abstract sculpture that has moving parts, driven either by motors or the natural force of wind. The word mobile was initially suggested by Marcel Duchamp (Duchamp, Marcel) for a 1932 Paris exhibition of such works by the American artist Alexander Calder (Calder, Alexander). One of Calder's first mobiles consisted of coloured spheres motorized to move up and down curving wires at different speeds. Later, he developed wind mobiles from flat metal shapes suspended by wires from movable rods, which allowed for rotation. The revolving parts created a new visual experience of constantly changing volumes and forms; Calder, as he expressed it, was “making one or two objects at a time find actual relationship in space.” Although experiments in kinetic sculpture with one moving element had been made in 1920 by the Russian-born artist Naum Gabo (Gabo, Naum), Calder's mobiles of the 1930s were the first full exploitation of the idea. Compare stabile.