1803 Thomas Young’s double-slit experiments appear to show that light is a wave.
1820 Hans Christian Ørsted demonstrates a link between electricity and magnetism.
1831 Michael Faraday shows that a changing magnetic field produces an electric field.
1900 Max Planck suggests that in some circumstances, light can be treated as if it were composed of tiny “wave packets,” or quanta.
1905 Albert Einstein shows that light quanta, today known as photons, are real.
1940s Richard Feynman and others develop quantum electrodynamics (QED) to explain the behavior of light.
The series of differential equations describing the behavior ...