Many people first encounter energy history in museums, where they learn about heroic steam powered engines and fossil-fueled technologies. The history of solar energy technologies, argues Frédéric Caille, is often either forgotten or repressed in these spaces. Such forgetting distorts our understanding of the past and narrows our sense of future possibilities. With his collaborative project to recover, reconstruct, and display forgotten solar water pumps from the 1970s, Caille and his colleagues frame forgotten solar technologies as “cosmograms”: objects which describe the world as it could have been, and could yet become.