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CesarAKG
2005-Mar-07, 05:00 PM
Hi!

I'm reading the excellent Isaac Asimov's "A choice of catastrophes" and I'm curious about a "mental exercise" (call it crazy fantasy, I don't care, it's fun and I have fun doing it, you should try it): "what if" a mini black hole (mass of an iceberg) "hit" the Sun? If it hits at a certain angle and velocity, it can be trapped by Sun gravity and goes to the core, and starts to devour our closest star. How long it will take to the Sun suffer it's own "big bang"?

In the core of the Sun, mass will be pushed to the mini blackhole (mbh, for short) by the pressure of the core, I'm right? So you have big pressure sending lots of matter into a small drain. Until some time has passed and some mass had absorbed, there's only the pressure. After certain time, the mass of the mbh is enought to accelerate mass by itself. More time, and the gravitational pull will be stronger than the pressure push, and sooner we will have X-Rays being emmited by matter that "falls" into de mbh (still a mini?). More time and the Sun "blows".

Is that a plausible scenery (forget about the extremely low probability of a mbh already hitting the Sun)? How long such catastrophe will take until the last act?

[]s

Russ
2005-Mar-07, 07:24 PM
I'm not really sure what would happen. A mbh with the mass of an ice burg would have a Schwartschild radius of a few ~75-150 microns. About the size of a virus maybe? I think the radiance at the photosphere of the Sun would blow it back into space or possibly it'd just float there at the surface gathering mass until it can sink to the center of the Sun.

Now that I think about it, a mbh that small might evaporate from Hawking radiation before it could "eat" the Sun.

Kristophe
2005-Mar-07, 11:15 PM
Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.

jfribrg
2005-Mar-08, 04:30 AM
Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.

I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.

Concerning Russ' post about the radiance of the Photosphere, what would be the mechanism that accelerates the mbh? Assume a proton or something enters the mbh's event horizon. Presumably the particle will bounce around inside the bh, but of course none of the particles will leave the event horizon. If this behavior causes the center of mass to move, then would this be considered information coming out of the bh? IIRC, the only things you can know about a black hole is its mass and its rotation, Hawking's recent announcement on the subject notwistanding.

In the same way, a photon entering the bh would add momentum to the system.

kenneth rodman
2005-Mar-08, 07:11 AM
actually the sun would stay with the blackhole till it got sucked into it. A blackhole is a blackhole.

Stregone
2005-Mar-08, 08:53 AM
Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.

Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. .
This statement means nothing. Mass does not overcome gravity. Earth (or the sun) doesn't have an escape mass, it has an escape velocity.

Evan
2005-Mar-08, 08:59 AM
I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.

Unless the black hole was part of the initial formation of the solar system it will have entered the system on a hyperbolic orbit. This means it will have an incoming velocity towards the sun greater than system escape velocity. It would pass through the sun as if it weren't there and keep right on going with a possible change in trajectory.

Such an object is so small in relation to the mass of the sun that it can be treated as a restricted case of the two body problem where one body has negligeble mass. This is relatively trivial to solve. There might be some unpredictable effects caused by the fact that a black hole has electric charge as one of its properties. This would interact with solar magnetic fields.

eburacum45
2005-Mar-08, 10:29 AM
An iceberg is a bit of a vague measure, since a large berg could be bigger than Yorkshire; but a billion tonne iceberg is perfectly possible, so let's go with that.
A black hole with that mass (a billion tonnes) would last two trillion years, so could easily have been created in the Big Bang and still be around.
It would be very small though; about ten times the diameter of a proton.
(see Jim Wisniewski's Black Hole calculator here (http://xaonon.dyndns.org/hawking/))

This is actually quite big enough to absorb protons from the Sun's core plasma, if it's hyperbolic orbit passes through that region; this interaction will act as a drag on the hole, and will change the orbit somewhat.
In the worst case, it might change the hyperbolic orbit into an elliptical orbit; the hole would come shooting out of the Sun, at a slower velocity than it went in; loop round the Solar system once (probably taking a number of years to do this) then plunge back in.
And be slowed down some more.
After a few passes through the Sun the aphelion of the black hole's orbit will be below the surface of our star; it's fate will then be sealed. But even then it will take a long time for a small black hole to absorb such a large object.
(don't know how long though; this is a more complex problem, beyond the range of Jim's excellent calculator)

Argos
2005-Mar-08, 01:44 PM
I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.

Unless the black hole was part of the initial formation of the solar system it will have entered the system on a hyperbolic orbit. This means it will have an incoming velocity towards the sun greater than system escape velocity. It would pass through the sun as if it weren't there and keep right on going with a possible change in trajectory.

I can“t see how a mbh could form in the vicinity (10 ly at least) of our solar system. If it wasn“t from the original solar system material, then it should have probably formed far away, a long time ago. Something like that wouldn“t have the time to reach the solar system. As Russ says, it would evaporate very fast, due to its small size.

Kristophe
2005-Mar-08, 02:40 PM
actually the sun would stay with the blackhole till it got sucked into it. A blackhole is a blackhole.

Black holes don't suck

Evan
2005-Mar-08, 02:54 PM
I wasn't proposing it formed as part of our system, just that that is the only way it wouldn't be on a hyperbolic orbit with better than escape velocity. Escape velocity at the sun's surface is 617 kps. It is reasonable to assume that such an object would be coming in with a terminal velocity of perhaps 1000kps at the sun. If it passed through the sun core it would transit in 23 minutes and the core in a few minutes. I wouldn't expect much slowing even if it did interact. The momentum of such an object is a rather large number at that velocity. The density of the core is perhaps ten time that of lead while the black hole may be considered to have nearly infinite density. From what I have read the suns core would have much the same effect as passing through a thin gas, which is to say none at all.

eburacum45
2005-Mar-08, 06:45 PM
Yes, that is true; scooping up a few protons isn't going to change the orbit of a billion tonne black hole very much. So the most likely outcome by a very long way is that the hole comes back out of the Sun into interstellar space.

It might happen all the time and we would be none the wiser.

JohnD
2005-Mar-08, 11:46 PM
1/ Several posts above refer to Hawking radiation (HR) terminating the BH. That radiation occurs in inverse proportion to the mass of the BH and its consequent radius - or rather that of its event horizon - so that the smaller the Hole, the faster it loses mass from HR. But that assumes the BH is in empty space - this one will also be gaining mass as it captures matter through the EH, and that will be increasing as the cube of its mass.

Can anyone say if the capture rate or the HR mass loss rate will win for a Gtonne BH in the heart of the Sun? If HR wins, how big must the BH be for it to lose and inexorably gain mass?

2/ Someone referred to a proton, bouncing around within the EH. We cannot (by definition) know what happens, but surely even a subatomic particle would be torn apart by tidal forces so that it is reduced to its component quarks, strings or whatever underlies them?
And bouncing around? The EH isn't a shell or a membrane. It is a zone, beyond which we know not, but we can assume that any particle that enters must continue it's descent towards the discontinuity.

3/ Read "The Hole Man" by Larry Niven. A miniBH will 'eat' Mars in something between months and years, not millenia. "The math is chancy...." As it was his speciality I suppose that Niven may have been advised by Robert Forward in that estimate, so however chancy that timing may be accurate.

John

bigsplit
2005-Mar-09, 12:22 AM
The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

Evan
2005-Mar-09, 12:25 AM
The way I see it an atomic scale black hole would basically drill an atom sized hole through the sun in the few minutes it would take to pass through. That doesn't amount to very much matter even if it ate it all.

The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

Kristophe
2005-Mar-09, 01:01 AM
The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

Yeah, I'm with Evan on this one.

A) How do you fill a black hole? Adding mass to a black hole increases its event horizon.

B) What would it become?

C) If we assume the black hole to be a frictionless sphere (someone laugh, darn-it!), then it's clear that the only forces affecting it would be the sun's gravity, and the change in momentum due to the absorption of protons. Since proton motion in the sun is random, the net change in direction of the black hole due to interactions with protons (assuming the black hole to be electrically neutral, for fun) would be due entirely to the gravity of the sun. So, why is it stopping?

kenneth rodman
2005-Mar-09, 06:52 AM
A BLACKHOLE is a BLACKHOLE. Its mass is so great that light itself is trapped by its gravitation strength. However small in size its event horizon is; it still has massive amount of gravitational strength beyound its event horizon. Now im aware that in principle there is no limit to how much or how little mass a black hole can have. Any amount of mass at all can in principle be made to form a black hole if you compress it to a high enough density.
The crux of the matter is that the only way i know of that a blackhole is naturally created is the colapse of a star with sufficient mass that the gravitational force is great enough to trap light. that mass is alot greater then the mass of our star; It is why I beleive our star would be doomed. This senario, though thank god its unlikely, is still a possiblity. If your stating that a Mini blackholes mass is being compressed by something other than its own gravity(an artificially created blackhole) then i suppose it would all depend on its velocity. if it was traveling fastenough it would pass right through our star with no ill effects, it could become trapped into an oliptical orbit around our sun, or it could get sucked into the sun itself. the sun In this case would still be fine because some force other than gravity is compressing this mini blackhole. I know im in effect doing a 180 on my original answer but i was thinking of a naturally occuring blackhole.

Evan
2005-Mar-09, 07:01 AM
See here. (http://www.absoluteastronomy.com/encyclopedia/P/Pr/Primordial_black_hole.htm)

Argos
2005-Mar-09, 02:14 PM
if it was traveling fastenough it would pass right through our star with no ill effects, it could become trapped into an oliptical orbit around our sun, or it could get sucked into the sun itself.

I think that if the mini BH (or primordial BH) were coming in from the interstellar space, it would be traveling, say, at some 200 km/s (maybe more). It would take 2 hours to traverse the Sun. It seems to me that it wouldn“t experience any "drag" from the plasma (somebody correct me if I“m wrong), so it wouldn“t decelerate. In fact it would still be accelerating inside the Sun, heading to the core. Once inside the Sun, due to the bh“s high speed, the particles wouldn“t have the time to "orbit" it prior to falling inside the EH (bh“s don“t suck). Only the matter right ahead on its trajectory would be possibly captured, a negligible amount. It would cross the sun like a red-hot needle punching a chunk of butter, and emerge on the other side with its hyperbolic orbit unaltered.

Evan
2005-Mar-09, 02:42 PM
think that if the mini BH (or primordial BH) were coming in from the interstellar space, it would be traveling, say, at some 200 km/s (maybe more).

Uh, no. The escape velocity of the Sun from the surface of the Sun is 617 kilometers per second. This means that if an object were placed at rest an infinite distance away (warning: though experiment!) that it would accelerate to 617 kps by the time it encountered the surface of the Sun. That is the minimum that an extrasolar object would accelerate to.

This velocity would be added to any already existing relative velocity the object has. It is reasonable to assume a few hundred kps intrinsic velocity that would be added to the 617 kps escape velocity of the Sun. So, the object would end up traveling at 1000 or so kps by the time it entered the Sun. It could easily be faster if it were extragalactic as the escape velocity of the Milky Way exceeds 1000 kps.

Bob
2005-Mar-09, 08:46 PM

CesarAKG postulated a mbh with the mass of an iceberg. Just for fun I assumed an iceberg 100 meters on a side (mass = 10**9 kg) and used the equations on the indicated link. Such a mbh would have an enormous temperature and be radiating an incredibly large amount of gamma radiation. I'm not sure it would absorb mass with that much photon flux pushing out of it. The collision would be spectacular, however.

wedgebert
2005-Mar-09, 09:11 PM
1/ Several posts above refer to Hawking radiation (HR) terminating the BH. That radiation occurs in inverse proportion to the mass of the BH and its consequent radius - or rather that of its event horizon - so that the smaller the Hole, the faster it loses mass from HR. But that assumes the BH is in empty space - this one will also be gaining mass as it captures matter through the EH, and that will be increasing as the cube of its mass.
John

A black hole the mass of an iceberg could form in the center of the sun and still radiate so much energy via Hawking Radiation that it would cease to exist.

A black hole the mass of an asteroid (few billion tons) would have a "temperature" of tens of millions degrees and would basically "explode" since it would convert all it's mass into Hawking Radiation.

Evan
2005-Mar-09, 10:13 PM
So postulate a MBH one thousand times more massive. The size grows to one tenth the size of a hydrogen atom and the luminosity falls to 356 watts. More important is that at a radius of a millimeter or so the gravity is less than one G. Inverse square law really kicks into gear when dealing with such a small object.

eburacum45
2005-Mar-10, 08:06 AM
A black hole the mass of an asteroid (few billion tons) would have a "temperature" of tens of millions degrees and would basically "explode" since it would convert all it's mass into Hawking Radiation.

Nope;
that is why I included the link to
Jim Wisniewski's Black Hole calculator here;
http://xaonon.dyndns.org/hawking/

a billion tonne black hole would have a temperature of a hundred billion degrees, but has such a smal radiating surface that it would last 8.4e19 seconds, which is a few hundred times the age of the universe.

DoktorGreg
2005-Mar-10, 08:38 AM
Have any sol stelar mass black hole candidates been discovered? It would seem if this were worth postulation you would need to find black hole candidates that have unusually small mass.

Argos
2005-Mar-10, 12:38 PM
Uh, no. The escape velocity of the Sun from the surface of the Sun is 617 kilometers per second. This means that if an object were placed at rest an infinite distance away (warning: though experiment!) that it would accelerate to 617 kps by the time it encountered the surface of the Sun. That is the minimum that an extrasolar object would accelerate to.

