ABSTRACT
The Friedmann-lemaitre-Robertson-Walker (FLRW) metric is a special, well-studied member of the general class of spherically-symmetric spacetimes describing systems undergoing gravitational collapse or expansion. An FLRW universe constrained by the zero active mass equation-of-state should leave a tell-tale signature on fundamental physics, given that it uniquely has a gravitational radius receding at light speed from the observer. This chapter begins to explore the impact of this null gravitational horizon on local physics by calculating the binding energy of a mass due to its gravitational attraction to that segment of the Universe with which it is causally connected. The identification of rest-mass energy with the binding energy inside our gravitational horizon is quite compelling. The fact that only a FLRW metric with the zero active mass equation-of-state, producing a null gravitational horizon, uniquely allows us to draw this conclusion is another important confirmation—along with the observational evidence concerning the redshift-age relation—of the theoretical argument.
