Hermann Bondi, Thomas Gold, and Fred Hoyle presented the steady-state theory of the universe, which posited that the universe was infinite, eternal, and unchanging. Although most astrophysicists now reject the theory in favor of the big bang model (which it was designed to contest), the steady-state universe was prominent for several years.
Since at least the time of the ancient Greek philosophers twenty-six centuries ago, these bold questions have been asked about the universe: How was the universe made? Has it always been here? If not, where did it come from? By the first half of the twentieth century, it was known that the sun is a star, one of hundreds of billions of stars that form the Milky Way galaxy. It was known that there are billions of galaxies like the Milky Way and that the farthest ones are more than a billion light-years away. In his theory of general relativity, Albert Einstein presented a framework grand enough that theories of the universe could be formulated within it. Unfortunately, it allows one to formulate many theories without telling which of the theories, if any, is correct.
In 1929, Edwin Powell Hubble showed that only models which allowed for the expansion of the universe could be correct, for he showed that distant galaxies in all directions are receding from the Milky Way and that the more distant a galaxy is, the faster it flees from our galaxy. The mathematical expression of these facts is called the Hubble law. Science, however, has been unable to come up with a better explanation of these facts other than to suppose that the universe itself is expanding.
An analogy that is frequently used is that of dots painted on a partially inflated balloon. If the balloon is further inflated, each painted dot becomes farther away from the other dots, because the space between the dots expands. One could note also that dots that were twice as far away would recede twice as fast, as Hubble’s observation requires. It should be understood, however, that the expansion of space has no effect on the small scale. For example, the Rock of Gibraltar is not growing larger because the space within it is expanding. The forces that hold the rock together also keep it from expanding with space. It is only on the largest scale—that of superclusters of galaxies—that the forces composing matter are weak enough to yield to the expansion. The distances between superclusters of galaxies do grow larger as space expands.
If the universe is expanding, it must have been smaller in the past. It seems to be a straightforward matter to use Hubble’s law to calculate when the universe began. If it is known how far away the parts are and how fast they are going, one should be able to calculate how long ago they were all together. Using Hubble’s original data, 2 billion years was given as the age of the universe. This was somewhat embarrassing since the accepted age of the earth was far older. The problem lies in measuring the distances to distant galaxies, a difficult and uncertain process. Using other data, the age of the universe is calculated to be between 10 and 20 billion years, which fits well with the accepted age of the earth of 4.6 billion years.
In 1927, Georges Lemaître proposed an expanding universe based upon a prediction of general relativity. He supposed that all of space, matter, and energy had been crushed together and then exploded outward. It is this explosion that Sir Fred Hoyle later named the “big bang.” Attracting little attention at first, Lemaître’s theory
The explosion of the big bang occurred over the whole universe—it was the whole universe. While common sense seems to demand that there be some place for the universe to expand to, mathematicians assure astronomers that expansion as such is not necessary. The universe is defined commonly to include all the space there is; to say that it grows larger does not, of necessity, require anything to lie beyond the boundaries of the universe. Here, the simple analogy with the expanding balloon fails completely, for a balloon and a universe obey different rules. Motivated by observations of radioactive decay, Lemaître supposed that at the instant of the big bang, all matter had been combined into a gigantic nucleus. This nucleus then decayed into the known elements, and thus the surrounding matter had come into being.
In 1948, George Gamow and Ralph Asher Alpher
In 1948, the big bang theory seemed unable to explain the existence of heavy elements, and it gave an age for the universe that was less than that of Earth. A further difficulty was the problem of forming galaxies. It seemed unlikely that matter flung outward in the violence of the big bang would be able ever to coalesce again in clumps large enough to form galaxies. To overcome these difficulties, Hermann Bondi and Thomas Gold proposed the steady-state theory in 1948. They based this theory on what they called the perfect cosmological principle: When considering a large enough volume, the universe will appear the same everywhere and at any time. This meant that the universe is infinitely old, obviously far older than Earth. Accepting the fact that the universe is expanding, they reached the astounding conclusion that matter must be continuously created uniformly throughout space. Seeing nothing to prevent it from doing so, it was assumed that the new matter would coalesce to form new galaxies.
Since the most abundant element in the universe is hydrogen, Gold and Bondi proposed that the new mass appear as hydrogen. Using the best estimate for the rate of expansion of the universe, they calculated that if only one new hydrogen atom popped into existence in each volume of space the size of a living room over every few million years, then the average number of galaxies in a given volume of space would remain constant.
While there was no way to observe directly the creation of such a tiny amount of matter, there should still be observable consequences. In more than a billion years or so, enough matter should collect in the space between galaxies to form new galaxies, while old galaxies should become giants as they gather in new matter. Thus, the steady-state theory predicts how galaxies should be grouped: There should be a small number of old massive galaxies visible to Earth, and these should be surrounded by groups of small, younger galaxies. Later in 1948, Hoyle joined the backers of the steady-state model. He showed how continuous creation of matter might be fit into the formidable framework of general relativity.
