Nuclear, High Energy, and Solid State Physics

The published version of this book chapter is available at

When Henry Rowland and 35 of his colleagues established the American Physical Society (APS) in 1899, the fields of nuclear, high energy, and solid state physics did not exist. Ernest Rutherford would not postulate the atomic nucleus until 1911, the cyclotron of Ernest Lawrence and M. Stanley Livingston would not accelerate its first particles until 1931, and no one would earnestly propose grouping physicists according to the phase of matter they studied until 1943. At the Society’s centenary in 1999 its membership topped 41,000 and these fields represented its largest and most powerful constituencies.

Understanding the transformation of American physics through the twentieth century requires examining how these specialties grew together and how they grew apart. American physics blossomed as European émigré scientists bolstered an ascendant domestic physics community in the 1930s. The prestige and political influence physicists earned with their contributions to Allied victory in World War II fueled rapid postwar expansion. The specialties discussed here, once established, benefited alike from favorable mid-century conditions, but they charted different, mutually reinforcing pathways to success within American science and Cold War society.

Common historical roots helped the United States excel in nuclear, high energy, and solid state physics, but so did the rivalries that developed between these fields. In becoming an internationally recognized scientific force, American physics also became larger and more diverse, supporting parallel visions of how best to wield the discipline’s prestige, funding, and political influence. Although they identified with the same broad scientific discipline, these three fields evolved different notions about the purpose and scope of that discipline and measured success in different ways. The viability of each of these trajectories, and the diversity they represented, combined to make physics the defining scientific endeavor of Cold War America.

American Physics Ascendant
In 1964 John Van Vleck, by then a hoary elder statesman of American physics, recalled the 1920s as a watershed decade: “The Physical Review was only so-so, especially in theory, and in 1922 I was greatly pleased that my doctor’s thesis was accepted for publication by the Philosophical Magazine in England […]. By 1930 or so, the relative standings of The Physical Review and Philosophical Magazine were interchanged” (quoted in Duncan and Janssen 2007: 566). The reversal of Physical Review’s fortunes owed much to its editor, John Torrence Tate, and his opportunistic reaction to the quantum revolution. Tate ensured that articles on quantum phenomena were published quickly. Under his stewardship, the previously lackluster American journal rode the cresting quantum wave to become a prestigious venue for both American and European physicists, and, in the 1930s, for European émigrés settling in the United States (Nier and Van Vleck 1975).

The reputational gains American physics made in the 1920s are remarkable in light of the community’s youth. American scientists had done little to contradict Alexis de Tocqueville’s observation that Americans had a knack for practical problems but little patience for abstract theoretical reflection. The few physical theorists the United States produced, such as Josiah Willard Gibbs who made foundational contributions to statistical mechanics and physical chemistry, labored largely in isolation. Americans who cultivated international repute typically did so on the strength of their experimental accomplishments.

These accomplishments included Rowland’s custom-made diffraction gratings, which were highly sought after in Europe (Sweetnam 2000). Albert Michelson’s meticulous interferometer experiments, designed to detect long-postulated signs of the earth’s motion through the luminiferous æther, won him continental accolades including the 1907 Nobel Prize (Goldberg and Stuewer 1988). But experiment and application have traditionally been less valued than theory in physics, and until recently in history of science as well (Johnson 2008). The judgment that the United States lagged behind in physics should be understood as an observation that American physicists did not make theoretical contributions that were recognized as valuable by their more established continental counterparts.

It would be fair to say that the rise of American physics in the 1920s was a quantum phenomenon. Quantum mechanics provided Americans multiple routes by which to achieve theoretical respectability. First, as the Rockefeller, Carnegie, and Mellon fortunes were directed toward eleemosynary ends, the sciences benefited. Foundation fellowships allowed many to travel to Europe either for their doctoral degrees or for postdoctoral fellowships (Kohler 1991). The likes of J. Robert Oppenheimer, who would go on to lead nuclear weapons research at Los Alamos, future president of MIT Julius Stratton, and physical chemist Harold Urey learned their quantum physics in Göttingen, Zurich, and Copenhagen, bringing the latest European developments with them when the returned.

