1 The Chapel Hill Conference in Context

Dean Rickles




Rickles, Dean (2011). The Chapel Hill Conference in Context. In: The Role of Gravitation in Physics: Report from the 1957 Chapel Hill Conference. Berlin: Max-Planck-Gesellschaft zur Förderung der Wissenschaften.

The Conference on the Role of Gravitation in Physics was the (official) inaugural conference of the Institute of Field Physics [IOFP] which had only just been established at Chapel Hill, with Cécile and Bryce DeWitt at the helm.1 The IOFP received its certificate of incorporation on September 7, 1955. In fact, it nearly had a very different name, “The Research Institute of the University of North Carolina”, which, quite naturally, won the unanimous approval from the University (and Bryce DeWitt), but not, it transpires, the approval of the primary funder, Mr Agnew Bahnson. Bahnson was a wealthy North Carolinian industrialist with a passion for physics (especially gravitational); he made his fortune from industrial air conditioning systems.

The initial meeting between Bryce DeWitt and Bahnson took place on July 9, 1955, in Raleigh, N.C. They were joined by Clifford Beck, who was head of physics at State College in Raleigh - Bahnson originally planned to have the IOFP at State College since they had a nuclear reactor there, which, as Bryce DeWitt puts it, Bahnson felt “might be useful for anti-gravity” [1]. Curiously, at the same time, the Glenn L. Martin Company (now Lockheed-Martin) was setting up its own research institute that would do work for the U.S. National Defense Service2 though of a rather different sort, industry sponsored, and not ensconced in a university. DeWitt had a meeting with its vice-president, George Trimble (or Bender - see footnote 2), to discuss a potential project involving gravitational physics research (more on this below). DeWitt flew to his meeting with Bahnson immediately after visiting the Glenn Martin Company in Baltimore - indeed, the airplane was owned by a friend of Bahnson’s, one Earl Slick of Slick Airways!

Bahnson had originally written to DeWitt on May 30, 1955. Just prior to this, DeWitt had already also been in correspondence with Roger Babson, another wealthy industrialist with a passion for gravity research. Babson had established the Gravity Research Foundation (GRF) in Salem, and had established an essay competition (governed by George Rideout) “for the best two thousand word essays on the possibilities of discovering some partial insulator, reflector or absorber of gravity waves” ([2], p. 344)! DeWitt won first prize in this competition (in 1953) with an essay dismissing the whole idea; or, as he put it: “[E]ssentially giving them hell for such a stupid - the way it had been phrased in those early years” [1]. DeWitt wrote the essay in a single evening: “... the quickest $1000 I ever earned!” (ibid).3 Given that the essay led to the original exchange between Rideout and Bahnson over Bryce4, it seems that this single night’s work might in fact have earned him rather more than $1000!

Babson clearly saw in DeWitt one who could lift the respectability of the GRF. Indeed, this seemed to be the case, for whereas the prize was previously avoided by ‘serious’ physicists, after DeWitt won, the floodgates opened. The next year, 1954, saw Arnowitt and Deser take first prize.5

The GRF could never really gain the prestige it so desired. Babson held too much control over what lines of research were investigated. Since he was no scientist, these tended to be crankish - in one GRF bulletin the biblical miracle of Jesus walking on water was offered up as evidence in the possibility of antigravity shields, as was the ability of angels to defy gravity! The GRF stood no chance (at least not in this form). Martin Gardner famously mocked Babson’s own gravity ideas in an article entitled “Sir Isaac Babson”.6. Gardner called the GRF “perhaps the most useless scientific project of the twentieth century” ([5], p. 93). He was referring to the stated aims of the GRF and its essay competition; namely to discover some kind of gravity screen (‘the right kind of alloy’ - cf. [2], p. 343). Gardner rightly points out that the concept of a material that is opaque to gravitational interactions was made obsolete by the shift to the general theory of relativity.

