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Asunto:[debunker] Anomalies in the History of Relativity-03
Fecha:Viernes, 16 de Noviembre, 2001  20:43:39 (-0500)
Autor:illu minati <illu03>

straight line. Since the measurements on the Principe plates
were taken by placing a Principe plate film to film with an
Oxford comparison plate so that the images of correspon-
ding stars nearly coincided (which was possible because the
Oxford plates were taken direct and the Principe plates by
reflection in a mirror), the almost straight-line distribution
of stars may have worsened the accuracy of fitting together
the pairs of plates. (A diagram of the stars can also be found
in Eddington, 1920, p. 120.)
By contrast, the Sobral expedition had experienced fine
weather; it had taken photographs using two telescopes,
one similar to the Principe one and another having a dif-
ferent aperture and focal length. The photographs were
also disappointing because the definition of the images
had been spoiled. When the photographs taken by the tel-
escope similar to the Principe one were measured, “The
measures pointed with all too good agreement to the ‘half-
deflection,’ that is to say, the Newtonian value which is
one-half the amount required by Einstein’s theory.”
(Eddington, 1920, p. 117.)
Eddington (1920) went on to give a reason for preferring
the Principe results: the astronomers at Principe had taken
“check-plates” of another portion of the sky to check
whether there was any effect of the 50-degree difference in
temperature between Principe in May, and England in
January, when the photographs were taken for comparison,
whereas no such check-plates were taken by the Sobral
expedition. However, the Sobral expedition had stayed in
Brazil for a further two months after the eclipse (Eddington,
1920, p. 117) to photograph the same region of the sky
before dawn, so it would appear that the large temperature
difference would not apply to the comparison of the pho-
tographs in that case. The published paper (Dyson et a!.,
1920) states why it was not feasible for the Principe expe-
dition to make a similar comparison:
Unlike the Sobral expedition, we were not able to take com-
parison photographs of the eclipse field at Principe, because
for us the eclipse occurred in the afternoon, and it would be
many months before the field could be photographed in the
same position in the sky before dawn. The check plates were
therefore specially important for us.

In any event, it seems strange to state after the fact that the
absence of check-plates of the Brazil expedition was a disad-
vantage. Either those check-plates were significant or they
were not; if it was considered necessary to take them, that
should have been decided in advance rather than being used
after the fact to downgrade or reject a whole set of observa-
tions. A somewhat different opinion of the importance of the
check-plates has been given by A.I. Miller (1996, pp. 88-89):
Although the weather was far better at Sobral, Eddington
insisted on emphasizing data from Principe. Clearly, a key
part of this experiment is to use the same instruments at the
same site for comparing data for the apparent and true star
positions, but this was not done. The comparison photo-
graphs were taken several months later at Oxford.

There is also a puzzling discrepancy between the two
accounts: although Eddington (1920, p. 117) states explicit-
ly that “there were no check-plates taken at Sobral,” the
other account (Dyson et a!., 1920) states on p. 298, referring
to the Sobral expedition, that “A few check plates of the
field near Arcturus were taken, but have not been used.”
Several authors have referred to the way in which
Eddington emphasized some photographic plates rather
than others. For example, Campbell (1923) wrote as follows:
Professor Eddington was inclined to assign considerable
weight to the African determination, but, as the few images on
his small number of astrographic plates were not as good as
those on the astrographic plates secured in Brazil, and the
results from the latter were given almost negligible weight.
the logic of the situation does not seem entirely clear.

As a minor addition to the history of the eclipse expedi-
tions, it may also be noted that, at the same meeting at
which Dyson reported Eddington’s disappointment (Fowler,
1919), Campbell reported on the results obtained at an ear-
lier eclipse on June 8, 1918, by saying, “It is my own opin-
ion that Dr. Curtis’s results preclude the larger Einstein
effect, but not the smaller amount expected according to
the original Einstein hypothesis.” (This refers to an earlier
version of Einstein’s prediction of the displacement, which
was half the amount predicted by the general theory.)
Even after the measurements have been made, there is still
the mathematical problem of extrapolating back to the edge
of the Sun, since no stars measured were within two solar
radii of the center of the Sun and small changes in the
observed deflections can cause a much greater change in the
computed deflection at the limb of the Sun. This problem
has been discussed by von KlUber (1960) and Bertotti, Brill,
and Krotkov (1962); in particular, Figure 6 of von KlUber’s
paper shows extremely widely scattered results from various
eclipse expeditions. A more recent eclipse expedition in 1973
has been described by Zirker (1995), who shows widely scat-
tered measurements (Figure 9.4, p. 179) and states that the
occurrence of a sandstorm limited the value of the results.
The problems of interpreting the results of the eclipse
expeditions have been well summarized by Guggenheimer
(1925), who made the following comment on the 1919
eclipse observations:
Any reader, though far from an expert astronomer or physi-
cist, who will study the description of the apparatus used in
these observations and the large margin of error possible by
reason of defects therein, will readily comprehend that, in
view of the required delicacy of measurement of the things
observed and of the error allowances both for apparatus
defects and other possible physical causes of the observed
phenomena, the greatest caution in the analysis of the results
is necessary. Some astronomers deny that the photographs
of the eclipse observations, when compared with those taken
of the same stars in the absence of the Sun, show deflections
approximating the amount or the direction predicted by
Professor Einstein. An examination of the various tables of
the deflections observed shows that many of them are far
away from the quantities predicted. The quantity approximat-
ing the predicted one is obtained by averaging a selected few
of the observations.

Announcement of the Eclipse Results
The results obtained by the British eclipse expeditions of
May 1919 were announced at the famous joint meeting of
the Royal Society and the Royal Astronomical Society held
on November 6, 1919. In spite of the poor accuracy and the
uncertainties surrounding the results, it was announced
that the evidence was decisively in favor of the value of dis-

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