Just to be sure, Stephen Hawking is a British theoretical physicist and string theorist, known among scientists mostly for groundbreaking works in quantum gravity and black hole thermodynamics, and among general audience for popular science books like "A brief history of time" (old one, with slight flavour of physics) and "The grand design" (relatively new one, with quite a taste of general ideology, which is OK 
). This year, on January 8th, he celebrates his 70th birthday.
It is worth to remind that when Hawking started his career, there was a strict separation between two fields of research in theoretical physics - quantum theory of elementary particles and general relativity (theory of gravity). Particle physics was the most popular and the most fascinating area, and the best scientists of that time were working on it. While general relativity was mostly ignored. The reason is, of course, that to compute observables, related to experiments, there is practically no need to take into account gravitational force - it is just too weak and can be neglected right away. Another reason is that Einsteinian theory of gravity - general relativity - can not be quantized the same way as fields, carrying other types of interaction, such as electromagnetic field. If you quantize it this way, then in the most naive framework you get incurable divergences. I want to notice right away that Hawking has little to do with this problem.
(in case of someone is interested - the problem is solved automatically by string theory).
Hawking was (still is, I am sure ) very good at quantum theory, but he decided to focus on the problems of gravity. He studied black holes, which in classical Einsteinian gravity are final products of evolution of heavy enough stars. At any rate, even microscopic black hole (BH) may be formed if some mass is squeezed into a sufficiently small volume. BH has a horizon, which separates interior and exterior of a BH. According to classical gravity - general relativity - nothing can escape from inside of a BH. However, what Hawking discovered was that BH gradually evaporates. The whole process is known now as a Hawking radiation. (As it was later understood by other scientists, and later admitted by Hawking, any information which falls into a BH, may be recovered later.)
There is a temperature of a BH, equal to a temperature of a gas of particles, evaporating "out of" a BH. Presence of a such concept as a temperature in the description of a BH means that there is a thermodynamic way to describe a BH. And it also means that one may compute the entropy (measure of disorder) of a BH. Corresponding formula, which states a proportionality between entropy of a BH and area of its horizon, is known as Bekenstein-Hawking formula. Later, thermodynamical approach to more general gravitational objects, such as black branes (extended black holes, roughly speaking, having some longitudinal dimensions), was applied by other physicists.
). This year, on January 8th, he celebrates his 70th birthday.It is worth to remind that when Hawking started his career, there was a strict separation between two fields of research in theoretical physics - quantum theory of elementary particles and general relativity (theory of gravity). Particle physics was the most popular and the most fascinating area, and the best scientists of that time were working on it. While general relativity was mostly ignored. The reason is, of course, that to compute observables, related to experiments, there is practically no need to take into account gravitational force - it is just too weak and can be neglected right away. Another reason is that Einsteinian theory of gravity - general relativity - can not be quantized the same way as fields, carrying other types of interaction, such as electromagnetic field. If you quantize it this way, then in the most naive framework you get incurable divergences. I want to notice right away that Hawking has little to do with this problem.
(in case of someone is interested - the problem is solved automatically by string theory).Hawking was (still is, I am sure
) very good at quantum theory, but he decided to focus on the problems of gravity. He studied black holes, which in classical Einsteinian gravity are final products of evolution of heavy enough stars. At any rate, even microscopic black hole (BH) may be formed if some mass is squeezed into a sufficiently small volume. BH has a horizon, which separates interior and exterior of a BH. According to classical gravity - general relativity - nothing can escape from inside of a BH. However, what Hawking discovered was that BH gradually evaporates. The whole process is known now as a Hawking radiation. (As it was later understood by other scientists, and later admitted by Hawking, any information which falls into a BH, may be recovered later.)There is a temperature of a BH, equal to a temperature of a gas of particles, evaporating "out of" a BH. Presence of a such concept as a temperature in the description of a BH means that there is a thermodynamic way to describe a BH. And it also means that one may compute the entropy (measure of disorder) of a BH. Corresponding formula, which states a proportionality between entropy of a BH and area of its horizon, is known as Bekenstein-Hawking formula. Later, thermodynamical approach to more general gravitational objects, such as black branes (extended black holes, roughly speaking, having some longitudinal dimensions), was applied by other physicists.
