Black Holes Weigh the Possibility of a Massive Photon

Black holes don’t usually get pushed around, but a very lightweight particle can theoretically stop a rotating black hole by setting off a so-called “black-hole bomb.” New calculations reported in Physical Review Letters show that photons, or photonlike particles, could be considered bomb-making material if they have a mass. A massive photon is not theoretically ruled out, but it would have implications for the dispersion of light and the existence of magnetic monopoles. However, the mere existence of spinning (unbombed) black holes constrains this possibility, thus allowing the authors to put the most stringent limit yet on the mass of the photon.