“May I ask why you are doing this?”

“Theory of Colors is part of the Program,” Isaac said-referring (Daniel knew) to a list of philosophical questions Isaac had recently written out in his Waste Book, and the studies he had pursued, entirely on his own, in hopes of answering them. Between the two young men in this room-Newton with his Program and Waterhouse with his God-given responsibility to keep the other from killing himself-neither had attended a single lecture, or had any contact with actual members of the faculty, in over a year. Isaac continued, “I’ve been reading Boyle’s latest- Experiments and Considerations Touching Colors-and it occurred to me: he uses his eyes to make all of his observations-his eyes are therefore instruments, like telescopes-but does he really understand how those instruments work? An astronomer who did not understand his lenses would be a poor philosopher indeed.”

Daniel might have said any number of things then, but what came out was, “How may I assist you?” And it was not just being a simpering toady. He was, for a moment, gobsmacked by the sheer presumption of a mere student, twenty-one years old, with no degree, calling into question the great Boyle’s ability to make simple observations. But in the next moment it occurred to Daniel for the first time: What if Newton was right, and all the others wrong? It was a difficult thing to believe. On the other hand, he wanted to believe it, because if it were true, it meant that in failing to attend so many lectures he had missed precisely nothing, and in acting as Newton’s manservant he was getting the best education in natural philosophy a man could ever have.

“I need you to draw a reticule on a leaf of paper and then hold it up at various measured distances from my cornea-as you do, I’ll move the darning needle up and down-creating greater and lesser distortions in the shape of my eyeball-I say, I’ll do that with one hand, and take notes of what I see with the other.”

So the night proceeded-by sunrise, Isaac Newton knew more about the human eye than anyone who had ever lived, and Daniel knew more than anyone save Isaac. The experiment could have been performed by anyone. Only one person had actually done it, however. Newton pulled the needle out of his eye, which was blood-red, and swollen nearly shut. He turned to another part of the Waste Book and began wrestling with some difficult math out of Cartesian analysis while Daniel stumbled downstairs and went to church. The sun turned the stained-glass windows of the chapel into matrices of burning jewels.

Daniel saw in a way he’d never seen anything before: his mind was a homunculus squatting in the middle of his skull, peering out through good but imperfect telescopes and listening-horns, gathering observations that had been distorted along the way, as a lens put chromatic aberrations into all the light that passed through it. A man who peered out at the world through a telescope would assume that the aberration was real, that the stars actually looked like that-what false assumptions, then, had natural philosophers been making about the evidence of their senses, until last night? Sitting in the gaudy radiance of those windows hearing the organ play and the choir sing, his mind pleasantly intoxicated from exhaustion, Daniel experienced a faint echo of what it must be like, all the time, to be Isaac Newton: a permanent ongoing epiphany, an endless immersion in lurid radiance, a drowning in light, a ringing of cosmic harmonies in the ears.

DANIEL BECOMES AWAREthat someone is standing over him as he lies on the deck: a stubby red-headed and -bearded man with a lit cigar in his mouth, and spectacles with tiny circular lenses: it’s van Hoek, the captain, just checking to see whether his passenger will have to be buried at sea tomorrow. Daniel sits up, finally, and introduces himself, and van Hoek says very little-probably pretending to know less English than he really does, so Daniel won’t be coming to his cabin and pestering him at all hours. He leads Daniel aft along Minerva ’s main deck (which is called the upperdeck, even though, at the ends of the ship, there other other decks above it) and up a staircase to the quarter-deck and shows him to a cabin. Even van Hoek, who can be mistaken for a stout ten-year-old if you see him from behind, has to crouch to avoid banging his head on the subtly arched joists that support the poop deck overhead. He raises one arm above his head and steadies himself against a low beam-touching it not with a hand, but a brass hook.

Even though small and low-ceilinged, the cabin is perfectly all right-a chest, a lantern, and a bed consisting of a wooden box containing a canvas sack stuffed with straw. The straw is fresh, and its aroma will continue to remind Daniel of the green fields of Massachusetts all the way to England. Daniel strips off just a few items of clothing, curls up, and sleeps.

When he wakes up, the sun is in his eyes. The cabin has a small window (its forward bulkhead is deeply sheltered under the poop deck and so it is safe to put panes of glass there). And since they are sailing eastwards, the rising sun shines into it directly-along the way, it happens to beam directly through the huge spoked wheel by which the ship is steered. This is situated just beneath the edge of that same poop deck so that the steersman can take shelter from the weather while enjoying a clear view forward down almost the entire length of Minerva. At the moment, loops of rope have been cast over a couple of the handles at the ends of the wheel’s spokes and tied down to keep the rudder fixed in one position. No one is at the wheel, and it’s neatly dividing the red disk of the rising sun into sectors.

IN THE GREAT COURTof Trinity there was a sundial Isaac Newton didn’t like: a flat disk divided by labeled spokes with a gnomon angling up from the center, naively copied from Roman designs, having a certain Classical elegance, and always wrong. Newton was constructing a sundial on a south-facing wall, using, as gnomon, a slender rod with a ball on the end. Every sunny day the ball’s shadow would trace a curve across the wall-a slightly different curve every day, because the tilt of the earth’s axis slowly changed through the seasons. That sheaf of curves made a fine set of astronomical data but not a usable timepiece. To tell time, Isaac (or his faithful assistant, Daniel Waterhouse) had to make a little cross-tick at the place the gnomon’s shadow stood when Trinity’s bell (always just a bit out of synchronization with King’s) rang each of the day’s hours. In theory, after 365 repetitions of this daily routine, each of the curves would be marked with ticks for 8:00a.m., 9:00a.m., and so on. By connecting those ticks-drawing a curve that passed through all of the eight o’clock ticks, another through all of the nine o’clock ticks, and so on-Isaac produced a second family of curves, roughly parallel to one another and roughly perpendicular to the day curves.

One evening, about two hundred days and over a thousand cross-ticks into this procedure, Daniel asked Isaac why he found sundials so interesting. Isaac got up, fled the room, and ran off in the direction of the Backs. Daniel let him be for a couple of hours and then went out looking for him. Eventually, at about two o’clock in the morning, he found Isaac standing in the middle of Jesus Green, contemplating his own long shadow in the light of a full moon.