150th Birthday of Constantin Carathéodory

Portrait of the Greek mathematician Constantin Carathéodory alongside a mathematical formula. The commemorative inscription "KΩNΣTANTINOΣ KAPAθEOΔΩPH 1873–1950" runs from lower left to upper right along the edge of the design, with the issuing state "ΕΛΛΗΝΙΚΗ ΔΗΜΟΚΡΑΤΙΑ" at lower right. Above it, the palmette of the Greek mint and the year 2023; the coin designer's initials "ΣTAM" appear on Carathéodory's shoulder.

Constantin Carathéodory is one of the most important mathematicians of the early 20th century and, despite his Greek origins, spent most of his academic career in Germany. Born in Berlin in 1873, the son of an Ottoman-Greek diplomat, he studied engineering in Belgium and turned to pure mathematics only in his early thirties — an unusually late decision that nonetheless carried him to the top of his field. He taught at the universities of Hanover, Breslau, Göttingen, Berlin, Smyrna, and finally Munich, where he remained until his death in 1950. His name is closely tied to measure theory and the calculus of variations, but his influence reached far beyond: Carathéodory provided one of the first fully axiomatic approaches to thermodynamics and contributed to what is known today as Carathéodory theory in function theory.

Despite his long years in Germany, Carathéodory's ties to Greece remained strong. In the early 1920s he worked to establish the University of Smyrna, which, however, never began operations due to the events of the Greco-Turkish War. In Greek scientific history he is regarded as an outstanding figure whose work helped shape the foundations of modern analysis. Greece honored him on his 150th birthday in 2023 with a 2-euro commemorative coin, publicly marking the standing Carathéodory holds in both national and international scientific history.