The neutrino sky at very high energies

Neutrino astronomy opens a new window for the observation and study of high-energy phenomena in our Universe. The emission of high-energy neutrinos in extragalactic sources or the cosmic environment is intimately related to that of γ - rays and cosmic rays. We will review the various indirect neutrino limits that arise from this cosmic connection and compare this to the present direct limits of neutrino observatories. Specific models of extragalactic TeV to PeV neutrino sources are already testable by large volume neutrino observatories like IceCube. At the EeV energy scale the flux of cosmogenic neutrinos associated with the propagation of ultra-high energy cosmic rays in the cosmic radiation background seems to be the most promising contribution to the diffuse neutrino background. We will discuss its model dependence w.r.t. chemical composition and evolution of the sources and provide simple bolometric scaling relations.