Mirror BallsKnown from nearly every disco the disco ball or mirror ball is covered with small mirrors and is usually mounted hanging out of reach of disco visitors. An electric motor rotates the ball slowly, with about one to three revolutions per minute. The lighting effect results from the reflection of a spotlight onto the rotating disco ball. The numerous small, slow-moving points turn in the room like a star filled sky. Rarely mirror balls are also used as part of other light installations.