Second, the growth of research universities and the expansion of graduate education in the United States produced the first crop of American-educated theorists who could compete internationally (Geiger 1986). Edwin Kemble at Harvard advised students such as Van Vleck and John Slater who, like others of their generation, took great pride in their domestic training (Assmus 1992). The pragmatic outlook common among American-trained scientists meant that they were less bothered than their counterparts across the Atlantic by the counterintuitive philosophical implications of quantum mechanics (Schweber 1986). The reputations Van Vleck, Slater, and their European-trained compatriots established during the 1920s ensured that when a wave of European physicists alit in the United States they put new roots into fertile soil.

American physics had matured in time to mobilize for World War II. As the United States entered the war in December of 1941, European savants were assimilating into American universities. Their expertise buoyed the war effort. Enrico Fermi migrated his nuclear research program from Rome to Columbia University, and then to the University of Chicago where he oversaw the first controlled nuclear chain reaction. Hans Bethe, established for some years at Cornell University, brought the latest in quantum theory to bear on bomb construction at Los Alamos. Felix Bloch, by then a fixture at Stanford University, proved critical for the radar research carried out largely in Cambridge, Massachusetts. In each case, European luminaries worked alongside able and energetic American counterparts.

Wartime research defined the complexion of postwar physics and the identity of postwar physicists. Nuclear, high energy, and solid state physics all trace their roots to groups of researchers and sets of problems brought together by the war. Nuclear weapons were the most visible and psychologically powerful legacy of wartime physics, but radar and operations research also drove the large-scale federal investment in physics through the 1940s and 1950s that supported its rapid growth. The National Science Foundation (NSF), established in 1950, was the official federal organ for supporting basic research, but the service agencies, in particular the Office of Naval Research and the Air Force Office of Scientific Research, supported a wide range of projects while the legislative machinery behind the NSF worked deliberately through the late 1940s (Geiger 1992). Physicists, flush with funding, also found unprecedented influence in the halls of government. Advisory committees within the National Academy of Sciences formed to guide the distribution of federal largess and scientists took on key advisory roles in the legislative and executive branches of government where they shaped funding decisions and defense policy (Kevles [1971] 2001).

The end of World War II heralded a new age for American physicists, who enjoyed a measure of social and economic stability that war-ravaged Europe could not match. After competing as underdogs against their better-established European colleagues for much of the early twentieth century, American physicists emerged from the war with an intact and cohesive community, tremendous momentum, generous federal support, and widespread social approbation. This was the environment in which new specialties with distinct professional interests began to form. If World War II instilled a sense of unity and common purpose in the American physics community, the Cold War presented the opportunity for newly established specialties to go their own ways.

Nuclear Physics
The notion that the atom confined tremendous amounts of energy originated in the early twentieth century. Physicists, though, considered applications remote even after Rutherford demonstrated in 1911 that the bulk of an atom’s mass resided in a small nucleus (Weart 2012). Understanding of the nucleus grew by leaps and bounds after James Chadwick’s discovery of the neutron in 1932. Italian physicist Enrico Fermi paced the investigations of nuclear structure, using neutrons to bombard various elements and examine their behavior. His most interesting results came from bombarding the heavy elements thorium and uranium, the results of which he interpreted as being new elements, but which were actually products of fission – the splitting apart of the atomic nucleus (Cooper 1999). In 1938 Otto Hahn and Fritz Strassman, building on Fermi’s experiments, published conclusive evidence of nuclear fission. They relied heavily on correspondence with Lise Meitner who by that time had fled Berlin for Sweden where, with her nephew Otto Frisch, she employed the liquid drop model of the nucleus to articulate a theoretical model of fission (Sime 1996; Stuewer 2010).

In the same year that Hahn and Strassman published their findings, the Hungarian-born Leó Szilárd joined the exodus of physicists from Europe to the United States, where he took up a post at Columbia University. For Szilárd, the discovery of fission was both a vindication and an ill omen. He had been promoting the idea of a self-sustaining nuclear chain reaction since 1933, shortly after learning about the neutron. Fission showed that his instincts were correct, but he also recognized that a fission-based weapon could decide the looming war. Szilárd’s concern that Germany had a head start prompted him to seek out another recent refugee from fascism; Szilárd and Albert Einstein drafted a now-famous letter to President Franklin Roosevelt urging him to commit the resources of the United States to nuclear research. Thus began the process that would lead to the establishment of the Manhattan Engineer District in 1942 and the eventual detonation of three nuclear weapons, one a test conducted at Alamogordo, New Mexico and two used against urban targets in Japan.

