  This year we are celebrating 101 years since the discovery of cosmic rays.
They are whizzing all around the Universe, and they occur at very different
energies, including the highest particle energies that exist. However, theory
predicts an abrupt suppression (a "cutoff") above a specific huge energy. This
is difficult to verify, the measurements are controversial, but it provides a
unique opportunity to probe established concepts of physics - like Lorentz
Invariance - under extreme conditions. If the observations will ultimately
contradict this "cutoff", this could require a fundamental pillar of physics to
be revised.
