Jean-Paul Sartre once wrote that a Calder mobile is a “piece of poetry that dances with the joy of life.” In the early twentieth century Calder’s mobiles provided a dynamic, new experience of sculpture that incorporated movement, activating their architectural settings and inviting viewers’ engagement. Freed from the traditional pedestal, the mobile—a type of kinetic sculpture innovated by Calder and named by the artist Marcel Duchamp—reflects Calder’s training as an engineer and his interest in astronomy. Viewers may find themselves comparing the elegantly suspended circulating spheres to the planets or stars.