A Beginner's Guide to Antimatter

Lab. for Energetic Particle Science A Penning Trap Penning traps use a combination of low temperatures and electromagnetic fields to store antimatter. While the traps can only store incredibly small quantities, the traps will help in developing the technologies needed for advanced propulsion concepts.

Interestingly, there is no real difference between particles and antiparticles in particle physics theories. They are equivalent. Most theoreticians believe that at the time of the Big Bang antiparticles and particles were created in almost equal numbers. But why, then, is antimatter so rare today?

The tentative answer (and it is tentative, since this question is a topic of on-going research) is in the word almost. Present theory suggests that if particles outnumbered antiparticles in the Big Bang by as little as one part in 100 million, then the present universe could be explained by those extra particles that were not annihilated by an antiparticle counterpart. Other theories suggest that even if identical amounts of antimatter and matter were created in the Big Bang, the physics of antimatter and matter are slightly different. This hypothesized difference would favour residual matter after all original antimatter had been annihilated.

So that's what antimatter is. Are we sure that there is no antimatter left in the universe?

Dr. Charles Meegan, an astrophysicist at the Marshall Space Flight Centre, noted that orbiting gamma-ray observatories have measured the sky in the range of energies that would have detected the telltale signature of antimatter annihilation.

"None of the instruments flown to date have uncovered evidence for vast amounts of antimatter in the universe," says Meegan.

There is evidence that very energetic reactions are taking place in isolated spots -- in the cores of some galaxies and quasars, for example -- that create antimatter which then annihilates. But this is not thought to be residual antimatter left over from the Big Bang.