D O C U M E N T 1 8 2 J A N U A R Y 1 9 2 6 1 9 7 two physically different cases, in the interpretation of the special th. of rel. One can only predict that the process under consideration, judged from two inertial systems, proceeds according to the same laws. Judging from the point of view of the general th. of r., that statement is also false since not only do the relative motions exist, but also the different gravitational fields in both cases (for coordinates which transform the star, or, as the case may be, the Earth to rest) that influence the process. That’s the end of it for now. 182. From Walter Schottky Rostock, Physics Institute, 26 January 1926 Dear Mr. Einstein, I was delighted that you wrote to me about the inversion issue.[1] Concerning the statistical problem linked to the one-sided repulsion,[2] I would think one would first have to seek the classical solution. And there it seems to be the case, e.g., with an acoustical apparatus equipped with a funnel, that an augmented reflection of the sound waves occurs at its back, at the place where the emission and absorption is applied, which delivers the necessary counterimpulses in the isotropic radiation field. There would thus be a plate optically absorbing forward and reflecting back- ward at the average impulse equilibrium. And for quantum structures there also seems to be something like a reflection ability of neighboring electrons during one- sided emission that, similar to the classical cases, must also somehow have an ef- fect on the waves arriving from behind. A related question has been puzzling me recently. The transition probabilities a and b of quantum theory for an angular range dΩ refer to radiation intensities or of radiation directed to one side. For radiation simultaneously coming from many sides, the transition probabilities superimpose without disturbance the pos- sible phase of two waves moving in opposite directions, for ex., does not matter. This probably only captures the analogy to temporally averaged classical processes in which the radiation impinging on the resonator from all sides can be presumed to be incoherent by averaging over all the directions. What is not captured, as it seems, are the interference effects the case of Wiener’s experiment seems to me to be particularly instructive here, where the absorbing atom is situated at a distance of wavelengths away from a reflective plate and, depending on the relative phase of the radiation incident from the opposite direction, either manifests ρν Kν n 2 -- - and n 2 -- - 1 4 -+--