My dissertation argues for a new understanding of science in Islamic culture during the transformative years of the long nineteenth century. I show that Islamic traditions of astronomy maintained an important place in Egyptian society. Although European astronomy was increasingly well-known in Egypt during these years, its authority was not self-evident. Rather, it was a product of new sites of knowledge: physical places like the Viceregal Observatory in Cairo, as well as discursive spaces like the Arabic press. In these spaces, social, cultural, and political transformations of authority made the superiority of European science a fact.