Vesto Slipher, Nebular Spectroscopy, and the Birth of Modern Cosmology, 1912–22

This article looks at Vesto Slipher’s work on nebular spectroscopy between 1912 and 1922 as well as related research by other astronomers of the period, and it examines the dissemination of their results more widely. Slipher’s observations are viewed as marking the dividing line between speculation about the universe in traditional astronomy and the advent of modern cosmology and the theory of an expanding universe. The intent is to document the dissemination of Slipher’s results in the period leading up to the publication of studies of relativistic cosmology by Willem de Sitter in 1917 and Alexander Friedmann in 1922. Themes touched on in the article include the unprecedented character of Slipher’s findings and the interaction of observation and theory in modern cosmology. A prominent concern is the role of technology in astronomical science over the past century and a half. Here reference is made to the writings of Paul Forman on historical shifts that have taken place in our understanding of the relationship of science and technology.