Fine-structure Constant
The coupling constant arises naturally in a quantum field theory. A special role is played in relativistic quantum theories by coupling constants which are dimensionless, i.e., are pure numbers. For example, the fine-structure constant,
(where is the charge of an electron, is the permittivity of free space, is the reduced Planck constant and is the speed of light) is such a dimensionless coupling constant that determines the strength of the electromagnetic force on an electron.
Read more about this topic: Coupling Constant
Famous quotes containing the word constant:
“If only he would not pity us so much,
Weaken our fate, relieve us of woe both great
And small, a constant fellow of destiny,
A too, too human god, self-pity’s kin
And uncourageous genesis . . .”
—Wallace Stevens (1879–1955)