Theories unifying gravity with other interactions suggest the spatial and temporal variation of the fundamental “constants” in the Universe. A change in the fine structure constant alpha (combination of electron charge, speed of light and “quantum” Planck constant) could be detected via shifts in the rest wavelengths of resonance transitions in quasar absorption systems. We have developed a new approach which improves the sensitivity of this method by an order of magnitude and measured alpha in 140 absorption systems covering look-back times from 0.2 to 0.9 times the age of the Universe. Our initial results published in 1999 hinted that alpha may have been smaller in the past. Startlingly, new results based on 3 independent data sets now support the same effect.

These data have inspired a more general discussion of possible variation of other constants. We have considered variation of strong interactions and quark masses and derived the limits on their relative change from (i) primordial Big-Bang Nucleosynthesis; (ii) Oklo natural nuclear reactor which was active about 2 billion years ago; (iii) quasar absorption spectra, and (iv) laboratory measurements of hyperfine intervals in atoms which are used as frequency standards.

Vladimir Dzuba, Victor Flambaum,
Michael Murphy and John Webb.