by Peter Byrne
Everett penciled in the margin,
Nonsense. Whole idea not to cut off till after final observ[ation] Q[uantum M[echanics] says it effected just like microsystem. Whence this magic irrevers[ibility]?
Groenewold continued:
Because all observable quantities may ultimately be expressed in statistical relations between measuring results and the latter are represented by essentially macrophysical recordings, the former ones may ultimately be expressed in macrophysical language.
In the margin Everett scribbled,
Epistemologically garbage. Lack of understanding of the nature of physical theory. Why base concept of reality on classical macrophysical realms?
When Groenewold complained that Everett’s theory could not avoid introducing the “cat”9 and Einstein–Podolsky–Rosen (EPR) paradoxes, Everett exclaimed, “Didn’t even read my paper … the paradoxes [are] more easily explained than usual.” In a subsequent letter, Groenewold insinuated that Wheeler and Everett had “abandoned the idea of interaction at a distance.” And, perhaps, they had—as Everett believed he had accounted for what he described as the “fictitious” EPR paradox.10
Not all of the reactions to Everett’s and Wheeler’s preprints were negative. Henry Margenau, wrote, “The problem with which you deal has irritated many minds. I, for one, find your disposal quite acceptable.”11
Norbert Wiener weighed in: “The inclusion of the observer as an intrinsic part of the observed system is absolutely sound.” But Wiener remarked that Everett was wrong to introduce a classical probability measure in the mathematical space of quantum mechanics. He concluded, “Your paper should be published, but more as comments on the present intellectual situation than as a definitive result.”12 Everett was disappointed that Wiener had seriously misconstrued his derivation of a probability measure. He wrote him a letter setting him straight about that error.13
But he did not reply substantively to Wiener’s complaint that, “I do not find an adequate discussion of what it means to say that a certain fact or a certain group of facts is actually realized.”14 This, of course, is a common complaint about the many worlds theory. On his copy of Wiener’s letter, Everett hand-wrote a detailed reply (which he did not send to Wiener). It is worth quoting:
In theory the universal state function is the realized fact. In superposition after measurement all elements actually realized. I am fully aware that this question of ‘actualization’ is a serious difficulty for convent. Q.M. and is in fact one of the main motives for present formulation. No problem in present form, however. [N]o such statements ever made in theory like ‘case A is actually realized,’ except relative to some other state. All possibilities ‘actually realized,’ with corresp. observer states.15
In May 1957, Everett wrote a critical letter to E. T. Jaynes, a physicist at Stanford University who was pioneering the use of von Neumann-Shannon-type information theory in physics. Jaynes had just published an article in Physical Review, “Information Theory and Statistical Mechanics,”16 on the relationship of entropy, information and probability. Jaynes wrote a long response17 to Everett’s critique of his paper saying that he thought that his own approach to statistics was “equivalent” to how Everett claimed to derive probability in his theory:
You claim that my theory is only a special case of your theory, with one particular information measure. I can, with equal justice claim that your theory is a special case of mine.
Jaynes went on to explain where he saw the equivalence, noting:
The strange thing about the information principle is that the difficulties are not mathematical, but conceptual. The mathematics is very elementary, but there is the greatest difficulty in finding the proper words to convey its meaning.
He thought it was a shame that information theory was not being used widely in quantum physics, saying,
I think the reason for it is that the subject appears so sensational at first; one has the impression that one is getting something for nothing.
It turns out that Everett’s theory had a very positive influence on the subsequent use of information theory in quantum physics.18
Everett, the philosopher
In May 1957, after more than a year of battling unsuccessfully with Wheeler and Bohr’s circle, Everett sent his and Wheeler’s preprints to Professor Philipp Frank, a philosopher of science at Harvard who had recently edited a collection of essays on “operationalism” and related interpretational approaches to physics.19 Frank had been a member of the “Vienna Circle” of logical empiricists in the 1920s. During the early and mid 20th century, he was a highly regarded physicist-philosopher.20 His widely read book, Modern Science and it’s Philosophy, was referenced by Wheeler in his Reviews of Modern Physics article praising Everett as a revolutionary thinker.
Frank observed,
Almost every new physical theory has to face the commonplace accusation that it stands in contradiction to everyday experience or, as it is sometimes put, that it contradicts common sense.21 … The special mechanism by which social powers bring about a tendency to accept or reject a certain theory depends upon the structure of the society within which the scientist operates. It may vary from a mild influence on the scientist by friendly reviews in political or educational dailies to promotion of his book as a best seller, to ostracism as an author and as a person, to loss of his job, or, under some social circumstances, even to imprisonment, torture, and execution.”22
Distressed by the rejection of his theory by people he viewed as having agendas, Everett wrote to Frank.
