Why is it so accepted that matter falls into black holes?

[Astroboy123]

It seems like black holes could just as easily be expelling the matter they rip up. Couldn't a black hole just be something that rips matter apart atom by atom and then blasts it back into space? In this case there wouldn't be a need for a singularity. Quasars are one example of how they expel matter/energy. Maybe nothing goes beyond the event horizon and instead just gets churned up and around and blasted back out.

 

[mathman]

Black holes are simply highly dense masses, defined by having a gravitational strength so great that the escape velocity is greater than the speed of light.

What goes on inside is an open question. The singularity is predicted by General Relativity, but quantum theory is not taken into account. When calculations are made using both theories, nonsense results.

 

[Astroboy123]

Black holes are simply highly dense masses, defined by having a gravitational strength so great that the escape velocity is greater than the speed of light.

If the escape velocity is greater than the speed of light then how does the material from quasars escape? I know they say that a black hole takes in too much matter than it can handle and expels it but how does that light escape?

 

[PAllen]

If the escape velocity is greater than the speed of light then how does the material from quasars escape? I know they say that a black hole takes in too much matter than it can handle and expels it but how does that light escape?

The light comes from matter well outside the event horizon. Black holes can tear apart approaching stars well before their matter settles near the horizon, leading to very strong radiation emission and jets.

 

[Jack21222]

I know they say that a black hole takes in too much matter than it can handle and expels it

Who says that?

Nobody says that.

 

[Ryan_m_b]

If the escape velocity is greater than the speed of light then how does the material from quasars escape? I know they say that a black hole takes in too much matter than it can handle and expels it but how does that light escape?

Once something has gone beyond the event horizon it cannot come out because to do so would require a velocity faster than light. In addition tidal forces around a black hole cause http://en.wikipedia.org/wiki/Spaghettification" .

By "expelled matter" you may be confusing the jets seen in http://en.wikipedia.org/wiki/Accretion_disc" .

 

[Drakkith]

Astroboy, a black hole acts EXACTLY like anything else with mass until you reach the event horizon. Other than strength and gradiant, the Earths gravitational field has the same effect on matter that a black hole does. One can orbit a black hole, use it for slingshot maneuvers, laugh at it's face for being supermassively fat (Bad black hole! *swats with newspaper* I told you TWO stars per million years! Two!), etc.

 

[Astroboy123]

Once something has gone beyond the event horizon it cannot come out because to do so would require a velocity faster than light.

Is anything known about the nature of things beyond the event horizon? Specifically how light is not fast enough to escape (once it goes beyond the event horizon), does this mean matter is falling into a black hole faster than light? If so, is this an exception to the cosmic speed limit?

 

[Drakkith]

Is anything known about the nature of things beyond the event horizon? Specifically how light is not fast enough to escape (once it goes beyond the event horizon), does this mean matter is falling into a black hole faster than light? If so, is this an exception to the cosmic speed limit?

In-falling matter does not exceed the speed of light. As to the why light cannot escape, I believe it has to do with the curvature of space inside the event horizon making it so that all paths available to a photon lead back to the black hole.

 

[CosmicEye]

I also think you are confusing the rad streams at the poles vs the eccretion disc. The disc or quasar is everything falling in or in the orbit.

To add on to this thread's question, how does the radiation at the poles escape if it starts below the EH? How is it launched out, + and - charged particles?

 

[PAllen]

I also think you are confusing the rad streams at the poles vs the eccretion disc. The disc or quasar is everything falling in or in the orbit.

To add on to this thread's question, how does the radiation at the poles escape if it starts below the EH? How is it launched out, + and - charged particles?

Nothing escapes from the event horizon (classically). Hawking radiation from astronomic black holes is much more dim than cosmic background radiation. Polar emissions from a rotating black holes system originate above the event horizon, strong EM fields playing the major role.

From the point of view of external observers (us) nothing ever reaches the event horizon, so it is not even conceivable to talk about escape from below the event horizon for an external observer.

 

[Cosmo Novice]

Once something has gone beyond the event horizon it cannot come out because to do so would require a velocity faster than light. In addition tidal forces around a black hole cause http://en.wikipedia.org/wiki/Spaghettification" .

