© David Kaplan.
The movie shows an electron (e-) and its anti-particle, the positron (e+), colliding at high energies and annihilating each other, creating a muon (μ-) and anti-muon (μ+) pair. This process has been seen millions of times at high-energy colliders, for example at the Large Electron-Positron collider at CERN. It reveals two stunning facts about Nature—that neither mass nor matter is conserved. The total energy, however, is always conserved.