The Newton's Cradle is a modern classic, invented in 1967, but demonstrating observations made by Newton, involving the action of a pendulum, and showing the Laws of Conservation of Momentum and Energy. When a ball at one end is pulled up and let go, it swings down and hits the next ball. The energy and momentum from that action is transferred through the balls at rest, which remain immobile, and then the ball at the other end is propelled outward. Now try with 2 balls,...3,.. Fascinating to watch! 110mm by 110mm, including base.