"God Said, Let Newton Be!"
The first popular hero of modern science was Isaac Newton (1642-1727). Before him, of course, there were others known across Europe for their mastery, real or imagined, of the forces of nature. Aristotle was the approved classic source. But when Roger Bacon (c. 1220-1292), the most celebrated European scientist of the Middle Ages, sought "to work out the natures and properties of things"--which included studying light and the rainbow and describing a process for making gunpowder--he was accused of black magic. He failed to persuade Pope Clement IV to admit experimental sciences to the university curriculum, he had to write his scientific treatises in secrecy, and was imprisoned for "suspected novelties." The legendary Dr. Faustus, fashioned after a real magician-charlatan of the sixteenth century, dramatized the perils of intruding into nature's secrets, and became a literary stereotype. In the unforgettable lines of christopher Marlowe and Goethe, he gratified audiences with the spectacle of his damnation.
But Newton, whose vision of nature's processes was more grandiose and more penetrating than Bacon's or Faustus', was publicly acclaimed and apotheosized. While earlier experiementalists were assumed to be in league with the Devil, Newton was placed at the right hand of God. Unlike Galileo, his greatest predecessor, Newton was swimming with the scientific currents of his time. He probably exercised greater influence over scientific thought than any secular figure since Aristotle. There would not be another such hero until Einstein. Although Newton's works are difficult or impossible for the layman to grasp, in his time he was understood well enough to be made a demigod. When Queen Anne knighted him at Trinity College, Cambridge, in 1705, he was the first person ever to be so honored in England for scientific achievements. This was only a small measure of his glamour as the Galahad of the Scientific Quest.
In Newton converged and climaxed the forces advancing science. His age, as we have seen, was already going "the mathematical way." New parliaments of science, for the first time, were exposing observations and discoveries for discussion, endorsement, correction, and diffusion. For a quarter-century as president of the Royal Society in London he made it an unprecedented center of publicity and of power for science.
Yet if a novelist had planned it so, the circumstances of his birth in 1642 and his youth could hardly have been better designed to feed Newton's feelings of insecurity. His father was a small farmer, a "yeoman" who could not sign his name. His ancestors on his father's side may have been of even lower station. He was weakly infant. At birth, it was said, he could have fitted into a quart mug, and it was doubtful whether he would survive. His father died three months before Isaac was born, and when he was only three his mother married and moved away to live with a well-to-do clergyman in the neighborhood, leaving the infant Isaac in the charge of his maternal grandmother in a lonely farmhouse. He so resented his mother's second marriage that at the age of twenty he could still recall "threatening my father and mother Smith to burne them and the house over them." When he was eleven, his mother, on the death of her second husband, returned to his household with her three young children. She withdrew him from school, hoping to make him into a farmer, but he was inept at farm chores. Encouraged b the local schoolteacher and a clergyman uncle, he went back to the schoolroom, where he acquired a good grounding in Latin but very little mathematics. At nineteen, older than the other undergraduates, he entered Trinity College, Cambridge, as a "subsizar," a poor scholar working his way through. Despite all his worldly honors he never lost the insecurity of those years. Very early he began calling himself a "gentleman" and claiming a family connection with lords and ladies. He would always overvalue the honors of the court and the dignity of inherited position. And he remained, in public at least, a scrupulous and loyal Anglican.
Newton received his Bachelor of Arts degree in the early summer of 1665 just when the university was being closed on account of the plague, and he retreated to his home in Lincolnshire for about two years. When the university reopened and he returned to Cambridge in 1667, he was elected a fellow of Trinity College, and two years later, at the age of twenty-six, was named Lucasian Professor of Mathematics. When Newton went to Cambridge, the physics of Aristotle, based on distinctions of qualities, was being displaced by a new "mechanical" philosophy of which Descartes (1596-1650) was the most famous exponent. Descartes described the physical world as consisting of invisible particles of matter in motion in the ether. Everything in nature, he said, could be explained by the mechanical interaction of these particles. According to Descartes's mechanistic view of the world, there was no difference, except in intricacy, between the operation of the human body, of a tree, or of a clock. Elaborated in various theories of atomism, Descartes's ideas dominated the new physical thinking in Europe. Everything in nature was to be explained by these minute invisible particles in motion and interaction. To Newton the prevalent philosophy seemed to depend on "things that are not demonstrable" and so were no more than "hypotheses." The physics or "natural philosophy" of the age when Newton came to Cambridge was replete with elaborations of Descartes's notions into "corpuscles," "atoms," and "vortices."
