Newton, Sir Isaac 1642 -1727.

Newton was born in the manor house at Woolsthorpe, eight miles south of Grantham Lincolnshire on 25th December 1642. Newton's father died at the age of 36, in October 1942, before the birth of his son. His mother married Barnabas Smith, Rector of North Witham Lincolnshire who died in his 1656. On his mother's second marriage Newton was left at Woolsthorpe in the charge of his grandmother Mrs Ayscough. He was sent in 1654 to the grammar school at Grantham then kept by Mr Stokes.

Newton made little advance in his education but after a fight with an older boy he grew keener and soon rose to be head of the school. At the age of 14 he was removed from the school by his mother, who had returned to Woolsthorpe on the death of her second husband in order to take part in the management of her farm. On the advice of his uncle he was sent back to school in 1660 and on 5th June 1661, Isaac Newton was matriculated at Trinity College Cambridge under Mr Pulleyne.

In 1664 he made some observations in on halos afterwards described in his "optics". He graduated B.A. in January 16th, 1665. His unrivalled genius for mathematical speculation declared itself almost in his boyhood and before coming to Cambridge he had read Sanderson's "logic" and Kepler's "optics". As an undergraduate he applied himself to Descartes' "Geometry" and Wallis's "Arithmetica Infinitorum" and attended Barrow's lectures.

His mental activity immediately after taking his degree during 1665 and 1666 was extraordinary. He found the method for approximating series and the rule for reducing the power of any binomial to such a series. This was the binomial theorum. In May he found the method of tangents of Gregory and Slusius and in the November the direct method of fluxions (ie. the elementsof the differential calculus) and in the next year in January had theory of colours, and in May following had entrance into the inverse method of fluxions (ie integral calculus). In the same year he began to think of gravity extending to the Orb of the Moon.

Newton was driven from Cambridge by the plague in 1665, and in that autumn "he fell into a speculation that the power of gravity is not found sensibly diminished at the remotest distance from the centre of the earth from which we can rise. It appeared reasonable to him that this power must extend much further than is usually thought. Why not as far as the moon?, and if so the motion must be influenced by it -perhaps she is retained in her orbit thereby." The story that this train of thought was caused by an apple was perpetuated by Voltaire, who had it from Newton's step neice, Mrs. Conduit.

Newton at this time by a simple deduction from Kepler's third law, proposed that if the Moon were kept in a an orbit approximately circular by a force directed to the centre of the earth, then that force must be inversely proportional to the square of the distance between the Moon and the earth. He proceeded therefore to compare the consequences of his theory with the observed motion of the Moon and found them to answer pretty nearly. Still the matter was laid aside and nothing more came of it for nearly 20 years. To make the calculation a knowledge of the Earth's radius was required. The common estimate in use among geographers before Newtons time was based on the supposition that there were 60 miles to a degree of latitude and Newton took this common estimate but added "as this is a very faulty supposition, each degree containing about 69 and a half miles" his computation did not answer expectation, and he concluded that some other cause must at least join with the power of gravity on the Moon.

Newton was elected a Fellow of the Royal Society 1672. He was unable to calculate the attraction of a large spherical body on a point near its surface until about 1685. It was in his "Principia" that Newton first publicly divulged the solution of that problem. He was elected a Fellow of Trinity College in 1667. During the next few years he turned his attention to his optical work and made his first reflecting telescope in 1668. It had an aperture of about one inch and was six inches long and with it he saw Jupiter's satellites.

At the end of 1668 Mercator had shown how to calculate the area of an hyperbola. A copy of this was sent by John Collins to Barrow, and shown by him to Newton. Newton recognised that the method was mainly the same as the more general one he had already devised for finding the area of curved surfaces and for solving other problems. Newton was chosen in 1669 to succeed Barrow in the Lucasian chair and was led to conclude from his optical experiments that it was impossible to perfect the refracting telescope and he applied himself to improving his reflecting instrument. Towards the end of the same year, 1671 he was busy enlarging his method of infinite series. He was proposed for election as a Fellow of the Royal Society in 1672. He wrote afterwards an account of the experiments with the prism bought in 1666 to try the celebrated phenomena of colours. The experiment had shown conclusively "that light consists of rays differently refrangible - that colours are not qualifications of light derived from refractions of natural bodies as was generally believed but original and connate properties in which divers rays are diverse that to the same degree of refrangability ever belongs to the same colour. The white light is never compounded and to its composition are requisite all the primary colours mixed in proper proportion". On this Hooke alone appears to have reported and his report was read at the next meeting. Hooke in the discussions about the telescope had already appeared as a critic of Newton. Descartes had in 1637 described the rainbow colours produced by refraction of light banded by shade through a prism and had elaborated a theory of colours. This theory had been adopted by with a modifications by Hooke in 1664 and he had described an experiment practically identical with that Newton's fundamental experiment with the prism.

Two theories have been proposed to account for optical phenomena. Descartes was the author of one of these, the emission theory which supposes light to consist of small particles shot out by the luminous body. Hooke, though his work was very incomplete, was the first to suggest an undulatory theory. In his micrographia, 1664, he asserts that light is a quick and short vibrating motion, "propogated every way through an homogeneous medium by direct or straight lines extended every way, like rays from the centre of a sphere.....every pulse or vibration of the luminous body will generate a sphere which will continually increase and grow bigger just after the same manner though indefinitely swifter as the waves or rings on the surface of water do swell into bigger and bigger circles about a point on it." On this hypothesis he gave an account of refraction, reflection, dispersion and the colours of thin plates, but his reasoning was vague and unsatisfactory

Extracted form the "Dictionary of National Biography". Go to Copresumy, the NEW REPLACEMENT for Newton’s Ideas