PURPOSE: To demonstrate the mathematical concept of chaos using the complex multiple reflections off four spheres.

DESCRIPTION: Four large shiny spheres - the type used as English garden gazing spheres - are placed together as shown in the photograph at the left above. Complex multiple reflections illustrate the behavior of fractals, as seen in the close-up photograph at the right. This apparatus may be in residence in a departmental showcase, in which case a smaller version will be delivered, one using Christmas balls.

SUGGESTIONS: If you are actually going to try to explain this, you had better think about it for a while first.

REFERENCES: (PIRA unknown.) See Demonstration Reference File for related articles, including the seminal article by University of Maryland physicists. A neat web site http://webs1152.im1.net/~dsweet/Spheres/ provides a lot of interesting information on this topic as well as other references.

EQUIPMENT: Four large gazing balls with mounted small light bulb.

SETUP TIME: None.