Introduction to the Highest Energy Particle Astrophysics

- Based on the Colloquim for the Physics Department of the University of Utah (October 28 1999) -

Mysterious Cosmic Rays: The Elite of the Universe

Earth's outer atmosphere is regularly blasted by subatomic particles packing so much energy that they defy explanation. These highest energy cosmic rays have baffled physicists for decades because no one has found sources powerful enough to generate them in our cosmic neighborhood. They have been the elite particles in the universe. Here we first summarize our current understanding of how they could be produced and reach the earth, then explain what we have seen by the Akeno Giant Air Shower Array (AGASA) we built at 140 km west of Tokyo to challenge the mystery of the elite. Our measurements have generated an even more fascinating puzzle and we briefely introduce one exotic but interesting and feasible possibility to explain the measurements: Neutrinos might Rule!