Translation:Once Again: Sagnac Effect and Aether

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Once Again: Sagnac Effect and Aether  (1914) 
by Hans Witte, translated from German by Wikisource
In German: Nochmals Sagnac-Effekt und Äther, Verhandlungen der Deutschen Physikalischen Gesellschaft, 16, p. 754-755

Once Again: Sagnac Effect and Aether;

by Hans Witte.

(Received July 24, 1914.)


Two papers by Sagnac published at the end of 1913[1], caused me to write a supplement in this proceedings at the beginning of 1914[2].

Sagnac has provided and executed an interference experiment, aimed at deciding the alternative "aether or relativity principle?"; I conclude that the "Sagnac effect" does not decide this alternative.

According to reports later given to me, I am able to add the following:

1. A similar interference experiment was already described by Michelson[3] already in 1904. The (not executed) Michelson experiment of 1904 and the Sagnac experiment of 1913 have the fundamental idea in common, to split a light ray in a rotating circle, and to circulate one ray counter-clockwise, and the other one clockwise. The difference consists mainly in the fact, that Sagnac uses a circle rotating relative to Earth, while Michelson wanted to use a circle at rest relative to Earth, thus he wanted to use the self-rotation of Earth.

2. In the year 1911, Laue[4] concluded that this expected Michelson effect cannot bring a decision between aether theory and relativity principle.

Consequently, the explanations of Laue in the main already contained the refutation of the basic tendency of the Sagnac experiment executed later.[5]


  1. G. Sagnac, L’éther lumineux démontré par l’effet du vent relatif d’éther, C. R. 157, 708, 27. October 1913; Sur la preuve de la réalité de l’éther lumineux, same place p. 1410, 22. December 1913.
  2. H. Witte, Verh. d. D. Phys. Ges. 16, 142, 1914.
  3. A. A. Michelson, Phil. Mag. (6) 8, 716, 1904.
  4. M. Laue, Über einen Versuch zur Optik der bewegten Körper. Sitzungsberichte d. Königl. Bayr. Akad. d. Wiss., math.-phys. Klasse, 1911, p.405.
  5. I am thankful to Sommerfeld (who at that time has submitted Laue's paper to the Academy of Munich) and to v. Laue for making accessible his work.