A theory of dark matter...

[Edgar L. Owen]

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

[spudb...@aol.com]

To better ascertain what dark matter is, you may need to give us a clue on your view on the volume of the cosmos. As in, just the Hubble Volume, 42 billion light years, 80 billion light years (both estimates have been given) or infinite? If it is infinite I guess that it will impact your theory, at least for gravatic influences. An infinite expanse would stretch whatever dark matter's impact on the 10^80 particle that we guess is normal matter, to zed.

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[Edgar L. Owen]

Spud,

I don't follow your argument, since the actual impact of dark matter is clearly real and measurable.

But the universe cannot be infinite since nothing actual can be infinite since infinity is not an actual number but the result of a never ending process (keep adding forever) which could never be realized.

Edgar

[spudb...@aol.com]

OK, you are invoking the asymptotic aspect of math. But I am not sure the cosmos needs to obey arithmetic, to function? But, please continue on topic. I recuse myself on this. 

[Pierz]

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.

[ghi...@gmail.com]

It's an idea but I don't really get why expanding one side and not the other  translates to a physical gradient.  Conceptual presentations of the difference in gradient terms are feasible, but nothing is carried by that alone.

 

I don't personally endorse  comparing one theory to another with a view to keep one and delete the other. I do think there is good method and bad method though. What your idea looks like to me, is a seed insight. That is the very first step on a pretty long road to a theory. IMHO it's really poor form to burn someone else's seed insight. But it's terrible form to present a seed insight as if it's more.

 

There needs to be a translation to some basic independent reality check. It doesn't have to be a lot, but getting a foothold there delivers something a million eloquent words will not. The idea is checkable in various ways. Whole clusters of galaxies may be gravitationally bound. Are you able to translate your idea to an expectation of some kind of distinction between halos around those galaxies?

 

Or, can your idea explain the unique properties of the galaxy + halo. Why is the result a gradient of gravity near enough from the centre to the edge, such that the orbital speed of bodies the orbital speed is near enough  constant throughout? Why the correlations with the supermassive black hole

 

I'm not trying to teach you to suck eggs. I respect your idea, and also your wider theory, that you fulfilled a life long dream to accomplish that. The most significant development - for me - about the 'Edgar' chapter in the voluminously unwritten History of Everything (list) is the by product of almost no progress being made, that saw variability and veneer fall away allowing distinctive traits to become much clearer to see.

 

A significant fraction of yours are arguably negative or counter-productive. But what they did real nail, is the basic authenticity of your story, because a lot of them are reasonable as offsets for the shortfalls of long term intellectual projects in effective isolation. While others go a long way to authenticating your ideas are substantially your own work, for example, that you find it hard to be interested in other peoples ideas, and that despite your obvious gifts and interest in precisely that, you never learned the core mainstream theories beyond the level of a well informed amateur (there's a definite worsening progression to your responses to hardening challenges).

 

It is a negative  in this context, but by the same coin, it all comes together as a substantial authentication of you as your claims about  you. The significance of that is actually considerable, Your idea about p-time looks wrong to me, and I think it's probably explained by the fact you had a really good seed insight about everything having to be massively more synchronized , with massively more sameness. I definitely buy that. But the consequence you computed about a single logical structure was slightly flawed because that is not the only possible explantion. Then you moved too quickly to a consequence for that before you had time (or perhaps maturity as this section you were really young) That was p-time.

 

It's possibly one of the least powerful insights of your whole theory, but it came right at the start, and got locked in because intuition became locked  in by the character of the sequence.

 

You don't have to agree...it's just part of what I think. But the other part comes by the authentication effect. You know, the amount you get right in that overall theory, for the level of isolation and personal gravity for the process of thinking your own ideas. I mean, so much of that is so right, and so anticipates the culmative position in science right now. THAT'S the accomplishment and the substance.

 

 

 

[Edgar L. Owen]

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

[ghi...@gmail.com]

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!

Edgar

 

Edgar, 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.

[Edgar L. Owen]

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

[Edgar L. Owen]

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.

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.

Edgar

[Russell Standish]

This para of Al's hits the nail on the head for me. To be convincing,
one needs to do the actual stress-strain calculations to see if it can
reproduce the well known empirical rotation curve of the Milky
Way. Realistically, this is beyond my capabilities at present, and
beyond my interest levels to learn :).

My gut feeling here is that space doesn't wrinkle near galactic
boundaries, but rather there would be a smooth pressure that increases
the further you are from the galactic centre, due to the expansion of
the universe. It boggles the mind that that would have been overlooked by
cosmologists, though.

Another thing to bear in mind is that all galaxies within the local
group are gravitationally bound, including the two best know members,
Andromeda and our own Galaxy. Taking your interpretation of MTW's
comment literally would imply we shouldn't see the affect of space
"wrinking" until we get to the halo of the local group, but the dark
matter problem is clearly observed in the rotation curve of the Milky Way.

Cheers
--

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[Edgar L. Owen]

Russell,

Sure of course. To repeat what I've already said above, the actual effects will be extremely complex simply because the actual distribution of matter is extremely complex and varies with time. One would need to actually calculate the cumulative effects over time of the warping and compare with the observed distribution of dark 'matter'.

I was careful to state this is a POSSIBLE dark matter effect, and not necessarily the only one. Nevertheless it should be a quite significant effect if the Hubble expansion has been producing it for 13.7 billion years.

Edgar

[ghi...@gmail.com]

On Tuesday, January 21, 2014 6:42:20 PM UTC, Edgar L. Owen wrote:

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).

 

Any unfairness wasn't intended that I'm aware.

 

Leaving aside the 'seed' part, the comment about the reality check was the bridge to commenting more generally about your work. You probably know already, that the part of what a theory says that is open to philosophy peaks very early - actually before the theory exists. The inner peak is about where the seed insight comes from. The arrow of everything after that, progressively takes everything away from the theorist, by shifting all of it up to the structure level.

 

It's obviously not the theory driving the shifting, but the successive decisions of the theorist.

 

The part of this that is widely understood is that we can't change the logical consequences of a theory. The part that isn't so widely known is that where it all actually ends up is translated to structure. And the consequences following from  that. One which being the mutual exclusivity of either choosing the prediction/verification as the driving force behind the progression of the theory, or giving primacy to self-consistency for the driving energy. which necessarily stacks as much as possible as near as possible to the initial conditions, and then generates successive consequences by holding the principles stacked at the start, constant.

 

You can't have both, because the initial conditions plus consequences plus consistency will quickly begin to see points where individual lines of consequences cross to the other side of eachother. As this effect builds up the criss-cross points will progressively draw ever smaller circles around spaces that all subsequent consequences must fit into to keep consistency. The crisscross points becoming characteristics that must define those consequences.

 

As such both the potential and the value of prediction wastes away, because the part that isn't set by the consequences that came first gets smaller and smaller.

 

The reason that only the prediction/test route is science, is that only this route generates the unanticipated new discovery, by continually adjusting to reality checks. and only the prediction/check route contains the properties of both directions together. The initial conditions + consistency + consequences route on its own progressively makes prediction, impossible, on the other hand.

