Abstract :
I show that a Planck-scale deformation of the relativistic dispersion relation, which has been independently considered in the quantum-gravity literature, can explain the surprising results of three classes of experiments: (1) observations of cosmic rays above the expected GZK limit, (2) observations of multi-TeV photons from the BL Lac object Markarian 501, (3) studies of the longitudinal development of the air showers produced by ultra-high-energy hadronic particles. Experiments now in preparation, such as the ones planned for the GLAST space telescope, will provide an independent test of this solution of the three experimental paradoxes.