D O C U M E N T 2 5 1 A P R I L 1 9 2 6 2 6 5 the university’s affairs. This would be a great blessing. In my opinion, it is even so essential that I feared that, without this driving energy, the development of the university could suffer serious harm. The leadership in Palestine is currently not abiding by the decisions of the Board of Governors, and does not possess the nec- essary insight to ensure beneficial development.[1] From here, it is currently impos- sible to see what kind of financial possibilities there are for new institutes, or with which degree of solidity the existing structure is funded. Moreover, it is impossible for me, from here, to picture how the constitution of the university would have to be drawn up in order to gain the approval of the American donors and doctors.[2] I would be very pleased if, before the next Board of Governors meeting, you could discuss the fundamental issues with me, so that we are able to act in concert. Above all, we must have, before the meeting, a clear picture of the money on hand and forthcoming, as well as the conditions under which it was given. Currently, there is the danger that the members of the Board of Governors out- side Palestine will come to the conclusion that the effort that they are expending on the university is pointless. For the local leadership alone has oversight and control of the finances and is largely ignoring the decisions of the Board of Governors.[3] With best wishes for your activities in Palestine and your well-being, warm re- gards, your A. Einstein 251. From Max Planck Grunewald, [11] April 1926 Dear Colleague, If I understand [you] correctly, you say in your postcard that the interference phenomenon that you conversationally suspected cannot be accessed by observa- tion because the incident bundle of rays is not parallel in the absolute sense but rather possesses a finite, if only small aperture O.[1] I too did not understand this otherwise either. Each individual ray direction within the spatial angle O yields after all a definite point P in the focal plane of the employed convex lens, in that the rays, which are parallel in this specific direction interfere with each other and the different ray directions yield different points next to each other. Now, it is a mat- ter of whether the intensity maximums and minimums are far enough apart for them to be distinguishable, just as is the case with light passing through a normal plane-parallel plate. Otherwise we can, of course, perhaps discuss this further on Thursday.[2] Kind regards, your Planck