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Johan Kepler - Windows to the Universe

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The Winter 2010 issue of The Earth Scientist includes a variety of educational resources, ranging from astronomy to glaciers. Check out the other publications and classroom materials in our online store.
Picture of Johan Kepler
The Bettman Archive. From engraving by MacKenzie

Johan Kepler

Johan Kepler was a German astronomer who lived between 1571-1630. He introduced three important laws of planetary motion and helped the Copernican model of the solar system gain general acceptance.

An original problem with Copernicus' heliocentric theory was its inability to explain the periodic retrograde (apparent backward motion) of planet Mars. Kepler inherited Tycho Brahe's observational data on Mars following Brahe's death and showed that Mars' orbit was really elliptical, and thus may occasionally appear to retrograde. In fact, all planetary orbits are elliptical. This new revelation contradicted the age old belief that heavenly bodies traced out perfect circles.

During his life, Kepler also cast horoscopes and wrote science fiction novels.


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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF