# Black holes

1. Jun 16, 2010

### Kat007

I was wondering if someone agrees:

Is it possible that on the other side of the black hole is an expanding universe? It seems an iteresting idea to me: in our universe a star collapses onto itself with an explosion, creating a black hole and on the other side a big bang happens with matter sucked in from our side, falling out on 'the other side'.. If nothing can escape the black hole it must be going somewhere...

A separate question: does a mass of the black hole keep increasing throught it's life? And does the black hole ever 'die'?

2. Jun 16, 2010

### vandegg

The mass of a black hole is just the mass of everything that has fallen into it (minus hawking radiation), so presumably black holes continue to get bigger throughout their life.

There is a way black holes can lose their mass, via hawking radiation. Black holes which are too small will eventually evaporate. This happens when the rate of energy radiated is larger than the rate of matter the black hole is absorbing. The temperature of a this radiation is inversely proportional to the size of the black hole. At some point a black hole will become so large (and so cold) that it will absorb from the background radiation of the universe more than it can radiate and so will only get bigger.

I have heard theories about our universe being inside a black hole or whatever. Everything i just said is completely theoretical and no one has any idea what happens inside of a black hole so it is hard to say anything meaningful about it right now.

3. Jun 16, 2010

### Kat007

I hope someone can comment on the first part of my post also. Interested to see the opinions out there.

4. Jun 18, 2010

### Calluuuum

In a sense your seperate question contradicts your initial thought. You asked about if a Black hole's mass can grow, if it did that means it's retaining the mass it absorbs. If it retains mass it absorbs, it can't be losing it to the "other universe" that was created. If it was losing any kind of mass to this new universe, it would be small and/or insignificant. With no mass being lost to the new universe (which would be lost as energy most likely), the universe wouldn't be able to sustain it's expansion.

5. Jun 18, 2010

### Kat007

Very good point! :) Oh, I thought I had such a good idea :) maybe not.

6. Jun 24, 2010

### piinthesky

This question(s) may be too speculative for the forum and it is certainly a bit convoluted. However, I will ask it anyway since it is a paradox that has been perplexing me for almost two years. It is this:

If there is such a thing as a graviton having both wave and particle attributes and it travels at the speed of light, how can it escape the gravitational field of a black hole? You can see the paradox here, at least it seems to be a paradox to me. Gravitation being the sine qua non of the black hole singularity, how could the absolute space-time distortion it demands allow the graviton to escape and create the black hole's gravitational field?

7. Jun 24, 2010

### Kat007

[QUOTE Black holes which are too small will eventually evaporate.[/QUOTE]
I'd like to ask about this bit actually, so why all the chaos about the CERN doing their experiments? I mean, ok it might create very small black holes, but if they are small they should just evaporate right?

8. Jun 24, 2010

### nismaratwork

I'd like to ask about this bit actually, so why all the chaos about the CERN doing their experiments? I mean, ok it might create very small black holes, but if they are small they should just evaporate right?[/QUOTE]

They should before they have a chance to begin accreting matter, but stellar mass BHs will wait a very very VERY long time for Hawking Radiation to be a factor, until the universe cools. Until then, it's a one way trip into the hole, and if HR is real, what comes out has nothing to do with what fell in, unless that information is somehow in the event horizon.

9. Jun 24, 2010

### Kat007

And as for the previous question, very interesting. I've read something up on it, here is the extract (it is from this link: http://sciastro.astronomy.net/sci.astro.4.FAQ).

Check out he last paragraph in particular:

"Subject: D.09 How can gravity escape from a black hole?
Author: Matthew P Wiener <weemba@sagi.wistar.upenn.edu>,
Steve Carlip <carlip@dirac.ucdavis.edu>

In a classical point of view, this question is based on an incorrect
picture of gravity. Gravity is just the manifestation of spacetime
curvature, and a black hole is just a certain very steep puckering
that captures anything that comes too closely. Ripples in the
curvature travel along in small undulatory packs (radiation---see
D.05), but these are an optional addition to the gravitation that is
have the fields that they do. Once formed, they and their gravity
just are.

In a quantum point of view, though, it's a good question. We don't
yet have a good quantum theory of gravity, and it's risky to predict
what such a theory will look like. But we do have a good theory of
quantum electrodynamics, so let's ask the same question for a charged
black hole: how can a such an object attract or repel other charged
objects if photons can't escape from the event horizon?

The key point is that electromagnetic interactions (and gravity, if
quantum gravity ends up looking like quantum electrodynamics) are
mediated by the exchange of *virtual* particles. This allows a
standard loophole: virtual particles can pretty much "do" whatever they
like, including travelling faster than light, so long as they disappear
before they violate the Heisenberg uncertainty principle.

