Why is the $SO(4)$ symmetry of the Hydrogen atom called dynamical?

Why dynamical?

My previous quantum mechanics teacher could not answer it.

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It involves the dynamics of the 1/r potential. The normal SO(3) symmetry that many systems exhibit is due entirely to spacetime symmetry; this has extra symmetry that is due to the nature of the interaction. –  jwimberley Jul 3 at 20:12