Newton's Cradle is an physics demonstration apparatus that effectively showcases the concepts of momentum and energy conservation. It consists of a line of suspended metal balls that are put into motion to exhibit the transfer of kinetic energy through a series of collisions, making it a great tool for demonstrating these fundamental principles. 

Observed in motion, Newton's Cradle reveals the transfer of energy as each sphere is released, resulting in a corresponding movement of the opposite sphere. This effect multiplies as more spheres are released, creating a mesmerizing and educational display of physics in action. The device was Sir Isaac Newton following his third law, for every force there is an equal and opposite force.