Christiaan Huygens (1629-1695), Dutch astronomer, mathematician and physicist, artwork. The inscription gives the Latin form of his name, Christianus Hugenius, and gives his birth date (14 April 1629) and his death date (8 June 1695). Huygens studied at the University of Leiden. He made his name as an astronomer by discovering the rings of Saturn, its moon Titan, the Orion Nebula and many of the markings on Mars. His greatest achievement was in the measurement of time. In 1656, Huygens made the first pendulum clock. This gave a vast improvement over the existing mechanical clocks. Huygens also worked on the law of the conservation of energy, the wave theory of light and the mathematics of probability.