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<blockquote data-quote="freyar" data-source="post: 6702207" data-attributes="member: 40227">Since you're not talking about the acceleration of an object due to gravity (the apple falling), I gather you mean the speed of gravitational waves.&nbsp; In general relativity or any similar theory of gravity, gravity waves travel at the speed of light in vacuum.&nbsp; So when those black holes collide, the gravitational waves (&quot;ringing of spacetime&quot;) travel outwards at the speed of light.&nbsp; Incidentally, the Advanced LIGO (that's the Laser Interferometer Gravitational-Wave Observatory) is just coming on line this month and has a very good chance of detecting gravitational waves from colliding black holes within the next few years.&nbsp; That would be the first direct measurement of gravitational waves.&nbsp; We have indirect evidence from watching two pulsars which are orbiting each other; their orbit is decaying precisely according to the prediction of energy loss to gravity waves (and the observations have won a Nobel prize).So the timing in ST: Generations is a bit fast.&nbsp; It would really take a few minutes for light or gravitational waves to get from an exploding star to a planet at an earth-like distance.&nbsp; That's not the only issue, either.&nbsp; To create a gravitational wave, the explosion of the star couldn't be spherical but would have to be quite asymmetric.&nbsp; It's been a while since I've watched the movie, but I don't think that explosion was really odd-looking enough.</blockquote>

[QUOTE="freyar, post: 6702207, member: 40227"] Since you're not talking about the acceleration of an object due to gravity (the apple falling), I gather you mean the speed of gravitational waves. In general relativity or any similar theory of gravity, gravity waves travel at the speed of light in vacuum. So when those black holes collide, the gravitational waves ("ringing of spacetime") travel outwards at the speed of light. Incidentally, the Advanced LIGO (that's the Laser Interferometer Gravitational-Wave Observatory) is just coming on line this month and has a very good chance of detecting gravitational waves from colliding black holes within the next few years. That would be the first direct measurement of gravitational waves. We have indirect evidence from watching two pulsars which are orbiting each other; their orbit is decaying precisely according to the prediction of energy loss to gravity waves (and the observations have won a Nobel prize). So the timing in ST: Generations is a bit fast. It would really take a few minutes for light or gravitational waves to get from an exploding star to a planet at an earth-like distance. That's not the only issue, either. To create a gravitational wave, the explosion of the star couldn't be spherical but would have to be quite asymmetric. It's been a while since I've watched the movie, but I don't think that explosion was really odd-looking enough. [/QUOTE]

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