Evidence for large-scale uniformity of physical laws

Consideration is given to the coincidence of redshifts deduced from 21 cm and resonance transitions in absorbing gas detected in front of four quasi-stellar objects which results in stringent limits on the variation of the product of three physical constants both in time and space. It is found that (sigma-squared) (gp) (m/M), where gp is the proton gyromagnetic ratio, is spatially uniform, to a few parts in 10,000, throughout the observable universe. These limits are shown to be largely model independent, relying only upon the cosmological interpretation of redshifts and the isotropy of the 3 K background radiation. It is concluded that a quantity as complex as gp being uniform throughout most of spacetime, even in causally disjoint regions, suggests that all physical laws are globally invariant.