Thunderstorms make antimatter

This is pretty cool. Apparently thunderstorms make antimatter. NASA have a space telescope called Fermi that has been orbiting earth for the last 3 years. It has detected gamma rays that have the energy which corresponds to an electron and a positron annihilating each other.

Fermi is designed to monitor gamma rays, the highest energy form of light. When antimatter striking Fermi collides with a particle of normal matter, both particles immediately are annihilated and transformed into gamma rays. The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.

Terrestrial gamma-ray flash at 2 ms

Thunderstorms create enormous magnetic fields which cause electrons to accelerate to high speed. When these high speed electrons hit air molecules they slow releasing energy in the form of gamma rays. This is similar to the mechanism by which we make x-rays. X-rays are created by speeding up electrons with a electric field in a vacuum and striking them on a metal plate. On slowing they release their energy as x-rays (a little more complicated than this). These x-rays are used for various purposes, frequently in medical diagnostic equipment. X-rays are high energy, but lower than that of gamma rays. Some of these gamma rays formed by the thunderstorm have high enough energy to turn into an electron-positron pair, the positron subsequently annihilating when it combines with another electron.

Wikipedia