FREE FACT: An oblate spheroid is a special case of an ellipsoid where two of the semi-principal axes are the same size. A special thanks to our Subbable.com supporters: Robby Weisenfeld Gustav Delius Ike https://www.youtube.com/TheNilFacts And to Audible.com - FREE audiobook at http://www.audible.com/minutephysics MinutePhysics is on Google+ - http://bit.ly/qzEwc6 And facebook - http://facebook.com/minutephysics And twitter - @minutephysics Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Music by Nathaniel Schroeder http://www.soundcloud.com/drschroeder Thanks to Nima Doroud for contributions.