First, read this; it's a two slit experiment carried out recently that is supposed to weaken the Copenhagen interpretation. http://en.wikipedia.org/wiki/Double-slit_experiment#Shahriar_Afshar.27s_experiment What are the stationary states physically? The problem with the stationary states is that they are stable i.e. if a particle is somehow in one of these states it remains in this state forever, if it does not interact with anything. I find it difficult to imagine a stable state that does not have the minimum energy possible, although such states are predicted by QM( I mean stable states having energies higher than the ground level). Second, what makes an electron attached to the atom? The smoke of mathematics involved in solving the Schrodinger equation for the hydrogen atom prevents me from seeing how does QM predict a stable atom? Also in books I am told that stationary states present no motion, so we have to build a superposition state to have time dependent expectations. Fine, let's pick an example to be specific, the harmonic oscilllator. Fine, then I find to my dismay that books compare the classical probability distribution for a classical "moving" harmonic oscillator to the stationary state probability distribution which comprises no motion. Also comparisons are carried out between the classical time averages and the expectation values for the same dynamical variables belonging to the stationary states.??????