The usual way I explain it is as a transfer of kinetic energy and momentum from the large body to the small one. The interaction is through gravity, rather than

The usual way I explain it is as a transfer of kinetic energy and momentum from the large body to the small one. The interaction is through gravity, rather than the mix of electrostatic, degeneracy, and strong/weak forces involved in collisions; but the equations are more or less the same. (Usually textbooks use a baseball bouncing off a semi truck to illustrate.)