l v i I N T R O D U C T I O N T O V O L U M E 1 2
straight line by an angle that he calculated to be easily observable. In a quantum
scenario, however, Einstein thought that this bending would not take place
(Einstein 1922a [Vol. 7, Doc. 68]).
Einstein was excited about the project, sometimes modestly referring to it as “in-
teresting” (Docs. 230, 247, 275), but also expressing great curiosity in its outcome:
“I am very curious about the outcome of our canal-ray experiment. My expecta-
tions are totally uncertain” (Doc. 261). In fact, we learn from a letter by Lorentz
(Doc. 298) that Einstein was entertaining ideas about a possible theory of emission
and propagation of light that would integrate the assumption of “a kind of spherical
wave” with “the directed energetic process” of quantum theory (Doc. 261).
Lorentz’s letter suggests that Einstein may have thought of the spherical radiation
field as an “interference radiation,” prescribing the probability of where the “ener-
gy radiation”—the indivisible, individual quanta—would hit a spot on a screen
placed in the path of the radiation. The interference radiation field would produce
a probability distribution whereby the quanta would build up an interference
pattern. However, Lorentz pointed out that such an interpretation would imply that,
according to both Maxwellian electrodynamics and to the new wave-plus-quantum
perspective, Einstein’s setup would exhibit a deflection in the dispersive medium
(Doc. 298). Thus, the experiment would not be able to decide the question for
which it had been designed.
Einstein remained undeterred by Lorentz’s argument, convinced that only the
classical theory predicts the deflection of canal ray light in the dispersive medium.
He still believed that the quantum picture of emission could be confirmed by the
absence of a deflection in this arrangement (see, e.g., Doc. 326).
Geiger informed Einstein of the first set of preliminary and uncertain results in
early November (Doc. 289), but soon fell ill with an ulcer (Doc. 303). His technical
mechanic, too, became sick, and further delays ensued (Docs. 316, 326). By mid-
December, Einstein, who had already submitted a paper outlining the experiment
and its implications to the Prussian Academy (Einstein 1922a [Vol.7, Doc. 68]),
still could not present any experimental results. But a week later they were in: no
deflection had been
observed.[65]
Classical theory, it seemed, had been dealt a
severe blow. The wave field, Einstein believed, had been shown to have “no real
existence,” and the emission of a quantum, a process that in terms of its energy
Einstein thought to be strictly governed by Bohr’s quantum condition, had to be
considered to take place instantaneously (Doc. 345).
A week before Einstein learned of the definitive outcome of the experiment, he
wrote Hermann Weyl that if the experiment were negative, i.e., if it did not exhibit
any deflection, then “the field theory is in principle inadmissible” (Doc. 326). By