Newton's Principia formulated the laws of motion and universal gravitation, which dominated scientists' view of the physical universe for the next three centuries. By deriving Kepler's laws of planetary motion from his mathematical description of gravity, and then using the same principles to account for the trajectories of comets, the tides, the precession of the equinoxes, and other phenomena, Newton removed the last doubts about the validity of the heliocentric model of the Solar System. This work also demonstrated that the motion of objects on Earth and of celestial bodies could be described by the same principles. His prediction that Earth should be shaped as an oblate spheroid was later vindicated by the measurements of Maupertuis, La Condamine, and others, which helped convince most Continental European scientists of the superiority of Newtonian mechanics over the earlier system of Descartes.
Newton built the first practical reflecting telescope and developed a theory of colour based on the observation that a prism decomposes white light into the many colours of the visible spectrum. He formulated an empirical law of cooling, studied the speed of sound, and introduced the notion of a Newtonian fluid. In addition to his work on calculus, as a mathematician Newton contributed to the study of power series, generalised the binomial theorem to non-integer exponents, developed a method for approximating the roots of a function, and classified most of the cubic plane curves.
Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge. He was a devout but unorthodox Christian and, unusually for a member of the Cambridge faculty of the day, he refused to take holy orders in the Church of England, perhaps because he privately rejected the doctrine of the Trinity. Beyond his work on the mathematical sciences, Newton dedicated much of his time to the study of biblical chronology and alchemy, but most of his work in those areas remained unpublished until long after his death. In his later life, Newton became president of the Royal Society. Newton served the British government as Warden and Master of the Royal Mint.
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Newton didn't attempt to publish some of his early discoveries, such as his work on the shape of orbits. Modesty and controversy made him hesitant to share his theories. His claim that all of natural philosophy -- the forebear to the natural sciences -- could be explained through mathematics was both groundbreaking and highly controversial when introduced in 1670 [source: The Newton Project]. That same idea formed the basis of his first masterwork, the Principia.
Eventually Newton's genius came to be widely known. His three laws of motion -- inertia, acceleration, and action and reaction -- remain a cornerstone of modern physics. His law of universal gravitation laid forth the theory that all particles in the universe exerted some gravitational force. In Newton's view, gravitational force was everywhere, from an apple falling from a tree to the moon being kept in orbit by its mutual attraction with Earth. While imperfect -- his law was later altered significantly by Einstein's theory of relativity -- Newton's conception of universal gravitation dominated physics for more than two centuries.
In his student years, Newton performed experiments in optics examining the nature of light. He found that normal, or "white," light is actually made up of a spectrum of colors. He used prisms to break apart white light into a rainbow of colors and recombine the disparate colors into white light. Despite his breakthroughs in optics, Newton didn't publish his conclusions until 1704, in "Opticks," which was considered his second great scientific treatise [source: The Newton Project].
Isaac Barrow, Newton's mentor, was instrumental in presenting one of Newton's major inventions to the scientific community. The refracting telescope commonly used during the period often couldn't produce clearly focused images. Newton replaced the mirrors of the refracting telescope with lenses. His new telescope, the reflecting telescope, was one-twelfth the size of conventional refracting telescopes and had more powerful magnification powers. Barrow's presentation of it to the Royal Academy earned Newton membership.
Newton also created calculus as a response to the insufficiencies in mathematics of the time. Originally called the fluxions or the "method of series and fluxions," calculus provided methods for solving complex problems about orbits, curves and other issues that classical geometry couldn't solve [source: The Newton Project]. Calculus is particularly suited to these challenges because it produces information about things that are continually changing -- like the speed of a falling object. In calculus, Newton laid the basic framework for understanding these problems and for making the calculations described by his laws of motion and gravitation.
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