Philosophy 167: Class 4 - Part 11 - Keplerian Orbital Theory: Defining the Keplerian Ellipse.
Smith, George E. (George Edwin), 1938-
Synopsis: Reviews Kepler's orbital theory by way of the ellipse.
Opening line: "So, how do you define a Keplerian ellipse? Well, his way of defining it is, the first thing you do is locate aphelion and. You do that by where it's fastest in the sky versus where it's slowest in the sky."