3 5 8 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
[13]This objection, together with the distinction between images of the first and second kind, was
also raised in Lenard 1918. Einstein responded to it briefly in Einstein 1918k (Doc. 13).
[14]Einstein appeals here to Mach’s principle as formulated in Einstein 1918e (Doc. 4), pp. 241–
242; see note 5 there for a discussion.
[15]Lenard may have been more emphatic in Bad Nauheim when remarking about the chasm that
separated his approach from Einstein’s. A contemporary report paraphrased Lenard’s reply as fol-
lows: “This concerns the opposition between experimental and mathematical physicists, which can-
not be overcome if the mathematical physicist is unable to pass from the images of the first kind, . . .
in which he is accustomed to thinking, to those of the second kind, the intuitive images in which the
experimental physicist thinks” (“Es handle sich um den Gegensatz zwischen experimentellen und
mathematischen Physikern, der nicht zu überbrücken sei, wenn der mathematische Physiker nicht von
den Bildern erster Art, . . . in denen er zu denken gewohnt sei, zu den Bildern zweiter Art übergehe,
den anschaulichen Bildern, in denen der Experimentalphysiker denke.” Vossische Zeitung, 24 Sep-
tember 1920, Evening Edition, p. 1).
[16]A more vivid variant of this exchange was given in Berliner Tageblatt, 24 September 1920,
Evening Edition, p. [3]:
“Lenard: I am not dealing with formulas but rather with actual processes in space. That is the
chasm between Einstein and me. I have nothing against his theory of special relativity. But his theory
of gravitation? If a traveling train brakes, the effects appear in fact only in the train itself, and not out-
side where all the church steeples remain standing!
“Einstein: The observable effects in the train are caused by a gravitational field, which is induced
by the totality of near and distant masses.
“Lenard: Such a gravitational field must certainly also bring about effects in other ways if I wish
to visualize its presence.
“Einstein: What human beings consider to be intuitive is subject to great change, and is a function
of time. A contemporary of Galileo would also have declared his mechanics to be very unintuitive.
These ‘intuitive’ conceptions have their defects, just like the oft-cited ‘healthy common sense.’
(Laughter).”
(“Lenard: Ich bewege mich nicht in Formeln, sondern in den tatsächlichen Vorgängen im Raume.
Das ist die Kluft zwischen Einstein und mir. Gegen seine spezielle Relativitätstheorie habe ich gar
nichts. Aber seine Gravitationslehre? Wenn ein fahrender Zug brennt [bremst], so tritt doch die Wir-
kung tatsächlich nur im Zuge auf, nicht draußen, wo alle Kirchtürme stehen bleiben!
“Einstein: Die Erscheinungen im Zuge sind die Wirkungen eines Gravitationsfeldes, das induziert
ist durch die Gesamtheit der näheren und ferneren Massen.
“Lenard: Ein solches Gravitationsfeld müsste doch auch anderweitig noch Vorgänge hervorrufen,
wenn ich mir sein Vorhandensein anschaulich machen will!
“Einstein: Was der Mensch als anschaulich betrachtet, ist großen Veränderungen unterworfen, ist
eine Funktion der Zeit. Ein Zeitgenosse Galileis hätte dessen Mechanik auch für sehr unanschaulich
erklärt. Diese ‘anschaulichen’ Vorstellungen haben ihre Lücken, genau wie der viel zitierte ‘gesunde
Menschensverstand.’ [Heiterkeit.]”)
[17]Lenard 1918 and 1920.
[18]Einstein’s reply appears to have been truncated. The text beginning with “Meine zweite Frage
lautet:” does not reproduce his words, but is a query posed by Lenard (see the editorial note, “Ein-
stein’s Encounters with German Anti-Relativists,” pp. 101–113). A report in Berliner Tageblatt, 24
September 1920, Evening Edition, p. [3], provides a partial reconstruction of the missing passage,
including Einstein’s reply:
“Lenard: . . . Another question: if the earth rotates, then, according to Einstein, one can just as well
say that the earth is at rest and all matter rotates around it. Then, however, the most distant stars take
on velocities that far exceed the speed of light. According to the theory, however, that [velocity]
should be a limiting velocity. This is a contradiction in itself.
“Einstein: No, the speed of light is a limiting velocity only for the uniform rectilinear motions of
special relativity; arbitrary velocities of light can occur in systems that undergo arbitrary motions.”
(“Lenard: . . . Eine andere Frage: Wenn die Erde rotiert, so sagt Einstein, man könne genau so gut
sagen, die Erde ruhe, und alle Materie rotiere um sie. Dann kommt man aber für die fernsten Gestirne