So how did we end up with the version of the big bang that we have with us today? It actually occurred in a few stages, each new version superceding the next, but still within the context of a singular event. The big bang theory is a product of the twentieth century. And in a moment we'll follow the stages that have given us the popular version. Let's compare where we were a few centuries ago to what has happened in this century, but again just generally.
The first idea of the big bang didn't come from science but from the literary pen of Edgar Allan Poe. Besides his creepy stories that many of us are familiar with, he was a popularizer of science and astronomy. In his essay “Eureka,” he put forth the idea that God exploded the universe into creation, expanding it up to a certain point and then collapsing back on itself. He rejected the idea of an infinite universe, and reasoned instead that it was governed by gravity and would eventually contract back on itself.
The cosmology of the seventeenth and eighteenth centuries reflected a world of unlimited progress—industrial, economic, and political revolutions. It was an infinite universe open to an infinite future that reflected an advancing society. But the world of the twentieth century, where advance was halted and World Wars, along with concentration camps, atomic bombs, and political assassinations dominated the attention of society, it's not too much of surprise to see the ideas and theories of a decaying, finite cosmos rear their heads again. Now this is not to say that there haven't been some very positive things that have occurred during this time. But when the big bang theory came into being, society was going through the events just mentioned. And it has entrenched itself since then.
During the process of developing his cosmological theories, Einstein introduced something that he later considered “the biggest blunder of his life.” In order to preserve his conception of a static universe, he added an equation called the cosmological constant. This mathematical term balanced the gravitational forces that were working to collapse the universe back together by introducing a repulsive force that kept it in a state of equilibrium. So the static nature would be preserved. Remember the point I made in the introduction that just because you believe something is true doesn't mean it really is? Einstein found this out firsthand.
At the heart of the big bang is the notion that the universe is an embodiment of preexisting mathematical laws. It doesn't begin with observation but with mathematics derived from unquestionable assumptions. And if observations conflict with theory, new concepts are introduced to perpetuate the theory. There are only a few cases of observed phenomena that support the big bang, but they're instances that have been interpreted to support the theory rather than to question it.
As a galaxy or star travels farther away from us, its light shifts to the red end of the light spectrum, similar to when a train whistle's pitch drops as it passes. (That's called the Doppler effect.) When light from a distant galaxy is put through a prism, the spectrum produced shows the change in frequency of the light wave, just as when you hear the pitch drop in the Doppler effect. This change in frequency, or redshift, indicates that the light source is moving away from us at a high velocity.
A singularity is a term given to the nature of the universe before the big bang. It is a theoretical single point that has no size, and has the characteristics of being infinitely small and infinitely dense. There are no laws of physics that can explain exactly what it is.
When George Gamow's theory was first presented, those in disagreement with it dubbed it “the big bang.” Fred Hoyle, the physicist who later proposed the steady state theory, coined the phrase. So the name that was originally used to poke fun at the idea has become the name in the accepted cosmology of today. Sort of ironic, isn't it?
For the idea of the big bang to take shape, a change had to occur in how the boundaries of the universe were defined. A few years after Einstein introduced his theory of general relativity, he put forth a cosmological view that had tremendous impact. He speculated that the universe was finite, a closed four-dimensional sphere, curved by the forces of gravity predicted in his theory. It was a static, unchanging universe governed by his elegant equations.
In 1919, the year that he had announced his views, World War I had just ended. People were recovering from the ravages of war. And progress, instead of leading to advancement, had led to death and destruction. A finite, unchanging universe was an appealing and reassuring idea from the famous man who the world liked more and more. So with that formulation the ground was laid for the development of the big bang. And contained within this view was another aspect that would have significant repercussions down through the cosmological theory of today. Einstein assumed that the universe as a whole was homogeneous, that matter is, on the largest scale, spread smoothly throughout space. You know that in general relativity, the larger the mass of an object the more it warps, or curves space. If the universe had the same density everywhere, in other words, smooth and homogeneous, all of the mass of the universe would curve space around onto itself, creating a finite sphere. But by 1919, there was sufficient evidence to support the fact that the universe was not homogeneous, but clumpy. This didn't bother Einstein. For philosophical and aesthetic reasons, a homogeneous universe worked better. And this precedent, to allow assumptions contrary to observation, with the idea the assumptions would eventually prove to be correct, led to that process being perpetuated down through our cosmology of today.
Without going into more detail about the development of a finite universe, let's look at the next stage in the birth of the big bang. The first version of the big bang was developed by a Belgian Catholic priest, George-Henri Lemaître (1894-1966). He had studied many of the observations made by astronomers, especially those of Edwin Hubble and Carl Wirtz. They had proposed that the universe was expanding based on the degree of redshift they had observed. Lemaître synthesized this information into a mathematical theory that showed two things:
This single point that Lemaître proposed he called the “primeval atom.” Remember the cascade effect of cosmic rays as they entered and collided with other particles in earth's atmosphere? This was his fireworks theory of the expansion of the universe. When the primeval atom exploded, it split up into smaller and smaller units, cosmic subatomic particles that became galaxies, with those decaying into suns and solar systems. As a matter of fact, he proposed this theory for explaining the existence of cosmic rays, and cosmic rays therefore proved his theory. Of course, most scientists scoffed at his idea. It had too many flaws in its fundamental hypothesis and many of the aspects of this theory just could not be philosophically accepted by most other scientists. So this first version of the big bang died.
With the advent of the Second World War and the development of the atomic bomb, the next version of the big bang came into existence. George Gamow, one of the Manhattan Project scientists, became the man who would push his view of the origin of the universe into the forefront of science. Upon seeing the explosion of the atomic bomb, he drew an analogy to the beginning of the universe. If the A-bomb can, in a hundred-millionth of a second, create elements still detected years later, why couldn't a huge explosion at the beginning of time produce all of the elements we have today? If the universe did come from a single point, using the equations from general relativity, Gamow theorized that the nuclear reactions created during the explosion would create all of the light elements like hydrogen and helium. And eventually as the universe continued to cool the heavier elements would be produced as well. By making some adjustments to the mathematics that explains the density of the matter in the universe, he was able to produce data that agreed pretty close to what was observed.
With theory in hand, George went on to popularize and publicize his ideas to the postwar population. Science writers and the general public quickly embraced his theory because it was easy to understand the analogy of atomic bomb explosion. And as the popularity of the theory increased, it became taken more as fact rather than theory. Of course this was helped along by the publication of Gamow's book, One, Two, Three, Infinity, in which he presented the big bang as fact in the last section.
It wasn't long before scientists and theologians began discussing the similarities between the big bang and the creation of the universe in the Bible. In 1951, Pope Pius XII made one of the first official statements of the Catholic Church regarding the big bang theory. He stated that, “Scientists are beginning to find the fingers of God in the creation of the universe.” And if you look at the cartoon on this page you can get another idea of how God's finger may have been used.
Excerpted from The Complete Idiot's Guide to Theories of the Universe © 2001 by Gary F. Moring. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.