Three Scientific Revolutions: How They Transformed Our Conceptions of Reality (9 page)

Whether it was this unfortunate early beginning or his homosexuality (as evinced by two nervous “disorders” due to the termination of two close male relationships) or both, he was an extremely sensitive, serious, and withdrawn person who shunned controversy and publicity to the extent that he refused to publish some of his articles to avoid disputes. His early education at the Free Grammar School of King Edward VI consisted of traditional religious studies, along with courses in Greek and Latin. Having shown considerable intellectual promise, the headmaster of the school urged his maternal uncle to have him take the necessary preparatory courses for admission to a college or university. Completing these, in the summer of 1661 he enrolled in Trinity College, Cambridge, where his uncle had attended.

At Trinity he pursued his former courses along with studying Aristotle's physics and cosmology, though he soon became more interested in the scientific works of Kepler, Galileo, Pierre Gassendi, Descartes, Robert Boyle, and Henry More. There being more interest in Cambridge University at the time in Descartes's optical research and theory of vortices than in Galileo's discoveries, Newton began studying Descartes; but finding shortcomings in his explanations of light and colors, as well as in his theory of vortices, because it did not explain eclipses or agree with Kepler's three laws, Newton presented his criticisms in a work entitled “Questiones” published in 1664. That was the beginning of his scientific career. He then became interested in the corpuscular-mechanistic theory introduced by Galileo and developed by Gassendi and Boyle. In addition, he began his mathematical studies that showed his brilliance as a mathematician that would prove so crucial to his scientific explanations.

He was elected to a fellowship at Trinity in 1664 at the age of twenty-two, and during the following two years of intense study, referred to as his “
anni mirabilis
” (or miracle years, foreshadowing Einstein), applying his newly acquired mathematical skills, he was able to write three original papers on the problem of motion. In one titled “The Laws of Motion” he made two theoretical discoveries that later were included in his system of dynamics presented in his great book
, Philosophiæ Naturalis Principia Mathematica
. In another he rejected Descartes's theory of vortices because it depended on direct contact to explain mutually reciprocating forces. In the third he introduced the principle of the conservation of momentum in mechanics.

Then, as a result of his critique of Descartes's theory of vortices, he began applying mathematics to the study of planetary motions. As he wrote in a famous letter to William Stukeley, another of his friends who was a fellow student at the grammar school in Grantham (which I was also shown during my visit to the Royal Society), it was while he was at home because of the closing of Cambridge University during the plague years of 1665–1666 that, when sitting in the orchard and seeing an apple fall, it occurred to him that the same gravitational force that caused the apple's fall could produce the elliptical deviation in Mars's orbit if extended that far. Thus the account is factual, not fictional, as sometimes alleged.

Moreover, having read Kepler's works at the time of his mathematical studies, this insight may have been reinforced by Kepler's explanation of the tides as being due to the mutual gravitational force between the earth and the moon. And since Kepler's third law states that a planet's periodic time is proportional to the 3/2
^th
power of its mean distance from the sun, it might have occurred to him that the strength of the earth's gravitational force on the moon could be in the same ratio. As quoted by Richard S. Westfall in his superb
A Biography of Isaac Newton
:

In the beginning of the year 1665 . . . I began to think of gravity extending to y
^e
orb of the Moon & . . . from Kepler's rule of the periodical times of the Planets being in sesquialterate [3/2
^th
] proportion of their distances from the center of their Orbs, I deduced that the forces w
^ch
keep the Planets in their Orbs must [be] reciprocally as the squares of their distances from the centers about w
^ch
they revolve: & thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the earth, & found them answer pretty nearly. All this was in the two plague years of 1665–1666. For in those days I was in the prime of my age for invention & minded Mathematicks and Philosophy more than at any time since.”
³²
(brackets added)

As Kepler had proposed in the
Epitome Astronomœ
Copernicanœ
, the laws that he originally applied only to Mars refer to all of the planets, including the moon and the satellites of Jupiter. This could have been a further influence on Newton.

