This article looks at Vesto Slipher’s work on nebular spectroscopy between 1912 and 1922as well as related research by other astronomers of the period, and it examines the dissem-ination of their results more widely. Slipher’s observations are viewed as marking the di-viding line between speculation about the universe in traditional astronomy and theadvent of modern cosmology and the theory of an expanding universe. The intent is todocument the dissemination of Slipher’s results in the period leading up to the publicationof studies (...) of relativistic cosmology by Willem de Sitter in 1917 and Alexander Friedmannin 1922. Themes touched on in the article include the unprecedented character ofSlipher’sfindings and the interaction of observation and theory in modern cosmology.A prominent concern is the role of technology in astronomical science over the past cen-tury and a half. Here reference is made to the writings of Paul Forman on historical shiftsthat have taken place in our understanding of the relationship of science and technology. (shrink)

The space-time expansion has a new perspective on the universe phenomena. In this article, the key features of the Space-Time Expansion Theory are summarized and discussed, with three postulates incorporating different insights into the behavior of space-time expansion, gravity, space-time curvature, and time itself. Gravity is not an attraction; it is a push. Inertia, free fall, the principles of the theory of relativity and some other phenomena support the author’s assertions. The expansion of space-time is universal, occurs everywhere, and produces (...) gravity instead of counteracting it. Being immersed in the same space-time acceleration, we only perceive the disturbance caused by the matter, which is the massive objects push. This study aims to offer scientists an alternative investigation. “Gravitation is not attraction; it’s a push.” All in accordance with hydrodynamic gravitation and expanding Universe. (shrink)