Isaac Newton is popularly remembered as the man who saw an apple fall from a tree, and was inspired to invent the theory of gravity. If you have grappled with elementary physics then you know that he invented calculus and the three laws of motion upon which all of mechanics is based. More fundamentally, Newton's mathematical approach has become so basic to all of physics that he is generally regarded as the father of the clockwork universe: the first, and perhaps the greatest, physicist.

Many biographers have conjectured that the roots of Newton's unquenchable competitiveness and paranoia lie in his mother's remarriage and abandonment of him at the age of 3 (6). Even though these unattractive qualities caused him to waste huge amounts of time and energy in ruthless vendettas against colleagues who in many cases had helped him (see below), they also drove him to the extraordinary achievements for which he is still remembered. And for all his arrogance, Newton's own summary of his life (574) was beautifully humble:

"I do not know how 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 prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me."

- Calculus. Descartes, in 1637, pioneered the use of coordinates to
turn geometric problems into algebraic ones, a method that Newton was
never to accept [399]. Descartes, Fermat, and others investigated
methods of calculating the tangents to arbitrary curves [28-30].
Kepler, Cavalieri, and others used infinitesimal slices to calculate
volumes and areas enclosed by curves [30], but no unified treatment of
these problems had yet been found.
- Mechanics & Planetary motion. The elliptical orbits of the planets
having been established by Kepler, Descartes proposed the idea of a
purely mechanical heliocentric universe, following deterministic laws,
and with no need of any divine agency [15], another anathema to
Newton. No one imagined, however, that a single law might explain
both falling bodies and planetary motion. Galileo invented the
concept of inertia, anticipating Newton's first and second laws of
motion (293), and Huygens used it to analyze collisions and circular
motion [11]. Again, these pieces of progress had not been synthesized
into a general method for analyzing forces and motion.
- Light. Descartes claimed that light was a pressure wave, Gassendi that it was a stream of particles (corpuscles) [13]. As might be guessed, Newton vigorously supported the corpuscular theory. White light was universally believed to be the pure form, and colors were some added property bequeathed to it upon reflection from matter (150). Descartes had discovered the sine law of refraction (94), but it was not known that some colors were refracted more than others. The pattern was the familiar one: many pieces of the puzzle were in place, but the overall picture was still unclear.

He invented differential and integral calculus in 1665-6, but failed to publish it. Leibniz invented it independently 10 years later, and published it first [718]. This resulted in a priority dispute which degenerated into a feud characterized by extraordinary dishonesty and venom on both sides (542).

In discovering gravitation, Newton was also barely ahead of the rest of the pack. Hooke was the first to realize that orbital motion was produced by a centripetal force (268), and in 1679 he suggested an inverse square law to Newton [387]. Halley and Wren came to the same conclusion, and turned to Newton for a proof, which he duely supplied [402]. Newton did not stop there, however. From 1684 to 1687 he worked continuously on a grand synthesis of the whole of mechanics, the "Philosophiae Naturalis Principia Mathematica," in which he developed his three laws of motion and showed in detail that the universal force of gravitation could explain the fall of an apple as well as the precise motions of planets and comets.

The "Principia" crystallized the new conceptions of force and inertia that had gradually been emerging, and marks the beginning of theoretical physics as the mathematical field that we know today. It is not an easy read: Newton had developed the idea that geometry and equations should never be combined [399], and therefore refused to use simple analytical techniques in his proofs, requiring classical geometric constructions instead [428]. He even made his Principia deliberately abstruse in order to discourage amateurs from feeling qualified to criticize it [459].

The Principia was Newton's crowning achievement. He revised and extended it, but most of the rest of his life was spent in administrative work as Master of the Mint and as President of the Royal Society, a position he ruthlessly exploited in the pursuit of vendettas against Hooke (300ff,500), Leibniz (510ff), and Flamsteed (490,500), among others. He kept secret his disbelief in Christ's divinity right up until his dying moment, at which point he refused the last rites, at last openly defying the church (576). His alchemical corpus was never publicized, and has only recently received serious attention from intellectual historians.

Numbers in brackets [..] are references to pages in Richard's Westfall's "Never at Rest" , Cambridge University Press, 1980.

Numbers in parentheses (..) are references to Gale Christianson's "In the Presence of the Creator", The Free Press (Macmillan), 1984.

For more, see:

Andrew McNab's "newton.org.uk"
[As of early 2002 this site has disappeared]

Medieval, Renaissance,
Reformation: Western Civilization, Act II

Copyright © Mark Alford (1995) alford(at)physics.wustl.edu Mark Alford's home page