The Pierre Auger Project is a large international undertaking aiming at cosmic ray study at extremely high energies, above 1019 eV. Cosmic rays are particles arriving to the Earth from the outer space. Most of them have relatively low energies, but few have energies very high indeed - more than 300 milion times higher than energies achieved in largest particle accelerators on the Earth.

  The origin of these very-high-energy particles is so far unknown. We don't know where in the Universe are their sources, nor how are they accelerated to the extreme energies observed. Nevertheless, there is no doubt these particles with extremely high energies really do arrive to us from the Cosmos; their origin and acceleration mechanism are one of the greatest puzzles in present-day astropysics.

  For experimental studies of these highest energy cosmic rays, a giant array of cosmic rays detectors was constructed: the Pierre Auger Observatory.