A physical constant’s value shouldn’t depend on how you measure it
Measurements in physics are funny things. You'd hope that attempts to quantify some of the fundamental properties of the Universe would follow a simple pattern: they'd start with large error bars, but, over time, measuring technology improves and the error bars shrink. Ideally, the value would then remain nicely within the previous error.
It almost never really works like that. In many cases, measurements cluster together for a while before a new set makes a leap to somewhere else, outside the error bounds. And, even as technology improves, some sets of error bars stubbornly refuse to overlap. A new paper out this week indicates that this is the case with the Fine Structure Constant, which describes the strength of the electromagnetic force. But instead of chalking it up to the vagaries of measurement, the researchers suggest that the difference could be real—and it tells us something about what physics might lie beyond the Standard Model.
The Fine Structure Constant is a measure of electromagnetic force, and that force shows up in a large number of phenomena. This means there are plenty of ways to do measurements that tell us something about the value of the Fine Structure Constant. When it comes to high-precision measurements, researchers have come up with two different ways of doing it. The first relies on particle physics and direct measurements of the magnetic properties of the electron. The second has been to study how atoms interact with light.