Talk:Retarded position

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Wrong for gravity

I think this is wrong for gravity, as it says the acclerrating masses produce gravitational waves which is not the case. For gravity the whole thing seems to be moved up one order higher (the field accounting for velocity and acceleration of the moving source, not just velocity as is the case in electrodynamics) and gravitational waves are emitted when the quadrupole moment of the distribution varies. 95.112.39.250 (talk) 16:34, 20 May 2019 (UTC)[reply]

As well as I know it, you keep taking derivatives until you get a wave. Or, maybe the other way, that is how nature does it. In the static case, the answer is obvious. (The first term.) As noted, the second term (first derivative) is the velocity correction. For EM, the EM wave case is the second derivative and for gravity the 3rd derivative. Gah4 (talk) 05:34, 11 September 2024 (UTC)[reply]

Finally!

I have been wondering about this one. The EM case is well described by Feynman here, especially equations 28.3. He explains the second term, the correction for the delay. But he doesn't explain the gravity case. I suspected that it had to be true for gravity, to make it consistent with special relativity, and that seems true here. Gah4 (talk) 03:13, 11 September 2024 (UTC)[reply]