From John D. Barrow and John K. Webb’s "Inconstant Constants: Do the inner workings of nature change with time?" (*Scientific American*: 23 May 2005):

One ratio of particular interest combines the velocity of light, c, the electric charge on a single electron, e, Planck’s constant, h, and the so-called vacuum permittivity, 0. This famous quantity … called the fine-structure constant, was first introduced in 1916 by Arnold Sommerfeld, a pioneer in applying the theory of quantum mechanics to electromagnetism. It quantifies the relativistic (c) and quantum (h) qualities of electromagnetic (e) interactions involving charged particles in empty space (0). Measured to be equal to 1/137.03599976, or approximately 1/137, has endowed the number 137 with a legendary status among physicists (it usually opens the combination locks on their briefcases).