Bern Switzerland, March 18, 1905

Einstein's sixth paper, On a Heuristic Point of View

Concerning the Production and Transformation of Light, Annalen der Physik 17: pg. 132-148.

Einstein expounded on the peculiar discrepancy between material bodies and radiation and introduced the concept of light quanta, or photons, providing the basis for much of the later work in quantum theory, especially Bohr's theory of the atom.

Challenging the wave theory of light, Einstein showed that electromagnetic radiation interacts with matter as if the radiation has a granular structure (the so-called photoelectric effect). He determined that a massless quantum of light, the photon, would have to impart the energy required according to Planck's radiation law to break the attractive forces holding the electrons in the metal. This theory was one of the milestones in the development of quantum mechanics, making Einstein the foremost pioneer in the field and opening the world of quantum physics. The first of the five great papers he published in 1905, it earned him the Nobel Prize in physics sixteen years later.