““Take an electron at rest. We can liberate its mass energy and transform it into different manifestations of energy by making it collide with a positron. The positron is the antiparticle of the electron: It has the same mass, but opposite charge. The total charge of the electron-positron system is zero; no conservation law forbids the transformation of an electron-positron system into pure energy. As a result, the collision between positron and electron (and, in general, particle and antiparticle) produces light of a very high energy, or of very high frequency. We might call it ultrablue light. In the process, the energies of both the electron and positron, of particle and of antiparticle, have been changed into radiation energy; into light.””
