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I was watching a relativity video, and although I am not sure, I felt that it was trying to tell that the effect of gravitation of a body is instantaneous, in the sense that a sudden change in the mass of a body will instantaneously be felt by any object at a distance, even before light can be exchanged between them. So I want to make sure if its true. You don’t have to explain me why this is so if you don’t wish to. Also, please tell me if this has been experimentally established, or it is just a theory.

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    $\begingroup$ Trying to figure out the effect of something that can not happen is, in this case, not very useful. $\endgroup$ – C. Towne Springer Jun 9 '14 at 5:00
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    $\begingroup$ But we could check this through an experiment, by introducing a mass in the gravitational field of a body and checking whether there is time lag between the instance when the object feels the gravitation of the introduced mass and the instant of introduction... Also i think the video also talked in such a manner... $\endgroup$ – Prem kumar Jun 9 '14 at 5:09
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    $\begingroup$ How do you propose to introduce a mass suddenly, and make it suddenly disappear? Until you figure out how to do this, the scenario described in your question can not occur. Also, relativistically, there is no concept of today because time is also relative. $\endgroup$ – Pranav Hosangadi Jun 9 '14 at 5:59
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    $\begingroup$ @Raja: in relativistic gravity, some local mass cannot be instantaneously introduced. Thus it will have gravitational effects while en route to its destination, and in general what happens depends on how it's introduced. (This is unlike to Newtonian law of gravity, which is completely fine with arbitrary insertions of mass.) However, if you're simply asking what happens if you do something to a gravitating body (e.g., blow it up), then yes, gravitational effects on whatever surroundings will be delayed by the speed of light. $\endgroup$ – Stan Liou Jun 9 '14 at 7:59
  • $\begingroup$ possible duplicate of The speed of gravity? $\endgroup$ – John Rennie Jun 9 '14 at 10:48
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W.r.t your original question, yes, we would feel the gravitational effects for 10 years from now. Changes in space-time propagate at the speed of light, so spacetime here would still be warped due to that star's gravity even if it disappeared today.

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