I'm not quite sure which forum I should post this in; it's related to my school work but I don't have any homework questions about it. Rather, I am just confused about what it really is and what it means. Hopefully it goes here. I get that the projection of the angular momentum along some reference axis is quantized. My question is what does this mean physically and how does it lead to the band splitting in the Stern-Gerlach experiment? Also, why is it called space quantization rather than angular momentum quantization? I read that the angular momentum is quantized against some reference axis, which may be arbitrary. This is precisely why I am confused about the S-G experiment. If the reference axis is arbitrary, then there is no reason to apply the same reference axis to all atoms in a collection. Therefore, why does the Stern-Gerlach experiment only show two bands, rather than a dispersion as each atom travels to a location on the plate as dictated by its own angular momentum projection? Finally, if it is "just" the angular momentum projection that's quantized, why is it called space quantization? Is this some sort of mild misnomer, or are the implications of angular momentum quantization going over my head? Does a.m. quantization imply something about quantization of position (or something else) across all coordinates in space? Thanks for any replies; I'm pretty confused on this topic.