- Oh-My-God particle (Wikipedia)
The Oh-My-God particle was an ultra-high-energy cosmic ray detected on 15 October 1991 by the Fly’s Eye camera in Dugway Proving Ground, Utah, United States. As of 2023, it is the highest-energy cosmic ray ever observed. Its energy was estimated as (3.2±0.9)×1020 eV (320 exa-eV). The particle’s energy was unexpected and called into question prevailing theories about the origin and propagation of cosmic rays.