### Topic Page: Newton, Isaac, 1642-1727

**Newton, Isaac 1642-1727,**from

*Dictionary of Energy*

English mathematician and natural philosopher considered by many to be the most influential scientist who ever lived. He summarized his discoveries in terrestrial and celestial mechanics in his 1687 work Philosophiae naturalis principia mathematica (Mathematical Principles of Natural Philosophy). Newton surpassed all scientists who came before him, concisely stating simple yet elegant scientific principles and methods that applied to every branch of science.

**Newton, Isaac (1642-1727)**

*The Hutchinson Dictionary of Scientific Biography*

Place: United Kingdom, England

Subject: biography, physics, maths and statistics

English physicist and mathematician who is regarded as one of the greatest scientists ever to have lived. In physics, he discovered the three laws of motion that bear his name and was the first to explain gravitation, clearly defining the nature of mass, weight, force, inertia, and acceleration. In his honour, the SI unit of force is called the newton. Newton also made fundamental discoveries in optics, finding that white light is composed of a spectrum of colours and inventing the reflecting telescope. In mathematics, Newton's principal contribution was to formulate calculus and the binomial theorem.

Newton was born in Woolsthorpe, Lincolnshire, on 25 December 1642 by the old Julian calendar, but on 4 January 1643 by modern reckoning. His birthplace, Woolsthorpe Manor, is now preserved. Newton's was an inauspicious beginning for he was a premature, sickly baby born after his father's death, and his survival was not expected. When he was three, his mother remarried and the young Newton was left in his grandmother's care. He soon began to take refuge in things mechanical, reputedly making water clocks, kites bearing fiery lanterns aloft, and a model mill powered by a mouse, as well as innumerable drawings and diagrams. When Newton was 12, he began to attend the King's School, Grantham, but his schooling was not to last. His mother, widowed again, returned to Woolsthorpe in 1658 and withdrew him from school with the intention of making him into a farmer. Fortunately, his uncle recognized Newton's ability and managed to get him back to school to prepare for university entrance. This Newton achieved in 1661, when he went to Trinity College, Cambridge, and began to delve widely and deeply into the scholarship of the day.

In 1665, the year that he became a BA, the university was closed because of the plague and Newton spent 18 months at Woolsthorpe, with only the occasional visit to Cambridge. Such seclusion was a prominent feature of Newton's creative life and, during this period, he laid the foundations of his work in mathematics, optics, dynamics, and celestial mechanics, performing his first prism experiments and reflecting on motion and gravitation.

Newton returned to Cambridge in 1666 and became a minor fellow of Trinity in 1667 and a major fellow the following year. He also received his MA in 1668 and became Lucasian Professor of Mathematics - at the age of only 26. It is said that the previous incumbent, Isaac Barrow, resigned the post to make way for Newton. Newton remained at Cambridge almost 30 years, studying alone for the most part, though in frequent contact with other leading scientists by letter and through the Royal Society in London, which elected him a fellow in 1672. These were Newton's most fertile years. He laboured day and night in his chemical laboratory, at his calculations, or immersed in theological and mystical speculations. In Cambridge, he completed what may be described as his greatest single work, the Philosophae naturalis principia mathematica/Mathematical Principles of Natural Philosophy. This was presented to the Royal Society in 1686, who subsequently withdrew from publishing it through shortage of funds. The astronomer Edmond Halley, a wealthy man and friend of Newton, paid for the publication of the Principia in 1687. In it, Newton revealed his laws of motion and the law of universal gravitation.

After the Principia appeared, Newton appeared to become bored with Cambridge and his scientific professorship. In 1689, he was elected a member of Parliament for the university and in London he encountered many other eminent minds, notably Christiaan Huygens. The excessive strain of Newton's studies and the attendant disputes caused him to suffer severe depression in 1692, when he was described as having ‘lost his reason’. Four years later he accepted the appointment of warden of the London Mint, becoming master in 1699. He took these new, well-paid duties very seriously, revising the coinage and taking severe measures against forgers. Although his scientific work continued, it was greatly diminished.

Newton was elected president of the Royal Society in 1703, an office he held until his death, and in 1704, he summed up his life's work on light in Opticks. The following year, Newton was knighted by Queen Anne. Although he had turned grey at 30, Newton's constitution remained strong and it is said he had sharp sight and hearing, as well as all his teeth, at the age of 80. His later years were given to revisions of the Principia, and he died on 20 March 1727. Newton was accorded a state funeral and buried in Westminster Abbey, an occasion that prompted Voltaire to remark that England honoured a mathematician as other nations honoured a king.

