Leonhard Euler 1707--1783: on the 300th birthday of a long-time Berliner by choice (Q2907571)

Since Euler's legacy is enormous in size and diverse in interests, the author decided to turn his attention to ``some less-known details of his life and work, namely to the following ones: 1. Upright take-off; 2. Craving for and delight in [doing mathematics]; 3. Lack of appreciation; 4. Mathemati(cian)cs in the service of faith; 5. Theory of music; 6. Hardships of everyday life; 7. The land of promise: analysis; Epilogue.'' By the ``upright take-off'' he means Euler's rapid career in the years 1720--1727, from immatriculation at Basel University to departure for Petersburg. Then he recalls Euler's declaration of belief in mathematics dated 1721 and his curious misinterpretation of Ovid's words concerning the taming power of mathematics. In 1727 Euler presented a habilitation paper in order to receive a certain position but he was refused and the author analyses the paper to discover possible causes. Euler was a convinced Christian, on frequent occasions defending the faith with arguments based upon mathematics. Euler's interests bordered music; in a paper from 1727 he offered an approach to its theory aimed at finding a criterion to distinguish consonance and dissonance. Concerning ``hardships'', the author discovers places where Euler lived in his Berlin period and describes some of his academy duties including reviewing mathematical projects (e.g., papers on circle squaring) or payments for bodies furnished to anatomy. When in 1760 the Russian army pillaged his estate near Berlin, he was afterwards richly compensated for it by the tsarine (Euler was a member of the Petersburg academy). The Berlin period was particularly productive and the author describes pictures which appeared on the title pages of Euler's books on analysis from the period as well as some characteristic features of his writings including the strong tendency towards generality. Throughout his life Euler enjoyed poetry, particularly Ovid in his youth and Vergil in his old age, what is illustrated by several quotations in the ``Epilogue''. The article well shows diverse sides of Euler's life and the omnipresence of mathematics in it.