I have received several of your works on the philosophy of science. I have found them extremely stimulating and valuable. I find that you have expressed a viewpoint which is very nearly identical with the one I have developed independently over the last few years, concerning the nature of physical reality.23
Everett described his theory to Frank as,
a completely abstract mathematical model which is ultimately put into correspondence with experience…. It has the interesting feature, however, that this correspondence can be made only by invoking the theory itself to predict our experience – the world picture presented by the basic mathematical theory being entirely alien to our usual conception of ‘reality.’ The treatment of observation itself in the theory is absolutely necessary. If one will only swallow the world picture implied by the theory, one has, I believe, the simplest, most complete framework for the interpretation of quantum mechanics today.24
The proof of my theory, said Everett, is that the world appears as it appears. Experience itself is the verification of the theory, because it is impossible to sense self-splitting, or the existence of multiple universes.
Concluding his letter to Frank, Everett offered to send him copies of various criticisms of his theory, suggesting he might be interested in reading them for psychological and sociological reasons (not as physics). Clearly, Everett believed that Copenhagen’s reaction to his theory had little to do with the validity of his argument.
And he was particularly struck by Frank’s essay on Nicolaus Copernicus, a 16th century scientist whose heliocentric theory was not fully recognized as true until Isaac Newton substantiated it a century after it was first proposed. As an example of scientific rigidity toward the counter-intuitive, Frank had cited the example of Francis Bacon—who had rejected the Copernican view because it did not accord to common sense. Frank elaborated,
Looking at the historical record, we notice that the requirement of compatibility with common sense and the rejection of ‘unnatural theories’ have been advocated with a highly emotional undertone, and it is reasonable to raise the question: What was the source of heat in those fights against new and absurd theories? Surveying those battles, we easily find one common feature, the apprehension that a disagreement with common sense may deprive scientific theories of their value as incentives for a desirable human behavior. In other words, by becoming incompatible with common sense, scientific theories lose their fitness to support de
sirable attitudes in the domain of ethics, politics, and religion.25
Frank wrote back warmly to Everett, saying he was “attracted” to his idea of a non-collapsing wave function, because he disliked the “traditional treatment of ‘measurement’ in quantum theory according to which it seems as if ‘measurement’ would be a type of fact which is essentially different from other physical facts.”26
Clearly influenced by reading Frank’s essay on Copernicus, Everett corresponded with Bryce DeWitt, who was guest editing the issue of Reviews of Modern Physics in which his edited thesis was slated to appear, alongside a collection of papers from the Chapel Hill conference. DeWitt had written to Wheeler that Everett’s paper was “valuable” and “beautifully constructed.” He said,
Everett’s removal of the ‘external’ observer may be viewed as analogous to Einstein’s denial of the existence of any privileged inertial frame.
But:
The trajectory of the memory configuration of a real physical observer … does not branch. I can testify to this from personal introspection, as can you. I simply do not branch.27
Everett rejoined in a letter to DeWitt that the same sort of objection was raised by Copernicus’ critics: When he asserted that the earth revolved around the sun, they said that was impossible because they could not feel it move. Everett poked DeWitt: “I can’t resist asking: Do you feel the motion of the earth?” He then remarked, “It is impossible to do full justice to the subject in so brief an article as the one you read.”
DeWitt recalled years later, “His reference to the anti-Copernicans left me with nothing to say but ‘Touché!’” DeWitt did not read the unexpurgated thesis until the early 1970s, but he said he put Everett’s paper in Reviews of Modern Physics because,
Although Everett had not been a conference participant and I had never met him, his paper was accompanied by (1) a strong letter from John Wheeler and (2) a paper by Wheeler assessing Everett’s ideas. Since Wheeler had been a very active conference participant and since Everett’s paper seemed to be relevant to the themes of the conference, I agreed to include it.28
Regarding the editing of Everett’s paper, DeWitt remarked, “I asked [Wheeler] why the original article, I mean the [Urwerk], wasn’t ever published. Wheeler said, ‘Because I sat down with Everett and told him what to say.’” Dewitt said, “The funny thing is, you have to read the Reviews of Modern Physics article very carefully, as I did, to see what’s really there. Whereas in the Urwerk it’s quite well spelled out, to me.”29
In the end, after the rebellious, anti-Bohr comments in the original work were excised, along with much of the explanatory language, and much of the formal argument, Everett’s dissertation was accepted by Wheeler. He passed his oral exam with a “very good,” the second highest rating, and became Dr. Everett.
One of his classmates, Chuck Rockman, congratulated him on finally having his thesis posted for reading in the physics department. Rockman noted,
Incidentally, did you know that there was a rumor here that there were no faculty members willing to be second and third readers on it? On checking, this was scotched by Charlie [Misner] who claimed it to be a sort of ploy by Wheeler who wanted you to keep rewriting until it was in shape to convince the world. How do you figure the odds on that?30
In mid-April 1957, Wheeler added a memo to Everett’s student file:
This work is almost completely original with Mr. Everett both as to the formulation of the problem and its solution. It is too early to assess its final contribution to physics, but there is a distinct possibility that Everett’s work may be a significant contribution to our understanding of the foundations of quantum theory.31
When Everett’s paper appeared in the July Reviews of Modern Physics, it included “splitting” in a footnote! He had inserted it when he proofed the galleys:32
In reply to a preprint of this article some correspondents have raised the question of the ‘transition from possible to actual,’ arguing that in ‘reality’ there is—as our experience testifies—no such splitting of observer states, so that only one branch can ever actually exist. Since this point may occur to other readers the following is offered in explanation.
