What speed Gravitation?

[iceworks]

If a planet orbits a star at a distance of eighty light minutes, and the star suddenly explodes, will it take eighty minutes for the gravitational pull of the sun on the planet to disappear? Or will the effect be instantaneous?

[renormalised]

80 minutes....as the change in the gravitational field can only travel as fast as light, which would also take 80 minutes to reach the planet. If the star went supernova, the change in the gravitational field the planet would feel would be inconsequential. The massive blast of high energy radiation would instantly fry and then vapourise the planet in question, before the gravitational effects even became noticeable.

[g__day]

About three years ago they did an experiment that confirms gravitational field changes radiate at lightspeed.

[Miaplacidus]

My kids say gravity travels at fatspeed.

[renormalised]

Yep, the rate of fall is proportional to the size of the "spare tire" one carries:D:D