A number of observations have been made by the largest cosmic-ray experiments Akeno Giant Air Shower Array (AGASA), High Resolution Fly's Eye Cosmic Ray Detector, the Pierre Auger Observatory and Telescope Array Project that appeared to show cosmic rays with energies above this limit (called extreme-energy cosmic rays, or EECRs). The observation of these particles was the so-called GZK paradox or cosmic-ray paradox.