### Abstract

The Universe has a gravitational horizon with a radius Rh = c/H 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 c, giving rise to the eponymously named cosmological model Rh = ct. As of today, this cosmology has passed over 20 observational tests, often better than νCDM. The gravitational radius Rh 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 m within the horizon and demonstrate that it is equal to mc2. 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 Rh. 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.

Original language | English (US) |
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Article number | 1950055 |

Journal | International Journal of Modern Physics A |

Volume | 34 |

Issue number | 10 |

DOIs | |

State | Published - Apr 10 2019 |

### Keywords

- General relativity
- exact solutions
- mathematical and relativistic aspects of cosmology
- observational cosmology
- relativity and gravitation

### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics
- Nuclear and High Energy Physics
- Astronomy and Astrophysics