There is no direct evidence to tell what Newton felt as he endured such solitude. But he did leave a powerful hint. In a notebook otherwise filled with expense records and geometry notes, he covered several pages in 1662 with what reads like a debtor's ledger of sins, entry after entry of transgressions large and small, a reckoning of the burden of debt owed to an unforgiving divine banker.
He admitted wrongs done to his fellow man: "Stealing cherry cobs from Eduard Storer / Denying that I did so"; "Robbing my mothers box of plums and sugar"; "Calling Derothy Rose a jade." He revealed an impressive urge to violence: "Punching my sister"; "Striking many"; "Wishing death and hoping it to some"; and in a brutal comment on his mother's remarriage, "Threatening my father and mother Smith to burne them and the house over them."
He admitted to gluttony, twice, and once, "Striving to cheat with a brass halfe crowne"—with hindsight, quite an admission for the man who would become the counterfeiters' scourge. He confessed to an escalating litany of crimes against God, petty misdemeanors like "Squirting water on Thy day" or "Making pies on Sunday night"; and then an agonized confession of mortal failure: "Not turning nearer to Thee according to my belief"; "Not Loving Thee for Thy self"; "Fearing man above Thee."
Worst of all, number twenty on his tally of fifty-eight failings convicted him of "Setting my heart on money learning pleasure more than Thee." Since the Temptation, money and the delights of the senses have been Satan's lures for the pious. But for Newton the true danger came from the snare that had captured Eve: an idolatrous love of knowledge. Trinity opened to Newton a world of ideas that had been closed to him in the countryside, and he entered it with ferocious concentration, so deep, it seems, that it drove God from his mind and heart.
Even at Cambridge, though, Newton had to find his own way. He recognized quickly that the traditional university curriculum, centered on Aristotle as the ultimate authority, was a waste of his time. His reading notes show that he never bothered to wade all the way through any of the assigned Aristotelian texts. Instead, Newton set himself to master the new knowledge that was trickling into Cambridge past the defenses of ancient authority. He did so mostly on his own—he had to, for his understanding soon surpassed that of all but one or two of the men on the faculty who could have instructed him.
He began with a glance at Euclid's geometry, but on first reading found its claims "so easy to understand that he wondered how any body would amuse themselves to write any demonstrations of them." More mathematics followed, and then he discovered mechanical philosophy—the notion that the entire material world could be understood as patterns of matter in motion. It was a controversial idea, mostly because it seemed, to some at least, to diminish the significance of God in daily life. But even so, Descartes and Galileo—and many others—had demonstrated the effectiveness of the new approach, to the point where the mechanical worldview reached all the way to the few receptive minds to be found in that backwater of European intellectual life, the University of Cambridge.
Newton's legendary capacity for study displayed itself here, in this first rush to master all that Europe knew of how the material world works. Sleep was optional. John Wickens, who arrived at Cambridge eighteen months after Newton, remembered that when Newton was immersed in his work, he simply did without. Food was fuel—and, as often as not, merely a distraction. He later told his niece that his cat grew fat on the meals he forgot to eat.
In 1664, after two hard years, Newton paused to sum up his learning in a document he modestly called Quœstiones quœdam Philosophicœ—Certain Philosophical Questions. He started by asking what was the first or most basic form of matter, and in a detailed analysis argued that it had to be those simple, indivisible entities dubbed atoms. He posed questions on the true meaning of position—location in space—and of time, and of the behavior of celestial bodies. He probed his new and temporary master, Descartes, challenging his theory of light, his physics, his ideas about the tides. He sought to grasp how the senses worked. He had purchased a prism at the Sturbridge Fair in 1663, and now wrote up his first optical experiments, the starting point for his analysis of light and color. He wondered about motion and why a falling body falls, though he was confused about the property called gravity. He attempted to understand what it might mean to live in a truly mechanical universe, one in which all of nature except mind and spirit formed a grand and complicated machine—and then he trembled at the fate of God in such a cosmos. He wrote that "tis a contradiction to say ye first matter depends on some other subject." He added "except God"—and then crossed out those last two words.
