The law of right-left symmetry was used in classical physics but was not of any great practical importance there. One reason for this derives from the fact that right-left symmetry is a discrete symmetry, unlike rotational symmetry, which is continuous.

The three discrete invariances - reflection invariance, charge conjugation invariance, and time reversal invariance - are connected by an important theorem called the CPT theorem.

The strongest interactions are the nuclear interactions, which include the forces that bind nuclei together and the interaction between the nuclei and the z mesons. It also includes the interactions that give rise to the observed strange-particle production.

Chen-Ning Yang Quotes