5 July 1687 July 4, 2015 Author: Staff Isaac Newton publishes Philosophiæ Naturalis Principia Mathematica. Famous Words of Inspiration..."The best way to cheer yourself up is to try to cheer somebody else up." Mark Twain — Click here for more from Mark Twain Related posts: 5 July 1687 17 October 1979 4 July 1569 5 July 1948 5 July 1948 5 July 1946 Categories: History Tags: 1687, 5 July