The theory of relativity suggested that anything – even light – crossing the event horizon of a black hole would be lost forever.

But physicist Stephen Hawking has suggested this may not be entirely true, and that he's found a solution to the "black hole information paradox" – the idea "black holes can simultaneously erase information and retain it".


Hawking, alongside colleagues from the University of Cambridge, suggest black holes have "soft hair", or "low-energy quantum excitations that release information when a black hole evaporates".

It's a theory Hawking first outlined in the 1970s, which suggested that when a particle-antiparticle pair was sucked into a black hole, one particle "radiates away into space" taking energy from the black hole with it.

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This means black holes could eventually disappear. However, this theory didn't take into account what the black hole swallowed – hence the paradox.

But now Hawking says black holes might actually have a "soft hair" halo surrounding them, which stores this lost information. This halo consists of "low-energy quantum excitations that release information when a black hole evaporates". Put more simply, this means they have a "signature" or record of everything the black hole had swallowed, even after the hole had disappeared.

But in an accompanying commentary, physicist Gary Horowitz said it was "important to note the paper does not solve the black hole information problem".


"But itself, it will likely not explain how all the information is recovered when a black hole evaporates, since it is unclear whether all the information can be transferred to the soft hair," he added.

"However, it is certainly possible that, following the path indicated by this work, further investigation will uncover more hair of this type, and perhaps eventually lead to a resolution of the black hole information problem."

The research is due to be published in Physical Review Letters later this week.