D O C U M E N T 1 3 7 J A N U A R Y 1 9 2 8 1 4 7 any influence on the deflections. A simple change in the direction of the arbitrarily weak field should thus cause a drastic change in the deflections. This is certainly paradoxical, but according to our understanding, it cannot be thought to be other- wise. It would perhaps be expedient to produce the inhomogeneous field by means of a current-carrying, water-cooled tube.— If you are already in possession of facts that supply the answers to these two questions, then I would request that you inform me about them. If that is, however, not the case, then it would certainly be worth the effort to deal with the questions experimentally. Warm greetings, your A. Einstein 137. To Paul Ehrenfest [Berlin,] 21 January 1928 Dear Ehrenfest, I write to you actually so that you will not suspect a matter of principle in my silence, but instead something that so to speak happens automatically. I do not feel any possibility of suggesting Langevin and Weiss for the Nobel Prize. Their achievements are indeed fundamental, but not current (statutes!).[1] I would find Heisenberg-Schrödinger, or Stern preferable, possibly also Geiger-Bothe.[2] The devil take it, they are all Germans, but that is not my fault. I have already told you, I believe, that the derivation of the law of motion from the theory of relativity has finally succeeded. But the result is simply that of clas- sical physics.[3] I think that Kaluza-Klein have shown the correct path for going ahead. Long live the fifth dimension.[4] I suggested an amusing experiment to Stern.[5] In a magnetic field, the molecular axes should be oriented and should fol- low slow changes in the field. Therefore, the following should apply: [6] Captions, left to right: molecular beam force molecular axis edge of Stern magnet If a molecule now passes through two inhomogeneous fields, then it reverses during its passage through the gap between the two fields. Since the field also [6]