Tycho & Kepler
Tycho makes good observations, but remains a geocentrist.
Kepler takes Tycho’s observations and figures out where Copernicus went wrong
1. Paths of the planets are ellipses with the sun at one focus
2. Orbits sweep out equal are in equal time (closer=faster)
3. Farther orbits take longer to complete. P2=a3
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But Kepler doesn’t figure out WHY his laws work