Astronomical Tests of General Relativity A thesis for the award of Doctor of Philosophy Keith John TRESCHMAN BSc, DipEd, BEdSt, BA, MEd, MSc 2015 i Abstract This thesis is an in depth investigation of the history of the acceptance of Einstein’s Theory of General Relativity by scientists and by the public through the media. It emphasises the key role that Australia played in that acceptance and in the verification of General Relativity. This contribution came from the 1922 total solar eclipse across the continent as well as the discovery in 2003 at Parkes Radio Telescope of the first, and to this date only, pair of pulsars in mutual orbit. This system provides a unique opportunity to plumb the theory in a much stronger gravitational field regime than previously. This historical scrutiny provides an insight into scientific revolutions in general. The examination of this particular development may then act as a template for the study of other scientific revolutions. One of the key findings is that the Theory of General Relativity was prematurely accepted. The main argument of the thesis is for 1928 being the year when sufficient evidence existed for scientists to begin accepting the theory based on gravitational deflection of light instead of the commonly accepted date of 1919. Emphasis is given to the explorations of the 1922 eclipse parties in Australia and the activities of the eight groups measuring light deflection at this eclipse. This work is gathered together here for the first time. The upshot is that it was 1928 before the results were published in full and a conclusion could be drawn. It is also established that the situation for Mercury needed a much longer time period to near the end of the twentieth century before a decisive verdict could be made. Similar to the situation for light deflection, it is found that 1928 is also the year in which spectroscopic data from spectral line frequency shifts of the Sun and white dwarfs had accumulated sufficiently so that a strong conclusion on the third of the classical tests of General Relativity could be made. From the late 1960s the radio region of the spectrum was employed more frequently to investigate gravitational deflection. As a result of a subsequent extension of this application to interferometry, the increased precision of experiments provided a greater level of testing. No astronomical test yet has refuted General Relativity and agreement has been reached at the 0.05% level with one parameter involving the double pulsar. In line with the emphasis of the 1922 eclipse in Australia, the Australian newspapers were gleaned up to 1928 to see how the 1919 British total solar eclipse results were regarded by the media and the public and to ascertain how the media explained the purpose for those 1922 expeditions in Australia. It is found surprisingly that the newspapers performed admirably in explaining difficult concepts in simple terms for the public during this time. This work provides an historical account of the astronomical tests of General Relativity. More broadly, this thesis demonstrates how the acceptance of a scientific revolution depends on the constant accumulation of data by many scientists and the communication of those results to the wider community. A century after it began, Einstein’s revolution in thinking provides a suitable model for space and time in the Universe. ii Certification of Thesis 24 Sep 2015 Acknowledgements The title of this thesis is ‘Astronomical Tests of General Relativity’. However, it had its origin with the theme ‘The Contribution to Physics of the Total Solar Eclipses in Australia 1830 – 1930’ and my supervisor was Dr Wayne Orchiston who guided me at James Cook University 2011-12. After Astronomy was discontinued at this institution, I transferred to the University of Southern Queensland where I was welcomed by Dr Brad Carter. He had been my supervisor for my Master of Science 2006-10. With him the topic morphed to the present one. From 2013-15 Brad has been my enthusiastic conductor. He has the ability to draw from me the crux of an issue when I am immersed in a lot of detail. After his reading of my work at many junctures during this period, his suggestions resulted in improvement in my communication. He is at his best in a brainstorming session when I am thrashing about attempting to find a direction. He has the keen ability to make links between different areas of research to develop a central theme. During the times when I wondered whether continuing with this study was worthwhile, his humanity was at the fore as he gently guided me to see the end game and what was necessary to achieve this. Brad’s positive support has been instrumental in my reaching this destination. When I commenced my Masters in Science in 2006 he