www.whyville.net Feb 17, 2000 Weekly Issue

Johannes Kepler

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     Have you noticed that the streets of Myville Old Town are all named after famous scientists and artists from the Renaissance? In case these folks aren´t so famous to you, you might want to follow along this series of articles, and get to know the person on whose street you´re living. This week's article is about Johannes Kepler, who figured out that planets travel not in circles, but ellipses.

by Lois Lee
Times Staff

Johannes Kepler
1571 - 1630

In 1571, Johannes Kepler was born in the village of Leonberg in Germany to a soldier and the daughter of an innkeeper. When Johannes was only five, his father left to fight in a war and never came back. Kepler and his mother went to live with his grandfather, and he grew up in his grandfather's inn.

Kepler??s early education was in a local school and then at a nearby seminary, from which, intending to be ordained, he went on to enroll at the University of T??bingen. Throughout his life, Kepler was a religious man. His writings contain many references to God, and he saw his work as part of his Christian duty to understand the works of God.

At the University, Kepler first learned about geocentric astronomy, the Ptolemaic system, in which all seven planets - Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn - moved round the Earth. At the end of his first year, Kepler got A??s in everything except mathematics. Still, Kepler must have shown promise to his teacher, who went on to teach him heliocentric astronomy, the Copernicus system, in which the Earth and the planets move around the Sun. At the time, this model was banned by the church and could not be taught in classrooms. Therefore, only a few very special students were taught the model.

In 1594, Kepler became a professor of mathematics at the Protestant seminary in Graz (in Austria). He was also made the district??s mathematician and calendar maker. At this time, every town had an astronomer and a mathemetician because they were needed for telling time. (Until the invention of radio, many cities, even in the United States, relied on local astronomers for setting the clocks!)

Johannes Kepler (University of St. Andrews, Fife, Scotland)
In 1600, Kepler moved to Prague to serve as Tycho Brahe's assistant until the latter??s death in 1601. After Tycho??s death, Kepler was made the Imperial Mathematician. There, in Prague, he discovered that the planets moved in ellipitical paths around the Sun. Prior to this, people thought that heavenly bodies moved in perfect circles. Kepler was the first to show that this wasn't true. Instead, planets moved in ellipses, which are flattened circles.

Things began to go very badly in late 1611. First, his seven year old son died. Then Kepler??s wife died. Then the Emperor Rudolf, whose health was not good, was forced to hand over the crown to his brother Matthias, who did not believe in tolerance toward Protestants. As a result, Kepler had to leave Prague.

From Prague, he moved to Linz, Austria to be their district mathematician. There, he married Susanna Reuttinger. The couple had six children. It was in Linz that Kepler published "De Vero Anno quo Aeternus Dei Filius Humanam Naturam in Utero Benedictae Virginis Mariae Assumpsit" (Concerning the True Year in which the Son of God assumed a Human Nature in the Uterus of the Blessed Virgin Mary). In this work, Kepler demonstrated that the Christian calendar was in error by five years, and that Jesus had been born in 4 BC, a conclusion that is now accepted.

Between 1617 and 1621 Kepler published Epitome Astronomiae Copernicanae ("Epitome of Copernican Astronomy"), which became the most famous introduction to heliocentric astronomy.

It was also while Kepler was in Linz that his mother was charged with witchcraft. Katharina Kepler was eventually released, at least partly because of technical objections arising from the authorities' failure to follow correct procedures in the use of torture.

In 1630, Kepler died in Regensburg, after a short illness. 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.

Johannes Kepler is remembered for discovering the laws of planetary motion, which he published in 1609 and 1619 and is credited as the father of modern astronomy. He also did important work in the study of light, discovered two new regular polyhedra, gave the first mathematical treatment of close packing of equal spheres (which led to an explanation of the shape of the cells of a honeycomb), gave the first proof of how logarithms worked, and contributed to the development of calculus. He also calculated the most exact astronomical tables known, whose continued accuracy convinced the world that the Earth moves around the Sun.

Click here or here to learn more about Johannes Kepler.


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