Newton's cradle, or the executive ball clicker, operates by passing the momentum of a moving ball through other balls of similar weight in sequence until it reaches the ball at the end of the line, causing it to swing away from the column. Gravity then causes the moving ball to slow and swing back to strike the column and pass momentum in the opposite direction.
The operation of this device depends on theories put forth by Newton, Descartes and other scientists. It demonstrates the principle of the conservation of momentum. Scientists calculate momentum as the product of the weight and velocity of an object. Since the weight of each ball is the same, the speed transfers to the ball at the end of the line. In an ideal situation, the process continues without stopping, but friction eventually slows the motion to a stop.
While the device carries Newton's name, the science behind its operation traces back to Christiaan Huygens. Huygens presented a paper to the Royal Society in 1662 on the principles of momentum responsible for the operation of the cradle. The device carries Newton's name, however, as he is the more famous scientist, and the device is dependant on his second law of motion.