Evidence for Time Variation of the Fine Structure Constant

A method offering an order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant $\alpha$. Applying the technique to a sample of 30 absorption systems, spanning redshifts $0.5<z1$, where $\Delta \alpha /\alpha =-2.6\pm 0.4\times 10^{-5}$. For $z<1$, $\Delta \alpha /\alpha =+0.2\pm 0.4\times 10^{-5}$, consistent with other known limits. Whilst we cannot rule out either a systematic error in the data, or some different physical explanation, we cannot reliably identify any such mechanism. These results are consistent with a time-varying $\alpha $.