Reality → Energy → Light → Einstein
Einstein’s greatest ideas - relativity and the photoelectric effect - are closely related with fundamental properties of light and electromagnetic radiation [1] . Motivated by Maxwell’s theory of electrodynamics [2] , Einstein formulated the special theory of relativity, which subsequently led to the broader general theory of relativity. Building on Planck’s discovery that some aspects of black body radiation can only be explained by assuming that energy occurs in quanta (see Quantization), Einstein explained the photoelectric effect by reasoning that light itself consists of particles (later named photons), while Planck believed that the emission of black body radiation was quantized by some unknown property of the reflecting wall’s material. Einstein’s hypothesis proved to be correct and in 1921 he received retroactively the Nobel prize in physics for his work.
In 1905, Einstein published four papers, three of which dealt with topics closely related to light: photoelectric effect, special relativity, and mass-energy equivalence (the fourth paper, his doctoral thesis, was about Brownian motion). Einstein received the 1921 Nobel Prize in Physics for his 1905 paper related to the photoelectric effect, the interaction between photons and electrons, or energy and matter. The work significantly contributed to the acceptance of wave-particle duality and quantization (both, energy and matter are 'atomized') as pillars of quantum mechanics.
Einstein’s first paper on relativity is titled Zur Elektrodynamik bewegter Körper. The ‘moving magnet and conductor problem‘ prompted the special relativity theory.