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Re:Gravitational waves provide dose of reality about extra d... by andrewla on Monday September 17, 2018 @10:40AM (#18006313)
Looking at just the Earth-Sun interaction, Earth is moving in a gravitational field that is unchanging. It's not that Earth is being pulled towards where the sun was eight minutes ago, but rather that it continues to move in free-fall in a region of space-time that is curved in a time-invariant manner.

If the sun were to vanish completely, then an observer above the elliptic of the solar system would see Earth transition from an apparently curved orbit to a straight-line path approximately 8 minutes after the sun's vanishing.

Re:Gravitational waves provide dose of reality about extra d... by BurnGpuBurn on Tuesday September 18, 2018 @03:20AM (#18013218)
Thank you for your answer. I've heard the "it's an unchanging gravitational field" argument before, but it doesn't really explain the question for me. If the suns gravity is a field, then why is the movement of that field (which is locked to the suns mass I presume) instantaneously "known" to the earth, so the earth "free falls" in the curved space time in the right direction holding its orbit. Why doesn't the earth, at 1 au, free fall into the space time curvature that was created by the sun 8 minutes ago? It certainly appears the earth "knows" where the sun is now, which would imply instant information travel.

I also think you contradict yourself in your last statement, in which you say that the gravitational field of the sun does take 8 minutes to reach earth.