>>11127494This. It's sad that this meme established itself.
Bounded spaces (orbits) where first found to give correct spectra/eigenvalues in what is today called functional analysis. Here, correct means quantized.
But in general, the spaces you look at are not compact (like the atom orbit, which is topologically S^1) and despite what it's name may be taken to suggest, "quantum theory" doesn't involve quantized (that is, discrete) spectra for all models it looks at.
The appearance of the Planck constant h in quantum mechanics mirrors it's simultaneous non-localization of conjugate variables w.r.t. the energy (e.g. position and momentum). It's doesn't prevent those observables from having expectation values on each point of the continuum.
