Sir Isaac Newton (1643-1727), British physicist, mathematician and astronomer. Newton's most famous works are Principia Mathematica (1687) and Opticks (1704). In Principia, 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. In Opticks, Newton discussed his studies into the spectrum of light, showing that it was a mixture of colours. He also invented the reflecting telescope. He was President of the Royal Society from 1703 to 1727, and was knighted in 1705.