Re:SETI Institute suspends search for aliens
by ramchip on Tuesday April 26, 2011 @05:46AM
(#2484545)
Instantaneous gravity exists in Newtonian mechanics but not in modern theories. Gravitation is thought to be transmitted by gravitational waves, which have a finite speed of c. It is not possible to transmit information at a faster speed than light in special relativity.
http://en.wikipedia.org/wiki/General_Relativity#Gravitationa...
http://en.wikipedia.org/wiki/Special_relativity#Causality_an...
Re:SETI Institute suspends search for aliens
by transphenomenal on Tuesday April 26, 2011 @05:03AM
(#2484467)
Gravity propogates at the speed of light. However, using gravity to send information will allow you to send information through most objects like Earth or the Sin without any satilites to redirect it around the object.
Consider gravity. Is its effect instantaneous? That is, gravity varies as the inverse of the square distance between two bodies. If, say, the Earth were to suddenly get much closer to the Moon, would that gravitational effect be "instant"? Or does it propagate at the speed of light?
If gravitation is somehow "instant", then one could imagine an apparatus which allows you to transmit information instantaneously. (You would need a way to measure the effect of gravity from the sending body; perhaps by measuring the height of waves formed in a planetary-sized sphere of water.)