Whose law describes how planets sweep out equal areas in equal times as they orbit the Sun?
Quick Answer
Johannes Kepler formulated the second of his three planetary laws in 1609. It says a planet moves faster when it is closer to the Sun and slower when it is farther away.
The Full Story
The law is part of Johannes Kepler’s work on planetary motion, published in 1609 in Astronomia Nova. It states that the line joining a planet and the Sun sweeps out equal areas in equal times. This means a planet does not move at a constant speed around its orbit; it speeds up near perihelion and slows down near aphelion. Kepler derived the law from Tycho Brahe’s precise observations, and it helped overturn the old idea of perfectly circular, uniform planetary motion.
Key Facts
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