 Ultra-high-energy cosmic ray

Ultra-high-energy cosmic rays (UHECRs) are extremely energetic particles originating from outer space that strike Earth with energies exceeding \(10^{18}\) electron volts (eV). To put this into perspective, these energies are several orders of magnitude greater than those produced in the most powerful man-made particle accelerators on Earth. UHECRs are primarily composed of protons, although they can also include heavier nuclei and possibly other types of particles.

Sometimes it feels like this could be how we finally make experiments to see what the theory of everything looks like, a bit like the first high energy experiments were from less exotic cosmic rays.