The Naked Scientists

The Naked Scientists Forum

Author Topic: What is the Ultimate Fate of a Black Hole  (Read 26076 times)

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5336
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
What is the Ultimate Fate of a Black Hole
« on: 03/03/2008 16:42:41 »
What happens to all of the material swallowed by a black hole? Does the black hole continue to grow forever, or does it reach a critical mass and then alter its behaviour?

Chris


 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #1 on: 03/03/2008 17:03:57 »
There are no theoretical limits to the size of black holes.

Taking things to the limit the ultimate fate of any simply expanding universe is to contain just one single black hole because it has swallowed all the other black holes stars planets and atoms.

This however does not take into account the acceleration of the expansion of the universe that appears to be happening.  This could result in there being isolated atoms or assemblies of atoms around for a long time. 

What happens to an isolated black hole then depends on whether the expansion of the universe has taken the microwave background temperature below the temperature of the black hole.  If the universe is cold enough it will evaporate incredibly slowly.  If the background is warmer it will grow slowly until the temperature drops low enough for the hole to start to evaporate.  This evaporation will also warm the universe a bit and will take vast orders of magnitude longer than the universe has existed since the big bang.
« Last Edit: 03/03/2008 17:07:49 by Soul Surfer »
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3818
  • Thanked: 19 times
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #2 on: 03/03/2008 18:58:56 »
If a black hole was sufficient large would we notice much difference whether we were inside or outside it?
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #3 on: 03/03/2008 20:38:34 »

Taking things to the limit the ultimate fate of any simply expanding universe is to contain just one single black hole because it has swallowed all the other black holes stars planets and atoms.

This however does not take into account the acceleration of the expansion of the universe that appears to be happening.  This could result in there being isolated atoms or assemblies of atoms around for a long time. 


Is that actually the case?

Surely, if the universe were expanding fast enough then you wouldn't just have "...isolated atoms or assemblies of atoms around for a long time.". there would be whole galaxies (or are you classing a galaxy as an assembly of atoms?) moving further & further away from each other's gravitational influence.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8655
  • Thanked: 42 times
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #4 on: 04/03/2008 19:10:07 »
" a black hole was sufficient large would we notice much difference whether we were inside or outside it?"

We might be in one, we call it the universe.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #5 on: 04/03/2008 19:40:02 »
A galaxy is an assembly of atoms but it could be disrupted if the acceleration of expansion got too great.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #6 on: 04/03/2008 20:53:16 »
But space inside galaxies isn't expanding, so why should that be?
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #7 on: 05/03/2008 08:06:21 »
The current rate of expansion of the universe is so small that it is just not detectable on the sacale of anything as small as a galaxy or even a cluster of galaxies.  It's not that it doesn't happen, you need distances of hundreds of millions of light years for it to be reliably detectable against the background "noise"  of things moving about under gravity.

If this accelerates in the future by a significant amount this may not be the case.

To put the current rate of expansion of the universe in a galactic/stellar  scale it is about 0.2 millimetres per second over a distance of one light year.

Many people misunderstand astronomical observations because the numbers are "astronomical" and they do not put them into the context of scales that they can understand and visualise.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #8 on: 05/03/2008 18:47:07 »
Quote
To put the current rate of expansion of the universe in a galactic/stellar  scale it is about 0.2 millimetres per second over a distance of one light year.

Can we really measure distances that accurately, or is it just theory?
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8655
  • Thanked: 42 times
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #9 on: 05/03/2008 19:25:19 »
It's a real measurement, albeit not a very accurate one (wiki tells me the error margin is about 15%).
BTW, it seems the general fate of a black hole is to be speculated about endlessly by physicists.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #10 on: 05/03/2008 22:22:20 »
Conversely, it's the ultimate fate of physicists to endlessly speculate about the ultimate fate of black holes  :D
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #11 on: 05/03/2008 23:57:46 »
The figure for the current expansion rate of the universe on a stellar scale is obviously totally unmeasurable.  I just gave you the figures to show you how tiny this expansion coefficient really is.  Its just that the visible universe is a very big place and we can see a very long way so the velocites get quite big and become quite significant with respect to the velocity of light.
« Last Edit: 06/03/2008 00:01:22 by Soul Surfer »
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #12 on: 06/03/2008 07:31:32 »
Its just that the visible universe is a very big place and we can see a very long way so the velocites get quite big and become quite significant with respect to the velocity of light.

I'm aware of that; but I thought that within galaxies gravity was holding the expansion in check.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #13 on: 07/03/2008 10:41:50 »
That is effectively what is happening the expansion is far too tiny to affect even the orbits of stars in the galaxy the intereactions between the stars totally dominate their motions  It does not even have much effect on the motion of galaxies in clusters of galaxies.
 

