“Archimedes was the first scientist, if you ask me.”

“Maybe so.” She frowned. “There were analeptic intrusions around Archimedes as well, actually. But you are the first modern scientist, the great martyr to science, the one everyone knows and remembers.”

“People don’t remember Archimedes?” Galileo asked incredulously, thinking: martyr?

She frowned. “I’m sure historians do. In any case, you are right to question Ganymede’s stated rationale. He may want your effect here in a prolepsis, or he may be shaping his analepsis by what he exposes you to here.”

Galileo mulled over the terms, which to him came from rhetoric. “A backward displacement?”

“Yes.”

“What year is it here, then?”

“Thirty twenty.”

“Thirty twenty? Three thousand years after Christ?”

“Yes.”

Galileo swallowed involuntarily. “That’s a long time off,” he said at last, trying to be bold. “Coming back to me is indeed an analepsis.” He recalled the stranger’s face in the market, his news of the telescope. From Alta Europa, Ganymede had said that first time. “How does that work? What does it mean?”

Again she frowned. “You are in need of an education in physics, but I am not the one to give it to you. Besides, there is no time. My seizure of his entangler, and of you, will be causing consequences, which may arrive soon to pester us. In the time we have, I want to talk to you about other things. Because now that they have made this analepsis into your time in Italy, it is likely to endure, and it will have effects on all the other temporalities entangled with it. Including your life, among other things. My feeling is that the more you know of the situation, the more you can resist the effects of Ganymede’s intervention. Which makes it safer for us, as our time is then likelier to endure in substantially its current form.”

“You mean it might not?”

“That’s why analepses are so dangerous. There are many temporal isotopes, of course, and they are all entangled, and braid together in ways that are impossible to comprehend, really, even if you are a mathematician specialized in temporal physics, to judge by what they say. What you need to know is that time is not simple or laminar, but a manifold of different potentialities that interpenetrate and influence each other. A common image is to think of it as a broad gravel riverbed with many braided channels, with the water running both upstream and downstream at once. The channels are temporal isotopes, and they cross each other, shift and flow, become oxbowed or even dry up, or become deeper and straighter, and so on. This is just an image to help us understand. Others speak of a kelp forest in the ocean, floating this way and that. Any image is inadequate to the reality, which involves all ten dimensions, and is impossible for us to conceptualize. However, to the extent that we understand, we see that your moment represents a big confluence, or a bend, or what have you.”

“So—I am important?”

Her eyebrows shot up; she was amused at him. He recognized the glance, felt he had seen it before. She gestured at the hellish surface gleaming below them. “Do you know how people came to be here?”

“Not at all.”

“Ultimately, we came here by conducting experiments and analyzing their results using mathematics. That is an idea, or a method, if you like, that changed forever the course of human history. And you were the one who had this idea, or invented this method, decisively and publicly, explaining the process so that all could understand it. You are Il Saggiatore, the Experimentalist. The first scientist. And so therefore everywhere, but especially here in the Galilean moons, you are much revered.”

“The Galilean moons?”

“That’s what we call the four big moons of Jupiter.”

“But I named them the Medicean Stars!”

She sighed. “So you did, but as I said to you before, this has always been regarded as a notorious example of science kissing the ass of power. No one but you ever called them that, and since your time very few people have remained interested in the sordid details of your supplications to a potential patron.”

“I see.” He paused. “Well, the Galileans is just as good a name, I suppose.”

“Yes.” She had several different looks of amusement, he was finding.

He considered all that she had said. “Martyr?” he asked, despite himself.

Now her look grew truly serious. She stared into his eyes, and he saw that her pupils were dilated, the oak brown of her irises a vivid ring between glossy blacks and whites. “Yes. I suppose we call these moons the Galileans to memorialize what happened to you. No one has ever forgotten the price you paid for insisting on the reality of this world.”

Galileo, thoroughly spooked, blurted, “What do you mean?”

She said nothing.

Now a kind of dread began to fill his stomach. “Do I want to know?”

“You do not want to know,” she said. “But I’ve been thinking I’m going to tell you anyway.”

She surveyed him in what now struck him as a cold way. “They are giving you amnestics before sending you back into your own time, while underneath that shaping what you learn here, trying to influence your actions at home in a certain direction. But I am thinking that I could give you an anamnestic to counteract their treatment, and teach you some other things, and if you therefore remember what you learn here, it might have a very good effect on your actions. It might change things, in your time and after. That could be dangerous. But then again, there is much since then that needs changing.”

She pointed at the pewter box she had taken from Ganymede, now lying on the polished yellow floor between them.

“What is that?” he quavered, feeling a squirt of fear slide through him.

“That’s what the entangler really looks like. The other entangler, in Italy, is at the event I want to show you.” She took him by the shoulders and moved him next to it, and said coldly, like inflexible Atropos, “I’m going to put you back there.” And she crouched and touched a tab on the side of the box.

THE PAIN WAS SUCH THAT he would have screamed immediately, but an iron muzzle clamped an iron gag into his mouth. A spike wrapped in the gag nailed his tongue up into his palate. It was as much as he could do to swallow the blood pouring into his mouth fast enough not to choke on it. His heart was racing, and when he saw and comprehended where he was, it beat even harder. Surely it would burst with the strain.

The hooded brothers of the Company of Saint John the Beheaded, also known as the Company of Mercy and Pity, had just finished strapping the muzzle and gag onto his head. Now they lifted him up onto the back of a cart. They were outside the Castel Sant’Angelo, down on the banks of the Tiber. The horses in harness jerked forward under the lash of the whip, and he tried to hold his head upright to keep it from hitting the sides of the cart. The cartwheels ground over the paving stones at a walking pace. Dominican monks flanked the cart and led the way. These Dogs of God barked at him as they went, hectoring him to recant, to confess his sins, to go to God with a clean conscience. I confess! he wanted to say. I recant, no question about it. The streets were lined on both sides with a ragged crowd, many falling in behind as they passed, joining the procession into the city. In all the shouting there was no chance anyone would hear his moans. It was assumed that he was past speech, he could see that in their eyes, which were feasting on the sight of him and of the cart, and needed no sound other than their own raw roar. He stopped trying to speak. Even to moan was to choke on blood, to drown on it. Perhaps he could choke on purpose at just the right time.

Slowly they crossed the city, from the great prison on the Tiber to the Campo dei Fiori, the Square of Flowers. Low dark clouds scudded overhead on a stiff wind. Priests in black prayed at him and tossed holy water on him, or thrust their crucifixes in his face. He preferred the hooded and impassive Dominicans to these grotesque faces, twisted by hatred. No hatred was like that of the ignorant for the learned—though now he saw that even greater was the hatred of the damned for the martyr. They saw the end they knew would eventually engulf them for their sins. Today they rejoiced that it was happening to someone else, but they knew their time would come and would be eternal, and so their fear and hatred exploded out of them, putting the lie to their pretended joy.