Agnew Bahnson was a close friend of George Rideout, the president of Babson’s GRF, and the one who had initially suggested the idea of a GRF to Babson. On the basis of how the initial organizational meetings went, Gardner’s critique perhaps offered up a ‘recipe’ for a more successful venture. Whereas Babson promoted a vision of spectacular technologies as a result of its gravitational research, Bahnson adopted a more sober approach. Thus, in the foreword of an early draft (dated November 17, 1955) for the IOFP’s promotional brochure Bahnson wrote (in stark contrast to Babson’s statements):

In the minds of the public the subject of gravity is often associated with fantastic possibilities. From the standpoint of the institute no specific practical results of the studies can be foreseen at this time.

In many ways, then, Babson’s GRF was used as a foil, highlighting things to adopt but (more importantly) things to avoid. A lengthy exchange of letters between Bahnson and several senior physicists (especially John Wheeler, whom Bahnson clearly admired a great deal) set to work on eradicating any aspects that might lead to claims that the institute was for crackpot research.

In 1955, G. S. Trimble, vice president of the Glenn Martin Company, wrote to Bryce DeWitt7 that:

During a recent conversation with Mr. George Rideout, president of Roger Babson’s Gravity Research Foundation, we were commiserating on the unfortunate state of the affairs that knowledgable folks do not wish to get “mixed up” in the field of gravity research. During the course of the conversation he reviewed with me your suggestion that perhaps his Gravity Research Foundation might be transformed from its present function into an active center of research concentrating on the field of gravity. He also told me that the foundation was not able to undertake such an expansion. (Letter from G. S. Trimble to Bryce DeWitt, dated, June 10, 1955)

It seems that DeWitt had suggested to Babson something along the lines of the Institutes for Advanced Study - a model he was very familiar with since both he and his soon to be wife Cécile Morette, had both spent time in several of them. This model fitted with the Glenn Martin Company’s plans. However, their goal was not pure research, but something grander, it seems - Trimble describes the proposed activity as an “industrial version of the Institute for Advanced Study”.8 The letter goes on:

It occurred to us sometime ago that our industry was vitally concerned with gravity. As time goes on we become more and more concerned because we feel certain that sooner or later man will invade space and we see it as our job to do everything possible to speed this event. At least one category of the things one must study, when he desires to bring space flight to a reality, is the laws of nature surrounding the force of gravity. (ibid.)

One wonders what Roger Babson would have made of the fact that it was Newton’s equations that got man into space!9 Trimble bemoans the fact that most of those working on gravitation are “mad men and quacks” - perhaps he has those connected with Babson’s own endeavour in mind? Indeed, notes Trimble, any relevant work that they had done on space flight had been contracted out to German scientists working within Germany.

Louis Witten (the father of Ed Witten, and participant in the Chapel Hill conference)10 was the first researcher hired by RIAS, of the Glenn Martin Company. He approached DeWitt in a bid to have him join RIAS, but DeWitt was then already being approached by Bahnson, offering more lucrative terms (both for him and Cécile): the promise of a position in a more traditionally academic environment, but with the freedom of an externally funded position, would ultimately win out. However, Trimble, and the Glenn Martin Company nonetheless played a role in helping the IOFP get off the ground. Not only did they purchase a ‘Founder’s Membership’ for the Institute of Field Physics, for the considerable sum of $5000, they also offered their support to solicit further funding (letter from Trimble to Bahnson). The letter reproduced in Fig. 1.1, from Bahnson to Bryce and Cécile DeWitt, shows just how tightly bound industry, military, and research were at this time, and also how much influence a single individual could possess.

Fig. 1.1: Letter from Agnew Bahnson to the DeWitts from the early phase of the development of the Institute of Field Physics, December 29, 1955.

Fig. 1.1: Letter from Agnew Bahnson to the DeWitts from the early phase of the development of the Institute of Field Physics, December 29, 1955.