The black hole event horizon is where normal matter (and forces) must
exceed the speed of light in order to escape, and thus are trapped.
The horizon is meaningless to a virtual particle with enough speed.
In particular, a charged black hole is a source of virtual photons
that can then do their usual virtual business with the rest of the
universe. Once again, we don't know for sure that quantum gravity
will have a description in terms of gravitons, but if it does, the
same loophole will apply---gravitational attraction will be mediated
by virtual gravitons, which are free to ignore a black hole event
horizon."

10. Jun 24, 2010

### Kat007

[QUOTE stellar mass BHs will wait a very very VERY long time for Hawking Radiation to be a factor... QUOTE]

Sorry could you please clarify: you are referring to stellar black holes, but the ones in question at CERN are 'quantum black holes', so how does what you said relate to that please?

11. Jun 25, 2010

### Calluuuum

Remember Kat, the panic about the mini black holes was just hype from the media and the public not actually knowing anything about it. They just hear "Black holes = doomsday" and suddenly everyone's repeating it, without actually finding out more about it themselves. The mini black holes would evapourate and do no damage at all, actually it would be nice to get some data about black holes. (;

12. Jun 25, 2010

### Kat007

OK cool cool, good to know!

13. Jun 25, 2010

### ThomasEdison

They should before they have a chance to begin accreting matter, but stellar mass BHs will wait a very very VERY long time for Hawking Radiation to be a factor, until the universe cools. Until then, it's a one way trip into the hole, and if HR is real, what comes out has nothing to do with what fell in, unless that information is somehow in the event horizon.[/QUOTE]

I would add a few more VERY's. The large black holes (assuming the idea of Hawking radiation is correct) take such a long time to fizzle out that the entire timeline of the Universe is skewed towards such large numbers that the Universe's age now appears like nothing.
The numbers I've seen thrown out were something on the order of 10^74th years for a black hole's life expectancy!

14. Jun 25, 2010

### Kat007

[QUOTE The numbers I've seen thrown out were something on the order of 10^74th years for a black hole's life expectancy![/QUOTE]

WOW! That is astonishing... Never knew that!

15. Jun 25, 2010

### nismaratwork

I would add a few more VERY's. The large black holes (assuming the idea of Hawking radiation is correct) take such a long time to fizzle out that the entire timeline of the Universe is skewed towards such large numbers that the Universe's age now appears like nothing.
The numbers I've seen thrown out were something on the order of 10^74th years for a black hole's life expectancy![/QUOTE]

Indeedy, but unfortunately I had run out of very's for the day, and so my point may have been lost.

16. Jun 25, 2010

### ThomasEdison

Indeedy, but unfortunately I had run out of very's for the day, and so my point may have been lost. [/QUOTE]

I'll correct myself the only link I can currently find says 1.2 x 10^67 years.http://dnausers.d-n-a.net/dnetGOjg/Black/Holes.htm
I did read 10^74 somewhere I know it.

Wiki for Heat Death timeline of the Universe says a Galaxy mass Black hole has a 10^100 year life expectancy.http://en.wikipedia.org/wiki/Heat_Death

My point though is this:
People tend to think that the Universe is ancient at 13 billion and some change years old. They are wrong. Compared to a human life 13 billion years is inconcievable ; but compared to a black hole's life 13 billion years is almost nothing.
The black holes might very well be the most common form that matter resides in now.

It's a brand spankin new Universe from a Black Hole's perspective.

Last edited by a moderator: Apr 25, 2017
17. Jun 26, 2010

### Chronos

I wouldn't much worry about the LHC. Cosmic rays have bombarded the earth's atmosphere with no ill effects for billions of years. Their energies are far greater than the LHC can match.

18. Jun 26, 2010

### Kat007

I just find the whole concept so strange... This space time distortion to the point of such extreme shape.

Hey do you know much about the dark energy? That one is quite intriguing as well. It accounts for so much mass in the universe that just makes you wonder... I mean normal matter only accounts for 5% of total mass! (70 - dark energy, 25 - dark matter).. That's crazy, just shows we only know about 5% of stuff really!

Do you think it also has particle-wave duality?

19. Jun 26, 2010

### Kat007

Yes a very good point.

20. Jun 26, 2010

### nismaratwork

I'll correct myself the only link I can currently find says 1.2 x 10^67 years.http://dnausers.d-n-a.net/dnetGOjg/Black/Holes.htm
I did read 10^74 somewhere I know it.

Wiki for Heat Death timeline of the Universe says a Galaxy mass Black hole has a 10^100 year life expectancy.http://en.wikipedia.org/wiki/Heat_Death

My point though is this:
People tend to think that the Universe is ancient at 13 billion and some change years old. They are wrong. Compared to a human life 13 billion years is inconcievable ; but compared to a black hole's life 13 billion years is almost nothing.
The black holes might very well be the most common form that matter resides in now.

It's a brand spankin new Universe from a Black Hole's perspective.[/QUOTE]

No argument from me, stellar generations have nothing on the lifespan of stellar-mass and larger black holes.

Last edited by a moderator: Apr 25, 2017