As a particle physicist, I was a bit surprised to hear Sidney Nagel speak of particle physics as holding “pride of place” in the discipline. I am not sure that my condensed matter physics colleagues would have characterized the field that way, even when the Superconducting Super Collider seemed alive and well. Perhaps what Nagel has hit upon is that very large projects take on a symbolic significance, and their cancellation can’t but have implications for the morale of the whole discipline of physics.
In the nearly ten years since the SSC was cancelled, the field of particle physics has remained vibrant and exciting. The Large Electron–Positron program at CERN and the Linear Collider at SLAC, after elevating the standard model to a precision branch of science, have recently shut down. The current experimental programs on B physics at both SLAC and KEK, Japan’s High Energy Accelerator Research Organization, have been enormously successful. Recent data from Kamiokande and the Sudbury Neutrino Observatory in Canada have provided compelling evidence for neutrino masses and mixing.
The upgraded Tevatron is running at Fermilab and has the potential to make major discoveries. On the theoretical front, particle physicists have worked hard in the past few years to understand the flood of new data, have made predictions for new facilities, and have addressed difficult questions about black holes, electric–magnetic duality, and other issues.
The international community, with vigorous US participation, is working on CERN’s Large Hadron Collider, which is currently scheduled to begin running in 2007. And in the last few years, an international consensus has crystallized as to the future after the LHC. The picture certainly has some clouds, particularly involving funding—but overall, there is cause for optimism.
Nagel raises a number of other important issues. Our parochialism is not new. When I was a graduate student, it was the nuclear physicists who ridiculed both condensed-matter and applied physics; my particle-theorist teachers admonished me that condensed matter had much to teach us, and even suggested that we might occasionally be able to contribute something to that field as well. The split between small and big science is inevitably a source of tension. It is important that researchers in big collaborations working on very large projects and those on smaller-scale efforts support each other. In my department, it is not uncommon to find, for example, our high-energy lab lending some of its resources to research in condensed matter (including soft condensed matter), and to find condensed matter physicists providing advice on detectors and detection strategies. But the exchange could be better.
As for hiring, when we serve on search committees in others’ sub-fields, we must often defer to colleagues, but I find that we usually have enough in common to exchange useful advice. A candidate search can be an opportunity to learn about what is interesting to our colleagues.
Nagel does not mention another field that has altered the physics landscape during the past decade. When I was a student, astrophysics was peripheral and cosmology disreputable. Today, many physicists, both theorists and experimentalists, from other subfields are spending much of their time on these subjects.
Cosmology and astrophysics highlight the issue of reductionism. The two fields are not exactly reductionist, but neither are they simply emergent. They are phenomenological in the most exciting sense. We are finding that the data fit into a fantastic picture. Cosmologists have used an impressive array of techniques from various fields to attack and apparently solve the classic problem of galaxy formation. Yet we don’t yet know the physical laws that account for dark matter, dark energy, inflation, and the very origin and nature of the universe. The reductionists, both theorists and experimentalists, are attacking these questions vigorously.
In the end, Nagel’s article gives me some hope for optimism. I, too, could list what I find to be the burning questions, and there would be a surprising amount of overlap. The question Nagel mentions of systems far from equilibrium arises frequently in particle physics and cosmology. Most recently it has been raised by the discovery—by astronomers, cosmologists, and astrophysicists—of a nonzero cosmological constant. Particle physicists and astrophysicists are proposing that these questions be studied further, using technologies developed in part by condensed matter physicists. So, while we face many challenges, ours remains a rich and exciting field.
