“My head hurts,” Galileo admitted.

“Then let’s go back,” Aurora said.

As she was flying him back into the world, Galileo experienced a moment of selfish curiosity. In his first tutorial, he had gotten a glimpse of his hero Archimedes, as clearly as if he had been through the tele-trasporta and seen the Greek face-to-face, or even lived his life. Someone had mentioned something about Ganymede visiting Archimedes before he visited Galileo; perhaps that explained it. Now, with Aurora absorbed in a private conversation with her assistants, Galileo murmured a request to the teaching machine to show him the historical background of the astronomer Galileo Galilei.

Immediately he was cast into a space like that which had surrounded Archimedes; not a moment but a life—his life. Instantly he was filled with his own life, in Florence, Pisa, Padua, then Bellos-guardo, then a smaller house he didn’t recognize, in a village. All of it filled him at once, fine-grained to the minute, and fearfully he cried out, “Stop! Take it away!”

Aurora now stood before him, looking surprised. “Why did you do that?”

“I wanted to know.”

“You thought you did. Now you will have to forget.”

“I hope I can! But I suppose you can give me an amnestic that will help me to deal with it?”

“No,” she said, looking at him curiously. “I can’t. That’s Hera’s kind of thing. You will have to cope with whatever you learned yourself.”

Galileo groaned. He struggled up from his big reclining chair, Aurora’s helmet on his head. He felt drained, frightened. The sensation of immediate powerful apprehension was still with him, but it all had to do with his life now. His past—the present moment—

People were talking. Aurora and her assistants. For a time he lost the sense of it. Thoughts in language, like the voice speaking in him; they were such simple things, like the twittering of birds. Pretty, even sometimes beautiful, but nowhere near as expressive as mathematics. Now he tried hard to remember, he tried hard to forget; some of it was there and some of it was gone, but not in the ways he would have hoped. Nothing to be done about it. The tutorial had happened in him, it had left marks; it would remain somewhere in him, in what they called e time, or in that evanescent present that always bloomed at the edge of c. Or headed back through antichronos, all the way back to the curious boy looking at the lamp swinging in the cathedral. Memory as a kind of precognition.

He regarded Aurora freshly. An ancient woman, who had, he now knew, a knowledge of mathematics, and of the physical universe, that far, far, far transcended his. That was rather amazing. He had never thought that any such person could exist.

“Do you believe in God?” he asked her.

“I don’t think so. I’m not sure I grasp the concept.” She hesitated. “Can we get something to eat? Are you hungry? Because I am.”

THEY SAT BESIDE A LOW TABLE next to the far railing. It was an altana, it seemed to him; just as in Venice, they made their ground on their rooftops. He sat by the railing and looked at this Venice under its pulsing green-blue sky. On the table between them were plates of small cubes and slices of a vegetable substance unknown to Galileo, the bits flavored with ginger or garlic or various peppery spices he was not familiar with, which made his tongue buzz and his nose run. The water was berry-flavored; he drank deeply, feeling suddenly very thirsty. He surveyed the dim turquoise and cobalt buildings beneath them. Europa was a world of ice, Io was a world of fire. Were Ganymede and Callisto then earth and air?

“Have you had more conversation with the thing under us?” he asked Aurora. “You were telling me about it before. It seems to know gravity well, you said?”

“Yes.”

“What about the compound temporality, the vector of three times?”

“That’s been hard to determine.”

“Show me the exchanges with it.”

Aurora smiled. “It’s been eleven years since the ice was broached and the sentience confirmed. Most of the interactions have come to dead ends. But an abstract of it can be found here.”

She indicated their table, and Galileo looked at it and saw long strings of mathematical symbols and graphically organized information. The tutorial pulsed in his head like a kind of headache. He tried to pilot that knowledge into this new problem.

“Interesting,” he said at last. “What physically constitutes the sentience, do you know? Have you located the bodily source of its mind?”

“It fills the ocean below us, but is not the ocean. The things like fish that you yourself saw, I believe—”

“I saw spirals of blue light, more like eels than fish.”

“Yes, well, these came from parts of a larger whole. Like brain cells of a sentience distributed across the group. But still it does not appear to be consciousness as we would recognize it. There is a kind of absence in its cognition, having to do with self-awareness and other-awareness. An absence that makes some suspect that what we are conversing with is part of a larger whole.”

“But what?”

“We don’t know. But there are people who want to find out.”

“Not all of you?”

“Oh no, not at all. There is a … disagreement. A very basic philosophical or religious disagreement. One might call it a dangerous disagreement.”

“Dangerous?” Galileo was apprehensive: “I was hoping you were all past that kind of thing by now.”

She shook her head. “We are human, and so we argue. And this is an argument that could lead to violence.”

Dissent among the Galileans. Well, he already knew that. Hera had kidnapped him, and Ganymede had rammed his ship into the Europans; he should not be surprised. It was people changing their nature that would have been surprising. “Actual violence?”

“People are much more likely to kill each other over ideas than over food,” she said. “It’s very clear in the historical record, a statistical fact.”

“Maybe,” Galileo ventured, “when food is secure, the grasp for certainty moves elsewhere.”

“Certainty,” she scoffed. “In the manifold of manifolds!” And she laughed.

As if to illustrate her point, out of the glass antechamber appeared Hera herself, ivory-armed and magnificent. She was trailed by her Swiss guard equivalent, a dozen bruisers even bigger than she.

Now she approached Galileo, shaking her head as if at a child who did not comprehend his transgression.

“You again!” he said sharply, angered by this look. “What is it this time?”

Then a loud group of locals spilled out of the next antechamber over. Hera saw them and said, “This rabble is trying to keep us from joining you, here in a public space. One moment—”

She and her gang ran at the Europans, and a brawl began. In Venice such a thing would have been dangerous, with knives pulled from sleeves. Here it was just shoving and shouting, and the occasional flailing roundhouse. Hera shouted, “You’ll be charged with assault! I hope you’ll get exile!”

“You’re the one who made the assault,” one of them shouted, and appealed to Aurora: “We did what we could. She stops at nothing.”

The mathematician regarded them without expression. “Then let her speak.”

Hera returned to Galileo’s side. “Take the entangler,” she said to her people, gesturing at the pewter box. She said to Aurora, “I’m the one who should have it, and you know it.” One of Hera’s guards went to the box and picked it up. Then without warning Hera grabbed Galileo by the arm, lifted him off his feet, and walked with him toward the glass closets, leaving a rear guard behind to protect her retreat.

“Kidnapping again?” Galileo inquired caustically, struggling to free himself from her grasp. It was galling that he could not even slow her down.