By "expelled matter" you may be confusing the jets seen in http://en.wikipedia.org/wiki/Accretion_disc" .

This is not neccesarily true - Hawking predicts that Black Holes lose mass via the process of Hawking radiation. The smaller the BH the more ,mass it radiates.

I do however concede that when "something" goes in it can only come out as "something else" - ie: there is no preservation of state.

 

[Ryan_m_b]

This is not neccesarily true - Hawking predicts that Black Holes lose mass via the process of Hawking radiation. The smaller the BH the more ,*** it radiates.

I do however concede that when "something" goes in it can only come out as "something else" - ie: there is no preservation of state.

To be fair Hawking radiation is not something escaping from beyond the event horizon. As I understand it (and my knowledge is based on pop-sci books I read years ago so I could be wrong) Hawking radiation works by the black hole making virtual particles-pairs real right on the cusp of the event horizon, it absorbs one of the pair that has negative energy (thus lowering the holes mass) causing the radiation of the positive energy particle.

 

[Cosmo Novice]

To be fair Hawking radiation is not something escaping from beyond the event horizon. As I understand it (and my knowledge is based on pop-sci books I read years ago so I could be wrong) Hawking radiation works by the black hole making virtual particles-pairs real right on the cusp of the event horizon, it absorbs one of the pair that has negative energy (thus lowering the holes mass) causing the radiation of the positive energy particle.

Yes I can concede this - the particles are not directly escaping from beyond the EH. I wanted to just outline a mechansim for mass loss.

 

[WannabeNewton]

Maybe nothing goes beyond the event horizon and instead just gets churned up and around and blasted back out.

Classically I don't see how this could be at all. Past the EH (r < 2M for schwarzchild Black holes) you will see that the time - like coordinate and space - like radial coordinate switch signs. Since r becomes time - like past the EH, r = 0 becomes inevitable. We know that a test particle can pass the EH in finite proper time and finite proper distance so why wouldn't it go through and, due to the aforementioned issue, meet the infinite tidal forces at r = 0?

 

[Astroboy123]

We know that a test particle can pass the EH in finite proper time and finite proper distance so why wouldn't it go through and, due to the aforementioned issue, meet the infinite tidal forces at r = 0?

You're referring to theoretical models? What if the EH is just a buzzsaw that shreds matter and then bats it back out into space? I don't see why it anything has to pass the EH.

 

[Drakkith]

You're referring to theoretical models? What if the EH is just a buzzsaw that shreds matter and then bats it back out into space? I don't see why it anything has to pass the EH.

We have nothing but theoretical models. Perhaps you do not know what a theoretical model actually means. Do you know what a scientific theory is?

 

[cueball B]

Can black holes still add to their own mass? If matter falls into a black hole, could it be that this matter is just absorbed and just makes the hole bigger? Or does a black hole have a finite amount of mass it can sustain?

 

[Ryan_m_b]

Can black holes still add to their own mass? If matter falls into a black hole, could it be that this matter is just absorbed and just makes the hole bigger? Or does a black hole have a finite amount of mass it can sustain?

Any mass that crosses the event horizon is added to the black hole. Think of it this way: if matter falls through Earth's atmosphere then it adds to Earth's mass. Simplistically the only difference between this and a black hole is that the escape velocity of a black hole is faster than light speed (thus an event horizon forms) and according to current understanding anything beyond an event horizon is crushed into a singularity of zero volume, infinite density. Though regarding the latter as I understand it the consensus is that our understanding of singularities is incomplete.

 

[jdt73]

there is nothing inside a black hole. at the event horizon matter is converted to zero point energy and ceases to exist as real mass.

 

[Ryan_m_b]

there is nothing inside a black hole. at the event horizon matter is converted to zero point energy and ceases to exist as real mass.

Evidence?

 

[Drakkith]

there is nothing inside a black hole. at the event horizon matter is converted to zero point energy and ceases to exist as real mass.

I seem to recall reading that you can survive far past the even horizon if you were falling into a supermassive black hole, as the gradiant is much less severe.

