Scientific Achievements
- Mathematics: Newton made fundamental contributions to analytic geometry, algebra, and calculus. Specifically, he discovered the binomial theorem, new methods for expansion of infinite series, and his 'direct and inverse method of fluxions.' The essential elements of his thought were presented in three tracts, the first appearing in a privately circulated treatise, De analysi (On Analysis),which went unpublished until 1711. In 1671, Newton developed a more complete account of his method of infinitesimals, which appeared nine years after his death as Methodus fluxionum et serierum infinitarum (The Method of Fluxions and Infinite Series, 1736). In addition to these works, Newton wrote four smaller tracts, two of which were appended to his Opticks of 1704.
- Optics: In 1665 -1666, Newton performed a number of experiments on the composition of light. Guided initially by the writings of Kepler and Descartes, Newton's main discovery was that visible (white) light is heterogeneous--that is, white light is composed of colors that can be considered primary. Through a brilliant series of experiments, Newton demonstrated that prisms separate rather than modify white light. Contrary to the theories of Aristotle and other ancients, Newton held that white light is secondary and heterogeneous, while the separate colors are primary and homogeneous. Of perhaps equal importance, Newton also demonstrated that the colors of the spectrum, once thought to be qualities, correspond to an observed and quantifiable 'degree of Refrangibility.'
- The crucial experiment: Newton's most famous experiment, the experimentum crucis, demonstrated his theory of the composition of light. Briefly, in a dark room Newton allowed a narrow beam of sunlight to pass from a small hole in a window shutter through a prism, thus breaking the white light into an oblong spectrum on a board. Then, through a small aperture in the board, Newton selected a given color (for example, red) to pass through yet another aperture to a second prism, through which it was refracted onto a second board. What began as ordinary white light was thus dispersed through two prisms. Newton's 'crucial experiment' demonstrated that a selected color leaving the first prism could not be separated further by the second prism. The selected beam remained the same color, and its angle of refraction was constant throughout. Newton concluded that white light is a 'Heterogeneous mixture of differently refrangible Rays' and that colors of the spectrum cannot themselves be individually modified, but are 'Original and connate properties.'
