From his early writings about solar geometry—the physics of sun and earth—Ralph Knowles has become increasingly interested in the cultural response, the rituals and built artifacts that respond to the sun. It is not only the trace of the shadow cast, it is the flux of life that responds, whether the movement of the Anasazi Indians in and around the pueblos to take advantage of daily and seasonal sun or activities of modern living. Life on earth follows the sun as it arches across our skies in predictable ways. Knowles’ early books were about that geometry.