Shortly after its inception, nuclear research was measured by its military applications. It was conducted with an urgency to match. European physicists arrived in the United States carrying the knowledge that nuclear weapons were possible and a grim tenacity born of first-hand experience of the danger Adolf Hitler posed. They provided the impetus for the Manhattan Project, which turned two billion government dollars toward synthesizing the knowledge and talents of European émigrés, the know-how of American scientists and engineers, and industrial infrastructure of previously unimagined scope (Rhodes 1986). This synthesis accelerated theoretical understanding of the nucleus. Knowledge of the number and velocity of the neutrons emitted in nuclear decay, for instance, was necessary to accurately predict the critical mass at which a fissile element would explode. In that sense, war research accelerated physics along a path it was already following, but it is most notable for the new directions it opened.

The Manhattan Project was a benchmark for postwar physics in several ways. Along with radar, it set a blistering standard for blackboard-to-battlefield turnaround time that conditioned expectations for subsequent technological development. It sensitized a generation of researchers to science on a grand scale. It eroded the boundaries physicists had tried to maintain between science and politics. Most critically, it normalized large government expenditures for scientific research. Science spending had not been a major budget item before the war (Dupree 1957; Kleinman 1995). Demobilization from World War II, however, coincided with a different kind of mobilization for a different type of war. By the middle of the 1950s, federal funding for research and development was more than 50 times its prewar levels (Westfall and Krige 1998). Nuclear physicists had demonstrated that seemingly arcane research might quickly result in earth-shaking technological advances. Wary of the Soviet Union’s global aspirations, the United States government was determined not to be caught napping on the next big breakthrough.

Nuclear physics was the foremost beneficiary of the federal government’s newfound enthusiasm for science, but financial support came at a price. Previously driven by curiosity about the composition and structure of matter and a spirit of open communication, nuclear physics in the Cold War was inextricably bound to US defense interests and became subject to pointed mission directives and intricate secrecy regimes (Wellerstein 2008). A field that began with theoretical questions about atomic structure became a technical enterprise directed at exploiting atomic energy either through bombs or reactors. Los Alamos, which had housed the laboratory charged with theoretical research and bomb assembly, remained a weapons lab. Aware that the basic principles of nuclear weapon design were well known, physicists estimated that it would be no more than five to ten years before the Soviet Union produced its first bomb. The estimate proved conservative, as the Soviets detonated their first nuclear weapon in 1949.

If the Manhattan Project catapulted nuclear physicists into a position of influence, the arms race ensured they would maintain it and that nuclear research would remain handsomely funded. Following the 1949 Soviet test, President Harry Truman made development of a fusion bomb – the so-called “super” that obsessed Hungarian émigré Edward Teller – a high priority. Teller and Stanislaw Ulam eventually overcame the technical obstacles that had made fusion weapons unfeasible and the first thermonuclear weapon, code named “Mike,” was detonated at Enewetak Atoll in 1952 (Rhodes 1995).

Whereas the physics community had been united behind the bomb work carried out as part of the war effort, it was divided over the wisdom of pursuing such an aggressive weapons program in peacetime. Many Manhattan Project veterans were appalled by the use of nuclear weapons against civilian targets in Japan and resisted efforts to expand the nuclear arsenal. The Red Scare exacerbated the tensions between weapons researchers and skeptics in the early 1950s when any opposition to a more powerful nuclear deterrent could be spun as support for communism.

Both the virulence of American anti-communism and the political clout of the defense establishment were tested in the Atomic Energy Commission (AEC) hearing on Oppenheimer’s security clearance. The former head of Los Alamos had opposed Teller’s push for fusion weapons. His visibility after the war as a public intellectual and advocate for international control of nuclear weapons made Oppenheimer a target for hawkish politicians and scientific administrators, who moved to suspend his clearance. The hearing saw both Teller and General Leslie Groves, who had recruited Oppenheimer to manage Los Alamos, testify that he was a security risk. His clearance was revoked in May 1954 (Cassidy 2005).

The defeat Oppenheimer and the long list of colleagues who testified on his behalf suffered speaks to the extent to which the defense establishment had captured nuclear physics, a trend that extended to so-called peaceful uses of nuclear power (Hewlett and Holl 1989). After the war, Manhattan Project research sites scattered across the country were converted into National Laboratories, administered by the AEC. Although science pursued in the National Laboratory System, from reactor and cyclotron research to, somewhat later, biological and ecological investigations, was considered non-military, it was nonetheless calibrated to advance the strategic interest of the United States, especially vis-à-vis the Soviet Union (Westwick 2003). Research on nuclear reactors, such as that conducted at Argonne National Laboratory outside of Chicago, led to civilian nuclear power. On the other hand, nuclear supremacy in all arenas, from weapons to electrical power, was seen as critical to Cold War economic and defense goals.

This duality defined Cold War nuclear research. A field that seemed remote from daily life, not to mention geopolitics, in the early part of the century became deeply enmeshed in a global ideological struggle by the 1950s. Nuclear physics no longer meant simply the study of the nature and structure of the atomic nucleus, but rather the exploitation of a few heavy elements in the service of national aims. The influence physicists could have over these aims shepherded them from obscurity to the center of American civic and political life. Nuclear physics became an outgrowth of national defense during the Cold War. Some physicists, however, were not content to let postwar public approbation and federal funding be directed entirely toward technological projects. No field exemplifies the new opportunities the postwar boom enabled better than high energy physics.

High Energy Physics
It took some time after World War II for nuclear and high energy physics (HEP) – known as particle physics in its early days – to become differentiated. Well into the 1950s, “nuclear physics” referred both to the weapons and reactor research and to investigations of the particles that composed the atomic nucleus. Two factors cleaved these traditions apart. The first was rooted in laboratory practice. Early cyclotron designs became the template for a family of new machines, which rapidly grew in size and power. Large particle accelerators required dedicated facilities, and those drawn to identifying and classifying the properties of elementary particles had little use for bombs or reactors. The second factor was ideological. Many Manhattan Project veterans were disillusioned with war work. Whereas nuclear physics became intertwined with the Cold War military–industrial complex, high energy physicists explored the most abstruse corners of the physical world, where they would be little troubled by the ethical quandaries weapons work had posed (Stevens 2003). In the absence of clear practical justifications for building expensive accelerator facilities, high energy physicists evolved a rhetoric of fundamentality, suggesting that the most profound and important truths about the physical world could be found among the smallest constituents of matter and energy.

Although HEP would come to be known for its theory of elementary particles and their interactions, the Standard Model, the field originated in an experimental innovation, the cyclotron. Today, we associate particle accelerators with vast underground tunnels and enormous detectors, but the first cyclotron fit in the palm of Lawrence’s hand. The cyclotron, when it appeared in 1931, offered meaningful advantages over linear accelerators, also new to the scene. By accelerating particles in a spiral, rather than a straight line, the cyclotron limited the space it took up and brought higher energies within reach.

The cyclotrons in Lawrence’s Radiation Laboratory, or “Rad Lab” as his facility at Berkeley was known, grew rapidly. Following the first diminutive 4.5” device, the 1930s saw 11”, 27”, 37”, and 60” iterations as Lawrence’s team pushed for higher energies. Like most of American physics, this rapid progress was channeled into the war effort in the early 1940s. Glenn Seaborg used the 37” cyclotron to bombard uranium, leading to the discovery of plutonium. As the pressing need to separate isotopes of uranium became clear, Lawrence used his machines to separate U-235 and U-238 electromagnetically (Heilbron and Seidel 1989).

Cyclotron research would blaze a very different trail than that of bombs and reactors after the war. The Rad Lab saw the same expanded funding and increased visibility that nuclear physics did by virtue of its wartime contributions, but as HEP split from nuclear physics it defined its own research agenda. The 184” cyclotron that went online in 1946 would be dedicated not to problems of immediate defense or economic importance, but rather to exploring a vast and puzzling menagerie of new particles. Larger machines meant that physicists could artificially generate new particles called “mesons” that had previously – and then only recently – been observed in cosmic ray research.