Reacting against these pretentious suppositions, Newton determined to stay on the strait path of mathematics. He believed that although he might seem now to explain less, in the long run his experimental philosophy would surely explain more. The versatile Descartes, also, had a genius for mathematics, he invented analytic geometry and made other advances in algebra and geometry. But he soared on to his expansive theories of sensation and of physiology, and he pretended even to have unraveled the secret of human reproduction. Equipped with his mechanistic dogma, Descartes would not admit any secrets of Nature to be beyond his reach. Although, as we shall see, Newton was by temperament no more modest than Descartes, he almost always managed to keep his scientific efforts channeled into the search for physical laws expressed in mathematical form.
As an undergraduate and during his two years of retreat in the Plague Years, Newton drew the main outlines for his experimental approach to nature. Even before his twenty-sixth year, when he would become a fellow of Trinity College, he had discovered the binomial theorem, and was well on the way to formulating the calculus. His "experimental philosophy" was a kind of self-discipline. In his often quoted disclaimer Newton was not being merely sententious. "I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me."
The essence of his new method was revealed in his very first significant experiments, his work with light and color. This, as historian Henry Guerlac has shown, proved to be a perfect parable of Newton's "experimental philosophy." For of all natural phenomena light was the most unlikely to be confined in the discipline of numbers. Yet this was precisely what the young Newton would manage. Just after he had received his bachelor's degree, as he reported to Henry Oldenburg:
in the beginning of the year 1666 (at which time I applied myself to the grinding of Optick glasses of other figures than Spherical) I procured me a Triangular glass-Prisme, to try therewith the celebrated Phaenomena of colours. And in order thereto having darkened my chamber, and made a small hole in my window shuts, to let in a convenient quantity of the Sun light, I place my Prisme at its entrance, that it might be thereby refracted to the opposite wall. It was at first a very pleasing divertisement, to view the vivid and intense colours produced thereby; but after a while applying myself to consider them more circumspectly, I became surprised to see them in an oblong form; which according to the received laws of Refraction I expected should have been circular . . . .
To explain this phenomenon, he devised what he called his experimentum crucis. Through a small hole he directed a part of the oblong spectrum--a ray of a single color--toward a second prism. He found that the light refracted from the second prism was not further dispersed, but remained a single color. From this he concluded simply "that Light consist of Rays differently refrangible, which . . . were, according to their degrees of refrangibility, transmitted towards diverse parts of the wall." Which meant that "Light itself is a Heterogeneous mixture of differently refrangible Rays." There was and exact correlation, he noted, between color and "degree of refrangibility"--the least refrangible being red and the most refrangible being a deep violet. In this way he disposed of the ancient commonsense notion that colors were modifications of white light. He then confirmed his surprising suggestion that all colors were the components of white by using a biconcave lens to bring the rays of the complete spectrum to a common focus. The colors disappeared altogether when they joined to produce white light. By these elegantly simple experiments, Newton had reduced the "qualitative" of color to quantitative differences. Or, as he put it, "to the same degree of Refrangibility ever belongs the same colour, and to the same colour ever belongs the same degree of Refrangibility."
