Mass density of the electromagnetic ether remains unknown

Ascertain the mass density of the electromagnetic ether (the Ω(1) substratum) through direct experimental or observational determination, and evaluate the consistency of empirical measurements with the theoretical estimate ρ1 = 5.831(02) × 10^−27 kg·m^−3 proposed in the vacuum mechanics framework.

Background

The paper proposes identifying dark energy with the Ω(1) substratum (electromagnetic ether) and provides a derivation of its mass density within vacuum mechanics, motivated in part by gravitational-wave observations suggesting c_gw ≈ c. Despite this theoretical estimate, the actual mass density lacks direct observational determination, constituting an explicit unknown highlighted by the authors.