But some numbers, called dimensionless numbers, have the same numerical value no matter what units of measurement are chosen. Probably the most famous of these is the "fine-structure constant," .... Physicists love this number not just because it is dimensionless, but also because it is a combination of three fundamental constants of nature.
John Archibald Wheeler, Geons, Black Holes, and Quantum Foam: A Life in Physics
fine-structure-constant, history-of-science, physics