The Buzz about Antimatter

This photograph shows particle tracks in a cloud chamber. As charged particles pass through the supersaturated vapor in this chamber, they leave behind a visible trail of tiny droplets.

Notice the pairs of curved trails that meet at the top of the image to form a curved, upside-down "v" shape. The curvature results from a magnetic field at right angles to the plane of the photograph, which bends the paths of charged particles into circular arcs. The opposite curvature of the lines that make each "v" shows that the charges of the two particles are opposite.

The positrons created in this experiment are one kind of antimatter. Each particle of ordinary matter, such as the electron and the proton, has an antimatter counterpart, with the same mass but opposite charge, as shown in the table. A high-energy photon that passes near a massive nucleus can decay into a particle-antiparticle pair. The cloud chamber photograph shows an example of how the energy of radiation changes into the energy of mass.

Imagine the opposite process—bringing an electron and a positron together. The result can be the annihilation of both particles and the creation of two gamma ray photons. In this case, the energy of mass changes into the energy of radiation.

Particle tracks in a cloud chamber