D O C . 3 1 I D E A S A N D M E T H O D S 2 7 9
ADS (NNPM, MAH 278). [2 070]. The document consists of 35 pages numbered in the upper right-
hand corner. Numbering is here provided in the margin in square brackets.
[1]Dated on the assumption that this document is the manuscript mentioned in Einstein to Robert
Lawson, 22 January 1920 (see note 3).
[2]The title Einstein chose for this essay echoes the title of Mach 1897. In his obituary of Mach,
Einstein emphasized the importance of Mach’s historico-critical approach (Einstein 1916c [Vol. 6,
Doc. 29], p. 102).
[3]The document presented here is, in all likelihood, a draft of an article for Nature that was never
published. Shortly after the announcement of the results of the British eclipse expeditions, Robert W.
Lawson (1890–1960) asked Einstein on behalf of the editor of Nature for a popular short article (about
3000 words) explaining his theories of relativity and gravitation (Robert W. Lawson to Einstein, 26
November 1919). Lawson had been honorary Assistent at the Vienna Radium Institute from 1913 to
1919, and was then appointed Lecturer of Physics at the University of Sheffield. On 12 December
1919, Einstein wrote to Lawson that he was prepared to write the article (as can be inferred from Rob-
ert Lawson to Einstein, 18 December 1919). A little over a month later, Einstein informed Lawson
that the article was almost ready, but that it was probably too long for publication in Nature. He sug-
gested that the article be published elsewhere (Einstein to Robert W. Lawson, 22 January 1920). Law-
son remained confident that the article would be published in Nature, but suggested that it also be
published as a separate booklet (Robert Lawson to Einstein, 2 February 1920). Two months later,
Lawson inquired where things stood with the manuscript (Robert W. Lawson to Einstein, 31 March
1920). Einstein eventually wrote back to him, saying that he was no longer satisfied with the article
(Einstein to Robert Lawson, 22 April 1920). In December 1920, at the request of the editor of Nature,
Einstein prepared a shorter manuscript (Doc. 50) that was published as Einstein 1921d (Doc. 53).
[4]Such criticism was voiced, for instance, by anti-relativists such as Ernst Gehrcke and Philipp
Lenard (see the editorial note, “Einstein’s Encounters with German Anti-Relativists,” pp. 101–113).
[5]Fizeau 1851. For earlier statements by Einstein on the importance of the Fizeau experiment, see
Einstein 1909c (Vol. 2, Doc. 60), p. 484; Einstein 1910a (Vol. 3, Doc. 2), p. 7 (where it is called an
“experimentum crucis”); Einstein 1911i (Vol. 3, Doc. 17), p. 3; an unpublished manuscript on special
relativity of 1912–1914 (Vol. 4, Doc. 1), [p. 15]; and Einstein 1917a (Vol. 6, Doc. 42), pp. 27–28
(where once again it is called an “experimentum crucis”).
[6]“ ” should be “v.”
[7]Lorentz 1892a, pp. 524–526. Einstein presented a similar derivation of the Fresnel coefficient in
his unpublished manuscript on the special theory of relativity (Vol. 4, Doc. 1), as well as in lectures
on special relativity at the University of Berlin in 1914 (Vol. 6, Doc. 7, [pp. 3–4]) and in 1918 (Doc.
12, [pp. 3–4]).
[8]In a lecture on special relativity (Doc. 64, [pp. 8–9]), Einstein explained in more detail why a
theory in which the earth drags along the ether in its vicinity cannot account for the phenomenon of
stellar aberration. In Einstein 1918l (Doc. 15), he pointed out that the attempt in Stokes 1845 to
explain aberration on the basis of such a theory leads to incompatible constraints on the motion of the
ether.
[9]Lorentz 1895.
[10]Poincaré 1890, pp. v–xix. Contrary to what Einstein suggests in this passage, James Clerk Max-
well (1831–1879) already realized that there would be an infinity of possible mechanical models for
the ether (see, e.g., Maxwell 1873, Vol. 2, sec. 831; for a discussion of Maxwell’s views on mechanical
models, see Harman 1998, secs. V.2 and VI.1). Henri Poincaré emphasized that for Maxwell it was
only the possibility of a mechanical explanation, not the construction of a concrete mechanical model,
that mattered (for a discussion of Poincaré’s reading of Maxwell, see Darrigol 1995).
[11]Michelson 1881, Michelson and Morley 1887.
[12]FitzGerald 1889, Lorentz 1892b.
[13]As in Einstein 1917a (Vol. 6, Doc. 42), p. 36, Einstein emphasizes in this passage that special
relativity essentially vindicates the contraction hypothesis before arguing that it was nonetheless
unsatisfactory in the context of Lorentz’s ether theory. The hypothesis is no longer called “ad hoc” as
in Einstein 1907j (Vol. 2, Doc. 47), pp. 412–413, and in Einstein 1915b (Vol. 4, Doc. 21), p. 707.
Lorentz had taken exception to Einstein’s characterization of the contraction hypothesis in the latter
v0