Everyday Antimatter

Today antimatter is used every day in medicine for brain scans. When electrons and positrons meet, at high energies, they can rematerialize as new particles and antiparticles, but at low energies, the electron-positron annihilations can used to reveal the workings of the brain in the technique called Positron Emission Tomography (PET). In PET, the positrons come from the decay of radioactive nuclei incorporated in a special fluid injected into the patient. The positrons then come in contact with electrons in nearby atoms. As the electrons and positrons are almost at rest when they come together, there is not enough annihilation energy to make even the lightest particle and antiparticle, so the energy emerges as two gamma rays that shoot off in opposite directions and can then be detected and analyzed to determine various aspects of the brain.

Cosmic rays from outer space were the first high-energy particles ever studied. A few cosmic rays pass through everyone every second of every day, It is difficult to work out the exact origin of cosmic rays, but many are thrown into space by supernovae, the huge explosions of dying stars. Cosmic rays hitting the outer atmosphere are mainly fast-moving, high-energy protons. As they hurtle towards the Earth, they collide with atoms in the air. Some of the collision energy reappears as the mass of new pairs of particles and antiparticles. Cosmic rays are thus a natural source of antiparticles.

Even though we see antimatter every day, we like to imagine the uses large amounts of it can be put to in our popular culture.