One atomic nucleus, moving at 99.99999999999999999999951% of light speed, slammed into the atmosphere with the punch of a hard-thrown baseball. Nothing in our galaxy could have launched it, and it shouldn't have survived the trip. Scientists named it the Oh-My-God particle — and they still can't explain it.
The best technical primer: how a single nucleus can carry macroscopic energy, and why its speed sits an unimaginable sliver below the speed of light itself.
Detected 15 October 1991 by the Fly's Eye detector at Dugway Proving Ground. At 3.2×10²⁰ eV, it remains the highest-energy particle humanity has ever recorded.
A punchy explainer on the sheer scale: 51 joules packed into something smaller than an atom, roughly 40 million times the energy the Large Hadron Collider can reach.
Quanta on the deep puzzle: how a particle this energetic breaks the theoretical ceiling for anything traveling to us across intergalactic space.
Meet the Greisen–Zatsepin–Kuzmin cutoff — the energy wall the cosmic microwave background should impose. The OMG particle sailed right past it.
In 2021 the Telescope Array caught a second monster, at 2.4×10²⁰ eV. Trace its path backward and it points to the Local Void — a stretch of near-empty space with nothing capable of firing it.
CNN on the 2023 announcement and the quote that sums up the whole field: 'What the heck is going on?' Two impossible particles, decades apart, from nowhere anyone can point to.