Discover LED color changing science in motion! The Newton’s cradle demonstrates the principles of Newton's third law “Every action has an equal and opposite reaction.” Watch in amazement as energy transmits the force through stationary spheres and pushes the sphere on the other end away. This balance ball set features translucent balls in LED red, blue, and green. A unique take on a classic desk toy that’s wonderful for relaxation. Measures 6” x 4-3/4” x 6”. Requires four 1.5V “AA” batteries (not included).