## Biography

(History of the World: The 17th and 18th Centuries)**Article abstract:** With his three laws of mechanics and his theoretical basis for the concept of gravity, Newton pioneered the science of physics, establishing principles that remained current until the twentieth century.

**Early Life**

Isaac Newton was born on Christmas Day, 1642, to a farmer and his wife, at Woolsthorpe Manor, just south of Grantham in Lincolnshire. His father died shortly before Newton’s birth, and when his mother remarried three years later, Newton remained at Woolsthorpe to be reared by his grandparents. He attended the grammar school in Grantham. His scientific aptitude appeared early when he began to construct mechanical toys and models, and aside from a brief period when his mother tried to persuade him to follow in his father’s footsteps and become a farmer (it is said that Newton tended to read books rather than watch sheep, with disastrous results), his education continued, and he was accepted as an undergraduate at Trinity College, Cambridge, in 1661. Although his mother provided a small allowance, Newton had to wait on tables at college to help finance his studies. Even at that time his fellow students remarked that he was silent and withdrawn, and indeed, Newton was, throughout his life, something of a recluse, shunning society. He never married, and some historians believe that Newton had homosexual leanings. Whatever the truth of this speculation, it is certain that he preferred work, study, experimentation, and observation, sometimes to the detriment of his own health, to social activity.

After returning to Grantham for a short time, while Cambridge was threatened by plague, Newton returned to the university as a don in 1667 with an established reputation for mathematical brilliance. Two early discoveries demonstrated his genius. Shortly after his graduation, he developed the differential calculus, a mathematical device for calculating rates of change (for example, that of acceleration) that had long evaded other scholars. As a result, in 1669 he was offered the Lucasian Chair of Mathematics at Cambridge, a position he held until 1701.

Newton’s second major contribution of this period was in the field of optics. His experiments with light had led him to build a reflecting telescope, the first one of its kind that actually worked. After further refinements, he presented it to the Royal Society, where he was asked to present a paper on his theory of light and colors. Shortly afterward, he was made a Fellow of this august body, which contained all the prominent intellectuals of the day. Newton’s paper offered new insights into the nature of color. While experimenting with prisms, Newton had discovered that white light is a mixture of all the colors of the rainbow and that the prism separates white light into its component parts. Newton’s theory was controversial, provoking strong feelings at the Royal Society and initiating a lengthy dispute with Robert Hooke concerning the nature of light. Hooke criticized Newton with such vehemence that Newton presented no more theories on the nature of light until 1704, after Hooke’s death.

**Life’s Work**

For a scientist such as Newton, the seventeenth century was an interesting period in which to work. Scientific theories were still dominated by the Aristotelian worldview, which had held sway for more than two thousand years, but cracks in that outlook were beginning to appear. Galileo Galilei had shown that, in fact, the planets traveled around the sun, which was positioned at the center of the universe, while Johannes Kepler had observed that this motion was regular and elliptic in nature. The task confronting scientists, in keeping with the aim of explaining the universe mathematically from first principles, was to find some logical reason for this phenomenon. Newton, among others, recognized that there had to be a set of universal rules governing motion, equally applicable to planetary and earthbound activity. His researches finally led him to a mathematical proof that the inverse square law of attraction between bodies regulates all motion. From this beginning, he was able to explain why planets travel in ellipses around the sun, why Earth’s tides move as they do, and why tennis balls, for example, follow the trajectories that they do. It also led him toward a notion of gravity which neatly tied his mathematics together. When Newton published this work, it led to another major confrontation with Hooke, who claimed that he had reached the proof of the inverse square law before Newton; the argument between the two was lengthy and acrimonious.

In 1684, Edmond Halley, then a young astronomer, went to Cambridge to visit Newton, who was reputed to be working in a similar field. There Halley found that Newton claimed that he had proved the inverse square law but had temporarily mislaid it. (Throughout his life, Newton worked on scraps of paper, keeping everything from first drafts to final copies, so this assertion has the ring of truth to it.) Halley was astounded: Here was a man who claimed to have solved the problem that was bothering many leading scientists of the day and he had not yet made it public. When Halley returned, Newton had found the proof, and Halley persuaded him to publish his nine-page demonstration of the law. Still, Halley was not satisfied. Realizing...

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