Each 3,000-gallon (12,000 liter) tank, separated from each of its neighbors by 1.5 kilometers, is completely dark inside - except when particles from a cosmic ray air shower pass through it. These energetic particles are traveling faster than the speed of light in water when they reach the detectors; therefore, their electromagnetic shock waves produce Cherenkov light that can be measured by photomultiplier tubes mounted on the tanks.

Searched words: Video: Station of the Surface Detector 1/2, Admin, webmaster@auger.org, Each 3,000-gallon (12,000 liter) tank, separated from each of its neighbors by 1.5 kilometers, is completely dark inside - except when particles from a cosmic ray air shower pass through it. These energetic particles are traveling faster than the speed of light in water when they reach the detectors; therefore, their electromagnetic shock waves produce Cherenkov light that can be measured by photomultiplier tubes mounted on the tanks.