When you are interested in physics you must read “Unbelievable“!
The experiments of Rutherford (1871-1937) lead to the first atomic model, which was named after him. The Rutherford-model, based on the diffraction of a-beams, could not explain the stability and the discrete energy level of atoms.
In order to be able to describe the existence of stable atoms and discrete energy levels, Bohr (1885-1962) introduced his thesis. Bohr, and Heisenberg, Dirac and Schrödinger in their work, lead to the complete mathematical solution of the atomic model.
The QM-solutions however are, to a certain degree, unsatisfactory because these solutions do not describe the physical processes that lead to, for example, the allowed discrete energy levels of atoms. Knowledge of the physical processes responsible for QM would endorse the already undisputable position.
The principal quantum number for atoms n coincides with fixed energy levels of the atom. The energy quantisation of the atom can be seen to originate from distance quantification. Analyzing this possibility we encounter strong direct and circumstantial evidence pointing to the existence of the Quantum Distance.
Next chapter: The Mechanical Free Rotator