Hawking radiation

[morgsboi]

I was wondering, what makes the particles shoot away from the event horizon? Or do they not and just orbit?

[questionposter]

I was wondering, what makes the particles shoot away from the event horizon? Or do they not and just orbit?

 

I think the way it works is a virtual particle pair forms near a black hole, and one get's sucked in and another doesn't. One virtual particle is just barely not close enough to get into the event horizon and so follows the curve of the fabric of space until (if ever) it get's at the right angle to travel away from a black hole.

[MigL]

I don't remember since its been a long time since I read it, but does Hawking's A Brief History Of Time include a simple explanation of Hawking radiation and its relationship to energy conservation and virtual particle behaviour near the event horizon of a black hole ?

 

It may be enlightening reading, questionposer.

[morgsboi]

I think the way it works is a virtual particle pair forms near a black hole, and one get's sucked in and another doesn't. One virtual particle is just barely not close enough to get into the event horizon and so follows the curve of the fabric of space until (if ever) it get's at the right angle to travel away from a black hole.

 

Thanks I had a dig around the net and came across "quantum tunnelling". Do you know anything about that?

 

I don't remember since its been a long time since I read it, but does Hawking's A Brief History Of Time include a simple explanation of Hawking radiation and its relationship to energy conservation and virtual particle behaviour near the event horizon of a black hole ?

 

It may be enlightening reading, questionposer.

 

I might read that. It sounds like it has the information I like.

[questionposter]

Thanks I had a dig around the net and came across "quantum tunnelling". Do you know anything about that?

 

Based on what I'm told in this forum, quantum tunneling is just when a particle of a high enough probability at a large distance exceeds the boundaries of another object as to allow the particle to be measured on the other side of something like of a wall. It would seem as though it's part of normal wave mechanics, but for it to happen on the macroscopic scale would take immense luck or energy, such as in the sun where protons are forced so close together at such a high energy that their high probability boundaries exceed each other's and so combine.

Edited January 26, 2012 by questionposter

[MigL]

Yes, chapter 7 of Hawking's 'A Brief History Of Time' has a reasonable if simplistic explanation of Black hole entropy>temperature>radiation. The book is available everywhere, even used or as a download.

[morgsboi]

I don't remember since its been a long time since I read it, but does Hawking's A Brief History Of Time include a simple explanation of Hawking radiation and its relationship to energy conservation and virtual particle behaviour near the event horizon of a black hole ?

 

It may be enlightening reading, questionposer.

 

Although that was aimed at questionposer, I decided to buy the book and it has arrived finally! In the acknowledgement, it mentions his previous book, The Large Scale Structure of Space Time. He said he didn't advice readers to purchase it but I was wondering if you had read it and if so, what it is like.

[DrRocket]

Although that was aimed at questionposer, I decided to buy the book and it has arrived finally! In the acknowledgement, it mentions his previous book, The Large Scale Structure of Space Time. He said he didn't advice readers to purchase it but I was wondering if you had read it and if so, what it is like.

 

The large scale structure of space time is a book co-authored by Hawking and C.F.R. Ellis. It is a study of the large scale structure of spacetime as described by the general theory of relativity using sophisticated methods of differential geometry. It includes many proofs and a thorough discussion of the singularity theorem that applies to the big bang. It is definitely not a popularization.

 

As this thread was started with Hawking radiation as a topic, it is worth mentioning that the book does not discuss Hawking radiation. Hawking radiation is predicted using quantum field theory on curved spacetime and that is beyond the scope of the Hawking and Ellis book.

 

I think the way it works is a virtual particle pair forms near a black hole, and one get's sucked in and another doesn't. One virtual particle is just barely not close enough to get into the event horizon and so follows the curve of the fabric of space until (if ever) it get's at the right angle to travel away from a black hole.

 

That is the explanation that one finds in popularizations. It is nice, neat, understandable. It would be even better if it were correct.

 

Unfortunately the prediction of Hawkiing radiation is based on quantum theory on curved spacetime. That is a theory that is somewhat shaky but one clear feature is that one looses the very notion of "particle" , real or virtual.

 

Another unfortunate fact is that virtual particles come with quantum field theories (on flat spacetime) while the event horizon comes from general relativity. General relativityand quantum field theories are not compatible. So it is rather dicey to predict the existence of virtual particles using quantum field theory and then predict their behavior near an even horizon using a theory that is incompatible with the theory that predicts their existence.

 

Final note: While Hawkiing's aargument for Hawking radiation is quite deep and ingenious, and while it is generally thought to be probably correct in its basic prediction, that is by no means to say that the existence of Hawking radiation is a certainty. It is a very small effect and there is at present no experimental confirmation of it.

Edited February 29, 2012 by DrRocket

[ajb]

It is definitely not a popularization.

 

I have to stress this. Hawking and Ellis is a very tough technical book. It is not the place to get the basic ideas of general relativity from.

 

That said, it is an all time classic and I recommend it to those ready for it. (I certainly was not the first time I picked it up! )

[derek w]

question?Is there some slight difference between matter and anti-matter,that when they separate on the event horizon,matter gets a slight kick away from the black hole and anti-matter gets a slight kick into the black hole?

 

I can not recall where,but i recall reading something about there appears to be a difference in their decay rates(0.8%).

Edited March 2, 2012 by derek w