Johannes Kepler

Episode #7 of the course “Unknown Scientists Who Changed The World”

Johannes Kepler changed humanity’s understanding of the universe. He was the first astronomer to explain the movement of planets and showed that the Earth and other planets orbit the sun. He explained how the tides were guided by the moon and developed the three laws of planetary motion. In addition to his astronomy exploits, he was a superb mathematician and physicist and contributed to theories in geometry and optics.

Kepler was born in the Free Imperial City of Weil der Stadt of the Holy Roman Empire in 1571. This is now is the Stuttgart region of Germany. He planned to become a minister, but while attending the University of Tübingen, Kepler became interested in studying the stars and planets. Kepler worked closely with astronomer Tycho Brahe for much of his career. Kepler was Brahe’s assistant, was funded by him for large portions of time, and used data collected by Brahe as well. Kepler also taught mathematics in Austria for a significant part of his career before passing away in 1630.

In 1601, Archduke Ferdinand made Kepler the imperial mathematician of the Holy Roman Empire, which allowed him to engage in his most important and influential work. These works also provided one of the foundations for Isaac Newton’s theory of gravity. He is most remembered for the laws of planetary motion, however. Those laws are:

1. That planets move in elliptical orbits around the Sun.

2. The “area law,” which states that the time needed to make one complete orbit is proportional to the distance from the Sun.

3. The “harmonic law,” which establishes a relationship between the distance of planets from the Sun and their orbital periods.

Kepler’s laws of planetary motion are ingrained into the foundation of modern astronomy and physics.

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