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Author Topic: Theoretically, how does gravity behave inside a black hole?  (Read 6653 times)

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #25 on: 07/10/2013 21:02:01 »
Quote from: lean bean
Pete, should that be...the matter never passes the horizon as seen by a distant observer?  But from the infalling matter's frame it does cross the horizon.
Yes. My appologies if I didn't make that clear.

This applies to observers outside the event horizon. Why they call them "distant" is beyond me. They could be very close in fact.
Dam, you answered whilst I was modifying my post.  :) :)

That is only theoretical. It could take an infinite time for the mass to collapse inside the radius.
 

Offline Pmb

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #26 on: 08/10/2013 03:58:32 »
Quote from: jeffreyH
That is only theoretical. It could take an infinite time for the mass to collapse inside the radius.
Why would you say "That is only theoretical"? It gives the impression that other things we accept as fact aren't really "only theoretical" such as the expansion of the universe.

I use that phrase "only theoretical" very rarely myself. I recommend that you do the same. It's not a useful statement to make. Everything in science is really theoretical if you want to be exact.
 

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #27 on: 08/10/2013 04:12:56 »
Quote from: jeffreyH
That is only theoretical. It could take an infinite time for the mass to collapse inside the radius.
Why would you say "That is only theoretical"? It gives the impression that other things we accept as fact aren't really "only theoretical" such as the expansion of the universe.

I use that phrase "only theoretical" very rarely myself. I recommend that you do the same. It's not a useful statement to make. Everything in science is really theoretical if you want to be exact.

Sorry a better phrasing would be it is only one theory and there could be competing theories that demonstrate equally valid hypotheses.
 

Offline Pmb

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #28 on: 08/10/2013 04:25:53 »
Quote from: jeffreyH
Sorry a better phrasing would be it is only one theory and there could be competing theories that demonstrate equally valid hypotheses.
You could say that everytime general relativity comes up. Is that a road you really want to go down?
 

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #29 on: 08/10/2013 04:27:22 »
I can't see there being enough gravitational field strength from this matter.

Enough field strength for what ?

Sorry I didn't answer this sooner. I don't think the mass leaving the accretion disk would produce the required gravitation as there probably wouldn't be enough. However the momentum and a compression factor may come into play. I am very unsure about any of this.
 

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #30 on: 08/10/2013 04:29:17 »
Quote from: jeffreyH
Sorry a better phrasing would be it is only one theory and there could be competing theories that demonstrate equally valid hypotheses.
You could say that everytime general relativity comes up. Is that a road you really want to go down?
[/quote

Pete at this point in time I can hardly see the actual road never mind find the direction. I am in a bit of a quantum fluctuation. :-)
 

Offline Pmb

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #31 on: 08/10/2013 04:44:52 »
Quote from: jeffreyH
Pete at this point in time I can hardly see the actual road never mind find the direction. I am in a bit of a quantum fluctuation. :-)
In that case here is a chapter on the philosophy of science that I recommend reading - http://home.comcast.net/~peter.m.brown/ref/philosophy_physics.pdf
« Last Edit: 08/10/2013 04:51:52 by Pmb »
 

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #32 on: 08/10/2013 06:51:09 »
Quote from: jeffreyH
Pete at this point in time I can hardly see the actual road never mind find the direction. I am in a bit of a quantum fluctuation. :-)
In that case here is a chapter on the philosophy of science that I recommend reading - http://home.comcast.net/~peter.m.brown/ref/philosophy_physics.pdf

OK There may be theories that not only account for relativistic effects but add new laws that expand on it.
 

lean bean

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #33 on: 08/10/2013 16:42:40 »
I don't think the mass leaving the accretion disk would produce the required gravitation as there probably wouldn't be enough. However the momentum and a compression factor may come into play. I am very unsure about any of this.
Jeff,  just moving your hand emits gravitational waves (very weak ones).
It's in the link I gave earlier...
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In fact any accelerating mass will emit gravitational waves in much the same way as an accelerating charged particle emits electromagnetic radiation. Even as you move your hand and mouse to read this web page your movements emit very weak gravitational waves.
My bold. From https://www.astro.cf.ac.uk/research/gravity/tutorial/?page=1blackholes
But, now I guessing you may mean by 'enough' ...enough for detection??




 
 

Offline Pmb

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #34 on: 09/10/2013 03:17:43 »
Let's make it clear what generates waves, both electromagnetic and gravitational.

Suppose there is a distribution of matter in a region of space Q and you measure the field (electromagnetic or gravitational as the case may be) at a location r. Now change the matter which generates the field. If the field remains unchanged at all r then no radiation will be produced. Simple, huh? :)

E.g. consider a spherically symmetric ball of charge. If you have the same ball but rotated about an axis of symmetry then the field the charge generates will remain unchanged, even though charge was moved. Note that I do not mean that one actually rotates the ball since that would actually generate an electric field because during the rotation charges would be in motion and that would create a magnetic field and this would generate an EM wave.
 

lean bean

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Re: Theoretically, how does gravity behave inside a black hole
« Reply #35 on: 09/10/2013 19:59:52 »
Pete
 I agree that a symmetrical rotating sphere would not produce gravitational waves.
But, I'm not following you in this part...
Suppose there is a distribution of matter in a region of space Q and you measure the field (electromagnetic or gravitational as the case may be) at a location r. Now change the matter which generates the field. If the field remains unchanged at all r then no radiation will be produced.
By accelerating the matter you are producing gravitational waves locally.
  That the waves may not be detected farther away is down to the waves losing energy through interacting with ‘matter’ along the way, and not down to no gravitational waves being produced at all.
I take the waves to be ‘disturbances’ in the gravitational field.
 Didn’t the book ’Exploring Black Holes’ describe them as ’travelling tidal accelerations’, something like that. :)
« Last Edit: 09/10/2013 20:04:10 by lean bean »
 

Offline syhprum

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Re: Theoretically, how does gravity behave inside a black hole?
« Reply #36 on: 09/10/2013 22:39:40 »
I believe there is nothing magical about black holes once we have passed thru the event horizon which should be quite un-traumatic for a large BH we will see a high density but nowhere infinite density object before us and we will gravitate towards it in the normal Newtonian manner.
 

Offline jeffreyH

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Re: Theoretically, how does gravity behave inside a black hole?
« Reply #37 on: 09/10/2013 23:42:55 »
I believe there is nothing magical about black holes once we have passed thru the event horizon which should be quite un-traumatic for a large BH we will see a high density but nowhere infinite density object before us and we will gravitate towards it in the normal Newtonian manner.

It all comes down to the c in e=mc^2. A combination of length and momentum. Einstein got just about all of it right but made the mistake of looking for a unified field theory when in fact he already had it.
 

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Re: Theoretically, how does gravity behave inside a black hole?
« Reply #37 on: 09/10/2013 23:42:55 »

 

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