|
Dromo's Den
|
|
[Up] [Dromo's Den] Johann Kepler Biography KEPLER, Johann (1571–1630). One of the world's greatest astronomers. He was born on Dec. 27, 1571, at Weil der Stadt in Württemberg, Germany. He was sickly in his early childhood, and his constitution remained weak throughout life. In 1584 he was sent to the cloister school in Adelberg and in 1586 to the academy in Maulbronn. On passing a brilliant maturity examination, he was admitted in 1589 to the University of Tübingen. Here he studied chiefly theology and the classics. At the same time he became acquainted with the teachings of Copernicus, which greatly influenced his later career. In 1594 he accepted the chair of astronomy and mathematics at Graz, which he held until 1600, when he was compelled to leave on account of religious difficulties. Tycho Brahe had been appointed mathematician and astronomer to Emperor Rudolph II in 1599, and in the following year Kepler became his assistant in the observatory near Prague. On Oct. 13, 1601, Tycho Brahe died, and Kepler succeeded him in both of his important posts. His compensation was to be 500 florins a year, but, owing to the desperate condition of the Imperial finances, it was never paid in full. While retaining this position, Kepler in 1612 accepted the office of mathematician to the states of Upper Austria. In 1626 he moved to Ulm, where he undertook the publication of the Rudolphine Tables. In July, 1628, he left the service of the Emperor Ferdinand II and entered that of Wallenstein, who promised to pay the amount of his former salary that still remained unpaid. Wallenstein,however, did not keep his promise. With the intention of presenting his case to the Imperial Diet, Kepler undertook a journey to Ratisbon. But on his way he was attacked by fever and shortly after reaching Ratisbon died, on Nov. 15, 1630. While in Graz, in 1597 he married Barbara von Mühleck, who died in 1611. Two years later he married Susanna Reutlinger, who survived him. Kepler early conceived that there must be some intelligible reason for the actual disposition of the solar system, and it was mainly the development of this idea that gained him a wide reputation and the friendship of Tycho Brahe and Galileo. In the capacity of Imperial mathematician he completed the Rudolphine Tables, which had been left unfinished by the death of his former patron, Tycho Brahe. But he was also compelled to discharge the duties of an astrologer, although he limited his astrological work to the vague estimation of tendencies and probabilities. His chief title to fame is his discovery of the three laws of planetary motion, viz., the laws of elliptical orbits, of equal areas, and of the relations between periods and distances. (See Astronomy;Gravitation.) The first two of these laws appeared in his greatest work, Astronomia Nova de Motibus Stellæ Martis ex Observationibus Tychonis Brahe (1609). Other important features of this work were discoveries in regard to gravitation and the explanation of the tides by lunar attraction. In 1616, in Linz, Kepler calculated the first ephemerides based on his laws. In 1619, in his treatise Harmonices Mundi, Libri V, he published his third law. In September, 1627, he finished the Rudolphine Tables, the appendix of which contained a catalogue of 1005 stars. In 1629 he called the attention of astronomers to the approaching transits of Mercury and Venus. That of Mercury, which occurred on Nov. 7, 1631, was the first transit of a planet across the sun ever observed. Kepler was also the founder of a theory of vortices and did pioneer work in several important scientific subjects. In 1604 he announced an approximation to the law of refraction, and on the invention of the telescope he gave the theory of refraction by lenses and the principle of the inverting telescope. His theory of infinitesimals prepared the way for Cavalieri's theory of indivisibles and the invention of the calculus by Newton and Leibnitz. He was also very active in introducing logarithms into Germany. His principal writings, besides those already mentioned, include: Prodromus Dissertationum Cosmographicarum seu Mysterium Cosmogra-phicum (1596); Ad Vitellionem Paralipomena quibus Astronomiæ Pars Optica Traditur (1604); De Stella Nova inPede Serpentarii (1606); Nova Stereometria Doliorum (1613); Ephemerides Novæ Motuum Cælestium (1616); Epitomes Astronomiæ Copernicanæ (1618-21); De Cometis (1619); Chilias Logarithmorum (1624); Somnium seu Opus Posthumium de Astronomia Sublunari (1634). His extant manuscripts were purchased by Empress Catharine II of Russia, donated by her to the Academy of St. Petersburg and deposited in the observatory of Pulkowa, where they remained inaccessible for a long time. A complete edition of Kepler's works, in eight volumes, was prepared by Frisch under the title Joannis Kepleri Opera Omnia (1858-71). The New International Encyclopaedia, Vol. XIII (New York: Dodd, Mead & Co., 1920) 186-197. |