had the vision for my achieving a Doctorate even though I did not have this in mind until I completed that Degree. My gratitude is extensive for my following his baton for a total of eight years throughout both qualifications. I experienced the skill of Dr John Mainstone as an associate supervisor for only a short time until his death in 2013. He was a master of the English language, had a broad level of knowledge and possessed a command of writing. From then I came under the influence of Dr Nick Lomb. His listening abilities are very skilful before he picks up a required thread and can weave this into a connection of ideas. Over time I have witnessed his capacity to supply gems of thought in this continuing saga. His ideas have been very welcomed and he has provided a new point of direction for me on many occasions. The feedback from Nick has been exceptionally prompt and he provides nuggets in his responses. I have valued his creative flair in our discussions. My wife Madonna has been a constant source of support throughout my many years of study. Whenever I encountered a brick wall, she had the ability to ask the right questions to redirect my efforts. She was able to look at things from a different perspective and encouraged me to continue this journey. Her emotional support has been outstanding. Our children Ursula, Monica and Paul have been patient and understanding as they saw me devote many hours to my study during their childhood and adolescence. For their positive attitudes, I am truly thankful. Now, as adults, they still display an interest in my academic pursuits and value the importance of learning. I have also received encouragement from my own high school students who exhibited a curiosity in my study. Anthony Lumsden has been of tremendous assistance with technical computer issues. iv Contents Abstract …………………………………………………………………………………………………….. ii Certification of Thesis …..........……………………………………………………………………. iii Acknowledgements …………………………………………………………………………………… iv Contents ……………………………………………………………………………………………………. v Papers for Thesis ….........……………………………………………………………………………. vi Paper 1 Contents ………………………………………………………………………………………. vii Paper 2 Contents ………………………………………………………………………………………. ix Paper 3 Contents ………………………………………………………………………………………. x Paper 4 Contents ………………………………………………………………………………………. xi Paper 5 Contents ………………………………………………………………………………………. xii Introduction ………………………………………………………………………………………………. 1-11 Paper 1 ………………………………………………………………………………………………………. 145-170 Paper 2 ………………………………………………………………………………………………………. 171-188 Paper 3 ………………………………………………………………………………………………………. 90-105 Paper 4 ………………………………………………………………………………………………………. 456-465 Paper 5 ………………………………………………………………………………………………………. 150-163 Discussion …………………………………………………………………………………………………. 96-109 v Papers for Thesis Paper 1 K J Treschman, Early astronomical tests of General Relativity: the gravitational deflection of light, Asian Journal of Physics. (2014) 23 (1 & 2): 145-170. Paper 2 K J Treschman, Early astronomical tests of General Relativity: the anomalous advance in the perihelion of Mercury and gravitational redshift, Asian Journal of Physics. (2014) 23 (1 & 2): 171-188. Paper 3 K J Treschman, Recent astronomical tests of General Relativity, International Journal of Physical Sciences. (2015) 10 (2): 90-105. Paper 4 K J Treschman, General Relativity support from the double pulsar, International Journal of Physical Sciences. (2015) 10 (15): 456-465. Paper 5 K J Treschman, General Relativity in Australian Newspapers: The 1919 and 1922 Solar Eclipse Expeditions, Historical Records of Australian Science. (2015) 26: 150-163. vi Paper 1: Early astronomical tests of General Relativity: the gravitational deflection of light 1 Introduction …………………………………………………………………………………………………….. 145 2 The aim of this paper ………………………………………………………………………………………. 146 3 Unsuccessful Efforts: 1911 – 1918 …………………………………………………………………… 146 4 Total Solar Eclipse of 1919 ………………………………………………………………………………. 147 4a The Brazilian Expedition of 1919 ………………………………………………………………….. 147 4b The Príncipe Expedition 1919 ………………………………………………………………………. 148 4c Combined Results 1919 ……………………………………………………………………………….. 148 5 Communication of the 1919 Results ………………………………………………………………… 150 6 The world response to Einstein ……………………………………………………………………….. 151 7 Philosophy of Science ………………………………………………………………………………………. 152 8 Campbell and the Total Solar Eclipse of 1922 …………………………………………………… 152 9 Royal Greenwich Observatory and German-Dutch Observations on Christmas Island 1922 ………………………………………………………………………………………………………. 155 9a Royal Greenwich Observatory Encounter on Christmas Island 1922 …………….. 155 9b German-Dutch Party Observations on Christmas Island 1922 ………………………. 156 10 Indian Results from Wallal 1922 ……………………………………………………………………….