An Historical View: The Discovery of Voids in the Galaxy Distribution

TL;DR

The discovery of cosmic voids in 1978 revolutionized our understanding of the universe's large-scale structure, revealing a cosmic web of filaments and voids supported by redshift survey observations and subsequent theoretical models.

Contribution

This paper provides a historical overview of the first identification of voids in galaxy distribution and discusses their impact on cosmological models and understanding of the universe's structure.

Findings

Void discovery shifted the paradigm to a cosmic web structure.

Wide-angle redshift surveys were crucial for identifying voids.

Theoretical models later explained the formation of voids and filaments.

Abstract

Voids in the large scale distribution of galaxies were first recognized and discussed as an astrophysical phenomenon in two papers published in 1978. We published the first (Gregory and Thompson 1978) and Joeveer, Einasto and Tago (1978) published the second. The discovery of voids altered the accepted view of the large scale structure of the universe. In the old picture, the universe was filled with field galaxies, and occasional density enhancements could be found at the locations of rich galaxy clusters or superclusters. In the new picture, voids are interspersed between complex filamentary supercluster structure that forms the so-called cosmic web. The key observational prerequisite for the discovery of voids was a wide-angle redshift survey displayed as a cone diagram that extended far enough in distance to show a fair sample of the universe (i.e., well beyond the Local Supercluster). The initial impact of the 1978 discovery of voids was stunted for several years by theoretical cosmologists in the West who were not quite sure how filaments and voids could emerge from what otherwise appeared to be a homogeneous universe. After it became clear several years later that theoretical models of structure formation could explain the phenomenon, the new void and supercluster paradigm became widely accepted.