Part 4 – Entropy and Hawking Radiation
In 1971, Stephen Hawking proved that the area of the event horizon of any classical black hole never decreases. This is similar to the second law of thermodynamics, where the role of the event horizon area corresponds to entropy. We can violate the second law of thermodynamics by bringing matter from our universe into the black hole and thus reduce the entropy of the entire universe. This is why Jacob Bekenstein hypothesized that black holes also have entropy and that its entropy is proportional to the area of the event horizon. However, 1974,
Hawking applied quantum field theory to the spacetime that curves around the event horizon of a black hole and discovered that black holes can radiate heat – the radiation emitted by black holes is known as Hawking radiation. Using the first law of black hole mechanics, the entropy of a black hole is found to be one quarter of the area of the event horizon. This is a universal result, applicable to the cosmological horizon in Sitter spacetime. Later, it was also suggested that black holes are objects with maximum entropy, i.e. in a certain region of spacetime, the maximum entropy is the entropy of the black hole occupying that region of spacetime. This leads to the hologram principle (also known as the hologram principle).
Hawking radiation originates from just outside the event horizon, and until now it was understood that it carried no information from inside the black hole because it was thermal radiation. However, this means that black holes are not completely black: this effect implies that the mass of a black hole will gradually decrease over time. Although this effect is very small for black hole researchers, it is only significant for theoretically predicted microscopic black holes, where quantum mechanics has a major impact. In fact, calculations show that small black holes can evaporate and eventually disappear in a burst of radiation. Thus, black holes without an additional source of their mass have a finite lifetime, and this time is related to their mass.
On July 21, 2004, Stephen Hawking announced that black holes would eventually release the information they swallow. [3], reversing his earlier view that information will be lost. He suggested that quantum perturbations to the event horizon could allow information to leak out of a black hole and affect Hawking radiation. [4]. The theory has yet to be challenged by scientists, but if accepted, it looks like we’ve solved the black hole’s information paradox.
There is more ….
