Speakable and unspeakable in physics of time

Abstract

In order to discriminate speakable and unspeakable in physics of time, the single ion optical atomic clock and the double time-slit experiments are considered. Their description clarifies that temporal quantities such as time and frequency are fundamentally unspeakable, while speakable is only related to ratios between wavelengths and to boundary conditions of stationary light beams. In addition, time intervals lower than the minimum period realized by the experimental apparatus are the results of an extrapolation out of the domain of definition of measurement operations. A toy model is employed to isolate the hidden source of self-recursivity in the definition of clocks and time, which resides in the abuse of language generated by terms such as duration and repetitive event, instead of interval extension and multiplicity. The timeless scenario which emerges from the experimental picture is theoretically supported by fundamental timelessness of the Hamiltonian formalism employed to define dynamics. Clock metrology, employed to parametrize dynamics in experiments, works successfully as it returns a discrete time variable, which approximates the parametrization of the trajectories in the phase space induced by the invariance of the action and of the time independent Hamiltonian.