Newton, Sir Isaac (1642-1727)
English physicist
In 1687, English physicist Sir Isaac Newton published a law of universal gravitation in his important and profoundly influential work Philosophiae Naturalis Principia Mathematica (Mathematical principles of natural philosophy). Newton articulated a law of universal gravitation that states that bodies with mass attract each other with a force that varies directly as the product of their masses and inversely as the square of the distance between them. This mathematically elegant law, along with Newton's laws of motion, became the guiding models for the future development of physical law.
Newton admitted having no fundamental explanation for mechanism of gravity itself. In Principia Newton stated, "I have been unable to discover the cause of those properties of gravity from phenomena, and I feign no hypotheses" (regarding its mechanism). Moreover, Newton asserted, "To us it is enough that gravity does really exist, and act according to the laws which we have explained, and abundantly serves to account for the motions of the celestial bodies and our seas." Newton's law of gravitation proved to be a precise and effective tool. A truly universal law, it could be verified by the simplest fall of an apple or measured against the most detailed observations of celestial movements. Ultimately, Newton's law of universal gravitation would provide, in the twentieth century, evidence of the existence of black holes. The Newtonian methodology of simplifying mass to a point mass (i.e., with regard to gravitational fields, all of the mass of a body can be considered to lie in a center of mass without physical space) also proved a brilliant simplification that enabled the mathematical advancement of mechanics and electromagnetism.
Because Newton's law of universal gravitation was so mathematically simple and precise it strengthened the idea that all the laws describing the universe should be mathematical.
Born in Woolsthorpe, Lincolnshire, England, Newton was a premature baby who was not expected to live. His father had died three months before the birth, and his mother remarried three years later, leaving Newton in the care of his grandparents. Newton did not distinguish himself in school, and his mother removed him in the late 1650s to work on the family farm, but Newton proved a worse farmer than scholar. His uncle, however, encouraged the boy to go to Cambridge in 1660. Five years later Newton graduated, even though he had failed a scholarship exam in 1663 due to his lack of knowledge concerning geometry.
Newton returned to the farm shortly thereafter to escape the Bubonic plague, which at the time was decimating London. While at the farm in 1666, Newton first developed his law of universal gravitation. When Newton made calculations of what the rate of fall for the Moon should be, he came up short of what was actually observed and was quite disappointed. The problem was twofold; first, the radius of the earth was not known with precision and the size Newton used was too small. Second, he was not absolutely certain he was correct in making his calculations based on the gravitational force at the center of Earth, as opposed to the surface. Because of these issues, he set aside his work on gravity for 15 years.
During this same time, Newton began to experiment with light. Newton passed a beam of sunlight through a prism of glass and observed it was refracted into a spectrum. He passed the spectrum through a second prism, and the light was recombined into a white spot. In 1672, Newton was elected to the Royal Society.
During his life Newton became involved in often bitter disputes with other scholars, especially his dispute with German mathematician Gottfried Wilhelm von Leibniz (1646–1716) over credit for the development of calculus. Although the notations and nomenclature used in modern calculus most directly trace back to the work of Leibniz, Newton has received the most credit for the development of the calculus in textbooks. Modern historians of science generally conclude that the feud between Newton and Leibniz was essentially groundless. A modern analysis of the notes of Newton and Leibniz clearly established that Newton secretly developed calculus some years before Leibniz published his version but that Leibniz independently developed the calculus so often credited exclusively to Newton.
Newton died on March 20, 1727, at the age of 84, and his vast influence upon science continued, later rivaled only by that of Charles Darwin and Albert Einstein.
Gravitational Constant; Gravity and the Gravitational Field; Relativity Theory
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