the term is multiplied by its complex conjugate,
to give unity for the time dependence.
This expresses the conclusion of Problem 11.12: the dipole moment
never gets larger or smaller, it just changes direction, and the
radiation pattern follows it. If you stood on top of it and
rotated with it (as we certainly do on the Earth) you would see
a fixed intensity profile and the fact that it radiates at all
would be confusing if you failed to notice that you were in a
rotating reference frame.
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