WHAT IS THE NATURE OF THE UNIVERSE
AND WHAT IS IT MADE OF?
WHAT ARE MATTER, ENERGY,
SPACE AND TIME?
HOW DID WE GET HERE AND
WHERE ARE WE GOING?
Throughout human history, scientific theories and
experiments of increasing power and sophistication
have addressed these basic questions about the
universe. The resulting knowledge has led to
revolutionary insights into the nature of the world
In the last 30 years, physicists have achieved a
profound understanding of the fundamental particles
and the physical laws that govern matter, energy, space
and time. Researchers have subjected this "Standard
Model" to countless experimental tests; and, again
and again, its predictions have held true. The series
of experimental and theoretical breakthroughs that
combined to produce the Standard Model can truly
be celebrated as one of the great scientific triumphs of
the 20th century.
Now, in a development that some have compared
to Copernicus's recognition that the earth is not the
center of the solar system, startling new data have
revealed that only five percent of the universe is made
of normal, visible matter described by the Standard
Model. Ninety-five percent of the universe consists
of dark matter and dark energy whose fundamental
nature is a mystery. The Standard Model's orderly and
elegant view of the universe must be incorporated into
a deeper theory that can explain the new phenomena.
The result will be a revolution in particle physics as
dramatic as any that have come before.
QUESTIONS FOR THE UNIVERSE
A worldwide program of particle physics investigation
is underway to explore the mysterious new scientific
landscape. Nine interrelated questions define the
ARE THERE UNDISCOVERED PRINCIPLES OF NATURE: NEW SYMMETRIES,
NEW PHYSICAL LAWS?
The quantum ideas that so successfully describe familiar
matter fail when applied to cosmic physics. Solving the
problem requires the appearance of new forces and new
particles signaling the discovery of new symmetries--undiscovered
principles of nature's behavior.
HOW CAN WE SOLVE THE MYSTERY OF DARK ENERGY?
The dark energy that permeates empty space and
accelerates the expansion of the universe must have
a quantum explanation. Dark energy might be related
to the Higgs field, a force that fills space and gives
ARE THERE EXTRA DIMENSIONS OF SPACE?
String theory predicts seven undiscovered dimensions
of space that give rise to much of the apparent
complexity of particle physics. The discovery of extra
dimensions would be an epochal event in human
history; it would change our understanding of the
birth and evolution of the universe. String theory
could reshape our concept of gravity.
DO ALL THE FORCES BECOME ONE?
At the most fundamental level all forces and particles
in the universe may be related, and all the forces might
be manifestations of a single grand unified force,
realizing Einstein's dream.
WHY ARE THERE SO MANY KINDS OF PARTICLES?
Why do three families of particles exist, and why
do their masses differ so dramatically? Patterns and
variations in the families of elementary particles suggest
undiscovered underlying principles that tie together
the quarks and leptons of the Standard Model.
WHAT IS DARK MATTER?
HOW CAN WE MAKE IT IN THE LABORATORY?
Most of the matter in the universe is unknown dark
matter, probably heavy particles produced in the
big bang. While most of these particles annihilated
into pure energy, some remained. These remaining
particles should have a small enough mass to be
produced and studied at accelerators.
WHAT ARE NEUTRINOS TELLING US?
Of all the known particles, neutrinos are the most
mysterious. They played an essential role in the
evolution of the universe, and their tiny nonzero mass
may signal new physics at very high energies.
HOW DID THE UNIVERSE COME TO BE?
According to cosmic theory, the universe began with
a singular explosion followed by a burst of inflationary
expansion. Following inflation, the universe cooled,
passing through a series of phase transitions and
allowing the formation of stars, galaxies and life on
earth. Understanding inflation requires breakthroughs
in quantum physics and quantum gravity.
WHAT HAPPENED TO THE ANTIMATTER?
The big bang almost certainly produced equal amounts
of matter and antimatter, yet the universe seems to
contain no antimatter. How did the asymmetry arise?
OPPORTUNITIES FOR DISCOVERY
We live in an age when the exploration of great questions is
leading toward a revolutionary new understanding of
"Opportunities have emerged for discovery about
the fundamental nature of the universe that we
never expected," Presidential Science Advisor John
Marburger said recently. "Technology places these
discoveries within our reach, but we need to focus
efforts across widely separated disciplines to realize the
Quantum Universe is a response to that challenge. It
serves as a guide to where the search for understanding
has taken us so far, and to where it is going. The
chapters that follow articulate how existing and
planned particle physics experiments at accelerators
and underground laboratories, together with space
probes and ground-based telescopes, bring within
reach new opportunities for discovery about the
fundamental nature of the universe.