2 8 8 D O C U M E N T 4 1 J U N E 1 9 2 0
TLS. [11 037].
[1]Adriaan D. Fokker (1887–1972) was Lector in theoretical physics at the University of Leyden.
[2]Einstein was inducted as foreign member of the Royal Academy of Sciences in Amsterdam on
29 May 1920 (on his election, see Doc. 35). On this occasion, Hendrik A. Lorentz, President of the
Academy, expressed the “admiration that we feel for your work, by which you have earned a place of
honor among physicists of all peoples and all times. We value the rare and keen genius with which
you, in all simplicity, succeed in forcing nature to unlock its secrets, that remain hidden to others.”
(“de bewondering die wij gevoelen voor uw werk, waardoor gij u een eereplaats onder de natuurkun-
digen van alle volken en alle tijden hebt verworven. Wij waarderen het zeldzame en doordringende
vernuft waarmede gij, in allen eenvoud, er in slaagt aan de natuur de ontraadseling van geheimen af
te dwingen, die anderen verborgen blijven.” Nieuwe Rotterdamsche Courant, 30 May 1920, Morning
Edition). Willem Julius further presented Julius and Cittert 1920 at this session (see also Doc. 8).
[3]Ernest Rutherford (1871–1937), Cavendish Professor of Experimental Physics at Cambridge
University.
[4]Fokker had collaborated in Zurich with Einstein during the winter of 1913–1914, and had spent
the summer of 1914 with Rutherford in Manchester. He was then drafted into the Dutch army in 1914,
serving until 1917.
[5]Margaretha Fokker-Kessler; Fokker was staying in a sanatorium in Arosa, Switzerland, to cure
his tuberculosis (see Adriaan D. Fokker to Einstein, 26 July 1919 [Vol. 9, Doc. 75]).
[6]Majorana 1920a. Quirino Majorana (1871–1957) was Professor of Physics at the Technical
University of Turin. His experiments used a sensitive balance to weigh a lead sphere both before and
after surrounding it with a large mass of mercury. Majorana reported that the lead weighed less with
the mercury surrounding it, suggesting a diminution of the Earth’s pull on the lead when it was
obliged to pass through the mercury. On these experiments and their reception by the science com-
munity, see Martins 1999.
[7]Fokker had corresponded with Einstein concerning his studies of Einstein’s formulation of
Mach’s principle the previous year (see Adriaan D. Fokker to Einstein, 26 July 1919 [Vol. 9, Doc. 75],
and Einstein to Adriaan D. Fokker, 30 July 1919 [Vol. 9, Doc. 78]).
[8]In fact, in January Einstein had recommended this problem (of the transverse Doppler shift pre-
dicted by special relativity) to the Göttingen physicist Rausch von Traubenberg (see Einstein to Hein-
rich Rausch von Traubenberg, 12 January 1920 [Vol. 9, Doc. 257]), who was performing experiments
with high-velocity canal rays. For Fokker’s own review of experiments measuring the inertial mass
of the electron, see Fokker 1918.
[9]Charles-Eugène Guye (1866–1942), Professor of Physics at the University of Geneva.
41. To Hans Vaihinger
Berlin, den 3. VI. 20.
Hochgeehrter Herr Kollege!
Leider war es wegen meiner Ernennung zum Mitglied der Amsterdamer Akade-
mie[1]
unbedingt nötig, dass ich in Amsterdam in der Sitzung vom 29. V. zugegen
war. Deshalb war es mir leider unmöglich, zur Als-Ob-Konferenz zu kommen, die
gewiss sehr interessant gewesen
ist.[2]
Beim Gedanken an Ihre Absicht ein „Einstein-Heft“ herauszugeben, beschleicht
mich ein peinliches Gefühl. Vielleicht könnte man das Heft der Relativitäts-Theo-
rie widmen statt mir persönlich. So viel Anerkennung, wie sie mir zu Teil wird, ist