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Whose work first explained why planetary orbits are ellipses rather than perfect circles?
Quick Answer
Johannes Kepler explained that planets move in elliptical orbits with the Sun at one focus. He published this in 1609 and 1619.
The Full Story
Johannes Kepler was the first to describe planetary orbits accurately as ellipses, not circles. He published the first two laws of planetary motion in 1609 and the third in 1619. This was a major breakthrough because it matched the careful observations of Tycho Brahe far better than earlier models. The elliptical-orbit idea became one of the foundations of modern astronomy and later helped Isaac Newton explain gravity mathematically.
Key Facts
1.Kepler published his main planetary laws in 1609 and 1619
2.The Sun lies at one focus of each elliptical orbit
3.The idea replaced the older perfect-circle model
YouTube Angle
Suggested video title for this topic:
"Planets do not orbit in perfect circles—and Kepler proved it"
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