A ray of radiation of extraterrestrial origin, consisting of one or more charged particles such as protons, alpha particles, and larger atomic nuclei. Cosmic rays entering the atmosphere collide with atoms, producing secondary radiation, such as pions, muons, electrons, and gamma rays. Cosmic rays (and secondary radiation) can be easily seen in a cloud chamber. The reigning explanation for cosmic rays has been that protons and other particles are accelerated by the leftovers of supernovas – the powerful explosions that occur when huge stars die. But new observations from Italy's space-based PAMELA cosmic ray detector appear to contradict that scenario and have researchers digging for a new explanation. Cosmic rays are particles that hit Earth and come from outer space. Most of these particles are protons , some are the insides of helium (alpha particles), some are electrons (beta particles), gamma rays or photons and a tiny fraction are even heavier particle...