Quantum Measurement, Gravitation, and Locality

This essay argues that when measurement processes involve energies of the order of the Planck scale, the fundamental assumption of locality may no longer be a good approximation. Idealized position measurements of two distinguishable spin-$0$ particles are considered. The measurements alter the space-time metric in a fundamental manner governed by the commutation relations $[x_i\,\,p_j]= i\hbar\,\delta_{ij}$ and the classical field equations of gravitation. This {\it in-principle} unavoidable change in the space-time metric destroys the commutativity (and hence locality) of position measurement operators.