Cyclic Models of the Relativistic Universe: The Early History

Abstract

Within the framework of relativistic cosmology oscillating or cyclic models of the universe were introduced by A. Friedmann in his seminal paper of 1922. With the recognition of evolutionary cosmology in the 1930s this class of closed models attracted considerable interest and was investigated by several physicists and astronomers. Whereas the Friedmann-Einstein model exhibited only a single maximum value, R. Tolman argued for an endless series of cycles. After World War II, cyclic or pulsating models were suggested by W. Bonnor and H. Zanstra, among others, but they remained peripheral to mainstream cosmology. The paper reviews the development from 1922 to the 1960s, paying particular attention to the works of Friedmann, Einstein, Tolman and Zanstra. It also points out the role played by bouncing models in the emergence of modern big-bang cosmology. Although the general idea of a cyclic or oscillating universe goes back to times immemorial, it was only with the advent of relativistic cosmology that it could be formulated in a mathematically precise way and confronted with observations. Ever since Alexander Friedmann introduced the possibility of a closed cyclic universe in 1922, it has continued to attract interest among a minority of astronomers and physicists. At the same time it has been controversial and widely seen as speculative, in part because of its historical association with an antireligious world view. According to Steven Weinberg, " the oscillating model … nicely avoids the problem of Genesis " and may be considered philosophically appealing for that reason (Weinberg 1977: 154). In spite of many problems and a generally bad reputation, cyclic models never vanished from the scene of cosmology. Indeed, they have recently experienced a remarkable revival, especially