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
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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
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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, Washington
15 June 2019
Copyright © 2019 by Paul F. Ross All rights reserved.
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A model for captivating scientific scholarly writing
Reviewed in the United States on May 20, 2019
I remember hearing a report on NPR about how scientific articles were more likely to be shared and cited if they were written in a story-like fashion. The reason: humans are natural storytellers who delight in narratives with compelling characters, struggles, and resolutions. This is why I'm giving 'No Shadow of a Doubt' five stars and applauding Daniel Kennefick's approach to the subject. It is precisely the type of writing we need more of in academia.This book depicts a fascinating page from history—the scientific expeditions that tested Einstein's theory of general relativity during the solar eclipse of May 29, 1919—with as much drama as if it were an Academy Award-winning movie. Key players in the expeditions are vividly illustrated, their methods and materials finely detailed, and the echos of the First World War rumble like a distant thunderstorm throughout the work. I found this fascinating and wonderfully refreshing as someone whose limited education in the sciences (Astronomy and Newtonian Mechanics) never featured such engaging readings. It is something I have always tried to emulate in historical fiction and which I was overjoyed to read.I consider this book a model for those interested in how otherwise exhaustive research can be presented in a way accessible and enjoyable to the public, those with anything from a professional to casual interest in the cosmos, and those shopping for ideas from history that would make a damn good screenplay.
Reviewed in the United States on May 20, 2019
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