We now know that antiparticles exist not only for electrons, but for all fundamental particles. Indeed, one may speculate that there are distant galaxies made entirely out of antimatter. Such galaxies would emit light identical to the light emitted by galaxies such as ours we would have no way of telling that these photons came from quantum jumps of positrons rather than electrons.

It would, however, be most unwise to handle a piece of antimatter! When a particle meets its antiparticle they mutually annihilate, and literally disappear in a puff of light. The energy released in such an annihilation is carried away by photons of light.

It is not necessary to go to a distant galaxy to search for antimatter. Positrons are emitted in the radioactive decay of certain radioactive isotopes. Some such positron-emitting decays are given below:



6Ü11 ^ 5Bn + e+

T = 20.3 min

9F17 ^ 8O17 + e+

T = 1.2 min

9F18 ^ 8O18 + e+

T = 110 min

11Na22 ^ 10Na22 + e+

T = 2.6 yr

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