Charles D. Dermer
Bright Gamma-ray flares observed from sources far beyond our Milky Way Galaxy are best explained if enormous amounts of energy are liberated by black holes. The highest-energy particles in nature - the ultra-highenergy cosmic rays - cannot be confined by the Milky Way’s magnetic field, and must originate from sources outside our Galaxy. In this talk, I summarize the themes of our book, just published by Princeton University Press, with the same title as this talk. We examine whether the Blandford-Znajek mechanism for energy extrac.on from rotating black holes can explain the differences between Gamma-ray blazars and radio-quiet AGNs, Fermi evidence for cosmic ray acceleration in blazars and GRBs, and whether black holes accelerate the ultra-high energy cosmic rays.