New limit placed on photon charge

From PhysicsWeb News: “A physicist in the US has analysed radio waves from distant galaxies to obtain a new upper bound on the electrical charge of the photon. Brett Altschul of Indiana University has found that the charge is no more than 10^-46 times the charge of the electron — assuming the existence of photons with positive and negative charges. This is 13 orders of magnitude better than the previous direct bound on the charge of a particle that we normally assume to be neutral”¹.

1. Phys. Rev. Lett. 98 261801 [↩]