Annual report of the Board of Regents of the Smithsonian Institution . f dimensionsthat a displacement, if due to gravitation, must follow this the results with the 4-inch lens, some kind of test of the law ispossible though it is necessarily only rough. The evidence is sum-marized in the following table and diagram, which show the radialdisplacement of the individual stars (mean from all the plates)plotted against the reciprocal of the distance from the eenter. Thedisplacement according to Einsteins theory is indicated by the heavyline, according to the Newtonian law by the dotted li
Annual report of the Board of Regents of the Smithsonian Institution . f dimensionsthat a displacement, if due to gravitation, must follow this the results with the 4-inch lens, some kind of test of the law ispossible though it is necessarily only rough. The evidence is sum-marized in the following table and diagram, which show the radialdisplacement of the individual stars (mean from all the plates)plotted against the reciprocal of the distance from the eenter. Thedisplacement according to Einsteins theory is indicated by the heavyline, according to the Newtonian law by the dotted line, and fromthese observations by the thin line. Radial displacement of individual stars. Star. Calcula-tion. Observa-tion. 11 10 6 5 4 2 3 Thus the results of the expeditions to Sobral and Principe canleave little doubt that a deflection of light takes place in the neighbor-hood of the sun and that it is of the amount demanded by Einsteinsgeneralized theory of relativity, as attributable to the suns gravita-. OISTANCE 90 60 SO 40 Fig. 2. 176 ANNUAL, REPOKT SMITHSONIAN INSTITUTION, 1919. tional field. But the observation is of such interest that it will prob-ably be considered desirable to repeat it at future eclipses. Theunusually favorable conditions of the 1919 eclipse will not recur, andit will be necessary to photograph fainter stars, and these will prob-ably be at a greater distance from the sun. This can be done withsuch telescopes as the astrographic, with the object glass stoppeddown to 8 inches, if photographs of the same high quality are ob-tained as in regular stellar work. It will probably be best to discardthe use of ccelostat mirrors. These are of great convenience forphotographs of the corona and spectroscopic observations, but forwork of precision of the high order required, it is undesirable to in-troduce complications, which can be avoided, into the optical would seem that some form of equator
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