Relativistic deficiency in observation probability: Requestion the acceleration of cosmic expansion

This article predicts the relativistic deficiency in event's observability, by connecting quantum uncertainties with speed. The relationship operationally defines mass-carrying \textit{events} as the exclusive building elements of physical reality. The observed event-size is the multiplicative product of conjugate quantum uncertainties, which entails event's speed-compromised observability. The faster the event is, the less observable; \textit{free} massless particles thus disappear. Observational deficiency of events permeates ``vacuum'' and mass, both of which manifest a relativistic dark-fraction, making cosmic objects deceptively farther/accelerating. Reanalysis of high-redshift standard-candles' observational data ``decelerates'' the cosmos to a near-critical expansion and greatly minimizes the upper bound of the vacuum dark-energy.