Can mass of a blackhole increase

[sharan]

General theory of relativity predicts that if for an observer in an inertial frame is watching an object going towards a black hole then from his frame it takes infinite time for it to go beyond the schwarzschild radius.Then what explains the existence of super massive black holes,if we can never see anything going inside?

[barkis]

At the rate they can devour stars when they get hungry, I would say yes, but that seems over simplified, and as I'm no expert, you will need to wait for a more learned member to answer your question.

Ron.

[brianb]

Then what explains the existence of super massive black holes,if we can never see anything going inside?

The matter does get inside, whether we see it going in or not. The gravitational influence of the attracted matter is based on where it thinks it is, not where we think it is. This all falls out of the equations of general relativity ...

[Bigwings]

The matter does get inside, whether we see it going in or not. The gravitational influence of the attracted matter is based on where it thinks it is, not where we think it is. This all falls out of the equations of general relativity ...

Now I am confused.... matter "thinks"??????

[themos]

General theory of relativity predicts that if for an observer in an inertial frame is watching an object going towards a black hole then from his frame it takes infinite time for it to go beyond the schwarzschild radius.Then what explains the existence of super massive black holes,if we can never see anything going inside?

This is like the "logic" puzzle that says that Achilles can never overtake the tortoise because he first has to get half way to it and then has to go half way to THAT and so on so it will take infinite time to overtake the tortoise.

In fact, there's no paradox. Light from close to the event horizon gets red-shifted without limit so it's as if the "movie" of the event is being slowed down and we wait for ever to watch the last frame. But the "movie" of the event is not the event.

[sharan]

It is not like Achilles heel.From the equations of relativity ,for an object to get inside the event horizon it must get a speed of velocity of light which is impossible and hence i think i must forever hover at the horizon ,getting nearer and nearer to it but never quite reaching it.

[sharan]

The matter does get inside, whether we see it going in or not. The gravitational influence of the attracted matter is based on where it thinks it is, not where we think it is. This all falls out of the equations of general relativity ...

But the result must be consistent with which what we observe.From my frame i see that there is no mass increase

[the_laughing_crow]

The result does not have to be consistent with what we observe.

If I may, Id like to point to two very good in depth lectures on black hole theory:

http://www.astrosociety.org/education/podcast/susskind.mp3

http://www.astrosociety.org/education/podcast/filippenko2.mp3

[sharan]

@ the laughing crow

com'mon , if theory and observation donot coincide how will we know that the theory is right?

[Bigwings]

@ the laughing crow

com'mon , if theory and observation donot coincide how will we know that the theory is right?

It then becomes a matter of faith.......ooops mods is that not religion.

Now according to the rules of SGL we cant discuss that so perhaps black holes are off the menu.......

[the_laughing_crow]

Listen to both of those lectures.

[themos]

I will listen to those because I realize I am not able to reconcile the claim that no information can escape the black hole with an increase in the gravitational pull of the black hole.

???

[George Jones]

I will listen to those because I realize I am not able to reconcile the claim that no information can escape the black hole with an increase in the gravitational pull of the black hole.

???

From Eric Poisson's book A Relativist's Toolkit: The Mathematics of Black-Hole Mechanics:

It is a remarkable feature of the event horizon that the entire future history of the spacetime must be known before its position can be determined ... this teleological property ...

[George Jones]

General theory of relativity predicts that if for an observer in an inertial frame is watching an object going towards a black hole then from his frame it takes infinite time for it to go beyond the schwarzschild radius.Then what explains the existence of super massive black holes,if we can never see anything going inside?

We have theories that make predictions. We can never prove that a theory is true, the best we can do is confirm to a given experimental tolerance the predictions of a theory. The general theory of relativity together with our theories of matter predict that black holes exist. They also predict that we should be able to observe certain phenomena from the space around black holes. If back holes exist, then we should be able to observe blah, blah, blah. We have have seen some of blah, blah, blah, and this gives us confidence that black holes exist, but we can never actually prove that black holes exist.

