Terrestrial and Extraterrestrial Limits on The Photon Mass

Rev. Mod. Phys. 43, 277 – Published 1 July 1971


We give a review of methods used to set a limit on the mass μ of the photon. Direct tests for frequency dependence of the speed of light are discussed, along with more sensitive techniques which test Coulomb's Law and its analog in magnetostatics. The link between dynamic and static implications of finite μ is deduced from a set of postulates that make Proca's equations the unique generalization of Maxwell's. We note one hallowed postulate, that of energy conservation, which may be tested severely using pulsar signals. We present the merits of the old methods and of possible new experiments, and discuss other physical implications of finite μ. A simple theorem is proved: For an experiment confined in dimensions D, effects of finite μ are of order (μD)2—there is no "resonance" as the oscillation frequency ω approaches μ (=c=1). The best results from past experiments are (a) terrestrial measurements of c at different frequencies μ2×10-43 g7×10-6 cm-110-10 eV (b) measurements of radio dispersion in pulsar signals (whistler effect) μ10-44 g3×10-7 cm-16×10-12 eV (c) laboratory tests of Coulomb's law μ2×10-47 g6×10-10 cm-110-14 eV (d) limits on a constant "external" magnetic field at the earth's surface μ4×10-48 g10-10 cm-13×10-15 eV. Observations of the Galactic magnetic field could improve the limit dramatically.

DOI: http://dx.doi.org/10.1103/RevModPhys.43.277

© 1971 by the American Physical Society

Authors & Affiliations


  • Institute for Theoretical Physics, State University of New York at Stony Brook, Stony Brook, New York 11790


  • The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark Department of Physics, University of California, Santa Barbara, California 93106

  • *Supported in part under the auspices of the United States Atomic Energy Commission.
  • Supported in part by the National Science Foundation.
  • Address after September 1, 1971: Department of Physics, Purdue University, Lafayette, Ind. 47907.

References (Subscription Required)

Authorization Required




Log In



Article Lookup
Paste a citation or DOI

Enter a citation
  1. Enter a citation to look up or terms to search.

    Ex: "PRL 112 068103", "Phys. Rev. Lett. 112, 068103", "10.1103/PhysRevLett.112.068103"