Searching for the Ether
y = - (v/c) cos D sin (9- 4) (3) NP
Fig. 2. This diagram shows the main geometrical parameters used in Courvoisier’s theoretical analysis of ether effects. The spherical surface represents the Earth, and the observer is at /, and the local directions Z, N, W correspond to Zenith, geographical North and West. The North Pole is in the direction NP. The velocity of the
Earth is V .
In Courvoisier's first method, as described above, light was reflected by a mirror. To derive the theoretical effect, it was necessary to study the influence of the motion of the mirror through the ether upon the direction of the reflected ray. Courvoisier made use of the non-relativistic analysis developed by Adolf von Hamack,15 that predicted that the angle of reflection would be different from the angle of incidence, relative to the proper reference system of the mirror (Fig. 3). This was one of Courvoisier’s main assumptions that was incompatible with the principle of relativity.
15 Adolf von Hamack, “Zur Theorie des bewegten Spiegels”. Annalen der Physik, series 4, xxxix (1912), 1053-8.
Roberto Martins Searching for the Ether
Fig. 3. Following a theoretical analysis by Adolf von Hamack, Courvoisier accepted that the angle of reflection of light in a moving mirror is influenced by its motion through the ether, and that there is a second-order effect that can be measured in the reference frame of the mirror.
Taking into account this “principle of the moving mirror”, Courvoisier predicted that the angle between the local vertical (zenith) and the direction of observation of a given star would be slightly different from the angle between the zenith and the direction of the star observed using a mercury mirror (Fig. 4).
Fig. 4. Courvoiser compared the direct measurement of the direction of a star with its direction observed by reflection on a mercury mirror.
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