The Importance of Nothing

To the casual observer the vacuum is boring, but to the true cognoscenti, there is a beauty, richness, and texture to nothing. Perhaps understanding nothing will allow us to understand everything in the universe. To grasp the basics of the inflationary origin of the primordial soup it isn't necessary to understand everything about nothing, just three little facts:

1. Nothing is something.
2. Nothing has energy.
3. Nothing can change.

1.Nothing is something. In fact, nothing is a lot. In a region of space one can remove all matter and radiation, but it is impossible to remove quantum uncertainty. Because of Heisenberg's uncertainty principle, at any point in space it is possible for a particle and antiparticle to emerge from the vacuum, seemingly violating conservation of energy momentarily before annihilating and returning to the vacuum. On submicroscopic scales the vacuum is a seething, writhing foam of particle-antiparticle pairs popping in and out of a virtual existence.

2. Nothing has energy. There is another important aspect to nothing, the Higgs field associated with unification of forces. All natural phenomena can be described by the action of four fundamental forces: the gravitational force, the electromagnetic force, the strong nuclear force, and the weak nuclear force. What a simple, beautiful picture. It is not necessary to invent different forces for different phenomena. We know that the force of the wind, the force of the tides, all of the forces at work on Earth, in the sun, and throughout the universe involve one or more of just four fundamental forces.

Figure 4: The four fundamental forces of nature.

It was once imagined that there were many more forces at work in nature. But nature seems to be simpler than that. Phenomena once thought to be caused by distinct forces are actually different manifestations of the same force. There are two famous examples of this "unification" of forces. In the 17th century Isaac Newton realized that the force causing an apple to fall on his head was the same force responsible for keeping the moon in orbit about Earth, and Earth and the other planets in orbit about the sun. This unification started the inner space/outer space connection, because it implied that the force responsible for motions of celestial bodies is amenable to study in the laboratory.

The second example of unification of forces is the synthesis of a single electromagnetic force out of the electric force and the magnetic force. Before the work of Michael Faraday and James Clerk Maxwell in the 19th century, electric forces and magnetic forces were thought to be distinct. The shocking realization that electricity and magnetism were different manifestations of a single phenomenon known as electromagnetism led to a great simplification of physics and a deeper understanding of nature, as well as illuminating the world with electricity.

We have witnessed another unification in our century. The work of many physicists in the 1960s and 1970s, most notably Sheldon Glashow, Steven Weinberg, and Abdus Salam, led to the realization that the electromagnetic force and the weak nuclear force are actually different manifestations of a single electroweak force.

There is strong evidence that there is a further unification of forces, and that perhaps all of the four forces are different aspects of a single superforce. If this idea of unification of all the forces is correct, at temperatures far exceeding what we are capable of producing in present-day accelerators, the four forces would behave in a similar way. Superforce temperatures may have been reached near the beginning of the early universe, and perhaps true unification was the initial state. If so, the temperatures required for superforce unification have not existed anywhere in the universe since the instant of the bang.

If the laws of nature have a deep and profound unifying symmetry, the symmetry is not manifest in the universe today since the observed character of the four forces is very different. One of the most beautiful ideas in modern physics is that the laws of nature can have symmetries that are hidden from us because the vacuum need not respect all the symmetries. The process by which the vacuum hides symmetry is known as the Higgs mechanism, named for the Scottish physicist Peter Higgs. In the Higgs mechanism there is a Higgs potential energy in the vacuum. For instance, electroweak unification involves a Higgs potential energy of 246-billion volts in the vacuum. Even this tremendous energy may be small compared to the energy that was once in the vacuum.

3.Nothing can change. True superunification was fleeting. As the universe expanded and cooled, the forces took on different characters as the nature of the vacuum changed. About 10^-43  seconds after the bang the gravitational force became distinct from the other forces. Then, around 10^-35  seconds later, the strong nuclear force split from the electroweak force. Finally, 10^-20  seconds AB, the electromagnetic force became distinguishable from the weak nuclear force.

If the strong nuclear force is unified with the electroweak force (grand unification), then the vacuum once possessed a tremendous potential energy, approximately 10^-43 billion volts higher than today. When the Higgs potential energy changed as the electroweak force split from the strong nuclear force approximately 10^-35 seconds AB, the tremendous potential energy in the vacuum would have been released to produce the hot primordial soup.

We are not sure of the exact time the primordial soup emerged from the vacuum pressure cooker, but we have a pretty good idea. In the spirit of Johannes Kepler's use of musical harmonic ratios to describe the velocities of planets orbiting the sun,one can describe the different epochs in the history of the universe as movements of a cosmic symphony. The symphony started at a frenzied pace, but the tempo of expansion decreased as the universe cooled.

The Cosmic Symphony (A Modern Harmonice Mundi)

Contributed by: Dr. Edward Kolb