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Preliminaries
18a. An Outline of Einstein's Contributions
In 1948, I undertook to put together the Festschrift in honor of Einstein's seven-
tieth birthday [Rl]. In a letter to prospective contributors, I wrote, 'It is planned
that the first article of the volume shall be of a more personal nature and, written
by a representative colleague, shall pay homage to Einstein on behalf of all con-
tributors' [PI]. I then asked Robert Andrews Millikan to do the honors, as the
senior contributor.* He accepted and his article is written in his customary forth-
right manner. On that occasion, he expressed himself as follows on the equation
E = hv — P for the photoelectric effect. 'I spent ten years of my life testing that
1905 equation of Einstein's and contrary to all my expectations, I was compelled
in 1915 to assert its unambiguous verification in spite of its unreasonableness,
since it seemed to violate everything we knew about the interference of light' [Ml].
Physics had progressed, and Millikan had mellowed since the days of his 1915
paper on the photoeffect, as is evidenced by what he wrote at that earlier time:
'Einstein's photoelectric equation ... appears in every case to predict exactly the
observed results.. .. Yet the semicorpuscular theory by which Einstein arrived at
his equation seems at present wholly untenable' [M2]; and in his next paper,
Millikan mentioned 'the bold, not to say the reckless, hypothesis of an electro-
magnetic light corpuscle' [M3]. Nor was Millikan at that time the only first-rate
physicist to hold such views, as will presently be recalled. Rather, the physics
community at large had received the light-quantum hypothesis with disbelief and
with skepticism bordering on derision. As one of the architects of the pre-1925
quantum theory, the "old" quantum theory, Einstein had quickly found both
enthusiastic and powerful support for one of his two major contributions to this
field: the quantum theory of specific heat. (There is no reason to believe that such
support satisfied any particular need in him.) By sharp contrast, from 1905 to
1923, he was a man apart in being the only one, or almost the only one, to take
the light-quantum seriously.
*It was decided later that L. de Broglie, M. von Laue, and P. Frank should also write articles of a
personal nature.357