On the Trouton-Noble Experiment

Abstract

The experiment of F. T. Trouton and H. R. Noble to detect the motion of the earth through the ether by means of electromagnetic torque on a charged, suspended, parallel-plate capacitor is reexamined. No previous explanation of the null result appears to be satisfactory because, as is shown herein, conventional relativistic electrodynamics predicts that the total electromagnetic field energy of the capacitor is different in the two orientations. Therefore, this combination predicts that the result should not be null. A new explanation of the null result is offered, based on a new equation for the energy density dU/dV in the electric E and magnetic H fields of a classical macroscopic charged body with a uniform speed β in units of the speed of light. This new equation dU/dV = (E2−H2)/8π(1−β2), in Gaussian units in vacuo, predicts that the total electromagnetic field energy of the capacitor is independent of its orientation in agreement with the null result of Trouton and Noble.

Drawing the line between kinematics and dynamics in special relativity

“…39 Laue (1912a) pointed out, for instance, that the physics of a thought experiment proposed by Lewis and Tolman (1909) involving a torque on a moving bent lever is essentially the same as the physics of the Trouton-Noble experiment. 40 It was only after Rohrlich's work in the 1960s, that it was recognized that one can eliminate the delicately balanced torques in Laue's accounts of the Trouton-Noble capacitor and the Lewis-Tolman bent lever altogether by adopting the alternative definition (42) of the four-momentum of spatially extended systems in Minkowski space-time (Butler, 1968;Janssen, 1995;Teukolsky, 1996). There has been some debate in the literature on the Trouton-Noble experiment-as there has been in the far more extensive literature on the classical electron model (see sec.…”

Interactions

“…Under the alternative Fermi-Rohrlich definition (see the discussion following eq. 14), there are no turning couples whatsoever (see Butler, 1968;Janssen, 1995;and Teukolsky, 1996). 26 Substituting the momentum, p = mv, of Newtonian mechanics for P EM in eq.…”

Radiation damping of a BPS monopole: An illustration ofSduality

“…In the sense that classical motions of the BPS monopole are completely fixed by the field equations with an asymptotic boundary condition, the problem of radiation reaction is perfectly well posed and self-contained. This is contrasted to the case of the electrodynamics, where the Abraham-Lorentz model [14] or the other attempts [15] in explaining the damping effect, are plagued with unnatural assumptions, and not sufficient in themselves [16]. We shall examine the radiation damping of the BPS monopole and compare the resulting expressions to those of the W boson.…”