Physicist (mathematical physics, atomic physics, theoretical physics, wave mechanics, quantum mechanics). On the mineralogy faculty at Georg-August Universitt̃ zu Gt̲tingen (1893-1897); on the mathematics faculty at Technische Universatt̃ Clausthal (1879-1900); on the mechanics faculty at the Technische Hochschule zu Aachen (1900-1906); and on the physics faculty at Universitt̃ M nchen from 1906.

Major affiliations include: Georg-August Universitt̃ zu Gt̲tingen, Gottingen, Germany, 1891-1905; Physikalisch-Technische Reichsanstalt, Berlin, Germany, 1922-1924; and Universitt̃ Berlin, Berlin, Germany, 1925-1933.