Adriaan Daniel Fokker (17.08.1887—1972) was a Dutch physicist and a member of the Royal Netherlands Academy of Arts and Sciences. He was born in Buitenzorg (Java). He graduated from the University of Leiden (1913), where he worked in 1917-18. In 1923-27 he was professor at the Higher Technical School in Delft, and in 1928 —55 he was head of the physics cabinet of Teylers Museum in Haarlem and professor at the University of Leiden.
His work was in the field of radioactivity, X-rays, electron theory, relativity, gravitation and the theory of fluctuations. He established a law (1914) for the distribution of the mean energy of a rotating electric dipole in a radiation field (the Fokker — Planck equation). In 1914, with A. Einstein, he developed Nordström's theory of gravitation with the use of tensor analysis.
He was the founder and editor (1933 — 59) of an international physics journal.