This animation shows a 40m square plane of 200MeV gamma rays incident upon the Milagro pond at a 20 degree angle. The purple line travels with the original showerfront at the speed of light. As the front of gamma rays converts into a front of Cherenkov photons several effects can be seen, including delayed refraction, bifurcation, and angle dependent smearing. In the next figure multiple scattering is turned off to isolate the second showerfront.