Black holes may not constrain varying constants
  New and rather controversial observations hint that the fine structure constant \alpha may have been smaller in the early universe, suggesting that some of the fundamental ``constants'' of physics may be dynamical. In a recent paper, Davies, Davis, and Lineweaver have argued that black hole thermodynamics favors theories in which the speed of light c decreases with time, and disfavors those in which the fundamental electric charge e increases. We show that when one considers the full thermal environment of a black hole, no such conclusion can be drawn: thermodynamics is consistent with an increase in \alpha whether it comes from a decrease in c, an increase in e, or a combination of the two. 
S. Carlip, S. Vaidya