Macroscopic Bodies in Quantum Theory

Abstract

It is shown that if the wave function of a massive body is $\ensuremath{\psi}=\ensuremath{\Sigma}{c}_{n}{\ensuremath{\psi}}_{n}$, where the ${\ensuremath{\psi}}_{n}$ are macroscopically distinguishable states, then the observation of interferences between the various ${\ensuremath{\psi}}_{n}$ requires inconceivable laboratory conditions (e.g., the experiment may last longer than the lifetime of the universe). It is therefore proposed to interpret $\ensuremath{\Sigma}{c}_{n}{\ensuremath{\psi}}_{n}$ as a mixture of states, and not as a superposition. This new interpretation of wave functions is consistent with experience and is free from the paradoxical features of the "orthodox" measurement theory.