Naiveview of the inert Oort cloud. It is defined as the region where neither the planets nor the galactic tides have substantial effects on the orbit of small bodies. In this schematic view, the planet scattering makes small bodies move horizontally, whereas the galactic tides and the isolated mean-motion resonances with planets (labelled “planet resonances” on the graph) make them move vertically. The orbital inclination of small bodies is not considered in this picture, though it is known to play a role as well (Saillenfest et al. 2017a).