In delineating a trajectory of human history, anthropology and other social sciences have tended to describe traditional life in particular geographic terms while leaving modem experience universal in scope. Studies of science and technology, while helping to locate and describe centers of modern practice, have less frequently explored their edges. Using a case study of the location of the primary French/european space launch site in French Guiana, this article examines technologies associated with the development of space beyond the atmosphere by (...) evaluating the impact of rockets and satellites on the construction of human space on the ground. Exploring the social significance of a modem sky and its transformation of one tropical margin into a technical center, the question of where things are becomes one of how they are defined. The modem appears less a placeless universal center and more a moving boundary, one dividing humans, nature, and technology into less stable domains. (shrink)