April 14, 1629 – July 8, 1695
Christiaan Huygens was a prominent Dutch mathematician, astronomer, physicist, and horologist. His work included early telescopic studies, investigations and inventions related to time keeping, and studies of both optics and centrifugal force.
Christiaan Huygens studied law and mathematics at the University of Leiden and the College of Orange in Breda before turning to science.
Huygens achieved note for his argument that light consists of waves, which became instrumental in the understanding of wave-particle duality. He generally receives credit for his role in the development of modern calculus and his original observations on sound perception.
In 1655, Huygens proposed that Saturn was surrounded by a solid ring, "a thin, flat ring, nowhere touching, and inclined to the ecliptic." Using a 50 power refracting telescope that he designed himself, Huygens also discovered the first of Saturn's moons, Titan. In the same year he observed and sketched the Orion Nebula. His drawing, the first such known of the Orion nebula, was published in Systema Saturnium in 1659. Using his modern telescope he succeeded in subdividing the nebula into different stars. (The brighter interior of the Orion Nebula bears the name of the Huygens Region in his honour.) He also discovered several interstellar nebulae and some double stars.
Huygens formulated also what is now known as the second law of motion of Isaac Newton in a quadratic form. Newton reformulated and generalized that law.
After Blaise Pascal encouraged him to do so, Huygens wrote the first book on probability theory, which he had published in 1657.
On May 3, 1661, he observed planet Mercury transit over the Sun, using the telescope of telescope maker Richard Reeves in London together with astronomer Thomas Streete and Richard Reeves.
The Royal Society elected Huygens a member in 1663. In the year 1666 Huygens moved to Paris where he held a position at the French Academy of Sciences under the patronage of Louis XIV. Using the Paris Observatory (completed in 1672) he made further astronomical observations. In 1684 he published "Astroscopia Compendiaria" which presented his new aerial (tubeless) telescope.
Huygens speculated in detail about life on other planets. In his book Cosmotheoros, further entitled The celestial worlds discover'd: or, conjectures concerning the inhabitants, plants and productions of the worlds in the planets, he imagined a universe brimming with life, much of it very similar to life on 17th-century Earth. The liberal climate in the Netherlands of that time not only allowed but encouraged such speculation. In sharp contrast, philosopher Giordano Bruno, who also believed in many inhabited worlds, was burned at the stake by the Italian authorities for his beliefs in 1600.
The Huygens probe: The lander for the Saturnian moon Titan, part of the Cassini-Huygens Mission to Saturn, Asteroid 2801 Huygens, a crater on Mars and Mons Huygens, a mountain on the Moon are named in his honor.