Through the 1950s accelerators became more powerful and high energy physicists developed more sophisticated methods for manipulating the data they produced. The invention of the bubble chamber by Donald Glaser in 1952 supplanted older cloud chamber and photographic emulsion detection by making it easier to produce high-quality images of particle collisions. Iconic images of the intricate swirling lines generated as charged particles forced hydrogen bubbles to dissolve from solution underscored both the precision and the beauty high energy physicists sought. These images proved a seemingly inexhaustible source of discovery. New particles such as the Xi-naught, Sigma-naught, and Omega-naught were first detected in bubble chambers, and bubble chamber data was instrumental in the detection of processes called weak neutral currents, which allowed theoretical unification of the weak nuclear force and the electromagnetic force (Brown, Dresden, and Hoddeson 1989; Galison 1987).

As bountiful as this data harvest was, the particle zoo troubled physicists who maintained ironclad conviction that the underlying structure of the universe should be simple and elegant. High energy theorists, irked by the expanding family of elementary building blocks and by the fact that experimentalists, with whom they were fiercely competitive, were driving the new physics, looked to make sense of the chaos (Traweek 1988). The result was a new theoretical model proposed by Murray Gell-Mann and George Zweig in 1964, which suggested that most observed particles, including protons and neutrons, were composed of smaller particles. Gell-Mann dubbed these “quarks,” borrowing the spelling from a line in James Joyce’s Finnegan’s Wake.

The quark was not immediately accepted, but it did become a working model for many theorists, who saw in it a way to cull the particle zoo. When the dust settled, the result was the Standard Model of particle physics. HEP has subsequently focused on elaborating the Standard Model, culminating recently with the discovery of the Higgs boson at CERN in 2012. This elaboration called for larger accelerators, huge research groups, and billions of dollars in funding – the hallmarks of big science.

The emphasis on larger, higher energy machines led in the late 1960s to the establishment of the National Accelerator Laboratory, better known as Fermilab, outside Chicago. The United States’ investment in Fermilab testifies to the power and influence of physics in Cold War America. Not only was the lab hugely expensive, but its first director, Robert Wilson, took care to justify it on anything other than practical grounds. When asked in Congress what the lab would do to benefit national defense, Wilson famously replied that physics at Fermilab, like great art or literature, “has nothing to do directly with defending our country except to make it worth defending” (quoted in Stevens 2003: 174).

The tendency to justify HEP on the basis of the ennobling knowledge it produced represented a break from the practical mindset that consumed nuclear physics. As HEP uncovered ever smaller bits of matter and energy, becoming ever more remote from technical applications, the field’s philosophical grounding adapted to fit. High energy physicists became outspoken proponents of reductionism, the view that knowledge about the smallest scale of the universe represented the most, and perhaps even the only truly fundamental truth (Cat 1998). In contrast to both nuclear and solid state physicists, high energy physicists wore their distance from practical concerns as a badge of pride, trading on the argument that modern society had a duty to support knowledge for its own sake.

The reductionist rational worked well during the Cold War. Tension with the Soviets ensured that support for basic research proceeded with the assumption that the next game-changing discovery might, like fission, come from unexpected quarters. The Cold War also meant that high energy physicists could deploy nationalistic rhetoric, as Wilson did, without invoking specific technological or economic outcomes. HEP maintained generous levels of funding by spending the political capital that nuclear physics earned during the Manhattan Project, and by leveraging the stranglehold it held on the intellectual prestige physics as a whole had earned after World War II. Its practitioners parlayed these circumstances into a license to pursue their research largely unfettered by the deliverables the federal government demanded from other sciences.

The unspoken agreement between the HEP community and the federal government that sustained large expenditures for blue-skies research collapsed with the Berlin wall and had devastating consequences for the Superconducting Super Collider (SSC). The enormous accelerator slated to be built in Texas was designed to complete the Standard Model, and, many hoped, push beyond it. When Congress pulled its funding in 1993, the machine came with a $11.8 billion price tag. Its demise resulted both from internal management difficulties and from post-Cold War political shifts. Administering a project of such scale posed insurmountable challenges even for seasoned scientific administrators, and with the Soviets no longer lurking in the background, legislators who had been elected with a mandate to cut spending began to demand economic justifications more specific and weighty than any the HEP community could provide (Hoddeson and Kolb 2000; Kevles [1971] 2001; Riordan 2000, 2001).

