Christian Huygens

Christiaan Huygens, FRS (/ˈhaɪɡənz/ or /ˈhɔɪɡənz/; Dutch: [ˈɦœy̆ɣə(n)s] (Latin: Hugenius) (14 April 1629 – 8 July 1695) was a prominent Dutch mathematician and scientist. He is known particularly as an astronomer, physicist, probabilist and horologist.

Huygens was a leading scientist of his time. His work included early telescopic studies of the rings of Saturn and the discovery of its moon Titan, the invention of the pendulum clock and other investigations in timekeeping. He published major studies of mechanics and optics, and a pioneer work on games of chance.

Christiaan Huygens was born on 14 April 1629 in The Hague, into a rich and influential Dutch family, the second son of Constantijn Huygens. Christiaan was named after his paternal grandfather. His mother was Suzanna van Baerle. She died in 1637, shortly after the birth of Huygens' sister. The couple had five children: Constantijn (1628), Christiaan (1629), Lodewijk (1631), Philips (1632) and Suzanna (1637).

Constantijn Huygens was a diplomat and advisor to the House of Orange, and also a poet and musician. His friends included Galileo Galilei, Marin Mersenne and René Descartes. Huygens was educated at home until turning sixteen years old. He liked to play with miniatures of mills and other machines. His father gave him a liberal education: he studied languages and music, history and geography, mathematics, logic and rhetoric, but also dancing, fencing and horse riding.

In 1644 Huygens had as his mathematical tutor Jan Jansz de Jonge Stampioen, who set the 15-year-old a demanding reading list on contemporary science. Descartes was impressed by his skills in geometry.

Shortly before his death in 1695, Huygens completed Cosmotheoros, published posthumously in 1698. In it he speculated on the existence of extraterrestrial life, on other planets, which he imagined was similar to that on Earth.

Such speculations were not uncommon at the time, justified by Copernicanism or the plenitude principle. But Huygens went into greater detail. The work, translated into English in its year of publication, has been seen as in the fanciful tradition of Francis Godwin, John Wilkins and Cyrano de Bergerac, and fundamentally Utopian; and also to owe in its concept of planet to cosmography in the sense of Peter Heylin.

Huygens wrote that availability of water in liquid form was essential for life and that the properties of water must vary from planet to planet to suit the temperature range. He took his observations of dark and bright spots on the surfaces of Mars and Jupiter to be evidence of water and ice on those planets. He argued that extraterrestrial life is neither confirmed nor denied by the Bible, and questioned why God would create the other planets if they were not to serve a greater purpose than that of being admired from Earth. Huygens postulated that the great distance between the planets signified that God had not intended for beings on one to know about the beings on the others, and had not foreseen how much humans would advance in scientific knowledge.

It was also in this book that Huygens published his method for estimating stellar distances. He made a series of smaller holes in a screen facing the sun, until he estimated the light was of the same intensity as that of the star Sirius. He then calculated that the angle of this hole was 1/27,664th the diameter of the Sun, and thus it was about 30,000 times as far away, on the (incorrect) assumption that Sirius is as bright our sun. The subject of photometry remained in its infancy until Pierre Bouguer and Johann Heinrich Lambert.