**Erich Bessel-Hagen** was a German mathematician and a historian of mathematics.

- There are a number of incorrect explanations of Bessel-Hagen's name in the literature, so we should explain where the slightly strange name originated.
- Although we have given Berlin as Erich Bessel-Hagen's birthplace, this is not quite accurate since he was actually born outside but close to that city.
- Bessel-Hagen attended the University of Berlin where he obtained a doctorate working under Constantin Carathéodory, with some help from Erhard Schmidt.
- While at Berlin, however, Bessel-Hagen had also heard lectures from the famous classicist, Ulrich von Wilamowitz-Möllendorf, and was inspired by him to a life-long devotion to classical antiquity as well.
- At Berlin, Bessel-Hagen met his fellow student Carl Siegel and the two became life-long friends.
- After graduating with his doctorate, Bessel-Hagen was appointed to Göttingen University.
- Felix Klein had an exceptionally strong influence on him, for not only did Bessel-Hagen live in Klein's house, but he was Klein's private assistant from 1921 to 1923.
- Bessel-Hagen was one of a small number who had attended these lectures delivered in Klein's home.
- Braun says that Siegel and Bessel-Hagen first met as students in Berlin.
- Bessel-Hagen revered Siegel for his mathematical ability, and Siegel in turn was gratified to be admired by someone he could accept.
- They were friends all their lives, until Bessel-Hagen's early death in 1946.
- Bessel-Hagen walked with a slight limp - Braun thought because of polio.
- Schaffeld, Siegel, and Bessel-Hagen were united in their attitude towards marriage.
- In contrast, Siegel couldn't resist baiting or playing sometimes cruel and humiliating practical jokes on Bessel-Hagen.
- Siegel had to review Bessel-Hagen's thesis for habilitation - perhaps as a friend, perhaps in some official capacity.
- However, it came to him at a time when he was deeply involved in his own research, and Bessel-Hagen's thesis was in a different area.
- he told Bessel-Hagen he had done him a favour.
- To make up, he invited Bessel-Hagen on a long vacation to Greece.
- Bessel-Hagen also played a major role in establishing the historical division, including an important library, as part of the mathematical seminar in Bonn.
- Bessel-Hagen was also involved in editing the works of Gauss.
- Bessel-Hagen wrote more than 200 reviews for Neugebauer's Zentralblatt.
- Béla Kerékjártó visited the University of Göttingen in 1922 and attended lectres by Bessel-Hagen.
- In the following year Kerékjártó published Vorlesungen über Topologie the index of which contains a reference to Bessel-Hagen.
- Turning to the indicated page, there is no mention of Bessel-Hagen.
- Bessel-Hagen was renowned for having large ears that stuck out of his head.
- At first this appears to be a rather cruel joke, but in fact Kerékjártó was merely following the teaching staff at Göttingen who all made jokes at Bessel-Hagen's expense.
- in 1935, Bessel-Hagen seems to have been the only one of his former colleagues to visit him.
- Bessel-Hagen was an excellent mathematician who, because of his shyness, did not publish much.
- Most of the other mathematicians at Bonn were conscripted so only Bessel-Hagen and Hans Beck remained to teach.
- After Beck died in 1942, Bessel-Hagen essentially became a one-man department.

Born 12 September 1898, Berlin, Germany. Died 29 March 1946, Bonn, Germany.

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Origin Germany

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive