# Speed Of Gravity?

This is a strange question that has probably been asked before but I could not find it... An example of my question would be this: If the Sun suddenly disappeared how long would it take for the Earth to no longer be affected by the Suns gravity? I'm not sure about this and I don't quite know how this would be proved..

Thanks,
Helical

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If this were to happen, we should feel the effects of the lost gravity at the same time as we see darkness. The force of gravity travels at the speed of light. I'm sure a more detailed description will come soon...:tongue2: I just don't have much time...

pervect
Staff Emeritus
The sun can't suddenly disappear (at least not according to GR). The differential form of the conservation of energy and momentum is built into General Relativity, therfore the equations have no solution in which the sun disappears.

You can, however, generate gravity waves by blowing up the sun asymmetrically, or better yet, by imploding the sun to form a black hole. The first gravity waves from the implosion or explosion event would reach the Earth at the speed of light.

Implosion would generate a much stronger gravity wave signal than explosion, BTW. (The implosion generates gravity waves only because the sun is rotating).

An explosion must not be spherically symmetrical if it is to generate gravity waves.

If you just planted a big bomb at the center of the sun and blew it up in a spherically symmetrical manner, there would not be any gravity waves or other gravitational effects on the Earth's orbit until the debris actually reached the Earth's orbit.