Physics and Astronomy Colloquium
		   Tuesday, January 29, 2002
	4:10 p.m., Room 118 Physics-Astronomy Building
     Refreshments served at 3:45 p.m. outside Room 224 PA

   **Informal discussion with students will be from 3:15-3:45 
	    in Room 224 Physics-Astronomy Building**


                The Pierre Auger Observatories:
               A Search for the Nature and Origin
               of the Highest Energy Cosmic Rays

			   Jim Cronin

		     Enrico Fermi Institute
		      University of Chicago

"The existence of cosmic rays with energies in excess of 10^20 eV (16
joules) is a mystery. While some hundred explanations of their origin
have been offered, none are satisfactory. The only way to make progress
is to construct a 3000 km^2 observatory in both the southern and northern
hemispheres. The nature of the mystery will be discussed. The design of
the observatory will be described. Some preliminary engineering results
from the first phase of the project will be presented. These results
demonstrate that the observatory will actually work."