Einstein Wrote Back. John W. Moffat

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СКАЧАТЬ a complete description of reality; he had contended it could not provide a useful starting point for a more profound theory. Einstein held this view in spite of the empirical successes of quantum mechanics: the theory agrees with all the data from subatomic systems, and there is no known experiment that contradicts it.

      In my answering letter, I discussed the pivotal issue of determinism versus non-determinism, where in classical physics the position and speed of a particle can both be determined with infinite accuracy, but through Heisenberg’s uncertainty principle, this cannot happen in quantum mechanics. Quantum mechanics is a non-deterministic system of physics, for it is based on statistical probability theory. I wrote:

      I feel subjected to the same indecision as Buridan’s ass, which was unable to choose any specific bundle of hay.* This so with respect to the controversy Determinism versus Indeterminism. In spite of this, my intuition tells me which specific bundle of hay it is most propitious to decide on. The scientific minded youth of today see this dilemma in a different light to those who developed and lived with the problem. Consequently, they do not realize any problem whatsoever; they believe the aim of Scientific Comprehension is “the second principle” (Indeter-minism) in the limiting realm of the “quanta.” This conception (purely conventional) is typical of the age; owing to this, I do not believe in it as final.

      What I was aiming to say to Einstein was that the younger physicists of the time simply accepted quantum mechanics without questioning whether it was a final and complete description of reality. However, today, more than fifty years later, the tide has turned, and many physicists are thinking about the foundations of quantum mechanics and questioning whether the present so-called Copenhagen interpretation of quantum mechanics is viable.

      In my letter to Einstein, I also discussed the importance of empirical verification of a physics theory, quoting from Lord Rutherford:“It seems to me unscientific and also dangerous to draw far-flung deductions from a theoretical conception which is incapable of experimental verification, either directly or indirectly.” As a twenty-year-old, I anticipated a basic problem that faces physics today, namely the difficulty in obtaining sufficient experimental data to verify and test such theories as string theory, quantum gravity and other highly speculative theories in cosmology. The only way to obtain new data is through increasingly large and expensive high-energy accelerators, which is leading to a crisis in physics today.

      I then wrote about theory versus experiment. “. . . It is always possible to modify a theoretical scheme (by additional artificial assumptions) in such a manner as to obtain immediate experimental verifications . . . One shall not modify the true aim of science (aim of complete comprehension) for the sake of momentary interests. However, if this is found necessary, the step shall only be understood as a temporary state of affairs . . .” Today, this problem of ad hoc physics is even worse than in Einstein’s day. Today we have the speculation that exotic “dark matter” and “dark energy” exist in order to explain astronomical and cosmological observations that do not follow from Einstein’s gravity theory.* Physicists today have “modified” Einstein’s gravity theory by adding in the “artificial assumption” of undetected exotic dark matter to “obtain immediate experimental verification.”

      Later in my eight-page letter, I confronted the problem of singularities in gravitation theory, which Einstein had discussed in his letter. I speculated on whether there might be a possible criterion for when the solutions in field theory and gravity theory are regular or non-regular (that is, non-singular or singular, respectively). I also discussed the issue of the cosmological constant as “corresponding to a universal field density.” * I was proposing that this energy field associated with the cosmological constant, which today is interpreted as the universal vacuum energy, or “dark energy,” had to be included in a truly unified theory. Yet Einstein did not like his cosmological constant because it introduced what he called a “heterogeneous piece” into his basic gravity equations.

      Finally, I wrote about how gravity theories should be purely geometrical in origin, avoiding a phenomenological description of matter such as Einstein had used in his gravity theory and in his first paper on cosmology, “Cosmological Considerations in the General Theory of Relativity,” published in 1917.** Einstein addressed the issue of a purely geometrical theory of gravity in a well-known quote:“Gravitational equations of empty space are the only rational well-founded case of a field theory.” He meant by this that the right-hand side of his field equations for gravity should be zero, not the phenomenological energy momentum tensor postulated in his papers on his general theory of relativity. Already early on in his research on gravity, Einstein was dissatisfied with the formulation of general relativity. Einstein was never entirely happy with the research he published. He was always looking ahead, ambitiously, to a more fundamental unified description of physics.

      I didn’t wait to hear back from Einstein, but I wrote to him again, on August 12, and this time my letter was much more technical. I also enclosed a manuscript I had just completed, entitled “Unified Field Theory.” In the letter and in my paper, I discussed the fact that in Einstein’s attempts to construct 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 СКАЧАТЬ