In this critical edition and translation of Nicole Oresme ?s On Seeing the Stars , the renowned 14th-century natural philosopher proposes that the stars are not where they seem. And perhaps nothing is where it seems. In this earliest treatise on atmospheric refraction, Oresme uses optics and infinitesimals to help solve this vexing problem of astronomy. He is the first to propose that light travels along a curve through the atmosphere ? two centuries before Hooke and Newton, who are credited with the discovery. Further, he calls all sense data into doubt. Oresme ?s argument concerning the curvature of light is a major milestone in the history of science, confirming that Oresme was one of the most innovative scientists of the pre-modern world.