Experiments of Rayleigh and Brace

Experiments of Rayleigh and Brace (1902, 1904) should show whether the Lorentz contraction leads to birefringence. It was one of the first optical experiments to measure the relative motion of earth and ether, which were accurate enough to determine the second order for v / c. The results were negative, which was responsible for the development of the Lorentz transformation and thus the relativity of great importance (see tests of special relativity ).

The experiments

To explain the negative result of the Michelson -Morley experiment, by George Francis FitzGerald (1889 ) and Hendrik Antoon Lorentz (1892 ) introduced the contraction hypothesis, according to which a body is shortened during its movement through the stationary ether.

Lord Rayleigh (1902 ) is now interpreted as Lorentz contraction than mechanical compression. This should mean that materials are optically anisotropic, the arising of different refractive indices lead to birefringence. To measure this effect he mounted on a rotatable board in relation to the earth moving a 76 cm long tube, which was sealed at its ends by glass. The tube was filled with either carbon disulfide or water, the liquid was located between two Nicol prisms. Due to the liquid light now been sent back and forth, which was used as a source of an electric lamp and in due course, especially the lime light. The experiment was just enough to observe delays of 1/6000 of a half wavelength, that of the order. Depending on the orientation relative to the earth moving, would be the expected delay by birefringence of the order, that is well within the measurement accuracy. Thus, it was next to the Michelson - Morley experiment and the Trouton -Noble experiment, one of the few experiments which were to prove sizes of second-order capable. However, the result was completely negative. Rayleigh repeated the experiment with layers of glass plates ( albeit at a slower by a factor of 100 accuracy), and also received a negative result.

These experiments were, however, of DeWitt Bristol Brace (1904 ) criticized. Rayleigh did not exactly take sufficiently into account both the effects of the contraction (instead ) and the refractive index, so that the results are far from conclusive. Brace led by so much more precise experiments. He used a case of 4.13 m long, 15 cm wide, and 27 cm deep, which was filled with water and which was rotated depending on the test to a vertical or a horizontal axis. Sunlight was passed through a system of lenses, mirrors and prisms reflecting in the water and 7 times reflected. Here, the beam lay back 28.5 m, where a delay would have been of observable. The result was negative, too. Another experimental arrangement with glass in place of the liquid ( accuracy: ) also produced no trace of birefringence.

The absence of birefringence was originally conceived of as a refutation of the Lorentz contraction Brace. However showed Lorentz (1904) and Joseph Larmor (1904), that if one keeps the contraction hypothesis and additionally performs the transformation of the coordinates corresponding to time, i.e., the complete Lorentz transformation is used, the negative output is explained. Referring now how Albert Einstein (1905 ) within the framework of special relativity, the relativity principle from the outset as valid, the negative result of self- understood, because a uniformly moving observers may themselves be stationary view and is therefore not affect its own learn movement. The Lorentz contraction is, therefore, for a moving observer can not be measured, and must be considered along with the time dilation, which was also confirmed later with the Trouton - Rankine experiment (1908 ) and the Kennedy - Thorndike experiment ( 1933). [A 1], [A 2],