Johannes Kepler and Adoption

Portrait of Kepler 1610



German Mathematician, Astronomer, and Astrologer

Kepler was born in Weil der Stadt, Swabia. His father was a merchant who went as a mercenary soldier to fight in the Spanish Netherlands when he was two. His mother was the daughter of an inn-keeper and former mayor, with such a bad reputation that she was very nearly burned at the stake as a witch (her aunt had actually been burned as a witch; Kepler was part of her defense team in 1620. His mother went to follow his father, leaving young Johannes to be raised by her parents, although she returned in a year or two, while his father died in the war.

He was a sickly child (he had smallpox) and badly near-sighted, but his mathematical gifts were obvious from an early age. He intended to be ordained as a Lutheran pastor, and trained at the seminary in Tübingen, but became sidetracked by mathematics and astronomy (he also had disagreements with some Lutheran doctrines, which led to his excommunication in 1612).

From Tübingen he moved to Graz, Austria, where he taught mathematics and astronomy and also became involved in astrology. He became interested in the movements of the planets and their relative distances from the sun - the Ptolemaic system, in which the planets and sun were believed to revolve around the earth was being overthrown by today's Copernican system, in which the planets are known to revolve around the sun - and this led eventually to the formulation of his famous three laws of planetary motion.

In 1610 he was the first person to use the term "satellite" to describe the moon of a planet. He was invited to Prague by Tycho Brahe, whom he succeeded as imperial mathematician in 1601. He recalculated the date of the birth of Jesus Christ to 4 BCE, which is still the accepted date. In 1612 he moved again, to Linz, but in 1626 he had to move to Ulm, to escape anti-Protestant persecution under the new emperor. There followed a short period back in Prague, and he died in Regensburg.

In addition to being one of the world's greatest astronomers, he was also an important figure in optics, geometry, and mathematics.

He married twice and had 11 children, six of whom died in childhood.


"Johannes Kepler (1571-1630." Available at: [Last visited: 10 September 2002] Van Helden, Albert. "Johannes Kepler (1571-1630)." [Includes portrait]. Available at: Field, J.V. "Kepler, Johannes." [Includes portraits]. Available at: