PIerz,No, you are wrong here. Space doesn't expand around objects without the objects moving along with it. The positions of objects are positions IN space. Thus there is not a smooth expansion but the warping around galaxies I've pointed out.If you were correct the Hubble expansion of space wouldn't carry far galaxies along with it and redshift them.You are simply wrong here. Please remember that the next time you accuse me of being wrong about something!Edgar
Gibbsa,Thanks for your comments. As I stated in my initial post this is a "possible" explanation of dark matter, not necessarily the only one. (so your "seed" comments are irrelevant).
Obviously it needs to be confirmed by comparing the predicted warping to the actual dark matter observations. And of course that needs to be done around galaxy clusters as well as individual galaxies. It is obvious that the effect will be complex due to the complexity of distribution of mass in space rather than just geometrically perfect halos. 1
But,of course expanding one side of a continuous space but not the other will lead to a boundary warping. That's simple geometry. Thus it should inevitably have some gravitational effect and that effect should be fairly significant due to the 13.7 billion year history of the Hubble expansion. Time for plenty of warping to have occurred.
Gibbsa,No, you misunderstand what I'm saying.Of course "the hubble rate can keep on going, passing the speed of light barrier, and forever onward and upward. Because, and precisely because, it's not generated by a physical translation in space."I agree with that and that's exactly what I'm saying. It's Pierz that is disagreeing with you. Pierz thinks space is expanding without taking any physical objects along with that expansion. If that were true nothing there would be no red shift and there would be no particle horizon beyond which the expansion of space carries galaxies so they can no longer be observed.Things move both IN space and WITH the expansion of space. Things moving with the expansion of space red shifts them, things moving RELATIVE TO the expansion of space gives variations of red and blue shifts for objects at the same distances in expanding space.The expansion of space occurs only in intergalactic space, but the space within galaxies, solar systems, etc. is gravitationally bound and is not expanding. Refer to Misner, Thorne and Wheeler's 'Gravitation' if you don't believe me....Our solar system is not expanding due to the Hubble expansion because it is gravitationally bound... If it was you'd have a violation of the laws of orbital motion.Therefore there must be a space warping at the boundaries of galaxies which must produce a significant gravitational effect over time which could explain the dark matter effect....Edgar
On Tuesday, January 21, 2014 12:11:25 PM UTC-5, ghi...@gmail.com wrote:
On Tuesday, January 21, 2014 4:22:34 PM UTC, Edgar L. Owen wrote:PIerz,No, you are wrong here. Space doesn't expand around objects without the objects moving along with it. The positions of objects are positions IN space. Thus there is not a smooth expansion but the warping around galaxies I've pointed out.If you were correct the Hubble expansion of space wouldn't carry far galaxies along with it and redshift them.You are simply wrong here. Please remember that the next time you accuse me of being wrong about something!EdgarEdgar, the opposite is true. The hubble effect is constant if the comparison is between any two pairs of adjacent galaxies, one pair compared to the other, obviously controlling for distance between them. It's constant in that sense whether or not the overall effect is accelerating as it is at the moment.If the galaxies are independently moving in space, the distance to adjacent galaxies is changing, and has to be controlled for, to keep that constant effect.If you skip a galaxy and want the rate of expansion between a galaxy and the second galaxy along, then you have to add the two adjacent rates together, controlling for changes in distance caused by independent movement of galaxies in space. If you want the next galaxy after that, it's adding 3 adjacent values.This is why the hubble rate can keep on going, passing the speed of light barrier, and forever onward and upward. Because, and precisely because, it's not generated by a physical translation in space.
On Tuesday, January 21, 2014 6:11:23 PM UTC, Edgar L. Owen wrote:Gibbsa,No, you misunderstand what I'm saying.Of course "the hubble rate can keep on going, passing the speed of light barrier, and forever onward and upward. Because, and precisely because, it's not generated by a physical translation in space."I agree with that and that's exactly what I'm saying. It's Pierz that is disagreeing with you. Pierz thinks space is expanding without taking any physical objects along with that expansion.
--
I once heard a cosmologist say that you can't feel the force of repulsion due to cosmological expansion between your fingers because at that distance it is imperceptibly small. But if your fingers were at either end of the universe you'd feel an immense pressure pushing them apart.
Yes, dark energy *is* what he was talking about. Thanks for that clarification. The original expansion is just a result of the residual inertia of the big bang.
