Wikipedia's article on macroscopic quantum tunneling says
Quantum phenomena are generally classified as macroscopic when the quantum states are occupied by a large number of particles (typically Avogadro's number) or the quantum states involved are macroscopic in size (up to km size in superconducting wires).
To comply with copyright laws, the following is an edited paraphrase of this reference, pp6-7.
http://assets.cambridge.org/97805218/00020/sample/9780521800020ws.pdf
The term “dynamical degrees of freedom” should be used carefully. Imagine a baseball moving through a wall without being compressed. Certainly, this phenomenon can be called a macroscopic tunneling; since the ball is a collection of atoms, the number of degrees of freedom is comparable to the number of atoms.
Macroscopic tunneling depends on the number of microscopic degrees of freedom like the positions of constituent atoms. Collective degrees of freedom are superior: they are singled out by rearranging the microscopic ones.
Are there any circumstances under which the ball could pass through the wall via macroscopic quantum tunneling, or is this wishful thinking?
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