A unified theory of high energy astrophysical phenomena, which is based on an SN-CR-GRB association and the Cannonball Model of highlyrelativistic astrophysical jets explains (a) the origin and main properties of the high energy cosmic rays (CRS) at all energies, (b) the origin and main properties of gamma ray bursts (GRBs) (c) the origin of the extragalactic gamma-ray background radiation (GBR), (d) the origin of Galactic and extragalactic magnetic fields (e) the missing heat source in \"cooling flow$quot; galaxy clusters.