x x x I N T R O D U C T I O N T O V O L U M E 7
Since 1911, Erwin Freundlich had hoped to find empirical support for Einstein’s
theory and had mounted an expedition to photograph the solar eclipse in the Crimea
in August 1914. Due to the outbreak of war, however, the scientists were impris-
oned, and their instruments were confiscated by Russian authorities. Back in Ger-
many, Freundlich concentrated his efforts on detecting the gravitational redshift of
spectral lines in the solar atmosphere.
The first observational test of general relativity would be performed by British
expeditions. Sir Frank W. Dyson, the Astronomer Royal, expected that the eclipse
of 29 May 1919 should be especially suitable, since it would happen with the sun
standing before the stellar cluster of the Hyades, hence offering an unusually high
number of bright stars in the direct vicinity of the sun. Dyson went ahead with a
plan that Freundlich could never dream of realizing, even with Einstein’s influen-
tial support. The measurements were performed in two locations: Sobral in north-
ern Brazil, and the island of Principe in the gulf of Guinea.
In September 1919, Arthur S. Eddington, one of the leaders of the expeditions
and an important supporter of general relativity since 1917, gave a report on the
expeditions at a meeting of the British Association for the Advancement of Sci-
ence. Preliminary results were conveyed to Hendrik A. Lorentz, who passed the
information on to Einstein in a telegram on 22 September, followed by a letter of 7
October. Einstein, who had been eagerly awaiting news for more than four months,
composed a short note Einstein 1919d (Doc. 23). Without claiming that the provi-
sional results confirmed general relativity, Einstein merely recapitulated the data
contained in Lorentz’s telegram.
The public triumph of general relativity came during a joint session of the Royal
Society and the Royal Astronomical Society on 6 November. Andrew C. Cromme-
lin, the co-leader of the Sobral team, gave the following final values: or
with an error of for the first Sobral telescope;
±
for the
second telescope; and
±
for the Principe telescope. Crommelin argued
that the results from the first telescope should be discarded, since the photographs
were out of focus due to a malfunctioning of the heliostat. The mean of the other
two values agreed “very closely with Einstein’s predicted value ,” he con-
cluded (Crommelin 1919). Based on these final values, Eddington announced that
“there can be no doubt that they [the values] confirm Einstein’s prediction. A very
definite result has been obtained that light is deflected in accordance with Ein-
stein’s law of gravitation” (The Observatory 152 [1919]: 391). Einstein was again
informed of the good tidings in a telegram from Lorentz (14 November 1919). The
news made headlines in both The Times of London and the New York Times, and
Einstein, who had been virtually unknown to the public outside of Germany,
quickly rose to international fame.
0.93″
0.99″ 0.3″ 1.98″ 0.12″
1.60″ 0.3″
1.75″