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An introduction to the science of anti-matter
So, how did the story of anti-matter begin?
The story began in 1928 when the British physicist Paul Dirac formulated a theory which described the behaviour of electrons in electric and magnetic fields. Theories like this had been formulated before, but Dirac’s was unique in that it included the effects of Einstein’s special theory of relativity and also the effects of quantum physics. Dirac’s equation worked very well, but in the same way as the equation x2 = 4 has two solutions (x = 2 or x = -2) so did this equation predict multiple solutions. This led to a surprising prediction that the electron must have an anti-particle having the same mass but a positive electrical charge, the opposite of a normal electron's negative charge.
Dirac interpreted this to mean that for every particle that exists there is a corresponding anti-particle, exactly matching the particle but with opposite charge. He won a Nobel Prize for this work, and in his Nobel Lecture, he even went as far as to speculate that there might be an entire universe of anti-matter.
The search for this anti-electron began in the 1930s and in 1932 Carl Anderson, a young professor at the California Institute of Technology, observed this new particle experimentally and it was named the "positron." In 1936 he won a Nobel Prize for his discovery.
The search for anti-protons then began, but it wasn’t until 1954, twenty-two years after positrons had been observed, that man had the power to create the necessary energy to produce anti-protons. The machine used to create this was the 'Bevatron', built at Berkeley by Nobel Prize winner Ernest Lawrence. Meanwhile, a team of physicists, headed by Emilio Segre, designed and built a special detector to see the anti-protons. They succeeded in detecting anti-protons, further proving the existence of anti-matter and winning Segre and his team a Nobel prize. Just twelve months after the discovery of the anti-proton, a second team working with the Bevatron discovered the anti-neutron.
Once all three particles that make up atoms (electrons, protons and neutrons) had been discovered, scientists wanted to find whether anti-particles bound together in anti-atoms were the basic units of anti-matter. They wanted to know if matter and anti-matter are exactly equal and opposite as Dirac had implied. In 1965, two teams of scientists, one headed by Antonino Zichichi and the other by Leon Lederman, made simultaneous observations of anti-deuteron, a nucleus made out of an anti-proton plus an anti-neutron.
In 1995, scientists created the first anti-hydrogen atom at the CERN research facility in Europe. Normal hydrogen atoms consist of one proton and one electron, so they created them by combining the anti-proton with a positron. When these anti-hydrogen atoms are produced, they are travelling at nearly the speed of light and typically last only about 40 nanoseconds.
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Content last updated: 16/06/2000
