Angela Olinto, University of Chicago
Deciphering the Extreme Universe

The nature and origin of the highest energy particles ever to be observed are still elusive. They are messengers of an extreme universe which can test the limits of physical laws. The largest cosmic ray experiments are starting to probe the extremely high-energy region where pointing to cosmic ray sources is feasible and a long awaited Greisen-Zatsepin-Kuzmin feature in the spectrum is expected. Past experiments have claimed opposing results: AGASA sees an intriguing excess of cosmic rays above 1020 eV that challenges most theoretical models while HiRes  does not confirm the excess. After reviewing the present state of the experiments and theoretical models for the highest energy cosmic rays, we will discuss the status of the newest  observatory,  the Pierre Auger project and possible outcomes.