History of The Big Bang Theory - 1950 To 1980s

1950 To 1980s

From around 1950 to 1965, the support for these theories was evenly divided, with a slight imbalance arising from the fact that the Big Bang theory could explain both the formation and the observed abundances of hydrogen and helium, whereas the Steady State could explain how they were formed, but not why they should have the observed abundances. However, the observational evidence began to support the idea that the universe evolved from a hot dense state. Objects such as quasars and radio galaxies were observed to be much more common at large distances (therefore in the distant past) than in the nearby universe, whereas the Steady State predicted that the average properties of the universe should be unchanging with time. In addition, the discovery of the cosmic microwave background radiation in 1965 was considered the death knell of the Steady State, although this prediction was only qualitative, and failed to predict the exact temperature of the CMB. (The key big bang prediction is the black-body spectrum of the CMB, which was not measured with high accuracy until COBE in 1990). After some reformulation, the Big Bang has been regarded as the best theory of the origin and evolution of the cosmos. Before the late 1960s, many cosmologists thought the infinitely dense and physically paradoxical singularity at the starting time of Friedmann's cosmological model could be avoided by allowing for a universe which was contracting before entering the hot dense state, and starting to expand again. This was formalized as Richard Tolman's oscillating universe. In the sixties, Stephen Hawking and others demonstrated that this idea was unworkable, and the singularity is an essential feature of the physics described by Einstein's gravity. This led the majority of cosmologists to accept the notion that the universe as currently described by the physics of general relativity has a finite age. However, due to a lack of a theory of quantum gravity, there is no way to say whether the singularity is an actual origin point for the universe, or whether the physical processes that govern the regime cause the universe to be effectively eternal in character.

Through the 1970s and 1980s, most cosmologists accepted the Big Bang, but several puzzles remained, including the non-discovery of anisotropies in the CMB, and occasional observations hinting at deviations from a black-body spectrum; thus the theory was not very strongly confirmed.