A thousand pardons. :)

Unforgivably, I didn“t take the Sun“s escape velocity into account while elaborating my post. I simply put out an abstract idea. Anyway, the core of the reasoning remains intact: it wouldn“t be trapped by the Sun. Thanks for pointing it.

Edited for style.

John Dlugosz
2005-Mar-10, 08:00 PM
Interesting that the mbh might not be slowed by the sun at all. Let's kick it up another notch: a mbh in orbit around the galaxy is sped up by its passage near the sun, as a gravitational slingshot.

bigsplit
2005-Mar-10, 08:19 PM
The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

Yeah, I'm with Evan on this one.

A) How do you fill a black hole? Adding mass to a black hole increases its event horizon.

B) What would it become?

C) If we assume the black hole to be a frictionless sphere (someone laugh, darn-it!), then it's clear that the only forces affecting it would be the sun's gravity, and the change in momentum due to the absorption of protons. Since proton motion in the sun is random, the net change in direction of the black hole due to interactions with protons (assuming the black hole to be electrically neutral, for fun) would be due entirely to the gravity of the sun. So, why is it stopping?

Once the mini black hole made contact with the Sun there would be some devastating effects. Since the matter falling into the BH has less density and the BH gravity well would be "polluted" with too large of particles for it to digest. Essentually, the MBH would be absorbed by the sun, or if you prefer, the inverse.

If the BH were bigger, would our sun simple pass through or bounce off the Sun. No, I don't think so. The gigantic sun would eat that MBH up and digest it. Whether it burps it out or just puts on a few pounds, I am not sure. I don't think it would vomit it right back out.

Evan
2005-Mar-10, 10:02 PM
Once the mini black hole made contact with the Sun there would be some devastating effects. Since the matter falling into the BH has less density and the BH gravity well would be "polluted" with too large of particles for it to digest. Essentually, the MBH would be absorbed by the sun, or if you prefer, the inverse.

That just doesn't make any sense.

wedgebert
2005-Mar-11, 03:43 AM
I don't believe there is such a thing as "too large a particle" or in a nother translation "too many particles" for a black hole to digest. The particle in question could be larger than the schwarzschild radius of the black hole, but as soon part of it crosses the event horizion, it's still going to be "sucked" in and torn apart. If there's too many particles, well the black hole doesn't care, they'll all end up occupying the same point in spacetime that we call a singularlity.

If you discount Hawking radiation (otherwise the mbh wouldn't exist for more than a very brief moment), if the mbh passes near the sun and doesn't reach escape velocity on the inbound leg, the sun is more than likely doomed. The only way for the sun to escape the mbh would be for the decaying orbit of the mbh to be so large that the sun continues it's normal life before the mbh is finally "caught".

If the mbh passes though the sun, it would absorb everything inside its swhwarzschild radius. As it does it will gain mass, increasing the SC radius, and there for absorbing more.

If the mbh has acheived escape velocity, then it will go about it's merry way. If it hasn't, it will eventually fall back into the sun. Once it does, this process will continue at an ever increasing rate until the sun is gone. Once that happens, life in the rest of the solar system will get quite dark and chilly, but otherwise continue on as normal.

Evan
2005-Mar-11, 07:05 AM
If the black hole is coming from outside the gravitational influence of the sun it must "reach" escape velocity. It's called a hyperbolic orbit. A hyperbolic orbit is mathematically "open". given that the black hole would certainly have some existing intrinsic velocity to approach this neighbourhood then it will have an excess above escape velocity. It isn't going to stick around.

It also isn't going to have the slightest problem swallowing whatever it encounters as the gravitational force at the event horizon is something like 10**40 G. But, because of the very small size that extreme G falls to less than one G at only less than a mm radius. The tidal forces are so extreme near the event horizon that the black hole may be able to rend particles. I have no idea what the consequence of that is but free quarks don't stay free for long. Go directly to jail.

I expect the passage of a MBH would be essentially frictionless or even accelerated by the attraction of matter on the leading edge. It may speed up as it encounters denser matter in the core of the sun. Once the matter enters the event horizon it is isolated from the universe.

According to the "no hair" principle black holes have only three properties, mass, spin and charge. Do they have inertia or momentum? It can only be accelerated or decelerated by gravity. There is no way to push or pull it with matter. It's like trying to push a wood chipper by sticking a pole in the throat. You just get back a shorter pole.

The interaction of a speeding black hole with dense matter is bound to be counter-intuitive.

Grey
2005-Mar-11, 07:18 AM
According to the "no hair" principle black holes have only three properties, mass, spin and charge. Do they have inertia or momentum? It can only be accelerated or decelerated by gravity.
I believe yes, they do have inertia (a direct result of having mass), and have momentum normally. Think of the black holes we've detected indirectly by their orbital behavior in binary star systems. And it would be possible to move a charged black hole with electric or magnetic fields.

Evan
2005-Mar-11, 07:38 AM
Re the magnetic fields I did mention that earlier. I'm not sure about the momentum and inertia. I guess that those are a consequence of the property "mass" and not a property themselves.

bigsplit
2005-Mar-11, 12:56 PM
As the mbh entered the sun, the explosion would disturb the curvature of gravity within the mbh. Given that there is more mass in the the sun that mBh is entering, these explosions would disturb the otherwise very organized spacetime curvature of the mBH to the extent that it would dissipate and all of its mass would be consumed by the sun. The process of ripping apart the mass that enters the mbh from the much more massive sun would take place far too quickly for the mbh to digest the mass and reorganize its spacetime curvature. The mbh would not make it.

Evan
2005-Mar-11, 02:36 PM
Absolutely not. The tidal effects of the Suns gravity are miniscule and would have no effect. A black hole does not have some sort of "appetite limit". Feeding it matter does not give it indigestion. Remember also we are talking about an object smaller than a hydrogen atom. It also has a surface gravity 10**38 (give or take a few orders) greater than the Sun. The only thing that could disrupt any black hole would be another black hole and it would merely eat it.

Nothing happens "far too quickly" for a black hole. At the event horizon the escape velocity is the speed of light with 100% time dilation.

Grey
2005-Mar-11, 02:38 PM
I'm not sure about the momentum and inertia. I guess that those are a consequence of the property "mass" and not a property themselves.
Right. Just like a black hole also has a radius to the event horizon, a temperature and so forth, but these can be determined from the mass. It's interesting to note, though, that Stephen Hawking now thinks black holes might have some hair after all.

Evan
2005-Mar-11, 04:34 PM
Yeah, but there is a lot of doubt about what Hawking is saying. Apparently a good deal of hand waving and short on specifics.

Grey
2005-Mar-11, 04:46 PM
Yeah, but there is a lot of doubt about what Hawking is saying. Apparently a good deal of hand waving and short on specifics.
I'd agree with that. I'll be intrigued to see how it works out.

pghnative
2005-Mar-11, 05:57 PM
If a black hole has momentum, which it seems it must, since it has both mass and velocity (a vector!), then why wouldn't it's momuntum change on interaction with other mass?

In other words, suppose I'm travelling at the same velocity (a vector!) as a companion black hole that is directly behind me (relative to our velocity), and I'm far enough outside the EH so I'm not torn apart. I aim my intergalactic space pistol (unlimited ammo) and continually shoot bullets toward the BH. (For giggles, I also use a second IGSP to shoot bullets at the same rate in the other direction, so that my velocity is unchanged). Eventually, won't the BH slow down relative to me, due to the conservation of momentum???

So by extension, wouldn't a BH travelling with a velocity relative to the sun, and travelling through the sun, interact with more particles on its leading edge, thereby slowing itself down??

Grey
2005-Mar-11, 06:07 PM
If a black hole has momentum, which it seems it must, since it has both mass and velocity (a vector!), then why wouldn't it's momuntum change on interaction with other mass?
It would.

In other words, suppose I'm travelling at the same velocity (a vector!) as a companion black hole that is directly behind me (relative to our velocity), and I'm far enough outside the EH so I'm not torn apart. I aim my intergalactic space pistol (unlimited ammo) and continually shoot bullets toward the BH. (For giggles, I also use a second IGSP to shoot bullets at the same rate in the other direction, so that my velocity is unchanged). Eventually, won't the BH slow down relative to me, due to the conservation of momentum???
Yes, that should be the case.

So by extension, wouldn't a BH travelling with a velocity relative to the sun, and travelling through the sun, interact with more particles on its leading edge, thereby slowing itself down??
I think the most important point is that the change in momentum would be small. Think of how many bullets you'd have to fire at that black hole to actually make a noticable difference. There are also issues of how its gravitational attraction to the nearby particles might affect its motion, so it might not be quite that simple, but its still going to be a small change.

Evan
2005-Mar-11, 06:56 PM
# First law of black hole dynamics: For interactions between black holes and normal matter, the conservation laws of mass-energy, electric charge, linear momentum, and angular momentum, hold. This is analogous to the first law of thermodynamics.

# Second law of black hole dynamics: With black-hole interactions, or interactions between black holes and normal matter, the sum of the surface areas of all black holes involved can never decrease. This is analogous to the second law of thermodynamics, with the surface areas of the black holes being a measure of the entropy of the system.

Note: No attribution. This is everywhere online.

Doodler
2005-Mar-11, 07:05 PM
Interesting that the mbh might not be slowed by the sun at all. Let's kick it up another notch: a mbh in orbit around the galaxy is sped up by its passage near the sun, as a gravitational slingshot.

Depending on the MBH's mass, planetary orbits and the Sun's proper motion could be seriously disrupted.

Evan
2005-Mar-11, 09:06 PM
Even a teratonne black hole is insignificant compared to the sun and planets. Also, the G drops with distance radically for such a tiny object. Because of this it can be considered as massless for the purpose of orbit calculation.

Bathcat
2005-Mar-11, 10:27 PM
"So by extension, wouldn't a BH travelling with a velocity relative to the sun, and travelling through the sun, interact with more particles on its leading edge, thereby slowing itself down??"

----

"I think the most important point is that the change in momentum would be small. Think of how many bullets you'd have to fire at that black hole to actually make a noticable difference. There are also issues of how its gravitational attraction to the nearby particles might affect its motion, so it might not be quite that simple, but its still going to be a small change."

----

Thought experiment: given a mini-black hole the size of a proton, calculate the number of particles -- say hydrogen nucleii, to make it simple -- it would encounter on a straightline path through the Sun, given its' extremely small cross-section.

(Sure the gravitational capture cross-section will be larger than the proton-sized Schwartzchild radius fo the BH, but as someone wisely noted the gravitational field loses strength so rapidly with distance that the effective cross-section will still be awfully small.)

Find the mass of that number of particles.

Compare that mass to the mass of a proton-sized black hole.

----

For a back-of-the-napkin guess, you could simply use the average density of the Sun I suppose in units of atomic-masses-per-cc and its mean diameter, and go from there.

Evan
2005-Mar-12, 12:33 AM
Ok. Assume the gigatonne MBH sweeps up all the matter in an approximately 0.5mm radius. To make it easy just assume it is sweeping out a sq mm. Average density of the Sun is 1.4 gm per cc. Diameter is 1,400,000 km. Total matter consumed by the MBH is only 200 tonnes. If we assume that this matter is all at rest with respect to the black hole and it all subtracts from the momentum of the black hole then the MBH slows by 0.00002 percent. Even if it swept out an entire square centimeter it would only slow by 0.02 percent.

Zoom.... See ya.

bigsplit
2005-Mar-12, 05:18 AM
Absolutely not. The tidal effects of the Suns gravity are miniscule and would have no effect. A black hole does not have some sort of "appetite limit". Feeding it matter does not give it indigestion. Remember also we are talking about an object smaller than a hydrogen atom. It also has a surface gravity 10**38 (give or take a few orders) greater than the Sun. The only thing that could disrupt any black hole would be another black hole and it would merely eat it.

Nothing happens "far too quickly" for a black hole. At the event horizon the escape velocity is the speed of light with 100% time dilation.

I am sorry Evan but you are completely wrong here. As the mass enters the black hole it begins to lose its energy through violent means. These violent explosions disrupt the curvature of spacetime within the blackhole. If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization. Eventually, the mass of the BH would blend in with the mass of the sun. I do not know what kind of theoretical nonsense you are grasping onto that does not allow you to understand this, but you need to think this through. Black Holes and ordinary matter do not get along and there will be a clash...the biggest will win.

The escape velocity will be altered due to the disturbances created by the violence of lots of new matter entering the BH, breaking down and releasing energy. So essentually, I am not saying anything will escape. A continuous flow of less dense mass being compressed will cause a chain of disruptions to the curvature within the event horizon that will alter the surface gravity of the BH, the mBH will not have the opportunity to reorganize its curvature and new mass is continually entering in our example. The mBH we have describe will break down in short order if such a thing were to enter the sun.

eburacum45
2005-Mar-12, 05:50 AM
Are you just making this up as you go along?

Or do you have any references for these assertions. As far as I can see they are all completely wrong, but you may know better.
Please note, this is the General Astronomy forum, not the Against the mainstream forum. Here you need to back up your statements.

Grey
2005-Mar-12, 05:57 AM
Please note, this is the General Astronomy forum, not the Against the mainstream forum. Here you need to back up your statements.
Hey, even in the Against the Mainstream forum you have to back up your assertions. :D

Evan
2005-Mar-12, 06:34 AM
Bigsplit,

# Second law of black hole dynamics: With black-hole interactions, or interactions between black holes and normal matter, the sum of the surface areas of all black holes involved can never decrease. This is analogous to the second law of thermodynamics, with the surface areas of the black holes being a measure of the entropy of the system.

