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**I INTRODUCTION**

Newton, Sir Isaac (1642-1727), mathematician and physicist,
one of the foremost scientific intellects of all time. Born at Woolsthorpe,
near Grantham in Lincolnshire, where he attended school, he entered Cambridge
University in 1661; he was elected a Fellow of Trinity College in 1667,
and Lucasian Professor of Mathematics in 1669. He remained at the university,
lecturing in most years, until 1696. Of these Cambridge years, in which
Newton was at the height of his creative power, he singled out 1665-1666
(spent largely in Lincolnshire because of plague in Cambridge) as "the
prime of my age for invention". During two to three years of intense
mental effort he prepared *Philosophiae Naturalis Principia Mathematica*
(*Mathematical Principles of Natural Philosophy*) commonly known as
the *Principia,* although this was not published until 1687.

As a firm opponent of the attempt by King James II to make
the universities into Catholic institutions, Newton was elected Member
of Parliament for the University of Cambridge to the Convention Parliament
of 1689, and sat again in 1701-1702. Meanwhile, in 1696 he had moved to
London as Warden of the Royal Mint. He became Master of the Mint in 1699,
an office he retained to his death. He was elected a Fellow of the Royal
Society of London in 1671, and in 1703 he became President, being annually
re-elected for the rest of his life. His major work, *Opticks,* appeared
the next year; he was knighted in Cambridge in 1705.

As Newtonian science became increasingly accepted on the Continent, and especially after a general peace was restored in 1714, following the War of the Spanish Succession, Newton became the most highly esteemed natural philosopher in Europe. His last decades were passed in revising his major works, polishing his studies of ancient history, and defending himself against critics, as well as carrying out his official duties. Newton was modest, diffident, and a man of simple tastes. He was angered by criticism or opposition, and harboured resentment; he was harsh towards enemies but generous to friends. In government, and at the Royal Society, he proved an able administrator. He never married and lived modestly, but was buried with great pomp in Westminster Abbey.

Newton has been regarded for almost 300 years as the founding examplar of modern physical science, his achievements in experimental investigation being as innovative as those in mathematical research. With equal, if not greater, energy and originality he also plunged into chemistry, the early history of Western civilization, and theology; among his special studies was an investigation of the form and dimensions, as described in the Bible, of Solomon's Temple in Jerusalem.

**II OPTICS**

In 1664, while still a student, Newton read recent work on
optics and light by the English physicists Robert Boyle and Robert Hooke;
he also studied both the mathematics and the physics of the French philosopher
and scientist René Descartes. He investigated the refraction of
light by a glass prism; developing over a few years a series of increasingly
elaborate, refined, and exact experiments, Newton discovered measurable,
mathematical patterns in the phenomenon of colour. He found white light
to be a mixture of infinitely varied coloured rays (manifest in the rainbow
and the spectrum), each ray definable by the angle through which it is
refracted on entering or leaving a given transparent medium. He correlated
this notion with his study of the interference colours of thin films (for
example, of oil on water, or soap bubbles), using a simple technique of
extreme acuity to measure the thickness of such films. He held that light
consisted of streams of minute particles. From his experiments he could
infer the magnitudes of the transparent "corpuscles" forming
the surfaces of bodies, which, according to their dimensions, so interacted
with white light as to reflect, selectively, the different observed colours
of those surfaces.

The roots of these unconventional ideas were with Newton by about 1668;
when first expressed (tersely and partially) in public in 1672 and 1675,
they provoked hostile criticism, mainly because colours were thought to
be modified forms of homogeneous white light. Doubts, and Newton's rejoinders,
were printed in the learned journals. Notably, the scepticism of Christiaan
Huygens and the failure of the French physicist Edmé Mariotte to
duplicate Newton's refraction experiments in 1681 set scientists on the
Continent against him for a generation. The publication of *Opticks,*
largely written by 1692, was delayed by Newton until the critics were dead.
The book was still imperfect: the colours of diffraction defeated Newton.
Nevertheless, *Opticks* established itself, from about 1715, as a
model of the interweaving of theory with quantitative experimentation.

**III MATHEMATICS**

In mathematics too, early brilliance appeared in Newton's
student notes. He may have learnt geometry at school, though he always
spoke of himself as self-taught; certainly he advanced through studying
the writings of his compatriots William Oughtred and John Wallis, and of
Descartes and the Dutch school. Newton made contributions to all branches
of mathematics then studied, but is especially famous for his solutions
to the contemporary problems in analytical geometry of drawing tangents
to curves (differentiation) and defining areas bounded by curves (integration).
Not only did Newton discover that these problems were inverse to each other,
but he discovered general methods of resolving problems of curvature, embraced
in his "method of fluxions" and "inverse method of fluxions",
respectively equivalent to Leibniz's later differential and integral calculus.
Newton used the term "fluxion" (from Latin meaning "flow")
because he imagined a quantity "flowing" from one magnitude to
another. Fluxions were expressed algebraically, as Leibniz's differentials
were, but Newton made extensive use also (especially in the *Principia*)
of analogous geometrical arguments. Late in life, Newton expressed regret
for the algebraic style of recent mathematical progress, preferring the
geometrical method of the Classical Greeks, which he regarded as clearer
and more rigorous.

Newton's work on pure mathematics was virtually hidden
from all but his correspondents until 1704, when he published, with *Opticks*,
a tract on the quadrature of curves (integration) and another on the classification
of the cubic curves. His Cambridge lectures, delivered from about 1673
to 1683, were published in 1707.

**The Calculus Priority Dispute**

Newton had the essence of the methods of fluxions
by 1666. The first to become known, privately, to other mathematicians,
in 1668, was his method of integration by infinite series. In Paris in
1675 Gottfried Wilhelm Leibniz independently evolved the first ideas of
his differential calculus, outlined to Newton in 1677. Newton had already
described some of his mathematical discoveries to Leibniz, not including
his method of fluxions. In 1684 Leibniz published his first paper on calculus;
a small group of mathematicians took up his ideas.

In the 1690s Newton's friends proclaimed the priority of Newton's methods of fluxions. Supporters of Leibniz asserted that he had communicated the differential method to Newton, although Leibniz had claimed no such thing. Newtonians then asserted, rightly, that Leibniz had seen papers of Newton's during a London visit in 1676; in reality, Leibniz had taken no notice of material on fluxions. A violent dispute sprang up, part public, part private, extended by Leibniz to attacks on Newton's theory of gravitation and his ideas about God and creation; it was not ended even by Leibniz's death in 1716. The dispute delayed the reception of Newtonian science on the Continent, and dissuaded British mathematicians from sharing the researches of Continental colleagues for a century.

**IV MECHANICS AND GRAVITATION
**

According to the well-known story, it was on seeing an apple
fall in his orchard at some time during 1665 or 1666 that Newton conceived
that the same force governed the motion of the Moon and the apple. He calculated
the force needed to hold the Moon in its orbit, as compared with the force
pulling an object to the ground. He also calculated the centripetal force
needed to hold a stone in a sling, and the relation between the length
of a pendulum and the time of its swing. These early explorations were
not soon exploited by Newton, though he studied astronomy and the problems
of planetary motion.

Correspondence with Hooke (1679-1680) redirected Newton
to the problem of the path of a body subjected to a centrally directed
force that varies as the inverse square of the distance; he determined
it to be an ellipse, so informing Edmond Halley in August 1684. Halley's
interest led Newton to demonstrate the relationship afresh, to compose
a brief tract on mechanics, and finally to write the *Principia.*

Book I of the *Principia* states the foundations
of the science of mechanics, developing upon them the mathematics of orbital
motion round centres of force. Newton identified gravitation as the fundamental
force controlling the motions of the celestial bodies. He never found its
cause. To contemporaries who found the idea of attractions across empty
space unintelligible, he conceded that they might prove to be caused by
the impacts of unseen particles.

