The information paradox
The existence of Hawking radiation creates a serious problem for theoreticians. It seems to be the only process in physics that deletes information from the universe. The basic properties of the material that went into making the black hole appear to be lost forever – the radiation that comes out tells us nothing about them.
This is the so-called information paradox that scientists have been trying to solve for decades. Hawking’s own take on the mystery, which was published in 2016, is that the information isn’t truly lost. It’s stored in a cloud of zero-energy particles surrounding the black hole, which he dubbed ‘soft hair’. But Hawking’s hairy black hole theorem is only one of several hypotheses that have been put forward, and to date no one knows the true answer.