How can gravity escape a black hole?

[CraigD]

Have we established the speed of gravity yet?

Theoretically, yes. Confirmed experimentally, the answer is a matter of some controversy.

 

According to Relativity, the speed of gravity is the same as the speed of light in vacuum.

 

So far, this hasn’t been directly confirmed, though a couple of big detectors, such as LIGO, VIRGO, GEO 600, and TAMA 300, and a lot of computers, have been looking for a while.

 

Why it’s so difficult to measure the speed of gravity, while it was so easy to measure the speed of light, is that gravity is so much weaker than light (about [math]10^{36}[/math] times, per most sources including the wikipedia article “fundimental interaction”). Rather than try to detect a change in gravity from some sudden, big change in the arrangement of the source of a big gravity well (supernovas and colliding black holes are believe to be among the biggest and the most sudden), which would be hopelessly lost in the “noise” of the gravitational attraction of even very small, nearby sources, detectors try to detect the slight change in geometry of space such event should produce, know as gravitational waves, which is predicted to result in shortening of the length of a laser beam on the order of [math]10^{-17} \,\mbox{m}[/math] for a 4 km long beam. This is a hard task, especially on Earth, where things constantly vibrate greater distances than this, and stuff like vehicle traffic on distant roads affect the vibration, so some of the most promising future detectors, such as LISA, are planned to be flown in space.

 

Proponents of an experiment involving observing Jupiter transiting a quasar claim to have successfully measured the speed of gravity in 2002, but many disagree (see SPACE.com -- Speed of Gravity Results 'Incorrect,' Physicist Says)

 

Since Relativity has been very accurate in predicting other effects related to its speed-of-gravity prediction (the confirmation of one winning the 1993 Physics Nobel prize), physicists and well-informed physics fans have high confidence in its speed of gravity prediction.

[modest]

My statement was stating that a Graviton per se is not "required" to be a "virtual" particle. I was not prohibiting from being so. If/when we can observe Gravitational waves (wave part of duality) - Feynman diagrams would note these then as Not "virtual".

I agree. It really is completely synonymous with a photon. The force mediating photons are virtual whereas the quantized waves (light) are not. Gravitational waves would equally be considered quantized and not virtual. Force-mediating gravitons would be virtual. Since we're not talking about gravitational radiation escaping a black hole, but rather the force of gravity then we are talking about the virtual variety.

 

It should probably go without saying that virtual photons which mediate the coulomb force are allowed to escape a black hole while quantized waves in the same field (i.e. visible photons) cannot escape. In other words: a black hole can have charge but light cannot escape.

 

I suppose you could look at it this way. Alternately (dimensionally) you could say that Gravity "leaks" into/out-of other dimensions/branes.

In string theory and brane theory gravitons would still need to travel FTL to escape a black hole in order to communicate gravitational information with the rest of the universe. It is true that brane theory supposes that the relatively weak force of gravity is due to gravitons leaking out of our dimension, but that doesn't negate the fact that the ones that remain in our dimension would behave how quantum mechanics and string theory says they should.

 

The escape velocity of a black hole is greater than c and any particle leaving a black hole to interact with the rest of the universe necessarily went faster than c. Of course, we're now relying on 3 unsubstantiated ideas; quantum gravity, string theory, and brane theory :singer:

 

Have we established the speed of gravity yet?

 

According to the wiki article Speed of gravity the speed of gravity is the same as the speed of light in general relativity. Newtonian gravity was assumed to travel instantaneously (spooky action at a distance).

Newton's theory of gravity offered no prospect of identifying any mediator of gravitational interaction. His theory assumed that gravitation acts instantaneously, regardless of distance. Newton had shown mathematically that if the gravitational interaction is not instantaneous, angular momentum is not conserved, and Kepler's observations gave strong evidence that in planetary motion angular momentum is conserved. (The mathematical proof is only valid in the case of an Euclidean geometry.)

 

According to Albert Einstein's theory of special relativity, instantaneous action-at-a-distance was seen to violate the relativistic upper limit on speed of propagation of information. If one of the interacting objects were suddenly displaced from its position, the other object would feel its influence instantaneously, meaning information had been transmitted faster than the speed of light.

