Christiaan Huygens (1629-1695), Dutch astronomer, physicist and inventor of the pendulum clock presenting one of his time pieces to King Louis XIV (1638-1715) of France in 1659. Huygens (right) 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, and may be said to be the beginning of truly accurate time measurement. Huygens also provided much of the groundwork for the law of conservation of energy, the wave theory of light and the mathematics of probability.