Introduction to Fine structure constant
The fine structure constant is an important dimensionless number in physics, usually expressed by the Greek letter α. The fine structure constant represents the ratio of the speed of electron movement on the first Bohr orbit and the speed of light in vacuum. The calculation formula is α=e2/(4πε0cħ) (where e is the charge of the electron, ε0 is the dielectric constant of vacuum, and H is approximately Planck constant, c is the speed of light in a vacuum).
The fine structure constant is a number with a dimension of 1 (or unitless) 1/α≈137 (more approximate to 137.03599976)