HOW do you detect the most energetic particles in the Universe? Easy,
according to two physicists based in the US and Spain. You just point a radio
telescope at the Moon and listen for the ping as “cosmic ray” particles drill
their way into the lunar soil.
The highest-energy cosmic rays, primarily protons and atomic nuclei, are
millions of times more energetic than those from Earth-bound particle
accelerators with energies of more than 1020 electronvolts. Such particles are
also exceptionally rare: each square kilometre of the Earth’s surface will be
struck by one only once a century on average.…
