|
The Story of High-Energy
Cosmic Rays
The history of cosmic ray research is a story of
scientific adventure. For three quarters of a century, cosmic ray
researchers have climbed mountains, ridden hot air balloons, and
traveled to the far corners of the earth in the quest to understand
these fast-moving particles from space. They have solved some
scientific mysteries -- and revealed many more. The Pierre Auger
Project continues the tradition as it begins the search for the unknown
source of the highest-energy cosmic rays ever observed.
The Mystery of High-Energy Cosmic Rays
Scientists love a mystery, because solving a mystery in
nature means the opportunity to learn something new about the universe.
High-energy cosmic rays are just such a mystery.
Something out there -- no one knows what -- is hurling
incredibly energetic particles around the universe. Do these particles
come from some unknown superpowerful cosmic explosion? From a huge
black hole sucking stars to their violent deaths? From colliding
galaxies? From the collapse of massive invisible relics from the origin
of the universe? We don't yet know the answers, but we do know that
solving this mystery will take scientists another step forward in
understanding the universe.
The Big Events
It was as if they went out to catch butterflies, and
caught an F-111. It wasn't supposed to happen. Cosmic ray researchers
were dumbfounded when their "Fly's Eye" detector in the high Utah
desert turned up an incoming particle from space with an energy six
times higher than their theory allowed. Two years later, on the other
side of the world, a Japanese detector recorded another of these
"impossible" events. These two carefully documented cosmic rays, whose
energy is so high it defies explanation, have spurred the effort to
build a new detector big enough to capture and study many more of these
high-energy particles, and to try to discover where they came from.
A Detector 30 Times the Size of Paris
Each second, about 200 cosmic ray particles with
energies of a few million electron volts strike every square meter of
the earth. While these low-energy cosmic rays are plentiful, cosmic
rays at higher energies are far rarer. Above the energy of 1018
eV, only one particle each week falls on an area of one square
kilometer. Above the energy of 1020 eV, only one particle
falls on a square kilometer in a century! To find and measure these
rare events, a high-energy cosmic ray study needs a truly giant
detector.
|
