English: A simulation of a cosmic ray shower formed when a proton with 1TeV (1e12 eV) of energy hits the atmosphere about 20km above the ground. The ground shown here is a 8km x 8km map of Chicago's lakefront. This visualization was made by Dinoj Surendran, Mark SubbaRao, and Randy Landsberg of the COSMUS group at the University of Chicago, with the help of physicists at the Kavli Institute for Cosmological Physics and the Pierre Auger Observatory. The simulation was done using the AIRES package by physicist Sergio Sciutto of the Universidad Nacional de La Plata, Argentina. Interactive animated 3d models of this and other cosmic ray showers, as well as instructions on how to make additional ones, can be found at http://astro.uchicago.edu/cosmus/projects/aires.