Isaac Newton & Gravity
Born: Jan 4th, 1643 [O.S. 25 Dec 1642 ] Woolsthaorpe - by - Colsterworth, Lincolnsire, England
Died: Mar 31 1727[ O.S. 20 Mar 1726 ] Kensington, Middlesex, England
Nationality : English
Known For: Newtonian mechanics, Universal gravitation Calculus, Newton's Law of Motion, Optics, Binomial Series, Principia, Newton's Method.
Award: FRS (1672), Knight Bachelor (1705)
Fields: Physics, Natural Philosphy, Alchemy Theology, Mathematics' Astronomy, Economics.
Sir Isaac Newton PRS (25 December 1642 – 20 March
1726/27[a]) was an English mathematician, physicist, astronomer, theologian,
and author (described in his own day as a "natural philosopher") who
is widely recognised as one of the most influential scientists of all time and
as a key figure in the scientific revolution. His book Philosophiæ Naturalis
Principia Mathematica (Mathematical Principles of Natural Philosophy), first
published in 1687, laid the foundations of classical mechanics. Newton also
made seminal contributions to optics, and shares credit with Gottfried Wilhelm
Leibniz for developing the infinitesimal calculus.
In Principia, Newton formulated the laws of motion and
universal gravitation that formed the dominant scientific viewpoint until it was
superseded by the theory of relativity. Newton used his mathematical
description of gravity to prove Kepler's laws of planetary motion, account for
tides, the trajectories of comets, the precession of the equinoxes and other
phenomena, eradicating doubt about the Solar System's heliocentricity. He
demonstrated that the motion of objects on Earth and celestial bodies could be
accounted for by the same principles. Newton's inference that the Earth is an
oblate spheroid was later confirmed by the geodetic measurements of Maupertuis,
La Condamine, and others, convincing most European scientists of the
superiority of Newtonian mechanics over earlier systems.
Newton built the first practical reflecting telescope and
developed a sophisticated theory of colour based on the observation that a
prism separates white light into the colours of the visible spectrum. His work
on light was collected in his highly influential book Opticks, published in
1704. He also formulated an empirical law of cooling, made the first theoretical
calculation of the speed of sound, and introduced the notion of a Newtonian
fluid. In addition to his work on calculus, as a mathematician Newton
contributed to the study of power series, generalised the binomial theorem to
non-integer exponents, developed a method for approximating the roots of a
function, and classified most of the cubic plane curves.
Newton was a fellow of Trinity College and the second
Lucasian Professor of Mathematics at the University of Cambridge. He was a
devout but unorthodox Christian who privately rejected the doctrine of the
Trinity. Unusually for a member of the Cambridge faculty of the day, he refused
to take holy orders in the Church of England. Beyond his work on the
mathematical sciences, Newton dedicated much of his time to the study of
alchemy and biblical chronology, but most of his work in those areas remained
unpublished until long after his death. Politically and personally tied to the
Whig party, Newton served two brief terms as Member of Parliament for the
University of Cambridge, in 1689–90 and 1701–02. He was knighted by Queen Anne
in 1705 and spent the last three decades of his life in London, serving as
Warden (1696–1700) and Master (1700–1727) of the Royal Mint, as well as
president of the Royal Society (1703–1727).
Mechanics and gravitation
Further information: Writing of Principia Mathematica
In 1679, Newton returned to his work on celestial
mechanics by considering gravitation and its effect on the orbits of planets
with reference to Kepler's laws of planetary motion. This followed stimulation
by a brief exchange of letters in 1679–80 with Hooke, who had been appointed to
manage the Royal Society's correspondence, and who opened a correspondence
intended to elicit contributions from Newton to Royal Society transactions.
Newton's reawakening interest in astronomical matters received further stimulus
by the appearance of a comet in the winter of 1680–1681, on which he
corresponded with John Flamsteed. After the exchanges with Hooke, Newton worked
out proof that the elliptical form of planetary orbits would result from a
centripetal force inversely proportional to the square of the radius vector.
Newton communicated his results to Edmond Halley and to the Royal Society in De
motu corporum in gyrum, a tract written on about nine sheets which was copied
into the Royal Society's Register Book in December 1684. This tract contained
the nucleus that Newton developed and expanded to form the Principia.
The Principia was published on 5 July 1687 with
encouragement and financial help from Edmond Halley. In this work, Newton
stated the three universal laws of motion. Together, these laws describe the
relationship between any object, the forces acting upon it and the resulting
motion, laying the foundation for classical mechanics. They contributed to many
advances during the Industrial Revolution which soon followed and were not
improved upon for more than 200 years. Many of these advancements continue to
be the underpinnings of non-relativistic technologies in the modern world. He
used the Latin word gravitas (weight) for the effect that would become known as
gravity, and defined the law of universal gravitation.
In the same work, Newton presented a calculus-like method
of geometrical analysis using 'first and last ratios', gave the first
analytical determination (based on Boyle's law) of the speed of sound in air,
inferred the oblateness of Earth's spheroidal figure, accounted for the
precession of the equinoxes as a result of the Moon's gravitational attraction
on the Earth's oblateness, initiated the gravitational study of the
irregularities in the motion of the Moon, provided a theory for the
determination of the orbits of comets, and much more.
Newton made clear his heliocentric view of the Solar
System—developed in a somewhat modern way because already in the mid-1680s he
recognised the "deviation of the Sun" from the centre of gravity of
the Solar System. For Newton, it was not precisely the centre of the Sun or
any other body that could be considered at rest, but rather "the common
centre of gravity of the Earth, the Sun and all the Planets is to be esteem'd
the Centre of the World", and this centre of gravity "either is at
rest or moves uniformly forward in a right line" (Newton adopted the
"at rest" alternative in view of common consent that the centre,
wherever it was, was at rest).
Newton's postulate of an invisible force able to act over
vast distances led to him being criticised for introducing "occult
agencies" into science. Later, in the second edition of the Principia
(1713), Newton firmly rejected such criticisms in a concluding General
Scholium, writing that it was enough that the phenomena implied a gravitational
attraction, as they did; but they did not so far indicate its cause, and it was
both unnecessary and improper to frame hypotheses of things that were not
implied by the phenomena. (Here Newton used what became his famous expression
"hypotheses non-fingo").
With the Principia, Newton became internationally
recognised. He acquired a circle of admirers, including the Swiss-born
mathematician Nicolas Fatio de Duillier.
