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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

Hoping for a Dark Noon

As early as 1912 it seemed possible to capture the necessary photographs with little fuss. In October of that year, a total solar eclipse was to run across the northern parts of South America, and the astronomical observatory of Córdoba in central Argentina was near enough to mount an expedition. Unhappily, almost all of South America was under clouds that day.

Another suitable eclipse loomed in August 1914, running northwest to southeast across eastern Europe. Erwin Freundlich, a young German astronomer, was determined to test Einstein's theory but encountered grave difficulty raising money for the trip. The scientific establishment in Germany was uninterested in paying for it, leading Einstein himself to offer his own none-too-abundant finances. With so few options, Freundlich appealed to other countries for collaborators that would help fund the expedition. He had only one taker: William Wallace Campbell and a team from the Lick Observatory in California. Later, the Berlin Academy provided additional support.

The eclipse was due August 21, but the team of Germans and Americans established a camp near Kiev well before that date to prepare for the event. Unfortunately, history intervened: On August 1, 1914, Germany declared war on Russia, and the German astronomers were taken prisoner. Russian forces expelled the older scientists and held the younger ones as prisoners of war. The Russians did allow the Americans to stay for the eclipse, but again the sky was totally clouded out. Campbell later wrote "I never knew before how keenly an eclipse astronomer feels his disappointment through clouds. One wishes that he could come home by the back door and see nobody."

The next year, at the height of the First World War, Einstein published his general theory of relativity. This timing greatly complicated the theory's dissemination because German scientific journals were then unavailable to the English-speaking world. It was an astronomer from neutral Holland who brought word of the new theory to Britain. Moreover, Britain was going through a period of almost hysterical opposition to all things German. Ardently opposed to this mindless, pervasive hatred, a young British astrophysicist named Arthur Stanley Eddington stood almost alone. Eddington was not only a rising star in astronomy but a Quaker—a religious pacifist. As such, he refused to fight in the war, although he was willing to risk his life providing aid to civilians caught in the violence. Because of his beliefs, Eddington lived on the verge of imprisonment during much of the war and suffered vicious attacks for his pacifism and efforts to counter his peers' nationalistic hostility toward German science.

Eddington learned of Einstein's general theory from the Dutch astronomer Willem de Sitter and was immediately taken with it. He was almost certainly the first (and, for a while, the only) English-speaker to understand the theory and appreciate its significance. Eddington grasped the fact that Einstein's new work meant that the eclipse experiment was an even more significant test of relativity—the general theory predicted twice as much deflection of light rays passing the Sun as did the special theory. Another suitable eclipse would occur in 1919, and although in 1915 there was no immediate hope for peace, the British Astronomer Royal, Frank Dyson, began to lay plans (no doubt at Eddington's prompting) for an expedition to photograph the event. Eddington, of course, was eager to lead such an expedition but worried that his uncertain standing with the authorities might cause difficulties for the project. Then, in a stroke of genius, Dyson wrote a carefully worded letter to officialdom. In response, the government notified Eddington that he was lucky so far in having avoided prison, and that his only hope of remaining that way was to lead Dyson's expedition, whether Eddington liked it or not! Eddington dutifully bowed to the hoped-for ultimatum.

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