Edmond Halley, an astronomer and mathematician, is the youngest of a trio of Royal Society members in London that includes the inventor and microscopist Robert Hooke and the famous architect Sir Christopher Wren, both of whom, with Isaac Newton at Cambridge, are attempting to find a mechanical explanation for planetary motion.
Halley, Wren and Hooke had had a conversation in January 1684, from which Hooke will later claim not only to have derived the inverse-square law, but also all the laws of planetary motion.
Newton, a physicist and mathematician, had in 1679 returned to his work on mechanics, i.e., gravitation and its effect on the orbits of planets, with reference to Kepler's laws of motion, and consulting with Hooke and Astronomer Royal John Flamsteed on the subject.
He had published his results in De Motu Corporum in Gyrum, which contains the beginnings of the laws of motion that will inform the “Philosophia Naturalis Principia Mathematica,” published on July 5, 1687 with encouragement and financial help from Halley, who had read De Motu Corporum to the Royal Society in December 1684.
In the Principia, Newton states the three universal laws of motion; they will not be improved upon for more than two hundred years.
He uses the Latin word gravitas (weight) for the force that will become known as gravity, and defines the law of universal gravitation.
In the same work he presents the first analytical determination, based on Boyle's law, of the speed of sound in air.
Moreover, Newton, like Leibniz, has discovered the calculus, called by the historian Carl Boyer “the most effective instrument for scientific investigation that mathematics has ever produced.” (Although a bitter dispute over priority will develop later between followers of the two men, it is now clear that they had each arrived at the calculus independently.)
Only after publication of Newton's laws of motion and gravitation does a scientific approach to the origin of the solar system became possible. (Even after this breakthrough, many years will elapse while scientists struggle with applications of Newton's laws to explain the apparent motions of planets, moons, comets, and asteroids.)
With the Principia, Newton becomes internationally recognized and acquires a circle of admirers, including the Swiss-born mathematician Nicolas Fatio de Duillier.
Newton has ushered in a tidal wave of changes in thought that will significantly accelerate the already ongoing scientific revolution by giving it tools that produce technologically valuable results, which had heretofore been otherwise unobtainable.
