The Hoberman Sphere, magic, myth or math?
A Hoberman sphere is an isokinetic structure patented by Chuck Hoberman that is capable of folding down to a fraction of its normal size by the scissor like action of its joints. Colorful plastic versions have become popular as children's toys: several toy sizes exist, with the original design capable of expanding from 9 inches in diameter to 30 inches.
A Hoberman sphere typically consists of six great circles which can be unfolded by allowing certain members to spread apart. This can be accomplished by feeding out a string or cable in the larger models. The operation of each joint is linked to all the others in a manner conceptually similar to the extension arm on a wall-mounted shaving mirror.
"The Hoberman Sphere has become a classic and a favorite of kids and adults everywhere. It expands from 9" to 30" in diameter with a magical motion that amazes everyone that sees it. Everyone in the house should have their own, because nobody will want to share.
All Spheres comes with a pulley, hardware and instructions to hang as a cool, kinetic mobile; an educational booklet about the geometry of the Sphere; and a 21 Cool Things to Do activity sheet.
Ages 4 and up."
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