But the main project was Maria Celeste. He had seen a lot of women’s bodies in his younger days, and like everyone else, he had seen a lot of people sicken and die. And so each day he walked down the lane that was the main street of Arcetri to the convent, and met her at the gate and kissed her cheeks and lifted her up, as if weighing her, as she once observed—and it was true. And each day therefore his stomach clenched, and he thought about the food on hand that could be made attractive that day. Of course for the most part he needed to be providing for all the nuns equally, so it had to be a matter of some bulk, usually something that could be made into a thirty-bowl soup. These soups were often pretty thin gruel, and they usually poured their wine in to give it a little more body. Maria Celeste complained of a cold stomach, and he could well believe it, as she had no fat on her. And so soups were always good. Galileo had suffered so much disease in his life that he knew all the signs of it, and knew what they meant; and so, watching her, although he threw himself into every day, he too always suffered a bit of a cold stomach, chilled by the fear in him. Even the sun beating on him in the garden could not warm that part. In her letters during his time away, she had written of her fear that she would not live long enough to see him return, and she was not the type to exaggerate fears, or even to speak of them. So it had been a true feeling. He knew how that felt, to sense that the end could be near; he had felt it himself more than once, and it was unmistakable. It marked you. And in her closeness to him she had not hesitated to write to him and let him know what she was feeling.

Well, this was life. You never really escape this fear. Once long before he had written,

Men are forced into their strange fancies by attempting to measure the whole universe by means of their tiny scale. Our deep hatred of death need not make fragility such a bad thing. Why should we want to become less mutable? We should thereby suffer the fate caused by the medusa’s head, being converted to marble and losing our senses and the qualities which could not exist in us without bodily changes, and the fact that we are always becoming something new and strange.

Easy to say, when you’re healthy. But healthy or not, it was still true.

As the days passed, he got used to her new gauntness. It was just the way she looked. She was as rapid and talkative as ever, like some finch turned into a woman, always babbling on about anything and everything, much as she had in her letters, but now it was music too—as if her letters had been only sheet music, written so that he could imagine her saying it all in his head, but only in the same way he could hear his father’s old melodies by looking at the sheet music he had left behind. Being in the presence of the musician herself, as she sang the music of her thoughts aloud in the air, was an entirely different thing. He soaked it up like sunlight, like church music. It was Kepler’s ridiculous music of the spheres, immanent in the world. Her brown eyes burned like Marina’s had. Her skin tone was a little hectic, the cold stomach notwithstanding. She acted hot. There were a lot of ways in which she resembled Marina.

In the tumble of days he watched her flitting around the convent, talking all the while. “The cedros aren’t dry enough to candy yet, and one of them has mold so I’m afraid if it rains we’ll lose them all, and there’s thirty scudi lost to the carpenter who tried to fix the door, Father, you will look at that door’s lower hinge, won’t you? Look at it. I said your penitential psalms for you, by the way, so you don’t have to think of that. Suor Francesca, please, don’t peel those here it will only make more work for Suor Luisa later, move over here if you would, that’s right, you’re a good soul, come with me Father, let’s sit in the garden and pick the lemons while it’s still cool—” and out there, while they picked, under a blue sky and tall puffy white clouds, she would enumerate every quattrini then available to them, this time in the hope of calculating if they had enough to make a first payment on two dozen blankets.

She effervesced. She could not keep up with the pace of her thoughts. It was a wonder that her letters managed to hold their chain of thought together as well as they did, the act of writing being so much slower than the speed of her thinking. When Galileo found his own thoughts racing ahead of him like that, he tended to focus on individual words, fingering them like pebbles to slow himself down; but she did not. She had perhaps inherited some of Galileo’s mental habits, along with her mother’s imperious will; and all of that power had to be vented into the battered confines of San Matteo. It made him think of Ariosto’s stanzas about the princess confined to a walnut shell and yet holding court there just as always. You could not help but love such a gift for sizing one’s ambition in accordance to a real situation. He had never been able to do that.

Once, he stopped work on the gears and pulleys of their balky old clock to sketch out a possible plan for a pendulum-based clock, which would rely on a spring pushing at the very top of the swing to keep it going. A fine idea it seemed on first inspection; the potential force that was forged into a spring, making it a kind of weight always pushing sideways, would be all you would need for a clock that might run for years. When Maria Celeste came in he told her the idea and she laughed to see his face. She looked over his shoulder and asked about the column of numbers he had written beside one sketch of his plan, and he tried to tell her what he had been thinking about. She nodded her comprehension, and so he went on, and eventually came to his rule of falling bodies, and she looked startled at the very idea that there was a ratio of distance to time, in a way that brought a tear to his eye.

“Yes,” he confirmed. “The world works by mathematical rules. This is much more amazing than people usually seem to realize. Consider it—numbers are ideas, they are qualities in our minds that we abstract by looking at the world. So we see that we have two hands, and that there are two sheep in the meadow, but we never see a two anywhere. It’s not a thing but an idea, and therefore intangible. Like souls in this world. And then we teach each other some games we can play with these ideas—we see how you can add them together and get resulting numbers, as if adding sheep to the meadow. We see for instance that any number can be added to itself by its own number of selves, two twos, four fours, we call them squares because they can be put into squared patterns with the same number of sheep on each side, and we see how larger numbers multiplied by themselves grow larger than the previous number very quickly, and that this rapid growth also happens in a proportion. An interesting idea. It makes a nice pattern in the mind or on the page. Then we look at the world around us. We drop a ball and watch it fall to the ground. It seems to be speeding up as it falls, the eye tells us that much, and so we measure the falls in various ways, and lo and behold, we find that all things fall at the same speed, and that the distance that something falls increases by the square of the increase in the time of the fall—this quite precisely!—and despite the fact that time and distance seem to be such very different things. Why should it be so? Why should the ratio be so simple and neat? Why should the two be related at all? All we can say is, they are. Things fall by rules, acting the same always, and the rules are simple—or then later, not so simple. But the world moves by mathematical laws! The world is proportionate to itself across things as disparate as time and distance. How can it be?“

“It can only be because God made the world that way.”