Observations and events

Whether a space-time event is observed or not, its physical nature will not depend on the inertial frame of reference used for its mathematical description. Hence one can produce a non-dispersive de Broglie wave packet whose center adds a localising function to the wave mechanical description of a particle. Once observed, the past history of this function will describe the track of the particle up to the observation. It is here shown that this packet turns the quantum mechanical description of a single particle from mathematical tool to understandable physical theory.