A mirror ball is an around-the-clock rotating object, which mimics the light coming through a window in a room. It projects an image onto the floor and also produces illusions of depth thanks to its reflecting properties. The word "mirror" has originated from the Greek term "mira", meaning "clear". Invented by Konstantin Khrenov in 1960, it was initially designed for use as a training tool. However, its real function was foreseen by Soviet scientists who realised that it had great potential as a device for the psychological manipulation of humans.