and Stokes-Planclcs SEtlier.
163
later on. In order to reduce the slip to ^ per cent, of a •condensation of about 60000 would be required *.
In view of this considerable condensation, required by the theory of Stokes-Planck, Lorentz made in 1909 (‘ Theory of Electrons/ pp. 173-4) the following characteristic remark:—
“In this department of physics, in which we can make no progress without some hypothesis that looks somewhat startling at first sight, we must be careful not rashly to reject a new idea, and in making his suggestion Planck has certainly done a good thing. Yet I dare say that this assumption of an enormously condensed ether, combined, as it must be, ivith the hypothesis that the velocity of Jiglit is not in the least altered by it, is not very satisfactory/’ [The last words are italicised for our present purpose.]
In fact, such a condensation, introduced ad hoc and serving only the negative purpose of not upsetting the theory of aberration, did not seem very satisfactory, and the present writer has as recently as 1914 expressed the same opinion in his book on Relativity (p. 63), not so much to defend Fresnel's and Lorentz’s fixed aether, as to prepare the reader’s mind for the complete abolition of the a?tber and thus to introduce him to Einstein’s “special” relativity of 1905. Such has been the position of things until recently.
3. Now, it so happens that, stimulated by the desire to test Einstein’s generalized relativity and theory of gravitation, the astronomers participating in the last Eclipse Expedition have found an undoubtedly positive effect, the bending of rays passing near the Sun. As I have pointed out on previous occasions, it seems premature to interpret this result us a verification of Einstein’s theory, not merely in view of the small outstanding discrepancies, but chiefly in view of the failure of detecting the spectrum shift predicted by the theory, with which the whole theory stands or falls. But the Eclipse result proves at any rate that there is an
alteration,99 a change of light-velocitv all around the Sun, which thus invalidates the words of Lorentz italicized in the quotation above. The condensation claimed by Planck's modification of Stokes’s theory, for the Sun as well as for the Earth and for all other material bodies, is no longer devoid of influence on observable phenomena. It suddenly acquires physical life, so to speak.
* Notice that the aberration is a first order effect, while such phenomena as that expected by Michelson-Morley are second order effects (v2/c2), so that the above condensation suiting the aberration up to 1 per cent, will reduce the Michelson-Morley effect to one ten-thousandth of its value, and thus practically annihilate it. There is thus no need for making <r larger than 10*2.
164 Dr. L. Silberstein on the recent Eclipse Results
In other words, the discovery made at Brazil naturally suggests the idea that the observed deflexion is due to the condensation of the cether around the Sun*, and although one has been an implacable enemy of any ajther at all, for the* last fifteen years, one does not hesitate to poiut out this, possibility—a last glimpse of hope, perhaps, for the banished medium.
Let us imagine for the moment that Einstein had never published his debatable, though undoubtedly beautiful, new theory—not even that of 1905. Then it is almost certain, that the Eclipse result would readily be acclaimed as.an evidence of the condensation of the aether near the Sun, as required by the theory of Stokes-Planck, and would encourage* the physicists to work out in detail the optical and associated! consequences of such a condensation. But even though Einstein's theory has been published, and is being made popular in a most sensational way, we cannot help clinging to the said idea. I just learn from 4 The Observatory ’ for August that Mr. Jonckheere suggested some months ago that refractions may, inter alias, be caused by “a hypothetical condensation of ether near the Sun.” My point, however,, is that such a source of refraction acquires a particular interest if it is treated in connexion with the half-forgotten theory of Stokes-Planck, when it ceases to be a detached hypothesis.
It is in this sense and in such an organic connexion that I should like to draw attention to this aspect of the subject.
Of course, the quantitative details of the suitable modification of the optical, or the electromagnetic, properties of the cether due to a radially symmetrical or any other condensation have to be worked out carefully. It is not the purpose of this Note to give a complete investigation of this kind, but only some hints at its possibility. Such hints, together with some remarks on the possible advantages of the advocated theory, will occupy our attention in the following sections.
4. If, merely to fix theideas, the Boyle law is still adhered to, the condensationoutside a radially symmetrical
gravitating mass is given, as in (1), by
Jf we assume, for places near the Earth’s surface, not more and not less than what is just needed for the theory of
* The logarithm of this condensation would amount, at the Sun’s surface, bv (1) and (E), to the enormous figure a — log s = 81100.. (f the following footnote.