# Isaac Newton

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Newton was born in Woolsthorpe, Lincolnshire, and educated at Grantham Grammar School and Trinity College, Cambridge. He began his researches at an early date, but his work was interrupted by the outbreak of the Great Plague in 1664, when the university was closed down for several years. In 1665 or 1666 he contemplated the fall of an apple in his garden, which led him to begin formulating the law of gravitation.

He was also concerned with the nature of light and the construction of telescopes. By a variety of experiments upon sunlight refracted through a prism, he concluded that rays of light which differ in colour differ also in refrangibility - a discovery which suggested that the indistinctness of the image formed by the object-glass of telescopes was due to the different coloured rays of light being brought to a focus at different distances. He concluded (correctly for an object-glass consisting of a single lens) that it was impossible to produce a distinct image, and was led to the construction of reflecting telescopes, of a type that was later developed further by William Herschel and the Earl of Rosse.

Newton became a Fellow of Trinity College, Cambridge, in 1667, and was appointed Lucasian Professor of Mathematics in 1669. By 1684 he had demonstrated the whole gravitation theory, which he expounded first in De Motu Corporum (1684). Newton showed that the force of gravity between two bodies, such as the Sun and the Earth, is directly proportional to the product of the masses of the bodies and inversely proportional to the square of the distance between them. He described this more completely in Philosophiae Naturalis Principia Mathematica (1687, 'The Mathematical Principles of Natural Philosophy'), his greatest work, edited and financed by Edmond Halley, who had encouraged him to develop his theories.

In the Principia Newton stated his three laws of motion: (1) that a body in a state of rest or uniform motion will remain in that state until a force acts on it; (2) that an applied force is directly proportional to the acceleration it induces, the constant of proportionality being the body's mass (F = ma); and (3) that for every 'action' force which one body exerts on another, there is an equal and opposite 'reaction' force exerted by the second body on the first.

In the political domain, Newton defended the rights of the university against the illegal encroachments of James VII and II, and thereby won a seat in the Convention parliament (1689-90). In 1696 he was appointed Warden of the Mint, and was Master of the Mint from 1699. He again sat in parliament in 1701 for his university. He solved two celebrated problems proposed in June 1696 by Jean Bernoulli, as a challenge to the mathematicians of Europe; and performed a similar feat in 1716, by solving a problem proposed by Gottfried Leibniz.

Newton was involved throughout his life in controversies with other scientists, in particular with John Flamsteed, whose Greenwich Observations Newton published, and Robert Hooke, who claimed priority of discovery for some of Newton's work on the attraction of lunar bodies. The controversy between Newton and Leibniz over the discovery of the differential calculus and the method of fluxions is still disputed, but the general opinion of science is that the methods were invented independently, with a greater debt owing to Leibniz for the superior facility and completeness of his method.

Newton, who was knighted by Queen Anne in 1705, is buried in Westminster Abbey. Throughout his life he also devoted much time to the study of alchemy and theology, and he left substantial discourses on transmutation, a remarkable manuscript on the prophecies of Daniel and on the Apocalypse, a history of creation, and a large number of miscellaneous tracts.

If I have seen further it is by standing on the shoulders of giants.

From a letter to Hooke, 1676.

Newton's theory of the Universe remained unchallenged until Einstein's discovery of Relativity over 200 years later. Even today, Newton's laws are still used for all practical purposes, including space travel.