It would be possible, then, to designate any color by a number indicating its degree of refrangibility. Here was the foundation for a science of spectroscopy. Even more important, it was a model of Newton's experimental method. Some belittled Newton by saying that he had really discovered nothing about the "nature" of light. His explanation of colors, they said, was only a "hypothesis." To which Newton firmly replied "that the doctrine which I explained concerning refraction and colours, consists only in certain properties of light, without regarding hypotheses, by which those properties might be explained. . . . For hypotheses should be subservient only in explaining the properties of thins, but not assumed in determining them; unless so far as they may furnish experiments. For if the possibility of hypotheses is to be the test of the truth and reality of things, I see not how certainty can be obtained in any science." It was enough for Newton's purpose to consider light as "something or other propagated every way in streight lines from luminous bodies without determining what that thing is." Of course, he admitted, Huygens was correct in saying that he had not described the mechanism by which colors are made. But that was the virtue and the rigor of Newton's experimental method.
This same rigor would characterize Newton's method when he came to describe the System of the World. As early as 1664, while still an undergraduate, Newton had begun thinking about ways of quantifying the laws of motion of all physical bodies. He had been stimulated, too, by various casual suggestions--Hooke's notion, based not on demonstrative data but on a hunch, that gravitational attraction might decrease as the square of the distance, and Edmund Halley's speculation derived from Kepler's third law, that the centripetal force toward the sun would decrease as the square of the distance of each planet from the sun. But these were mere suggestions. It was left for Newton to see the univesality of the principles, to make the calculations to prove them, and to show that the elliptical orbits of the planets would follow.
In response to a request from Halley, Newton prepared a nine-page "curious treatise, De motu; which, upon Mr. Halley's desire, was . . . promised to be sent to the Society to be entered upon their register." This, as we have seen, was Oldenburg's device for ensuring credit to all "first inventors" while inducing communications to the Royal Society. On this occasion, Oldenburg's incentives had paid off. For Halley "was desired to put Mr. Newton in mind of his promise for the securing his invention to himself till such time as he could be at leisure to publish it." Newton's few pages "On the Motion of Bodies in and Orbit," showed that he had already arrived at the crux of his grand theory by demonstrating, among other things, that an elliptical orbit could be explained by suggesting an inverse square force to one focus. In revising the De motu, Newton elaborated his first and second law: (I) the law of inertia, and (2) the law that rate of change of motion is proportional to the impressed force.
The power and the grandeur of Newton's system consisted, of course, in its universality. He finally offered one common scheme for terrestrial and celestial dynamics. He had brought the heavenly bodies down to earth, and at the same time provided a framework, and new limits, for man's grasp on the heavenly bodies. The legend of Newton and the apple is not entirely without foundation. The grand "notion of gravitation" came to him, Newton himself said, "as he sat in a contemplative mood" and "was occasioned by the fall of an apple." He had the bold imagination to think of the apple not simply as falling on his head but as being attracted to the center of the earth. Newton noted that the moon was sixty times as far from the center of the earth as the apple was, and therefore, by the inverse square law, should have an acceleration of free fall of 1/(60)2 = 1/3600 of the acceleration of the apple. By applying Kepler's third law, then, he could test his theory. There were a number of practical difficulties in the way--including Newton's incorrect value for the radius of the earth. But his simple insight had put him on the way to his System of the World. He unified all the physical phenomena on earth with those in the heavens by the generality of his laws, expressed mathematically. For all the motions of earthly and heavenly bodies could be seen, observed, and measured. The grand unifying force in Newton's system, even before gravitation, was mathematics.
Newton's "mathematical way" was a way of discovery. But it was also a way of humility, for the mathematical way was a method of self-discipline as well as an instrument for exploring. the title of Newton's great work, Mathematical Principles of Natural Philosophy (Philosophiae Naturalis Principia Mathematica, 1687; English translation, 1729) made as plain as he could that he was displacing all the widespread pretensions to reveal the mechanics of nature. Continental reviewers again objected to the narrowness of Newton's stated purpose. He had not explained why the physical world behaved as it did but had only provided mathematical formulae. Therefore, they said, what he offered was not really "natural philosophy" at all. Of course, they were quite right again, but at the same time they unwittingly described the new strength of Newton's method. Just as in his Opticks, so at the very end of the Principia, Book III, "The System of the World," Newton took pains to define the limits of his method and of his achievement. After his concluding paean to the God who "exists always and everywhere," he explained that "We have ideas of his attributes, but what the real substance of anything is we know not," and hence God could be known only "from the appearances of things."
