Once upon a time, I was involved in an abortive attempt to measure the variation of the fundamental constants. Thanks to that experience, I’ve always had an interest in these measurements, so a new paper describing an alternative way to detect changes in fundamental constants caught my eye.
The fundamental constants—the speed of light, Planck’s constant, the charge of the electron, etc.—are taken to be fixed in value. But there is no theory to explain the fundamental constants, nor is there a reason for them to be constant. They could have been different in the past, and they may be different in the future. Spectroscopic measurements of stars and galaxies at ever-increasing distances tell us that if the fundamental constants were different, it wasn’t by much. We now know that the limit for the relative variation of alpha is 10-17 per year.
Which constants should we measure?
When it comes to these measurements, physicists and astronomers generally focus on alpha and mu. Alpha, otherwise known as the fine structure constant, is a combination of the electric charge, the speed of light, and Plank’s constant. It describes the strength in binding energy between negatively charged electrons and the positively charged nucleus of an atom. Hence, it can be directly measured in the light emitted by hydrogen in distant stars.