# Christiaan Huygens

Christiaan Huygens [ hœi̯ɣəns ] (? Pronunciation / i) ( born April 14, 1629 in The Hague, † July 8th, 1695 ibid ), also Christianus Hugenius, was a Dutch astronomer, mathematician and physicist. Huygens is true even though he never used the undeveloped during his lifetime Calculus, as one of the leading mathematicians and physicists of the 17th century. He is the founder of the wave theory of light, put it in his studies of the elastic collision a relativity principle and designed the first pendulum clocks. With improved telescopes of him he achieved important astronomical discoveries.

## Life

### Background and education

Huygens was born as the son of Constantijn Huygens, the language scholar, diplomat, composer and then leading poets of Holland had. Through his father Christiaan he soon came into contact with eminent personalities, including Rembrandt, Peter Paul Rubens and René Descartes. Christiaan was taught as a child by his father. Later he studied at the University of Leiden, first law, but then changed her soon to mathematics and science.

His first published work (1651 ) dealt with the quadrature of cones and showed an error in an alleged proof of the quadrature of the circle. He also dealt with the circle number π (pi), logarithms and made important preparatory work for the calculus on which then could build Leibniz and Newton. In 1657 he published the first treatise on the theory of dice game ( De ludo aleae ), which he regarded as one of the founders of probability theory today. It was preceded by correspondence between Blaise Pascal and Pierre de Fermat, Huygens about its content, but nothing as he was alleged known. An analysis of the solutions of the 5 listed at the end of his essay problems, must be supposed that he must have known Pascal's ideas, but not the combinatorial paths of Fermat.

### Turning to the natural sciences

Increasingly, Huygens was also interested in the then fashionable areas of natural science, optics, and astronomy with telescopes. He was in contact with Antoni van Leeuwenhoek, the then leading lens grinder and designer of microscopes. Short term also examined Huygens small objects under the microscope. But he soon began to grind himself lenses for telescopes and constructed together with his brother Constantijn Huygens Junior his first telescope. Huygens developed the wave theory of light, which enabled him, lentils with less aberration ( aberration) to grind and so to build better telescopes; his discoveries caused also an increase in image sharpness in the camera obscura and magic lantern. He formulated the first named after him Huygens' principle, which is the basis of wave optics. Like many other physicists of his time Huygens also developed his own theory to an ether for light and gravitation.

Huygens discovered his home-made telescope in 1655 for the first time Saturn's moon Titan. Thus, the Saturn was the second planet after Jupiter ( besides Earth ), in which a moon could be detected (Galileo Galilei had already in 1610 the four largest moons of Jupiter discovered ). Moreover he could see by the better resolution of his telescope, that what Galileo had called the ears of Saturn, were in reality Saturn's rings.

He also found out that these rings had no connection to the planet and her mysterious disappearance every 14 years thus came about that one then saw it exactly from the side, they were too thin to be seen from Earth can.

More astronomical achievements Huygens ' were the discovery of the rotation of Mars and the calculation of the rotation period ( Martian day ) with approximately 24 hours and the resolution of the trapezoid in the center of the Orion Nebula in four individual stars. In his honor, is also called Huygens region, the brightest region of the Orion Nebula. He also discovered more fog and double star systems, and expressed the belief that Venus is shrouded by a dense cloud cover.

### Mechanics, pendulum clock and exoplanets

Besides astronomy Huygens also interested in mechanics. He formulated the laws of impact and dealt with the principle of inertia and centrifugal forces. His investigations of vibrations and oscillations he could use for the construction of pendulum clocks. Even Galileo had such a designed, but not built. Huygens could, however, apply for a patent his clock. The built in his behalf by Salomon Coster clocks showed an accuracy of ten seconds per day, a level of accuracy that could be surpassed only a hundred years after that. Later, he also designed pocket watches with coil springs and balance.

Christiaan Huygens published in 1673 in his treatise Horologium Oscillatorium a gang accurate pendulum clock with a Zykloidenpendel, in which he took advantage of the fact that the evolute of the cycloid is itself a cycloid again. The advantage of the gear accuracy is offset by the increased friction.

