File:Annual report of the Board of Regents of the Smithsonian Institution (1919) (14594854467).jpg

Identifier: annualreportofbo1919smithso (find matches)
Title: Annual report of the Board of Regents of the Smithsonian Institution
Year: 1846 (1840s)
Authors: Smithsonian Institution. Board of Regents United States National Museum. Report of the U.S. National Museum Smithsonian Institution. Report of the Secretary
Subjects: Smithsonian Institution Smithsonian Institution. Archives Discoveries in science
Publisher: Washington : Smithsonian Institution
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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onian law, this leads to an apparent displace-ment of a star close to the suns limb amounting to 0.87outward. (3) The course of a ray of light is in accordance withEinsteins generalized relativity theory. This leads to an ap-parent displacement of a star at the limb amounting to 1.75outward. In either of the last two cases the displacement is inversely pro-portional to the distance of the star from the suns center, the dis-placement under (3) being just double the displacement under (2). It may be noted that both (2) and (3) agree in supposing thatlight is subject to gravitation in precisely the same way as ordinarymatter. The difference is that, whereas (2) assumes the Newtonianlaw, (3) assumes Einsteins new law of gravitation. The slightdeviation from the Newtonian law, which on Einsteins theory causes 1 Reprinted by permission from Philosophical Transactions of the Royal Society ofLondon, Series A, vol. 220, pp. 291-333. 12573°—21 10 133 Smithsonian Report, 1919.—Dyson and Oth
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A Half-Tone Reproduction of One of the Negatives Taken with the 4-Inch Lens at Sobral. 134 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. an excess motion of perihelion of Mercury, becomes magnified as thespeed increases, until for the limiting velocity of light it doubles thecurvature of the path. 2. The displacement (2) was first suggested by Professor Einstein2in 1911, his argument being based on the principle of equivalence, viz,that a gravitational field is indistinguishable from a spurious fieldof force produced by an acceleration of the axes of reference. Butapart from the validity of the general principle of equivalence therewere reasons for expecting that the electromagnetic energy of abeam of light would be subject to gravitation, especially when it wasproved that the energy of radioactivity contained in uranium wassubject to gravitation. In 1915, however, Einstein found that thegeneral principle of equivalence necessitates a modification of theNewtonian law of gravitation, an

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