George Gamow proposed the theory that the universe resulted from the explosion of a hot, dense primordial fireball, which later expanded and condensed into galaxies and then suns. The theory would become the dominant model for the beginnings of the universe.
After World War II, George Gamow, a professor at George Washington University in Washington, D.C., began a series of calculations based on the rate of galactic expansion. Calculating backward from observable conditions, Gamow produced a description of a time when all matter was confined to an extremely small space (perhaps thirty times the sun’s diameter) at a temperature of quadrillions of degrees. He presumed that the density of the radiation was greater than the density of the matter, a condition that caused an explosion, leading to the formation of the present universe. This explosion was dubbed the “big bang,” and Gamow’s theory became known as the big bang theory.
Gamow’s big bang theory was based upon the cosmological implications of Edwin Powell Hubble’s discovery in 1929 of the directly proportional relationship of distance and velocity of recession for the distant galaxies. This relationship implied that the universe was expanding, contradicting Albert Einstein’s
Einstein had been forced to introduce a “constant of repulsion”
The primary motive for Gamow’s proposal was not to resolve the issue of a static versus a dynamic universe but to explain how the heavier elements could have formed in their observed relative abundances. Hydrogen and helium are presumed to constitute approximately 99 percent of the matter in the universe. The other 1 percent consists of the heavier elements, which decline in abundance through the periodic table until zinc is reached. At this point, roughly halfway down the periodic table, the abundance flattens out and approximately the same amount of all the remaining elements occur. Gamow, in these early days, reasoned that this pattern could not be the result of the stellar formation of the heavy elements.
Gamow proposed that these elements were formed in the first thirty minutes of the initial explosion, before the universe’s temperature had cooled too much. He believed he could explain how deuterium (heavy hydrogen) could be formed in the big bang, and he was convinced that it would be destroyed only in stellar interiors. He also believed that helium was too abundant to have formed in stars. Thus, it had to have resulted from the initial explosion as well. Finally, the uniform distribution of helium implied that it was not the consequence of stellar activity. This portion of his initial ideas tended to be confirmed by later calculations and observations. Gamow also devoted extensive attention to stellar dynamics in his 1940 book The Birth and Death of the Sun.
Gamow enlisted the aid of two physicists to calculate the mathematics involved in heavy-element formation: Ralph Asher Alpher, a Ph.D. candidate at Johns Hopkins University, and Robert C. Herman, enlisted because of his skills with the early computers used by the Bureau of Standards. A major element of their theory came from a surprising source. During World War II, Donald Hughes
Although Alpher and Herman devoted extensive efforts to demonstrating how the elementary particles could combine under extreme conditions, serious problems remained with the formation of the heavy elements if the temperature dropped below a billion degrees, which implied that all the heavy elements had to form during the first thirty minutes of the big bang. There were no stable elements with atomic number 5 or 8, which meant that there would be a gap in the buildup of atoms of the heavier elements between helium and lithium.
Other astronomers regarded this gap as evidence that the buildup would result only in the formation of hydrogen and helium in the initial big bang, a position that would become generally accepted. While Gamow devised a theoretical means of bridging the gap, the low probability of his proposed sequence of events led to a severe time constraint in the cooling state of the early universe. He conceded eventually that the heavy elements were not created in the initial big bang. While the assumption that the dynamics of self-gravitating gaseous clouds caused condensation of the cooling gases into galaxies and stars presented difficulties, Gamow believed that the outline of the theory was firm enough to present it publicly to the scientific community in 1948. He published an article called “The Evolution of the Universe”
Many astronomers were troubled by Gamow’s proposal, especially the implications of a beginning and an ending to the universe. By 1950, Fred Hoyle of the University of Cambridge proposed what came to be called the “steady state” universe
While Gamow’s presentation of the big bang was accepted by many astronomers as a proper interpretation of the astronomical evidence, the specific proof of the theory was slower in coming. Alpher and Herman pointed out in 1948 that the level of radiation had steadily declined since the big bang to a level that they estimated to be 5 Kelvins (above absolute zero). They thought that it might still be detectable, not as light but perhaps as a low-level microwave radiation.
In 1965, Robert H. Dicke
The expansion of the universe, combined with a reasonable explanation of the manner in which it evolved, changed conceptions of a static universe that prevailed in the 1920’s. In that sense, big bang cosmology has been successful as a means of stimulating cosmological theory and research. As a means of explaining the relative abundance of the elements, as Gamow originally proposed it, the theory was only partially successful. The formation of the heavier elements was later presumed to take place not during the big bang but rather in the stars themselves, where hydrogen and helium were assumed to be the result. Because of the problem with heavy elements, there was some early neglect of the success of the theory in explaining the buildup of helium and the abundance of hydrogen and helium compared with the rest of the elements.
Gamow’s team was successful in identifying the process of heavy element formation through neutron capture. They merely had the wrong location, the big bang, instead of in the interiors of massive stars. One attractive feature of Gamow’s theory was that the original explosion was of such force that he did not have to hypothesize a “constant of repulsion” as Einstein had done in his gravitational field equations in order to counterbalance gravitation to maintain a static universe.
Gamow’s general outline became the standard cosmology, although the level of sophistication of the theory and its mathematical foundations changed dramatically. The principal difficulty of his theory eventually forced Gamow to accept Fred Hoyle’s explanation of heavy-element formation in the interior of stars. The success of this portion of Hoyle’s theory explained why the rest of his steady-state cosmology enjoyed some temporary success in opposition to Gamow’s proposal. It was eventually decided that heavy elements were built from fundamental particles during the radiative life of massive stars and dispersed into space through supernova explosions.
Gamow is appropriately regarded as a far-seeing pioneer of big bang cosmology. His prediction of basic evidence to support his theory in microwave radiation is properly regarded as a brilliant insight that was inappropriately neglected, but which has established the big bang as the most reasonable explanation for the observable state and behavior of the universe.
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Gamow, George. My World Line: An Informal Biography. New York: Viking Press, 1970. The afterword contains a brief description of his scientific achievements after coming to the United States. The first half of the chapter relates to the big bang from a personal perspective. -
Gribbin, John. In Search of the Big Bang. New York: Bantam Books, 1986. A popular, accurate, and comprehensive statement of the currently accepted cosmology, which contains an excellent summary of Gamow’s contribution. -
Harrison, Edward R. Cosmology: The Science of the Universe. Cambridge, England: Cambridge University Press, 1981. Contains a compact and clear sketch of the big bang and continuous creation cosmologies. Includes their strengths and why they were accepted and abandoned. One of the best overviews with an excellent bibliography. -
Hoyle, Fred. Frontiers of Astronomy. New York: Harper & Row, 1955. Chapters 17 through 20 contain Hoyle’s presentation of the steady-state cosmology, which he believed pointed up the weaknesses of Gamow’s theory and provided a more philosophically acceptable explanation of the origin of the universe. -
Singh, Simon. Big Bang: The Origin of the Universe. New York: Fourth Estate, 2004. Comprehensive history of big bang theory, beginning with an overview of cosmological theories from antiquity to 1900, delving into the science behind the big bang, and concluding with a discussion of unresolved issues. Includes description of the competing claims of big bang and solid-state theories of cosmology. Bibliographic references and index.
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