Black Hole Entropy and Soft Hair, the last paper of Hawking, caught a lot of attention worldwide due to its amazing theories.

A world-renowned physicist, the late Stephen Hawking is not a new personality for most us. In one way or another, we have come across his incredible achievements. He was always interested in understanding the mystery behind the working of a black hole. A black hole is an entity with a gravitational force so strong that even light cannot escape it. Recently, the last paper he was working on, “Black Hole Entropy and Soft Hair”, has finally been published.

The paper revolves around the study of what happens to objects when they enter a black hole. The seemingly obvious answer is that the object is destroyed. However, according to the rules of quantum physics, information is never lost. Hawking put down a theory, according to which, black holes have temperatures of their own and because hot objects lose their heat in space, black holes eventually vaporize into nothingness. But this again contradicts with quantum physics: information is never lost. This creates the information paradox. What happens to the information?

Before Stephen Hawking’s black hole theories, a black hole was thought of as having only three measurable features: Its charge, mass, and spin. Adding temperature to the equation was a good start to dig deeper into the science of black holes. All this brought us to another property related to heat: Entropy. In simpler words, entropy refers to the measure of an object’s degree of disorder or randomness. If an object has heat, it’s bound to have entropy. In case of a black hole, the event horizon, the point where even light gets sucked in, may very well be the area where information of its entropy is stored.

The event horizon is surrounded by a layer of photons which is called “soft hair”. The Information Paradox presents the idea that we may be able to use the “soft hair” to view the information related to the entropy of a black hole. Even though physicists have yet to come up with a definitive conclusion, one thing is for certain, this paper is a huge advancement in this field. Malcolm Perry, a Professor of Theoretical Physics at Cambridge and a Co-author of the paper, suggested that by saying,

“It’s a step on the way, but it is definitely not the entire answer. We have slightly fewer puzzles than we had before, but there are definitely some perplexing issues left. The difficulty is that if you throw something into a black hole it looks like it disappears. How could the information in that object ever be recovered if the black hole then disappears itself?”

Perry related to an incident just before the death of Stephen Hawking. He told the world that he was not aware of how ill Hawking was at the time when he was asked to be put in contact with him. Perry was put on the loudspeaker and when he finished explaining the concept, Stephen Hawking had a huge smile on his face. Perry himself acknowledged that Hawking knew the result all the time while he was speaking. Juan Maldacena, a Theoretical Physicist at the Institute for Advanced Studies in Princeton, said,

“Hawking found that black holes have a temperature. For ordinary objects, we understand temperature as due to the motion of the microscopic constituents of the system. For example, the temperature of air is due to the motion of the molecules: the faster they move, the hotter it is. For black holes, it is unclear what those constituents are, and whether they can be associated to the horizon of a black hole. In some physical systems that have special symmetries, the thermal properties can be calculated in terms of these symmetries. This paper shows that near the black hole horizon we have one of these special symmetries.”

Scientists are still not sure how the information is stored in the photons surrounding the event horizon or how information is ejected as a black hole eventually vaporizes. Furthermore, it is also unknown as to how the temperature behaves in a black hole as compared to the molecules here on Earth. Will we finally have more information about black holes available soon? One thing is for certain, Hawking’s theory will be further investigated given the enormous scale of attention it has caught worldwide.