20mm Desktop Newton is Cradle Plastic Base Balance Balls(Silver)1. Newton Cradle is a timeless, classic desktop science "toy" that is the good blend of science and art. 2. Lift one steel ball and allow to fall back at one end, the ball at the opposite end will swing out the same distance. 3. Fascinating to watch. What happens when you swing two? Or three? 4. Also known as "Balance Balls", "Newton Pendulum" and "Newton Balls", this executive office toy demonstrates the law of conservation of momentum. Using Newton