The real thing |
 Electron-positron pairs in a hydrogen bubble chamber photograph. The paths of particles are visible as a line of tiny bubbles due to the ionizing effect, that is responsible for the line of droplets in a Wilson cloud chamber, and for the cascade of charge in a Geiger counter. |
| The opposite sign of the members of the pairs (formed apparently out of nothing as a gamma ray interacts with matter) is disclosed by their opposite curl in the vertical magnetic field. The paths are spirals rather than circles because collisions quickly reduce the particle energy and velocity. |