Prolegomena

In these preliminary remarks we discuss our motivations for holding the San Vito di Cadore conference as well as some personal reflections on the history and current status of the origin of cosmic rays. We argue that it is time to think beyond the ‘standard model’ and contemplate the possibility of sources other than SNRs contributing to the observed cosmic ray flux even if the bulk originate in SNRs. In fact everyone tacitly assumes that at the very highest energies we do in fact see a new extra-Galactic component, but what it is and where exactly the transition occurs remain subjects of investigation. Similarly the positron excess seen by PAMELA and confirmed by AMS clearly points to an additional source of high-energy leptons in our Galactic neighbourhood. The recent observation by Agile and Fermi of the remarkable Crab gamma-ray flares point to some non-standard and very rapid form of particle acceleration which, if it occurs in other environments, may contribute to the acceleration of cosmic rays. In summary, it is clear that the origin of cosmic rays is a richer field of study than just diffusive shock acceleration in SNRs.