The whole issue of the transition from ‘possible’ to ‘actual’ is taken care of in the theory in a very simple way—there is no such transition, nor is any such transition necessary for the theory to be in accord with our experience. From the viewpoint of the theory all elements of a superposition (all ‘branches’) are ‘actual,’ none any more ‘real’ than the rest. It is unnecessary to suppose that all but one are somehow destroyed, since all the separate elements of a superposition individually obey the wave equation with complete indifference to the presence or absence (‘actuality’ or not) of any other elements. This total lack of effect of one branch on another also implies that no observer will ever be aware of any ‘splitting’ process.33
Touché.
19 The Chapel Hill Affair
The one story I remember Hugh telling us was that he once said that Wheeler was a really, really wonderful thesis advisor because you’d go in to talk to him about what you were thinking about and he’d say ‘Gee, that’s a great idea. That’s wonderful.’ And then he said there was this one day that he happened to be walking down the hall and the door to Wheeler’s office was open and there was a guy in there who was some obvious nut talking about some completely crazy thing and Wheeler was saying, ‘Gee, that’s a great idea. You ought to develop that.’
Harvey Arnold, 20071
In January 1957, the efforts of Wheeler’s relativity study group were showcased at a conference on quantizing gravity held at the University of North Carolina in Chapel Hill. This conference was the first public trashing of Everett’s work—by no lesser a light than Feynman. But before discussing the conference, we explore why Wheeler was so attracted to Everett’s theory that he was willing to risk Bohr’s displeasure.
It was all about quantum gravity.
The unification problem
In 1918, shortly after he invented the general theory of relativity, Einstein remarked that the most important problem in physics was uniting special and general relativity with quantum mechanics “in a single logical system.”2 Nearly a century later, this goal continues to elude seekers, but not for lack of trying.
Special relativity broke with Newtonian physics by demonstrating that there is no such thing as absolute space, nor absolute time, nor absolute simultaneity of events in the universe. It equated mass and energy; it established the invariance of the speed of light; it wove together three dimensions of space, and one of time, into a new concept: “space-time.”
General relativity revealed mass and gravity as dance partners shaping the geometry of space-time. The force of gravity is infinitesimal compared to the electro-magnetic force that influences photons and electrons. But when transmitted between large objects, as waves or particles, gravity becomes powerfully attractive.
By the mid 1950s, the developers of quantum electrodynamics—notably Dirac, Feynman, Tomonaga, Schwinger, Hans Bethe, and Freeman Dyson—had pummeled quantum mechanics into rough accord with Einstein’s theory of special relativity. A theory of quantum gravity, however, was proving to be more elusive. Basically, that was because the equations of general relativity deal with the classical motions of macroscopic objects, whereas quantum mechanics roams the probabilistic microcosm. The mathematical coordinate systems we use to describe motion inside these two realms do not match up. Relativity cannot predict the motion of particles through time, and quantum mechanics cannot predict the effects of gravitational attraction.3 This is a problem because in the real world, gravity and the quantum of action interlace.
It was this theoretical disunity that Wheeler was determined to fix. He figured that since Feynman’s path integral method meshed quantum mechanics with special relativity, it might also work with general relativity.
Quantizing gravity at Chapel Hill
The six-day “Confere
nce on the Role of Gravitation in Physics” was organized by Wheeler, and two professors at the University of North Carolina, Bryce DeWitt and Cecile DeWitt-Morette, (who were married to each other).4 Three dozen physicists from academia, industry, and the military attended, including Feynman, whose work on quantum electrodynamics was a focus of the historic meeting.
Decades later, DeWitt explained, “Most of you can have no idea how hostile the physics community was, in those days, to persons who studied general relativity. It was worse than the hostility emanating from some quarters today towards the string-theory community.” He said that the editor-in-chief of a leading physics journal had decided in the mid 1950s to no longer accept “papers on gravitation or any other fundamental theory,” but that Wheeler dissuaded him from “behind the scenes.”5
The conference was dominated by the work of Wheeler and his relativity students. In fact, he wrote or co-wrote six of the 23 conference papers, including his positive assessment of Everett’s theory. Everett did not attend, but, at Wheeler’s insistence, his edited dissertation was included in the official proceedings of the conference, published six months later in Reviews of Modern Physics in a special section edited by Bryce Dewitt.
A major theme of the conference was the possibility of quantizing gravity by considering it as a “field” and not a particle. (Fields are energetically more extensive than particles, which can be considered as the “quanta” of fields.) Misner’s dissertation on quantizing gravity was published in the conference proceedings.6 At the conference, he remarked that,