1 9 6 D O C U M E N T S 1 8 0 , 1 8 1 J A N U A R Y 1 9 2 6 Unfortunately, I am now firmly convinced of the impossibility to derive the laws of electricity from a generalization of Riemann’s conceptual scheme.[10] All of that effort was futile. Kind regards to you from your A. Einstein 180. From Arnold Sommerfeld Munich, 23 January 1926 Dear Einstein, When I visited you last fall, we discussed, among other things, aberration and Thirring’s notes in that regard.[1] Emden’s lecture, which is being sent to Natur- wiss[enschaften] today,[2] echoes, as I see it, your view and seems to me to appeal- ingly and forcefully justify the confusion created by Lenard,… etc.,[3] in part also by Thirring. When you find the time, it would be very nice if you would read it and send it back to Emden (Habsburger Str. 7) with possible marginal notes. Then, in his revision, he could take into account your possible comments. We have diligently pursued Bose statistics and drawn a few valuable conclu- sions (cf. Heitler, in press), even concerning hydrogen intensities (cf. Sommerfeld & Unsöld, soon forthcoming).[4] With best wishes, your A. Sommerfeld 181. To Arnold Sommerfeld [Berlin, between 23 and 28 January 1926] Dear Sommerfeld, I cannot agree with the argumentation of our colleague Emden on the pivotal point.[1] Thus it would probably be best if I briefly presented my standpoint, whereby I elaborate on the first paragraph of Mr. Emden’s exposition, which presents the sophism: “Relativity theory knows no absolute motion.” This is correct. Further on, it reads, “the aberration can therefore only depend on the relative motion Earth-star” This, however, is false.[2] From the point of view of the special th. of relat., this statement is not valid in the case of the orbiting star, because according to the spe- cial th. of r., acceleration is absolute. Orbiting star and orbiting Earth hence signify