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The terms ''eccentric'' and ''circular'' are antonyms.  

The terms ''eccentric'' and ''circular'' are antonyms.  

A pair of line segments drawn from one [[focal point]] of an ellipse to the curve and from their to its other focal point form an angle whose bifurcating line is always perpendicular to the tangent of the curve. This feature of an ellipse has been exploited in rooms having elliptical walls or (more dramatically) elliptical ceilings. A whisper at one focal point is easily heard at the the other focal point.

A pair of line segments drawn from one [[focal point]] of an ellipse to the curve and from there to its other focal point form an angle whose bifurcating line is always perpendicular to the tangent of the curve. This feature of an ellipse has been exploited in rooms having elliptical walls or (more dramatically) elliptical ceilings. A whisper at one focal point is easily heard at the the other focal point.

Ellipses really became famous in the early 1600s, when Kepler proved that planets orbiting the sun always follow elliptical paths. This helped overturn the [[Ptelomaic theory]], vindicated [[Galileo]], and led to [[Issac Newton]]'s [[law of gravitation]].  

Ellipses really became famous in the early 1600s, when Kepler proved that planets orbiting the sun always follow elliptical paths. This helped overturn the [[Ptelomaic theory]], vindicated [[Galileo]], and led to [[Issac Newton]]'s [[law of gravitation]].  

The orbits of planets observable in Kepler's times were very circular. Comets, on the other hand, have highly eccentric orbits with only one focal point inside the sun.

The orbits of planets observable in Kepler's times were very circular. Comets, on the other hand, have highly eccentric orbits with only one focal point inside the sun.