MARGINALIA
Judging Einstein
Before most physicists would believe the claims of relativity, they required proof—which would come in the form of a solar eclipse
J. Donald Fernie
Weighing the Data
Many months later, back in England, Eddington pondered the
inconsistent results. Einstein's theory predicted a displacement of
1.75 arcseconds, but none of the experiments was in perfect
agreement with the theory. The usable photos from Principe showed an
average difference of 1.61±0.30 arcseconds, the astrograph in
Brazil indicated a deflection of about 0.93 arcseconds (depending on
how one weighted the individual spoiled photos), and the little
10-centimeter telescope gave a result of 1.98±0.12
arcseconds. The smaller device, in addition to yielding the most
precise data, afforded a wider field of view and supported
Einstein's theory of how the displacement should vary with angular
distance from the edge of the Sun. But the validation of relativity
required exact measurements, particularly because physicists had
realized that Newtonian theory alone could predict a stellar
displacement that was half that of Einstein's, or about 0.83 arcseconds.
Eventually, Eddington, after much discussion with Dyson, suggested
an overall measurement of 1.64 arcseconds, which he took to be in
pretty good agreement with Einstein, but he also gave the separate
results from each telescope so others might weight them as they saw
fit. Moreover, Dyson offered to send exact contact copies of the
original photographic glass plates to anyone who wished to make
their own measurements, which should have gone far to refute the
occasional allegation that Eddington had cooked the results.
Ironically, confirmation of Eddington's conclusion (and the theory
of relativity) came from Campbell's team at an eclipse in Australia
in 1922, for which they determined a stellar displacement of
1.72±0.11 arcseconds. Campbell had been open in his belief
that Einstein was wrong, but when his experiment proved exactly the
opposite, good scientist that he was, Campbell immediately admitted
his error and never opposed relativity again.
Acknowledgment
I am indebted to Dr. Jeffrey Crelinsten for granting access to
his unpublished work on this topic and for providing comments on
an earlier version of this article.
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