Johannes Kepler (Kepler Johann)

(1571-1630)
Born December 27, 1571 in Weil der Stade latest newcomer in the principality of Wurttemberg. After graduating from the church school in Alderberge, in 1586 entered the seminary at higher Maulbornskom Monastery. In 1589 was admitted to the University of Tц?bingen, where for three years he studied theology, mathematics and philosophy. Astronomy at the University read M. Mestlin that Kepler gave private lessons and introduced him to the theory of Copernicus. In 1591, Kepler defended his master's thesis, and in 1593 graduated from university and was recommended for the post of professor of mathematics at the Gymnasium Graz (Upper Styria). Here in 1594 he lectured on astronomy. In 1596 came the publication of his first work The Mystery of the Universe (Prodromus dissertationum mathematicarum continens mysterium cosmographicum, 1596), in which Kepler attempted to find a balance between the elements of planetary orbits. This work attracted the attention of Tycho Brahe, who invited Kepler as an assistant for the analysis of observations of the planets. The cooperation of astronomers took about two years until the death of Tycho Brahe 24 October 1601. Soon the Emperor Rudolf II appointed Kepler for the post of court mathematics, which he held until the end of life.
During the life of Tycho Brahe Kepler attempted mathematical description of the laws of motion of the planet Mars in the then existing theories (Ptolemy, Tycho Brahe, Copernicus). As a result of long reflection Kepler came to the empirical laws of planetary motion (Kepler's laws). According to the first two, the planets orbit around the Sun in elliptical orbits, the focus of which is shining, the radius vector of each planet sweeps out equal areas in equal intervals of time. These results were published in the book New Astronomy (Astronomia Nova, 1609), which has become on a par with De Revolutionibus Copernicus and Newton's Principia.

The idea of the heliocentric world system was proposed Aristarchus, believe that all the planets move at constant speed around the sun. However, his theory contradicts the observations that led Ptolemy to develop a system of complex geometry eccentric circles and epicycles. After 14 centuries, Copernicus tried to include some geometrical ideas of Ptolemy (eccentric circle) in the system of Aristarchus, considering that the motion of the planets should be uniform and circular. And only Kepler realized that the orbits are elliptical in shape, and the planets move through it with an angular velocity is inversely proportional to the square of the distance from the Sun. These laws are within the observational accuracy is fully consistent with the data of Tycho Brahe, and later found minor discrepancies were explained in the framework of Newtonian mechanics.

Publication of the New Astronomy and the almost simultaneous invention of the telescope marked a new era. These events were a turning point in the life and scientific career Kepler. After the death of Rudolf II scholar position at the court in Prague has become increasingly uncertain. So he turned to the new emperor for permission to temporarily occupy the post of Mathematics province of Upper Austria in Linz, where he spent the next 15 years. Kepler's main achievement in this period was the opening of the third law of planetary motion: the squares of the periods of the planets are correlated as the cubes of their semi-major axes of elliptic orbits. This law was formulated in the book The Harmony of the world (De Harmonice Mundi, 1619). The next 9 years, Kepler worked on drafting tables of the planets, based on the new laws of motion.

The events of the Thirty Years War and religious persecution forced Kepler in 1626 to run in Ulm. With no means of livelihood, he in 1628 entered the service of an astrologer to the imperial commander Wallenstein. The last major work of Kepler became Tycho's meant to be planetary tables, published in Ulm in 1629 under the name of Rudolf table (Tabulae Rudolphianae). In autumn 1630 Kepler went to Regensburg, which met at the Diet, in the hope of obtaining an order of the issuing of a permanent salary.

Kepler died in Regensburg, November 15, 1630.