Yes, dark energy *is* what he was talking about. Thanks for that clarification. The original expansion is just a result of the residual inertia of the big bang.
On Thursday, January 23, 2014 7:40:03 PM UTC+11, Liz R wrote:On 23 January 2014 20:09, Pierz <pie...@gmail.com> wrote:
I once heard a cosmologist say that you can't feel the force of repulsion due to cosmological expansion between your fingers because at that distance it is imperceptibly small. But if your fingers were at either end of the universe you'd feel an immense pressure pushing them apart.
If he's talking about dark energy, fair enough, although since we don't know what it is, I'm not sure how he could make that statement with confidence (about the force being there between your fingers, I mean).
However, if he wasn't talking about dark energy, I don't understand. I don't think that the hubble flow itself involves a force. That is, the contents of the universe are moving apart (except where they're gravitationally bound) and they are interacting via gravity and dark energy, whatever that is.... and that's all that's involved. Cosmological expansion is simply movement, galaxies on either side of the universe aren't being pushed apart by anything other than dark energy, and not being pulled together by anything except gravity (as far as we know). There isn't a force of repulsion making the universe expand - apart from dark energy - it simply IS expanding.
WAS he talking about Dark Energy?
I don't think you can look at it that way. If were just the motion, as away from the center of an explosion, then even the most distant parts could not exceed c. But if it's the expansion of space as in the FRW solutions to Einstein's equation then sufficiently distant parts are receding faster than c.On 1/23/2014 1:34 AM, Pierz wrote:
Yes, dark energy *is* what he was talking about. Thanks for that clarification. The original expansion is just a result of the residual inertia of the big bang.
Now the obvious effect of this (as I'm the first to have pointed out so far as I know) is that space will necessarily be warped at the boundaries of galaxies, and as is well know from GR any curvature of space produces gravitational effects, and of course dark matter halos around the EDGES of galaxies were invented to explain the otherwise unexplained extra gravitational effects on the rotation of galaxies.
Thus, this simple effect of space warps around the boundaries of galaxies caused by the Hubble expansion may be the explanation for the dark matter effect.
And there is nothing to prevent these warps, once they are created, to have a life and movement of their own, as we now know that dark matter is not just concentrated around galactic halos but may indicate where they used to be....
Of course it depends on what DE is. The most common theory is that it's just the cosmological constant term in Einstein's equation. If that's the case then it's just another geometric effect of the dynamics of space. It's not really a "force", it's just part of gravity.
Liz,Once the warp is formed it can easily separate from the matter that caused it. At that point it is effectively just another mass of matter. That is why it's called dark matter. And of course masses separate from each other all the time.Don't think of it like it's continued existence depends on the original galactic mass. Once it's created it exists as a separate dark mass that can go anywhere it likes under gravitational forces just like VISIBLE matter can...
A warp in space that is bound together by its own gravitation is what is known as a black hole.
Note that Hawking as just posted a paper casting doubt on their existence:
http://arxiv.org/abs/1401.5761
On 25 January 2014 11:59, meekerdb <meek...@verizon.net> wrote:
A warp in space that is bound together by its own gravitation is what is known as a black hole.
Technically I believe there is still a mass inside it,
however, even if it has been crushed to a point. It isn't a "free-floating space warp" which is what Edgar was suggesting (I asked him, to double check, and he affirmed it). If that was possible, then presumably any space warp could become detached from its source
and "drift off into the aether" ... the Earth might leave a furrow in space behind it as it orbits the Sun, into which dust and asteroids would tumble...
There are "free-floating space warps", of course, namely gravity waves. But as far as I know, they don't appear to be a major contributor to "dark matter".
Note that Hawking as just posted a paper casting doubt on their existence:
http://arxiv.org/abs/1401.5761
I will read that with interest, thank you! I have long suspected that black holes don't exist as specified in GR - I mean, that they aren't infinitely dense singularities inside an event horizon. Nice to see Stephen coming round to my way of thinking :-)
No, seriously, a lot of alternatives to Black Holes have been suggested, and some even seem quite likely to my poor little brain. Presumably GR breaks down at some point before it reaches infinity (otherwise all your "finitist numerologists" are in trouble :-)
No, it's massive, i.e. it warps space around it, but I don't think it makes sense to say it has a mass inside it; it's a solution to Einstein's equation without any T_u_v, i.e. a vacuum.On 1/24/2014 3:12 PM, LizR wrote:
On 25 January 2014 11:59, meekerdb <meek...@verizon.net> wrote:
A warp in space that is bound together by its own gravitation is what is known as a black hole.