It means just what it says. No matter what happens in interactions with normal matter the size of a black hole does not decrease, let alone disappear. What you say is impossible within the accepted and theoretically consistent behaviour of black holes.

Kaptain K
2005-Mar-12, 12:56 PM
If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization.
The mas within a black hole has no organization! It is a singularity. A point mass (zero height, zero width, zero depth) of infinite density! There is no internal structure to disrupt!

wedgebert
2005-Mar-12, 03:33 PM
I am sorry Evan but you are completely wrong here. As the mass enters the black hole it begins to lose its energy through violent means. These violent explosions disrupt the curvature of spacetime within the blackhole. If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization. Eventually, the mass of the BH would blend in with the mass of the sun. I do not know what kind of theoretical nonsense you are grasping onto that does not allow you to understand this, but you need to think this through. Black Holes and ordinary matter do not get along and there will be a clash...the biggest will win.

The escape velocity will be altered due to the disturbances created by the violence of lots of new matter entering the BH, breaking down and releasing energy. So essentually, I am not saying anything will escape. A continuous flow of less dense mass being compressed will cause a chain of disruptions to the curvature within the event horizon that will alter the surface gravity of the BH, the mBH will not have the opportunity to reorganize its curvature and new mass is continually entering in our example. The mBH we have describe will break down in short order if such a thing were to enter the sun.

And you accuse Evan of grasping on to theoritcal nonsense?

What do you mean by "disruptions to the curvature within the event horizion?" Excluding the mass that's currently falling into the singularity, ALL the mass of a black hole resides at the singularity. Basically, a black hole is a POINT object. No amount of external gravity can change that because there is only one point to affect.

You can't "break down" a black hole anymore than you can break down the letter "A" into smaller letters.

Also, to address your second sentence, as a matter falls into a black hole, it actually GAINS energy. The matter is being accelerated which results in increased energy. This is how we detect black holes, the extra energy exites the atoms in the matter and it begins to give off EM radiation.

To be blunt, every point in your post is wrong. (so just forget the words and sing along...sorry Weird Al moment)

Evan
2005-Mar-12, 05:00 PM
Back to summing up the answer to the question posed by this topic:

1: Almost certainly a MBH will arrive from interstellar space and therefore be on a hyperbolic orbit with velocity in excess of solar system escape velocity.

2 A gigatonne or teratonne black hole will last long enough to still exist since BB.

3: The matter accreted during passage through the Sun is insignificant.

4: The passage of the MBH through the Sun is essentially "frictionless".

5: The black hole will leave the solar system.

The only question to answer is what effect if any will this have on the Sun.

Grey
2005-Mar-12, 05:16 PM
The only question to answer is what effect if any will this have on the Sun.
I'd expect none of note. As you've pointed out, the amount of mass removed is insignificant and the gravitational effect will be negligible. It might be shining brightly enough that we'd at least see it, or detect some high energy gamma rays, but that's probably about it. And I'm not even sure about seeing it. It will have a high temperature, but a really small surface area, so I wouldn't imagine that the luminosity would be very high.

wedgebert
2005-Mar-12, 07:10 PM
Ok. Assume the gigatonne MBH sweeps up all the matter in an approximately 0.5mm radius. To make it easy just assume it is sweeping out a sq mm. Average density of the Sun is 1.4 gm per cc. Diameter is 1,400,000 km. Total matter consumed by the MBH is only 200 tonnes. If we assume that this matter is all at rest with respect to the black hole and it all subtracts from the momentum of the black hole then the MBH slows by 0.00002 percent. Even if it swept out an entire square centimeter it would only slow by 0.02 percent.

Zoom.... See ya.

I found a nice page that will calculate all kinds of BH data here (http://xaonon.dyndns.org/hawking/). Not sure if it's 100% correct, but it looks good so far.

Anyways, according to that site, a gigaton bh would only have a radius of 0.000001484852 nanometers which would result in much less mass being absorbed and thus even less deceleration on the part of the mbh.

In fact, with a temperature of 1.227*10^11 Kelvin, the mbh might still experience a net loss in energy and mass.

eburacum45
2005-Mar-12, 08:56 PM
heh heh...
I've linked to that page twice now, Wedgebert;
and incidentally, Jim is a sometime contributor to OA- one of his stories can be found here:
Chaos Under Heaven (http://www.orionsarm.com/stories/Chaos_Under_Heaven.htm)

Grey
2005-Mar-12, 09:55 PM
It will have a high temperature, but a really small surface area, so I wouldn't imagine that the luminosity would be very high.
So, converting the luminosity to a magnitude, a gigaton black hole at the same distance as the Sun would be something like magnitude +19. You could spot it in a decent telescope, but you probably wouldn't see it unless you were looking for it, picked it up by chance, or its path through the solar system happened to take it much closer to Earth.

Bathcat
2005-Mar-12, 11:05 PM
The escape velocity will be altered due to the disturbances created by the violence of lots of new matter entering the BH, breaking down and releasing energy.

I'm not sure, of course, but perhaps what is meant here is the observation that infalling matter causes the singularity to oscillate chaotically. More correctly, if I recall, the tidal gravitation near the singularity would oscillate chaotically -- a 'mixmaster singularity' I think Kip Thorne called it in his book.

But he does NOT say that the singularity is unstable or will be destroyed: quite the contrary. As far as I can remember, outside of evaporation through the Hawking radiation (reference (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html)) mechanism there ain't nothing known that destroys a black hole.

And I don't think that Thorne's description of a mixmaster singularity implies that the event horizon of the black hole shows any signs of the tidal turmoil within. As far as the Sun and any observers are concerned, it is utterly impossible to see any sign that the singularity itself is 'disturbed'. One cannot even tell if it prefers Budweiser or Pepsi: the black hole hides everything about itself except its mass, spin, and electric charge.

----

No doubt hydrogen nucleii and free electrons pulled from the Sun's plasma and falling toward the mini-black hole's event horizon would accelerate. But...isn't the main cause of energetic emissions from black-hole accretion disks the compression and heating of the infalling material?

Look at the real physics of the thing: the mBH is particle-sized, the dimensions of a proton or smaller. There is no accretion disk to speak of, only a microscopic swirl of protons and electrons falling, in a matter of microseconds, into the hole.

I am just not convinced there would be any appreciable radiation from this microscopic swirl. I think that, as implied by others, the Hawking radiation of the mBH itself would be more energetic than the radiation produced by the trickle of infalling matter.

----

Here's a problem for a physics student: a black hole and a star like the Sun are pretty simple objects overall. One should be able to calculate the gravity at various distances from the center of mass for a gigatonne mBH. One should be able to find the kinetic energy of the particles in the Sun at various temperature/pressures (it seems to me that their energy would determine the radius of the capture sphere for a mBH of given mass).

I would think that from that one could find the radius of capture -- (terminology??) -- for a spectrum of conditions inside the Sun and pin down the rate of particle capture as the mBH moves through the layers of the Sun. (More tightly than the excellent back-of-the-napkin calc already provided, which I would bet is a very generous upper limit on the accreted matter.)

One ought to be able to figure out the dimensions of the infall area, and the density change in the infalling matter -- its compression, and therefore its change in temperature.

I'm not going to try it, 'cos my maths ain't able. But it should be doable, right?

JohnD
2005-Mar-12, 11:06 PM
That's counterintuitive!

A point that small, that bright, and it would last longer than the Universe? Somehow I had the impression that by the time a miniBH got small enough to shine in visible light it would rapidly annihilate itself. Wow!

John

Evan
2005-Mar-12, 11:28 PM
I would think that from that one could find the radius of capture -- (terminology??) -- for a spectrum of conditions inside the Sun and pin down the rate of particle capture as the mBH moves through the layers of the Sun. (More tightly than the excellent back-of-the-napkin calc already provided, which I would bet is a very generous upper limit on the accreted matter.)

Yeah. I intentionally made it as generous as possible without choking. For one thing one half of the protons swept up should have some motion in the direction the black hole is traveling although it should average to zero. It really doesn't matter much because the loss of momentum is so slight that it can be effectively ignored.

I wonder how a MBH compares to a neutrino in terms of how much lead it takes to bring it to a halt? The key factor is what is the radius of accretion? Keep in mind that if the MBH is clipping along at 1000 kilometers per second then any atom or particle not directly in its path has a LOT of relative angular momentum.

Bathcat
2005-Mar-13, 12:30 AM
Yeah, Evan, I had understood that you were making the most generous assumptions and thereby were giving an upper bound for the amount of matter accreted. That's very useful of course 'cos it gives an idea what the limiting case might be.

I'd guess that the thing with comparing neutrinos and subatomic-sized black holes is that neutrinoes are tremendously light-mass, while mBHs would be unutterably massive compared to any subatomic particle.

Geez -- interesting comparison you've brought up. Neutrinos have very little momentum, right? I mean their mass is quite tiny, so although they travel very fast they would be stopped dead if only they interacted electromagnetically with protons and electrons.

It's only 'cos they interact only through the weak force and gravity that they zip through the Earth as if it was less than a kleenex tissue.

But mBHs would have immense mass compared to a neutrino or even a proton -- utterly IMMENSE. And so even though they might be expected to be traveling much slower than a neutrino, they would have immense momentum.

Um. I'm thinking as I type, which generally leads me to boneheadedness...

A mBH would not interact electromagnetically, right? It's not expected to have a charge (at least I've never understood that a black hole would become electrically charged by any known physical mechanism?). So effectively it couples to surrounding particles gravitationally but not electromagnetically or via the weak or strong forces?

Now gravity being a very wimpy force as far as subatomic particles are concerned, and a mBH's momentum being absolutely immense as far as subatomic-sized entities are concerned...

Hmmm! I have to go away and think a bit.

Grey
2005-Mar-13, 01:19 AM
A mBH would not interact electromagnetically, right? It's not expected to have a charge (at least I've never understood that a black hole would become electrically charged by any known physical mechanism?). So effectively it couples to surrounding particles gravitationally but not electromagnetically or via the weak or strong forces?
A black hole doesn't have to be charged, but it can be. So it's at least possible for it to interact electromagnetically. I've never really thought about whether it could interact via the strong or weak nuclear forces. If it doesn't preserve baryon or lepton number, my offhand thought would be no, but I imagine we might need a quantum theory of gravity to really answer that question.

Bathcat
2005-Mar-13, 01:43 AM
Grey: "...but I imagine we might need a quantum theory of gravity to really answer that question ."

In quantum mechanics we disregard gravitation because it is so weak it plays no perceptible role in particle interactions.

A proton-sized black hole would be a [i]quantum-scale entity with a very perceptible gravitational field.

We do not have a theory which adequately describes such entities, right? Gravitation has not yet been reconciled with quantum physics.

But surely some bright young star, somewhere, has considered mini-black holes as quantum objects? What other reason do universities keep grad students hungry and anxious if not to spur them to consider the inconsiderable??

Grey
2005-Mar-13, 03:34 PM
A proton-sized black hole would be a quantum-scale entity with a very perceptible gravitational field.

We do not have a theory which adequately describes such entities, right? Gravitation has not yet been reconciled with quantum physics.
Exactly. And not even just a perceptible field, but one strong enough that we'd absolutely have to use general relativity to describe it.

But surely some bright young star, somewhere, has considered mini-black holes as quantum objects? What other reason do universities keep grad students hungry and anxious if not to spur them to consider the inconsiderable??
This (http://xxx.lanl.gov/abs/gr-qc/9803049) paper looks particularly relevant, and this (http://xxx.lanl.gov/abs/gr-qc/0304042) one looks interesting as well.

bigsplit
2005-Mar-13, 10:24 PM
I am sorry Evan but you are completely wrong here. As the mass enters the black hole it begins to lose its energy through violent means. These violent explosions disrupt the curvature of spacetime within the blackhole. If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization. Eventually, the mass of the BH would blend in with the mass of the sun. I do not know what kind of theoretical nonsense you are grasping onto that does not allow you to understand this, but you need to think this through. Black Holes and ordinary matter do not get along and there will be a clash...the biggest will win.

The escape velocity will be altered due to the disturbances created by the violence of lots of new matter entering the BH, breaking down and releasing energy. So essentually, I am not saying anything will escape. A continuous flow of less dense mass being compressed will cause a chain of disruptions to the curvature within the event horizon that will alter the surface gravity of the BH, the mBH will not have the opportunity to reorganize its curvature and new mass is continually entering in our example. The mBH we have describe will break down in short order if such a thing were to enter the sun.

And you accuse Evan of grasping on to theoritcal nonsense?

What do you mean by "disruptions to the curvature within the event horizion?" Excluding the mass that's currently falling into the singularity, ALL the mass of a black hole resides at the singularity. Basically, a black hole is a POINT object. No amount of external gravity can change that because there is only one point to affect.

You can't "break down" a black hole anymore than you can break down the letter "A" into smaller letters.

Also, to address your second sentence, as a matter falls into a black hole, it actually GAINS energy. The matter is being accelerated which results in increased energy. This is how we detect black holes, the extra energy exites the atoms in the matter and it begins to give off EM radiation.

