  The recognition that physical space (or space-time) is curved is a product of
the general theory of relativity, such as dramatically shown by the 1919 solar
eclipse measurements. However, the mathematical possibility of non-Euclidean
geometries was recognized by Gauss more than a century earlier, and during the
nineteenth century mathematicians developed the pioneering ideas of Gauss,
Lobachevsky, Bolyai and Riemann into an elaborate branch of generalized
geometry. Did the unimaginative physicists and astronomers ignore the new
geometries? Were they considered to be of mathematical interest only until
Einstein entered the scene? This paper examines in detail the attempts in the
period from about 1830 to 1910 to establish links between non-Euclidean
geometry and the physical and astronomical sciences, including attempts to find
observational evidence for curved space. Although there were but few
contributors to "non-Euclidean astronomy," there were more than usually
supposed. The paper looks in particular on a work of 1872 in which the Leipzig
physicist K. F. Zoellner argued that the universe is closed in accordance with
Riemann's geometry.
