Hello everyone, thanks for reading. We all know that Quantum mechanics can be "ignored" when working with systems in which the typical distances and energies are big enough (compared to h, or other quantum constants). However, when I try to think of an explanation for it I'm not sure I hit the right one. Let's say I want to work out the Earth-sun System with Quantum Mechanics. That would mean I'd have to build a wave function for every atom in the system, or generally one terrible wave function describing the probabilities of all atoms to be found in certain positions. Well - when I think about it like that, I imagine a terribly chaotic function. Does the resolution has to do with the fact that probable deviations of the atoms from their most probable location are in the scale of 10-10[m]? Or is it something else? Thanks a lot. Tomer.