The Hoberman Sphere is an expanding and contracting ball. It cleverly combines mathematics and geometry to create a surprising motion that fascinates children and adults alike. Its basic structure consists of six large intersecting rings. Each ring is made up of lots of small plastic links joined together in pairs which fold and unfold in a scissor-like motion. Grab a link at each side of the Sphere, pull outwards and it will grow from 23 cm in diameter to a whopping 77 cm! Give it a slight push and it will contract back to its original size. This patented method of folding was discovered by Chuck Hoberman, an inventor with degrees in art and mechanical engineering. The Hoberman Original Sphere comes with a pulley, hardware and instructions to hang it as a kinetic mobile. It also contains an educational booklet about the geometry of the Sphere and an activity sheet detailing 21 fun tricks and activities you can do with it. Here are some of them: Flip Down Hold the closed Sphere by one hub on top of your open palm. Flip the Sphere over and watch it open, then flip it back to the top of your palm and let it close. When you?ve mastered this, try it with your other hand. Open Bounce Hold the Sphere fully open with two hands and throw it down to the floor. If you spin it towards you, it will bounce back. Two-Handed Open-to-Close Spin Hold the opposite hubs of an open Sphere between your thumbs and first two fingers. Using your thumbs, twirl the Sphere backwards as you close it and push in so the hubs are spinning on the palms of your hands. This takes practice, but looks really cool. Floor Spin Open the Sphere and place it on the floor. Holding the upper hub, spin the Sphere and watch it move. Try spinning it on a hub, then a triangle, then a pentagon ? notice the different way it moves on each of these shapes.