No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity by Daniel Kennefick (PDF)

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On their 100th anniversary, the story of the extraordinary scientific expeditions that ushered in the era of relativityIn 1919, British scientists led extraordinary expeditions to Brazil and Africa to test Albert Einstein’s revolutionary new theory of general relativity in what became the century’s most celebrated scientific experiment. The result ushered in a new era and made Einstein a global celebrity by confirming his dramatic prediction that the path of light rays would be bent by gravity. Today, Einstein’s theory is scientific fact. Yet the effort to “weigh light” by measuring the gravitational deflection of starlight during the May 29, 1919, solar eclipse has become clouded by myth and skepticism. Could Arthur Eddington and Frank Dyson have gotten the results they claimed? Did the pacifist Eddington falsify evidence to foster peace after a horrific war by validating the theory of a German antiwar campaigner? In No Shadow of a Doubt, Daniel Kennefick provides definitive answers by offering the most comprehensive and authoritative account of how expedition scientists overcame war, bad weather, and equipment problems to make the experiment a triumphant success.The reader follows Eddington on his voyage to Africa through his letters home, and delves with Dyson into how the complex experiment was accomplished, through his notes. Other characters include Howard Grubb, the brilliant Irishman who made the instruments; William Campbell, the American astronomer who confirmed the result; and Erwin Findlay-Freundlich, the German whose attempts to perform the test in Crimea were foiled by clouds and his arrest.By chronicling the expeditions and their enormous impact in greater detail than ever before, No Shadow of a Doubt reveals a story that is even richer and more exciting than previously known.

User’s Reviews

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐Review of Kennefick’s “No shadow of a doubt” by Paul F. Ross Daniel Kennefick, in 2019, takes on the critics of Eddington and Dyson, astronomers who traveled from England to an island off west Africa and to an inland observing spot in Brazil, respectively, to observe the 29 May 1919 eclipse of the Sun as a means for testing Einstein’s 1915 theory that light consists of particles that are deflected by gravity as they move through a strong (the Sun’s) gravitational field. Prior to Einstein’s new theory, scientists thought of light as consisting of waves that vibrate in the ether, having no substance. Astronomers Eddington at Cambridge Observatory and Dyson at the Royal Greenwich Observatory understood the upcoming opportunity, had the help of a Joint Permanent Eclipse Committee composed of astronomers in England in the process of winning____________________________________________________________________________________________Kennefick, Daniel “No shadow of a doubt: The 1919 eclipse that confirmed Einstein’s theory of relativity” 2019, Princeton University Press, Princeton NJ, viii + 405 pages____________________________________________________________________________________________government funding, were immersed in uncertainty by the ongoing WWI while planning, but planned anyway. The war ended. They found transport to their separate viewing sites. Observing time for a total eclipse lasts only a few minutes. The Sun’s disk is completely covered by the Moon with only the Sun’s limb visible. Stars are visible both near the Sun and some distance from the Sun. If Einstein is right, the light from the stars appearing near the Sun’s edge is bent as it passes the Sun. Light from stars located some distance away from the Sun is not bent or, at least, is bent less. The two parties set up their equipment. They made their observations on film. And then the data analysis began, most of it done at their respective observatories back in England. One needs a view of those same stars taken at night when the Sun is not in the segment of sky being viewed. One then measures – using a micrometer while examining the developed film – the distances between the reference stars and compares each star’s apparent position (with respect to the other stars) when the Sun is in the field of vision during the eclipse with the same stars’ positions when the Sun is not in the field. If the Sun’s gravity bends light, as Einstein says, the stars near the Sun will appear in a slightly different position on the film during the eclipse than they do when the Sun is not in the field of view. The photos during the eclipse must be captured during the few minutes of full eclipse since that is the only time when the stars around the Sun can be seen. The comparison photos of the same piece of sky must be captured at night when the Earth is at approximately the same place in its annual orbit that it was at the time of the eclipse … within a day or two of the eclipse or as much as a year earlier or later. If the film requires a minute or two to record the light of the dim stars, the telescopes must be able to track the apparent motion of the stars or the star images appear as streaks on the film rather than a precise point. Einstein’s theory said the bent-light would make the star appear to be displaced less than a full diameter of the image of a star. Imagine what that demands of the analyst using the micrometer to measure distances on the film! Doing the observations accurately in 1919 was delicate business and doing the measurements comparing the eclipse images with the reference images was equally delicate. Using images from both Principe (Eddington’s observing location off west Africa) and Brazil (Dyson’s observing location), Eddington said Einstein’s theory was confirmed. Dyson’s “best” telescopes had failed to produce images that were interpretable. Announcing their results, Einstein, virtually unknown before, almost instantly became world famous and remained so for the rest of his life. In recent decades, physicists and astronomers reviewing the Eddington and Dyson data and reports, particularly the reviewers who doubt Einstein’s theory, conclude that Eddington’s conviction that Einstein was right, a conviction Eddington held before making the observations, caused Eddington to have biases which influenced his data evaluation and judgment. Kennefick writes his book to defend the validity of Eddington’s data and findings. Kennefick strengthens the 1919 findings by introducing data taken from subsequent eclipses observed by other astronomers and processed by improved methods. The book’s index (of all places!) has a list of total-eclipse dates from 28 May 585 BCE to 21 August 2017 CE under the index entry “eclipse (dates).” Seeing a review of Kennefick’s book and another book-length discussion of the 1919 results in a May 2019 issue of Science, having read the two reviews, I purchased Kennefick’s book. As a behavioral scientist, I quickly admired Kennefick’s attention to the effects of politics (war, government policy, inter-institutional competition) and attitudes (favoring or not favoring Einstein’s theory, defending or not needing to defend Newton’s theory of gravity, etc.) on the conduct of science. There is reality in those observations. Doing the reading, however, I soon found myself wrestling with the difficulties of Kennefick’s book. He seldom writes a simple sentence or organizes a series of paragraphs with a reasonable progression of topics. He refers to each eclipse expedition or critic by the last name of the leading astronomer or physicist. By the time the list grows to what must be at least twenty, I could not remember what cluster of data and ideas each “expedition leader’s or critic’s last name” represented. Kennefick’s chapter outline is by themes he sees as important – this chapter about critics who see Eddington as biased, the next about the institutions represented, another about the equipment used. Kennefick does not follow the timeline of the increasing data and advancing technology such as from May 1919 to September 1922 to June 1973 to August 2017, attitudes changing, evidence accumulating, equipment changing, analysis changing as time progressed. Kennefick concludes that Einstein’s theory is right, that Eddington and Dyson had it right in 1919-1920, and that the critics’ views can be understood and set aside. I suspect Kennefick has most things right. But the reading is hard work. I wish Kennefick had had a take-charge editor at Princeton University Press, one who would have insisted on a massive rewrite. Kennefick’s interest in detail, technological and social, could be even more interesting if presented in the right story-telling framework.Bellevue, Washington15 June 2019Copyright © 2019 by Paul F. Ross All rights reserved.

