We have measured the interaction probability (also known as cross section) for two protons coming at each other with various energies. While colliders provide a probe to very high energies, the highest energies are only accesible in cosmic ray experiments. Not only can cosmic rays be used to probe particle physics, they are the only means of doing so at the highest energies.

The red data points are from the LHC, with the red dashed line is the farthest the LHC will get. The blue data points are from cosmic rays, and the dashed line is the highest energy cosmic ray observed to date.