March 2012 FHP sessions at the APS meeting in Boston

Peter Pesic, Co-Chair, FHP Program Committee 2011-2012

2012 marked two anniversaries that the Forum on History of Physics wanted to observe through sessions at the APS March meeting in Boston. In the period 1861-63, James Clerk Maxwell assembled and published his version of what we still call his equations, so fundamental to physics even one hundred fifty years later that this seemed an apt occasion to look back to this seminal passage in physics. Paul Cadden-Zimansky, a member of our Executive Committee representing students and early-career physicists who was then a postdoc at Columbia University (and now has accepted a post at Bard College), gave the original impetus to this observance by reminding us that 1862/2012 marked the anniversary of Maxwell’s essay "On Physical Lines of Force," which set out in clear, uncomplicated prose his understanding of how Michael Faraday’s work on electrodynamics marked out a path to a new mathematical and physical understanding of those phenomena in their wholeness.

Our Forum uniquely bridges the concerns and perspectives of active physicists, of students, of historians of physics, and all interested in the development of science. To do justice to this rich variety of audiences and interests, our session on February 27, 2012 entitled "One Hundred Fifty Years of Maxwell’s Equations," chaired by Edward Gerjuoy (University of Pittsburgh), enlisted five distinguished speakers to approach Maxwell’s achievement in different ways, to show how Maxwell discovered his equations, how they affected the physics of his time and our own, including current perspectives on this seminal discovery.

The first three speakers addressed him primarily in the context of his own time and its immediate aftermath. C. W. F. Everitt (Stanford University) began by presenting his account of "The discovery of Maxwell’s equations." Everitt, author of a wonderful short biography of Maxwell, discussed the blend of physical modeling and mathematical innovation that enabled Maxwell to write his equations. Presenting many unfamiliar and interesting images from Maxwell’s time, Everitt also surprised us by noting that Leonhard Euler had earlier put forward a concept of lines of force, usually attributed to Faraday and Maxwell. Bruce Hunt (Univ. of Texas) addressed "The Maxwellians and the Remaking of Maxwell’s Equations," bringing forward a rich variety of material concerning the rethinking of Maxwell’s work in the generations immediately following him, drawing on Hunt’s outstanding book on this period and new work he has in progress, especially concerning the role of the transatlantic telegraph cables in the development of electrodynamics. Jed Buchwald (Caltech) brought the story still further forward in his account of "Using Maxwell’s equations in the late 1800s," the period in which the equations more and more closely approached the form now most familiar to physicists. Buchwald’s amazing command of the intricate technicalities revealed to the audience the full sophistication and achievement of late nineteenth century electrodynamics, in the hands of physicists like Oliver Heaviside. His exposition, in concert with those by Everitt and Hunt, helped us see the strata of inference and changing perspectives that lie under the textbook treatments of Maxwell’s equations, so often presented as if they came from nowhere.

The final two speakers looked back at Maxwell’s equations from presentday physics and its concerns. Roy Glauber (Harvard) gave an overview of "Maxwell’s equations and quantum optics," a daunting task, given the vast scope and manifold ramifications of quantum electrodynamics, its practical and theoretical consequences, throughout the twentieth century, up to the present day. Glauber’s deep familiarity and long involvement in these developments, especially in connection with the optical model for which he was awarded a Nobel Prize, gave his presentation special interest. Finally, Frank Wilczek (MIT) talked about "Taking off from Maxwell’s equations," especially the development of gauge field theories that ultimately stem from Maxwell’s discoveries. Wilczek, a Nobel laureate for his work on quark confinement, gave a dynamic overview of the development of gauge theories into the Standard Model as it stands today, harking back at many points to Hermann Weyl and ultimately to Maxwell as its founders and pioneers. Wilczek’s talk was filled with nice explanatory touches and moments of new insight; he illustrated that vacuum polarization provides a natural scale of a new sort, using amazing animations produced by computer calculations of quantum chromodynamics. The large audience present seemed deeply interested by this series of talks.

2012 also marks the centenary of the birth of Edward Purcell, whose seminal work brought nuclear magnetic resonance (NMR) into the world and transformed radio astronomy, among other signal accomplishments as teacher and researcher. Our session on "The Scientific Legacy of Edward Purcell (1912-2012)," held on leap year day (February 29, 2012), was in itself a rare and special event. Chaired by Gerald Holton (Harvard), on this unique occasion several of Purcell’s closest collaborators remembered his work and assessed its enduring significance.

Nicolaas Bloembergen (Univ. of Arizona), one of Purcell’s first graduate students and himself a Nobel laureate for his work stemming from NMR, gave a unique and touching account of "Purcell and NMR." Bloembergen arrived at Harvard just after Purcell’s experiments that first demonstrated NMR; he was able to give many insights into that discovery and its immediate consequences in his own work. We learned how Purcell was able to make great discoveries on a shoestring, using borrowed equipment on weekends. This was especially apparent in the contribution by Harold I. Ewen (EK Associates) on "Purcell and the development of radioastronomy." "Doc Ewen" (as he became known), as Purcell’s graduate student, received the challenge to detect the hyperfine transition of hydrogen in interstellar space. Unfortunately, personal reasons prevented Doc from attending and speaking, but his talk as read by Prof. Holton (who had been a much-admired teacher of his at Harvard) still brought forward the flavor of those times, when an "impossible" task (as some thought) came to pass. Doc Ewen showed the full effect of Purcell’s constant insight and generous advice (and his finding a $500 grant at a crucial moment, when sums like that could make or break a project). As several people observed, modern radio astronomy really began with this discovery, which almost immediately enabled the first mapping of the Milky Way galaxy (and which some thought was worthy of a Nobel prize of its own).

Howard Berg (Harvard) gave a wonderful talk "On small things in water moving around: Purcell’s contributions to biology," with which Berg had been long involved. Berg’s engagingly informal and perceptive account described his own transition from medical school to graduate study in physics and thence to work in biological physics, to which Purcell signally contributed. Berg brought forward many examples, including Purcell’s lovely work on "life at low Reynolds number," the problem of bacterial locomotion and swimming. From his long and extraordinary perspective in this field, Richard Garwin (IBM Watson Research Center) gave a detailed account of "Purcell’s work advising the government," opening a striking perspective on the changing role of scientists advising the government and Purcell’s own crucial role therein. Garwin was able to use a number of recently declassified documents to describe for the first time a number of the projects on which Purcell had worked, especially concerning high-altitude reconnaissance.

Finally, but by no means last in significance, John Rigden (Washington Univ.) gave an eloquent portrayal of "Purcell the Teacher: In and Out of the Classroom." As editor of the American Journal of Physics, Rigden had worked closely with Purcell on his long-standing series of columns, "The Back of the Envelope," which posed and (in later issues) solved intriguing physics problems using simple methods of estimation. Speaking with passion and armed with many examples, Rigden reminded us that, above all, Purcell considered himself a teacher. Coming from someone so celebrated a researcher, this avowal should remind all of us of the centrality of teaching in physics, considered in its broadest sense of thoughtful questioning, learning, and discussing. If Purcell was such a learner, we should try our best to do likewise.

The large audience present seemed appropriately moved to have participated at a unique gathering of very special speakers, an occasion which probably will never happen again on this earth. Such opportunities to hear about the history of physics from some of its most important protagonists are history itself.

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