Sir Isaac Newton PRS MP (25 December 1643 – 20 March 1726/7) was an English physicist and mathematician (described in his own day as a "natural philosopher"). His book Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations for classical mechanics. Newton made seminal contributions to optics, and he shares credit with Gottfried Leibniz for the development of calculus. More: