Isaac Newton (1642-1727), English astronomer, mathematician and physicist. Newton's most famous work is his Principia Mathematica (1687) in which he stated his universal laws of motion and defined his law of universal gravitation. This would form the basis of physics for the next two hundred years. Newton also studied the spectrum of light, showing that it was a mixture of colours, and he invented the reflecting telescope. In mathemetics, his achievements included developing calculus. He became President of the Royal Society (founded 1660) in 1703, and was knighted in 1705. Engraving by F. Scriven (published in 1859), from a picture by Vanderbank, held by the Royal Society.