Offline Mw-theoritician

  • First timers
  • *
  • Posts: 5
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #14 on: 14/03/2008 00:20:35 »
hmm maybe once all other matter in the univers is engulfed by one black hole the black hole itself could devour itself, maybe resulting in an explosion of hurrendous preportions, which could result in the re-creation of the universe.  this being a very vague theory..
« Last Edit: 14/03/2008 16:19:29 by Mw-theoritician »
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #15 on: 14/03/2008 19:14:22 »
hmm maybe once all other matter in the univers is engulfed by one black hole the black hole itself could devour itself, maybe resulting in an explosion of hurrendous preportions, which could result in the re-creation of the universe.  this being a very vague theory..

I don't see how a black hole could devour itself. The black hole's gravity will already have caused the matter inside to be compressed to its ultimate state. However, something happening inside the black hole to make it explode could be the cause of an oscillating universe.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
What is the Ultimate Fate of a Black Hole
« Reply #16 on: 15/03/2008 10:30:42 »
OK matter trying to fall into a black hole can create some spectacular effects getting rid of its excess angular momentum but in the whole black hole event horizons are pretty boring things.  It's what might be going on inside where the interesting stuff might happen.  unfortunately however violent things are inside nothing will appear on the outside.  That is the nature of event horizons.
 

Offline JazzRoc

  • First timers
  • *
  • Posts: 5
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #17 on: 06/05/2008 21:24:14 »
The universe, as a whole, fits the requirements of a black hole....
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8655
  • Thanked: 42 times
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #18 on: 07/05/2008 19:36:12 »
Dear me! I hope that pun was intentional.
 

Offline hurricane221

  • First timers
  • *
  • Posts: 3
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #19 on: 29/05/2008 03:10:30 »
hmm maybe once all other matter in the univers is engulfed by one black hole the black hole itself could devour itself, maybe resulting in an explosion of hurrendous preportions, which could result in the re-creation of the universe.  this being a very vague theory..



isnt this essentially the big crunch theory? (universe collapses under its gravitatonal force, vets very small, explodes, expands, ect.)
 

Offline roboter

  • First timers
  • *
  • Posts: 2
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #20 on: 22/07/2008 13:38:44 »
The fate of a black hole is it starts consuming everything in its gravity. our milky way has a black hole in it,black holes make galaxies and all galaxies have been made by black holes. After a couple of hundred million years the black hole becomes dormant and just sits there waiting for a unfortunate planet or comet to come to close for its gravity to suck it in. We don't know for sure what will happen to the black holes in every galaxy,maybe they will last forever,nobody knows but they do know that the universe is expanding so maybe you can figure out whats going to happen and have it printed in a famous magazine with a title saying( Physics boy wonder has broken the secret of black holes)
 

Offline livingod101

  • Jr. Member
  • **
  • Posts: 15
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #21 on: 11/08/2008 16:35:30 »
What happens to all of the material swallowed by a black hole? Does the black hole continue to grow forever, or does it reach a critical mass and then alter its behaviour?

Chris

I thought I saw a Discovery Channel show regarding Black Hole and Steven Hawkings, where he suggested a possible "Black Hole Radiation", which according to what I understood if a black hole is not getting constant materials the expelled radiation would eventually deplete the Black Hole and space around it will go back to normal.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #22 on: 13/08/2008 09:57:23 »
What happens to all of the material swallowed by a black hole? Does the black hole continue to grow forever, or does it reach a critical mass and then alter its behaviour?

Chris

I thought I saw a Discovery Channel show regarding Black Hole and Steven Hawkings, where he suggested a possible "Black Hole Radiation", which according to what I understood if a black hole is not getting constant materials the expelled radiation would eventually deplete the Black Hole and space around it will go back to normal.

That's the theory - sort of. Strangely enough, it's called Hawking Radiation (or Bekenstein-Hawking radiation) ;D

Energy fluctuations in the vacuum cause particle-antiparticle pairs to be created near the event horizon of the black hole. One of the particles gets sucked into the black hole and the other escapes. To an outside observer, it would look as if the black hole had emitted a particle.

The particle that is emitted has to have positive energy, so the particle that gets sucked into the black hole must have negative energy (conservation of energy blah blah blah). By absorbing the negative energy of the particle the black hole loses energy, and, due to E=mc2, also loses mass.

Obviously, the lost mass is miniscule so the black hole would take quite a long time to evaporate; longer even than it takes my mate Bob to buy a round of drinks!
« Last Edit: 13/08/2008 10:09:22 by DoctorBeaver »
 

Offline Gabe2k2

  • Jr. Member
  • **
  • Posts: 32
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #23 on: 11/09/2008 21:41:52 »
As I have detailed in the thread " Is a black hole a point " Id like to postulate that the fate of a black hole greatly depends on the forces acting upon it !
 

Offline Juniorjoey

  • First timers
  • *
  • Posts: 1
    • View Profile
What is the Ultimate Fate of a Black Hole
« Reply #24 on: 21/09/2008 21:42:17 »
I have a question.

If space and time co-exist and matter creates space, then if a black hole sucks in everything in the entire universe does time and space cease to exist outside of the black hole? Or does dark matter not get sucked into a black hole and keeps time and space outside of the black hole?
 

The Naked Scientists Forum

What is the Ultimate Fate of a Black Hole
« Reply #24 on: 21/09/2008 21:42:17 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums