This amazing device throws a 3-foot loop of fluorescent string into the air. Watch the string seem to defy gravity as it floats, crawls, curls, and even walks along a flat surface. Its built-in UV black light makes it fascinating to watch in a darkened room. Place your finger on the moving string and observe the effect of an outside force. Great for teaching inertia, momentum, and the change between kinetic and potential energy! Requires 4 AA batteries. Colors may vary.