by Ramona Taylor

Created on: February 14, 2011   Last Updated: February 15, 2011

For countless ages, man has marveled at the stars.  From Aristotle to Einstein, humans have attempted to bring order and understanding to the very nature of the planets, moons and stars; however, it wasn’t until Johannes Kepler, a German born scientist presented his theories on planetary motion that man’s study of the heavens seemed clear.

Johannes Kepler

Kepler was born in Swabia, Gernany in 1571.  As a young child, he worked in his grandfather’s inn, but showed a competence in mathematics.  Kepler’s formal education was received at University of Tübingen, where he studied astronomy and mathematics. 

During his lifetime, Kepler challenged the old views on planetary movement, and remastered refractive telescopes for more accurate study of the stars.  By the time of his death, in 1630, Kepler had laid the foundation for astronomy and influenced the works of other notable scientists, including Sir Isaac Newton.

Early Influences and Theories

While Kepler studied at Tübingen, the general theories of planetary motion were based on the Ptolemaic system. Under this system, it was believed that the seven known planets, Mercury, Venus, Mars, Jupiter, Saturn, Sun and Moon, circled the Earth.  The terra-centric view was based on Aristole’s early interpretation of the Universe. 

However, prior to Kepler’s birth, Italian astronomer Nicolas Copernicus has proposed a theory that the Sun and not the Earth was the center of the solar system.  This heliocentric theory seemed to offer a new explanation for planetary motion, but had not been widely regarded. 

Another influential mind of the day was Tycho Brahe, a Danish nobleman and astronomer.  While studying the night skies, Brahe made numerous observations that could not be explained by the Ptolemaic theories of the planets.  Brahe’s study of the 1572 Supernova, accurate observations of celestial bodies, and a more acceptable theory of geo-heliocentric universe brought him recognition; however, Brahe died in 1601 before the true importance of his observations could be realized. It was also Brahe for whom Kepler had served as an assistant at the University of Prague.

Kepler’s Laws of Planetary Motion

During Kepler’s time, observations about planetary movements were in conflict with the theories of the day.  In particular, the standing Ptolemaic theory did not explain the usual behavior of Mars.  It

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