D O C U M E N T 8 1 M A R C H 1 9 2 2 9 9 —Vero asked me a few days ago why whether the transversal Doppler effect of rapid anode rays has been measured, resp. what experiments exist at in this area. I don’t know anything more specific about it either.[7] One thing I’m actually not quite clear about either is what effect how the first- order effect fares in the theory of Jupiter’s satellites, assuming a velocity against the ether of, e.g., 10 km/sec in the naïvely used theory of a resting ether. Born thinks that the discrepancy would be very large[8] — I still remain doubtful but I think I recall you saying back then already, that if one this would not automati- cally be the case, If I imagine that the [light veloc] I believe because in taking into account the relative velocities of light one would get another position and form dimension of the planetary orbit than the one otherwise given. Intrinsic interest in this issue, at the current state of r[el.] t[h.], is actually very meager but it can play a part in teaching.– —In a spherical space I have two touching, infinite perfectly straight rods , straight rods that therefore eventually meet up with themselves again. After a com- parison of their masses has taken place, one of them is brought to a velocity relative to the other along its length. What happens there to the Lorentz contraction? Does it come out somewhat thus: that the masses produced by the “rotating” spherical space are in motion and therefore however another spherical space might have to result in a different radius? Warm regards from all of us, yours, Michele. 81. To the Prussian Academy of Sciences Berlin, 13 March 1922 Esteemed Colleagues, It is now the third time this year that I received an invitation of a public nature from Paris the first time from the “League of Human Rights,”[1] the second time from the French Philosophical Society,[2] the third time from the Collège de France, asking me to give a few guest lectures.[3] The invitation is issued by the teaching faculty of the Collège de France and was conveyed to me by my friend and fellow colleague in the profession, Langevin. The letter by the latter explicitly points out that this event should serve the restoration of relations between German and French scholars. The relevant passage states: “The interest of science dictates that relations be reestablished between German scholars and ourselves. You can