Science magazine news report: “Textbook electrodynamics may contradict relativity”

Calling to mind—though never mentioning—the recent sensational European experiment in which neutrinos were suspected of exceeding the speed of light, Adrian Cho’s one-page News and Analysis article in the 27 April issue of Science opens this way:

To frame the report before continuing, Cho quotes two scientists. Stephen Barnett, a theorist at the University of Strathclyde in Glasgow, UK, says, “If it’s true, it’s astonishing"—though he suspects there’s a “subtle” explanation not at odds with relativity. But Rodney Loudon, a retired theorist from the University of Essex, UK, says, “As far as I can tell, [the analysis] is right.”

Cho reviews the nature of the Lorentz force, cites what he calls the irony that physicists invoke it “in the textbook example of how electrodynamics and relativity mesh,” and then summarizes Mansuripur’s argument. (According to the abstract shown below in this media report, that argument includes an assertion that the “theoretical evidence of the incompatibility of the Lorentz law with the fundamental tenets of special relativity” is “incontrovertible"—the key word from another recent high-visibility physics discussion, the dispute within the American Physical Society concerning APS’s statement on climate change.)

Cho also reports a complication that involves both a formula “that Einstein and Jakob Laub proposed in 1908 but Einstein later repudiated” and the contrast between the microscopic and macroscopic contexts. At the end, Cho quotes Daniel James of the University of Toronto: “The microscopic picture of electrodynamics is clear, and if the macroscopic picture of electrodynamics doesn’t follow from that, I’d be surprised.”

Early on 27 April, a search of the Physical Review Letters website yielded this abstract:

Trouble with the Lorentz law of force: Incompatibility with special relativity and momentum conservation

Masud Mansuripur

Accepted Wednesday Mar 14, 2012

The Lorentz law of force is the fifth pillar of classical electrodynamics, the other four being Maxwell’s macroscopic equations. The Lorentz law is the universal expression of the force exerted by electromagnetic fields on a volume containing a distribution of electrical charges and currents. If electric and magnetic dipoles also happen to be present in a material medium, they are traditionally treated by expressing the corresponding polarization and magnetization distributions in terms of bound-charge and bound-current densities, which are subsequently added to free-charge and free-current densities, respectively. In this way, Maxwell’s macroscopic equations are reduced to his microscopic equations, and the Lorentz law is expected to provide a precise expression of the electromagnetic force density on material bodies at all points in space and time. This paper presents incontrovertible theoretical evidence of the incompatibility of the Lorentz law with the fundamental tenets of special relativity. We argue that the Lorentz law must be abandoned in favor of a more general expression of the electromagnetic force density, such as the one discovered by A. Einstein and J. Laub in 1908. Not only is the Einstein-Laub formula consistent with special relativity, it also solves the long-standing problem of “hidden momentum” in classical electrodynamics.

Steven T. Corneliussen, a media analyst for the American Institute of Physics, monitors three national newspapers, the weeklies Nature and Science, and occasionally other publications. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and is a science writer at a particle-accelerator laboratory.