Hitherto we have explained the phenomena of the heavens and of our sea by the power of gravity, but have not yet assigned the cause of this power . . . . But . . . I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses; for whatever is not deduced from the phenomena is to be called an hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy. In this philosophy particular propositions are inferred from the phenomena, and afterwards rendered general by induction. Thus it was that the impenetrability, the mobility, and the impulsive force of bodies, and the laws of motion and of gravitation, were discovered. And to us it is enough that gravity does really exist, and act according to the laws which we have explained, and abundantly serves to account for all the motions of the celestial bodies, and of our sea.
The most influential of Newton's eighteenth-century disciples, the scientific editor of Diderot's Encyclopedie, Jean le Rond d'Alembert (1717-1783), acclaimed Newton for his refusal to play God, seeing nature "only through a veil which hides the workings of its more delicate parts from our view. . . . Doomed . . . to be ignorant of the essence and inner contexture of bodies, the only resource remaining for our sagacity is to try at least to grasp the analogy of phenomena, and to reduce them to a small number of primitive and fundamental facts. Thus Newton, without assigning the cause of universal gravitation, nevertheless demonstrated that the system of the world is uniquely grounded on the laws of this gravitation." Against the pitfalls of common sense, d'Alembert warned that "the most abstract notions, those that ordinary men regard as most inaccessible, are often those that shed the brightest light."
Newton proved so effective an apostle of the bright light of mathematics precisely because he was so acutely aware of the enshrouding darkness. Who but God could penetrate the inmost workings of the universe? Newton's Hermeticsim--his feeling for the mystery beneath the unity of the world--grew with the passing years. But throughout his life he saw the limits of the capacity of human reason to encompass experience, which explained, too, his unflagging interest in the Bible and in Prophecy. Newton's experimental and mathematical genius was overcast by a religious and mystical temperament. His copious manuscripts on alchemy (650,000 words) and on Biblical and theological topics (1,300,000 words) baffle Newtonian scholars, who try to fit them into the rational frame of Newton's universe. Without doubt, Newton took the Prophets seriously, exercising all his linguistic learning to seek a common meaning for the mystical terms used by John, Daniel, and Isaiah. But he was wary of priestly pretensions. "The folly of interpreters," he warned, was "to foretell times and things by this Prophecy, as if God designed to make them Prophets." In the Prophetic books God's intention was not to make men Prophets of future events but rather that "the event of things predicted many ages before, will htn be a convincing argument that the world is governed by providence." Therefore he applied his sophisticated techniques of astronomical dating to confirm the literal truth of events related in the Bible. Newton never became a thoroughgoing mystic, for he seemed aware of the truth, noted by Roger Fry, that "mysticism is the attempt to get rid of mystery." That Newton never wanted and never dared.
While Newton was widely apotheosized for his mathematical mastery of the world, only a few would sense his awe of the world's mystery--expressed in the line that his mathematics itself drew between man and God. In the next century, both the romantic idealization of Newton and the failure of common sense to encompass his vision were dramatized at a festive literary dinner on December 28, 1817, which Benjamin Haydon (1786-1846), and English historical painter in the grand manner, gave in his studio. Among others there, he reported, were Charles Lamb, John Keats, and William Wordsworth, who "abused me for putting Newton's head into my picture; 'a fellow,' said he, 'who believed nothing unless it was as clear as the three sides of a triangle.' And then he and Keats agreed that he had destroyed all the poetry of the rainbow by reducing it to its prismatic colours. It was impossible to resist him, and we all drank 'Newton's health, and confusion to mathematics.'"
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