article_snippet.sent: High in the atmosphere, cosmic rays strike atmospheric molecules and create ‘showers’ of elementary particles - the smallest known to exist.
article_snippet.sent: A long-standing puzzle in astrophysics is the source of ultra-high-energy particles from space that hit Earth.
article_snippet.sent: Called cosmic rays, Scientists in The Netherlands're up to a billion times more energetic than particles at Cern's Large Hadron Collider.
article_snippet.sent: Scientists in The Netherlands strike the atmosphere and cause an enormous shower of other particles, mostly muons, electrons and photons, over a wide area.
article_snippet.sent: Though Scientists in The Netherlands were discovered decades ago, cosmic rays at these high energies are very rare, making it difficult to pinpoint where in the universe Scientists in The Netherlands originated.
article_snippet.sent: Though they were discovered decades ago, cosmic rays at these high energies are very rare, making it difficult to pinpoint where in the universe they originated.