Technically I believe there is still a mass inside it,A black hole crushes it's source into a singularity (in the classical approximation).however, even if it has been crushed to a point. It isn't a "free-floating space warp" which is what Edgar was suggesting (I asked him, to double check, and he affirmed it). If that was possible, then presumably any space warp could become detached from its source
Gravity waves can't exactly be 'free floating' because they travel at the speed of light and only interact gravitationally.and "drift off into the aether" ... the Earth might leave a furrow in space behind it as it orbits the Sun, into which dust and asteroids would tumble...
There are "free-floating space warps", of course, namely gravity waves. But as far as I know, they don't appear to be a major contributor to "dark matter".
So unless they are strong enough to close up on themselves and make a black hole, they will radiate off to infinity.
Brent,Obviously the space outside a black hole event horizon is warped. That's experimentally confirmed. My question is HOW does it become warped from the mass inside the black hole which you now claim doesn't even exist? There must be some cause. It's much more reasonable to assume the mass that enters a black hole does exist inside the black hole as it does produce a gravitational effect. My question is how that gravitational effect, which must travel at the speed of light, propagate from the interior of the black hole when nothing else can because it would have to travel at FASTER than the speed of light to do so?
Re your implication of gravitation perhaps not being mediated by force carrying particles. I think there are a number of reasons to doubt the existence of gravitons.1. For a flow of gravitons to explain gravity they would all continuously have to flow in the same direction since gravity acts only in one direction (between masses at least). That means there would have to be an inexhaustible source of gravitons flowing from ONLY OUT from every mass. What's the source of that inexhaustible flow?2. Gravity is the only force that cannot be shielded. Thus if gravitons existed they would have to flow effortlessly THROUGH everything that exists (NON-interaction) at the same time they cause gravitational effects (INTERACTION). An apparent contradiction....3. There is no empirical evidence whatsoever that gravitons actually exist.4. Gravitons are not part of the Standard Model.So all and all I think there is plenty of reason to doubt the existence of gravitons...Edgar
On Friday, January 24, 2014 10:31:41 PM UTC-5, Brent wrote:On 1/24/2014 4:41 PM, Edgar L. Owen wrote:
> Brent,
>
> No, my proposed dark matter effect has nothing to do with black holes. Black holes are
> caused by accumulations of actual visible matter, not by the Hubble expansion of space...
>
> However I do have a question for you. Since gravitational changes propagate at the speed
> of light how does the mass inside a black hole produce gravitational effects outside the
> black hole? If light can't come out how can gravitational effects come out?
You are thinking of gravity as mediated by force particles, like photons mediate the EM
forces. But (at least classically) gravity isn't a force, it's just a shape of space and
as I responded to Liz, there's not mass in a black hole, no T_u_v term in the Einstein
equation. It's a vacuum solution. That's why it doesn't make any different what falls in
to create the black hole. The effects outside the event horizon are just that the space
is warped there just *as if* the black hole were a massive object.
Brent
--
On 1/25/2014 5:29 AM, Edgar L. Owen wrote:
Brent,
We have to be careful to be precisely accurate here.
1. The structure of a black hole is not just a singularity inside an event horizon. The entire interior of a black hole is not a singularity. The singularity exists only at the very center of a black hole, there is plenty of volume between the event horizon and the singularity.
Actually there is plenty of *time* between the horizon and the singularity - if the black hole is large enough. The singularity isn't at a different place, it's in the future, once you're inside the event horizon.
2. We have to clearly distinguish gravity WAVES from gravity itself. Gravity waves are NOT gravity, they are small fluctuations in gravity.
Of course they are small warps in space. But warps in space *are* gravity.
So yes, gravity WAVES can radiate away, but the gravitational force itself remains unless the mass that produces it vanishes.
If, as you propose, mass vanishes inside a black hole (no one else believes this BTW) black holes would produce NO gravitational effect....
Of course matter doesn't vanish just because it crosses the event horizon. But so far as the classical theory goes it vanishes at the singularity. It takes some time to get to the singularity, but it's relatively short for a black hole that forms from a star.
But even though the mass vanishes the black remains and warps space around it. Which everybody who ever solved Einsteins equations for the Schwarzschild solution knows. It's a *vacuum* solution. There's no matter in it. It is because Einsteins equations are non-linear gravity acts on itself and so can act as it's own source of gravity.
