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Sir Isaac Newton

Reflecting Telescope

Newton Isaac Newton was one of an elite group of individuals considered to have possessed one of the greatest scientific minds in history.  His achievements span a variety of fields he considered connected, including mathematics, chemistry, optics and philosophy, and his discoveries, which encompass fundamental principles that formed the basis for Calculus, laws of motion, gravitational theory and theories of color, have clearly stood the test of time.

Born January 4, 1643, (according to the Gregorian calendar) in Woolsthorpe, Lincolnshire, England, his mother had wished him to take up farming, but when it became clear to her that his aptitudes lied elsewhere, Newton, at 17, was sent back to school to prepare for university, and entered Cambridge University’s Trinity College in 1661.

Newton became interested in mechanical philosophy at Cambridge after studying the ideas of philosophers and mathematicians such as Rene Descartes. He sought a fellowship at Cambridge in order to pursue mathematical studies and was elected to a scholarship in 1664 that would guarantee his place there for four years. He was awarded a bachelor’s degree in 1665. However, that year, a plague forced the university to close temporarily and he returned home to Woolsthorpe. At home in 1666 he is said to have begun to develop some of his most groundbreaking theories, including the generalized binomial theorem, and he later produced three papers that contributed to the formulation of calculus. His achievements in this area, which he hid for a number of years for fear of ridicule, would in time earn him recognition as a mathematical genius.

During his hiatus from Cambridge, Newton also began working on theories of motion that led him to author what is known as the Law of Universal Gravitation. He also developed theories of color after he discovered that white light was actually made up particles and of various colors. This line of study would lead him to invent a device which helped to seal his reputation as a scientific visionary, the reflecting telescope.

This Newton would create a year after his return to Cambridge in 1667, the same year he was elected a fellow of the College of the Holy and Undivided Trinity. He took his M.A. degree in 1668; he would remain at Trinity for another 20 years.

Newton experimented with light using a prism, where he observed that the spectrum of colors that can be seen when white light passes through a prism is inherent in the white light. It was not, he noted, added by the prism as had been previously believed. He also demonstrated that by using a lens and a second prism it was possible to reconstruct the rainbow of colored light into white light. 

Thus he began to theorize that telescopes as they existed at the time were limited in terms of resolution by their very design. These refracting telescopes used glass lenses to collect light, and different lenses bent different colors of light at slightly different levels, which could cause distortion and limit resolution to the detriment of the viewer.  A telescope that used mirrors instead of lenses, he believed, would eliminate this problem since mirrors reflect all colors of light by the same amount.

Though others had documented ideas for a reflecting telescope in the past, including Scottish scientist James Gregory in 1663, Newton was the first to actually build one. His design used a mirror to collect light and focus it to a second mirror, which would direct the beam of light toward an eyepiece. This, Newton believed, would allow for greater focus even at great magnification, and indeed this was the case. The Newtonian reflecting telescope as it came to be called was much smaller than the refracting telescopes common to the time, and magnified over 30 times despite its six-inches long and one-inch diameter size.  Newton demonstrated his device to the Royal Society in 1671.

In connection with this creation Newton wrote up his theory of colors, which argued that light is composed of particles, published in his “Hypothesis of Light” of 1675.  This he later expanded into his “Opticks.” His body of work in this area became the subject of scrutiny, however, after another optical expert of the time, Robert Hooke, refuted some of Newton’s claims and accused him of plagiarism. Shortly thereafter Newton gave up optics and took up chemistry. He also began work on a history of religion and produced many writings in this area; in fact he is said to have spent as much time, if not more, studying religion as science.
Also, in 1679, Newton resumed work in the area of mechanics, including gravity and astronomy, and began laying the groundwork for what would become his seminal work “The Philosophiae Naturalis Principia Mathematica,” or “the Principia,” published in 1687. This tome includes Newton’s three Universal Laws of Motion as well as a formal presentation of his Law of Universal Gravitation.

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