Gravity Qustion

[Timmulus]

If you turned off the suns gravity, how long would it take for the earth to begin to leave it's orbit and why?

[bluesurge863]

If you turned off the suns gravity, how long would it take for the earth to begin to leave it's orbit and why?

Approximately 8 minutes.

Gravitational disturbances travel at the speed of light. The sun is 93 million miles away. This, divided by c (the speed of light) gives a time of around 8 minutes.

[jck200]

I am not sure about that, thinking about it if we only detect the affects of gravity indirectly then we would more likely relate them to the indirect information than the actual information.

john

[K^2]

I am not sure about that, thinking about it if we only detect the affects of gravity indirectly then we would more likely relate them to the indirect information than the actual information.
What?

Gravitational waves travel at speed of light, so bluesurge's answer is absolutely correct.

[Timmulus]

Approximately 8 minutes.

Gravitational disturbances travel at the speed of light. The sun is 93 million miles away. This, divided by c (the speed of light) gives a time of around 8 minutes.

How do we know gravitational disturbances travel at the speed of light?

[Kevin_Axion]

This is stated in Einstein's field equations, and if it was instantaneous than it would violate our fundamental understanding of the universe. Gravitational disturbances are generally very difficult to observe unless you have a super-sensitive apparatus that is focused on analyzing black hole combinations or binary pulsars, this is what LISA (Laser Interferometer Space Antenna) does.

[jck200]

Are gravitational affects around black holes different to the rest of the universe?

Sorry not too well up on gravitational waves would that be space waves? How do we detect if the space is creating waves?

If it is mathematical equations or indirect detection I can accept that answer.

john

[K^2]

Gravity around black holes appears to follow Einstein's Field Equation.

Gravitational waves are propagating distortions of space-time curvature. Nobody has been yet able to actually detect these. It takes an enormous catastrophic event, such as collapse of a star, to produce gravitational waves strong enough for us to detect, and it would have to happen somewhere relatively close.

So yes, at this stage, they are purely a mathematical prediction, but based on a very well established theory.

[Timmulus]

This is stated in Einstein's field equations, and if it was instantaneous than it would violate our fundamental understanding of the universe. Gravitational disturbances are generally very difficult to observe unless you have a super-sensitive apparatus that is focused on analyzing black hole combinations or binary pulsars, this is what LISA (Laser Interferometer Space Antenna) does.

Has our fundamental understanding of the universe ever been violated before?

[Timmulus]

Gravity around black holes appears to follow Einstein's Field Equation.

Gravitational waves are propagating distortions of space-time curvature. Nobody has been yet able to actually detect these. It takes an enormous catastrophic event, such as collapse of a star, to produce gravitational waves strong enough for us to detect, and it would have to happen somewhere relatively close.

So yes, at this stage, they are purely a mathematical prediction, but based on a very well established theory.
So at this stage gravitational waves and the speed at which they travel is unproven?

[K^2]

So at this stage gravitational waves and the speed at which they travel is unproven?
They have not been experimentally verified, but GR itself has been verified by experiment to an incredible precision, so there is absolutely no reason to suspect a different outcome.

[pallidin]

The speed of gravity is currently not known.
As suggested, it is assumed to be at the speed of light, but has not yet been proven.

[K^2]

The speed of gravity is currently not known.
As suggested, it is assumed to be at the speed of light, but has not yet been proven.
Speed of light enters Einstein's Field Eqn. If it was wrong, we'd notice, because it would predict wrong orbits for planets. So while we have no experiment to directly measure speed of gravitational waves, we do know that they should travel at the speed of light.

[Drakkith]

I think it's safe to say that CURRENTLY our understanding is that gravity waves travel at light speed. If it turns out tomorrow that we were wrong, then so be it. We will have to modify things. We currently just have no reason to assume that they dont travel at light speed.

[K^2]

The assumption that gravitational waves propagate at the speed of light is at the base of deriving GR equations. These equations are tested to 10-12. I can't say that this can't be false, but the odds of us making a mistake like this and still getting the right answer with that sort of precision are incredibly low.

[pallidin]

The assumption that gravitational waves propagate at the speed of light is at the base of deriving GR equations. These equations are tested to 10-12. I can't say that this can't be false, but the odds of us making a mistake like this and still getting the right answer with that sort of precision are incredibly low.

If that's the case, I tend to agree.

[Timmulus]

I think it's safe to say that CURRENTLY our understanding is that gravity waves travel at light speed. If it turns out tomorrow that we were wrong, then so be it. We will have to modify things. We currently just have no reason to assume that they dont travel at light speed.

Your willingness to see GR, SR and everything ever postulated by Einstein as something less than sacrosanct is refreshing. I appreciate your emphasis on the word "CURRENTLY". It shows a mind open to challenge and change, willing to consider alternate possibilities. A good attribute, in my opinion, for a scientific mind to possess. So, assuming gravity waves do exist, do they travel at light speed because, according to GR, nothing can exceed the speed of light? If the speed of light were 187,000 mps would that be the speed at which gravity waves would travel?

[sweet springs]

Hi.
We call maximum speed of interaction c as 'speed of light' traditionally. All the massless particles, e.g. photon, graviton travel at the same speed c.
Regards.

[K^2]

So, assuming gravity waves do exist, do they travel at light speed because, according to GR, nothing can exceed the speed of light?
First of all, according to GR speed of light can be exceeded. It only has to be obeyed locally, and that's a huge loophole.

And speed of gravitational wave propagation comes from linearized GR, in which equations for G-field are analogous to Maxwell's equations. The permeability constants for the gravitational and gravitomagnetic fields end up such that the speed of wave propagation is still c.