1629-1695

Dutch physicist best known for inventing the wave theory of light. Working with his brother Constantijn he invented a two-lens eyepiece, which dramatically reduced chromatic aberration, and he constructed improved telescopes with which he discovered Saturn's largest satellite Titan (1655), correctly described Saturn's rings (1655), and first observed markings on Mars (1659). Huygens also invented the first successful pendulum clock, so useful for accurate time keeping in astronomical measurements, and independently discovered conservation of momentum.