 

One of the conditions that a relativistic theory of gravitation must meet is to be mediated with a speed that does not exceed lightspeed. It could be seen from the previous success of electrodynamics that the relativistic theory of gravitation would have to use the concept of a field or something similar.

 

This problem has been resolved by Einstein's theory of general relativity in which gravitational interaction is mediated by deformation of space-time geometry.

 

Action at a distance (physics) - Wikipedia, the free encyclopedia

 

~modest

[buddha elämuni]

I really like that guestion and that thread. Because of that thread, i am here.

 

I just think, there is no drawing force at all.

 

I open new thread, there is no gravity at all and there i told why you cant explain force like drawing force

[Curvedview]

I was just passing by and thought the question interesting but .... The question seems to imply that gravity can be collected like photons are as they cross the event horizon.

I think a paradox is formed here. If the Graviton creating the gravity, if it exists as a communicator particle is consummed as it enters a black hole, then how might it continue to exert, communicate, any force at all. In other words, If its consumming it self shouldn't we see some balancing off between consumtion of gravitons and the maintaining of gravitational force. Or perhaps some tidal shifts in size.

Please correct me here, but isn't there a suggestion of a limiting factor on the amount of entropy a black hole can have and suggest that what lies beyond the event horizon is inert. The communication mechanism of the graviton might be seen as having some componant force in excess of the gravity we experience and the gravity it would seem to be governing.

 

In short, I suggest we may be looking at the problem from te wrong angle. Let suppose that gravitons don't move and the permiate all space. Doesnt't work, but it was suggested earlier by another who shifted the focus to the lesser question of "the Gravitons Communication of what to whom".

 

The theory: What if the graviton is like a sheet of netting with gravitons residing at every point if intersection, for simplicity sake, a 2D grid. Lot of things might easily pass through. But we will say mass cannot pass because the graviton bumps into it, interacts in a retardent way. But for this to work a force which would explain attraction need to be.

 

I think there's a candidate, The photon. and I'll have to come back to this later. I think it may play a role in gravity we haven't looked at.

 

Just some thoughts.

[HydrogenBond]

The simplest explanation is gravity is an acceleration, while energy is a velocity at C. Velocity can't escape a black hole, but an acceleration can. It is not the entire acceleration d/t/t that escapes, just the extra time t (potential), with the d/t staying.

 

Say t (potential) escapes, it can have an impact on velocity outside the black hole. The impact of the extra t will turn velocity into acceleration, which we see as gravity.

[Little Bang]

Gravity does not need to escape the BH. The dilation of time is what can come out and of course I claim that is what makes gravity work.

[HydrogenBond]

I am going to repeat myself but add a few extra considerations. Gravity is an acceleration with dimensions d/t/t. Energy is based on frequency and wavelength with dimensions d/t. The difference, dimensionally is the extra t. Since energy can't escape a blackhole, then d/t can not escape. This leaves only the extra t the ability to escape.

 

Let us look at this conceptually. What would happen if time could escape, but this time is not associated or integrated with distance. The effect would be an integration in time, that is independent of distance. It is not subject to the speed of light, since the speed of light has a connection to distance via d/t, which can not escape.

 

One way to explain this is the blackhole reference has space-time or d/t contracted to zero making the universe appear to overlap in distance and time. The extra dimension of time escaping, acts with all distance overlapping, create a simultaneity in time that is not a function of distance or space-time. it is not under the speed of light since d/t can not escape the blackhole.

 

This explains how galaxies can form integrated shapes even at distances where light needs to travels for millions of years. They coordinate in time, independent of d/t or reference differences through the galaxy. Having a blackhole in the center of a galaxy helps, because of the extra time given off at point reference, where light of d/t not be a factor.

[Janus]

I am going to repeat myself but add a few extra considerations. Gravity is an acceleration with dimensions d/t/t. Energy is based on frequency and wavelength with dimensions d/t. The difference, dimensionally is the extra t. Since energy can't escape a blackhole, then d/t can not escape. This leaves only the extra t the ability to escape.

