Kepler
Name:Johannes Kepler
Achievements: Kepler’s Laws of Motion, which influenced Newton and all modern science. The founder of modern astronomy.
Born: December 27, 1571; Weil der Stadt, near Stuttgart, Germany
Died: November 15, 1630; en route to Regensburg, Bavaria (Aged 58)
Field & Discipline: Science; Astronomy; Astronomer
Education: Leonberg Schreibschule, 1576; Leonberg Latin School, 1577-78;
Adelberg Theological Seminary, 1584-86; Maulbronn School, 1586-88;
University of Tubingen, 1588-91
Major Work:
“Astronomia Nova” (1609)
Life & Times:
At the Protestant University of Tübingen Kepler studied theology,philosophy, and mathematics (under the astronomer [taught by] Maestlin*, who introduced him to [follower of] Copernicus*’ work. Kepler intended to become a Lutheran minister, and after graduating in 1591, started a three-year program of theological training.Kepler's theological studies were interrupted in 1594, when he was nominated by his tutors for a teaching post in mathematics and astronomy at the Academy in Graz (now in Austria) where he stayed for four years, and began to concentrate on both astrology (he remained a believer in astrology until his death) and astronomy, working with Maestlin on optics and planetary orbits.
His first astronomical work, 'Mysterium Cosmographicum' (1596), attmepted to fit planetary orbits to Copernican theory. Demonstrating that the five ‘Platonic Solids’: i.e. the only regular polyhedrons (the tetrahedron, cube, octahedron, dodecahedron, and icosahedron) could be fitted sequentially inside a series of spheres to form a "nest" which reproduced ( with the exception of Mercury) the scale of distances of the planets from the Sun, Kepler showed how the planetary orbits fitted between these spheres.
In 1597 he sent copies to several leading astronomers, including [corresponded with] Galileo* and [assistant to] Brahe*.In 1588 a purge of Protestants forced him to leave Graz for a month, but in 1599 (the year the Italian philosopher and scientist [work related to] Bruno* was burned at the stake in Rome for his belief in the same Copernican system) Kepler was again expelled, and in January 1600 arrived in Prague where Brahe, much impressed with the originality and boldness displayed in his book, invited him to work as his assistant at Benatky Castle, near Prague.Kepler served as Brahe's assistant for 22 months until Brahe’s death in 1601, during which time his genius became apparent to visiting astronomers, including [visited by] Snell*. Within a few days of Brahe's death, Kepler was appointed Imperial Mathematician, the most prestige appointment in mathematics in Europe, for the rest of his life.
Kepler stayed in Prague from 1600-12. During the years following Brahe's death, Kepler, assisted by the Swiss mathematician and inventor [assistant was] Burgi*, spent much time attempting to fit the apparent positions of the planet Mars, as observed by Tycho, to the various cosmologies (of [work related to] Ptolemy*, Brahe, and Copernicus). During this work he identified the elliptical orbit of Mars, and developed the planetary laws named after him.
Meanwhile, in 1604, his attention was diverted from the planets by his observation of the appearance of a new star ("Kepler's nova") and the same year he published his: 'The Optical Part of Astronomy', in which he explained the principles of atmospheric refraction, spectacle lenses and his improved [improved the] camera obscura* (first used by the 11th-century mathematician and physicist [work related to] Al Hazen* and the forerunner of the photographic camera), and gave the modern explanation of the workings of the eye.
In 1609 he produced: 'A New Astronomy, or A Physics of the Stars', which included an explanation of two of his three planetary laws. The First Law states that planets travel in elliptical rather than circular orbits, and that the Sun is at one of the two foci of the ellipses. The Second Law states that the line joining the Sun and a planet crosses equal areas of space in equal periods of time, so that the planets move more quickly when they are nearer the Sun.
This established the Sun as the source of the attractive force (Kepler called it “Holy Spirit force”) governing the orbits of the planets. Kepler also showed that the orbital velocity of a planet is inversely proportional to the square of its distance from the Sun. Kepler also suggested that the Sun itself rotates (confirmed by observing the sunspots discovered by Galileo).In 1612, on Emperor Rudolph's death, he accepted the job of District Mathematician at Linz, Austria, where he was to spent the next 15 years.
His next work was 'The Harmony of the World' (1619), an almost mystical text (giving an all-embracing synthesis of geometry, music, astrology, and astronomy) in the fifth book of which is buried the last of his planetary laws. Kepler's Third Law describes in precise mathematical language the link between the distances of the planets from the Sun and their velocities:- that the square of the time of a planet's periodic revolution is proportional to the cube of its mean distance from the Sun.
In 1619, he gave a copy of 'The Harmony' to the visiting English poet [was visited by] Donne* to deliver to King James I of England, to whom the work was dedicated.
Kepler's second major work to be published at Linz, the 'Epitome of Copernican Astronomy' (1618-21), intended by the author as an introduction to Copernican astronomy, is in fact a summary of Kepler's entire work in theoretical astronomy, and describes a Solar System essentially the same as the one we know today.This was Kepler's largest work - published in seven books over four years - and proved to be the most important systematic exposition of astronomy since Ptolemy's 'Almagest', with more impact than any other astronomical text of the mid-17th century.Kepler then worked for nine years to complete his crowning achievement in practical astronomy:- the Rudolphine Tables of planetary positions, based on Brahe's observations and Kepler's new laws.
Kepler was again forced to move as a result of political upheaval caused by the Thirty Years' War, and in 1626 he settled in Ulm, Germany, where he remained for the next two years, finally publishing the Rudolphine Tables in 1627.These tables enabled the calculation of the positions of the planets at any time in the past, present or future, and included a map of the world, a catalog of stars, and the latest aid to computation: logarithms (originally developed by his assistant at Prague, Burgi, independently of [spread logarithms of]John Napier* in Scotland).
Extra Connections: His new astronomy provided the basis for [laid basis of] Newton*’s work.
His work influenced [influenced] Leibniz* and (with the camera obscura) [influenced] Cheselden*.
His work related to that of [work related to] Toscanelli*, [work related to] Al Battani, [work related to] *Hobbes*, [work related to] Andreae* and the [work related to] Cassini* family
His biography was written by [biography by] Brewster*
Influenced by [influenced by] della Mirandola* and [influenced by] Witelo*
He studied the work of [studied] ben Gershom*
His astronomy was followed up by [work followed up by] Borelli*
Assessment: His three Laws of Motion are considered to be the basis of our understanding of the Solar System.
Oneliner: Johannes Kepler, who introduced orbital dynamics
Language: German
Father: Heinrich Kepler
Mother: Katharina Guldenmann
Siblings: Five brothers and one sister
Spouse: Barbara (d. 1611), married 1596; Susanna Reuttinger, married 1613
Children: Five children by first wife, three surviving infancy: Susanna (b.
1602, married Kepler's assistant Jakob Bartsch in 1630); Friedrich
(1604-1611), and Ludwig (1607-1663). Six children by second wife, threedying in infancy.
Bibliography:
- Dictionary of Scientific Biography.
- Encyclopedia Britannica.
- Biographical Dictionary of Astronomers.
- Caspar, Max, Kepler, tr. C. Doris Hellman (first ed. 1959), reprinted with introduction and references by Owen Gingerich, New York: Dover, 1993.