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When did Johannes Kepler publish his first two laws of planetary motion?
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Johannes Kepler
Johannes Kepler, engraving by N. Dietz.
Johannes Kepler published his first two laws of planetary motion in his 1609 work titled Astronomia Nova (New Astronomy).1
These foundational principles describe the movement of planets within the solar system:
- First Law: The paths of planets are ellipses with the Sun located at one focus.1
- Second Law: A planet moves at a variable speed such that a line connecting it to the Sun sweeps out equal areas in equal times.1
While the second law was actually discovered by Kepler before the first, both were formally presented to the scientific community in the 1609 publication.1