Newton's life can be divided into three quite distinct periods. The first
is his boyhood days from 1643 up to his graduation in 1669. The second
period from 1669 to 1687 was the highly productive period in which he
was Lucasian professor at Cambridge. The third period (nearly as long
as the other two combined) saw Newton as a highly paid government official
in London with little further interest in mathematics.
Isaac Newton was born in the manor house of Woolsthorpe, near Grantham
in Lincolnshire. Although he was born on Christmas Day 1642, the date
given on this card is the Gregorian calendar date. (The Gregorian calendar
was not adopted in England until 1752.) Newton came from a family of farmers
but never knew his father who died before he was born. His mother remarried,
moved to a nearby village, and left him in the care of his grandmother.
Upon the death of his stepfather in 1656, Newton's mother removed him
from grammar school in Grantham where he had shown little promise in academic
work. His school reports described him as 'idle' and 'inattentive'. An
uncle decided that he should be prepared for the university, and he entered
his uncle's old College, Trinity College, Cambridge, in June 1661.
Newton's aim at Cambridge was a law degree. Instruction at Cambridge was
dominated by the philosophy of Aristotle but some freedom of study was
allowed in the third year of the course. Newton studied the philosophy
of Descartes, Gassendi, and Boyle. The new algebra and analytical geometry
of Vi¨¨te, Descartes, and Wallis, and the mechanics of the Copernican astronomy
of Galileo attracted him. Newton's talent began to emerge on the arrival
of Barrow to the Lucasian chair at Cambridge.
His scientific genius emerged suddenly when the plague closed the University
in the summer of 1665 and he had to return to Lincolnshire. There, in
a period of less than two years, while Newton was still under 25 years
old, he began revolutionary advances in mathematics, optics, physics,
While Newton remained at home he laid the foundation for differential
and integral calculus, several years before its independent discovery
by Leibniz. The 'method of fluxions', as he termed it, was based on his
crucial insight that the integration of a function is merely the inverse
procedure to differentiating it. Taking differentiation as the basic operation,
Newton produced simple analytical methods that unified many separate techniques
previously developed to solve apparently unrelated problems such as finding
areas, tangents, the lengths of curves and the maxima and minima of functions.
Newton's De Methodis Serierum et Fluxionum was written in 1671 but Newton
failed to get it published and it did not appear in print until John Colson
produced an English translation in 1736.
Barrow resigned the Lucasian chair in 1669 recommending that Newton (still
only 27 years old) be appointed in his place.
Newton's first work as Lucasian Professor was on optics. He had reached
the conclusion during the two plague years that white light is not a simple
entity. Every scientist since Aristotle had believed that white light
was a basic single entity, but the chromatic aberration in a telescope
lens convinced Newton otherwise. When he passed a thin beam of sunlight
through a glass prism Newton noted the spectrum of colours that was formed.
Newton argued that white light is really a mixture of many different types
of rays which are refracted at slightly different angles, and that each
different type of ray produces a different spectral colour. Newton was
led by this reasoning to the erroneous conclusion that telescopes using
refracting lenses would always suffer chromatic aberration. He therefore
proposed and constructed a reflecting telescope.
Newton was elected a fellow of the Royal Society in 1672 after donating
a reflecting telescope. Also in 1672 Newton published his first scientific
paper on light and colour in the Philosophical Transactions of the Royal
Newton's paper was well received but Hooke and Huygens objected to Newton's
attempt to prove, by experiment alone, that light consists of the motion
of small particles rather than waves. Perhaps because of Newton's already
high reputation his corpuscular theory reigned until the wave theory was
revived in the 19th C.
Newton's relations with Hooke deteriorated and he turned in on himself
and away from the Royal Society. He delayed the publication of a full
account of his optical researches until after the death of Hooke in 1703.
Newton's Opticks appeared in 1704. It dealt with the theory of light and
colour and with (i) investigations of the colours of thin sheets (ii)
'Newton's rings' and (iii) diffraction of light.
To explain some of his observations he had to use a wave theory of light
in conjunction to his corpuscular theory.
Newton's greatest achievement was his work in physics and celestial mechanics,
which culminated in the theory of universal gravitation. By 1666 Newton
had early versions of his three laws of motion. He had also discovered
the law giving the centrifugal force on a body moving uniformly in a circular
path. However he did not have a correct understanding of the mechanics
of circular motion.
Newton's novel idea of 1666 was to imagine that the Earth's gravity influenced
the Moon, counter- balancing its centrifugal force. From his law of centrifugal
force and Kepler's third law of planetary motion, Newton deduced the inverse-
In 1679 Newton applied his mathematical skill to proving a conjecture
of Hooke's, showing that if a body obeys Kepler's second law then the
body is being acted upon by a centripetal force. This discovery showed
the physical significance of Kepler's second law.
In 1684 Halley, tired of Hooke's boasting, asked Newton whether he could
prove Hooke's conjecture and was told that Newton had solved the problem
five years before but had now mislaid the paper. At Halley's urging Newton
reproduced the proofs and expanded them into a paper on the laws of motion
and problems of orbital mechanics.
Halley persuaded Newton to write a full treatment of his new physics and
its application to astronomy. Over a year later (1687) Newton published
the Philosophiae naturalis principia mathematica or Principia as it is
The Principia is recognised as the greatest scientific book ever written.
Newton analysed the motion of bodies in resisting and non resisting media
under the action of centripetal forces. The results were applied to orbiting
bodies, projectiles, pendulums, and free-fall near the Earth. He further
demonstrated that the planets were attracted toward the Sun by a force
varying as the inverse square of the distance and generalised that all
heavenly bodies mutually attract one another.
Further generalisation led Newton to the law of universal gravitation:
all matter attracts all other matter with a force proportional to the
product of their masses and inversely proportional to the square of the
distance between them.
Newton explained a wide range of previously unrelated phenomena:- the
eccentric orbits of comets, the tides and their variations, the precession
of the Earth's axis, and motion of the Moon as perturbed by the gravity
of the Sun.
After suffering a nervous breakdown in 1693, Newton retired from research
to take up a government position in London becoming Warden of the Royal
Mint (1696) and Master(1699).
In 1703 he was elected president of the Royal Society and was re-elected
each year until his death. He was knighted in 1708 by Queen Anne, the
first scientist to be so honoured for his work.
His assistant Whiston said
Newton was of the most fearful, cautious and suspicious temper that I
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A Rupert Hall, Isaac Newton, Adventurer in Thought (1992).
D T Whiteside, The mathematical principles underlying Newton's Principia,
Journal for the History of Astronomy 1 (1970), 118-119.
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Mathematiker (Berlin, 1983).
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37 (1994), 210-229.