Johannes Kepler is one name that will always be remembered in the field of astronomy. He was the chief founder of contemporary astronomy and also a great mathematician and astrologer. The German astronomer was the first person to explain planetary motion. His three laws on planetary motion were codified by later astronomers based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astronomy. They also served as the basis for Isaac Newton’s theory of universal gravitation. Moreover, his publication Stereometrica Doliorum formed the foundation of integral calculus, and he also made imperative advances in geometry.
Johannes Kepler was born on December 27, 1571, in Weil der Stadt in Swabia, in southwest Germany. He had six siblings, three of which died already at an early age. His father, Heinrich Kepler, was a soldier and mother, Katharina Guldenmann was a healer and herbalist. His Grandfather Sebald Kepler, had been Lord Mayor of the town but by the time Kepler was born, the family had become very poor. As a child, Kepler led a very unfortunate life, recovering from smallpox at the age of four with crippled hands and eyesight permanently weakened. He also lost his father when he was just five years old.
In 1576, the family moved to Leonberg where Johannes began his schooling first in the German School and then is the Latin School. In 1583, he passed the exam in Stuttgart and the following year he went to seminar Adelberg, a convent school. After two years he was accepted at a higher seminar in Maulbronn, also a convent school. Upon achieving a scholarship he joined the University of Tuebingen in 1589 where he studied philosophy under Vitus Müller and theology under Jacob Heerbrand.
Johannes excelled in mathematics and proved himself as a skilled astrologer, casting horoscopes for fellow students. Under the guidance of Michael Maestlin, Tübingen’s professor of mathematics, he gained knowledge about both the Ptolemaic system and the Copernican system of planetary motion. He became a Copernican at that time. In 1594 shortly before finishing his studies, he went to Graz as the teacher of mathematics and astronomy and remained there until 1600.
In 1600, he met the great mathematician and court astronomer, Tycho Brahe in Prague. Tycho Brahe was working for Emperor Rudolf II and had the most accurate empiric data and precise measuring instruments of his time. Kepler became his assistant and saw the opportunity to test his astronomical theories empirically. The team work of the two men was disturbed because of differing point of views; Brahe was more convinced of the geocentric world view and Kepler more of the heliocentric one. Both of them worked together on planets and Brahe also gave Kepler the task to define the motion of planet Mars. During 1601, emperor Rudolph II appointed him to succeed his patron as imperial mathematician. The first works completed by him at Prague were, nevertheless, homage to the astrological proclivities of the emperor. In De fundamentis astrologiae certioribus (1602), he declared his purpose of preserving and purifying the grain of truth which he believed the science to contain. In 1604 Astronomia pars Optica appeared, in which he treated both atmospheric refraction and lenses. In 1606 he published De Stella Nova which was about the new star that had appeared in 1604. Five years later, in 1609 he published Astronomia Nova, which contained his first two laws on planetary motion. In 1612, he moved to Linz where he served as a teacher at the district school and provided astrological and astronomical services. In 1619, he published Harmonice Mundi where we find his third law besides his derivation of the heliocentric distances of the planets and their periods from considerations of musical harmony.
Kepler married twice in his life. His first marriage was to Barbara Müller on April 27, 1597. Later after the death of his wife, he remarried on October 30, 1613, to Susanna Reuttinger. He died in Regensburg, Germany, on November 15, 1630. Like many geniuses, Kepler had never known fame or fortune, but his determination and persistence led to many discoveries that enable us to understand the universe today.
