In 1992 the fastest object known to mankind hit the Earth's atmosphere at a speed within a billion-trillionth of one percent of the speed of light, carrying an energy far above that of the most powerful particle accelerator ever built. That object was a cosmic ray.Over 100 cosmic ray particles pass through our bodies every second. Some of these have enormous energies, far above those accessible using man-made particle accelerators. Many of them have traveled millions of light years across the Universe, and they bring with them clues about exotic astronomical systems like neutron stars, supernovae, quasars, and black holes.In Cosmic Bullets leading cosmic ray experts Roger Clay and Bruce Dawson tell the incredible story of the discovery and study of these messengers from deep space. They point out that despite a century of intensive research, it is still far from certain where most cosmic rays come from or how they were created. Nevertheless, the little-known story of their discovery and subsequent study holds many sudden twists and wonderful surprises. The authors have captured the excitement and mystery of astrophysical research, and the human drama of science, in this story of discovery.