 Particle physicists found astrophysics necessary due to difficulty in producing particles with comparable energy to those found in space.For example, the cosmic ray spectrum contains particles with energies as high as 1020 eV, where a proton-proton collision at the Large Hadron Collider occurs at an energy of ~1012 eV.The field can be said to have begun in 1910, when a German physicist named Theodor Wulf measured the ionization in the air, an indicator of gamma radiation, at the bottom and top of the Eiffel Tower.