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Author Topic: How fast does gravity travel?  (Read 4357 times)

Eric

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How fast does gravity travel?
« on: 29/04/2009 00:30:02 »
Eric asked the Naked Scientists:
   
Chris,

I've heard it said that if the sun were to suddenly vanish, the earth would cease its orbit instantly, even though we would still enjoy the light from the sun for eight more minutes.  Is this fact?  Or fiction?  Does gravity travel
faster than light?

What do you think?
« Last Edit: 30/04/2009 12:16:55 by chris »


 

Offline Mad Mark

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Re: How fast does gravity travel?
« Reply #1 on: 29/04/2009 00:41:19 »
I don't think that has been prooven yet,,but space time itself is not restricted to the speed of light so earth,s orbit probably could changed instantly.
 

Ethos

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Re: How fast does gravity travel?
« Reply #2 on: 29/04/2009 02:23:11 »
Looks like the solution to this question is still up in the air.


...............Ethos
« Last Edit: 29/04/2009 02:24:45 by Ethos »
 

Offline lightarrow

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Re: How fast does gravity travel?
« Reply #3 on: 29/04/2009 08:42:27 »
Eric asked the Naked Scientists:
   
Chris,

I've heard it said that if the sun were to suddenly vanish, the earth would
cease its orbit instantly
No, it wouldn't. Gravitational perturbations travel at c.
 

Offline Vern

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Re: How fast does gravity travel?
« Reply #4 on: 29/04/2009 19:06:53 »
Some Google results indicate that the physics community has not fully settled the speed-of-gravity question. There seems to have been controversy ever since Einstein claimed that Newton's instant gravity was wrong. Einstein thought gravity propagated at the speed of light.

Quote from: the link
Physicists leveled heavy criticism Thursday on a report from last week that claimed the speed of gravity had been determined by observation and was equal to the speed of light.

One physicist called the interpretation of the finding "nonsense". Others were more diplomatic, suggesting that the experiment, involving observations of the bending of light from a distant galaxy as the light sped by the planet Jupiter, had instead measured other phenomena.

The brewing controversy, which illustrates the fits and spurts with which science sometimes grudgingly moves forward, appears to have ground to a stalemate for now as the two scientists who conducted the experiment categorically defended their work.

"The claim that they've measured the speed of gravity is simply incorrect," said Clifford Will, a physicist at Washington University in St Louis, Missouri, and an expert in the field.

Interestingly, Will is friends with one of the researchers whose work he knocks.
 

Offline techmatt

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Re: How fast does gravity travel?
« Reply #5 on: 29/04/2009 21:42:31 »
I might be way off here so please excuse me if I am wrong.

I picture space-time as a blanket that is being held tight. When you put a big heavy ball in the middle it sinks in. The dimple is gravity. Now if you take a smaller ball and toss it around the outer edge of the dimple it will rotate around the dimple. To test the theory of the sun disappearing then you need to have someone cut the blanket just under the big ball. The smaller ball would go flying off the blanket because the dimple is no longer there.

We could not see the sun do the disappearing act right away because by the time the light hit the 8 light minute mark would be further away. Therefore it would take longer for the light to reach us. Not to mention the light would be distorted by the space time rebound. The rebound might distort time enough to rip the planet apart. We may never see the sun simply disappear, we might be dead before we could see it.
 

Offline erickejah

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Re: How fast does gravity travel?
« Reply #6 on: 29/04/2009 22:07:44 »
We may never see the sun simply disappear, we might be dead before we could see it.
:) no chaos, excellent.
 

ScientificBoysClub

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How fast does gravity travel?
« Reply #7 on: 30/04/2009 16:57:42 »
Velocity of G = velocity of C !!!
 

Offline techmatt

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How fast does gravity travel?
« Reply #8 on: 30/04/2009 20:57:36 »
On a more realistic note. Gravity would not have a speed, as it is just a warped part of space time. Speed is distance per time and space it distance and time so for the warping of space time and speed has no reference.
 

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How fast does gravity travel?
« Reply #8 on: 30/04/2009 20:57:36 »

 

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