Newton, Sir Isaac (1643-1727), English mathematician and physicist, considered one of the greatest scientists in history, who 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 (the other was German mathematician Gottfried Wilhelm Leibniz). He also solved the 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.

Newton received his bachelor's degree in 1665. After an intermission of nearly two years to avoid the plague, 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 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.

**The Fluxional Method**

Newton's first achievement was in mathematics. 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**

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. Its appearance in the Royal Society's
Philosophical Transactions led to a number of criticisms that
confirmed his fear of publication, and he subsequently withdrew as
much as possible into the solitude of his Cambridge study. In 1704,
however, Newton published *Opticks*, which explained his theories in
detail.

**The Principia**

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. In the summer of 1693 Newton showed symptoms of a severe emotional disorder. Although he regained his health, his creative period had come to an end.

Newton's connections with the leaders of the new regime in England led to his appointment as warden, and later master, of the Royal Mint in London, where he lived after 1696. In 1703 the Royal Society elected him president, an office he held for the rest of his life. As president, he ordered the immediate publication of the astronomical observations of the first Astronomer Royal of England, John Flamsteed. Newton needed these observations to perfect his lunar theory. This matter led to a difficult conflict with Flamsteed.

Newton also engaged in a violent dispute with Leibniz over priority in the invention of calculus. Newton used his position as president of the Royal Society to have a committee of that body 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.

In addition to science, Newton also showed an interest in alchemy, mysticism, and theology. Many pages of his notes and writings particularly from the later years of his career are devoted to these topics. However, historians have found little connection between these interests and Newton's scientific work.

Contributed by:

Richard S. Westfall

Further Reading

"Newton, Sir Isaac," Microsoft (R) Encarta. Copyright (c) 1994 Microsoft Corporation. Copyright (c) 1994 Funk & Wagnall's Corporation.