Concerning the Aether

from "Über den Äther" (1918)
in Verhandlungen der Deutschen Physikaler Gesellschaft, 20, 165-169.
(originally submitted 5 September 1918)

Translation: © R.R.Traill (2002, 2005):
consult CAL: info@copyright.com.au — all rights reserved;
here provided with the permission of the original publishers (DPG)

Ernst Gehrcke (1878-1960) played a significant part in the criticism of relativity in the early 1920s. He and Einstein both lived in Berlin at that time, so their paths crossed — notably at the protest meeting at the Philharmonic in August 1920, (see "PS(ii)" below). Scientifically, Gehrcke is probably best remembered today for the Lummer-Gehrcke optical interference plate.

Also see Einstein's brief reply in German (1918, ibid. p261) to this present Gehrcke paper, or the translation of it on this website: Comment on E. Gehrcke's Note: Über den Äther . By now, there is also presumably an official translation in Einstein's collected papers (volume 7), but I do not have ready access to it.

Brief background information:   http://www.wikipda.de/infos/a/an/antirelativismus.html  which lists Gehrcke, Lenard, and some others of like mind at that period. (Text in German).

Very extensive source: www.ekkehard-friebe.de/kap0.pdf to www.ekkehard-friebe.de/kap8.pdf (a 1159-page online book by G.O.Mueller) — best accessed by trying to call-up the non-existent chapter www.ekkehard-friebe.de/kap9.pdf which then results in a menu of those chapters which do exist. Although the main text is mostly in German, there is still much here for non-German readers interested in relativity criticism, including   (i) a large number of references to publications and sources, many in English, (together with their descriptive-titles if you look in the right place, e.g. at the end of each subsection in chapter 2, in Arial font);   (ii) multiple lists and chronologies, sorted various ways;   (iii) occasional important quotations in English.   [File sizes are as follows: kap0=223KB; kap1=147KB;  kap2=752KB;  kap3=775KB;  kap4=2274KB;  kap5=166KB;  kap6=561KB;  kap7=520KB;  kap8=220KB.   ——  "kap"="Kapitel"=Chapter.]

[1]   For some time, it has been said that the aether is dead. However it is rising again to new life as is shown, for example, in a recent account by Lenard ⁽¹⁾ . In support of this scientific trend, which once again recognizes the aether and respects it as an indispensible aid to theory, I would like to contribute the following note.

[2]   At present it is a rather widely-held assumption, that the finding of the famous Michelson mirror-research into the detection of an aether-drag with the moving Earth is inconsistent with the fact of the aberration of [light from the] fixed stars; and that the aberration could only be understood in terms of a [universally]-resting aether, not-dragged by the Earth. However this view is wrong. Already Stokes has shown that, if one pictures the Earth as carrying the [local] aether with it, then aberration follows naturally, qualitatively and quantitatively. Then also the negative finding of Michelson's investigation is immediately clear. —
There is, e.g., a brief account referring to Stokes' theory in the 3^rd edition ⁽²⁾ of Drude's Optik; and a fuller reference by H.A.Lorentz⁽³⁾, who, although he is the chief advocate for the rival notion of an absolutely resting, immobile aether, has put the case for Stokes' theory with commendable objectivity. In these circumstances it is surprising that Stokes' theory^A,B has not generally been accepted as a serious and original attempt at solving the problem of aberration.

[3]   However at first sight it now seems that, for the concept of the Earth-accompanying aether, there is a certain difficulty: that there are known to be several laboratory-experiments which hardly allow any other interpretation than that the light-carrier, the aether, would not be drawn along by moving matter.
This is what we find e.g. in Fizeau's interference experiment,^C that a light-ray, which propagates in the direction of the streaming water by which it is in no way carried along: the light-carrying aether in the streaming water remains lying motionless. In other experiments one observes the same: here the observers declare themselves uneasy about the assumption that the aether would remain stationary and not be dragged by moving bodies.

[5]   A beautiful experiment by Sagnac ⁽⁴⁾ shows most directly that the aether remains with the slow motions of earthly bodies: A mirror-configuration for achieving interference fringes, an analogue of the Michelson mirror-experiment, is set up on a rotating disc. The whole apparatus, including the light-source, rotates with constant angular velocity. If the aether were caught up in this rotation, there would be no displacement of the interference fringes.
However Sagnac finds a displacement proportional to the angular velocity and eliminates the actual [rectilinear?] magnitude and direction, so that his apparatus rotates "in the aether-wind" . This finding, which is positive, in opposition to the negative attempt by Michelson, thus supports the earlier experiments of Fizeau etc. in the sense of a Fresnel aether, not [wholly] dragged.

[6]   The Sagnac experiment allows yet further prospects. Apart from the above, one could use Sagnac's arrangement to investigate whether the aether also stays at rest if the rotating body is a compact mass of lead which surrounds the investigated light-ray thickly on all sides. —
This question cannot be answered without experiment, though that would be worth the effort. —
Apart from posing this and similar experimental questions, one can also extract an interesting fundamental aspect of the problem from the the Sagnac experiment. His result suggests the impression: that absolute rotation is optically provable. Here the "absolute" rotation would be understood as being relative to the aether.^D

So simple is this experiment to set up in thought, but so difficult does it turn out in its real-life execution, especially since the second power of the velocity-ratio is negligible.^E However it means despairing of the advance of science if one holds that whatever is difficult today, will forever be unattainable — and it would be somewhat audacious on that account to hold that no proof of absolute translation was possible, simply because until now no-one has succeeded.

[7]   To close this exposition one might be permitted a short word on the work of Gerber^F on the gravitation, brought to light by me. Herr von Seeliger⁽⁵⁾ has contested the correctness of this theory and taken pains to show up a "mistake" in Gerber's derivation. Herr von Seeliger has however firstly not stressed that Gerber's formula for the Mercury-[orbit] perturbation is independent of the paths chosen by Gerber. However one need only change the constants of Weber's^G electrodynamic potential:

V = (μ/r) [1 - (1/c²)(dr/dt)²]

and substitute (3/c²) instead of (1/c²), in order to immediately achieve Gerber's force-law in the usual way^H

K = -(μ/r²) [1 - (3/c²)(dr/dt)² + (6r/c²)·(d²r/dt²)]

Consolidated References in Chronological Order
Gehrcke's own details are in dark blue.
The translator's additions are coloured violet.