Kepler's revolutionary laws of planetary motion
Kepler's theory of the solar system.
Encyclopædia Britannica, Inc.
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Encyclopædia Britannica, Inc.Learn about wolves that were spotted in Denmark in 2017, the first time the species had been seen in the country since 1813.
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Encyclopædia Britannica,-Inc.The Earth may be less spherical and more football-shaped than you thought.
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Encyclopædia Britannica, Inc.In many parts of the world, weather cycles through the four seasons like clockwork: spring, summer, autumn, and winter.
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Encyclopædia Britannica, Inc.History of the big-bang model.
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Encyclopædia Britannica, Inc.Ptolemy's theory of the solar system.
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Encyclopædia Britannica, Inc.How big is our world?
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Encyclopædia Britannica, Inc.Aristotle's theory of the solar system.
Transcript
NARRATOR: In the early 17th century, Johannes Kepler challenged two features of the Copernican system. In the Copernican system the planets moved uniformly in circles, much like the Ptolemaic model. However, through observations of Mars, Kepler came to several conclusions. Published in 1609, Kepler's first law states that planets move in elliptical orbits, with the Sun at one focus. Kepler's second law states that a planet's orbital speed is not uniform. A planet moves slower when it is farther from the Sun and faster closest to the Sun. The relationship between time and area, however, remains constant. Kepler's laws destroyed the last vestiges of Aristotle's model of the universe.