The plan of the IOFP was to house an institute within an academic institution, so as to avoid the conflict that physicists felt working in an industrial setting. The chosen location was the physics department at the University of North Carolina, Chapel Hill. In order to lend further prestige to the IOFP, Bahnson secured letters of comment from several of the most prominent physicists of the day, including Belinfante, Oppenheimer, Dyson, Teller, Feynman, and Wheeler. Wheeler did much behind the scenes sculpting of the IOFP, and was, next to Bahnson, perhaps most responsible for the bringing about of the IOFP. For example, it was Wheeler who tempered Bahnson’s own (somewhat Babsonesque) proposal entitled “The Glorious Quest”, to make it more attractive to funding agencies: “Ebullient as you and I are, I suspect sober going may go further when it comes to getting money from a foundation” (Wheeler to Bahnson, August 29, 1955). Then, writing to the acting president of the University of North Carolina, Harris Purks, November 25, 1955, Wheeler writes of:

the absolute necessity to avoid identification with so-called “anti-gravity research” that may be today’s version of the last century’s search for a perpetual motion machine. [...]

Unfortunately, there are sensationalists only too willing to confuse in the public mind the distinction between so-called “anti-gravity research” ... and responsible, well informed attempts to understand field physics and gravitational theory at the level where it really is mysterious, on the scale of the universe and in the elementary particle domain.

He goes on to applaud the step (in fact suggested by Wheeler himself, earlier) of attaching to every piece of IOFP publicity a ‘disclaimer’ to the effect that the IOFP is in no way connected to anti-gravity research. This “Protection Clause” would be attached to each IOFP statement:

The work in field physics and gravitation theory carried on at the University of North Carolina at Chapel Hill, and financed by the Institute of Field Physics, as fund raising agency, has no connection with so-called “anti-gravity research” of whatever kind and for whatever purposes. Its scientists, basing their investigations upon verifiable data, accept the Newton-Einstein analysis of gravity as free of a single established exception, and as the most comprehensive physical description we have today. They seek the implications of gravity and other fields of force at the level of the elementary particles. More generally, the Chapel Hill project is a modest attempt to learn more about the nature of matter and energy.

This expedient, Wheeler argued, is necessary to avoid discouraging both sponsors and scientists. The message that anti-gravity connotations must be avoided at all costs runs through much of the correspondence and foundation documents like a mantra. It clearly played a vital role (in the minds of physicists) in establishing the legitimacy of the enterprise.

Wheeler did not hold back on the need for the IOFP, though his claims were moderated somewhat by a knowledge that progress might well be very slow:

It is hard to see how one can get to the bottom of the elementary particle problem - the central issue of modern physics - without coming to the very foundations of our physical world and the structure of space and time. Gravity, fields and particles must in the end be all one unity. The absence of any paradox or discrepancy in gravitation theory at the human and astronomical levels creates an obligation to apply Einstein’s ideas down to smaller and smaller distances. One must check as one goes, until one has either a successful extension to the very smallest distances, or a definite contradiction or paradox that will demand revision. ... The challenge cannot be evaded. Exactly how to proceed is a matter of wisdom, skill, judgement, and a good idea. Nobody guarantees to have a good idea, but the DeWitts, fortunately, have a very sound plan of what to do while searching for a good idea. They propose to do something that has long needed doing - help make clear the fundamental facts and principles of general relativity so clearly and inescapably that every competent worker knows what is right and what is wrong. They can do much to clear away the debris of ruined theories from the rocklike solidity of Einstein’s gravitation theory so its meaning and consequences will be clear to all. This is a great enterprise. Einstein’s theory of the space-time-gravitation field is even richer than Maxwell’s theory of the electromagnetic field. That field has been investigated for many years, and now forms the foundation for a great science. One cannot feel physics has done its job until a similarly complete investigation has been made for the gravitational field. (John Wheeler, letter to Bahnson, November 25, 1955)

Though there is, of course, a good deal of colourful rhetoric in this passage, it nonetheless shows the importance in Wheeler’s mind of the role that the IOFP (and the DeWitts) would play. (Note that Wheeler had only just recently had to intervene in a proposal of Samuel Goudschmidt’s to impose an embargo on all papers dealing with general relativity and unified field theory from the pages of Physical Review - cf. [6], p. 414.)