Book II inaugurates the theory of fluids: Newton solves problems of fluids in movement and of motion through fluids. From the density of air he calculated the speed of sound waves.

Book III shows the law of gravitation at work in the universe: Newton demonstrates it from the revolutions of the six known planets, including the Earth, and their satellites. However, he could never quite perfect the difficult theory of the Moon's motion. Comets were shown to obey the same law; in later editions, Newton added conjectures on the possibility of their return. He calculated the relative masses of heavenly bodies from their gravitational forces, and the oblateness of Earth and Jupiter, already observed. He explained tidal ebb and flow and the precession of the equinoxes from the forces exerted by the Sun and Moon. All this was done by exact computation.

Newton's work in mechanics was accepted at once in Britain,
and universally after half a century. Since then it has been ranked among
humanity's greatest achievements in abstract thought. It was extended and
perfected by others, notably Pierre Simon de Laplace, without changing
its basis and it survived into the late 19th century before it began to
show signs of failing. *See* Quantum Theory; Relativity.

**V ALCHEMY AND CHEMISTRY
**

Newton left a mass of manuscripts on the subjects of alchemy
and chemistry, then closely related topics. Most of these were extracts
from books, bibliographies, dictionaries, and so on, but a few are original.
He began intensive experimentation in 1669, continuing till he left Cambridge,
seeking to unravel the meaning that he hoped was hidden in alchemical obscurity
and mysticism. He sought understanding of the nature and structure of all
matter, formed from the "solid, massy, hard, impenetrable, movable
particles" that he believed God had created. Most importantly in the
"Queries" appended to "Opticks" and in the essay "On
the Nature of Acids" (1710), Newton published an incomplete theory
of chemical force, concealing his exploration of the alchemists, which
became known a century after his death.

**VI HISTORICAL AND CHRONOLOGICAL
STUDIES**

Newton owned more books on humanistic learning than on mathematics
and science; all his life he studied them deeply. His unpublished "classical
scholia"—explanatory notes intended for use in a future edition of
the *Principia*—reveal his knowledge of pre-Socratic philosophy; he
read the Fathers of the Church even more deeply. Newton sought to reconcile
Greek mythology and record with the Bible, considered the prime authority
on the early history of mankind. In his work on chronology he undertook
to make Jewish and pagan dates compatible, and to fix them absolutely from
an astronomical argument about the earliest constellation figures devised
by the Greeks. He put the fall of Troy at 904 BC, about 500 years later
than other scholars; this was not well received.

**VII RELIGIOUS CONVICTIONS
AND PERSONALITY**

Newton also wrote on Judaeo-Christian
prophecy, whose decipherment was essential, he thought, to the understanding
of God. His book on the subject, which was reprinted well into the Victorian
Age, represented lifelong study. Its message was that Christianity went
astray in the 4th century AD, when the first Council of Nicaea propounded
erroneous doctrines of the nature of Christ. The full extent of Newton's
unorthodoxy was recognized only in the present century: but although a
critic of accepted Trinitarian dogmas and the Council of Nicaea, he possessed
a deep religious sense, venerated the Bible and accepted its account of
creation. In late editions of his scientific works he expressed a strong
sense of God's providential role in nature.

**VIII PUBLICATIONS**

Newton published an edition of *Geographia generalis*
by the German geographer Varenius in 1672. His own letters on optics appeared
in print from 1672 to 1676. Then he published nothing until the *Principia*
(published in Latin in 1687; revised in 1713 and 1726; and translated into
English in 1729). This was followed by *Opticks* in 1704; a revised
edition in Latin appeared in 1706. Posthumously published writings include
*The Chronology of Ancient Kingdoms Amended* (1728), *The System
of the World* (1728), the first draft of Book III of the *Principia*,
and *Observations upon the Prophecies of Daniel and the Apocalypse of
St John* (1733).

Contributed By:

Alfred Rupert Hall

**"Sir Isaac Newton" Microsoft®
Encarta®. Copyright © 1998 Microsoft Corporation.
**