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Stagnation and Restoration of General Relativity...

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HPSC10001 – From Plato to Einstein Semester 2, 2019 Essay Topic 8. Why was there so little interest in Einstein’s general theory of relativity among physicists between 1925 to 1955 and what factors led to its revival after the Second World War?

General Relativity’s Transformation Stagnation and Restoration

(Image: © NASA)1

General relativity’s transformation 1 Redd 2019

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Introduction In the second half of 1910s, Einstein published the theory of general relativity to introduce give an explanation about the nature of the universe. His discovery had strikingly surprised the science community with the use of spacetime model, which provided more accurate measurements, e.g. for the Mercury’s orbit, than the Newtonian theory of gravitation. However, unlike many other theories which would be exploited after its success, general relativity’s popularity quickly dropped from mid-1920s and it was not until 1955 that we see the revival of general relativity with the rise in number of people started to pursue this path. The theory has remained intact and made a lot of successful contributions to our understanding of physics, the universe as well as advanced techniques until today. In this essay, I will focus on the transformation of Einstein’s general relativity, from the difficulties the theory has met leading to its oblivion since mid- 1920s and how it reentered the mainstream physics during post-world war II. In order to observe the development history of general relativity, the historical and political context, which include the world war II’s activity, will be discussed since it had the most influence on the society and the tendency of every aspect of science.

The sinking of general relativity Although there was a growth of interest in that field since its first publish, the mid 1920 onward marked the massive declination of interest in general relativity with the evidence that only a small number of scientists, especially mathematicians pursue to study this theory. The reason for this is theory appeared to be much complicated and hard to understand due to its highly mathematical formulation, which would take a lot of time for scientists to fully understand before further work on it. The fact that it used space-time which is the combination of three-dimensional (Euclidean) space and one-dimensional time to generate a single curved space has largely differentiates it from Newton’s theory which used Euclidean space. During that period of time, the model was quite new, unfamiliar and appeared to be complicated for the majority of science students and physicists to work on compared to Newton’s theory. More importantly, Newtonian theory has made a great contribution to science and technologies for more than two centuries, and a new-born theory of gravitation provides only a small correction to it would hardly make a strong shift of students and scientists’ interest into following it. 2 At that time anyone who chose to study that theory was considered as taking risk as it gave no sign of promising future for science and society and it was inevitably that general relativity would easily become a shadow of Newtonian theory. Another aspect that shaped the progression of general relativity was the historical period. The publication time of this theory paralleled to the period of preparation for War World II which enormously demanded advanced technologies, and the recruitment for scientists to serve military physics tremendously grew, leaving the theory with shortage specialists to work on. Moreover, quantum mechanics, nuclear physics, electrodynamics, etc. dominated physics in the number of specialists and practitioners, and students3 since these were the major science that required to develop atomic bombs,

2 Blum, A., Lalli, R. and Renn, J. (2016). Einstein's Theory of General Relativity. pp. 345

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radar technology, etc. which were in urgent demand during the war and had a wide variety of interesting activities happening; as a result general relativity theory was no longer in any concern of physicists. A theory that is considered as successful has to make a lot of contributions to applied science; general relativity, however, fails to achieve this. In fact, people’s interest shifted to scientific applications and there were no special demands for answering theoretical questions, hence no observations were made, abandoning the theory. The theory lost its status in the scientific community, experienced no financial, which mainly went into military services, to be able to operate, causing the withdrawal of many relativists from the field4, evidencing the drastic declination of published papers (figure 1).

Figure 1: Number of articles in general relativity as a percentage of the total number of publications in physics from 1915 to 19555

In the preface to his Relativity: the General Theory (1960), John Synge wrote: “Of all physicists, the general relativist has the least social commitment. He is the great specialist in gravitational theory, and gravitation is socially significant, but he is not consulted in the building of a tower, a bridge, a ship, or an aeroplane, and even the astronauts can do without him until they start wondering which ether their signals travel in”.6 The humorous tone of the passage displayed how unpopular general relativity were and remarkably criticized that general relativity did not make any contribution to experiments and technological application. The unappreciation for this field definitely set a physical barrier to prevent more people from pursuing this path unless they wanted a blurry future. The complexity, lack of funding and applications created a bad reputation for general relativity for students and scientists; the shortage of specialists resulted in its sinking and disappearance in the map of science.

3 Blum, A., Lalli, R. and Renn, J. (2015). The Reinvention of General Relativity: How and why it happened. pp. 599. The majority of physicists, including relativists shifted to particle physics. 4 Eisenstaedt, J., & Sangallia, A. (2006), pp. 246 5 Eisenstaedt, J., & SANGALLI, A. (2006). 6 Eisenstaedt, J., & Sangallia, A. (2006), The Ivory Tower, mechanical scientists criticized the study of general relativity, pp. 252

