"This Mandala is based on the mathematical principle of a cardioid, which is literally a map of the path of a fixed point on a circle which rolls around the perimeter of another circle. Ptolemy unknowingly drew this design in drawing the paths of the planets, as seen from a fixed point on the surface of the earth. In its design, 15 rotations of the basic cardioid are formed, which create an inner sphere of higher energy. Its ..." http://www.stringmandalas.com/Mandalas/ChiBall/ChiBallIndex.html