Huygens, Christiaan

Huygens, Christiaan (1629-1695), Dutch astronomer, mathematician, and physicist, born in The Hague. His numerous, original scientific discoveries won him wide recognition and honours among scientists of the 17th century. His discoveries include the principle (later named after him) that states that every point on an advancing wavefront is itself a source of new waves (see Optics; Huygens’ Principle). From this principle he developed the wave theory of light. In 1655 he found a new method of grinding and polishing lenses. The sharper definition obtained enabled him to discover a satellite of Saturn and to give the first accurate description of the rings of Saturn. The need for an exact measure of time for observing the heavens led to his applying the pendulum to regulate the movement of clocks. In 1656 he devised a telescope eyepiece that bears his name. In Horologium Oscillatorium (1673) he determined the true relation between the length of a pendulum and the period of oscillation and developed theories on centrifugal force in circular motion which helped the English physicist Isaac Newton to formulate the laws of gravity. In 1678 he discovered the polarization of light by double refraction in calcite.