One of the “Impossible Sculptures” series. “Metronome” is loosely based on the “Ain, Ain Soph, Ain Soph Aur” of the Mystical Qabala. (“Light”, Light in Extension”, “Limitless Light”.) Eagle-eyed Qabalists will notice an extra line joining the circle to the first arc. This is just to make the movement more apparent and has no meaning.