Roberto De Andrade Martins. Searching for the Ether: Leopold Courvoiser’s Attempts to Measure the Absolute Velocity of the Solar System // DIO, vol. 17, december 2011

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Roberto Martins Searching for the Ether DIO 17

If we compare all the series of measurements, we notice that the right ascension varied between 60° and 104° (more than the estimated errors); the declination varied between 39° and 44° (within the estimated errors);20 and the speed varied between 652 and 927 km/s (within estimated errors). Notice that it is very hard to explain away Courvoisier's results as due to instrument errors, because the observed effect varied with periods of one sidereal day and half sidereal day. All common causes of error (gravity changes, temperature changes, etc.) would vary with periods of one (or half) solar day. Tidal influences due to the Moon would have periods that could also be easily distinguished from the effects predicted by Courvoisier. Besides that, the data used by Courvoisier was obtained with different instruments at different places, and covered a time span of 80 years. The results presented by Courvoisier are therefore highly impressive and cannot be dismissed lightly.

Courvoisier's device for measuring the absolute speed of the earth

In the first method used by Courvoisier, the stars work as mere point-like light sources. There is nothing peculiarly “astronomical” in the observed effect because, according to Courvoisier's theory, this was ascribed to the “principle of the moving mirror”. Therefore, similar effects should occur for terrestrial light sources, too.

Accordingly, Courvoisier was led to build a new instrument: an optical device for measuring absolute motion (Fig. 6).21 He used two small telescopes that were placed in an underground room where the temperature was fairly constant. Both telescopes pointed obliquely (zenithal distance = 60°) to a mercury mirror that was placed between them. They were mounted in a vertical plane in the East-West direction. One of the telescopes had a small electric light close to its reticule, and this was the light source that was observed from the second telescope. Both telescopes were first adjusted so that it was possible to see the reflection of the illuminated reticule of the first telescope from the second telescope. They were then fastened in those directions. Of course, the angles of the telescopes with the local vertical were sensibly equal. The experiment did not try to measure any difference between those angles. It attempted to detect small periodical changes of the position of the image of the first telescope reticule as observed from the second one. The apparent motion of

20 The slight variations of the values found for the declination led Courvoisier to assume this value as known, as remarked above (note 18), in all cases when it was impossible to compute A, D and v/c.

21 Leopold Courvoisier, “Bestimmungsversuche der Erdbewegung relativ zum Lichtäther II”, Astronomische Nachrichten, ccxxx (1927), 425-32; idem, “Über die Translationsbewegung der Erde im Lichtäther”, Physikalische Zeitschrift, xxviii (1927), 674-80.

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Roberto Martins

Searching for the Ether

DIO 17

the reticule was measured with the aid of the ocular micrometer of the second telescope.

Using this device, Courvoisier made two series of observations in 1926 and 1927. Afterwards, he had a special instrument built for this purpose, and made a third series of observations in 1932.

In his first experiments the telescopes were placed in a vertical plane in the East-West direction. In 1926 and 1928 Courvoisier built two new instruments that could be rotated. He expected that this would improve his measurements. However, he found out that it was impossible to compare measurements when the device was rotated, due to mechanical problems, and the instruments could only be effectively used in a fixed position.

The equation used to compute the effect was similar to that used in the case of the observation of stars, but instead of the North component of the speed, it was necessary to take into account the West component. As in the former case, the resulting equation has a constant term plus variable components with periods of one sidereal day and half sidereal day.

Fig. 6. Courvoisier’s double telescope apparatus for measuring the motion of the Earth through the ether.

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