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Author Topic: Can a Black Hole both emit radiation and not decrease?  (Read 1867 times)

Offline MikeS

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In 1972, Stephen Hawking showed that the area of the horizon of a black hole can not decrease.
He also proposed they emit radiation which reduces mass and they eventually evaporate.

My maths aren't up to his standard but I can manage this

1 - 1 = 1 ?


==

Please make the caption into a question the next time.
Thanks.
« Last Edit: 08/05/2011 20:50:16 by yor_on »


 

Offline imatfaal

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Can a Black Hole both emit radiation and not decrease?
« Reply #1 on: 09/05/2011 11:30:03 »
Can you provide a link to where Hawking said this - it seems at odds to my understanding (which is very vague) of Hawking's 1974 paper.  there is the problem of information loss in black hole evaporation per the original ideas of Stephen Hawking - but various strategies have emerged to prevent information loss.  Bekenstein showed that information and entropy was linked and proportional to the surface area of the black hole - but Hawking for many years had no problem with that information being lost during evaporation (he has now admitted that he was probably wrong and paid off on a famous bet) so I am not sure why he would be adamant that the surface are did not change
 

Offline graham.d

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Can a Black Hole both emit radiation and not decrease?
« Reply #2 on: 09/05/2011 13:36:23 »
As far as I know Mini Black Holes evaporate quite quickly. I assume that this means that the surface area must decrease unless there is some quirk in the maths that refutes what seems, at first glance, obvious.
 

Offline MikeS

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Can a Black Hole both emit radiation and not decrease?
« Reply #3 on: 09/05/2011 17:45:41 »
Can you provide a link to where Hawking said this - it seems at odds to my understanding (which is very vague) of Hawking's 1974 paper.  there is the problem of information loss in black hole evaporation per the original ideas of Stephen Hawking - but various strategies have emerged to prevent information loss.  Bekenstein showed that information and entropy was linked and proportional to the surface area of the black hole - but Hawking for many years had no problem with that information being lost during evaporation (he has now admitted that he was probably wrong and paid off on a famous bet) so I am not sure why he would be adamant that the surface are did not change

 
http://en.wikipedia.org/wiki/Timeline_of_black_hole_physics
http://en.wikipedia.org/wiki/Hawking_radiation

Perhaps this is the bet I don't know but as I understood it the bet had not been resolved.

http://en.wikipedia.org/wiki/Thorne%E2%80%93Hawking%E2%80%93Preskill_bet
 

Offline imatfaal

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Can a Black Hole both emit radiation and not decrease?
« Reply #4 on: 09/05/2011 18:27:38 »
Can you provide a link to where Hawking said this - it seems at odds to my understanding (which is very vague) of Hawking's 1974 paper.  there is the problem of information loss in black hole evaporation per the original ideas of Stephen Hawking - but various strategies have emerged to prevent information loss.  Bekenstein showed that information and entropy was linked and proportional to the surface area of the black hole - but Hawking for many years had no problem with that information being lost during evaporation (he has now admitted that he was probably wrong and paid off on a famous bet) so I am not sure why he would be adamant that the surface are did not change

 
http://en.wikipedia.org/wiki/Timeline_of_black_hole_physics
http://en.wikipedia.org/wiki/Hawking_radiation

Perhaps this is the bet I don't know but as I understood it the bet had not been resolved.

http://en.wikipedia.org/wiki/Thorne%E2%80%93Hawking%E2%80%93Preskill_bet

From my reading of one of Hawkings 1972 papers (which is the one I guess wiki-author based that date upon) what I think he is saying (from looking at the pictures and not much more) is completely prior to any notion that black holes could radiate in any way.  Not long after he wrote that paper Bekenstein predicted that Black holes should have a non-zero temperature that was related to their size, and Hawking came up with a methodology that would allow radiation to happen.  Few things to bear in mind - 1) Scientists often prove themselves wrong through a revision of their own theory, 2) in any useful time period for blackholes in space Hawking is correct as no blackhole will be a net radiator till the universe cools down a lot more 3) the wikipage does specify classical blackhole - in physics this means without the action of quantum effects, Hawking radiation is a quantum effect

On the bet - you were reading about the wrong bet (quote from your link)

Quote
In 2004, Hawking announced that he was conceding the bet, and that he now believed that black hole horizons should fluctuate and leak information, in doing so providing Preskill with a copy of Total Baseball, The Ultimate Baseball Encyclopedia.[1] Comparing the useless information obtainable from a black hole to "burning an encyclopedia", Hawking later joked, "I gave John an encyclopedia of baseball, but maybe I should just have given him the ashes."

On the method - no this has not been agreed. Lenny Susskind has postulated a hologrpahic universe which I do not understand and haven't read up on yet
« Last Edit: 09/05/2011 18:32:12 by imatfaal »
 

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Can a Black Hole both emit radiation and not decrease?
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