D O C U M E N T 7 9 J U L Y 1 9 1 9 1 1 9
Einstein had long been acquainted with Arosa, where he used to sail. In January he visited there
with his son Eduard (see Docs. 1 and 3). Four days earlier, Fokker had mentioned discussions with
many Germans who had also stayed in the sanatorium (possibly, e.g., Wilhelm von Siemens, president
of the board of trustees of the Kaiser Wilhelm Institute of Physics, president of the board of Siemens
& Halske, and head of the Siemens-Schuckert Werke in Berlin; see Doc. 75 and entry of 15 October
1919 in Calendar). Germans complained about the German defeat in World War I and the Treaty of
Versailles, which was dubbed a “violent act” (“Gewaltakt”) and a “forced peace” (“Gewaltfrieden”),
especially after the rejection of German counterproposals (see “Annahme des Gewaltfriedens,” Voss-
ische Zeitung, 24 June 1919, Morning Edition).
U. S. President Woodrow Wilson (1856–1924) was a strong advocate of the League of Nations,
and championed a less punitive peace with Germany.
Einstein recapitulates considerations about the “cosmological problem”; see Vol. 8, the editorial
note, “The Einstein–De Sitter–Weyl–Klein Debate,” pp. 351–357, for further discussion.
The cosmological constant was introduced in Einstein 1917b (Vol. 6, Doc. 43). In Doc. 75 Fok-
ker had objected to the term’s introduction on aesthetic grounds.
These trace-free field equations were published in Einstein 1919a (Vol. 7, Doc. 17), wherein
Einstein proposed an empirical role for the cosmological constant in explaining the stability of the
Weyl 1918b, which Einstein had reviewed in Einstein 1918h (Vol. 7, Doc. 10).
A reference to Weyl’s generalization of general relativity by introducing a differential form
that governs the transport of vector lengths l by the definition .
Given a metric tensor field , gauge invariance then postulates the invariance under simultaneous
transformations and for a scalar function λ. The term “Aich-
Invarianz” was also used in Einstein to Hermann Weyl, 29 November 1918 (Vol. 8, Doc. 661 and its
note 5), when discussing a manuscript of Weyl 1919b, although in the published version of that paper
the term “gauge invariance” (“Eichinvarianz”) was used. In Weyl 1918a, 1918c, it was referred to as
“measuring rod invariance” (“Maßstab-Invarianz”).
For another, more explicit version of this “measuring rod objection” (“Maßstab-Einwand”), see
Einstein 1918g (Vol. 7, Doc. 8) appended to Weyl 1918a.
For Erwin Freundlich’s work on the redshift in the spectra of fixed stars, see Doc. 14 and Ein-
stein’s reply praising Freundlich’s work (Doc. 15).
In Doc. 75, Fokker had suggested that Weyl’s theory might provide room, whereas general rel-
ativity, as Einstein emphasizes here, did not, for an explanation of the failure of solar spectroscopists
to find evidence for a gravitational redshift in the Sun. See Doc. 75, note 18, for others who shared
It was Einstein’s contention that the lack of measuring rod invariance in Weyl’s theory was
inconsistent even with the existence of characteristic spectra in atoms (see references in note 10
79. To Auguste Hochberger
Luzern. Sanatorium Rosenau. 30. Juli.
Zu meiner grossen Freude höre ich, dass Du Mama hier besuchen willst. Wie
sehr sich Mama darüber freut, ist gar nicht zu sagen, aber Du wirst es ihr selbst
nachfühlen. Dein Besuch ist für sie eine umso grössere Wohlthat, als ich jetzt bald
abreisen muss, und meine Schwester doch viel an das Haus gebunden ist. Falls Du
dϕ ϕidxi = δl
dxi ldϕ + 0 ≡ ≡
λgmn = ϕidxi
ϕidxi dlogλ – =