Abstract
The detection of Mg ii fine structure and hydrogen hyperfine absorption lines toward the radio source AO 0235 + 164 allows us to place upper limits on the variability of three products of the fine-structure constant, the nuclear factor of the proton, and the ratio of electron to proton mass, viz. , and . Since the spectral lines are observed at a high red shift, , the limits obtained on the variation with time of these quantities (adopting as a measure of the Hubble expansion) apply over at least 35% of the age of the universe.
- Received 25 February 1976
DOI:https://doi.org/10.1103/PhysRevLett.37.179
©1976 American Physical Society