He offered no definitive answers. This was the work of an apprentice mastering his tools. But it is all there in embryo, the program that would lead Newton toward his own discoveries and to the invention of the method that others could use to discover yet more. And while the Newtonian synthesis was decades away from completion, the Quœstiones captures the extraordinary ambition of an anonymous student working on the fringes of the learned world, who nonetheless proclaims his own authority, independent of Aristotle, of Descartes, of anyone.
Newton was fearless in the pursuit of anything he wanted to know. To find out whether the eye could be tricked into seeing what wasn't there, he stared directly at the sun through one eye for as long as he could bear the pain, then noted how long it took to free his sight from the "strong phantasie" of the image. A year or so later, when he wanted to understand the effect of the shape of an optical system on the perception of color, he inserted a bodkin—a blunt needle—"betwixt my eye and y e bone as near to ye backside of my eye as I could." Next, by "pressing my eye wth ye end of it (so as to make ye curvature ... in my eye)" he saw several "white dark and coloured circles"—patterns that became clearer when he rubbed his eye with the point of his needle. To that description Newton helpfully added a drawing of the experiment, showing how the bodkin deformed his eye. It is impossible to look at the illustration without wincing, but Newton makes no mention of pain, nor any sense of danger. He had a question and the means to answer it. The next step was obvious.
He pressed on, pondering the nature of air, wondering whether fire could burn in a vacuum, taking notes on the motion of comets, considering the mystery of memory and the strange and paradoxical relationship of the soul to the brain. But, caught up as he was in the whirlwind of new thoughts, new ideas, he still had to deal with the ordinary obstacles of university life. In the spring of 1664, he sat for the one examination required of undergraduates at Cambridge, a test that would determine whether he would become one of Trinity's scholars. Pass, and he would cease to be a sizar; the college would pay his board and give him a small stipend for the four years it would take to become master of arts. Fail, and it was back to the farm.
He survived the ordeal, receiving his scholarship on April 28, 1664. But his renewed studies at the college were interrupted within months. Early in 1665, rats turned up on the docks along the Thames which had almost certainly come by way of Holland, perhaps in ships carrying prisoners from the Dutch wars or smuggled bales of cotton from the Continent. The rats carried their own cargo of fleas across the North Sea, and the fleas in turn ferried into England the bacterium Yersinia pestis. The fleas leapt from the rats; they bit; the bacteria slid into human veins, and dark buboes began to sprout. The bubonic plague had returned to England.
At first the disease proceeded slowly, a troubling backdrop to the daily routine. The first named victim died on April 12 and was buried in haste that same day in Covent Garden. Samuel Pepys noted "Great fears of the Sicknesse" in his diary entry for April 30. But the great naval victory over the Dutch at Lowestoft distracted him and many others. Then, in early June, Pepys found himself, "much against my Will," walking in Drury Lane, where he saw "two or three houses marked with a red cross upon the doors and 'Lord have mercy upon us' writ there."
That day, Pepys bought a roll of tobacco to chew, "which took away the apprehension." But the epidemic had taken hold, and no amount of nicotine could h
old back panic. A thousand a week died in London, then two, until by September the death toll reached one thousand each day.
The very concept of a funeral collapsed under the weight of corpses. The best that could be done was disposal, landfill. As Daniel Defoe described it: A death cart enters a cemetery, halting at a broad pit. A man follows, walking behind the remains of his family. And then, "no sooner was the cart turned round and the bodies shot into the pit promiscuously, which was a surprise to him," Defoe wrote, "for he at least expected they would have been decently laid in." Instead, "Sixteen or seventeen bodies; some were wrapt up in linen sheets, some in rags, some little other than naked, or so loose that what covering they had fell from them in the shooting out of the cart, and they fell quite naked among the rest; but the matter was not much to them, or the indecency much to any one else, seeing they were all dead, and were to be huddled together into the common grave of mankind." This was democracy at last, "for here was no difference made, but poor and rich went together; there was no other way of burials, neither was it possible there should, for coffins were not to be had for the prodigious numbers that fell in such a calamity as this."
