Gavitational potential originating from distant masses of the universe is about 108 times larger than the Sun's gravitational potential at the Earth's distance, and yet the latter can keep the Earth in its orbit.
It cannot be excludd that luminal speed according to c2 = 2GMu/Ru is essentially determined and limited by the gravitational potential of distant masses (subscript u). Notably, Einstein 1911 found light deflection close to the Sun to result from locally enhanced gravitational potential.
So it also cannot be excluded that electromagnetic properties of vacuum space according to 1/(ε0µ0) = 2GMu/Ru are essentially determined by the gravitational potential from distant masses.
Accidentally or not, it appears noticeable that the potential energy of a mass m at the gravitational potential of the universal masses approximately corresponds to the relativistic energy equivalent E = mc2.
Finally, a characteristic deceleration observed on rapidly spinning rotors also indicates a possible interaction with distant masses.