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Hi All,

Gravity is (in String Theory at least) mediated by gravitons. Why is it these are the only "particles" that can convey information instantaneously even where light is retarded to the point of being super-red-shifted?

Thanks,
Wallis
 

DrChinese

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There is nothing currently known that would suggest that gravitons (if they exist) could transmit information any faster than photons. Photons (light) always travel at c in a vacuum, even when their frequency is red-shifted.
 
Well as Chinese has pointed out...gravitons wouldn't *instantaneously* pass on any information faster than light....if getting deep into the theory...Given that light travels at C *Usually* always (Unless passing through BEC as that experiment slowed it down to 36mph :O) nothing, according to relativity can travel faster than the speed of light...of course, if the speed of light at its average velocity is in fact the average...otherwise of course, if it was slowed at 36mph then it could travel faster.... interesting to grasp the concept of that
 
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Schrodinger's Dog

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ShadowX3 said:
Well as Chinese has pointed out...gravitons wouldn't *instantaneously* pass on any information faster than light....if getting deep into the theory...Given that light travels at C *Usually* always (Unless passing through BEC as that experiment slowed it down to 36mph :O) nothing, according to relativity can travel faster than the speed of light...of course, if the speed of light at its average velocity is in fact the average...otherwise of course, if it was slowed at 36mph then it could travel faster.... interesting to grasp the concept of that
hmm, confusing I always thought there was no average in any scenario, that light simply always propogates at the speed of light, but absorption and re-emission can slow it. Could you explain that?
 
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Schrodinger's Dog said:
hmm, confusing I always thought there was no average in any scenario, that light simply always propogates at the speed of light, but absorption and re-emission can slow it. Could you explain that?
That is simply because it is no longer the same light!
For the sake of argument we could have a electron absorbing a photon and an hour later emitting one. Now is it the same photon?
 

Schrodinger's Dog

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MeJennifer said:
That is simply because it is no longer the same light!
For the sake of argument we could have a electron absorbing a photon and an hour later emitting one. Now is it the same photon?
The speed of light is a constant not a mean value, that is in fact how I understood it. No the photon is not the same, same quanta maybe, but the speed of emission photons is not average it is constant. I guess it's nit picking but that is how I understood it, what you should be saying is that the slowing effect is not actual slowing the light but a consequence of photon interaction, the passing of bundles of energy,emission & reabsorption.

Mean speed of light(photons) is c which is a constant, light cannot propogate faster or slower than light. the mean of the sum of a million ones is one. Unfortunately magazines often dumb down these experiments so people walk away with the abusrd notion that light is propogating at 36mph or is stopped. AFAIK that is just plain wrong. But am open to criticism as I'm far from being an authority on the subject.
 
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Wallis said:
Gravity is (in String Theory at least) mediated by gravitons. Why is it these are the only "particles" that can convey information instantaneously even where light is retarded to the point of being super-red-shifted?
Gravitons are conjectural, Wallis. For example, if you think about a black hole, how could any particles climb out of the event horizon to exert an influence on surrounding objects?
 

selfAdjoint

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Farsight said:
Gravitons are conjectural, Wallis. For example, if you think about a black hole, how could any particles climb out of the event horizon to exert an influence on surrounding objects?
Gravity would be carried by virtual gravitons. You have the same problem with charge, how can a black hole carry an electric charge when that is mediated by photons, and they, by definition, can't get past the event horizon? Answer, they are virtual photons, and don't meet the energy conditions that constrain real coherent ones that carry light..
 
selfAdjoint: I'm not satisfied with virtual photons mediating charge either, and rather see that as another unsatisfactory aspect of the messenger particle model when it comes to black holes.
 
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Thanks All,

I see that although black holes have been observed (9 or is it 11 now) at the Milky Way galactic centre, this forum still does not officially accept they exist. If they were to exist, then yes, it would prove gravitons have a very hard time indeed existing. Thanks for the affirmation. Gravitons are not a good explanation, unless "they're special", in which case, you could simply call them "the geometry of space-time" and have done with it.
 

DrChinese

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Thanks All,

I see that although black holes have been observed (9 or is it 11 now) at the Milky Way galactic centre, this forum still does not officially accept they exist. If they were to exist, then yes, it would prove gravitons have a very hard time indeed existing. Thanks for the affirmation. Gravitons are not a good explanation, unless "they're special", in which case, you could simply call them "the geometry of space-time" and have done with it.
Welcome back, Wallis! Don't be a stranger (since I note that you started this thread 5 years ago) !!

I would say that black holes are generally accepted as existing. There is plenty of evidence for them. Here is an one example, and there are probably hundreds more I could provide:

http://arxiv.org/abs/astro-ph/0209041

It is the graviton which is in dispute.
 
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Thank you DrChinese,

I see there are changes afoot. I was swayed like the reed as they say. Last time I posted quoting black holes, I was told off for positing black holes on the forum as they were purely conjectural.

So, having exposed the graviton as not so good a candidate for gravity, and having space-time sitting there flying in the face of grand unification, do I gather that grand unification is having a hard time? Apparently not. HoYava gravity seems to have it all, so my deposing of the graviton might be too early yet... and back comes the concertina Universe so mocked some years ago! How these things come in circles... SelfAdjoint, I still think charged black holes are conjectural. I have seen no direct evidence of them. Are they still theoretical models?

But still, how does the graviton escape the clutches of the black hole to draw us in? If charge too can escape, is light the only mediator affected by the Schwarzschild radius?

Regards,
 
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