 

That is why that direction goes back to pre-scientific philosophy, and why powerful science is always a process that builds in regular reality checks as predictions.

 

 

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

 

 Do you say here that the halo us is both the space not expanding in galaxies, and the mass as well? Where does this leave a space for gravity?

 

By the way, the fact that conventional gravity creates a very significant gradient around the bounds of a galaxy, is also a strong candidate for the kind of up front barrier that would prevent the expansion of spacing on the one side physically detecting the non expansion on the other side in the first place. The gradient is already and that's already a major boundary.

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.

 

I think traditional gravity is the obstacle you and the expanding space will need to get past, for any such effect.  

[ghi...@gmail.com]

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!

Edgar

 

Edgar, 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)

[ghi...@gmail.com]

[Pierz]

On Wednesday, January 22, 2014 6:42:30 PM UTC+11, 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.

No that isn't what I meant. If you read the balloon analogy carefully you'll see I was saying something else. Imagine several soft disks sitting lightly on top of the balloon as it expands. The disks will not grow due to the internal forces that prevent the slight friction from the expanding balloon surface from causing them to expand. However, they will move apart from one another as the balloon expands. That was my understanding. 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. So my understanding was that cosmological expansion exists right here in this room, but is more than compensated for by the other forces tending to hold objects together, including gravity. Where I think I erred was in separating gravity and expansion in my mind - there is only one underlying time-space continuum which is being operated on by the two forces. Within galaxies gravity holds sway and space does not expand. Far enough away from galaxies, gravity gives way to expansion. I don't see the inevitability of warping because the counteracting effects of gravity will attenuate slowly as you move away from a galactic centre. It's not like there's a row of pins around the galactic edges which hold space in place.

[LizR]

One always finds out what Edgar doesn't mean...

--

[LizR]

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?

[Pierz]

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.

[LizR]

On 23 January 2014 22:34, Pierz <pie...@gmail.com> 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.

OK, cool, sorry to be nitpicking.

[LizR]

Well not sorry, exactly, I wanted the clarification! :-)

[Edgar L. Owen]

Liz,

It was Pierz that said that's not what HE meant, not me.

It would be nice if you would actually READ and comprehend what you are replying to for a change. You are obviously replying to your own prejudices here rather than to the actual post which you didn't even read correctly!

Edgar

[meekerdb]

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.

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 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.

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.

Brent

WAS he talking about Dark Energy?

[Edgar L. Owen]

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

[LizR]

On 24 January 2014 07:33, meekerdb <meek...@verizon.net> wrote:

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.

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.

Yes, good point, clearly space is expanding, and matter is sitting there in space, going along for the ride (with a bit of residual momentum, but not much in the cosmic scheme of things, and presumably it cancels out over large enough distances).

However, as far as I know this expansion doesn't in itself cause a force to act on the matter within it, somehow pushing it apart, which was the point at issue.

(Or at least it appeared to be - it turned out that the real point was dark energy).

[LizR]

On 21 January 2014 05:01, Edgar L. Owen <edga...@att.net> wrote:

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. 

Dark matter was first postulated (in 1932 iirc) to explain both the rotation curves of galaxies, and how galactic clusters are gravitationally bound together. So any theory of DM needs to explain both these phenomena.

I believe there is also a need for DM to flatten the overall curvature of the universe (as measured by WMAP or COBE or one of those observatories). That is, the density of the universe has to be something like 4x (?) higher than is accounted for by visible "baryonic" matter, and the rest can't be baryonic because if it was, that would have changed the rates of nucleosynthesis in the big bang (there would be 4x more fuel available and the reactions would have gone a lot faster, and the universe would be a lot fuller of helium than is observed - or something like that). Hence something other than baryonic matter is needed to give the observed flatness.

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.

This sounds vaguely similar to MOND - modifying the force of gravity at some boundary. (Does your theory make testable predictions that differentiate it from MOND?)

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....

Are you suggesting that space has a sort of memory of the curvature that was caused by the matter it used to contain?

So for example when the galaxies in the bullet cluster collided, these warps - the imprint of the galaxies on space - got stuck together in the middle of the impact, while the visible parts of the galaxies carried on moving outwards?

How would the warp get detached from the matter causing it?

[LizR]

On 24 January 2014 07:33, meekerdb <meek...@verizon.net> wrote:

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.

Yes, it depends on what it is, which is why I didn't think he could necessarily say it existed between someone's fingers.

Of course gravity isn't a force either. The term is being used to simplify the discussion, it's a lot easier to type "force" than "effect of the curvature of space" (it also seems a valid shorthand usage because it would be experienced in a similar manner to a force, i.e. it would cause an acceleration).

[Edgar L. Owen]

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...

Edgar

[Samiya Illias]

I always wonder why physicists insist on 'gravity' when 'space-time curvature' is the more scientific explanation. Isn't 'gravity' something that needs to be 'taken on faith'?  
Samiya 

[LizR]

On 25 January 2014 02:01, Edgar L. Owen <edga...@att.net> wrote:

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...

OK. so that's a yes to my last question. It would be nice if you addressed all the points I made, though. 

[meekerdb]

On 1/24/2014 5:01 AM, Edgar L. Owen wrote:
> 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

Information Preservation and Weather Forecasting for Black Holes
S. W. Hawking
(Submitted on 22 Jan 2014)

It has been suggested [1] that the resolution of the information paradox for
evaporating black holes is that the holes are surrounded by firewalls, bolts of outgoing
radiation that would destroy any infalling observer. Such firewalls would break the CPT
invariance of quantum gravity and seem to be ruled out on other grounds. A different
resolution of the paradox is proposed, namely that gravitational collapse produces
apparent horizons but no event horizons behind which information is lost. This proposal is
supported by ADS-CFT and is the only resolution of the paradox compatible with CPT. The
collapse to form a black hole will in general be chaotic and the dual CFT on the boundary
of ADS will be turbulent. Thus, like weather forecasting on Earth, information will
effectively be lost, although there would be no loss of unitarity.

Brent

[LizR]

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 :-)

[Edgar L. Owen]

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?

Edgar

[meekerdb]

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,

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.

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

A black hole crushes it's source into a singularity (in the classical approximation). 

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".

Gravity waves can't exactly be 'free floating' because they travel at the speed of light and only interact gravitationally.  So unless they are strong enough to close up on themselves and make a black hole, they will radiate off to infinity.

Brent

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 :-)

[meekerdb]

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

[LizR]

On 25 January 2014 16:02, meekerdb <meek...@verizon.net> wrote:

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,

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.

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

A black hole crushes it's source into a singularity (in the classical approximation). 

Yeeees. Are you saying something I didn't? The point is that wasn't what Edgar described, and it still isn't.

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".

Gravity waves can't exactly be 'free floating' because they travel at the speed of light and only interact gravitationally.

Why isn't travelling at the speed of light "free floating" ? How freely do you have to float, exactly? 

 

  So unless they are strong enough to close up on themselves and make a black hole, they will radiate off to infinity.

Yes, true, and? I was trying to find something that vaguely matched what Edgar described. 

