D O C U M E N T 1 4 5 O C T O B E R 1 9 1 9 2 0 9

bestätigt. Das wird Dir ja vielleicht ganz interessant sein.

Gestern hörte ich von Harms, daß Zeeman in Amsterdam gerade jetzt einen neu-

en Versuch zur Optik bewegter Körper veröffentlicht hat, bei welchem sich das

Licht in einem Glas- oder Quarzkörper statt, wie beim Fizeauschen Versuch, in

Wasser fortpflanzt.[5] Das ist ein Grund mehr, nunauch den Harressschen Versuch

in Ordnung zu bringen.

Mit herzlichem Gruß, auch an Planck Dein

M. Laue.

TLS. [16 020]. There are calculations in Einstein’s hand on the verso of the second page of the 2-page

document. These calculations show the transformation law of the Christoffel symbols going from

unprimed to primed coordinates and vice versa; a sketch illustrating the geometrical relations of

stereographic and orthographic projection of a circle with radius R and the equation

, where is the orthographic projection, x the stereographic projec-

tion of a point with vertical distance from the circle’s diameter and the change in sign results from

looking at the lower resp. upper half-circle; the equation ; a

calculation of Hamilton’s principle with a Lagrangian L depending on coordinates and ; and

the additional assumption that the variation also pertains to the time coordinate.

In the upper right corner, Einstein wrote the chemical relations:

“Na[+]⏐Cl[-] → Na+⏐Cl” and “NaCl → Na⏐ Cl”

and the following four lines:

“1) Ionisierungsarbeit .d. Metalls =

?

Gitterarbeit.”

“2) Neutrale Trennungsarbeit =

?

Arbeit zur Lockerung eines Elektrons vom [Io]n.”

“Aus 1) Gitterarbeit unabhängig von Rest.”

“ ″ 2) Neutrale Trennungsarbeit unabh. von Metall.”

[1]Franz Harress’s doctoral dissertation Harress 1912 at the University of Jena was published in

revised form by his teacher Otto Knopf (1856–1945), Professor of Astronomy and director of the

observatory, and appeared as Knopf 1920. Earlier, Harress’s results had been criticized by Paul Harzer

(1857–1932), Professor of Astronomy at the University of Kiel and director of its observatory (see

Harzer 1914a). In his turn, Harzer was criticized by Einstein (see Einstein 1914l and 1914m [Vol. 6,

Docs. 4 and 6] and Harzer’s responses Harzer 1914a, 1914b).

[2]Harress had measured the dragging coefficient for two wavelengths. Laue compares the value

for the shorter wavelength (0.577) to its theoretical value 0.5977. Fizeau’s experiment to measure the

dragging coefficient of light propagating in a moving medium was regularly cited by Einstein as one

of the key experimental results which underpinned the theory of (special) relativity, as, e.g., in Ein-

stein 1907j (Vol. 2, Doc. 47), p. 416, as well as in his lectures (see, e.g., Vol. 7, Doc. 12).

[3]Emil Warburg; Ernst Gehrcke (1878–1960) was an Oberregierungsrat at that institute, working

mainly in spectroscopy.

[4]The paper was published as Laue 1920, which followed Knopf 1920 in the same issue of the

Annalen der Physik.

[5]Karl Harms; see Zeeman 1919 and Zeeman and Snethlage 1919 for Zeeman’s results, which

were in agreement with special relativity.

t′ t

vx

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x

x′

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r-

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2R

R + R2 r′2 – –

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d2xν

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·