In addition to these investigations and discoveries, he began his experiments on light being dissatisfied with the current theories of color proposed by Descartes, Boyle, and Robert Hooke. It was then thought that light was homogeneous, the different colors produced by it being refracted when striking the retina. Red and blue were considered the dominant colors arising from the greatest refraction of light while the other colors were inadequate when Newton began his prismatic experiments that displayed his remarkable experimental ingenuity complementing his mathematical expertise.

Discovering that ordinary light when refracted through a prism disperses into a spectrum of particular colors that he called “rays,” he surmised that the retina acts as a prism refracting ordinary light into the various distinct colors. This was confirmed when he redirected the dispersed rays into another prism and they again became blended. He also concluded that this would explain the rainbow that had puzzled scientists throughout the ages and noticed that the circular lenses he used to measure the dimensions of the colors produced rings of color now called “Newton's rings.”

Believing the corpuscular-mechanistic theory to be the basic infrastructure of the universe, this undoubtedly influenced his interpretation of light rays as corpuscular, along with the discovery that the sharp edges of shadows supported this interpretation, despite such scientists as Hooke and Christiaan Huygens defending the wave theory. As Westfall states: “No other investigation of the seventeenth century better reveals the power of experimental inquiry animated by a powerful imagination and controlled by rigorous logic” (p. 164). Later Newton would encounter evidence of the wave theory but persist in defending the view that the rays of light are corpuscular.

Not until the nineteenth century would there be evidence that light is an electromagnetic radiation with wave properties, and it was not until Einstein's explanation in 1905 of blackbody radiation as caused by light consisting of discrete units of energy later called “photons,” that the disconcerting notion of the dual nature of light as “wavicles” would be introduced, either property depending on the experimental conditions.

Despite these scholarly accomplishments, the criteria then for promotion to a fellowship—a precondition at Cambridge University for attaining a permanent university position—being based mainly on social status, patronage, and strong academic affiliations that Newton lacked, his prospects were not encouraging. This was increased by his being examined on Euclid by Isaac Barrow, the Lucasian Professor of Mathematics at Cambridge, in connection with the fellowship, and his belief that he had not performed well because at the time he had been studying Descartes's geometry rather than Euclid's. Nonetheless, for whatever reason, he was elected a Minor Fellow on October 1, 1667, and as a Major Fellow nine months later.

But several years later, when he showed Barrow his method for calculating an infinite series, this so impressed Barrow that he sent a copy to John Collins, one of the outstanding mathematicians at the time and disseminator in Europe of unusual mathematical developments, describing Newton as “a fellow of our College, & very young . . . but of an extraordinary genius and proficiency in these things” (p. 202). This was most fortunate because there was no one better positioned to evaluate Newton's mathematical achievements and promote his reputation. Collins later sent him complex problems that he would solve in a short time and return. Impressed, Collins distributed copies to other mathematicians in England, Scotland, and Europe, but terminated the correspondence when he encountered resistance from Newton, who was adverse to publicity and possible disputes.

Nonetheless, the initial correspondence enhanced Newton's reputation, which may explain why Barrow resigned his Lucasian Professorship and recommended Newton as his successor following Newton's appointment as a Major Fellow. Thus, at the early age of twenty-seven he attained the very lucrative and prestigious chair of Lucasian Professor. But though the appointment to the status of Major Fellow “would follow automatically when he was created Master of Arts nine months hence,” it was not without its adverse conditions. With two exceptions, the recipients “were required to take holy orders in the Anglican church within seven years of incepting M.A.” And so on October 1667 Newton

became a fellow of the College of the Holy and Undivided Trinity when he swore “that I will embrace the true religion of Christ with all my soul . . . and also that I will either set Theology as the object of my studies and will take holy orders when the time prescribed by these statues arrives, or I will resign from the college.” (p. 179)