Sorry but just nitpicking trivial points and more or less repeating what I said doesn't help.

[LizR]

I believe Richard Feynmann was asked the same question (about how gravity "escapes" a black hole). Of course gravity WAVES can't escape a black hole... 

[Edgar L. Owen]

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

[Edgar L. Owen]

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.

2. We have to clearly distinguish gravity WAVES from gravity itself. Gravity waves are NOT gravity, they are small fluctuations in 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....

Edgar

[Richard Ruquist]

On Sat, Jan 25, 2014 at 8:19 AM, Edgar L. Owen <edga...@att.net> 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. 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?

Gravitation like electrostatics is faster than the speed of light- seemingly instantaneous 

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

--

[Edgar L. Owen]

Richard,

No, that's not correct. Gravitation is NOT faster than the speed of light. Once a gravitational field is established it is remains there only so long as the mass that produces it is. Remove that mass and the removal of the associated gravitational force propagates at the speed of light as ALL gravitational changes (effects) do.

So if the sun were to vanish, it would still keep the earth in its orbit for 8 minutes...

Edgar

[Richard Ruquist]

So how do you explain that gravitational effects escape a black hole.

And while you are at it explain how electrostatics are instantaneous.

[Edgar L. Owen]

Richard,

Can you explain in more detail what you mean by electrostatics being instantaneous?

EM fields propagate at the speed of light but once established their effects are "instantaneous" because the field is coterminous with whatever it reacts with or has an effect on. Is that what you mean?

A standing EM field is set up at the speed of light but once established it is right where it interacts with something so the effect is then instantaneous.

Edgar

[meekerdb]

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

[Richard Ruquist]

The best example of what I am referring to is the propagation of EM waves thru a layer where attenuation is dominant.

Empirically the EM waves leave the layer at the same instant that they enter. That is a well known near field effect.

You might read up on near field scanning microscopes where instantaneous effects are also well known.

The fundamental connection of gravity and electrostatics is that the solutions for a point charge is the same as the field of a point mass. Regarding black holes, all that can be known of their properties is their mass, their charge and their spin.

Both the black hole gravity field and its electrostatic field are near field effects as the wavelength of either is infinite.

[Richard Ruquist]

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.

 

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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[LizR]

On 26 January 2014 07:25, Richard Ruquist <yan...@gmail.com> wrote:

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.

If time becomes the radial dimension, it doesn't vanish inside the event horizon. It vanishes at the singularity, which is to say the signularity acts as a future "big crunch" to anything that falls in; the BH is like a collapsing universe.

(I've used this to illustrate that future constraints can act as boundary conditions on the behaviour of macroscopic objects, by the way, when discussing time symmetry in physics :)

[meekerdb]

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.

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.

I don't trust your intuition as to what's "reasonable" - and you shouldn't either.

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?

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".

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?

See above comment.

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.

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.

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...

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.

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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[LizR]

On 26 January 2014 10:58, meekerdb <meek...@verizon.net> wrote:

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 assume most physicists nowadays think classical GR breaks down at some point before a singularity forms, so in practice there is something in there (though no one knows what, and it may be at - or below - the Planck length)....?

[Edgar L. Owen]

Brent,

You seem to be saying 1. that the matter that enters a black hole through the event horizon warps space as it enters and 2. that then that space warp persists as the matter disappears into the singularity.

1. is of course correct but 2. isn't. Consider a mass traveling through empty space. As it travels it obviously does warp the space around it but as soon as it moves away that warping dissolves. The warping is carried along by the mass and exists only around a mass. So by your thinking the warping should persist all along the path of any traveling mass but it doesn't. The earth and sun don't leave permanent trails of space warping behind them as they move through space. The warping travels WITH the moving mass and is maintained only by the continuing presence of the mass.

So there can be no warping left around a black hole if the matter falling into it actually were to disappear. The warping is maintained ONLY by the continuing presence of mass, just like it is around a mass traveling through empty space.

Do you understand my point here?

Edgar

[Edgar L. Owen]

Brent,

PS: The Schwartzchild solution just gives the radius of the event horizon of a non-spinniing black hole. It says nothing about any matter disappearing. In fact it assumes the continual presence of the matter that creates the black hole.

So I don't see your first point ...

Edgar

[meekerdb]

Right.  I think LQG predicts an Einstein-Rosen bridge.  I don't know that string theory has made definite prediction.

Brent

[meekerdb]

On 1/25/2014 4:55 PM, Edgar L. Owen wrote:
> Brent,
>

> You seem to be saying 1. that the matter that enters a black hole through the event
> horizon warps space as it enters and 2. that then that space warp persists as the matter
> disappears into the singularity.
>
> 1. is of course correct but 2. isn't. Consider a mass traveling through empty space. As
> it travels it obviously does warp the space around it but as soon as it moves away that
> warping dissolves. The warping is carried along by the mass and exists only around a
> mass. So by your thinking the warping should persist all along the path of any traveling
> mass but it doesn't. The earth and sun don't leave permanent trails of space warping
> behind them as they move through space. The warping travels WITH the moving mass and is
> maintained only by the continuing presence of the mass.
>
> So there can be no warping left around a black hole if the matter falling into it
> actually were to disappear. The warping is maintained ONLY by the continuing presence of
> mass, just like it is around a mass traveling through empty space.
>
> Do you understand my point here?

Yes, I understand you're still trying to use your Newtonian intuition of predict what a BH
does. Just look up the derivation of the Schwarzschild metric and explain what it means
that T_u_v=0.

Brent

[meekerdb]

On 1/25/2014 4:59 PM, Edgar L. Owen wrote:
> Brent,
>

> PS: The Schwartzchild solution just gives the radius of the event horizon of a
> non-spinniing black hole. It says nothing about any matter disappearing. In fact it
> assumes the continual presence of the matter that creates the black hole.

No, it assumes ZERO matter, T_u_v=0. It's a VACUUM solution.

Brent

[LizR]

Hopefully they will let us know as and when :-) 

[Edgar L. Owen]

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?

Edgar

[Richard Ruquist]

Edgar,

Electric fields also come out if the BH singularity has a charge.

Richard

--

[Jesse Mazer]

According to general relativity, neither gravity nor electric fields actually "come out of" the black hole's event horizon, rather the gravity and EM field felt by observers outside the horizon is a sort of frozen snapshot of the gravity/EM fields from all the matter that approached the horizon in the past. Keep in mind that external observers can never actually see anything cross the horizon, instead they see it moving more and more slowly as it gets arbitrarily close to the horizon--the redshift is continually increasing as it approaches horizon so in practice an external observer can't see an object stuck on the horizon forever, but in principle you could if you could detect light with arbitrarily huge wavelengths, and if light was a classical EM wave rather than being quantized into photons.

The Usenet Physics FAQ at http://math.ucr.edu/home/baez/physics/ has some good summaries:

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_gravity.html

'How does the gravity get out of a black hole?

