I’ve just added this to the “Eclipse Stories” section for the new edition of my Under-Standing of Eclipses:
1919 May 29, solar total, South America to central Africa. Arthur Eddington was the English astronomer best placed to understand Einstein’s 1915 general theory of relativity (because he was skilled in mathematics and free of anti-German prejudice). One of its predictions was that starlight passing close to the Sun would be bent by a certain small angle; this could be tested only during an eclipse. The 1914-18 war was still on, but an expedition was planned to observe the eclipse from Principe, then a Portuguese colony, now part of the two-island nation Sao Tomé and Principe, in the Gulf of Guinea. Eddington, a Quaker pacifist, was nearly conscripted for army service; the Astronomer Royal, Frank Dyson, won exemption for him on the ground of the expedition’s importance. Eddington went to Principe, succeeded in photographing stars of the Hyades close to the eclipsed Sun, resulting in confirmation of Einstein and worldwide fame for him and Eddington.
This is, as it has to be, compressed. The more you learn about Eddington, the more interesting. Was the indeterminism he believed in the same as Heisenberg’s uncertainty principle? Did he really cycle 84 miles on 84 occasions? What were his tribulations on Principe, one degree north of the equator?
In the August issue of Sky & Telescope, Donald Bruns explains how he will try to repeat Eddington’s relativity test, probably with even greater accuracy, from Wyoming at the August 2017 eclipse.