To help deal with the problem of retrograde motion, a new layer of complexity was introduced. The planets would not move simply in a circle but they would rotate on a circle, which in turn, rotated around the sun. The smaller circle is the epicycle and the larger circle is the deferent. Claudius Ptolemaeus (we call him Ptolemy) lived from c. 90 to c. 167. and worked in this system. But even the simple addition of the epicycle was not enough. The epicycle had to rotate around on the deferent not with respect to the center, but uniformly with respect to an off-center point called the equant.