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This question already has an answer here:

Do quantum physics apply universally at all scales?

Where do quantum physics apply?

Does the nucleus of an atom abide by the laws of quantum physics?

Like do we know the definitive/velocity position of a proton or that of a neutron-proton pair?

In other words, to which bodies does the Uncertainty Principle apply?

Are there wave functions for neutrinos, protons, neutrons, quarks or just for electrons?

And can you make a wave function for a larger body such as a molecule?

Where is the limit?

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marked as duplicate by Danu, Ben Crowell, Rob Jeffries, ACuriousMind, Kyle Kanos Oct 28 '14 at 0:06

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Everywhere. $\endgroup$ – ACuriousMind Oct 27 '14 at 22:29
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    $\begingroup$ @ACuriousMind - Nice job making everywhere bold and following it with a period. The four characters needed to make everywhere bold plus the period were just enough to hit the 15 character limit on what constitutes a valid comment. Good thing the uncertainty principle doesnt apply to counting characters! I gave that comment a plus one just because of that. If I could give it a plus two I would because QM, as far as we know, is indeed valid everywhere. $\endgroup$ – David Hammen Oct 27 '14 at 23:01
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At our current state of knowledge, we would expect that quantum mechanics applies everywhere including at the scale of nuclei. However at the macroscopic everyday scale of objects (cars trucks buses planes), what it predicts is not generally different from the predictions of Newtonian mechanics, whereas at the size of atoms and atomic nuclei, the predictions of the behaviour of particles by quantum mechanics differs completely from what one would predict using Newtonian mechanics. There may be circumstances (distance scales, time scales,energy scales for example) in which quantum mechanics as we presently know it, is not an adequate description of nature. Those we are still seeking!

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