On the winding way back down the campanile stairs, Galileo was joined on one dark landing by the stranger, who then clomped down the iron stairs beside him. Galileo’s heart leaped in his chest like an animal trying to escape. The man was dressed in black, and must have lurked in waiting for Galileo, like a thief or an assassin.

“Congratulations on this success,” the man said in his hoarse Latin.

“What brings you here?” Galileo asked.

“It seems you listened to what I told you before.”

“Yes, I did.”

“I was sure you would be interested. You of all people. Now I will return to northern Europe.” Again: Alta Europa. “When I come back to your country, I will bring a spyglass of my own, which I will invite you to look through. Indeed I invite you now.” Then, when Galileo did not reply (they were nearing the bottom of the stairs and the door to the Piazzetta), he said, “I invited you.”

“It would be my pleasure,” Galileo said.

The man touched the case Galileo carried from his shoulder. “Have you used it to look at the moon?”

“No—not yet.”

The man shook his head. If his face was a blade, his nose was its sharpened edge, long and curved, tilted off to the right. His big eyes gleamed in the stairwell’s dim light. “When you achieve a power of magnification of twenty or thirty times, you will find it really interesting. After that, I will visit you again.”

Then they reached the ground floor of the campanile, and walked together out onto the Piazzetta, where they were interrupted by the Doge himself, waiting there to escort Galileo back to the Signoria: “Really, my dear Signor Galileo, you must do us the honor of returning with us to the Sala del Senato to celebrate the incredible success of your extraordinary demonstration. We have arranged a small meal, some wine—”

“Of course, Your Beneficent Serenity,” Galileo said. “I am yours to command, as you know.”

In the midst of this exchange the stranger had slipped away and disappeared.

Unsettled, distracted by the memory of the stranger’s narrow face, his black clothing, and his odd words, Galileo ate and drank with as much cheer as he could muster. A chance meeting with a colleague of Kepler’s was one thing; a second encounter, deliberately made, was something else—he wasn’t sure what.

Well, there was nothing to be done now but to eat, to drink more wine, and to enjoy the very genuine and fulsome accolades of Venice’s rulers. Two full hours of the celebration of his accomplishment were marked by the giant clocks on the sala’s walls, before the lookouts on the campanile sent word down that they had spotted a fleet approaching San Niccolo. The room erupted in a spontaneous cheer. Galileo turned to the doge and bowed, then bowed again to all of them: left, right, center, then again to the doge. Finally he had invented something that would make money.

CHAPTER TWO

I Primi Al Mondo

Having come to this pass, I appealed out of my innocent soul to the high and omnipotent gods and my own good genius, beseeching them of their eternal goodness to take notice of my wretched state. And behold! I began to descry a faint light.

—FRANCESCO COLONNA, Hypnerotomachia Poliphili (Poliphili’s Strife of Love in a Dream)

THE NEXT NIGHT, BACK IN PADUA, Galileo went out into his garden and aimed his best occhialino at the moon. He left Mazzoleni sleeping by the kitchen fire, woke none of the servants; the house was asleep. This was the hour, as on so many nights, when his insomnia took hold of him.

Now his mind was filled with the stranger’s blade of a face, his intense gaze. Have you looked at the moon? The moon tonight was near its first quarter—the bright part almost exactly half the whole, the dark part easily visible against the night sky. An obvious sphere. Galileo sat on a low stool, held his breath, then brought his right eye to the eyepiece. The little black circle of glass was marked on its left side by a luminous white patch. He focused on it.

At first he saw nothing but a chiaroscuro flecking of grayish black and brilliant white, the tremble of the white seeming to flow over the dark spots. Ah; hills. A landscape. A world seen from above.

A view from world to world.

He loosened the screw on the tripod head and tapped the tube, trying to capture in the glass the tip of the moon’s upper crescent. He tightened the screw, looked again. Brilliant white horn; and a dark gray in the curve of the horn, a blackness just slightly washed with white. Again he saw an arc of hills. There, at the border of light and dark, was a flat dark patch, like a lake in shadow. The sunlight was obviously shining horizontally over the landscape—as it would be, of course, as he was looking at the area experiencing dawn. He was looking at a sunrise on the moon, twenty-eight times slower than a sunrise on Earth.

There was a little round valley; there another one. Any number of circles and arcs, in fact, as if God had been fooling around up there with a compass. But the strongest impression remained the range of hills, there on the border of black and white.

The moon was a world, like the Earth was a world. Well, of course. He had always known this.

As for the assertions the Aristotelians made about the moon, that because it was in the heavens it was therefore a perfect sphere, made of some unearthly crystal that was of unchanging purity—well, its ordinary appearance had always rendered that a very suspicious statement. Now it was clearer than ever that Aristotle had been wrong. This was no great surprise—when indeed had he been right in the natural sciences? He should have stuck to his strength, which was rhetoric. He had had no mathematics.

Galileo got up and went into the workshop to get his current folio, and a quill and inkpot. He wondered if he should wake Mazzoleni, then decided against it. There would be other nights. He could feel his blood pounding in his head; his neck muscles were sore. This was his night. No one had ever seen these things. Well, perhaps the stranger had, but Galileo suppressed that thought in order to glory in his own moment. All the years, all the centuries had come and gone, the stars rotating above them night after night, and only now had someone seen the hills of the moon.

The moon must rotate on its axis at the same speed it circled the Earth, to keep the same side always facing it; this was odd, but no odder than many other phenomena, such as the fact that the moon and the sun were the same size in the sky. These things were either caused, or accidental; it was hard to tell. But it was a rotating sphere, that was clear. And so was the Earth also a rotating sphere? Galileo wondered if Copernicus’s advocacy of this old Pythagorean notion could be correct.

He looked through the glass again, relocated the white hills. The dark part west of them was extremely interesting. Land in shadow, obviously. Perhaps there were lakes and seas too, though he could see no sign one way or the other. But it was not as black as a cave or a dark room at night. One could make out dim large features, because the area was very slightly illuminated. That could not be direct sunlight, obviously. But just as the moonlight illuminating his garden at this moment was really sunlight bouncing off the moon to him, he was no doubt also seeing the dark part of the moon illuminated by sunlight that had bounced off the Earth and struck it—and then bounced back yet again, of course, to get to his eyes. From sun to Earth to moon and then back to him—which would explain the successive diminutions in brightness. As sunlight was to moonlight, moonlight was to the dark side of the moon.