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.
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.
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.
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.
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.
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.
t < 10, 000 years
t > 10, 000 years
The Cosmic Symphony (A
Modern Harmonice Mundi)
Contributed by: Dr. Edward Kolb