Brent
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At least for a spherically symmetric black hole, the GR solution indicates that the time dimension becomes the radial dimension of the black hole. Thus time vanishes inside the event horizon of a spherical black hole.
Brent,
Obviously the space outside a black hole event horizon is warped. That's experimentally confirmed. My question is HOW does it become warped from the mass inside the black hole which you now claim doesn't even exist? There must be some cause.
It's much more reasonable to assume the mass that enters a black hole does exist inside the black hole as it does produce a gravitational effect.
My question is how that gravitational effect, which must travel at the speed of light, propagate from the interior of the black hole when nothing else can because it would have to travel at FASTER than the speed of light to do so?
Re your implication of gravitation perhaps not being mediated by force carrying particles. I think there are a number of reasons to doubt the existence of gravitons.
1. For a flow of gravitons to explain gravity they would all continuously have to flow in the same direction since gravity acts only in one direction (between masses at least). That means there would have to be an inexhaustible source of gravitons flowing from ONLY OUT from every mass. What's the source of that inexhaustible flow?
2. Gravity is the only force that cannot be shielded. Thus if gravitons existed they would have to flow effortlessly THROUGH everything that exists (NON-interaction) at the same time they cause gravitational effects (INTERACTION). An apparent contradiction....
3. There is no empirical evidence whatsoever that gravitons actually exist.
4. Gravitons are not part of the Standard Model.
So all and all I think there is plenty of reason to doubt the existence of gravitons...
Edgar
On Friday, January 24, 2014 10:31:41 PM UTC-5, Brent wrote:On 1/24/2014 4:41 PM, Edgar L. Owen wrote:
> Brent,
>
> No, my proposed dark matter effect has nothing to do with black holes. Black holes are
> caused by accumulations of actual visible matter, not by the Hubble expansion of space...
>
> However I do have a question for you. Since gravitational changes propagate at the speed
> of light how does the mass inside a black hole produce gravitational effects outside the
> black hole? If light can't come out how can gravitational effects come out?
You are thinking of gravity as mediated by force particles, like photons mediate the EM
forces. But (at least classically) gravity isn't a force, it's just a shape of space and
as I responded to Liz, there's not mass in a black hole, no T_u_v term in the Einstein
equation. It's a vacuum solution. That's why it doesn't make any different what falls in
to create the black hole. The effects outside the event horizon are just that the space
is warped there just *as if* the black hole were a massive object.
Brent
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Sure. In the case of a star that collapses to a BH the cause is the matter which became so compressed that a singularity formed - and then the matter disappeared into it. That's why the Schwarzschild metrice is a vacuum solution, no matter.
--
On Sat, Jan 25, 2014 at 12:02 PM, meekerdb <meek...@verizon.net> wrote:
On 1/25/2014 5:29 AM, Edgar L. Owen wrote:
Brent,
We have to be careful to be precisely accurate here.
1. The structure of a black hole is not just a singularity inside an event horizon. The entire interior of a black hole is not a singularity. The singularity exists only at the very center of a black hole, there is plenty of volume between the event horizon and the singularity.
Actually there is plenty of *time* between the horizon and the singularity - if the black hole is large enough. The singularity isn't at a different place, it's in the future, once you're inside the event horizon.
At least for a spherically symmetric black hole, the GR solution indicates that the time dimension becomes the radial dimension of the black hole. Thus time vanishes inside the event horizon of a spherical black hole.
Jesse,No.First you have a basic misunderstanding of relativistic time in your first paragraph. External observers DO see objects fall through the event horizon of a black hole with no problem at all. They don't get stuck somehow to the surface of the event horizon as you suggest. They accelerate according to the usual laws of gravitation and fall right through the event horizon at ever increasing speed.The effect you are speaking of is simply that their CLOCKS SLOW (from the frame of the external observer) as their speed increases but primarily because of the increasingly intense gravitation, but their MOTION through the event horizon DOES NOT SLOW from the POV of the external observer.
PS: In my post below that should read electric FIELDS can come out of a black hole, not electric CHARGES.Pardon the typo!Edgar
On Sunday, January 26, 2014 12:41:07 PM UTC-5, Edgar L. Owen wrote:Richard,Well, electric charges can theoretically come out of a black hole, just NOT the singularity in particular as you suggested.
Jesse,
No, you are just plain wrong here. It's simple relativity theory. Just because observer A sees observer B's clock slow down does NOT mean observer A sees observer B's MOTION slow down. In fact it is the increase in velocity (or equivalently gravitation) that CAUSES his clock to slow in observer A's frame.
Jesse,
PS: It's not my theory, it's mainstream relativity theory. Any physicist and probably some others here can set you straight....Edgar
Jesse,
Respectfully, I don't have time to argue what is well known. If you don't believe me ask others here, or a physicist.
If what you claim was true everything that fell towards a black hole would never enter it and would be perpetually stuck around the boundary.
OK, time for THE ANSWER TO MY QUESTION of how gravity can escape from a black hole....
Liz, Brent, and Richard,
OK, nobody got the answer so I'll explain it myself. It's pretty simple but still pretty profound and thought provoking....
Gravity IS what needs to be escaped. So it doesn't even make sense to ask how gravity could escape ITSELF.
There wouldn't even be a black hole if gravity hadn't already escaped the black hole to create its gravitational effect.
So what this means is that gravity is the only thing than CAN escape a black hole because it is gravity itself that creates the gravitational field that must be escaped!
Thus gravity, and only gravity, can manifest freely OUTSIDE a black hole the effects of its INSIDE mass.
Thus gravity is the only thing that freely COMES OUT of a black hole through the event horizon, because what stops everything else from coming out is gravity itself. But obviously gravity can't stop itself from coming out through the event horizon, because only its already manifesting presence is what stops everything else from coming out through the event horizon, but it already must have come out to stop everything else from coming out...
Thus before gravity comes out through the event horizon, there is nothing to stop anything from coming out. Thus gravity can freely emerge through the event horizon and only by doing so is it able to prevent anything else from coming out....
Hope I'm explaining this clearly?
Also note that this is just a quirk of how Schwarzchild coordinates are defined, you can define other coordinate systems on the same curved spacetime that don't have this issue, like Kruskal-Szekeres coordinate:
In KS coordinates the "time" coordinate remains timelike inside the horizon, and the "radial" coordinate remains spacelike (these coordinates also have the nice feature that worldlines of light rays always have a 45 degree angle on the coordinate diagrams, just like in diagrams of inertial coordinate systems in special relativity). And in principle, even in the ordinary flat spacetime of special relativity you can define some kind of non-inertial coordinate system where a coordinate that is timelike in one region switches to becoming spacelike in another, and vice versa--this sort of thing isn't any type of physical effect, it's just due to the way you define your coordinate system.
Jesse,
No.
First you have a basic misunderstanding of relativistic time in your first paragraph. External observers DO see objects fall through the event horizon of a black hole with no problem at all. They don't get stuck somehow to the surface of the event horizon as you suggest. They accelerate according to the usual laws of gravitation and fall right through the event horizon at ever increasing speed.
The effect you are speaking of is simply that their CLOCKS SLOW (from the frame of the external observer) as their speed increases but primarily because of the increasingly intense gravitation, but their MOTION through the event horizon DOES NOT SLOW from the POV of the external observer.
Brent, Liz and Jesse,OK, now I understand the effect you guys are referencing...I thought Jesse had been saying that things don't ACTUALLY fall into black holes, they just pile up on the event horizon surface, because their motion actually slows down as they approach the surface BECAUSE their clocks slow down from the intense gravity. That of course is incorrect.But of course things actually DO fall into black holes continuously accelerating as they do so. Otherwise black holes could never form, could not exist, and we would not be observing them..But I see now what you guys are referencing is just how it appears to an outside observer as the falling object approaches c as it nears the event horizon.
PS: In my post below that should read electric FIELDS can come out of a black hole, not electric CHARGES.Pardon the typo!Edgar
On 1/25/2014 5:19 AM, Edgar L. Owen wrote:
Brent,
Obviously the space outside a black hole event horizon is warped. That's experimentally confirmed. My question is HOW does it become warped from the mass inside the black hole which you now claim doesn't even exist? There must be some cause.
Sure. In the case of a star that collapses to a BH the cause is the matter which became so compressed that a singularity formed - and then the matter disappeared into it. That's why the Schwarzschild metrice is a vacuum solution, no matter.I don't trust your intuition as to what's "reasonable" - and you shouldn't either.
