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Sir Isaac Newton

Isaac Newton (1642-1727) (Jupiter Changer)

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. See Gravitation; Mechanics. Newton was born on December 25, 1642 (according to the Julian calendar then in use; the date was January 4, 1643, according to the Gregorian calendar in use today), 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.

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 was another area of Newton’s early interests. In trying to explain how colors occur, he arrived at the idea that sunlight is a heterogeneous blend of different rays-each of which represents a different color-and that reflections and refractions cause colors to appear by separating the blend into its components. Newton demonstrated his theory of colors by passing a beam of sunlight through a type of prism, which split the beam into separate colors. In 1672 Newton sent a brief exposition of his theory of colors 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.

Newton discovered the nature of light when he darkened his room and “made a small hole in my shuts to let in a convenient quantity of the sun’s light.” He passed this beam of sunlight through a prism. When the light came out of the prism is was not white but was of seven different colours: Red, Orange, Yellow, Green, Blue, Indigo and Violet. The spreading into rays was called DISPERSION by Newton and he called the different coloured rays the SPECTRUM. He learnt that when the light rays were passed again through a prism the rays turned back into white light. If only one ray was passed through the prism it would come out the same colour as it went in. Newton concluded that white light was made up of seven different coloured rays. The rays were dispersed through the prism because the rays were reflected at different angles. Newton wondered whether the different colours of the spectrum travelled at different speeds. He wrote to Flamstead to ask if when he observed an eclipse whether the colour changed all at once of at different times. Flamstead wrote back to him to say that the colours changed all at once.

Because Newton was working with light in 1668 he made the first reflecting telescope. The light was collected and reflected from a curved mirror instead of being refracted through a lens. It was far superior from the refracting telescopes at that time because it reflected all the light in the same way. It did not produce colour fringing or blurring which occurred in the early refracting telescopes.

By Linda Dinh