Exit the frog, enter the human: Physiology and experimental psychology in nineteenth-century astronomy

This paper deals with one of the first attempts to measure simple reactions in humans. The Swiss astronomer Adolph Hirsch investigated personal differences in the speed of sensory transmission in order to achieve accuracy in astronomy. His controversial results, however, started an intense debate among both physiologists and astronomers who disagreed on the nature of these differences. Were they due to different eyes or brains, or to differences in skill and education? Furthermore, they debated how to eliminate them. Some, for example, wanted to eliminate the observer, and prescribed the use of new technologies like the electro-chronograph or photography, while others believed in discipline and education. By debating the nature of these differences, astronomers and physiologists sketched both different conceptions of 'man' and different paths to objectivity. These diverse conceptions, moreover, were tied to current nineteenth-century debates, such as the benefits or disadvantages of railroads, telegraphy and the standardization of time and longitudes. By focusing on the debates surrounding the speed of sensory transmission, this paper reevaluates the history of astronomy, physiology and experimental psychology. Furthermore, in investigating astronomy's relation to the human sciences, it uncovers profound connections in the traditionally separate histories of objectivity and the body.