Christiaan Huygens, (HY guhnz), (1629-1695), was a Dutch physicist, astronomer, and mathematician. In 1678, Huygens proposed that light consists of series of waves. He used this theory in investigating the refraction (bending) of light.

Huygens's wave theory competed for many years with the corpuscular theory of the English scientist Isaac Newton. Newton maintained that light is made up of particles. Today, scientists believe that light behaves as both a particle and a wave.

Huygens was born on April 14, 1629, in The Hague, the Netherlands. He studied mathematics and law at the University of Leiden and the College of Orange at Breda. Huygens worked with his brother Constantijn to develop skill in grinding and polishing spherical lenses. With these lenses, they built the most powerful telescopes of their time. Huygens also discovered Saturn's moon Titan and asserted that what astronomers called "Saturn's arms" was a ring. In mathematics, he refined the value of pi . In the 1650's, Huygens invented a clock with a freely suspended pendulum. He died on July 8, 1695.

The European Space Agency honored Huygens's discovery of Titan by naming a space probe after him. The Huygens probe, designed to drop through Titan's atmosphere, was launched aboard the Cassini spacecraft in 1997.

Contributor: Ronald S. Calinger, Ph.D., Associate Professor of History, Catholic University of America.

How to cite this article: To cite this article, World Book recommends the following format: Calinger, Ronald S. "Huygens, Christiaan." World Book Online Reference Center. 2004. World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar268300.