The steady-state theory had both a cultural and a scientific impact. It had great philosophic appeal for many because it proclaimed a universe of order, an infinite and eternal universe, one that was fit for astronomers and always would be. Its organization was simple: Viewed on a grand enough scale, the universe was the same everywhere and for all time. The ready market for the many popular books written by Hoyle, Bondi, and others says something about the public’s fascination with the steady-state theory. According to science historian Wolfgang Yourgrau, the introduction of the steady-state theory caused a tremendous sensation among cosmologists (those who study models of the universe). It stimulated much theoretical and empirical work as they sought either to prove the theory false or to find evidence to support it. Astronomers looking for the distribution of young and old galaxies predicted by the steady-state theory did not find it. Instead, they found that all galaxies close enough to be so studied have at least some old stars. It appears that all galaxies formed at approximately the same time and that there are no intrinsically young galaxies. Furthermore, the most abundant type of galaxy that is dominated by old stars is small.
Hoyle, who became the chief spokesman for the steady-state theory, worked on the problem of the origin of the heavy elements. He and others were able to show that heavy elements can form under the fantastic densities and temperatures that exist in the cores of stars and that these elements are flung back into space during supernova explosions. Eventually, heavy elements are incorporated into a new generation of stars and perhaps planets. It is interesting to contemplate that while humankind is made of the dust of the earth, that dust is stardust. At any rate, the origin of heavy elements was no longer a problem for the steady-state theory, but this was also true of the big bang theory.
Another prediction of the steady-state theory was that, by and large, the universe has always been the same. Strangely enough, the universe as it was in the past is spread out. For example, the Andromeda nebula is more than 2 million light-years away; this means the light that reaches Earth now left the Andromeda nebula more than 2 million years ago. Today, one sees this galaxy as it was then. Likewise, when one looks billions of light-years out into space, the universe is seen as it was billions of years in the past. Contrary to the steady-state theory, as astronomers looked far out into space, they found increasing evidence that the universe of long ago was different. Perhaps the most spectacular difference is that quasars were once abundant in the universe, but there are scarcely any within a billion light-years of Earth. This means that there are few, if any, quasars left today.
As evidence against the steady-state theory mounted, Hoyle and his companions eventually abandoned it. It had been useful to stimulate science and to fire the imaginations of many, but its day had passed. With the discovery of the remnant primordial fireball radiation by Arno A. Penzias and Robert W. Wilson in 1965, the big bang theory reigned supreme. In its turn, however, the steady-state theory has since been displaced by a variation of the big bang theory called the inflationary theory, which holds the promise of overcoming some of the problems of the old theory. This is the fashion in which science advances.
-
citation-type="booksimple" xlink:type="simple">Bondi, Hermann. The Universe at Large. Garden City, N.Y.: Anchor Books, 1960. Popular-level book with chapters on stars and gravitation, and several chapters dealing with cosmology. Recommended for the general reader. -
citation-type="booksimple" xlink:type="simple">Bonnor, William. The Mystery of the Expanding Universe. New York: Macmillan, 1964. Covers basic observations and compares them with various cosmological theories. Includes a fine nonmathematical treatment of the cosmological models of general relativity. Good chapter on the steady-state theory. Highly recommended for the interested layperson. -
citation-type="booksimple" xlink:type="simple">Harrison, Edward R. Cosmology, the Science of the Universe. Cambridge, England: Cambridge University Press, 1981. This is one of the best general works on the subject. In addition to discussions of the big bang and steady-state cosmologies, there are discussions of space, time, cosmic horizons, life in the universe, and the like. There are numerous helpful diagrams. At the end of each chapter are bibliographies, along with a few pages of thought-provoking quotations. While the general reader will benefit from browsing through it, the well-prepared layperson will find it to be a gold mine. -
citation-type="booksimple" xlink:type="simple">Hoyle, Fred. The Nature of the Universe. Rev. ed. New York: Harper and Brothers, 1960. Popular work about the solar system, stars, and the universe. There is a fine chapter on the expanding universe that discusses both the big bang and the steady-state theories. Recommended for the layperson. -
citation-type="booksimple" xlink:type="simple">Munitz, Milton K., ed. Theories of the Universe: From Babylonian Myth to Modern Science. Glencoe, Ill.: Free Press, 1957. This is a marvelous historical collection of essays on the nature of the universe. Representative works by Plato, Aristotle, Copernicus, Galileo, Einstein, Lemaître, Gamow, Bondi, Hoyle, and many others are included. Almost all of the articles are nonmathematical. Highly recommended. -
citation-type="booksimple" xlink:type="simple">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. -
citation-type="booksimple" xlink:type="simple">Yourgrau, Wolfgang, and Allen D. Breck, eds. Cosmology, History, and Theology. New York: Plenum Press, 1977. Cosmological models from the past to modern times are discussed, with considerable emphasis on the latter. As intended, most of the articles will aid in placing cosmological theories in cultural perspective, especially as it pertains to history and theology. While a few of the articles are technical, the majority of the articles can be recommended for the interested reader.
Reber Publishes the First Radio Maps of the Galaxy
Gamow Develops the Big Bang Theory
Penzias and Wilson Discover Cosmic Microwave Background Radiation