To be blunt, every point in your post is wrong. (so just forget the words and sing along...sorry Weird Al moment)

I am not wrong, sorry to tell you. Inside the event horizon is all singularity. If the diameter of the event horizon is the size of the pea, the singularity is the size of a pea. At the event horizon all things are accelerated at the speed of light and gravity cannot be any stronger, so their is no "point of mass", it could well be anywhere withing the event horizon. Any disturbance to the event horizon will result in leakage of mass and a disturbance of the sigularity. If the mass of the BH is greater BH will grow, if the source of mass has a greater mass then the mass of the BH will "decompress" if you will. It is not really that difficult, honestly.

Bathcat
2005-Mar-13, 11:59 PM
"Inside the event horizon is all singularity."

Not according to the physics I've read.

Thorne (co-author of Gravitation, with Misner and Wheeler) describes the hypothetical view of an astronaut falling through the event horizon. His physics leads him to conclude that for a very massive black hole the astronaut would notice nothing unusual as he passed the location of the event horizon.

The astronaut would continue to fall toward the singularity at the center, though once past the critical circumference nothing he could do could make his spacecraft reverse course and head away from the singularity. He could not even stop falling. But it would be through 'ordinary' spacetime that he falls.

As he approached the singularity he would begin to feel the squeeze-and-stretch of tidal gravitation. Eventually it would be so strong he would be destroyed.

Thorne describes the singularity itself as as subatomic-sized region at the center of the black hole where space (possibly) degenerates into quantum probabilities and time is destroyed.

Anyways, amigo, with all respect, what you describe is not the understanding reached by relativistic physicists.

addendum, later: The above sounds like I'm arguing from a position of received wisdom or arguing on authority. That's not my intent. What I am trying to say is that the standard model with regard to relativity and black holes does not follow the outline you suggest.

---

Grey -- thanks for the links. I'm into the last section of the first one, the part on a canonical treatment of quantum gravitation. Sheesh -- heavy going for a layman, but fascinating.

bigsplit
2005-Mar-14, 01:40 AM
"Inside the event horizon is all singularity."

Not according to the physics I've read.

Thorne (co-author of Gravitation, with Misner and Wheeler) describes the hypothetical view of an astronaut falling through the event horizon. His physics leads him to conclude that for a very massive black hole the astronaut would notice nothing unusual as he passed the location of the event horizon.

The astronaut would continue to fall toward the singularity at the center, though once past the critical circumference nothing he could do could make his spacecraft reverse course and head away from the singularity. He could not even stop falling. But it would be through 'ordinary' spacetime that he falls.

As he approached the singularity he would begin to feel the squeeze-and-stretch of tidal gravitation. Eventually it would be so strong he would be destroyed.

Thorne describes the singularity itself as as subatomic-sized region at the center of the black hole where space (possibly) degenerates into quantum probabilities and time is destroyed.

Anyways, amigo, with all respect, what you describe is not the understanding reached by relativistic physicists.

addendum, later: The above sounds like I'm arguing from a position of received wisdom or arguing on authority. That's not my intent. What I am trying to say is that the standard model with regard to relativity and black holes does not follow the outline you suggest.

---
.

I do not understand why the "tidal forces" would not rip him apart as he was entering the event horizon. Within the event horizon I visualize raw energy, with little or no coupling. I see everything within the event horizon as a single particle essentually . Once you enter the EH there will be no center of gravity and time is indistiguishable at this point and gravity has reached its limit. A sorta contained lake of energy in a vacuum is how I see a BH. The entire system is a singularity, not in a 3D point, but in a 4D sense. The 3D can grow and be large or small, but the 4th D is fixed and is what make it a singularity.

wedgebert
2005-Mar-14, 03:11 AM
I am not wrong, sorry to tell you. Inside the event horizon is all singularity. If the diameter of the event horizon is the size of the pea, the singularity is the size of a pea. At the event horizon all things are accelerated at the speed of light and gravity cannot be any stronger, so their is no "point of mass", it could well be anywhere withing the event horizon. Any disturbance to the event horizon will result in leakage of mass and a disturbance of the sigularity. If the mass of the BH is greater BH will grow, if the source of mass has a greater mass then the mass of the BH will "decompress" if you will. It is not really that difficult, honestly.

Yes, according to all theories of physics, you are wrong.

When a black hole forms, its gravity is powerful enough to overcome the Pauli Exclusion Principle which says that no two fermions can share the same quantum numbers. Or more simply, two particles cannot occupy the same position at the same time.

Sufficed to, for a Schwarzschild black hole (one that does not rotate), aside from stuff still falling into the singularity, all the mass of the BH is in a single point, probably a Planck length across.

For a Kerr (rotating) black hole, the singularity forms more of a torus, depending on how fast the black hole spins. This leads to all kinds of interesting things, the most interesting of which is the addition of a second event horizion and the possiblity of a naked singularity.

Either way, the event horizion is not a balloon that can be "popped" or "deflated" as you speak. The ONLY way for a black hole to "die" is via Hawking Radiation.

You're right, it's not that difficult though. If the temperature generated by Hawking radiation is greater than what the black hole can eat, the black hole will shrink, otherwise it will grow. It doesn't matter if it's a million solar mass black hole eating a small planet, or a megaton black hole falling into a neutron star. Given the temperature differential, the black hole wins, regardless of mass.

bigsplit
2005-Mar-14, 03:43 AM
I am not wrong, sorry to tell you. Inside the event horizon is all singularity. If the diameter of the event horizon is the size of the pea, the singularity is the size of a pea. At the event horizon all things are accelerated at the speed of light and gravity cannot be any stronger, so their is no "point of mass", it could well be anywhere withing the event horizon. Any disturbance to the event horizon will result in leakage of mass and a disturbance of the sigularity. If the mass of the BH is greater BH will grow, if the source of mass has a greater mass then the mass of the BH will "decompress" if you will. It is not really that difficult, honestly.

Yes, according to all theories of physics, you are wrong.

When a black hole forms, its gravity is powerful enough to overcome the Pauli Exclusion Principle which says that no two fermions can share the same quantum numbers. Or more simply, two particles cannot occupy the same position at the same time.

Sufficed to, for a Schwarzschild black hole (one that does not rotate), aside from stuff still falling into the singularity, all the mass of the BH is in a single point, probably a Planck length across.

For a Kerr (rotating) black hole, the singularity forms more of a torus, depending on how fast the black hole spins. This leads to all kinds of interesting things, the most interesting of which is the addition of a second event horizion and the possiblity of a naked singularity.

Either way, the event horizion is not a balloon that can be "popped" or "deflated" as you speak. The ONLY way for a black hole to "die" is via Hawking Radiation.

You're right, it's not that difficult though. If the temperature generated by Hawking radiation is greater than what the black hole can eat, the black hole will shrink, otherwise it will grow. It doesn't matter if it's a million solar mass black hole eating a small planet, or a megaton black hole falling into a neutron star. Given the temperature differential, the black hole wins, regardless of mass.

Well, I guess since no will will ever be able to go into one and report back as to what they see, we will never know for sure.

I still think that once mass crosses the EH it is destroyed and reduced to pure energy. I do not think all of the mass is maintain in a single point or a torus, since everything is accelerating at the speed of Light, the mass could be anywhere and everywhere within the event horizon. Once mass enters the BH and the EH is disturbed, mass can be lost. Certainly, the BH in most cases would be dominate enough to recapture any lost mass, but the mBH we were discussing would not be such a beast in relation to the sun. Further, since the energy within the EH is in free flow, there would be instances of the reassemble of particles from the energy at the event horizon all of the time. As this occurs the particle is recapture and ripped apart again. This may be the source of hawkins radiation as some particles may be able to escape the Gravity. That is if such a thing as hawkins radiation exists at all.

Evan
2005-Mar-14, 05:28 AM
Bigsplit,

You are espousing utter nonsense. I hesitate to say this so strongly but there is no school of thought that agrees with you. As I pointed out twice before, the second "law" of black hole dynamics states that a black hole radius can only INCREASE in an encounter with matter. There is no other option. It is equivalent to the laws of thermodynamics. What you propose is equivalent to complete reversal of entropy. This is no more possible than an over unity machine.

Kaptain K
2005-Mar-14, 06:29 AM
I still think that once mass crosses the EH it is destroyed and reduced to pure energy. I do not think all of the mass is maintain in a single point or a torus, since everything is accelerating at the speed of Light, the mass could be anywhere and everywhere within the event horizon.

bigsplit,

The universe does not care what you think!

Doodler
2005-Mar-14, 01:59 PM
If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization.
The mas within a black hole has no organization! It is a singularity. A point mass (zero height, zero width, zero depth) of infinite density! There is no internal structure to disrupt!

You sure about that? Last I checked, no one had seen anything below the event horizon and given that black holes do evaporate, matter below the horizon obviously escapes at some point. I can buy it being an ultradense object, but you're not getting a singularity without extraordinary proof of this.

bigsplit
2005-Mar-14, 03:00 PM
Bigsplit,

You are espousing utter nonsense. I hesitate to say this so strongly but there is no school of thought that agrees with you. As I pointed out twice before, the second "law" of black hole dynamics states that a black hole radius can only INCREASE in an encounter with matter. There is no other option. It is equivalent to the laws of thermodynamics. What you propose is equivalent to complete reversal of entropy. This is no more possible than an over unity machine.

Technically, any conclusion about what goes on inside a blackhole is nonsense, since we cannot use any of our senses to observe what is going on in there. So any "law" about the dynamics of a blackhole is pretencious babbleing, particularily since they make absolutely no sense at all. Once you accelerate to the speed of light, which is the speed of gravity all particles are broken down via a "big rip", all that is left is unorganized energy. This energy is not concentrated at an 3D singularity of plank size....ridiculous. The entire area within the EH is a singularity. The entire area is essentually a single particle. Within the EH there is no varying gradient of G, it is a dead zone, G has a limit and it is reached at the EH. The area of the black hole can expand with addition of more mass, I agree. Within the blackhole there is no center of gravity. As mass enters the BH there are disturbances to the EH that would allow mass to escape.

Grey
2005-Mar-14, 03:15 PM
Technically, any conclusion about what goes on inside a blackhole is nonsense ... So any "law" about the dynamics of a blackhole is pretencious babbleing, particularily since they make absolutely no sense at all.

This energy is not concentrated at an 3D singularity of plank size....ridiculous. The entire area within the EH is a singularity. The entire area is essentually a single particle.
Now, I don't necessarily agree with your first statement here. But assuming that you do (since you wrote it, after all), you would seem to be describing your next statements as "nonsense" and "pretencious babbleing [sic]" that "make absolutely no sense at all".

Evan
2005-Mar-14, 04:05 PM
Once you accelerate to the speed of light, which is the speed of gravity all particles are broken down via a "big rip", all that is left is unorganized energy. This energy is not concentrated at an 3D singularity of plank size....ridiculous. The entire area within the EH is a singularity. The entire area is essentually a single particle. Within the EH there is no varying gradient of G, it is a dead zone, G has a limit and it is reached at the EH

Why do you think this is so? It is NOT consistent with the mathematics that describe a black hole. The mathematics predict a singularity of infinite density and therefore infinitely small. Both conditions are a requirement for a black hole to exist within the logical mathematical framework that describes a black hole. The event horizon is not a physical structure and has no existence except as a consequence of the amount of mass in the singularity. The event horizon does not contain the singularity, it hides it.

Arkyan
2005-Mar-14, 04:40 PM
An event horizon is not some mystical or mysterious barrier beyond which matter transforms, nor is it some kind of physical barrier that contains a black hole. It is simply a defined radius around a black hole inside which gravity is so strong that not even light can escape. Because information cannot (theoretically) escape the event horizon, for all practical intents and purposes one might describe the EH as being the boundary of the black hole itself, from from a standpoint of physics and the arguments above, the surface of the black hole does not coincide with the event horizon!

bigsplit
2005-Mar-14, 05:07 PM
An event horizon is not some mystical or mysterious barrier beyond which matter transforms, nor is it some kind of physical barrier that contains a black hole. It is simply a defined radius around a black hole inside which gravity is so strong that not even light can escape. Because information cannot (theoretically) escape the event horizon, for all practical intents and purposes one might describe the EH as being the boundary of the black hole itself, from from a standpoint of physics and the arguments above, the surface of the black hole does not coincide with the event horizon!

At the EH what is the speed of gravity so that not even light can escape? The gravity can get no stronger as I understand its limit is C universally. So, within the EH there is no gravitational Gradiant it is uniformly C and no special direction towards any 3D singularity it is a gravitational Duldrum. As for matter transforming, the Big Rip theory says as an object's acceleration approaches C, it is ripped apart. What am I missing here?

wedgebert
2005-Mar-14, 05:19 PM
If everything inside the event horizion is the singularity, how do you explain the dual event horizions of a rotating black hole?

According to current theory, basically what happens when you cross the event horizion is that spacetime becomes so warped by the gravity of the singularity, that space and time are swapped. The singularity is no longer X distance way, now it's X time away. You cannot escape because the singularity is now a point in your future instead of a point in space beside you.

Now when you cross the second event horizion of a rotating black hole, space and time flip-flop again. The singularity once again becomes a point in space, not time. However you're still doomed because you cannot remain motionless.

The radius of the inner event horizion is determined by how fast the singluarity is rotating. Again, according to theory, if the rotational energy of the black hole exceeds the gravitational energy, the second event horizion will extend past the first and you'll be left with a "naked singularity". This is basically a singularity that has no event horizion.

