by Charlotte Michiels
Born : 4 January 1643 in Woolsthorpe
Died : 31 March 1727 in London
Sir Isaac Newton (1643-1727), English mathematician and physicist, considered one of the greatest scientists in history, made important contributions to many fields of science. His discoveries and theories laid the foundation for much of the progress in science since his time. Newton was one of the inventors of the branch of mathematics called calculus (another was the German mathematician Gottfried Wilhelm Leibniz). He also solved mysteries of light and optics, formulated the three laws of motion, and derived from them the law of universal gravitation.
Newton was born on January 4, 1643, at Woolsthorpe, near Grantham in Lincolnshire. When he was three years old, his widowed mother remarried, leaving him in the care of his grandmother. Eventually his mother, by then widowed a second time, was persuaded to send him to grammar school in Grantham. Later, in the summer of 1661, he was sent to Trinity College, at the University of Cambridge.
Soon after Newton had taken his BA degree in May 1665, the Cambridge colleges were shut down because of an outbreak of plague. They remained closed for the next two years and Newton returned to Woolsthorpe. During these two years of intense creativity, Newton laid the foundations of all his major discoveries - on infinite series, calculus, optics and gravitation. After this intermission of almost two years , Newton returned to Trinity, which elected him to a fellowship in 1667. He received his master's degree in 1668. Newton ignored much of the established curriculum of the university to pursue his own interests: mathematics and natural philosophy. Proceeding entirely on his own, he extended his researches, publishing nothing but communicating some of his results privately. He investigated the latest developments in mathematics and the new natural philosophy that treated nature as a complicated machine. Almost immediately, he made fundamental discoveries that were instrumental in his career in science.
After a bad experience with critics when he published his findings on the nature of light, Newton tended to keep his discoveries to himself. It was not until a visit by Sir Edmund Halley in 1684 that Newton revealed and finally consented to publish all of his scientific discoveries. The result was the Principia, considered by some people to be the most impressive scientific work ever written. According to De Morgan's statement, Halley even paid for the first printing of the Principia.
There were several periods of Newton's life when he largely lost interest in mathematics and physical science. During the 1670s his life was dominated by chemical and alchemical studies. At about this time, Newton took up a new field of study : theology. Like a magician, he regarded the Universe as a secret which could be solved by applyiing pure thought to certain clues left by God. To him these clues were to be found partly in the natural word, and partly in certain mystic traditions. His researches led him to espouse the historical Arian(or Unitarian) position, as opposed to the Trinitarian doctrine of Athanasius which became the orthodoxy of the Church in the fourth century. Thanks to the influence at court of his friend Barrow, he managed to obtain a royal dispensation exempting him from taking holy orders.
In April 1696 he moved to London to become Warden of the Royal Mint. He entered into the duties with such zeal that his scientific activities almost ceased. The great natural philosopher became a most faithful and conscientious public servant. In 1699 he was promoted to the position of Master of the Mint, later elected President of the Royal Society and even knighted by Queen Anne.
Newton's first achievement was in mathematics.The essence of his approach, using infinite series, was to combine the concepts and techniques of three hitherto largely separate branches of maths : coordinate geometry, the calculus and the expansion of functions as infinte series. By developing a method of dealing with infinite series, and manipulating them as if they were polynomials, Newton greatly increased the power of maths. The crucial element in Newton's treatment of infinite series was his discovery of the general binomial theorem.
He generalized the methods that were being used to draw tangents to curves and to calculate the area swept by curves, and he recognized that the two procedures were inverse operations. By joining them in what he called the fluxional method, Newton developed in the autumn of 1666 a kind of mathematics that is now known as calculus. Calculus was a new and powerful method that carried modern mathematics above the level of Greek geometry.
Although Newton was its inventor, he did not introduce calculus into European mathematics. In 1675 Leibniz arrived independently at virtually the same method, which he called differential calculus. Leibniz proceeded to publish his method and received sole credit for its invention until Newton published a detailed exposition of his fluxional method in 1704. Always fearful of publication and criticism, Newton kept his discovery to himself. However, enough was known of his abilities to effect his appointment in 1669 as Lucasian Professor of Mathematics at the University of Cambridge.
Optics was another area of Newton's early interests. In trying to explain how colours occur, he arrived at the idea that sunlight is a heterogeneous blend of different rays each of which represents a different colour and that reflections and refractions cause colours to appear by separating the blend into its components. Newton demonstrated his theory of colours by passing a beam of sunlight through a type of prism, which split the beam into separate colours.
In 1672 Newton sent a brief exposition of his theory of colours to the Royal Society in London which led to a number of criticisms that confirmed his fear of publication. In 1704, however, Newton published Opticks, which explained his theories in detail.
