Slipher's redshifts as support for de Sitter's model and the discovery of the dynamic universe

TL;DR

This paper discusses how Slipher's redshift observations supported de Sitter's dynamic universe model, leading to the discovery that the universe is expanding, contrasting earlier static models by Einstein and others.

Contribution

It highlights the role of Slipher's redshift data in supporting the dynamic universe concept and compares the contributions of Friedman and Lemaitre in this discovery.

Findings

Slipher's redshifts supported de Sitter's model.

Redshifts indicated an expanding universe.

Lemaitre's model incorporated a dynamic, evolving universe.

Abstract

Of the first two relativistiv world models, only the one by de Sitter predicted redshifted spectra from far away astronomical objects. Slipher's redshifts therefore seemed to arbitrate against Einstein's model which made no such predictions. Both models were trying to describe a static universe. However, Lemaitre found that de Sitter's construct resulted in a spatially inhomogeneous universe. He then opted for a model that correspondes to Einstein's closed, curved universe but allowed the radius of curvature to change with time. Slipher's redshifts suggested to him that the universe is dynamic and expanding. We also discuss the respective merits of Friedman and Lemaitre in revealing the dynamic nature of the universe.