Arkyan
2005-Mar-14, 06:01 PM
At the EH what is the speed of gravity so that not even light can escape? The gravity can get no stronger as I understand its limit is C universally. So, within the EH there is no gravitational Gradiant it is uniformly C and no special direction towards any 3D singularity it is a gravitational Duldrum. As for matter transforming, the Big Rip theory says as an object's acceleration approaches C, it is ripped apart. What am I missing here?

Okay. I'm not saying that things don't change within the EH, just that the EH is a function of the black hole's gravity and not an independent construct of its own. I don't see how the "big rip" theory applies to matter falling into a black hole, as far as I know matter is torn up by tidal forces and not a big rip when falling into a black hole, but, I don't know enough about the theory to say. As far as gravity having an upper limit to its strength? That's a new one on me. We all know that gravity propagates at C, yes, but to say that gravity has a "limit" at which it can't pull any further, I'm not sure what you are referring to. Even if, as you say, there is a gravitational "doldrum" and lack of gradient beyond the EH, and we assume you are right in saying that incoming matter cannot be accelerated any further, the source of the gravity is still a point at the center of the black hole and matter will still be pulled toward that singulartiy, not suddenly cease movement just because it stops accelerating!

bigsplit
2005-Mar-14, 06:51 PM
At the EH what is the speed of gravity so that not even light can escape? The gravity can get no stronger as I understand its limit is C universally. So, within the EH there is no gravitational Gradiant it is uniformly C and no special direction towards any 3D singularity it is a gravitational Duldrum. As for matter transforming, the Big Rip theory says as an object's acceleration approaches C, it is ripped apart. What am I missing here?

Okay. I'm not saying that things don't change within the EH, just that the EH is a function of the black hole's gravity and not an independent construct of its own. I don't see how the "big rip" theory applies to matter falling into a black hole, as far as I know matter is torn up by tidal forces and not a big rip when falling into a black hole, but, I don't know enough about the theory to say. As far as gravity having an upper limit to its strength? That's a new one on me. We all know that gravity propagates at C, yes, but to say that gravity has a "limit" at which it can't pull any further, I'm not sure what you are referring to. Even if, as you say, there is a gravitational "doldrum" and lack of gradient beyond the EH, and we assume you are right in saying that incoming matter cannot be accelerated any further, the source of the gravity is still a point at the center of the black hole and matter will still be pulled toward that singulartiy, not suddenly cease movement just because it stops accelerating!

Upper limit to strength no, speed yes....the additional strenghth will be translated into size of the BH.

Here is something new.

http://rl.channel.aol.com/natgeo?id=20050303090609990001

Enough said....I will be looking for my nobel soom.......lol.

Kaptain K
2005-Mar-14, 07:30 PM
If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization.
The mas within a black hole has no organization! It is a singularity. A point mass (zero height, zero width, zero depth) of infinite density! There is no internal structure to disrupt!

You sure about that? Last I checked, no one had seen anything below the event horizon and given that black holes do evaporate, matter below the horizon obviously escapes at some point. I can buy it being an ultradense object, but you're not getting a singularity without extraordinary proof of this.
Blac holes do not evaporate by particles escaping from the interior. The strength of the gravitational field is so strong at the EH that virtual pairs are created in normal space. Occasionally, one of the two particles can escape, resulting in a net loss of energy (ergo - mass, from E=mc^2).

bigsplit
2005-Mar-14, 07:40 PM
If the black hole is constantly exposed to a continuous inflow of matter eventually the disruptions to the spacetime curvature within the hole will be too great for the mass within the black hole to maintain its organization.
The mas within a black hole has no organization! It is a singularity. A point mass (zero height, zero width, zero depth) of infinite density! There is no internal structure to disrupt!

You sure about that? Last I checked, no one had seen anything below the event horizon and given that black holes do evaporate, matter below the horizon obviously escapes at some point. I can buy it being an ultradense object, but you're not getting a singularity without extraordinary proof of this.
Blac holes do not evaporate by particles escaping from the interior. The strength of the gravitational field is so strong at the EH that virtual pairs are created in normal space. Occasionally, one of the two particles can escape, resulting in a net loss of energy (ergo - mass, from E=mc^2).

The energy that creates the virtual pair has to come from the interior. The mechanism that causes these particles to be generated outside of the EH is the question. However, the energy must have come from inside the BH or it would not lose mass.

In my argument of a BH that has radom distribution of its mass as energy, this energy could leak just beyound the EH where the G is less than C, this energy could then form particles as the nuclear forces could couple the energy. These particles would be destoyed almost instantly allowing the possibility of some form of evaporation. Let's face it, a new model of BHs is needed.

Kristophe
2005-Mar-14, 07:53 PM
In my argument of a BH that has radom distribution of its mass as energy, this energy could leak just beyound the EH where the G is less than C, this energy could then form particles as the nuclear forces could couple the energy. These particles would be destoyed almost instantly allowing the possibility of some form of evaporation. Let's face it, a new model of BHs is needed.

But your argument is complete jibberish. No one here has been able to follow it, and you've gone so far as to say 'we have no idea what goes on inside the event horizon of a black hole... so I'm right.' So, why should we throw out the math -- all of which is based on GR, which has stood up to all of the tests so far. The only problems come about when you get down to quantum scales, which you seem to be claiming isn't necessary since the singular point -- the singularity if you will -- doesn't exist.

Tensor
2005-Mar-14, 07:56 PM
The energy that creates the virtual pair has to come from the interior. The mechanism that causes these particles to be generated outside of the EH is the question. However, the energy must have come from inside the BH or it would not lose mass.

Not true, the energy comes from the space-time warpage outside the EH. It is the gravitational energy outside the EH that keeps the hole together. It is part of the mass of the hole and is constantly regenerated by due to the non-linearity of Gravity.

In my argument of a BH that has radom distribution of its mass as energy, this energy could leak just beyound the EH where the G is less than C,

In Newtonian gravity, this could happen. Not in General Relativity. Particles inside the hole would have to travel faster than c to get out of the hole.

this energy could then form particles as the nuclear forces could couple the energy. These particles would be destoyed almost instantly allowing the possibility of some form of evaporation.

It is the gravitational energy of the hole that the virtual particles borrow to become real particles. Those created real particles usually recombine with each other and no energy (or mass is lost) (it is given back to the hole). If one particle happens to fall into the hole and the other escapes, then the energy (and mass) of the hole has decreased.

Let's face it, a new model of BHs is needed.

Nope, just your understanding of Black Holes as described by the current combination of General Relativity and QM.

bigsplit
2005-Mar-14, 09:12 PM
In my argument of a BH that has radom distribution of its mass as energy, this energy could leak just beyound the EH where the G is less than C, this energy could then form particles as the nuclear forces could couple the energy. These particles would be destoyed almost instantly allowing the possibility of some form of evaporation. Let's face it, a new model of BHs is needed.

But your argument is complete jibberish. No one here has been able to follow it, and you've gone so far as to say 'we have no idea what goes on inside the event horizon of a black hole... so I'm right.' So, why should we throw out the math -- all of which is based on GR, which has stood up to all of the tests so far. The only problems come about when you get down to quantum scales, which you seem to be claiming isn't necessary since the singular point -- the singularity if you will -- doesn't exist.

Jibberish???

No one has yet to explain how a gradiant is formed within the EH that would generate a singularity....where is this math.....the acceleration of G cannot exceed C, nothing can according to GR. So how is this 3D singularity formed within a 0 gradient area that is much larger than plank? If the mass is all at a 3D singularity within the BH how is it that the EH has an acceleration of G which is the same acceleration at the singularity, given the inverse square law. What kinda fuzzy math figured this out. Sorry, the antiquated ideas about Black Holes need revision.

I am sorry I am unable to articulate to you the idea that at the speed of C matter breaks down into pure energy. I am sorry that you cannot see that inside a BH including all of the area within the EH has no gravitational gradient to generate a plank size singularity and that the entire area represents a singularity as their is no applicability of GR in the BH or any special location. I am also sorry that you cannot understand that as matter enters a BH that the sigularity is disturbed creating conditions in which GR again becomes applicable at the EH. The duration and magnetude of such an event would be directly related to the size and frequency of the mass entering the BH. If the frequency and amount of mass are great enough, the sigularity could be destroyed.

The basic argument between us is what is a singularity, I say that it is only a 4th dimensional phenomena with varying 3D sizes. All of the area within the EH is a singularity.

Evan
2005-Mar-14, 09:19 PM
No, the basic argument is your postulate that a black hole can be detroyed interacting with normal matter. Regardless of what is inside a black hole normal matter cannot destroy a black hole in any interaction. It would be a reversal of entropy. A black hole is a maximum entropy object and adding energy cannot increase the degree of order of the object. All the information about the structure of the matter inside of the black hole is lost. To destroy the black hole would require somehow regaining that lost information. It no longer exists so it isn't possible.

The recent change announced by Hawking is not applicable as it deals with a loose end known as the information paradox. He claims that if the matter enering the black hole is in a pure quantum state then it should be possible to recover this information. Since it isn't likely that the matter infalling a black hole is a Bose-Einstein Condensate this changes nothing.

bigsplit
2005-Mar-14, 09:40 PM
No, the basic argument is your postulate that a black hole can be detroyed interacting with normal matter. Regardless of what is inside a black hole normal matter cannot destroy a black hole in any interaction.

The event horizon of the mBH described in this thread earlier, would be eaten away at the EH and eventually the bonbardment of mass from the sun would dissipate the entire singularity, exposing it to the world of GR. The mass of the sun would increase in direct proportion to the mass of the mBH. Likewise if the sun enter a mBH with more mass that itself, it would disturb the EH and massive fireworks would result, but in such a case the BH would win as it would destroy the sun and eventually calm down into a more massive black hole.

But one problem that I cannot answer is if the bombardment of mass from the sun would be more rapid than the recovery time of the EH. That is a question we are not even close to answering. So to that effect, I am not as sure about my conclusion as I project. If the recovery time of the mBH is quicker that the bombardment of mass, the sun would eventually be consumed and become a BH.

Now run that through your standard model calculator, how long does it take for the EH (gravitational gradient) to stabalize after mass enters it?

John Dlugosz
2005-Mar-14, 11:30 PM
The radius of the inner event horizion is determined by how fast the singluarity is rotating. Again, according to theory, if the rotational energy of the black hole exceeds the gravitational energy, the second event horizion will extend past the first and you'll be left with a "naked singularity". This is basically a singularity that has no event horizion.

But the rotational energy of a black hole can't get that high. I forget the percentage, but it's somewhere like a third or a half.

Basically, the only way for a BH to gain angular momentum is to swollow mass that's spinning around the BH. The object can't be circumnavigating the black hole any faster than the speed of light at the E.H. If the rotational energy of a BH were too high, then swollowing any possible object would make the BH slow its rotation.

--John

Bathcat
2005-Mar-15, 02:13 AM
Bigsplit, you would probably enjoy Thorne's book for non-physicists, Black Holes and Time Warps: Einstein's Outrageous Legacy. It's available here on Amazon (http://www.amazon.com/gp/product/0393312763/104-1694441-2576723?_encoding=UTF8) and probably in any good public library.

If you want a mathematical description of spacetime curvature -- the 'gradient' you mentioned -- I'm sure the Misner, Thorne, and Wheeler textbook would provide those.

In regard to the tidal gravity of a very large black hole -- say one with an event horizon the circumference of Neptune's orbit -- Thorne's calculations show that the tidal stretch-and-squeeze of the black hole would be pretty minimal at the event horizon circumference.

An acceleration of an infalling astronaut to velocity c does not occur. This is intuitive: According to relativity, it takes an infinite amount of energy to accelerate massive objects to lightspeed (as a proper velocity).

The energy needed is not linear: it goes up logarithmically.

Does a black hole have infinite energy available, that is to say, more than the finite energy of the entire rest of the universe?

No. Of course not. It has only the gravitational energy of an object of five solar masses. Or a hundred, or a thousand. But it most emphatically does not have infinite energy. Matter cannot be accelerated to proper velocity c at the event horizon.

---

Do check out Thorne's book, it's really quite good.

bigsplit
2005-Mar-15, 04:22 AM
Bigsplit, you would probably enjoy Thorne's book for non-physicists, Black Holes and Time Warps: Einstein's Outrageous Legacy. It's available here on Amazon (http://www.amazon.com/gp/product/0393312763/104-1694441-2576723?_encoding=UTF8) and probably in any good public library.

If you want a mathematical description of spacetime curvature -- the 'gradient' you mentioned -- I'm sure the Misner, Thorne, and Wheeler textbook would provide those.

In regard to the tidal gravity of a very large black hole -- say one with an event horizon the circumference of Neptune's orbit -- Thorne's calculations show that the tidal stretch-and-squeeze of the black hole would be pretty minimal at the event horizon circumference.

An acceleration of an infalling astronaut to velocity c does not occur. This is intuitive: According to relativity, it takes an infinite amount of energy to accelerate massive objects to lightspeed (as a proper velocity).

The energy needed is not linear: it goes up logarithmically.

Does a black hole have infinite energy available, that is to say, more than the finite energy of the entire rest of the universe?

No. Of course not. It has only the gravitational energy of an object of five solar masses. Or a hundred, or a thousand. But it most emphatically does not have infinite energy. Matter cannot be accelerated to proper velocity c at the event horizon.

---

Do check out Thorne's book, it's really quite good.

Thanks Bobcat, I will read it. I do need to understand how acceleration is not C and yet light cannot escape.

