Retarded position
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Einstein's equations admit gravity wave-like solutions. In the case of a moving point-like mass and in the linearized limit of a weak-gravity approximation these solutions of the Einstein equations are known as the Lienard-Wiechert gravitational potentials. The gravitational field at any point of space at some instant of time t is generated by the mass taken in the preceding (or retarded) instant of time s < t on its world-line at a vertex of the null cone connecting the mass and the field point. The position of the mass that generates the field is called the retarded position and the Lienard-Wiechert potentials are called the retarded potentials. The retarded time and the retarded position of the mass are a direct consequence of the finite value of the the speed of gravity, the speed with which gravity propagates in space.
