
58 Questioning the Universe: Concepts in Physics
7.4.4 MATTER-ANTIMATTER SYMMETRY (MATTER REFLECTION)
Some of you may have heard about antimatter before, possibly in some science c-
tion story. Antimatter is real but very rare. It can be produced in particle accelerators,
in some radioactive decays, and naturally in cosmic rays from outer space. In fact,
for every type of ordinary matter there is its corresponding antimatter. An antipar-
ticle has the same mass as its particle partner, but all other properties are opposite.
For instance, the electron has a negative electric charge, while its antiparticle, known
as the positron, has a positiv ...