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In two experiments in 1974 and 1975, utilizing a radio interferometer of 35-km base-line, the relative positions of three radio sources were monitored over a period of a month when the sun was within 10 deg of the sources. The mean gravitational deflection is 1.007 ±{} 0.009 (standard error) times the value predicted by general relativity. These results exclude the Brans-Dicke theory of gravitation with a scalar coupling constant ω<23 at the 99% confidence level.
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Fomalont et al. (1976) studied this question.
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