what is the speed of gravity propagation?
24 Feb 2005 10:29:02 UTC
Topic 187936
(moderation:
it is right to say that the speed of gravity waves is equal to the speed of light (max speed of information propogation for all known force fields)
If so - is gravity propogation speed affected by gravity sources ? It seems to me it is not (unlike light which is trapped in black holes).
what is the speed of gravity propagation?
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I was waiting for someone to give you a more scientific and potentially better researched answer. Perhaps, I can offer a seed that someone else will expand on.
Do gravity waves propogate at the speed of light? That's the $64 question. Since gravity waves haven't been directly observed, only theoretically postulated, no one is quite sure. In theory, yes. There are lesser held theories that suggest that they may not. If I were forced to bet, I'd say yes.
As to whether or not these theoretical waves are affected by gravity sources, I'd say it's anybody's bet. Can gravity waves escape past the event horizon? Beats me.
Is the entire radiation from a gravity wave dispersed in space, rather than time? Dunno. It all depends on the observations (indirect, of course) of gravitons.
For more info, click here
This article says that the propogation speed of gravity is far higher than lightspeed.
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FYI, This article says it's
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FYI, This article says it's been measured as the speed of light. Unless I'm confusing two forces.
And, Here is an article that says the previous experiment was carried out wrong.
That's the wonderful thing about Theoretical Physics. You get to choose what ever you want to think. Until The Big Proof, it comes down to what you can prove mathmatically.
There are two secrets to life: 1) Don't tell everything you know...
Interestingly this makes a
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Interestingly this makes a distinction between gravity propogation caused by gravity sources ( its speed much bigger than the speed of light c and estimated to be >= 2 x 10^10 c )and gravitational radiation (which speed is equal to the speed of light c) caused by changes in the curvature of the space-time.
I was not aware of the distinction between the two.
> I was not aware of the
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> I was not aware of the distinction between the two.
I saw that too. That was one of the articles that confused me. I've read it about 10 times trying to figure out what the differnce in the two forces was. Until I learn something more, I'm going to stick to General relativity (Wikipedia). Maybe some Physics guru can straighten me out.
There are two secrets to life: 1) Don't tell everything you know...
> > I was not aware of the
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> > I was not aware of the distinction between the two.
>
> I saw that too. That was one of the articles that confused me. I've read it
> about 10 times trying to figure out what the differnce in the two forces was.
as i understood the arthor does not believe that gravity is caused by curved space-time, instead he suggests that gravity is a characteristic of flat space-time. When light travels through that flat space it gets affected by more and less gravity-dense regions. In such scenario gravity radiation does not exist but is rahter an artifact of Einstein general relativity (GR) theory.
That point of view renders E@H effort to detect gravity radiation waves (those caused by changes in space time curvature) to be futile :(
To say true GR does not explain how gravity can escape black whole, but playing with gravity as propogation of densities in flat space-time has a potention to explain it.
> Interestingly
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> Interestingly href="https://einsteinathome.org/%3Ca%20href%3D"http://www.ldolphin.org/vanFlandern/gravityspeed.html">http://www.ldolphin.org/vanFlandern/gravityspeed.html">this[/url] makes a
> distinction between gravity propogation caused by gravity sources ( its speed
> much bigger than the speed of light c and estimated to be >= 2 x 10^10 c
> )and gravitational radiation (which speed is equal to the speed of light c)
> caused by changes in the curvature of the space-time.
>
> I was not aware of the distinction between the two.
>
You need to be careful about the websites you pull up when researching science such as this. Tom Van Flandern has some really out there theories and shouldn't be taken as a representation of the science where working on here.
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> > Interestingly >
)
> > Interestingly
> href="https://einsteinathome.org/%3Ca%20href%3D"http://www.ldolphin.org/vanFlandern/gravityspeed.html">http://www.ldolphin.org/vanFlandern/gravityspeed.html">this[/url] makes
> a
> > distinction between gravity propogation caused by gravity sources ( its
> speed
> > much bigger than the speed of light c and estimated to be >= 2 x 10^10
> c
> > )and gravitational radiation (which speed is equal to the speed of light
> c)
> > caused by changes in the curvature of the space-time.
> >
> > I was not aware of the distinction between the two.
> >
>
> You need to be careful about the websites you pull up when researching science
> such as this. Tom Van Flandern has some really out there theories and
> shouldn't be taken as a representation of the science where working on here.
>
Well, I'm a bit of a neuby to this, but having read that page, I have to admit that the reason he quotes a considerably superluminal speed for gravity, based on the two observations that if it was C speed limited, how does gravity actually get out past the event horizon of a black hole?, and the doppler shift effect that would have highly visible effects on orbiting bodies which we can find little of no evidence of with our crude observations...
Gravity seems to have no problem escaping a black hole, and gravity pulls objects straight to where the massive body is now, and not where it was, say 8 minutes ago in the case of our own star, which we call the sun.
But, isn't that what this project is all about? Finding a physicaly proveable handle we can use to bring gravity fully into a TOE? Remember, it (gravity) was still the odd man out the last time I checked. If indeed it can be merged, then there should be some way of applying the laws of conservation of energy and build a field generator that nullifies gravity by converting it into some other form of energy, prefereably a mass acceleration in the opposing vector. A 100% conversion would of course only imply an effectively zero weight, leaving it up to us to figure out how to accelerate it in the direction that we wish to go. Presumably the mass is still there. Heck, even a 25% conversion would reduce the launch pad weight of something like the shuttle by at least that amount, with a commensurate reduction in burn time to orbit, or a heck of a lot more weight into orbit, or a higher orbit. The tradeoffs would be huge.
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Cheers, Gene
Don't forget that general
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Don't forget that general relativity speaks about gravitational waves as waves in 4-D space-time and not in 3-D space we are accustomed to.
The black hole's gravitational field exists in space-time and not in space alone.
So the question is not in how the gravity projection into 3-d space escapes the black hole's event horizon but rather how the information about changes in black hole gravitational field manages to update itself beyond black hole - how does information about interior of event horizon leacks to outside world.
Maybe you can answer this for
)
Maybe you can answer this for me debugas? Ive seen diagrams of black holes with X-rays escaping from the center. If the escape velocity of a black hole is greater than the speed of light how do x-rays escape. Also would gravitational waves be able to pass through a black hole?
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> Maybe you can answer this
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> Maybe you can answer this for me debugas? Ive seen diagrams of black holes
> with X-rays escaping from the center. If the escape velocity of a black hole
> is greater than the speed of light how do x-rays escape. Also would
> gravitational waves be able to pass through a black hole?
Neither X-rays, nor anything else, can 'escape' a BH. Those diagrams should have made clear that the X-rays originate in the accretion disk, which extends down to the event horizon (though I'm doubtful that any X-rays that we see come from near there).
A stable, stationary BH would not emit GW; indeed, any GW would not come from the BH, but from the matter on its way to its doom.