Einstein Wrote Back. John W. Moffat

a unified field theory, he had not included a field associated with the strong and weak nuclear forces. These forces were already known to be important in the early 1950s, and had been discovered by observing particle collisions in early accelerators. I really felt that Einstein needed to include these forces in his theory. It was clear to me that without them, he could never hope to achieve a correct and complete unified field theory.

      Einstein must have responded almost immediately to this letter, for his next one to me was dated August 24. “Dear Mr. Moffat!” he began, in another handwritten letter:

      Our situation is the following. We are standing in front of a closed box which we cannot open, and we try hard to discuss what is inside and what is not. The similarity of the theory [his unified field theory] with the one by Maxwell [electromagnetism] is only superficial. Thus we cannot simply take over the concept of a “force” from this theory to the asymmetric field theory. If this theory is useful at all, then one cannot separate the particle from the field of interaction. Also there is no concept at all of the motion of something that is more or less rigid. The question here is exclusively: Are there solutions without singularities? Is there energy preferably localized in such a way as it is required by our knowledge of the atomic and quantum character of reality? The answer to these questions is indeed not achievable with present mathematical means. Thus I do not see how one should suspect whether some remote action and some objects, as far as we have gained a semi-empirical knowledge of them, are represented by the theory. Thus our pertinent complete ignorance does not begin with “nuclear forces.” Here the situation is different from the pure theory of gravitation, where one can approximate the masses through singularities.

      Einstein was willing to accept that he was ignoring the nuclear forces. However, he was trying to justify this omission by saying that we are not able to understand these nuclear forces with the mathematical tools available at that time.

      “The only thing that is in favor of the new theory,” he continued, still referring to his unified field theory, “is the fact that it appears to be the only natural generalization of the equations of the pure gravitational field.”

      I wrote two more letters to Einstein, enclosing further calculations based on his nonsymmetric unified field theory. I discussed some critical aspects of his field equations. He responded in October 1953 with a short note, advising me to be careful about publishing this work prematurely. I took his advice and continued developing his theory.

      When I wrote to Einstein in 1953, he was one of the most celebrated physicists in the world, and had won the Nobel Prize long before, in 1921.* But he had isolated himself from the rest of the physics community by his problematic stand on quantum mechanics. He felt that “God does not play dice with the universe,” a metaphorical swipe at the random, probabilistic nature of quantum mechanics. His disagreements with Niels Bohr on the interpretation of quantum mechanics were legendary. His work on unified field theory and gravitation was disconnected from the mainstream of physics, which at that time was concentrating on developing nuclear physics and atomic physics. Most other physicists dismissed Einstein’s attempts to find a generalization of his gravity theory that unified it in a geometrical framework with James Clerk Maxwell’s equations for electromagnetism. Indeed, Einstein was ostracized by his physicist peers.

      This ostracism began as early as the 1930s, when Einstein appeared before a committee at the Institute for Advanced Study, requesting financial assistance to bring Leopold Infeld from Poland to the institute to assist Einstein in his calculations of the motion of particles in his gravitation theory. He was denied this request. This prompted Einstein and Infeld to write a bestselling popular book together, titled The Evolution of Physics.Money from the sales of this book paid for Infeld to travel to Princeton and begin the collaboration. Much later, in the late 1940s and early 1950s, when Robert Oppenheimer was director of the institute, he dissuaded the young physicists there from associating with Einstein because he believed that Einstein would be wasting their time; he didn’t want Einstein influencing the younger generation.

      Is it possible that Albert Einstein showed interest in corresponding with me, an unknown, self-taught student of physics in Denmark, because I had shown critical interest in his work? Unlike his esteemed peers, I, a young aspiring physicist, was taking him and his recent work seriously. Also, in opposing the consensus view of what physics was worth doing and what was not, I had positioned myself as an outsider at the Niels Bohr Institute circle, just as Einstein himself had become an outsider.