Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsEllipses and Hyperbolas with the Same Focal Pointshttp://demonstrations.wolfram.com/EllipsesAndHyperbolasWithTheSameFocalPoints/]]>http://demonstrations.wolfram.com/EllipsesAndHyperbolasWithTheSameFocalPoints/Comet Moving about the Sunhttp://demonstrations.wolfram.com/CometMovingAboutTheSun/]]>http://demonstrations.wolfram.com/CometMovingAboutTheSun/