The various letters of support (dating from between October 1955 and January 1956), for which the preceding letter from Wheeler to Purks provides a cover letter, highlight the recognition that general relativity and gravitational research had been unfairly neglected, and the need for a renewal of interest. Oppenheimer writes that he “shares with most physicists the impression that this field has been rather neglected by us”. Dyson seconds this (as does Nordheim), but adds some conditions for success, more or less reiterating what Wheeler had already said: that immediate results should not be expected, and that (“to avoid becoming isolated and sterile”) the institute should be settled as firmly as possible in “the framework of normal university life”. Edward Teller remarks in his letter that “a comprehensive examination of general relativity and high-energy physics, together with an investigation of the interaction between these two fields may very well lead to the essential advance for which we are all looking”.

Feynman too voiced the opinion that “the problem of the relation of gravitation to the rest of physics is one of the outstanding theoretical problems of our age”. However, he was less positive about the chances of the proposed institute in (what he thought was) its original form. Feynman was not convinced that an industrially funded institute, detached from a university, could possibly deliver the requisite flexibility to develop new fundamental knowledge: that required absolute freedom to bounce around between topics, as one chose. On learning that the institute was to be housed in a university, Feynman was unreservedly positive about the proposal (letter to Wheeler, dated December 2, 1955).

John Toll, head of physics at the University of Maryland, writes, directly discussing the other letters:

Most of my colleagues have pointed out in their comments that the field of general relativity has not received the attention which it deserves and that it is particularly important to attempt to obtain some synthesis of the methods and concepts used in general relativity with the ideas now employed to discuss elementary particles. One reason for the neglect of general relativity has been the great difficulty of work in this field which challenges even the best theoretical physicists; solution of the major problems involved will probably require a determined program which may extend over many years. A second and related reason has been the difficulty of obtaining adequate support for this field; the problems are not of the type which are supported by federal agencies which finance so much of the research in physics in the United States by short term contracts, mostly in fields which appear to have more immediate applicability to defence problems. (Letter from J. S. Toll to John Wheeler, dated December 28, 1955.)

This was all written towards the end of 1955.11 By 1957 the picture looked remarkably rosier. Whether it was due to some degree of influence of the IOFP12 and/or RIAS (or the beginnings of the ‘Space Race’ and the Cold War), the Air Force and the Department of Defense in fact soon began to fund fundamental research in gravitational physics. Rather fortuitously, Joshua Goldberg was, at the time of the establishment of the IOFP and the conference, in charge of aspects of the Air Force’s funding of general relativity, in the ‘modern physics research branch’ (based at the Aeronautical Research Laboratory at Wright Patterson Air Force Base). In addition to a $5000 grant, one of the (very crucial) things he was able to do was secure MATS (Military Air Transport Service) transportation to and from the USA (initially just for Géhéniau, Rosen, and Laurent, but later this would include transportation for Behram Kursunoglu from Turkey and Ryoyu Utiyama from Japan, extending to 11 nations in all). In a letter to Bryce DeWitt (dated October 3, 1956), Goldberg notes that the suggestion to use Air Force transportation to bring over physicists from Europe had been Peter Bergmann’s idea - Goldberg gives a personal account of his role in the Air Force’s support of general relativity (and the possible reasons behind the military support of research in gravitation) in [8]. Such free transportation became commonplace for the IOFP at this time, and since many commentators who lived through this experience have suggested that the ability to be able to network, made possible by the availability of easy transportation, played a key role in the reemergence of gravitational physics. Later funding would also take the form of free computing time on IBM’s best machines13, and (in limited cases) free flights on TWA’s line.

Securing additional funding for the conference was time-consuming. In May 1956, the DeWitts visited the National Science Foundation in Washington, to explain the nature of their project - a visit that met with success. The same week Bryce DeWitt gave a layman’s talk to the Winston-Salem Rotary Club - at which various industrialists and wealthy interested parties were present - in which he described the various technological innovations that have emerged from ‘pure research’. It seems (from a memorandum Bahnson sent to his fellow funders) that the Chapel Hill conference was virtually entirely externally funded (i.e. independent of the IOFP’s own funds). This, he notes, is almost entirely thanks to the work of Cécile DeWitt (Bahnson, “Memorandum No. 9”, May 7, 1957) - in a letter to Bahnson dated November 5, 1956, Bryce DeWitt notes that in the space of two weeks, Cécile composed 52 letters and placed 10 long distance calls, chasing potential funding for the conference.

