By Ron Cowen
Imagine a single proton smashing into Earth’s atmosphere with as much punch as a fast-pitch baseball. For decades, scientists have suspected that protons and other particles with such huge energies, known as ultra-high-energy cosmic rays, arise in the tumultuous surroundings of giant black holes at the centers of galaxies.
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Now, the sprawling Pierre Auger Observatory in Argentina has found the first solid evidence linking these exceedingly rare cosmic rays—the most energetic particles in the universe—to supermassive black holes in nearby galaxies.