 

[cterry86]

Is anything known about the nature of things beyond the event horizon? Specifically how light is not fast enough to escape (once it goes beyond the event horizon), does this mean matter is falling into a black hole faster than light? If so, is this an exception to the cosmic speed limit?

perhaps matter is so dense within the hole that it cannot make an exchange from matter to energy, or perhaps the gravity of a black hole is strong enough to bend the direction of photons creating a kind of orbit around its mass. it would appear black if no photons were making it out, yes?

 

[Ryan_m_b]

perhaps matter is so dense within the hole that it cannot make an exchange from matter to energy, or perhaps the gravity of a black hole is strong enough to bend the direction of photons creating a kind of orbit around its mass. it would appear black if no photons were making it out, yes?

The event horizon is formed because of the strength of gravity. Current theories predict a singularity to exist however this makes no sense and current theories are incomplete. So at the moment we don't know for certain the conditions beyond the event horizon.

 

[Cosmo Novice]

perhaps matter is so dense within the hole that it cannot make an exchange from matter to energy, or perhaps the gravity of a black hole is strong enough to bend the direction of photons creating a kind of orbit around its mass. it would appear black if no photons were making it out, yes?

This seems to be thinking in a Newtonian sense, remember it is curvature of spacetime not a traditional attractive force.

 

[cterry86]

i tend to have a hard time believing in infinities, you know, a two pound weight is infinitely heavy when weighed on a one pound scale

do you have anything on zero point past event horizon? I'm trying to figure out how this is supported

 

[cterry86]

This seems to be thinking in a Newtonian sense, remember it is curvature of spacetime not a traditional attractive force.

what is "it" in your statement?

 

[phinds]

The event horizon is formed because of the strength of gravity. Current theories predict a singularity to exist however this makes no sense and current theories are incomplete. So at the moment we don't know for certain the conditions beyond the event horizon.

When you say "the even horizon is formed" that would seem to imply that the EH is SOMETHING, but it is not, it is just a place beyond which nothing can reach escape velocity and it has no other physical meaning if I have read things correctly.

I also have read that objects passing the EH don't even know they have done so. What they DO notice is tidal forces and those have nothing to do with the EH.

 

[cterry86]

I'm thinking about the light and trying to think outside Newtonian law and in spacetime soooo...

couldn't the dip made by a black hole create a lensing effect that locks light into an "orbit" around the hole past the EH?

keep in mind i am a physics hobbyist, i just have ideas

 

[Ryan_m_b]

When you say "the even horizon is formed" that would seem to imply that the EH is SOMETHING, but it is not, it is just a place beyond which nothing can reach escape velocity and it has no other physical meaning if I have read things correctly.

I also have read that objects passing the EH don't even know they have done so. What they DO notice is tidal forces and those have nothing to do with the EH.

Yeah I know, but I still think my statement makes sense. When an object collapses into a black hole at some point an observable event horizon will form, it may not be a thing itself but it is a marker.

 

[Astroboy123]

couldn't the dip made by a black hole create a lensing effect that locks light into an "orbit" around the hole past the EH?

This is a cool idea. Also, wouldn't light that is close but not beyond the event horizon experience strong lensing as well? There are cases when astronomers see duplicate images of galaxies due to strong gravitational lensing so it seems like a black hole would create a significant observational distortion. Maybe some of the objects we see swirling around black holes are figments of distortion.

 

[tkav1980]

I am probably totally wrong here but...

Imagine you just made your bed. You reach down at the exact center of the sheet and ball it up in your fist. When you do that the part of the sheet outside of your fist gets wrinkles and waves. All of the wrinkles and waves have troughs that start at your fist and extend out away from it. Now flip that picture upside down and imagine that sheet is very rigid. Pick any wave and put a bb in it. It can't climb the wave and get out because it doesn't have enough energy. It can only roll down toward your fist. The steeper the slope from flat sheet to your fist, the more energy it would take for the bb to roll up and out. Gravity kind of works like that, The bigger an object is the deeper the "dent" it makes in space. Esentially a steeper slope that you have to fight to get away from it.


Now with a black hole, it hase the deep dent of at least the mass of a large star, but all that weight on the sheet is focused at a single point. Imagine you made a dent in a sheet with a BB that weighed as much as a bowling ball.

