Stephen Hawking knows how to find things lost in black holes

Physicist Stephen Hawking © Lucas Jackson
If you suspect that a black hole has consumed all of those stray items that you just can’t find, don’t give up: Stephen Hawking thinks he knows how to retrieve them. He says black holes’ “soft hair” captures data about all that has disappeared into them.

When the black hole evaporates – a possibility Hawking first mentioned in 1975 – this “soft hair” would release the information that had been stored inside, according to a paper cowritten by Hawking, Malcolm Perry of the University of Cambridge and Andrew Strominger of Harvard University. 

Last year, the celebrated physicist created a sensation when he announced in his famous robot voice that black holes are not “the eternal prisons they were once thought,” and that things can actually escape and even appear in a different universe. 

Hawking explained that information is not stored in the interior of the black hole, but in its boundary, called the event horizon, from which light cannot escape.

This new, peer-reviewed paper is really a follow-up of his the theory because now he knows more about black holes and that “storing” mechanism.

The answer lies in what Hawking and his colleagues call “soft hair,” or a halo pattern on the event horizon that stores information. When a charged particle passes the threshold of a black hole, it moves the “soft hair,” in a process called a “supertranslation”.

This finding seriously challenges a theory pt forward by physicist John Wheeler, who nearly 50 years ago said that “black holes have no hair.” He really meant that black holes are featureless and can only be characterized by three parameters: mass, electric charge and angular momentum.

Hawking also said that black holes would not last forever, but would rather “leak” and explode, radiating particles. At the time it was not quite clear what would happen to all of the information that went in, which at the time, he thought would be erased.

Now Hawking believes that, even though the particles falling into the abyss may be gone forever, their information sticks at the edge of the hole in this “soft hair” of quantum particles.

“The researchers demonstrate that when a charged particle falls into the black hole, it excites some of this soft hair,” the research published in Physical Review Letters reads. “The exact conservation of the new charges implies that when a black hole evaporates, the information about the hair on the horizon must come out in the Hawking radiation.”

This new theory is a big deal, not only to Hawking but to the scientific community, because it might be a key to the so-called “black hole information problem,” something that Hawking has been working on for four decades.

However, Hawking, Perry and Strominger are not yet sure if “soft hair” alone is enough to capture all the information about what falls into a black hole and whether all the information can be transferred.