5 2 8 D O C U M E N T 3 3 6 O C T O B E R 1 9 2 4 I recorded it on paper as soon as I went home and found that a good portion of it may be of interest to the general public. I hope I have repeated your words as adequately as possible. But if you think necessary to add or change anything, please do so at your discretion. Will you forgive me for looking forward to a favourable reply? I trust in this case you will be good enough to return to me the manuscript at your earliest conveni- ence. With apologies for the wilful indignation I am asking you to sanction, I beg to remain Yours sincerely, Thomas Greenwood RELATIVITY OR THE QUANTA? A conversation with Prof. Einstein An adept of the new relativistic doctrines would hardly go to Berlin without try- ing to meet the genial author of the new picture of the universe. I was fortunate enough to learn that Prof. Einstein was in town and so as not to miss him, I decided to make an impromptu call on him at his private house in Haberlandstrasse. Directly, I was in Prof. Einstein’s study, sitted in a comfortable armchair, while my host was standing in front of me, leaning on the back of a chair as if he was going to give a lecture. —You are very interested I believe, began Einstein, in the developments of the Theory of Relativity. —Exactly, I replied, and what would interest me at the present moment would be to know the actual tendencies of the Theory of Relativity, the aim to be attained and the method to be used. —I understand quite well your question. The Theory of Relativity which has de- veloped from certain principles rather than from facts, is now faced with the exper- imental results of the Quantum Theory, which cannot, at present, be accounted for by means of the mathematical theory of Relativity. What will be the issue of this disagreement between reason and reality? How will be decided the question be- tween continuity and discontinuity? I am afraid, I shall rather surprise you. But the more I think, the more I am convinced that the classical theory of the electron will have to be abandoned. We shall have to build up a new electronic theory on the fun- damental discontinuity of matter as revealed to us by the Quanta. —What becomes then of Bohr’s theory? If I understand him well, Niels Bohr takes the electromagnetic field as the fundamental element of reality, and this im- plies the continuity of matter.