Johannes+Kepler+(1571-1630)



Johannes Kepler played a vital role in the 17th century astronomical revolution. He was a German mathematician, astronomer and astrologer and is well known for his eponymous laws of planetary motion. These were codified by later astronomers, based on his works Astronomia Nova, Harmonices Mundi, and Epitome of Copernican Astronomy. Kepler's laws provided foundations for Isaac Newton's theory of Universal Gravitation. He also did elementary work in the field of optics, especially in inventing an improved version of the refracting telescope, the Keplerian Telescope. Kepler even helped to legitimize the telescopic discoveries of Galileo Galilei.

Kepler's Early Years
Johannes Kepler was born on December 7, 1571, in Wurttenberg, Germany. Kepler grew up during tultoumus times in Germany.  His paternal grandfather, Sebald Kepler, was a respected craftsman who served as mayor of the city; his maternal grandfather, Melchior Guldenmann, was an innkeeper and mayor of the nearby village of Eltingen. His father, Heinrich Kepler, was "an immoral, rough and quarrelsome soldier," according to Kepler, and he described his mother in similar unflattering terms. He was a sickly child and his parents were poor. From 1574 to 1576 Johannes lived with his grandparents; in 1576 his parents moved to nearby Leonberg, where Johannes entered the Latin school. In 1584 he entered the Protestant seminary at Adelberg, and in 1589 he began his university education at the Protestant university of Tübingen. Here he studied theology for the [|Lutheran ministry] and read widely. He passed the M.A. examination in 1591 and continued his studies as a graduate student. Because of the Peace of Ausburg, Wurttenberg was allowed to keep a lutheran based faith system, but Kepler chose to refuse both the Lutheran faith, and its Catholic counterpart.

Kepler's teacher in the mathematical subjects was Michael Maestlin (1550-1635). Maestlin was one of the earliest astronomers to subscribe to Copernicus's heliocentric theory, although in his university lectures he taught only the Ptolemaic system. Only in what we might call graduate seminars did he acquaint his students, among whom was Kepler, with the technical details of the Copernican system. Kepler stated later that at this time he became a Copernican for "physical or, if you prefer, metaphysical reasons."

In 1594 Kepler accepted an appointment as professor of mathematics at the Protestant seminary in Graz (in the Austrian province of Styria). He was also appointed district mathematician and calendar maker. Kepler remained in Graz until 1600, when all Protestants were forced to convert to Catholicism or leave the province, as part of Counter Reformation measures. For six years, Kepler taught arithmetic, geometry (when there were interested students), Virgil, and rhetoric. In his spare time he pursued his private studies in astronomy and astrology. In 1597 Kepler married Barbara Müller. In that same year he published his first important work, //The Cosmographic Mystery//, in which he argued that the distances of the planets from the Sun in the Copernican system were determined by the five regular solids, if one supposed that a planet's orbit was circumscribed about one solid and inscribed in another.

In the early 1600s, Johannes Kepler proposed three laws of planetary motion. Kepler was able to summarize the carefully collected data of his mentor - Tycho Brahe - with three statements which described the motion of planets in a sun-centered solar system. Kepler's efforts to explain the underlying reasons for such motions are no longer accepted; nonetheless, the actual laws themselves are still considered an accurate description of the motion of any planet and any satellite.

Kepler published his first two laws in 1609 in his book //Astronomia Nova//. The last law he published in 1619 in his //Harmonices Mundi//

While Kepler was working on his //Harmony of the World//, his mother was charged with witchcraft.

Throughout his life, Kepler was a profoundly religious man. All his writings contain numerous references to God, and he saw his work as a fulfilment of his Christian duty to understand the works of God.

Kepler died in Regensburg, after a short illness. He was staying in the city on his way to collect some money owing to him in connection with the //Rudolphine Tables//. He was buried in the local church, but this was destroyed in the course of the Thirty Years' War and nothing remains of the tomb.

Illustration of Kepler's geometrical model of the solar system  **A List of Kepler's Firsts** In his book //Astronomia Pars Optica//, for which he earned the title of founder of modern optics he was the: In his book //Dioptrice// (a term coined by Kepler and still used today) he was the: In addition:
 * First to correctly explain planetary motion, thereby, becoming founder of celestial mechanics and the first "natural laws" in the modern sense; being universal, verifiable, precise.
 * First to investigate the formation of pictures with a pin hole camera;
 * First to explain the process of vision by refraction within the eye;
 * First to formulate eyeglass designing for nearsightedness and farsightedness;
 * First to explain the use of both eyes for depth perception.
 * First to describe: real, virtual, upright and inverted images and magnification;
 * First to explain the principles of **how** a telescope works;
 * First to discover and describe the properties of total internal reflection.
 * His book //Stereometrica Doliorum// formed the basis of integral calculus.
 * First to explain that the tides are caused by the Moon (Galileo reproved him for this).
 * Tried to use stellar parallax caused by the Earth's orbit to measure the distance to the stars; the same principle as depth perception. Today this branch of research is called astrometry.
 * First to suggest that the Sun rotates about its axis in //Astronomia Nova//
 * First to derive the birth year of Christ, that is now universally accepted.
 * First to derive logarithms purely based on mathematics, independent of Napier's tables published in 1614.
 * He coined the word "satellite" in his pamphlet //Narratio de Observatis a se quatuor Iovis sattelitibus erronibus//