A Hoberman sphere typically consists of six
great circles corresponding to the edges of an
icosidodecahedron. The Hoberman sphere can be unfolded by allowing certain members to spread apart. The operation of each joint is linked to all the others in a
scissors mechanism like those used to mount
pantograph mirrors, or how a
folding chair operates. In larger models, this can be accomplished by feeding out a string or cable instead. The largest existing Hoberman sphere is in the
AHHAA Science Center in
Tartu, Estonia. Fully expanded, it is in diameter. The motorized sphere weighs , is constructed of aircraft-grade aluminum, and continually oscillates between its compact and expanded states. The sphere is suspended above the center's Science Court and is actuated with a computer-based motion control system. This system opens and closes the sphere in a programmed series of lyrical motions choreographed to music, lighting and special effects.{{cite web An earlier, similar but slightly smaller Hoberman sphere is in the atrium of
Liberty Science Center in
Jersey City, New Jersey. The sphere, when fully expanded, measures in diameter.{{cite web In 1993 a smaller geodesic sphere was installed at the
Swiss Science Center Technorama in Winterthur, Switzerland.{{cite web ==See also==