'Purely in terms of general relativity, there is no problem here.  The gravity doesn't have to get out of the black hole.  General relativity is a local theory, which means that the field at a certain point in spacetime is determined entirely by things going on at places that can communicate with it at speeds less than or equal to c.  If a star collapses into a black hole, the gravitational field outside the black hole may be calculated entirely from the properties of the star and its external gravitational field before it becomes a black hole. Just as the light registering late stages in my fall takes longer and longer to get out to you at a large distance, the gravitational consequences of events late in the star's collapse take longer and longer to ripple out to the world at large.  In this sense the black hole is a kind of "frozen star": the gravitational field is a fossil field.  The same is true of the electromagnetic field that a black hole may possess.'

They then go on to discuss how the picture is altered by virtual particles in quantum field theory, but the above is a good explanation of how it works with classical general relativity and classical electromagnetism. And this entry from the FAQ discusses how in general nothing is actually seen to cross the horizon by external observers:

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html

'Won't it take forever for you to fall in?  Won't it take forever for the black hole to even form?

'Not in any useful sense.  The time I experience before I hit the event horizon, and even until I hit the singularity—the "proper time" calculated by using Schwarzschild's metric on my worldline—is finite.  The same goes for the collapsing star; if I somehow stood on the surface of the star as it became a black hole, I would experience the star's demise in a finite time.

...

'A more physical sense in which it might be said that things take forever to fall in is provided by looking at the paths of emerging light rays.  The event horizon is what, in relativity parlance, is called a "lightlike surface"; light rays can remain there.  For an ideal Schwarzschild hole (which I am considering in this paragraph) the horizon lasts forever, so the light can stay there without escaping.  (If you wonder how this is reconciled with the fact that light has to travel at the constant speed c—well, the horizon is traveling at c! Relative speeds in GR are also only unambiguously defined locally, and if you're at the event horizon you are necessarily falling in; it comes at you at the speed of light.) Light beams aimed directly outward from just outside the horizon don't escape to large distances until late values of t.  For someone at a large distance from the black hole and approximately at rest with respect to it, the coordinate t does correspond well to proper time.

'So if you, watching from a safe distance, attempt to witness my fall into the hole, you'll see me fall more and more slowly as the light delay increases.  You'll never see me actually get to the event horizon. My watch, to you, will tick more and more slowly, but will never reach the time that I see as I fall into the black hole.  Notice that this is really an optical effect caused by the paths of the light rays.

'This is also true for the dying star itself.  If you attempt to witness the black hole's formation, you'll see the star collapse more and more slowly, never precisely reaching the Schwarzschild radius.

'Now, this led early on to an image of a black hole as a strange sort of suspended-animation object, a "frozen star" with immobilized falling debris and gedankenexperiment astronauts hanging above it in eternally slowing precipitation.  This is, however, not what you'd see.  The reason is that as things get closer to the event horizon, they also get dimmer.  Light from them is redshifted and dimmed, and if one considers that light is actually made up of discrete photons, the time of escape of the last photon is actually finite, and not very large.  So things would wink out as they got close, including the dying star, and the name "black hole" is justified.'

[Jesse Mazer]

On Sat, Jan 25, 2014 at 1:25 PM, Richard Ruquist <yan...@gmail.com> wrote:

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.

It would be more correct to say that the "time" dimension of the Schwarzschild coordinate system becomes spacelike, so inside the horizon, a path through spacetime that has a constant "position" coordinate but a varying "time" coordinate would actually be a spacelike path (the question of whether a path through spacetime is timelike, spacelike, or lightlike is one that has an objective answer that doesn't depend on the choice of coordinate system, see https://en.wikipedia.org/wiki/Spacetime#Spacetime_intervals and https://en.wikipedia.org/wiki/Spacetime#Spacetime_in_general_relativity ). However, it is likewise true in Schwarzschild coordinates that the "radial" dimension becomes timelike, so inside the horizon a path with a constant "time" coordinate but varying "radial" coordinate would be a timelike path. So, time in a physical sense doesn't actually vanish inside the horizon, it's just that the coordinate separation between ticks of your clock would be best measured using the "radial" coordinate of Schwarzschild coordinates, not the "time" coordinate.

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:

https://en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates#Qualitative_features_of_the_Kruskal-Szekeres_diagram

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

[Richard Ruquist]

Jesse, Please excuse my simple-minded model:

"Electric fields also come out if the BH singularity has a charge."

Richard

[Edgar L. Owen]

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.

You are confusing the frames....

Second for the answer to my question of how gravity can escape the event horizon see my response to Liz on the Tegmark's New Book thread...

Edgar

[Jesse Mazer]

On Sun, Jan 26, 2014 at 11:49 AM, Edgar L. Owen <edga...@att.net> wrote:

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.

If by "POV of the external observer" you mean what the external observer would see if they were receiving continuous light signals from the falling observer (rather than talking about what happens in some coordinate system used by the external observer), then you're incorrect, the external observer would see the falling observer inch closer and closer to the position of the horizon but never quite reach it. This is in fact an obvious *consequence* of the fact that the falling observer's clock is seen to run slower and slower and never quite reach the time at which the falling observer crossed the horizon--all observers in relativity always agree about which events coincide at the same local point in space time, so if there are a series of markers hovering above the horizon, all observers must agree about the time on the falling observer's clock at the moment he passed locally next to each marker. Thus if the falling observer noticed his clock read 10 seconds when passing marker A, 20 seconds when passing marker B, and 30 seconds when passing marker C, external observer must agree that these local events coincide. So if the external observer sees the falling observer's clock slowing, so that it takes much longer for it to go from 20 to 30 than it took to go from 10 to 20, that means they must also see the falling observer take much longer to cross from marker B to marker C than he took to cross from marker A to marker B.

If you disagree, please explain which part of the argument you disagree with. Do you disagree with the basic principle that all observers agree on which local events coincide, so they all agree on what the falling observer's clock read at the moment he passed locally next to each marker? Or do you disagree that external observers see his clock slowing in such a way that it never quite reaches the time at which he locally crossed the horizon? Or something else?

Also, I'm sure it wouldn't be hard to find some references written by physicists saying that external observers would see the falling observer getting closer to the horizon but never quite reaching it. Are you claiming that this is incorrect in the standard understanding of general relativity by physicists, or are you just telling me it's incorrect in your personal theories which disagree with mainstream physics? If the former, would you be open to changing your mind if I could find you some such references?

Jesse

[Edgar L. Owen]

Richard,

Well, electric charges can theoretically come out of a black hole, just NOT the singularity in particular as you suggested. Nobody actually knows what happens in the singularity itself, or at least there is no consensus. I made one suggestion with reference to a bouncing universe and gravitation and entropy reversal in a previous post.

However due to the almost impossible task of compressing any significant electrically charged matter to black hole densities black holes are not expected to exist with any significant electric charges....

Edgar

[Edgar L. Owen]

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.

Again you are confusing frames here. Think it through and you should understand your error....

Edgar

[Edgar L. Owen]

Jesse,

PS: It's not my theory, it's mainstream relativity theory. Any physicist and probably some others here can set you straight....