The erosion of financial and political support for the SSC was a turning point for American HEP and for American physics as a whole. Debates over whether to fund the SSC coincided with the establishment of the Human Genome Project, which would anoint biology the standard bearer for American science (Kevles 1997). Although the Tevatron at Fermilab would remain the world’s most powerful accelerator until the Large Hadron Collider overtook it in 2009, high energy physicists understood the SSC’s demise as a sign that the United States was no longer prepared to underwrite big physics. As of this writing, the future of HEP is being hotly debated, but it seems clear that whatever form it takes in the future, the combination of ever larger machines running at ever higher energies and an unabashedly reductionist ideology that caused the field to burn so brightly for the second half of the twentieth century was the product of distinctive, now extinguished, Cold War conditions.

Solid State Physics
Solid state physics (SSP) was a professional innovation; it began as a strategy for bringing academic and industrial researchers into closer contact. This made it unlike nuclear physics, which coalesced around questions about the atomic nucleus and applications of nuclear energy, and high energy physics, which centered on a type of experimental investigation and the theories used to codify its results. The intended scope of the field covered the properties of solid matter, encompassing thermodynamics, optics, acoustics, electromagnetism, mechanics, and quantum mechanics as they manifested in solids, a list that includes almost all of the main topical divisions of physics that existed before World War II. This breadth was unusual within a community that traditionally identified its topics with well-defined problems or methods. The reasons SSP was unorthodox, and the manner in which it navigated that unorthodoxy, are critical for understanding how it emerged as a successful area of American physics, and the largest, during the Cold War (Hoddeson et al. 1992).

SSP first became a recognizable professional entity in the late 1940s, when the American Physical Society’s Division of Solid State Physics (DSSP) was established. The society’s third topical division came into being circuitously. In 1943 Roman Smoluchowski, a research physicist at General Electric (GE), began mustering support for a Division of Metals Physics within the APS. Like many of his colleagues at GE and other industrial laboratories where physicists were employed in growing numbers, Smoluchowski resented the lack of representation industrial researchers had within the APS and worried that physics fields with industrial relevance might branch off into new engineering specialties. The APS was largely an ivory tower institution and had not adapted to the needs of industry. The APS Council shot down several proposals for a Division of Industrial Physics on the grounds that it was not a “subject,” as required by the 1931 amendment to the Society’s constitution that had made divisions possible. Metals, Smoluchowski reasoned were close enough to a subject of physics to pass muster with the Council, but also central enough to the day-to-day work of industrial researchers that such a division would attract them (Weart 1992).

The Council was reluctant, in no small part because of vocal opposition by some powerful members to any and all divisions. John Van Vleck decried the “Balkanization” of American physics and favored a community subdivided as little as possible (Weart 1992). Nonetheless, Smoluchowski persisted and his division was approved on the condition that it devote itself to “solid state” instead of “metals” on the grounds that the theoretical and methodological differences between metals and other solids were too slight to merit cordoning off the former. SSP thus represented a compromise between forces defending a traditional pure science ideal and those who favored embracing the applications of physics as part and parcel of the discipline.

The early years of SSP cemented its relationship with industry. In 1948 John Bardeen, Walter Brattain, and William Shockley invented the transistor at Bell Laboratories. The implications of a solid state device that could amplify and rectify electrical currents was immediately clear in a technological environment that relied heavily on vacuum tubes, which were clunky by comparison and prone to breaking (Riordan, Hoddeson and Herring 1999). Other breakthroughs came in nuclear magnetic resonance (NMR) and superconductivity, which permitted applications in magnetic resonance imaging, and maser and laser technology, which were also adapted for industrial and commercial purposes (Bromberg 1991). With these contributions to its credit, SSP developed a strong claim to strategic importance in an increasingly technological economy and evolved from a broad and messy constellation of specialties into a field dominated by a smaller set of research programs, notably but not exclusively semiconductor, superconductor, NMR, and laser research. The success of these research programs made the DSSP the largest division of the APS by the early 1960s. By the end of the 1980s it enrolled a full quarter of the Society’s total membership.

