Newton's Principia Mathematica — Law of Universal Gravitation
Newton published the Principia in 1687 and gave the world a single set of laws that applied to falling apples and to planets. The book exists because of a bet. Halley, Wren and Hooke had argued in a coffee house about whether an inverse-square attraction would produce elliptical orbits, and Halley went to Cambridge to ask Newton, who said he had calculated it years earlier and could not find the paper. He rewrote it, and then kept going for eighteen months. What resulted is three books in Latin: the laws of motion, the mechanics of bodies moving in resisting media, and the system of the world, deriving Kepler's laws, the tides, the precession of the equinoxes and the paths of comets from universal gravitation. The mathematics is geometrical rather than calculus, which Newton had invented and did not use here, partly because his readers would not have followed it. Halley paid for the printing himself, the Royal Society having spent its publication budget on a book about fish. Hooke claimed the inverse-square law and Newton removed every reference to him from the third book in response. The general scholium added in 1713 contains the phrase about framing no hypotheses: he had described how gravity acts and declined to say what it is. The Principia held for 218 years, until Mercury's orbit and then Einstein required something else, and it remains accurate enough to fly spacecraft with. Newton spent far more of his life on alchemy and biblical chronology than on physics, and considered the latter the more important work. Keynes, who bought a trunk of his papers at auction in 1936, called him the last of the magicians rather than the first of the scientists.
- Year: 1687 CE
- Category: Scientific