Edgar

On Sunday, January 26, 2014 12:22:58 PM UTC-5, jessem wrote:

[Richard Ruquist]

Edgar,

Regarding " Nobody actually knows what happens in the singularity itself",

Poplawski using Einstein equations with spin has determined what happens inside a black hole:

"In 2011, Nikodem Popławski showed that a nonsingular Big Bounce appears naturally in the Einstein-Cartan-Sciama-Kibble theory of gravity.^[7] This theory extends general relativity by removing a constraint of the symmetry of the affine connection and regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between torsion and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. Such an interaction averts the unphysical Big Bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic, providing a physical alternative to cosmic inflation."

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

Richard

[Edgar L. Owen]

PS: In my post below that should read electric FIELDS can come out of a black hole, not electric CHARGES.

Pardon the typo!

Edgar

[Edgar L. Owen]

Thanks Richard, quite interesting, though obviously the jury is still out...

Edgar

[Richard Ruquist]

On Sun, Jan 26, 2014 at 12:57 PM, Edgar L. Owen <edga...@att.net> wrote:

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.

Pardon me Edgar but I did not say where the electric fields come out of.

[Jesse Mazer]

On Sun, Jan 26, 2014 at 12:47 PM, Edgar L. Owen <edga...@att.net> wrote:

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.

You seem to be confused about special relativity vs. general relativity, the idea that time dilation is a direct function of velocity is only true in inertial frames in special relativity, it doesn't apply in the type of arbitrary non-inertial coordinate systems used in general relativity (inertial frames can only be used in flat spacetime, all coordinate systems covering non-infinitesimal regions of curved spacetime are considered non-inertial...and even in flat spacetime you are free to use a non-inertial coordinate system where time dilation is not just a function of velocity, as with "Rindler coordinates" discussed at https://en.wikipedia.org/wiki/Rindler_coordinates ). Gravitational time dilation in general relativity is considered a separate phenomenon from velocity-based time dilation in special relativity, see for example https://en.wikipedia.org/wiki/Time_dilation#Time_dilation:_special_vs._general_theories_of_relativity

What's more, I wasn't even talking about "frames" (coordinate systems) in my previous comment at all, I was talking about frame-independent claims about what the distant observer *sees* in terms of light-signals from the falling observer--in other words, what the distant observer's own clock (i.e. his own proper time) reads at the moment he receives various light signals from the falling observer. To say he sees the falling observer's clock tick slower and slower means he records a greater and greater proper time on his own clock between receiving light-signals showing successive ticks of the falling observer's clock, a statement that doesn't refer to any specific frame of reference. This is again a matter of which events *locally* coincide (which light signals arriving at his location coincide with which readings on his own clock), which is how objective frame-independent facts are generally defined in relativity.

Can you please answer the question I asked in the previous comment about whether you understand that in relativity, all observers and all frames must agree on the question of which events locally coincide at the same point in spacetime? In other words, for statements like this:

"at the moment that the falling observer passed locally next to marker A hovering above the horizon, his own clock read 10 seconds"

and

"at the moment that the distant observer received a light signal showing that the falling observer's clock read 10 seconds, the distant observer's own clock read 100 seconds"

...do you agree that such statements are totally objective in the sense that all observers and frames must agree about them? Please answer yes or no, and your answer will suggest how this discussion should proceed (if "yes" I can ask you some more specific questions about my thought-experiment involving markers hovering above the horizon and how long the distant observer sees the falling observer take to pass successive pairs...if "no" then that suggests you are confused about a really basic point in relativity, which might explain your confusion about subjects like the sense in which the twins in the twin paradox have different ages at the "same time" when they reunite and compare ages locally).

Jesse

[Jesse Mazer]

On Sun, Jan 26, 2014 at 12:51 PM, Edgar L. Owen <edga...@att.net> wrote:

Jesse,

PS: It's not my theory, it's mainstream relativity theory. Any physicist and probably some others here can set you straight....

Edgar

If you think this is mainstream physics, then can you please answer the question I asked earlier about whether you're open to being shown you are incorrect about the mainstream view if I can find comments from physicists explaining that the falling observer is seen to approach the horizon but never cross it? Or would you resolutely stand by this opinion even if I could find numerous such quotes, and even if you could not find a single example of a mainstream physicist saying that the falling observer *is* seen by external observers to reach the horizon in a finite time?

Jesse

[Edgar L. Owen]

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. That would include all the matter which would never enter the black hole and thus a black hole could never even be formed, but of course we know they are formed.

Edgar

[Jesse Mazer]

---

Date: Sun, 26 Jan 2014 10:53:42 -0800
From: edga...@att.net
To: everyth...@googlegroups.com
Subject: Re: A theory of dark matter...

[Jesse Mazer]

On Sun, Jan 26, 2014 at 1:53 PM, Edgar L. Owen <edga...@att.net> wrote:

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.

You are being evasive--you want me to "ask a physicist" but "don't have time" to tell me if you would change your mind if I could present clear evidence that actual physicists disagree with you and agree with me? If I email a physicist and report back what they say, would you listen then, or are you so absolutely convinced of your perfect understanding of relativity that you would assume I was lying or that the physicist in question is mistaken?

I also asked you a simple question about whether you agree about the principle that if one observer/frame says a given pair of events coincide at the same point in spacetime, all observers/frames must agree on this--surely you have time to answer this basic question yes or no.

 

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.

No, because what I claim is only about what is seen by observers outside the black hole in terms of light signals, not what actually happens to the falling observer himself. It is a standard textbook result that the falling observer does cross the horizon at a finite proper time on their own clock, but that observers on the outside only see light from readings earlier than this finite proper time.

Jesse

[meekerdb]

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

[Edgar L. Owen]

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

[meekerdb]

On 1/26/2014 7:29 AM, Jesse Mazer wrote:

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:

https://en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates#Qualitative_features_of_the_Kruskal-Szekeres_diagram

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.

Which is also a good illustration of why proper-time (i.e. clock-time along a path) is regarded as fundamental in physics.  It's the same however to label the events with coordinates, whereas coordinate time can be changed arbitrarily to make the picture simple.

Brent

[meekerdb]

On 1/26/2014 8:49 AM, Edgar L. Owen wrote:

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.

You're wrong and Jesse is right.  For the observer far from the BH it takes an infinite time to see the infalling object reach the event horizon.  There's a good explanation here:




Notice that in the infalling worldline move inward less and less as the observer views it from t1, t2, t3,... and only in the limit t->inf does the outside observer see it reach the event horizon.  If you think you can show differently I suggest you publish - a Nobel prize awaits.

Brent

[LizR]

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).

[Edgar L. Owen]

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.

So, given that I stand corrected!

Thanks,

Edgar

[Jesse Mazer]

On Sun, Jan 26, 2014 at 4:31 PM, Edgar L. Owen <edga...@att.net> wrote:

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.

What do you mean "approaches c"? Again, if we are talking about what the external observers *sees* visually (and ignoring the difficulty of seeing highly redshifted light), he sees the falling observer getting closer and closer to the horizon but never quite reaching it--so visually the falling observer would seem to slow down, inching closer and closer to the horizon but forever appearing to remain outside it, from the visual POV of the external observer. But of course the falling observer doesn't experience it taking forever to reach the horizon, he crosses it at some finite proper time and then passes into the interior.

