Kepler's Second Law: Equal Area in Equal Time

[harp AP 2010]

How did Kepler figure out his second law: Equal area in equal time?

 

[zhermes]

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

 

[Matterwave]

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.