English polymath Isaac Newton was born #OTD in 1642.
Newton's book Philosophiæ Naturalis Principia Mathematica, first published in 1687, achieved the first great unification in physics and established classical mechanics. Newton also made seminal contributions to optics, and shares credit with German mathematician Gottfried Wilhelm Leibniz for formulating infinitesimal calculus, though he developed calculus years before Leibniz.