It's much more reasonable to assume the mass that enters a black hole does exist inside the black hole as it does produce a gravitational effect.It doesn't have to propagate. Each bit of matter falling in already had warped the space around it and as it crosses the event horizon it leaves this bit of warpage outside contributing to the total of the BH. You've got and 17th century view of gravity as something that "reaches out and pulls on stuff".
My question is how that gravitational effect, which must travel at the speed of light, propagate from the interior of the black hole when nothing else can because it would have to travel at FASTER than the speed of light to do so?See above comment.
Re your implication of gravitation perhaps not being mediated by force carrying particles. I think there are a number of reasons to doubt the existence of gravitons.
1. For a flow of gravitons to explain gravity they would all continuously have to flow in the same direction since gravity acts only in one direction (between masses at least). That means there would have to be an inexhaustible source of gravitons flowing from ONLY OUT from every mass. What's the source of that inexhaustible flow?That's not quite true. The prediction of slowing of rapidly orbiting double stars due to energy loss to gravitational radiation has been confirmed by observation. If that radiation is quantized, which it must be to be consistent with QM, then it consists of spin-2 bosons, aka gravitons.
2. Gravity is the only force that cannot be shielded. Thus if gravitons existed they would have to flow effortlessly THROUGH everything that exists (NON-interaction) at the same time they cause gravitational effects (INTERACTION). An apparent contradiction....
3. There is no empirical evidence whatsoever that gravitons actually exist.
Since the theory is non-linear, gravitons are probably just a weak field approximation. There is also Sakaharov's gravity theory and the entropic gravity theory. Unfortunately gravity is so weak it's hard to get any experimental evidence for or against these theories.
4. Gravitons are not part of the Standard Model.
So all and all I think there is plenty of reason to doubt the existence of gravitons...
Brent
Edgar
On Friday, January 24, 2014 10:31:41 PM UTC-5, Brent wrote:
On 1/24/2014 4:41 PM, Edgar L. Owen wrote:
> Brent,
>
> No, my proposed dark matter effect has nothing to do with black holes. Black holes are
> caused by accumulations of actual visible matter, not by the Hubble expansion of space...
>
> However I do have a question for you. Since gravitational changes propagate at the speed
> of light how does the mass inside a black hole produce gravitational effects outside the
> black hole? If light can't come out how can gravitational effects come out?
You are thinking of gravity as mediated by force particles, like photons mediate the EM
forces. But (at least classically) gravity isn't a force, it's just a shape of space and
as I responded to Liz, there's not mass in a black hole, no T_u_v term in the Einstein
equation. It's a vacuum solution. That's why it doesn't make any different what falls in
to create the black hole. The effects outside the event horizon are just that the space
is warped there just *as if* the black hole were a massive object.
Brent
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If what you claim was true everything that fell towards a black hole would never enter it and would be perpetually stuck around the boundary.
Jesse,
Respectfully, I don't have time to argue what is well known. If you don't believe me ask others here, or a physicist.
Brent,
There is no confusion.
Sure, that's just the standard kiddy book diagram of a black hole with which everyone agrees (except Jesse Mazur who thinks nothing actually enters a black hole but instead piles up on the event horizon boundary - see his posts).
But that doesn't address the point of my question.
What "is in there and has to come out" is the gravitational effect of the mass that falls in which was the point of my question and my answer.
Edgar
On Sunday, January 26, 2014 2:22:58 PM UTC-5, Brent wrote:On 1/26/2014 5:01 AM, Edgar L. Owen wrote:
OK, time for THE ANSWER TO MY QUESTION of how gravity can escape from a black hole....
Liz, Brent, and Richard,
OK, nobody got the answer so I'll explain it myself. It's pretty simple but still pretty profound and thought provoking....
Gravity IS what needs to be escaped. So it doesn't even make sense to ask how gravity could escape ITSELF.
There wouldn't even be a black hole if gravity hadn't already escaped the black hole to create its gravitational effect.
So what this means is that gravity is the only thing than CAN escape a black hole because it is gravity itself that creates the gravitational field that must be escaped!
Thus gravity, and only gravity, can manifest freely OUTSIDE a black hole the effects of its INSIDE mass.
Thus gravity is the only thing that freely COMES OUT of a black hole through the event horizon, because what stops everything else from coming out is gravity itself. But obviously gravity can't stop itself from coming out through the event horizon, because only its already manifesting presence is what stops everything else from coming out through the event horizon, but it already must have come out to stop everything else from coming out...
