Sir Arthur Eddington and The World War One Eclipses

From the report of Sir Arthur Eddington on the expedition to verify Albert Einstein‘s prediction of the bending of light around the sun. May 29, 1919.

Just weeks after the start of World War One, German astronomer Erwin Finlay-Freundlich led an expedition into Russian-controlled Crimea to photograph the total solar eclipse on August 21, 1914. An American expedition, led by William Wallace Campbell from the Lick Observatory, arrived in Kiev with similar intentions. Earlier that spring, the Royal Astronomical Society in London had prepared to send multiple British teams into Ukraine and the Baltic to observe the eclipse before the rapid mobilization of the Russian military in response to the assassination of Archduke Ferdinand on June 28th, 1914 put an end to their plans. Despite the deteriorating political situation, both the German and American teams hoped the eclipse might prove (or disprove) Albert Einstein’s general relativity theory.

Erwin Finlay-Freundlich

Using Einstein’s assertion that gravity bends light, the astronomers planned to measure the position of a star near the limb of the sun to determine the deflection of light caused by the sun’s gravitation field. Einstein’s theory suggested that the stars’ positions in the sky would change during an eclipse, and he further attempted to calculate the extent of the shift. Prior to his 1914 expedition, Freundlich spent years analyzing photographs of historical eclipses, but failed to find any images where the stars were clear enough to test Einstein’s theory. When that method failed, he began the fundraising efforts to finance an expedition for the long-awaited 1914 eclipse. It was unfortunate that his arrival in Crimea coincided with Germany’s invasion of Belgium. Russian soldiers arrested Freundlich’s entire team, accused them of espionage, and confiscated all of their astronomical instruments.

The American expedition, under Campbell’s direction, fared a little better. They managed to avoid imprisonment but clouds obscured their view of the eclipse. Before they could return home, the Russians impounded their specialized eclipse camera and failed to release it back to the Lick Observatory for the duration of the war. As a result, the Lick Observatory team missed the 1916 eclipse in Venezuela and, because much of Europe was embroiled in the war efforts, the opportunity passed. An alternative option to test Einstein’s theory arose in in 1918 when the moon’s shadow traced a path among the Columbia River between Washington State and Oregon. Though Russia hadn’t yet returned their camera, the Lick Observatory funded another expedition but their secondary equipment left the photos blurry and inconclusive. The race to test Einstein’s theory continued.

British astronomer Sir Arthur Eddington was the Secretary of the Royal Astronomical Society throughout World War One and, as a devout Quaker, he was a pacifist. This meant that while much of Europe was actively engaged in fighting what was then called “the war to end all wars,” Eddington was still highly interested in resolving the new theories proposed by a German physicist. In 1916, the British government passed the Military Service Act which introduced conscriptions among the able populace in Britain for the first time in the nation’s history. Eddington planned to apply as a conscientious objector, but Cambridge University intervened on his behalf and requested an exemption based on the value of his work. Eddington’s exemption stood untested until 1918 but, after three years of brutal warfare, the British military once again needed to replenish its ranks and began to review past cases.

Sir Arthur Stanley Eddington

At that time, a conscientious objector status wasn’t formally recognized and, when Eddington met with military officials to request a continued exemption based on his religious objections, the court was unconvinced. They called for a second hearing a month later. When the court reconvened on July 11, 1918, Eddington offered them a letter from Frank Dyson, Britain’s Astronomer Royal and chair of the Joint Permanent Eclipse Committee of the Royal Astronomical Society. In the letter, Dyson argued that Eddington’s essential role in an upcoming solar eclipse expedition to Príncipe in May 1919 was grounds to release him from military service based on its expected implications for Einstein’s theory. According to Dyson, the 1919 eclipse was of unusual importance to counteract “a widely spread but erroneous notion that the most important scientific researches are carried out in Germany.” It was a clever appeal to wartime politics, and Eddington, he argued, was central to the study. The court granted Eddington a further twelve months exemption dependent on his continued preparations for the Príncipe expedition.

