An introduction to Cosmic Rays and Gamma-Ray Bursts, and to their simple understanding

I review the subjects of non-solar cosmic rays (CRs) and long-duration gamma-ray bursts (GRBs). Of the various interpretations of these phenomena, the one best supported by the data is the following. Accreting compact objects, such as black holes, are seen to emit relativistic puffs of plasma: `cannonballs' (CBs). The inner domain of a rotating star whose core has collapsed resembles such an accreting system. This suggests that core-collapse supernovae (SNe) emit CBs, as SN1987A did. The fate of a CB as it exits a SN and travels in space can be studied as a function of the CB's mass and energy, and of `ambient' properties: the encountered matter- and light- distributions, the composition of the former, and the location of intelligent observers. The latter may conclude that the interactions of CBs with ambient matter and light generate CRs and GRBs, all of whose properties can be described by this `CB model' with few parameters and simple physics. GRB data are still being taken in unscrutinized domains of energy and timing. They agree accurately with the model's predictions. CR data are centenary. Their precision will improve, but new striking predictions are unlikely. Yet, a one-free-parameter description of all CR data works very well. This is a bit as if one discovered QED today and only needed to fit $\alpha$.