What are Stephen Hawking's Theories?

[The_ArtofScience]

I've been trying to mine the web and Wikipedia but all I can find is his personal life, former students and some scanty information about his theories. Can someone explain to me some of his theories at least? I'd like to know what made this guy in a wheelchair so famous

 

[Swapnil]

There was this good documentry I watched on the Science channel a while back. I don't have a great memory but I am going to try to tell you what I remember (but please remember that what I say might not be totally true )

So I think he kinda started his career by doing something cool with the Big-band theory...perhaps he popularized it. I think he also spent a lot of his carrier on promoting something called the Information paradox and was trying to prove how information is lost inside a black hole. But a lot of scientists hated this idea and they gave him a hard time. In the end, though, he himself disproved his information paradox and said that information is indeed "conserved." Although, he had to make references to alternate universes and something about summing over all the histories of all the universes that host a black hole... I think currently he is working on formalizing this proof of his but progress is slow because his condition is getting worse. Also, he is specially known for his work on black holes...

I would recommend you search Youtube for some videos that talk about his life and his achievements.

 

[AlphaNumeric]

He's responsible for a number a well known theories, either on his own or working with people like Penrose. You can find them on Wikipedia, but perhaps not if you don't know what you're looking for.

He's responsible for The First and Second Laws of Black Hole Mechanics, which basically say that black holes do have temperature and entropy and you can measure these quantities in terms of the black holes mass and event horizon area. This then lead onto Hawking Radiation, the mechanism by which black holes can emit particles/radiation (which they must do if they have temperature)

He's also proved a series of singularity theorems with Penrose which show that given general relativity, it's inevitable that singularities will form in space-time, hence showing that black holes aren't a strange quirk of relativity but a natural solution.

He also proved, along with Gibbons, Perry and someone I don't remember the Positive Energy Theorem in assymptotically Anti-deSitter space-time.

He's proved plenty of other things too but those are the 'big few' I think that he's most known for. While these results are extremely impressive, it can't be denied that his celebrity status isn't at least partly due to his illness and the university he works at (Cambridge). Having the same maths chair that Newton held and having done most of these results while confined to a wheelchair, unable to use pen or paper, has certainly added to the general impressiveness of his work. Of course there are people through history in similar circumstances but are less famous. Euler was blind for the last 10 years of his life but was still enormously prolific. Beethoven was deaf but still wrote symphonies. The media as it is today didn't exist back then though. While someone like Witten might have done more physics, Hawking is probably a better 'symbol' and certainly has done a lot to bring theoretical physics into more mainstream areas from the publics point of view.

 

[dextercioby]

Euclidean quantum gravity.

Daniel.

 

[Dense]

Did you spell his name right? Info on him is pretty easy to Google.


From his website (www.hawking.org.uk):[/URL]

Stephen Hawking has worked on the basic laws which govern the universe. With Roger Penrose he showed that Einstein's General Theory of Relativity implied space and time would have a beginning in the Big Bang and an end in black holes. These results indicated it was necessary to unify General Relativity with Quantum Theory, the other great Scientific development of the first half of the 20th Century. One consequence of such a unification that he discovered was that black holes should not be completely black, but should emit radiation and eventually evaporate and disappear. Another conjecture is that the universe has no edge or boundary in imaginary time. This would imply that the way the universe began was completely determined by the laws of science.

It also has a 14-page PDF of his writings at [PLAIN]www.hawking.org.uk/pdf/pub.pdf[/URL]



And from Wikipedia:

Hawking's principal fields of research are theoretical cosmology and quantum gravity.

In the late 1960s, he and his Cambridge friend and colleague, Roger Penrose, applied a new, complex mathematical model they had created from Albert Einstein's general theory of relativity. This led, in 1971, to Hawking proving the first of many singularity theorems; such theorems provide a set of sufficient conditions for the existence of a singularity in space-time. This work showed that, far from being mathematical curiosities which appear only in special cases, singularities are a fairly generic feature of general relativity.

Hawking also suggested that, after the Big Bang, primordial or mini black holes were formed. With Bardeen and Carter, he proposed the four Laws of black hole mechanics, drawing an analogy with thermodynamics. In 1974, he calculated that black holes should thermally create and emit subatomic particles, known as Hawking radiation, until they exhaust their energy and evaporate.

In collaboration with Jim Hartle, Hawking developed a model in which the Universe had no boundary in space-time, replacing the initial singularity of the classical Big Bang models with a region akin to the North pole; while one cannot travel North of the North pole, there is no boundary there. While originally the no-boundary proposal predicted a closed Universe, discussions with Neil Turok led to the realization that the no-boundary proposal is consistent with a Universe which is not closed also.