gamma rays

Physicists report an explanation for how a photon with an energy of 300 teraelectronvolts could have traveled to Earth, a finding reported by Physics World. Such extreme-energy gamma rays are difficult to account for because they should be destroyed or degraded over long distances, so the work addresses how the particle survived its journey to our planet.

New research using cosmic gamma rays is probing whether the speed of light is truly constant, a cornerstone of Einstein's relativity. By studying high-energy photons that travelled vast cosmic distances, physicists are searching for tiny deviations that could point to quantum gravity effects and challenge the limits of Einstein's theory.