On the Interpretation of Cosmic Acceleration

The usual cosmic acceleration concept, labeled as $q$, is based on distances in a 3D space-like coordinate, representing events that lack causal connection. While using $q$ isn't inherently wrong, it requires extending observations (such as luminosity distance) into non-observable territories, leading to an inaccurate interpretation of the physics behind the observations. For a correct interpretation, we propose a new measure, $q_E$, based on the distance between causal events in 4D null space. We compare $q_E$ and the standard $q$ using data from supernovae (SN) and radial galaxy/QSO clustering (BAO). The usual $q$ analysis shows tension between SN and BAO, but this tension vanishes with $q_E$, indicating that our new definition better aligns with observations. The data indicates that cosmic expansion is actually decelerating, with events seemingly enclosed within an Event Horizon, similar to the interior of a Black Hole. Instead of a new dark energy or modified Gravity, it appears that $\Lambda$ acts as a boundary force causing an attractive force, akin to a rubber band preventing further expansion. Thus, contrary to common belief, it's more accurate to interpret current measurements of cosmic expansion as deceleration rather than acceleration.