The following is a paper by H. Aspden published in Lettere al Nuovo Cimento, v. 38, pp. 568-572 (1983).


Abstract: New optical experiments aimed at testing light speed anisotropy to first-order in v/c are proposed on the basis of an intuitive enquiry into the physical processes by which the vacuum exhibits zero dispersion when regulating the propagation of light waves. Such experiments can be justified because standing waves are present in experiments of the Michelson-Morley type and these may have a disturbing influence on light propagation speed in the standing wave region. Though a null result from an initial experiment is reported, the outcome of a second experiment yet to be performed is needed to reach a conclusion from this investigation.

Commentary: The author had, at the time, been involved with correspondence with E.W. Silvertooth, who performed the first experiment mentioned and advised the null finding, but, as yet (1993), the second experiment has not been performed. Note that the experiment, being of first-order in v/c, should allow the laboratory measurement of the Earth's eastward speed. It was later that Silvertooth advised he had performed an experiment which sensed a motion at 378 km/s in the direction of constellation Leo.

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