  Cosmological variations in the fine structure constant, alpha, can be probed
through precise velocity measurements of metallic absorption lines from
intervening gas clouds seen in spectra of distant quasars. Data from the
Keck/HIRES instrument support a variation in alpha of 6 parts per million. Such
a variation would have profound implications, possibly providing a window into
the extra spatial dimensions required by unified theories such as
string/M-theory. However, recent results from VLT/UVES suggest no variation in
alpha. The COsmic Dynamics EXperiment (CODEX) spectrograph currently being
designed for the ESO OWL telescope (Pasquini et al 2005) with a resolution high
enough to properly resolve even the narrowest of metallic absorption lines,
R>150,000, will achieve a 2-to-3 order-of-magnitude precision increase in
Delta\alpha/alpha. This will rival the precision available from the Oklo
natural fission reactor and upcoming satellite-borne atomic clock experiments.
Given the vital constraints on fundamental physics possible, the ELT community
must consider such a high-resolution optical spectrograph like CODEX.
