Cosmic Times

Origin of Everything: Hot Bang or Ageless Universe?

The primary message of this article is that as of 1955, there were two equally probable theories for the origin of the Universe – the steady-state theory and the evolutionary Universe theory (later known as Big Bang theory). At the time, the observational evidence was insufficient to decide between the two theories.

In the 1950s there were two theories regarding the nature of the universe: the Steady State and the Big Bang. At that time, there was not sufficient observational evidence to clearly favor or disprove either of them.

The British astronomer Fred Hoyle was the champion of the Steady State theory. He, Tommy Gold, and Hermann Bondi developed this theory after seeing the movie Dead of Night, which ends the way it begins. Hoyle thought that the universe could be unchanging but dynamic. So as the universe expands, matter is created to fill the space. It would require only 1 hydrogen atom per cubic meter every 300,000 years (comparable to "a few hundred atoms per year per galaxy"). Hoyle developed the "Perfect Cosmological Principle", which states that the universe is the same at any place and at any time.

The "Evolutionary" model for the universe (a.k.a. "Big Bang") was built on theoretical work in the 1920s and 1930s. In the 1940s, George Gamow was trying to solve the problem of the origin of the chemical elements. He determined that most elements could not form in the early universe - the right conditions of temperature and density would not last long enough. With Alpher, he showed that hydrogen and helium would form (and in the right proportions), but nothing heavier. (Later astronomers figured out how heavier elements could be made in the dense hot core of stars.). In doing this, Gamow developed many of the fundamental ideas about the early "evolutionary" universe. He developed the relation between temperature and mass density, recognized that atoms (not just nuclei) would form only after the universe had cooled sufficiently, and developed the theory of early galaxy formation. In 1949 Alpher and Herman redid these calculations, and in doing so predicted a "relic primordial radiation" with a temperature of about 5 K. They didn't think this would be detectable, and indeed instruments at the time could only detect a background radiation of only 20 K.

Both theories made predictions. Some are described in the table below

Issue
Steady State
Big Bang
Density of the Universe The density is constant The density changes, but do known physical laws apply at early time of very high density?
Age of the Universe Ageless In 1955, Big Bang gave an age less than known age of solar system
Rate of Expansion Expansion is constant Expansion should slow
Ages of Galaxies Old and young Galaxies should be mixed in space Galaxies age with time
Background Microwave Radiation There should be none It should exist, with a temperature of about 5 K

In the 1950s, the evidence was mixed. A number of observations seemed to favor the Big Bang, but it was not definitive. The fact that the age derived for the Big Bang was less than the known age of the Solar System was a major problem. However, there was no conclusive evidence for one theory or the other.

Interestingly, the presence of the Steady State as a competing theory provided the impetus to make the observations to test the theories.

Side Notes:

  • Interestingly, one of Thomas Bondi's major contributions to astronomy came with the discovery of pulsars in 1967. He was the first to explain them as rotating neutron stars, which turned out to be correct.
  • As a bit of joke, Gamow asked Hans Bethe if his name could be included on the paper Gamow was writing with Alpher. Bethe, who had not participated at all in the research, agreed. So the initial paper on the Big Bang was authored by Alpher, Bethe and Gamow, reminiscent of the first three letters of the Greek alphabet.
  • Alpher was Gamow's graduate student, and only after many years did he get full credit for working out Gamow's ideas, and predicting the cosmic microwave background. In the mid-1950's Alpher and Herman's theories were challenged by supporters of the Steady State. Alpher and Herman were nearly forgotten when Penzias and Wilson discovered the cosmic microwave background in 1965 (although Penzias mentioned their work in his Nobel lecture in 1978). Alpher received honors starting in the 1970's culminating with the National Medal of Science (the highest scientific honor in the US) two weeks before he died in 2007.

Other resources

The following web pages have more detailed information:

  • Arno Penzias' Nobel Prize Lecture describes the development of the Big Bang theory and how astronomers wrestled with the problem of the origin of the chemical elements.
  • Big Bang or Steady State? - an article from the American Institute of Physics describing the issues surrounding these two theories.
A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC