Electromagnetic particle shower. Particle tracks (moving from right to left) showing multiple electron-positron pairs created from the energy of high-energy gamma ray photons produced by neutrino collisions. The positron is the anti-particle of the electron, and this process is called pair-creation. Electrons and positrons are charged particles and form these paired spirals as they curve away from each other in a magnetic field. As they do so, they radiate photons, which in turn produce new electron-positron pairs. This shower of particle creation continues until the energy of the original photon is used up. This photograph was taken in the 15-foot bubble chamber at Fermilab. The region shown here is about 2 metres wide.