Any consideration of Newton must take account of the imperfections of his character, for the size of his genius was matched by his ambition. A hypersensitivity to criticism and possessiveness about his work made conflicts with other scientists a prominent feature of his later life. This negative side of Newton's nature may be well illustrated by his dispute with Gottfried Leibniz. These two great mathematicians worked independently on the development of a differential calculus, both making significant advances. No one today would seriously question Leibniz's originality and true mathematical genius, but Newton branded him a plagiarist and claimed sole invention of calculus. When Leibniz appealed to the Royal Society for a fair hearing, Newton appointed a committee of his own supporters and even wrote their, supposedly impartial, report himself. He then further proceeded to review this report anonymously, later remarking that ‘he had broken Leibniz's heart with his reply to him’. The partisan and ‘patriotic’ views that resulted from this controversy served to isolate English mathematics and to set it back many years, for it was Leibniz's terminology that came to be used.

A similar dispute arose between Newton and Robert Hooke, one of the more brilliant and versatile members of the Royal Society, who supported Huygens's wave theory of light. Although, in the past, he had collaborated with Hooke, Newton published results without giving credit to their originator. Hooke, however, was notably disputatious and better able to stand up for himself than Leibniz. On the other hand, Newton remained faithful to those he regarded as friends, appointing several to positions in the Mint after he took charge, and part of his quarrel with the Astronomer Royal, John Flamsteed, was that Flamsteed had fallen out with Newton's friend Halley.

Newton's work itself must be considered in many parts: he was a brilliant mathematician and an equally exceptional optical physicist; he revolutionized our understanding of gravity and, throughout his life, studied chemistry and alchemy, and wrote millions of words on theological speculation and mysticism.

As a mathematician, Newton developed unusually late, being well through his university career when he studied the work of Pierre de Fermat, René Descartes and others, before returning to Euclid, whom he had previously dismissed. However, in those two plague years of 1665 and 1666, Newton more than made up for this delay, and much of his later work can be seen as a revision and extension of the creativity of that period. To quote one of his own notebooks: ‘In the beginning of the year 1665 I found the method for approximating series and the binomial theorem. The same year I found the method for tangents of Gregory and in November had the direct method of fluxions [differential calculus] and in January [1666] had the theory of colours [of light] and in May following I had entrance into the inverse method of fluxions [integral calculus] and in the same year I began to think of gravity extending to the orb of the moon ...’

The zenith of his mathematics was the Principia, and after this Newton did little mathematics, though his genius remained sharp and when Leibniz composed problems with the specific intention of defeating him, Newton solved each one the first day he saw it. Both in his own day and afterwards, Newton influenced mathematics ‘following his own wish’ by ‘his creation of the fluxional calculus and the theory of infinite series’, which together made up his analytic technique. But he was also active in algebra and number theory, classical and analytical geometry, computation and approximation, and even probability. For three centuries, most of his papers lay buried in the Portsmouth Collection of his manuscripts and only now are scholars examining his complete mathematics for the first time.

Newton's work in dynamics also began in those two years of enforced isolation at Woolsthorpe. He had already considered the motion of colliding bodies and circular motion, and had arrived at ideas of how force and inertia affect motion and of centrifugal force. Newton was now inspired to consider the problem of gravity by seeing an apple fall from a tree - a story that, according to Newton himself, is true. He wondered if the force that pulled the apple to the ground could also extend into space and pull the Moon into an orbit around the Earth. Newton assumed that the rate of fall is proportional to the force of gravity and that this force is inversely proportional to the square of the distance from the centre of the Earth. He then worked out what the motion of the Moon should be if these assumptions were correct, but obtained a figure that was too low. Disappointed, Newton set aside his considerations on gravity and did not return to them until 1679.

Newton was then able to satisfy himself that his assumptions were indeed true and he also had a better radius of the Earth than was available in the plague years. He then set to recalculating the Moon's motion on the basis of his theory of gravity and obtained a correct result. Newton also found that his theory explained the laws of planetary motion that had been derived earlier that century by Johannes Kepler on the basis of observations of the planets.

Newton presented his conclusions on dynamics in the Principia. Although he had already developed calculus, he did not use it in the Principia, preferring to prove all his results geometrically. In this great work, Newton's plan was first to develop the subject of general dynamics from a mathematical point of view and then to apply the results in the solution of important astronomical and physical problems. It included a synthesis of Kepler's laws of planetary motion and Galileo's laws of falling bodies, developing the system of mechanics we know today, including the three famous laws of motion. The first law states that every body remains at rest or in constant motion in a straight line unless it is acted upon by a force. This defines inertia, finally disproving the idea, which had been prevalent since Aristotle had mooted it in the 4th century BC, that force is required to keep anything moving. The second law states that a force accelerates a body by an amount proportional to its mass. This was the first clear definition of force and it also distinguished mass from weight. The third law states that action and reaction are equal and opposite, which showed how things could be made to move.

