Fine-Structure Constant
Introduction Among the many constants that appear in physics, few have attracted as much attention as the fine-structure constant, commonly denoted by the Greek letter alpha (α). The inverse of this constant has a value close to 137 and has fascinated physicists, mathematicians, and philosophers for more than a century. The fine-structure constant occupies a unique place in science. Unlike many physical constants, it is dimensionless; it has no units of length, mass, time, or charge. It is therefore a pure number. In modern physics, the fine-structure constant determines the strength of the electromagnetic interaction and appears throughout quantum electrodynamics, atomic physics, chemistry, and the structure of matter itself. The importance of the constant has led many prominent scientists to reflect upon its meaning. The physicist Richard Feynman famously described the fine-structure constant as one of the greatest mysteries of physics. Despite the extraordinary success of mode...