A cosmic conundrum

Each charged elementary particle has a counterpart with the opposite charge, which is known as an antiparticle. The antiparticle partner of the negative electron, for example, is the positive positron, which was predicted by Paul Dirac in 1930 and discovered by Carl Anderson in 1932; while for the proton it is the antiproton, which was discovered by Emilio Segré and Owen Chamberlain in 1955. Just like normal particles, antiparticles can combine, forming atoms of "antimatter". Dirac's theory suggested that the laws of physics were exactly the same for matter and antimatter; so given this symmetry, why is our visible universe made of matter with no antimatter? This is the question addressed by Helen Quinn and Yossi Nir in The Mystery of the Missing Antimatter .