A cosmological basis for E = mc2

Abstract

The Universe has a gravitational horizon with a radius [Formula: see text] coincident with that of the Hubble sphere. This surface separates null geodesics approaching us from those receding, and as free-falling observers within the Friedmann–Lemaître–Robertson–Walker space–time, we see it retreating at proper speed [Formula: see text], giving rise to the eponymously named cosmological model [Formula: see text]. As of today, this cosmology has passed over 20 observational tests, often better than [Formula: see text]CDM. The gravitational radius [Formula: see text] therefore appears to be highly relevant to cosmological theory, and in this paper we begin to explore its impact on fundamental physics. We calculate the binding energy of a mass [Formula: see text] within the horizon and demonstrate that it is equal to [Formula: see text]. This energy is stored when the particle is at rest near the observer, transitioning to a purely kinetic form equal to the particle’s escape energy when it approaches [Formula: see text]. In other words, a particle’s gravitational coupling to that portion of the Universe with which it is causally connected appears to be the origin of rest-mass energy.