Number 189 (Story #1), August 9, 1994 by Phillip F. Schewe and Ben Stein A GEOMAGNETIC LIMIT ON PHOTON MASS can be obtained through satellite measurements of the Earth's magnetic field. In this way a Purdue-Goddard-Johns Hopkins- Hughes team of scientists has used data recorded by the Charge Composition Explorer spacecraft to derive a limit of 8 x 10**-16 eV/c**2 for the mass of photons. Besides constraining the possibility of a nonzero-mass photon, the data were also used to set limits on the range and strength of hypothetical fields that would coexist with conventional electromagnetic fields. (E. Fischbach et al., Physical Review Letters, 25 July 1994.)