Chatroom
 

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Bad Astronomy and Universe Today Forum > General > Questions and Answers
Register FAQ Members List Calendar Mark Forums Read

   

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 10-July-2006, 10:56 AM
rambo07 rambo07 is offline
Junior Member
 
Join Date: Apr 2004
Location: nottingham ,england
Posts: 28
Default disappearing black holes

Mr Hawking has famously said that Black holes can dissappear ? into nothing ?.
but what about the mass? what are your opinions?
has the black hole moved into another universe by pushing its self into another dimension or popped into the past or future or jumped to another part of the universe or has the mass just gone poof!!!!
Reply With Quote
  #2 (permalink)  
Old 10-July-2006, 11:35 AM
Jeff Root Jeff Root is offline
Senior Member
 
Join Date: Dec 2004
Location: Minneapolis
Posts: 3,770
Default

How can you know about it without knowing even the first thing
about it? There are probably hundreds of different websites which
explain Hawking's theory regarding evaporation of black holes,
plus existing threads discussing it on BAUT and other forums.
And, if all else fails, you can get a copy of Hawking's ridiculously
popular book, 'A Brief History of Time', and read what he had to
say about it in his own words.

-- Jeff, in Minneapolis
__________________
http://www.FreeMars.org/jeff/

"The other planets?
Well, they just happen to be there, but the point of rockets is to explore them!"
-- Kai Yeves
Reply With Quote
  #3 (permalink)  
Old 10-July-2006, 11:42 AM
antoniseb's Avatar
antoniseb antoniseb is offline
Moderator
 
Join Date: Jul 2005
Location: Irvine CA
Posts: 14,860
Default

Quote:
Originally Posted by rambo07
Mr Hawking has famously said that Black holes can dissappear ? into nothing ?. but what about the mass?
The mass is still here. The black hole has a process by which particles and energy can escape from it owing to quantum effects. In this way, mass from inside the even horizon is converted to mass outside the event horizon.

Personally, I don't see why the particles created just outside the event horizon don't just fall back in again, they'd need a lot of initial energy to be able to escape.
__________________
Forming opinions as we speak
Reply With Quote
  #4 (permalink)  
Old 10-July-2006, 12:13 PM
Sock puppet's Avatar
Sock puppet Sock puppet is offline
Senior Member
 
Join Date: Feb 2005
Location: Dublin
Posts: 245
Default

Quote:
Originally Posted by antoniseb
Personally, I don't see why the particles created just outside the event horizon don't just fall back in again, they'd need a lot of initial energy to be able to escape.
Mostly, they do, especially with large black holes. However, with smaller black holes, tidal effects get bigger (i.e. the difference in gravitational attraction at two nearby points is greater at the event horizon of small holes) allowing one to be captured while its neighbour can escape.
__________________
"Last Thursday, in a major breakthrough for the science of astrology, everyone born under the sign of scorpio was run over by milk trucks...."
Reply With Quote
  #5 (permalink)  
Old 10-July-2006, 12:22 PM
astromark's Avatar
astromark astromark is offline
Senior Member
 
Join Date: Jun 2004
Location: Wanganui, New Zealand.
Posts: 2,439
Default

I agree with you Antoniseb. I can not see how the mass that might be converted to energy in the singularity, BH., could melt away, leak out or, other wise dissolve the BH., Its like the idea of the universe not being infinite. The detectable universe might be 13.7 billion LY from us. We are told this might be expanding at an ever faster rate that could prohibit us ever seeing it. What stops there being others. Much farther away doing the same thing. We will not see them until the distance between us is less than the time its image might take to reach us. Its like asking your speed in space. You can not answer these questions. Because there is no reference point. Nothing in space is still ( motion less ). If some thing is coming straight at us at a speed greater than its light image can travel. We will not know it is here till its been. Do not attempt to make to much of my ramblings. I have just confused myself. . . .
Reply With Quote
  #6 (permalink)  
Old 10-July-2006, 04:13 PM
rambo07 rambo07 is offline
Junior Member
 