If we're talking about velocities rather than just visual rates of movement as seen by some far away observer, hopefully you understand that all statements about the velocity of anything depend on the choice of coordinate system you use to assign position and time coordinates to events. In the "waterfall" coordinates that Brent mentioned (described at http://jila.colorado.edu/~ajsh/insidebh/waterfall.html ), it is true that if an observer starts out at rest at infinity and falls into the black hole, his velocity reaches c at the horizon. In other commonly-used coordinate systems for a black hole this isn't the case though--in Schwarzschild coordinates the coordinate velocity of anything falling into the hole (even light) always approaches 0 at the event horizon, and it takes an infinite coordinate time to cross the horizon (but still a finite proper time). With Kruskal-Szekeres coordinates which I mentioned earlier in a post to Richard, the coordinate system has the nice property that light has a constant coordinate speed just like in an inertial frame in special relativity (which isn't true of some other commonly-used coordinate systems like Schwarzschild coordinates and waterfall coordinates, where the coordinate speed of light rays varies), while all massive objects have a coordinate speed less than light, and in these coordinates the horizon itself expands outward at the speed of light. So this gives another way of thinking about why nothing can escape the horizon once it's entered it--it's the same reason you can't "escape" the future light cone of some event once you've entered it.

Jesse

[Jesse Mazer]

On Sun, Jan 26, 2014 at 12:57 PM, Edgar L. Owen <edga...@att.net> wrote:

PS: In my post below that should read electric FIELDS can come out of a black hole, not electric CHARGES.

Pardon the typo!

Edgar

I don't think it's right to say fields "come out of" the black hole. In classical electromagnetism, the field at any given point in spacetime can be entirely determined by the presence and motion of all charged matter in the past light cone of that point. And for any point outside the event horizon, every point in its past light cone is also outside the horizon. So the field at that point is entirely determined by the past existence and motion of charged matter outside the horizon, what might exist inside the horizon is irrelevant to the field felt outside.

Jesse

[Jason Resch]

On Sat, Jan 25, 2014 at 3:58 PM, meekerdb <meek...@verizon.net> wrote:

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.

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.

I don't trust your intuition as to what's "reasonable" - and you shouldn't either.

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?

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".

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?

See above comment.

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.

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.

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?

Jason

 

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...

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.

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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[meekerdb]

On 1/26/2014 10:53 AM, Edgar L. Owen wrote:

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.

You're not paying attention.  The disagreement was whether a far away observer ever *sees* the infalling object reach the event horizon.  He doesn't because the closer the object get to the horizon the longer it takes a photon to get out to the observer.  But the object does fall through the horizon in finite (even short) time and into the singularity a short time later.

Brent

[meekerdb]

On 1/26/2014 10:53 AM, Edgar L. Owen wrote:

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.

You already asked a physicist.  I'm a physicist, and what you're selling is not only not well known, it's well known to be wrong.

Brent

[Edgar L. Owen]

Brent,

Read my response to Liz addressed also to you and Jesse also before commenting please...

Edgar

[meekerdb]

On 1/26/2014 11:32 AM, Edgar L. Owen wrote:

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).

I saw his posts and he quite correctly said that objects *appear* to pile up on the horizon as they red shift to invisibility.

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.

But that's a nonsense answer to asking the wrong question.  If you're an observer several Scharzshild radii from a ten solar mass star and it collapses to a black hole, nothing changes in the gravitational field at your location.  No "effect" had to "come out", it was already "out".

Brent

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

--

[LizR]

On 27 January 2014 14:11, Jason Resch <jason...@gmail.com> wrote:

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?

I think the warping of space explanation can be shown to be an apparent effect in a flat spacetime but I forget how...

Maybe once spacetime is treated properly as a quantum object it will be clearer... 

[meekerdb]

On 1/26/2014 12:40 PM, LizR wrote:

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).

That's a very controversial theory though, since in the cat's (or elephant's) frame there is notable about the horizon (per GR). Ahmed Almheiri, Donald Marolf, Joseph Polchinski, James Sully 

http://arxiv.org/abs/1207.3123

and also Leonard Susskind have been proposing that there must be a "firewall" at the horizon to prevent this kind of entanglement, because otherwise it would violate quantum monogamy. 

http://quantumfrontiers.com/2012/12/03/is-alice-burning-the-black-hole-firewall-controversy/

Hawking just delivered a somewhat cryptic paper saying there is no well defined horizon.

http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583

I'm afraid SciAm has fallen into the trap of trying to compete with "Discovery" and the tabloids.

Brent

[LizR]

There is always that temptation. Almost every week "New Scientist" has a cure of cancer and an explanation of how the universe REALLY works...

Yes sorry, I shouldn't have added the contraversial BH complementarity comment to the uncontentious one about what a distant observer sees. Somehow the idea of the elephant tickled my fancy...

 

[Edgar L. Owen]

Brent,

The way it works is that objects do NOT appear to pile up at the event horizon. What happens is that they (as you correctly mentioned) appear to slow their approach to the event horizon to an external observer because the photons they emit take longer and longer to climb out of the increasing gravity well to reach the external observer.

But that same effect simultaneously means that that fewer and fewer photons per unit time reach that external observer so that the object approaching the black hole fades away proportionally to the degree it slows. So by the time it reaches the event horizon and appears to slow to zero it simultaneously vanishes from view.

Thus there is NO "pile up at the event horizon" period...

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. I'm not sure whether he actually meant that or not or I misunderstood what he said but so long as the true picture I give above is understood it doesn't matter.

So there is NO pile up at the event horizon because the approaching objects fade away as they get there in the view of an external object. By the time they are actually beyond the event horizon they are long gone from view. NO PILEUP!

Edgar

Edgar

[Edgar L. Owen]

PS: A slight correction to one sentence in my post below. The rest is good ....

My sentence "By the time they (the falling objects) are actually beyond the event horizon they are long gone from view." is ambiguous because it doesn't specify whose clock time is being referenced. It should be possible for the object to have already crossed the event horizon in the frame of the event horizon and there still be a faint image of the object still outside the event horizon on its way back to the external observer, not to mention the traversal time of the light going all the way back to that external observer...

Second Brent's statement "..as they red shift towards invisibility" is misleading. The fading from view is not due to a red shift towards invisibility (though a red shift is occurring). The red shift is due to the object's increasing velocity deeper into the gravitational well (which slows the object's comoving clock thus reducing the frequency of the light it emits), while the fading is due to fewer photons per unit time reaching the external observer.

