BA Festival of Science Lecture Sept 8^th 2005 – Trinity College Dublin

Published in Realta 2005 Deirdre Kelleghan

Speaker – Professor Jocelyn Bell Brunell CBE – Oxford University
“Oh leave the Wise our measures to collate
One thing at least is certain, light has weight
One thing is certain and the rest debate
Light rays, when near the Sun, do not go straight. “ A.S.Eddington

Professor Brunell came to Trinity College Dublin not to speak about her own field of radio Astronomy and her involvement in the discovery of Pulsars. The great professor came to deliver a lecture on Arthur Stanley Eddington (1882-1944) an English born astronomer who was instrumental in expounding the theories of Albert Einstein. Jocelyn Bell Brunell has an interest in the public understanding of science and has a penchant to present physics topics among non traditional groups. 

A. S. Eddington was born in Kendal in 1882. As a child he had a fascination with numbers and Professor Burnell told the anecdote of the child Eddington attempting to count all the stars in the sky, he was also driven to count all the words in the bible.

He excelled academically and did a maths degree in the short space of two years. Shortly after graduating he won the Smiths prize and was appointed to the Royal Observatory Greenwich where he improved and developed practical observational techniques. She relayed that Eddington was a popular member of “The Dinner Club” as he did not drink and if you sat beside him at dinner you were likely to get his share of wine as well. He was made secretary of The Royal Observatory Greenwich in 1912 and at the age of 31 he became Plumian Professor of Cambridge. Eddington never married or had children, he was a Quaker by faith and his primary belief that there is god and good within everybody.  was significant in his life in that he did not get caught up in the mass hysteria of anti-German feeling that permeated in Europe prior to the outbreak of WW1. Eddington was a pacifist and he avoided the war as a consciences objector. He did get called to account for his stance but still managed to get out of fighting by being proved far too valuable a scientist.

Eddington was one of the few people to read and understand Albert Einstein’s Theory of Relativity, at that time German scientists were being expelled from The Royal Society and the scientific work of Germans was hardly getting any attention from the rest of the world. Albert Einstein gave up his nationality in 1901 and became a Swiss citizen, but this failed to protect him from the welling anti German climate of the time. Eddington with his fundamental belief in the good in everyone set out to prove Einstein’s ideas in a practical way. He used the solar eclipse of May 29^th 1919 to show one of the principals of Relativity.
A known group of stars the Hades star cluster is observed at night as usual, then in the unusual circumstances of a total solar eclipse the sun is observed against the same star cluster, some of the stars in this cluster appeared out of position as their light had bent around the mass of the sun. Sir Arthur Eddington stationed himself on an island off the western coast of Africa and sent another group of British scientists to Brazil. Their measurements of several of the stars in the cluster showed that the light from these stars was indeed bent as it grazed the Sun, by the exact amount of Einstein's predictions.Eddingtons and his team in Brazil exposed 16 photographic plates in 5 minutes to capture the eclipse and the possible shift or apparent shift in the position of the stars.Eddington and his team were so busy in recording the eclipse that they did not get to see it or enjoy it in their pursuit of their goal. This research eventually confirmed Albert Einstein's theory that as light passes a very massive star; its path is bent due to gravity. Einstein became a celebrity overnight when the results were announced. Now this is a not so well written paragraph that fails to state clearly this concept so here is the way I have thought it trough.

The Hyades cluster is well known in the night sky

Eddington knew that the Suns position on the 19th of May 1919 was in front of the Hyades cluster in daylight at the moment of the solar eclipse.

One would expect one or some of the stars to be masked by the Sun as it is a very massive star, as the solar eclipse revealed the Hyades cluster in the temporary night in the daylight at the moment of the solar eclipse. The sun in fact appeared to sit along beside them in the sky and cause the apparent position of a few of them to shift a bit.

Eddington exposed photographic plates to record the eclipse and reveal that the stars of the cluster were not masked by the Suns mass, but the light from them was bent or curved by the Suns mass and gravitational field and continued to shine down on the earth, and appear on the developed plates.

As light from Stars is coming from a very great distance, it takes many thousands of years and light years to travel to our eyes or to Eddington's photographic plates.

The fact that the stars concerned appeared on his photographic plates and were not masked by the Sun, therefore Eddington proved this prediction of Einstein correct.

Because the light from a star is traveling through time and space - when it bends around a large mass like the Sun - therefore time and space are temporally bent or curved or misshapen.

This effect occurs close to the Sun at the 96 million mile mark, it is then the kink happens.
The apparent displacement of light results from the warping of space in the vicinity of the massive object through which light travels. The light never changes course, but merely follows the curvature of space. Astronomers now refer to this displacement of light as gravitational lensing.

According to Professor Brunell, Eddington was a wonderful communicator of science theory and was at the forefront of popularizing Einstein’s work. There were few people in the world at the time that could understand the theory of Relativity yet alone explain it. A poster at the time announcing on of his talks on the subject claimed it was “A Book for 12 Wise Men” Arthur Stanly Eddington made Albert Einstein’s work popular and famous by his understanding and his desire to qualify Einstein’s theory for general consumption.

Professor Jocelyn Bell Brunell in her lecture on September 8^th 2005 continued that wonderful achievement for both Albert Einstein and Arthur Eddington.

I would like to thank Professor Jocelyn Bell Brunell for her kind support in the development of this article.