Kaptain K
2005-Mar-15, 11:28 AM
I do need to understand how acceleration is not C and yet light cannot escape.
For one thing "C", or more accurately "c", is the speed of light. It is not acceleration. Acceleration is a change of speed.

Another thing you need to remember is that mass and energy are equivalent - E = m c^2. Even if, as you say, matter is converted to energy when it crosses the EH, it has absolutely no effect on the gravitational field of the black hole!

bigsplit
2005-Mar-15, 12:59 PM
I do need to understand how acceleration is not C and yet light cannot escape.
For one thing "C", or more accurately "c", is the speed of light. It is not acceleration. Acceleration is a change of speed.

Another thing you need to remember is that mass and energy are equivalent - E = m c^2. Even if, as you say, matter is converted to energy when it crosses the EH, it has absolutely no effect on the gravitational field of the black hole!

I never question its effect on the gravity of the blackhole. What I question is the distribution of mass/energy within the BH. I think it is dispursed radomly and the entire BH represents a singularity not a 3D point singularity.

If mass is distributed as I premise, then certainly some mass can escape a BH as ordinary matter crosses the EH, the amount and the fate of the BH would depend on the Mass and frequency in which this ordinary matter enters the BH.

Tensor
2005-Mar-15, 01:36 PM
I do need to understand how acceleration is not C and yet light cannot escape.
For one thing "C", or more accurately "c", is the speed of light. It is not acceleration. Acceleration is a change of speed.

Another thing you need to remember is that mass and energy are equivalent - E = m c^2. Even if, as you say, matter is converted to energy when it crosses the EH, it has absolutely no effect on the gravitational field of the black hole!

I never question its effect on the gravity of the blackhole. What I question is the distribution of mass/energy within the BH. I think it is dispursed radomly and the entire BH represents a singularity not a 3D point singularity.

You misunderstand what a singularity is. A singularity is the at the point where the equations of GR break down. In a black hole, all the mass ends up during a gravitational collapse at a point and GR predicts the density of the point tends to infinity. (If you remember that density is mass/volume as the mass collapses to a point, you end up dividing by zero, which is why the equations break down). For the matter to be distributed randomly (as you seem to think) something would have to stop the collapse of the mass under the influence of gravity.

If mass is distributed as I premise, then certainly some mass can escape a BH as ordinary matter crosses the EH,

Again, you misunderstand. Although the BH (and the EH) formed during the initial collapse of the object, matter falling in can be distributed randomly. At some point it will fall into the singularity. However, nothing can cross outwards through the EH.

the amount and the fate of the BH would depend on the Mass and frequency in which this ordinary matter enters the BH.

You also seem to think that mass entering the BH would somehow disrupt it. Not true. All it does is add to the mass-energy of the hole making it bigger.

bigsplit
2005-Mar-15, 02:51 PM
This hypothetical point I assume started as a single point of some spherical mass. I hope you understand that such a single point would be difficult to achieve in a dynamic system. There would be a zone in which the "point" would vary. There is a point in which mass build up becomes strong enough to consume all light that comes in contact and we call this a black hole. The rules and equations of GR breakdown at the Event Horizon, I think. So as a 4D singularity the entire diameter of the BH represents a single point. In 3D however this "point" is much larger than plank. If it is below the event horizon it is beyond GR at that point.

Radomly distributed mass within the EH is because GR is in a freezeframe.
When Ordanary Matter passes this zone, it begin a less than instantanious breakdown of many chemical and electromagnetic relationships. This ordanary matter brings a period of instability to the uniform nature of the singularity. This causes some of the singularities mass in the form of energy to be able to escape on this "log in the whirlpool" as an analogy. This matter may be pulled back in eventually, but for some x amount of time it is possible to move beyond the EH.

Tensor
2005-Mar-15, 05:03 PM
This hypothetical point I assume started as a single point of some spherical mass.

Not a point, the radius of the object collapsing.

I hope you understand that such a single point would be difficult to achieve in a dynamic system.

Why?

There would be a zone in which the "point" would vary.

Only in a spinning black hole.

There is a point in which mass build up becomes strong enough to consume all light that comes in contact and we call this a black hole.

We call it the event horizon.

The rules and equations of GR breakdown at the Event Horizon, I think.

You think wrong. They break down at the singularity. Within the event horizon, the equations still work,

So as a 4D singularity the entire diameter of the BH represents a single point. In 3D however this "point" is much larger than plank. If it is below the event horizon it is beyond GR at that point.

Nope. Where did you get that information?

Radomly distributed mass within the EH is because GR is in a freezeframe.

What exactly is that? GR says the equations still work inside the EH, right up to the singularity.

When Ordanary Matter passes this zone, it begin a less than instantanious breakdown of many chemical and electromagnetic relationships.

I'll say it's less than instantaneous. Matter will last as matter right to where tidal effects tear it apart, which is near the singularity.

This ordanary matter brings a period of instability to the uniform nature of the singularity.

You have some support for this, or is it just a feeling?

This causes some of the singularities mass in the form of energy to be able to escape on this "log in the whirlpool" as an analogy.

This matter may be pulled back in eventually, but for some x amount of time it is possible to move beyond the EH.

You have some serious misconceptions on how GR treats and describes Black Holes. I high recommend you take Bathcat's suggestion of reading Kip Thorne's book. Mostly descriptive, with very little math.

John Dlugosz
2005-Mar-15, 05:13 PM
Thanks Bobcat, I will read it. I do need to understand how acceleration is not C and yet light cannot escape.

Without learning how to do all the math myself, I have to know who to trust when someone says that he has done the math and figured it out and here is what he gets. That means "accepted" results that have been published in peer-reviewed journals. Furthermore, not fresh publications, but results that have been built upon by others over a period of years.

Also, we have to know what we don't know. Where does the model break down? In the case of GR, it appears to be very very good. If it starts to diverge from reality, it would be where the scale is small enough to start to interact with the quantum realm. Obviously, the "singularity" is a single point where the math literally blows up. But the formula might start to be incorrect, at an outside guess, at a scale of the size of an atom.

So I'd have to say that the taffy-pulling description given by Thorne, Hawking, etc. of what happens after crossing the distance known as the Event Horizon is still dead-on accurate. But I would concede that (only!) near the center, a few proton-diameters from where G.R. says there is a singularity, things might indeed be different from what is predicted.

As a corollary, I would have to concede that the description of a mBH with an event horizon smaller than this might not act in the same way as a macro-scale BH. Have to wait a few years for mBH's to be created in the lab to push this "known boundary" of observed knowledge father inward, closer to the Plank length scale.

--John

Grey
2005-Mar-15, 05:13 PM
If mass is distributed as I premise, then certainly some mass can escape a BH as ordinary matter crosses the EH, the amount and the fate of the BH would depend on the Mass and frequency in which this ordinary matter enters the BH.
If mass is constrained to move below the speed of light, and the escape velocity at the even horizon is lightspeed, how would it be possible for matter the escape the black hole, even if it were just inside the event horizon? Wouldn't it have to be moving faster than light to do so?

bigsplit
2005-Mar-15, 07:09 PM
If mass is distributed as I premise, then certainly some mass can escape a BH as ordinary matter crosses the EH, the amount and the fate of the BH would depend on the Mass and frequency in which this ordinary matter enters the BH.
If mass is constrained to move below the speed of light, and the escape velocity at the even horizon is lightspeed, how would it be possible for matter the escape the black hole, even if it were just inside the event horizon? Wouldn't it have to be moving faster than light to do so?

So below the event horizon the escape velocity will increase to well beyond the speed of light? Wouldn't this imply that matter can move faster than the speed of light within a BH? If the escape velocity is continuously the speed of light along the entire radius of the BH, wouldn't this imply no gravitational gradient, meaning space cannot be curved for any practical purpose other than freefall? I do not see how there can be any curvature of space within the BH?

Either way GR breaks down at the EH. Either because faster than light velocity is possible, or because it is not possible. Certainly in mathematics it is possible to control particular inputs and develop models...but are such model apllicable to the real world?

Faster than light velocity = GR Breaks down.
No gravitational Gradient = Singularity of the 4th D and GR breaks down.

Grey
2005-Mar-15, 07:18 PM
So below the event horizon the escape velocity will increase to well beyond the speed of light? Wouldn't this imply that matter can move faster than the speed of light within a BH?
Why would that be the case? The escape velocity is the velocity at which something would need to move to escape a gravitational field. There need be no physical objects actually moving at that speed (and indeed, for an escape velocity higher than light, there cannot be any such objects).

But that isn't what I asked. The escape velocity at the event horizon is the speed of light. Whether the escape velocity further in is higher than that or just stays the same, how would it be possible for anything material to escape, since it cannot move that fast?

bigsplit
2005-Mar-15, 07:50 PM
So below the event horizon the escape velocity will increase to well beyond the speed of light? Wouldn't this imply that matter can move faster than the speed of light within a BH?
Why would that be the case? The escape velocity is the velocity at which something would need to move to escape a gravitational field. There need be no physical objects actually moving at that speed (and indeed, for an escape velocity higher than light, there cannot be any such objects).

But that isn't what I asked. The escape velocity at the event horizon is the speed of light. Whether the escape velocity further in is higher than that or just stays the same, how would it be possible for anything material to escape, since it cannot move that fast?

The escape velocity is changed locally at the point of entry due to the composition of the matter moving into it. The matter will disrupt the curvature of the space locally, yeilding a less the SoL escape velocity.

Further, since an escape velocity of greater than the speed of light is impossible, all the space within the BH cannot be distinguished by GR. There is no special place within a BH, it is all a singularity in terms of a uniform curvature of space based on the limits imposed by the Speed of Light.

Evan
2005-Mar-15, 08:11 PM
Show the math that describes that. GR doesn't.

wedgebert
2005-Mar-15, 08:13 PM
For one, I don't see why an escape velocity greater c is impossible. Having an acceleration of 2c/sec doesn't mean you're travelling at 2c.

In fact, depending on the size of the black hole, it's theoretically possible to survive crossing the event horizion. What kills you in a black hole is the tidal forces. Eventually you reach a point where the gravity on your feet is much much stronger than that on your head and you'll be torn in half. Then the same thing will happen to your remains. And so on and so forth until every particle in your body has been torn apart as you get closer and closer to the singularity.

Now with a small black hole, this happens pretty quickly, possbily even outside of the event horizion. However with a very massive black hole, the tidal forces don't kick in until you get well inside the event horizion.

Finally, even if you're experiencing a 10c/sec acceleration, it doesn't mean you'll ever go faster than c. Relativity is fun like that.

ToSeek
2005-Mar-15, 09:10 PM
For one, I don't see why an escape velocity greater c is impossible. Having an acceleration of 2c/sec doesn't mean you're travelling at 2c.

Escape velocity is a speed, not an acceleration.

wedgebert
2005-Mar-15, 10:08 PM
You're right, I just badly worded my reply. I'm at work after all and my boss frowns upon me doing too much research instead of work.

Anyways, my point still stands, there's nothing wrong with having an escape velocity greater than c as far as I know. An escape velocity of 2c is different than an object travelling at 2c.

bigsplit
2005-Mar-15, 10:31 PM
You're right, I just badly worded my reply. I'm at work after all and my boss frowns upon me doing too much research instead of work.

Anyways, my point still stands, there's nothing wrong with having an escape velocity greater than c as far as I know. An escape velocity of 2c is different than an object travelling at 2c.

So you all agree that you can accelerate faster than c.?.?

wedgebert
2005-Mar-15, 11:00 PM
No, I said you can have an acceleration greater than c, but objects cannot themselves accelerate faster than c. I could be wrong of course, but that's how I understand it.

TinFoilHat
2005-Mar-16, 12:20 AM
So you all agree that you can accelerate faster than c.?.?

You're confusing your units. C is a velocity, measured in distance per time. Acceleration is measured in distance per time per time. You can't speak of an acceleration greater than C because C is not a measure of acceleration.

It is impossible (so far as current theories predict) for any object to travel faster than C. This does not mean that there cannot be a region of space with an escape velocity greater than C. And having a region of space with an escape velocity greater than C does not imply that it is possible for an object to travel faster than C.

bigsplit
2005-Mar-16, 03:18 AM
So you all agree that you can accelerate faster than c.?.?

You're confusing your units. C is a velocity, measured in distance per time. Acceleration is measured in distance per time per time. You can't speak of an acceleration greater than C because C is not a measure of acceleration.

It is impossible (so far as current theories predict) for any object to travel faster than C. This does not mean that there cannot be a region of space with an escape velocity greater than C. And having a region of space with an escape velocity greater than C does not imply that it is possible for an object to travel faster than C.

The third law of motion means there cannot be a region of space with an escape velocity greater than C if it is impossible for any object to travel faster than C. If it takes a greater velocity than C to escape that means there is a force that is strong enough to pull an object at a speed greater than C.

BTW, I made the acceleration statement because I knew that it was a flawed premise from the previous post. It is good that we a confronting these issue....very educational and lots of fun.

01101001
2005-Mar-16, 04:26 AM
The third law of motion means there cannot be a region of space with an escape velocity greater than C if it is impossible for any object to travel faster than C. If it takes a greater velocity than C to escape that means there is a force that is strong enough to pull an object at a speed greater than C.
Nobel prize material! Alert the science journals.

Waitaminute. Wikipedia: Newton's law's of motion (http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion):

As a rule of thumb, Newton's Laws apply for any speed up to a third of the speed of light, after which point the error becomes too big to be ignored.
Nevermind...