Though not quite a cascade, the IOFP had enough funding in its heyday to attract several first-rate postdoctoral fellows. These included Peter Higgs, Heinz Pagels, and Ryoyu Utiyama. Among the first postdoctoral fellows at the institute was Felix Pirani, who had previously belonged (and would later return) to Hermann Bondi’s Relativity and Gravitation group at King’s College, London (Clive Kilmister was another long term member of this group).14 Pirani received his (first) doctorate under Arthur Schild (who would later head the Center for Relativity) at The Carnegie Institute of Technology - he received a second doctorate from Cambridge University, under Hermann Bondi.

Peter Higgs too had been part of Hermann Bondi’s Relativity and Gravitation group at King’s College, London, since 1956. It was Pirani who urged him to take more interest in quantum gravity, prompting him to take up the position at the IOFP. Though invited to the institute to study gravitation, Peter Higgs ruefully admits that he spent his time there working on symmetry breaking in quantum field theory.15 Higgs first encountered Bryce DeWitt in 1959, in Royamont France. This was the second GRG conference16, and it was shortly after that the International Committee on General Relativity and Gravitation was formed (see Kragh [11], p. 362). He met him again at the GRG3 conference in Warsaw, in 1962. After 1956, following Pirani’s advice, Higgs began looking at quantum gravity - at the time he was working with Abdus Salam at Imperial College. Here he wrote on the constraints in general relativity [12]. This led, in 1964, to DeWitt’s invitation to Higgs to spend a year at the institute, which he did, arriving in September 1965, after a year’s postponement. Bahnson died tragically in an airplane crash the year prior on June 3, 1964 - a chair was established at UNC in his honour, to be occupied by Bryce DeWitt.

A follow up meeting focusing purely on ‘Exploratory Research on the Quantization of the Gravitational Field’ was held in Copenhagen, June 15 to July 15, the same year as the Chapel Hill conference. This meeting involved DeWitt, Deser, Klein, Laurent, Misner, and Møller. Again, MATS was utilised for this meeting, courtesy of Goldberg and the ARL. Møller and Laurent would return to Chapel Hill as visiting fellows for two months, starting in February. Their brief was to work on the role of gravitation in artificial Earth satellites and also atomic clocks (Bahnson, Memorandum #11, Feb. 3, 1958).17

There are similarities between the Chapel Hill conference and the 1955 conference to celebrate the 50th anniversary of Einstein’s theory of special relativity, held in Berne. Einstein was, of course, to have attended but he fell ill during the planning and died just before the event took place, prompting Pauli to declare that “This important moment in history is a turning point in the history of the theory of relativity and therefore physics” ([13], p. 27). Pauli himself died not long after, in 1958. Somewhat surprisingly, this jubilee celebration was in fact the first ever international conference devoted solely to relativity. As it would turn out, the conference dealt almost exclusively with general relativity, special relativity being more or less a finished enterprise, formally, experimentally, and conceptually. The conference would later come to be known as “GR0”, the zeroth conference in a series which continues to this day, and of which Chapel Hill was the first, GR1.18

The proceedings (replete with post-talk discussions) were quickly edited by André Mercier and Michel Kervaire. This proceedings volume, and the conference itself, played a central role in the future evolution of classical and quantum gravity. However, it was no Shelter Island. Whereas that conference had been driven by the younger generation of physicists - Feynman, Schwinger, Wheeler, and others - the Berne Jubilee conference was dominated by older, more established physicists. In his own report on the Chapel Hill conference, Bahnson noted that he had talked to a physicist (unnamed) who had also participated in the Berne conference, who had remarked that the Chapel Hill conference had “greater informality” and that “the younger participants contributed to more discussion and exchange of information”. The Chapel Hill conference on the Role of Gravitation in Physics, that would happen just two years later, did for general relativity and gravitation what Shelter Island did for quantum electrodynamics. The Chapel Hill conference was a genuine break from the Berne conference, both in terms of its organization, its content, but more so its spirit.



