This often puzzles the young students. It is closely related to role of symmetries in nuclei. A spherically symmetric wave function, representing a spherical nucleus, remains invariant under rotation about any of the three principal axes. It does not involve any change in its observables like energy, angular momentum etc. You simply cannot tell if it has rotated. Such a presumed rotation does not involve any change in energy or any other observable. It is therefore not allowed physically. One may also say that it does not exist.
Prof. Ashok Jain Changed status to publish October 15, 2024