Segments of this large, fractious community were not content to be typecast as technical specialists. Although technical relevance ensured reliable funding, that funding was often tied to specific outcomes. Solid state physicists resented the comparatively free rein high energy physicists enjoyed. That some high energy physicists derided the intellectual contributions of solid state work did little to ease tensions between the sibling fields. The tendency to regard research on complex systems as inelegant and intellectually inferior traced to the quantum revolution and one of its architects, Wolfgang Pauli, who reportedly referred to the physics of solids as “Schmutzphysik,” or “dirt physics.” The English equivalent of the slight, in which “solid state physics” becomes “squalid state physics,” is attributed to Gell-Mann. These insults were often repeated as rallying cries by solid state physicists themselves as they fought for intellectual esteem (Joas 2011).

Foremost among those concerned about the intellectual reputation of the field was Philip Anderson, a Bell Laboratories theorist and PhD student of John Van Vleck. Anderson’s paper “More is Different” (1972) launched a headlong assault on the high energy physicists’ strong reductionist picture of the physical world, which excluded other enterprises from access to fundamental knowledge. Anderson acknowledged that physicists might learn a great deal by reducing systems to their constituents, but argued that it was folly to leap to the conclusion that knowledge of those constituents alone would suffice to reconstruct the reduced whole. Behavior at higher levels of complexity, in other words, is novel, unpredictable from lower level data, and just as fundamental as anything happening at the quark scale.

By this time the DSSP, having attracted industrial physicists along with their academic counterparts, was the largest division of the APS by a comfortable and widening margin. “More is Different” resonated with a large proportion of this plurality, many of whom had previously seen dreary prospects for sharing in the prestige and influence other physical fields wielded. The revived effort to boost SSP’s intellectual status and create distance from its industrial roots adopted a new name, “condensed matter physics.” The term “solid state physics” had long had its critics. Dwight Gray, editor of the AIP Handbook of Physics, summed up the difficulty many had with the moniker, writing: “Adding [SSP] to the conventionally labeled group of mechanics, heat, acoustics, and so forth is, of course, a little like trying to divide people into women, men, girls, boys, and zither players” (Gray 1963: 40). “Condensed matter” acknowledged that the methods physicists used to study solids were often just as suitable to other dense materials, such as liquids, gels, polymers, and plasmas. Defining a field that emphasized this class of methods, proponents of condensed matter hoped, would highlight intellectual contributions over industrial applications (Martin 2015).

The high-profile political scraps that preceded the SSC’s demise gave condensed matter physicists a chance to showcase their ideology. Before Congress and in the popular press, Anderson and his colleagues attacked the reductionist rhetoric used to justify the SSC, maintaining that their field was just as fundamental as HEP, while also being more technologically and economically relevant. This was a delicate dance. Condensed matter physicists did not want to undermine funding for exploratory research. At the same time, they recognized that some claim to short-term relevance was essential to survive in the post-Cold War environment.

The failure of the SSC was in some measure a result of the new priorities of a new context, one to which SSP was better adapted, despite efforts from some segments of the community to shed the field’s association with technology. A close and successful collaboration with industry had helped SSP grow into a powerful force, and although efforts to reimagine the field as a basic research enterprise did change the internal character and constitution of the community, they were less successful in branding solid state research for more general consumption. Solid state physicists, who envied the public recognition enjoyed by their nuclear and high energy colleagues, never managed to attain the same level of visibility, in part because they lacked a compelling public spokesperson. John Bardeen, winner of two Nobel Prizes in 16 years, might easily have traded his success for celebrity akin to that of an Oppenheimer or a Richard Feynman had he not been notoriously humble and unremittingly laconic (Hoddeson and Daitch 2002). Nevertheless, the desire solid state physicists retained to partake of the acclaim physics enjoyed kept their field from migrating into engineering. When combined with an impressive track record of technical accomplishment, that meant that SSP permitted physics as a whole, including HEP, to present itself to its patrons and to the public as a field that both probed the inner secrets of the universe and exploited them to practical ends.

Between 1939 and 2014, 86 physicists from the United States received the Nobel Prize in Physics. Before 1939, only four had been similarly recognized. The starkness of these numbers indicates a phase change in American physics around mid-century when the fields described above asserted themselves. The independent paths to success they plotted, when braided together, gave American physics tremendous strength and versatility. For all their squabbling and ideological differences, these were interdependent endeavors.

