March 11, 1955
This evening, as one week earlier, and even more so, Einstein was of unusual concentration. We read the second half of my paper On the Four Systems of the World. We sat at the round low table in his study, he at my left, not in an easy chair as he was wont, light shining on the paper that we read passage after passage, stopping and discussing. We started at 8:30 and continued till after 11:15, for two and three quarter hours. This time, in order to keep Miss Dukas awakeher fatigue was usually the cause of our breaking upI brought with me the first of the three triple-ring binders with Stargazers and Gravediggers, the story of the suppression of Worlds in Collision; I did not intend it for Einstein but for her, to have my discussion with Einstein unburdened by the usual sight of Dukas, vivid at the beginning of a session, but tired after a day of the many chores of both the household and the secretarial work, when it was close to eleven oclock. She and my wife were regularly present at our meetings, she (Dukas) rarely leaving the room. She was usually interested in what was talked about, but not in physical problemsand on one of the previous evenings, when Einstein and I were concentrating on reading my paper, she said to my wife: Dies sind für mich Bömische Wälderor These to me are Bohemian forestsimpenetrable woods with no path through them, an expression of utter unfamiliarity with a subject. For an intelligent person associated with Einstein for twenty-five years this actually was a bit of insecurity that should have been overcome; it is a fact that she could carry on intelligently Einsteins correspondence.
Now she was immersed in reading the account of my experiences. In the quiet atmosphere of the evening, with no exchange of sentences between Dukas and Elisheva, no telephone calls, no doorbell rings, Einstein and I took up passage by passage. That evening we read the third and fourth systems. The third systemthe one which has the sun, planets, and satellites carrying static electrial charges, providing the mechanism of attraction, was included for the sake of completeness; the argument that if the sun attracts the earth because of the opposite signs of their charges, it would repel the moon which, in such a plan must have a charge of a sign opposite to that of the earth, but of the same sign as the sun, disposes of this system; it is an obvious argument, and it was also used by Einstein in one of his letters when he did not suspect that my own interpretation of the electromagnetic effects in the solar system was similar at least in some respects to a rather different model, which model was presented as the fourth system. According to it, the central bodythe suncarries an appreciable charge, and by rotating creates an extended electromagnetic field; charged planets move through the fieldor are carried by it; those that rotate create magnetic fields and their satellites move through them; their motion is counterclockwise, or clockwise, depending at least in some cases upon the sign of the charge.
Einstein was obviously greatly interested and intrigued by the fourth model. When reading the text we encountered the issue of the decrease of the intensity of a field issuing from a dipole, as the inverse cube of the distance, which would require a greater charge for planets more remote from the sun in order that the overall effect should still follow the inverse square law, and by way of analogy I mentioned that this is the arrangement in the atom, where the electrons on external orbits carry more energy than those on internal orbits; Einsteins face immediately lightedhe was obviously struck by the analogy. This lighting of the face I observed twice that evening: it was as if a hunter suddenly perceived his game.
"And why do you need gravitation at all? asked he, obviously fascinated by the model. But immediately he corrected himself: Oh yes, in order to account for the phenomena on earth.
It is immaterial whether Einstein thought, as it appeared to me, that there could be truth in this system of the world; as a theoretician he was obviously fascinated by the model. It certainly appealed to him as a construction. Actually, I was presenting him with what I challenged him to produce at a meeting over a year earlier: I gave you, Albert Einstein, a very unusual mind and, what is still rarer, the recognition and admiration of your contemporaries: Now build a working plan for another universe; only dont apply gravitation that propagates at the inverse square, but electricity and magnetism you may use as much as you need. And why do you need gravitation? he soon asked again, and again trapped himself"yes, because of the terrestrial phenomena.
For the second time his face uprighted and lighted up when I mentioned that in this system the satellites, depending in part on the sign of their charge, revolve directly (counterclockwise) or retrogradely (clockwise).
His concentration that evening, the omission of counter-argument on his part, usual in our debates, and the great delight that he experienced in reading for three hours the few pagesthe second halfof my paper, made us feel closer to each other than at any other meeting. And it was this that made him say at the end of that evening: I think that it is a great error that the scientists do not read your bookthere is much that is important in it ; and even more, that made him confess to me that among the scientists he had met during his lifetime he valued completely, as a human being, only one manLorentz of Holland, all others having shown human deficiencies. He expressed himself strongly, and it was a surprise to me that he, regarded by all as so humane and so forgiving, in his unique position which brought him recognition and admiration from everybody, should be so severe a judge of the human nature of all the scientists he knew, famous and obscure. He was standing, animated, telling me what, possibly, he had never said to any outsider; yet Miss Dukas, who was kept awake during the quiet evening by reading my Stargazers, now by her response to Einsteins words displayed her knowledge of his attitude. Experience had taught him to regard his fellow men with suspicion and to see their moral inadequaciesit sounded almost as if he were a misanthrope, and this suprised me greatly; but I also felt that he was taking me into his confidence as he had possibly never taken anybody of the outside world. He was certainly very good to me that evening; I felt some tie of great tenderness, and goodwill, and confidence.
"A theory, he said, has a much greater chance for acceptance if it can predict a phenomenon ; with these words he parted with me and then he went down the stairs to the door to press my hand again; he said also something about how he enjoyed the evening with me. In his words about a theory attaining success if it can predict a phenomenon was clearly a wish that I should be able to produce such a prediction, and there sounded a sincere desire that my theory should prove true.
I felt as if Einstein blessed me that night. And he said, Let me go, for the day breaketh. And he said, I will not let thee go, except thou bless me. I probably did not think of these words that I had sent him several months earlier; but I felt an achievement: after all these months of debate about the participation of electromagnetic forces in the working of the universe, now for the first time I had made him understand how I envisaged the plan. The classical plan was compromised by evidence; the static electricity plan did not stand up against argument; but the other two plansin both of which electromagnetic effects take part in varying degreesvie for the position of the true system of the world. Now he knew that I was not contemplating a model in which electromagnetism played a static role of attraction and repulsion, but one in which it played predominantly a dynamic role. I presented my discourse in the dispassionate terms of a brief review of four contestants, and left it to reason, calculation, and experiment to make the selection.
The magnetic field of the earth, the origin of which is a mystery, would be a direct effect of a charged body in rotation; the great, almost unimaginable energies measured in billion billion electron volts with which some cosmic rays approach the earth could be explained by the magnetic field in space but especially by the charge of the earthand in consequence, the linear acceleration experienced by these ray-particles.
I certainly left Einstein with food for thought that night.