A New Experimental Test of Special Relativity.
J. Shamir and E. Fox Department of Physics, Technion-Israel Institute of Technology - Haifa
(ricevuto il 23 Gennaio 1969)
Summary. — Although the special theory of relativity is almost generally accepted as a verified theory, existing experiments cannot distinguish it from a number of other rival theories that assume the existence of a preferred frame of reference (ether), and physical Lorentz contractions. It is shown that the Michelson-Morley experiment, performed in a solid transparent medium, is capable of such a distinction. The negative result of this experiment enhances the experimental basis of special relativity.
1. - Introduction.
It is almost generally accepted that the special theory of relativity (STB) is fully verified experimentally. There are however a number of rival theories, based on the existence of a preferred frame of reference often called the « ether », that are also in agreement with existing experimental results. The present reason for singling out STB is, therefore, its elegance and relative simplicity, rather than its better agreement with experiment. One of these rival theories is the well-known Lorentz theory of the electron (x) (1904). Ives (2'4) (1937, 1945) also obtained the Lorentz transformation based on the existence of an ether. JAnossy (5'7) (1962, 1963, 1966) on the other hand
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constructs a theory where the absolute frame of reference is produced by gravitational fields and again obtains the Lorentz transformation. Eecently, (1962) Gordon (8) also obtained the Lorentz transformation from a theory based on a preferred frame.
The discovery of the cosmic-micro wave background radiation (9) makes the existence of a preferred reference frame even more of a possibility. In principle this radiation can serve as a reference frame since it should be possible to detect motion through it (10). An observer moving through the black-body radiation in space will see different temperatures in different directions. We can define a preferred frame of reference as the frame in which the 3 °K black-body radiation is isotropic.
Because the cosmic background radiation brings new meaning to the notion of a preferred reference frame, experiments that might help to distinguish between STB and the rival theories mentioned above become imperative. We are interested in experiments that assume the Lorentz contraction as a physical process and are sensitive to the motion with respect to a possible « ether ». One such experiment was performed in (1937) by Wood, Tomlinson, and Essen (11). The vibration period of a quartz rod was determined very accurately while it was being rotated in a horizontal plane. The constancy of the vibrating frequency indicated that a physical Lorentz contraction is unlikely, although not excluded.
We performed a second experiment that distinguishes between STB and the rival theories, based directly on the propagation of light, which is reported here.
The Michelson-Morley experiment (MME) did not yield a strictly zero result (12). The nonzero result might have been real and due to the fact that the experiment was performed in air and not in vacuum. The effect of the lengthened optical path due to the presence of air, in contrast to vacuum, would not be cancelled by a physical Lorentz contraction. The MME would then yield a zero result only if performed in vacuum. We performed the MME in a solid transparent medium which would enhance the possible effect of the refractive index.
In Sect. 2 we analyse the MME when performed in a solid transparent medium. In Sect. 3, we describe the experiment while the measurements, results and conclusions are presented in Sect. 4.
(8) C. N. Gordon: Proc. Phys. Soc80, 569 (1962).
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(10) C. V. Heer: Phys. Her.. 144, 1611 (1968).
(n) A. B. Wood, G. A. Tomlinson and L. Essex: Proc. Roy. Soc.. 158. 606 (1937i.
(12) A. A. Michelson: Studies in Optics (Chicago. 1927).
