Demonstration of Quantum Mechanics in the Large

An example is given which demonstrates in a straightforward and dramatic manner that when two particles like ($K^0+{\overline{K}}^0$) or ($2\gamma$) are created simultaneously, the probabilities involved in observing any further events related to their simultaneous creation must be calculated quantum mechanically and are correlated, even for macroscopic distances in absorbing media. In particular, a correlation in the polarization of the two $\gamma$ rays from positronium annihilation as a function of the thickness of magnetized iron through which they are passed is pointed out by way of a proposed experiment.