Thus before gravity comes out through the event horizon, there is nothing to stop anything from coming out. Thus gravity can freely emerge through the event horizon and only by doing so is it able to prevent anything else from coming out....
Hope I'm explaining this clearly?
Yes, it's clear that you're confused. You think there's "something in there" that has to "come out" and pull stuff in. Here's a more accurate picture from Lawrence Crowell:
Think of a river with a water fall. You row your canoe at a constant speed, which mimics the speed of light. The flow of water increases as it approaches the falls. There is then a boundary of no return where once you cross it you can’t row faster than the flow rate of the water. You are inexorably going to reach the falls. A black hole is similar to that. The flow of space as it evolves by the diffeomorphism of general relativity is such that at the horizon that flow exceeds the speed of light.
Brent
--
This is something I have always wondered: if gravitons are real, does it make the "warping of space" explanation of gravity redundant? What was the evidence that space warps to begin with? The only thing I could think of was gravitational time dilation, but are there other reasons?
It's common knowledge - well, amongst people who are interested in this sort of thing - that an outside observer sees an infalling object get stuck just outside the event horizon of a black hole (and then fade away as it redshifts towards infinity)
This was explained in a (relatively) recent "scientific american" article using an elephant as the example. The point is that the BH creates a superposition - the elephant is a "schrodinger's cat" which is in both states (alive outside the BH, and dead inside). I found it fascinating that this well known quantum thought experiment could be done for real (in theory).
Once again my initial response to Jesse was because he claimed there was a pile up and their isn't
and second that he claimed (or at least that's the way I read his post) that the slowing of velocity was due to the slowing of the clock of the object approaching the black hole which it isn't.
Brent,I don't think my statement is confused. Your response is ambiguous because it doesn't specify frames of reference correctly.The object's clock DOES tick slower according to the external observer's clock, but obviously not by the object's OWN comoving clock. It is of course ACTUALLY objectively ticking slower because it is falling into a gravity well which is an absolute, not a relative phenomenon.
On Sun, Jan 26, 2014 at 10:42 PM, Edgar L. Owen <edga...@att.net> wrote:Once again my initial response to Jesse was because he claimed there was a pile up and their isn't
No I didn't. The very first comment of mine on the subject (you can review it at http://www.mail-archive.com/everything-list@googlegroups.com/msg47085.html ), which prompted your dismissive "you have a basic misunderstanding of relativistic time in your first paragraph" response, clearly stated the difference between what would be seen by the external observer "in practice" and what could be seen "in principle" if classical EM were exactly correct:
Hi Jesse,Sorry if I misunderstood you and for the dismissive comment.... I apparently misread your comments...As for your other comments in this post. The slowing of the clock in a gravity well is an absolute phenomenon, not a relative one.
Finally there is no "pile up" at the horizon, as I thought you claimed (you did use the term I think), because all infalling objects will fade away proportionally to how much they appear to slow.
So by the time they would begin to appear to pile up they are already fading from view. Therefore NO PILEUP, period. I'm still not clear if you understand this. It's NOT because of the red shift (which is occurring) but because the slowing means fewer and fewer photons per unit time are reaching the external observer.
That is because it takes them longer and longer to climb out of the increasing gravity well. Contrary to what you seem to say that's an absolute phenomenon, not just a matter of frames.
The external observer is just in a minimally relativistic frame suitable to measuring this effect fairly accurately. It will of course be measured differently in other frames themselves subject to strong relativistic effects.By GR, gravitational time dilation is an ABSOLUTE effect, contrary to the time dilation of constant relative velocity, which is a RELATIVE SR effect. The way you can tell is that if the black hole suddenly vanished the previously infalling object's clock would still be reading a past clock time even though it would now be running at the same rate as the clock of the external observer.