⭐Here is what I wrote to the author:”Dear Professor Kennefick,I wanted to drop you a quick note telling you how much I enjoyed reading “No Shadow of a Doubt”. I am a retired engineer who loves physics and the history of physics. I have been slowly teaching myself general relativity. I have also read 20 or more books on great physicists. Your wonderful book helped to solidify my appreciation of both Einstein and Eddington, and introduce me to the greatness of Dyson. Also, your description of the experimental challenges of measuring gravitational light bending was very informative and new for me. Your book reads like a “labor-of-love.”Thank you for your wonderful research and book.”

⭐This is an extremely detailed story around Eddington and the famous eclipse .Almost 400 pages!It is more an historical book than a technical book (no equation).A few diagrams help along the way.I regret the lack of explanation why the correct value of the deviation was double that first predicated by Einstein.Anyway the style must be good since i practically read it till the end….

⭐There is a lot of science here. And a lot about science in general. Early on, the author describes Einstein’s theories in what I thought were rather clever ways. But the book’s main focus is the 1919 solar eclipse (100 years ago this year) which led to strongly supporting evidence for Einstein’s general theory of relativity – particularly Eddington’s participation in that eclipse. Eddington was so convinced of the theory’s correctness that today some scholars wonder if he was biased enough to somehow subconsciously influence the results from the data gathered in the eclipse expeditions in favor of Einstein. Through meticulous historical research, the author analyses these claims with a fine-toothed comb and arrives at what would seem to be the most likely answer to this intriguing question.I enjoyed this book very much. There is much about how science is done and how science should be done – particularly according to the writings of various philosophers. But the parts of the book that I had difficulties with were the intricate details given about the finickiness of some of the equipment used in some of the observations and in what was required for the data analysis and how it was done. I feel that if that many details are to be given, then they should be accompanied by clear diagrams to support the text. There were no such diagrams. Otherwise, I found the book to be a fun and captivating read that should appeal to most serious science enthusiasts.

⭐Clear, detailed and thorough but accessible and a great in-site into how theoretical and experimental science work together to change our understanding of the universe.

⭐There is a lot of science here. And a lot about science in general. Early on, the author describes Einstein’s theories in what I thought were rather clever ways. But the book’s main focus is the 1919 solar eclipse (100 years ago this year) which led to strongly supporting evidence for Einstein’s general theory of relativity – particularly Eddington’s participation in that eclipse. Eddington was so convinced of the theory’s correctness that today some scholars wonder if he was biased enough to somehow subconsciously influence the results from the data gathered in the eclipse expeditions in favor of Einstein. Through meticulous historical research, the author analyses these claims with a fine-toothed comb and arrives at what would seem to be the most likely answer to this intriguing question.I enjoyed this book very much. There is much about how science is done and how science should be done – particularly according to the writings of various philosophers. But the parts of the book that I had difficulties with were the intricate details given about the finickiness of some of the equipment used in some of the observations and in what was required for the data analysis and how it was done. I feel that if that many details are to be given, then they should be accompanied by clear diagrams to support the text. There were no such diagrams. Otherwise, I found the book to be a fun and captivating read that should appeal to most serious science enthusiasts.

⭐wenn auch etwas lang, ein sehr schönes Buch!

⭐

⭐Loved it

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