4 8 4 D O C U M E N T 4 8 6 F E B R U A R Y 1 9 2 7 know whether I could prevail with him. It is probably no longer possible to help him, and I don’t doubt that the matter will turn out very badly. I would very much like for Tete to come here during his Easter holiday. Be- cause that would be best for him and is also nicest for me. It is also good for him to get to know people a bit so he won’t be ensnared like Albert. But then I will come visit you in the summer. I’m pleased that our relationship has become so good. I’m always telling everyone how good things are with my ex-wife and how well accepted I am in your home, and Else is pleased that my boys and you are no longer so hostile toward her. I have agreed that Brazilian dollar bonds be purchased for the repaid securities in America. Warm regards, your Albert 486. To Teodor Schlomka [Berlin,] 23 February 1927 Dear Colleague, 1) I entirely agree with your second observation method. Gondola as reference system. Compass housing adjusted precisely relative to the gondola. Needle read- ings against compass housing. Apparatus precisely oriented relative to the gondola. Needle result relative to Earth’s surface. I had good success in my experiment with a compass whose housing was filled up completely with castor oil. 2) Your theoretical consideration is entirely correct, up to the final statement: “Now, as it is supposedly entirely the same whether the observer is at rest and the sphere is rotating, or the sphere is at rest and the observer is moving around the sphere.” This is incorrect. The Maxwell equations are not valid with reference to a rotating system thus this equivalence does not hold. You could conclude just as well this way: a) resting sphere and resting observer: no magnetic field b) rotating sphere and observer rotating along: no magnetic field. This result is reached by the same method as yours and contradicts it. In reality, both ways of reasoning are false for the indicated reason. According to relativity theory, the following reasoning is correct, however: a) resting sphere, resting observer B: at B no electromagnetic field b) " " , moving observer B' (at location of B) likewise, no electromag- netic field relative to B'.