A bouncy ball or rubber ball is a spherical toy ball, usually fairly small, made of elastic material which allows it to bounce against hard surfaces. When thrown against a hard surface, bouncy balls retain their momentum and much of their kinetic energy (or, if dropped, convert much of their potential energy to kinetic energy). They can thus rebound with an appreciable fraction of their original force. Natural rubber originated in the Americas, and rubber balls were made before European contact, including for use in the Mesoamerican ballgame. Christopher Columbus witnessed Haitians playing with a rubber ball in 1495.