Changes

Ellipses became important in [[astronomy]] in the early 1600s, when [[Kepler]] proved that planets revolving the sun always follow elliptical [[orbit]]s, with the sun at one of the foci. This helped overturn the [[Ptolemaic theory]], and led to [[Issac Newton]]'s [[law of gravitation]].  

Ellipses became important in [[astronomy]] in the early 1600s, when [[Kepler]] proved that planets revolving the sun always follow elliptical [[orbit]]s, with the sun at one of the foci. This helped overturn the [[Ptolemaic theory]], and led to [[Issac Newton]]'s [[law of gravitation]].  

[[category:geometry]]

[[category:Plane Geometry]]