Benefits of Particle Physics to Society
BENEFITS OF PARTICLE PHYSICS TO SOCIETY
Compared to most scientific endeavors, though not to space exploration or to some defense-related technology research, high-energy physics is an expensive enterprise. Modern accelerator facilities capable of expanding the high-energy frontier, such as Fermilab or the European Laboratory for Particle Physics (CERN) Large Hadron Collider (LHC) project, are big science, involving the concerted efforts of thousands of people and costing several billions of dollars. High-energy physics has been supported almost entirely by government agencies and thus ultimately by taxpayers. It is entirely appropriate that scientists who promote these expenditures should be expected to justify this investment by society as a whole, by explaining its benefits to society as a whole.
The primary aim of research in high-energy physics is easily stated. It is, simply, to produce a better understanding of fundamental physical law by following a reductionist strategy. That is, scientists attempt to understand the behavior of matter in general by working up from profound understanding of the properties and interactions of its elementary constituents.
This strategy has proven remarkably fruitful and successful, especially over the course of the twentieth century. We have discovered that strange but precise and elegant mathematical laws, summarized in the so-called Standard Model, govern the laws of physics on subatomic scales. There is every reason to think that these laws, as presently formulated, are adequate to serve as the foundation for materials science, chemistry (including biochemistry), and most of astrophysics.
One must be careful in interpreting this sort of statement, which superficially might appear quite arrogant. Chemists in pursuit of their profession are rarely, if ever, concerned with the equations of quantum chromodynamics (QCD). They take the existence and basic properties of atomic nuclei as given. For most chemical purposes it is adequate to approximate nuclei as pointlike concentrations of charge and mass. In a few applications nuclear spin also plays a role, but rarely any other aspect of nuclear structure. So in saying that QCD provides part of the "foundation" for chemistry, one means no more (and no less) than that it provides equations which in principle should allow one to derive the existence of nuclei, and to calculate a few of their properties, from a few proven properties of their constituent quarks and gluons. It does not thereby directly solve, or even address, any properly chemical problems. In the same spirit, it might be said that acoustics provides the foundation for music or lexicography the foundation for literature.
As the inner frontier of the reductionist program has moved from explaining matter in terms of atoms to explaining atoms in terms of electrons and nuclei and then from explaining nuclei in terms of protons and neutrons to explaining protons and neutrons in terms of quarks and gluons, the models it creates have become ever more accurate and more broadly applicable. But with this progression, the domain of phenomena in which the new models provide qualitatively new insights, as opposed to better foundations, has grown increasingly remote from everyday life. Subatomic physics allowed us to understand and refine the basic principles of chemistry and to design materials with desired electric and magnetic properties; nuclear physics allowed us to understand the energy source of stars and the relative abundance of the elements; quark-gluon physics allowed us to understand the behavior of matter in the very early universe. Future developments may help us to penetrate more deeply into the early moments of the Big Bang or to recognize and understand yet undiscovered extreme astronomical environments, but apart from this, it is hard to anticipate their direct application to the natural world. It would be quite disingenuous to hold out the promise of economically significant new technologies based on future discoveries in high-energy physics.
From a broader perspective, however, the picture looks quite different. Over recent history, again and again fundamental, curiosity-driven research has led to unexpected developments and spin-offs whose economic value far exceeds the cost of the investments that spawned them. Sometimes the payoff was delayed by many decades and came from directions that no one remotely anticipated. The whole world of radio and wireless communication grew from Michael Faraday's vision of empty space as a dynamical medium and the experiments it inspired. Lasers and digital cameras grew from struggles of Max Planck and Albert Einstein to understand the strange wave-particle dualism of light-photons. Modern microelectronics, with all its ramifications, grew out of J. J. Thompson's discovery of electrons and the revolutionary insights of Niels Bohr, Werner Heisenberg, and Erwin Schrödinger in quantum theory.
Nor do we lack examples closer to the present, recognizably belonging to the modern era of high-energy physics. The central tool of the field, the accelerator, has become a ubiquitous medical device. The simplest and most familiar incarnation, perhaps, is the X-ray machine, but other particle beams are used in cancer therapy and for diagnosis. Who would have thought that reconciling quantum theory with special relativity would lead to important clinical technologies? Yet Paul Dirac's theory predicated antimatter, and positron emission tomography (PET scans) has become a powerful tool for looking inside the brain. Another fascinating application of accelerators is mass spectroscopy. The ability this technique supplies, to analyze accurately the chemical and isotopic composition of very small samples and thereby to characterize and date them, has supported significant contributions to geology, archaeology, and art history.
At this moment, synchotron light sources are providing new, cutting-edge tools for investigations in structural biology and chemical dynamics. For high-energy physics the production of synchotron radiation as an inevitable accompaniment of charged particle acceleration was regarded as a nuisance, draining energy from the particles of interest. But it turns out that this "waste product" allows scientists to look at molecules with unprecedented resolution in space and time. So now special accelerators are designed specifically to be sources of synchotron radiation. The new windows they are opening will undoubtedly reveal extraordinary new vistas.
Besides its direct impact, the development of high-energy accelerators has also spurred progress in a number of supporting technologies. Notably, these accelerators require large powerful magnets to guide the particle orbits. Such magnets have become the workhorse of magnetic resonance imaging (MRI), another major medical technology.
A completely unanticipated, quite recent spinoff may become the most important of all. Modern high-energy physics experiments typically involve many tens or even hundreds of collaborators, who must share their data and their analyses. It was to facilitate this process that Tim Berners-Lee, a software engineer working at CERN, developed the concept of the World Wide Web and the first browser-editor, thus initiating the Internet revolution. Many other innovations in high-speed electronics, less well known but central to commercial computing and communication technology, were developed in response to the challenges of guiding vast numbers of particles moving at velocities very close to the speed of light and interpreting the complicated results their collisions produce.
