancient one gestured weakly. “Cartophilus is just a … performance. No one is really there. One tries not to be there. Only four dimensions out of ten—it’s not so much.”

Galileo, startled, looked at him closely. “But what sadness this sounds like! What guilt!”

“Yes. A crime.”

“Well,” Galileo said. “Still, it must be in the past. Now is now.”

“But the crime goes on. All I can do now is … deal with it.”

Galileo’s eyes narrowed. “Do you know what happens to me? Are you trying to make it happen? Have you already made it happen?”

The old man raised his hand like a beggar warding off a blow. “I’m not trying anything, maestro. Truly. I’m just here. I don’t know what I should do. Do you?”

“No.”

“Does anybody?”

All Galileo’s friends, and the Linceans especially, wanted him to reply to the attacks that had been made on him in the work on the comets published under the name Sarsi, which everyone told him was a pseudonym for the Jesuit Orazio Grassi. Galileo had avoided writing this response for a long time, feeling there was nothing to be gained by it, and much to be lost. Even now he was unwilling to venture it, and complaining about the situation. But with Paul V gone, and Bellarmino also gone, Galileo’s friends in Rome were convinced that a new opportunity lay before them. And Galileo was their Achilles in the ongoing war with the Jesuits.

Mostly Galileo ignored these pleas for action, but a letter from Virginio Cesarini, a young aristocrat he had met at the Academy of Lynxes the last time he was in Rome, caused him to laugh, then groan. Knowing you has marvelously inflamed in me a desire to know something. This was the laugh. What happened to me in listening to you was what happens to men bitten by little animals, who do not yet feel the pain in the act of being stung, and only after the puncture become aware of the damage received. This was the groan. “Now I’m a wasp,” Galileo groused. “I’m the mosquito of philosophy.”

I saw after your discourse that I have a somewhat philosophical mind.

The strange thing was, he did. Typically people were quite wrong when they felt they were philosophical, as one of the chief features of incompetence was an inability to see it in oneself. But Cesarini turned out to be quite a brilliant youth, sickly but serious, melancholy but intelligent. And so, if he too was writing to ask Galileo to write about the comets, adding his aristocratic position and wealth to the influence of Cesi, Galileo’s best advocate in Rome …

“God damn it.”

This was in the workshop. Mazzoleni regarded him with his cracked grin. He had heard all about it, a thousand times or more. “Why not just do it, boss?”