In 1905 Albert Einstein published four groundbreaking papers in what today would be considered at least three distinct fields: condensed matter, statistical physics, and fundamental physics. Physics has become increasingly specialized in the past century, and today a similar scholar would be expected to publish four times in the same field.
Arguably, that specialization is a natural consequence of the division of labor enabled by the exponential growth of physics. In 1905 only several hundred physics papers were published each year; today the number surpasses 100 000. That huge increase in volume reflects the degree to which researchers are fleshing out increasingly detailed parts of a field. Focusing on a specific area of study has made possible many advances, such as the discovery of the Higgs boson in 2012 or the capture of an image of a black hole in 2019.
During university studies, physics is generally taught as a unified set of disciplines in which research in separate subfields contributes to a more complete picture of the natural world. In a research environment, however, the focus becomes highly specific, and often researchers from different fields seem to be speaking different languages. How physics is presented greatly differs from how it is done.
As current graduate students, we (the authors of this article) have noticed how rapidly our skills and knowledge are diverging from each other’s and from those of our fellow students. Even now, when simply talking to peers about our research, we struggle to share ideas and come to grips with important questions because of the differences in jargon between fields, like a modern Tower of Babel. Those peers are the very same classmates with whom only recently we were taking courses in which general skills, such as reasoning from a small number of physical principles and model building, are valued most. Despite that common background, an ever-widening gap is beginning to form between us as researchers, and that gap impedes the understanding and appreciation of important problems and results in different fields.
Why should researchers work broadly or even be widely read? After all, isn’t specialization more efficient? Perhaps, but historically, research that spans multiple fields has been incredibly fruitful. A classic example is the Anderson-Higgs mechanism, famous for explaining the masses of W and Z vector bosons in high-energy physics but actually rooted in superconductor physics. In his 1964 paper describing the mechanism, Peter Higgs noted that he was inspired by Philip W. Anderson’s work and explained that the mechanism is “the relativistic analog of the plasmon phenomenon to which Anderson has drawn attention.”
On a personal level, how can we strike the right balance in our work between having our own specialized topic and being generally informed beyond our specific field? On a larger scale, how can the wider physics community stay coherent as a whole and continue to make interdisciplinary advances? To answer those questions, we asked several career physicists to reflect on their experiences.
Leave the comfort zone
The continued success of physics requires specialists. But defaulting to the study of narrowly focused research areas creates pitfalls. Teachers typically counsel young researchers to, as theoretical physicist Sabine Hossenfelder of the Frankfurt Institute for Advanced Studies puts it, “create your own niche—a very specific topic that typically gets handed to you with your PhD.” Hossenfelder feels that such career advice is not sound. “If you specialize in one particular thing, it could go well, or if you’re unlucky, it could go dramatically wrong,” she emphasizes. Being a one-trick pony is a risky strategy.
“There is safety and security in staying in your own subfield,” Simons Foundation President and astrophysicist David Spergel says. “There is a lowest energy state you settle into, and you need to get nudged out of that.” Doing so, however, requires discipline. “Step outside your comfort zone,” Spergel recommends. “Go to colloquia. Be willing to ask dumb questions. Whether you are a student or faculty member, it’s important to ask dumb questions!” Working broadly is a matter of personal accountability, not a hobby.
That strategy has paid dividends for Spergel. Ten years after his PhD in astrophysics in 1985, he decided to teach himself optics. He read Max Born and Emil Wolf’s classic textbook, Principles of Optics (1959), and attended weekly meetings outside his field on exoplanets. He wondered, “Could I design a new coronagraph as a toy problem to figure out if I understand optics?” As a theoretical cosmologist, Spergel was familiar with asymptotic properties of Bessel functions that turned out to be useful tools for designing coronagraphs for exoplanet discovery. He succeeded, and his design is being used by NASA’s Nancy Grace Roman Space Telescope, which is set to launch in 2025.
Not only do individuals benefit from working broadly, but the inflow of external ideas is essential for the progression of fields. Without it, subjects such as cosmology, which uses ideas from various subjects from particle physics to statistical physics to general relativity, would stagnate. Hence, the community should encourage individual broadness and creativity.
The dead-time fallacy
Institutions, as collections of individuals who collaborate and share ideas, set the norm, and individuals follow suit. Therefore, institutional practices crucially reinforce both the positives and negatives of specialization at the individual level.
The incentives to specialize start in graduate school. “If you did your PhD on a particular topic and worked on this for three, four, five years, then that is your identity,” Hossenfelder says. “You could not go and say, ‘Tomorrow I will do something else,’ because you will not get a grant, and no one will give you a job in academia.” In that way, young researchers are compelled to follow a narrow career path.
Tim Palmer is an example of someone who did decide to radically change his career as a young physicist. After completing his PhD in classical general relativity in 1977, he switched tracks to climate physics in the hopes of making a larger impact on society. He says, “I realized a lot of the physics and mathematics that I knew was actually quite relevant to climate physics.” Nonlinearity in particular was a key theme common to both subjects. “When you do GR, you’re studying a very nonlinear theory. Climate is also very nonlinear; all the complexities of climate and its conceptual difficulties essentially arise because it is a nonlinear dynamical system,” Palmer explains. That connection made him realize that he could make a transition. He is now a professor of climate physics at the University of Oxford.
Palmer is skeptical, however, about whether he would get the same opportunity now. “I think it would be much more difficult for me to be recruited today, with the background I had, than 40 years ago. Administrators want quick results; all their budgets are predicated on getting something out in a year or two.” However, Palmer says the notion that hiring nonspecialists costs too much dead time is a fallacy. “The spin-up time is much shorter than people think, if you get the right people,” he asserts. To solve today’s problems, climate science and other fields need the world’s best minds, not its greatest specialists.
The bias toward specialization is amplified by many funding bodies because they outsource their decision making for grants and fellowships to the community by soliciting reviews. The reviews are submitted by highly specialized individuals, who naturally believe further specialization is necessary. “It is not the funding bodies themselves, but they reimport this prejudice that they already have in the community,” Hossenfelder says. That process prevents new voices from entering the echo chamber, and in the long run, it adversely affects the diversity of ideas in a field.
Clearly, how institutions are set up defines which behaviors are encouraged within the physics community. Funding bodies should be mindful to reward promising candidates on the basis of their broader knowledge alongside their specialized, in-depth skills.
Grants that support researchers learning new fields would be a positive way to break the vicious cycle of self-reinforcing specialization. Such grants could fund established top-class physicists during their “spin-up” time, enabling them to learn new skills and thus bring their established expertise into a different field. The grants could additionally work as a pressure valve that helps researchers who feel stuck in their particular niche switch tracks. One example is the Schmidt Science Fellows program, which funds exceptional PhD students to conduct a special postdoctoral study outside their field of expertise.
We stress that there is no one right way to do research and acknowledge that specialization has worked and is still needed. But diverse research strategies are an advantage, and being a specialist should not mean working only in a narrow niche. Institutions should be mindful of the long-term benefits of hiring people from different disciplinary backgrounds, as great ideas often come from forays outside one’s own field.
Keeping physics robust and creative is a responsibility that lies with both the individual and the community at large.
Liam L. H. Lau is a graduate student at Rutgers University in New Brunswick, New Jersey. Ethan van Woerkom is a master’s student at the University of Amsterdam in the Netherlands.