The research leading up to this finding consisted of an analysis of electromagnetic radiation data that has been compiled and published by several independent research groups since the 1980's. In our analysis, John Ralston and I studied polarization measurements of electromagnetic synchrotron radiation emitted by distant radio galaxies. Extensive, computer aided calculations indicates that this radiation exhibits an unconventional rotation of its polarization plane. The effect is small, and comes in addition to other known, conventional polarization rotation effects.
The polarization rotation has the characteristic property that it depends systematically on the angle between the radiation's direction of travel and a fixed direction in space. This result indicates that electromagnetic interactions are anisotropic in nature. It defies the notion that, in electromagnetism, all spatial directions are equivalent.
Our research has also focused on constructing a theoretical generalization of electrodynamics that incorporates anisotropy in a way consistent with the observed data.
Some popular accounts:
Physics News Update
The New York Times
The Associated Press