Those who could fled as fast as possible, but the disease ran with the refugees, and the dread of the plague reached farther and farther into the countryside. Cambridge emptied early, becoming a ghost town by midsummer 1665. The great fair at Sturbridge—England's largest—was canceled. The university ceased to offer sermons in Great St. Mary's Church, and on August 7, Trinity College acknowledged the obvious by authorizing the payment of stipends to "all Fellows & Scholars which now go into the Country on occasion of the Pestilence."
Newton was already long gone, escaping before the August stipend came due. He retreated to Woolsthorpe, its isolation a sanctuary from any chance encounter with a plague rat or a diseased person. He seems not to have noticed the change of scene. No one now dared set the prodigal to the plow. In the last months before Newton abandoned Cambridge, his mind had turned almost exclusively to mathematics. In the quiet of his home, he continued, building the structure that would ultimately revolutionize the mathematical understanding of change over time. Later in the plague season, he would take the first steps toward his theory of gravity, and thereby toward his understanding of what governs motion throughout the cosmos.
The disease cut through England all that summer and fall, murdering its tens of thousands. Isaac Newton paid it little mind. He was busy.
2. "The Prime of My Age"
THE PLAGUE OF 1665 raged on through the fall. In December, a bitter cold settled across the south of England. Samuel Pepys wrote that the hard frost "gives us hope for a perfect cure of the plague." But the disease persisted—up to thirteen hundred Londoners a week were still dying—and prudent folk shunned crowds if they could.
Isaac Newton was cautious to a fault. He celebrated his twenty-third birthday that Christmas Day at home, safely distant from the infectious towns. He stayed there into the new year, working, he said, with an intensity he never again equaled: "In those days," he remembered fifty years on, "I was in the prime of my age for invention & minded Mathematicks & Philosophy more then at any time since."
Mathematics first, continuing what he had started before his enforced retreat from Cambridge. The critical ideas emerged from the strange concept of the infinite, in both its infinitely large and infinitesimally small forms. Newton would later name the central discovery of that first plague year the "method of fluxions." In its developed form, we now call it the calculus, and it remains the essential tool used to analyze change over time.
He did not complete this work in total isolation. In the midst of his thinking about infinitesimals, the epidemic seemed to ease in the east of England. By March, Cambridge town had been free of plague deaths for six consecutive weeks. The university reopened, and Newton returned to Trinity College. In June, though, the disease reappeared, and on the news of more deaths, Newton again fled home to Woolsthorpe. Back on the farm, his attention shifted from mathematics to the question of gravity.
The word already had multiple meanings. It could imply a ponderousness of spirit or matter—the affairs of nations had gravity, and to be said to possess gravitas was a badge of honor for the leaders of nations. It had a physical meaning too, but what it was—whether a property of heavy objects or some disembodied agent that could act on objects—no one knew. In the Quœstiones, Newton had titled one essay "Of Gravity and Levity," and he wrestled there with concepts that he found to be vague and indistinct. He wrote of "the matter causing gravity" and suggested that it must pass both into and out of "the bowels of the earth." He considered the question of a falling body and wrote of "the force which it receives every moment from its gravity"—that is, force somehow inherent in the object plummeting toward the ground. He wondered whether "the rays of gravity may be stopped by reflecting or refracting them." For the time being, all that Newton knew about the connection between matter and motion was that one existed.
Now, in his enforced seclusion, Newton tried again. According to legend, the key idea came to him in one blinding flash of insight. Sometime during the summer of 1666, he found himself in the garden at Woolsthorpe, sitting "in a contemplative mood," as he remembered—or perhaps invented, recalling the moment decades later, in the grip of nostalgia and old age. In his mind's eye the apple tree of his childhood was heavy with fruit. An apple fell. It caught his attention. Why should that apple always descend perpendicularly to the ground, he asked himself. Why should it go not sideways or upward but constantly to the earth's center?
