Astronomy: Johannes Kepler

Johannes Kepler was born on December 27, 1571 in Weil der Stadt in Swabia. Kepler was always a very religious man and he believed God created the universe in a mathematical arrangement. He used mathematics to try and understand God’s plan. He attended the protestant University of Tuebingen where he was exposed to astronomy. His Astronomy professor was Michael Maestlin. Although Maestlin taught the Ptolemaic system, he secretly believed in Copernicus's heliocentric system. Kepler also believed in the Copernican view and defended it publicly. Therefore, he was not offered a teaching position at his alma mater. The church did not want him encouraging students to believe in the Copernican system. In 1594 he was offered a teaching position in Graz, Styria. Unfortunately, the school was closed in 1598 by the Archduke Ferdinand of Hapsburg. The Archduke was Catholic and supported the counterreformation. Consequently, the next year he was given the choice of converting to Catholicism or being kicked out of Austria. He tried to go back to Tuebingen, but they did not want him because he believed in the Copernican system. Luckily, Tycho Brahe invited him to come and work with him in Prague. Kepler departed for his new job on January 1, 1600. Brahe believed in the Ptolemaic system of the universe and kept his data from his assistants. He did not want his observations used to try and support Copernican views. In 1601, Brahe died of a bladder infection and Kepler succeeded Brahe as Imperial Mathematician. Kepler held this position until 1612. Kepler fought to get access to Brahe’s data, and finally got access to the data on Mars. Kepler used the Mars data to try and predict where the plant would be in a circular orbit. After countless calculations he could never determine the correct spot. However, when he used the data to determine the planets location with an elliptical orbit, he was able to predict the correct location. From his work he developed three laws of planetary motion:

1. The path of each planet about the sun is an ellipse with the Sun at one focus.

2. Each planet moves so that an imaginary line drawn from the Sun to the planet

sweeps out equal are in equal periods of time.

3. The ratio of the squares of the periods (the time needed for one revolution

about the Sun) of any two planets revolving about the Sun is equal to the ratio of the cubes of their mean distances from the Sun.

In 1610, Kepler read about Galileo findings with the telescope. He immediately wrote a letter of support entitled Dissertatio cum Nuncio Sidereo or Conversation with the Sidereal Messenger. He eventually found a telescope to use and published his observations of Jupiter’s satellites. Kepler’s support was very helpful since people were very skeptical of Galileo’s findings. The telescope Galileo designed had a convex lense with a concave lens for the eyepiece. In 1611, Kepler published a new design of telescope with two convex lenses. It is such a good design we refer to it just as the astronomical telescope instead of the Keplerian telescope. Kepler’s mother was accused of being a witch during the witch hunts from 1615-1616. In t1620 Kepler defended her at her trial and she was finally set free. In addition to his astronomy achievements, Kepler also had a family life; he married Barbara Müller on April 27, 1597 and they had three children together: Susanna, Friedrich, and Ludwig. Kepler was an incredible man who greatly contributed to our understanding of the universe