Past exam of the physics B course of the University of Cambridge / 2018 / Paper 1 / Section C / C11 / b / Solution

Take a transverse offset $\mathbf{b}\cdot \mathbf{R}=0$. Its distance from the source changes only at second order, but the direction of the gravitational force changes at first order:in its first-order vector expansion. Subtracting the reference acceleration givesIt compresses the transverse separation. Together with the radial result, this is point-mass tidal stretching and squeezing, with tensor eigenvalues $(2,-1,-1)GM/R^3$.