Birth of the Theory
Albert Einstein placed light at the center of his new ideas concerning relativity in 1905, and in 1913 introduced the general theory of relativity. This led Alexander Friedmann, in 1922, to resolve Einstein’s equations, showing that the universe was neither eternal nor static, but had a point of origin and was expanding and evolving (expansion of spacetime). This was the birth of the big bang theory, or the standard model of cosmology. Seven years after Friedmann’s prediction of an expanding universe, Edwin Hubble’s careful observations of several dozen galaxies showed this was indeed the fact.
In The Beginning
About 14 billion years ago, all of spacetime was compressed into a tiny point smaller than a grain of sand. When this point reached critical mass it exploded in a cataclysmic event far beyond the imagination of man. About one hundred-thousandth of a second after the explosion, the universe had expanded and cooled enough to allow the formation of protons and neutrons, and about 1/100 of a second later, the nuclei of the most primitive atoms began to form - almost all of them hydrogen, as well as smaller amounts of helium, deuterium (or heavy hydrogen) and lithium.
Let There Be Light
For the next hundred thousand years or so the universe continued to expand and cool. At that time, the great roiling mass of primitive matter had cooled enough for atomic nuclei to capture electrons, and the first atoms were formed. This was a pivotal development in the evolution of the universe, because for the first time light was free to travel across space. Before the formation of atoms, the electrical charges of the free electrons interfered with the movement of the photons of light, and the universe was a fuzzy haze, an opaque whiteness.
A billion years after the bang, galaxies and stars began to form. The stars evolved and lived out their life cycles. The large ones, now burned out, were crushed under the force of their own gravity and exploded as supernovae. In these nuclear furnaces the heavy elements formed, elements such as oxygen and iron that make up the Earth and the living creatures on it. One of those creatures, man, some 14 billion years after the fact, has pieced together a reasonable theory of the origin of the cosmos that can be tested against observations. How much faith should we place in this theory?
Testing the Theory
Astronomers can see light that was produced by galaxies just a few billion years after the bang. Within the limits of the equipment and methods available, the theory portrays things just as we have found them to be. Theory corresponds with observation to that point in time.
Enter cosmic background radiation. By the 1960s, scientists had realized that the entire universe should be permeated by a background of microwave radiation. Quite by accident, two physicists working for Bell Laboratories discovered this very radiation. Since then both theory and experiment have been refined, and the standard cosmology confirmed back to the time, a hundred thousand years or so after the bang, when photons were first able to move freely across space.
Using nuclear theory and the laws of thermodynamics, scientists are able to predict the relative amounts of helium, deuterium and lithium that should be present in the universe. Careful measurements have shown that the predictions match the reality. This takes the threshold of time back to about 1/100 of a second after the bang, when the nuclei of these elements were first formed. All of the data we possess, without exception, indicates that this cosmology is essentially correct.
The Final Analysis
Not all of the questions are answered, and it seems doubtful that man will ever be able to look on the other side of the bang and see what is behind it. But that is as it should be. What would life be without mystery? One thing has been discovered though, and that is where the big bang happened. We have located the center of the universe; it is right where you are sitting now -- and everywhere else. All of the things and places we see as separate and distant now were the same place then, and that is something to think about.
References
- The Elegant Universe, Brian Greene, W.W. Norton and Co., New York, 1999.
- Red Giants and White Dwarfs, Robert Jastrow, Harper & Row, New York
