THE REALITY OF MOLECULES 89approval the favorable reports by Kleiner and by Burkhardt, who had been asked
by Kleiner to check the most important parts of the calculations. The faculty
approved (Burkhardt had failed to note a rather important mistake in Einstein's
calculations—but that comes later). Einstein was now Herr Doktor.
It is not sufficiently realized that Einstein's thesis is one of his most fundamental
papers. Histories and biographies invariably refer to 1905 as the miraculous year
because of his articles on relativity, the light-quantum, and Brownian motion. In
my opinion, the thesis is on a par with the Brownian motion article. In fact, in
some—not all—respects, his results on Brownian motion are by-products of his
thesis work. This goes a long way toward explaining why the paper on Brownian
motion was received by the Annalen der Physik on May 11, 1905, only eleven
days after the thesis had been completed.
Three weeks after the thesis was accepted, this same journal received a copy
(without dedication) for publication. It was published [E5] only after Einstein
supplied a brief addendum in January 1906 (I shall refer to this paper as the
1906 paper). As a result of these various delays, the thesis appeared as a paper in
the Annalen der Physik only after the Brownian motion article had come out in
the same journal. This may have helped create the impression in some quarters
(see, for example, [L2]) that the relation between diffusion and viscosity—a very
important equation due to Einstein and Sutherland—was first obtained in Ein-
stein's paper on Brownian motion. Actually, it first appeared in his thesis.
In the appendix to the 1906 paper, Einstein gave a new and (as turned out
later) improved value for TV:Quite apart from the fundamental nature of some results obtained in the thesis,
there is another reason why this paper is of uncommon interest: it has had more
widespread practical applications than any other paper Einstein ever wrote.
The patterns of scientific reference as traced through the study of citations are,
as with Montaigne's description of the human mind, ondoyant et divers.
The history of Einstein's influence on later works, as expressed by the frequency
of citations of his papers, offers several striking examples. Of the eleven scientific
articles published by any author before 1912 and cited most frequently between
1961 and 1975, four are by Einstein. Among these four, the thesis (or, rather, the
1906 paper) ranks first; then follows a sequel to it (to which I return later in this
section), written in 1911. The Brownian motion paper ranks third, the paper on
critical opalescence fourth. At the top of the list of Einstein's scientific articles cited
most heavily during the years 1970 to 1974 is the 1906 paper. It was quoted four
times as often as Einstein's first survey article of 1916 on general relativity and
eight times as often as his 1905 paper on the light-quantum [C5].
The large difference between this value and his value of eight months earlier was
entirely due to the availability of better data on sugar solutions.