We can built one say, with cobalt, magnets and electron detectors which detect the presence of b-decay electrons and count them. Then we will have a mirror clock which counts less and so different time. This meant that some parts of right and left symmetry were still maintained but it was interconnected to matter , antimatter relationship and matter to the right was symmetrical with matter to the left. This implies a cosmic favoritism for matter over antimatter. A certain number called the baryon number was introduced as a conservation law.
Baryon number is and has been constant throughout the life of the universe.
The special assumptions about the begining of the universe tells an equality of particles to antiparticles. The problem with this assumption in this assumption is that it meant that we should be seeing 1018 photons for every proton or antiproton today which is not the case. Now, that we have basic knowledge about symmetries, we can approach where CP-violation arises from. Combinations of these symmetries also take place. Describes the interaction of charged particles through the electromagnetic force.