After years of failed attempts within the international scientific community, the 1919 eclipse was particularly important. For one, it would last more than six minutes, making it one of the longest in the twentieth century, and it would appear amidst a full background of stars, making it uniquely suited to test Einstein’s theory. The following spring Eddington led his team to the small Portuguese-controlled island off the west coast of Africa and, this time, it was a success. Pictures from the Príncipe expedition supported the light bending Einstein predicted. Even as the upcoming Treaty of Versailles and the end of World War One dominated the international news cycle, Eddington’s expedition became a major story, particularly as the indirect cooperation between a British and German scientist added an appealing notion of postwar reconciliation. When he formally published his results that November, it was featured on the front page of the New York Times. It similarly impacted Eddington’s career, and he became of prominent speaker on both relativity and the expedition as watershed moments in the history of science.

From the report of Sir Arthur Eddington on the expedition to verify Albert Einstein‘s prediction of the bending of light around the sun. May 29, 1919.

At one such event, Eddington was scheduled to give a lecture at the Great Hall of Trinity College to announce the results of his expedition. Four tickets were made available to students at Newnham College, the women’s college associated with the University of Cambridge, and almost by accident, a young women named Cecilia Payne found herself in attendance. She’d received the ticket from a friend who was unable to attend herself. In her later autobiography, she called the lecture “a complete transformation of [her] world picture.” Payne returned to her room and wrote down the lecture word for word. She didn’t sleep for three days, and compared the experience to “something very like a nervous breakdown.” The very next day she changed her course of study from biology to physics.

While at Cambridge, Payne attended every lecture she could on astronomy and through a later introduction to Eddington, gained access to the astronomical library. She completed her studies, though she wasn’t awarded a degree, as Cambridge didn’t grant degrees to women until 1948. When she realized teaching was the only career path available to her in the U.K., Payne looked to the United States for further opportunities. In May 1922, Harlow Shapley, the newly appointed Director of the Harvard College Observatory, was visiting England and spoke at the Royal Astronomical Society. After the lecture, Payne wrote him a letter expressing her desire to continue her studies at the Harvard Observatory. She moved from England to the United States a year later.

While under his tutelage, Shapley persuaded Payne to write a doctoral dissertation, though at the time, Harvard didn’t offer an advanced degree in astronomy and the Chairman of the Physics Department refused to accept a woman candidate. The resulting de facto organization of the astronomy degree essentially created the Harvard Astronomy Department on the doctoral level, and Cecilia Payne became the first person to earn a PhD from Radcliffe College of Harvard University. Cecilia Payne-Gaposchkin (her married name) remained at the Harvard for the rest of her career. Russian-American astronomer Otto Struve later called her thesis on stellar atmospheres, “the most brilliant Ph.D. thesis ever written in astronomy.”

Cecilia Payne-Gaposchkin

***The African continent has a rich astronomical history that both pre-dates and post-dates European (and later American) intervention in the region. While Sir Eddington’s expedition is undoubtably worthy of celebration for its significance to scientific discovery, it simultaneously benefited from colonial imperialist policy. The following articles provide additional context towards the history of astronomical inquiry in the region:

  • Dubow, Saul. “200 Years of Astronomy in South Africa: From the Royal Observatory to the ‘Big Bang’ of the Square Kilometre Array.” Journal of Southern African Studies 45, no. 4 (2018): 663-87.
  • Holbrook, Jarita C., Rodney. Medupe, and Johnson O. Urama. African Cultural Astronomy : Current Archaeoastronomy and Ethnoastronomy Research in Africa. Astrophysics and Space Science Proceedings. Berlin?]: Springer, 2008.
  • Selin, Helaine, and Xiaochun, Sun. Astronomy Across Cultures. Vol. 1. Science Across Cultures: The History of Non-Western Science. Dordrecht: Springer Netherlands, 2000.
  • Smedegar, K. “Problems and Prospects in the Cultural History of South African Astronomy.” African Skies, no. 11, (June 2007): 27-32.

Cowen, Ron. “The 1919 Solar Eclipse and General Relativity’s First Major Triumph.” Scientific American Blog Network, Scientific American, 28 May 2019,

Dickinson, David. “Remembering the ‘World War I Eclipse.’” Universe Today, 23 Dec. 2015,

Gingerich, Owen. “The Most Brilliant Ph.D. Thesis Ever Written in Astronomy,” In The Starry Universe The Cecilia Payne-Gopaschken Centenary, ed. A.G. Davis Philip and Rebecca A. Koopmann (Schenectady, NY: L. Davis Press, 2000), 4.

Payne-Gaposchkin, Cecilia. The Dyers Hand: an Autobiography. Privately Printed, 1979.

Struve, O., & Zebergs, V. (1962). Astronomy of the 20th Century. New York, NY: Macmillan.