Читать книгу String Theory For Dummies - Andrew Zimmerman Jones - Страница 92

In an internal symmetry, some property of the system can undergo a change without changing anything that we may measure in an experiment.

For example, changing every particle with its antiparticle — changing positive charges to negative and negative charges to positive — leaves the electromagnetic forces involved completely identical. This is a form of internal symmetry called charge conjugation symmetry.