Isaac Newton (1642-1727)
Isaac Newton was an English physicist and mathematician, and a key figure in the 17th century scientific revolution, widely acknowledged to be one of the greatest scientists.
He was born on 25 December 1642 into a prosperous farming family in Woolsthorpe, Lincolnshire, England. His father died three months before he was born. Newton was born prematurely, tiny and weak, and was not expected to survive long, but survive he did for the benefit of mankind. When Newton was three, his mother remarried and went to live with her new husband, Newton being left in the care of his maternal grandmother. Newton never reconciled to his mother remarrying and his hostility towards his stepfather was evidenced by his threat to burn his house down. Thus, Newton had a lonely childhood, manifesting in his later life as acute sense of insecurity. Although it is said that he was once engaged, Newton never married.
At the age of 12, Newton was reunited with his mother after her second husband died. At that time Newton was studying in King’s School, learning mainly Latin and chemistry. His mother promptly pulled him out of school, intending to make him take care of the family farm. But Newton did not like farming and was soon sent back to King’s School. After Newton finished his basic education there, his uncle, a graduate of the University of Cambridge’s Trinity College, sensed his nephew’s intellectual abilities and persuaded Newton’s mother to have him enter the university.
Newton entered Trinity College, University of Cambridge, in 1661. He was older than most of his fellow students, but despite the fact that his mother was financially well off, he entered as a sizar. A sizar at Cambridge was a student who received an allowance toward college expenses in exchange for waiting tables and cleaning rooms for the fellows (faculty) and the wealthier students. Though Newton graduated with no honors or distinctions, three years later, in 1664, he was elected a scholar, guaranteeing four years of financial support for future education. In 1665, Newton returned home because Cambridge was closed on account of plague. He spent two years working on problems in mathematics and physics. It was during this period that he conceived the method of calculus, set foundations for his theory of light and colour, and gained significant insight into the laws of planetary motion. It was at this time, Newton experienced his famous inspiration for gravity watching the apple fall to the earth.
Newton returned to Cambridge in 1667. Soon he became a professor at Cambridge. His first major public scientific achievement was the invention, design and construction of a reflecting telescope, one which ensured his election to membership in the Royal Society. The mirror used in this telescope gave a sharper image than was possible with a large lens because a lens focuses different colours at slightly different distances, an effect called chromatic aberration. Nowadays, the usage of compound lenses cuts out this aberration, but mirrors are still used in large telescopes.
By the end of 1675 Newton worked out the corpuscular or emission theory of light, and showed how it would account for all the various phenomena of geometrical optics, such as reflection, refraction, colours, diffraction, etc.
In a 1679 letter, Robert Hooke wrote to Newton, suggesting that a formula involving the inverse squares might explain the attraction between planets and the shape of their orbits. After a series of exchanges with Hooke, Newton broke off the correspondence and formulated his own work on planetary motion, reaching some definite conclusions by 1680, though he kept his discoveries to himself. In 1684, Edmond Halley met Newton at Cambridge to motivate him to work on Hooke’s ideas on planetary motion and cast them mathematically. Newton claimed to have solved the problem some 18 years earlier during his hiatus from Cambridge during the plague, but he was unable to find the notes. With Halley’s encouragement and financial support, in 1687, after 18 months of intense and effectively nonstop work, Newton published his most acclaimed work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) – physics and science were known in those days as Natural Philosophy – hailed as the single most influential book on physics.
Newton’s Laws Of Motion:
The Principia offered an exact quantitative description of bodies in motion in three basic laws:
1) A stationary body will stay stationary unless an external force is applied to it.
2) Force is equal to mass times acceleration, and a change in motion is proportional to the force applied.
3) For every action, there is an equal and opposite reaction.
These three laws and his theory of universal gravitation helped explain not only elliptical planetary orbits but nearly every other motion in the universe: how the planets are kept in orbit by the pull of the sun’s gravity; how the moon revolves around Earth; and how comets revolve in elliptical orbits around the sun. The laws also allowed Newton to calculate the mass of each planet, calculate the flattening of the Earth at the poles and the bulge at the equator, and how the gravitational pull of the sun and moon create the Earth’s tides.
Upon the publication of the first edition of Principia, Robert Hooke immediately accused Newton of plagiarism, claiming that he had discovered the theory of inverse squares and that Newton had stolen his work. The charge was unfounded, as most scientists knew, for Hooke had only theorized on the idea and had never brought it to any level of proof. However, Newton was furious and strongly defended his discoveries. But Hooke did not give in, keeping alive his contentions until his death in 1703.
Most modern historians believe that Newton and Leibniz developed calculus independently, although with very different notations. But Newton published almost nothing about it until 1693, and did not give a full account until 1704, while Leibniz began publishing a full account of his methods in 1684. This led to a longstanding dispute between Leibniz and Newton as to who was the first to have developed calculus.
The Whitest Soul:
In appearance Newton was short, and towards the close of his life rather stout, but well set, with a square lower jaw, brown eyes, a broad forehead, and rather sharp features. His hair turned grey before he was thirty, and remained thick and white as silver till his death. As to his manners, he dressed untidily, was rather disinclined to physical effort, and was often so absorbed in his own thoughts as to be anything but a lively companion. In character he was religious and conscientious, with an exceptionally high standard of morality, having, as Bishop Burnet said, “the whitest soul’’ he ever knew. He suffered nervous breakdown twice, once in 1678 and a second time in 1693.
Newton summed up his own estimate of his work thus: “I do not know what I may appear to the world; but to myself I seem to have been only like a boy, playing on the sea-shore, and diverting myself, in now and then finding a smoother pebble, or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.’’ However, most agree with the English poet Alexander Pope, that:
“Nature and Nature’s laws lay hid in night; God said “Let Newton be” and all was light.”