Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session G02: Centennial of the Eddington Eclipse ExpeditionInvited Undergraduate
Sponsoring Units: FHP DGRAV
Chair: Beverly Berger, Stanford University
Room: Sheraton Plaza D
Sunday, April 14, 2019
8:30AM - 9:06AM
G02.00001: No Shadow of Doubt: Eddington, Einstein and the 1919 Eclipse
Invited Speaker: Daniel Kennefick
In 1919, British scientists led extraordinary expeditions to Brazil and Africa to test Albert Einstein’s theory of general relativity in the century’s most celebrated scientific experiment. The result ushered in a new era and made Einstein a global celebrity by confirming his dramatic prediction that the path of light rays would be bent by gravity. Today, Einstein’s theory is scientific fact. Yet the effort to “weigh light” by measuring the gravitational deflection of starlight during a solar eclipse on May 29, 1919, has become clouded by myth and skepticism. Could Arthur Eddington and Frank Dyson have gotten the results they claimed? Did the pacifist Eddington falsify evidence to foster peace after a horrific war by validating the theory of a German antiwar campaigner? Whatever their motives, these scientists overcame war, bad weather, and equipment problems to make the experiment a triumphant success. This talk follows Arthur Stanley Eddington on his voyage to Africa through his letters home, and delves with Frank Dyson into how the complex experiment was accomplished, through his notes. Other characters include Howard Grubb, the brilliant Irishman who made the instruments; William Campbell, the American astronomer who confirmed the result; and Erwin Findlay-Freundlich, the German whose attempts to perform the test in Crimea were foiled by clouds and his arrest. The argument is made that the eclipse teams made an unbiased and justified finding which confirmed Einstein's theory and falsified Newtonian gravity.
Sunday, April 14, 2019
9:06AM - 9:42AM
G02.00002: Repeating the Experiment that Made Einstein Famous
Invited Speaker: Donald Bruns
After Einstein developed his General Theory of Relativity, astronomers were anxious to test his calculations by observing the small gravitational deflections of stars observed near the sun. This obviously required a total solar eclipse, severely constraining the observing opportunities. The first marginal success was completed in 1919 by Eddington. After nearly 100 years and only a dozen attempts, the results still had large error margins. Using a small refractor, a CCD camera, and results from the just-released Gaia star catalog, the experiment was repeated in Wyoming in August 2017. The final results matched Einstein's predictions to the highest ever accuracy and precision during a solar eclipse. The techniques used and the processing steps are presented here. There are several opportunities in the next eight years to repeat the experiment with even better results, if lessons learned here are successfully applied.
Sunday, April 14, 2019
9:42AM - 10:18AM
G02.00003: Einstein's Jury: Trial By Telescope
Invited Speaker: Jeffrey Crelinsten
While Einstein’s theory of relativity ultimately laid the foundation for modern studies of the universe, it took a long time to be accepted. Its acceptance was largely due to the astronomy community, which at Einstein’s urging undertook precise measurements to test his astronomical predictions. This paper focuses on astronomers’ attempts to measure the bending of light by the sun’s gravitational field. The work started in Germany and America before Einstein had completed his general theory, which he published during the depths of the First World War. Only a handful of astronomers, including Arthur Stanley Eddington in England, could understand the theory. Most astronomers were baffled by it and focused on testing its empirical predictions. The well-known 1919 British eclipse expeditions that made Einstein famous did not convince most scientists to accept relativity. The 1920s saw numerous attempts to measure light bending, amid much controversy and international competition.
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