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+A pre-heliocentric model of planetary motion.
+
This draws the path traced out by a point on the edge of a
circle. That circle rotates around a point on the rim of another
-circle, and so on, several times. These were the basis for the
-pre-heliocentric model of planetary motion.
+circle, and so on, several times.
http://en.wikipedia.org/wiki/Deferent_and_epicycle