If any other scholar had asked for data on such seemingly disparate topics he’d have revealed himself to be a crank. The mere fact that Isaac was thinking about all of them at the same time was as good as proof that they were all related. Tides obviously had something to do with the moon because the formers’ heights were related to the latter’s phase; but what influence could connect the distant sphere of rock to every sea, lake, and puddle on the earth? Jupiter, orbiting along an inside track, occasionally raced past Saturn, lumbering along on the outer boundary of the solar system. Saturn had been seen to slow down as Jupiter caught up with it, then to speed up after Jupiter shot past. The distance separating Jupiter from Saturn was, at best, two thousand times that between the moon and the tides; what influence could span such a chasm? And comets, almost by definition, were above and outside of the laws (whatever they might be) that governed moons and planets-comets were not astronomical bodies, or indeed natural phenomena at all, so much as metaphors for the alien, the exempt, the transcendent-they were monsters, thunderbolts, letters from God. To bring them under the jurisdiction of any system of natural laws was an act of colossal hubris and probably asking for trouble.
But a few years earlier a comet had come through inbound, and a bit later an outbound one had been tracked, each moving on a different line, and John Flamsteed had stuck his neck out by about ten miles and asked the question, What if this was not two comets but one?
The obvious rejoinder was to point out that the two lines were different. One line, one comet; two lines, two comets. Flamsteed, who was as painfully aware of the vagaries and limitations of observational astronomy as any man alive, had answered that comets didn’t move along lines and never had; that astronomers had observed only short segments of comets’ trajectories that might actually be relatively straight excerpts of vast curves. It was known, for example, that most of a hyperbola was practically indistinguishable from a straight line-so who was to say that the supposed two comets of 1680 might not have been one comet that had executed a sharp course-change while close to the Sun, and out of astronomers’ view?
In some other era this would have ranked Flamsteed with Kepler and Copernicus, but he was living now, and so it had made him into a sort of data cow to be kept in a stall in Greenwich and milked by Newton whenever Newton became thirsty. Daniel was serving in the role of milk-maid, rushing to Cambridge with the foaming pail.
There was much in this that demanded the attention of any European who claimed to be educated.
(1) Comets passed freely through space, their trajectories shaped only by (still mysterious) interactions with the Sun. If they moved on conic sections, it was no accident. A comet following a precise hyperbolic trajectory through the ?ther was a completely different thing from Daniel’s just happening to trace a roughly hyperbolic course through the English countryside. If comets and planets moved along conic sections, it had to be some kind of necessary truth, an intrinsic feature of the universe. It did mean something. What exactly?
(2) The notion that the Sun exerted some centripetal force on the planets was now becoming pretty well accepted, but by asking for data on the interactions of moon and sea, and of Jupiter and Saturn, Isaac was as much as saying that these were all of a piece, that everything attracted everything- that the influences on (say) Saturn of the Sun, of Jupiter, and of Titan (the moon of Saturn that Huygens had discovered) were different only insofar as they came from different directions and had different magnitudes. Like the diverse goods piled up in some Amsterdam merchant’s warehouse, they might come from many places and have different values, but in the end all that mattered was how much gold they could fetch on the Damplatz. The gold that paid for a pound of Malabar pepper was melted and fused with the gold that paid for a boat-load of North Sea herring, and all of it was simply gold, bearing no trace or smell of the fish or the spice that had fetched it. In the case of C?lestial Dynamics, the gold-the universal medium of exchange, to which everything was reduced-was force. The force exerted on Saturn by the Sun was no different from that exerted by Titan. In the end, the two forces were added together to make a vector, a combined resultant force bearing no trace of its origins. It was a powerful kind of alchemy because it took the motions of heavenly bodies down from inaccessible realms and brought them within reach of men who had mastered the occult arts of geometry and algebra. Powers and mysteries that had been the exclusive province of Gods, Isaac was now arrogating to himself.
ASAMPLE CONSEQUENCE OF THIS alchemical fusing of forces would be that a comet fleeing the Sun on the out-bound limb of a hyperbola, traveling an essentially straight line, would, if it happened to pass near a planet, be drawn towards it. The Sun was not an absolute monarch. It did not have any special God-given power. The comet did not have to respect its force more than the forces of mere planets-in fact, the comet could not even perceive these two influences as being separate, they’d already been converted to the universal currency of force, and fused into a single vector. Far from the Sun, close to the planet, the latter’s influence would predominate, and the comet would change course smartly.
And so did Daniel, after riding almost straight across the fenny country northeast of Cambridge for most of a day, and traversing the pounded, shit-permeated mud flat where Stourbridge Fair was held, suddenly swing round a bend of the Cam and drop into an orbit whose center was a certain suite of chambers just off to the side of the Great Gate of Trinity College.
Daniel still had a key to the old place, but he did not want to go there just yet. He stabled his horse out back of the college and came in through the rear entrance, which turned out to be a bad idea. He knew that Wren’s library had started building, because Trinity had dunned him, Roger, and everyone else for contributions. And from the witty or despairing status reports that Wren gave the R.S. at every meeting, he was aware that the project had stopped and started more than once. But he hadn’t thought about the practical consequences. The formerly smooth greens between the Cam and the back of the College were now a rowdy encampment of builders, their draft-animals, and their camp-followers (and not just whores but itinerant publicans, tool-sharpeners, and errand-boys, too). So there was a certain amount of wading through horse-manure, wandering into blind alleys that had once been bowling-greens, tripping over hens, and declining more or less attractive carnal propositions before Daniel could even get a clear view of the library.
Most of Cambridge had fallen into twilight while Daniel had been seeking a route through the builders’ camp. Not that it made much of a difference, since the skies had looked like hammered lead all day. But the upper story of the Wren Library was high enough to look west into tomorrow’s weather, which would be fine and clear. The roof was mostly on, and where it wasn’t, its shape was lofted by rafters and ridge-beams of red oak that seemed to resonate in the warm light of the sunset, not merely blocking the rays but humming in sympathy with their radiance. Daniel stood and looked at it for a while because he knew that any moment of such beauty could never last, and he wanted to describe it to the long-suffering Wren when he got back to London.
The bell began to toll, calling the Fellows to the dining hall, and Daniel slogged forward through the Library’s vacant arches and across Neville’s Court just in time to throw on a robe and join his colleagues at the High Table.