How constant is the fine-structure constant?

How constant is the fine-structure constant? The most prominent dimensionless parameter in nature, α = e ²/4π∈ ₀ ħc ≈ 1/137, is fundamental to understanding atomic structure. Modern attempts at unified theories allow α and the other fundamental coupling constants to change with time. Since 1999, John Webb and his colleagues at the University of New South Wales in Australia have been reporting astronomical evidence purporting to show that α has changed slightly over cosmological time. They measure α at different redshifts z by looking for deviant spacings between absorption lines of quasar spectra due to intervening gas clouds along the line of sight. Now, using data from the high-resolution spectrometer at the 10-m Keck I telescope, they report that, during the cosmological epoch from z = 0.5 to 3.5, the average value of α was almost a part in 10⁵ less than it is now. It was a four-standard-deviation effect. A result so potentially important cries out for confirmation—or refutation. (J. K. Webb et al.., Phys. Rev. Lett. 87, 091301, 2001 http://dx.doi.org/10.1103/PhysRevLett.87.091301 .)