When Alexander Calder landed in Paris, in 1926, Salvador Dalí and the Surrealists were holding court in cafés across the capital, cigars and champagne in hand. Piet Mondrian was painting rectilinear grids filled with meticulous color, and Picasso was swinging between neoclassicism, a loosened-up Cubism, and sheer strangeness. The city, as Ernest Hemingway would later describe it, was “a moveable feast.”

Calder would take five years to mark out his own terrain, and it involved thermodynamics. In 1930, while visiting Mondrian’s studio at 26 Rue de Départ, he saw light coming into the room from the left and the right, absorbed by colored rectangles the painter had tacked to the wall. “I suggested to Mondrian that perhaps it would be fun to make these rectangles oscillate,” Calder recounted in his 1969 autobiography. Mondrian said, “No, it is not necessary, my painting is already very fast.”