INCERTO TEMPORE, INCERTISQUE LOCI - CAN WE COMPUTE THE EXACT TIME AT WHICH A QUANTUM MEASUREMENT HAPPENS

Without addressing the measurement problem (i.e., what causes the wave function to ''collapse,'' or to ''branch,'' or a history to become re alized, or a property to actualize), I discuss the problem of the timi ng of the quantum measurement: Assuming that in an appropriate sense a measurement happens, when precisely does it happen? This question can be posed within most interpretations of quantum mechanics. By introdu cing the operator M. which, measures whether or not the quantum measur ement has happened I suggest that, contrary to what is often claimed, quantum mechanics does provide a precise answer to this question, alth ough a somewhat surprising one.