Air-Showers in Space and Z-Showers in Universe for Neutrino Astronomy   and Spectroscopy
  Amplified Tau-airshower at horizons may well open a novel powerful windows, at PeV-EeV energy, to Neutrino Astronomy. Neutrino induced air-showering astronomy rise because of neutrino masses, their mixing and the consequent replenishment of tau flavor during neutrino flight into spaces; Tau-Air-Showers escaping the Earth are the main traces amplified by its millions muon, billions gamma and thousand billions photon secondaries. Earth edges and its sharp shadows is the huge beam-dump detector for UHE neutrino and the almost noise-free screen for tau air-showers (as well as for PeVs anti-neutrino electron scattering on air electrons by resonant interactions). Crown array detectors for horizontal Cherenkov signals on mountains, on balloons and satellites widening the solid angle view are being elaborated; deep and wide valleys are considered. MAGIC Telescopes pointing downward to terrestrial grounds acts, for EeV Tau neutrino air-showers astronomy, as a massive tens of km^3 water equivalent detector, making (in a given direction) it at present the most powerful dedicated neutrino telescope at PeVs. MAGIC facing the sea edges must also reveal mirrored downward UHECR Air-showers (Cherenkov) flashes. Magic-crown systems may lead to largest neutrino detectors in near future. They maybe located on top mountains, on planes or balloons or in satellite arrays. They may be screened in deep valleys. MILAGRO (and past MILAGRITO or future larger detectors) on a mountain top might already hide records of horizontal up-going muon bundles due to far UHECR and less far (but rarer) tau air-showers at EeV. UHE neutrino may also scatter on relic light (0.1-0.2 eV) ones, showering in the Universe at ZeV energies Cosmic Rays. 
D. Fargion