Why not indeed. The myth that has endured from that time to this declared that that was all it took: on the spot, Newton made the leap of reason that would lead to the ultimate prize, his theory of gravity. Matter attracts matter, in proportion to the mass contained in each body; the attraction is to the center of a given mass; and the power "like that we here call gravity ... extends its self thro' the universe."
Thus the story of what one author has called the most significant apple since Eve's. It has the virtue of possessing some residue of fact. The tree itself existed. After his death, the original at Woolsthorpe was still known in the neighborhood as Sir Isaac's tree, and every effort was made to preserve it, propping up its sagging limbs until it finally collapsed in a windstorm in 1819. A sliver of the tree ended up at the Royal Astronomical Society, and branches had already been grafted onto younger hosts, which in time bore fruit of their own. In 1943, at a dinner party at the Royal Society Club, a member pulled from his pocket two large apples of a variety called Flower of Kent, a cooking apple popular in the 1600s. These were, the owner explained, the fruit of one of the grafts of the original at Woolsthorpe. Newton's apple itself is no fairy tale; it budded, it ripened; almost three centuries later it could still be tasted in all the knowledge that flowed from its rumored fall.
But whatever epiphany Newton may have had in that plague summer, it did not include a finished theory of gravity. At most, the descent of that apple stimulated the first step in a much longer, more difficult, and ultimately much more impressive odyssey of mental struggle, one that took Newton from concepts not yet formed all the way to a finished, dynamic cosmology, a theory that reaches across the entire universe.
That first step, of necessity, turned on the existing state of knowledge, both Newton's and that of European natural philosophers. Earlier in the plague season, Newton had studied how an object moving in a circular path pushes outward, trying to recede from the center of that circle—a phenomenon familiar to any child twirling a stone in a sling. After a false start, he worked out the formula that measures that centrifugal force, as Newton's older contemporary, Christiaan Huygens, would name it. This was a case of independent invention. Huygens anticipated Newton but did not publish his result until 1673. That is: Newton, just twenty-two, was working on the bleeding edge of contemporary knowledge. Now to push further.
He did so by testing his new mathematical treatment of circular motion on the r
evolutionary claim that the earth did not stand still at the center of a revolving cosmos. One of the most potent objections to Copernicus's sun-centered system argued that if the earth really moved around the sun, turning on its axis every day as it went, that rotation would generate so much centrifugal force that humankind and everything else on the surface of such an absurdly spinning planet would fly off into the void. With his new insight, however, Newton realized that his formula allowed him to determine just how strong this force would be at the surface of the turning earth.
To begin, he used a rough estimate for the earth's size—a number refined over the previous two centuries of European exploration by sea. With that, he could figure the outward acceleration experienced at the surface of a revolving earth. Next, he set out to calculate the downward pull at the earth's surface of what he called gravity, in something like the modern sense of the term. Galileo had already observed the acceleration of falling bodies, but Newton trusted no measurement so well as one he made himself, so he performed his own investigation of falling objects by studying the motion of a pendulum. With these two essential numbers, he found that the effect of gravity holding each of us down is approximately three hundred times stronger than the centrifugal push urging us to take flight.
It was a bravura demonstration, an analysis that would have placed Newton in the vanguard of European natural philosophy, had he told anyone about it. Even better, he found he could apply this reasoning to a larger problem, the behavior of the solar system itself. What was required, for example, to keep the moon securely on its regular path around the earth? Newton knew one fact: any such force would strain against the moon's centrifugal tendency to recede, to fly off, abandoning its terrestrial master. At the appropriate distance, he realized, those impulses must balance, leaving the moon to fall forever as it followed its (nearly) circular path around the center of the earth, the source of that still mysterious impulse that would come to be called gravity.
Newton and the Counterfeiter: The Unknown Detective Career of the World's Greatest Scientist Page 2