I don't quite understand why macroscopic objects we encounter in everyday life don't exhibit quantum probabilistic behavior. For example, the car standing in front of my house has a definite position and definite boundaries rather than being dissolved in some cloud where it's not clear whether it stands in front of my house or on the other side of the street. I have heard that the reason is because the quantum wave lengths of particles are very small relative to the size of macroscopic objects. If this is true, how large is the wave length of an electron? Doesn't the wave spread out across all universe? Or is the probability of the electron's position distributed in such a way that significant probabilities are concentrated in a very small area, perhaps a fraction of a milimeter, while the rest of the wave has negligible probabilities? Another reason I have heard is decoherence - that quantum waves are somehow suppressed because of interactions of particles. I'm not sure this answers my question though, because it is claimed that decoherence has been avoided for example in superconductors, but still I suppose that a macroscopic piece of superconductor has a definite position and boundaries and is not jumping unpredictably from one corner of the laboratory to another?