Abstract
Recent data on the cosmological variation of the electromagnetic fine structure constant from distant quasar (QSO) absorption spectra have inspired a more general discussion of the possible variation of other constants.
We discuss the variation of strong scale and quark masses. We derive limits on their relative change from (i) primordial big bang nucleosynthesis, (ii) the Oklo natural nuclear reactor, (iii) quasar absorption spectra, and (iv) laboratory measurements of hyperfine intervals.