Kepler's Second Law: Equal Area in Equal Time

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Kepler's Second Law, stating that a line segment joining a planet to the Sun sweeps out equal areas during equal intervals of time, was derived from his careful observations of planetary motion. He formulated this law based on empirical evidence rather than an understanding of angular momentum, which was developed later by Newton. The law reflects the conservation of angular momentum as planets travel along elliptical orbits. Newton later provided a theoretical framework that explained Kepler's laws through his own laws of motion and universal gravitation. Kepler's insights were foundational in the field of astronomy, demonstrating the relationship between orbital dynamics and observational data.
harp AP 2010
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How did Kepler figure out his second law: Equal area in equal time?
 
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harp AP 2010 said:
How did Kepler figure out his second law: Equal area in equal time?

Wikipedia has the derivation. It comes from conservation of angular momentum while following the elliptical path.

http://en.wikipedia.org/wiki/Kepler's_laws
 
zhermes said:
Wikipedia has the derivation. It comes from conservation of angular momentum while following the elliptical path.

http://en.wikipedia.org/wiki/Kepler's_laws

This may be the "modern" overview (modern = after Newton), but since Kepler was around before Newton, I highly doubt he knew anything about how to manipulate orbital angular momentum.

I think Kepler formulated his laws based purely on observational evidence. He noticed from the observations that these 3 "laws" seem to hold. Later Newton proved that these laws are directly derivable from his mechanics and law of gravitation.
 

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