ISAAC NEWTONS LIFE INTRODUCTIONNewton, Sir Isaac (1642-1727), mathematician andphysicist, one of the foremost scientific intellects ofall time.Born at Woolsthorpe, near Grantham inLincolnshire, where he attended school, he enteredCambridge University in 1661; he was elected aFellow of Trinity College in 1667, and LucasianProfessor of Mathematics in 1669
He remained at the university, lecturing in mostyears, until 1696. Of these Cambridge years, inwhich Newton was at the height of his creativepower, he singled out 1665-1666 (spent largely inLincolnshire because of plague in Cambridge) as"the prime of my age for invention".During two to three years of intense mental efforthe prepared Philosophiae Naturalis PrincipiaMathematica (Mathematical Principles of NaturalPhilosophy) commonly known asthe Principia, although this was not published until1687.
As a firm opponent of the attempt by King James IIto make the universities into Catholicinstitutions, Newton was elected Member ofParliament for the University of Cambridge to theConvention Parliament of 1689, and sat again in1701-1702. Meanwhile, in 1696 he had moved toLondon as Warden of the Royal Mint.He became Master of the Mint in 1699, an office heretained to his death. He was elected a Fellow ofthe Royal Society of London in 1671, and in 1703he became President, being annually re-elected forthe rest of his life. His majorwork, Opticks, appeared the next year; he wasknighted in Cambridge in 1705.
s Newtonian science became increasingly acceptedon the Continent, and especially after a generalpeace was restored in 1714, following the War ofthe Spanish Succession, Newton became the mosthighly esteemed natural philosopher in Europe.His last decades were passed in revising his majorworks, polishing his studies of ancient history, anddefending himself against critics, as well as carryingout his official duties.Newton was modest, diffident, and a man of simpletastes. He was angered by criticism or opposition,and harboured resentment; he was harsh towardsenemies but generous to friends.
In government, and at the Royal Society, he provedan able administrator. He never married and livedmodestly, but was buried with great pomp inWestminster Abbey.Newton has been regarded for almost 300 years asthe founding examplar of modern physical science,his achievements in experimental investigationbeing as innovative as those in mathematicalresearch.With equal, if not greater, energy and originality healso plunged into chemistry, the early history ofWestern civilization, and theology; among hisspecial studies was an investigation of the form anddimensions, as described in the Bible, of SolomonsTemple in Jerusalem.
OPTICSIn 1664, while still a student, Newton read recentwork on optics and light by the English physicistsRobert Boyle and Robert Hooke; he also studiedboth the mathematics and the physics of the Frenchphilosopher and scientist René Descartes.He investigated the refraction of light by a glassprism; developing over a few years a series ofincreasingly elaborate, refined, and exactexperiments, Newton discoveredmeasurable, mathematical patterns in thephenomenon of colour.
He found white light to be a mixture of infinitelyvaried coloured rays (manifest in the rainbow andthe spectrum), each ray definable by the anglethrough which it is refracted on entering or leaving agiven transparent medium.He correlated this notion with his study of theinterference colours of thin films (for example, of oilon water, or soap bubbles), using a simpletechnique of extreme acuity to measure thethickness of such films.He held that light consisted of streams of minuteparticles. From his experiments he could infer themagnitudes of the transparent "corpuscles" formingthe surfaces of bodies, which, according to theirdimensions, so interacted with white light as toreflect, selectively, the different observed colours ofthose surfaces.
The roots of these unconventional ideas were withNewton by about 1668; when first expressed(tersely and partially) in public in 1672 and 1675,they provoked hostile criticism, mainly becausecolours were thought to be modified forms ofhomogeneous white light.Doubts, and Newtons rejoinders, were printed inthe learned journals. Notably, the scepticism ofChristiaan Huygens and the failure of the Frenchphysicist Edmé Mariotte to duplicate Newtonsrefraction experiments in 1681 set scientists on theContinent against him for a generation.
The publication of Opticks, largely written by1692, was delayed by Newton until the critics weredead.The book was still imperfect: the colours ofdiffraction defeated Newton.Nevertheless,Opticks established itself, from about1715, as a model of the interweaving of theory withquantitative experimentation.
MATHEMATICSIn mathematics too, early brilliance appeared inNewtons student notes. He may have learntgeometry at school, though he always spoke ofhimself as self-taught; certainly he advancedthrough studying the writings of his compatriotsWilliam Oughtred and John Wallis, and ofDescartes and the Dutch school.
Newton made contributions to all branches ofmathematics then studied, but is especially famousfor his solutions to the contemporary problems inanalytical geometry of drawing tangents to curves(differentiation) and defining areas bounded bycurves (integration).Not only did Newton discover that these problemswere inverse to each other, but he discoveredgeneral methods of resolving problems ofcurvature, embraced in his "method of fluxions" and"inverse method of fluxions", respectivelyequivalent to Leibnizs later differential and integralcalculus.
Newton used the term "fluxion" (from Latin meaning"flow") because he imagined a quantity "flowing"from one magnitude to another.Fluxions were expressed algebraically, as Leibnizsdifferentials were, but Newton made extensive usealso (especially in thePrincipia) of analogousgeometrical arguments.Late in life, Newton expressed regret for thealgebraic style of recent mathematical progress,preferring the geometrical method of the ClassicalGreeks, which he regarded as clearer and morerigorous.
Newtons work on pure mathematics was virtually hidden from all but his correspondents until 1704, when he published, with Opticks, a tract on the quadrature of curves (integration) and another on the classification of the cubic curves. His Cambridge lectures, delivered from about 1673 to 1683, were published in 1707.
In 1687, English mathematician Sir IsaacNewton published Principia, which hypothesizesthe inverse-square law of universal gravitation. Inhis own words, “I deduced that the forces whichkeep the planets in their orbs must [be] reciprocallyas the squares of their distances from the centersabout which they revolve: and thereby comparedthe force requisite to keep the Moon in her Orb withthe force of gravity at the surface of the Earth; andfound them answer pretty nearly.
Newtons theory enjoyed its greatest success whenit was used to predict the existence of Neptunebased on motions of Uranus that could not beaccounted for by the actions of the other planets.Calculations by both Jhon Couch Adams andUrbain Le Verrier predicted the general position ofthe planet, and Le Verriers calculations are whatled Johann Gottfried Galle to the discovery ofNeptune.
A discrepancy in Mercury’s rbit pointed out flaws in Newtons theory. By the end of the 19th century, it was known that its orbit showed slight perturbations that could not be accounted for entirely under Newtons theory, but all searches for another perturbing body (such as a planet orbiting the Sun even closer than Mercury) had been fruitless. The issue was resolved in 1915 by Albert Einsthein’s new theory of which accounted for the small discrepancy in Mercurys orbit.
Although Newtons theory has been superseded,most modern non-relativisticgravitationalcalculations are still made using Newtons theorybecause it is a much simpler theory to work withthan general relativity, and gives sufficientlyaccurate results for most applications involvingsufficiently small masses, speeds and energies.