Evan
2005-Mar-16, 06:09 AM
Black holes are therefore regions of space that are so densely packed with matter that nothing, not even light can escape. More specifically, the escape velocity of matter with the region bounded by the black hole is greater than the speed of light.

http://theory.uwinnipeg.ca/mod_tech/node61.html

The bending of light under gravity predicts black holes. It is a natural consequence of general relativity. The escape velocity applies to light. If the escape velocity is greater than the velocity of light, then the object is a black hole.

http://www.physics.fsu.edu/courses/spring99/phy1020/section2/Chapter12-13.html

A black hole is a star that has collapsed down to a point. Within a certain radius, known as the event horizon, the escape velocity is greater than the speed of light. Since nothing can exceed the speed of light, anything crossing over the event horizon becomes trapped forever within a black hole.

http://hypertextbook.com/physics/mechanics/gravitational-energy/

Etc. etc. etc....

TinFoilHat
2005-Mar-16, 01:28 PM
The third law of motion means there cannot be a region of space with an escape velocity greater than C if it is impossible for any object to travel faster than C.
Third law of motion: "For every action, there is an equal and opposite reaction."
I don't see how this backs up your statement. Even if it did, Newton's laws don't accurately model relativistic conditions, and can't be used to explain what happens near or inside an event horizon. You have to use relativity for that. And relativity does allow escape velocities greater than C, even though nothing is allowed to travel faster than C.

wedgebert
2005-Mar-16, 03:34 PM
I would like to point out that relativity doesn't allow for anything to be accelerated faster than light. I don't believe it has a problem super-luminal speeds, it just requires a negative mass.

2005-Mar-16, 05:07 PM
Whew! A lot of unit confusion on the board.

As many keep saying, the speed of light, c, is a velocity. You cannot
"accelerate" at the speed of light. You can change your velocity by a delta v
of c in one second, but not for very long (like less than one second, in fact.)

I am a bit suprised that no one has yet mentioned David Brin's book
Earth. In that book, a small BH is created in a lab, and "dropped."
Oops. Now David happens to be a Ph. D. physicist, so aside from the
initial hand-waving he had to do the create the darn thing, his science in
the book is sound. (There's also some touchy-feely save the earth eco
tree-hugging mysticism, but just look at the science.)
Anyway, if you read the book, David answers many of the questions and
problems mentioned in this board. If you haven't already, go find it and

Grey
2005-Mar-16, 06:54 PM
I would like to point out that relativity doesn't allow for anything to be accelerated faster than light. I don't believe it has a problem super-luminal speeds, it just requires a negative mass.
Actually, it requires imaginary mass, rather than negative mass. The total energy comes out negative real, though.

I am a bit suprised that no one has yet mentioned David Brin's book Earth.
I'd agree, it is a good book (even with the save the earth eco tree-hugging mysticism :) ), and Brin's science fiction is indeed always built on a solid understanding of the real science, even if he then imagines beyond it.

bigsplit
2005-Mar-16, 10:57 PM
Newton's third law absolutely applies to our little thought experiment. Since nothing can move faster than the speed of light, nothing can pull with a force that would cause greater than light speeds. There is no strengthening of gravity past the event horizon, the singularity does not pull any stronger than does the event horizon. If the velocity of light is x the force of gravity at the event horizon and throughout the BH could be considered -X. If some object were miraculously able to travel at a velocity of c+1, then it would be able to excape from any point within the BH.

The mass entering the BH is converted into energy, not by tidal forces, but rather by the decoupling of the chemical and electrondynamic bonds. The forces applied by the gravity overpower and destroy any chemical, molecular or quantum structuring via their resistance to the speeds in which they are traveling, they are ripped apart. All the mass becomes pure energy and is in free flow about the BH.

Tensor
2005-Mar-17, 02:40 AM
Newton's third law absolutely applies to our little thought experiment. Since nothing can move faster than the speed of light, nothing can pull with a force that would cause greater than light speeds.

Where exactly in Newton Gravity does it say that nothing can move faster than light? You are mixing the two theories, That's a no-no. If you want to use Newtonian Gravity, use it (although it isn't applicable for the way current theory describes a black hole). If you want to use relativity, use that. But, the third law doesn't work in relativity the same as in Newtonian Gravity, which is why you can't accelerate past c.

There is no strengthening of gravity past the event horizon, the singularity does not pull any stronger than does the event horizon.

Where is your source for this? That is not how GR describes it. As the mass of the object collapses toward the singularity, the horizon forms . The curvature gets larger, the closer you get to the singularity.

If the velocity of light is x the force of gravity at the event horizon and throughout the BH could be considered -X. If some object were miraculously able to travel at a velocity of c+1, then it would be able to excape from any point within the BH.

... All the mass becomes pure energy

Depends on what you mean by pure energy The mass entering the black hole adds to the gravitational energy of the hole.

... and is in free flow about the BH.

Nothing is in free flow within the black hole. Timelike vectors become spacelike and spacelike vectors become timelike. As a result, all matter entering the EH will end up at the singularity. The singularity is in the future of all the matter entering the horizon. The singularity, in this case, is a destination in time, not a destination in space. Think of it in the same way as next Saturday is a destination in time, you can't avoid it.

bigsplit
2005-Mar-17, 03:49 AM
Newton's third law absolutely applies to our little thought experiment. Since nothing can move faster than the speed of light, nothing can pull with a force that would cause greater than light speeds.

Where exactly in Newton Gravity does it say that nothing can move faster than light? You are mixing the two theories, That's a no-no. If you want to use Newtonian Gravity, use it (although it isn't applicable for the way current theory describes a black hole). If you want to use relativity, use that. But, the third law doesn't work in relativity the same as in Newtonian Gravity, which is why you can't accelerate past c.

There is no strengthening of gravity past the event horizon, the singularity does not pull any stronger than does the event horizon.

Where is your source for this? That is not how GR describes it. As the mass of the object collapses toward the singularity, the horizon forms . The curvature gets larger, the closer you get to the singularity.

If the velocity of light is x the force of gravity at the event horizon and throughout the BH could be considered -X. If some object were miraculously able to travel at a velocity of c+1, then it would be able to excape from any point within the BH.

... All the mass becomes pure energy

Depends on what you mean by pure energy The mass entering the black hole adds to the gravitational energy of the hole.

... and is in free flow about the BH.

Nothing is in free flow within the black hole. Timelike vectors become spacelike and spacelike vectors become timelike. As a result, all matter entering the EH will end up at the singularity. The singularity is in the future of all the matter entering the horizon. The singularity, in this case, is a destination in time, not a destination in space. Think of it in the same way as next Saturday is a destination in time, you can't avoid it.

The source for x=speed of light and -x represents the strength of gravity at the EH should not be hard to follow. I further assert it is the third law that I used to deduce that if their is a force of gravity equal to say 2(-X) then there must be some form of mass capable of traveling 2x or commonly 2c. Since 2c is impossible then so is 2(-c). I am the souce if you wish, but I give credit to Einstein and Newton.

As for Newtonian Gravity, I would not qualify utilizing the 3rd law as being dependent of Newtonian Gravity in opposition to GR. If you claim this is what I am doing, then so be it, maybe I am. And maybe some others should too. It is just hard for me to believe that I am the only one who can see that if there is a configuration of mass capable applying a certain force to an object, there must be a configuration of mass that will react oppositely and equally.

I am not arguing that the curvature does not get larger as you approach the singularity, I assert that the curvature cannot get any "larger" than it is at the EH which is the beginning of an area we call a BH that is all a singularity, which is equivilant to -c....this is basic conservation and is the way it is.

John Dlugosz
2005-Mar-17, 05:31 AM
It is just hard for me to believe that I am the only one who can see that if there is a configuration of mass capable applying a certain force to an object, there must be a configuration of mass that will react oppositely and equally.

Deep breath time. This has been a while in the building.

It's because you're not making any sense!!

C is a velocity. You need to divide by another time unit to get acceleration. You didn't say what. Any acceleration is "greater than c" if the time unit is large enough. For example, if a rocket thrusted at one earth "G", it would eventually reach a speed of C using Newton's math. You can calculate the time and call it one eon. So the acceleration of the rocket is one c per eon, or 186282 miles per second per eon.

But, you know that's not what happens, since special relativity surplants Newton's laws at high speeds.

If the acceleration was greater than 186282 miles per second per second, then you could keep up the acceleration for less than one second and not reach the speed of light. But again, that's not what happens: if the force is constant the acceleration will diminish because the object gains mass or loses time (depending on whether the force is external or generated by a rocket).

For an object falling toward a large mass, you can't even use Special Relativity. You have to use General Relativity, or get nonsence results.

So you are twice removed from reasoning about it using Newton's rules! Even if your statement concerning "acceleration faster than C" made semantic sence in the first place.

You can't imagine what's going on because you are using intuition that only applies to inertial reference frames at low velocity. Adding a dash of relativity as spice to bandaid it only makes us cringe, and doesn't make any sence.

So take your lithium, or move it to ATM, or just wake up. Your assertions are not in accordance with accepted "mainstream" physics. This forum is for education in such.

--John

Arkyan
2005-Mar-17, 06:32 AM
A couple of thoughts that I think are causing some confusion here. Having an escape velocity of C at the event horizon does not mean the same thing as having a gravitational pull of C at the event horizon. The escape velocity at the surface of the Earth is some 11 km/s, but this does not mean an object is necessarily going that fast if it falls to the surface. An object would have to fall from pretty high up before it reaches that speed. An object can certainly fall to the Earth without reaching escape velocity, such as the cup I just knocked off my desk! By the same reasoning, just because escape velocity is C at the event horizon, an object could reasonably fall into the EH having a velocity much lower than C. C is the speed it'd take to get out - that does not imply it is the speed reached upon going in.

Bathcat
2005-Mar-17, 07:37 AM
Perhaps this sheds some light on the dysunderstanding we have going on here:

Evan: "The escape velocity of the Sun from the surface of the Sun is 617 kilometers per second. This means that if an object were placed at rest an infinite distance away (warning: thought experiment!) that it would accelerate to 617 kps by the time it encountered the surface of the Sun. That is the minimum that an extrasolar object would accelerate to."

If I intuit BigSplit's thinking correctly, he's using the same mathematical logic as Evan here: since the escape velocity at the event horizon of a black hole is necessarily c, any object falling into a black hole will have that as a minimum velocity.

And if I understand the counter-reasoning, it's that Evan's statement about the Sun's gravitational acceleration on an infalling object is valid because the velocity involved is Newtonian. It's not fast enough to need a substantial correction from GR in order to realistically describe what happens in the universe.

Then, again if I guess correctly, BigSplit is understanding that matter accelerated to proper velocity c can only become pure energy. Therefore, matter is destroyed at the event horizon and not at a submicroscopic central singularity.

The counter-argument is that because relativitistic calculation of acceleration and velocity results in a most emphatically sub-c velocity for infalling matter, matter survives past the event horizon and persists until it is torn apart at the central singularity.

----

If I think about it, BigSplit's position is pretty reasonable, really. I also think, however, that there are a number of things about relativity and the behavior of gravitation near black holes that is quite unreasonable...but probably correct. :)

For example, Gršµ^ttszch the silica-skinned alien would watch her-his robotic probe falling toward the event horizon and see it slowing down and then freeze in place as it reached the EH. Even though he-she (sometimes it) could calculate that it should have been accelerating toward the hole, he would see it come to a virtual stop instead (his-her pentoculars correct automatically for the redshifting of light from the probe so that her-his five eyes receive light in the visible spectrum).

And so at Gršµ^ttszch's clock-time of 34:00 the probe fades from view as its light redshifts into microwaves and fades out. It's eternally stuck at the EH, and cannot fall through. But onboard the robotic probe the clock might be reading 31:15 and the robot, now several thousand kilometers inside the event horizon, is radioing frantically that its rocket engines have failed and it cannot decelerate as it plunges toward the hole's center of mass.

Quite unreasonable. Counterintuitive. But...correct?

TinFoilHat
2005-Mar-17, 02:00 PM
Bigsplit-

You still continue to confuse units. You can't speak of a gravitational force equal to C because C is a measure of velocity, not acceleration or force. In Newtonian mechanics, any acceleration could get you to the speed of light, if applied long enough. In relativity, you can't reach the speed of light no matter how strong the force accelerating you.

bigsplit
2005-Mar-17, 02:44 PM
Bigsplit-

You still continue to confuse units. You can't speak of a gravitational force equal to C because C is a measure of velocity, not acceleration or force. In Newtonian mechanics, any acceleration could get you to the speed of light, if applied long enough. In relativity, you can't reach the speed of light no matter how strong the force accelerating you.

Thanks tinfoilhat, but as I said before, if it takes greater than c to escape, the force applied must be c (or some translation) or greater. Contunually, if nothing can travel past c, nothing can pull greater than c. No mass can pull any harder when the escape velocity is greater than c (remember c+ (-c) = singularity), it would violate basic conservation principle implied by the third law.

Argos
2005-Mar-17, 02:50 PM
If I intuit BigSplit's thinking correctly, he's using the same mathematical logic as Evan here:

The only logic possible here is that one j. Dlugosz (among others) pointed out. Bigsplit is talking about the way he wished the universe worked. But the universe does not give a darn for what we wish. :wink:

TinFoilHat
2005-Mar-17, 03:22 PM
Thanks tinfoilhat, but as I said before, if it takes greater than c to escape, the force applied must be c (or some translation) or greater. Contunually, if nothing can travel past c, nothing can pull greater than c.
You still aren't getting it. C is not a force or an acceleration. C is a velocity. To say "nothing can pull greater than C" or "force applied must be C" is mathematically meaningless. You aren't going to understand black holes until you can at least understand why this is important.

