Christiaan Huygens was born on <nobr>14 April 1629</nobr> in Den Haag and died there on <nobr>8 July 1695</nobr>.

He is known as the founder of the wave theory of light and formulated the basic postulate of wave theory: Every point on a wavefront is the source for a new spherical wave (Huygens principle). Furthermore he calculated the laws of elastic collision and the pendulum. He invented the pendulum clock and the spring watch with balance wheel. He discovered the polarisation of light and explained the birefringence of calcite as well as the Orion nebula, the flatting of the Martian poles, the form of the rings of Saturn and its largest moon - Titan - among other things.