An initial ‘get to know each other’ meeting of the IOFP was held June 8-10, 1956, at Roaring Gap in North Carolina, where Bahnson had a summer house. This was open to all members of the IOFP and a few select others, including Freeman Dyson and Lothar Nordheim, potential funders and a reporter from the Winston-Salem Journal & Sentinel. As Bahnson put it, in his “4th Memorandum” (of June 20, 1956) the purpose of the meeting was “to introduce members of the Institute and their guests to Mr and Mrs DeWitt“ and “to define more clearly” the problems to be dealt with at the IOFP (with gravity as “the focal point of interest” (letter from Cécile DeWitt’s own archive; henceforth, unless otherwise specified, references will be to documents contained in this archive).

This would become RIAS, or the Research Institute for Advanced Study. It is possible that DeWitt’s meeting was with the director of RIAS, Welcome Bender, who was in charge of recruitment, and who also attended the Roaring Gap conference on behalf of the Glenn Martin Company. However, there certainly was correspondence between DeWitt and Trimble.

In a section entitled ‘Purposes, Objects and Powers’ of the document of incorporation of the Gravity Research Foundation formed by Babson, Clause (1) states that the purpose of the corporation is to “Observe the phenomena of nature and encourage, promote and support investigations in search of underlying knowledge of these phenomena. Conduct theoretical and experimental studies to discover the laws which affect them and evolve new technological concepts for the improvement and welfare of mankind” (Bryce DeWitt Archives, Center for American History, University of Texas at Austin). Babson had a curious view of gravity as a kind of ‘natural evil’ ( a “dragon”), caused by his sister’s and grandson’s drowning by, as he saw it, the downward pull of gravity - see [3].

Note that Bryce concluded his GRF essay with the words “External stimuli will be urgently needed in the near future to encourage young physicists to embark upon gravitational research in spite of the odds,” which clearly resonated with both Babson and Bahnson.

Much to the chagrin of Robert Oppenheimer who was supervising both of them at the Princeton Institute for Advanced Study. Oppenheimer thought that entering the competition and accepting the prize brought the IAS into disrepute. He believed that Arnowitt and Deser exploited their positions at the institute (see [1]). Note that Pascual Jordan was placed in 5th position this same year, with his essay on his theory of a variable gravitational constant. James L. Anderson submitted an essay on the Measurability of Gravitational Fields, but was not placed at all - the same is true of Dennis Sciama who wrote on a possible method of shielding gravitation using Mach’s principle. Frederik Belinfante took 1st prize in 1956 for his paper on gravitational absorbers and shields. In the 1957 competition, Thomas Gold took 1st prize for a paper on the gravitational interaction of matter and anti-matter, that he co-authored with Philip Morrison (John Wheeler took second prize, and Felix Pirani took 3rd).

This is a reference to Babson’s penchant for all things Newtonian. This penchant led to the establishment of one of the largest collections of “Newtonia” (as he calls it, [2] p. 340) in the world, on the campus of the Babson Institute in Wellesley, Massachusetts. One of the library’s rooms is an actual room used by Newton while in his final years in London. This was purchased by Babson’s wife when she discovered the building was being demolished, shipped over from the UK, and rebuilt on site as Newton would have used it “with the same walls, doors and even the identical shutters containing the hole through which he carried on his first experiments in connection with the diffusion of light” (loc. cit., p. 340). David Kaiser has a useful discussion of this curious episode in his PhD thesis, Making Theory: Producing Physics and Physicists in Postwar America (Harvard University, 2000). See also Kaiser [4]

At this time senior research physicist, Radiation Laboratory, University of California, Berkeley and Livermore, then working on detonation hydrodynamics.

Trimble makes an interesting remark concerning the tight relationship between scientific research and society: “[W]e feel morally obligated to push forward in the basic sciences and we believe as a dynamic industry we can provide the motivation for advances that can be obtained in no other way”. In other words, for better or for worse, the pursuit of certain areas of basic research demand some kind of motivation beyond the search for deeper knowledge. Practical applications are one way to motivate such study.

Curiously, DeWitt later did a report on “The scientific uses of large space ships”, for the Department of Defense (General atomic report GAMD 965, 1959).