Edgar 

[meekerdb]

On 1/26/2014 8:13 PM, Edgar L. Owen wrote:
> PS: A slight correction to one sentence in my post below. The rest is good ....
>
> My sentence "By the time they (the falling objects) are actually beyond the event
> horizon they are long gone from view." is ambiguous because it doesn't specify whose
> clock time is being referenced. It should be possible for the object to have already
> crossed the event horizon in the frame of the event horizon and there still be a faint
> image of the object still outside the event horizon on its way back to the external
> observer, not to mention the traversal time of the light going all the way back to that
> external observer...
>
>
> Second Brent's statement "..as they red shift towards invisibility" is misleading. The
> fading from view is not due to a red shift towards invisibility (though a red shift is
> occurring). The red shift is due to the object's increasing velocity deeper into the
> gravitational well (which slows the object's comoving clock thus reducing the frequency
> of the light it emits),

That's confused. The object's clock, assuming it carries one, doesn't tick slower along
its world line. Physical, i.e. clock, time doesn't "tick" at different rates, it's just
that path lengths may be different between the same two events and the interval between
signals received by distant observers depends on the signal paths.

> while the fading is due to fewer photons per unit time reaching the external observer.

That's true; there is both red shift and apparent slower emission but they are the same
phenomena. I've never seen it analyzed but there is also the possibility of seeing the
object by scattered light (which is the way we see most things). Outside the event
horizon at 3M is the photosphere where photons are caught in circular orbits. I think
they are unstable, so they wouldn't collect there, but there might be a lot between 2M and
3M that are falling in, depending on the nearby illumination sources (e.g. another star).
So there might be a lot of photons reflected off an object as it falls in.

Brent

[Jesse Mazer]

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/everyth...@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:

"the redshift is continually increasing as it approaches horizon so in practice an external observer can't see an object stuck on the horizon forever, but in

principle you could if you could detect light with arbitrarily huge

wavelengths, and if light was a classical EM wave rather than being

quantized into photons."

 

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.

What I said was that you can derive the fact that he would (in principle) see the falling observer take forever to reach the horizon from the fact that he would (in principle) see the falling observer's clock running slower and slower as it approaches the horizon, never quite reaching the time that the falling observer actually crosses the horizon. Again this is a statement about how he *sees* the falling observer's clock behave (the distant observer's own clock time when light from various ticks of the falling observer's clock reaches his own local position), not about any non-visual "slowing of the clock of the object", like the rate it's ticking relative to coordinate time in some coordinate system.

It's still not clear if you understand the difference between objective statements about which events coincide locally (you never did answer my question about whether you agree that all observers/frames agree about which events coincide locally at the same point in space and time) vs. coordinate-dependent facts that depend on one's choice of coordinate system. For example, you say "the photons they emit take longer and longer to climb out of the increasing gravity well to reach the external observer", but do you understand there's no objective truth about how long the light takes to climb out of the gravity well, that this depends entirely on the choice of coordinate system? Likewise, the issue of how much the falling clock slows down as it approaches the horizon can only be defined relative to a coordinate system (looking at the rate the clock's proper time increases relative to coordinate time). Even if we completely ignore the issue of the time for light to travel from the falling observer to the distant observer, in Schwarzschild coordinates it is true that the falling observer's clock ticks more and more slowly as it approaches the horizon, with the rate of clock ticks approaching zero as it gets arbitrarily close, so that it takes an infinite coordinate time to reach the horizon. But in other coordinate systems like ingoing Eddington-Finkelstein coordinates or Kruskal-Szekeres coordinates, the falling clock reaches the horizon in a finite coordinate time. Also note that in KS coordinates, light emitted outward  by the falling observer travels at exactly the same coordinate speed no matter how deep in the gravity well it was emitted--though in these coordinates the distant observer hovering at a constant Schwarzschild radius is actually accelerating away from the black hole, with an ever-increasing radial coordinate in KS coordinates.

Jesse

[Edgar L. Owen]

Brent and Liz,

It seems to me that the whole notion of the elephant being in two places at the SAME TIME presupposes a common present moment. Surely Liz and SA didn't mean that? That would be agreeing with Edgar's present moment of p-time!

Remember that this elephant is in different moments of clock time in two different frames. So how, unless there is a common present moment, can it be SIMULTANEOUSLY anywhere?

That'a basically just saying that any object that is at two different clock times in two different frames has some actual existence at the same present moment in which it is at both of those different clock times.

Seems to me this is an implicit argument that ALL of relativistic clock time variation actually takes place in a common present moment and that it's not really different relativistic views but an actual quantum splitting of that object into various probability states, one in each view. 

It seems to be an argument that relativity non-simultaneity produces Schroedinger's cats everywhere it occurs, and all those cats exist in a common present moment.

Correct me if I'm wrong as I haven't read the SA article....

Edgar

[Edgar L. Owen]

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.

Contrary to what you said, the object's comoving clock DOES actually 'physically' (your words) tick slower. it's just that the infalling clock can't measure its own slowing...

Obviously one can't tell how fast a clock is ticking by comparing the clock to itself. That's proper time which always appears to tick at the same rate, but ONLY because all comoving processes tick in synch. Proper time does NOT measure an actual gravitational time dilation, or any time dilation for that matter.

The infalling observer has an ABSOLUTE slowing of its clock due to increasing gravitation but just cannot locally measure that slowing.

Thus in the infalling observer's experience as his clock slows he will never actually reach the event horizon because his clock comes to a complete ACTUAL PHYSICAL stop at that point.

What happens inside the black hole is up for grabs...

Edgar

[Jesse Mazer]

On Mon, Jan 27, 2014 at 8:22 AM, Edgar L. Owen <edga...@att.net> wrote:

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.

No it isn't, not in the theory of relativity! Maybe you believe it's absolute since you believe in an absolute "present moment", i.e. an absolute truth about which pairs of events are simultaneous. But in relativity one can use many different coordinate systems with different simultaneity conventions, and they are all considered equally valid (you can use the same laws of physics in each of them to get predictions about which events locally coincide, and they will all make the same predictions about such local events). 

Say the falling observer sets his clock to read 0 seconds at the moment he passes the hovering observer, who also sets his clock to read 0 at that moment. Then according to one definition of simultaneity, it might be true that the event of the falling clock reading 50 seconds is simultaneous with the event of the hovering clock reading 100 seconds--in this coordinate system the falling clock is ticking slower as it travels deeper into the gravity well. But one could certainly design a different coordinate system with a different definition of simultaneity, where the event of the hovering clock reading 100 seconds is simultaneous with the event of the falling clock reading 150 seconds (assuming the falling clock makes it to 150 seconds before hitting the singularity)--in this coordinate system it would be the distant hovering clock that's ticking slower, not the falling clock. 

To emphasize: IN RELATIVITY THERE IS NO OBJECTIVE TRUTH ABOUT WHICH OF TWO DISTANT CLOCKS IS TICKING SLOWER. If you disagree with this, you are getting confused between how things work in your own personal theory of a "universal present" (which seems to be entirely faith-based, since you never explain how to define "true" simultaneity experimentally) and how things work in mainstream relativity.

Jesse

[Edgar L. Owen]

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. There is an actual absolute slowing of clock time in a gravity well. However it is obviously true that it will be measured differently in different frames and my other posts have discussed some of those ways it is.

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.

But in the case of relative velocity (NO acceleration or gravitation) both observers each see the other's clock slow relative to their own and both effects are equal. In this SR case if the relative velocity instantly stops (assuming no acceleration needed to stop it) then both clocks would instantly be running at the same rate and reading the same clock time. Thus that effect is relative, not absolute, because it does not persist after the source effect stops.