Join Date: Apr 2004
Location: nottingham ,england
Posts: 28
Default

Yes you are right I dont know anything at all about Black holes or what happens to them when they dissappear all I know is that most people in the know don't agree with him ,I'm just interested in what your opinion is ? .I can only guess (what is wrong in that) i.e if matter can't be distroyed then the black hole can't just dissappear into nothing can it . this is logical isn't it ,I dont have to be bright as you to know that ,,,, my uneducated guess is that it must be somewhere else ,,, blackholes are associated with time travel i.e if you travel around one of them you can go back in time ,dont make me explain it (i'm thick) if the black hole collapes in on its self spining faster than light could it act as a time machine ? (i dont know ) and I can only count to three so I can't do the Math ,,,but the matter isnt there or where the black hole was .i am awear that some black holes throw back out the matter they consume , I'm not talking about those ,becauce we know where the matter is .
Reply With Quote
  #7 (permalink)  
Old 10-July-2006, 04:25 PM
jlhredshift's Avatar
jlhredshift jlhredshift is offline
Senior Member
 
Join Date: Jan 2006
Location: Madison, Ohio
Posts: 932
Default

A test of Hawking's theory is that there should have been BH's formed at the beginning(?) of the universe wherein there has been enough time for them to evaporate to a small enough size that exponential decay occurs and a massive explosion results that would have a charecteristic energy spectrum. This has not been observed (?) yet(?).
Reply With Quote
  #8 (permalink)  
Old 10-July-2006, 04:40 PM
eburacum45's Avatar
eburacum45 eburacum45 is offline
Senior Member
 
Join Date: Jun 2003
Location: old york
Posts: 4,663
Default

Actually the mass that escapes a black hole by Hawking radiation is in the form of energy; small holes effectively radiate very energetic photons as if they were very hot. This radiation escapes at the speed of light.
Energy is of course equivalent to mass, so the hole loses mass.
Larger black holes are effectively cooler, and radiate less energy.
Reply With Quote
  #9 (permalink)  
Old 10-July-2006, 08:18 PM
Sock puppet's Avatar
Sock puppet Sock puppet is offline
Senior Member
 
Join Date: Feb 2005
Location: Dublin
Posts: 245
Default

Quote:
Originally Posted by jlhredshift
A test of Hawking's theory is that there should have been BH's formed at the beginning(?) of the universe wherein there has been enough time for them to evaporate to a small enough size that exponential decay occurs and a massive explosion results that would have a charecteristic energy spectrum. This has not been observed (?) yet(?).
I wouldn't be so sure. Gamma Ray Bursts may be the signature of primordial black holes evaporating.
__________________
"Last Thursday, in a major breakthrough for the science of astrology, everyone born under the sign of scorpio was run over by milk trucks...."
Reply With Quote
  #10 (permalink)  
Old 10-July-2006, 08:35 PM
jlhredshift's Avatar
jlhredshift jlhredshift is offline
Senior Member
 
Join Date: Jan 2006
Location: Madison, Ohio
Posts: 932
Default

I agree with the possibilty but nothing firm yet(?) And while I'm at it I thought it was particle ant_particle production at the event horizon wherein one was captured and one escaped which could still be seen as a photon if it was the anti-particle that escaped and subsqently annihlated.
Reply With Quote
  #11 (permalink)  
Old 11-July-2006, 09:09 AM
eburacum45's Avatar
eburacum45 eburacum45 is offline
Senior Member
 
Join Date: Jun 2003
Location: old york
Posts: 4,663
Default

That is the way it is often described, yes, but I think that description is a little over simplified to be realistic.
Have a look at this page which explains it a little more technically.
http://math.ucr.edu/home/baez/physic...s/hawking.html
And no, I don't really understand this description myself...
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT. The time now is 04:02 PM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.
LinkBacks Enabled by vBSEO 3.0.0
©  2006 Bad Astronomy and Universe Today