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The revival Before 1950s general relativity became an interest for mathematicians and philosophers to work on because of its novel properties and so many questions about it had not been addressed 7, while remaining isolated by physics. However, post-war world II remarked the explosion of highly new technologies together with the concern that fundamental science almost came into oblivion. In the letter to the Secretaries, Sir Ralph Fowler and Professor Blackett worried that “fundamental physics might be relativity neglected in comparison with applied physics”8 since it is the foundation for new discovery and the government should aim to fund for reviewing some of the science subjects that had been neglected in pre-war. This letter plus the successes of the war in terms of advanced technologies encouraged entrepreneurs and the government to invest into science. Technologies obtained from the war were temporary; in order to evolve it is necessary to keep working on theoretical science, as a result, substantial funding flowed into theoretical physics9 that did benefit general relativity research. This indeed opened an opportunity for a science subject like general relativity to be recovered with the help of technological advances made during the war, which enabled more observations to be made. Not only had the war brought many technologies back to daily life science, it also had helped train an enormous number of young scientists that then would have much more experience and could potentially work independently. Nevertheless, technological advances do not necessarily determine the return of general relativity.10 Another factor that potentially accounts for the “Renaissance”11 of general relativity is the flexibility of moving into different places permits more interactions between scientists and scientific institutions to exchange knowledge and experience. Many scientists valued the international collaboration for producing important findings12 and the annual science conference accelerated these interactions, in turns raising concern about theoretical questions and problems. The key to regain reputation for general relativity took place in a conference held in Bern in 195513 where relativists were connected and intercontinentally resettled down their field, and following this event was the productive period of general relativity and the theory was remarkably developed between 1960 and 1962 by the cooperation of many workers around the world, thereby enhancing the quality of science.14 While the evolution of technologies did not serve the main factor for this incident, novel discoveries in other scientific fields require the presence of general relativity to induce a plausible explanation and this 7 Blum, A. (2015). The Renewal of Einstein’s Theory of Relativity in the Post-War Era. The theory provides the basis explanation for the universe as a whole which attracted philosophers 8 Bullard, E., Lovell, B., & Deacon, G. (1975), pp.525. The letter was written in October 1943 with the aim to review theoretical science and determine the next steps of science after the world. 9 Blum, A., Lalli, R. and Renn, J. (2015). The Reinvention of General Relativity, pp. 347 10 Blum, A., Lalli, R. and Renn, J. (2015). The Reinvention of General Relativity. pp. 600. “since the theoretical tools used to explain the novel discoveries were developed by an increasing number of theoretical physicists and mathematicians working in the field before those observations had actually been made”. 11 Blum, A., Lalli, R., & Renn, J. (2016). The renaissance of General Relativity. Renaissance refers to the return of general relativity’s productivity. 12 Lalli, R. (2017). pp. 60 13 Blum, A. (2015). 14 Lalli, R. (2017). pp. 60. Ezra Ted Newman stated “Between 1960 and 1962 […] the entire theory of gravitational radiation was developed by the strong interaction of many workers from Syracuse, London, Hamburg, and Warsaw via personal contacts and world of communication” followed by the high quality of science.

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signifies the importance of different branches on the development of science as a whole. This potentially explains why general relativity was mentioned in the conference followed by the exploitation of the theory. A typical example is the proof of gravitational waves and the nature of gravitational fields of very dense and massive stars15 relies on the fundamental of general relativity to derive a logically concise explanation. In summary, from 1955 general relativity escaped its dead period and returned to mainstream physics , a lot of research had been done on this field together with the growth of other branches of science but it was the field that strikingly expanded. Out of all branches of physics, general relativity was the one with highest amount of paper published each year. The number of astronomers appealed to it extended at the same time and ultimately formed a new branch of science “Relativistic Astrophysics”. The requirement for study other materials and the help of scientific conferences reintroduced general relativity into mainstream physics and its revival was remarkably amazing, proving general relativity’s significance for every aspect of science.

Conclusion Having seen the stagnation of general relativity for more than 30 years, it was possibly thought that this theory would come to an end. However, its sudden revival 10 years post-world II was unexpected. Due to the limited resources to study general relativity and the historical impact of World War II, general relativity almost disappeared in the map of science. Despite that, World War II became the fundamental base that boosted the comeback of general relativity by providing larger funding to theoretical science and technological advances. Clearly, general relativity had been underrated for a while, yet a huge recognition of its potential by some science communities had given the theory a key to today’s success, allowing it to provide us a more “correct” nature of the universe and make new spatial explorations possible, and more importantly reshaping the way we look at science today.

References Redd, N. (2019). Einstein's Theory of General Relativity. https://www.space.com/17661-theory-general-relativity.html Blum, A., Lalli, R., & Renn, J. (2016). The renaissance of General Relativity: How and why it happened. Annalen Der Physik, 528(5), 344-349. doi: 10.1002/andp.201600105

15 Lalli, R. (2017). pp. 61, also see Blum, A. (2015).

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Eisenstaedt, J., & SANGALLI, A. (2006). An Unpopular Theory. In The Curious History of Relativity: How Einstein's Theory of Gravity Was Lost and Found Again (pp. 244-254). PRINCETON; OXFORD: Princeton University Press. http://www.jstor.org.ezp.lib.unimelb.edu.au/stable/j.ctv39x6bc.15 Bullard, E., Lovell, B., & Deacon, G. (1975). The Effect of World War II on the Development of Knowledge in the Physical Sciences [and Discussion]. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, 342(1631), 519-536. http://www.jstor.org.ezp.lib.unimelb.edu.au/stable/78751 Blum, A., Lalli, R., & Renn, J. (2015). The Reinvention of General Relativity: A Historiographical Framework for Assessing One Hundred Years of Curved Space-time. Isis, 106(3), 598-620. doi: 10.1086/683425 Goenner, H. (2017). A golden age of general relativity? Some remarks on the history of general relativity. General Relativity And Gravitation, 49(3), 1-16. doi: 10.1007/s10714-017-2203-1 Blum, A. (2015). The Renewal of Einstein’s Theory of Relativity in the Post-War Era | MPIWG. https://www.mpiwg-berlin.mpg.de/content/renaissance-relativity-reinvention-einstein%E2%80%99stheory-post-war-era Lalli, R. (2017). Building the General Relativity and Gravitation Community During the Cold War (pp. 5573). New York: Springer.

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