A disco ball (also known as a mirror ball or glitter ball) is a roughly spherical object that reflects light directed at it in many directions, producing a complex display. Its surface consists of hundreds or thousands of facets, nearly all of approximately the same shape and size, and each having a mirrored surface. Usually it is mounted well above the heads of the people present, suspended from a device that causes it to rotate steadily on a vertical axis and illuminated by spotlights, so that stationary viewers experience beams of light flashing over them, and see myriad spots of light spinning around the walls of the room. Miniature glitter balls are sold as novelties and used for a number of decorative purposes, including dangling from the rear-view mirror of an automobile or Christmas tree ornaments. Glitter balls may have inspired a homemade version in the sparkleball, the American outsider craft of building decorative light balls out of Christmas lights and plastic cups. History What are now usually called "disco balls" were first widely used in nightclubs in the 1920s. They were patented in 1917. An early example can be seen in the nightclub sequence of Berlin: Die Sinfonie der Großstadt, a German silent film from 1927. In the 1960s, 1970s and 1980s, these devices were a standard piece of equipment in discothèques, and by the turn of the millennium, the name "disco ball" had grown quite popular. A Louisville, Kentucky company known as Omega National Products claims to have made 90% of the disco balls used in the United States during the disco craze, and remains a supplier. Popular culture The 1942 movie Casablanca featured a disco ball in a flashback sequence. The English rock band Yes used a variant of the disco ball in their 1972 "Close to the Edge" tour. This was a slowly spinning vertical mirror disk mounted atop a tall ladder, with a single spotlight aimed at it, used for the opening and closing birds/waterfall-sounds sequences of the title song Close to the Edge. The Grateful Dead featured a disco ball in the band's 1977 concert documentary The Grateful Dead Movie. The film includes several sequences where glittery reflections from a disco ball fill San Francisco's Winterland Ballroom during a series of 1974 performances. "A twirling mirror ball overhead also adds some visual flash to the image," notes a reviewer. U2 also featured a lemon-shaped