Coherence, Entropy, and the Arrow of Time: Why Time Has a Direction in a Phase Ontology

Coherence, Entropy, and the Arrow of Time: Why Time Has a Direction in a Phase Ontology (Phase Ontology — Part V) proposes a phase-centered explanation for one of physics’ strangest asymmetries: microscopic laws are largely time-symmetric, yet macroscopic reality is not. Cups shatter but do not reassemble; heat flows from hot to cold; correlations decay; memories accumulate. This paper argues that the arrow of time becomes conceptually clear once phase coherence is treated as ontologically primary. In this framework, time is not fundamental. It emerges operationally from countable phase evolution in physical clocks (all clocks are oscillators) and from synchronization between systems. A shared “global time” is therefore a relational structure sustained by coherence, not a background substance that governs dynamics. The paper then reframes entropy growth as the loss of accessible phase information in open systems. As systems interact with environments that contain many degrees of freedom, phase correlations disperse outward and become physically inaccessible, even if not destroyed in principle. Decoherence is elevated from a technical detail to the central engine of macroscopic irreversibility: reversing decoherence would require re-phasing an astronomically large environment, which is practically impossible. Building on Part III, the paper also interprets measurement as phase locking: once a macroscopic coupling stabilizes one local configuration, alternative phase possibilities are effectively dispersed into the environment. Classical definiteness and temporal irreversibility are thus treated as two faces of the same process—coherence flow. This manuscript is Part V of a seven-part series (Parts I–VII). It connects Parts I–IV to time asymmetry and points forward to Part VI (mass, inertia, gravitation) and Part VII (experimental implications and falsifiability).