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May's solar eclipse

Dr. Einstein published his prediction in Germany in 1915 during the Great War between England and Germany. A Dutch astronomer smuggled a copy of Dr. Einstein's paper out of war-torn Europe into England where it was read by Arthur Stanley Eddington, Plumian professor of Astronomy and Experimental Philosophy at Cambridge University. This was the same position Newton held when he developed his theory of gravity.

Other astronomers had read earlier versions of Einstein's paper and tried to test his prediction during total solar eclipses in 1912 and 1914. They were not successful in their attempts due to cloudy weather and the start of the Great War. When astronomers studied the conditions of the 1919 eclipse, it appeared the Sun would be well placed in a group of bright stars. Also, the Sun's light would be totally blocked by the Moon for over five minutes which would allow enough time for the Sun and the stars to be photographed at the same time.

Professor Eddington decided to lead a group to the island of Principe near the western coast of Africa where the eclipse could be photographed. He also convinced Sir Frank Dyson, Director of the Royal Observatory, to send another group to a different location to reduce the chance that clouds might block the eclipse and prevent photographing the Sun. This other group led by Dr. Andrew Crommelin from the Royal Observatory, traveled to northern Brazil to view the eclipse.

If the weather was clear at either of these locations on the day of the eclipse, it would be possible to take a set of photographs of the totally eclipsed Sun along with a number of bright stars that appeared close to the Sun.

Map showing the path of totality of the 1919 solar eclipse

The path of totality for the eclipse of May 29, 1919 spanned the Atlantic (dark line); the eclipse was very long — nearly seven minutes at its maximum duration. The two dots indicate the positions of the expeditions led by Dr. Crommelin for the Royal Greenwich Observatory (left) and Prof. Eddington for Cambridge University (right). Click image for larger version.

Image credit: Royal Observatory Greenwich

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This page last updated: Wednesday, 24-Feb-2016 11:16:53 EST