New Scientist is carrying this article on the discovery that another "universal constant", well, isn't. This time it's the Mu constant, the ratio of a proton’s mass to that of an electron. By examining the hydrogen spectra of extremely distant quasars, a group of scientists are claiming to have discovered evidence that this constant has changed about 0.002% in the past 12 billion years. If confirmed, it could provide a powerful boost to string theory, whose multidimensional structure predicts just this thing.

Update: Link now works.