To estimate the energy of any cosmic ray event detected by the Pierre Auger Observatory, the detectors have to be calibrated.
On August 17, 2017 the LIGO and Virgo collaboration measured a gravitational wave originating from a binary neutron star merger.
Ever since the existence of cosmic rays with individual energies of several Joules was established in the 1960s, speculation has raged as to whether cosmic particles of mean energy of 2 Joules are created in our Milky Way or in distant extragalactic objects.
Interesting article in the October 2016 issue of the American bi-weekly magazine ScienceNews.
Cosmic rays are mostly charged particles that reach Earth from outer space.