Christiaan Huygens (April 14, 1629 - July 8, 1695) was a Dutch mathematician and physicist; born in The Hague. Huygens is commonly associated with the Scientific Revolution. He was the son of Constantijn Huygens.
Christiaan is generally given minor credit for his role in the development of modern calculus. He is also notable for his arguments that light consisted of waves; see: wave-particle duality. In 1655, he discovered Saturn's moon Titan. He also examined Saturn's planetary rings, and in 1656 he found out those rings consisted of rocks. In the same year he observed the Orion Nebula. Using his modern telescope he was able to divide the nebula into different stars. The brighter interior of the Orion Nebula is called the Huygens Region. He also discovered several interstellar nebulae and some double stars.
He also worked on the construction of accurate clocks, suitable for naval navigation. In 1658 he published a book on this topic called Horologium. Huygens was elected a member of the Royal Society in 1663. In the year 1666 Huygens moved to Paris where he held a chair at the French Royal Society. Using the Parisianian observatory, which was completed in 1672, he made further astronomical observations.
Huygens was one of the first writers to speculate in detail about life on other planets (although we do not know to which extent ancient writers exercised such speculation, since most of their work has not survived). In his book 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. It was the liberal climate in the Netherlands of that time which not only allowed but encouraged such speculation. In sharp contrast, Italian philosopher Giordano Bruno, who also believed in many inhabited worlds, was burned at the stake for his beliefs in 1600.
The lander for the Saturn moon Titan that is part of the Cassini probe was named after Huygens.