Arthur and the eclipse

by @ulaulaman about #ArthurEddington #AlbertEinstein #GeneralRelativity

On the 17th November 1922, Albert Einstein, accompanied by his wife, arrived in Kobe (see the report of the visit published on the AAPPS Bulletin - pdf). Here he was surrounded by journalists and fans: while the first asked him questions, the latter were on the hunt for an autograph from one of the most famous physicists and scientists of the time. Einstein, as written by Naoki Urasawa on the initial pages of Billy Bat #9, to a specific question on why he won the Nobel Prize for the photoelectric effect and not for the theory of special and general relativity, replied:

Because, that can't be verified.

But the mangaka committed a chronological mistake, probably caused by the Urasawa's need to focus on the innovation represented by the Einstein's theories: the point, in fact, is that just three years earlier, on the 6th November, 1919, during a meeting of the Royal Society and Royal Astronomical Society, Arthur Eddington presented the results of the celestial observations made ​​in mid-spring of that year. The interest and the importance of the discovery was such that the next day, the Times headlined:
Revolution in Science: New Theory of the Universe: Newton's Ideas Overthrown, by Joseph John Thomson:

Our conceptions about the structure of the universe must be changed in a fundamental way

So, when Einstein went to Japan, the evidence of the correctness of his theory had already been around.

Arthur Eddington, born on the 28th December, 1882, was not the first who tried to measure the curvature of spacetime, but it was the first that completed this measure.
He lost his father in childhood, and as consequence he spent his early years in not so prosperous conditions. In every case, he shown good results at school: he awarded, not yet sexteenth, a scholarship to enter university.
After a first, multidisciplinary year, he devoted his studies to physics: his poverty remain, but he was able to win scholarships every year, since 1904, when he graduated with good grades.
After his graduation he changed a lot of research jobs: first of all he tried to start a research project at the Cavendish Laboratory, but not grim at ease; then he tried with mathematical research, without the hopefull success. Before the end of 1905, fortunately, he found his way: as a child he loved watching the stars, and he built himself a telescope when he was less than ten years. So, in some sense, it was a sign of destiny the opportunity to enter the Royal Observatory in Greenwich.
In Greenwich, he began to work on ordinary problems of astronomy, such as the determination of accurate values of the solar parallax, proper motion of the stars, the statistical classification of the stars. In 1914 he became Director of the Observatory. Quaker observant, he declared himself a conscientious objector and does not participate in active form to the Great War; and in 1915, when the world is really on fire, began to take a serious interest in General Relativity. One of his favorite topics is, incidentally, the anomalous advance of the Mercury's perihelion: there was all elements to design the experimental test of Einstein's theory.
On the 29th May 1919 Eddington left for the Príncipe Island, in West Africa, while a second expedition led by Andrew Crommelin went at Sobral in Brazil.
After the conclution of the detections, three sets of measures are available, because the Sobral's telescope did not work properly and the Brazilian group was forced to use the smaller reserve. The best measures were precisely those produced by the latter and by the expedition on the Príncipe Island, with a curvature respectively of 1.98 and 1.61 seconds of arc. The telescope large, however, reported a value of about 0.93 seconds of arc. During the conference on 6 November of that year, Eddington rather than to propose a statistical processing of the three set of data, he decided to expose them separately explaining the experimental problems that led to those measures. In every case it was the first, real direct measure of the validity of Einstein's general relativity, in addition to the first real use of the gravitational lens, effect widely used in the search for exoplanets.
And Eddington himself was among the first to realize the importance of this effect:

(...) gravitational field round a particle will act like a converging lens.

All this was known therefore to Einstein when, in 1922, came to Japan: that trip was possible thanks to the fame achieved by the German physicist also thanks to the revolutionary results of Arthur Eddington.

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Dyson F.W., Eddington A.S. & Davidson C. (1920). A Determination of the Deflection of Light by the Sun's Gravitational Field, from Observations Made at the Total Eclipse of May 29, 1919, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 220 (571-581) 291-333. DOI: 10.1098/rsta.1920.0009