Finite Inertia and the Cosmological Decay of Kinetic Energy

This theoretical work proposes a thermodynamic reinterpretation of inertial motion in which macroscopic kinetic energy is viewed as a temporary borrowing from a primordial energy reservoir associated with the initial state of the universe. Newton’s first law is treated as an excellent approximation on human and astronomical timescales, while uniform rectilinear motion is hypothesized to be metastable and subject to ultra-slow decay on cosmological scales. A simple phenomenological discrete model is presented to illustrate the gradual repayment of kinetic energy to potential and distributed forms, preserving global energy conservation. The hypothesis aligns the apparent eternity of inertia with the universal thermodynamic tendency toward maximum entropy and the eventual heat death of the universe, without contradicting established physics in accessible regimes. No empirical violation of Newtonian or relativistic mechanics is claimed within current observational limits. Keywords inertia; kinetic energy decay; primordial energy reservoir; thermodynamic cosmology; metastable motion; heat death; Big Bang excitation; energy borrowing; Newton’s first law; cosmological timescales; energy conservation; phenomenological model; uniform rectilinear motion; entropy maximization; isolated systems