The Great Debate

TL;DR

This paper reviews the historic 1920 Great Debate on the scale of the universe, highlighting contrasting views on whether the universe consists of many galaxies or a single galaxy.

Contribution

It provides a historical analysis of the debate, illustrating how early cosmological models were contested and how they influenced modern understanding.

Findings

Curtis argued for multiple galaxies as separate entities.

Shapley proposed a single, large galaxy with the Sun far from the center.

The debate shaped subsequent astronomical research.

Abstract

A hundred years ago (1920) in the auditorium of the Smithsonian Institution's U.S. National Museum there were two lectures under the auspices of the George Ellery Hale Lecture series, what has come to be called the 'Great Debate'. In the debate, Harlow Shapley and Heber Curtis argued over the 'Scale of the Universe'. Curtis argued that the Universe is composed of many galaxies like our own and they are relatively small. Shapley argued that the Universe was composed of only one big Galaxy. In Shapley's model, our Sun was far from the center of this great island Universe.