Christiaan Huygens was a Dutch mathematician, physicist, and astronomer born on April 14, 1629. He is best known for his work in optics and for formulating the wave theory of light. Huygens also invented the pendulum clock, which greatly improved timekeeping accuracy. In astronomy, Huygens discovered Titan, the largest moon of Saturn, and made significant contributions to the study of Saturn's rings. His work laid the foundation for future scientists, influencing figures like Isaac Newton and shaping the fields of physics and astronomy. Huygens passed away on July 8, 1695.