Black holes put new spin on light - physics-math - 13 February 2011 - New Scientist

Black holes put new spin on light: According to general relativity, spinning black holes drag the fabric of the surrounding space around with them. Fabrizio Tamburini of the University of Padua in Italy, and colleagues, calculated how light rays emitted by matter spiralling into a black hole are distorted by this effect, called frame dragging. They calculated that it transforms ordinary light into the corkscrew type that possesses orbital angular momentum.