75 years of physics

The American Institute of Physics was founded in 1931, and Spencer Weart (Director of the Center for History of Physics at AIP in College Park, Maryland) looks back at the last 75 years to "guess where physics will be 75 years from now." What strikes us immediately in the section on the state of physics in 1931 is the youthful exuberance of it all:

Physicists had understood for two decades that atoms were composed of electrons and nuclei, but at that point they had gotten stuck. Now in 1931, Paul Dirac proposed that the electron has an antiparticle, what would come to be called the positron. This was a hint that particles come in families with positive, negative, and perhaps neutral members. Dirac was a year short of his 30th birthday. Younger still, at 26, was Caltech student Carl Anderson, just getting into the cosmic-ray studies that in 1932 would demonstrate the positron's existence.

All kinds of bizarre ideas about particles were in the air. Wolfgang Pauli, for example, was developing the neutrino hypothesis, although he wasn't quite ready to publish it. On the experimental side in 1931, Ernest Lawrence at the University of California, Berkeley, completed a little prototype cyclotron that accelerated protons to 1 MeV on the way to higher energies that he hoped would break into the nucleus. He had just turned 30; so had Robert Van de Graaff, who was developing another type of particle accelerator.

The article mentions quite a few young ones who were already stars (or, were marked out for stardom): Robert Oppenheimer, Linus Pauling, Eugene Wigner, Frederick Seitz. Which brings me to something that belongs in the annals of academic put-downs; this quote appears in a NYTimes review of books on Robert Oppenheimer:

American Prometheus does capture the world in which Oppenheimer established his credentials: thick with future Nobelists, bristling with innovation, cattily competitive. (As one of his fellow scholars remarked about another: “So young and already so unknown.”) [via]

Weart's article has this to say about the 'progress' in the training of physics graduate students:

Physics is not just an intellectual exercise, but also a community of people and their institutions. The first step we should look at in the physicist's career is education. The students of 1931, transported to a physics department of comparable size today, would find many familiar things in the setup of textbooks, courses, examinations, seminars, and thesis mentoring. For better or worse, graduate education in the 21st century retains most of the structures that originated in 19th-century Germany.

So, what is the largest sub-field of physics today? The honour goes to Condensed Matter Physics, with which my own field, Materials Science (and Engineering) has rather intimate connections:

Today the largest field in physics, encompassing more than a fifth of all the PhDs granted in the last decade and a still higher fraction of physicists' careers, is the study of "condensed matter." The term replaced "solid-state" in the 1960s following successes in the study of fluids. Since then, the rubric "materials science" has been added, pointing toward the proliferation of practical applications.

Weart then goes on to say how physics has become revitalized by growing tentacles that he calls hyphenated fields: astro-physics, geo-physics, bio-physics, medical physics, etc.

To me, the interesting part of the article is the one about the future. Weart hedges his bets by saying, "Historians will tell you that the one thing you can learn from history is that it's unpredictable. You can't project every linear trend forward." Then he offers his ideas on the way forward:

[Here] are at least two obvious paths forward. On the one hand, we are challenged by deep unknowns in the fundamental nature of matter. On the other hand, we can go much farther in straightforward understanding and manipulation of the immediate material world. On the first path, we can hope for strange insights into both fundamental particles and cosmology, with unforeseeable uses. On the other, we can hardly fail to find more wonders in the physics of condensed matter, and beyond in the realms of nanophysics and biophysics.

What about advances that we can't predict? In the past we have seen many unanticipated discoveries. And most of them—from lasers to dark matter, from medical physics to climate change—depended on new instrumentation (including computers) and extensive observational programs. Today's student should pay special attention to new developments in instrumentation and collaborative organization. We could try to predict what new instruments and programs may come along in the next couple of decades. Beyond that we can only be confident that they will keep coming, each building on what came before.

Weart covers a lot of ground, and as they say, you really ought to read the whole thing.