To fulfill the conditions he would have had to “set theology as the object of my studies and . . . take holy orders,” which meant remaining celibate and embracing the Athanasian Creed. While remaining celibate was not a problem for personal reasons mentioned earlier, nor was studying theology since he had spent a number of years researching early church history. But swearing to adhere to the Athanasian Creed was a problem. As a result of his extended studies he had decided that the Council of Nicaea's decision to adopt the Trinitarian doctrine of the Athanasian Creed that God, Jesus, and the Holy Spirit were “consubstantial” was a “massive fraud, which . . . had perverted the legacy of the early church” (p. 313). Thus he embraced the Arian Creed that Jesus and the Holy Spirit had been created by God, not consubstantial with Him.

Fortunately, to prevent his having to resign his fellowship along with the Lucasian Chair at Trinity, an official dispensation was passed on April 27, 1675: “By its terms, the Lucasian professor was exempted from taking holy orders unless ‘he himself desires to . . .'” (p. 333). Furthermore, the “dispensation was granted to the Lucasian professorship in perpetuity, not just to Isaac Newton, fellow of Trinity. It was probably Barrow's last service to his protégé” (pp. 333–34). Although a diversion from the main history, this episode is significant in showing how influential the Anglican Church was in university affairs at that time.

A further example of Newton's unusual dexterity was his invention of an improved reflecting telescope. During his optical experiments he found that reflecting telescopes had produced chromatic aberration that distorted the focusing and decided to design and build a reflecting telescope that would eliminate the problem. Unlike Galileo who had hired a technician to help in constructing his telescope, Newton describes in detail how he had “cast and ground the mirror from an alloy of his own invention,” along with “the tube and the mount” (p. 233). Only about six inches long, it still magnified an object “nearly forty times in diameter” (there is a Royal Society's drawing of it on p. 235). When informed of his invention and to commend his achievement he was elected to The Royal Society on January 11, 1672, the beginning of many honors to be bestowed on him.

Dr. Edmond Halley (of Halley's comet fame) conveyed the impression that it had been
his
visit to Newton in 1684 that renewed Newton's interest in celestial mechanics and instigated his writing of what is generally considered the greatest scientific work ever written, the
Principia Mathematica
. But as argued by Westfall and as indicated in Newton's account of the visit, he was already engaged in research on celestial mechanics that was a prologue to writing his book. During Halley's visit, as related to Abraham DeMoire by Newton,

after they had been some time together, the D
^r
asked him what he thought the Curve would be that would be described by the Planets supposing the force of attraction towards the sun to be reciprocal to the square of their distance from it. S
^r
Isaac replied . . . that it would be an Ellipsis, the Doctor struck with joy & amazement asked him how he knew it, why saith he I have calculated it, whereupon D
^r
Halley asked . . . for his calculation. . . . S
^r
Isaac looked among his papers but could not find it, but he promised him to renew it, & then send it to him. . . . (p. 403)

Thus, according to Westfall, “Halley did not extract the
Principia
from a reluctant Newton. . . . The treatise
De Motu
[On Motion] which Halley received in November, bore marks testifying that the challenge was at work already” (p. 405). What surprises me about this quotation is that though seventy-five years had elapsed since Kepler had published his law in 1609, scientific knowledge was still so restricted that a person of Halley's knowledge would not have mentioned it in his original question.

Keeping his promise, Newton sent Halley a treatise of nine pages entitled
De motu corporum in gyrum
(On the Motion of Bodies in an Orbit). As Westfall states:

Not only did it demonstrate that an elliptical orbit entails an inverse-square force to one focus, but it also sketched a demonstration of the original problem: An inverse-square force entails a conic orbit, which is an ellipse for velocities below a certain limit. Starting from postulated principles of dynamics, the treatise demonstrated Kepler's second law and third laws as well. It hinted at a general science of dynamics by further deriving the trajectory of a projectile through a resisting medium. (p. 404)