Live Science recently interviewed John Matthews of the Telescope Array Project as part of its "Life's Little Mysteries" series. The article discusses the speed and energy of ultra-high energy cosmic rays in comparison to photons, neutrinos, and other particles. Much of the article deals with the ways that these phenomena interact with the Earth's atmosphere and other substances.
Matthews notes that although cosmic rays can't move faster than the speed of light in a vacuum, they can and often do move faster than the speed of light through the atmosphere. Ultra-high energy cosmic rays travel very close to the speed of light. Matthews points out that when they enter the atmosphere, "by their nature, they just continue to barrel ahead, so they're exceeding the speed of light in the atmosphere."
The article goes on to discuss the Oh-My-God particle and how incredibly high its energy was, even compared with the highest energy particles created in particle accelerators like CERN.
The full article can be found here.
