10. Symmetry and CPT invariance

Charge conjugation(C), Parity(P) and Time reversal(T) can be thought as three special mirrors where reflected phenomena are sometimes identical to the original phenomenon.
P acts exactly like a mirror reversing the space coordinates.
T reverses time (i.e. t is replaced by -t in physical laws).
C reverses the electric charge and all quantum numbers transforming matter in antimatter.

Each of these symmetries can be individually violated, but scientists thought that C+P would always be valid. It came as a shock when an experiment with elementary particles showed that this is not true.

But what about C+P+T and why we should care? Well, many experiments are studying this matter that has some surprising consequences. For example some symmetry violation can explain why the Universe is made only of matter.

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