Ghibbsa,The effect of the gravity gradient you keep mentioning is well known NOT to account for the dark matter effect. The fact that it doesn't is why dark matter was postulated in the first place. So I don't see that your mention of a gravity gradient "I have to get past" is relevant...Edgar
On Wednesday, January 22, 2014 2:45:08 AM UTC-5, ghi...@gmail.com wrote:
On Wednesday, January 22, 2014 7:42:30 AM UTC, ghi...@gmail.com wrote:
On Tuesday, January 21, 2014 6:11:23 PM UTC, Edgar L. Owen wrote:Gibbsa,No, you misunderstand what I'm saying.Of course "the hubble rate can keep on going, passing the speed of light barrier, and forever onward and upward. Because, and precisely because, it's not generated by a physical translation in space."I agree with that and that's exactly what I'm saying. It's Pierz that is disagreeing with you. Pierz thinks space is expanding without taking any physical objects along with that expansion. If that were true nothing there would be no red shift and there would be no particle horizon beyond which the expansion of space carries galaxies so they can no longer be observed.Things move both IN space and WITH the expansion of space. Things moving with the expansion of space red shifts them, things moving RELATIVE TO the expansion of space gives variations of red and blue shifts for objects at the same distances in expanding space.The expansion of space occurs only in intergalactic space, but the space within galaxies, solar systems, etc. is gravitationally bound and is not expanding. Refer to Misner, Thorne and Wheeler's 'Gravitation' if you don't believe me....Our solar system is not expanding due to the Hubble expansion because it is gravitationally bound... If it was you'd have a violation of the laws of orbital motion.Therefore there must be a space warping at the boundaries of galaxies which must produce a significant gravitational effect over time which could explain the dark matter effect....Edgar
On Tuesday, January 21, 2014 12:11:25 PM UTC-5, ghi...@gmail.com wrote:
On Tuesday, January 21, 2014 4:22:34 PM UTC, Edgar L. Owen wrote:PIerz,No, you are wrong here. Space doesn't expand around objects without the objects moving along with it. The positions of objects are positions IN space. Thus there is not a smooth expansion but the warping around galaxies I've pointed out.If you were correct the Hubble expansion of space wouldn't carry far galaxies along with it and redshift them.You are simply wrong here. Please remember that the next time you accuse me of being wrong about something!EdgarEdgar, the opposite is true. The hubble effect is constant if the comparison is between any two pairs of adjacent galaxies, one pair compared to the other, obviously controlling for distance between them. It's constant in that sense whether or not the overall effect is accelerating as it is at the moment.If the galaxies are independently moving in space, the distance to adjacent galaxies is changing, and has to be controlled for, to keep that constant effect.If you skip a galaxy and want the rate of expansion between a galaxy and the second galaxy along, then you have to add the two adjacent rates together, controlling for changes in distance caused by independent movement of galaxies in space. If you want the next galaxy after that, it's adding 3 adjacent values.This is why the hubble rate can keep on going, passing the speed of light barrier, and forever onward and upward. Because, and precisely because, it's not generated by a physical translation in space.As mentionesd in the last post, large gradients are already in place around galaxies, this this probably the boundary that forbids your idea from breaking as a causality in the first place.Other than that the distinctions you make for redshift so on, definitely puts us both on the page as regarding to that, and correctly redirectly my ire to the other guy :O)
On Monday, January 20, 2014 10:12:54 PM UTC-5, Pierz wrote:I don't know why the warping effect is "obvious". All space is expanding, including that inside galaxies but the gravity effect keeps the expansion from causing the galaxy to spread out. Imagine a soft disk sitting on top of a balloon that is being blown up. The balloon surface (space) both under and around the disk is expanding, but the object keeps its size because of its internal forces. It's not as if there's some boundary at the edge of galaxies at which expansion starts.
On Tuesday, January 21, 2014 3:01:03 AM UTC+11, Edgar L. Owen wrote:All,Here's one more theory from the many in my book on Reality:As Misner, Thorne and Wheeler note briefly in their book on Gravitation, INTERgalactic space is continually expanding with the Hubble expansion, however INTRAgalactic space is NOT expanding because it is gravitationally bound.Now the obvious effect of this (as I'm the first to have pointed out so far as I know) is that space will necessarily be warped at the boundaries of galaxies, and as is well know from GR any curvature of space produces gravitational effects, and of course dark matter halos around the EDGES of galaxies were invented to explain the otherwise unexplained extra gravitational effects on the rotation of galaxies.Thus, this simple effect of space warps around the boundaries of galaxies caused by the Hubble expansion may be the explanation for the dark matter effect.It may or may not be the cause of the entire effect, but it certainly must be having SOME effect, and over the lifetime of the universe one would expect that warping effect to be quite large.And there is nothing to prevent these warps, once they are created, to have a life and movement of their own, as we now know that dark matter is not just concentrated around galactic halos but may indicate where they used to be....I'd be interested to see if anyone else sees how this effect might explain dark matter...Edgar