# Does gravity attract instantaneously?

1. Feb 19, 2012

for example, if a star theoretically came into existence 10 light minutes away, would we feel its pull instantaneously? or would it take 10 minutes for us to feel its pull?

2. Feb 19, 2012

### phyzguy

It would take 10 minutes for us to feel the pull. Changes in gravity propagate at the speed of light. The easiest way to see this is by linearizing Einstein's equations of general relativity, so that the metric is a flat metric plus a small perturbation. Then it's easy to show that such perturbations travel at the speed of light and are called gravitational waves.

3. Feb 19, 2012

### Bill_K

Conservation of energy and momentum is an essential ingredient in general relativity. Any question that postulates a mass that suddenly appears or disappears violates the theory, and there is no answer to what will happen as a result.

Sudden changes can occur that conserve energy and momentum, for example the sun could hypothetically (!) explode and split in two, one half going north, the other south. In such a case the change in the gravitational field will propagate at the speed of light, and we will feel the difference with an eight minute delay.

4. Feb 19, 2012

### dpa

Is not acubierre drive, though hypothetical, related with gravitational waves. So are gravitational waves not supposed to not have any limit.
Are gravitational waves different from constant fluctuation of structure of space-time continium.
I a novice and have no knowledge even of E.F.E. Let alone solving it. But just ideas.
Forgive me if i am wrong.

5. Feb 19, 2012