# Realistic clocks for a Universe without time

## TL;DR

This paper explores using a damped harmonic oscillator as a realistic clock within the conditional probability interpretation of a timeless universe, addressing issues of time in quantum gravity.

## Contribution

It demonstrates the viability of a damped harmonic oscillator as a realistic clock and analyzes its consistency with the conditional probability approach to timeless quantum cosmology.

## Key findings

- The damped harmonic oscillator can serve as a consistent clock system.
- Optimal clock performance is not necessarily achieved with minimal damping.
- Restrictions on damping factors are established for clock viability.

## Abstract

There are a number of problematic features within the current treatment of time in physical theories, including the "timelessness" of the Universe as encapsulated by the Wheeler-DeWitt equation. This paper considers one particular investigation into resolving this issue; a conditional probability interpretation that was first proposed by Page and Wooters. Those authors addressed the apparent timelessness by subdividing a faux Universe into two entangled parts, "the clock" and "the remainder of the Universe", and then synchronizing the effective dynamics of the two subsystems by way of conditional probabilities. The current treatment focuses on the possibility of using a (somewhat) realistic clock system; namely, a coherent-state description of a damped harmonic oscillator. This clock proves to be consistent with the conditional probability interpretation; in particular, a standard evolution operator is identified with the position of the clock playing the role of time for the rest of the Universe. Restrictions on the damping factor are determined and, perhaps contrary to expectations, the optimal choice of clock is not necessarily one of minimal damping.