The Dirac equation is a fundamental equation in physics that successfully combines the principles of quantum mechanics with Einstein’s theory of special relativity. It was formulated by British physicist Paul Dirac in 1928 to describe the behavior of spin-½ particles, such as electrons.
Unlike the Schrödinger equation, which works well at low speeds, the Dirac equation accounts for particles moving close to the speed of light and incorporates intrinsic spin naturally. It predicts several profound results, including the existence of antimatter—particles identical in mass but opposite in charge to their corresponding matter particles. The first such particle discovered was the positron, the electron’s antiparticle.
The Dirac equation also correctly explains the fine structure of atomic spectra and provides a framework for understanding particle behavior in quantum field theory. It laid the foundation for much of modern particle physics and quantum electrodynamics (QED), making it one of the cornerstones of theoretical physics.