Einstein’s 1905 reformulation of kinematics may be read as the extraction of the Poincareinvariant content already latent in Maxwell electrodynamics. In that extraction, the electricand magnetic fields cease to be invariantly separate entities and become observer-dependentprojections of a single two-form Fµν. The standard historical account usually stops there:Maxwell supplied the invariant light cone, Einstein supplied the kinematics. This paper isolatesa more precise residual problem. Source-free Maxwell theory in four spacetime dimensionspossesses a conformal covariance larger than the ten-parameter Poincare group used in ordinaryspecial relativity. The full conformal algebra contains, in addition to translations and Lorentztransformations, one dilation and four special conformal generators. These five generatorspreserve null structure but not the scale structure introduced by massive matter, finite detectors,atomic transitions, cavities, apertures, plasma frequencies, material response functions, andpreparation protocols. Thus the question is not whether Maxwell theory is conformally covariant;that result is classical and well established. The question is whether the non-Poincare conformalsector has operational content once physical preparations and measurements are included.We formulate the Maxwell–Einstein symmetry gap as an observable-classification problem.First, we review the Lorentz-covariant field decomposition used implicitly in Einstein’s resolutionof the magnet–conductor asymmetry. Second, we derive the conformal covariance of the fourdimensional Maxwell action, the trace-free form of the electromagnetic stress tensor, andthe associated Poincare, dilation, and special conformal currents. Third, we identify theobstructions: sources, point-particle masses, detector energy gaps, finite boundary conditions, andnonzero material scales prevent the elevation of conformal covariance to a symmetry of completeexperiments. Fourth, we define four classes of electromagnetic observables: conformally covariantvacuum observables, Lorentz-covariant but scale-broken observables, boundary-induced conformalresidues, and quantum/semiclassical anomaly-sector observables. The proposed research programis falsifiable. If every candidate residue reduces to gauge redundancy, coordinate relabeling,dimensional scaling, source scaling, transformed apparatus response, or boundary engineering,the symmetry gap has no independent physical content. If a finite electromagnetic observabletransforms nontrivially under the dilation or special conformal generators while remainingirreducible to those effects, then Maxwell theory contains a residual operational sector notexhausted by the ordinary Einsteinian kinematic reading.
SIKX HILTON (Mon,) studied this question.