# Isaac Newton

## Newton, Sir Isaac

Sir Isaac Newton, 1642–1727, English mathematician and natural philosopher (physicist), who is considered by many the greatest scientist that ever lived.

**Early Life and Work**

Newton studied at Cambridge and was professor there from 1669 to 1701, succeeding his teacher Isaac Barrow as Lucasian professor of mathematics. His most important discoveries were made during the two-year period from 1664 to 1666, when the university was closed and he retired to his hometown of Woolsthorpe. At that time he discovered the law of universal gravitation, began to develop the calculus, and discovered that white light is composed of all the colors of the spectrum. These findings enabled him to make fundamental contributions to mathematics, astronomy, and theoretical and experimental physics.

**The Principia**

Newton summarized his discoveries in terrestrial and celestial mechanics in his Philosophiae naturalis principia mathematica [mathematical principles of natural philosophy] (1687), one of the greatest milestones in the history of science. In it he showed how his principle of universal gravitation provided an explanation both of falling bodies on the earth and of the motions of planets, comets, and other bodies in the heavens. The first part of the Principia is devoted to dynamics and includes Newton's three famous laws of motion; the second part to fluid motion and other topics; and the third part to the system of the world, i.e., the unification of terrestrial and celestial mechanics under the principle of gravitation and the explanation of Kepler's laws of planetary motion. Although Newton used the calculus to discover his results, he explained them in the Principia by use of older geometric methods.

**Later Work**

Newton's discoveries in optics were presented in his Opticks (1704), in which he elaborated his theory that light is composed of corpuscles, or particles. His corpuscular theory dominated optics until the early 19th cent., when it was replaced by the wave theory of light. The two theories were combined in the modern quantum theory. Among his other accomplishments were his construction (1668) of a reflecting telescope and his anticipation of the calculus of variations, founded by Gottfried Leibniz and the Bernoullis. In later years Newton considered mathematics and physics a recreation and turned much of his energy toward alchemy, theology, and history, particularly problems of chronology.

**Later Life**

Newton was his university's representative in Parliament (1689–90, 1701–2) and was president of the Royal Society from 1703 until his death. He was made warden of the mint in 1696 and master in 1699, being knighted in 1705 in recognition of his services at the mint as much as for his scientific accomplishments. Although Newton was known as an open and generous person, at various times in his life he became involved in quarrels and controversies. The most notable was his dispute with Leibniz over which of them had first invented calculus; today they are jointly ascribed the honor.**Bibliography**

An eight-volume edition of Newton's mathematical papers (ed. by D. H. Whiteside et al., 1967–81) has been published. See biographies by R. S. Westfall (1980), G. E. Christianson (1984), and J. Gleick (2003); J. Herivel, The Background to Newton's Principia (1965); A. Koyré, Newtonian Studies (1965); I. B. Cohen, Introduction to Newton's Principia (1971) and The Newtonian Revolution (1983); M. S. Stayer, ed., Newton's Dream (1988).

*The Columbia Encyclopedia, 6th ed. Copyright© 2015, The Columbia University Press.*