Peering into the heart of a black hole

Quantum mechanics might be capable of stripping bare a black hole to reveal the mysterious and unseeable 'singularity' that exists at its heart, say George Matsas and André da Silva of the São Paulo State University in Brazil. It has long been suspected that these singularities "where the known laws of physics break down" are always decorously veiled behind the 'event horizon', a boundary beyond which light cannot escape from the fearsome gravitational pull of a black hole. Theoretically, nothing within an event horizon can ever be perceived or investigated by an outside observer, because no light can escape. So the singularities remain insulated from the rest of the Universe. This amounts to what in 1969 physicist Roger Penrose called 'cosmic censorship', whereby the laws of physics conspire to save us from having to gaze on the unthinkable. According to Einstein's general theory of relativity, in the middle of a black hole, its mass collapses in on itself to form an infinitely small, infinitely dense point, where space-time itself is punctured. Even causality " the relation of a cause and its effect " breaks down, which seems to defy not only physics but logic. "Penrose's motivation seemed to be to preserve the decorum of physics," Matsas says. But physicists have wondered whether event horizons are ever stripped away, leaving these absurdist singularities naked. One possibility, for example, is that the event horizon might vanish if a black hole spins very fast. Light and matter might then be flung out by centrifugal force.

"It is widely believed that quantum gravity will unveil the structure of the singularities."In September, physicists Arlie Petters of Duke University in Durham, North Carolina, and Marcus Werner of the University of Cambridge, UK, proposed that singularities stripped naked by fast rotation should be detectable by astronomers because they act as very strong 'gravitational lenses', bending the light coming from stars behind them by their distortion of space-time.