Nuclear physicists reaped the rewards of physics’ centrality to national defense. High energy physicists exploited its newfound intellectual prestige to focus the world’s largest machines on the universe’s smallest constituents. Solid state physicists forged connections with industry to exploit physics’ untapped technological potential. Neither of these trajectories could have been fully realized except against the background of the others. Nuclear and high energy physics gave solid state a level of esteem and political influence to which to aspire and kept it grounded in the search for general physical principles when it might easily have diffused into engineering. High energy physics relied on the practical benefits of nuclear and solid state to conduct research that could not have commanded the huge quantities of funding it required without the political will secured by other areas of physics. Nuclear physics retained its strong policy influence in part because it was not narrowly diverted into weapons and reactor design, but, on the strength of its sibling fields, showed potential for new and unexpected breakthroughs.

American physics established itself in the second half of the twentieth century because of its diversity. Physicists fleeing a fractured Europe injected new perspectives into a fledgling American community as new specialties expanded opportunities for growth. World War II galvanized American physics and sold the public on a field about which it previously knew little, but physics succeeded after the war precisely because it abandoned a common purpose. By developing competing ideologies, nuclear, high energy, and solid state physics gave physics writ large a range of influence it lacked when it existed as a more uniform entity. American physics did not succeed because of its defense applications, its intellectual achievements, or its industrial relevance alone. It succeeded because these elements of the physics community, even when at loggerheads, worked in consonance.

Bibliographic Essay
The core interpretive frameworks in the history of American physics over the past decades have focused on the factors that made American science distinctive (Reingold 1991). Literature on “big science” or “big physics” emphasizes the scale of the machines, research groups, funding, and impact of Cold War physics (Heilbron and Seidel 1989; Hoddeson, Kolb, and Westfall 2008; Kevles 1997; Westfall 2003b). A lively segment of the historiography examines the relationship between basic and applied research (Crease 1999; Johnson 2008; Kevles [1971] 2001; Kleinman 1995; Leslie 1993), a distinction that exerted considerable policy influence in the Cold War. A segment of the historiography that focuses on conceptual developments has devoted considerable attention to the unity and fundamentality of physical knowledge (Cat 1998; Galison and Stump 1996; Kragh 2011; Pais 1988; Stevens 2003).

Aside from these traditions, histories of American physics are broadly split between studies of the community of American physics and attention to its conceptual development. Kevles ([1971] 2001) provides a touchstone for many of the community studies. The influence of the European diaspora of the 1930s has been thoroughly examined, as have the strides the American physics community made before receiving a boost from European émigrés (Assmus 1992; Holton 1981; Schweber 1986). Considerations of the Cold War era have emphasized the influence of the distinctive pressures competition with the Soviet Union placed on American physicists (Forman 1987; Wang 1999; Wolfe 2012).

Conceptual historians have addressed both the theoretical and experimental aspects of American physics. The former have turned to quantum mechanics to craft a large-scale narrative of twentieth-century physics (Kragh 1999, Pais 1988). Recent scholarship has challenged the longstanding assumption that quantum mechanics was developed in terms of fundamental problems and only later applied to more complex systems. Joas (2011) argues that the so-called “applications” of quantum mechanics to molecules, plasmas, and solid state systems was integral to the development and articulation of the theory. Histories of experiment in the early twentieth century have tended to focus on major individuals in American science and their influence, including Albert Michelson (Goldberg and Stuewer 1988), Arthur Compton (Stuewer 1975), Henry Rowland (Sweetnam 2000), and Ernest Lawrence (Heilbron and Seidel 1989). Studies of the post-World War II era shift their attention to apparatus and material culture (Galison 1997; Riordan, Hoddeson and Herring 1999; Westfall 2003a).

Recent historiographical concerns about overspecialization have promised to change the way historians approach American physics. Whereas previous historical scholarship generally focused on well-defined topical areas that mirrored those used by scientists themselves, recent work calls for historians of science to articulate their work in terms of broadly relevant historical themes (Kaiser 2005b; Kohler 2005). Many of the foundational works on American physics addresses themes such as textbooks and pedagogy (Kaiser 2002, 2004, 2005a; Midwinter and Janssen 2013), experimental practice (Crease 1999; Galison 1987, 1997; Westfall 2003a, 2003b), and the influence of patronage on scientific knowledge (Bromberg 2006; Forman 1987; Hounshell 1997; Kevles 1990). This variety of thematic – as opposed to topical – categorization represents the current modus operandi for the history of American physics.

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