In August 1684 Newton's solitude was interrupted by a visit from Edmund Halley, the British astronomer and mathematician, who discussed with Newton the problem of orbital motion. Newton had also pursued the science of mechanics as an undergraduate, and at that time he had already entertained basic notions about universal gravitation. As a result of Halley's visit, Newton returned to these studies.
During the following two and a half years, Newton established the modern science of dynamics by formulating his three laws of motion. Newton applied these laws to Kepler's laws of orbital motion formulated by the German astronomer Johannes Kepler and derived the law of universal gravitation. Newton is probably best known for discovering universal gravitation, which explains that all bodies in space and on earth are affected by the force called gravity. He published this theory in his book Philosophiae Naturalis Principia Mathematica in 1687. This book marked a turning point in the history of science; it also ensured that its author could never regain his privacy.
The Principia's appearance also involved Newton in an unpleasant episode with the English philosopher and physicist Robert Hooke. In 1687 Hooke claimed that Newton had stolen from him a central idea of the book: that bodies attract each other with a force that varies inversely as the square of their distance. However, most historians do not accept Hooke's charge of plagiarism.
In the same year, 1687, Newton helped lead Cambridge's resistance to the efforts of King James II to make the university a Catholic institution. After the English Revolution in 1688, which drove James from England, the university elected Newton one of its representatives in a special convening of the country's parliament. The following four years were filled with intense activity for Newton, as, buoyed by the triumph of the Principia, he tried to put all his earlier achievements into a final written form.
Newton engaged in a violent dispute with Leibniz over priority in the invention of calculus. Using his position as president of the Royal Society, he founded a committee to investigate the question, and he secretly wrote the committee's report, which charged Leibniz with deliberate plagiarism. Newton also compiled the book of evidence that the society published. The effects of the quarrel lingered nearly until his death in 1727.
The story that Newton's hypothesis of universal gravitation was prompted by the fall of an apple, is probably true because several reliable accounts from the last few years of his life which record him describing such an event. Even Voltaire, who was in London for the last year of Newton's life, stated in one of his essays : "Sir Isaac Newton walking in his garden had the first thought of his System of Gravitation, upon seeing an apple falling down from the tree.". From this event Newton asked himself : why should that apple always descend perpendicularly to the ground ? not sideways ? or upwards ? but constantly to the earth's centre ? And that power of gravity, bringing the apple from the tree to the ground, is it limited to a certain distance from the earth or does it extend much farther around the Earth and in the whole universe ? Why not as high as the moon ? and if so this power must influence her motion and perhaps retain her in her orbit !
To develop his theory of gravitation, Newton first had to develop the science of forces and motion called mechanics. Newton proposed that the natural motion of an object is motion at a constant speed on a straight line, and that it takes a force to slow down, speed up, or change the path of an object. Because Newton also invented calculus, this important tool was a fundamental help in the calculations of his theory of gravitation.
During the two plague years of 1665-1666, Newton laid the foundations of all his major discoveries - on infinite series, the calculus, optics and gravitation. From his own recollections in old age we read : "I began to think of gravity extending to the Orb of the Moon, and having found out how to estimate the force with which a globe revolving within a sphere presses the surface of the sphere. From Kepler's Rule of the periodical times of the Planets, I deduced that the forces which keep the Planets in their Orbs must be reciprocally as the squares of their distances from the centres about which they revolve : and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth, and found them to answer pretty nearly".
By the 1670s, the mechanics of the uniform circular motion were well known and the inverse square law of gravity was widely discussed by Hooke and others. However Newton was the only man who could give a full mathematical analysis of the dynamics of the Solar System, including an explanation of Kepler's three laws!
In 1687 Newton proposed his law of gravitation in the Principia and stated that every particle in the universe attracts every other particle in the universe with a force that depends on the product of the two particles' masses divided by the square of the distance between them. According to Newton, the force acts along a line between the two particles. In the case of two spheres, it acts along the line between their centers. The attraction between objects with irregular shapes is more complicated. Every bit of matter in the irregular object attracts every bit of matter in the other object. A simpler description is possible near the surface of the earth where the pull of gravity is approximately uniform in strength and direction. In this case there is a point in an object (even an irregular object) called the center of gravity, at which all the force of gravity can be considered to be acting.
Newton's law affects all objects in the universe, from raindrops in the sky to the planets in the solar system. lt is therefore known as the universal law of gravitation.
" I don't know what I may seem to the world, but, as to myself, I seem to have been only like a boy playing on the sea shore, 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 "
- "Newton, Sir Isaac," Microsoft (R) Encarta.
Copyright (c) 1994 Microsoft Corporation. Copyright (c) 1994
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