The silver rings of this beguiling desktop mobile spin gracefully around a central sphere. The motion is continuous and, at first glance, impossible to fathom. The secret lies in the base; a battery-powered motor spins a powerful magnet, which in turn exerts a variable force on the pendulum weight attached to the outer ring. Even when you know exactly how it works, the perpetual, rhythmic movement and gravity-defying structure still fascinate. Packed with retro geek-appeal this is an excellent curiosity gift line for adults.