D O C . 4 6 B A D N A U H E I M D I S C U S S I O N S 3 5 7

Published in Physikalische Zeitschrift 21 (1920): 650–651, 662, 666–668.

[1]Six lectures on the theory of relativity were delivered on 23–24 September 1920 at the Bad Nau-

heim meeting of the Gesellschaft Deutscher Naturforscher und Ärzte (GDNA). These lectures were

organized as a special joint session of the Deutsche Physikalische Gesellschaft and the Deutsche

Mathematiker Vereinigung (see Weyl 1922b, p. 51). Prompted by the anti-relativists’ attacks of one

month earlier and acting on Einstein’s request, the organizers agreed to hold an open discussion fol-

lowing the lectures (see Einstein 1920f [Doc. 45], closing paragraph). Einstein allegedly said: “The

best proof that I by no means dodge criticism is that I myself arranged that the theory of relativity be

discussed at the meeting of the GDNA in Nauheim” (“Daß ich die Kritik durchaus nicht scheue, dafür

ist der beste Beweis, daß ich selbst angeregt habe, auf dem Naturforschertag in Nauheim die Relati-

vitätstheorie zur Erörterung zu stellen.” Vossische Zeitung, 29 August 1920, Morning Edition, Sup-

plement 4, p. 1). For further background on the Bad Nauheim meeting, see the editorial note,

“Einstein’s Encounters with German Anti-Relativists,” pp. 101–113. The participants in these discus-

sions were Einstein, Philipp Lenard, Hermann Weyl, Gustav Mie, Wolfgang Pauli, Ernst Reichen-

bächer, Georg Hamel, Heinrich Rudolph, Melchior Palágyi, Max Born, and Oskar Kraus. For a

contemporary account, see Weyl 1922b. For background on the Einstein-Lenard duel, see Beyerchen

1977, pp. 85–91; Fölsing 1993, pp. 526–528; and Goenner 1993, pp. 123–127.

The first discussion followed a presentation by Hermann Weyl, “Electricity and Gravitation”

(“Elektrizität und Gravitation”), in which he presented and discussed his unified field theory first pro-

posed in Weyl 1918a.

[2]Einstein 1919a (Doc. 17).

[3]“N-Kern” should read “H-Kern,” i.e., hydrogen nucleus.

[4]Pauli’s skepticism with regard to the theories of Einstein, Mie, Hilbert, and Weyl was expressed

soon after in Pauli 1921.

[5]Ernst Reichenbächer soon hereafter published Reichenbächer 1920, a critical article that

appeared in Die Naturwissenschaften alongside Einstein’s response in Einstein 1920k (Doc. 49).

Some of the issues discussed therein elaborated on controversial points that were touched upon in Bad

Nauheim.

[6]For details on Einstein’s objections to Weyl’s theory, see Einstein to Weyl, 29 November 1918

(Vol. 8, Doc. 661).

[7]Mie’s remarks and Weyl’s reply deal with another side of the main issue raised by Lenard,

namely the proper role of Anschaulichkeit in theoretical physics. Here, Mie states his preference for

Einstein’s pseudo-Riemannian space-time geometry over Weyl’s non-Riemannian geometry based on

its purported superiority for “picturing” physical events. Weyl stresses, however, that his generalized

spaces can be projected onto Euclidean four-space, even if they cannot be embedded in a higher-

dimensional Euclidean space. This exchange between Mie and Weyl underscores that both felt that

the intuitive qualities of a mathematical model were highly significant. This stands in sharp contrast

to Lenard’s strict distinction between mathematical physics, which lacks intuitive appeal, and theo-

retical physics, which draws its strength from empirical sources (see note 15).

[8]This discussion followed a lecture by Max von Laue, “Theoretical Remarks on Recent Optical

Observations Concerning the Theory of Relativity” (“Theoretisches über neuere optische Beobach-

tungen zur Relativitätstheorie”), in which Laue derived the fact that light rays follow geodesics from

the relativistic Maxwell equations and showed that the gravitational redshift is not merely a coordi-

nate effect, but also appears in the frequency observed by a distant observer.

[9]Georg Hamel (1877–1954) was Professor of Mathematics at the Technische Hochschule Berlin.

[10]For a discussion of Einstein’s position in 1920 on the fundamental importance of the gravita-

tional redshift, see Hentschel 1998, pp. 484–491.

[11]See note 1 for the role and history of the “general discussion.”

[12]Most of Lenard’s remarks in this discussion repeat his arguments against general relativity in

Lenard 1918 in defense of his own ether-based gravitational theory. Lenard complained that Ein-

stein’s generalization of gravitational fields to include inertial effects flies in the face of the natural

scientist’s “common sense.” Lenard rejected the admissibility of “fictitious” gravitational fields

induced by accelerating frames unless the acceleration was caused by gravitation, hence his demand

that accelerations be proportional to the quantity of mass present.