Maggie McKee in New Scientist:
A new study of distant galaxies is adding a fresh perspective to the debate over whether a fundamental physical constant has actually changed over time. The work suggests the number has not varied in the last 7 billion years, but more observations are still needed to settle the issue.
The controversy centres on the fine-structure constant, also called alpha, which governs how electrons and light interact. Alpha is an amalgam of other constants, including the speed of light. So any change in alpha implies a change in the speed of light – and indeed in the entire standard model of physics – with string theories touting extra spatial dimensions stepping in to fill the breach.