So contrary to what you seem to be saying Gravitational time dilation is ABSOLUTE. The time dilation of relative motion is RELATIVE.

Best,

Edgar

On Monday, January 27, 2014 12:51:28 AM UTC-5, jessem wrote:

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:

[Jesse Mazer]

On Mon, Jan 27, 2014 at 8:50 AM, Edgar L. Owen <edga...@att.net> wrote:

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.

Are you claiming this is true in relativity, or in your own theories about an absolute present? If you're talking about mainstream relativity you are incorrect, there is no "absolute" slowing of the clock. All arbitrary smooth coordinate systems are equally valid in general relativity, and one can certainly design a coordinate system whose simultaneity convention is such that the falling clock elapses more ticks in a given interval of coordinate time, not less (as in my example where both clocks read 0 when they pass next to each other, but simultaneity is defined in such a way that the falling clock reads 150 simultaneously with the hovering clock reading 100).

If you disagree, please tell me which of my two claims you're disagreeing with (or if you disagree with both):

1. All smooth coordinate systems are equally valid in general relativity, the equations of GR work the same in all of them (see Einstein's statement at http://www.bartleby.com/173/28.html about arbitrary non-rigid reference frames, which he cutely calls "reference-mollusks", and his statement that "The general principle of relativity requires that all these mollusks can be used as reference-bodies with equal right and equal success in the formulation of the general laws of nature; the laws themselves must be quite independent of the choice of mollusk." Also see the "constructing an arbitrary reference frame" discussion on p. 8 of http://physics.mq.edu.au/~jcresser/Phys378/LectureNotes/VectorsTensorsSR.pdf )

2. Among all these arbitrary smooth coordinate systems, it's possible to come up with some where the falling clock ages more than the hovering clock between a pair of "simultaneous" moments in this coordinate system

You could also try asking Brent, who mentioned that he's a physicist--I'm sure he would confirm what I'm saying.

 

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.

I did use the term, but only after I had already specified that I was talking about what would be true "in principle" if classical EM were exactly correct, and that the distant observer could detect EM waves that had been redshifted to arbitrarily high wavelengths.

 

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.

As I said, I was talking about what would be true in classical EM, where light is not quantized into photons.

 

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.

Not in relativity it's not. The arbitrary "reference mollusks" that Einstein talks about would include coordinate systems where the coordinate time for successive light signals to travel from the falling clock to the hovering clock was actually decreasing, not increasing.

 

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.

I don't think there is any allowable spacetime (respecting the equations of GR) where "the black hole suddenly vanishes", so this isn't a physically meaningful scenario. One thing you could do would just be to bring the falling clock back up to the same position as the hovering clock, and compare their times locally--as I keep saying, the only objective truths in relativity are local comparisons at a common point in spacetime, all coordinate systems agree in their predictions about which events locally coincide. But even though it's true that the falling clock has elapsed less time when it's brought back up to the hovering clock and their readings are compared locally, you could have a coordinate system whose simultaneity convention was such that the falling clock had been ticking faster during its freefall towards the horizon, but then the hovering clock ticked even faster during the period when the fallen clock was brought back up to it, with the net result that the clock that fell had elapsed less time in total even though it elapsed *more* time during the freefall period.

Jesse

[ghi...@gmail.com]

On Thursday, January 23, 2014 8:09:40 PM UTC, Edgar L. Owen wrote:

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

 

Edgar how do you envisage there would be no large scale resolution of the combined gravity of the galaxy? I'd doubt that is what is being said, because there's no way for that to make any sense. The planets have their gravity, around suns with their gravity, out to the whole galaxy including all the dust and gas, get far enough back and that's approximately a mass, with a gravity.

 

The dark matter component accounts extra gravity the radial velocities of the galaxy say to be there.

 

As an aside I was going to mention (since you expressed curiosity in your original post) that ages ago over on FoAR, I didn't speculate the same thing but sort of related, in that I wondered whether gravity might behave slightly differently as it compounded for increasing scales and density. I'm thinking the more gravity stacks up vertically, the more rapidly, the slower it falls away relative to the thin end where its furtherest extent current is.

 

Not in that the big vertical stack falls away more slowly. That's the part that stays exactly inverse with r^2.

 

But that where the thicker slice is adjacent to the thinner slice (imagining two cross sections jingling against each other) the slightly thicker slice is very slightly pulled back toward the even thicker slice right behind and so on. The overall proportionality is then preserved by transferring a tiny bit of the thinner adjacent back to the thicker behind it. Which it in turn rebalances by pulling a little slice from the one ahead.

 

Another way to do this would be to keep all slices constant in the summed gravitational energy, by making slices near the massive object itself infinitesimal thickness, and each slice subsequent however much thicker it needs to be, to be the same summed gravitational energy. So the thickness of the slices get ever longer the ever smaller the gravity becomes.

 

It would only require a very tiny imbalance back in the direction of increasing gravity, for the effect to be well into resolving toward the edge of the galaxy as decreasing as expecting, and then suddenly WHAM, off a cliff, almost vertically straight down to nothing (because  the tail accelerated its thinning away to effectively nothing at an ever more resolved juncture)

 

 

What sort of effect would that be in spacetime fabric? What would the acceleration be like when objects approach the galaxy and suddenly fall off a gravity cliff accerating wildly toward the centre, but also in the tangential direction as well.

 

Anyway, the reason I thought it might make sense, is firstly the effect would literally not exist in any gravity that we could accurately measure. It'd pretty much be as expected right out to the cliff, because the tiny imbalance was paid for entirely by the tail end.

 

Secondly, it wouldn't be just one cliff. There would be some direct correspondence with the rate at which the galaxy becomes more dense, varies then tails off end to end.

 

Galaxies aren't necessarily symmetrical in a straight line from one end to the other through the middle. What's interesting about that, is that the same effect would exist in both directions, but the 'pattern' would be a mirror reflection each side..opposite...reflecting the distinct increase/decrease in structure one way vs the other.

 

Something else would be what this would look like in the case of the supermassive blackhole at the centre. The immense gravity could see the end to end process to completion a relatively short R from the supermassive blackhole.

 

Which would see a still very large tail end doing something slightly different. But the effect on bodies near the black hole would be almost nothing, then whoosh, off a massive cliff toward the centre of the blackhole, but tangentially also. so massively accelerating the orbital speed, possible passing escape velocity (assuming not passed event horizon). But then hitting that gravity cliff from the bottom end, and so bouncing off it back toward the centre.

 

So real instability of orbiting stuff, for fasting than expected orbital speed, but trapped by what is effectively a second event horizon further out in the form of that cliff. So the friction and collsions would be extreme, the heat and speed more than expected, and maybe some resistence to crossing the event horizon until the friction slows everything down. Maybe that's why the really huge supermassive's can sometimes produce that vast jet...maybe the energy has to escape that second event horizon, and can only make it up the hill as pure energy of the moistest extremely uncivilized sort.

 

Just a load of bananas

 

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!

Edgar

 

Edgar, 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