Annus mirabilis papers

The annus mirabilis papers (from Latin: annus mirabilis, lit. 'miraculous year') are four papers that Albert Einstein published in the scientific journal Annalen der Physik (Annals of Physics) in 1905. As major contributions to the foundation of modern physics, these scientific publications were the ones for which he gained fame among physicists. They revolutionized science's understanding of the fundamental concepts of space, time, mass, and energy.

These four papers, together with quantum mechanics and Einstein's later general theory of relativity, are the foundation of modern physics.

At the time the papers were written, Einstein did not have easy access to a complete set of scientific reference materials, although he did regularly read and contribute reviews to Annalen der Physik. Additionally, scientific colleagues available to discuss his theories were few. He worked as an examiner at the Patent Office in Bern, Switzerland, and he later said of a co-worker there, Michele Besso, that he "could not have found a better sounding board for my ideas in all of Europe". In addition, co-workers and the other members of the self-styled "Olympia Academy" (Maurice Solovine and Conrad Habicht) and his wife, Mileva Marić, had some influence on Einstein's work, but how much is unclear.

Through these papers, Einstein tackled some of the era's most important physics questions and problems. In 1900, Lord Kelvin, in a lecture titled "Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light", suggested that physics had no satisfactory explanations for the results of the Michelson–Morley experiment and for black body radiation. As introduced, special relativity provided an account for the results of the Michelson–Morley experiments. Einstein's explanation of the photoelectric effect extended the quantum theory which Max Planck had developed in his successful explanation of black-body radiation.

Despite the greater fame achieved by his other works, such as that on special relativity, it was his work on the photoelectric effect that won him his Nobel Prize in 1921. The Nobel committee had waited patiently for experimental confirmation of special relativity; however, none was forthcoming until the time dilation experiments of Ives and Stilwell (1938 and 1941) and Rossi and Hall (1941).

The article "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt" ("On a Heuristic Viewpoint Concerning the Production and Transformation of Light") received 18 March and published 9 June, proposed the idea of energy quanta. This idea, motivated by Max Planck's earlier derivation of the law of black-body radiation (which was preceded by the discovery of Wien's displacement law, by Wilhelm Wien, several years prior to Planck) assumes that luminous energy can be absorbed or emitted only in discrete amounts, called quanta. Einstein states,

Energy, during the propagation of a ray of light, is not continuously distributed over steadily increasing spaces, but it consists of a finite number of energy quanta localised at points in space, moving without dividing and capable of being absorbed or generated only as entities.

In explaining the photoelectric effect, the hypothesis that energy consists of discrete packets, as Einstein illustrates, can be directly applied to black bodies, as well.