HUYGENS Christian (Huygens Christiaan)

(1629-1695)
Born April 14, 1629 in The Hague. He studied at the universities of Leiden (1645-1647) and Brad. In 1665-1681 he lived in Paris from 1681 - in The Hague.
The first work devoted to the Huygens classic problems: the theorems of the quadrature of the hyperbola, ellipse and circle size range. Using the algebraic approach, he explained the value of p. In 1657 wrote a treatise on the calculations for gambling (De ratiociniis in ludo aleae) - one of the first works on the theory of probability.

Huygens became known for the invention of the pendulum clock. On this discovery, he said in his work hours (Horologium, 1658). Subsequent years devoted problems of mechanics. In 1673 in Paris came out of his fundamental work Swinging clock, . or on the motion of a pendulum (Horologium oscillatorium, . sive de motu pendulorum ad horologia aptato demostrationes geometrica), . in which the motion of solid bodies in a cycloid, . was given scan and identification of length of curves, . The problem of determining the center of oscillation of a physical pendulum and the period of its oscillations, . Theorems on Centrifugal Force, . was given a type of device hours - with a circular pendulum,
. In a paper presented at the contest in the Royal Society in 1669, Huygens studied the collision of elastic bodies, and brought its laws.

In 1678 Huygens presented to the Paris Academy of Sciences Treatise on light (Trait de la lumire), which outlined the wave theory of light. Under this theory, the scientist explained the mechanism of propagation of light, reflection, refraction, atmospheric refraction, birefringence, seen as a form of lenses. The central point of the theory is well-known principle of construction of the envelope wave (Huygens' principle). There are studies Huygens applied nature: he perfected the refracting telescope, in particular the lens, designed the ocular (eyepiece Huygens), began to apply the diaphragm, invented the micrometer (instrument for measuring small angles). With the help of a telescope constructed in 1655 discovered a ring of Saturn and its moon Titan, defined period of Titan around the world.

Huygens died in The Hague on 8 July 1695.