How did air currents move Alexander Calder’s later mobiles?

Alexander Calder’s later mobiles were designed to be activated by air currents, which move the suspended sheet metal and wire assemblies through space.1

While his earliest experiments involved motorized spheres, Calder later developed wind-driven mobiles consisting of flat metal shapes suspended by wires from movable rods. These structures allowed the elements to rotate, creating a constantly changing visual experience of volumes and forms as the air currents caused the parts to revolve. By utilizing these natural forces, Calder was able to make his objects find an actual relationship in space.2