{"id":321548,"date":"2020-01-21T14:31:20","date_gmt":"2020-01-21T17:31:20","guid":{"rendered":"https:\/\/revistapesquisa.fapesp.br\/?p=321548"},"modified":"2020-01-21T14:56:40","modified_gmt":"2020-01-21T17:56:40","slug":"daniel-kennefick-the-importance-of-sobral-2","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/daniel-kennefick-the-importance-of-sobral-2\/","title":{"rendered":"Daniel Kennefick: The importance of Sobral"},"content":{"rendered":"
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University of Arkansas <\/span><\/a> The researcher is launching a book on the eclipseUniversity of Arkansas <\/span><\/p><\/div>\n

In the early 2000s, Irish astrophysicist and science historian Daniel Kennefick, now at the University of Arkansas, joined the team at the Einstein Papers Project, an extensive endeavor that began in 1986 and that is still underway today. Coordinated by researchers at the California Institute of Technology (Caltech), the Project concerns the publication, with commentary, of thousands of scientific and nonscientific writings, such as letters and other documents, written by Albert Einstein (1879\u20131955). Kennefick joined the project during the editing of the volume for 1919, the year of the total solar eclipse that provided the first experimental proof that the general theory of relativity was correct. Upon seeing the documents from the era, he noticed that from time to time an author would make a claim that Kennefick had heard before but had not paid much attention to: namely, that British astronomer Arthur Eddington (1882\u20131944), who coordinated one of the two British expeditions that observed the 1919 eclipse (on the African island of Pr\u00edncipe), had been a great supporter of Einstein\u2019s ideas and would have therefore deliberately favored the interpretation that the light of stars curves according to the calculations predicted by the theory of relativity and not as Newton\u2019s theory of gravity predicted.<\/p>\n

Read:<\/strong>
\n– When light bent<\/a>
\n– In the British expedition\u2019s shadow<\/a><\/div>\n

Kennefick became interested in this question and, along with his work as a theoretical physicist in the area of gravitational waves, decided to investigate it in depth. In recent years, he has visited British archives to consult the writings and letters of the time. The result of this work is the book No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein\u2019s Theory of Relativity<\/em>, which will be released in English by Princeton University Press at the end of April. In this interview, the astrophysicist relates the details of the two expeditions, refutes the thesis that Eddington was biased towards Einstein, and points out that without the Sobral data, the 1919 eclipse would not have been useful in confirming the predictions of general relativity.<\/p>\n

\"\"<\/a>

No shadow of a doubt
Daniel Kennefick
Princeton University Press
416 pages
US$20.00<\/p><\/div>\n

Why does Eddington\u2019s work analyzing the 1919 eclipse data still generate some controversy, especially in academic circles?<\/strong>
\nEddington was a supporter of the theory of relativity in the United Kingdom and eventually became the most famous scientist associated with the 1919 eclipse observations. Some astrophysicists and historians imply that he would have deliberately favored Einstein\u2019s ideas when analyzing the eclipse data. Fortunately, this kind of allegation didn\u2019t gain much traction among nonspecialist audiences. However, one can read comments on the Amazon website from lay readers regarding various works that reiterate this type of criticism of Eddington. Moreover, the role of Frank Dyson [1868\u20131939], who was the Royal Astronomer of the United Kingdom and the main organizer of the expeditions, has been unfairly neglected. Eddington wasn\u2019t involved in any way with the Sobral data. In addition to not having been in Brazil and therefore not having participated in the production of these records, he didn\u2019t analyze the data from this expedition. This was handled by people from the Greenwich Observatory, basically Dyson, who was the director, and his subordinates.<\/p>\n

Is it correct to say that the two British expeditions, one to Sobral and the other to Pr\u00edncipe, acted independently, although they were coordinated?<\/strong>
\nYes. Dyson and Eddington got along well and had a friendly relationship. For a time, before 1919, Dyson was Eddington\u2019s boss when he worked at the Greenwich Observatory. Both knew the importance of the 1919 eclipse. They organized the studies, but the expeditions acted separately. In 1919, each of them was the director of an English observatory: Dyson was at Greenwich, and Eddington directed the observatory at the University of Cambridge. They were in positions that allowed them to mount their own expeditions. Dyson didn\u2019t travel with his expedition to Sobral; he sent two assistants. Eddington took part in the expedition to Pr\u00edncipe. Because his assistants had died in World War I, he also took a watchmaker who had worked on the instruments in the lab.<\/p>\n

Subsequent expeditions were unable to improve on the 1919 measurements in any significant way<\/p><\/blockquote>\n

Why didn\u2019t Dyson take part in any of the expeditions?<\/strong>
\nHe never said why he didn\u2019t participate, but there are two likely explanations. The most likely reason is that there was a very important meeting in the summer of 1919 that founded the International Astronomical Union, which to this day is the leading international organization of astronomers. He attended the meeting and became one of the principal leaders in the field. Dyson wanted to be at this meeting. In addition, there were few people at the Greenwich Observatory from 1914 to 1918 because of the war, and he didn\u2019t think that he could go away. It was probably a combination of both.<\/p>\n

