Christiaan (1629–1695), Dutch physicist, astronomer, and mathematician. Huygens was one of the foremost scientists of the 17th century. In 1655 he developed a method of grinding lenses that minimized light aberration. The new lenses that he made enabled him to discover another one of Saturn's satellites and the true shape of the planet's rings. He investigated other astronomical phenomena and experimented further with telescopes. He made lenses of large focal length and invented an achromatic eyepiece. He made the first pendulum-regulated clock in 1657 and investigated the principles of gravity. Above all, Huygens is known for his discoveries concerning light. In 1678 he wrote a treatise in which he discussed the wave nature of light and presented the theory that every point of an advancing wave front generates new waves. His theory also explained the refraction of light. He also discovered the polarization of light.