Newton also developed his general theory of gravitation as a universal law of attraction between any two objects, stating that the force of gravity is proportional to the masses of the objects and decreases in proportion to the square of the distance between the two bodies. Though, in the years before, there had been considerable correspondence between Newton, Hooke, Halley and Kepler on the mathematical formulation of these laws, Newton did not complete the work until the writing of the Principia.

‘I was in the prime of my age for invention’ said Newton of those two years 1665 and 1666, and it was in that period that he performed his fundamental work in optics. Again it should be pointed out that the study of Newton's optics has been limited to his published letters and the Opticks of 1704, its publication delayed until after Hooke's death to avoid yet another controversy over originality. No adequate edition or full translation of the voluminous Lectiones opticae exists. Newton began those first, crucial experiments by passing sunlight through a prism, finding that it dispersed the white light into a spectrum of colours. He then took a second prism and showed that it could combine the colours in the spectrum and form white light again. In this way, Newton proved that the colours are a property of light and not of the prism. An interesting by-product of these early speculations was the development of the reflecting telescope. Newton held the erroneous opinion that optical dispersion was independent of the medium through which the light was refracted and, therefore, that nothing could be done to correct the chromatic aberration caused by lenses. He therefore set about building a telescope in which the objective lens is replaced by a curved mirror, in which aberration could not occur. In 1668 Newton succeeded in making the first reflecting telescope, a tiny instrument only 15 cm/6 in long, but the direct ancestor of today's huge astronomical reflecting telescopes. In this invention, Newton was anticipated to some degree by James Gregory (1638-1675) who had produced a design for a reflecting telescope five years earlier but had not succeeded in constructing one.

Other scientists, Hooke especially, were critical of Newton's early reports, seeing too little connection between experimental result and theory, so that, in the course of a debate lasting several years, Newton was forced to refine his theories with considerable subtlety. He performed further experiments in which he investigated many other optical phenomena, including thin-film interference effects, one of which, ‘Newton's rings’, is named after him.

The Opticks presented a highly systematized and organized account of Newton's work and his theory of the nature of light and the effects that light produces. In fact, although he held that light rays were corpuscular in nature, he integrated into his ideas the concept of periodicity, holding that ‘ether waves’ were associated with light corpuscles, a remarkable conceptual leap, for Hooke and Huygens, the founder of the wave theory, both denied periodicity to light waves. The corpuscle concept lent itself to an analysis by forces and established an analogy between the action of gross bodies and that of light, reinforcing the universalizing tendency of the Principia. However, Newton's prestige was such that the corpuscular theory held sway for much longer than it deserved, not being finally overthrown until early in the 1800s. Ironically, it was the investigation of interference effects by Thomas Young that led to the establishment of the wave theory of light.

Although comparatively little is known of the bulk of Newton's complete writings in chemistry and physics, we know even less about his chemistry and alchemy, chronology, prophecy, and theology. The vast number of documents he wrote on these matters have yet to be properly analysed, but what is certain is that he took great interest in alchemy, performing many chemical experiments in his own laboratory and being in contact with Robert Boyle. He also wrote much on ancient chronology and the authenticity of certain biblical texts.

Newton's greatest achievement was to demonstrate that scientific principles are of universal application. In the Principia mathematica, he built logically and analytically from mathematical premises and the evidence of experiment and observation to develop a model of the universe that is still of general validity. ‘If I have seen further than other men,’ he once said with perhaps assumed modesty, ‘it is because I have stood on the shoulders of giants’; and Newton was certainly able to bring together the knowledge of his forebears in a brilliant synthesis. Newton's life marked the first great flowering of the scientific method, which had been evolving in fits and starts since the time of the ancient Greeks. But Newton really established it, completing a scientific revolution in Europe that had begun with Nicolaus Copernicus and ushering in the Age of Reason, in which the scientific method was expected to yield complete knowledge by the elucidation of the basic laws that govern the universe. No knowledge can ever be total, but Newton's example brought about an explosion of investigation and discovery that has never really abated. He perhaps foresaw this when he remarked ‘To myself, I seem to have been only like a boy playing on the seashore, 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.’

With his extraordinary insight into the workings of nature and rare tenacity in wresting its secrets and revealing them in as fundamental and concise a way as possible, Newton stands as a colossus of science. In physics, only Archimedes and Albert Einstein, who also possessed these qualities, may be compared to him.

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