Are the reasons given for discarding the data from the larger telescope used in Sobral reasonable?<\/strong>
\nI think so. It\u2019s not true that they only discarded the data from that telescope after having obtained a result for the deflection of the light that didn\u2019t match up with Einstein\u2019s theory. I consulted Davidson\u2019s notes, who was Dyson\u2019s assistant in Sobral. They were written a day or two after the eclipse. Davidson said that they had examined the plates from the larger telescope and that they looked horrible, that they couldn\u2019t extract much data from them. Right away, they knew something had gone wrong with the observations with that instrument. They were disappointed, and this problem served as the basis for their later decision to discard these measurements.<\/p>\n

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Luiz Queiroz <\/span><\/a> An aerial view of the Eclipse Museum in Sobral, inaugurated in May 1999 and closed since 2014Luiz Queiroz <\/span><\/p><\/div>\n

And the data obtained on Pr\u00edncipe? How much weight did they have in the final verdict?<\/strong>
\nThose data were used but weren\u2019t considered good. In this case, the problem wasn\u2019t due to a malfunctioning telescope but due to the presence of clouds at the time of the eclipse. They wouldn\u2019t have been able to make any confirmations with a serious impact if they had needed to rely solely on the Pr\u00edncipe data. Without Sobral, they wouldn\u2019t have been able to reach a conclusion.<\/p>\n

Can the fact that Eddington went to Pr\u00edncipe, rather than Sobral, be interpreted as an indication that the African expedition was seen as more important than the expedition to Sobral?<\/strong>
\nThe British were afraid of bad weather. Therefore, they planned on going to two places to minimize that risk. That way they would increase the project\u2019s chances of success. I think that\u2019s basically what led them to choose two locations. They probably would have come to Brazil anyway. They had trouble finding a place to observe the eclipse in Africa. The greater part of the continent where the eclipse would be visible was in the jungles of the Congo and inaccessible to them. In 1912, Eddington observed an eclipse in Brazil. Sobral was one of the few places in the eclipse\u2019s path that had a relatively dry climate, which increased the chances of experiencing good weather there.<\/p>\n

\"\"

Smithsonian Institution<\/span><\/a> Eddington…Smithsonian Institution<\/span><\/p><\/div>\n

Why did the data from the 1919 eclipse take years to be fully accepted by scientists?<\/strong>
\nI wouldn\u2019t say that other scientists\u2014especially astronomers\u2014didn\u2019t believe the data; I believe they thought that the measurements needed to be confirmed by other studies. This is typical behavior in science, which mustn\u2019t simply accept someone\u2019s word about something. Under normal circumstances, scientists immediately try to replicate a result that is so important. However, in the case of Einstein\u2019s theory, we had to wait for the occurrence of another eclipse to try to do that. This particularity made that situation special. It was necessary to wait for years to try to make new measurements. This added a certain drama to the situation. Although they confirmed the data from Dyson and Eddington, subsequent expeditions failed to significantly improve the accuracy of the measurements.<\/p>\n

Einstein really didn\u2019t interfere in Dyson and Eddington\u2019s final conclusions?<\/strong>
\nHe didn\u2019t communicate with any of the English astronomers, not even Eddington, whom he later came to know reasonably well. Through the media, Einstein knew that the British scientists had gone on an expedition to try to prove his theory. Einstein wasn\u2019t an astronomer and was never involved in this kind of a measurement. However, he encouraged people to take on this kind of an enterprise and even helped raise money for a German expedition before 1919.<\/p>\n

\"\"

US Library of Congress <\/span><\/a> …and Dyson, the British coordinators of the expeditions to Pr\u00edncipe and SobralUS Library of Congress <\/span><\/p><\/div>\n

What did you see as interesting in the archives from the British expeditions?<\/strong>
\nI\u2019ve read the letters that Eddington sent to his mother\u2019s house and notes from the committee meetings that organized the expeditions. However, what was most important was obtaining access to the data analysis produced by the Dyson team. They kept records of the data and of their calculations. Thus, I was able to see how they did the analyses and came to their important conclusion of rejecting the data from the larger telescope used in Sobral.<\/p>\n

Was this kind of data unavailable from Eddington\u2019s expedition to Pr\u00edncipe?<\/strong>
\nUnfortunately, for some reason I\u2019m unaware of, no data from this expedition has survived. The photographic plates were lost. I\u2019ve talked to many archivists and no one knows what happened. The loss must have occurred more than 50 years ago. The plates from Sobral survived and were used in a reanalysis of the eclipse data, which was done by other researchers in 1979. However, I\u2019ve never seen them. I talked to some astronomers about this. They say that after 1979, the Sobral plates were moved and no one could tell me exactly where they are. They must be mixed in among other plates.<\/p>\n","protected":false},"excerpt":{"rendered":"An astrophysicist and science historian reports that without the observation of the eclipse in the city of Cear\u00e1, the experimental results of 1919 would probably have been inconclusive","protected":false},"author":475,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[156,161],"tags":[205,235],"coauthors":[785],"class_list":["post-321548","post","type-post","status-publish","format-standard","hentry","category-cover","category-interview","tag-astronomy","tag-physics"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/321548","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/475"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=321548"}],"version-history":[{"count":3,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/321548\/revisions"}],"predecessor-version":[{"id":325628,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/321548\/revisions\/325628"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=321548"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=321548"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=321548"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=321548"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}