Macroscopic Bodies in Quantum Theory

It is shown that if the wave function of a massive body is ψ=Σc_nψ_n, where the ψ_n are macroscopically distinguishable states, then the observation of interferences between the various ψ_n requires inconceivable laboratory conditions (e.g., the experiment may last longer than the lifetime of the universe). It is therefore proposed to interpret Σc_nψ_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.