Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

The origin of extraterrestrial energetic particles ("cosmic rays") has puzzled scientists since the pioneering discovery by Victor Hess in 1912. In the last decade, however, modern supercomputers and multi-wavelength observations have opened new windows to address the problem. I present state-of-the-art kinetic simulations of supernova remnant shocks and discuss the main successes (and pitfalls) of the standard paradigm for the acceleration of electrons, protons, and heavier ions, as compared to gamma-ray observations of Galactic sources. Finally, I outline the theoretical and observational challenges in unraveling the sources of the extra-galactic cosmic rays (accelerated up to 10^20 eV), in the light of the latest data by the P. Auger Observatory.