 

 

Stuff and nonsense. Gravity is not an acceleration. You can have acceleration due to gravity, but this is not the same as gravity being acceleration.

 

Dimensionally, energy is not d/t, but:

 

md²/t².

 

While the energy of a photon depends on its frequency [/i]or wavelength, you use either one or the other, not both. (is is just silly to say that it depends on frequency and wavelength, because these two qualities are co-dependent)

 

And to relate either to energy you have to use Planck's constant which is

 

6.626e-34 m²kg/s which dimensionally becomes:

 

d²m/t

 

Relating energy to frequency gives us

 

E=hf

(h being Planck's constant)

 

the frequency is measured in units of 1/t

 

So dimensionally it becomes

 

E= d²m/t/t = md²/t²

 

which is what I gave above

 

Using wavelength you get

 

E= hc/w

(w measured as distance)

 

Dimensionally:

 

E= (d²m/t)(d/t)/d= md²/t²

 

which again is what I gave above. and is dimensionally consistent with any other formula for energy such as:

 

E= mv²/2

 

E=mc²

 

E=Fd (F is force)

 

E = -GMm/r (gravitational potential energy)

 

etc.

 

Science is precise, and it can't be done by mere word association as you appear to want to do.

[HydrogenBond]

Energy and mass can not escape a blackhole. But we know gravity can, which is the topic of this discussion. Therefore the gravity effect, being given off by the blackhole, can not be mass or energy related because these can not escape. It comes back to the extra time dimension manifest in the effect we see as acceleration, without matter or energy being the mediator. I call this time potential.

 

Although the speed of light stays the same, as energy moves toward a blackhole, there is an acceleration of d-t or wavelength and frequency. We get a blue shift as the energy gains energy due to the d/t/t acceleration. We model this in terms of space-time reference changing. But this it can also be expressed as space-time as a function of time potential density.

[Rade]

How can gravity escape a black hole?

 

Is it possible the answer requires that we look at phenomenon we lump together as being "gravity" as having two forms (1) an attractive potential--gravity (2) a repulsive potential--antigravity. That is, both matter and energy that we "observe" and "measure" are the result of a superposition of interaction of (1) attractive potential-gravity and (2) repulsive potential-antigravity. Thus, perhaps black hole allow a repulsive potential in the form of gravity that operates on matter+antimatter superposition to escape, but never an attractive potential. Just asking.

[Little Bang]

I agree with Hydro. This from another post and I think explains why gravity can escape.

 

I hope the reader will agree that any particle can be considered it's own clock ( an observer ) and that a clock even one nanometer higher in a gravity well will run slightly faster than a clock one nanometer lower. Suppose we had a frictionless tube, one meter long, whose inside diameter is just large enough to allow a diatomic hydrogen molecule to move freely up and down in the tube. We fill the tube with diatomic hydrogen at STP and stand the tube up perpendicular to the surface of the Earth. Each molecule is moving up and down in the tube colliding with the molecule above and below. Let’s observe the path of a particular molecule which we call B. The molecule above we call A and the one below we call C. We start watching B as it moves down the tube toward C with velocity d/t. The molecule B (clock/observer) will calculate it's momentum, at the instant before the collision with C, using it's clock which is running slightly slower than when it collided with A. It will find it's momentum at C to be greater than the momentum of the collision with A. Doesn't this suggest that gravity is strictly a function of time dilation? This would also explain why we can't tell the difference between gravity and inertia. If gravity is the result of a graviton how does it get out? Time on the other hand does not have to worry about anything but it's own dilation.

[modest]

If gravity is the result of a graviton how does it get out?

 

I think it's a great question, and this might bear repeating:

 

We can thank Janus for this gem. He quoted it in another forum:

 

Author: Matthew P Wiener <[email protected]>, Steve Carlip <[email protected]>

 

In a classical point of view, this question is based on an incorrect picture of gravity. Gravity is just the manifestation of spacetime curvature, and a black hole is just a certain very steep puckering that captures anything that comes too closely. Ripples in the curvature travel along in small undulatory packs (radiation---see D.05), but these are an optional addition to the gravitation that is already around. In particular, black holes don't need to radiate to have the fields that they do. Once formed, they and their gravity just are.