In his last scientific paper in 1690 Huygens formulated the idea that there could be many other suns and planets in the universe, and speculated already about extraterrestrial life.

Christiaan Huygens and Samuel Sorbiere (1615-1670) were the first two foreign scientists who were taken in June 1663 in the Royal Society. 1666 Huygens was the first director of this year founded the French Academy of Sciences. Newton described him as the most elegant mathematician of his time.

### Acoustic (Music)

Huygens discovered the relationship between sound velocity, length and pitch of a whistle. He worked intensively with the mean tone and calculated in 1691 the division of the octave into 31 equal steps to correct the error of the Pythagorean comma in the sound system of music.

### Retirement

In the 1680s worsened Huygens ' health, so that he often does not leave his house. In the last years of his life, the researchers dealt with the theory of music. 1695 Christiaan Huygens died unmarried and childless in The Hague.

## Works (selection)

- Traité de la lumière, 1690 - Treatise on reflection and refraction, wave theory of light, German, Leipzig, W. Engelmann, 1890: Treatise on Light
- Weltbeschauer, or reasonable conjecture that the planets are not inhabited and less geschmükt be, as our earth. ( Translator's of Cosmotheoros 1698 ), Zurich, 1767th Another German translation ( by v. Wurzelbau ) appeared in 1703, 1743 in Leipzig
- Lettre touchant le cycle harmonique (Rotterdam 1691, his sound system )
- De ludo aleae ratiociniis in 1657, Dutch translation Van reeckening in spelen van Geluck ( Translator Frans van Schooten ) on probability theory
- Horologium oscillatorium sive de motu pendularium, 1673 ( on the pendulum clock, also in Volume 18 of the Collected Works ), German translation, the pendulum clock, Ostwald's classic 1913
- De vis centrifuga 1673 ( German edited by Felix Hausdorff in 1903, via the centrifugal force)
- Opuscula posthuma 1703, with the first treatment of the elastic collision ( 1656) De motu corporum ex percussione ( German edited by Felix Hausdorff 1903) and the description of the building of Planetariums Descriptio automatic planetarii
- Christian Huygens ' posthumous treatises: The Movement of the body by the shock; About the centrifugal force. Edited by Felix Hausdorff. Leipzig, W. Engelmann, 1903

- Oeuvres complètes, The Hague from 1888 to 1950, 22 volumes, published by D. Bierens de Haan, John Bosscha, Diederik Johannes Korteweg, Albertus Antonie Nijland, JA Vollgraf Tome I: Correspondance 1638-1656 ( 1888).
- Tome XI: Travaux Mathématiques 1645-1651 (1908 ).
- Tome XII: Travaux Mathématiques pure 1652-1656 (1910).
- Tome XIV: Calcul des probabilites. Travaux de Mathématiques pure 1655-1666 (1920).
- Tome XV: Observations astronomiques. Système de Saturne. Travaux astronomiques 1658-1666 (1925 ).
- Tome XVI: Mécanique jusqu'à 1666 percussion.. Question de l' existence et de la perceptibilité du mouvement absolute. Force centrifuge ( 1929).
- Tome XVII: L' horloge à pendule de 1651 à 1666 Travaux divers de physique, de mécanique et de technique de 1650 à 1666 Traité des couronnes et des parhélies (1662 ou 1663 ) ( 1932).. .
- Tome XVIII:. L' horloge à pendule ou à balancier de 1666 à 1695 Anecdota (1934 ).
- Tome XIX:. Mécanique théorique et physique de 1666 à 1695 Huygens à l' Academie Royale des Sciences (1937 ).
- Tome XX: Musique et mathématique. Musique. Mathématiques de 1666 à 1695 ( 1940).
- Tome XXII: Supplément à la correspondance. Varia. Biography de Chr Huygens. Catalogue de la vente des livres de Chr Huygens ( 1950).