Thats the way i visualize it in my head since its a 2D sheet bending into a 3rd dimension. I assume, again just guessing, that the distortion of space is exponentially more complex than that simple picture.


Now for light not getting out because its velocity isn't great enough I take that picture of a heavy BB in the center of a crumbled sheet and twist the sheet around. That takes all those paths and twists them up. Then I imagine that its twisted so much that no matter how hard you roll a lighter bb it either can't get up the twisted ramp at all or when it gets to the end of its twisted ramp and almost out it ends up at the mouth of the next ramp which directs it back down toward out heavier BB.

I'm not educated in the field but after a lot of reading and seeing different graphics on black holes and large bodies in space this picture makes sense to me when I am reading and tying to imagine what's going on. A friend of mine who is a graduate student in physics said the best way he could explain it to me so I could actually understand it was that the geometery of space time inside the EH was such that light can't find a path out. The space is warped in a way that it kind of curls back into itself. So if a photon thinks its going straight and heading for the EH its actually following a curved path that will never reach the EH.


Keep in mind he was trying to convey in words something he said is really better defined mathematically, and to top it off explaining it to someone who really won't actually understand it without understanding the math.

Hope that helps and if it doesn't I'd love for someone to tell me where I am going wrong.

 

[DaveC426913]

I am probably totally wrong here but...

Imagine you just made your bed. You reach down at the exact center of the sheet and ball it up in your fist. When you do that the part of the sheet outside of your fist gets wrinkles and waves. All of the wrinkles and waves have troughs that start at your fist and extend out away from it. Now flip that picture upside down and imagine that sheet is very rigid. Pick any wave and put a bb in it. It can't climb the wave and get out because it doesn't have enough energy. It can only roll down toward your fist. The steeper the slope from flat sheet to your fist, the more energy it would take for the bb to roll up and out. Gravity kind of works like that, The bigger an object is the deeper the "dent" it makes in space. Esentially a steeper slope that you have to fight to get away from it. Now with a black hole, it hase the deep dent of at least the mass of a large star, but all that weight on the sheet is focused at a single point. Imagine you made a dent in a sheet with a BB that weighed as much as a bowling ball.

Thats the way i visualize it in my head since its a 2D sheet bending into a 3rd dimension. I assume, again just guessing, that the distortion of space is exponentially more complex than that simple picture. Now for light not getting out because its velocity isn't great enough I take that picture of a heavy BB in the center of a crumbled sheet and twist the sheet around. That takes all those paths and twists them up. Then I imagine that its twisted so much that no matter how hard you roll a lighter bb it either can't get up the twisted ramp at all or when it gets to the end of its twisted ramp and almost out it ends up at the mouth of the next ramp which directs it back down toward out heavier BB.

I'm not educated in the field but after a lot of reading and seeing different graphics on black holes and large bodies in space this picture makes sense to me when I am reading and tying to imagine what's going on. A friend of mine who is a graduate student in physics said the best way he could explain it to me so I could actually understand it was that the geometery of space time inside the EH was such that light can't find a path out. The space is warped in a way that it kind of curls back into itself. So if a photon thinks its going straight and heading for the EH its actually following a curved path that will never reach the EH. Keep in mind he was trying to convey in words something he said is really better defined mathematically, and to top it off explaining it to someone who really won't actually understand it without understanding the math.

Hope that helps and if it doesn't I'd love for someone to tell me where I am going wrong.

Remove the part about all the folds and waves. The funnel is a perfectly smooth curve, thus:
[URL]http://www.timeenoughforlove.org/images/blackhole6.jpg[/URL]Also, it's not that light can't "find" a way out, it's that all paths (which are smooth curves) lead back into the BH, rather than outward.

(One path passes outside the EH, the path crosses the EH, and as such will never cross it again.) (EH not shown).
[URL]http://www.strings.ph.qmul.ac.uk/~bigdraw/penrose/funnel-main.jpg[/URL]

 

[Drakkith]

I just wanted to point out that Daves picture is just a 2d visual representation of the concept. In reality spacetime is not curved "down" or "up" and massive objects don't make dents in 2d sheets. Or trampolines. So don't imagine a large object above that funnel.