Black holes may grow quantum 'hair'

What falls into a black hole, stays in a black hole, at least according to the laws of general relativity. But now, new research suggests that the material inside the black hole may leave a quantum imprint on the gravitational field outside of it.

If true, this finding would resolve a long-standing problem in physics, Stephen Hawking's black hole information paradox. In the 1970s, Hawking calculated that black holes might not be entirely one-way streets; they could emit thermal radiation, now known as Hawking radiation. However, this Hawking radiation is simple thermal radiation, or heat, and does not carry any information about the origin of the black hole or the matter that had disappeared inside it. In other words, measuring the radiation itself wouldn't tell you anything about its history.