Concept
Version 9
Created by Boundless
Kepler's First Law

Ellipses and Kepler's First Law
(a) An ellipse is a closed curve such that the sum of the distances from a point on the curve to the two foci (
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"OpenStax College, College Physics. January 28, 2013."
http://cnx.org/content/m42144/latest/?collection=col11406/1.7
OpenStax CNX
CC BY 3.0.