ToSeek
2005-Mar-17, 03:46 PM
Let's imagine that we are in a Newtonian universe with two objects, one black-hole-caliber one (i.e., with an escape velocity greater than c) and one that we're going to drop from an infinite distance onto the BHC object. So at some point the dropped object will be moving faster than the speed of light. In fact, it will start doing so right at where the event horizon would be if we were in a GR universe instead of a Newtonian one.

If we do the same experiment in our (GR) universe, the dropped object will eventually begin to experience relativistic effects as it approaches c, i.e., it will gain mass and experience time dilation. However, it will never exceed c, not even at the event horizon.

Does this help at all?

2005-Mar-17, 04:20 PM
Let's try this. What is an escape velocity? It is the velocity which, if you
have attained it, your kinetic energy exceeds the potential energy
of the gravity holding you bound to a massive object, like a planet or a black hole.
Once you attain that speed, no matter how you got there, you are out of
there! Bye bye, see ya later. Acceleration doesn't matter, as long as you
get to the escape velocity somehow.

The trick is at the EH, you need to attain a velocity greater than c. Uh uh, no
can do. Bad bunny. You can't do it, light can't do it, information can't do it.
This is a basic tenet of Special Relativity, and I would not go dissing it without
a darn good reason. Which I have not yet heard.

John Dlugosz
2005-Mar-17, 05:47 PM
sn't matter, as long as you
get to the escape velocity somehow.

The trick is at the EH, you need to attain a velocity greater than c. Uh uh, no
can do. Bad bunny. You can't do it, light can't do it, information can't do it.
This is a basic tenet of Special Relativity, and I would not go dissing it without
a darn good reason. Which I have not yet heard.

The meaning of escape velocity as the speed required to escape refers to the instantanious speed followed by a ballistic trajectory. I.e. the speed needed by a cannon ball. I can escape from the Earth without going any faster than 2 miles per hour by using a very large stairway. The force is sustained, rather than coasting.

The Newtonian idea of an escape velocity doesn't explain why you can't hoist/climb out at a much lower velocity. It takes G.R. to explain why you can't even climb out past the EH. It would seem to be an infinite climb, I suppose, because of spacetime warping.

bigsplit
2005-Mar-17, 06:07 PM
Let's try this. What is an escape velocity? It is the velocity which, if you
have attained it, your kinetic energy exceeds the potential energy
of the gravity holding you bound to a massive object, like a planet or a black hole.
Once you attain that speed, no matter how you got there, you are out of
there! Bye bye, see ya later. Acceleration doesn't matter, as long as you
get to the escape velocity somehow.

The trick is at the EH, you need to attain a velocity greater than c. Uh uh, no
can do. Bad bunny. You can't do it, light can't do it, information can't do it.
This is a basic tenet of Special Relativity, and I would not go dissing it without
a darn good reason. Which I have not yet heard.

I am going to use your thoughts here to try to allow others to see as I see. The kenetic energy of a body cannot exceed c. The Event Horizon is the shell of a black hole that has potential energy that will not allow the kenetic energy of less than c escape (the potential energy of the EH equals C). If the kenetic energy cannot exceed c, then how can the potential of greater than c exist as a result of mass, which is the cause of the BH to begin with? Even if such an impossible potential existed, it would be useless because no mass could ever utilize its potential, a failure of economies. Why would we develope a mathematical model of a wasteful system in which the source of the waste has little baring of events outside the BH. What happens below the event horizon as described by many is a severe violation of Occam's Razor. It is much simplier to assume that the potential within the black hole cannot exceed c as well. BEC's could be flying all over the place, there is a smooth gravitational potential throughout the BH.

At the Event Horizon this smoothness will most definately be temporarily disturbed by mass entering a system with a potential to pull it at the speed of light, this mass will introduce GR at the EH for atleast a minimum time lowering the potential energy by the introduct of Kenetic. It would take some measureable amount of time before the kinetic energy is completely converted into potential, allowing the opportunity for at least some measurable time for mass in the form of energy to escape. I would also argue that most mass that makes it to the event horizon will be in the forms of dust clouds and torn apart debris. The velocity will certainly begin drastic alterations as the velocity of the mass approaches the EH. I think you would find it hard pressed to find an intact solar system make it to the event horizon. At distances close to the EH you would probable have trouble finding a molecule. Once it hits that c potential of the EH, say goodbye to all quantum structuring, it would all be pulled apart by the pressure of "gaining mass and time dialtion", but less than instantly.

I hope this helps.

pghnative
2005-Mar-17, 06:13 PM
...The kenetic energy of a body cannot exceed c....
Dude, you gotta learn units.

Energy has units of mass*length/time^2. C has units of length/time. You cannot compare the two. Energy cannot be less than, equal to, or exceed speed.

2005-Mar-17, 06:16 PM
The meaning of escape velocity as the speed required to escape refers to the instantanious speed followed by a ballistic trajectory. I.e. the speed needed by a cannon ball. I can escape from the Earth without going any faster than 2 miles per hour by using a very large stairway. The force is sustained, rather than coasting.

Well, no you actually cannot. If you keep going 2 miles per hour, you will
always be gravitationally bound to the earth theoretically no matter how
far away you get. Whenever you stop applying whatever force is giving
you the 2 mph, you will start dropping back down. You need an infinite
staircase; very hard to build. Practically speaking, influences from other
bodies (planets, the Sun, stars) will at some point mitigate this.

This is just a potential and kinetic energy deal. Once you attain escape
velocity, you don't need any additional force, you're gone! So yes, it is
"ballistic" in that sense. Also, it is not "Newtonian." This all holds fine
in Special and General Relativity, as long as you calculate the respective
energies properly (that is, using v/c and tensors.)

Grey
2005-Mar-17, 06:28 PM
Well, no you actually cannot. If you keep going 2 miles per hour, you will always be gravitationally bound to the earth theoretically no matter how far away you get. Whenever you stop applying whatever force is giving you the 2 mph, you will start dropping back down. You need an infinite staircase; very hard to build. Practically speaking, influences from other bodies (planets, the Sun, stars) will at some point mitigate this.
Not quite true. Remember that escape velocity varies with distance, so eventually you'd get far enough away that the escape velocity was less than 2 mph, and at that point, the next step you take will launch you off the stairway unless you hold tight to the railing.

Or, to think about it terms of energy, as you get further and further away, your gravitational potential is becoming steadily smaller (well, less negative, technically). Even if your kinetic energy remains constant, you'll eventually reach the point where the kinetic energy exceeds the magnitude of the potential energy, and you're no longer bound.

ToSeek
2005-Mar-17, 06:30 PM
The meaning of escape velocity as the speed required to escape refers to the instantanious speed followed by a ballistic trajectory. I.e. the speed needed by a cannon ball. I can escape from the Earth without going any faster than 2 miles per hour by using a very large stairway. The force is sustained, rather than coasting.

Well, no you actually cannot. If you keep going 2 miles per hour, you will
always be gravitationally bound to the earth theoretically no matter how
far away you get.

Not true! You just have to get far enough away so that the escape velocity is 2 mph! By my reckoning, you only need stairs that are 600 billion miles high. ;)

EDIT: ToSeeked because I stopped to do the math!

2005-Mar-17, 06:43 PM
Not true! You just have to get far enough away so that the escape velocity is 2 mph! By my reckoning, you only need stairs that are 600 billion miles high. ;)

Oops. My bad. I was too locked into thinking about circular/parabolic orbits,
and surfaces of planets and/or asteroids. I'll go back to sleep now . . .

Grey
2005-Mar-17, 06:45 PM
EDIT: ToSeeked because I stopped to do the math!
Hah! I knew that working out the math would be a mistake! That's the first time I've ever ToSeeked you, ToSeek. I feel like I've just achieved a BABB milestone. 8)

Evan
2005-Mar-17, 06:50 PM
Bigsplit,

Aside from your continuing confusion with units, you said:

I think you would find it hard pressed to find an intact solar system make it to the event horizon. At distances close to the EH you would probable have trouble finding a molecule. Once it hits that c potential of the EH, say goodbye to all quantum structuring, it would all be pulled apart by the pressure of "gaining mass and time dialtion", but less than instantly.

What? The tidal forces at the event horizon are directly dependent upon the size of the BH.

The point at which the tidal forces become fatal depends on the size of the black hole. For a very large black hole such as those found at the center of galaxies, this point will lie well inside the event horizon, so the astronaut may cross the event horizon painlessly and live . Conversely, for a small black hole, those tidal effects may become fatal long before the astronaut reaches the event horizon.

http://en.wikipedia.org/wiki/Black_hole

ToSeek
2005-Mar-17, 06:53 PM
EDIT: ToSeeked because I stopped to do the math!
Hah! I knew that working out the math would be a mistake! That's the first time I've ever ToSeeked you, ToSeek. I feel like I've just achieved a BABB milestone. 8)

Maybe I should start giving out t-shirts....

Grey
2005-Mar-17, 07:29 PM
Maybe I should start giving out t-shirts....
That would be a great idea, except that walking anywhere would probably take longer if I had to keep stopping to explain what the heck "I ToSeeked ToSeek!" meant to inquisitive passerby.

Bathcat
2005-Mar-17, 07:43 PM
Well, here's another math thing:

We know that the escape velocity at a black hole's event horizon equals c.

We are pretty sure that it would take an infinite amount of energy to accelerate any physical object to proper velocity c .

And we know that a black hole simply does not have an infinite gravitational potential -- it can't accelerate any physical object to velocity c. Not even all the mass in the universe could do that, 'cos that would still be a finite quantity and we need an infinite one.

So, back to Evan's excellent thought experiment: what if we take a quiescent, non-spinning black hole and a test body initially at rest with respect to the BH, and then let the BH have its gravitational way with the test body?

What will be the proper velocity of the test body when it reaches the event horizon?

Evan
2005-Mar-17, 07:59 PM
c-(1/infinity)

:D :D

bigsplit
2005-Mar-19, 03:27 PM
The meaning of escape velocity as the speed required to escape refers to the instantanious speed followed by a ballistic trajectory. I.e. the speed needed by a cannon ball. I can escape from the Earth without going any faster than 2 miles per hour by using a very large stairway. The force is sustained, rather than coasting.

Well, no you actually cannot. If you keep going 2 miles per hour, you will
always be gravitationally bound to the earth theoretically no matter how
far away you get.

Not true! You just have to get far enough away so that the escape velocity is 2 mph! By my reckoning, you only need stairs that are 600 billion miles high. ;)

EDIT: ToSeeked because I stopped to do the math!

No matter you still need a constant force to climb the steps or to acheive and maintain 2mph. In the case of the black hole not even light can overcome this force holding it back. Nothing can generate enough enough power to overcome this force. This force however cannot become any stronger, geometically the curvature has reached its limits. The power fo this force is limited by a gravitational potential "speed limit" that is the equivalent to the force or curvature at the EH of a black hole.

Grey
2005-Mar-19, 03:54 PM
No matter you still need a constant force to climb the steps or to acheive and maintain 2mph. In the case of the black hole not even light can overcome this force holding it back. Nothing can generate enough enough power to overcome this force.
That's true, although you've said otherwise several times when you talk about outside matter interfering and allowing matter to escape.

This force however cannot become any stronger, geometically the curvature has reached its limits. The power fo this force is limited by a gravitational potential "speed limit" that is the equivalent to the force or curvature at the EH of a black hole.
This, however, is simply mistaken. Take a look here (http://casa.colorado.edu/~ajsh/schwp.html) for a discussion of the Schwarzschild geometry.

bigsplit
2005-Mar-19, 05:05 PM
According to the Schwarzschild metric, at the Schwarzschild radius rs, proper radial distance intervals become infinite, and proper time passes infinitely slowly. Inside the Schwarzschild radius, proper radial distances and proper times appear to become imaginary (that is, the square root of a negative number).

Historically, it took decades before this strange behaviour was understood properly

Do they understand it at all now, lets see the line of logic they used.

[/quote]The problem with the Schwarzschild metric is that it describes the geometry as measured by observers at rest. It is now realized that once inside the Schwarzschild radius, there can be no observers at rest: everything plunges inevitably to the central singularity. In effect, the very fabric of spacetime falls to the singularity, carrying everything with it. No pressure can withstand the inexorable collapse.

To paraphrase Misner, Thorne &amp; Wheeler (1973, ``Gravitation'', p. 823), that same unseen power of the world which impels everyone from age 20 to 40, and from 40 to 80, impels objects inside the horizon irresistably towards the singularity.
[quote]

"Unseen powers"???, the passage of time requires proper radial distance intervals that are not infinate. Our aging is the result of the passage of proper time that can only take place in frames where gravity is weak enough to allow less than c velocities. Otherwise it is all a singularity within the Swartzchild radias with the same gravitational potential throughout.

Evan
2005-Mar-19, 05:23 PM
Inside the Schwarzschild radius, proper radial distances and proper times appear to become imaginary (that is, the square root of a negative number).

The line of logic stems from this equality:

E = mc2/sqrt(1 - v2/c2)

If v > c then the denominator becomes imaginary and so does m. This is the equation to find the energy of a particle where m is the mass of a particle and v is the velocity.