THE world’s most sensitive cosmic-ray detector has failed to find the ultra-high energy cosmic rays spotted by a smaller Japanese detector – leaving the standard model’s limit for cosmic ray energies intact for now.
By the time cosmic rays from outside our galaxy reach Earth, the standard model says they should have a maximum energy of 5 × 1019 electronvolts, known as the Greisen-Zatsepin-Kuzmin (GZK) limit. This is because cosmic rays lose energy through collisions with photons from the cosmic microwave background as they race through space at close to light speed.
But Japan’s Akeno Giant Air Shower Array (AGASA) has…
