For every billion or so matter–antimatter pairs that annihilated into light, roughly one matter particle survived, and every star and every human body is built from that residue. The ratio is read off the microwave background, so it is a measurement rather than a guess. In 1967 Sakharov set out three conditions for generating such an imbalance: baryon number violation, violation of C and CP, and a departure from thermal equilibrium. The Standard Model meets all three, but the CP violation measured in kaons and B mesons is far too weak for the observed surplus, so a missing piece of physics remains.
For every billion or so matter–antimatter pairs that annihilated into light, roughly one matter particle survived, and every star and every human body is built from that residue. The ratio is read off the microwave background, so it is a measurement rather than a guess. In 1967 Sakharov set out three conditions for generating such an imbalance: baryon number violation, violation of C and CP, and a departure from thermal equilibrium. The Standard Model meets all three, but the CP violation measured in kaons and B mesons is far too weak for the observed surplus, so a missing piece of physics remains.
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