I am not asking about a boundary between classical and QM objects. There are many questions on this site about such a boundary. I am simply asking about an object being able to be at rest (in the lab frame).
Matter around us is built up of quarks and electrons. Both quarks and electrons are QM objects, and they cannot be at rest (have zero momentum, HUP).
With this answer I am trying to stress that at the level of nanometers and below, the atomic and molecular dimensions, the concept of "at rest" is a classical concept that has no meaning in a quantum mechanical system. The classical framework has to be abandoned once the dimensions and momenta are constrained by the HUP.
Although quarks and electrons both possess rest mass, this is just invariant mass (the length of the four vector), and has nothing to do with the electrons or quarks being at rest.
Objects though, that are being built up by electrons and quarks, around us, can be at rest (relative to us).
If I start by building quarks (protons and neutrons) and electrons together, then bind more atoms via covalent bonding, I will have to reach a level at which the object will be able to stay at rest in the lab frame.
I have not found any such experiment, and I do not know if this has anything to do with Avogadro's number.
I do believe that the true underlying world is QM, and all objects are QM, but I would like to know if there is a level at which the ability of being at rest (relative to the lab frame) becomes apparent.
- How many elementary particles (or atoms) do I have to bind together to create an object that is able to stay at rest (in the lab frame)?