Similarly, the theory of quarks predicts that if quarks exist, then we should be able to observe bleh, bleh, bleh. We have have seen some of bleh, bleh, bleh, and this gives us confidence that quarks exist, but we can never actually prove that quarks exist.

There is a good chance that, within a decade or so, we should be able to "image" the astrophysical black hole at the centre of our galaxy. See

Portrait of a Black Hole: Scientific American

[astro-ph/0607279] Testing General Relativity with High-Resolution Imaging of Sgr A*.

I hope to get back to this thread and to compare an infinite-time horizon effect in the uncontroversial special theory of relativity that is analogous to the infinite-time horizon effect for black holes.

[sharan]

We have theories that make predictions. We can never prove that a theory is true, the best we can do is confirm to a given experimental tolerance the predictions of a theory. The general theory of relativity together with our theories of matter predict that black holes exist. They also predict................................................................................................black holes.

KK,that all if ifne.But here what GR predicts looks to be directly against observation.

[George Jones]

KK,that all if ifne.But here what GR predicts looks to be directly against observation.

Do you mean "There are predictions of general theory of relativity that are unobservable"? Look at things the other way around. As far as I am aware, there are no observations, with respect to black holes or anything else, that directly conflict with predictions of general relativity. There are observations that are consistent with the existence of black holes. This is the best that we can do in science, with respect to the existence of black holes, or quarks, or anything else.

We don't see what happens inside black holes because we choose not to see what happens inside black holes. If we chose to see what happens inside black holes, we could see what happens inside black holes! If I write my post that compares (Killing) horizons in special relativity to black hole event horizons, I'll expand on these deliberately cryptic and tautological and seeming paradoxical statements.

[brianb]

If we chose to see what happens inside black holes, we could see what happens inside black holes!

But not outside them....

[sharan]

Do you mean "There are predictions of general theory of relativity that are unobservable"? Look at things the other way around. As far as I am aware, there are no observations, with respect to black holes or anything else, that directly conflict with predictions of general relativity. There are observations that are consistent with the existence of black holes. This is the best that we can do in science, with respect to the existence of black holes, or quarks, or anything else.

We don't see what happens inside black holes because we choose not to see what happens inside black holes. If we chose to see what happens inside black holes, we could see what happens inside black holes! If I write my post that compares (Killing) horizons in special relativity to black hole event horizons, I'll expand on these deliberately cryptic and tautological and seeming paradoxical statements.

No ,I mean if what i think here is true then the existence of supermassive blackholes is against what GR predicts.

[brianb]

the existence of supermassive blackholes is against what GR predicts.

Did you take into account mutual rotation?

[gordyb]

I thought hawking radiation proved that of 2 particles 1 goes into the black hole and the other one escapes.When black holes cannot take more matter in they spout two massive jets of (Gamma or Radio) waves as in a quasar.I Think

[George Jones]

But not outside them....

Exactly!

No ,I mean if what i think here is true then the existence of supermassive blackholes is against what GR predicts.

But this isn't what the world's relativity experts think. According to Sir Roger Penrose, one of the world's leading experts on black holes, supermassive black holes do form:

All that is required is for sufficient mass to fall into a small enough region. For the central regions of a large galaxy, for example, the required concentration could occur with the stars in the region still being separated from each other

If enough stars congregate together, they can form a black hole even before they're close enough together to touch!

[sharan]

Exactly!

But this isn't what the world's relativity experts think. According to Sir Roger Penrose, one of the world's leading experts on black holes, supermassive black holes do form:

I know that.But i dont understand where the error in my line of logic is

[Ags]

This confuses me too. But surely as matter aggregates around the event horizon (assuming this is what an outside observer would see), the matter would contribute to the gravitational well, and make the event horizon larger? could the event horizon grow to consume the objects on the periphery of the event horizon?

Didn't Carl Sagan talk about stuff levitating above the event horizon in "Cosmos"?

I think the only solution is taking a close look at an actual black hole with the Extremely Large Telescope when it is built (or more likely with the EMELT - Even More Extremely Large Telescope :-).

[themos]

The general theory of relativity together with our theories of matter predict that black holes exist.

I am not aware of an exact solution of GR equations that describes formation of a black hole.