4 8 0 D O C U M E N T 4 8 3 F E B R U A R Y 1 9 2 7 3.) I imagine the course of the experiment, in principle, as follows: The pilot flies according to demarcations fixed on the ground that indicate the north–south direction for him. The observer records the direction of the compass needle, one time when the airplane is flying from south to north, and another time when it is flying from north to south. The difference between the immediately recorded posi- tions of the North Pole in one direction, and of the South Pole in the other direction, then indicates twice the amount of the predicted effect. Further, at the moment of the com- pass readings, a photograph of the ground is taken by a camera at- tached to the airplane floor, and af- terward the airplane is brought back to this spot of the airfield and the position of the compass needle is now likewise read off in this way one obtains the single value of the effect. [4] 1st direction of flight [5] 2nd direction of flight 4.) Even at the risk of seeming in- corrigible to you, I would like to come back once more to the electro- magnetic field of a rotating charged sphere. Please answer the following questions: Given two spherical shells with the radii and the smaller one (with radius ) has the surface charge +e the larger one, the sur- face charge –e. [Therefore, in absolute terms, both spheres have charges of equal size!] a.) What kind of field will an observer es- tablish if the spheres as well as observer B are at rest? [Rest against each other and against the system of fixed stars.] b.) What kind of field will observer B detect if both spheres are rotating at angular velocity ω, but the observer is not participating in that motion? [4] [5] a1 a2 a1