Steven Hawking’s latest scientific work on black holes and the “paradox of information” was posthumously published by the other physicists with whom he had collaborated.
The study is another attempt to understand what happens to information when an object falls into a black hole. It does not give a definitive answer, but paves the way in that direction. The work, which ended a few days before the death of the famous British physicist and cosmologist this March, was published online by colleagues from the Cambridge and Harvard universities.
The “paradox of information”, discovered by Hawking 43 years ago, has been at the heart of his life and thought since then, as Cambridge professor of theoretical physics, Malcolm Perry, who co-authored the swan song of the emblematic scientist , who was wheelchair-bound and spoke electronically due to a serious illness.
The so-called “paradox of information” arises from the fact that, according to Hawking, black holes have heat and produce thermal radiation (now known as “Hawking radiation”). Because all the warm objects in nature gradually lose that heat in space (due to entropy), the ultimate fate of a black hole will theoretically be its evaporation. However, according to quantum mechanics, information is never lost, so what happens to the information contained in an object when it is gravitationally absorbed by a black hole?
As Perry said, “the difficulty lies in the fact that if you throw something in a black hole, it seems to disappear. But how could the information on this object be recovered once if the black hole itself disappears? ”
In their last work, Hawking, Perry, Sasha Hako and Andrew Strominger show that the entropy of a black hole (and therefore information) can be captured by the photons surrounding the black hole’s “horizon of events”, ie the border beyond which light can not escape due to the enormous gravitational pull exerted by the black hole. These photon-recorders of information are called metaphorically “soft hairs”.
On the other hand, according to Perry, “we do not know if the Hawking entropy includes everything that can be thrown into a black hole, so we have actually done a pretty good step, but there is still a lot of work to do” a complete answer to the “paradox of information”. Such a response, as the British physicist has said, will basically “marry” Einstein’s general theory of relativity (gravity and space-time) with quantum mechanics, which to date remain incompatible.
One key issue to be investigated is how entropy-related information is stored as a natural entity in soft hair, and how this information then comes out of the black hole when the latter goes out.