NEWTON, JSAAC. — Scientist, born at Woolsthorpe, County of Lincoln, England, on 25 December 1642 (5 January 1643 according to the Gregorian calendar). From a very young age he showed particular aptitude for the study of natural phenomena, as well as for constructing ingenious mechanisms and sundials; his mother therefore consented to his devoting himself to the sciences and preparing for admission to the celebrated Trinity College, Cambridge. He entered it by competitive examination in June 1661, and the well-known J. Barron, professor of mathematics, encouraged him in his studies for eight years and in 1669 secured for him the appointment as « Lucasian Professor of Mathematics », yielding him the position. N., who had already published several noteworthy studies, among them the famous theorem for the expansion of the binomial for any exponent, was able to devote himself without further concerns to his preferred studies.
The twenty years between 1667, the year in which he obtained the degree of « Fellow » at Trinity College, and 1687, when he published Philosophiae naturalis principia mathematica, were undoubtedly the period of N.’s most intense and fruitful work. He alternated theoretical studies and experiments in optics, which he presented in his lectures, with fundamental studies on general mechanics and the gravitation of bodies, while also devoting himself to studies of mathematics and geometry; little, however, is known about their distribution throughout that period. Those who lived with N. at the time remember him constantly absorbed in meditation, often forgetful of food and sleep, averse to every pastime but always steadfast in religious and charitable practices. It is nevertheless known that in the early years of that period N. invented his reflecting telescope, which is still constructed today in enormous examples, and this earned him appointment in January 1672 as a fellow of the Royal Society of London, although he did not escape the usual criticisms of the envious. Of exceptional importance among his other achievements are two discoveries: the systematization of the foundations of mechanics and the discovery of the law of universal gravitation, expounded at length in the Principia. Those discoveries, through their concurrence, unquestionably placed N. among the greatest geniuses. Although one often speaks of Newtonian dynamics, it must not be forgotten that its general conception is due to the application of Galileo’s experimental criterion. The first of his three laws, that of inertia, is unquestionably due to Leonardo da Vinci and Galileo; the second, concerning the action of forces on material bodies, is fundamentally due to Galileo, who applied it extensively and recognized its great significance; N. merely formulated it axiomatically, so as to make it serve the subsequent systematic developments. Since, however, the application of forces (actions) to a given body necessarily implies the intervention of another body, a complete consideration of the dynamic phenomenon required consideration also of the effects it underwent: hence the third axiomatic law, ordinarily called that of action and reaction, which is entirely due to N. On the basis of these three laws and a few definitions of fundamental concepts, he succeeded in systematically establishing the dynamics that still satisfies most of the requirements of physics.
The discovery of universal gravitation (v. GRAVITAZIONE), or rather of its law, since there was already some awareness of the general notion, cost N. alternating hopes and disappointments. The first and perhaps still rather vague investigations date back to 1665, and a legend claims that they were prompted by the fortuitous fall of an apple from a tree, and by the thought that the force acting on the apple and compelling it to fall toward the earth with uniformly accelerated motion must be identical in nature with that which kept the moon in its orbit around the earth. They were resumed fourteen years later and then abandoned once again because, on introducing into the calculations the value assigned to the earth’s diameter on the basis of Snellius’s measurements, certain numerical discrepancies appeared when the same calculations were finally resumed. At last, in 1683, using the more precise measurements of the meridian arc carried out by Picard for the earth’s diameter, N. achieved the hoped-for result, namely the universally known law that he expounded in the third book of the Principia. The following year the celebrated astronomer Halley, visiting N. at Cambridge, was informed of the situation and reported it to the Royal Society of London, which immediately commissioned him to obtain a communication of the distinguished work; it was presented to the Society on 28 April 1685. The authoritative body undertook the publication under its patronage, and this took place in 1687. Subsequently, for more than a century, the triumphs of celestial mechanics led physics to regard as its ideal the development of its theories in the direction of hypothetical actions at a distance of the Newtonian type, including the new electrical, magnetic, and electromagnetic theories of the first half of the nineteenth century, forgetting that N. himself had openly expressed his reluctance to attribute any character of reality to such actions. Only the reaction of Faraday-Maxwell later altered that tendency.
In the years immediately following, N., somewhat exhausted by the immense labor, devoted himself principally to perfecting and publishing his earlier studies, almost all of which had already been presented in his lectures. From 1695, when he was appointed inspector and then director of the Mint, he became involved in the unpleasant controversies concerning his contributions to the creation of infinitesimal calculus in comparison with Leibniz. Surrounded by esteem such as no other scientist had enjoyed, and in an eminent financial position, N. devoted his final years to biblical studies, the fruits of which were a commentary on the Apocalypse and a work on the prophet Daniel. He died on 31 March 1727 and was buried, with the highest honors, in Westminster Abbey.