Whats up with the Disco Ball?
A disco ball, mirror ball, glitter ball, ball mirror, or specular sphere is obviously not like lighted signs, but 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 mirored surface. Usually it is mounted well above the heads of the people present,(as most lighted signs) 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.
What are now sometimes called "disco balls" were first used in nightclubs in the 1920s. They were already in existence and use before then, appearing in a description of a ballroom dance in 1897 in Boston. In the 1960s, '70s and '80s, these devices were a standard piece of equipment in discotheques, and by the end of the 20th century, the name "disco ball" had grown quite popular. A mirrored ball can be seen above the bandstand in this 1919 photo of the Louisiana jazz band.
Miniature glitter balls are sold as novelties and used for alot of decorative reasons, including dangling from the rear-view mirror of an automobile or using them as christmas tree ornaments. Glitter balls have inspired a homemade version in the sparkleball, the American craft of building decorative light balls out of christmas lights and plastic cups. The UK television show "Strictly Come Dancing" awards competition winners a "Glitter Ball Trophy".