“The mystery about α is actually a double mystery. The first mystery – the origin of its numerical value α ≈ 1/137 has been recognized and discussed for decades. The second mystery – the range of its domain – is generally unrecognized.” -Malcolm H. MacGregor
We assume that the fundamental constants are truly constant, but they don’t have to be. The speed of light is the same everywhere, but it could have been different elsewhere, either in space or in time. The same is true for other constants, like Planck’s constant, the gravitational constant, or even the fundamental charges or masses of particles. You might not think it’s likely, but the evidence indicated otherwise.
Spatial variations in the fine-structure constant are indicated from a previous, 2011 study. Image credit: J.K. Webb et al., Phys. Rev. Lett. 107, 191101 (2011).
Over the past 20 years, time variations and spatial variations in the fine structure constant, which determines the force of the electromagnetic coupling, have been observed to about 5 parts in a million in different locations and at different distances. It was a disputed but intriguing finding, but new evidence was just released conflicting with those results. Instead, the fundamental constant, α, once again appears to be truly constant, to better than 1.3 parts in a million, thanks to the new results from Arecibo.
An ultra-distant quasar will encounter gas clouds on the light’s journey to Earth, allowing us to measure α. Image credit: Ed Janssen, ESO.