The fundamental constants are central to our theories of physics, yet those theories offer no understanding of the constants, no way to calculate them. If the constants were found to vary, we might learn what they depend on and perhaps glimpse a more fundamental theory, perhaps 'the' theory. For a decade we've found that a, the fine-structure constant, which characterises electromagnetism's strength, is slightly smaller in distant galaxies, at least those appearing in the northern sky, than on Earth. But now, with measurements over both hemispheres, we find evidence for a dipole-like variation in a across the sky. The fine-structure constant a could be the first fundamental constant that isn't.
Vol. 49, no. 2 (2012), pp. 43-48