 

In a quantum point of view, though, it's a good question. We don't yet have a good quantum theory of gravity, and it's risky to predict what such a theory will look like. But we do have a good theory of quantum electrodynamics, so let's ask the same question for a charged black hole: how can a such an object attract or repel other charged objects if photons can't escape from the event horizon?

 

The key point is that electromagnetic interactions (and gravity, if quantum gravity ends up looking like quantum electrodynamics) are mediated by the exchange of *virtual* particles. This allows a standard loophole: virtual particles can pretty much "do" whatever they like, including travelling faster than light, so long as they disappear before they violate the Heisenberg uncertainty principle.

 

The black hole event horizon is where normal matter (and forces) must exceed the speed of light in order to escape, and thus are trapped. The horizon is meaningless to a virtual particle with enough speed. In particular, a charged black hole is a source of virtual photons that can then do their usual virtual business with the rest of the universe. Once again, we don't know for sure that quantum gravity will have a description in terms of gravitons, but if it does, the same loophole will apply---gravitational attraction will be mediated by virtual gravitons, which are free to ignore a black hole event horizon.

 

See R Feynman QED (Princeton, ???) for the best nontechnical account of how virtual photon exchange manifests itself as long range electrical forces.

 

http://sciastro.astronomy.net/sci.astro.4.FAQ

 

~modest

 

 

 

 

 

It comes back to the extra time dimension manifest in the effect we see as acceleration, without matter or energy being the mediator. I call this time potential.

 

Your dimensional analysis is flawed. The force of gravity, acceleration, and energy all have units of time squared in the denominator as has been shown.

 

~modest

[Little Bang]

I don't have the skills to prove or disprove my idea about gravity. The logic itself appears unassailable to me but the proof lies in calculating the difference in momentum due to the tiny time dilation experienced by the molecule. I'll use an extreme example. Let's say it is ten meters between the collision of B with A and B with C. After the collision with A, B is traveling at 10m/s which means it should take one second for it to collide with C. During B's trip from A to C it's clock slows (from time dilation) to 0.5 seconds. I'll use an extreme example. Let's say it is ten meters between the collision of B with A and B with C. After the collision with A, B is traveling at 10m/s which means it should take one second for it to collide with C. During B's trip from A to C it's clock slows (from time dilation) to 0.5 seconds. As far as B is concerned it's collision with C will be faster than 10m/s. So in this example the momentum at C is higher than the momentum at A. Of course this is not right because the clock slows as it falls down the gravity well so the actually calculations would be very complicated.

[DaddyUnit]

Hey everyone,

 

I keep trying to get my friend Jerry to sign up and post directly in the forum, but no luck so far.

 

He has, however, devoted an entire blog entry responding to this thread. The blog just went up a few minutes ago at C-R Theory Blog

 

Thanks for your continued interest and comments.

[Buffy]

Well, I pestered Jerry to joining us in the comments for his blog post. I think Comedy-Recycling theory might well fit in nicely here! But we'd really like to hear what he thinks in his own words here....

 

Good humor is a paradox. The unexpected juxtaposition of the reasonable next to the unreasonable,

Buffy

[Astrojan]

Gravity does NOT escape from black hole

 

Its GO INSIDE !! Thats pushing gravity, caused by gravitons and gravitons absorbed onto the mass of black hole. The force vector directed inside. Smaller black holes may more or less transparent for gravitons, but there is a limit size and the bigger BH-s may totally shield DVAG gravitons (gravitons has one way ticket).

[modest]

Gravity does NOT escape from black hole :naughty:

 

Its GO INSIDE !! Thats pushing gravity, caused by gravitons and gravitons absorbed onto the mass of black hole. The force vector directed inside. Smaller black holes may more or less transparent for gravitons, but there is a limit size and the bigger BH-s may totally shield DVAG gravitons (gravitons has one way ticket).

 

Can you perhaps provide a scientific link or reference supporting your assertion.

 

Thank you :lol:

 

~modest