Bob Bass, who coauthored the paper with Witten in this conference report, was the first person to be hired by Witten, in 1956. Bass, together with Witten, would later manage to hire R. E. Kalman and Solomon Lefschetz, in 1956 and 1957 respectively.

December 7, 1955 saw DeWitt deliver a paper focusing on current research in gravitational physics to the American Astronautical Society (published as [7]). By this time he was able to give his position as ‘Director of the IOFP’. The talk was clearly intended as a piece of propaganda for the IOFP. DeWitt opened by distancing his work from any foreseeable practical applications. He then notes the lack of serious research being carried out, counting just seven institutions with gravitation research projects: Syracuse, Princeton, Purdue, UNC, Cambridge, Paris, and Stockholm - with RIAS, Inc, on the industrial side. DeWitt mentions even at this early stage of quantum gravity history the problems that would plague the quantum geometrodynamical approach throughout its existence (until it transformed into loop quantum gravity): these are the problems of defining the energy and the quantities that are conserved with respect to it (i.e. the observables), and the factor ordering problem. (This problem refers to an issue caused by the straightforward canonical quantization of general relativity, based on the metric variables. According to the standard quantization algorithm, when one meets a momentum term, one substitutes a derivative. However, when this procedure is applied in general relativity, one faces situations were one has products, and so one has to multiply as well as differentiate. The order in which one does this matters for the form of the final wave equation.) The former was studied by Bergmann’s group at Syracuse, while the latter problem was studied by DeWitt’s own group at the IOFP.

Not so far fetched as it might sound. Bahnson notes in a letter to Bryce and Cécile of December 29, 1956, that by then the Air Force had expressed interest in their work (this he heard directly from Glenn Martin) - see Fig.1.1.

This possibility was initially raised by IBM’s representative, Dr John Greedstadt, at the Roaring Gap meeting, though apparently trying to define problems to run on the machines was not an easy task. It is, however, worth mentioning that Bryce DeWitt would later be a pioneer of numerical relativity; also, the issue of putting general relativity on a computer arises in the Chapel Hill report: p. 75.

As Ezra Newman pointed out in his recollections of the early history of general relativity ([9], p. 379), Pirani completely abandoned physics for a life as an author of children’s books. See also [10].

Letter to Cécile DeWitt.

Or the third, depending on whether one counts the conference in Berne in 1955 to mark the Jubilee of Einstein’s theory of special relativity. This conference is often referred to as GR0.

Cold War paranoia can be clearly seen in this memorandum. Bahnson mentions a recent report (apparently reported in American Aviation magazine) of a “graviplane” about to be produced by the Russians, based on “the extension of Einstein’s theories by Dr. Foch (sic.) of Leningrad” - though Bahnson admits it is likely a “propaganda trap.”

Schweber traces the “reawakening of interest in the field [of GR]” ([14], p. 526) to the Berne conference, GR0, in 1955. He also notes that interest in quantum gravity was made “respectable” as a result of Feynman’s course at Caltech between 1962 and 1963 (loc. cit., p. 527). The Berne conference was important. But it was distinctly a European affair. In the United States, as we have seen, there were several converging lines of attack leading to a reawakening of interest. Indeed, I would argue that since the Berne conference consisted mostly of an older generation who had persistently thought about general relativity and quantum gravity for decades, the phrase ‘reawakening of interest’ is not really appropriate. Klein, Pauli, and Rosenfeld, for example, were veterans when it came to the study of both. In fact, there was an earlier conference in honour of Bohr to which many of the same people contributed, and gave very similar talks. Further, to trace the respectability of quantum gravity research to Feynman’s course is over-stretching. Wheeler had been including material on quantum gravity from the time he began teaching his general relativity course at Princeton. One can even find quantum gravity problems posed within his earlier advanced quantum theory course. In addition to this, there were, as Schweber himself notes, several strong ‘schools’ concentrating on gravitation research by the end of the 1950s. That Feynman’s course happened was as a result of the increased respectability already in operation - moreover, Feynman’s interest was surely stimulated as a result of his participation in the Chapel Hill conference, though he seems to have already been investigating the subject by 1955.