Today, someone asked me why "the warped space-time warps itself" (he read it in Kip Thorne's: The Science of Interstellar). I guess this is related to the gravitational self-interaction. But I don't really understand the gravitational self-interaction. Why the curvature in general relativity influences itself? What term in the Lagrangian will cause this effect? Is there something like an energy tensor of the gravitation field (I read something in the textbook of Landau and Lifschitz).