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The Hoberman Sphere: An All-Purpose Prop

Participants at the recent Wendy's International Trainers' Conference wanted more information about "the shrinking and expanding sphere". Actually, I borrowed that sphere from Raja Thiagarajan. Here is his own explanation of the Hoberman Sphere. -- Thiagi

ISPI 1998 -- 99 Seconds Presentation

The Hoberman Sphere: An All-Purpose Prop

Raja Thiagarajan, Workshops by Thiagi, Inc.

Technical Info

The Hoberman Sphere was invented by Chuck Hoberman, an inventor with degrees in art and mechanical engineering. It isn't really a sphere: Technically, it's a icosadodecahedron, which means that it is a geometric solid consisting of 20 triangles and 12 pentagons. Or you can look at is as a collection of six great circles, approximated by polygons.

The Hoberman sphere expands and contracts with its hubs moving in straight lines radiating from the center. Each point of intersection reinforces the structure. If you fully expand the sphere and rest it on a pentagonal face, it will hold its shape. If you turn it slightly so that it's resting on a hub, it will quickly close.

The largest Hoberman sphere in existence is in the atrium of the Liberty Science Center in Jersey City, NJ. It is 18 feet in diameter (when fully expanded), made of aluminum and stainless steel, and weighs 700 pounds.

Using the Hoberman Sphere

You can use the Hoberman sphere as a dynamic analogy for many things. Here are some examples:


The Hoberman sphere is available from many sources. We recommend The Discian Group. They have a nice a Hoberman sphere page, including ordering information.