More difficult to identify specifically, but also important, are spin-offs from conceptual developments in high-energy physics. Quantum field theory was developed as the rigorous language of elementary processes but also turns out to be the appropriate tool to understand superconductivity. The renormalization group, first developed as a technical tool within quantum field theory, turns out to be the key to understanding phase transitions and is playing a dominant role in the emerging theories of pattern formation, chaos, and turbulence.
Why do such valuable surprises occur so regularly? Can more be anticipated in the future? There is a simple, yet profound explanation. In essence, it was put forward by William James, who spoke of "the moral equivalent of war." It is the fact that human beings can be inspired by difficult problems and challenges to work very hard and selflessly and to find more in themselves than they knew existed. Especially in youth, they even seem driven to seek—or manufacture!—such problems. Perhaps evolution selected this ability to rise to the occasion partly in response to the pressures of human conflict. In any case, we should cherish the opportunity to direct it into constructive channels.
Certainly, high-energy physics offers an abundance of tough challenges. Ultimate questions about the closure of fundamental dynamical laws and the origin of the observed universe begin to seem accessible. Tantalizing hints point toward new worlds of phenomena involving supersymmetry and unified field theory, but present ideas contain many loose ends and unsatisfactory details. The great challenge of reconciling general relativity with quantum mechanics might be met with superstring theory, but as yet this is far from reaching fruition in specific world-models. And the great embarrassment of the cosmological term, whose measured value is many orders of magnitude smaller than current theories suggest, threatens to upset the whole applecart. On the experimental side the challenges are more tangible and no less awesome. The next generation of accelerators will be engineering projects of grandeur, both in their size and in their precision. They will be modern civilization's answer to the pyramids of Egypt, but nobler, built to improve our understanding rather than to appease superstition and tyrannical theocracy. We must learn how to handle the tremendous flow of data these accelerators will generate. The ATLAS experiment already planned for CERN's Large Hadron Collider is expected to collect 1015 bytes/year—equivalent to a million human genomes. Amidst this torrent we must identify the fraction, probably a mere trickle, which does not fit the Standard Model. New ultrafast methods of communication and computation will need to be developed. It would be surprising if the effort of rising to these challenges did not produce some spectacular by-products.
In short, the economic fruits of fundamental investigation, though unpredictable in detail, have arrived with wonderful reliability and have been reliably wonderful. Investment in this area is ultimately an investment in people, specifically in the power of great problems to inspire great efforts.
In this connection, it is appropriate to emphasize that the human effects of big scientific projects ramify far beyond their immediate research community. Construction of a modern high-energy accelerator, its detectors, and its information infrastructure brings engineers into intimate contact with exotic frontiers of technology and with problems of a quite different nature from those they would ordinarily encounter. Also, most of the young people going into these projects will not find permanent academic employment. They enter this life with open eyes, foregoing security for the opportunity to participate in something great. When these engineers and researchers return to the outside world, they bring with them unique skills and experience.
Finally, the visible commitment of society to high-profile scientific endeavors sends an important message to young people considering what career to enter, encouraging them in scientific and technological directions. This is important, since our society needs capable scientists and engineers, and they are always in great demand.
In addition to spin-offs and indirect benefits, there is also the intrinsic worth of the prospective knowledge. There are several identifiable questions that seem ripe for progress.
Universal Condensate and the Origin of Mass
The theory of the weak and electromagnetic interactions postulates that what is ordinarily regarded as empty space is in fact filled with a pervasive condensate. It is only by interacting with this condensate that many particles, notably including the W and Z bosons, which mediate the weak interaction, acquire their mass. Although the theory is extremely successful, this central aspect has not been tested directly. Physicists hope to excite the condensate, either producing so-called Higgs particles, or revealing some more complex structure.
Unification of the Theory of Matter
The Standard Model, containing both the theory of weak and electromagnetic interactions and QCD (the theory of the strong interaction) provides a remarkably complete theory of the behavior of matter. The different pieces of the Standard Model have related mathematical structures, embodying various symmetries, and it is tempting to speculate that there is a master symmetry encompassing them all. There appears to be a compelling candidate for such a "grand unified" symmetry. Will it hold up to further scrutiny?
The unification mentioned above, when pursued quantitatively, requires another important addition: supersymmetry. This idea postulates the addition of extra quantum-mechanical dimensions. Motion of particles in these dimensions will make them appear to be particles with quite different, but broadly predictable, properties. So far none has been found, but according to theory they must begin to show up in higher-energy collisions.
The Arrow of Time
A few exceptional microscopic processes that exhibit a preferred direction in time (that look different when run backward) have been observed. This phenomenon is vital to understanding how the cosmic asymmetry between matter and antimatter arose. To understand it properly, we need to see more examples of how it works, especially at high energy.
Unification with Gravity
Gravity is not deeply integrated into the Standard Model or even its unified extensions. But there are bold ideas for how a completely unified theory, including both the Theory of Matter and gravity, might be constructed. Some of these ideas lead to predictions of new particles, and patterns among their masses, that could be observed. In this way, we might for the first time acquire empirical information on the nature of quantum gravity, or indications of the existence of extra curled-up spatial dimensions.
Transcending whatever specific answers it supplies, continued pursuit of the reductionist program expresses society's commitment to some of the deepest ideals of our scientific culture: to pursue the truth wherever it leads; to ground our working picture of nature in empirical realities and challenge that picture; and to see whether the marvelous simplicity and mathematical beauty of the description that has emerged from previous investigations can be refined further, or whether it reaches some limit.
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