Tradition has it that Newton was sitting under an apple tree when an apple fell on his head, and this made him understand that earthly and celestial gravitation are the same. A contemporary writer, William Stukeley, recorded in his Memoirs of Sir Isaac Newton’s Life a conversation with Newton in Kensington on April 15, 1726, in which Newton recalled “when formerly, the notion of gravitation came into his mind. It was occasioned by the fall of an apple, as he sat in contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself. Why should it not go sideways or upwards, but constantly to the earth’s centre.”
Sir Isaac Newton, English mathematician, philosopher, and physicist, was born in 1642 in Woolsthorpe-by-Colsterworth, a hamlet in the county of Lincolnshire. His father had died three months before Newton’s birth, and two years later his mother went to live with her new husband, leaving her son in the care of his grandmother. Newton was educated at Grantham Grammar School. In 1661 he joined Trinity College, Cambridge, and continued there as Lucasian professor of mathematics from 1669 to 1701. At that time the college’s teachings were based on those of Aristotle, but Newton preferred to read the more advanced ideas of modern philosophers such as Descartes, Galileo, Copernicus, and Kepler. In 1665, he discovered the binomial theorem and began to develop a mathematical theory that would later become calculus.
However, his most important discoveries were made during the two-year period from 1664 to 1666, when the university was closed due to the Great Plague. Newton retreated to his hometown and set to work on developing calculus, as well as advanced studies on optics and gravitation. It was at this time that he discovered the Law of Universal Gravitation 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.
Arguably, it is for Newton’s Laws of Motion that he is most revered. These are the three basic laws that govern the motion of material objects. Together, they gave rise to a general view of nature known as the clockwork universe. The laws are: (1) Every object moves in a straight line unless acted upon by a force. (2) The acceleration of an object is directly proportional to the net force exerted and inversely proportional to the object’s mass. (3) For every action, there is an equal and opposite reaction.
In 1687, Newton summarized his discoveries in terrestrial and celestial mechanics in his Philosophiae naturalis principia mathematica (Mathematical Principles of Natural Philosophy), one of the greatest milestones in the history of science. In this work 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, devoted to dynamics, includes Newton’s three laws of motion; the second part to fluid motion and other topics; and the third part to the system of the world, in which, among other things, he provides an explanation of Kepler’s laws of planetary motion.
This is not all of Newton’s groundbreaking work. In 1704, his discoveries in optics were presented in Opticks, in which he elaborated his theory that light is composed of corpuscles, or particles. 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.
Newton achieved many honors over his years of service to the advancement of science and mathematics, as well as for his role as warden, then master, of the mint. He represented Cambridge University in Parliament, and was president of the Royal Society from 1703 until his death in 1727. Sir Isaac Newton was knighted in 1705 by Queen Anne. Newton never married, nor had any recorded children. He died in London and was buried in Westminster Abbey.
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