DOCUMENT 468 AUGUST 1913 551 In dieser Sache könnt Ihr Astronomen nächstes Jahr der theor. Physik einen geradezu unschätzbaren Dienst leisten. Wir werden eine sichere Auskunft er- langen darüber, ob es richtig ist, die Relativitätstheorie weiter zu verallge- meinern, oder ob wir bei dem ersten Schritt stehen bleiben müssen Mit den besten Grüssen Ihr A. Einstein P.S. In einem amerik. Journal zeigte mir unser hiesiger Astronom eine kurze Arbeit, worin vorgeschlagen wird, mehrere optische Systeme starr zu verbinden, statt mit einem Instrument gleichzeitig beide Sonnenränder zu photographieren. Meinem laienhaften Gehirn kommt das vernünftig vor. ALS (NNPM, MA 4725 (4)). [11 203]. This letter is dated on the assumption that it was written shortly before the next letter to Freundlich (Doc. 472). See Docs. 281 and 287 for earlier correspondence with Freundlich on the possibility of testing Einstein's prediction of gravitational light-deflection. Einstein's calculation in Einstein 1911h (Vol. 3, Doc. 23) for the magnitude of the grav- itational light deflection gave the same result as had been derived in Soldner 1801 in the frame- work of Newton's emission theory of light (see Jaki 1978 for a historical discussion). It is un- certain whether Einstein knew Soldner's paper. In the final version of Einstein's general theory of relativity an effect is predicted that is twice as large (see Einstein 1915c). See Einstein and Grossmann 1913 (Vol. 4, Doc. 13), which was published mid-June (see Docs. 441 and 448). See also Vol. 4, the editorial note, "Einstein on Gravitation and Relativity: The Collaboration with Marcel Grossmann," for a discussion of this paper. See Doc. 343, note 3, for more on the discussion between Max Abraham and Einstein on gravitation. Gustav Mie (1868-1957) was Professor of Physics at the University of Greifswald. For his theory of matter, which includes a theory of gravitation, see Mie 1912a, 1912b, 1913. See also the discussion on Mie's theory between Mie and Einstein following Einstein's lecture on 23 September 1913 to the 85th meeting of the Gesellschaft Deutscher Naturforscher und Ärzte in Vienna (published as Einstein et al. 1913 [Vol. 4, Doc. 18]) and its continuation in Mie 1914a, 1914b and Einstein 1914e (Vol. 4, Doc. 25). Gunnar Nordström was lecturer in theoretical physics at the University of Helsingfors (now Helsinki). He spent summer 1913 in Zurich where he was in close contact with Einstein (see, e.g., entry of 29 June 1913, in Diary "I," NeLR, Ehrenfest Archive, Notebooks, ENB:4- 15). His (scalar) theory of gravitation is developed in Nordström 1912, 1913a, 1913b. Einstein discussed Nordström's theory in his Vienna lecture (Einstein 1913c [Vol. 4, Doc. 17] see also the preceding note), the manuscript of which he had submitted on 11 August (see Doc. 464). In 1914 Einstein and a collaborator published a joint paper on Nordström's theory, in which they analyzed the theory from the point of view of absolute differential calculus (see Einstein and Fokker 1914 [Vol. 4, Doc. 28]). See also Isaksson 1985 for more on Nordström's work. The total solar eclipse of 21 August 1914 (see Doc. 492). A determination of the positions of stars close to the sun, possible during a total eclipse, would allow a test of Einstein's pre- diction. Julius Maurer (see Doc. 477).