Very cool. As I understand it GPS satellites already have to have compensations built into their timing/frequency to account for time-related effects due to General Relativity. So GR is entering into the realm of practical engineering. Who'd have thought?
I do not have any deep or proper understanding of GR, but I gather the result means that inertial frames are dragged along with the Earth's rotation. I'm not sure how that would affect the path of light, though. I recall from long ago that equatorial paths around a rotating black hole could give very different results for the passage of time, depending on which way you went around.
I'm not sure, but maybe it means that there is a small gravitational force vector in the direction of the Earth's rotation. IOW, that if you approached the Earth, directly toward the center on a free-fall trajectory, that your velocity vector would begin to deviate away from the Earth's center, toward the direction of the direction of the Earth's rotation (due to the non-zero gradient of the speed of the inertial frames as you got closer).
22 Nov 2011, 1:59 pm
